acest 431 MARTENSITIC STAINLESS STEEL BAR 431 s a high chromium-low nickel high hardenabiity Martensti stainless ste! with high strength and good corrosion resistance, as ‘generally supplied hardened and tempered in the tensile range 850 - 1000 Mpa {condition 7) Brinell range 248 - 302.Characlerised by ‘ery good corrosion resistance in general atmospheric corrosive environments, good resistance to mild marine and industrial ‘atmospheres, resistant to many organic materials nitric acid and petroleum products coupled with high tensile and high yield strength plus excellent toughness in the hardened and tempered condition. 431 due to its excellent hardenability is capable of being through hardened up to Rc44, depending upon carbon content and section size, Small sections can be air cooled and larger sections oll quenched for maximum through haraness.Pre hardened and tempered 431 vill also respond readily to nitriding achieving a typical surface hardness of over Rc65. The nitriding process however reduces the corrosion resistance and is therefore not generally recommended except for critical applications where the benefit outweighs all other considerations. Used extensively for parts requiring a combination of high tensile strength, good toughness and good corrosion resistant properties, ‘Typical applications are: Aircraft Parts and Components, Bolts and Nuts, Fasteners, Purp Shafi Valve Parts etc Propellor Shafts, Studs, Material magnetic in all congito Colour Code Stocked Sizes Purple 16,35 to 260 mm diameter, (Gar, Peeled, Cold Drawn ‘Tummed and Polished, and Centreless Ground. Related Specifications Australia AS 2837-1986 431 Germany WN 2.4057 x20crNin7 2 Great Britain 185970 Part3 1991 432529 85970-1955 ENS Japan WS 64303 Sus 431 USA ASTM A276-98b 431 SAE 51431 Als! 431 Ns $4320 Chemical Compo: Max % Carbon 02 0.20 sil ° 1.00 Manganese 0 1.00 Nickel 125 3.00 Chromium 15.00 18.00 Phosphorous ° 0.04Sulphur 0 0.03 ‘Carbon range can vary considerably ‘Nickel adcition optional Mechanical Property Requirements For Material in the Annealed and Heat Treated - Condition T To AS2837 - 1986 432 ‘and 85970 Part 1991 431529 Condition Annealed | Tensile Strength [Min 850 ee Max 1000 0.2% Yield Strength | Min 635 Mpa Elongation on Min 0 5165090 % taod impact Valua | Min Basa mm ks 20 Hardness HB (Min 248 Wax a7 302 ‘Material stocked generally in condition T. NB. Check the mil certificate if critica for end use. ‘Typical Mechanical Properties At Room Temperature - “Hardened and Temp Tensile Strength Mpa 940 0.2% Yield Strength Mpa 750 Elongation in 50mm % 19 Impact Izod J 65 Hardness 280 Re 30 ‘Typical Hardening Temperatures 980°C -1020°C ‘Typical Tempering Temperatures 640°C - 660°C 590°C - 610°C ‘Typical Mechanical Properties At Room Temperature - Hardened By Oil Quench at 980°C and Tempered as Indicated Tempering Temperature*C 250 370 480 590 650 Tensile Strengt Mpa 1370 1390 1410 980 920 0.2% Yield Strength Mpa 1030 1130 1200 790 690 Elongation in 50mm % 16 16 16 19 20 Impact Charpy J 54 34 "16 65 79 Hardness HB 410 420 425 295 270 Re 44 45 46 32 29 High tensile strength and high yield strength with slightly lower impact properties when tempered below 370°C. Section Size 30mm ‘Note drop in impact properties Tempering within the range 370°C - 565°C should be avoided Elevated Temperature Properties 431 displays good resistance to scaling in continuous service up to 700°C. Its use however at these higher working temperatures results in a substantial drop in tensile strength and hardness, with subsequent increase in ductity. ‘Typical Mechanical Properties at Elevated Temperatures, Hardened at 1010°C and Tempered at 30°C Above Working Temperature Tempering Temperature*C 510 570 620 Working Temperature*c 480 540 590 Tensile Strengt Mpa 1350 720 435, Elongation in 50mm % B 20 26Room Temperature Hardness after [HB 440 330 280 est Re a7 37 30 NB, Creep and stress rupture strength is also substantially reduced at these higher working temperatures, Low Temperature Properties 431 Is not recommended for use at sub-zero temperatures due to a substantial drop in impact properties consistent with most steels. ‘other than the austenitic steel types. Cold Bending In the hardened and tempered as supplied condition will be extremely dificult due to the high yield strength and isnot generally recommended, Hot Bending In the hardened and tempered as supplied condition itis not recommended due toils affect on the mechanical properties within the heat affected zone. Corrosion Resistance 431 has the highest corrosion resistance of all the Martensitic stainless steels, and while not as high as the austenitic stainless steels it isin certain corrsive environments similar to that of 301 and 302 grades NB. It has optimum corrosion resistance in all environments in the hardened and tempered condition, and is not therefore recommended for use in the annealed condition. It's most important that oxygen is always allowed to circulate freely on al stainless steel surfaces to ensure that a chrome oxide film is always present to protect it. If this is not the case, rusting will occur as with