vacuum heat treatment process principle

According to the principle of vacuum heating, increasing the preheating temperature can reduce the temperature difference between the inside and outside of the workpiece and shorten the preheating time, while the final holding time should be appropriately extended to make the carbide in the steel fully dissolved. In this way, not only the quality is guaranteed, but also the work efficiency is improved. The duration of heat preservation is also related to the following factors:

① Charging capacity: if the furnace capacity is large when the workpiece size is the same, the burn through time should be prolonged; otherwise, it should be shortened.

② Placement form of workpieces: since the vacuum furnace is radiation heating, generally speaking, if the shape of workpieces is the same, the workpieces should be placed in order as much as possible to avoid blocking the thermal radiation, and a certain space (< d) should be set aside to ensure that the workpieces can receive the maximum thermal radiation; for the same furnace of different workpieces, in addition to calculating the holding time according to the maximum workpieces, the burning through time should be increased. When the space is less than D, the empirical formula is as follows:


Where G is the charging capacity (kg)

The meanings of other symbols are the same as before.

in addition

For small workpiece (effective thickness d ≤ 20mm)

Or the space between workpieces ≥ D

Holding time can be reduced:



For large workpiece (effective thickness d ≥ 100mm)

The final holding time can be reduced


③ Heating temperature: high heating temperature can shorten the holding time.

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