What is the quenching structure and what is the purpose of quenching?

Quenching refers to a metal heat treatment process in which a metal workpiece is heated to a certain appropriate temperature and held for a period of time, and then immersed in a quenching medium for rapid cooling. Solution treatment of materials such as aluminum alloys, copper alloys, titanium alloys, tempered glass, etc., or heat treatment processes with a rapid cooling process are usually referred to as quenching.

According to the different cooling methods and cooling mediums, quenching can be divided into single liquid quenching (the most common quenching method), double media quenching, martensitic graded quenching and bainite isothermal quenching.

The strength, toughness and fatigue strength of the metal can be greatly improved through quenching and tempering at different temperatures, and different matches between these properties (comprehensive mechanical properties) can be obtained to meet different application requirements. In addition, quenching can also make some special properties of steel obtain certain physical and chemical properties, such as quenching to enhance the ferromagnetism of permanent magnet steel, and improve the corrosion resistance of stainless steel.

The most common quenching of steel is to heat the steel to a temperature above the critical temperature AC3 (sub-eutectic steel) or AC1 (super-eutectic steel), hold it for a period of time to make it fully or partially austenitic, and then cool the steel to below ms (or isothermal near ms) at a cooling rate greater than the critical cooling rate to make the steel undergo martensite (or bainite) transformation.

Quenching is just an intermediate process that prepares the ground for tempering below. Generally quenched structure is martensite!

The main causes are the coarse heart tissue and the insufficient induction quenching temperature.

Because the tissue is coarse and belongs to a non-equilibrium structure, the tissue is not easy to austenitize when heated, so it is easy to cause drosnitic structure in the presence of ferrite during induction hardening.

You didn't say what alloy it was?

Surface quenching is done with a high-frequency machine, and the overall quenching is done in the furnace, and the surface quenching is only the hardness on the surface, and there is no hardness in it, so that the whole is elastic, and the overall quenching is more brittle.

Quenching is a heat treatment process method that heats the steel above the critical temperature, keeps it warm for a certain time, and then cools it at a temperature greater than the critical cooling rate, so as to obtain an unbalanced structure dominated by martensite (bainite or single-phase austenite is also obtained as needed).

The purpose of quenching is to make the supercooled austenite carry out martensite or bainite transformation to obtain the martensite or bainite structure, and then cooperate with tempering at different temperatures to greatly improve the rigidity, hardness, wear resistance, fatigue strength and toughness of steel, so as to meet the different requirements of various mechanical parts and tools.

The purpose of quenching is to make the supercooled austenite undergo martensite or bainite transformation to obtain martensite or bainite structure, and then cooperate with tempering at different temperatures to greatly improve the rigidity, hardness, wear resistance, fatigue strength and toughness of steel, so as to meet the different requirements of various mechanical parts and tools. Quenching is a heat treatment process method that heats the steel to above the critical temperature and dissipates the liquid, keeps it warm for a certain time, and then cools it at a temperature rate greater than the critical cooling rate, so as to obtain an unbalanced structure dominated by Ma's Li Huiti.

The quenching and holding time is determined by various factors such as the heating method of the equipment, the size of the parts, the composition of the steel, the amount of furnace and the power of the equipment. In the case of integral quenching, the purpose of heat preservation is to make the internal temperature of the workpiece uniform and consistent. For all types of quenching, the holding time ultimately depends on obtaining a good quenching heating structure in the area where quenching is required.

The hardness of the quenched workpiece affects the quenching effect. Quenched workpieces are generally determined by a Rockwell hardness tester to determine their HRC value. The HRA value can be determined for quenched thin hard steel plates and surface quenched workpieces, while the HRC value of quenched steel plates with a thickness of less than 5 mm, shallow surface quenched workpieces and quenched steel rods with a diameter of less than 5 mm can be determined by a Rockwell hardness tester instead.

Quenching is more suitable for parts with small thickness and diameter, and for parts that are too large, the quenching depth is not enough, and carburizing also has the same problem, so it should be considered to add alloys such as chromium to the steel to increase strength.