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Sulphuric acid is oxidising when concentrated but is reducing at low and ‘intermediate’ concentrations.  The response of most stainless steel types is that in general they are resistant at either low or high concentrations, but are attacked at intermediate concentrations. Commercially concentrated acid is around 96 wt % (sg = 1.84). The improvement in corrosion resistance moving from stainless steel 304 /1.4301 to 316 / 1.4401 is due to the addition of molybdenum. Further additions of moybdenum and copper in the 1.4539 904L grade extend the corrosion resistance in these reducing acid conditions. The molybdenum in types 316 stainless steel and grade 1.4539 also helps improve resistance to chloride attack, when present as impurities in the acid. Corrosion resistance of stainless steel In the following iso-corrosion diagrams, each line shows the 0.1mm/year corrosion rate. This is usually regarded as the boundary between acceptable and unacceptable performance. (The broken line represents the boiling point) 18-10 (1.4301, 304) – limited use in dilute acids 5% maximum at room temperature. Increasing temperature quickly makes the steel useless. Acceptable above about 90% at room temperature. 17-12-2.5 (1.4401, 316) – This grade offers a significant advantage over stainless steel 304 at low concentrations, up to 22% at room temperature only gradually falling with temperature up to 40 deg C and then more quickly to about 5% at 60 deg C. Duplex Steels – 2304 (1.4362) is similar to 1.4401 (316) at room temperature but only gradually falls off with temperature, still allowing about 8% at 80 deg C. 1.4462 (2205) is acceptable to as high 40% at room temperature falling to about 12% at 80 deg C. Super duplex 2507 (1.4410) offers only limited improvement to 45% at room temperature. 904L (1.4539) – This steel was specifically developed for sulphuric acid use and van be used across the whole concentration range up to 35 deg C. Concentrated Acids Care needed with very concentrated (98-100%) acid at higher temperatures as slight changes to the conditions that help resistance ie the high concentration falling by dilution. Increases in velocity or reductions in oxidising conditions, can affect the corrosion resistance anticipated. Impurities he presence of chlorides in sulphuric acids can be an additional hazard. Hydrochloric acid (HCl) can be liberated from sodium chloride by sulphuric acid, depending on the temperature, making the mixture more aggressive. Influence of alloy additions to stainless steels on corrosion resistance The alloying addition of copper is most beneficial to extending the resistance of stainless steel in intermediate concentrations of sulphuric acid. Duplex stainless steel containing copper, such as grade 1.4501 can also be considered for sulphuric acid service. Silicon stainless steels such as grade 1.4361 should be considered for hot, very concentrated acid applications. Risk of corrosion from ‘self-dilution’ of sulphuric acid Sulphuric acid has a strong affinity for water, extracting water from its surroundings and hence diluting itself. The result can be that acid thought to be ‘safely’ concentrated for contact with 304 type stainless steels, say above 90%, can actually attack the steel if water has been picked up. This can occur in open topped containers where moisture from the air dilutes the acid and results in corrosion around the ‘liquid-line’. The resistance of stainless steels also depends on temperature. As heat is generated when the acid is diluted warmer conditions can be present locally, which can add to the risk of attack in the diluter acid. The sensitivity to temperature can also be a hazard at ‘hot wall’ effects in heating circuits or with heat exchanger elements. Affect of aeration and oxidising conditions Aeration or the presence of oxidising ‘agents’ in sulphuric acid contributes to the corrosion resistance of stainless steels. Stainless Steels have lower resistance to de-aerated sulphuric acid. Reducible ions such as Fe3+, Cu2+, Sn4+ are effectively oxidising agents and can reduce corrosion if present in the acid. Similarly oxidizing agents like chromic or nitric acid reduce corrosion rates, if present in the sulphuric acid. Dissolved sulphur trioxide (SO3) present in sulphuric acid over 97% concentrations, can also reduce corrosion rates. Chromium content is important to the resistance of the steel and so 310 can be considered when oxidising agents are present, making use of the extra chromium (25%). The moderately oxidising conditions in dilute sulphuric acid can result in localised intercystalline attack (ICC), especially if the chromium is locally reduced, as is the case when ‘standard’ carbon 304 or stainless steel 316 types are ‘sensitised’. This why the stainless steel 304L types, or the stabilised types such as 