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How to choose the heat treatment process for steel
Category：answer Publishing time：2025-09-16 22:54:24 Browse： Times
Steel, as one of the most widely used metal materials in modern industry, its performance directly affects the quality and service life of products. In order to meet the requirements of different working conditions, steel often needs to be heat treated during the processing process. Heat treatment is to change the internal microstructure of steel by controlling the heating, holding and cooling processes, thereby improving its mechanical properties, processing properties or service properties. Therefore, how to scientifically and reasonably select the heat treatment process is particularly important.
1. Understanding the chemical composition and application of steel
The primary basis for selecting a heat treatment process is the chemical composition of the steel. Different types of steel (such as carbon steel, alloy steel, tool steel, stainless steel, etc.) have different phase transformation characteristics, hardenability, and tempering stability due to their different chemical compositions, and therefore have different requirements for heat treatment.
For example, low-carbon steel usually adopts normalizing or annealing treatment to improve cutting performance; while high-carbon steel often adopts quenching + low-temperature tempering to obtain high hardness and wear resistance. For alloy steel, due to the addition of alloying elements which improve the hardenability, quenching + high-temperature tempering (i.e., tempering treatment) is usually adopted to obtain good comprehensive mechanical properties.
In addition, the specific application of steel is also an important factor in determining the heat treatment method. For example, steel used to manufacture gears requires high hardness and wear resistance, and surface hardening or carburizing quenching is often adopted; while steel used for structural parts pays more attention to the balance of toughness and strength, and is suitable for tempering treatment.
2. Clarify the target performance of heat treatment
The purposes of heat treatment are diverse, including increasing hardness, enhancing strength, improving toughness, eliminating residual stress, and improving processing properties. Therefore, before selecting a heat treatment process, it is necessary to clarify the performance indicators to be achieved.
- Improve hardness and wear resistance: Suitable for materials such as tool steel and mold steel, and the commonly used method is quenching + low-temperature tempering.
- Enhance comprehensive mechanical properties: Suitable for parts such as shafts and connecting rods, and tempering treatment is commonly used.
- Refine grain size and improve tissue uniformity: Normalizing treatment can be adopted.
- Eliminate internal stress and reduce hardness: Suitable for parts after cold working, using annealing or stress-relieving annealing.
3. Consider the feasibility and economy of the process
In addition to meeting performance requirements, the practical feasibility and economic cost of the heat treatment process should also be comprehensively considered. For example:
- Equipment conditions: Quenching requires a rapid cooling medium, and if there is a lack of suitable quenching fluid or equipment, it may be necessary to choose normalizing or air cooling treatment.
- Deformation control: For precision parts, it is advisable to avoid excessive deformation caused by heat treatment, and methods such as分级淬火 (step quenching) and isothermal quenching can be selected.
- Energy consumption and environmental protection: The heat treatment process has high energy consumption, and it is advisable to choose energy-saving processes and consider the impact of emissions on the environment.
4. Case analysis in practice
Taking 45 steel (carbon content about 0.45%) as an example, it is widely used in the manufacture of mechanical parts. If it is used to manufacture shaft-type components, it requires good comprehensive mechanical properties, and tempering treatment is often adopted - that is, quenching at about 850℃ and then high-temperature tempering to a hardness range of 200~300HB, in order to obtain excellent strength and toughness. While if it is used to make gears, the surface requires high hardness and the interior maintains certain toughness, surface induction hardening treatment may be adopted.
Conclusion
In summary, the selection of steel heat treatment process is a systematic project, which must be comprehensively considered with material composition, usage requirements, process feasibility, and economic factors. Only on the basis of a full understanding of the material characteristics and the principles of the process can a scientific and reasonable heat treatment plan be formulated, thus fully tapping the potential performance of steel, improving product quality and service life.
Steel, as one of the most widely used metal materials in modern industry, its performance directly affects the quality and service life of products. In order to meet the requirements of different working conditions, steel often needs to be heat treated during the processing process. Heat treatment is to change the internal microstructure of steel by controlling the heating, holding and cooling processes, thereby improving its mechanical properties, processing properties or service properties. Therefore, how to scientifically and reasonably select the heat treatment process is particularly important.
1. Understanding the chemical composition and application of steel
The primary basis for selecting a heat treatment process is the chemical composition of the steel. Different types of steel (such as carbon steel, alloy steel, tool steel, stainless steel, etc.) have different phase transformation characteristics, hardenability, and tempering stability due to their different chemical compositions, and therefore have different requirements for heat treatment.
For example, low-carbon steel usually adopts normalizing or annealing treatment to improve cutting performance; while high-carbon steel often adopts quenching + low-temperature tempering to obtain high hardness and wear resistance. For alloy steel, due to the addition of alloying elements which improve the hardenability, quenching + high-temperature tempering (i.e., tempering treatment) is usually adopted to obtain good comprehensive mechanical properties.
In addition, the specific application of steel is also an important factor in determining the heat treatment method. For example, steel used to manufacture gears requires high hardness and wear resistance, and surface hardening or carburizing quenching is often adopted; while steel used for structural parts pays more attention to the balance of toughness and strength, and is suitable for tempering treatment.
2. Clarify the target performance of heat treatment
The purposes of heat treatment are diverse, including increasing hardness, enhancing strength, improving toughness, eliminating residual stress, and improving processing properties. Therefore, before selecting a heat treatment process, it is necessary to clarify the performance indicators to be achieved.
- Improve hardness and wear resistance: Suitable for materials such as tool steel and mold steel, and the commonly used method is quenching + low-temperature tempering.
- Enhance comprehensive mechanical properties: Suitable for parts such as shafts and connecting rods, and tempering treatment is commonly used.
- Refine grain size and improve tissue uniformity: Normalizing treatment can be adopted.
- Eliminate internal stress and reduce hardness: Suitable for parts after cold working, using annealing or stress-relieving annealing.
3. Consider the feasibility and economy of the process
In addition to meeting performance requirements, the practical feasibility and economic cost of the heat treatment process should also be comprehensively considered. For example:
- Equipment conditions: Quenching requires a rapid cooling medium, and if there is a lack of suitable quenching fluid or equipment, it may be necessary to choose normalizing or air cooling treatment.
- Deformation control: For precision parts, it is advisable to avoid excessive deformation caused by heat treatment, and methods such as分级淬火 (step quenching) and isothermal quenching can be selected.
- Energy consumption and environmental protection: The heat treatment process has high energy consumption, and it is advisable to choose energy-saving processes and consider the impact of emissions on the environment.
4. Case analysis in practice
Taking 45 steel (carbon content about 0.45%) as an example, it is widely used in the manufacture of mechanical parts. If it is used to manufacture shaft-type components, it requires good comprehensive mechanical properties, and tempering treatment is often adopted - that is, quenching at about 850℃ and then high-temperature tempering to a hardness range of 200~300HB, in order to obtain excellent strength and toughness. While if it is used to make gears, the surface requires high hardness and the interior maintains certain toughness, surface induction hardening treatment may be adopted.
Conclusion
In summary, the selection of steel heat treatment process is a systematic project, which must be comprehensively considered with material composition, usage requirements, process feasibility, and economic factors. Only on the basis of a full understanding of the material characteristics and the principles of the process can a scientific and reasonable heat treatment plan be formulated, thus fully tapping the potential performance of steel, improving product quality and service life.