other types of non stainless steels.For optimum corrosion resistance surfaces must be free of scale and foreign particles, Finished parts should be passivated. Forging Heat uniformly to 1150°C - 1200, hold until temperature is uniform throughout the section, De not soak but commence forging immediately.D0 not overheat as this will cause a loss of toughness and ductility. Do not forge below 900°CFinished forgings ‘should be cooled as slowly as possible in dry lime or ashes to room temperature and sub-critical annealed immediately Heat Treatment ‘Sub-Critical Annealing Heat uniformerly to 620°C - 660°C hold until temperature is uniform throughout the section, Soak as required - suggested time 6 to 12 hours but can be longer, cool in air. Annealing Heat to 950°C - 1020°C, hold until temperature is uniform throughout the section. *Soak as require. ‘Quench in all or air cool. Temper immediately while stil hand warm.Note: Best impact properties achleved by hardening from above 1020°C, Best corrasion resistance plus mechanical properties achieved by hardening from about 980°C and tempering above 590°, Hardening Heat to 950°C - 020°C, hold until temperature Is uniform throughout the section, *Soak as required,Quench in ol or alr cool. Temper immediately while stil hand warm. Note: Hardening from 1020°C - 1060°C wil give optimum corrosion resistance, but hardening from about 980°C will give the best combination of corrosian resistance and mechanical properties Nitriding Prior to nitriding, the chrome oxide ilm which protects the surface must be broken down by pickling ar fine sand blasting Nitriding is ‘carried out at 500°C - 550°C followed by slow cooling (no quench) reducing the problem of distortion. Parts can therefore be machined to near final size, leaving a grinding tolerance only. Always ensure that the tempering temperature employed during the intial heat ‘treatment was higher than the nitriding temperature otherwise the care strength will be affected, ‘Tempering (Condition T) Heat to 590°C - 680°C as required hold until temperature is uniform throughout the section, soak as required, cool in ar. ‘A Double Tempering Treatment,as follows is recommended for optimum toughness.Heat to 640°C - 680°C. *Soak as required, cool in ar. Followed by: Re heat to 590°C - 610°C. #Seak as required, coal in air.431 can of course be tempered at much lower temperatures producing much higher tensile strengths with subsequent lower impact properties. NB. Tempering however within the range 370°C - 565°C shoula bee avoided due to temper brittleness, resulting in a considerable reduction in impact properties and loss of corrosion resistance.*Heating temperatures, rate of heating, cooling and soaking times will vary due to factors such as work piece size/shape, also furnace type employed, quenching medium and work piece transfer facilities etc.Please consult your heat treater for best results. Machining 431 machines best in the hardened and tempered as supplied condition and is regarded as being readily machineable with all ‘operations such as turning and dling etc. capable of being carried out satisfactorily It does not work harden to the same extent as ‘the 300 series austenitic stainless steels, bt is more similar inthis respect tothe low allay high tensile steels such as 4140 ‘etc Allowing therefore for its high tensile properties, all machining should be carried out as per machine manufacturers recommendations for suitable tool type, feeds and speeds, Welding 431 |s not generally recommended for welding in ether the annealed or hardened and tempered condition, due to its alr hardening ‘capability which can lead tothe formation of Brittle martensite, resulting in cold cracking due to contraction stresses within the weld ‘and heat affected zone. The higher the carbon content the higher the hardening capabilty and the greater the risk of cracking Pre heating and interpass temperature control during welding, plus very slow cooling and post-weld annealing is the best method to prevent cracking, The following welding procedure and post-weld heat treatment may be taken as a guide only if welding is necessary, Welding Procedure Welding electrades or rods should be low hydrogen types 410 or ‘similar when good strength Is required otherwise an austenitic stainless electrode or rod such as 308 or *similar may be used resulting In a more ductile weld when strength isnot so critical and post-weld annealing isnot possible or intended. Pre-heat at 200°C - 300°C and maintain interpass temperature at 200°C minimum. On ‘completion of welding cool slowly as possible until hand warm if possible: Post-weld sub-crtical anneal at 620°C - 660°C, and cool in air-Please consult your welding consumables supplier. Interlay believes the information provided is accurate and reliable, However no warranty of accuracy, completeness or reliability is given, nor will any responsiblity be taken for errors or omissions. 316L due to its low carbon content has greater resistance to intergranular corrosion than al the austenitic stainless steel grades except 304L grade and 321 titanium stabilized grade.