321, are used where weld heat affected zone (HAZ) areas cannot be re-solution heat-treated. It is important to be careful with corrosion data, as small variations in impurities or conditions can affect service corrosion rates and hence potential durability of stainless steels in sulphuric acid. Affect of velocity of flow Stainless steels are more suitable than carbon steels for handling high flow rates of concentrated acid (90-98%). The passive layer on stainless steels is more stable than the ferrous sulphate layer formed on carbon steel in turbulent flow conditions. Flow rates can become a problem as the active/passive region of concentration and temperature is approached. Use of stainless steels in contact with battery acid Battery Acid is sulphuric acid with a weight percentage concentration of over 35 i.e. at a ‘fully charged’ specific gravity of 1.28. The selection of stainless steel 304 or stainless steel 316 types for applications involving prolonged contact, such as storage tanks, is not advisable. A concentration limit of 22% maximum at 20 degC can be taken for stainless steel 316, from the iso-corrosion diagram. For storage applications or where either long plant service life or safety considerations are important, ‘battery’ concentration sulphuric acid, austenitic grades such as 1.4539 or 1.4563 should be considered. The stainless steel 316 types may be suitable for applications involving short term or intermittent contact such as battery disposal plant or spillage trays. As this application is a ‘borderline’ case, care should be taken to ensure that the acid concentration is not allowed to increase through water evaporation (drying out) and that temperatures are maintained as low as possible. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Nitric acid is strongly oxidising and promotes the resistance of stainless steel to corrosion. Generally stainless steel are resistant to corrosion in nitric acid. Nitric acid is used in the chemical passivation of stainless steel. Commercially concentrated acid is around 65 wt % (sg = 1.40). Higher concentrations obtained by removing water, which can involve the use of sulphuric acid, which has a high affinity for water. Corrosion resistance of stainless steel Nitric acid is strongly oxidising and attacks most metals but due to its powerful oxidising nature, it promotes the resistance of stainless steel to corrosion. Generally stainless steel are resistant to corrosion in nitric acid over a wide range of concentration and temperature. The ‘helpful’ oxidising properties of nitric acid are used in the chemical passivation of stainless steel. The iso-corrosion diagram 0.1mm/year lines for the 304 and 316 types coincide (purple). (The broken line represents the boiling point) This shows that the 304 types can be used over a wide range of concentration and temperature, up to 95%, for storage applications. The 304 types are preferable to 316 types for nitric acid applications however. This is an exception to the ‘general rule’ for stainless steels where the 316 types are normally found to be more corrosion resistant than 304 types. Over 95% concentration, aluminium alloys should be considered OR 4% silicon stainless steels. Any additional chlorides or fluorides in nitric acid may increase corrosion rates by pitting. Risk of localised corrosion in concentrated acids Localised attack at grain boundaries (IC) can occur in hot concentrated nitric acid. This can occur in the heat-affected-zone (HAZ) of welds. Prolonged heating in a range of around 600-800 degC, followed by exposure to concentrated nitric acid, can also result in localised attack, due to the precipitation of the brittle “intermetallic” (iron-chromium) compounds (sigma phase). Avoiding localised attack in concentrated acid To avoid the risk of localised corrosion, especially where post weld heat treatment is impractical, the low carbon, 304L types should be considered. Solution heat treatment (1050 -1100 degC followed by fast cooling) on the standard carbon 304 types can be considered as an alternative. These treatments should also re-dissolve any sigma formed. Compostions of 304L types have been used with silicon, phosphorous & sulphur limited to very low residual levels to improve the resistance in hot concentrated nitric acid. Uses for nitric acid with stainless steels Nitric acid is widely used in the chemical ‘passivation’ of stainless steels. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Acetic acid is a weak reducing acid. It is used in plastics manufacture and is a constituent of foods as vinegar. Ferritic stainless steels such as 430 type can be considered but normally the 304 types are used for most applications, including handling and storage.  