MARTENSITE FORMATION A THREAT TO WELDED JOINTS.

The welding of reinforcing bars - to other structural members, in the construction of wire cages, or to each other - is becoming increasingly common in reinforced concrete construction, a situation which is not surprising since welded connections provide convenience and speed both to designer and contractor. It is, of course, essential that the welds be of good quality: anything less is likely to lead to delay and attendant costs at the very least and, at worst, collapse of the structure. In three fairly recent cases welding of reinforcing bars was not carried out according to good practice. In each case the metallurgical problem was basically the same: the reinforcing bar was a medium or high carbon steel which had been welded and in which the heat-affeced zones of the weld junctions transformed to (brittle) martensite on cooling.