Investigation results are presented to improve the structural strength (cold crocking resistance) of weld joints in high-strength steels with the yield limit over 600 MPa. The effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and diffusion hydrogen saturation of build-up and fused base metals was experimentally studied. The diffusion hydrogen saturation of build-up (arc and hybrid welding) and fused (laser welding) metals was chromatographically examined. In gas-shielded arc welding, the diffusion hydrogen content in the fused base metal was shown to be limited to the concentration that does not exceed 0.4 ml/100 g due to an increase in the welding speed from 18 to 50 m/h. In laser and hybrid laser-arc welding of high-strength steels with the yield limit over 600 MPa, the diffusion hydrogen content in the fused metal makes up 0.07 and 0.2–0.3 ml/100 g, respectively, regardless of the welding speed. The cold cracking resistance was evaluated by a commonly accepted procedure of special reference butt samples. Optical and transmission microscopic studies permitted of revealing the effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and gaining detailed information on the dislocation density distribution. The relation between the level of local internal stresses and the structural factors of dislocation density distribution in the weld metal was established. In arc and laser welding, local internal stresses were shown to be reduced to the values that do not exceed 0.22 of the theoretical metal strength if the welding speed would make up 50 m/h. In hybrid laser-arc welding at 72–110 m/h, maximum local internal stresses are also less than 0.22 of the theoretical metal strength. An increase in the cold cracking resistance in butt weld joints of high-strength 14KhGN2MD and N-A-XTRA-70 steels was established to be reached due to a low concentration of diffusion hydrogen in fused metal and formation of the fine-grained structure of lower bainite with the uniform dislocation density distribution.

中文翻译：

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不同焊接技术的高强度钢对接接头的抗冷裂性

提出了研究结果，以提高屈服极限超过600 MPa的高强度钢中焊接接头的结构强度（耐冷裂性）。实验研究了电弧，激光和混合激光电弧焊接条件对堆焊金属和熔合贱金属的焊接金属结构和扩散氢饱和度的影响。色谱分析了堆积金属（电弧焊和混合焊接）和熔融金属（激光焊接）的扩散氢饱和度。在气体保护电弧焊中，由于将焊接速度从18 m / h提高到40 m / h，因此熔融母材中的扩散氢含量被限制在不超过0.4 ml / 100 g的浓度。在屈服极限超过600 MPa的高强度钢的激光和混合激光电弧焊接中，无论焊接速度如何，熔融金属中的扩散氢含量分别为0.07和0.2–0.3 ml / 100 g。耐冷裂性通过特殊参考对接样品的公认方法进行评估。光学和透射显微镜研究允许揭示电弧，激光和混合激光电弧焊接条件对焊接金属结构的影响，并获得有关位错密度分布的详细信息。建立了局部内应力水平与焊缝金属中位错密度分布的结构因素之间的关系。在电弧焊和激光焊接中，如果焊接速度达到50 m / h，局部内应力将减小到不超过理论金属强度的0.22的值。在72–110 m / h的混合激光电弧焊中，最大局部内部应力也小于理论金属强度的0.22。确定高强度14KhGN2MD和NA-XTRA-70钢的对接焊缝的抗冷裂性提高是由于熔融金属中扩散氢的浓度较低以及形成了下贝氏体细晶粒组织具有均匀的位错密度分布。