2W + C = W₂C
W + C = WC
The tungsten oxide WO₃ hydrotreated was reduced to prepare tungsten powder (average particle size 3 to 5μm). The tungsten powder is then pressing the mixture of the carbon black (mixed with a ball mill drying by a ball mill), and press molding at a pressure of around 1T / cm². The pressurized molded block is placed in a graphite disc or a crucible, and the graphite resistance furnace or the induction electric furnace is heated to 1400 to 1700℃ (preferably 1550 to 1650) with a graphite resistance furnace or induction electric furnace (pure hydrogen using a dew point of -35℃) (preferably 1550 to 1650)℃) so that the carbon is carburized to form a WC.
The reaction begins around tungsten particles because W₂C is generated in the initial stage of the reaction, since the reaction is not complete (mainly low in reaction temperature), except for unreacted W and intermediate product W₂C in addition to the WC. Therefore, it must be heated to the above high temperature. The highest temperature should be determined according to the size of the raw material tungs. If the average particle size is between 150μm, the reaction is carried out at a high temperature of 1550 to 1650℃.
WO₃ + 3H₂ → W + 3H₂O
2WO₃ + 3C → 2W + 3CO₂
2W + C = W₂C
W + C = WC
The carbon tungsten carbide WC particle size is used according to the hard alloy of different purposes, using different particle size tungsten carbide; hard alloy cutter, such as cutting machine blade V-CUT knives, finishing alloy adopts superfine Dine particle tungsten carbide; coarse processing alloy adopts medium-granulated tungsten carbide; alloys in gravity cutting and heavy cutting of coarse particles do raw materials; mine tool rock hardness high impact load is large with crude particulate tungsten carbide; rock impact small impact load Small, using medium particulate tungsten carbide to do raw material wear parts; the Lord.
Tungsten carbide theory contains 6.128% (50% atom), and free carbonization (Wc + C) occurs in tungsten carbon tungsten carbon, and free carbon is sintered when carbonized carbon content is greater than the theoretical amount of carbon. The tungsten grain grew up, causing the hard alloy crystal grains uneven; tungsten carbonized carbon high (≥6.07%) free carbon (≤0.05%), the total carbon is determined in the production process and scope of use of cemented carbide.
Under normal circumstances, paraffin process vacuum sintered tungsten carbon tungsten carbon mainly decided that the compound oxygen content in the sintered front block contains a part of oxygen to increase by 0.75 parts of carbon, Tc total carbon = 6.13% + oxygen content% × 0.75 (assuming sinter In the furnace, the neutral atmosphere is actually the carbonized carbon tungsten carbon tungsten carbon tungsten carbon tungsten carbon carbon carbon carbon carbon atmosphere is less than the calculated value). China’s total carbon content is generally divided into three paraffinic process vacuum sintered with tungsten carbon tungsten carbon, about 6.18±0.03% (free carbon will increase) paraffin process hydrogen sintering tungsten carbonate total carbon content is 6.13 ± 0.03 % Rubber process hydrogen sintering Tungsten carbide total carbon = 5.90±0.03% The above process sometimes cross-proceeds, thus determining total carbon carbon tungsten carbon according to specific situations.
Different use ranges, different cobalt content, total carbon of WC used in different grain size alloys can do some small adjustments. Low cobalt alloy can be used for tungsten carbide of total carbon, and high cobalt alloy can be used for tungsten carbide with low carbon. In summary, the specific use requirements of the carbide use different requirements for tungsten tungsten tungsten particles.