Acetic anhydride (CH3CO)2O can be aggressive to either 304 or 316 types in the absence of any water and in the presence of chlorides. Peracetic acid CH3C(O)OOH (peroxyacetic acid) should be safe with stainless steel.Vinyl acetate C4H6O2 may be considered with the 316 grades for ambient temperature storage applications. Commercially concentrated acid is around 99wt. % (glacial acetic acid). Corrosion resistance of stainless steel Ferritic stainless steel such as the 430 / 1.4016 type can be considered for most acid concentrations at ambient temperatures, but normally austenitic are preferred as pitting corrosion has been reported in industrial plant and equipment. The 304 types are normally considered as suitable grades for most applications, including handling and storage. The iso-corrosion diagram 0.1mm/year lines for the 316 / 1.4401 (red) types show that they can be expected to provide better resistance over about 5% concentrations, at temperature over 90 degC, than the 304 (blue) types. (The boiling point corresponds to the red line for 316 types) At concentrations above about 80%, the 316 types are usually considered a better choice than the 304 types, especially where temperatures exceed 70 degC, where there is a risk of localised attack to the 304 types. For processing equipment, 316L is considered a better choice than the 30 4/304L or 316 types. Intergranular attack can be an issue in weld heat affected zones, if acid contact temperatures exceed around 60 degC. As with other similar acid contact applications, the low carbon, 304L should be considered rather than the standard 304 types. In common with most acid handling applications, chloride contamination can cause pitting corrosion and so in these cases more pitting resistant grades may need to be considered. Contamination of acetic acid with the more aggressive formic acid (HCOOH) can result in an unexpected reduction in corrosion resista nce of the 316 types. The 304 types may be particularly vulnerable under these conditions. Acetic anhydride (CH3CO)2O Acetic anhydride (CH3CO)2O can be aggressive to either 304 or 316 types in the absence of any water and in the presence of chlorides. The risk of pitting corrosion can be reduced if grades such as the austenitic 1.4539 or the 6% molybdenum grades are considered in these extreme conditions. Peracetic acid CH3C(O)OOH Peracetic acid CH3C(O)OOH which is also known as peroxyacetic acid, is used as a disinfectant (sanitiser) in food, medical and water treatment related industries. It should be safe for uses that involve contact with stainless steel items. Vinyl acetate C4H6O2 Vinyl acetate C4H6O2 is an intermediate product used in the manufacture of chemicals such as adhesives and paints. The only information available suggests that the 316 types should be suitable for ambient temperature storage applications. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Sodium hypochlorite only exists in solutions. The solution can be unstable, giving off chlorine gas. Sodium hypochlorite is not stable as a solid chemical. The hypochlorites, although alkaline, are oxidising. Commercially concentrated Sodium hypochlorite is around 15-wt %. Household bleach solutions are around 5.25% sodium hypochlorite. The hypochlorite ion (OCl-) is aggressive to stainless steel, acting in a similar way to wet chlorine gas, and like the chloride ion (Cl-), is a dangerous pitting corrosion hazard. Corrosion resistance of stainless steel Pitting or crevice corrosion can occur on most stainless steel grades in a 5% solution at ambient temperature. There is an additional risk of stress corrosion cracking (SCC) at higher temperatures. Stainless steel should not be considered suitable for storage or transport tank applications with concentrated (15%) hypochlorite solutions or bleaches (5%). Contact with household bleach Pitting corrosion has been reported from household bleach spills on stainless steel (304 type) sinks in domestic environments. If this occurs immediate dilution by rinsing should avoid pitting, but if left overnight, pitting can result. Disinfecting or sanitising 304 stainless steel or 316 stainless steel items with dilute hypochlorite solutions can be done with care, but it is important that the temperature and contact time is kept to a minimum and that the solution is thoroughly rinsed away afterwards. Safe residual water chlorine levels for sterilization As a guide, 15-20 ppm (mg/lt) residual chlorine solutions at ambient temperatures should be safe with 316 stainless steel types for a 24-hour maximum contact time, if followed by rinsing. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

