CRH3高速列车转向架构架焊接接头组织与性能研究

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	CRH3高速列车转向架构架焊接接头组织与性能研究
	王鑫
学位类型	硕士
导师	陆善平
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料加工工程
关键词	高速列车转向架熔化极活性气体保护焊热处理工艺含ti焊缝金属含ti析出相 High Speed Train Bogie Metal Active Gas Welding Heat Treatment Process Ti-bearing Weld Metal Ti-bearing Precipitate
摘要	"CRH3高速列车转向架构架材料为一种控轧控冷微合金钢，所用焊接材料为进口Ni-Cu系耐候焊丝，目前国内尚没有与之相匹配的焊接材料。进口焊材名义成分范围宽泛，微合金元素控制不明确。本文围绕CRH3（时速300-350km/h）高速列车转向架构架用焊接材料研制，系统分析了焊接材料中合金元素对焊接接头组织和性能的影响，制定了焊材成分内控范围，研制的焊接材料及焊接接头各项性能均达到CRH3转向架指标要求。首先设计了五种不同成分的焊接材料，并采用富氩基气体保护焊工艺，对S355J2W钢板进行焊接工艺试验，研究了合金元素在焊接过程中的烧损规律，发现C元素的烧损规律与焊丝中原始C含量有关，Mn、Si、Ni、Cr、Ti元素在MAG焊过程中均发生较大烧损。焊缝金属组织和性能的实验结果表明，随着C含量的增加，焊缝金属组织得到细化，强度增加。在此基础上，确定了适用于CRH3高速列车转向架材料S355J2W钢的焊接材料中C元素的成分控制范围。研究了微量合金元素Ti在焊态和焊后退火态下对焊缝金属组织和焊接接头性能的影响。结果表明：Ti的加入细化了先共析铁素体，改善了焊缝金属低温冲击性能而对焊缝金属的强度和延伸率无明显影响。经焊后去应力退火处理，消除了焊缝金属内的残余应力，同时引起位错回复，含Ti焊缝金属冲击韧性得到改善，延伸率和强度略有降低。透射电镜观察结果表明： Ti以含Ti析出相的形式在Mn-Si氧化物夹杂的内部析出，夹杂物周围存在贫Mn区，在相变过程中提供针状铁素体形核的动力，从而细化先共析铁素体。研究了正火工艺对含Ti焊缝金属组织和冲击韧性的影响。结果表明：随着正火保温时间的延长和正火温度的升高，含Ti焊缝金属的冲击韧性显著下降。珠光体是影响焊缝金属冲击韧性的主要因素。细小的珠光体（<15μm）有利于焊缝金属冲击韧性的提高。正火热处理过程中，含Ti析出相的消失，引起了珠光体的粗化。因此，为了使含Ti焊缝获得较高的冲击韧性，正火温度不能超过900℃，正火保温时间不能超过5h。"
其他摘要	" The material for CRH3 high speed train bogie frame is a kind of microalloyed TMCP (Thermo-Mechanically Controlled Process) steel and the welding consumable for CRH3 high speed train bogie is a kind of weathering resistant welding wire with Ni-Cu. At present, there is no welding consumables matching the steel and replacing the imported welding wire. The nominated chemical compositions of the imported welding wire are wide and the control of microalloy element is not clear. In this paper, the effect of alloy elements on the microstructures and properties of welded joint is studied systematically and the internal control range of the microalloy element is confirmed, centering the welding wire for CRH3 high speed train (300-350km/h) bogie frame. The properties of the welded joint welded by developed welding consumables meet the requirement for CRH3 high speed train bogie. Firstly, five kinds of welding wires with different compositions were designed for the CRH3 high speed train bogie material S355J2W microalloyed steel. Burning loss rule for alloy elements under Argon rich gas shielded welding (MAG) has been investigated. Results show that the burning loss rule of C relates to the original contents of C element in the welding wire and Mn, Si, Ni, Cr and Ti elements will burn greatly during the MAG welding process. The microstructure and mechanical properties have shown that with the increase of the C contents in the welding wire, the microstructure of the weld metal is refined and the weld metal strength increases. On the base of experimental research, the composition ranges of C in the welding wire fit for the CRH3 high speed train bogie frame material S355J2W steel are optimized and confirmed. Secondly, the influences of microalloy element Ti on the microstructure and properties of as-welded and as-annealed weld metal have been investigated systematically. The results have shown that the addition of Ti element refines the primary ferrite, improves the impact toughness but has no obvious effects on strength and elongation of the weld metal. Stress relief annealing eliminates the residual stress, reverts the dislocations in weld metal, improves impact toughness and lowers the strength of the Ti-bearing weld metal weakly. TEM analysis results have shown that Ti in the form of Ti-bearing precipitate presents in the Mn-Si oxide inclusions in the as-welded weld metal, which causes the Mn-depletion zone much larger. The Mn-depletion zone increases the driving force for the nucleation of AF and refines the primary ferrite during the phase transformation. The effect of normalizing heat treatments on the microstructure and impact toughness of the Ti-bearing weld metal has been investigated. It has been shown that for the Ti-bearing weld metal the impact toughness decreases significantly against the prolonging holding time and increasing normalizing temperature. The Pearlite after normalizing is the main factor affecting the impact toughness of Ti-bearing weld metal. Fine Pearlite(<15μm) can increase the impact toughness of weld metal. For the normalizing heat treatment, the dissolve of Ti-bearing precipitates causes coarsement of the Pearlite. Therefore, in order to get higher toughness for the weld metal, the normalizing temperature could not be set in 900-950℃ and the holding time should not be longer than 5h."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64537
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	王鑫. CRH3高速列车转向架构架焊接接头组织与性能研究[D]. 北京. 中国科学院金属研究所,2012.