78 MODERN SCIENCE READER 



In the apparatus that is used for welding the same 

 two oxygen and hydrogen bottles are used and the gas is 

 piped from these to the same mixer that is used in cutting. 

 Here, however, the similarity ceases as the extra nozzle for 

 oxygen is not used. A torch with a single nozzle is sub- 

 stituted and the gas that enters the torch is piped through 

 a single pipe from the mixer ; thus only one line of armored 

 hose, leading to the torch, is needed in place of the two. 



The welding done by this method leaves the metal its 

 ductility. If the welded joint is submitted to a slight 

 hammering, while it is cooling down to a dull red, or even 

 to a heat treatment after it has cooled, the steel in most 

 cases can be brought back to its original structure and the 

 joints can be made nearly as strong as the original metal. 



In welding thick plates, say from three eighths of an 

 inch upward, by any of the fusion methods, it is usual to 

 bevel or chamfer the two edges of the joints and fill the V 

 thus formed by melting metal from a rod, with the torch. 

 If the metal is properly fused by this method a fairly good 

 joint is obtained, but if the operator allows globules of 

 metal to fall from the rod and drop on metal which has 

 not been properly melted, the two do not fuse together and 

 a poor joint is the result. 



The German Oxyhydric Company adopted a different 

 method of welding metals from three eighths to one inch 

 thick, and have made many successful welds thereby. This 

 method is to put the two ends of the metal together with- 

 out overlapping, but in contact with each other. They are 

 thus heated by two oxyhydric torches, one above and the 

 other below the metal, and exactly opposite each other, and 

 are given as extensive a heating zone as possible. 



When the metal begins to show signs of melting on the 

 outside, the interior of the sheets are doubtless at a white 

 welding heat; the torches are then removed and an anvil 

 and hammer brought into use for lightly hammering the 

 joint. This causes a readjustment of the molecules, and 

 they join together in the weld. 



