Studies on the Thermit Welding of Reinforcing Bars (Report 3)

On Research for the Effect of Heat Input, Shape of Groove and Heat Treatment on Weld Joint

Abstract

The use of self-preheating thermit welding for reinforcing bars had been investigated and described by the author in the previous reports.
In order to determine the field-welding condition, in this report, the author applied the method which had been developed in ealier work, and studied the soundness of weld joint in changing heat input, shape of groove and heat treatment.
The results are as follows :
1) The increasing of heat input resulted in some effects on penetration and impact value. However, tensile strength changed slightly with the increasing of heat input.
Conclusively, little effective change resulted in weld joint with going as high as about 60% of heat input.
2) Although the change of cutting methods of reinforcing bars such as saw, gas and shear cutting resulted in shape of groove, the change of them had no effect on joint strength.
Oil, paint and rust produced bad effects on joint strength.
3) Sufficient joint strength was obtained even in as-welded condition, but better results were gained by normalizing in a short time. For example, the number of repeating bending test and the value of V-notch Charpy at 0°C increased about twice as compared with those of as welded.
4) The welding of different sizes of reinforcing bars was possible when the difference in diameter was not more than 6 mm.