Small diamond saw blade vacuum sintering

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At present, the production process of small diamond saw blades is roughly as follows: batching – mixing – feeding – cold pressing – sintering. Among them, in the sintering process, pit-type batch furnaces and reducing atmosphere furnaces are mainly used to process the sintering of the diamond matrix. In the sintering process, the mixture of hydrogen and nitrogen decomposed by ammonia gas is used as a protective atmosphere to sinter the diamond matrix. The main disadvantages of this process are: 1) If the dew point control of the reducing atmosphere is not paid attention to, it is easy to cause sintering problems; 2) A large amount of gas needs to be consumed during the sintering process, and the production cost is high; 3) The gas discharged from the furnace is easy to be mishandled Explosion, the safety performance is extremely unreliable; 4) The quality of the carcass is unstable, and it is prone to cutting consumption too fast or too dull.

In view of the above points, the sintering process of small diamond saw blades adopts vacuum sintering instead of hydrogen as a protective atmosphere for sintering. Thus, the hardness, strength and impact toughness of the diamond matrix are further improved. Enhance the holding power of the matrix to the diamond, which obviously improves the service life and cutting efficiency of the diamond tool.

Vacuum sintering equipment
Vacuum sintering equipment mainly includes YD-100 hydraulic press, vacuum furnace and vacuum pump.
Selection of vacuum degree and control of relative dew point
The sintering of diamond saw blades should pay attention to the control of vacuum degree and relative dew point. Vacuum refers to the state of a gas below one standard atmosphere in a designated space. When the number of molecules of the gas in the vacuum tank is less than that of the atmospheric state, it is manifested as low air pressure. The fewer the number of molecules in the gas, the lower the pressure, so the degree of vacuum is expressed in pressure. The pressure of low vacuum degree is generally 102~105Pa, and the pressure of medium vacuum degree is generally 10-1~102Pa.

In the protective gas sintering diamond, the dew point of the reducing atmosphere should be controlled, and the protective gas should be treated with silica gel and molecular sieve to reduce the gas dew point, and then pass it into the sintering furnace. This is because the protective gas contains water vapor, and the amount of water vapor is represented by the dew point (the temperature at which the water vapor condenses). Each metal element has a critical dew point. The dew point of the reducing gas is higher than this critical point, and the metal is oxidized. Only below this dew point, the reducing gas can reduce the oxide of the metal. Sintering can only be guaranteed if the dew point of the reducing gas is low. In vacuum sintering, the control of dew point is very easy. As long as a certain degree of vacuum is controlled, there will be a very low dew point.

In the atmospheric state, the oxygen content is 21%, and when the vacuum degree is 13.3Pa, the oxygen content is 0.4%. Therefore, it can be regarded as an oxygen-free state in a vacuum state. When the vacuum state is 13.3Pa, the oxygen content is (13/105)×21%=27.3×10-6, and the relative dew point is -59℃, which is equivalent to a high-purity gas state with a purity of 99.99%. Therefore, the vacuum degree of 13Pa is selected as the best value in sintering. This can only be achieved by a first-stage vacuum pump.

crafting process:
The press-fitted metal powder (Fe-Sn-Ni-Al-Zn) is mixed with diamond in a certain proportion and evenly loaded into the mold. After cold pressing, it is put into the furnace. After pre-extracting the gas in the furnace for 5-8min, heat the furnace to make the temperature of the furnace body reach 200℃, control the vacuum degree in the furnace to 13Pa. Fill with argon with a purity of 99.99%, and continue heating to make the temperature in the furnace reach 860-900℃. And keep a certain positive pressure in the furnace when winding, the pressure is 1.5 atmospheres. Heat preservation for 1h, take out the saw blade and air-cool.

The vacuum degree of vacuum sintering is about 13Pa, and the dew point is -59℃. At this time, it is more favorable for sintering. The comprehensive mechanical properties of vacuum sintered carcasses are obviously better than those of protective atmosphere sintered carcasses. In terms of cost, since sintering in a protective atmosphere consumes much more gas than sintering in vacuum, vacuum sintering can greatly reduce the manufacturing cost of diamond tools.

Equipment selection: The RVS vacuum sintering furnace provided by SIMUWU is an excellent product for processing this kind of process. It has the characteristics of good temperature uniformity and high temperature control accuracy. SIMUWU provides a professional team of engineers who can solve various problems encountered in the production process and are committed to giving customers the most convenient and efficient experience.