What are the types of tempering What are the characteristics of tempering?

What does normalizing, annealing, quenching, and tempering mean? Have you figured it all out?

Answer: 1. What are the types of tempering? In production, it is often based on the requirements for the performance of the workpiece.

According to the different heating temperatures, tempering is divided into low-temperature tempering, medium-temperature tempering, and high-temperature tempering. The heat treatment process of quenching and subsequent high-temperature tempering is called quenching and tempering, that is, it has a high degree of strength and good plastic toughness.

1) Low temperature tempering: 150-250, m back, reduce internal stress and brittleness, improve plastic toughness, and have high hardness and wear resistance. It is used to make gages, knives and rolling bearings, etc.

2) Medium temperature tempering: 350-500, t back, with high elasticity, certain plasticity and hardness. It is used to make springs, forging dies, etc.

3) High temperature tempering: 500-650, s back, with good comprehensive mechanical properties. It is used to make gears, crankshafts, etc.

2. What are the characteristics of tempering? The role of tempering is to:

Improve the stability of the workpiece, so that the workpiece will no longer undergo tissue transformation during use, so that the geometric size and performance of the workpiece remain stable.

Internal stresses are relieved in order to improve the performance of the workpiece and stabilize the workpiece geometry.

Adjust the mechanical properties of steel to meet the requirements of use.

The reason why tempering has these effects is that when the temperature rises, the activity ability of the atoms increases, and the atoms of iron, carbon and other alloying elements in the steel can diffuse relatively quickly, realizing the rearrangement and combination of atoms, so that the unstable unbalanced organization is gradually transformed into a stable equilibrium organization. The elimination of internal stresses is also associated with a decrease in the strength of the metal as the temperature increases.

The purpose of tempering: the structure of the steel after quenching is martensite and residual austenite, which is in a metastable state, and tempering is the treatment to make it tend to a stable state. Get the required organization according to the requirements of the part.

It is divided into low temperature tempering, medium temperature tempering and high temperature tempering;

Low temperature tempering (150 250) obtains tempered martensitic structure, which reduces the quenching stress and brittleness of the steel while preserving high hardness;

Tempering at medium temperature (350 500) yields a tempered tostenite structure with a hardness of HRC40 50. This kind of tissue has a high elastic limit and yield limit, has good toughness, and is mainly used for elastic elements, etc.;

High temperature tempering (500 650 ) High temperature tempering to obtain tempered sostenite structure. It has excellent comprehensive mechanical properties, and is mostly used for tempering after quenching of structural parts. Quenching + high-temperature tempering is called quenching and tempering.

Tempering process of carbon steel

The microstructure transformation during tempering of quenched carbon steel is representative for all steels. The tempering process includes four types of reactions: martensite decomposition, carbide precipitation, transformation, aggregation and growth, ferrite recovery and recrystallization, and residual austenite decomposition. Schematic diagram of the transformation of low and medium carbon steel tempering process.

Depending on their reaction temperature, they can be described as four stages that overlap each other.

After tempering at 250 °C, the martensitis remains about carbon. Martensite with a carbon content of less than 200 does not occur when tempered below 200 - carbide precipitation, only carbon segregation, and tempering at higher temperatures directly decomposes cementite.

Tempering is a process of metal heat treatment in which the quenched workpiece is reheated to an appropriate temperature lower than the lower critical temperature ac1, and then cooled in air or water, oil and other media after holding it for a period of time. It is generally used to reduce or eliminate the internal stress in the hardened steel, or to reduce its hardness and strength to improve its ductility or toughness. Tempering is generally carried out immediately after quenching, the purpose of which is to eliminate the residual stress generated during the quenching of the workpiece and prevent deformation and cracking; Adjust the hardness, strength, plasticity and toughness of the workpiece to meet the performance requirements; Stabilize the structure and size, ensure accuracy, etc.

Low temperature tempering: 1. The workpiece is tempered at 150 250.

2. The purpose is to maintain the high hardness and wear resistance of the quenched workpiece, reduce the residual stress and brittleness of quenching, and obtain tempered martensite after tempering, which refers to the structure obtained when quenched martensite is tempered at low temperature.

3. Scope of application: Mainly used in all kinds of high-carbon steel tools, cutting tools, measuring tools, molds, rolling bearings, carburizing and surface quenching parts, etc.

According to the different performance requirements of the workpiece, according to the different tempering temperatures, tempering can be divided into the following types:

1. Low temperature tempering (150 250 degrees).

The tissue obtained by low temperature tempering is tempered martensite. Its purpose is to reduce the internal stress and brittleness of quenched steel on the premise of maintaining its high hardness and high wear resistance, so as to avoid chipping or premature damage during use.

It is mainly used for all kinds of high-carbon cutting tools, measuring tools, cold stamping dies, rolling bearings and carburized parts, etc., and the hardness after tempering is generally HRC58 64.

2. Tempering at medium temperature (250 500 degrees).

The tissue obtained by tempering at medium temperature is tempered dronther. The aim is to obtain high yield strength, elastic limit and high toughness. Therefore, it is mainly used for the treatment of various springs and hot work molds, and the hardness after tempering is generally HRC35 50.

3. High temperature tempering (500 650 degrees).

The structure obtained by high temperature tempering is tempered sostenite. It is customary to combine quenching and high temperature tempering heat treatment as quenching and tempering treatment, which is to obtain comprehensive mechanical properties with good strength, hardness, plasticity and toughness. Therefore, it is widely used in automobiles, tractors, machine tools, etc., such as connecting rods, bolts, gears and shafts.

After tempering, the hardness is generally HB200 330.

The purpose of tempering:

1) Reduce or eliminate the internal stress generated during the quenching of the workpiece, and prevent the deformation and cracking of the workpiece.

2) Improve the toughness of the steel through tempering, and adjust the strength and hardness of the steel appropriately to meet the performance requirements of different workpieces.

3) Stabilize the organization, so that the workpiece does not change in the process of use, so as to ensure that the shape and size of the workpiece remain unchanged, and ensure the accuracy of the workpiece.

Common tempering methods:

According to the different tempering temperatures, it can be divided into low temperature tempering (150 250), medium temperature tempering (250 450) and high temperature tempering (450

The heat treatment process of high-temperature tempering of the quenched steel is called quenching and tempering treatment, which can make the steel obtain comprehensive mechanical properties with good strength, toughness and plasticity.