After coarse pestle, it should be fine pestle on vertical steel ball machine. It uses grinding plate as grinding tool and the lower grinding plate opening 90 ° symmetrical V-groove, milled plate installation alignment groove runout less than 0.02mm, which groove also should be pre-grinding by standard ball to ensure the precision.

Afterwards, tungsten carbide ball should be polished by vertical lathe and uses oak plate as grinding tool to turn arc groove with 0.5R. It has grooved boards with four claw chuck clamping, alignment grooves within 0.1mm, with W5 / W7 diamond paste (Old GB model, or about 4000 mesh / 3000 mesh) as a polishing paste, applied to certain pressure on the grinding plate does not move, speed control in 60r / min, the polishing process can be carried out for 4-6 hours, making the ball appear like a mirror.

Finally, cooling tungsten carbide polished ball about 5min. Then use kerosene to remove the stains on the surface and wipe out by clean cloth. Testing and packaging: The amount of change in the diameter of the grant requested diameter ball is detected using a micrometer or ruler for detecting extremely; roundness detected; the surface roughness using observation and comparison assay. It is required soft cushion apart between the balls and the ball use soft cushion apart, to prevent the collision of the balls and the ball, so that it is deformed or worn.

The specific requirements of each procedure of tungsten carbide polished ball as follow: Coarse grinding at the beginning, machined by vertical steel ball machine and uses 100# diamond resin grinding wheel (grain size is 100). Before the grinding, the grinding wheel to be ball milled with the corresponding specifications of the groove. In addition, the groove depth is generally equal to 1/5-1/3 of tungsten carbide polished ball and runout groove should ensure that within 0.03mm.

Then the fine grinding, which also machined on vertical steel ball grinding machine and uses 150# diamond grinding wheel (the grain size is 150, finer suitable for fine grinding). It is similar to coarse grinding, the grinding wheel to be ball milled with the corresponding specifications of the groove. The groove depth is generally equal to 1/5-1/3 of tungsten carbide polished ball and runout groove should ensure that within 0.03mm.

The next is coarse pestle, which uses grinding plate for machining on vertical steel ball machine. The lower grinding plate opening 90 ° symmetrical V-groove, milled plate installation alignment groove runout less than 0.02mm. Before the grinding, the groove should be pre-grinding by the standard ball, which adopts concentration 30% grinding fluid and 140/170# SiC （grain size is 140/170） as grinding compound. Disposable add a little abrasive, with a smaller flow, pressure control in 4KN-6KN, speed 25-30r / min, grinding to a balance of + 0.03mm-0.04mm, 0.001mm in control of roundness, approved changes in diameter assurance within 0.002mm, the surface roughness of less than Ra0.4.

Reduction of Ammonium Paratungstate Generated during Hydrometallurgical Processing of Tungsten-Copper Borings

Tungsten-copper (W-Cu) alloy is employed for manufacturing heavy duty contactors, relays,switches etc. During production of such components, W-Cu turnings/borings are generated. At CSIR-NML, a process for recovering tungsten and copper from tungsten-copper borings containing 46.01% W, 53.78% Cu, 0.13% Fe and other minor metals as high purity tungsten powder and copper powder has been developed. In the present work, a detailed investigation on reduction of ammonium paratungstate (APT) having purity 99.95% by hydrogen gas to produce high purity tungsten powder is presented. The various process parameters such as temperature, time and flow rate of hydrogen gas have been optimized. At the temperature of 800°C and 0.1 l pm flow rate a reduction of 77.78% was observed up to 2h time. At 900°C, with increase in flow rate from 0.1 l pm to 0.3lpm the increase in reduction was found to be from 63.88% to 99.99% at 1h time.At still high temperature of 1000°C, almost complete reduction was obtained at 0.1 l pm flow rate in 1h time. The effect of bed-depth was also carried out. At all temperatures chemical reaction was the rate determining step.

Coarse crystal ammonium paratungstate as white crystals, is flake or needle, slightly soluble in water, the solubility in water less than 2% at 20℃, insoluble in alcohol. Coarse grain ammonium paratungstate (APT) as a raw material of powder metallurgy industry, with the continuous increasement of subsequent product performance and quality requirements, domestic and foreign requirements increase by year, and thus it has become a hot seller in recent years.

Coarse ammonium paratungstate features
Coarse grain ammonium paratungstate (APT) as a raw material of powder metallurgy industry, has the features like simple production process, high purity finished products, high density, good flowability, easy storage and so on. With the continuous development of new carbide and filament varieties, its excellent performance makes people come to realize that it will have a profound impact on the performance of the subsequent productions tungsten powder and tungsten carbide products as the physical appearance of the raw material APT.

Except tungsten copper electrode, there are some copper alloy electrodes, such as pure Cu, CrCu, BeCu and so on.

3. BeCu: Be (Beryllium) as the main part, which also called beryllium bronze. It has the best elastic in copper alloy, high strength, high hardness, good fatigue resistance, small elastic hysteresis, corrosion resistance, wear-resisting, high electrical conductivity, non-magnetic and some excellent physical, chemical and mechanical properties. The density is 8.3g/cm³, tensile strength ≥ 100MPa, thermal conductivity ≥ 105w/m·k20℃.

4. W-Cu: Tungsten copper, it is manufactured by powder metallurgy (PM), which suitable for tungsten carbide molding. Tungsten copper has low wastage of electrode and high material removal rate (MRR), which is the most widely used in EDM. The density reaches 14 g/cm³, the hardness is HV184, the electrical conductivity is 42%IACS.

More infomations about tungsten copper electrode and other material comparison, click here:

http://news.chinatungsten.com/en/tungsten-information/81199-ti-10478

Except tungsten copper electrode, there are some copper alloy electrodes, such as pure Cu, CrCu, BeCu and so on.

1. Cu (also called red Cu, pure Cu): It has high purity, uniform distribution, lower oxygen content, no porosity, excellent thermal and electrical conductivity, etc. After heating treatment, the electrode has no direction and the molding precision has been improved. Despite heat pressing or cold pressing process, tungsten copper can be widely used in wires, cable, electric brush and some occasions requires high thermal and electrical conductivity. Cu≥99.95%, oxides ≤ 0.003%, the electrical conductivity ≥ 57%IACS, the hardness ≥ HV85.2.

2. CrCu: The hardness ＞ HRB75, the electrical conductivity ＞ 75%IACS, it has high strength and hardness at 400℃, excellent abrasion resistance and anti-attrition. After aging and hardening treatment, its thermal and electrical conductivity will be remarkably improved and easily for welding and brazing. CrCu has good corrosion resistance in the water or atmosphere, and good antioxidation at high temperature, can well withstand the pressure processing in the cold and hot states, but its drawback is a strong sensitivity to the gap in the gaps and corners causing stress concentration, prone to mechanical damage.