Is the deformation of workpiece in high-pressure gas quenching certain to be less?

Answer: At present, the deformation of high-pressure gas quenching workpieces in China is relatively large. The reason is that the furnace shape of typical domestic vacuum high-pressure gas quenching furnace is a circular furnace, and quenching cooling nozzles are evenly arranged around the furnace to obtain a uniform airflow field. In fact, the air flow uniformity of cooling in the furnace with this structure is very poor. The air flow velocity near the end face of the front and rear furnaces is very low, and the cooling capacity is poor. The cooling speed at one end near the furnace door is faster than that at the other end. In the effective size range of the charge, the cooling air velocity is also low, and the gas velocity on the cylindrical surface facing the nozzle is high, while the cooling capacity between two adjacent nozzles is very low, and the spray cooling trace of the workpiece facing the nozzle is obvious. The cooling of workpieces in the same furnace at different positions varies greatly. This situation leads to large quenching deformation of the workpiece and inconsistent tempering resistance of the workpiece.

Avoid contact between heat treatment products and electric heating elements

In particular, copper, aluminum, zinc, tin, lead, etc. should be in contact with the electric heating elements, whether it is fine powder, molten liquid or steam, to prevent the formation of "pockmarks" on the surface of the electric heating body, reduce the cross section, and finally burn off due to overheating.

Pay attention to the positioning and binding methods of temperature measuring contacts

When testing the furnace temperature uniformity, pay attention to the positioning and binding method of the temperature measuring contact, as well as the distance from the heating element.

In the vacuum tempering furnace, the furnace and brick laying shall be cleaned frequently (at least monthly) with a brush, broom or compressed air, vacuum cleaner, etc., to prevent impurities such as oxide skin in the furnace from falling on the electric heating element, causing short circuit, or even burning the brick laying. The heat-resistant steel components such as base plate, crucible and furnace tank should be lifted and knocked to remove the oxide skin after being used for a period of time. If impurities such as iron oxide scale are not removed in time, they will melt and react with refractory bricks to melt furnace wire.

After the vacuum furnace is heated, the furnace door cannot be opened for a long time

When the temperature is higher than 400 ℃, sharp cooling is not allowed. The electric heating element is easy to cause oxidation and peeling when the temperature is high and the temperature changes greatly. For molybdenum heating furnace, EI should be cooled to below 200 ℃ before stopping sending protective gas during regular use and maintenance.

Ensure that the lead out bar and wire clamp are in good contact

The lead out bar shall not be red, and the maximum temperature rise of the wire clamp during power supply shall not exceed 60 ℃. Note that due to the thermal expansion, cold contraction and creep elongation during heating and shutdown, the bolts of the lead out bar wiring clamp are easy to be oxidized and loose, forming a virtual connection short circuit, and should be checked and tightened regularly.