Method for vacuum electron beam welding of twinning-induced plasticity (twip) steel and use thereof

A method for vacuum electron beam welding of twinning-induced plasticity (TWIP) steel, comprising the following steps:

• (1) welding preparation, comprising:
• placing butt-jointed TWIP steel workpieces in a vacuum chamber of a welding machine, and vacuumizing the vacuum chamber of the welding machine until a vacuum degree in the vacuum chamber is less than 1×10−4 mbar;
• (2) preheating welding, comprising:
• performing electron beam defocus preheating on a butt joint of the TWIP steel workpieces, wherein the electron beam defocus preheating process is carried out with the following parameters:
• a welding speed of 5-10 mm/s, a focused beam current of 2,300-2,600 mA, an electron beam current of 10-30 mA, electron beam deflection scanning in a sine wave mode with a scanning amplitude of 2-5 mm and a frequency of 500-1,000 Hz, and an accelerating voltage of 150 kV;
• (3) tack welding, comprising:
• performing symmetrical tack welding on a butt joint of the TWIP steel workpieces subjected to the preheating welding, wherein the symmetrical tack welding process is carried out with the following parameters:
• a welding speed of 5-15 mm/s, a focused beam current of 2,100-2,400 mA, an electron beam current of 2-5 mA, and an accelerating voltage of 150 kV;
• (4) deep penetration welding, comprising:
• performing deep penetration welding on the butt joint of the TWIP steel workpieces subjected to the tack welding, wherein the deep penetration welding process is carried out with the following parameters:
• a welding speed of 5-15 mm/s, a focused beam current of 2,050-2,350 mA, an electron beam current of 5-50 mA, electron beam deflection scanning in a circular wave mode with a scanning amplitude of 0.5-2 mm and a frequency of 50-1,000 Hz, and an accelerating voltage of 150 kV;
• and
• (5) cooling the TWIP steel workpieces subjected to the deep penetration welding to obtain a welded molded part, wherein
• in steps (2)-(4), an interval between the preheating welding, the tack welding and the deep penetration welding is 5-15 min;
• and
• the chemical composition of the TWIP steel workpieces in step (1) is as follows:
• by mass percentage, 0.6%-0.9% of C, 20%-30% of Mn, 0.3%-1.0% of Si, 0.3%-1.0% of Al, ≤0.015% of P, ≤0.005% of S, 0.3%-0.6% of V, 0.2%-0.5% of Nb, ≤0.1% of impurities, and the balance Fe.