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One of the key advantages of stainless steel lies in the materials sheer versatility. The fact that the precise composition of stainless steel can be altered to create a metal which is perfectly suited to a particular task means that it’s basic properties – strength, malleability and resistance to staining and corrosion – can be brought to bear in a wide range of situations. Stainless steels have traditionally been pided into types depending on their microstructure at room temperature, which gives a rough indication of their composition and properties. wilsonpipeline’s stainless steels can be pided into four main types: ferritic stainless steel, martensitic stainless steel and precipitation hardening stainless steel, duplex stainless steel, and austenitic stainless steel – the best steel for you depends on the application. The different stainless steel types are created by adding different levels of various alloys such as chromium or nickel during the manufacturing process. Put simply, there are five basic stainless steel types, each with its’ own inpidual composition and therefore with particular properties which are called for in specific working environments. The types of stainless steel in common use, their properties and composition, are as follows: Ferritic stainless steel Low carbon and nickel content Good corrosion resistance Good weldability and toughness Magnetic The standard ferritic grades are alloyed with chromium (11.2–19%), but with no, or a very small, addition of nickel. As nickel is one of the most expensive alloying elements, and experiences high price volatility, the low nickel content of the ferritic grades makes them more price stable compared to grades with high nickel content. Molybdenum is added to some grades to improve corrosion resistance, while alloying with niobium and/or titanium improves weldability. The ferritic grades are magnetic due to their ferritic microstructure. There are also ferritic grades with increased resistance to high temperatures (800–1,150 °C). These grades are typically alloyed with more carbon than standard ferritic grades to increase creep strength, and with silicon and aluminum to improve resistance to oxidation. Martensitic and precipitation hardening stainless steel High strength High wear resistance Limited corrosion resistance Magnetic The martensitic grades are the smallest group of stainless steels. For improved strength and hardenability they have a higher carbon content compared to other grades, and nitrogen is sometimes added to further improve strength. These grades contain no, or small, amounts of nickel, and molybdenum is seldom added. Adding some nickel and reducing the carbon content improves the poor weldability of martensitic grades. Sometimes sulfur is added to improve the machinability. The precipitation hardening grades are hardened by a special mechanism involving the formation of precipitates within the microstructure. Both martensitic and precipitation hardening stainless steels are magnetic. Duplex stainless steel High strength and toughness Very good corrosion resistance Good weldability Lightweight Magnetic Duplex stainless steel grades have a ferritic-austenitic microstructure that combines many of the beneficial properties of ferritic and austenitic stainless steels. The duplex stainless steel microstructure also contributes to high strength and high resistance to stress corrosion cracking. Duplex stainless steels are characterized by high chromium content (20.1–25.4%) and low nickel content (1.4–7%) compared to austenitic grades. The low nickel content makes duplex stainless steel grades more price stable. Molybdenum (0.3–4%) and nitrogen are added to improve corrosion resistance, while nitrogen also increases strength. The duplexstainless steel grades LDX 2101 and 2304 are sometimes referred to as lean duplex stainless steel grades, while the duplexstainless steel grades 2507 and 4501 are also called 25Cr super duplex stainless steel grades. Due to their ferrite content the duplex stainless steel grades are magnetic. Austenitic stainless steel Good to excellent corrosion resistance Good weldability and formability Good creep resistance Non-magnetic The austenitic stainless steel grades are the largest stainless steel types, and can be pided into five sub-groups: Cr-Mn grades – also referred to as 200-series grades have some of the nickel replaced with manganese and nitrogen Cr-Ni grades – general-purpose grades mainly alloyed with chromium and nickel, but with no molybdenum Cr-Ni-Mo grades – also general-purpose grades, but with increased corrosion resistance due to alloying with molybdenum High-performance grades – high alloying content for use in very demanding environments High-temperature grades – high chromium and nickel content, but no molybdenum, for use at temperatures exceeding 550 °C The austenitic stainless steel grades have good to excellent corrosion resistance, as well as good formability and weldability. Their high impact strength at low temperatures is often exploited in cryogenic applications. The austenitic grades are non-magnetic in the solution-annealed condition. Cold working increases their strength and certain grades are therefore supplied in the temper rolled condition and may then be magnetic due to the presence of some martensite. Glossary Precipitation hardening Hardening by a special mechanism involving the formation of precipitates within the microstructure. Toughness The ability to absorb energy in the plastic range. Creep The time-dependent slow plastic deformation of metals under a constant stress. Oxidation (1) Loss of electrons in a chemical reaction. (2) Corrosion of a metal that is exposed to an oxidizing gas at elevated temperatures. The stainless steel reacts with O2, H2O, CO2 and forms an oxide on the stainless steel surface. Lean duplex stainless steel The duplex stainless steel grades LDX 2101 and 2304 are sometimes referred to as lean duplex grades due to their “lean” chemical composition. 