摘要：双相不锈钢由于其优越的性能，拥有强度高、耐蚀性好等特点使其在日常工业使用中越来越普遍，而在工业中对双相不锈钢的焊接是常见的一种工艺，但是在焊接中会对焊接接头的力学性能和耐蚀性产生影响。

本文通过2205双相不锈钢焊接后得到的焊接接头，通过金相观察、拉伸和硬度测试、电化学测试、扫描电镜观察来研究焊接接头组织和耐蚀性的关系。

焊接接头受到热循环的影响，在焊缝的中下部的晶界、铁素体和热影响区会有析出相的生成。在拉伸试验中焊接接头中铁素体相上会发生准解理断裂，硬度试验中焊缝区域由于焊接时氮元素的损失使得焊缝的硬度比母材低，在热影响区由于析出相的存在使得硬度增加，所以热影响区的硬度和母材相当或略高于母材。通过电化学测试发现焊缝区域的耐蚀性与母材的耐蚀性相当，热影响区的耐蚀性能低于母材，导致整个焊接接头的耐蚀性比母材差。通过测量焊接接头的临界点时温度发现其低于母材的临界点蚀温度，通过扫描电镜观察焊接接头的点蚀形貌，焊接接头有有害析出相的产生导致接头在析出相位置形成点蚀核，降低焊接接头的耐蚀性。关键词：双相不锈钢电化学测试焊接接头

Abstract：Duplex stainless steel is becoming more and more popular in the daily industry because of its superior performance, the characteristics of high strength ， Excellent corrosion  resistance.  And  welding  duplex  stainless  steel  is  a  process   flow   in industry .However, welding will affect the mechanical properties and corrosion resistance of welded joints.

In this paper, the relationship between microstructure and corrosion resistance of welded joints was studied by metallographic observation, tensile and hardness test, electrochemical test and scanning electron microscope observation of welded joints obtained from 2205 duplex stainless steel.

The welding joint is affected by the thermal cycle. The precipitates in the middle and lower part of the weld grain boundaries, ferrite and heat affected zone will be formed. In the tensile test, the quasi-cleavage fracture occurs in the ferrite phase of the welded joint. In hardness test, the hardness of weld is lower than that of base metal due to the loss of nitrogen in welding area. The hardness of the heat affected zone is equal to or slightly higher than that of the base metal due to the presence of precipitated phases. Electrochemical tests showed that the corrosion resistance of the weld zone was the same as that of the base metal, and the corrosion resistance of the heat affected zone was lower than that of the base metal, which resulted in the corrosion resistance of the whole welded joint worse than that of the base metal. By measuring the critical point of the welded joints, the temperature was found to be lower than the critical pitting temperature of the base metal. The pitting corrosion morphology of the welded joints was observed by SEM. The occurrence of harmful precipitates in the welded joints resulted in pitting holes, reducing the corrosion resistance of welded joints.

Key words: Duplex stainless steel; electrochemical test; Corrosion resistance

目录

第一章绪论 1

1.1前言 1

1.2双相不锈钢简介 1

1.2.1双相不锈钢的性能介绍 1

1.2.2双相不锈钢的腐蚀 3

1.2.3双相不锈钢的组织缺陷 4

1.3双相不锈钢的焊接 5

1.3.1双相不锈钢的焊接方法