THICK HIGH-TENSILE-STRENGTH HOT-ROLLED STEEL SHEET HAVING EXCELLENT LOW-TEMPERATURE TOUGHNESS AND PROCESS FOR PRODUCING THE SAME,申请号JP20100016828-传众专利搜索

THICK HIGH-TENSILE-STRENGTH HOT-ROLLED STEEL SHEET HAVING EXCELLENT LOW-TEMPERATURE TOUGHNESS AND PROCESS FOR PRODUCING THE SAME

申请公布号：JP2010196165(A)

申请号：JP20100016828

申请日期：2010.01.28

申请公布日期：2010.09.09

申请人：

JFE STEEL CORP

发明人：KAMI TSUTOMU;NAKADA HIROSHI;NAKAGAWA KINYA

分类号：C22C38/00;C21D8/02;C22C38/14;C22C38/58

主分类号：C22C38/00

摘要：<P>PROBLEM TO BE SOLVED: To provide a process for the production of a thick high-tensile-strength hot-rolled steel sheet which combines high strength and high toughness. Ž<P>SOLUTION: When a steel material having a composition containing 0.02 to 0.08% C, 0.01 to 0.10% Nb and 0.001 to 0.05% Ti, where C, Ti and Nb satisfy (Ti+(Nb/2))/C<4, is heated and hot-rolled, and is then subjected to accelerated cooling; the residence time from the sheet thickness central temperature T(°C) to a temperature (T-20°C) is controlled to ≤20s upon the start of the accelerated cooling, and then, accelerated cooling at a cooling rate of ≥10°C/s in the center of the sheet thickness is performed for ≤30s from the T(°C) to below a specified cooling end temperature dependent on the cooling rate, and taking up is performed at below a specified take up temperature dependent on the amounts of the alloy elements. In this way, the thick high-tensile-strength hot-rolled steel sheet, where the average crystal grain size of a ferrite phase in the center of the sheet thickness is ≤5 μm, while the structural fraction of the second phase is ≤2% and the structural uniformity in the sheet thickness direction is excellent, and low temperature toughness and, particularly, DWTT characteristics are remarkably improved, is obtained. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž