Research on welding technology of ASTM B708 R05252 tantalum plate

R05252 is the tantalum plate grade in the ASTM standard, which corresponds to the tantalum-tungsten alloy with the domestic standard grade Ta2.5W. Tantalum is a refractory metal with high density, good thermal conductivity, low linear expansion coefficient, high elastic modulus, and good high-temperature strength and mechanical processing properties. Because tantalum has good corrosion resistance and tungsten has a high melting point, tantalum sheet products are mainly used in corrosive environments. Tantalum tungsten alloy has very good corrosion resistance in most inorganic acids. In addition to hydrofluoric acid, fluorine, fuming sulfuric acid and alkali, it can withstand the corrosion of most chemical media and has important uses in the sulfuric acid industry.

Tantalum materials are rare and expensive, so the plates are usually thinner. The application form of tantalum plates is mainly composite plates or linings. However, it is difficult to weld tantalum composite plates or linings, because the melting point of tantalum and steel is quite different. The melting point of tantalum is 2996℃, and the melting point of steel is 1400℃. It often happens that the tantalum has not melted during welding. Phenomenon that has melted into molten iron. Therefore, tantalum lining pressure vessels are usually used in the actual production process, that is, the tantalum lining parts are welded and formed and then connected with the surface of the lining workpiece by tantalum screws, riveting, brazing and other methods.

Tantalum-tungsten alloy can be welded by electron beam, inert gas shielded welding, brazing and other methods. When the material thickness is less than 1mm, it is often welded by self-fusion welding. When the thickness is more than 1mm, it is often welded by plate cutting wire as the welding wire. R05252 tantalum plate uses GTAW argon. Arc welding and cutting wire welding. Tantalum-tungsten alloy welds have a slow cooling rate, low plasticity, and are prone to welding hot cracks. Therefore, GTAW argon arc welding is carried out with argon protection on the front and back sides and low heat input, so that the deposited metal is less exposed to air and reduces the production of brittle compounds or Prone to thermal cracking. The welding performance of R05252 tantalum plate was analyzed, and argon arc welding GTAW shear wire welding was used. The mechanical properties, bending performance and corrosion resistance of two kinds of post-weld heat treatment processes were tested on the obtained welded joints, and the research and analysis were carried out. The results show that whether it is in the welded state or the post-weld annealing state, the GTAW welding process can obtain a welded joint with good performance, the metallographic structure of the joint is normal, and the corrosion performance is qualified.

When manufacturing the R05252 tantalum plate lined pressure vessel with the actual plate thickness of 2 mm, the GTAW welding process is adopted, and the performance of the vessel inspection and welding test plate meets the design requirements. The test results show that reasonable structural design, appropriate process parameters and strict welding protection measures are the key to ensuring the welding quality of tantalum plates during the welding process of the thin tantalum lining of pressure vessels. The formulation and actual production of pressure vessel welding technology is of great significance.