Abstract
The heat treatment deformation of steel products is reviewed and the thermal stress, which is one of the initiators of the deformation, is theoretically analysed taking into account transformation. Other initiators are also discussed, i.e. stress relaxation on heating, creep at high temperature, and change of microstructure on tempering. It was found that the thermal stress during quenching changes the profile of steel products, decreased long axis, increased short axis, and convex cross–section for non–hardenable and for marquenched or oil–quenched small steel parts, and increased long axis, decreased short axis, and concave cross–section for water/oil–quenched hardenable steels. These differences are the results of the different strain hardening rates of the various phases and the temperature distribution through the cross–section over the temperature range of martensite transformation. Some solutions to the problems of deformation are also discussed.
MST/21
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