【作者】 王振江；

【导师】 陈思杰；

【作者基本信息】 河南理工大学 ， 材料加工工程， 2009， 硕士

【摘要】 随着我国电站机组容量、规模和参数的不断提高,锅炉管道承受的蒸汽温度和压力不断增大,新型耐热钢的研发和相应焊接工艺成为制约电站发展的关键课题。采用传统的焊接方法,容易产生焊接变形以及焊接残余应力,瞬时液相扩散焊连接温度低,界面连接强度高,应用到电站锅炉管道的焊接具有很好的市场前景。本文介绍了电站三种常用钢管的TLP扩散连接,用新研制的FeNiCrSiB非晶箔作中间层,氩气保护,连接压力均为2MPa,连接工艺为:20/20钢,单温工艺,等温温度1200℃,等温时间3min;T91/T91钢,双温工艺,高温温度1260℃,加热0.5min,等温温度1230℃,等温时间3min;T91/12Cr2MoWVTiB钢,双温工艺,高温温度1260℃,加热1/3min,等温温度1250℃,等温时间3min。研究表明,等温温度和等温时间对TLP连接接头界面特征影响显著,上述好的工艺下降熔元素扩散比较充分,没有脆性相形成,随着温度升高,接头中心硬度明显下降。三种TLP连接接头的整体特征是:20/20钢连接界面比较明显,T91/T91钢连接界面模糊不清,而T91/12Cr2MoWVTiB异种钢的连接界面在T91一侧模糊不清,在12Cr2MoWVTiB钢一侧比较明显。界面特征不同的原因为:一是中间层与母材成分上的差异,二是降熔元素和主要合金元素扩散的充分性。根据三种TLP连接接头不同的界面特征,对电站钢管典型的TLP扩散连接界面进行了定义以及区域划分,TLP连接接头可分为接头中心区、接头扩散区、母材扩散区三部分。从试验角度研究了20钢管TLP扩散连接的动力学过程,推测出了连接过程的四个阶段。等温凝固时间10s时焊缝宽度达到最大,此时中间层熔化以及增宽已经完成;等温凝固时间60s时,界面变得平直,等温凝固阶段完成,随后进入接头的均匀化阶段。用EPMA测定了降熔元素的扩散过程,发现在等温凝固时间10s时,降熔元素B、Si的扩散已经很明显,而在10s到60s的等温凝固阶段,B、Si的扩散变化不大,到180s时,B、Si的扩散都比较充分。更多还原

【Abstract】 As the capacity, scale and parameters of China’s power station unit continuously improving, the temperature and pressure of boilers steam pipes are increased, the development of new heat-resistant steels and corresponding welding technology becomes a key issue. Using traditional welding methods easily lead to welding distortion and welding residual stress, but transient liquid phase diffusion bonding(TLP) has low tempreture and can obtain high intensity, so it has good market prospects to use TLP bonding connecting power plant boiler tubes.This paper introduced three TLP joints of the power station commonly used tubes , their respective better technics were found using newly developed amorphous foil FeNiCrSiB as middle layer in argon atmosphere at pressure 2MPa. The results indicated that: 20/20 steel with single temperature process at 1200℃for 3min; T91/T91 steel with double temperature process at high temperature 1260℃for 0.5 min and isothermal temperature 1230℃for 3min; 12Cr2MoWVTiB/T91 steel with double temperature process at high temperature 1260℃for 1/3 min and isothermal temperature 1250℃for 3min. The research showed that temperature and time had a significant effect on interface character of TLP bondings. In good process, melting point depressant elements(MPD) diffused absolutely, there was no brittle phase formation. With the temperature increasing, the center hardness of joints decreased significantly.Overall characteristics of three TLP joints demonstrated that: the interface of 20/20 steel was clear, but the interface of T91/T91 steel was vague. For dissimilar steel T91/12Cr2MoWVTiB, the interface was vague at the side of T91 whlie the interface was clear at the side of 12Cr2MoWVTiB. The interface characteristics of the three TLP joints had a tremendous distinct , the main reason was as follows: first, the composition of middle layer was different with base metal; second, the difussion was full or not for MPD elements and main alloying elements. In accordance with three different interface characteristics of TLP joints, the joint of TLP bonding was definited and district boundaries was demarcated. The joint include three parts: joint central area, joint diffusion area, and parent material diffusion area. The dynamic process of 20 steel TLP bonding was studyed from experimental angle. The four stages of TLP bonding were speculated out , melt and broaden of the middle layer was completed when isothermal solidification time was 10s, the weld width became maximum at the same time. Isothermal solidification completed when the time was 60s ,and the interface became straight. Then the joint entered homogenization stage. The diffusion process of MPD elements was detected by using EPMA. The results showed that:, the diffusion of MPD elements B, Si was already quite obvious when the time was 10s, but the diffusion had no big change during the time 10s and 60s. The diffusion of B, Si was quite full when the time became 180s.更多还原