1. Experimental Materials and Methods
1.1 The composite and base materials used for testing are ASMESB265 Gr.2 and ASME SA516 Gr.70, with specifications and quantities of 5 mm × 4 450 mm × 6 820 mm, 4 pieces respectively; 31 mm x 4 350 mm x 6 720 mm, 4 pieces.
1.2 Test Method
1.2.1 Explosion welding test
Using a combination of high and low explosive velocity explosives and segmented explosive composite, with the same static process parameters (charge height, support distance, flash margin, energy gathering diameter, etc.), segmented explosive distribution is shown in Figure 1. Explosive detonation velocity Vd1>Vd2>Vd3 Figure 1 Schematic diagram of segmented charging
1.2.2 Selection of explosion velocity
According to the basic theory of explosion process parameters [14], a test was conducted on the combination of high and low explosive detonation velocities. The explosive used was a low detonation velocity expanded ammonium nitrate explosive, formulated as ammonium nitrate explosive+industrial salt, and the measurement method for detonation velocity was the single-stage probe method. Choose four combinations of high and low detonation speeds, as shown in Table 1.
Based on the flat distribution of a single explosive and the segmented distribution of multiple explosives, combined with the formula for explosive detonation pressure, the length from the detonation point is taken as the horizontal axis, and the detonation pressure is taken as the vertical axis, as shown in Figure 2.
Figure 2 shows the distribution law of explosion pressure for a single explosive spread evenly. After stable detonation, the detonation pressure stabilizes. With the increase of time, the pressure impulse increases linearly. The longer and larger the length and area of the explosive composite, the greater the increase in detonation pressure impulse, resulting in greater differences in the uniformity of interface welding quality. This indicates that a single explosive spread evenly has certain limitations on the plate width of explosive welding, especially for two immiscible metals (such as titanium and steel), which poses a great threat to their explosive welding quality.
The interface bonding of a single explosive laid flat in explosive welding is shown in Figure 3. At the beginning of detonation, the front waves collide in a nearly circular form, causing plastic deformation of the two metals. At the initial collision, the thermal energy generated by the explosive detonation and the thermal energy jet generated by the deformation of the two metals are relatively weak, which is not enough to cause harm to the bonding interface. After the diameter of the circle is completed, the explosive detonation pressure impulse gradually increases; Simultaneously, the explosion of explosives generates thermal energy and the thermal energy of collision deformation forms a high-temperature jet; In addition, the detonation sparse waves generated by the two long sides and the deformation disturbance of the composite plate caused by the explosion jointly affect the high-temperature jet to be sprayed outward in a turbulent form in the bonding interface layer, resulting in the high-temperature jet spraying and disorderly discharge, causing uneven bonding deformation at the bonding interface, inconsistent bonding uniformity of the entire plate, and unstable product quality.
