Comparison of the Influences of Phosphorus and Sulfur on the Reheat Cracking Sensitivity of Cr-Mo Steels

概要

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The influences of phosphorus and sulfur on the reheat cracking sensitivity of 1%Cr-0.5%Mo steels were investigated using experimental steel specimens doped with phosphorus or sulfur. The cracking sensitivity was evaluated by terms of critical restraint stress obtained by an implant test. And the metallugical experiments were made on the phosphorus segregation to the austenite grain boundary, and on the diffusible sulfur concentration. Phosphorus segregation was measured by the grain boundary etching method, and sulfur was measured dividing into dissolved sulfur in iron matrix and combined sulfur as sulfide. As the results of the cracking tests, it was found that there exists a critical content of phosphorus for the reheat cracking sensitivity, above which the cracking sensitivity is steeply increased with an increasing phosphorus content. When the phosphorus content exceeds the critical value, it segregates to austenite grain boundary during welding and its segregation is intensified by tempering after welding. In the case of sulfur-doped steels, the dissolved sulfur concentration is the major factor governing the cracking sensitivity. The critical value of its concentration, above which the cracking sensitivity is steeply increased, was determined. The dissolved sulfur concentration depends both on the bulk sulfur and manganese contents.
Faculty of Engineering, Mie Universityの論文
1988-12-20