25Cr super duplex stainless steel The duplex stainless steel grades 2507 and 4501 are sometimes referred to as super duplex stainless steel grades as the chromium content is close to 25% in these grades. Annealing Heat treatment that alters the microstructure of a material causing changes in properties such as strength, hardness, and ductility. Established in 2008, wilsonpipeline Pipe Industry Co., Limited is a professional organizer and one-stop-shop supplier for steel piping system products, including steel pipe and tube, forged flange and fittings, butt-welding pipe fittings, elbow, tee, reducer, stub end, gaskets, fasteners, valves, Sanitary Services etc. in China. We have devoted to providing the best solutions of steel materials and industrial equipment for our respected customers. Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)

347 Stainless Steel Bar Spec: AMS 5646 347 Stainless Steel Bar AMS 5646 UNS S34700 Nominal Composition Iron 68% Chromium 18% Nickel 11% Columbium+Tantalum 10 x Carbon minimum Description Type 347 Stainless Steel is a columbium/tantalum stabilized austenitic chromium-nickel stainless steel which was developed to provide an 18-8 type alloy with improved intergranular-corrosion resistance. Type 347 Stainless Steel is stabilized against chromium carbide formation by the addition of columbium and tantalum. Since columbium and tantalum have a stronger affinity for carbon than chromium, columbium-tantalum carbides precipitate within the grains instead of forming at the grain boundaries. Type 347 Stainless Steel should be considered for applications requiring intermittent heating between 800ºF (427ºC) and 1650ºF (899ºC), or for welding under conditions which prevent a post-weld anneal. Properties Non-magnetic. The corrosion resistance of Type 347 stainless steel is similar to Type 304 stainless steel. Type 347 Stainless Steel is used for welded equipment which cannot be annealed and for equipment which is operated between 800-1500°F (427-816°C). The elevated temperature stress rupture and creep strength of Type 347 are higher than Type 304 stainless steel. The room temperature yield strength and tensile strength are approximately 35,000 psi and 85,000 psi, respectively. Hardness The hardness of Aerodyne stock is typically 170 BHN and is supplied in the fully annealed condition. Type 347 is not hardenable through heat treatment, but small sections can be cold work hardened. Room temperature yield strength is typically 40,000 psi with tensile strength of 90,000 psi. Machinability RATING: 80% of B-1112 TYPICAL STOCK REMOVAL RATE: 90 surface feet/minute with high speed tools. COMMENTS: Type 347 Stainless Steel machines with tough and stringy chips and has a high rate of work hardening and requires a rigid set-up, plenty of power and positive cuts. Use as heavy a cut as possible to prevent surface work hardening and glazing. Density: 0.288 lbs/in3, 7.97 g/cm3 Standard Inventory Specifications AMS 5646 ASTM-A 193 ASTM-A 276 ASTM-A 479 QQS 763 Line marked over 0.5 inches in diameter Predominantly produced by AOD process. Annealed, centerless ground or rough turned. Lengths: 10-12 feet Established in 2008, wilsonpipeline Pipe Industry Co., Limited is a professional organizer and one-stop-shop supplier for stainless steel piping system products, including stainless steel pipes and stainless steel tubes, stainless steel forged flanges and butt-welding stainless steel pipe fittings, stainless steel pipe fittings, stainless steel elbows, stainless steel tees, stainless steel reducer, stainless steel stub end, stainless steel gaskets, stainless steel fasteners, stainless steel valves, Sanitary Services, stainless steel bar, etc. in China. We have devoted to providing the best solutions of steel materials and industrial equipment for our respected customers. We supply not only commonly used stainless steel materials (SS304/L,SS316/L,SS321), but also duplex and super duplex steel 1.4547, 1.4462, 1.4410 (S31254,S31803,S32750,S32760), special austenite stainless 310S, 347H, 347, 317L, 904L… wilsonpipeline products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining,Sewage treatment, Natural gas and Pressure vessels and other industries. Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)

Stainless steel is usually pided into 5 types: Precipitation hardening (PH) Stainless Steels – These stainless steels can develop very high strength by adding elements such as Copper, Niobium and Aluminium to the stainless steel. With a suitable “aging” heat treatment, very fine particles form in the matrix of the stainless steel which imparts strength. These stainless steels can be machined to quite intricate shapes requiring good tolerances before the final aging treatment as there is minimal distortion from the final treatment. This is in contrast to conventional hardening and tempering in martensitic stainless steels where distortion is more of a problem. Corrosion resistance is comparable to standard austenitic stainless steels like 1.4301 (304). Austenitic Stainless Steels – These stainless steels are the most common. Their microstructure is derived from the addition of Nickel, Manganese and Nitrogen. It is the same structure as occurs in ordinary stainless steels at much higher temperatures. This structure gives these stainless steels their characteristic combination of weldability and formability. Corrosion resistance can be enhanced by adding Chromium, Molybdenum and Nitrogen. They cannot be hardened by heat treatment but have the useful property of being able to be work hardened to high strength levels whilst retaining a useful level of ductility and toughness. Standard austenitic stainless steels are vulnerable to stress corrosion cracking. Higher nickel austenitic stainless steels have increased resistance to stress corrosion cracking. They are nominally