Precautions for processing titanium alloy parts during processing

The welding performance of titanium, titanium alloy, and titanium wire has many remarkable characteristics. These welding characteristics are determined by the physical and chemical properties of titanium and titanium alloy. When welding titanium and titanium alloys, the possibility of hot cracks in the welded joints is very small. This is because the content of impurities such as S, P, and C in titanium and titanium alloys is small, and the low melting point eutectic formed by S and P is not easy to appear On the grain boundary, coupled with the narrow effective crystallization temperature range, the shrinkage of titanium and titanium alloys is small during solidification, and the weld metal will not produce thermal cracks. When welding titanium and titanium alloys on time, cold cracks can appear in the heat-affected zone, which is characterized by cracks that occur several hours or even longer after welding, which is called delayed cracks. Studies have shown that this kind of crack is related to the diffusion of hydrogen bombs during welding. During the welding process, hydrogen diffuses from the high-temperature deep pool to the lower-temperature heat-affected zone. The increase in hydrogen content increases the amount of TiH2 precipitated in this zone, which increases the brittleness of the heat-affected zone. In addition, the volume expansion during the precipitation of hydrides causes greater structural stress. , Coupled with the diffusion and accumulation of hydrogen atoms to the high-stress parts of the region, resulting in the formation of cracks. The method to prevent this kind of delayed cracking is mainly to reduce the source of hydrogen in the welded joints. When invoices are issued, the fire suppression treatment is also carried out.

When welding titanium and titanium alloys, porosity is a common problem. The root cause of the formation of pores is the result of the influence of hydrogen. The formation of pores in the weld metal mainly affects the fatigue strength of the joint. The main technological measures to prevent pores are:

(1) The protective neon gas should be pure, and the purity should not be less than 99.99%

(2) Thoroughly remove organic matter such as oxide scale and oil stains on the surface of the weldment and the surface of the welding wire.

(3) Apply good gas protection to the molten pool, and control the flow and flow rate of argon to prevent turbulence and affect the protection effect.

(4) Correct selection of welding process parameters and increase the right to use the deep pool residence time to allow bubbles to escape, which can effectively reduce pores.

The gas shielding problem of titanium and titanium alloy welding is the primary factor affecting the quality of welded joints. When welding titanium and titanium alloys, the heat input should be as small as possible. The source of hydrogen should be strictly controlled to prevent cold cracks. At the same time, attention should be paid to prevent the generation of pores. As long as welding is carried out in strict accordance with the welding process requirements and effective gas protection measures are taken, high-quality welded joints can be obtained.
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