Zhang Q.,Jiangsu Ship Metallice Materials Quality Supervision and Testing Center |
Wang S.-Q.,Jiangsu Ship Metallice Materials Quality Supervision and Testing Center |
Bao X.-J.,Jiangyin Xingcheng Special Steel Co Ltd |
Gan M.-L.,Jiangsu Ship Metallice Materials Quality Supervision and Testing Center |
And 2 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2015
Effect of different heat treatment on fracture toughness of new type R5 mooring chain steel was investigated by crack tip opening displacement (CTOD) test. Microstructure and fracture of the crack propagation zone in CTOD samples were analyzed by SM, OM and SEM. The -20℃ low-temperature mechanical properties of R5 mooring chain steel were tested by high-low temperature tension tester. The results indicate that CTOD fracture toughness of R5 mooring chain steel is greatly influenced by tempering temperatures. The microstructure keeping lath martensite phase direction, the flake and long strip carbides are not evenly distributed on the original austenite grain boundary, the original martensite boundaries and inter martensite lathes when tempering at the range of 570-600℃. It is easy to cause local stress concentration and larger crack growth rates, the CTOD characteristic value approach zero under the action of stress. With the increasing tempering temperature, the carbides of the sample at the range of 600-690℃ gradually aggregate and spheroidize, and distribute uniformly in matrix. It is not easy to cause local stress concentration, crack propagating path deflects and prolongs, crack propagating inhibit, the CTOD characteristic value increasing constantly. After quenching at 950℃ and tempering at the range of 600-690℃, R5 mooring chain steel has high strength and good CTOD fracture toughness. ©, 2015, Editorial Office of Transactions of Materials and Heat Treatment. All right reserved.