Analysis of welding requirements for titanium coils, titanium plates, titanium rods and other titanium products
The welding properties of titanium products such as titanium coils, titanium plates, and titanium rods have many remarkable characteristics. These welding characteristics are determined by the physical and chemical properties of titanium and titanium alloys.
1. The influence of gas and impurity pollution on welding performance At room temperature, titanium and titanium alloys are relatively stable. However, the test results show that in the welding process, the liquid droplet and molten pool metal have a strong effect of absorbing hydrogen, oxygen and nitrogen, and in the solid state, these gases have already interacted with them. As the temperature increases, the ability of titanium and titanium alloys to absorb hydrogen, oxygen and nitrogen also increases significantly. It begins to absorb hydrogen at about 250 °C, oxygen from 400 °C, and nitrogen from 600 °C. , After these gases are absorbed, it will directly cause the embrittlement of the joint, which is a very important factor affecting the welding quality.
2. Welded joint crack problem
When welding, the possibility of hot cracks in the joint is very small, because the content of S, P, C and other impurities in titanium and titanium alloys is very small, and the low melting point eutectic formed by S and P is not easy to appear on the grain boundary.
In addition, the crystallization temperature range is narrow, and the shrinkage of titanium and titanium alloys is small during solidification, and the weld metal will not produce hot cracks. During welding, cold cracks can occur in the heat-affected zone, which is characterized by the fact that cracks occur several hours or even longer after welding, so they are also called delayed cracks.
3. The problem of pores in the weld
When welding, porosity is a common problem. The root cause of the formation of pores is the result of the influence of hydrogen. The formation of porosity in the weld metal mainly affects the fatigue strength of the joint. to avoid gas
The process measures of the hole mainly include:
1) The protective gas should be pure, and the purity should not be less than 99.99%
2) Clean the surface of titanium coils, titanium plates, titanium rods and other titanium products, and organic substances such as oxide skin and oil on the surface of the welding wire.
3) Apply good gas protection to the molten pool, and control the flow and flow rate of argon gas to avoid turbulence and affect the protection effect.
4) Correctly select the welding process parameters and increase the residence time of the molten pool to facilitate the escape of bubbles.
