Research Of Titanium Clad Steel Plate Properties In Laser Cladding Preparing Process

As the substitute of pure titanium plate, titanium clad steel plate is composited by titanium plate and carbon steel or low alloy steel. It has good corrosion resistance of titanium and mechanical property of carbon steel, while the processibility is much better than pure titanium. The titanium clad steel plate has been widely applied in the petroleum chemical industry and seawater desalination field, because its price is only 1/5-1/10 of pure titanium. Currently the metal laminate is mainly prepared by explosive welding and rolling bonding processes, all of which our country cannot master to prepare the laminate whose overall thickness laminate is less than 4mm. The stainless steel-carbon steel has been prepared by laser cladding and has good bonding strength, which has proved that laser cladding is a feasible technology in preparing thin composite plate. The thesis tries to prepare titanium clad steel plates whose overall thickness is 2mm and 3mm by laser cladding, and the microstructure and mechanical properties of the samples would be tested. Besides, in order to improve the bonding strength, interlayer material is introduced by laser cladding. The main work and results are as follows:(1) Studying the influence of laser parameters on cladding layers. It is found in the experiment that the unidirectional powder feeding and two-way scanning is a better mean of laser cladding. Firstly, use single factor test method to analysis the influence rule of each laser parameter on cladding layer’s height and width, determining a reasonable parameter ranges. Then orthogonal test is carried out to get the order of importance of each factor. At last a set of optimal parameter is obtained to preparing a certain area of titanium clad steel plate sample with a suitable overlapping ratio.(2) The microstructure, element analysis and mechanical properties tests of the titanium clad steel plates prepared by laser cladding in the mean of unidirectional powder feeding and two-way scanning are done. The microstructure and phase composition of titanium cladding layer and heat-affected zone of the Q235 matrix are analyzed through optical microscopy, EPMA and XRD techniques, revealing the bonding mechanism of titanium layer and steel substrate in the process of laser cladding. The mechanical properties such as micro-hardness distribution in cross-section and tensile of the titanium clad steel plate are tested, which are explained by the microstructure and phase composition analysis.(3) In order to improving the bonding strength of the titanium layer and Q235 steel substrate for preparing titanium clad steel of thick titanium layer, interlayer materials are added. Microstructure and phase composition of the laminate is detected by optical microscopy, SEM and EDS analysis. Tensile-shear test has done and the fracture morphology is researched. The results show that: the cladding layer is uniform and dense in microstructure; in tensile test, the fracture mechanisms are mainly cleavage fracture in the titanium layer and dimple fracture in interlayer; in shear test, intergranular brittle rupture is its main character, and fractured face locates at the interface of the titanium layer and interlayer material.Laser cladding technology and improved process are used to preparing titanium clad steel plate in the paper, extending the methodology for preparation of titanium clad steel plate. The microstructure and mechanical properties are analyzed. The thesis provide experiments on bonding two materials whose thermal physical properties are quite different.