| 摘要 |
PURPOSE:To reduce residual stresses and to maintain strength and toughness by subjecting a roughly formed roll die material which is austenitized prescribed temps. to a heat treatment under prescribed conditions. CONSTITUTION:A roughly formed roll die material consisting of material of high strength and high toughness die steel type is heated at 1,000-1,100 deg.C, whereby it is austenitized. Such high temp. material is immersed successively in the 1st stage hot bath of a middle temp. of 500 deg.C and in the 2nd stage hot bath of a low temp. of 250 deg.C, whereby it is cooled. In the 1st stage bath, the material is quickly cooled at such cooling rate at which it does not get to the nose in the transformation region of pro-entectoid carbide, pearlite, etc. and in the 2nd stage bath, it is cooled down to the temp. right above the martensite transformation region in a short time in such a way that it does not get to the nose in the bainite transformation region. Thereafter, the material is allowed to cool with air, whereby it is hardened. |
