铸造冷作模具钢焊接接头组织和性能研究
发布时间：2019-03-23 17:19
【摘要】：随着汽车工业的迅速发展,汽车模具市场需求日趋庞大,新型模具钢不断被开发并应用于汽车模具的制造。为了应对新型模具在反复使用过程中可能出现的失效问题,对新型模具钢修复方法的研究也越发迫切。探究新型模具钢焊接接头的组织及性能特点为模具的翻新修复提供试验数据和理论依据,对我国模具的发展具有重要意义。本文以新型冷作模具钢5CrMoV为研究对象,研究其热处理后组织特点及过冷奥氏体的转变过程。研究结果表明,珠光体向奥氏体转变的开始温度为773℃,结束温度为786℃。5CrMoV钢铸态组织主要是层片状珠光体和少量铁素体;退火组织为层片状珠光体和块状铁素体;淬火组织为细小的板条状马氏体;回火组织是回火索氏体。基于连续冷却过程中的过冷奥氏体产物—铁素体、珠光体、贝氏体和马氏体,利用JMatPro分析得出马氏体的临界冷却是20℃/s,获得珠光体的冷却速度要小于1℃/s。研究了5CrMoV钢热影响区的微观组织和性能特点以及不同焊接热输入下热影响区的组织和性能变化规律。结果表明,过热区组织主要是由粒状贝氏体,针状铁素体和先共析铁素体组成;完全重结晶区组织是由粒状贝氏体,多边形铁素体和少量的针状铁素体组成;不完全重结晶区组织主要为铁素体、贝氏体和回火索氏体;回火区是由回火索氏体组成。在焊接热循环的作用下,热影响区出现明显的软化现象,不完全重结晶区和回火区交界处是热影响区力学性能最薄弱的部分。焊接热输入对热影响区组织结构及力学性能具有明显的影响。随着焊接热输入的增加,过热区中晶粒尺寸显著增加,针状铁素体的板条逐渐粗化;完全重结晶区晶粒尺寸略有增加,多边形铁素体的体积分数增大;在不完全重结晶区和回火区中碳化物不断析出并且聚集长大,回火区的平均晶粒尺寸没有明显变化。此外,随着热输入的增加,热影响区硬度值降低,热影响区的宽度和软化区增大,抗拉强度呈现下降的趋势。研究了多层焊接焊缝组织特点以及焊接热输入对多层焊缝的组织和性能的影响规律。研究结果表明,打底层焊缝是由下贝氏体、残余奥氏体和和少量的碳化物组成;填充层焊缝主要是由马氏体、残余奥氏体和板条δ-铁素体组成;盖面层焊缝组织是粗大板条马氏体、残余奥氏体和骨骼状的δ-铁素体。对于多层焊,后一层焊接热输入会使得前一层焊缝性能得到改善,因而填充层组织较为均匀,具有更好的性能。随着焊接热输入的增加,打底层焊缝中柱状晶粒尺寸增大,没有δ-铁素体出现;填充层中δ-铁素体的形态由长而连续的板条转变为短而断续的板条;盖面层中的δ-铁素体含量减小,δ-铁素体骨骼状网格密度降低。随着热输入的增加,多层焊缝的硬度降低,拉伸强度值呈现下降的趋势。
[Abstract]:With the rapid development of automobile industry, the demand of automobile mould market is increasing, and the new die steel has been developed and applied to the manufacture of automobile die and mould. In order to deal with the possible failure of the new die in the process of repeated use, it is more and more urgent to study the repair method of the new type of die steel. It is of great significance for the development of dies in our country to explore the microstructure and properties of welded joints of new die steel and provide experimental data and theoretical basis for the renovation and repair of dies and dies. In this paper, the microstructure characteristics and the transformation process of supercooled austenite of a new type of cold working die steel 5CrMoV after heat treatment are studied. The results show that the initial temperature of the transformation from pearlite to austenite is 773 鈩，
本文编号：2446072
[Abstract]:With the rapid development of automobile industry, the demand of automobile mould market is increasing, and the new die steel has been developed and applied to the manufacture of automobile die and mould. In order to deal with the possible failure of the new die in the process of repeated use, it is more and more urgent to study the repair method of the new type of die steel. It is of great significance for the development of dies in our country to explore the microstructure and properties of welded joints of new die steel and provide experimental data and theoretical basis for the renovation and repair of dies and dies. In this paper, the microstructure characteristics and the transformation process of supercooled austenite of a new type of cold working die steel 5CrMoV after heat treatment are studied. The results show that the initial temperature of the transformation from pearlite to austenite is 773 鈩，
本文编号：2446072
本文链接：https://www.wllwen.com/kejilunwen/jiagonggongyi/2446072.html
