It takes a long time for the complete quenching of fire machine equipment, especially for low temperature martensitic stable carbon steel. If the martensitic steel is rapidly cooled to a temperature slightly less than Ar1 isothermal, the change of A to P, and then air-cooled to indoor temperature, the quenching time can be greatly shortened. This quenching method is called isothermal annealing.
Isothermal annealing process of quenching machine equipment: heat treatment method of heating steel to a temperature higher than Ac3 (or Ac1) and cooling water rapidly to a temperature in ferrite region after a moderate time of heat insulation, and maintaining isotherm to change martensite into ferrite, and then air cooling to indoor temperature of the manufacturer of Zhongla Return Equipment.
Isothermal annealing of quenching machine equipment: Similar to thorough quenching, change is the easiest to control. Suitable for A more stable steel: high carbon steel (wc > 0.7%), alloy tool steel, high alloy steel (total output of aluminium alloy elements > 12%). Isothermal annealing is also beneficial to obtain uniform mechanism and properties. However, the discomfort is applied to large cross-section cast iron castings and large quantities of burden. Because isothermal annealing is not easy to make the internal temperature of steel parts or large quantities of steel parts exceed the isothermal temperature.
Heat treatment is to raise the temperature of steel to the critical temperature (or above) and keep it insulated for a certain period of time, then slow cooling water in the furnace, the final structure obtained is the transformation chemical substance.
The main purpose of heat treatment is that loose steel is beneficial to milling and manufacturing; eliminating welding stress to prevent bending deformation of iron castings; improving crystallization and structure to improve the manufacturing characteristics of steel; removing acetylene gas to avoid small white spots.
Because of the different composition of steel, the purpose of heat treatment is different. The treatment methods are also different. There are so-called complete heat treatment, incomplete heat treatment, external diffusion heat treatment, spheroidizing annealing, in-situ stress relief heat treatment and so on. Isothermal annealing is a new heat treatment method to replace complete heat treatment and incomplete heat treatment. The structure and characteristics obtained after treatment are similar to each other, but the necessary time for treatment can often be greatly shortened.
The operation steps of isothermal annealing can be divided into several steps.
(1) Raise the temperature of steel to the critical temperature (sub-eutectoid steel is up and down, eutectoid steel and sub-eutectoid copper are up and down), the necessary time for heat insulation and heat preservation is needed to obtain austenite structure.
(2) The steel that has been warmed up earlier is put into another furnace with a temperature slightly lower than that, or the steel is kept isothermally with the temperature from the furnace cooling to a little lower, so that the ultra-low temperature austenite can be completely transformed into the chemical substance.
(3) After the transformation of steel and steel is carried out, air-cooled, oil-cooled and even water-cooled heat dissipation can be taken out, but generally air-cooled.
The trend diagram of isothermal annealing operation process is shown in the figure. After isothermal annealing, the steel can reduce its compressive strength, improve its structure and eliminate acetylene gas.