MAKING AND WORKING OF WROUGHT IRON 395 



The process of welding, as already stated, consists in joining 

 two pieces of wrought metal at a white heat. The metal pieces 

 at this temperature are in a plastic or semifused condition and 

 when placed together and properly hammered readily unite, 

 causing a solid body or j oint. It is necessary to take the metals 

 from the fire at just the proper time. If removed too early, the 

 pieces cannot be successfully welded, and if left in the fire too 

 long, the metal will be burned and rendered useless for service. 

 Great care should be exercised in heating both pieces evenly 

 and to the same temperature. 



Unless the iron or steel is properly heated a scale will form 

 which prevents the uniting of the two pieces. This scale or 

 oxide melts at a lower temperature than the iron, and as a 

 result the weld will be good if the proper heat has been secured. 

 When using soft steel or Norway iron, the scale melts at a 

 higher temperature than the welding heat and to overcome 

 this difficulty, it is necessary to use a flux to soften or melt 

 the scale. 



Fluxing is the application of some good welding prepara- 

 tion to the joint. A good, clean beach sand serves the pur- 

 pose, as it melts and combines with the scale, causing it to 

 liquefy, in which form it is easily forced from between the 

 pieces to be welded. For welding tool steel to iron or soft 

 steel, the flux consists of borax and sand. 



444. Welding Processes. There are two classes of weld- 

 ing forge or pressure welding, and autogenous welding. 

 Forge or pressure welding is applied to two pieces of metal 

 heated to a plastic state, which are forced together by pres- 

 sure or hammering. The familiar example of this is the weld 

 which the blacksmith makes by heating two pieces of steel or 

 iron in the forge fire and then hammering the ends together 



