Avoid contact between heat treated products and electrical heating elements
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In particular, copper, aluminum, zinc, tin, lead, etc. are in contact with electric heating elements, whether it is fine powder, melt or steam, etc., to prevent the formation of “pit pit” on the surface of the electric heating body, the cross section becomes smaller, and finally the heat is overheated. Broken.
Vacuum tempering furnace pay attention to the positioning and binding method of temperature measuring contacts
When testing the uniformity of the furnace temperature, attention should be paid to the positioning and binding method of the temperature measuring contact and the distance from the heating element.
In the furnace, the furnace and the brick are often cleaned (at least monthly) with a brush, broom or compressed air, vacuum cleaner, etc., to prevent impurities such as oxide scale from falling into the electric heating element, causing a short circuit or even burning the brick. For each period of use of the heat-resistant steel members such as the bottom plate, the crucible, and the furnace pot, it is preferable to lift the tap and remove the scale. If impurities such as iron oxide scale are not removed in time, they will melt and react with the refractory bricks to melt the furnace wire.
After the vacuum furnace is warmed up, the furnace door cannot be opened for a long time.
When the temperature is higher than 400 ° C, it must not be cooled sharply. For the electric heating element, when the temperature is high and the heat and cold change greatly, it is easy to cause oxidative peeling. For molybdenum heating furnaces, EI is often used for maintenance and should be cooled to below 200 °C to stop the shielding gas.
Ensure that the lead bar and the wire clip should be in good contact
The lead bar should not be reddened, and the temperature rise of the wire clip should not exceed 60 °C. Note that due to thermal expansion and contraction and creep elongation during heating and shutdown, the bolts leading to the rod wiring clip are prone to oxidation loosening, forming a virtual short circuit, and regular inspection and tightening.
When a vacuum furnace is used to treat a titanium alloy, it is not preferable to use nitrogen as a cooling gas because titanium and nitrogen react at a high temperature to form golden yellow titanium nitride.
The movable connection parts of the vacuum furnace are all sealed by O-rings, and this part is cooled by water.
When the workpiece is quenched under vacuum, vacuum quenching oil should be used, which has a lower saturated vapor pressure.
The maintenance of the vacuum furnace should be under vacuum or pure nitrogen, so as to avoid inhalation and moisture absorption when not in use.
The pressure rise rate of domestic vacuum furnaces should be no more than 1.33Pa/h, and the standard of some foreign enterprises is 0.67Pa/h.
The vacuum heating is mainly based on radiation, and the workpiece should be kept in the furnace.
During the heating process, the workpiece and the material in the furnace will deflate, causing the vacuum to decrease.