non-magnetic but usually exhibit some magnetic response depending on the composition and the work hardening of the stainless steel. Martensitic Stainless Steel – These stainless steels are similar to ferritic stainless steels in being based on Chromium but have higher Carbon levels up as high as 1%. This allows them to be hardened and tempered much like carbon and low-alloy stainless steels. They are used where high strength and moderate corrosion resistance is required. They are more common in long products than in sheet and plate form. They have generally low weldability and formability. They are magnetic. Duplex Stainless Steels – These stainless steels have a microstructure which is approximately 50% ferritic and 50% austenitic. This gives them a higher strength than either ferritic or austenitic stainless steels. They are resistant to stress corrosion cracking. So called “lean duplex” stainless steels are formulated to have comparable corrosion resistance to standard austenitic stainless steels but with enhanced strength and resistance to stress corrosion cracking. “Superduplex” stainless steels have enhanced strength and resistance to all forms of corrosion compared to standard austenitic stainless steels. They are weldable but need care in selection of welding consumables and heat input. They have moderate formability. They are magnetic but not so much as the ferritic, martensitic and PH grades due to the 50% austenitic phase. Ferritic Stainless Steels – These stainless steels are based on Chromium with small amounts of Carbon usually less than 0.10%. These stainless steels have a similar microstructure to carbon and low alloy stainless steels. They are usually limited in use to relatively thin sections due to lack of toughness in welds. However, where welding is not required they offer a wide range of applications. They cannot be hardened by heat treatment. High Chromium stainless steels with additions of Molybdenum can be used in quite aggressive conditions such as sea water. Ferritic steels are also chosen for their resistance to stress corrosion cracking. They are not as formable as austenitic stainless steels. They are magnetic. Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)

347 stainless steel is variant of the basic austenitic 18/8 Grade 304 with added Columbium – the introduction of Columbium stabilizes the steel and eliminates carbide precipitation which subsequently causes intergranular corrosion. The steel has excellent forming and welding qualities and excellent toughness even at cryogenic temperatures. Benefits of 347 Stainless Steel Higher creep stress and rupture properties when compared with 304 Ideal for high temperature service Overcomes sensitization and intergranular corrosion concerns Can be used in elevated temperature applications for ASME Boiler and Pressure Vessel Code applications Due to stabilisation the material offers better overall corrosion resistance when compared to 304/304L Excellent mechanical properties A high carbon version (347H) is also available Typical Uses Heat exchangers High temperature steam service High temperature chemical process Both 347H/347 Stainless Steel are used primarily in elevated temperature applications. Chemical CompositionUNS NoGradeCSiMnPSCrMoNiNOtherS347003470.080.752.000.0450.03017.00/19.00–9.00/13.00–Cb:10xC1.00 Mechanical PropertiesUNS NoGradeProof Stress 0.2% (MPa)Tensile Strength (MPa)Elongation A5(%)Hardness MaxHBHRBS347003472055154020192 Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)

Stainless steel type 347 is part of a family of stainless steel alloys (301, 302, Type 347 stainless steel has slightly improved corrosion resistance over type 321 stainless steel in strongly oxidizing environments., 303, 304, 316, 347). Stainless steel type 347 is a columbium/tantalum stabilized austenitic chromium-nickel stainless steel which was developed to provide an 18-8 type alloy with improved intergranular-corrosion resistance. Stainless steel type 347has a slightly improved corrosion resistance over other types of stainless steel in strongly oxidizing environments as a result of the addition of columbium and tantalum. Columbium-tantalum carbides precipitate within the grains instead of forming at the grain boundaries. Stainless steel type 347 should be considered for applications requiring intermittent heating between 800ºF (427ºC) and 1650ºF (899ºC), or for welding under conditions which prevent a post-weld anneal. Nominal Composition in Percentage: Ni                    11.00 Cr                    18.00 Fe                  Balance Si                    1.00 Mn                   2.00 C                     0.080 P                     0.045 S                     0.030 Cb+Ta            10 x C UNS Number: S34700 Other Standard Specifications: AMS 5512 300 Series—austenitic chromium-nickel alloys Stainless Steel Type 301—highly ductile, for formed products. Also hardens rapidly during mechanical working. Good weldability. Better wear resistance and fatigue strength than 304. Stainless Steel Type 302—same corrosion resistance as 304, with slightly higher strength due to added carbon. Stainless Steel Type 303—free machining version of 304 via addition of sulfur and phosphorus. Also referred to as “A1” in accordance with ISO 3506. Stainless Steel Type 304—the most common grade; the classic 18/8 (18% chromium, 8% nickel) stainless steel. Outside of the US it is commonly known as “A2 stainless steel”, in accordance with ISO 3506 (not to be confused with A2 tool steel). Stainless Steel Type 316—the second most common grade (after 304); for food and surgical stainless steel uses; alloy addition of molybdenum prevents specific forms of corrosion. It is also known as marine grade stainless steel due to its increased resistance to chloride corrosion compared to type 304. 