Szczucka-Lasota Bożena, Węgrzyn Tomasz, Szymczak Tadeusz, Jurek Adam
Faculty of Transport and Aviation Engineering, Silesian University of Technology, Krasińskiego 8, 40-119 Katowice, Poland.
Department of Vehicle Type-Approval & Testing, Motor Transport Institute, ITS, Jagiellońska 80, 03-301 Warsaw, Poland.
Materials (Basel). 2021 Feb 16;14(4):936. doi: 10.3390/ma14040936.
Modern means of transport will play a significant role in the smart city. In the automotive industry, high-strength steels such as Docol are employed more often. This kind of material is relatively not very well weldable. The main reason is related to the Heat Affect Zone, the region in which cracks occur. Another disadvantage is connected with differences in values of ultimate strength of parent and weld material. The differences can be diminished using the correct welding process, which employs nickel and molybdenum electrode wires at much lower sulfur content. The weld metal deposit contains mainly martensite and bainite with coarse ferrite, while the parent material contains mainly martensite and rather fine ferrite. New technology, micro-jet cooling after the joining process enables to obtain the microstructure of weld metal deposit at acceptable parameters. Welding with micro-jet cooling could be treated as a very promising welding Docol steels process with high industrial application. Results of non-destructive inspections on macro samples corresponded with further destructive test results (tensile strength, hardness, fatigue, metallographic structure analyses). This article aims to verify fatigue behavior of Docol 1200 M steel after welding supported by the cooling using the micro-jet technique. For the first time, micro-jet cooling was used to weld this kind of steel to check the mechanical properties of the joint, especially to determine the fatigue limit. This study is formulated as follows: investigating fatigue resistance of the Docol 1200 M weld manufactured at the cooling process with micro-jets. The joints were produced in the MAG (Metal Active Gas) technology modified by micro-jet cooling. The results collected in the fatigue test were processed in the form of the Wöhler's S-N diagram following the fatigue limit of the weld examined. All data have indicated the possibility of obtaining a new method of welded joints with high fatigue limit minimum of 480 MPa. It could be important to achieve a tensile strength of 700 MPa while maintaining the best relative elongation at the level of the base material.
现代交通方式将在智慧城市中发挥重要作用。在汽车行业，多科尔（Docol）等高强度钢的使用越来越频繁。这种材料的可焊性相对较差。主要原因与热影响区有关，即出现裂纹的区域。另一个缺点与母材和焊接材料的极限强度值差异有关。使用正确的焊接工艺可以减少这种差异，该工艺采用硫含量低得多的镍和钼电极丝。焊缝金属沉积物主要包含马氏体、贝氏体和粗大铁素体，而母材主要包含马氏体和相当细小的铁素体。新技术，即连接过程后的微喷射冷却，能够在可接受的参数下获得焊缝金属沉积物的微观结构。微喷射冷却焊接可被视为一种非常有前景的多科尔钢焊接工艺，具有很高的工业应用价值。宏观样品的无损检测结果与进一步的破坏性测试结果（拉伸强度、硬度、疲劳、金相结构分析）相符。本文旨在验证采用微喷射技术冷却焊接后的多科尔1200M钢的疲劳行为。首次使用微喷射冷却来焊接这种钢，以检查接头的机械性能，特别是确定疲劳极限。本研究的内容如下：研究在微喷射冷却过程中制造的多科尔1200M焊缝的抗疲劳性能。接头采用经微喷射冷却改进的熔化极活性气体保护焊（MAG）技术生产。疲劳试验中收集的结果以韦勒（Wöhler）S-N图的形式进行处理，以确定所检查焊缝的疲劳极限。所有数据都表明有可能获得一种新的焊接接头方法，其疲劳极限至少为480MPa，在保持与母材相同的最佳相对伸长率水平的同时，实现700MPa的拉伸强度可能很重要。
