BWELDY960Q钢焊接接头力学性能及组织演变机理研究

发布时间：2018-05-31 14:25

本文选题：BWELDY960Q钢 + 焊接热模拟　；参考：《沈阳工业大学》2015年博士论文

【摘要】：焊接结构用BWELDY960Q钢为低合金高强度钢,具有较高的强度、良好的韧性,可以减轻焊接结构件的自重,节约材料。这类钢在工程机械、矿山、港口、水电等领域得到广泛的应用,采用焊接性较好的低合金高强度钢可以使焊接结构壁厚减薄、重量减轻,从而减少焊接的工作量,促进工程结构向大型化、轻量化和高效能方向发展。焊接是影响低合金高强度钢应用的关键技术问题,从一些工程实际出发,在各种焊接条件下,低合金高强度钢焊接接头出现冷裂纹的产生,韧性的恶化和软化失强等问题。此外,苛刻的使用条件要求低合金高强度钢焊接接头性能不断提高。低合金高强钢焊接所面临要解决的问题是在保证满足高强度要求的同时,提高焊缝金属和焊接热影响区的韧性及防止裂纹的产生。本文采用焊接热模拟技术研究BWELDY960Q钢在经历单次热循环和二次热循环后热影响区的组织与性能的变化规律,找到热影响区的薄弱区域。采用常规MAG焊接方法焊接BWELDY960Q钢,研究焊接接头的组织与性能,确定最佳的焊接规范参数,并将热模拟与实际焊接热影响区的组织与性能进行对比分析。同时在常规焊接方法的基础上施加机械振动,通过改变振动频率和振动幅值,研究振动工艺参数对焊接接头组织与性能的影响。热模拟试验结果表明,模拟BWELDY960Q钢单次热循环热影响区,峰值温度Tp1为1320℃和1200℃粗晶区、800℃不完全重结晶区,均发生脆化现象。粗晶区的韧性损失达到母材的82.17%,脆化最为严重,为单次热循环热影响区韧性恶化的区域。不完全重结晶区的韧性损失达到母材的46.53%,脆化程度仅次于粗晶区。当焊接线能量在10kJ/cm-40kJ/cm范围内变化时,随着焊接线能量的增加,粗晶区的韧性降低,焊接线能量达到30kJ/cm时,粗晶区的韧性不再继续降低。模拟BWELDY960Q钢二次热循环再热粗晶区,粗晶区再经历不同峰值温度的二次热循环后,其韧性有不同程度的提高,峰值温度Tp2为1200℃未转变再热粗晶区和800℃临界再热粗晶区的韧性损失分别达到母材的73.26%和67.32%,脆化现象较严重,为再热粗晶区韧性恶化的区域,并且两区存在“组织遗传”现象。焊接试验结果表明,采用常规MAG焊接方法,焊接电流在180-240A范围内变化,当焊接电流为220A时,焊接接头的力学性能最佳。此时,焊接接头的抗拉强度为872MPa,断面收缩率为41%,延伸率为12.5%,焊缝的冲击功为60J(-20℃),熔合区的冲击功为34J(-20℃)。在振动焊接条件下,当焊接电流、振动频率和振动幅值三个参数均发生变化时,采用正交试验获得最优的振动焊接工艺参数,即焊接电流为220A,振动幅值为0.05mm,振动频率为40Hz时,BWELDY960Q钢焊接接头的焊接接头的抗拉强度为883MPa,焊缝冲击功为64J(-20℃),其力学性能达到最佳。焊接电流为220A时,BWELDY960Q钢焊接接头的力学性能随振动参数的变化而变化。随着振动频率和振动幅值的增大,焊接接头的力学性能呈现出先提高后降低的趋势,在不同的振动频率与振动幅值条件下焊接接头的抗拉强度位于790-883MP之间,延伸率位于9-14%之间,焊缝的冲击功位于50-64J之间。此外,焊接过程中施加机械振动可以改善焊缝的低温冲击韧性,常规焊接时焊缝的韧脆转变温度为-73.70℃,施加振动焊接后焊缝的韧脆转变温度为-75.02℃。通过热模拟与实际焊接热影响区组织与性能的对比分析,热模拟热影响区的奥氏体晶粒比实际焊接相应区域的晶粒要大很多,热模拟粗晶区、细晶区的硬度值有所降低,不完全重结晶区的硬度值会略有提高,虽然热模拟和实际焊接热影响区组织与性能会有所差别,但利用焊接热模拟技术可以揭示热影响区组织与性能的变化规律。
[Abstract]:BWELDY960Q steel is a low alloy and high strength steel for welding structure. It has high strength and good toughness. It can reduce the weight of welding structure and save material. This kind of steel is widely used in the fields of engineering machinery, mine, port, hydropower and so on. The use of low alloy and high strength steel with good weldability can reduce the thickness of welding structure and weight. Reducing the amount of quantity, thus reducing the workload of welding, promoting the engineering structure to be large, lightweight and efficient, welding is the key technical problem that affects the application of low alloy and high strength steel. From some engineering practice, under various welding conditions, the cold crack appears, the toughness is deteriorated and the toughness is deteriorated in various welding conditions. In addition, the hard use conditions require the performance of low alloy high strength steel welded joint to be improved continuously. The problem facing low alloy high strength steel welding is to improve the toughness of weld metal and welding heat affected zone and prevent crack. This paper uses welding hot die. The proposed technique studies the change of microstructure and properties of BWELDY960Q steel in the heat affected zone after a single thermal cycle and two heat cycles. The weak region of the heat affected zone is found. The conventional MAG welding method is used to weld the BWELDY960Q steel. The microstructure and properties of the welded joint are studied, the optimum welding parameters are determined, and the thermal simulation and actual welding are used. The structure and performance of the heat affected zone are compared and analyzed. At the same time, the mechanical vibration is applied on the basis of the conventional welding method. By changing the vibration frequency and vibration amplitude, the influence of the vibration process parameters on the microstructure and properties of the welded joint is studied. The results of the thermal simulation test show that the peak temperature is simulated in the single thermal cycle of BWELDY960Q steel. The degree Tp1 is 1320 C and 1200 C coarse-grained