NACE MR 0175/ISO 15156 is a Materials Standard issued by the National Association of Corrosion Engineers. It is originally a US standard intended to assess the suitability of materials for oilfield equipment where sulphide (sulfide) stress corrosion cracking may be a risk in hydrogen sulphide (sour) environments. However, the world standards body ISO has issued it under its own “brand”. The latest edition includes technical corrigenda from 2005. The standard specifies the types of corrosion resistant materials including stainless steel that can be used in specific oilfield environments and places limits on the hardness of the material. This applies both to parent and weld material. The maximum hardness is usually defined in terms of the Rockwell ‘C’ scale. No conversion to other hardness scale is given in MR 0175 which presents one problem as softened stainless steel hardness are measured using either the Rockwell ‘B’, Vickers or Brinell scales. Approximate conversions are available. Summary of MR 0175 Requirements A wide range of materials is covered by the standard including most types (families) of stainless steel. The table below shows some of these grades. However, this summary is intended to only give a general idea of this complex standard and is not a substitute for the original document.Stainless Steel TypeGrades Included                                 Comments                                                                                         Ferritic Stainless Steel405,430, 409, 434, 436, 442, 444, 445, 446, 447, 448Hardness up  to 22 HRCMartensitic Stainless Steel410, 420Hardness up to 22 HRCMartensitic Stainless SteelF6NMHardness up to 23 HRCMartensitic Stainless SteelS41425Hardness up to 28 HRCAustenitic Stainless Steel201, 202, 302, 304, 304L, 305, 309, 310, 316, 316L, 317, 321, 347, S31254(254SMO), N08904(904L), N08926(1925hMo)Solution annealed, no cold work to enhance properties, hardness up to 22 HRCAustenitic Stainless SteelS20910Hardness up to 35 HRCDuplex Stainless Steel S31803 (1.4462), S32520 (UR 52N+),S32750 (2507), S32760 (Zeron 100), S32550(Ferralium 255)PREN >30 solution annealed condition, ferrite content 35% to 65%, or 30 to 70% in welds. Note that the general restriction of 28 HRC in previous editions is not found in this latest edition of the standard. There is a specific restriction on HIP’d S31803 to 25HRC. For some applications cold worked material is allowed up to 36HRC Precipitation Hardening17-4 PH33 HRC Age hardening at 620 deg CPrecipitation Hardening  S4500031 HRC Age hardening at 620 deg CPrecipitation HardeningS6628635 HRC Free machining grades such as the 303 and 416 types are excluded from of NACE MR 0175/ISO 15156 Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Duplex 2304 is a 23‰ Cr, 4‰ Nickel, Mo free duplex stainless steel (23.04). We hold stock of duplex alloys in plate, flanges, pipes, and bars from our warehouse in the CN. We often meet specialist alloy profiling requirements and are a global supplier. The alloy lean duplex 2304 has similar corrosion resistance properties to 316L. Furthermore, its mechanical properties i.e. yield strength, are twice those of 304/316 austenitic grades. This allows the designer to save weight, particularly for properly designed pressure vessel applications. The alloy is particularly suitable for applications covering the -50°C/+300°C (-58°F/572°F) temperature range. Lower temperatures may also be considered, but need some restrictions, particularly for welded structures. With its duplex microstructure, low nickel and high chromium contents, the alloy has improved stress corrosion resistance properties compared to 304 and 316 austenitic grades. Tensile Strength Properties (Minimum Values)°CRp 0.2 MPaRp 1.0 MPaRm MPa20400440600100330365570200280310530300230260490 °FYS 0.2% KSIYS 1.0% KSI  UTS KSIElongation %6858648725212485383253924145772057233387120 Values obtained for hot rolled plates (th ≤ 2”). Duplex 2304 (S32304 1.4362) must not be used for a long time at temperatures higher than 300°C (572°F), where precipitation hardening phenomenon occurs. Toughness Values (KCV Minimum Values)Temp. -50°C+20°C -60°F+70°FSingle 75 J/cm90 J/cm 54 ft.lbs65 ft. lbsAverage (5) 90 J/cm150 J/cm 65 ft.lbs87 ft.lbs Hardness (Typical Values)Average (5)HV10 180-230HB : 180-230HRC _ 20 Applications: Duplex 2304 is generally used in the same applications in which Alloys 304 and 316L are used. Some examples of these applications include: Chloride containing environments Welded pipe systems within the Pulp and Paper, Chemical and Petrochemical, and Water Treatment industries Transportations Heat exchanger tubes Duplex 2304 Pipe Architecture, building, construction Pressure vessels Caustic solutions, organic acids Food industry Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

