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采用插销试验方法测定了国产T23钢在不预热、预热150℃和预热250℃三种焊接工艺条件下的临界断裂应力,观察了断口形貌及断口附近的显微组织,综合分析了该钢的焊接冷裂纹敏感性。结果表明,不预热条件下T23钢插销的临界断裂应力高于其屈服强度,粗晶区为板条马氏体和下贝氏体混合组织,插销断口为解理和准解理特征,并出现二次裂纹;随着预热温度的升高,插销临界断裂应力增大,粗晶区下贝氏体比例增多,马氏体比例相应减少,插销断口二次裂纹减少,解理面缩小,材料的塑性增加,对裂纹的阻碍作用增强。说明国产T23钢的冷裂纹敏感性很小,预热能明显改善其抗冷裂纹能力。
The critical fracture stresses of domestic T23 steel under three welding conditions of without preheating, preheating at 150 ℃ and preheating at 250 ℃ were measured by the method of pin test. The morphology of the fracture and the microstructure near the fracture were observed. The cold weld susceptibility of the steel. The results show that the critical fracture stress of T23 steel pin is higher than its yield strength under the condition of no preheating. The coarse grain region is composed of lath martensite and lower bainite. The fracture of the bolt is cleavage and quasi-cleavage. With the preheating temperature increasing, the critical stress of the bolt increases, the proportion of bainite in the coarse grain zone increases, the proportion of martensite decreases correspondingly, the secondary cracks in the pin fracture decrease, the cleavage plane shrinks, The plasticity of the material increases, which hinders the crack growth. This shows that the cold crack sensitivity of domestic T23 steel is very small, and the preheating can obviously improve its capability of cold crack resistance.