Design Guidelines

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of Stainless Steel 1Guidelines for Resistance5 Material Selection 5Mechanical Physical Properties9 Austenitic 9 Ferritic 9 Martensitic 11 Precipitation Mechanical Transfer Shapes and 18Hot Forming 18Cold Forming 25Machining 27Joining28 Welding28 Soldering29 Brazing29 Fastening 29Surface Protection Cleaning 30Appendix A Corrosion B Figures 35References 52The Specialty Steel lndustry of NorthAmerica SSINA and the it represents have madeevery effort to ensure that the in this handbook is However neither the SSlNA norits member companies warrants theaccuracy of the information contained inthis handbook or its suitability for anygeneral and specific use and assumesno liability or responsibility of any kind inconnection with the use of this informationThe reader is advised that the herein should not be used orrelied on for any specific or without first advice Stainless steels are ironbase alloys containing 105 or morechromium They have been used for many industrial and consumer applications for over a half century Currentlythere are being marketed a number of stainless steels by the American lron and Steel lnstitute AISI as standardalloys Also commercially available are proprietary stainless steelswith special See Appendix A With so many stainless steels from which to choose have a ready source of information on the of these useful alloys To fill this need the Committee ofStainless Steel Producers initially prepared this booklet The datawas reviewed and updated by the Specialty Steel lndustry of NorthAmerica SSINA Written especially for design engineers it presentsan overview of a broad range of stainless steels both standard andproprietary their compositions their properties their fabricationand their use More detailed information on the standard gradeswith special emphasis on the manufacture finish designations anddimensional and weight tolerances of the product forms in whichthey are marketed is contained in the lron and Steel Society of theAlME the American lnstitute of Mining Metallurgical and Steel Products Manual Stainless and Heat The AlME undertook the publication updating and sale ofthis manual after the AlSl discontinued publication in 1986 Reference is often made to stainless steel in the singular sense asif it were one material Actually there are well over 100 stainless steelalloys Three general are used to identify They are 1 Metallurgical Structure 2 The AlSl namely 200 300 and 400 Series numbers 3 The System which was developed by American Society forTesting Materials ASTM and Society of Automotive Engineers SAEto apply to all commerical metals and alloys There are also a number of grades known by common names thatresemble AlSl designations and these are recognized by ASTMThese common names which are neither trademarks nor with a single producer are shown and identified in thetables These common nonAISI names also appear in the Nearly all stainless steels used in North America haveUNS designations On the following pages there is a description of these 15 list stainless steels according to metallurgical ferritic martensitic precipitation hardening and duplex 3050 K Street NW Washington DC 20007 TEL 202 3428630 or 800 9820355 FAX 202 3428631 1 Austenitic stainless steels Table 1 Ferritic stainless steels Table 2 are chromium and nickel are 400 Series types that steels Table 4 are as 300 Series types Alloys cannot be hardened by heat treatment types some containing other chromium nickel and and only moderately hardened by cold elements such as copper or are identified as 200 Series working They are magnetic have good They can be hardened by solutiontypes The stainless steels in the austenitic ductility and resistance to corrosion and treating and aging to high strengthgroup have different compositions and oxidation Type 430 is the but many common character stainless of the ferritic groupistics They can be hardened by cold Table 4working but not by heat treatment In the PRECIPITATION condition all are essentially Table 2 STAINLESS although some may FERRITIC STAINLESS STEELS UNS UNSbecome slightly magnetic by cold Equivalent Equivalent S13800 S17400working They have excellent corrosion TYPE UNS TYPE UNS S15500 unusually good formability 405 S40500 430FSe S43023and increase in strength as a result of 409 S40900 434 S43400cold work Duplex stainless steels Table 5 have 429 S42900 436 S43600 an annealed structure which is typically Type 304 sometimes referred to as 430 S43000 442 S44200188 stainless is the most widely used about equal parts of austenite and ferrite 430F S43020 446 S44600alloy of the austenitic group It has a Although not formally defined it isnominal composition of 18 chromium generally accepted that the lesser phaseand 8 nickel will be at least 30 by volume Martensitic stainless steels Table 3 Duplex stainless steels offer several are 400 Series types advantages over the common austenitic that are hardenable by heat treatment