Tempering of Steel – Process, Effects

Tempering is a combined heat treatment process consisting of hardening and high tempering. The aim of quenching and tempering is to adjust the ratio of toughness and strength.  The aim is to achieve the highest possible toughness with increased strength.

The importance of tempering

The main aim of tempering is to achieve a balance between hardness and ductility, making the material suitable for a wide range of industrial applications. The increased tempering temperature increases toughness, which provides protection against brittle fracture (especially at low temperatures and under impact load). In addition, the fatigue strength and yield strength are increased by tempering.

Process of tempering explained

After hardening the steel, a high tempering temperature of between 450°C and 650°C must be selected. The tempering time is usually 1 – 3 hours. Quenching media such as oil, water or air are used for tempering. Depending on the material, however, tempering temperatures between 370°C and 500°C should be avoided if possible in order to prevent so-called temper embrittlement.

When using the tempered components, it must be ensured that the operating temperature is below the selected tempering temperature, otherwise the strength will drop.

Precise temperature control

The tempering process requires precise temperature control in order to achieve the desired material properties. At lower tempering temperatures, tempering serves to improve toughness and achieve a high tensile strength. At higher tempering temperatures, the tensile strength decreases while the toughness increases significantly.

Stages of tempering

Tempering stages 3 and 4 are used for tempering, each of which has its own special features and effects:

  • Third stage (320°C – 400°C): cubic martensite is depleted of carbon and causes ferrite formation. Cementite is formed and 500°C embrittlement occurs between 370°C and 500°C.
  • Fourth stage (400 °C – Ac1): Crystal recovery occurs and the cementite coarsens. Secondary hardening occurs in alloyed steels.

Modern applications of tempering

Tempering is not just a theoretical concept; it has practical applications that span multiple industries. From automotive components to construction materials and even kitchenware, the tempering process plays a pivotal role in enhancing material properties for specific uses. For instance, tempered steel is commonly used in gears, springs, and cutting tools, where a balance between hardness and ductility is essential.

Elevate your material properties with specialized treatments!

While the article focused on the tempering process to enhance ductility and toughness, there are other specialized treatments to consider for different material requirements. Bortec Group offers a range of services tailored to improve wear resistance, corrosion resistance, and more.

Take the next step in material treatment and explore Bortec Group’s specialized services to meet your specific needs!