Some Experiments with the Dynamic Restraining Test Apparatus

Abstract

To study the individual and correlated effects of mechanical and thermal restraints on weld cracking behaviours of steels and electrodes, two types of dynamic cracking testers have been used in the present paper, that is, a Murex type bending cracking tester and a new type tensile cracking tester. In the latter, one piece in a butt weld specimen is tensile and can be displaced at any constant speed against the other stationary piece during or after welding at an arbitrary instant.
Dynamic cracking tests of several mild steel coated electrodes showed that these two testers were satisfactory for classifying cracking susceptibility. Among the tested electrodes, the low hyd-rogen type showed the least, the high titania type the greatest and the high cellulose and illmenite types medium. susceptibility to both hot and cold cracking of weld metal.
Stainless steel coated electrodes could be satisfactorily evaluated with this dynamic cracking tester concerning the suitability for the first pass welding of a clad steel.
Comparing the two cracking test methods, the tensile restraint cracking tester was found to be more sensitive and reproducible than the Murex type bending restraint cracking tester. An instant of weld cracking in the former tester can be determined very successfully by observing a corres-ponding discontinuous change in the tensile load across the test weld. Further studies are being continued with the tensile restraint cracking tester.