316 is often used for building nuclear reprocessing plants. Density: 0.29 lbs/in Exceptional Properties Of Stainless Steel Type 347: Toughness, durability, corrosion resistance, weldability, high temperature, high creep and stress rupture properties. Mechanical Properties at Room Temperature of Stainless Steel Type 347 Properties: Annealed Ultimate Tensile Strength: 75 KSI min (515 MPA min) Yield Strength (0.2% offset): 30 KSI min (205 MPA min) Elongation: 40% min Hardness: Rb 92 max Properties: Tempered Type 347 stainless steel can be cold rolled various tempers.  Contact Ulbrich Technical Services for additional information. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Can I use stainless steel at low temperatures? Austenitic stainless steels are extensively used for service down to as low as liquid helium temperature (-269 deg C). This is largely due to the lack of a clearly defined transition from ductile to brittle fracture in impact toughness testing. Toughness is measured by impacting a small sample with a swinging hammer. The distance which the hammer swings after impact is a measure of the toughness. The shorter the distance, the tougher the steel as the energy of the hammer is absorbed by the sample. Toughness is measured in Joules (J). Minimum values of toughness are specified for different applications. A value of 40 J is regarded as reasonable for most service conditions. Steels with ferritic or martensitic structures show a sudden change from ductile (safe) to brittle (unsafe) fracture over a small temperature difference. Even the best of these steels show this behaviour at temperatures higher than -100 deg C and in many cases only just below zero. In contrast austenitic steels only show a gradual fall in the impact toughness value and are still well above 100 J at -196 deg C. Another factor in affecting the choice of steel at low temperature is the ability to resist transformation from austenite to martensite. Can I use stainless steel at high temperatures? Various types of stainless steel are used across the whole temperature range from ambient to 1100 deg C. The choice of grade depends on several factors: Maximum temperature of operation Time at temperature, cyclic nature of process Type of atmosphere, oxidising , reducing, sulphidising, carburising. Strength requirement In the European standards, a distinction is made between stainless steels and heat-resisting steels. However, this distinction is often blurred and it is useful to consider them as one range of steels. Increasing amounts of Chromium and silicon impart greater oxidation resistance. Increasing amounts of Nickel impart greater carburisation resistance. This is where a batch of steel meets more than one specification or grade. It is a way of allowing melting shops to produce stainless steels more efficiently by restricting the number of different types of steel. The chemical composition and mechanical properties of the steel can meet more than one grade within the same standard or across a number of standards. This also allows stockholders to minimise stock levels. For example, it is common for 1.4401 and 1.4404 (316 and 316L) to be dual certified – that is the carbon content is less than 0.030%. Steel certified to both European and US standards is also common. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are many different types of surface finish on stainless steel. Some of these originate from the mill but many are applied later during processing, for example polished, brushed, blasted, etched and coloured finishes. The importance of surface finish in determining the corrosion resistance of the stainless steel surface cannot be overemphasised. A rough surface finish can effectively lower the corrosion resistance to that of a lower grade of stainless steel. The European standards for stainless steels have attempted to define the most common surface finishes. However, due to the proprietary nature of many suppliers’ finishes, it is unlikely that complete standardisation is possible. This is a summary of the most common types for each product form Common Surface Finishes for Stainless Steel Flat Products from EN 10088-2 (for full list see Specifying finishes for stainless steel flat products (sheet and plate) Surface Finish Code Description Mill finishes 1D Hot rolled, heat treated, pickled. The most common hot rolled finish. A non reflective, rough surface. Not normally used for decorative applications 2B Cold rolled, heat treated, pickled, pinch passed. The most common cold rolled mill finish. Dull grey slightly reflective finish. Can be used in this condition or frequently is the starting point for a wide range of polished finishes. 2D Cold rolled, heat treated, pickled. 2H Work hardened by rolling to give enhanced strength level. Various ranges of tensile or 0.2% proof strength are given in EN 10088-2 up to 1300 MPa and 1100 MPa respectively dependent on grade 2Q Cold rolled hardened and tempered. Applies to martensitic steels which respond to this kind of heat treatment. 2R Cold rolled and bright annealed, still commonly known as BA. A bright reflective finish. Can be used in this condition or as the starting point for polishing or other surface treatment processes e.g. colouring In the following codes “1” refers to hot rolled being the starting point and “2” as cold rolled Special Finishes 1G or 2G Ground. Relatively coarse surface. Unidirectional. Grade of polishing grit or surface roughness can be specified 1J or 2J Brushed or dull polished. Smoother than 1G/2G. Grade of polishing grit or surface roughness can be specified 1K or 2K Satin polish. Similar to 1J/2J but with maximum specified Ra value of 0.5 micron. Usually achieved with SiC polishing belts. Alumina belts are strongly discouraged for this finish as this will have detrimental effect on corrosion resistance. Recommended for external architectural and coastal environments where bright polish (1P/2P) is not acceptable. 1P/2P Bright polished. Non-directional, reflective. Can specify maximum surface roughness. The best surface for corrosion resistance. 