| The surfacing layer of stainless steel welding strip is in the harsh environment of high temperature,high pressure and hydrogen for a long time.The quality of the cladding metal in the surfacing layer affects the effective service life of hydrogenation reactor and other equipment to a certain extent,so its quality requirements are very high.Independent development of stainless steel welding belt not only has good economic benefits,but also helps to accelerate the pace of industrialization of resource-saving stainless steel plate in China,improve the localization level of high-end stainless steel materials in China,and promote the development of domestic high-end equipment manufacturing industry.In this test,309 L and 316 L of stainless steel welding strips are submerged arc surfacing on the surface of Q345 R base metal,in which309 L of the stainless steel welding strip is the transition layer and 316 L of the stainless steel welding strip is the functional layer.Test the cladding metal after surfacing according to the standard;The residual stress and microhardness tests were carried out on the surfacing specimens.The microstructure and chemical composition distribution of the 309 L layer,Q345 R layer and the fusion line were observed by electron backscattering technique and scanning electron microscopy.The metallographic structure of stainless steel welding strip 309 L,316L and base material Q345 R was compared with each layer of the surfacing sample.The results are as follows:(1)The content,chemical composition,bending test and intergranular corrosion test of cladding metal ferrite after surfacing welding of stainless steel welding strip developed by Taiyuan Iron and Steel Group Co.,Ltd.meet the standard requirements,and are equivalent to similar imported welding strips.(2)After heat treatment,the residual stress near the interface of the surfacing specimen is compressive stress.The maximum residual stress of the surfacing specimen is 240 MPa,which appears near the interface between 316 L and 309 L.The minimum residual stress of the surfacing specimen is 160 MPa,which appears near the upper surface of the 316 L layer.Along the thickness direction,the residual stress from the deposited metal surface to the base metal increases gradually,then decreases gradually and finally increases gradually.(3)The hardness value of the cladding metal in the surfacing layer is about 181 HV,and the hardness value of the carbon steel in the matrix Q345 R is about 175 HV.In the vicinity of the interface between 309 L and Q345 R,the hardness value of the cladding metal is significantly improved,and the hardness value of the cladding metal is greater than that of the carbon steel in the matrix Q345 R.(4)The 309 L layer has large grain size,columnar crystal morphology,and obvious texture characteristics of <100>.Q345 R has a BCC structure in a region of 35?m-40?m width extending from the fusion line on the matrix side to the surfacing layer.The average grain size of Q345 R is between 30?m and 40?m in the superheated coarse-grain region.The average grain size is between 10?m and 20?m in the fine grain area.Most of the grains in the fine grain region near Q345 R have recrystallized,and the average grain size is 20?m-25?m.The degree of internal distortion of the grains is greatly reduced,and the average grain orientation difference is 30.5°.(5)There will be grain refinement near the interface of carbon steel Q345 R and stainless steel 309 L,which leads to small residual stress near the interface.The residual stress of Q345 R near the fusion line is less than that far away from the fusion line. |
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