region, and the incompletely recrystallized zone at 800 C is embrittlement. The toughness loss of the coarse-grained region is 82.17% and the embrittlement is the most serious. It is the area where the toughness of the single thermal cycle heat affected zone is deteriorated. The toughness loss of the incomplete recrystallization area is 46.53% of the parent material, and the degree of embrittlement is second only to the coarse-grained zone. When the energy of connection is changed in the range of 10kJ/cm-40kJ/cm, with the increase of the energy of the welding line, the toughness of the coarse-grained region is reduced, and the toughness of the coarse-grained region is no longer reduced when the welding line energy reaches 30kJ/cm. The two heat cycle reheat roughing region of the BWELDY960Q steel is simulated, and the coarse grain region has undergone two thermal cycles without the same peak temperature. With the increase of the same degree, the ductile loss of the unconverted reheat coarse grain region at the peak temperature of Tp2 and the critical reheat roughing zone at 800 degrees centigrade is 73.26% and 67.32% respectively, and the embrittlement phenomenon is serious, which is the area of the toughness deterioration of the reheat coarse grain region, and the "tissue heredity" phenomenon exists in the two zone. The welding test results show that the conventional MAG welding is used. The welding current is changed in the range of 180-240A. When the welding current is 220A, the mechanical performance of the welded joint is the best. At this time, the tensile strength of the welded joint is 872MPa, the section shrinkage is 41%, the elongation is 12.5%, the impact work of the weld is 60J (-20 C), the impact work of the fusion zone is 34J (-20 C). When the three parameters of the flow, the vibration frequency and the amplitude of the vibration are all changed, the optimum vibration welding parameters are obtained by orthogonal test, that is, the welding current is 220A, the vibration amplitude is 0.05mm and the vibration frequency is 40Hz, the tensile strength of the welded joint of the BWELDY960Q steel is 883MPa, the weld impact work is 64J (-20), and the mechanical properties of the welding joint. When the welding current is 220A, the mechanical properties of the welded joint of BWELDY960Q steel vary with the change of the vibration parameters. With the increase of vibration frequency and vibration amplitude, the mechanical properties of the welded joint show a tendency to increase first and then decrease, and the tensile strength of the welded joint under the conditions of different vibration frequency and vibration amplitude is 7. Between 90-883MP, the extension rate is between 9-14%, the impact work of the weld is between 50-64J. In addition, the mechanical vibration of the welding process can improve the low temperature impact toughness of the weld. The toughness and brittleness transition temperature of the weld is -73.70 C during conventional welding, and the toughness and brittleness transition temperature of the weld is -75.02. Compared with the microstructure and properties of the heat affected zone, the austenite grain in the thermal simulated heat affected zone is much larger than that in the actual welding area. The hardness value of the thermal simulated coarse grain region and the fine crystal region will be reduced, the hardness of the incomplete recrystallization zone will be improved slightly, although the microstructure and properties of the thermal simulation and the actual welding heat affected areas will be organized and properties. There are some differences, but the welding thermal simulation technology can reveal the change rule of microstructure and properties in the heat affected zone.
【学位授予单位】：沈阳工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG457.11

【相似文献】