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Chromium on the corrosion resistance of stainless steel decisive role in the definition of stainless steel, ω (Cr) ≥ 10.5%, which is the main element of stainless steel, corrosion resistance, the higher the chromium, corrosion resistance higher possible. This is because the steel in the oxidation of the medium can be formed to Cr2O3 as a stable substrate surface protection film (about 10μm), that generate passive phenomenon, in which enrichment of the chromium layer membrane. Meanwhile, the chromium effectively improve solid solution (ferrite, martensite or austenite) of the electrode potential, so that the original iron (low carbon steel) of the electrode potential from negative to positive, so that the steel from corrosion. Adding chromium stainless steel, the electrode potential follows the n / 8 occur on a volume change. When the chromium content of each atom to 1 / 8, 2 / 8, 3 / 8, … … n / 8, or 12.5%, 25%, 37.5% … … the mole fraction, the electrode potential there is a jump, corrosion weakened. Atomic concentration of chromium and 1 / 8 (or 12.5%, molar fraction), if compared to 11.7% by mass, so the chromium content of chromium stainless steel is generally 12% (by mass) above. When the chromium atom content reaches 25%, there will be second mutation, this time the corrosion resistance of chromium steel to further improve. In addition, the chromium on the mechanical properties of stainless steel and technological properties have very good role. Chromium can increase the hardenability of stainless steel, in low-alloy structure has been widely used. Such as reduced chromium austenite to ferrite and carbide transformation rate, so that the isothermal transformation diagram of austenite was shifted to the right, thus reducing the critical cooling rate of quenching of stainless steel, resulting in increased hardenability of steel Some martensitic stainless steel air quenching martensite are available. Chromium can improve the oxidation resistance of stainless steel, with the increase of chromium content of steel significantly improved oxidation resistance. In the martensitic chromium stainless steel, oxidation resistance higher than ordinary stainless steel, 4 to 9 times, martensitic chromium stainless steel can not afford the skin temperature is about 700 ~ 850 ℃.  Chromium is passivated the steel and stainless steel to give good corrosion resistance of industrial use of the only elements of value. With the increase of chromium content, can increase resistance to atmospheric corrosion. In the oxidizing medium (such as dilute nitric acid), with the chromium content increases, the corrosion resistance of stainless steel increased; but in reducing media, with the chromium content increases, the corrosion resistance of stainless steel decreased. Chromium can affect the physical properties of steel were as follows: chromium can increase the steel lattice constant than the increase in volume with chromium content increases linearly, and significantly lower iron-chromium alloy thermal conductivity, but also increase the resistance of steel. Resistance of martensitic chromium stainless steel is common 4 to 6 times. In the quenching conditions, due to the increase in the stability of chromium ferrite increased, thereby reducing thehardness and tensile strength of steel. In the annealed condition, the low carbon iron – chromium alloys with chromium percentage increased, strength and hardness increase, while elongation decreased slightly.  Chromium in pure γ-Fe in the maximum solubility is about 12.0%; when ω (C) ≈ 0.5%, the maximum solubility in austenite is about 20%. In pure α-Fe solubility in the infinite. In Cr-Mn-N steel can increase the N solubility. The formation of chromium carbides in the steel tendency than manganese, and less than tungsten. Chromium steel, the temperature can increase strength and wear resistance of high carbon steel. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Chromium in stainless steel performance decision has become the main element, the fundamental reason is to add chromium steel as an alloying element, the internal contradictions of its campaign in favor of resistance to the development of corrosiondamage. Such a change can be obtained from the following description: 1. Chromium Fe-based solid solution so that the electrode potential to improve  2. Chromium electronic absorption of iron so that iron-passivated  Anodic passivation is due to be prevented from arising from reaction of metal and alloy corrosion resistance phenomenon can be improved. Passivation of metals and alloys constitute the theory of many major film theory, deals with the electronic order of adsorption. Valency states of chromium The valency (oxidation state) of chromium metal as an alloying constituent of stainless steel is 0 (zero). Chromium atoms are present in stainless steel in ‘substitutional’ lattice positions, replacing iron atoms. This is the same as other ‘large’ atoms from elements such nickel. The atoms are held together in the lattice structure by the ‘metallic bond’. This involves the sharing of electrons between atoms with no loss or gain of electrons from atom to atom. The valency state is therefore taken as 0 (zero). The chromium in solid stainless steel should not be regarded as a health hazard. In contrast ionic bonding in compounds, such as sodium chloride (common salt), involves the exchange of electrons between atoms and hence valency states of 1, 2, 3 etc depending on how many electrons the element has lost or gained. It is compounds involving chromium ‘ions’ with a valency state of 6 (which includes chromates) that have been identified as a cause for health concerns. This valency state is also referred to as ‘chromium 6’, ‘hexavalent chromium’ or ‘Cr6+’ Release of chromium if stainless steel corrodes If stainless steel are subject to corrosion metal ions are released from the alloy into the surrounding environment. Under these conditions, chromium ions should be in the trivalent state (Cr3+), which like the chromium in the un-corroded steel, should not be a health hazard. Chromium in stainless steel welding fumes Fumes from welding stainless steel may contain hexavalent chromium ions, depending on the process and any fluxes used Efficient local exhaust ventilation systems should normally be suitable for maintaining exposure limits below the 0.05 mg/m3 limit for hexavalent chromium ions. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Chemical elements are known to have more than 100 kinds of industrial materials used in steel can be encountered in about more than 20 kinds of chemical elements. For people in the fight against corrosion for long term practice of this particular form of stainless steel series, the most commonly used in a dozen elements, in addition to the basic elements of the composition of steel other than iron, the performance of stainless steel and organizations most affected. The elements are: Carbon, Chromium, Nickel, Manganese, Silicon, Molybdenum, Niobium, Titanium and Miobium, Nitrogen,Copper, Cobalt, Aluminum, Sulfur and Selenium.  These elements, in addition to carbon, silicon, other than nitrogen, are located in the periodic table of chemical elements of transition. In fact the application of the stainless steel tube industry at the same time there are several elements as well as a dozen, when the number of elements co-exist in a continuum of stainless steel tube, they separate the impact of the presence of more much more complex, because in this cases not only have to consider the role of the various elements of their own, and they should pay attention to the impact of each other, so the organization decided to stainless steel pipe of various elements in the sum of the impact. 1. Various elements on the performance of stainless steel and the impact and role of organizations 1-1. Chromium in the stainless steel a decisive role in stainless steel is a decision of only one element, that is, chromium, stainless steel each contain a certain amount of chromium. To date, no non-chromium stainless steel. Chromium stainless steel performance decision has become the main element, the fundamental reason is to add chromium as an alloying element, the internal contradiction of campaign in favor of resistance to the development of corrosion damage. Such a change can be obtained from the following description: 1. Chromium Fe-based solid solution so that the electrode potential to improve  2. Chromium electronic absorption of iron so that iron-passivated  Anodic passivation is due to be prevented from arising from reaction of metal and alloy corrosion resistance phenomenon can be improved. Passivation of metals and alloys constitute the theory of many major film theory, deals with the electronic order of adsorption. 