Titanium metal has low specific gravity (specific gravity is 4.5), high strength, good high and low temperature resistance, and excellent crack resistance and corrosion resistance in wet chlorine gas.

The mechanical properties and welding of titanium are related to the purity of titanium material. The higher the purity, the better the performance, the lower the purity, the sharp decline in plasticity and toughness, and the worse the welding performance.

Titanium is very active above 300℃, and it is easy to absorb hydrogen, oxygen and nitrogen atoms at high temperature, making the material brittle. Titanium began to absorb hydrogen at 300℃, oxygen at 600℃ and nitrogen at 700℃.

Argon arc welding machine should have high frequency arc ignition, current attenuation and gas delay protection, and the mechanical properties of welding wire for pulse device should be equivalent to that of base metal.

The protective cover should be made of purple steel or titanium, and the shape is convenient to protect the weld, so that the weld does not change color. Stainless steel wire mesh should be installed in the protective cover to play the role of gas buffer.

Second, the operation technology of titanium welding

Cleaning before welding:

Chamfer the material with gear hobbing machine to remove scale, grease, burr, dust, etc. Within 25mm on both sides, it should be polished with a wire brush, and then wiped with acetone or ethanol.

Welding protection:

Before welding, learn argon protection. When protecting, one person holds the shield to protect the top and the other person holds the shield to protect the bottom. The protector must cooperate with the welder. After welding, the protective cover cannot be loosened until the weld is cooled. One-sided welding and double-sided molding should pay special attention to the protection of the back. If there is no protection, the welding liquid will not flow and will not form.

When welding, the weld should have enough 3-5mm gap to facilitate the formation of arc pits;

Hold the welding torch with the right hand as far as possible to lower the tungsten electrode of the welding torch, hold the welding wire with the left hand, and hold the welding wire with the thumb and middle finger to feed forward;

When feeding welding wire, it is necessary to maintain continuity and stability, and both hands should cooperate well to keep the weld flat;

Eyes should always observe the depth of the molten pool and the flow of welding liquid, and the current should be adjusted according to regulations, and it is strictly forbidden to be too large.

Keep 5ml of argon gas at the nozzle, 25ml of shielding gas and 20ml at the back to ensure that the weld seam behind the protective cover does not change color. When welding twice, it is necessary to leave a certain cooling time to reduce the surface temperature to below 200℃, otherwise cracks and embrittlement will easily occur, and the welding position should be as flat as possible and the nozzle should be rotated.

When welding, the room should be dry and dust-free, and the wind speed should be less than 2m/s, which is easy to cause arc instability. When welding the cover surface, try to use the pulse device to make the weld shape beautiful.

Three, titanium equipment manufacturing technology and maintenance technology

The materials for processing titanium pipes, titanium elbows and titanium cans shall meet the requirements, and their toughness, strength and flexibility shall have the quality certificate of plates. Each titanium plate must be adjusted with crutches, and the size should be calculated when blanking to prevent the surplus material from being too large;

Shearing machine should be used when cutting plates, and gas cutting should be avoided as far as possible. When using pipelines, the lines should be clear and accurate, and it is forbidden to reuse gas cutting. After the plate is cut, the bevel should be processed by chamfering machine, and the breach should be uniform.

After the plate of the plate bending machine is initially formed, the weld should be concave inward to facilitate the secondary forming after welding. Due to the high price of titanium (raw material is about 140 yuan /Kg, and processing 400 yuan /Kg), waste should be eliminated.

The maintenance and processing of titanium plate are quite different, mainly due to environmental factors, material changes and so on. Weld can be protected. If it can't be protected on both sides, and the weld can't be welded at the original weld after cracking, it should be welded by repairing the plate.

Under normal circumstances, when the welding site is windy, there should be shielding devices, such as tarpaulin or iron plate. When taking over, because there is no internal protection, there should be gaps or dislocation welding, and the weld should be widened and thickened appropriately.