2L Coloured by chemical process to thicken the passive layer and produce interference colours. A wide range of colours is possible. 1M/2M Patterned. One surface flat. 1S/2S Surface coated e.g. with tin = Terne coating 2W Corrugated. Similar to patterned but both surfaces are affected Bead blastingNot in EN 10088-2. Work being undertaken to more accurately define finishes. Established in 2008, wilsonpipeline Pipe Industry Co., Limited is a professional organizer and one-stop-shop supplier for stainless steel piping system products, including stainless steel pipes and stainless steel tubes, stainless steel forged flanges and butt-welding stainless steel pipe fittings, stainless steel pipe fittings, stainless steel elbows, stainless steel tees, stainless steel reducer, stainless steel stub end, stainless steel gaskets, stainless steel fasteners, stainless steel valves, Sanitary Services, stainless steel bar, etc. in China. We have devoted to providing the best solutions of steel materials and industrial equipment for our respected customers. We supply not only commonly used stainless steel materials (SS304/L,SS316/L,SS321), but also duplex and super duplex steel 1.4547, 1.4462, 1.4410 (S31254,S31803,S32750,S32760), special austenite stainless 310S, 347H, 347, 317L, 904L… wilsonpipeline products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining,Sewage treatment, Natural gas and Pressure vessels and other industries. Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)

What Is Stainless Steel? Stainless steel is an alloy of Iron with a minimum of 10.5% Chromium. Chromium produces a thin layer of oxide on the surface of the steel known as the ‘passive layer’. This prevents any further corrosion of the surface. Increasing the amount of Chromium gives an increased resistance to corrosion. Stainless steel also contains varying amounts of Carbon, Silicon and Manganese. Other elements such as Nickel and Molybdenum may be added to impart other useful properties such as enhanced formability and increased corrosion resistance. When was stainless steel discovered? There is a widely held view that stainless steel was discovered in 1913 by Sheffield metallurgist Harry Brearley. He was experimenting with different types of steel for weapons and noticed that a 13% Chromium steel had not corroded after several months. However, the picture is much more complex than this. What is stainless steel used for? Stainless steels of various kinds are used in thousands of applications. The following gives a flavour of the full range: Domestic – cutlery, sinks, saucepans, washing machine drums, microwave oven liners, razor blades Architectural/Civil Engineering – cladding, handrails, door and window fittings, street furniture, structural sections, reinforcement bar, lighting columns, lintels, masonry supports Transport – exhaust systems, car trim/grilles, road tankers, ship containers, ships chemical tankers, refuse vehicles Chemical/Pharmaceutical – pressure vessels, process piping. Oil and Gas – platform accommodation, cable trays, subsea pipelines, stainless steel flanges, stainless steel pipe fittings, stainless steel pipes. Medical – Surgical instruments, surgical implants, MRI scanners. Food and Drink – Catering equipment, brewing, distilling, food processing. Water – Water and sewage treatment, water tubing, hot water tanks. General – stainless steel springs, stainless steel fasteners (bolts, nuts and washers), stainless steel wire. Is stainless steel non-magnetic? It is commonly stated that “stainless steel is non-magnetic”. This is not strictly true and the real situation is rather more complicated. The degree of magnetic response or magnetic permeability is derived from the microstructure of the steel. A totally non-magnetic material has a relative magnetic permeability of 1. Austenitic structures are totally non-magnetic and so a 100% austenitic stainless steel would have a permeability of 1. In practice this is not achieved. There is always a small amount of ferrite and/or martensite in the steel and so permeability values are always above 1. Typical values for standard austenitic stainless steels can be in the order of 1.05 – 1.1. It is possible for the magnetic permeability of austenitic steels to be changed during processing. For example, cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel. A familiar example is in a stainless steel sink where the flat drainer has little magnetic response whereas the pressed bowl has a higher response due to the formation of martensite particularly in the corners. In practical terms, austenitic stainless steels are used for “non-magnetic” applications, for example magnetic resonance imaging (MRI). In these cases, it is often necessary to agree a maximum magnetic permeability between customer and supplier. It can be as low as 1.004. Does stainless steel corrode? Although stainless steel is much more resistant to corrosion than ordinary carbon or alloy steels, in some circumstances it can corrode. It is ‘stain-less’ not ‘stain-impossible’. In normal atmospheric or water based environments, stainless steel will not corrode as demonstrated by domestic sink units, cutlery, saucepans and work-surfaces. In more aggressive conditions, the basic types of stainless steel may corrode and a more highly alloyed stainless steel can be used. Can I use stainless steel at low temperatures? Austenitic stainless steels are extensively used for service down to as low as liquid helium temperature (-269 deg C). This is largely due to the lack of a clearly defined transition from ductile to brittle fracture in impact toughness testing. Toughness is measured by impacting a small sample with a swinging hammer. The distance which the hammer swings after impact is a measure of the toughness. The shorter the distance, the tougher the steel as the energy of the hammer is absorbed by the sample. Toughness is measured in Joules (J). Minimum values