Guide to Choosing Heat Treating Controllers

When it comes to heat treatment, precision and stability are key. Heat treating controllers ensure that you’re able to precisely control the temperature of your oven or furnace throughout each stage of the heat treat process. 

Why is this important? Whether you’re making knives, swords, or industrial components, correct temperature and soak time determine whether your metalwork has the intended properties.

Definition of Heat Treatment

Before getting into the ins-and-outs of heat treating controllers, let’s define heat treatment and explore common types of heat treatments.

Heat treatment is a process of heating and cooling metals and alloys in a controlled manner to alter their physical and mechanical properties, such as hardness, ductility, malleability, temperature resistance, and material strength. Heat treatment has a wide range of applications and is used for everything from making knives or other simple tools to building aerospace components! 

Stages of Heat Treat

At an extremely high level, every type of heat treatment involves 3 main stages:

• Heating: Heating the metal or alloy to a specific temperature, ensuring that it heats evenly.
• Soaking (or Holding): Keeping the metal at temp for a specific period of time.
• Cooling: Bringing the metal or alloy back to room temperature. 

Depending on the application and the desired properties of the metal, these stages may be repeated multiple times or may have specific requirements regarding Ramp Rate (how quickly the metal is brought to temp) or Cooling Rate (how quickly the metal is cooled to room temperature).

Common Methods of Heat Treatment

Below are common heat treating methods, as well as the effects they have on the metal:

• Normalizing: The metal is heated to an extremely high temperature for a defined period of time and then air-cooled. Normalizing relieves internal stress and ensures uniformity, resulting in harder, stronger metals.
• Annealing: The metal is heated beyond the upper critical temperature and then slowly cooled to soften it and increase its workability. Annealing increases ductility and toughness, while relieving stress, making the metal more resistant to fractures.
• Hardening: The metal is heated until it forms an even solution and then allowed to cool to increase its hardness. 
• Case Hardening: Only the outside of the metal is hardened, creating a durable outer layer while ensuring the metal retains flexibility and doesn’t become brittle.
• Quench Hardening: After heating, the metal is cooled rapidly by dipping it into an oil, polymer, or water, resulting in very hard, very brittle metal.
• Tempering: After hardening, the metal is heated to a lower temperature to reduce excessive hardness and relieve internal stress. Tempering makes metals less brittle.

What to Look for in a Heat Treating Controller

Regardless of the application, when choosing a heat treating controller it’s important to look for 3 main features:

• Precision: Since temperature dictates the properties of the metal, it’s important to select a heat treating controller that precisely controls the temperature of your kiln or oven. PID (Proportional Integral-Derivative) controllers, such as the TAP Digital Controllers from SDS Industries, will result in the highest degree of precision, making them ideal for heat treatment.
• Reliability: Consistency and stability are important considerations when buying a heat treating controller. High quality components, onboard diagnostics to verify input/output, energy-efficient design, and preventative maintenance alerts ensure reliability and consistent results.
• Ease-of-Use: In 2023, heat treating controllers should make life easy for metalworkers, whether you do your heat treatments at home or in an industrial setting. The best digital controllers include touchscreen controls, mobile app integration, alerts, alarms, and the ability to create, name, and save unlimited schedules.