国产T23钢焊接冷裂纹敏感性插销试验研究

Study on Cold Cracking Susceptibility of Domestic T23 Steel Using Implant Tests

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。

Under no preheating, preheating at 150℃ and preheating at 250℃, the critical fracture stresses of domestic T23 steel were determined by implant test, the fracture morphology and microstructure near fracture were observed, the welding cold crack sensitivity was analyzed. The results indicate that under the condition of no preheating, the critical fracture stress of T23 implant sample is higher than its yield strength, and the fracture surface is cleavage fracture and quasi-cleavage fracture, on which secondary cracks appear, with wattle martensite and lower bainite mixing in the coarse grain zone. When preheating temperature rises, the critical fracture stress increases, the proportional of lower bainite of coarse grain area is more, the martensite proportion reduces correspondingly, the secondary cracks of implant fracture decrease and cleavage plane becomes narrow. So, the plasticity of material is strengthened, the crack is blocked. The results show that domestic T23 steel has a weak cold crack sensitivity, and preheating can obviously improve the anti-cold crack ability.