Vacuum tempering and recrystallization of nonferrous metals
Vacuum annealing furnace is mainly used for tool steel, die steel, high speed steel, super high strength steel, titanium alloy and other materials after vacuum quenching, vacuum tempering after solid solution treatment, recrystallization annealing and vacuum aging of non-ferrous metals. So what should be paid attention to in the heating process of vacuum annealing furnace? Let's see!
Avoid contact between heat treated products and electrical heating elements
In particular, sufficient copper, aluminum, zinc, tin, lead and other electrical heating elements contact, no matter it is fine powder, liquid or steam, prevent the erosion of the surface of the electrical heating body to form "pit", section smaller, finally overheating and burning off.
Pay attention to the positioning and binding mode of temperature measuring contact
When testing the uniformity of furnace temperature, attention should be paid to the positioning and binding mode of temperature measuring contact, as well as the distance from the heating element.
Often inside furnace (at least every month) with bristle brush, broom or the clean furnace chamber such as compressed air, vacuum cleaner and put brick, want to prevent the impurity such as oxidation skin inside furnace to drop on electrothermal element, produce short circuit, burn even put brick. Bottom plate, crucible, furnace pot and other heat resistant steel components for a period of time, it is best to lift knock, remove its oxide skin. Iron oxide and other impurities, such as timely removal, will melt and refractory brick reaction, melting furnace wire.
The shell is made of steel plate and shaped steel into cylindrical furnace. The inner surface of the furnace cover is made of stainless steel. The lining is built with ultra-light 0.6g/cm3 energy-saving micro-hole refractory insulation brick. Lining and shell interlayer aluminum silicate fiber felt insulation, gap filled with expansion insulation powder. The resistance wire is made of 0Cr25Al5 high resistance alloy wire wound into spiral shape and installed on the shelf wire brick in the furnace. Stainless steel charging basket is placed inside the furnace. Furnace cover adopts manual lifting bar. In order to ensure uniform heating of the workpiece, a hot air circulating fan made of heat-resistant stainless steel shaft and wind blades is installed on the cover of the furnace. In the heating process of the workpiece, hot air circulates up and down in the furnace to ensure uniform heating of the workpiece. To ensure safe operation, a limit switch is installed near the lifting mechanism, which is interlocked with the power supply of the control cabinet of the furnace. The control power is cut off when the time limit position switch is opened, so the power of the heating element is cut off at the same time to ensure safe operation.
Strict vacuum sealing: as is known to all, the metal parts are treated with vacuum heat in a closed vacuum furnace. Therefore, it is of great significance to obtain and maintain the original air leakage rate of the furnace and ensure the working vacuum degree of the vacuum furnace to ensure the quality of the vacuum heat treatment of the parts. So a key problem of vacuum heat treatment furnace is to have reliable vacuum sealing structure. In order to ensure the vacuum performance of vacuum furnace, a basic principle must be followed in the structure design of vacuum heat treatment furnace, that is, the furnace body should adopt airtight welding, at the same time, the furnace body should be less open or no open holes, less or avoid the use of dynamic sealing structure, in order to minimize the chance of vacuum leakage. The components and accessories installed on the vacuum furnace body, such as water-cooled electrode and thermocouple export device, must also be designed with sealing structure.