Blue Tungsten Oxide Reducing Tungsten Powder

Blue tungsten oxide is short for BTO. Broadly speaking, blue tungsten oxide is powder mixing material composed by various tungsten compounds including ATB, HTB, WO3, WO2.9 and WO2.72.

Blue tungsten oxide firstly appears from abroad. China starts producing BTO since 1980s. In a narrow sense, BTO refers to WO2.9. Due to its stable property and strong activity, it is easy for doping, so it takes place of tungstic acid and yellow tungsten oxide and become main raw material for producing tungsten powder.

Like other types of tungsten oxide, BTO is produced in hydrogen reduction in single tube reducing furnace. Take medium grain tungsten powder for example, its processing condition is first band furnace temperature 730 ℃±10 ℃, second band is 850 ℃±10 ℃, third band is 910 ℃±10 ℃, hydrogen flow rate is (2.6 ±0.1)m3h-1.

Study found that when reducing temperature is 500 ℃～ 600 ℃, WO3 will be reduced into WO2.9, small part of it turns into WO2 and then reduced into tungsten powder. When reducing temperature is 600 ℃～800 ℃, WO3 is reduced to WO2. When reducing temperature is 770 ℃～900 ℃, WO3 will be reduced to WO2.72.

Main phase content β-oxide (WO2.9) has rough surface and some cracks. The roughness, crack size and quantity as well as WO2.9 content are related to calcinating temperature, time and hydrogen flow. Control BTO phase content is very important to control tungsten powder grain appearance. If condition is well controlled, then it will decide final property of tungsten powder.

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