In the welding process, hydrogen diffuses from the high-temperature deep melting pool to the low-temperature heat affected zone. The increase of hydrogen content increases the amount of TiH2 precipitated in this area, which increases the brittleness of heat affected zone. In addition, the volume expansion during hydride precipitation will lead to greater structural stress. In addition, hydrogen atoms diffuse and accumulate to the high stress region, resulting in the formation of cracks. The main way to prevent this delayed cracking is to reduce the hydrogen source in the welded joint.
Porosity in weld
Porosity is a common problem in welding titanium and titanium alloys. The root cause of pore formation is the result of the influence of hydrogen. The formation of weld metal pores mainly affects the fatigue strength of the joint. The main technical measures to prevent air holes are:
(1). The shielding gas shall be pure, and the purity shall not be less than 99%, 99% titanium equipment
(2). Completely remove the organic matters such as oil stain on the surface of weldment, oxide skin and welding wire.
(3). Good gas protection shall be provided for the molten pool, and the flow and flow rate of argon shall be controlled to prevent turbulence from affecting 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.
