(1) Air atmosphere, air atmosphere furnace is a simple structure of the furnace type, the workpiece in the furnace above 560°C heating will be oxidized and decarburized.
(2) Flame atmosphere, flame atmosphere is the fuel furnace combustion product atmosphere. The combustion products are mainly composed of CO2, H2O and N2. There may also be excess O2 or burning CO. The nature of the flame atmosphere is mainly oxidizing, and it is weak oxidizing or weak reducing only when the amount of CO is large.
(3) Controlled atmosphere, controlled atmosphere is the atmosphere that people deliberately add to the furnace, mainly to control carbon potential, nitrogen potential or atmosphere reducibility.
According to the nature of the controlled atmosphere, there are:
(1) Neutral atmosphere, mainly nitrogen, adding other components on the basis of N2 to form a nitrogen-based atmosphere, whose properties change with the nature of the additive.
(2) Reductive atmosphere, mainly H2. H2 has the advantages of low density, low viscosity, high thermal conductivity and strong reducibility, so it has the advantages of small heat capacity, good flow state and high temperature uniformity.
(3) Carbon-containing atmosphere, carbon-containing atmosphere is formed by cracking or burning hydrocarbons, there are two categories of endothermic and exothermic, and this atmosphere can be generated in the furnace outside the processing furnace.
(4) Bath medium, the commonly used bath medium has salt bath, lead bath and oil bath, its nature is neutral, and sometimes other substances are added on the basis of neutral salt bath to form a salt bath with corresponding material characteristics, such as salt bath containing carbon, nitrogen and boron.
(5) Vacuum state, less than 101.325kPa rarefied gas state, are called vacuum state. Heat treatment in the high vacuum state has the dual role of improving product quality and protecting the environment, which is one of the main directions of the development of heat treatment equipment.
(6) Operation mode: The heat treatment furnace equipment is divided into two categories according to the operation mode: intermittent operation furnace and continuous operation furnace.