*2.1. Raw Materials and Multi-Pass Rolling*

The 17-mm-thick carbon steel plate (Q235B: C-0.18%; Mn-0.17%; Si-0.13%; S-0.017%; P-0.018%; Fe-Bal.) and 3-mm-thick commercial pure titanium sheet (TA1: Fe-0.023%; C-0.0024%; Ti-Bal.) were used as the raw materials for explosion welding. The explosion welded TA1/Q235B composite plates with a 2000 mm × 1000 mm × 20 mm size were prepared by Hunan Phohom New Material Technology Co., Ltd. (Changsha, China). The flyer plate (TA1) and base plate (Q235B) were placed parallel to the ground and the explosive was spread over the flyer plate. An emulsion explosive was selected and the explosive process follows the Jones–Wilkins–Lee (JWL) equation as Equation (1), as shown [23].

$$p = A(1 - \frac{\omega}{R\_1 V})\mathbf{e}^{-R\_1 V} + B(1 - \frac{\omega}{R\_2 V})\mathbf{e}^{-R\_2 V} + \frac{\omega E}{V} \tag{1}$$

where *A*, *B*, *R*1, *R*2, ω are constants relating to JWL equation, *E* is the energy per volume, *V* is relative specific capacity and p is pressure. Moreover, *D* (the detonation velocity) and ρ<sup>0</sup> (the density of explosive) are physical parameters relating to emulsion explosive. Before the explosive welding experiment, according to the physical parameters of the explosive and the characteristics of the flyer plate and base plate, the JWL equation was simulated and optimized by computer. By adjusting the constants of the JWL equation, the appropriate explosion equation was obtained, and then the explosive welding experiment was carried out. The relevant parameters of the JWL equation and the physical parameters are shown in Table 1.

**Table 1.** The parameters of the Jones–Wilkins–Lee (JWL) equation and physical parameters.


The preparation process of the TA1/Q235B sheets is shown in Figure 1. The size of explosive welded TA1/Q235B plates is 1000 mm × 2000 mm × 20 mm (3-mm-thick TA1 plate and 17-mm-thick Q235B plate). The sample with a size of 40 mm × 50 mm × 20 mm was cut from the center of the explosive welded TA1/Q235B composite plate with wire-electrode cutting. Then the samples were hot rolled at the temperatures of 1003 K, 1053 K and 1103 K, respectively. The rolling direction was consistent with the explosive direction. After nine passes of hot rolling, the TA1/Q235B sheets were obtained. The thicknesses and reduction of TA1 and Q235B before and after hot rolling are shown in Table 2.

**Figure 1.** Schematic diagram of the preparation process of 2-mm-TA1/Q235B composite sheets.

**Table 2.** The thickness and reduction of TA1/Q235B Sheets.

