30CrMnSiA delivery state is mostly normalised, annealed, high temperature tempered or delivered without heat treatment.
1, normalising: the workpiece is heated to the appropriate temperature, held for a period of time from the furnace to cool the metal heat treatment process in the air. The difference between normalising and annealing is that the normalising cooling rate is slightly faster than the annealing cooling rate, and thus the normalising organisation is finer than the annealing organisation, and its mechanical properties are also improved. In addition, normalising furnace cooling does not take up equipment, high productivity, so the production of normalising instead of annealing as far as possible;
2, annealing: the metal is slowly heated to a certain temperature, maintained for a sufficient period of time, and then cooled at an appropriate rate (usually slow cooling, sometimes controlled cooling) of a metal heat treatment process. The purpose is to make after casting, forging, rolling, welding or cutting processed materials or workpieces soften, improve the plasticity and toughness, so that the chemical composition of the uniformity of the removal of residual stress, or get the expected physical properties. Annealing process with the purpose of different and a variety of, such as recrystallisation annealing, isothermal annealing, homogenisation annealing, spheroidal annealing, stress relief annealing, recrystallisation annealing, as well as stabilisation annealing, magnetic field annealing and so on. It is a heat treatment process in which the material is exposed to high temperatures for a long period of time and then slowly cooled. The main purpose is: (1) to release stress, (2) to increase the ductility and toughness of the material, (3) to produce a special microstructure.
3, tempering: quenching into martensite steel heated to a temperature below the critical point A1, holding appropriate time, and then cooled to room temperature of a heat treatment process. The purpose of tempering is to eliminate quenching stress, so that the organisation of steel into a relatively stable state. Improve the plasticity and toughness of steel under the condition of not reducing or appropriately reducing the hardness and strength of steel to obtain the desired properties.
