4-47. WELDING OF VARIOUS ALLOYS.

T.O. 1-1A-9 w. ZE10A - Used for low cost, moderate strength sheet and plate. No stress relief required after welding. Hot work at 500 900°F. Anneal 400F. Weld by shielded arc or resistance methods. AZ61A or EX33A rod is preferred for welding. x. ZE41A - A good strength, pressure tight, weldable alloy, where temperatures are below 200 F. Age 2 hours at 625F, air cool; 16 hours at 350F air cool. Shield arc weld with EZ33A rod, then stress relieve. Foreign equivalent British RZ5. y. ZH42A - Used in sand castings for aircraft engines and airframe structures where high strength at room temperatures and moderate long-time creep resistance at temperatures up to 480 F are required. The alloy is a precipitation hardening one from the as-cast condition and requires no solution heat treatment. Minimum hardness is developed at 480°F in 24 hours. More ductility and better shock resistance may be obtained by overaging at temperatures such as 7500°F. For T51 condition treat at 480°F for 24 hours; T4 condition 750 F for 24 hours. Weld by shield arc method using ZH42A, ZH62A or EZ33A rod in that order. z. ZH62A - Used as a high strength good ductility structural alloy at normal temperatures and has the highest yield strength of any alloy except ZK61A-T6. Heat treat at 480F for 12 hours. Weld with shielded arc using ZH62A or EZ33A rod then stress relieve. Foreign equivalent is British T26. aa. ZK21A - An alloy of moderate strength for extrusion fabrication. Good weldability using shielded arc and AZ61A or AZ92A, rod. Resistance welding also satisfactory. ZK51A - Used for high yield strength, good ductility, sand castings. Heat treat for 12 hours at 350F. Weldable to a limited degree using shielded arc and EZ33A or base metal rod. Stress relieve after welding. Foreign equivalent is British Z52. ab. ZK60A - Used as a wrought alloy for extruded shapes and press forgings. Has high strength and good ductility characteristics. Hot work at 600°7500F. Shortness temperature is 950°F. Age at300°F for 24 hours, air cool. Use resistance or shielded arc welds for joining although arc welding is somewhat difficult since the alloy is susceptible to hot short crack ring. Use AZ92A welding rod. Crack force welds exhibit high efficiency. Foreign equivalent is German ZW6. ac. ZK61A - Casting Alloy. Solution heat treat at 925-935F for 2 hours or 895-905 F for 10 hours. 4-47. WELDING OF VARIOUS ALLOYS. 4-48. Tables 4-10 and 4-11 provide information relative to the welding of various alloys. Successful welding of the varied alloys can be accomplished by one or more methods such as inert-gas welding, gas welding and resistance welding which includes spot, seam and flash methods. In any of these methods fusion of the metal is done at comparatively low temperatures because of the metals' low melting point, low fusion heat and specific heat per unit volume. Distortion should be guarded against since the high thermal-conductivity and high thermal expansion co- efficient of the metal will lead to this condition unless precaution is exercised. Another factor that requires special attention to prevent detrimental effects while welding with arc or gas methods, is the characteristic of the metal to oxidize very fast when heated to its melting point in normal atmosphere. This characteristic can be successfully overcome by shielding the metal with an inert gas during arc welding and a suitable flux when the gas type is used. 4-49. WELDERS TRAINING AND QUALIFICATION . Personnel assigned to accomplish magnesium welding must meet the qualification requirements of MIL-T5021, Tests, Aircraft and Missile Welding Operators qualification. In addition, they should be trained in fabrication procedures, identifying magnesium alloys and their composition, blue print reading, cleaning and treating methods, safety rules and procedures and use of applicable hand and machine tools. Personnel proficiency should be maintained at a high level by periodic testing in accordance with MIL-T-5021 and inspection of the workmanship of the individual. Al parts produced must meet the requirements of their applicable specifications, i.e., blueprints, drawings technical orders, etc. 4-50. As the alloy element content is increased the solidification temperature range increases proportionally, and the melting point and shrinkage decreases Alloys with up to 10% aluminum content are most weldable. Hot shortness or cracking tendencies under heat Is increased by the zinc content. 4-51. Failure in material in the area of welds can be a result of base metal grain growth caused by the weld heating cycle or from the annealing overaging effects of the weld temperatures on the metal. Cracking in the weld or weld area some time after welding may be from the effects of stress corrosion caused by the failure to properly relieve stress built up by heat during welding. Stress relieving is discussed in paragraph 4-76 and under discussions on welding methods. 4-22