Preparation of zirconium sheet before welding
  I. Overview

Zirconium (Zr) is a rare element found in the Earth's crust in small quantities. At room temperature, zirconium has good corrosion resistance and toughness in acid, alkali and various media, but the mechanical properties and corrosion resistance of zirconium and zirconium alloy decrease with the increase of temperature. When it is above 500℃, the corrosion resistance will be lost and the mechanical properties will be reduced. Therefore, zirconium and its alloy weldment can only be used in the environment below 500℃. In addition, zirconium is a chemically reactive element that is easily contaminated by gases, especially nitrogen and hydrogen. When the temperature is lower than 400 ~500℃, the effect of zirconium and nitrogen is very weak. At 800~900℃, zirconium and nitrogen have a strong effect, forming zirconium nitride; At 900~1000℃, zirconium can strongly absorb hydrogen, forming ZrH2, and is very easy to produce hydrogen pores.

Welding characteristics of pure zirconium sheet: the arc welding process of zirconium and zirconium alloy is close to the welding process of titanium and titanium alloy. The welding welding effect is higher than that of titanium and titanium alloy, and various welding measures should be stricter than that of titanium and titanium alloy. The distance h between the tow cover and the weldment on the welding gun should be as small as possible (h≤6mm). The argon gas flow rate of the main nozzle and the tow cover should be coordinated well, neither too large nor too small, and the gas vortex at the main nozzle should not be formed, which will affect the protection effect.

Two, before welding preparation

(1) The weldment material is pure zirconium (Zr-1) plate.

(2) The size of the weldment is 4mm thick.

(3) Groove form: groove form of Zr-1 plate

(4) Welding material :ERZr-2 welding wire, diameter of 1.6mm.

(5) Tungsten pole :WCe-5 type, diameter of 2mm, tungsten pole, can arc stability and sufficient penetration, usually used cone Angle of 30°~60°, to grind, diameter of about 0.4mm.

(6) Welding equipment WS-400 welder 1 set. Direct current connection is adopted.

(7) The volume fraction of pure argon is 99.99%, and the dew point is -45℃.

(8) Auxiliary tools and measuring tools angular grinding machine, wire brush, and weld gauge, etc.