Titanium clad steel plate integrates the excellent corrosion resistance of titanium alloys and the strength and toughness of steel and has been widely used in petroleum, chemical, electric power, and nuclear energy fields. In recent years, the application fields of titanium-steel composite plates are gradually expanding, such as protective materials for marine steel structures, transition joints between ship steel structures and titanium structures, seawater pipelines, etc. At the same time, the production technology of titanium-steel composite plates has also made great progress.
At present, the main production methods of the titanium-steel clad plate are the explosion cladding method, explosion-rolling cladding method, and direct rolling cladding method. Among them, the direct rolling composite method has become the main research direction of the steel mill, which is mainly due to the introduction of large-scale wide rolling mills and vacuum blanking equipment. Compared with the explosion cladding method and the explosion-rolling cladding method, the direct rolling cladding method can produce clad plates with wide sheet width, thin cladding, and uniform interface properties. At the same time, the direct rolling composite method also has the advantages of high production efficiency and low cost. However, the vacuum forming process of the direct rolling composite method is relatively complicated, and the rolling process requires high equipment capacity. For domestic iron and steel enterprises, there are still some key technologies that need to be broken through in the production process of direct rolling clad titanium steel clad plates.
The main parameters of the rolling process of titanium steel clad plate are heating temperature, reduction, and rolling speed, and the heating temperature is the most critical process parameter. This is mainly because the heating temperature not only affects the forming process of the titanium layer and the steel layer but also affects the microstructure, the strength, and toughness of the steel layer, and the interface bonding performance. Temperature directly affects the formation of interfacial brittle phases such as TiC, FeTi, and Fe2Ti, and the thickness of interfacial brittle phases has a decisive influence on the bonding properties.
The results show that the interfacial shear strength is inversely proportional to the thickness of the intermetallic layer. As the temperature increases, the thickness of the intermetallic compound of the titanium-stainless steel clad plate increases. When the heating temperature is 850℃, the thermal simulation composite titanium stainless steel sample obtains the best bonding performance. However, the current related research results are mainly based on experimental phenomena, which are related to the relationship between temperature, interface product type, thickness, and interface bonding performance, and do not deeply analyze how temperature affects the interface reaction product type and thickness. Therefore, the effect of temperature on the interfacial reaction phase needs to be further studied. In addition, there is also a lack of systematic evaluation of the influence of heating temperature on the microstructure, the strength and toughness of the substrate, and the interfacial bonding strength.
1) When the heating temperature is 850~950℃, the strength and toughness of the base material, the interface shear performance, and the bending process performance of the titanium steel composite plate all meet the requirements of the index, and the shear strength is greater than 200MPa. With the increase in heating temperature, the interfacial shear performance decreased gradually.
2) When the heating temperature is 850, 875 and 900 °C, the cooling temperature after rolling is low, the enrichment ability of C at the bonding interface is strong, the reaction-diffusion of Fe in Ti is weak, and the reaction phase of TiC and β-Ti is formed at the bonding interface.
3) With the increase of heating temperature, the thickness of the brittle phase TiC layer and Fe-Ti intermetallic compound layer increases. When the heating temperature rises above 925°C, Fe-Ti intermetallic compounds and TiC coexist at the bonding interface. The diversification of the brittle phase and the increase of the thickness make the interfacial shear strength of the titanium-steel clad plate decrease.
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