of toughness are specified for different applications. A value of 40 J is regarded as reasonable for most service conditions. Steels with ferritic or martensitic structures show a sudden change from ductile (safe) to brittle (unsafe) fracture over a small temperature difference. Even the best of these steels show this behaviour at temperatures higher than -100 deg C and in many cases only just below zero. In contrast austenitic steels only show a gradual fall in the impact toughness value and are still well above 100 J at -196 deg C. About wilsonpipeline Pipe Industry Co., Limited Established in 2008, wilsonpipeline Pipe Industry Co., Limited is a professional organizer and one-stop-shop supplier for steel piping system products, including stainless steel pipes and stainless steel tubes, stainless steel forged flanges and butt-welding stainless steel pipe fittings, stainless steel pipe fittings, stainless steel elbows, stainless steel tees, stainless steel reducer, stainless steel stub end, stainless steel gaskets, stainless steel fasteners, stainless steel valves, Sanitary Services etc. in China. We have devoted to providing the best solutions of steel materials and industrial equipment for our respected customers. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Most decisions about which stainless steel to use are based on a combination of the following factors: What is the corrosive environment? – Atmospheric, water, concentration of particular chemicals, chloride content, presence of acid. What is the temperature of operation? – High temperatures usually accelerate corrosion rates and therefore indicate a higher grade. Low temperatures will require a tough austenitic stainless steel. What strength is required? – Higher strength can be obtained from the austenitic stainless steels, duplex stainless steels, martensitic stainless steels and PH stainless steels. Other processes such as welding and forming often influence which of these is most suitable. For example, high strength austenitic stainless steels produced by work hardening would not be suitable where welding was necessary as the process would soften the stainless steel. What welding will be carried out? – Austenitic stainless steels are generally more weldable than the other types. Ferritic stainless steels are weldable in thin sections. Duplex stainless steels require more care than austenitic stainless steels but are now regarded as fully weldable. Martensitic stainless steels and PH stainless steels grades are less weldable. What degree of forming is required to make the component? – Austenitic stainless steels are the most formable of all the types being able to undergo a high degree of deep drawing or stretch forming. Generally, ferritic stainless steels are not as formable but can still be capable of producing quite intricate shapes. Duplex stainless steels, martensitic stainless steels and PH stainless steels grades are not particularly formable. What product form is required? – Not all grades are available in all product forms and sizes, for example sheet, bar, tube. In general, the austenitic stainless steels are available in all product forms over a wide range of dimensions. Ferritics are more likely to be in sheet form than bar. For martensitic stainless steels, the reverse is true. What are the customer’s expectations of the performance of the material? – This is an important consideration often missed in the selection process. Particularly, what are the aesthetic requirements as compared to the structural requirements? Design life is sometimes specified but is very difficult to guarantee. There may also be special requirements such as non-magnetic properties to take into account. It must also be borne in mind that stainless steel type alone is not the only factor in material selection. Surface finish is at least as important in many applications, particularly where there is a strong aesthetic component. See Importance of Surface Finish. Availability. There may be a perfectly correct technical choice of material which cannot be implemented because it is not available in the time required. Cost. Sometimes the correct technical option is not finally chosen on cost grounds alone. However, it is important to assess cost on the correct basis. Many stainless steel applications are shown to be advantageous on a life cycle cost basis rather than initial cost. The final choice will almost certainly be in the hands of a specialist but their task can be helped by gathering as much information about the above factors. Missing information is sometimes the difference between a successful and unsuccessful application. Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)

Stainless steel is engineering material with good corrosion-resistance, strength and fabrication characteristics. They can readily meet a wide range of design criteria, including load, service life and low maintenance. Selecting the proper stainless steel grade 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. The corrosion, heat resistance and mechanical properties are all affected by the chemical composition of the stainless steel. As the composition of the steel is varied, so are the properties. The major alloying elements of stainless steel include: Chromium Forms a passive surface film to make stainless steel resistant to corrosion. Increases the scaling resistance, tensile strength and wear resistance. Manganese Improves hot-working properties. Up to 2% has no effect on strength, ductility and toughness. Above 2% increases yield strength and tensile strength (as in the 201 grade). Important as a partial replacement of nickel in the 201 grade. Stabilizes the austenitic structure. Molybdenum Increases creep resistance; strength at high temperatures; and corrosion resistance, particularly in sulfite, sulfate, acetic acid and acetate solutions and in a salt-water atmosphere. Expands range of passivity and counteracts tendency to