Cleaned Tungsten Rod
Alkali wash is a chemical cleaning method. Use sodium hydroxide and sodium carbonate or trisodium phosphate formulated to make a high strength lye to soften, loosen, emulsifying and dispersing deposits. Some surfactant is often added to enhance the cleaning effect. Time of alkali wash is generally 6 ~ 12h, it may be extended depending on the circumstances. Before recrystallization annealing, the surface of cleaned tungsten rod need for electrolytic alkaline cleaning. Usually tungsten rod would be passed continuously by 25% KOH solution and energizing, and residual lye of the surface would be wash away in hot water about 80℃. Finally, remove feculence, scale and micro-cracks of tungsten rod surface to improve the surface quality of products, improving the processing performance of the products.
Before annealing, tungsten rod surface needs to remove oxide skin and surface contamination, or it may cause the embrittlement, and even the remove oxide would enter into the tungsten in subsequent processing due to mechanical deformation,affecting the performance tungsten materials. If tungsten rod continuous electrolytic washing in the electrolytic cell, so that the oxide skin and an alkaline electrolyte would react with each other in the principle of electrochemical corrosion, to achieve the purpose of cleaning the surface of the tungsten rod. In order to adjust the tungsten rod internal grain structure and improve the processing performance of tungsten rod, it should be used recrystallization annealing. General annealing i\can be divided into ways: direct electrical heating and high frequency induction heating.