1-2. Carbon in the stainless steel tube in the dual nature of Carbon steel is the industry one of the key elements, steel and organizational performance to a large extent determined by the carbon content in steel and its distribution in the form of the impact of carbon stainless steel is particularly significant. Carbon in the stainless steel on the impact of organizations mainly in two ways, on the one hand is stable austenite carbon element, and the extent of the role of a large (approximately 30 times for nickel), on the other hand, as a result of the affinity of carbon and chromium is large, with the formation of chromium – series of complex carbides. Therefore, the candle from the intensity and decay properties, both in terms of carbon in the role of stainless steel are mutually contradictory. Recognizing the impact of the law, we can use from different requirements of different carbon content stainless steel. For example, most widely used in industry, but also the stainless steel at least – 0Crl3 ~ 4Cr13 five standard steel grade chromium amount is 12 ~ 14%, that is, the carbon to form chromium carbide and chromium factors taken into account after determined that the purpose is to make the combination of carbon and chromium as chromium carbide, the solid solution of chromium in the amount of not less than 11.7% of the minimum amount of chromium. No. 5 on the steel is due to the different carbon content, strength and corrosion resistance is also differentiated, 0Cr13 ~ 2Crl3 better corrosion resistance of steel but lower than the 3Crl3 and 4Cr13 strength steel, used in the manufacture of the structure of many parts, after As the No. 2 steel with higher carbon intensity will be high and more used in the manufacture of springs, cutting tools, such as high strength and wear-resistant parts. Another example is in order to overcome the 18-8 Cr-Ni stainless steel intergranular corrosion, can be carbon steel to 0.03% below, or by adding chromium and carbon affinity than the larger elements (titanium or niobium), so that does not form a carbide chromium, Another example is when the high hardness and wear resistance as a major requirement, we can increase the carbon content of steel at the same time to suitably increase the amount of chromium so that not only satisfy the requirements of the hardness and wear resistance, but also take into account – will be corrosion-resistant function, used for industrial bearings, has a stainless steel blade measuring and 9Cr18 and 9Cr17MoVCo steel, although the carbon content as high as 0.85 ~ 0.95%, due to their chromium also increased accordingly, it is still guaranteed the corrosion resistance of requirements. Generally speaking, the current industry access to the application of the carbon content of stainless steel pipe are relatively low, most of the carbon content of stainless steel in the 0.1 ~ 0.4%, and acid-resistant carbon steel with 0.1 to 0.2% of the majority. Greater than 0.4% carbon content of stainless steel grade is only a small fraction of the total, which is used because in most conditions, to corrosion-resistant stainless steel is always the primary purpose. In addition, the lower carbon content is also a process for some requirements, such as the ease of welding and cold deformation. 1-3. Nickel in the role of stainless steel and chromium in the play after the Nickel is an excellent corrosion-resistant materials, is also an important steel alloying elements. Nickel in the austenitic stanless steel pipe is the formation of the elements,such as 304,316,321.but the low-carbon steel to obtain pure nickel austenite, the volume of nickel to achieve 24%; and only when 27 percent nickel steel, in some medium resistance significant changes in corrosion. Thus alone can not constitute a nickel stainless steel. But at the same time the existence of nickel and chromium in the stainless steel, the nickel-containing stainless steel but has many valuable properties. Based on the above circumstances, we can see that nickel as alloying elements in the role of stainless steel is that it allows high-chromium steel changes, so that corrosion resistance of stainless steel and certain to improve process performance. 1-4. Manganese and Nitrogen can substitute for Ni-Cr-Ni stainless steel Cr-Ni austenitic steels Although many of the advantages, but in recent decades as a result of nickel-based heat-resistant nickel alloy and the heat below 20% of the large number of strong steel development and applications, as well as the growing chemical industry of the increasing demand of stainless steel The greater the amount of the nickel deposits less concentrated in a few areas, it appeared in the world and the need for nickel in the conflict area. Therefore, in stainless steel alloys and many other fields (such as a large forging steel, tool steel, heat strong steel, etc.), especially the lack of nickel resources of the country, carried out extensive section of nickel and nickel on behalf of other elements in the scientific research and production practice, in this regard the research and application is based on a relatively large number of manganese and nitrogen to replace the stainless steel and heat-resistant nickel steel. For the role of manganese and nickel austenitic similar. But to be more exact, the role of manganese does not lie in the formation of austenite, but it reduced the critical quenching rate of steel in cooling to increase the stability of austenite and suppress the decomposition of austenite, so that the formation of high temperature austenite to room temperature is maintained. In improving the corrosion resistance of steel, the manganese plays a minor role, such as manganese steel increased from 0 to 10.4% change, do not make steel in the air with the acid corrosion resistance of significant change. This is because the manganese to iron-based solid solution to increase the electrode potential does not help the formation of the protective role of the oxide film is very low, so the industry although some of the austenitic manganese steel alloys (such as 40Mn18Cr4, 50Mn18Cr4WN, ZGMn13 steel, etc.), but they can not be used as the use of stainless steel. Manganese in steel is about the role of a stable austenitic nickel half, that is 2% of nitrogen in steel is the role of austenite stability and the role of larger than nickel. For example, to save with 18% chromium steel austenitic at room temperature under the body to manganese and nitrogen on behalf of low-nickel stainless steel and nickel chromium nickel element nitrogen does not induce manganese steel has been applied in industry, and some has successfully replaced the classic chrome-nickel stainless steel 18-8. 1-5. Stainless steel Titanium or Niobium Canada is to prevent intergranular corrosion. 1-6. Molybdenum and Copper can increase some of the corrosion resistance of stainless steel. 1-7. Other elements on the performance of stainless steel and organizational impact More than nine major elements of stainless steel performance and the impact of organizations, in addition to these elements and organizational performance of stainless steel elements of a greater impact, the stainless steel contains a number of other elements. Some, like steel and general for the regular deposit of impurity elements, such as silicon, sulfur and phosphorus. Also some specific purpose in order to join, such as cobalt, boron, selenium, and other rare earth elements. From the stainless steel corrosion resistance of the nature of the main, these elements have been discussed in relation to the nine elements are non-key aspects, although the case, but can not be completely ignored because their performance of stainless steel and organizations have also taken place in the same impact. Silicon is a ferrite forming element, in general, always keep the stainless steel for the impurity elements. Cobalt as alloying elements in steel by the application of small, this is because the high price of cobalt and in other ways (such as high-speed steel, carbide, cobalt-based heat-resistant alloys, magnetic or hard magnetic alloy, etc.) has a more important purposes. Stainless steel in the general increase in the cobalt alloy elements for not more commonly used stainless steel, such as 9Crl7MoVCo (including 1.2-1.8% cobalt) plus cobalt, the purpose is not to improve corrosion resistance and to improve hardness, which are mainly used for stainless steel slicing machinery manufacturing cutting tools, such as scissors and blades. Boron high-chromium ferritic stainless steel Crl7Mo2Ti plus 0.005% of boron, can in boiling 65% acetic acid can enhance the corrosion resistance. Add small amount of boron (0.0006 ~ 0.0007%) austenitic stainless steel will enable the plastic to improve the thermal state. A small amount of boron due to the formation of low melting point eutectic, so that when austenitic steel welding hot cracking tendency to increase, but contains more boron (0.5 ~ 0.6%) when it prevents the emergence of hot cracking . When containing 0.5 ~ 0.6% of boron, the formation of austenite – two-phase boride organizations to lower the melting point of weld. Coagulation bath temperature is below half the melting zone, the base metal in the cooling of the tensile stress generated by the liquid is. Solid- state under the weld metal, is at this time without causing cracks even in the near seam zone formed a crack, it can be in liquid – solid metal by filling the pool. B-containing austenitic stainless steel of the Cr-Ni in the atomic energy industry has a special purpose. Phosphorus in the general impurity elements are stainless steel, but its in danger of austenitic stainless steel in general is not as significant in steel, it allows a higher concentration, if the information up to 0.06%, to control in favor of smelting. Inpidual austenite manganese steel output of about 0.06% phosphorus (such as steel 2Crl3NiMn9) and 0.08% (for example, steel Cr14Mnl4Ni). The use of phosphorus on the strengthening of the role of steel as well as age-hardening increases phosphorus alloying elements of stainless steel, PH17-10P steel (containing 0.25% phosphorus) is a PH-HNM steel (containing 0.30 P) and so on. Sulfur and selenium in the general stainless steel is also often of impurity elements. However, China and Canada to the stainless steel 0.2 ~ 0.4% of sulfur, can improve the cutting performance of stainless steel, selenium also has the same effect. Sulfur and selenium to improve the cutting performance of stainless steel because they reduce the toughness of stainless steel, such as the 18-8 Cr-Ni stainless steel in general the impact of the value of up to 30 kg / cm 2. Containing 0.31% sulfur 18-8 steel (0.084% C, 18.15% Cr, 9.25% Ni) the impact of the value of 1.8 kg / cm2; containing 0.22% selenium 18 -8 steel (0.094% C, 18.4% Cr, 9% Ni) the impact of a value of 3.24 kilograms / square centimeters. Both sulfur and selenium to reduce the corrosion resistance of stainless steel, so the practical application of them as a stainless steel alloy of the rare element. Rare-earth element rare-earth element used in stainless steel pipe, the key is to improve the process performance. Crl7Ti such as the steel and steel plus Cr17Mo2Ti a small number of rare earth elements, can be eliminated in ingot caused by hydrogen bubbles and the reduction of cracks in the slab. Austenitic and austenitic – ferritic stainless steel in 0.02 ~ 0.5% increase in the rare earth elements (Ce-La alloy), can significantly improve the performance of forging. Had a 19.5 percent containing chromium, nickel 23% copper and molybdenum austenitic manganese steel, due to thermal processing performance in the past only the production of castings, after the increase of rare earth elements can be rolled into various sections.