stainless steels The duplex grades are Table 1 They are magnetic They resist corrosion highly resistant to chloride stress AUSTENITIC in mild environments They have fairly corrosion cracking have excellent pitting STAINLESS STEELS good ductility and some can be heat and crevice corrosion resistance and Equivalent Equivalent treated to tensile strengths exceeding exhibit about twice the yield strength as TYPE UNS TYPE UNS 200000 psi 1379 MPa conventional grades Type 329 and 2205 201 S20100 310 S31000 Type 410 is the generalpurpose alloy are typical alloys 202 S20200 310S S31008 of the martensitic group With respect to the Unified Numbering 205 S20500 314 S31400 System the UNS designations are 301 S30100 316 S31600 shown alongside each AlSl type number 302 S30200 316L S31603 Table 3 in Tables 15 except for four stainless 302B S30215 316F S31620 MARTENSITIC steels see Table 4 for which UNS 303 S30300 316N S31651 STAINLESS STEELS designations only are listed 303Se S30323 317 S31700 304 S30400 317L S31703 Equivalent Equivalent TYPE UNS TYPE UNS 304L S30403 317LMN S31726 Table 5 302HQ S30430 321 S32100 403 S40300 420F S42020 304N S30451 330 NO8330 410 S41000 422 S42200 DUPLEX 305 S30500 347 S34700 414 S41400 431 S43100 STAINLESS STEELS 308 S30800 348 S34800 416 S41600 440A S44002 TypeName UNS 309 S30900 384 S38400 416Se S41623 440B S44003 329 S32900 309S S30908 420 S42000 440C S44004 2205 S31803 2205 hi N 304 202 General N Mn Purpose partially replaces Ni 302B 205 201 Si added N Mn N Mn to increase partially partially scaling replaces replaces resistance Ni Ni 317 316 309S 308 305 303 301 More Mo added 309S Higher 302 Ni increased S added Cr Ni Mo Cr Higher C to increase CR Ni CR Ni to lower to improve lowered to added for for increased better corrosion increased used work machining increase strength corrosion resistance for high primarily hardening work resistance temperature for welding hardening 317L 316L 310S 347 321 304L 384 303Se C reduced C reduced 310S Cb Ti added C reduced More Ni Se added for for Same as added to prevent even to lower for better welding welding 309 only to prevent carbide further work machined more so carbide precip hardening surfaces precip 317LMN 316N 314 348 304N S30430 316F Mo added N added Si increased Ta Co N added Cu added SP N added to for highest restricted to increase to improve increased increase heat for nuclear strength cold to improve strength resistance applications working machining 330 Ni added to resist carburization thermal Al Aluminum P Phosphorus shock C Carbon S Sulfur Cr Chromium Se Selenium Cb Columbium Si Silicon Co Cobalt Ta Tantalum Cu Copper Ti Titanium Mn Manganese V Vanadium Mo Molybdenum W Tungsten N Nitrogen SCC Stress Corrosion Ni Nickel Cracking 3FERRITIC 430 General Purpose 405 409 434 446 442 429 Lower Cr Lower Cr 430F Mo added Cr Cr Slightly AI added PS Primarily for improved increased increased Less Cr to prevent added for used for corrosion to improve to improve for better hardening improved when colled automotive resistance scaling scaling weldability machining from elevated exhaust in auto trim resistance resistance temperatures 430F Se 436 Se added Mo Cb added for corrosion for better heat machined resistance surfaces improved 410 General Purpose 431 414 403 420 416 440C Cr increased Ni added Select Increased PS C increased Ni added for better quality C to increased for highest for corrosion resistance corrosion for turbines improve to improve hardness Good resistance and highly mechanical machining Cr increased Mechan stressed properties for corrosion Properties parts resistance 422 416 Se 440B Strength Se added C decreased toughness to for better slightly to 1200F via machined improve addition of surface toughness Mo V W 420F 440A Al Aluminum P Phosphorus PS Same as C Carbon S Sulfur increased 440B only Cr Chromium Se Selenium to improve more so Cb Columbium Si Silicon machining Co Cobalt Ta Tantalum Cu Copper Ti Titanium Mn Manganese V Vanadium Mo Molybdenum W Tungsten N Nitrogen SCC Stress Corrosion Ni Nickel FOR SELECTION Material Selection The above comments on the suitability Stainless steels are engineering Many variables characterize a of stainless steels in various with good corrosion resistance corrosive environment ie chemicals are based on a long history of and fabrication and their concentration atmospheric application but they are intended only asThey can readily meet a wide range of conditions temperature time so it is guidelines Small differences in chemicaldesign criteria load service life low difficult to select which alloy to use content and temperature such as etc Selecting the proper without knowing the exact nature of the occur during processing can steel essentially means environment However there are corrosion rates The magnitude can beweighing four elements In order of guidelines considerable as suggested by Figures 2importance they are Type 304 serves a wide range of and 3 Figure 2 shows small quantities of 1 Corrosion or