Effect of postweld heat treatment on interface microstructure and metallurgical properties of explosively welded bronze-carbon steel

The effects of postweld heat treatment on the microstructure and metallurgical properties of a bronze-carbon steel (st37) explosively bonded interface were studied. Explosive welding was done under 1.5- and 2-mm standoff distances and different conditions of explosive charge. Samples were postweld heat treated for 4 and 16 h in the furnace at 250 A degrees C and 500 A degrees C and then air cooled. Laboratory studies using optical microscopy, scanning electron microscopy, and microhardness testing were used to evaluate the welded samples. Microstructural examinations showed that by increasing the standoff distance and the explosive charge, the interface of bronze to steel became wavier. The microhardness test result showed that the hardness of the samples was higher near the joint interface compared with other areas because of the intensive plastic deformation, which was caused by the explosion force. The results show that increasing the heat treatment temperature and time caused the intermetallic compounds' layer thickness to increase, and, because of the higher diffusion of copper and tin, the iron amount in the intermetallic compounds decreased. Also, because of the increase in heat treatment temperature and time, internal stresses were released, and the interface hardness decreased.