If the material type or stainless steel grade carbon content percentage you know? hardness test is a simple way to verify that a material has been properly heat treated. Hardness testers such as Rockwell, Brinell, and Vickers can be useful to check metals for actual hardness. Hardness tests are generally considered nondestructive, hardness testing does leave a small pit in the surface; therefore, hardness tests should not be used on sealing surfaces, fatigue critical parts, load bearing areas,etc., components which will be used in critical applications . These hardness tests provide a convenient means for determining, within reasonable limits, the tensile strength of steel. It has several limitations in that it is not suitable for very soft or very hard stainless steel pipe. Hardness testing of aluminum alloys should be limited to distinguishing between annealed and heat-treated material of the same aluminum alloy. In hardness testing, the thickness and the edge distance of the specimen being tested are two factors that must be considered to avoid distortion of the metal. Several readings should be taken and the results averaged. In general, the higher the tensile strength, the greater its hardness. The Shore (Scleroscope) Hardness Test The Scleroscope test consists of dropping a diamond tipped hammer, which falls inside a glass tube under the force of its ownweight from a fixed height, onto the test specimen. The height of the rebound travel of the hammer is measured on a graduated scale.The harder the material, the higher the rebound. The scale of the rebound is arbitrarily chosen and consists on Shore units, pided into 100 parts, which represent the average rebound from pure hardened high-carbon steel. The scale is continued higher than 100 to to allow for metals having greater hardness.  The shore scleroscope test does not normally mark the material under test. The Shore Scleroscope measures hardness in relation to the elasticity of the material.    Advantages of this method are portability and non-marking of the test surface.  Knoop The Knoop indenter has a polished rhombohedral shape with an included longitudinal angle of 172° 30’ and an included transverse angle of 130° 0’. The narrowness of the indenter makes it ideal for testing specimens with steep hardness gradients and coatings. Knoop is a better choice for hardness testing of hard brittle materials.  Jominy Hardenability The Jominy test involves heating a test specimen of stainless steel 25mm diameter and 100mm long to an austenitising temperature and quenching from one end with a controlled and standardized jet of water. After quenching, the hardness is measured at intervals taken form the quenched end. The hardness gradient along the test surface provides an indication of the material’s hardenability. Moh’s Hardness Scale The Moh’s hardness scale consists of 10 minerals arranged in order from 1 to 10.    Diamond is rated as the hardest and is indexed as 10; talc as the softest with index number 1. Each mineral in the scale will scratch all those below it as follows: Diamond 10 Corundum 9 Topaz 8 Quartz 7 Orthoclase (Feldspar) 6 Aptite 5 Fluorite 4 Calcite 3 Gypsum 2 Talc 1 Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In this test a standard constant load, usually 500 to 3,000 kg, is applied to a smooth flat metal surface by a hardened steel ball type indenter, 10 mm in diameter. The 500-kg load is usually used for testing nonferrous metals such as copper and aluminum alloys, whereas the 3,000-kg load is most often used for testing harder metals such as stainless steel tube and cast irons. The numerical value of Brinell Hardness (HB), is equal to the load, pided by the surface area of the resulting spherical impression. ​ The Brinell hardness test consists of indenting the test material with a 10 mm diameter hardened steel or carbide ball subjected to a load of 3000 kgf (29 430 N). For softer materials the load can be reduced to 1500 kgf (14 715 N) or 500 kgf (4 905 N ) to avoid excessive indentation. The full load is normally applied for 10 to 15 seconds for harder ferrous metals and 30 seconds for other metal softer metal. The diameter of the indentation left in the test material is measured with a microscope. The Brinell hardness number is calculated by piding the load applied by the surface area of the indentation. Where P is the load, in kg; D is the diameter of the ball, in mm; and d is the diameter of the indentation, in mm. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The most common seamless stainless steel tubing is the 300 series of alloys, which are available in varieties of high-performance, corrosion-resistant types and sizes. These stainless steel alloys most commonly include chromium, nickel, molybdenum and titanium, and are ideal for seamless coil tubing because they are easy to maintain and can withstand high pressures and temperatures. Series & Characteristics Type 300L Series The difference between a 300 and 300L series stainless steel is that an ‛L’ series has 0.03% maximum carbon content.  This lower carbon level is preferred for welding conditions. Low carbon levels increase the resistance to intergranular corrosion (IGC) whereas standard 300 series carbon levels are limited to of 0.08% maximum.  