1、 High frequency welding process

Technical principle: Instantaneous high temperature is generated at the contact surface between the fins and titanium tubes through high-frequency current, causing the metal surface to melt and achieve metallurgical bonding.

Advantages and Characteristics:

Welding speed>10m/min, heat affected zone<0.5mm, to avoid coarsening of titanium grains;

Combining strength of over 90% of the base material, suitable for thin-walled titanium pipes with a wall thickness of 0.3-1.5mm.

2、 Cross rolling perforation technology

1. Tube blank preparation:

Three roll oblique rolling perforation: After heating the titanium alloy ingot to 950 ℃, perforation can be carried out to produce thin-walled tube billets with a diameter/wall thickness ratio greater than 10, and the yield rate can be increased to 85%;

Two roll oblique rolling perforation: Low cost but prone to surface peeling defects, suitable for low-alloy titanium pipes.

2. Cold rolling finishing:

Multi pass cold rolling, combined with vacuum annealing at 650-750 ℃ to eliminate hardening;

The surface roughness Ra of the finished pipe is ≤ 0.4 μ m, and the dimensional tolerance is ± 0.02mm.

3、 Composite processing method

Extrusion molding: Hot extrusion under glass lubrication protection;

Rolling forming: Roll the root of the fins without a core shaft, with a circular edge accuracy of ± 0.05mm;

Hydraulic bulging: Fill the tube with liquid and increase the pressure to 30-50MPa, synchronously expanding the spacing between fins.

4、 Processing taboos and precautions

1. Thermal sensitivity control: Welding/hot working should be carried out under argon protection to avoid high-temperature oxidation embrittlement;

2. Cold processing restrictions: The cold bending radius of titanium pipes should be ≥ 3 times the pipe diameter, otherwise micro cracks are prone to occur;

3. Economic comparison: The cost of high-frequency welding is 40% lower than that of laser welding, but the oblique rolling perforation technology is more suitable for mass production.