High performance Fe-C-Mn-Si high carbon steel wire rod produced by in-line salt bath heat treatment
LI Yang1,2, ZHEN Xian-feng1,2, WANG Guang-shun1,2, ZHENG Tong-liang1,2, XU Kai1,2
1. Qingdao Branch, CITIC Pacific Special Steel Research Institute, Qingdao 266409, Shandong, China; 2. Wire Rod Research Institute, Qingdao Special Steel Co., Ltd., Qingdao 266409, Shandong, China
Abstract：In order to meet the demand of wire making industry for raw materials of thick diameter, high strength and high plasticity wire rods, Qinggang Multi-purpose In-line heat Treatment with salt bath (QMIT) process was developed and the influence of QMIT process parameters on microstructure, mechanical properties and scale of Fe-C-Mn-Si high carbon steel wire rod was studied. Compared to the traditional air-cooling process, QMIT process greatly reduces the occurrence rate of abnormal structures such as coarse pearlite, proeutectoid cementite, free ferrite, divorced pearlite and martensite in the center of wire rod. The YL82B wire rod can obtain ultra-high tensile strength of 1 215-1 325 MPa combined with the reduction of area of 40%-48% after QMIT processing. Moreover, the difference of tensile strength for all tested samples taken from one coil of wire rod is less than 35 MPa. The iron oxide scale of QMIT wire rod is divided into two layers, of which the white and bright outer layer is Fe3O4, and the gray inner layer is FeO. In addition, spherical or island proeutectoid Fe3O4 with different quantities and sizes are distributed in the inner FeO layer. With the increase of salt bath temperature, the thickness of scale layer retains the same basically, but the size and quantity of island proeutectoid Fe3O4 distributed in the inner FeO layer increase significantly. In general, QMIT process can obtain wire rods with good microstructure and mechanical properties and oxide scale easy to mechanical descaling under lower salt bath temperature.
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2023, Vol. 33 
