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Aviation History
1937
1937 - 1107.PDF
APRIL 29. 1937 23 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT 420c Fig. 4 (Right).—Aluminium weld, cold-hammered and blowpipe-annealed. and the mechanical properties are rendered equal to or better than the unwelded sheet. The structure of a ham mered and annealed weld in aluminium is shown in Fig. 4, and the improvement is very evident. Not only does hammering cause a refinement in struc ture, but it also helps to relieve contractional stresses, to remove surface porosity and to consolidate the surface of the weld. The choice of a welding rod depends, of course, upon the nature of the material being welded and the class of work. There are three main classes of rods in general use —pure aluminium, silicon-aluminium and copper-alumin ium. We shall proceed to give a few notes on the nature, properties and uses of these three welding rods. Welding Rods Pure Aluminium Welding Wire.—This rod is composed of commercially pure aluminium. It contains about 99.3 per cent, or more pure aluminium, the remainder being small amounts of silicon, iron, etc. The mechanical pro perties of an all-weld-metal specimen deposited by the oxy- acetylene flame are as follows, the microstructure of such a specimen being that shown by the micrograph (Fig. 5). Yield stress . . . . 1.6 Tons/sq. in. 4.1 Tons/sq. in. 38.0% in 2in. 13-7 12.8 ft./lb. Ultimate stress Elongation Brinell Hardness Izod Impact Value This rod is widely used for the welding of sheet alumin ium for petrol tanks, oil tanks, foodstuff containers, chemi cal plant and aluminium vessels of all kinds and descrip tions. The pure aluminium welding wire should always be used for the welding of aluminium articles which are subsequently submitted to "anodic" treatment. •4??. 1 ;^-i h f$m •• * V V-,-; ' '• * "v >;£• -'\ '••>•- X- U.!Vi-*?V^ f* y »W„ tf.iSH ..." ^~^sv*-5c"=3? ^-T™*; "V i- ', w .'s^ ' i-§^. - . ^ ** ". r1^ ? ,;-.-. • *./ < • ^:" •. "•**""" - .j-if- -^ jri*< «• ^fe^^ *" "'-"il *~, .• ., -:*"•*-! •' •";S-^-\" *S5p >' —^? „. s A* ,:" BS*»«ftsiJ**wj*.-----¥ ' "'"-"V ij^%^ >*C--f^tv :; A, • ~i - ',^'^' X- ' *'r.-^e f7-.--^-J- "- ]&:X'£E >: •>?;• =>HC? I \i i-J;-;.-fe- *~VP^' -•'^ *>* * s-^' ^^w .s-A • i --x,,.-^*- '^cv *'-" ' V.—T . HJS^- 0 • »-. • *^?»(rf*^ •*»v-~ « >i.' ^..., ^*-,.. ;. - wi • • rV-J '*» Fig. 5.—Pure aluminium welding wire. Fig. 6.—Five per cent, silicon-aluminium. This welding wire should be used when a rod having a slightly lower melting point than pure aluminium is required. The deposit has greater tensile strength and hardness than pure aluminium.
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