However, lower carbon levels (‛L’ series) in stainless steel tend to render the material softer than higher carbon levels, where the hardness and strength of the material may be an important factor in the applications.  As for cost, in most cases 300 series stainless steel and 300L are equally priced.  Yet prices vary widely when introducing ‘exotic’ materials, as we will discuss later. Type 304/304L Stainless Steel Tubing This non-magnetic alloy is the most widely used of all stainless steels and is also among the least expensive. Both 304 and 304L are austenitic stainless steels with approximately 18% chromium and 8% nickel.  Alloy 304 has excellent weld ability and forming characteristics and is used for heat exchangers, chemical processing, and milder chemicals. Type 304 stainless steel is resistant to moderately aggressive organic acids, such as acetic acid and reducing acids.  In addition, post-welding heat treatment and rapid quenching improves corrosion resistance in this alloy. Applications Include: ⇒Cryogenic ⇒Chemical processing ⇒Food processing ⇒Dairy ⇒Pharmaceutical ⇒Mining Type 316/316L Stainless Steel Tubing This is an austenitic chromium-nickel stainless steel containing molybdenum and is also ideal for seamless tubing.  The addition of molybdenum ensures more resistance to pitting and crevice corrosion in chloride-containing environments.  Properties are similar to those of alloy 304, except 316 tubing also provides greater creep, stress-to-rupture, and tensile strength properties at higher temperatures. 316L is a low-carbon modification of standard 316 tubing.  The control of the carbon to a maximum of 0.035% minimizes the problem of carbide precipitation during welding and permits the use of the steel in the as-welded condition in a wide variety of corrosive seamless coil tubing applications. Applications Include: ⇒Architectural ⇒Marine ⇒Chemical processing ⇒Food processing ⇒Pulp/paper/textile ⇒Mining ⇒Pharmaceutical ⇒Oil & Gas Type 316/316L (2.5% Min. Moly) Stainless Steel Tubing Alloy 316/316L 2.5% minimum Moly is enhanced with an addition of 2.5% (min.) to 3.0% (max.) molybdenum, which provides superior corrosion resistance for seamless tubing compared to alloy 304 or even standard 316 tubing with lesser controlled Mo content.  It has improved resistance to pitting and crevice corrosion as well as sulfates, phosphates and other salts, such as sea water.  It helps reduce acids and solution of chlorides, bromides and iodides.  In environments that are sufficiently corrosive to cause intergranular corrosion of welds and areas affected by heat, 316L is preferable because of its low carbon content. It is important to note that this alloy is susceptible to intergranular corrosion (IGC) if it is exposed to temperatures above 800 °F (427 °).  In addition the yield and tensile strengths reduce as service temperatures increase. Applications Include: ⇒Fluid transfer with compatible pumps & valves ⇒Paper/pulp machinery ⇒Chemical processing equipment ⇒Oil & Gas Type 317L Stainless Steel Tubing This is a molybdenum-bearing low carbon grade stainless steel that exhibits greatly increased resistance to chemical attack and IGC in seamless stainless steel tubing compared to 304L and 316L. It offers higher creep, stress-to-rupture, and tensile strength for seamless coil tubing at higher temperatures compared to more common stainless steels.  In addition, because of the higher molybdenum content of 3.0% to 4.0%, alloy 317L has superior resistance to many organic and inorganic chemicals. Applications Include: ⇒Paper/pulp machinery ⇒Chemical processing equipment ⇒Petrochemical processing equipment ⇒Condensers in fossil ⇒Nuclear fueled power generation stations ⇒Textile equipment Type 321 Stainless Steel Tubing For those applications that require material to perform at higher service temperatures, titanium-stabilized 321 stainless steel is the best, yet more expensive choice.  Alloy 321 is similar to 304 in its chemical makeup, yet contains the addition of titanium of at least five times the carbon content.  This addition reduces or eliminates chromium carbide precipitation, which results from welding or exposure to high temperatures.  Maximum stabilization is accomplished by annealing between 1,750° and 1,850°F. This alloy has extensive use in seamless coil tubing where operating temperatures are greater than 800°F, and where corrosive conditions are not too severe due to its resistance to scaling and vibration fatigue.  As with all 300 series stainless steels the yield and tensile strengths reduce as service temperatures increase. Applications Include: ⇒Bellows ⇒Aircraft exhaust system components ⇒Heating element sheath tubing ⇒Furnace parts ⇒Heat exchangers ⇒Chemical processing equipment ⇒Thermal expansion joints Type 347 Stainless Steel Tubing Alloy 347 seamless tubing has excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range from 800 to 1,500°F.  