Improvement of the Straightness of Flame Cut Edge

Abstract

The straightness of flame cut edge is often quite unsatisfactory to a great extent, and this is causing many troubles in the works done after cutting, especially in the submerged-arc welding. In this report the authors have clarified the factors affecting the straightness and the efficiency of the water cooling method which we have tried to obtain perfectly straight edge. The essential particulars of the results are as follows : (1) Besides the accuracy of the machine itself, there exist three major factors affecting the straightness. The first is the plate motion in lateral direction, the second is distortion during cutting and the third is shrinkage distortion after cutting. The former two cause deviation of the line to be cut from the path of the cutting tip. (2) Of course these distortions are caused by the cutting heat, and experimental formulas, which can predict the heat absorbed by plate and the consequential distortions, have been obtained. (3) The water cooling reduces these distortions, and under the optimum cooling condition the straightness is improved very noticeably. This condition can be learned by a calculation. (4) The beneficial water cooling like this, on the other hand, lowers the notch toughness of the steel in as-cut condition. This seems to be due to the more intense quench-hardening of the cut edge by accelerated cooling. However, this behavior is of little significance as the cut edge will be welded subsequently.