1989 Volume 7 Issue 4 Pages 496-501
Influence of alloying elements in the matrix of the Heat-Affected Zone on the stress relaxation behavior during the reheat treatment process was studied. Reheat cracking tests on 3 type High Tensile strength steels (2 type H.T. 80 and H.T. 100) were carried out by means of ring type specimens and three point bending method. Influence of microstructure of synthetic HAZ at high temperature during the reheat treatment process was investigated by atomic absorption spectrometry and scanning electron microscopic observation. The relation between alloying elements concentration of the precipitated carbides and their concentration in the matrix of synthetic HAZ were investigated. The results are summarized as follows.
1) The critical stress of Lath-martensitic structure specimens (Water Quenched) was higer than that of Bainitic-Ferritic structure specimens (Air Cooled).
2) The reheat cracking susceptibility could be explained by the stress relaxation behavior of specimens and change of alloying elements concentration in the matrix during the reheat treatment process.
3) Air cooled specimens which showed the higher cracking susceptibility had not so many alloying carbides and showed a poor deformability. Water quenched specimens, lower cracking susceptibility had many precipitates and showed a good deformability.
4) The concentration of alloying elements (Mo+V) in the matrix showed a good correspondence to the stress relaxation behavior. Decreasing of (Mo+V) concentration in the matrix leads to a good deformability of the matrix.