Heat treatment is a key process in the production and processing of mold steel, which directly determines the mechanical properties (hardness, toughness, wear resistance) of the mold steel and further affects the service life of the mold. Many mold failures (such as cracking, deformation, and wear) are caused by improper heat treatment. In this article, we will explain in detail how heat treatment affects the service life of mold steel, introduce common heat treatment processes, and share precautions to help you avoid mistakes and extend the service life of your molds.

The Core Purpose of Mold Steel Heat Treatment

The main purpose of mold steel heat treatment is to improve the performance of the steel to meet the working requirements of the mold. Specifically, it includes the following aspects:

• Improve Hardness and Wear Resistance: Through heat treatment (such as quenching and tempering), the hardness of the mold steel can be significantly improved, making it more wear-resistant and reducing mold wear during use.
• Enhance Toughness: Proper heat treatment can eliminate internal stress in the steel, improve the toughness of the steel, and avoid mold cracking caused by impact load during use.
• Uniformize Structure: Heat treatment can make the internal structure of the mold steel uniform and dense, reducing internal defects (such as segregation, inclusions) and improving the stability of the steel performance.
• Improve Machinability: Some heat treatment processes (such as annealing) can reduce the hardness of the steel, making it easier to process and reducing processing costs.

Common Heat Treatment Processes for Mold Steel

Different mold steel grades and application scenarios require different heat treatment processes. The following are the most common heat treatment processes for mold steel and their functions:

1. Annealing: The steel is heated to a certain temperature (usually 700-800℃), kept warm for a period of time, and then slowly cooled. The purpose is to reduce the hardness of the steel, eliminate internal stress, and improve machinability. It is usually used before the processing of mold steel.
2. Quenching: The steel is heated to the austenitizing temperature (different grades have different temperatures), kept warm for a period of time, and then quickly cooled (oil cooling, water cooling, or air cooling). The purpose is to improve the hardness and wear resistance of the steel. However, quenched steel is brittle and needs to be tempered in time.
3. Tempering: The quenched steel is heated to a temperature lower than the austenitizing temperature (usually 200-600℃), kept warm for a period of time, and then cooled. The purpose is to eliminate the brittleness caused by quenching, improve the toughness of the steel, and stabilize the structure and size of the steel. Tempering is usually carried out immediately after quenching.
4. Solution Annealing: Mainly used for stainless mold steel (such as S136). The steel is heated to a high temperature (1000-1100℃), kept warm, and then cooled quickly. The purpose is to dissolve the carbides in the steel, make the structure uniform, and improve corrosion resistance and polishability.

Heat Treatment Specifications for Different Mold Steel Grades

Different mold steel grades have different chemical compositions, so their heat treatment specifications are also different. The following are the recommended heat treatment specifications for common mold steel grades, which you can directly refer to:

Common Heat Treatment Mistakes and Consequences

Improper heat treatment will seriously affect the service life of the mold steel. Here are the most common mistakes and their consequences:

• Excessively High Quenching Temperature: If the quenching temperature is too high, the grain of the steel will grow, which will reduce the toughness of the steel and make it easy to crack during use. In severe cases, the steel may be burned and scrapped.
• Insufficient Holding Time: If the holding time during heating is insufficient, the austenitization of the steel will be incomplete, resulting in uneven structure and performance of the steel, and the hardness and wear resistance will not meet the requirements.
• Too Fast or Too Slow Cooling: Too fast cooling (such as water cooling for high-carbon steel) will increase internal stress and cause mold cracking; too slow cooling will reduce the hardness of the steel and affect its wear resistance.
• Not Tempering After Quenching: Quenched steel is brittle. If it is not tempered in time, it will be easy to crack under impact load, and the service life of the mold will be greatly shortened.

If you are not sure about the heat treatment process of mold steel, our professional engineer team can provide you with free consultation and customized heat treatment solutions. We provide one-stop services from mold steel selection to heat treatment and processing, ensuring that your mold steel has the best performance and the longest service life. Contact us now to get professional advice!