GR2 Titanium Clad Plate

Titanium/steel interface will be formed at high-temperature β- The crystallographic information of Ti, TiC, FeTi or Fe2Ti and other phases is

shown in Table 2 In these phases, TiC, FeTi and Fe2Ti show intrinsic brittleness, and the order of brittleness from large to small is TiC>FeTi>Fe2Ti Among them, TiC fracture toughness is only 5.7 MPa · m − 1/2, which has the greatest damage to the interface bonding quality; When TiC, FeTi and Fe2Ti coexist at the interface, the damage to the interface is more serious than when they exist alone At the same temperature, the order of Gibbs free energy of standard formation of TiC, Fe2Ti and FeTi reaction products is TiC

The interfacial bonding strength of GR2 Titanium Clad Plates decreases with the increase of TiC layer thickness. The thickness of TiC layer can be changed by heat treatment at 555~850 ℃ and 1~3 h When a thin and uniform TiC layer is formed at the titanium/steel interface, it is beneficial to improve the interface bonding quality; When the thickness of the interface TiC layer is not uniform, brittle fracture will easily occur in the area with thick TiC, which will damage the interface bonding strength; Both the surface treatment method and the interface vacuum degree will affect the continuity and uniformity of the interface TiC layer. When the interface vacuum degree is low, the titanium/steel interface will produce more unbound areas, and the interface will also generate randomly distributed TiN. These unbound areas and the presence of TiN will destroy the diffusion uniformity of Ti and Fe at the interface, destroy the continuity of the interface TiC layer, and damage the interface bonding quality The formation temperature of FeTi and Fe2Ti at the interface is α- Ti→ β- Ti phase transition point is above 882 ℃, while Fe is β- Ti stable element, the diffusion of Fe at the interface into the Ti base will reduce the phase transition temperature, resulting in α- Ti transforms into β- Ti, resulting in the formation of FeTi and Fe2Ti at the interface Because TiC, FeTi, and Fe2Ti will precipitate at the interface of titanium/steel at the same time above the temperature of Ti transformation point, which will seriously deteriorate the interface bonding quality, the temperature of titanium/steel direct composite is generally lower than the temperature of transformation point.

The requirements for tensile strength, elongation after fracture, and shear strength of titanium/steel composite plate are specified in GB/T 8547-2019 titanium-steel composite plate and GB/T 8546-2017 titanium-stainless steel composite plate. The lower limit of tensile strength Rmj is calculated according to the formula:

Where: t1 is the thickness of steel base material, mm; T2 is the thickness of titanium coating material, mm; Rm1 is the standard lower limit of tensile strength of steel base material, MPa; Rm2 is the tensile strength standard of titanium clad material

The lower limit value, MPa. The elongation after fracture A of titanium/steel composite plate shall not be less than the lower elongation after fracture specified in the steel base material or titanium clad material standard The interface shear strength of class 0 titanium/steel composite plate is ≥ 196 MPa, and the interface shear strength of class 1 and class 2 titanium/steel composite plate is required to be ≥ 140 MPa. At present, the interface shear strength of titanium/steel composite plate without adding transition layer metal can reach 200~250 MPa, and the interface shear strength of titanium alloy coating is significantly higher than that of pure titanium coating; The interfacial shear strength of titanium/steel composite plate prepared by adding transition layer metal and strictly controlling process parameters can be as high as 500 MPa.

Because the plastic deformation ability and thermal expansion coefficient of titanium and steel differ greatly, it is difficult to compound titanium and steel At present, the main preparation methods of titanium/steel composite plates include explosive bonding, explosive-rolling bonding, diffusion bonding, and hot rolling bonding.

2.1 Explosive composite method

The explosion-composite method is a kind of metal composite plate preparation method, which uses explosives as energy source and uses the impact force generated by the explosion to make two or more layers of metal plates collide violently, plastic deformation, melt and inter-atomic diffusion, and realize the solid bonding of the interface There are two assembly methods of explosive composite blank: parallel method and angle method.

The method is applicable to large-area metal composite plates, and the angle method is applicable to high detonation velocity explosives and small-area metal composite plates. Its assembly is shown in Figure 1.

2.2 EXPLOSION - ROLLING COMPOUND METHOD

Explosive-rolling composite method is a kind of preparation method to obtain a metal composite plate by cold rolling or hot rolling after explosive composite of the metal plate to be composite The general process flow of explosion - rolling composite method is: metal plate preparation → surface treatment → explosive composite → post-explosion heat treatment → hot rolling → cold rolling → leveling Due to the explosion of titanium.

The work hardening of the interface of the steel clad plate will affect the subsequent rolling effect, so it is necessary to eliminate the work hardening of the interface through post-explosion heat treatment; During heat treatment, the temperature should be controlled below 850 ℃ to avoid the formation of Fe2Ti and FeTi at the interface The interfacial bonding strength of titanium/steel composite plate increases with the increase of rolling reduction This is because with the increase of rolling reduction rate, the wavy interface of titanium/steel composite plate formed by explosion gradually becomes straight, and the intermetallic compound at the interface is broken into discontinuous distribution, which is conducive to the improvement of interface bonding strength Wang Jingzhong et al. first compounded titanium plate and DT4 pure iron transition layer by explosive composite method, and then compounded Ti/DT4 and Q235 steel plate by hot rolling composite method to prepare Ti/DT4/Q235 composite plate; The influence of the preparation process on the interfacial bonding strength was studied. It was found that the interfacial intermetallic compounds were the least when the hot rolling temperature was 830~880 ℃ and the annealing temperature was 550~650 ℃, and the interfacial bonding strength reached 250 MPa.

The interface bonding quality as an important performance index of titanium/steel composite plate has always been the focus of attention. Surface treatment method, hot rolling temperature, transition layer metal, and heat treatment process as the key process factors affecting the interface bonding quality have also been the research focus in this field.