How to use vacuum heat treatment furnace for annealing

The annealing process system is determined according to the requirements of alloy properties, work hardening degree and product technical conditions. The main process parameters of annealing are annealing temperature, holding time, heating speed and cooling method.
The determination of the annealing process system should meet the following three requirements:
① Ensure uniform heating of annealed materials to ensure uniform organization and performance of materials;
② Ensure that annealed materials are not oxidized and have bright surfaces;
③ Save energy, reduce consumption and improve yield.
Therefore, the annealing process system of copper materials and the equipment used should be able to meet the above conditions. Such as reasonable furnace design, fast heating speed, protective atmosphere, precise control, easy adjustment, etc.
Selection of annealing temperature: In addition to alloy properties and hardening degree, the purpose of annealing should also be considered. For example, for intermediate annealing, the annealing temperature should be set at the upper limit and the annealing time should be appropriately shortened; for finished product annealing, the focus is on ensuring uniform product quality and performance, the annealing temperature should be set at the lower limit, and the fluctuation of annealing temperature should be strictly controlled; the annealing temperature for thick specifications should be higher than that for thin specifications; the annealing temperature for large loading should be higher than that for small loading; the annealing temperature for plates should be higher than that for strips.
Annealing heating rate: It should be determined according to alloy properties, loading, furnace structure, heat transfer method, metal temperature, temperature difference in the furnace and product requirements. Because rapid heating can improve productivity, fine grains and less oxidation, intermediate annealing of semi-finished products mostly adopts rapid heating; for finished product annealing, small loading and thin thickness, slow heating is adopted.
Insulation time: When the furnace temperature is designed, in order to increase the heating speed, the temperature of the heating section is relatively high. When heated to a certain temperature, insulation is required. At this time, the furnace temperature is close to the material temperature. The insulation time is based on ensuring that the annealed material is evenly heated through.
Cooling method: The finished product annealing is mostly air-cooled, and the intermediate annealing can sometimes be water-cooled. For alloy materials with severe oxidation, the oxide scale can be cracked and fallen off under rapid cooling. However, alloys with quenching effect are not allowed to be rapidly cooled.
Selection of vacuum heat treatment furnace
The following conditions should be considered when selecting a vacuum heat treatment furnace: that is, to meet the requirements of the vacuum heat treatment process and ensure quality and performance; to select a suitable heat source to meet the needs of production; the furnace has a simple structure, accurate temperature control, durability, and low investment; a high degree of automation, high production efficiency, good working conditions, and easy operation.
During annealing heating, the space for loading is evacuated into a vacuum, and the annealed material is not in contact with any medium. There are two forms of vacuum annealing: external heating and internal heating. The external heating type is that the heating element is placed outside the furnace and electric heating is adopted. The external heating vacuum furnace has a simple structure, is easy to manufacture, and is convenient for loading and unloading. However, the temperature rises slowly, the heat loss is large, and the furnace life is short. The internal heating type is that the heating element is inside the furnace, and the heat treatment material is also placed inside the furnace. Tungsten, molybdenum, graphite and other materials are often used as heating elements. The characteristics are fast heating, high heating temperature and long furnace life. However, the structure of the furnace is complex, the investment is large, and the temperature drops slowly. When vacuum annealing is adopted, pure copper adopts a vacuum degree of (10-1~10-2)×133.3Pa, and most copper alloys adopt a vacuum degree of (10-2~10-3)×133.3Pa. When vacuum annealing is adopted, the vacuum can only be broken when the temperature drops below 100℃ when the material is taken out of the furnace to prevent the annealing material from oxidizing.

Vacuum Annealing Furnace