Question

22. Which of the following are common gases used for shielding in are welding? c. Oxygen a. Nitrogen b. Hydrogen f. Helium d. Argon e. Propane 23. What are the various surface hardening methods? Draw a schematic of ONE of them 24. Which of the following is/are NOT the usual objective(s) of heat treatment? a. Relieve stresses b. increase melting temperature c. reduce brittleness d. reduce density e. increase hardness f. increase recrystallization temperature 12

Answer 1

ding gases are Cnert or semi - tnert aa ses that are Commonly used tn Several weldîng Proc easesrost notably gas metal aTt veldtng and gas metal ax welding an aS t umgsten arc we lding » tmg Axgon is the common shfelding gas, uwidely used as the ba se for the more 8pec lalize as yes. Helim İs ltehter than aor largeY flow rates are required o Oxygen is used in small amounts as an addftio-n to other gases 9 kypfcally as 2-5%, add onto argom。 yd is used for welding of mtckel and Some stainess steels, es pe tiall thicker pieces . the voxious Sur^ae hardentno methodls avie 2 3 r2) s C busin r9 (3) Cyanid mg

ead may which cools the sos fate The flame h ho Integral ua ter conn eons o Comtrol, of heating cud oo openations, the tore u not affeted by treat ment The thictness ofthe hordened layer is Usually-m The Stutture of this loyer roper maytensfe The Shudue fonder lyimg la yers is troosto - martensrte Advantae There sno distbition of work pite braus e enly smaectoof Ssteeli heateod Asheating Tate is high the suafare e work γ。mains clean。 3 The process Can be easily auto math S+ vey economical fo laewo Dis ADANTAGES O Very thin section may Jet distarted erce sive Over hea ting my Case cacks APPLICA TIONs 9t ts used to impore wear resistance and Su s of pfstom pfnc , Jarge Sea*s, hand tol

heat treament - optiom bcrease methirymesa opton d reduce den sity oplion f tretaeysalzatom tempesatuse