Vacuum Furnace Heating Chamber
Selection of vacuum furnace heating chamber:
Graphite Reflector Screen
Generally, there are two kinds of hard felt and soft felt used in vacuum furnace. They are suitable for quenching, tempering and annealing of general steel. High temperature brazing, powder metallurgy and sintering.
Metal heat shield
Stainless steel and molybdenum are commonly used in vacuum furnaces. Molybdenum reflective screen is suitable for quenching, annealing, brazing and sintering of high temperature materials (such as superalloys, titanium alloys, magnetic materials, etc.) which require higher environment in the furnace. Stainless steel rice shooting screen is suitable for tempering, low temperature annealing, aging, vacuum aluminium brazing, and some low temperature furnace type selection.
Selection of Vacuum Degree
Medium vacuum (general limit 4X10-1P a) can be used for quenching heat treatment, and two-stage pumps (front pump and Roots pump) such as bearing steel, die steel and structural steel can be used for vacuum heat treatment.
For some products requiring high vacuum, such as vacuum heat treatment or high temperature brazing of superalloys, titanium alloys, magnetic materials, etc. Three-stage pump (front pump) can be selected. Roots pumps, diffusion pumps, etc.) generally require a vacuum limit of 10-4 Pa.
Basic knowledge of vacuum furnace:
Nitrogen should not be used as cooling gas when titanium alloy is treated in vacuum furnace, because titanium and nitrogen react at high temperature to form golden titanium nitride.
All the movable connections of the vacuum furnace are sealed by O-ring, which is cooled by water.
When the workpiece is quenched in vacuum, vacuum quenching oil should be used, which has lower saturated vapor pressure.
Vacuum furnace maintenance should be in the vacuum or pure nitrogen state, to avoid the usual use of inspiration, moisture absorption.
During the heating process, the workpiece and the material in the furnace will be deflated, which will reduce the vacuum.
The heating temperatures of vacuum tempering, vacuum annealing, vacuum solid solution treatment and vacuum aging are generally the same as those of conventional treatment.
Vacuum tempering furnace should have quick cooling device. The pressure of cooling water should be greater than 0.2 Mpa and the flow rate should be adjustable.