Heat Resistance applications It withstands ordinary hydrofluoric and sulfuric acids having athe primary reason for specifying rusting in architecture it is resistant to serious effect on Type 316 stainless steelstainless The specifier needs to know food processing environments except in an environment of 25 phosphoricthe nature of the environment and the possibly for conditions acid and Figure 3 shows effects ofdegree of corrosion or heat resistance involving high acid and chloride temperature on Types 304 and 316 inrequired contents it resists organic chemicals very concentrated sulfuric acid 2 Mechanical Properties with dyestuffs and a wide variety of inorganic Service tests are most reliable inparticular emphasis on strength at room chemicals Type 304 L low carbon determining optimum material andelevated or low temperature Generally resists nitric acid well and sulfuric acids ASTM G 4 is a recommended the combination of corrosion at moderate temperature and for carrying out such tests Tests and strength is the basis for concentrations It is used extensively for cover conditions both during storage of liquified gases equipment for and shutdown For instance sulfuric 3 Fabrication Operations and use at cryogenic temperatures 304N sulfurous and polythionic acid condenhow the product is to be made is a third appliances and other consumer sates formed in some processes duringlevel consideration This includes forging products kitchen equipment hospital shutdowns may be more corrosive thanmachining forming welding etc equipment transportation and waste the process stream itself Tests should 4 Total Cost in considering total water treatment be conducted under the worst operatingcost it is appropriate to consider not only Type 316 contains slightly more nickel conditions and production costs but the than Type 304 and 23 molybdenum Several standard reference volumeslife cycle cost including the costsaving giving it better resistance to corrosion discuss corrosion and corrosion of a product than Type 304 especially in chloride including Uhligs Corrosion Handbookhaving a long life expectancy environments that tend to cause pitting LaQue and Copsons Corrosion Resistance Type 316 was developed for use in Of Metals and Alloys Fontana andCORROSION RESISTANCE sulfite pulp mills because it resists Greens Corrosion Engineering A Guide Chromium is the alloying element that sulfuric acid compounds Its use has to Corrosion Resistance by Climaximparts to stainless steels their corrosion been broadened however to handling Molybdenum Company the qualities by combining with many chemicals in the process Data Survey by the National to form a thin invisible chromium industries of Corrosion Engineers and the ASMoxide protective film on the surface Type 317 contains 34 molybdenum Metals Handbook Corrosion dataFigure 1 Figures are shown in Appendix higher levels are also available in this specifications and recommendedB Because the passive film is such an series and more chromium than Type practices relating to stainless steels areimportant factor there are precautions 316 for even better resistance to pitting also issued by ASTM Stainless steelswhich must be observed in designing and crevice corrosion resist corrosion in a broad range ofstainless steel equipment in Type 430 has lower alloy content than conditions but they are not immune the equipment and in Type 304 and is used for highly polished every environment For example and use of the equipment to trim applications in mild atmospheres It steels perform poorly in reducingavoid destroying or disturbing the film is also used in nitric acid and food environments such as 50 sulfuric In the event that the protective passive processing and hydrochloric acids at elevatedfilm is disturbed or even destroyed it Type 410 has the lowest alloy content temperatures The corrosive attackwill in the presence of oxygen in the of the three generalpurpose stainless experienced is a breakdown of theenvironment reform and continue to give steels and is selected for highly stressed protective film over the entire metal surfacemaximum protection parts needing the combination of Such of stainless The protective film is stable and strength and corrosion resistance such steels are rare and are usually in normal atmospheric or mild as fasteners Type 410 resists corrosion The types of attack which are more likelyaqueous environments but can be in mild atmospheres steam and many to be of concern are pitting by higher chromium and by mild chemical environments attack stress corrosion cracking andmolybdenum nickel and other alloying 2205 may have advantages over Type intergranular corrosion which areelements Chromium improves film 304 and 316 since it is highly resistant to discussed in Appendix Astability molybdenum and chromium chloride stress corrosion cracking and isincrease resistance to chloride about twice as and nickel improves filmresistance in some acid environments Table 6 lists the relative corrosion