Titanium/steel composite plates not only have the excellent corrosion resistance of titanium, but also have the high strength and good thermal conductivity of steel, while reducing the use of precious metal titanium and lowering production costs. They are widely used in fields such as petrochemicals, power equipment, salt production equipment, and marine engineering. At present, the main methods for industrial production of titanium steel composite plates include explosive composite method, explosive rolling composite method, and hot rolling composite method. Compared with other preparation methods, the titanium steel composite plate prepared by hot rolling composite method has the advantages of good product quality, high production efficiency, and no environmental pollution. It has significant advantages in the production of large-area and wide width composite plates, and is gradually replacing other preparation methods in industrial production. However, when preparing titanium/steel composite plates using hot rolling composite method, in order to avoid oxidation of the composite interface under high temperature conditions, it is necessary to use vacuum pumping method or vacuum electron beam welding method for billet preparation to ensure that the composite interface is in a vacuum state. However, vacuum billet production may have welding defects that can lead to vacuum failure, resulting in a decrease in the qualification rate of composite plate production. Moreover, the complex production process and high equipment costs limit the promotion and application of rolling method for producing composite plates. In addition, at high temperatures, brittle compounds such as TiC, FeTi, and Fe2Ti are easily generated at the interface of directly hot-rolled titanium/steel composite plates, leading to a decrease in the shear performance of the composite plates. Moreover, with the increase of heating temperature, the types and thickness of compounds generated at the composite interface increase significantly. After studying the effect of rolling temperature on the composite strength of titanium/steel composite plates
The results indicate that at a rolling temperature of 850~1050 ℃, as the rolling temperature increases, the number of compounds generated at the composite interface increases, and the shear strength shows a significant decrease. Yu Wei et al. [20] conducted rolling composite experiments of industrial pure titanium TA1 and Q345 in the range of 840~930 ℃. The study found that the composite plate rolled at 870 ℃ had better performance. With the increase of heating temperature, the titanium side structure underwent phase transformation, and more intermetallic compounds were generated at the interface, reducing the shear strength of the interface.
In order to suppress the formation of intermetallic compounds at the titanium/steel composite interface during hot rolling, a suitable metal layer is usually added between titanium and steel as an intermediate layer to improve the coordinated deformation and diffusion conditions of the interface. For example, SABOK TAKIN R M et al. [21] conducted hot-rolled titanium/steel composite experiments using Cu as an intermediate layer at different temperatures, which suppressed the formation of TiC and Fe Ti intermetallic compounds, and no reaction layer was generated at the composite interface between carbon steel and copper. However, various Ti Cu intermetallic compounds were generated at the composite interface between copper and titanium, reducing the shear strength of the composite plate.
A titanium/steel composite plate was prepared by hot rolling pure iron DT4 as the intermediate layer. At a heating temperature of 850 ℃, the composite plate achieved a maximum shear strength of 237 6 MPa; As the heating temperature increases to 950 ℃, a thick brittle layer forms at the composite interface, resulting in a significant decrease in the bonding strength of the composite plate. CHAI X Y et al. effectively prevented the formation of brittle phases at the composite interface by adding two different intermediate layers, Nb and Mo. The shear strength of the composite plate increased by 65 and 20 MPa, respectively, compared to not adding an intermediate layer. LI B X et al. [24] prepared titanium steel composite plates by hot rolling IF steel, V, and IF steel+V as intermediate layers. The study found that no brittle phase was detected at the composite interface when IF steel+V was used as the intermediate layer, and the shear strength was higher than that of a single material as the intermediate layer, reaching 241 at 900 ℃ and a reduction rate of 93% At 8 MPa, as the heating temperature increases, the thickness of the σ phase at the V/IF steel interface increases, severely weakening the shear strength of the composite plate.
From the above research, it can be seen that under higher temperature conditions, hot-rolled titanium/steel composite plates will generate brittle phases regardless of whether an intermediate layer composite interface is added, leading to a decrease in the bonding quality of the composite plate. To avoid the formation of brittle compounds during high-temperature rolling and cooling processes, Bai Yuliang proposed a scheme of rolling titanium/steel composite plates using high-frequency electromagnetic induction heating and a cold hot two-step method. By utilizing the fast heating speed of electromagnetic induction, the heating time is shortened and the precipitation of intermetallic compounds at the interface is controlled. GUO X W et al. [26] conducted hot rolling experiments on TC4/304 composite plates using the electric pulse assisted method at different temperatures and reduction rates. The study showed that the use of electric pulse assisted rolling can effectively promote the metallurgical bonding of metals. High quality TC4/304 composite plates were successfully prepared under rolling processes with lower temperatures and lower reduction rates, with a maximum shear strength of 286 MPa. In response to the problems in the preparation of titanium/steel composite plates by hot rolling composite method, this paper proposes using pure iron as the intermediate layer, utilizing the good fluidity of pure iron to improve the deformation conditions of the interface matrix, and preparing high-performance titanium/steel composite plates by simply stacking asymmetric billets under inert gas protection and using electromagnetic induction heating at lower temperatures. This method not only simplifies the production process, but also avoids the formation of brittle compounds at the composite interface by utilizing the characteristics of short heating speed and low temperature of electromagnetic induction. This article intends to study the microstructure and properties of the interface of titanium/steel composite plates prepared by induction heating and rolling with different thicknesses of DT4 as intermediate layers.
