Research On Process And Microstructure And Properties Of TC4 Titanium Alloy/X65 Pipeline Steel Clad Plate By Vacuum Hot-Rolling

Titanium and titanium alloys have excellent corrosion resistance,it is the best anticorrosion materials marine engineering facilities,but its high price limits its widespread use.Titanium clad steel plate not only resistant to corrosion,but also has excellent mechanical properties of the substrate.Vacuum Rolling Cladding(VCR)technology,increasingly replacing the traditional explosive cladding,becomes the main method to manufacture wide and high quality titanium clad steel plates.Based on VCR technology,in this thesis,TC4 titanium alloys/X65 pipeline steel plates were produced by hot rolling cladding using vacuum electron beam equipment.In view of these materials,the element diffusion of interface,products of interface and changes in properties were systematic research by different processes of compositeThe main work and the research results of this thesis are as follows:(1)Ti-Fe compound was generated when TC4 titanium alloy and steel were directly welded,which cannot guarantee the vacuum degree of the interface.The interface of titanium-steel cannot be oxidized during heating by using symmetrical cladding block system.The bonding strength of interface is greatly effected under different surface treatment of titanium and steel.The surface of titanium alloy and pipeline steel flatness is good when they treated by water belt.There is no residual oxide and the interface bonding strength is higher.(2)The element diffusion behavior of the cladding interface occurs during the heating stage.The Ti element is diffused to the side surface of steel and forms TiC with the C element.The heating temperature has a great influence on the interface element diffusion and rolling deformation,and the diffusion distance of Fe atoms increases with the increase of temperature.The change of temperature leads to the formation of intermetallic compounds(IMC)in the composite interface.The higher the temperature is,the more IMC is generated in the interface.The formation of TiC suppresses the diffusion of Fe atoms and decreases the thickness of IMC.At 850?,titanium alloy and steel cannot fully soften,and the interface cannot fully plastic deformation and high temperature creep,leading to low strength.At 900?,the content of IMC in the interface is small and the microstructure is uniform.Titanium/pipeline steel clad plate with good mechanical properties is obtained.(3)The effect of total reduction rate on inclusions and element diffusion in cladding interface was studied by using by VRC technology to manufacture titanium alloy/pipeline steel clad plate.The results show that the higher rolling reduction rate is,the closer the interface is,the atom of the composite interface is fully activated and diffused,and the bonding strength is increasing.The 50%reduction rate can meet the national standard,and the average shear strength reaches as high as 214 MPa.(4)The heat treatment has a great effect on the elements diffusion of the interface and bonding strength of cladding plate after rolling.With the cooling rate gradually decreased after rolling,the elements diffusion of the composite interface becomes larger,the interface generates more TiC and IMC,resulting in the bonding strength of interface reduced.The annealing treatment can homogenize the interfacial microstructure,and the distribution of TiC becomes linear distribution from the point distribution at the interface,which leads to the bonding strength of interface fluctuates less.The mechanical properties of the base material and the interfacial bonding strength all meet the requirements of technical specification,obtaining excellent overall performance of titanium/pipe steel clad plate.