热处理对不锈钢药芯焊丝堆焊过渡层的影响

Effect of Heat Treatment on Transition Layer of Stainless Steel Flux Cored Wire Weld Overlay

压力容器在石油化工、电站锅炉及能源制造等行业广泛应用.然而随着社会进步和科技的创新,越来越多的压力容器在高温、高压和强腐蚀等特殊工况下工作.因此,在制造过程中常在压力容器表面堆焊不锈钢来提高构件综合性能.不锈钢堆焊后采用焊后热处理来消除异种钢焊接接头在焊接过程中产生的应力来提高使用安全性.然而,堆焊构件熔合线两侧合金元素在热作用下发生扩散,形成脱碳层、增碳层和马氏体区域.在使用过程中易发生开裂,降低构件使用寿命.为研究不锈钢药芯焊丝堆焊过渡层在热处理条件下的变化,本试验设计多组热处理工艺来分析不锈钢堆焊试样成分变化、组织演变和性能差异.结果表明,富Cr碳化物析出是造成不锈钢堆焊弯曲开裂的主要原因.通过对比不同工艺条件下Q345R堆焊构件发现,随着热处理温度升高,保温时间延长,碳化物析出越剧烈,硬化程度加剧.通过比较Q345R和15CrMo两种材料发现,在相同热处理条件下Q345R堆焊构件中碳原子迁移能力更强,析出碳化物程度更剧烈,弯曲更易开裂.通过显微硬度测试发现,不锈钢药芯焊丝过渡层熔合区附近最高硬度值小于350HV_(0.025),堆焊试件弯曲性能合格,并提出针对于Q345R和15CrMo两种材料适用的两种热处理工艺参数.该研究工作为不锈钢药芯焊丝堆焊热处理工艺的制定提供了依据.

The wide adoption of pressure vessels in petrochemical,power plant boilers,and energy manufacturing has been demonstrated.However,with social development and technological innovation,an increasing number of pressure vessels are operating under extreme conditions of strong corrosion,high temperature,and high pressure.Thus,stainless steel is generally overlaid on the surface of pressure vessels to improve overall performance.After the stainless steel overlaying process,heat treatment on the component is necessary to eliminate the localized stress and improve the pressure vessels’reliability.However,heat treatment leads to alloy elements’diffusion,resulting in decarburized layer formation.The carburized layer and the martensite area near the fusion line are crack-prone,which reduces the pressure vessels’lifespan.Multiple groups of heat treatment processes were employed to analyze the composition change,microstructure evolution,and performance difference in the stainless steel weld overlay samples to explore the transformations of the stainless steel flux cored wire weld overlay transition layer under the heat treatment condition.The results show that the precipitation of Cr-rich carbide plays a prominent role in the bending crack of stainless steel weld overlays.When comparing a Q345R component under different process conditions,the precipita-tion of the carbides becomes more intense,and the degree of hardening increases with increasing heat treatment tem-perature and holding time.Compared to a 15CrMo sample under the same heat treatment process,carbon atoms in the Q345R base metal have stronger migration ability,resulting in a more severe Cr-rich carbide precipitation and higher crack tendency.The microhardness test results revealed that the highest hardness value near the fusion zone of the stainless steel flux cored wire weld overlay layer is less than 350HV_(0.025) to ensure bending performance.For Q345R and 15CrMo,two suitable heat treatment process parameters are proposed.This research work provides a basis for the heat treatment process formulation of stainless steel flux cored wire weld overlay.