It is stabilized by the addition of columbium and tantalum.  It is also ideal for high temperature seamless stainless steel tubing due to its good mechanical properties.  In addition, when compared to alloy 304 and 304L, 347 alloy provides increased stress rupture and creep properties. Applications Include: ⇒Engines ⇒Power generation ⇒Welded fabrications ⇒Aircraft systems ⇒Heat exchangers ⇒Steam service ⇒Chemical processing Price Differences Between Grades of Stainless Steel Mechanical properties, and corrosion and heat resistance all affect the chemical composition of the stainless steel.  As the composition of the steel changes, so do the properties.  This affects the performance of the material in differing applications and ultimately the price. More expensive, ‘exotic’ alloys demand a higher price.  For instance, 321 stainless steel that incorporates titanium is much more expensive than a 304 with the same physical dimensions.  A standard 316 chromium-nickel stainless steel containing 2.0% molybdenum is less expensive than its 2.5% minimum molybdenum counterpart. Selecting the proper stainless steel grades involves weighing four qualities in the following order of importance: Corrosion or Heat Resistance, the primary reason for specifying stainless.  The specifier needs to know the nature of the environment and the degree of corrosion or heat resistance required. Mechanical Properties, particularly strength at room, elevated or low temperature.  The combination of corrosion resistance and strength is the basis for selection. Fabrication Operations and how the product will be made (e.g., forging, machining, forming, welding, stamping, roll forming, four-slide operations). Total Cost, including material and production costs and considering the cumulative savings of a maintenance-free product with longevity. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

These stainless steel have the good heat-resisting performance, is suitable in the steam environment or 55 0℃ and the above temperature. 310S Stainless Steel | 309S Stainless Steel | 304H Stainless Steel | 321H Stainless Steel | 347H Stainless Steel Standard: ASTM A213,EN 10216-5  Anticorrosion environment: The temperature may reach 800 ℃  Application: Boiler 1.4828-X15CrNiSi20-12  Standard :SEW 470,DIN EN 10095  Equal to :Avesta 4828,Uginox R20-12,Cronifer 2012  Anticorrosion environment: The temperature may reach 1000 ℃ , the oxygen content low azotic gas.  Apply to: Makes the furnace, the petrochemical industry 1.4841-X15CrNiSi25-21  Standard :SEW 470,DIN EN 10095  Equal to :Cronifer 2520  Anticorrosion environment: The temperature may reach 1100 ℃ , the oxidation and the reducing gas (low sulphur content)  Apply to: Makes the furnace, the petrochemical industry 1.4876-X10NiCrAITi32-21  Standard:SEW 470,VdTUV-Wbl.412,DIN EN 10095  Equal to:Nicrofer 3220/3220H,Incoloy 800  Anticorrosion environment: The temperature may reach 1100 ℃ , the long time barometric pressure or the vapor tension  Apply to: The heat change installment, the steam response ins tallment, make the furnace, the petrochemical industry Table 1 Short Term Tensile Strength vs Temperature (in the annealed condition except for 410)Temperature304 Stainless Steel & TS ksi316 Stainless Steel YS ksi309 Stainless Steel & TS ksi309S Stainless Steel YS ksi310 Stainless Steel & TS ksi 310S Stainless Steel YS ksi410* Stainless Steel TS ksi YS ksi430 Stainless Steel TS ksi YS ksiRoom Temp.844290459045110857550400°F823680388434108856538600°F773275368231102826236800°F742871347828928055351000°F702664307026747038281200°F582353275925444022161400°F342035204124——1081600°F241825202622——54 * heat treated by oil quenching from 1800° F and tempering at 1200° F Table 2 Generally Accepted Service TemperaturesMaterialIntermittent  Service TemperatureContinuous  Service TemperatureAustenitic Stainless Steel 304 Stainless Steel 1600°F (870°C)1700°F (925°C)316 Stainless Steel1600°F (870°C)1700°F (925°C)309 Stainless Steel1800°F (980°C)2000°F (1095°C)310 Stainless Steel1900°F (1035°C)2100°F (1150°C)Martensitic Stainless Steel 410 Stainless Steel1500°F (815°C)1300°F (705°C)420 Stainless Steel1350°F (735°C)1150°F (620°C)Ferritic Stainless Steel 430 Stainless Steel1600°F (870°C)1500°F (815°C) Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel have good strength and good resistance to corrosion and oxidation at elevated temperatures. Stainless steel are used at temperatures up to 1700° F for stainless steel 304 and stainless steel 316 and up to 2000 F for the high temperature stainless steel grade 309(S) and up to 2100° F for 310(S). Stainless steel is used extensively in heat exchanger, super-heaters, boiler, feed water heaters, valves and main steam lines as well as aircraft and aerospace applications. Figure 1 gives a broad concept of the hot strength