Nickel is the formation of austenite of alloying elements, but the role of nickel and chromium to only be fully demonstrated. If the simple use of nickel, nickel stainless steel in the low-carbon austenitic phase to obtain pure organizations need to nickel content up to 24% (by mass) or more, in fact, need to reach 27% nickel content (mass fraction), can significantly improve the corrosion resistance of stainless steel, so there is no separate stainless steel to nickel as alloying elements. When the nickel and chromium complex, the nickel role in improving the corrosion resistance of steel can be shown significantly, such as ferritic stainless steel to add a small amount of nickel, can make the single-phase microstructure of ferrite into austenite – Organization of ferrite phase, so that you can to increase its strength by heat treatment. Further increase of nickel content, you can become a single phase of austenite, such as ω (Cr) = 18% of steel with 8% (by mass) of nickel, the availability of fully austenitic. This is widely used in chrome-nickel austenitic 18-8 stainless steel, it with high corrosion resistance and good deformation, welding, and is not magnetic. Nickel in the role of stainless steel and chromium in the play after the Nickel is an excellent corrosion-resistant materials, is also an important steel alloying elements. Nickel in the austenitic stanless steel is the formation of the elements,such as304,316,321.but the low-carbon steel to obtain pure nickel austenite, the volume of nickel to achieve 24%; and only when 27 percent nickel steel, in some medium resistance significant changes in corrosion. Thus alone can not constitute a nickel stainless steel. But at the same time the existence of nickel and chromium in the stainless steel, the nickel-containing stainless steel but has many valuable properties. Based on the above circumstances, we can see that nickel as alloying elements in the role of stainless steel is that it allows high-chromium steel changes, so that corrosion resistance of stainless steel and certain to improve process performance. Nickel in pure α-Fe in the maximum solubility of 25% to 30%, when the stay was still contains carbon in ferrite, the effect is not hardened by solid solution of steel intensive. Passivation of nickel to expand the scope to improve corrosion resistance, especially in non-oxidizing media (such as sulfuric acid) in the.  Nickel-iron carbide formation tendency is weaker than can promote graphitization, and weakly increased the hardenability of steel on steel is not sensitive to cold shock play a role. In carbon and high carbon steel containing an effective concentration, the quenching preferred to retain austenite. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Matching the consumable to the parent material The chemical composition of stainless steel welding consumables is matched with the base or parent material. The chemical analysis (composition) of the consumables used are usually balanced to optimise the welding process and avoid hot cracking. Austenitic stainless steel Low carbon levels are normally used to reduce the risks of intergranular corrosion (intercystalline) following cooling through temperatures from around 850 down to 450 C after weld solidification. Corrosion mechanisms in stainless steel. Consumables such as 19 9 and 19 12 2 with higher carbon levels should give higher strength welds, more suited for high service temperatureapplications. The titanium stabilized steel, 321 and 316Ti are welded with consumables containing niobium, rather than titanium. The very high melting point titanium carbides that would be present in the consumable would be unlikely to melt during the welding process, whereas the niobium carbo-nitrides in the niobium type consumables have lower melting points and are a better choice. Ferrite levels of austenitic consumables are normally balanced between 4 and 12 %, to reduce the risk of hot cracking at temperature just below the solidification point of the weld metal. For welding the special low / zero ferrite grades, intended for special corrosion resistant, cryogenic temperature or low magnetic permeability service conditions, matching low /zero ferrite consumables, such as 18 15 3 L, should be used. Ferritic, martensitic and precipitation hardening stainless steel Generally, either matching consumables, or an austenitic filler with matching chromium and molybdenum contents, can be used. Austenitic fillers are used where good weld toughness is essential, but these are not a good idea where the weld appearance (colour), mechanical strength (in the case of welds between martensitic and precipitation hardening parent material) and physical properties (thermal expansion) need to be matched with the parent material. Duplex stainless steel In contrast to the austenitic consumables, duplex fillers, such as 22 9 3 N L are balanced to produce more austenite in the weld than in the parent metal. This is done to optimise weld mechanical properties and corrosion resistance and is achieved by adding more nickel and usually nitrogen to the consumable than is present in the matched base metal. Compositions of consumables The consumable alloy symbols are common in the European standards. The compositions can vary, however, for the various consumable types between EN 1600, EN 12072 and EN 12073 for the same ‘Alloy symbol’ used in each standard. For each specific consumable type the particular standard should be consulted. As a guide the table below gives the compositions in EN 1600. For these coated electrode types, the type of covering determines to a large extent the usability characteristics of the electrode and properties of the weld metal. Two symbols are used to describe the type of covering: R for Rutile covering and B for Basic covering. A description of the characteristics of each of the types of covering is given in Annex A of BS EN 1600. (See also paragraph 4.3 of the standard) Alloy symbolsChemical composition (% by mass – max unless stated).CSiMnPSCrNiMoOthers130.121.01.50.0300.02511.0/14.0–––13 40.061.01.50.0300.02511.0/14.53.0/5.00.4/1.0–170.121.01.50.0300.02516.0/18.0–––19 90.081.22.00.0300.02518.0/21.09.0/11.0––19 9 L0.041.22.00.0300.02518.0/21.09.0/11.0––19 9 Nb0.081.22.00.0300.02518.0/21.09.0/11.0–Nb-8x%C min, 1.1%max19 12 20.081.22.00.0300.02517.0/20.010.0/13.02.0/3.0–19 12 3 L0.041.22.00.0300.02517.0/20.010.0/13.02.5/3.0–19 12 3 Nb0.081.22.00.0300.02517.0/20.010.0/13.02.5/3.0Nb-8x%C min, 1.1%max19 13 4 N L0.041.21.0/5.00.0300.02517.0/20.012.0/15.03.0/4.5N 0.2022 9 3 N L0.041.22.50.0300.02521.0/24.07.5/10.52.5/4.0N 0.08/0.2025 7 2 N L0.041.22.00.0350.02524.0/29.06.0/9.01.0/3.0N .02025 9 3 Cu N