高强钢热轧板拉伸试样表面起皮开裂原因分析

对12 mm厚高强钢热轧板拉伸试样表面起皮开裂缺陷进行了金相分析及工艺分析。金相分析结果表明,钢坯在加热时上下表面受热不同步,下表面脱碳严重,使轧制后的钢板形成一层均匀的全脱碳层;当受到拉伸应力作用时,表面脱碳层翘起、开裂。工艺分析结果表明,钢坯加热的保温时间是控制下表面脱碳与否的主要因素。通过测定成品热轧板断裂韧性指标得知,钢板表面脱碳层所形成的裂纹深度远小于材料失稳扩展临界值。

Analysis on Cause Leading to Peeling and Cracking on Surface of Tensile Sample Taken from High Strength Hot-Rolled Steel Plate

Analysis on the causes leading to peeling and cracking defects on the surface of tensile samples taken from a hot-rolled high strength steel plate with thickness of 12 mm is carried out by metallography analytical method and technology analytical method. The analysis results by metallography analytical method show that the surface at the bottom of a billet has serious decarburization because of non-synchronous heating on the surface at the top and bottom of billet, which results in forming the uniformity decarburization layer on the rolled steel plate, and the decarburization layer on the surface of the billet is buckled and then cracked when the tensile stress is applied. The results by technology analytical method show that the holding time for heating billets is the main factor to control whether the decarburization on the bottom surface of billets is happened or not. Based on determining the fracture toughness of a hot-rolled steel plate, it is found that the crack depth formed at the decarburization layer on the surface of the steel plate is far smaller than the critical value of the unstable crack growth of the steel plate.