Aluminum is very sensitive to oxygen; so an excess of acetylene in the flame is desirable when welding it. The metal does not run readily and must be puddled into place with a rod of iron. It should be hammered to toughen after welding, has a low melting point, and is difficult to weld. Figs. 115 and 110 show a successful piece of work with an aluminum casting.
Fig. 115. Broken Aluminum Outing Courtesy of Davis-Bournonville Company.
Fig. 116. Aluminium casting Welded by Gas Toreh Courtesg 0f Davis-Bournonville Company.
Brass can be welded readily with a moderately large flame, but the cone of the flame should be kept away from the metal. Borax is used as a flux for brass and the weld is usually not very strong because the material after being melted is merely cast brass.
Fig. 117. Split Steel Bolster Welded by Gas Torch Courtesy of Oxweld Acetylene Company.
Fig. 118. Immense Shear Casting Broken and Welded by the Gas Torch Courtesy of Davis-BournoneiUe Company.
Copper should be welded with a low temperature flame and hammered afterwards to restore its toughness. Acetylene attacks copper, so care must be exercised to see that there is no excess in the flame as it may form acetylide of copper, which is a fulminate and can be exploded by striking with a hammer, or even by high friction.
Cast iron can be welded but is very liable to crack when cooling, so careful preheating is necessary before welding and slow cooling afterwards. High silicon cast-iron melt-bars, which are low in sulphur and phosphorus, are used, and borax forms this flux. Cast iron runs freely and a mold should be made around the spot to be welded to retain it, and the work must be done horizontally.
Wrought iron becomes cast iron when it cools - unless it is very tow in silicon - and as it loses its structure it should be hammered to toughen it. It does not readily melt to a fluid but becomes a sort of thin paste and must be worked into place with the melt bar.
Fig. 119. Section of Boiler Flue Ready toiWeld.
Fig. 120. Welded Boiler Flue.
Courtesy of "The American Machinist".
Steel, with a small percentage of carbon, welds more easily than high carbon steel, and the carbon is liable to burn out or so change its structure near the weld as to destroy its essential properties. High carbon steels require careful heat treatment after welding to restore their original properties, and soft steel should be hammered to toughen it. Steel may be welded to iron or copper by proper manipulation but these are uncertain operations and are very seldom necessary.
Alloys of nearly all kinds may be welded with oxy-acetylene apparatus; the principal point to look out for is to be sure that the composition of the alloy is known before starting. If the flame is adjusted to suit the most sensitive metal and its action watched, there should be no serious trouble.
The applications of oxy-acetylene welding are almost as numerous as are the articles to be welded and apparatus of this type is in use in almost all lines of manufacture and repair. The low cost of the apparatus helped to give this system its present foothold and in many lines it has given entire satisfaction, especially on light work and where convenience is of greater importance than the cost of operation. Castings, forg-ings, sheets, and tubes of iron, steel, Fig. 118, copper, aluminum, etc., may be welded within the limitations just mentioned, and there is apparently no limit to the size of the piece which may be handled successfully, Fig. 118. Large articles cost more in proportion than small ones because of the greater amount of heat wasted in keeping them hot, but users of the system weld practically everything that comes along. Steel tanks are frequently welded instead of being riveted; car roof seams are welded instead of being soldered; steel furniture is welded in all the joints; cracked cast-iron cylinders are welded; boilers are patched and the flues welded in, Figs. 119 and 120; engine frames, crank cases, and automobile frames are repaired by welding. A good weld is stronger than a riveted joint and the cost is about the same.
The cost of acetylene welding is very moderate on work of small or medium size but it becomes somewhat high on large work on account of the relative amount of heating to be done while welding. However, the advantages to be gained in quantity of production and even more so in cases of repairs because of the cost of new pieces, makes the system very valuable in many establishments. The cost of welding sheet steel per foot of length of seam is given in Table XIV and it will be interesting to compare this with the cost of doing the same work with the electric-arc system. This table was furnished by the Davis-Bournonville Company.
It is difficult to get accurate figures on the cost of doing miscellaneous repair work because the average repair man does not like to tell, but the following are the charges made in one automobile repair shop and will give an idea of what such work costs because the profits charged are usually 100 per cent of the cost.
Thickness of Metal in Inches
Consumption of Acetylene in Cu. Ft.
Consumption of Oxygen in Cu. Ft. Per Hour
Proper Pressure in Pounds for
Cost of Labor Per Hour
Total Cost Per Hour
Cost per Lineal Foot
1/32 to 1/16
8 to 10
1/16 to 3/32
10 to 12
3/32 to 1/8
12 to 14
1/8 to ¼
14 to 18
¼ to 5/16
18 to 22
5/16 to 7/16
20 to 25
1/16 to ½
22 to 27