前言强度为800MPa级的螺栓,一般使用S45C(相当中国的45号钢)等中碳钢。为了提高锻造时的成型性,首先要进行预先热处理——球化退火处理。其后,为了得到所规定的机械性能,进行淬火回火处理,即所谓调质型工艺。通过省略工序来降低成本,已成为螺栓工业界的重要课题。日本神钢公司为了满足用户的这种要求,已经开发了不需要球化退火处理及淬火回火的非调质螺栓用线材KNCH8。非调质螺 Preface The strength of the 800MPa bolt level, the general use of S45C (equivalent to China’s No. 45 steel) and other carbon steel. In order to improve the formability of the forging, it is necessary to carry out a pre-heat treatment - spheroidizing annealing treatment. Thereafter, in order to obtain the prescribed mechanical properties, a quenching and tempering treatment, a so-called quenching and tempering process, is performed. Reducing costs by omitting processes has become an important issue in the bolt industry. In order to meet this requirement of users, Kobelco has developed KNCH8, a non-tempering bolt wire that does not require ball annealing and quenching and tempering. Non-Tweezer