Q345C钢焊接接头组织转变和力学行为研究
发布时间：2018-10-22 13:17
【摘要】：目前我国列车转向架典型材质为进口高强耐候钢S355J2W(H)、SMA490BW,以及国产的Q345系列钢。由于进口钢的疲劳性能较好,低温冲击性能较优越,因此高速列车转向架多依赖进口钢。在地铁等轨道交通领域,国产Q345钢应用较多,但在服役环境较为苛刻的城市还是多采用进口钢种,由此看来转向架用钢的国产化程度不高。在推进转向架钢国产化的进程中,对国产钢的焊接性研究十分重要。研究材料的焊接性,通过一定的方法对焊接接头的组织转变和力学行为进行研究,可以对材料本身的组织、性能等建立基础数据库,此外,通过对焊材匹配性和焊接工艺的研究,匹配不同的焊接材料、选择合适的焊接工艺参数,达到提高其焊接接头性能的目标,从而为国产钢的应用推广提供便利。本文通过对Q345C钢和利用ER50Q、ER80S-G焊接得到的焊接熔敷金属进行连续冷却转变试验,分析在不同的冷却速度下材料的组织转变规律和硬度变化;通过对热模拟得到的Q345C焊接热影响区和实际的焊接接头进行组织转变分析和力学性能测试,得到以下结论:Q345C的SHCCT曲线可以分为四个区,按照温度从高到低转变顺序依次为铁素体、珠光体、贝氏体和马氏体。其中贝氏体区转变范围较宽,从冷却速度0.2℃/s～100℃/s可在微观组织中分别看到上贝氏体、粒状贝氏体和竹叶状的下贝氏体;应用彩色金相技术,可以观察到由于不同位向而呈不同颜色的块状多边形铁素体组织,在金相显微镜下即可观察到上贝氏体铁素体板条间的残余奥氏体;另外,在区分贝氏体和马氏体时,应用彩色金相技术,可以清晰的观察到呈竹叶状的下贝氏体和在较高的冷却速度下呈板条状规则排列的低碳马氏体,成功地达到辨认组织并对组织进行定量分析的目的;SHCCT曲线的准确性较好,也适用于激光-MAG复合焊等新型工艺方法;两种熔敷金属的SWCCT曲线可分为三个区,分别为铁素体、珠光体和贝氏体区,贝氏体转变范围较宽,包含针状铁素体、粒状贝氏体、板条贝氏体以及无碳贝氏体等,ER80S-G熔敷金属中针状铁素体在较低冷速和较高的温度区间开始产生,含量高于ER50Q熔敷金属;Q345C焊接接头中ER50Q焊缝和ER80S-G焊缝的第一道和第二道焊缝由块状铁素体、针状铁素体、珠光体组成,第三道和第四道焊缝由沿晶界析出的条状先共析铁素体、晶内的针状铁素体、贝氏体和少量的珠光体组成,ER80S-G焊缝中的先共析铁素体较少,针状铁素体较多;ER80S-G焊缝的硬度、抗拉强度和屈服强度均高于ER50Q焊缝,两者均高于母材;ER80S-G焊缝和ER50Q焊缝的FATT50分别为-5.6℃和-1.1℃,ER80S-G焊缝的韧脆转变温度较低;可选择ER80S-G焊丝来提高焊缝的强度和韧性;采用准确性较好的乌威经验公式可实现焊接工艺参数与t8/5之间的换算;应用第四道焊接工艺参数计算ER50Q和ER80S-G第四道焊缝的t8/5,通过对ER50Q焊缝和ER80S-G焊缝的第四道焊缝的组织观察和硬度对比,与SWCCT曲线中相同t8/5下的组织硬度相当,进一步验证了试验测得的SWCCT曲线是准确的。
[Abstract]:At present, the typical material of China's train bogie is imported high-strength weather-resistant steel S355JW (H), SMA490BW, and domestic Q345 series steel. Because the fatigue property of imported steel is good, the low-temperature impact performance is superior, so the high-speed train bogie depends on imported steel. In the field of rail transit such as subway, domestic Q345 steel has more applications, but in more demanding cities or more imported steel grades in the service environment, it appears that the degree of localization of steel used for bogie is not high. It is very important to study the weldability of domestic steel in the process of propelling bogie steel. The welding property of the material is studied, the microstructure and mechanical behavior of the welding joint are studied by a certain method, and the basic database can be established for the structure and the property of the material itself. In addition, the welding materials are matched by the research of the matching property and the welding process of the butt welding material, The proper welding process parameters are selected to achieve the aim of improving the welding joint performance, thus facilitating the application and popularization of home-made steel. In this paper, the microstructure transition rule and hardness change of the material under different cooling rates are analyzed by the continuous cooling transformation test of the welding fusion metal obtained by welding Q345C steel and using ER50Q and ER80S-G. The results show that the SHCCT curve of Q345C can be divided into four regions, which is ferrite and pearlite in turn from high to low transition sequence according to the temperature. bainite and martensite. wherein the transformation range of the bainite region is wide, the upper bainite, the granular bainite and the bamboo leaf-like lower bainite can be seen in the microstructure respectively from the cooling speed of 0. 2 DEG C/ s to 100 DEG C/ s, and the color gold phase technology is applied, It can be observed that the residual austenite between upper bainite ferrite strips can be observed under the gold phase microscope due to the mass polygonal ferrite structure with different colors and different colors; in addition, when the bainite and martensite are distinguished, the color gold phase technology is applied, can clearly observe the lower bainite which is in the form of bamboo leaves and the low-carbon martensite which is arranged at a high cooling speed in a strip-shaped rule, so that the purpose of identifying the tissue and quantitatively analyzing the tissue is successfully achieved, the accuracy of the SHCCT curve is good, The SWCCT curve of two welding metals can be divided into three regions, namely ferrite, pearlite and bainite region, bainite transformation range is wide, acicular ferrite, granular bainite, lath bainite and carbon-free bainite are contained, The acicular ferrite in the ER80S-G cladding metal is produced at a lower cold speed and a higher temperature interval, the content is higher than that of the ER50Q fusion coating metal, the first and second welding seams of the ER50Q weld and the ER80S-G weld in the Q345C welding joint consist of massive ferrite, acicular ferrite and pearlite, The third and fourth welds consist of ferrite, acicular ferrite in the crystal, bainite and a small amount of pearlite, which are precipitated along the grain boundaries. The first co-evolution ferrite in the ER80S-G weld is less, the acicular ferrite is much more, the hardness of the ER80S-G weld is higher, The tensile strength and yield strength are higher than that of ER50Q weld, both of which are higher than that of parent material; the FATT50 of ER80S-G weld and ER50Q weld is -5. 6 鈩，
