35SiMn大型工矿用铸钢件辊皮产品,经过铸造、正火及调质处理后,发现整个缸体内外壁和端面,都出现严重的龟斑裂纹。通过对化学成分、力学性能及金相组织检测和对该失效件进行分析,结果表明在正常加热温度的正火处理过程中,由于加热速度过快,工件内外温差过大,热膨胀系数不一致,在工件的次表层产生极大的热应力,在静置过程中热应力的释放,铸钢件的表面产生大量的裂纹。采用高温扩散退火加完全退火后,工件的组织得到细化强韧性提高。同时采用阶梯式缓慢加热的方式降低热应力,工件表面开裂倾向显著减少。经过工艺改进,工件表面开裂率由原来的65%左右降低为现在不到2%,极大地提高了生产效率和控制了生产成本。 35SiMn large mining cast steel roller products, after casting, normalizing and quenching and processing, found that the entire cylinder inside and outside the wall and the end face, there are serious turtle spot cracks. Through the chemical composition, mechanical properties and microstructure testing and analysis of the failure of the pieces, the results show that the normal heating temperature normalizing process, due to the heating rate too fast, the temperature difference between inside and outside the workpiece is too large, the thermal expansion coefficient is not in the Sub-surface of the workpiece has a great thermal stress, the release of thermal stress in the static process, the surface of steel castings produce a large number of cracks. Using high temperature diffusion annealing plus complete annealing, the work piece of the organization to be refined strength and toughness improved. At the same time using stepwise slow heating mode to reduce thermal stress, the workpiece surface cracking tendency significantly reduced. After the process improvement, the cracking rate of the workpiece surface is reduced from about 65% to less than 2% at present, which greatly improves the production efficiency and controls the production cost.