The so-called induction heating means putting the heated workpiece on intermediate frequency or high frequency AC current sensor circle. So within the workpiece, as a result of induction, the induced current has same frequency with the induction coil current.
The induced current distribution is uneven on the workpiece inside the vertical to the direction of power section. The present density of central part is nearly zero, while the surface current density is great. That is known as the skin effect. Higher the present frequency is, thinner the surface layer might be. Usually any kind of metal has a certain resistance. So with the functions of current concentrated at the surface, it should produce large amounts of joule heat and the surface will likely be heated rapidly.
The sintering temperature of the spark sintering indirectly reflects the heating temperature of the manganese powder from the mold, the temperature than the metal powder of diamond sintered products at much lower temperatures, so the spark sintering of sintered diamond products more appropriate. The spark sintering heating speed for the following reasons: First, sintering and spark a special mechanism to discharge the heat coupled with the joint role of the Joule heat; spark sintering of power loss, high energy utilization. Spark sintering heating rate without soaking time, so the upper the change of temperature measurement methods and measurement components to make the measured temperature is a true reflection of the real-time temperature of the sintered powder, requiring temperature measurement methods and measurement components higher, for the measured temperature to really reflect the actual-time temperature of the sintered powder, require Thermometer has high sensitivity. Sometimes the temperature measurement devices in a really short time and the temperature of the metal powder, because the insulation still 4min soaking time after the sintering temperature is reached, reflecting the temperature is essentially the true temperature of the sintered powder.
Spark sintering temperature results as far as possible to actually reach the temperature of the sintering process should do the test temperature and temperature parts, especially the very short sintering time occasions, equivalent to the entire sintering process in seconds calculation, the temperature the more important. The flow resistance of the metal powder is very loose than small, in order that the fluidity of the powder, loose powder is just too large, can not be pretended. Early in the production of magnetic materials and Powder Metallurgy products production which had been used granulation, because the production of large, into one hundred tons, 10 tons of powder granulation sintering suppress the production of diamond tools in the means of granulation, can separate metal powder granulation, can with granulating diamond and metal powder diamond nuclei, coated metal powder, granulation of the latter can be reduced as a result of differences within the proportion brought on by mixing inequality and improve the performance of the tool.
Foe the application of ultra-fine metal powder, granulation is a technical way. If the granulation process will not be properly, it will reduce performance of the tools. Normally, after the granulation, it should be broken by cold pressing. Then the processes are sintering or hot pressing. If sintering or hot pressing is taken immediately after granulation, the effect is easy to imagine. It is not powder metallurgy after the granulation. So the diffusion is difficult to realize and it has high porosity. To stop this phenomenon, people must first put on broken nibs. It requires enough mold strength. The graphite mold may not become suitable. Although the switch to steel mold or carbide mold will increase costs, but it might get compensation from the better tool performance.Source:http://www.mhcmp.com