resistance of the AlSl standard numbered stainless steels in seven broad categories of corrosive environments Table 7 details more specific environments in which various grades are used such as acids bases organics and 5Table 6Relative Corrosion Resistance of AISI Stainless Steels 1 Mild Atmos Atmospheric Chemical TYPE UNS pheric and Number Number Fresh Water Industrial Marine Miild Oxidizing Reducing 201 S20100 x x x x x 202 S20200 x x x x x 205 S20500 x x x x x 301 S30100 x x x x x 302 S30200 x x x x x 302B S30215 x x x x x 303 S30300 x x x 303 Se S30323 x x x x 304 S30400 x x x x x 304L S30403 x x x x x S30430 x x x x x 304N S30451 x x x x x 305 S30500 x x x x x 308 S30800 x x x x x 309 S30900 x x x x x 309S S30908 x x x x x 310 S31000 x x x x x 310S S31008 x x x x x 314 S31400 x x x x x 316 S31600 x x x x x x 316F S31620 x x x x x x 316L S31603 x x x x x x 316N S31651 x x x x x x 317 S31700 x x x x x x 317L S31703 x x x x x 321 S32100 x x x x x 329 S32900 x x x x x x 330 N08330 x x x x x x 347 S34700 x x x x x 348 S34800 x x x x x 384 S38400 x x x x x 403 S40300 x x 405 S40500 x x 409 S40900 x x 410 S41000 x x 414 S41400 x x 416 S41600 x 416 Se S41623 x 420 S42000 x 420F S42020 x 422 S42200 x 429 S42900 x x x x 430 S43000 x x x x 430F S43020 x x x 430F Se S43023 x x x 431 S43100 x x x x 434 S43400 x x x x x 436 S43600 x x x x x 440A S44002 x x 440B S44003 x 440C S44004 x 442 S44200 x x x x 446 S44600 x x x x x S13800 x x x x S15500 x x x x x S17400 x x x x x S17700 x x x x x The X notations indicate that a specific stainless steel type may be considered the member companies When selecting a stainless steel for any corrosive as resistant to the corrosive environment categories environment it is always best to consult with a corrosion engineer and if possible conduct tests in the environment involved under actual operating conditions This list is suggested as a guideline only and does not suggest or imply a warranty on the part of the Specialty Steel Industry of the United States or any of6Table 7Where Different Grades Are Used 15 Environment Grades Environment Grades Acids Hydrochloric acid Stainless generally is not recommended except when solutions are very dilute and at room temperature Mixed acids There is usually no appreciable attack on Type 304 or 316 as long as sufficient nitric acid is present Nitric acid Type 304L or 430 is used Phosphoric acid Type 304 is satisfactory for storing cold phosphoric acid up to 85 and for handling concentrations up to 5 in some unit processes of manufacture Type 316 is more resistant and is generally used for storing and manufacture if the fluorine content is not too high Type 317 is somewhat more resistant then Type 316 At concentrations up to 85 the metal temperature should not exceed 212 F 100 C with Type 316 and slightly higher with Type 317 Oxidizing ions inhibit attack and other inhibitors such as arsenic may be added Sulfuric acid Type 304 can be used at room temperature for concentrations over 80 Type 316 can be used in contact with sulfuric acid up to 10 at temperatures up to 120 F 50 C if the solutions are aerated the attack is greater in airfree solutions Type 317 may be used at temperatures as high as 150 F 65 C with up to 5 concentration The presence of other materials may markedly change the corrosion rate As little as 500 to 2000 ppm of cupric ions make it possible to use Type 304 in hot solutions of moderate concentration Other additives may have the opposite effect Sulfurous acid Type 304 may be subject to pitting particularly if some sulfuric acid is present Type 316 is usable at moderate concentrations and temperatures Bases Ammonium hydroxide Steels in the 300 series generally have good corrosion resistance at virtually all concentrations and temperatures in sodium hydroxide weak bases such as ammonium hydroxide In stronger bases such as sodium hydroxide there may be some attack caustic solutions cracking or etching in more concentrated solutions and at higher temperatures Commercial purity caustic solutions may contain chlorides which will accentuate any attack and may cause pitting of Type 316 as well Type 304 Organics Acetic acid Acetic acid is seldom pure in chemical plants but generally includes numerous and varied minor constituents Type 304 is used for a wide variety of equipment including stills base heaters holding tanks heat exchangers pipelines valves and pumps for concentrations up to 99 at temperatures up to about 120 F 50 C Type 304 is also satisfactory for contact with 100 acetic acid vapors and if small amounts of turbidity or color pickup can be tolerated for room temperature storage of glacial acetic acid Types 316 and 317 have the broadest range of usefulness especially if formic acid is also present or if solutions are unaerated Type 316 is used for fractionating equipment for 30 to 99 concentrations where Type 304 cannot be used for storage vessels pumps and process equipment handling glacial acetic acid which would be discolored by