L0.041.22.50.0300.02524.0/27.07.5/10.52.5/4.0N 0.10/0.25 Cu 1.5/3.525 9 4 N L0.041.22.50.0300.02524.0/27.08.0/10.52.5/4.5N 0.20/0.30 Cu 1.5 W 1.018 15 3 L0.041.21.0/4.00.0300.02516.5/19.514.0/17.02.5/3.5–18 16 5 N L0.041.21.0/4.00.0350.02517.0/20.015.5/19.03.5/5.0N 0.2020 25 5 Cu N L0.041.21.0/4.00.0300.02519.0/22.024.0/27.04.0/7.0Cu 1.0/2.0 N 0.2520 16 3 Mn N L0.041.25.0/8.00.0350.02518.0/21.015.0/18.02.5/3.5N 0.2025 22 2 N L0.041.21.0/5.00.0300.02524.0/27.020.0/23.02.0/3.0N 0.2027 31 4 Cu L0.041.22.50.0300.02526.0/29.030.0/33.03.0/4.5Cu 0.6/1.518 8 Mn0.201.24.5/7.50.0350.02517.0/20.07.0/10.0––18 9 Mn Mo0.04/0.141.23.0/5.00.0350.02518.0/21.59.0/11.00.5/1.5–20 10 30.101.22.50.0300.02518.0/21.09.0/12.01.5/3.5–23 12 L0.041.22.50.0300.02522.0/25.011.0/14.0––23 12 Nb0.101.22.50.0300.02522.0/25.011.0/14.0–Nb-8x%C min, 1.1%max23 12 2 L0.041.22.50.0300.02522.0/25.011.0/14.02.0/3.0–29 90.151.22.50.0350.02527.0/31.09.0/12.0––16 8 20.081.02.50.0300.02514.5/16.57.5/9.51.5/2.5–19 9 H0.04/0.081.22.00.0300.02518.0/21.09.0/11.0––25 40.151.22.50.0300.02524.0/27.04.0/6.0––22 120.151.22.50.0300.02520.0/23.010.0/13.0––25 200.06/0.201.21.0/5.00.0300.02523.0/27.018.0/22.0––25 20 M0.35/0.451.22.50.0300.02523.0/27.018.0/22.0––18 360.251.22.50.0300.02514.0/18.033.0/37.0–– Suggested consumables for welding stainless steel Euro Inox publication ‘Welding of Stainless Steels’ tabulates suggested consumables for welding a range of stainless steel base or parent grades. This publication can be viewed or down loaded in pdf format from the Euro Inox web site, www.euro-inox.org by selecting the Materials and Applications sub menu. This table is shown below. Base MaterialWelding ConsumablesEN 10088 NumberAISI GradeEN 1600EN 12072EN 120731.4301304E 19 9G 19 9 LT 19 9 L1.4306/1.4307304LE 19 9 LG 19 9 LT 19 9 L1.4541321E 19 9 NbG 19 9 NbT 19 9 Nb1.4401316E 19 12 2G 19 12 2 LT 19 12 2 L1.4404316LE 19 12 3 LG 19 12 3 LT 19 12 3 L1.4571316TiE 19 12 3 NbG 19 12 3 NbT 19 12 3 Nb1.4438317LE 19 13 4 N LG 19 13 4 LT 19 13 4 N L1.4310301E 19 9G 19 9 LT 19 9 L1.4318301LE 19 9 LG 19 9 LT 19 9 L1.4833309SE 22 12G 22 12 HT 22 12 H1.4845310SE 25 20G 25 20T 25 201.4438317LE 19 13 4 N LG 19 13 4 N LT 19 13 4 N L1.4512409E 19 9 LG 19 9 LT 13 Ti1.4016430E 17 or 19 9 LG 17 or 19 9 LT 17 or 19 9 L1.4510430Ti (439)E 23 12 LG 23 12 LT 23 12 L1.4521444E 19 12 3 LG 19 12 3 LT 19 12 3 L1.4509441E 23 12 LG 23 12 LT 23 12 L1.4113434E 19 12 3 LG 19 12 3 LT 19 12 3 Nb1.4362(2304)E 25 7 2 N LG 25 7 2 N LT 22 9 3 N L1.4462(2205)E 25 7 2 N LG 25 7 2 LT 22 9 3 N L1.4006410E 13 or 19 9 LG 13 or 19 9 LT 13 or 19 9 L1.4021420E 13 or 19 9 LG 13 or 19 9 LT 13 or 19 9 L1.4028420E 13 or 19 9 LG 13 or 19 9 LT 13 or 19 9 L Notes Only the steel number is shown. The original Euro Inox table also has the steel name. AISI is the American Iron and Steel Institute Wire electrodes covered by EN 12072 may use the following prefixes G for GMAW (MIG), W for GTAW (TIG) P for PAW (plasma arc), or S for SAW (submerged arc). Tubular cored electrodes are sometimes referred to as flux cored electrodes. Releated References Welding of Stainless Steels Euro Inox, Materials and Applications Series, vol.3 Welding of Stainless Steels and Other Joining Methods The Nickel Institute, AISI Designers Handbook Series No 9002

The traditional ‘free machining’ stainless steel have been based on sulphur (S) additions in the UK or alternatively, selenium (Se) additions, which have been favoured in the United States. The addition of these elements is in the region of 0.15 – 0.35%. In practice, it is impossible to obtain the selenium treated steel from European producers. These additions form manganese rich sulphides (selenides), which provided they are evenly distributed through the stainless steel, act as chip breakers for machining operations and so can offer higher machining speeds and improved cutting tool life. These ‘non-metallic’ inclusions can also provide a source of solid lubricant to the tool / workpiece interface which may in turn also result in improvements in surface finish. British standard free machining grades Free-machining types have been specified as alternatives to some of the popular grades, but grade rationalisation has resulted in some of the options being withdrawn from standards. EN 10088 grades with permitted sulphur additions Although purpose designed free machining grades are limited in the European standard, EN 10088 does allow machinable grade variants with 0.015 / 0.030% S additions to some grades. Un-Treated TypeMachinability AdditionBS Free Machining GradesNearest BS EN 10088 Grade420S416S211.4005416S29–416S371.4029Se416S41–431S441S29–Se441S49–304S303S211.4305Se303S41–321S325S21–316Se326S36–316S–1.4598 BS EN 10088 grades with permitted sulphur additions Although purpose designed free machining grades are limited in the European standard, BS EN 10088 does allow machinable grade variants with 0.015 / 0.030% S additions to some grades. Selenium additions are not allowed in this European standard. 1.4006410 type – 0.08 / 0.15 %C1.4021420 type – 0.16 / 0.25 %C1.4028420 type – 0.26 / 0.35 %C1.4031420 type – 0.36 / 0.42 %C1.4057431 type – 0.12 / 0.22 %C1.4112440B type – 0.85 / 0.95 %C1.4125440C type – 0.95 / 1.20 %C1.454217/4 PH type1.4307304L type1.4541321 type1.4401316 type1.4404316L type Proprietary enhanced machinability grades Proprietary sulphur and selenium grades have been marketed, including ferritic 430 and martensitic 440 types. Proprietary alternatives based on controlled non-metallic inclusion levels are also available. These are usually based on calcium de-oxidisation steelmaking techniques and include grades based on 304, 316 austenitic, 2205 (1.4462) duplex and 17-4 PH (1.4542) precipitation hardening types. The levels of calcium or oxide type inclusions are not part of the grade specification, the grades being identified only by their proprietary names. Many manufacturers of stainless steel bars market these enhanced machinability grades with brand names, for example: CompanyBrandAcerinoxRoldamaxCogneIMCOOutokumpuPRODECSchmolz and BickenbachUgimaValbrunaMaxival Other additions deliberately made to enhance machinability include copper. This helps improve machinability of austenitic types by reducing the cold work hardening tendency. (Copper works like nickel as a powerful ‘austenite’ phase stabiliser, reducing the formation of strain induced martensite during cold working). The cold forging grades are copper bearing types. Disadvantages of free machining grades The ‘machining’ grades may not perform as well as the ‘standard’ grades, from which they are derived. When specifying and working with these types of stainless steels it is important to bear in mind that they can be inferior to the un-treated types.

