Design And Application Of Stainless Steel Flux Cored Wire Composition

At present,due to the huge resource waste and economic loss caused by wear and tear in industrial production,there is a higher demand for flux-cored wire having excellent wear resistance.However,the development level of flux-cored wire in China is relatively low,and the quality of the alloy after the production of the flux-cored wire is poor,which cannot fully meet the requirements of wear resistance in industrial production.Therefore,it is important to study a stainless steel flux-cored wire with excellent wear resistance.In this paper,stainless steel flux-cored wire was used to prepare surfacing alloy by bright arc surfacing,and the effects of C,Cr and Nb content on the microstructure and properties of surfacing alloy were studied.Firstly,according to the performance requirements of the surfacing alloy,the alloy system of the flux-cored wire is determined.The Pandat software is used to analyze and optimize the content range of each element,and then the three-factor and three-level orthogonal test method is used to design the initial composition of the flux-cored wire.Surfacing method was used to prepare a surfacing sample on the Q235 substrate.The OM,XRD,SEM,EDS,Rockwell hardness tester,friction and wear tester and other equipment were used to characterize and test the surfacing samples.The optimum flux cored wire composition is obtained by orthogonal optimization and tested for practical application.The experimental results show that the main components of the stainless steel flux-cored wire surfacing alloy consist of ?-Fe+Fe-Cr eutectic structure+M7C3 type carbide+NbC hard phase.Among them,M7C3 type carbide and NbC hard phase can form a wear-resistant"skeleton"structure,reduce the grinding and splitting effect of the matrix,and improve the wear resistance of the surfacing alloy.However,the excessive content of M7C3 type carbide and NbC hard material makes the toughness of the surfacing alloy decrease and the brittleness increases,and the wear resistance first increases and then decreases.The C element in the surfacing alloy has a great influence on the performance of the surfacing alloy,and the influence of Nb and Cr is less.When the C content is 3%,the main structure of the weld overlay alloy is a eutectic carbide and a Fe-Cr eutectic matrix structure.Insufficient C content makes carbide difficult to grow,the grain size is very small,and the weldability of the surfacing alloy is high,but the hardness is poor,and the hardness is up to 54.9 HRC.When the C content is increased to 5%,the eutectic carbide in the surfacing alloy is transformed into the nascent M7C3 type carbide,and the structure is transformed from the eutectic structure to the hypoeutectic structure,and the primary phase is the M7C3 type carbide and NbC particles.The increase of C content makes the nascent carbide grow and becomes the wear-resistant skeleton of the surfacing alloy,which greatly improves the hardness and wear resistance of the surfacing alloy.The hardness is up to 64HRC and the average friction coefficient is 0.30.Nb in the surfacing alloy is also a forming element of strong carbide,which can synthesize NbC particles in situ in the ?-Fe phase.The formation of primary NbC particles consumes carbon atoms,and the carbon content in the pearlite reduces the toughness,and The dispersed NbC particles can hinder the growth of the M7C3 phase,refine the grains to improve the toughness of the alloy,and reduce the adverse effects of increased carbide content on the alloy.When the alloy solidifies,the NbC particles act as a heterogeneous nucleation core,which can refine the microstructure and improve the wear resistance of the alloy.However,if the Nb content is too high,it will hinder the diffusion rate of carbon atoms,inhibit the formation of carbides,and reduce the wear resistance of the alloy.Through orthogonal analysis and optimization,the order of influence of elements on the hardness of surfacing alloy is:C element>Nb element>Cr element;and the optimal combination of surfacing alloy composition is:C content is 5%,Cr content is 16%.The Nb content is 6%.The optimized flux-cored wire is tested by practical application.The result is:the optimized flux-cored wire has good welding process and excellent surfacing quality,which can meet the repair of damaged roll in actual production.Claim.