Type 304 Type 316 is likewise applicable for parts having temperatures above 120 F 50 C for dilute vapors and high pressures Type 317 has somewhat greater corrosion resistance than Type 316 under severely corrosive conditions None of the stainless steels has adequate corrosion resistance to glacial acetic acid at the boiling temperature or at superheated vapor temperatures Aldehydes Type 304 is generally satisfactory Amines Type 316 is usually preferred to Type 304 Cellulose acetate Type 304 is satisfactory for low temperatures but Type 316 or Type 317 is needed for high temperatures Citric formic and Type 304 is generally acceptable at moderate temperatures but Type 316 is resistant to all concentrations at tartaric acids temperatures up to boiling Esters From the corrosion standpoint esters are comparable with organic acids Fatty acids Up at about 300 F 150 C Type 304 is resistant to fats and fatty acids but Type 316 is needed at 300 to 500 F 150 to 260 C and Type 317 at higher temperatures Paint vehicles Type 316 may be needed if exact color and lack of contamination are important Phthalic anhydride Type 316 is usually used for reactors fractionating columns traps baffles caps and piping Soaps Type 304 is used for parts such as spray towers but Type 316 may be preferred for spray nozzles and flakedrying belts to miniimize offcolor products Synthetic detergents Type 316 is used for preheat piping pumps and reactors in catalytic hydrogenation of fatty acids to give salts of sulfonated high molecular alcohols Tall oil pump and Type 304 has only limited usage in talloil distillation service Highrosinacid streams can be handled by Type 316L paper industry with a minimum molybdenum content of 275 Type 316 can also be used in the more corrosive highfatty acid streams at temperatures up to 475F 245 C but Type 317 will probably be required at higher temperatures Tar Tar distillation equipment is almost all Type 316 because coal tar has a high chloride content Type 304 does not have adequate resistance to pitting Urea Type 316L is generally required Type 316 is usually selected for all parts in contact with the product because of its inherent corrosion resistance and greater assurance of product purity 7 010 min8MECHANICAL AND PHYSICAL New Design Specification of two notations in this Room Temperature Until recently design engineers 1 The maximum thickness for Type wanting to use austenitic stainless steels 409 ferritic stainless used in the Stainless Steels structurally had to improvise due to the is limited to 015 inches The austenitic stainless steels cannot lack of an appropriate design specification 2 The maximum thickness for Type 430be hardened by heat treatment but can The familiar American lnstitute for Steel and 439 ferritic stainless steels is limitedbe strengthened by cold work and thus Construction and AlSl design specifications to 0125 inchesthey exhibit a wide range of mechanical for carbon steel design do not apply to This is in recognition of concerns forproperties At room temperature the design of stainless steel members the ductile to brittle stainless steels exhibit yield because of differences in strength temperature of the ferritic stainless between 30 and 200 ksi 207 properties modulus of elasticity and the in structural application It should be1379 MPa depending on composition shape of the stress strain curve Figure noted that these alloys have been usedand amount of cold work They also 17 shows that there is no welldefined in plate thickness for other good ductility and toughness yield point for stainless steel Generally toughness in the annealedeven at high strengths and this good condition decreases as the and toughness is retained at content increases Molybdenum tendscryogenic temperatures The chemical Table 9 to increase ductility whereas and nominal mechanical TYPICAL ENDURANCE LIMITS OF tends to decrease ductility of annealed austenitic ANNEALED CHROMIUMNICKEL stainless steels can be used for steels are given in Table 8 STAINLESS STEEL SHEET 2 applications as noted above as well as The difference in effect of cold work of AISI Endurance such traditional applications as kitchenTypes 301 and 304 is indicated by the Type limit ksi MPa sinks and automotive appliance andstress strain diagrams in Figure 11 301 35 241 luggage trim which require good Carbon and nitrogen contents affect 302 34 234 resistance to corrosion and bright highlyyield strength as shown by the 303 35 241 polished among Types 304 304L 304 35 241 When compared to lowcarbon steelsand 304N The effect of manganese and 316 39 269 such as SAE 1010 the standard on strength can be seen by 321 38 262 AlSl ferritic stainless steels such ascomparing Types 301 and 302 against 347 39 269 Type 430 exhibit somewhat higher yieldTypes 201 and 202 and tensile strengths and low elongations Figures 12 13 14 and 15 illustrate Thus they are not as formable as theother effects of small composition Now the American Society of Civil lowcarbon steels The