advantages of stainless steel in comparison to low carbon unalloyed steel. Table 1 shows the short term tensile strength and yield strength vs temperature. Table 2 shows the generally accepted temperatures for both intermittent and continuous service. With time and temperature, changes in metallurgical structure can be expected with any metal. In stainless steel, the changes can be softening, carbide precipitation, or embrittlement. Softening or loss of strength occurs in the 300 series (304, 316, etc.) stainless steel at about 1000° F and at about 900° F for the hardenable 400 (410<, 420, 440) series and 800° F for the non-hardenable 400 (409, 430) series (refer to Table 1). Carbide precipitation can occur in the 300 series in the temperature range 800 – 1600° F. It can be deterred by choosing a grade designed to prevent carbide precipitation i.e., 347 (Cb added) or 321 (Titanium added). If carbide precipitation does occur, it can be removed by heating above 1900° and cooling quickly. Hardenable 400 series with greater than 12% chromium as well as the non-hardenable 400 series and the duplex stainless steel are subject to embrittlement when exposed to temperature of 700 – 950° F over an extended period of time. This is sometimes call 885F embrittlement because this is the temperature at which the embrittlement is the most rapid. 885F embrittlement results in low ductility and increased hardness and tensile strength at room temperature, but retains its desirable mechanical properties at operating temperatures. Table 1 Short Term Tensile Strength vs Temperature (in the annealed condition except for 410)Temperature304 Stainless Steel & TSksi316 Stainless Steel YSksi309 Stainless Steel & TSksi309S Stainless Steel YSksi310 Stainless Steel & TSksi 310S Stainless Steel YSksi410* Stainless Steel TSksi YS ksi430 Stainless Steel TSksi YS ksiRoom Temp.844290459045110857550400°F823680388434108856538600°F773275368231102826236800°F742871347828928055351000°F702664307026747038281200°F582353275925444022161400°F342035204124——1081600°F241825202622——54 * heat treated by oil quenching from 1800° F and tempering at 1200° F Table 2 Generally Accepted Service TemperaturesMaterialIntermittent  Service TemperatureContinuous  Service TemperatureAustenitic 3041600°F (870°C)1700°F (925°C)3161600°F (870°C)1700°F (925°C)3091800°F (980°C)2000°F (1095°C)3101900°F (1035°C)2100°F (1150°C)Martensitic 4101500°F (815°C)1300°F (705°C)4201350°F (735°C)1150°F (620°C)Ferritic 4301600°F (870°C)1500°F (815°C) It may seem to be illogical that the “continuous” service temperature would be higher than the “intermittent” service temperature for the 300 series grades. The answer is that intermittent service involves “thermal cycling”, which can cause the high temperature scale formed to crack and spall. This occurs because of the difference in the coefficient of expansion between the stainless steel and the scale. As a result of this scaling and cracking, there is a greater deterioration of thesurface than will occur if the temperature is continuous. Therefore the suggested intermittent service temperatures are lower. This is not the case for the 400 series (both ferritic and martensitic grades). The reason for this is not known. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

High temperature Stainless Steel Pipes maintain their mechanical properties when exposed to elevated temperatures on either a short- or long-term basis. All materials selection must be determined by the application and operating conditions in each inpidual case. With their increased concentration of chrome, silicon and aluminium they are especially resistant under the influence of hot gases as well as in salt and metal melting. However, the inpidual corrosion resistance is always dependent on the surrounding conditions, and can therefore not be precisely determined in a single testing. Besides the common Austenitic High Temperature Alloys above (i.e., 1.4948, 1.4878,1.4828, 1.4833, and 1.4845), there are three proprietary Stainless steel alloys: 153 MA, 253 MA, and 353 MA. These three Stainless steel alloys are based on the same concept. Improved oxidation resistance by an increased silicon content and addition of very small quantities of rare earth metals (micro-alloying => MA). Enhanced creep strength due to increased contents of nitrogen (and carbon for 253 MA). In many cases, theproperties of these steels have proved to be equivalent or even superior to those of grades with higher contents of alloying elements. 153 MA is normally intended for use at somewhat lower service temperature than the other two grades.  Depending on the area of application these temperatures can rise e.g. to – 500°C (932°F) in chemical processes – 700°C (1,292°F) in power plant applications – 1,000°C (1,832°F) for furnace engineering Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)