Trade Names Associated With Stainless Steel table Note, where ‘Non-SS’ is shown in the Nearest Grade column, this indicates that the trade name as not a stainless steel. Use the ‘Ctrl’ and ‘F’ keys to ‘find’ a particular name.Trade NameNearest GradeDescription1925hMo1.4529Austenitic20% chromium, 25% nickel, 6% molybdenum superaustenitic stainless steel (Krupp Thyssen Nirosta)22051.4462 Duplex22% chromium, 5% nickel, 3% molybdenum duplex stainless steel253MA1.4835 Heat Resisting21% chromium, 11% nickel, 1.5% silicon heat resisting stainless steel (AvestaPolarit)254SMO1.4547Austenitic20% chromium, 18% nickel, 6% molybdenum superaustenitic stainless steel (AvestaPolarit)520B1.4594Martensitic-PH13.5% chromium, 5.5% nickel, 1.5% molybdenum precipitation hardening grade904L1.4539Austenitic20%chromium, 25% nickel, 4.5% molybdenum austenitic stainless steelAbrazoNon-SSBritish Steel wear platesAbroNon-SSWear plates from James Fairley Abra Service Division 0121-327 7522Alencoflex–Flexible hoses with stainless steel braid outer covers from Alenco Hilyn, EnfieldAlloy 1601.47131.4713 Heat resisting grade 7% Cr, Al – Bohler UK 0121-552 2575 – See Sicromal 8Aluchrom–VDM Trade Name for Fe-Cr alloysAquamet 22Nitronic 50Nitronic 50 type for propeller shaft applications – see Clements Engineering (St.Neots)Ltd for detailsArmourcote–PTFE stainless composite coating for reducing friction from Armourcote Surface TreatmentsBattle–Stainless steel holloware from GW Pearce, BirminghamBrightrayNon-SSNickel alloys from Inco AlloysBundyNon-SSBrake pipe material from Armco also see FulbraizChemicoNon-SSGeneral purpose cleaner for stainless steel from The County Chemical Company, Birmingham 0121-744 2294Chichester–Stainless steel ware from Goodwood Metalcraft TEL 01243-784626 (also see Dexam International)ColorcoatNon-SSPrepainted mild steel strip from British Steel (Corus Strip products)Compass B555Non-SSWear plate with Brinell Hardness of 555HB – Sleema Engineers TEL 01922-408088Corrbloc–Mild steel strip clad with stainless steelCorten ANon-SSWeathering steel from Corus Strip (British Steel)Corten BNon-SSWeathering steel from Corus Plates (British Steel)Cres–US military abbreviation for “Corrosion Resistant” implies any stainless steel ie not grade specificCrominox–Aciers Crominox, Luxembourg now merged with Cromweld Steels as a 3Cr 12 supplierCromweld 3Cr121.4003 Ferritic3Cr12 ferritic stainless from Cromweld Steels, Stoke on Trent TEL 01782-374139Cronifer–Krupp VDM Trade Names for stainless steelsCronix–Krupp VDM Trade Names for Ni-Cr heating element alloysCuniferNon-SSKrupp VDM Trade Names for copper-nickel alloysDamac DL12Non-SSSpot test paste supplied by Broadway ProductsDelcromeNon-SSSee Stellite – Product of Deloro Stellite, SwindonDeloroNon-SSSee Stellite – Product of Deloro Stellite, SwindonDessoxNon-SSOakite Ltd descaling compoundsDuranel–Clad plates involving combinations of stainless steel, aluminium and copperDurasteelNon-SSSteel sheet with organic coating over zinc-nickel plated surface, originally from Japan (Nissan). Cape-Durasteel, Wellingborough TEL 01933-440555Durbar304, 316Floor or chequer plate – 304 & 316 now imported from Belgium (ALZ), stocked by Ancon CCLDureheteNon-SSHeat resisting bar grades for bolting applications from Corus Engineering Steels, RotherhamE-Brite 26-1–Ferritic stainless steel with 26% Cr and extra low carbon (0.005% Max) from Airco Vacumetal, USAEM 528–Rolls Royce specification for 448 type turbine blade steelEssheteNon-SSHeat resisting steel grades from Corus Engineering SteelsEzeform–Patterned stainless steel strip from Atlas Steels, Canada for roofing applicationsFAK 2232205Also see “FALC 223” Duplex Stainless Steel of a 2205 type from KruppFDP1.4541Austenitic“Firth’s Decay Proof” (321) – see Firth Vickers ‘Staybrite’Fecralloy–Heat resistance wire, strip, bar grade 20% Cr, 5% Al,0.1% Y (yttrium) from Resistalloy, Sheffield TEL 0114-244 8634Ferralium 2551.4507 DuplexSuper duplex stainless steel available from Langley Alloys Ltd, Newcastle-under-LymeFerritescope–Magnetic permeability meter calibrated to show percentage of ferrite in austenitic stainless steels. from Fischer InstrumentationFerro-Di–Die casting process for stainless steel, GKN Crewe Technical CentreFMB1.4401/1.4436Austenitic“Firth’s Moly Bearing” (316, 2.25-3.0% Mo) – see Firth Vickers ‘Staybrite’Fliteline–PTFE flexible tubing with stainless steel braided wire sheathing for steam & water tubes from Unitubes, Slough TEL 01753-34931GenkleneNon-SSSolvent containing trichloroethylene (not advised for health & environment reasons)Hadfields Manganese SteelNon-SSManganese steel, 12-14%Mn, for extreme wear resistant applications. Available from Corus Scunthorpe 01724-405779 Tim PeregrineHastelloyNon-SSNickel based alloysHaynes AlloysNon-SSNickel based alloys, see Haynes Alloys brochures on shelf No2, cabinet No1 TEL 0161-223 5054HexmetalNon-SSArmours for refractory linings from Causeway Steel Products, Gravesend TEL 01474-67871Hi-Proof316LNNitrogen bearing austenitics eg 316 bar for reinforcement, warm worked for 460 N/mm2 strength classHR 3C31025Cr – 20Ni – Nb – N variant of 310 as sulphurizing resistant grade from Sumitomo Metal Ind.HWT430TiHot Water Tank grade similar to 430Ti, with 19% Cr from Allegheny LudlumHydroloy–Hydroloy HQ913 low erosion weld deposit austenitic grade available as weld deposit electrodes from Deloro StelliteHyform 4091.4512 FerriticAvestaPolarit 409 type with titanium for automotive silencer tubing etcHyplus 29Non-SSCorus Plates productHypressNon-SSC steel strip grade from Corus Strip Products, BrinsworthImmac 51.4845 Heat ResistingHeat resisting 310 (25 / 20) type originally a Firth Brown trade nameImmaculate V–Heat resisting 310 (25 / 20) with vanadiumIN744X–Micro duplex super plastic experimental stainless steelIncocladNon-SSNickel cladding alloysIncoloyNon-SSNickel heat resisting alloys (Incoloy DS 37Cr – 18Ni , Incoloy 800 same as Esshete 800)InconelNon-SSNickel alloysInox–French (Spanish, Italian) general term for “stainless”, not grade specificInvar (Nilo 36)Non-SSNickel alloy with 36% iron zero thermal expansion rateJethete–Martensitic stainless steel for aircraft turbine blades & engine casingsKanthalNon-SSHeat Resistant & heating element alloys for furnace heating applications from Kanthal Ltd, Stoke on Trent TEL 01782-224800Kromar D70–Cobalt containing stainless steel used for cluster bomblet flights made by Hunting Engineering. Believed to be an obsolete application.Kunifer 10Non-SSBrake pipe grade from Yorkshire Imperial Metals TEL 01532-701107M153D–Proprietary specification for a 316 free machining type with titanium additions type from IMI WittonMacalloyNon-SSReinforcement bar from Allied Steel & Wire (McCalls) TEL 0114-242 6704MeehaniteNon-SSCast Irons from The International Meehanite Metal Co, Reigate TEL 01737-244786MEKNon-SSMethylethyl ketone – solvent for removing plastic film & adhesives from stainless steel sheetMeten 91.4828 Heat ResistingHeat resisting stainless steel grade similar to Red Fox 34 from Mechanical Engineers, LondonMonelNon-SSNickel-copper alloysMu MetalNon-SSAlloy of 77% Ni,5% Cu, 4% Mo & Iron – Soft magnetic alloy with a high magnetic permeabilityNACENon-SSNational Association of Corrosion Engineers (US)Ni-HardNon-SSAbrasion resistant castings 3.5/4.5 % NiNichromeNon-SSNickel Chromium heat resisting alloys for furnace heating elementsNicorrosNon-SSNickel-copper alloys.NicroferNon-SSVDM Trade Name for Ni-Cr-Fe & Ni-Cr-Fe-Mo alloys (TEL 01372-67137) – Nicrofer 3220=Incoloy 800,Nicrofer 3718=Incoloy DS,Nicrofer 4221=Incoloy 825,Nicrofer7216=Inconel 600,Nicrofer 7520=Nimonic75NiloNon-SSLow expansion nickel alloyNimarNon-SSMaraging Steels from Corus Engineering SteelsNimonicNon-SSNickel based heat resisting eg Nimonic 75, 80, 90NiresistNon-SSNickel cast iron from Lennox Foundry TEL 01322-383281Niroflex–Stainless steel safety clothing – CMT Industrial Supplies, Swansea 01792-798600Nirosta–Krupp Thyssen Nirosta (KTN) trade names for stainless steels, use Werkstoff numbers for grades eg “Nirosta 4301” as 1.4301 (304)NitralloyNon-SSOld ESC trade names for nitriding alloys En 41A & B, try Henry