Thread Content
1) Through base metal restraint strengthening, it is possible to achieve a strength level in which the low-strength matched welded joint has the same strength as the base metal. Studies show that as long as the strength of the weld metal is not less than 80% of the strength of the base material, the joint can still maintain the same strength as the base material ； A strength of the weld metal that is 10-15% lower than that of the base material does not result in a decrease in the overall strength of the joint ； Experiments have shown that for steels with yield strengths of 960 MPa and 1100 MPa respectively, a reduction in the strength of the weld metal by 23% does not result in a decrease in the strength of the joint. (2) Compared with equal-strength or high-strength matches, low-strength match joints exhibit relatively lower peak levels of welding residual stress. Meanwhile, the reduced strength requirements lead to a decrease in the alloy content of the weld metal, which in turn reduces the tendency for the microstructure to harden. As a result, the propensity for welding cold cracks is lower, allowing for reduced requirements for processes such as preheating and post-heating. Experiments show that, compared with equal-strength or high-strength welds, low-strength matching can effectively reduce welding residual stresses. Meanwhile, the weld metal exhibits higher plasticity and fracture toughness, reducing its sensitivity to welding cold cracking, thereby allowing the preheating temperature to be significantly lowered. In fact, its fatigue crack growth rate is comparable to that of equiaxial matched welds. The weld metal of low-strength matched joints possesses relatively high plasticity and fracture toughness, as well as lower peak levels of welding residual stress, which contributes to improving the fracture resistance of the joints to a certain extent. The concept of low-strength matching has been applied to the welding of high-strength steels used in submarine structures, effectively reducing the difficulty of controlling weld cold cracks. Russia has been using low-strength matching welding technology to build various types of submarines. Joint research by the United States and Japan has confirmed the effectiveness of low-strength match welding. Currently, Japan has applied low-matching welding technology to the construction of submarine structures.