Due to the characteristics of heating and heat dissipation, the surface temperature of the treated parts is uneven. It is an important factor to ensure the same temperature on the surface of parts to ensure the quality of ion nitriding and reduce the deformation. Therefore, reasonable charging is very important.
In consideration of temperature uniformity, the following requirements are put forward for furnace charging:
1. The parts of the same furnace should be the same parts. If the parts are mixed, the ratio of surface area and weight of various parts should be close. The larger the surface area, the greater the energy obtained and the lighter the weight, the less heat required to rise to the nitriding temperature. When charging, do not treat the inner and outer nitriding parts with the same furnace as the parts with only outer nitriding, otherwise their temperature will differ by tens of degrees or even hundreds of degrees.
2. For parts with different materials or different surface finish, even if their surface area / weight is the same or close, the temperature of the same furnace treatment is often uneven. The darker and rougher the surface color is, the larger the gray coefficient is, so the heat radiation loss is also large. If they get the same glow discharge energy, it is obvious that the darker the color is, the lower the temperature of the parts with rough surface will be.
3. When the parts are placed in the furnace, attention shall be paid to the uniformity of position, that is, the distance between each part and anode shall be approximately equal, and the distance between each part shall be uniform, and the distance shall be greater than 15mm. The larger the area of the adjacent surfaces of the two parts, the larger the distance between them should be, in order to avoid the high local temperature caused by the concentration of glow and the influence of mutual thermal radiation.
4. Distance between yin and Yang. According to the discharge theory, the glow discharge can be maintained as long as the distance between the anode and the cathode is greater than DK in the cathode drop region. However, in order to improve the temperature uniformity of parts, the distance between anode and cathode should not be too small, and 30-70mm is the best.
The reasonable charging of ion nitriding can guarantee the uniformity of the surface temperature of the workpiece to the greatest extent, thus ensuring the nitriding quality and reducing the deformation.
On 2018-08-08 11:45:46
