The Effects of Alloying Elements on Weldability

Abstract

The most important problem in welding high strength steels is weld cracking sensitivity in the heat affected zone.
The weld cracking is said to be caused by the diffusible hydrogen in the weld metal, metallurgical hardening effect and restraining forces.
In this study the effects of alloying elements on some weldability tests and mechanical properties were investigated by the use of design of experiment.
The conducted weldability tests were y-slit type weld cracking test, TRC-test (tensile restraint cracking test) and maximum hardness test.
The test results are summarized below. 1) The alloying elements which affected the y-slit type cracking test results were found to be C, Mn, Cr and B.
There was remarkable interaction between the effect of C and that of Mn, i.e. the increase of C content raised the injurious effect of Mn and the same thing could be said about the case of Mn.
The weld cracking sensitivity was affected by C and Mn substantially.
2) From the result of TRC-test, it was found that the critical stress, cc, was lowered by C, Mn, Mo, Cr and Ni. The effect of C was much greater'than those of the other alloying elements.
Certain correlation could be seen between the y-slit type cracking test results and the critical stresses.
3) The maximum hardness of weld heat affected zone was raised by almost all the alloying elements. But these effects had the tendency to saturate in the upper range.
There was little correlation between the cracking sensitivity and maximum hardness.
4) The tensile strength was raised by Mo substantially.
There was certain interaction between the effect of C and that of Mn in the Charpy transition temperature.