pit. Nickel Stabilizes the austenitic structure. Increases high-temperature strength; ductility, which makes stainless steel easier to form; and corrosion resistance, particularly in industrial and marine atmospheres and the chemical-, food- and textile-processing industries. Silicon Increases scaling resistance by forming a tight initial scale that will withstand cyclic temperature changes; also slightly increases tensile strength and hardness. Resists carburizing at high temperatures. When 1% or more, improves resistance to strong sulfuric acid but offers little improvement for dilution and is unfavorable in nitric-acid service. *Note: Ductility decreases as silicon content increases. Sulfur – Phosphorous – Selenium Increases machinability. Decreases ductility and transverse tensile strength. Titanium – Columbium – Tantalum Prevents intergranular corrosion by stabilizing the carbon as titanium or columbium carbides. Produces finer grain size. Reduces stretcher strains from drawing and forming by their addition to type 430. Stainless Steel Grade Comparison For a comparison of chemical and mechanical properties of common austenitic and ferritic grades of stainless steel according to ASTM A240, see our website: www.wilsonpipeline.com

Stainless steels are iron-based alloys containing a minimum of about 10.5% chromium; this forms a protective self-healing oxide film, which is the reason why this group of steels has their characteristic “stainlessness” or corrosion resistance. The ability of the oxide layer to heal itself means that the steel is corrosion resistant, no matter how much of the surface is removed. This is not the case when carbon or low alloy steels are protected from corrosion by metallic coatings such as zinc or cadmium or by organic coatings such as paint. Although all stainless steels depend on the presence of chromium, other alloying elements are often added to enhance their properties. The categorisation of stainless steels is unusual amongst metals in that it is based upon the nature of their metallurgical structure – the terms used denote the arrangement of the atoms which make up the grains of the steel, and which can be observed when a polished section through a piece of the material is viewed at high magnification through a microscope. Depending upon the exact chemical composition of the steel the microstructure may be made up of the stable phases austenite or ferrite, a “duplex” mix of these two, the phase martensite created when some steels are rapidly quenched from a high temperature, or a structure hardened by precipitated micro-constituents. Austenitic Stainless Steels This group contains at least 16% chromium and 6% nickel (the basic grade 304 is referred to as 18/8) and range through to the high alloy or “super austenitics” such as 904L and 6% molybdenum grades. Additional elements can be added such as molybdenum, titanium or copper, to modify or improve their properties, making them suitable for many critical applications involving high temperature as well as corrosion resistance. This group of steels is also suitable for cryogenic applications because the effect of the nickel content in making the steel austenitic avoids the problems of brittleness at low temperatures, which is a characteristic of other types of steel. Ferritic Stainless Steels These are plain chromium (10.5 to 18%) grades such as Grade 430 and 409. Their moderate corrosion resistance and poor fabrication properties are improved in the higher alloyed grades such as Grades 434 and 444 and in the proprietary grade 3CR12. Martensitic Stainless Steels Martensitic stainless steels are also based on the addition of chromium as the major alloying element but with a higher carbon and generally lower chromium content (e.g. 12% in Grade 410 and 416) than the ferritic types; Grade 431 has a chromium content of about 16%, but the microstructure is still martensite despite this high chromium level because this grade also contains 2% nickel. Duplex Stainless Steels Duplex stainless steels such as 2304 and 2205 (these designations indicate compositions of 23% chromium, 4% nickel and 22% chromium, 5% nickel but both grades contain further minor alloying additions) have microstructures comprising a mixture of austenite and ferrite. Duplex ferritic – austenitic stainless steels combine some of the features of each class: they are resistant to stress corrosion cracking, albeit not quite as resistant as the ferritic steels; their toughness is superior to that of the ferritic steels but inferior to that of the austenitic stainless steels, and their strength is greater than that of the (annealed) austenitic stainless steels, by a factor of about two. In addition the duplex stainless steels have general corrosion resistances equal to or better than 304 and 316, and in general their pitting corrosion resistances are superior to 316. They suffer reduced toughness below about –50°C and after exposure above 300°C, so are only used between these temperatures. Precipitation Hardening Stainless Steels These are chromium and nickel containing steels that can develop very high tensile strengths. The most common grade in this group is “17-4 PH”, also known as Grade 630, with the composition of 17% chromium, 4% nickel, 4% copper and 0.3% niobium. The great advantage of these steels is that they can be supplied in the “solution treated” condition. In this condition the steel is just machineable. Following machining, forming etc. the steel can be hardened by a single, fairly low temperature “ageing” heat treatment which causes no distortion of the component. Characteristics Of Stainless Steels The characteristics of the broad group of stainless steels can be viewed as compared to the more familiar plain carbon “mild” steels. As a generalisation the stainless steels have: •         Higher work hardening rate •         Higher ductility •         Higher strength and hardness •         Higher hot strength •         Higher corrosion resistance •         Higher cryogenic toughness •         Lower magnetic response (austenitic only) •         Must retain corrosion resistant surface in the finished product. These properties apply particularly to the austenitic family and to varying degrees to other grades and families. These properties have implications for the likely fields of application for stainless steels, but also influence the choice of fabrication methods and equipment. Table 1 (Part A). Comparative Properties of stainless steel families. Alloy Group Magnetic Response1 Work Hardening Rate Corrosion Resistance2 Hardenable Austenitic Generally No Very High High By Cold Work Duplex Yes Medium Very High No Ferritic Yes Medium Medium No Martensitic Yes Medium Medium Quench & Temper Precipitation Hardening Yes Medium Medium Age Harden 1 = Attraction of steel to a magnet. Note some grades can be attracted to a magnet if cold worked. 2= Varies significantly within between grades within each group e.g. free machining grades have lower corrosion resistance, those grades higher in molybdenum have higher resistance. Table 1 (Part B). Comparative Properties of stainless steel families. Alloy Group Ductility High Temperature Resistance Low Temperature Resistance3 Weldability Austenitic Very High Very High Very High Very High Duplex Medium Low Medium High Ferritic Medium High Low Low Martensitic Low Low Low Low Precipitation Hardening Medium Low Low High 3= Measured by toughness or ductility at sub-zero temperatures. Austenitic grades retain ductility to cryogenic temperatures. Standard Classifications There are many different varieties of stainless steel and the American Iron and Steel Institute (AISI) in the past designated some as standard compositions, resulting in the commonly used three digit numbering system. This role has now been taken over by the SAE and ASTM, who allocate 1-letter + 5-digit UNS numbers to new grades. The full range of these standard stainless steels is contained in the Iron and Steel Society (ISS) “Steel Products Manual for Stainless Steels”, and in the SAE/ASTM handbook of Unified Numbering System. Certain other grades do not have standard numbers, but are instead covered by other national or international specifications, or by specifications for specialised products such as standards for welding pipes. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Martensitic and precipitation hardening stainless steels are heat treatable and can therefore provide hardness and strength in a wide range. Allowing to workability they are supplied in solution annealed condition. The downstream manufacturer performs final heat treatment to meet the mechanical properties required. Martensitic grades are basically Fe-Cr alloys with a higher carbon content than ferritics which enables them to harden on cooling in air, oil or water. Depending on grade and intended use, ductility is improved by tempering. Typical applications for martensitic grades: cutting utensils surgical and dental instruments fasteners, springs and ball bearings press plates steam and gas stainless steel tubes Precipitation hardening grades have higher alloying contents than martensitic grades. They contain nickel, and in order to achieve hardening by aging additions of copper, aluminium, titanium, niobium and molybdenum. Depending on chemical composition their microstructure after final heat treatment is austenitic, semi-austenitic or martensitic. Typical applications for precipitation hardening grades: retaining rings, spring holders, springs chains, valves and gears aircraft parts pressure vessels and stainless steel tubes Grade properties High strength and hardness distinguish martensitic stainless steels from the other stainless steel families. After austenitizing cooling is performed in air, water or oil, depending on steel grade. If the intended application requires a high level of hardness (e.g. knives, HRC55), only stress relief annealing will be performed. Normally martensitic stainless steels are tempered in order to acquire useful mechanical properties, i.e. a certain level of toughness (A5 ≥ 15 %). Nickel-martensitic steels are superior to traditional martensitic grades regarding strength in combination with toughness. Their microstructure contains stable austenite after hardening and tempering which accounts for good toughness without drawbacks concerning corrosion resistance. Precipitation hardening stainless steels provide remarkable levels of high strength and hardness in a very wide range. With the exception of the martensitic alloys (e.g. 1.4542) cold formability is satisfactory. Weldability Traditional martensitic steels with a carbon content > 0.20 % are difficult to weld; assistance is advised. The hardenable high-carbon grades are not suitable for welding. Low-carbon nickel-martensitic grades have relatively good weldability. Welding of precipitation hardened grades is possible, but depending on grade some limitations might have to be regarded. Corrosion resistance Corrosion resistance of martensitic stainless steels may vary considerably depending on chemical composition (C, Cr, Mo), surface finish and especially heat treatment. Smooth polished surfaces experience higher resistance than rougher finishes. In terms of heat treatment the hardened condition is more favourable, since the elements promoting corrosion resistance are in solution and therewith effective. Tempering may lead to carbide precipitation which impairs corrosion resistance. This is always the case for traditional martensitic grades, whereas nickel-martensitic grades with max 0.06 % carbon and 3-6 % nickel (e.g. 1.4313 and 1.4418) do not sacrifice corrosion resistance by tempering. Corrosion resistance of precipitation hardening steels is higher compared with heat treatable martensitic stainless steels ranking between ferritic Cr  and austenitic CrNi steels. Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)