proprietary For example at a given Engineers ASCE in conjunction with stainless steels on the other hand withamount of cold work Types 202 and 301 the SSINA has prepared a standard lower carbon levels have higher yield and tensile strengths ANSIASCE890 Specification for the ductility and formability comparable withthan Types 305 and 310 Design of ColdFormed Stainless Steel that of lowcarbon steels Because of the Austenitic stainless steels which can Structural Members This standard higher strength levels the ferritic stainlessbe cold worked to high tensile and yield covers four types of austenitic stainless steels require slightly more power to formstrengths while retaining good ductility steel specifically Types 201 301 304 Micro cleanliness is important to goodand toughness meet a wide range of and 316 and three types of ferritic formability of the ferritic types becausedesign criteria For example sheet and stainless steels See Ferritic section inclusions can act as initiation sites forstrip of austenitic steels usually Types below This standard requires the use of cracks during forming301 and 201 are produced in the structural quality stainless steel as Type 405 stainless is used where thefollowing tempers defined in general by the provisions of annealed mechanical properties and the American Society for Testing and corrosion resistance of Type 410 are Tensile Yield Materials ASTM specifications satisfactory but when better weldability is Strength Strength Some of the physical properties of desired Type 430 is used for formed Temper Minimum Minimum austenitic stainless steels are similar to products such as sinks and decorative ksi MPa ksi MPa those of the martensitic and ferritic trim Physical properties of Type 430 are stainless steels The modulus of elasticity shown in Table 10 Types 434 and 43614Hard 125 862 75 51712Hard 150 1034 110 758 for example is 28 x 106 psi 193 GPa are used when better 175 1207 135 931 and density is 029 Ib per cu in 8060 resistance is required and for 185 1276 140 965 Kgm3 The physical properties of severe stretching annealed Type 304 are shown in Table 10 For fasteners and other machined parts In structural applications the Types 430F and 430F Se are often usedtoughness and fatigue strength of these Ferritic Stainless Steels Ferritic stainless steels contain approxi the latter being specified when forming issteels are important At room required in addition to machining mately 12 chromium and up Thetemperature in the annealed condition Types 442 and 446 are heat resisting chemical composition of the standardthe austenitic steels exhibit Charpy grades grades are shown in Table 11 along withVnotch energy absorption values in Type 409 which has the lowest nominal mechanical properties Alsoexcess of 100 ftlb The effect of cold chromium content of the stainless steels several proprietary grades see Type 301 on toughness is is widely used for automotive exhaust A have achieved relatively in Figure 16 This shows Type systems commercial acceptance301 to have good toughness even after Three ferritic stainless steels namelycold rolling to high tensile strengths Types 409 430 and 439 are included in Fatigue or endurance limits in bending the ASCE Specification for the Design ofof austenitic stainless steels in the ColdFormed Stainless Steel condition shown in Table 9 are Members Designers should be awareabout onehalf the tensile strength 9 Stainless Steels lmpact tests on martensitic grades The densities of the martensitic The martensitic grades are so named show that toughness tends to decrease stainless steels about 028 Ib per cubecause when heated above their critical with increasing hardness Highstrength in 7780 Kgm3 are slightly lower 1600F or 870C and cooled highcarbon Type 440A exhibits lower those of the carbon and alloy steels Asrapidly a metallurgical structure known as toughness than Type 410 Nickel a result they have excellent is obtained In the hardened increases toughness and Type 414 has damping the steel has very high strength a higher level of toughness than Type The martensitic stainless steels areand hardness but to obtain optimum 410 at the same strength level generally selected for moderate resistance ductility and impact Martensitic grades exhibit a ductile to corrosion relatively high strength andstrength the steel is given a stress brittle transition temperature at which good fatigue properties after suitable heatrelieving or tempering treatment usually notch ductility drops very suddenly The treatment Type 410 is used for fastenersin the range 300700F 149371C transition temperature is near room machinery parts and press plates If Tables 12 13 and 14 give the chemical temperature and at low temperature greater hardenability or higher and mechanical properties about 300F 184C they become very is required Type 414 may be used andof martensitic grades in the annealed and brittle as shown by the data in Figure 19 for better machinability Types 416 orhardened conditions