超低碳超高强X120管线钢焊接热影响区粗晶区的组织转变

采用热模拟试验方法分析了超低碳超高强X120管线钢焊接热影响区粗晶区的组织转变.粗晶区连续转变曲线（SH-CCT）表明,在较宽的冷却速度范围内（0.8～25℃/s）,X120管线钢粗晶区组织为贝氏体;当冷却速度小于0.8℃/s和大于25℃/s时,分别有少量准多边形铁素体和少量马氏体形成.热模拟焊接热输入在12～25 kJ/cm的范围时,粗晶区组织为贝氏体;硬度（276～297 HV 0.2）与室温冲击吸收功（208～225 J）稳定.结果表明,X120管线钢可适用较大范围热输入的焊接,这主要与超低碳设计有关.     

超高强度管线钢的开发现状与趋势

为满足长距离输送管道经济效率的考虑,管线钢朝着超高强度方向发展。本文从超高强度管线钢的性能要求、成分设计、强化机理和韧性提高等几个方面阐述了超高强度管线钢的研究与开发现状。围绕高强、高韧与焊接性的优良匹配,讨论了超高强度管线钢的技术难点,简述了超高强管线钢的生产工艺和焊接工艺的发展趋势。     

A new post-weld heat treatment to improve toughness of 9Cr-1Mo steel weld metals

9Cr-1Mo ferritic steels have been used in the conventional power generation plants due to their excellent creep resistance. However, one of the main obstacles in welding 9Cr-1Mo steels is the formation of undesirable coarse columnar grains in weld metal whieh ean severely compromise the toughness. A new post-weld heat treatment （PWHT） is developed in the present work. Unlike the conventional processes in which the post-weld heat treatment is carried out below Ac1 , the use of temperatures above the Ac1 of 9Cr-1Mo alloy is considered. The new PWHT at a temperature above Ac1 improves the toughness of 9Cr-1Mo weld metals effectively. The improvement in toughness is mainly due to refinement and homogenization of mierostruetures. Key words     

改善高强韧管线钢焊接热影响区粗晶区韧性的现状与趋势

从高强韧管线钢的成分设计、微细夹杂物控制、奥氏体晶粒大小、热影响区微观组织、焊接工艺等几个方面阐述了各个因素对管线钢粗晶区韧性的影响,提出了改善高强韧管线钢焊接热影响区粗晶区韧性的思路与方法在于控制管线钢的合金元素、奥氏体晶粒大小、MnS的析出、控制中温转变组织以及特殊焊接工艺的开发。     

焊前预热对X120超高强管线钢焊接接头性能的影响

钎对焊接预热对X120超高强管线钢焊接接头性能的影响进行了研究,结果表明:焊接预热不能提高X120焊接接头的强度,反而降低了X120焊接接头的冲击韧性.其原因在于,预热减缓焊后冷却速度,造成熔合线M-A组元的增多和粗晶区晶粒的长大,但由于预热温度较低,其性能变化程度不大.     

Investigation on the weldability of a Zr-Ti microalloyed X120 linepipe

Three-wire submerged arc welding was utilized to weld a newly developed Zr-Ti microalloyed X120 linepipe with heat input of 21kJ/cm. The microstructure in the heat-affected zone (HAZ), predominantly consisted of bainite, was examined by means of optical and scanning electron microscope. The average Vickers hardness of grain coarsening heat-affected zone (GCHAZ) is about 290HV0.2. The lowest Vickers hardness in HAZ is about 265HV0.2. No obvious softening occurred in HAZ. The average impact toughness at -30℃ in HAZ was 186-191J. The tested results indicated that HAZ of newly developed Zr-Ti microalloyed X120 linepipe steel had high strength and excellent low temperature toughness which met the requirements of API 5L standard.     

Zr-Ti复合微合金化高强高韧结构钢的焊接性

通过热模拟试验建立了F550钢板的焊接热影响区连续冷却转变曲线，研究了焊接热影响区组织转变与性能变化规律．结果表明，钢板经过Zr-Ti复合脱氧处理后，在钢中形成了许多可以在焊接过程中钉扎焊接粗晶区奥氏体晶界的细小弥散Zr-Ti复合氧化物粒子，同时采用低碳设计，并进行镍、铬、铜、钼的适量合金化，所以在较大焊接热输入范围内（25—100kJ／cm）可以获得优良强韧性的贝氏体组织，M—A组元细小呈弥散分布．50kJ／ern的实际埋弧焊接粗晶区V形冲击韧性结果表明，该钢焊接粗晶区在-60℃下具有良好的低温冲击韧性．     

Mechanical properties and grain refinement by acicular ferrite in high strength high toughness weld metal

The volume fraction and morphology of acicular ferrite evolution in a high strength high toughness weld metal were studied and the mechanical properties of weld metal under heat input of 21 kJ/cm with and without fast cooling were tested.The results show the weld metal can obtain a large proportion of acicular ferrite during a wide range of cooling rate and the sizes of acicular ferrite in length and thickness decrease with cooling rate increasing.The weld metal exhibited high tensile strength(895 MPa and 870 MPa) and good low temperature toughness(average A_(KV-30℃) 104 J and 79.2 J).The higher tensile strength and better low temperature toughness of the weld metal under fast cooling are due to the more refined grain of acicular ferrite.     

超高强度船体结构钢焊接性的研究现状和趋势

基于对超高强度船体结构钢及其焊接接头力学性能的总结和讨论，揭示了超高强度船体结构钢的焊接性问题，即在大线能量焊接条件下热影响区粗晶区的低温韧性较差。从马-奥(M-A)组元的生成和粒状贝氏体的生成两方面，分析了产生该焊接性问题的本质原因。总结了改善超高强度船体结构钢焊接性的途径：应用氧化物冶金技术、引入Cu沉淀强化和提高Ni含量。综合对当前超高强度船体结构钢研究现状的分析，认为超低C和高Ni含量的设计可成为进一步改善超高强度船体结构钢焊接性的思路。     

振动时效应用在工程机械臂架生产上的研究

混凝土工程机械因其生产周期的缩短和臂架长度的逐步增大,使得臂架箱体组焊后戏余应力的释放引起后期组装误差等一系列问题,越来越成为现今关注的对象,认为臂架生产需要引进新的工艺。本文着重分析了振动时效在处理残余应力上的效果,可减小焊接接头的残余应力,缩短臂架的整体变形时间,臂架生产有必要引入振动时效处理。通过合理化选择激振力、激振频率和激振时间,可以提高臂架装配的稳定性及臂架作业时的稳定性。