Whitham,Sheffield TEL 0114-244 0744Nitronic 50–Also marketed as “Aquamet”NovametNon-SSMetal flakes from Hart Coating Technology TEL 01384-291513Nu Eli t–18/2 ferritic stainless, titanium stabilized ferritic stainless (low interstitial) – old Nyby Uddeholm brandsNu Monit–Titanium stabalised ferritic stainless (low interstitial) – old Nyby Uddeholm brandsNuovinox–Aberneath Industries clad stainless bar products TEL 01639-820666Oztelloy–Stainless steel plating on various substrates – Tri-Kem Ltd Wellingborough – 01933-228877PerniferNon-SSKrupp VDM Trade Names for 36% nickel-iron low expansion alloyPlanclad–Ductile Planetary Mill Ltd clad strip 304L, 430 & 410 stainless on carbon steel substratePolarisNon-SSPolaris stainless steel reviver (cleaner-polisher for table ware, sinks etc) – Dexam InternationalPoral–Porous sheet and strip (Pechiney Ugine Kulmann), not now availableProdec–Avesta Sheffield free machining grades (Degerfors plate & bar)Red DiamondNon-SSWear resistant plates (Spartan Redheugh Ltd, Gateshead now closed)Red Fox–Corus Engineering Steels Heat Resisting types RF310, RF309 & RF34 (RF34 also known as Meten 9 – 1.4828)Regaflex316Flexible tube for flue linings in 316 type from Rega Metals ProductsRemanit–Originally Thyssen trade name — usually has werkstoff number added eg Remanit 4301Rigitube–Patterned tube for vehicle handrails (grab rails) – Rimex (Rigidized Metals)Sanicro–Sandvik trade name eg Sanicro 28 (UNS N08028)Sanmac–Sandvik improved machinability barSea-Cure446Ferritic grade for seawater heat exchanger tubing- 26Cr, 3Mo, 2.5Ni UNS S44660Sicromal 101.4742 Heat ResistingHeat resisting grade 17% Cr, AL – (Energy Alloys Rotherham 01709-788000)Sicromal 121.4762 Heat ResistingHeat resisting grade 24% Cr, Al – (Energy Alloys Rotherham 01709-788000)Sicromal 81.4713 Heat ResistingHeat resisting grade 7% Cr, Al – Bohler UK 0121-552 2575 as Alloy 160 or Energy Alloys Rotherham 01709-788000Silver Fox–Samuel Fox, later British Steel (Corus) Engineering Steels trade namesSistema Men–Loose lay stainless steel floor tiles from Inova Furniture Contracts Ltd, LondonSnaptite–Quick fitting couplings for fluid transfer lines in stainless steel with teflon seals from Adflow International Tel 01734-713733Sno-Trik–High-pressure stainless steel pipe fittings from Techmation Ltd (UK agents for Sno-Trik Co.) Tel “01-958 3111”SS (41,400)Non-SSJapanese Structural GradesSt (37,52 etc)Non-SSGerman Structural Grades See BSEN 10025Staballoy–UNS S28200 – 17 Cr, 20 Mn 0.55 NStaybrite–Generic trade names for Firth Vickers grades, such as FSL,FDP, FMB etcStavax420Tool steel type 0.38 C 13 Cr ie martensitic 420 type originally Uddeholm, later VEW Special Steels 0121-552 5681Steelex304,316Stainless steel roofing systems from Lee Steel Strip, Sheffield (now AvestaPolarit Strip)SteelitNon-SSComplete Paint system for SS items from Stainless Steel Coatings IncStelliteNon-SSCobalt hardfacing alloys – Deloro Stellite, Swindon TEL 01793-822451StelvetiteNon-SSCorus Strip plastic coated carbon steel strip productsSupatube–Welded SS Tube – weld bead drawn for hygienic & heat exchanger applications – Stelco Hardy, TreorchySuperDux 64–Super plastic duplex stainless steel from Nippon Yakin Kigyo Co 25 Cr, 6.5 Ni, 3.2 MoTemet 25Nitronic 50Propeller shaft bar grade from Teignbridge Propellers Ltd, Newton Abbott TEL 01626-333377 FAX 01626-60783Thyroplast–Thyssen stainless steel generic trade name, Werksoff number used to identify specific gradeTriclad–Sandwich with mild steel core & stainless surfaces from Allegheny, USA – see TriplyTrinsul–Insulated profiled stainless steel sheet from Precision Metal Forming, Cheltenham 01242-527511Triply–Sandwich with mild steel core & stainless surfaces from Universal Cyclops, USA – see TricladTufftriding–Salt bath nitrocarburising. Improves wear, seizure and galling resistance of 304 and 316 austenitic stainless steels, available from Keighley Laboratories Ltd.Uginox–ArcelorMittal Stainless Europe trade names covering range of steel gradesUltiMet–180 & 240 grit satin finishes from WS Metalstock LtdUranus–Creusot Loire trade names examples Uranus B6, 50, 45N, 47 etc – stockist is James Fairley AthenaV2A304Krupp (Germany) trade names covering 304 typesV4A316Krupp (Germany) trade names covering 316 typesWaspalloyNon-SSNickel-chromium alloysWaukeshaNon-SSNickel alloy for anti-galling applications from Dewramet Ltd, GlasgowZalutiteNon-SSAL, Zn Si coating on mild steel for car exhausts – Corus Strip ProductsZeron 1001.4501 DuplexSuper duplex stainless steel (Rolled Alloys)ZintecNon-SSZinc coated mild steel from Corus Strip Products

In the past, stainless steel used in many applications for high-grade, aesthetic considerations, to improve the standard of living demand. Stainless steel isn’t the people indispensable necessities of life ‘s. From the” energy-saving emission reduction”, to avoid the” greenhouse effect” in a new perspective, stainless steel shall be treated as the sustainable development of the necessities of life. In the process of production, stainless steel compare with ordinary carbon steel, has obvious benefits of energy conservation and emission reduction. Generally speaking, in the iron and steel production. Adopted from the electric furnace of the steel began to hot rolled stainless steel tube sheet. Production of stainless steel more than 55% energy saving than carbon steel. From the use of electric furnace steel, the hot rolledstainless steel tube sheet products .So far, stainless steel short process production technology of steel CO2 emissions to 507 kilograms; including the use of ironmaking system begins. Considering the short technological process of stainless steel production accounts for about 70% of the total output of stainless steel, the long process of carbon steel output accounted for about the total yield of 90% carbon steel. The overall average social comprehensive energy consumption of per ton steel, stainless steel is 383.5 kilograms, average social comprehensive energy consumption of carbon steel 590.5 kilograms. Social average stainless steel CO2 emissions to 912.9 kilograms, average social carbon steel CO2 emissions to 1724.7 kg. By this is visible, the production of 1 tons of hot rolled stainless steel tube sheet, than the production of 1 tons of ordinary hot rolled carbon steel tube sheet, can save more than 35% of energy consumption, can reduce the more than 47% of the CO2 emissions. Two in the application areas, the more obvious advantages of stainless steel. Because the stainless steel is a boutique, with no rust, corrosion resistance, appearance and high strength, one hundred percent recyclable and other characteristics, in the practical application, can further show the energy saving and emission reduction of social benefits. For example, using the hot rolled stainless steel tube sheet to produce a new type of stainless steel and ordinary carbon steel manufacturing trucks using domestic raw general-purpose gondola car compared with stainless steel truck wagon, can reduce the initial steel consumption 15%, the entire life cycle can reduce the steel consumption of about 55%. According to the life cycle of tons of coal consumption calculation of steel, can save more than 75%. So, every increase production 1 tons of stainless steel, it can replace more than 4 tons of carbon steel. Only stainless steel manufacturing process and Application Process saving steel the factors to consider than ordinary carbon steel, stainless steel 84.25% energy saving, reducing emissions of CO2 87.16%. Further consideration of stainless steel in nuclear applications make nuclear energy promotion becomes possible, and thermal power compared to further reduce CO emissions. In water supply and drainage system, by reducing water pollution and waste thereby further reducing CO2 emission. The applications in water treatment, in seawater desalination aspects of the application, in the clean food applications, in order to raise energy efficiency, the application in one hundred percent recyclable applications etc. Stainless steel,” energy-saving emission reduction”, to avoid the” greenhouse effect ” effect is bigger.

