The welding process of pure zirconium sheet is close to the welding process of titanium and titanium alloys, the welding seam protection effect is higher than that of titanium and titanium alloys, and the various measures taken during welding are stricter than those of titanium and titanium alloys. The distance h between the torch and the welding part is as small as possible (h≤6mm), the main nozzle and the argon flow of the trailing cover should be well matched, neither too large, nor too small, do not form a gas vortex at the main nozzle, affecting the protection effect. Zirconium (Zr) is not very abundant in the earth's crust and is a rare element. At room temperature, zirconium has good corrosion resistance and strong toughness in acids, alkalis and various media. However, the mechanical properties and corrosion resistance of zirconium and zirconium alloys decline with increasing temperature, and above 500°C they lose their corrosion resistance and their mechanical properties are reduced. Therefore, weldments of zirconium and its alloys can only be used in environments below 500°C. In addition, zirconium is a chemically active element and is easily contaminated by gases, especially in nitrogen and hydrogen atmospheres. At temperatures below 400 ~ 500°C, the effect of zirconium and nitrogen is very weak; at 800 ~ 900°C, the effect of zirconium and nitrogen is very strong, forming zirconium nitride; at 900 ~ 1000°C, zirconium absorbs hydrogen strongly, forming ZrH2, and it is very easy to produce hydrogen gas holes.
1. Pure zirconium plate welding preparation
(1) Material of the welded part is pure zirconium (Zr-1) plate.
(2) The size of the welded part is 4mm thick.
(3)Bevel form:Bevel form and size of Zr-1 plate.
(4) Welding material: ERZr-2 welding wire, diameter 1.6mm.
(5) Tungsten electrode: WCe-5, diameter 2mm, using the tip of the tungsten electrode, can ensure the stability of the arc and sufficient depth of melt, usually using the cone angle of 30 ° ~ 60 °, the tip to be ground flat, the diameter of about 0.4mm.
(6) Welding equipment WS-400 type welding machine 1 set. Use DC positive connection.
(7) Argon gas pure argon volume fraction of 99.99%, dew point of -45 ℃.
(8) Auxiliary tools and gauges such as angle grinders, wire brushes, and weld gauges.
2. Pure zirconium plate positioning welding
(1) Grinding before welding: the weld is first wiped with acetone within 80mm on each side of the bevel with oil and dirt, then polished with a stainless steel wire wheel and remove the oxidation skin within 30mm on each side of the bevel until a metallic lustre is revealed.
(2) positioning of the weld: positioning welding on the back of the weld, positioning weld length of 50mm, positioning welding from both ends of the weld appropriate to leave empty. The welding parameters for Zr-1 (pure zirconium) plate positioning welding are the same as the formal welding parameters.
(3) Installation of the grooved copper pad: The grooved copper pad is installed on the finished welded part.
3. Pure zirconium plate formal welding
(1) Before the welding arc is induced, argon gas is led to the pad, drag cover and torch nozzle to remove the air from the area and then the arc is induced.
(2) Select the welding parameters according to the standard welding parameters.
(3) to weld the molten pool to fill the molten droplets of wire, wire heating end to be carried out within the protective layer of argon gas.
(4) Welding to focus on heat input energy to heat the weld and accelerate the cooling rate, to avoid oxidation of zirconium welded parts for a long time at high temperatures.
(5) Try to weld in an argon tank if possible.
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