With continuous improvements, structural steels are available in even higher strength grades above 1000 MPa yield strength. As the great majority of these steels are used in welded structures, their weldability needs to be taken into account. Several factors can cause difficulties during welding of these steels, but in this paper the softening behavior and the toughness characteristics of the heat-affected zone (HAZ) are examined. As the critical parts of the HAZ in a real welded joint are relatively small, their investigating ability is limited. However, the physical simulation provides a way of evaluating specimens made from a given material to produce the specified HAZ areas in a suitable size range for subsequent testing. In this research work, three different strength categories of high-strength structural steels (with yield strength of 960 MPa, 1100 MPa, and 1300 MPa) are investigated by physical simulation. In the case of different technological variants of gas metal arc welding (GMAW) process, the effect of the cooling time t_8/5 is investigated in different HAZ subzones considered to be critical. The thermal cycles were determined according to the Rykalin 3D model. The investigated cooling times were t_8/5 = 5 s, 15 s, and 30 s. The properties of the selected coarse-grained, intercritical and intercritically reheated coarse-grained zones are analyzed by laser scanning microscope, scanning electron microscope, hardness test, and instrumented Charpy V-notch impact toughness test. Furthermore, additional investigation like JMatPro calculations, electron backscatter diffraction measurements, and prior austenite grain size calculation were carried out. As a result of the tests, the investigated heat-affected subzones indicated higher sensitivity to the welding heat input compared to conventional structural steels. Overall, the results of the tests show that the application of shorter t_8/5 cooling time can be beneficial for the investigated high-strength steel grades, since significant toughness reduction and the risk of softening occur in the whole cooling time range.

随着不断改进，结构钢的强度等级甚至超过 1000 MPa 屈服强度。由于这些钢绝大多数用于焊接结构，因此需要考虑其可焊性。有几个因素可能会在这些钢的焊接过程中造成困难，但本文研究了热影响区（HAZ）的软化行为和韧性特征。由于实际焊接接头中热影响区的关键部位相对较小，其调查能力有限。然而，物理模拟提供了一种评估由给定材料制成的样本的方法，以产生适合后续测试的尺寸范围内的指定热影响区区域。在这项研究工作中，通过物理模拟研究了三种不同强度类别的高强度结构钢（屈服强度为960 MPa、1100 MPa和1300 MPa）。在熔化极气体保护焊 (GMAW) 工艺的不同技术变型的情况下，在被认为至关重要的不同 HAZ 子区域中研究了冷却时间t _{8/5的影响。}热循环根据 Rykalin 3D 模型确定。研究的冷却时间为t _8/5  = 5 s、15 s 和 30 s。通过激光扫描显微镜、扫描电子显微镜、硬度试验和仪器化夏比V型缺口冲击韧性试验，对选定的粗晶区、临界区和临界区再加热粗晶区的性能进行了分析。此外，还进行了 JMatPro 计算、电子背散射衍射测量和预先奥氏体晶粒尺寸计算等附加研究。测试结果表明，与传统结构钢相比，所研究的热影响分区对焊接热输入具有更高的敏感性。总体而言，测试结果表明，应用较短的t _8/5冷却时间对于所研究的高强度钢种是有益的，因为在整个冷却时间范围内会发生显着的韧性降低和软化风险。