Fracture Toughness of Weld Metal of 440 MPa Grade High-strength Steel
Weld joints of 440 MPa grade high-strength steel were prepared via metal active-gas welding technique with a homemade Si-Mn-Ni gas-shielded solid welding wire as filler.Then the fracture toughness of the weld metals was studied by impact test,fatigue crack growth rate test,and crack tip opening displacement test at different temperatures,aiming to clarify the relation of microstructure and fracture toughness,so that to provide data support for the engineering application of the welding wire.The results show that the ductile-brittle transition temperature of the weld metal is about-48.4℃;With the increase of constant amplitude load(13～17 kN),the number of load cycles(N)and the fatigue life de-creases continuously.Moreover,when the stress intensity factor range(△K)keeps the same,the fatigue crack growth rate(da/dN)decreases gradually with the increase of constant amplitude load;The CTOD value(δ)of weld metal is 0.481～0.781 mm,the effective characteristic value(δ0.2BL)is 0.5103 mm,and the dispersion coefficient of CTOD value(δ)is only 16.5％,The weld metal has good fracture toughness and meets the technical requirements of marine engineering;Acicular ferrite has the strong ability to block crack propagation,thus improving fracture toughness,while quasi-polygonal ferrite has the weak ability to block crack propagation and M-A constituent is easy to induce microcracks,thus reducing fracture toughness.
万方数据
维普
