Lincoln Electric Welding Tools & Equipment Users Guide

1 Stainless SteelsWelding GuideSTAINLESS STEELSPROPERTIES HOW TO weld THEMWHERE TO USE THEMA description of the physical and mechanical properties of avariety of commercial stainless steels. Recommendations on theapplications of each type and how to arc weld each includingfiller OF Introduction .. Types of Stainless Ferrite Austenite Neutral Weldability of Stainless Steels .. Ferritic Stainless Martensitic Stainless Austenitic Stainless Hot Precipitation Hardening Stainless Duplex Stainless Physical Properties.

2 Mechanical Properties .. Selection of a Stainless Design for Welding Stainless Selection of Filler Metals .. Selection of a Welding Shielded Metal Arc Submerged Arc Gas Metal Arc Flux Cored Arc Gas Tungsten Arc Procedures for Welding Stainless Welding with the ShieldedMetal Arc Welding with the Submerged Arc Welding with the Gas Metal Arc Welding with the Gas Tungsten Arc Process2 Welding OF STAINLESS INTRODUCTIONS tainless steels are defined as ironbase alloys which contain at chromium.

3 The thin butdense chromium oxide film whichforms on the surface of a stainlesssteel provides corrosion resistanceand prevents further oxidation. Thereare five types of stainless steelsdepending on the other alloyingadditions present, and they rangefrom fully austenitic to fully TYPES OF STAINLESS STEELSA ustenitic stainless steelsincludethe 200 and 300 series of whichtype 304 is the most common. Theprimary alloying additions arechromium and nickel. Ferriticstainless steelsare non-hardenableFe-Cr alloys. Types 405, 409, 430,422 and 446 are representative ofthis group.

4 Martensitic stainlesssteelsare similar in composition tothe ferritic group but contain highercarbon and lower chromium topermit hardening by heat 403, 410, 416 and 420 arerepresentative of this group. Duplexstainless steelsare supplied with amicrostructure of approximately equalamounts of ferrite and contain roughly 24% chromiumand 5% nickel. Their numberingsystem is not included in the 200,300 or 400 groups. Precipitationhardening stainless steelscontainalloying additions such as aluminumwhich allow them to be hardened bya solution and aging heat are further classified into subgroups as martensitic, semiausteniticand austenitic precipitation hardeningstainless steels.

5 They are identifiedas the 600-series of stainless steels( , 630, 631, 660).The alloying elements which appearin stainless steels are classed asferrite promoters and austenitepromoters and are listed FERRITE PROMOTERSC hromium provides basiccorrosion provides hightemperature strength and increasescorrosion (Columbium), Titanium strong carbide AUSTENITE PROMOTERSN ickel provides high temperaturestrength and carbide former, increases strength,reduces EFFECT Regarding Austenite & FerriteManganese sulfide formerSilicon wetting agentSulfur and Selenium improvemachinability, cause hot cracking in WELDABILITY OF STAINLESS STEELSMost stainless steels are consideredto have good weldability and may bewelded by several Welding processesincluding the arc Welding processes,resistance Welding .

6 Electron andlaser beam Welding , friction weldingand brazing. For any of theseprocesses, joint surfaces and anyfiller metal must be coefficient of thermal expansionfor the austenitic types is 50%greater than that of carbon steel andthis must be considered to minimizedistortion. The low thermal andelectrical conductivity of austeniticstainless steel is generally helpful inwelding. Less Welding heat isrequired to make a weld because theheat is not conducted away from ajoint as rapidly as in carbon steel. Inresistance Welding , lower current canbe used because resistivity is steels which require specialwelding procedures are discussed inlater FERRITIC STAINLESS STEELSThe ferritic stainless steels to 30% Cr, up to C andsometimes ferrite promoters Al, Nb(Cb), Ti and Mo.

7 They are ferritic atall temperatures, do not transform toaustenite and therefore, are nothardenable by heat treatment. Thisgroup includes the more commontypes 405, 409, 430, 442 and Ilists the nominal compositionUNSC omposition - Percent * x %C min. ** Mo430 FSe** min. Se430Ti x %C - Ti Mo;5 x %C (Cb) + Mo, + 4 (%C + %N);(Ti +Nb(Cb) ) N18-2FM** Al; Mo; ;(E-Brite) Cu; (Ni+Cu)26-1Ti Mo; N; Cu; Mo29-4-2 MoMonit Mo; (Ti + Nb(Cb) )Sea-cure/ Mo.

8 + 4 (%C + %N)(Ti + Nb(Cb) )of a number of standard and severalnon-standard ferritic stainless are characterized by weld andHAZ grain growth which can result inlow toughness of weld the ferritic stainless steels,filler metals should be used whichmatch or exceed the Cr level of thebase alloy. Type 409 is available asmetal cored wire and Type 430 isavailable in all forms. AusteniticTypes 309 and 312 may be used fordissimilar joints. To minimize graingrowth, weld heat input should beminimized, Preheat should be limitedto 300-450 F and used only for thehigher carbon ferritic stainless steels( , 430, 434, 442 and 446).

9 Manyof the highly alloyed ferritic stainlesssteels are only available in sheet andtube forms and are usually weldedby GTA without filler MARTENSITIC STAINLESS STEELSThe martensitic stainless steelscontain 11 to 18% Cr, up to Cand small amounts of Mn and Niand, sometimes, Mo. These steelswill transform to austenite on heatingand, therefore, can be hardened byformation of martensite on group includes Types 403, 410,414, 416, 420, 422, 431 and standard and non-standardmartensitic stainless steels are listedin Table II.

10 They have a tendencytoward weld cracking on coolingwhen hard brittle martensite and carbon content of thefiller metal should generally matchthese elements in the base 410 filler is available as coveredelectrode, solid wire and cored wireand can be used to weld types 402,410, 414 and 420 steels. Type410 NiMo filler metal can also beused. When it is necessary to matchthe carbon in Type 420 steel, Type420 filler, which is available as solidwire and cored wire, should be 308, 309 and 310 austeniticfiller metals can be used to weld themartensitic steels to themselves or toother steels where good as-deposited toughness is and interpass tem pera turein the 400 to 600 F (204 to 316 C)range is recommended for most3*Single values are maximum values.