Vacuum annealing of high quality spring steel, tool steel, precision steel wire, stainless steel products and titanium alloy, for bright annealing can be treated with vacuum. The lower the annealing temperature, the higher the degree of vacuum. In order to prevent the evaporation of chromium and accelerate the heat conduction, the carrier gas heating (heat preservation) method is generally adopted.
Vacuum quenching vacuum quenching furnace with cooling gas quenching oil quenching method is divided into two categories, according to the station number is divided into single chamber and double chamber, 904 mountain, fear of ridicule is cycle furnace. Vacuum oil quenching furnace is double room after room, the electric heating element is arranged at the lower part of the oil tank room. Complete the workpiece after heating, insulation into the room, closing the door after the room filled with inert gas to move around 2.66%26times; lO ~ 1.01%26times; 10 Pa (200 ~ 760mm Hg), oil. Oil quenching can cause the surface deterioration. Due to the high surface activity, the thin layer carburizing can be produced under the action of transient high temperature oil film. The development of vacuum quenching technology mainly lies in the development of gas quenching furnace with excellent performance and single station. The double chamber furnace can be used for gas quenching (in the jet cooling) double type operation, but the mass charging production difficulty, also easy to cause the workpiece deformation in high temperature moving or changing range to increase the quenching deformation of workpiece. A single station gas quenching furnace is in the heating room after the completion of the heat in the air cooling. The cooling rate of gas cooling is not as fast as that of oil cooling, but also lower than that of the conventional quenching method. Therefore, increasing the pressure of the spray chamber and increasing the flow rate, as well as the inert gas helium and hydrogen, which are smaller than the molar mass of nitrogen and argon, are the mainstream of the development of vacuum quenching technology. In the late 70s, the pressure of nitrogen spraying was increased from 1 to%26times (10Pa = 2) to%26times (10Pa = 6), and the cooling capacity was close to that of oil under normal pressure. In the middle of the 80s, the super high pressure gas quenching, with (10 ~ 20)%26times; 10Pa helium, the cooling capacity is equal to or slightly higher than the oil quenching, has entered the industrial practice. In the early 90s, the cooling capacity of 40%26times, 10Pa hydrogen, close to water quenching, is still in its infancy. Industrial developed countries have progressed to high pressure (5 ~ 6)%26times; 10. Pa gas quenching is the main body, and the relationship between the vapor pressure (theoretical value) and the temperature of the gas produced in China is still in the stage of 10Pa (2%26times).
Results vacuum carburizing is a process of vacuum carburizing and quenching. After the vacuum carburizing temperature and heating to make insulation surface cleaning, activation, pass into thin rich carbon gas (see controlled atmosphere heat treatment), at about 1330Pa (10T0rr) of infiltration under negative pressure, then stop gas diffusion (buck). After carburizing, the quenching of the precision steel pipe adopts a quenching method, that is to say, the power is cut off, the nitrogen is cooled to the critical point of A, and the internal phase change occurs, then the gas is stopped, the pump is opened, and the temperature is increased to Ac1, Accm. Quenching method can be used for gas or oil cooling. The latter is after austenitizing into the front room, filled with nitrogen to atmospheric pressure, oil. Vacuum carburizing temperature is generally higher than ordinary gas carburizing, often using 920 to 1040 DEG C infiltration and diffusion can be shown in the following two stages, can also be used pulse type ventilation, gas stop, multi section of the infiltration of the expansion phase, the effect is better. Due to the high temperature, especially the surface clean, active, the formation of vacuum carburizing layer faster than ordinary gas, liquid and solid carburizing, such as the requirements of the infiltration layer for 1mm, at 927 5h, while only 1h.