1. Metallic properties and welding parameters of titanium
Titanium has a small specific gravity (specific gravity is 4.5), high strength, good resistance to high and low temperatures, and excellent crack resistance and corrosion resistance in wet chlorine. The mechanical properties and welding of titanium are related to the purity of titanium materials. 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°C and easily absorbs hydrogen, oxygen and nitrogen atoms at high temperatures, making the material brittle. Titanium begins to absorb hydrogen at a high temperature of 300°C, oxygen at 600°C, and nitrogen at 700°C.
Argon arc welding machines should have high-frequency arc ignition, current attenuation, gas delay protection, and pulse device welding wires require mechanical properties equivalent to the parent material.
The material of the protective cover should be purple steel or titanium, and the shape should be convenient for protecting the weld to prevent the weld from changing color. A stainless steel wire mesh should be installed inside the protective cover to play a gas buffering role.
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2. Titanium welding operation technology
Cleaning before welding:
The material is grooved with a rolling angle machine, and the oxide scale, grease, burrs, dust, etc. within 25mm on both sides are polished with a wire brush, and then wiped with acetone or ethanol.
Welding protection:
Before welding, you must first learn argon protection. When protecting, one person holds the protective cover to protect the upper side, and the other person holds the protective cover to protect the lower side. The protector must cooperate well with the welder. After welding, the protective cover can only be released after the weld cools down. For single-sided welding and double-sided forming, special attention should be paid to the protection of the back side. If it is not well protected, the welding liquid cannot flow, and there will be no forming.
When welding, the weld should have enough gap of 3-5mm to form an arc pit. Hold the welding gun in your right hand and try to lower the tungsten electrode of the welding gun. Hold the welding wire in your left hand and use your thumb and middle finger to clamp the welding wire and send it forward. When sending the welding wire, you should maintain continuity and stability. The two hands should cooperate well to keep the weld flat. The eyes should always observe the depth of the molten pool and the flow of the welding liquid. The current should be adjusted according to regulations and excessive current is prohibited.
The nozzle argon gas is kept at 5ml, the shielding gas is kept at 25ml, and the back is kept at 20ml to ensure that the weld does not change color after the protective cover. When welding twice, a certain cooling time should be left to reduce the surface temperature to below 200℃, otherwise cracks and brittleness will easily occur. Flat welding and nozzle rotation welding should be used as much as possible.
When welding, the room should be dry and dust-free, the wind speed should be less than 2 meters/second, and strong winds can easily cause arc instability. When capping welding, try to use a pulse device to make the weld beautiful.
3. Manufacturing process and maintenance technology of titanium equipment
The materials used for processing titanium tubes, titanium elbows, and titanium tanks must meet the requirements. Their toughness, strength, and elasticity must have a plate certificate. Each titanium plate must be adjusted with a ruler. The size must be calculated when cutting materials to prevent excessive scraps. Shearing machines must be used when cutting plates, and gas cutting should be avoided as much as possible. The lines must be clearly and accurately marked when using pipelines. Repeated use of gas cutting is strictly prohibited. After cutting the plate, the chamfering machine must be used to make the groove. The cracks must be uniform. After the plate is rolled by the plate rolling machine for the first time, the weld should be slightly concave to facilitate the second shaping after welding. Because the price of titanium materials is high (about 140 yuan/Kg for raw materials and about 400 yuan/Kg after processing), waste must be avoided.
There is a big difference between the maintenance and processing of titanium plates. The main factors include environmental factors, material changes, etc. The weld should be protected if it can be protected. If it is really impossible to protect both sides, use small current single-sided protection. After the weld cracks, do not weld on the original weld. Welding should be done by patching the plate. When the welding site is windy, there should be a wind shelter, and tarpaulin or iron plate should be used for shielding. When taking over the pipe, there should be a gap or staggered welding because the inside cannot be protected. The weld should be appropriately widened and thickened.
Post time: Sep-12-2024
