Manufacturing Processes of Tungsten Bar

Manufacturing processes of tungsten bar mainly depend on seven steps. The first is to be formulated doped tungsten powder.  While formulating, weighing raw wolfram powder in according with the percentage of weight of wolfram powder, put the content of 0.2 ~ 0.6wt% silicon dioxide and burnt potash which contains 0.2 ~ 0.6 wt% of silicic acid  and caustic potash mixed solution as well as aluminum nitrate solution containing 0.02 ~ 0.1wt% alumina into the blender. Then at a temperature of 50 ℃ ~ 60 ℃, it is mixed for 3 to 5 hours. Then it was dried for 3 to 6 hours, dried at a temperature to 100 ℃ ~ 200 ℃ finally obtain blue doped wolfram powder.

The next step is reduction treatment. Firstly, load doped wolfram powder in tungsten boat, reduction treatment should be last for 8 to 12 hours in a hydrogen atmosphere under the temperature of 500 ℃ ~ 950 ℃. After cooling, make it go though screen mesh for 100 meshes ~ 200 meshes, and obtain doped wolfram powder. Then scouring doped wolfram powder for 30 to 60 minutes by 3 ~ 6wt% of dilute hydrochloric acid, then removing the supernatant, and then add a concentration of 3 ~ 6wt% hydrofluoric acid, washing powder until the concentration of Si is lower 250ppm, and concentration of Al content is lower 30ppm, and then dried it in vacuum at a temperature of 70 ~ 150 ℃ for more than 10 hours. After drying, make it go though screen mesh for 160 meshes ~ 200 meshes and remove impurities.

Tungsten powder will be compressed into wolfram billet under a 150 ~ 250MPa pressure, and it will be put into the boat, sintering at the atmosphere of hydrogen and a temperature of 1100 ~ 1400 ℃, sintering time is 30 ~ 60 minutes. Self-resistance heating sintering is to a put the pre-sintered billet into the vertical furnace, under hydrogen and 70 to 92% of the fusing current situation to self-resistance heating sintering for 10~25 minutes. After the cooling, obtain a not dense potassium wolfram bar. Finally, put wolfram bars which are obtained above steps into the IF furnace or tungsten bar furnace, sintering for 2 to 6 hours under hydrogen and temperature of 2000 ~ 2300 ℃, and obtain finished product.

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