The conclusive methods for determining the grade of a sample of metal, believed to be a stainless steel is by a chemicalanalysis method. Normally spectrographic methods are used. These quantitative methods, provided they are properly calibrated using samples of known composition, give accurate figures for the important elements (chromium, nickel, molybdenum) in the sample. In most cases this enables a stainless steel grade to be assigned to the sample. Additional analysis may still be needed to differentiate between low carbon (0.03% maximum) and ‘normal’ carbon (0.06/0.07%) variants eg 304L (1.4307) and 304(1.4301) or for detecting nitrogen additions in the steel. Without specialist analysis equipment differentiating between stainless steel grades or checking if a sample is a stainless steel rather than a low alloy or carbon steel type, is difficult. This article attempts to provide some guidance on non-laboratory detection methods, firstly looking at physical, mechanical and corrosion resisting properties of metals. Often a combination of tests will be needed to reach any sort of meaningful conclusion on the steel type. Finally, a summary step-by-step procedure is suggested. Colour Metals such as copper and gold and their alloys (eg brasses & bronzes) are easily distinguishable from other metals. To the untrained eye however trying to differentiate between most other metals is not practical. It may be possible to differentiate between polished pieces of austenitic (eg 1.4301, 304) and ferritic (eg 1.4016, 430) on colour. The austenitic has a yellow tinge, the ferritic a blue, more ‘metallic’ tinge. A magnet test is however more conclusive. Density (weight) Most ferrous alloys (ie steel and cast irons) have similar densities and even laboratory methods would not be able to distinguish between carbon steel and stainless steel. Away from the laboratory only significant differences in density would give any clues in sorting metals. Heavier (more dense) metals like lead or tungsten or lighter metals like aluminium or magnesium may be easy to recognise from their relative weights. Metals with densities closer to those of iron, eg nickel, chromium and zinc are very unlikely to be distinguishable from their relative weights. Sound (ring) Iron alloys, provided they are free of gross internal defects, usually have a characteristic metallic ring ie like a bell, when struck or dropped onto a hard surface. Some metals, notably, lead and aluminium have a ‘duller’ sound, if tested in the same way. Magnetism Iron, nickel and cobalt are ferromagnetic at normal (ambient) temperatures. This means that they strongly attracted to a permanent magnet. Most iron alloys are also ferromagnetic, including grades in the ferritic, martensitic and duplex stainless steel families. Softened austenitic stainless steel however are not ferromagnetic and so are not attracted to a permanent magnet. This can provide a basis for sorting between softened austenitics and other stainless and non-stainless steels. If austenitic stainless steel are cold worked, they can behave as “partially” ferromagnetic, showing some attraction to a permanent magnet. With complex shape formed components the partial magnetic attraction is usually non-uniform and is more marked at formed corners or near drilled holes or machined faces. This uneven distribution is often useful in confirming the steel as an austenitic type. This variation in attraction to a magnetic does not occur with other stainless steel, carbon steel or metals like aluminium. Grinding sparks (frictional sparking) Grinding sparks have been used traditionally in metal manufacturing industries as a method of sorting steel types. The pattern and colour of sparks produced when a piece of metal is touched against a grinding wheel can indicate the steel type. This method requires a good deal of experience for it to be a reliable sorting method and is not usually suitable for on-site use. Mechanical methods Hardness The assessment of mechanical properties usually involves specific testing techniques. Relative hardness levels of materials can sometimes be used in sorting by checking the tendency of a surface to become scratched. There is unlikely to be a noticeable difference in the scratch resistance of different steel types, unless they have been heat treated to give high tensile and hardness levels. Although this could separate the softer ferritic, austenitic andduplex stainless steel from hardened martensitic stainless steels, it alone, would not distinguish between hardened martensitic stainless and non-stainless steel. The hardness of a piece of softened martensitic stainless steel would similar in a scratch test, to that of the other stainless steel type. Effect of heating on properties If there is a heat source capable of heating the steel to around 1000 degrees C (a light orange glow in subdued light conditions) then some complementary sorting tests can be done if there is a small piece of metal available for testing . Heating to this light orange colour and quick cooling, preferably in water, can produce different properties, depending on the steel type. (Aluminium melts at 660 deg C so heating in this way would easily distinguish a sample from steels or nickel alloys) An austenitic stainless steel that may have had some cold work before heating (some hardness and magnetic attraction) should show much less magnetic attraction after this heating and cooling cycle and be uniformly soft. Ferritic and duplex stainless steel will also be softened by this heating cycle, but no differences in magnetic attraction will be evident. In contrast, if the steel is harder following this heating and cooling cycle (more scratch resistant) then indicates that the sample is probably a martensitic type. This does not in itself confirm that the steel is a martensitic stainless, as carbon and low alloy steel will also respond in this way. No differences in magnetic attraction will be evident on a martensitic steel, in the same way as ferritic and duplex steels. Chemical (corrosion) Methods It is important that the surfaces of metals being chemically tested are scale-free, coating-free, free of grease and any iron contamination and clean. Otherwise the test solution cannot interact properly with the metal surface. Ideally the surface should be lightly abraded. ‘Wet and dry’ aluminium oxide based paper is suitable for this.  To make sure the surface is clean and grease free, simple washing in soapy water and rinsing in clean water, followed by drying with a clean paper tissue should be satisfactory. Alcohol based solvents can also be used for final degreasing. Water test A large drop of tap water left on a steel surface and left overnight will normally produce a rust stain on a carbon or low alloy steel, but not on a stainless steel. This will not however distinguish between different stainless steel families or grades. Copper sulphate solution test A simple 5 percent copper sulphate solution, applied in the same way as the water drop test, should confirm the differences between non-stainless steel and stainless steel. A metallic copper coloured deposit should form easily on non-stainless steels, but the solution should remain free of copper colour if the sample is a stainless steel. Nitric acid test Nitric acid is a more hazardous chemical to store and handle than copper sulphate and so is not a simple testing choice for on-site use. However a dilute solution of nitric acid will readily attack non-stainless steel, leaving most stainless steel unaffected. Some attack can indicate that the sample could be a martensitic type stainless, but this may not be conclusive. Concentrated nitric acid can be used to distinguish some nickel alloys from stainless steel, by the appearance of greenish-blue or pale green colours. Acidified copper sulphate and copper chloride tests ASTM A380 outlines a more refined test solution than the simple copper sulphate test. A 250 ml batch of test solution is made using distilled water and 10ml sulphuric acid sp gr 1.84 4g copper sulphate If a copper deposit forms slowly, but during a period of 6 minutes of swabbing the steel surface with the solution, then this can indicate that the steel is likely to be either a ferritic or martensitic stainless steel. If not then the sample is likely to be an austenitic type. (This may also be the case for most duplex steel as they have similar or better passivity than austenitic types). An alternative is a copper chloride solution acidified with hydrochloric acid. 13ml concentrated hydrochloric acid 10g copper chloride 50 ml distilled water If the steel surface becomes copper plated when a drop is left on for one minute, then the sample is likely to be either a ferritic or martensitic stainless steel type. If not then the sample is likely to be an austenitic or duplex type. The sulphur test This method can be used to differentiate between sulphurized machinablity enhanced grades such as 1.4305 (303) and non-sulphurized grades like 1.4301 (304). The test will not differentiate between stainless and non-stainless machinability enhanced grades. It is based on the ‘sulphur-print’ steel defect test, where a piece of slow speed photographic paper is soaked for a few minutes in dilute (approx 5%) sulphuric acid and then placed in contact with a clean steel surface. Sulphide inclusions in the steel react with the acid to form hydrogen sulphide gas, which can be seen on the paper as dark brown spot. If tests are done on samples of both steel the darker paper shows that sample to be a sulphurized grade. The papers can be developed and fixed with photographic solutions to confirm the ‘sulphur image’ but on-site, in-situ testing with the sulphuric acid soaked paper alone should be reasonably conclusive. Other acid solution tests There are other phosphoric acid, sulphuric acid and hydrochloric acid based tests that with the appropriate facilities and operator skill level can be used to sort various grades of stainless steel. These methods however usually involve using concentrated acids, some at high temperature and so are not appropriate for on-site grade sorting. Proprietary chemical testing kits