本文编号：2287259
[Abstract]:At present, the typical material of China's train bogie is imported high-strength weather-resistant steel S355JW (H), SMA490BW, and domestic Q345 series steel. Because the fatigue property of imported steel is good, the low-temperature impact performance is superior, so the high-speed train bogie depends on imported steel. In the field of rail transit such as subway, domestic Q345 steel has more applications, but in more demanding cities or more imported steel grades in the service environment, it appears that the degree of localization of steel used for bogie is not high. It is very important to study the weldability of domestic steel in the process of propelling bogie steel. The welding property of the material is studied, the microstructure and mechanical behavior of the welding joint are studied by a certain method, and the basic database can be established for the structure and the property of the material itself. In addition, the welding materials are matched by the research of the matching property and the welding process of the butt welding material, The proper welding process parameters are selected to achieve the aim of improving the welding joint performance, thus facilitating the application and popularization of home-made steel. In this paper, the microstructure transition rule and hardness change of the material under different cooling rates are analyzed by the continuous cooling transformation test of the welding fusion metal obtained by welding Q345C steel and using ER50Q and ER80S-G. The results show that the SHCCT curve of Q345C can be divided into four regions, which is ferrite and pearlite in turn from high to low transition sequence according to the temperature. bainite and martensite. wherein the transformation range of the bainite region is wide, the upper bainite, the granular bainite and the bamboo leaf-like lower bainite can be seen in the microstructure respectively from the cooling speed of 0. 2 DEG C/ s to 100 DEG C/ s, and the color gold phase technology is applied, It can be observed that the residual austenite between upper bainite ferrite strips can be observed under the gold phase microscope due to the mass polygonal ferrite structure with different colors and different colors; in addition, when the bainite and martensite are distinguished, the color gold phase technology is applied, can clearly observe the lower bainite which is in the form of bamboo leaves and the low-carbon martensite which is arranged at a high cooling speed in a strip-shaped rule, so that the purpose of identifying the tissue and quantitatively analyzing the tissue is successfully achieved, the accuracy of the SHCCT curve is good, The SWCCT curve of two welding metals can be divided into three regions, namely ferrite, pearlite and bainite region, bainite transformation range is wide, acicular ferrite, granular bainite, lath bainite and carbon-free bainite are contained, The acicular ferrite in the ER80S-G cladding metal is produced at a lower cold speed and a higher temperature interval, the content is higher than that of the ER50Q fusion coating metal, the first and second welding seams of the ER50Q weld and the ER80S-G weld in the Q345C welding joint consist of massive ferrite, acicular ferrite and pearlite, The third and fourth welds consist of ferrite, acicular ferrite in the crystal, bainite and a small amount of pearlite, which are precipitated along the grain boundaries. The first co-evolution ferrite in the ER80S-G weld is less, the acicular ferrite is much more, the hardness of the ER80S-G weld is higher, The tensile strength and yield strength are higher than that of ER50Q weld, both of which are higher than that of parent material; the FATT50 of ER80S-G weld and ER50Q weld is -5. 6 鈩，
本文编号：2287259
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