Oxy-acetylene Welding Practice ... by Robert Joseph Kehl Chicago American school

Author:Robert Joseph Kehl , Chicago American school
Language: eng
Format: epub
Publisher: American technicalsociety
Published: 1920-03-25T05:00:00+00:00

chamfered or beveled to form a V-groove, the width of this V being equivalent, or nearly so, to the thidmess of the metal.

Expansion and G)ntraction. With heavy sheet, expansion and contraction are cared for by observing the same rules of spacing, Fig. 58, and clamping. Fig. 59, or,-in some cases, tacking, in order to hold the work in position for welding, as described for light sheets on page 47.

Welding Heavy Sheet* Select a welding head and a piece of iron welding rod of the proper size to accomplish the work in hand.

Because steel is sensitive to the carbonizing and oxidizing flames, it is necessary to maintain the correct oxygen pressure and a neutral flame at all times. In ordinary heavy sheet welding there are two general methods of procedure, either of which will produce a good weld when properly executed. These methods may be called welding by sections, and continuous welding.

Welding by Sections. Welding is started by first playing the flame of the blowpipe along the edges of the pieces to be welded. This is done merely as a preliminary heat treatment. The flame is then played on the bottom of the groove at the beginning of the weld until the edges are in a molten condition, at which time the blowpipe is momentarily withdrawn and the molten metal allowed to flow together. This is done without the aid of any filling material. Care must be exercised at this point, because successful welding depends upon complete penetration and perfect union of the bottom edges. When a perfect union of the two members is secured for about one or two inches, the welding rod is brought into use. By playing the flame around the welding rod in contact with the edges of the weld instead of directly on the welding rod, it is possible to bring them both to the point of fusion simultaneously. The rod is then gradually added to the weld, layer by layer, until this particular section of the weld is built up to the required height. The flame is then played on the face of the metal just added and on the bottom of the groove until fusion of these parts is secured. The welder then repeats the operation described above imtil the next small section of the groove is filled up to the proper level. The welding progresses by means of these small sections, each being built up completely before another is started.

While the metal is in a fused condition, the velocity of the flame will cause the molten metal to become slightly indented. The flame should be withdrawn momentarily, from time to time, thus

allowing the fluid metal to flow back to its nonnal level, in which position it will solidify. Skill in steel welding depends greatly on this manipulation, as the flowing together of the different molten centers produces the weld.

Contimuyus Welding. In this method the weld advances continuously with each addition of metal. By this method the metal is added in short layers, sloping rather than horizontal.

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