Perhaps the most common mix of steel grades that needs to be sorted is the non-molybdenum austenitic 1.4301 (304) types from the molybdenum-containing 1.4401 (316) types. These tests produce distinctive colour changes depending on the presence of molybdenum in the steel. More expensive but comprehensive chemical test kits intended to identify a range of stainless steel grades can be obtained from the USA. One such kit is the Alloy Detector 410L from Systems Scientific Laboratories Inc A simple step-by-step procedure for identifying a stainless steel Metals such as titanium or nickel alloys are relatively rare, except in particular industries such as aerospace or very demanding (chemically aggressive) processing plant. In more general engineering or building and construction applications low alloy (carbon) steel and stainless steel are more widely used. In this stepwise procedure we have assumed that the metal is assumed to be a steel, but of unknown type, with no grade or standard markings. Often a combination of tests is needed to narrow the choices to a type of grade. Stainless steel is abbreviated to stainless steel  Low alloy or carbon steel is abbreviated to carbon steelTestObservationConclusion1. Initial appearancePaint coating or oiled surfacesstainless steel is rarely painted. carbon steel sections often supplied primed, sometimes oiled to prevent corrosionBare metal surface with heavy grey scale or a rust coveringMill produced stainless steel usually supplied descaled Unless contaminated with carbon steel a stainless steel surface will not show rust stains If the surface has general light rusting it is likely to be a carbon steel2. Water drop or copper sulphate solution testsCopper colour quickly developsSteel very likely to be a carbon steel3. MagneticattractionA hand magnet is either not attracted or only weakly attracted in certain areasSoftened or moderately cold worked austenitic SS. Next use moly. spot test to show if it is a 304 or 316 type. A sulphur test will show if the steel is a free machining type, such as 303.4. Acidified copper sulphate OR copper chloride testCopper deposits slowly ie within a few minutesLikely to be either ferritic or martensitic stainless steel, otherwise assume it is austenitic or duplex5. Sulphur testPaper shows distinct brown marksSteel is a sulphurized grade (could be either carbon steel or stainless steel however)6. Moly. spot testDarkening of yellow spot testMolybenum containing SS (316,317,444,904L,6% Mo types, and mostduplex steel)

Sometimes stainless steel is considered to be an expensive material. However, experience has shown that using a corrosion resistant material in order to avoid future maintenance, downtime and replacement costs can produce economic benefits which far outweigh higher initial material costs. Life cycle costing (LCC) quantifies all the costs – initial and ongoing – associated with a project or installation. It uses the standard accountancy principle of discounted cash flow to reduce all those costs to present day values. This allows a realistic comparison to be made of the options available and the potential long term benefits of using stainless steel to be assessed against other material selection. The present day value represent the amount of money which would have to be invested today in order to meet all the future operating costs – including running costs, maintenance, replacement and production lost through downtime. These are added to the initial costs to give the total LCC: whereAC = initial materials acquisition costs IC = initial fabrication and installation costs N = desired service life of project in years i = discount rate (calculated from interest and inflation rates) OC = operating and maintenance costs in year n LP = lost production and downtime costs in year n RC = replacement costs in year n Once the cost data have been gathered, the calculation of the life cycle cost is straightforward. Software packages are available which prompt the user to collect the relevant data, carry out the calculation and allow different options to be compared easily. Example (Refer to “Applications for stainless steel in the water industry”) Galvanised carbon steel and Type 316 stainless steel were both candidate materials for ductwork to remove odorous fumes in a sewage inlet works. The galvanised steel required a multi-stage site-applied painted coating whereas the stainless steel could be installed in a single operation. The galvanised steel was expected to need maintenance every 5 years, and replacement after 15 years. The stainless steel equipment was designed for a 30 year service life, with maintenance every 10 years. A 10% interest rate and 5% inflation rate were assumed, giving a discount rate of 4.76%. Not only was the stainless steel option only slightly more expensive initially (because of the lower installation cost) but it showed a distinct life cycle cost advantage following the anticipated replacement of the galvanised steel plant after 15 years (refer to graph). The stainless steel option was chosen. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Unlike carbon steel, there have not been listings of open section sizes for stainless steel structural sections, until Sections Directory in May 2004. This gives the full range of ‘standard’ stainless steel sections that are readily available and the companies who supply them. The directory distinguishes between producers and distributors as well as showing the main stainless steel grades available from each supplier across the complete size range. Hollow Sections The hollow sections listed in the directory are available in stainless steel grades 1.4301 (304), 1.4307 (304L), 1.4401 (316), 1.4404 (316L) and1.4571 (316Ti). Normally hollow sections are welded from strip or plate. The design strength of ‘as-formed’ austenitic stainless steel tube is generally higher than for the same grade of annealed tubes. For most structural applications either annealed or ‘as-formed’ supply conditions can be expected to provide comparable corrosion resistance. Section Tables Available The directory can be downloaded from Structural Sections. Section tables available Manufacturing MethodSection TypeHot Rolled (Part 1.1)Channels.Equal Sided Angles.Unequal Sided Angles.Unequal T-ProfilesHot Extruded & Special Sections (Part 1.2)Z Profiles.I Beams.Channel (parallel).Channel (taper).Equal Sided Angles.Unequal Sided Angles.Equal T Profiles.Unequal T profilesCold Formed Sections (Part 2).RolledEqual Sided Angles.Unequal Sided Angles.Channel sFormedZ Profile.Special Sections (doors and windows)DrawnEqual Sided Angles.Unequal Sided Angles.T ProfilesWelded Sections (Part 3)I Profiles.H Profiles.Channels.Equal Sided Angles.Unequal Sided Angles.Equal Sided T Profiles.Unequal Sided T ProfilesCircular Hollow Sections (Part 4.1).Square Hollow Sections (Part 4.2).Rectangular Hollow Sections (Part 4.3). Approximate Range of Available Dimensions Circular Hollow Sections 1.0-30mm thick 6.0-914mm diameter Square Hollow Sections 1.0-25mm thick 10 x 10-800 x 800 width Rectangular Hollow Sections 1.0-25mm thick 20 x 10-900 x 600mm width. Approximate range of available dimensions: Circular hollow sections:thickness: 0.25 to 8.0 mm,diameter: 3 to 250 mmRectangular hollow sections:thickness: 1.0 to 8.0 mm,width: 20×10 to 300×150 mmSquare hollow sections:thickness: 1.0 to 8.0 mm,width: 10×10 to 300×300 mmOval hollow sections:thickness: 1.0 to 3.0 mm,diameter: 61×37 to 121×76 mm Open sections Open sections, including many masonry support section types, can be press formed from flat sheet or plate. These are available as standard products or to special design and include formed and welded sections, such as I sections made up of two channels welded, back to back. Thicker sections are manufactured from welded flat plate, but may be subject to final straightness limitations. Heavier sections sizes may be hot formed, either by extrusion or rolling. Open sections can usually be sourced in stainless steel grades 1.4301 (304) and 1.4401 (316). Some less common and more ‘specialised’ grades, including 1.4713 (a 6-8% chromium heat resisting ferritic steel) are also available. For information on how to select the most suitable grade for internal or external building applications, see articles Selection of stainless steels for building internal applications and Selection of stainless steels for building external applications Stainless Steel bars Stainless Steel Round bars, stainless steel square bars, stainless steel rectangular and hexagonal solid bars are generally widely available in stainless steel grades 304 (1.4301) and 316 (1.4401) and additionally in other more specialised stainless steel grades, including duplex 2205 (1.4462). Approximate range of available dimensions: Circular:diameter: 2 to 450 mmFlats:thickness: 3.0 to 25 mm, width: 12×150 mmSquare:width: 3 to 300 mmHexagonal:across flats: 5 to 100 mm Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Soil corrosivity is often classified by its resistivity. 0 – 1500 ohm.cm very corrosive 1500 – 2500 ohm.cm corrosive 2500 – 5000 ohm.cm mildly corrosive 5000 – 10000 ohm.cm slightly corrosive > 10000 ohm.cm non-corrosive Experience suggests that there is little likelihood of corrosion of 304 and 316 stainless steel with soil resistivities of 2000 ohm.cm and above if the pH is greater than 4.5 and there is clean drainage and backfill. As with other environments, chloride levels in relation to pitting and crevice corrosion may also influence the performance of stainless steel in soils and where higher chloride levels are anticipated inland or for non-tidal coastal areas or just where a greater degree of confidence is required, type 316 would be preferred. For coastal areas and other situations where a greater degree of resistance may be required, 2205 duplex stainless steel or super duplex stainless steel can be considered. If thought necessary, external protection such as appropriate protective casings or tapes (taking care to ensure an effective overlap to avoid crevice corrosion) may be used. Stainless steel can also be cathodically protected. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)