This effect depends on composition 416 Se are used Springs flatware knife The martensitic stainless steels fall into heat treatment and other variables blades and hand tools are often madetwo main groups that are associated with Clearly if notch ductility is critical at from Type 420 while Type 431 is frequentlytwo ranges of mechanical properties room temperature or below and the used for aircraft parts requiring high yieldlowcarbon compositions with a maximum steel is to be used in the hardened strength and resistance to shock of about Rockwell C45 and the condition careful evaluation is required consumes most of Types 440A and Bhighercarbon compositions which can If the material is to be used much below whereas Type 440C is frequently used forbe hardened up to Rockwell C60 The room temperature the chances are that valve parts requiring good wear hardness of both groups in the Type 410 will Highcarbon martensitic condition is about Rockwell not be satisfactory While its notch ductility steels are generally not recommendedC24 The dividing line between the two is better in the annealed condition down for welded applications although Typegroups is a carbon content of to 100F 73C another type of stainless 410 can be welded with relative 015 steel is probably more appropriate Hardening heat treatments should follow In the lowcarbon class are Types 410 The fatigue properties of the forming operations because of the poor416 a freemachining grade and 403 a martensitic stainless steels depend on forming qualities of the hardened grade The properties heat treatment and design A notch in aperformance heat treatment and structure or the effect of a of these three stainless steels environment can do more to reduceare similar except for the better fatigue limit than alloy content or of Type 416 treatment On the highcarbon side are Types Figure 20 gives fatigue data for Type440A B and C 403 turbine quality stainless at three Types 420 414 and 431 however test temperatures The samples weredo not fit into either category Type 420 smooth and polished and thehas a minimum carbon content of 015 atmosphere was airand is usually produced to a carbon Another important property is of 0304 While it will not or wear resistance Generally the harderharden to such high values as the 440 the material the more resistance totypes it can be tempered without abrasion it exhibits In applications loss in corrosion resistance corrosion occurs however such as inHence a combination of hardness and coal handling operations this ductility suitable for cutlery or rule may not hold because the oxide filmplastic molds is attained is continuously removed resulting in a Types 414 and 431 contain 125 high apparent rate250 nickel which is enough to increase Other mechanical properties but not enough to make martensitic stainless steels such asthem austenitic at ambient temperature compressive yield shear strength areThe addition of nickel serves two purposes generally similar to those of carbon and1 it improves corrosion resistance alloy steels at the same strength levelbecause it permits a higher chromium physical and 2 it enhances toughness of Type 410 are shown in Table 10 The Martensitic stainless steels are subject property of most interest is modulus ofto temper embrittlement and should not elasticity The moduli of the martensiticbe heat treated or used in the range of stainless steels 29 x 106 psi 200 GPa800 to 1050F 427566C if toughness is are slightly less than the modulus ofimportant The effect of tempering in this carbon steel 30 x 106 psi 207 GPa butrange is shown by the graph in Figure are markedly higher than the moduli of18 Tempering is usually performed other engineering materials such asabove this temperature range aluminum 10 x 106 psi 67 GPa Hardening 260 ksi 1793 MPa tensile can be Precipitation hardening Steels achieved exceeding even those of steels have high strength relatively good The principle of precipitation hardening the martensitic stainless steels while ductility and good corrosion resistanceis that a supercooled solid solution corrosion resistance is usually superior at moderate temperatures They aresolution annealed material changes its nearly equal to that of Type 304 utilized for aerospace structure on aging The stainless Ductility is similar to components fuel tanks landing gearprincipal advantage is that products can corresponding martensitic grades at the covers pump parts shafting boltsbe fabricated in the annealed condition same strength level Table 15 shows the saws knives and flexible bellowstypeand then strengthened by a relatively chemical composition and the nominal expansion 9001150F 482620C mechanical properties of four AlSl Physical properties of UNS S13800 aretreatment minimizing the problems standard precipitation hardening shown in Table 10associated with stainless steels in solution treated andtreatments Strength levels of up to age hardened conditions1213

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