Abstract
The conventional vacuum tempering furnaces have many faults to get the constantly same effect on samples.
This comes, at first, from the fact that usual furnace has a so thick heat insulating material to secure the good temperature distribution that its heat capacity is very much and needs long time to elevate and down its temperature. So even if the operator finds the pressure is not suitable to continue tempering, and intends to bring down furnace temperature, he cannot do it quickly.
The second fault is very difficult to understand but often happens in the factory, that the operator neglect the vacuum gauge, and to force to rise up furnace temperature. In this case the samples also have had effect.
To conqure these faults, the author made an automatic controlled vacuum tempering furnace which the temperature cannot be rised up until the pressure become quite suitable to do so, and during heating if the pressure rises unexpectedly, the furnace can be cooled quickly.
The automatic control system is illustrated in Fig. 2, and the standard operation is tabulated.
