Quench Hardening and Cracking in Electron Beam Weld Metal of Carbon and Low Alloy Hardenable Steels

概要

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Using seventeen kinds of hardenable steel of plain carbon, Ni-Cr, Cr-Mo, Ni-Cr-Mo low alloy and partly 13 Cr steels the hardenability was investigated for the electron beam weld metals which were welded with a change in welding parameters and preheating temperature, Then a generalized prediction equation for the hardness of electron beam weld metal was established using the concepts of the carbon equivalent and the cooling time from 800℃ to 500℃. Hereafter the hardness of the weld metal can be estimated in advance when the chemical compositions of steel, the welding parameters, the preheating temperature and the penetration depth are given. Moreover the occurrence of four kinds of carck in weld metal, Horizontal Crack, Vertical Crack (I), Vertical Crack (II) and Cold Shut, was macro-and microscopically investigated. As a result the Vertical Crack (II) is only related to weld metal hardening, while the other cracks occur during solidification of weld metal.
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