Development Of New Kind Of Steel For High Strength Round Chain For Mining Of Ф34×126–C

With the demands for larger-size C round link chain increasingly and the situation of its production by expensive steel of 23MniCrMo54, two kinds of experimental steels were designed and prepared for 34×126-C round link chain for mining, one contains Cr(220#)and the other contains Ni (WR1). The characteristics of microstructure transformation and microstructure morphology in different heat treatment processes were analyzed by OPM and SEM. On this bases, the mechanical properties including tensile mechanical properties and impact toughness, as well as corrosion resistance in H2S environment were examined. Therefore, the product of 34*126-C round link chain were fabricated by the experimental steel contains Cr and its mechanical properties, impact toughness of welding joint were tested, and the microstructure morphology of welding joint was analyzed.Experiment results shown that the microstructure of two steels 220# and WR1 after normalized was complex microstructure dominated by granular bainite, as well as little massive ferrite and pearlite, with hardness in the range of 20 ~ 23HRC. The hardenability, and mechanical property including impact toughness of 220# steel after quenched and tempered were better than WR1 experimental steel. The H2S corrosion resistance of experimental steel do not much concern with the alloy elements Cr and Ni addition. The stress corrosion cracking behaviour is caused by absorbing hydrogen resulted from synthesis action between stress and electrochemistry . The the experimental steel containing Cr produced in industrial production condition, with hardness below 25HRC after hot rolled to bar ofФ34mm, was complied with the requirement of shearing process of round link chain. The research on the role of novable element Mo addition shown that the hardenability as well as mechanical properties including impact toughness were enhanced, concerned with the obvious inhibition effect on the precipitation of proeutectoid ferrite in condition that the content Mo from 0.1% to 0.31%. At last, the product of 34×126-C round link chain were fabricated under industrial production line by 220# steel. The product tensile properties, impact toughness and bending resistance better than national standard requirements, with the excellent flash butt welding performance due to all tension failure at matrix but weld joint. The impact fracture at weld joint appears dimples ductile fracture characteristics. The new kind of 220# steel was proved ideal material for larger-size C round link chain with strong market competitiveness.