【摘要】 用插销试验法研究了CO2 气保焊条件下ZG2 0MnMo钢热影响区 (HAZ)的氢致裂纹敏感性、裂纹形貌及产生裂纹的主要原因。结果表明 :在不预热和 16kJ cm线能量条件下 ,ZG2 0MnMo钢热影响区的氢致裂纹敏感性很强 ,临界断裂应力 (σcr)只有 6 0MPa,D((σNT-σcr) σNT,σNT,为无氢时的抗断强度 )值高达 96 %。断口具有典型的氢致延迟裂纹特征 ,断口形貌与拘束应力水平有关。低应力水平条件下 ,断裂方式为冰糖状的沿晶 (IG) +氢致准解理穿晶 (QCHE) ,而且出现较多沿晶界和板条界二次裂纹 ;高应力水平时 ,主要为冰糖状的IG ,QCHE比例减少 ,而且QCHE中撕裂棱的塑性变形和二次裂纹都明显减少。氢致裂纹的产生主要与HAZ的淬硬程度高有关 ,近缝区形成粗大的马氏体组织 ,硬度值高达4 93HV ,这种组织容易发生氢脆 ,氢脆指标I(I=80lgHV - 130 (% ) )为 85 2 % ,即使氢的含量很低 ,HAZ也会萌生裂纹并扩展。更多还原

【Abstract】 Implant tests were performed on the 20MnMo cast steel by using of CO 2 gas shielded welding process.The susceptibility of the hydrogen-induced cracking (HIC), the fracture morphology and the main cause of cracking in heat affected zone(HAZ)were investigated.The results indicate that in the case of heat input of 16kJ/cm and no preheating,the HIC susceptibility of 20MnMo cast steel is so high that the critical fracture stress(σ cr) of implant is only 60MPa and the HIC index, D｛(σ NT-σ cr)/σ NT ,σ NT is tensile srength of implant with no hydrogen ｝is up to 96%. The typical HIC fracture,which consists of intergranular(IG)fracture and quasi-cleavage(QC HE)fracture,is observed for the implant specimen.The fraction IG and QC HE fracture depends on the stress levels.At high stresses, IG fracture become the dominant fracture mode and at lower stresses approaching σ cr,QC HE fracture is dominant.The tendency to produce HIC is dependent on the hardenability of HAZ for 20MnMo cast steel.The microstructure of over heated zone near the weld interface is largely coarse lath martensite with hardness 493HV,which is very susceptibile to the hygrogen embrittlement and the index I(801gHV-130(%))is up to 85^2%.Even though the content of hydrogen is very low in welding joints,the cracking will be easily initiated and propagated.更多还原