Tool Steel Heat Treatment: Process, Benefits, and Quality Control

Tool steel is widely used in industrial processes due to its extreme hardness and dimensional stability properties. The two key types include hot work and cold work steel. Other important categories include high-speed and shock-resistant varieties. Heat treatment is considered the single most important factor in the production, since it effectively determines the quality, and hence the price of acquiring it from a reputable facility.

Key Steps of the Heat Treatment Process

The two key phases in this process are the creation of the austenite and its subsequent transformation into Martensite.

1. Preheating Phase: Preheating the alloy to different temperature levels, such as 650° C and 850° C, prepares the material to resist thermal shocks. This ensures that the material does not show cracks and maintains a uniform temperature between the surface and the core.
2. The Hardening Phase: The material is heated to an extremely high temperature that is determined depending on the grade of the steel. The high temperature impact creates the Austenite phase, when the carbon and the alloys dissolve into the metal matrix.
3. The Quenching Phase: The raw material must undergo rapid cooling process after extreme heat. This effectively ‘freezes’ Austenite into Martensite. Cooling methods include the application of oil, air, or pressurized gas.
4. The Tempering Phase: The Martensite is reheated at a specific lower temperature. This helps to restore the toughness. Also, quenching is essential to relieve internal stresses. The purpose of this phase is to ensure that all retaining Austenite is transformed into Martensite.
5. The Cryogenic Phase: This is an optional phase where the steel is frozen to sub-zero temperatures that finally ensure all traces of Austenite are converted into Martensite.

Benefits of Applying Heat Treatment

Here are the key benefits of heat treatment of tool steel.

1. Preventing Deformation: The deformation can be easily avoided. Heat treatment ensures dimensional stability of steel. This helps to prevent deformation during high-impact or high-temperature operational conditions.  
2. Developing Wear Resistance: Wear resistance assures the tool resists abrasion. It must resist erosion, or galling. This works even during repetitive use.
3. Excellent Hardness and Strength: A key benefit is that the steel develops extreme hardness and sharp cutting edges, even in high-pressure applications.

Quality Control Methods in Heat Treatment

Although the hardness test is considered a standard quality control procedure. It alone is not sufficient. However, additional quality control methods include:

• Real-Time Temp. Monitoring: The temperature monitoring done properly. Thermocouples ensure the core part has the target temperature.
• Using Vacuum Technology: Advanced facilities ensure the heat treatment within a vacuum chamber. This prevents decarburization and oxidation.
• Microstructural Analysis: The ‘grain’ size and carbide distribution ratio are assessed to ensure that the steel has been sufficiently ‘soaked’. This does not have an over-grained microstructure.
• Non-Destructive Testing: The application of advanced NDT by eddy current testing or ultrasonic waves. It ensures that the steel does not have internal cracks.

Conclusion

You need to find the right manufacturer who can ensure you get the right type of steel for your industrial needs. Opt for services like Kushal Metals, the reputed supplier in Mumbai, who can provide high-quality, premium grade tool steel.