| In recent years,with the continuous improvement of industrial environment on the comprehensive performance requirements of stainless steel clad plate,the traditional austenitic and ferrite stainless steel clad plate has been unable to meet the needs of special industries.Duplex stainless steel not only has the higher strength and chloride stress corrosion resistance of ferrite stainless steel,but also has the excellent toughness and weldability of austenitic stainless steel.The price of duplex stainless steel is expensive,in order to reduce the cost,but also to meet the requirements of corrosion resistance,domestic and foreign experts and scholars began to study duplex stainless steel composite plate.2205 is a representative type of duplex stainless steel.In this paper,the microstructure and properties of 2205/Q235 B duplex stainless steel composite plate were studied systematically,and the friction stir welding process was explored.Firstly,the influence of heating process parameters on the characteristics and properties of 2205/Q235 B composite interface was studied.It was found that only under the action of temperature and depending on the mutual diffusion of elements,the interfacial gaps between billets 2205 and Q235 B could be fully closed.With the increase of heating temperature and the extension of holding time,the diffusion distance of elements at the composite interface gradually increased.After compression deformation,the diffusion distance of elements was significantly reduced.Secondly,vacuum rolling process of 2205/Q235 B composite plate was systematically studied from three aspects of total reduction rate,pass reduction rate and final rolling temperature.It was found that the shear strength of composite plate was much higher than the standard requirements under the conditions of the total reduction rate was greater than 34.39%,or the pass reduction rate was not less than16.3%,or the final rolling temperature was not higher than 970℃,and the composite plates achieved good metallurgical bonding.At the same time,the shear strength increased with the increase of the total reduction rate and the pass reduction rate.The shear strength decreased with the increase of the final rolling temperature.Thirdly,the influence of Fe,Ni and Nb interlayers on the element diffusion,shear strength and corrosion resistance at the composite interface was further studied.The interaction between different interlayers and 2205 duplex stainless steel and Q235 B low-carbon steel was analyzed from the microscopic mechanism.The test results showed that the shear strength of 2205/Q235 B composite plates decreased slightly after Ni interlayer was added,but it can effectively prevented the mutual diffusion of elements at the composite interface and improve the corrosion resistance of the composite plate.Finally,the friction stir welding process of 2205/Q235 B composite plates was explored.When welding from the 2205 side,laminated structural defects occured on the advanced side.All welded joints were broken here,and the strength and elongation droped significantly.When welding from Q235 B side,the welded joints were all broken at the base material,and the welded joints have good performance.After the addition of Ni interlayer,the hole defect in the retreated side gradually disappeared when the rotation speed was increased,which was conducive to improving the performance of the welded joint.When the rotation speed increased to500 rpm,the sample broke at the base material. |
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