The Role of Softening in Heat Treating

There are a number of different metallurgical services in Gastonia, NC that can be used to change the composition and characteristics of your metal parts. We might not think of metal as being “soft” and flexible, normally, but softening metal is an important part of heat treating. It can remove the residual stress from parts, restore ductility and even change the electromagnetic properties of the metal. In fact, softening metal can increase its hardness and strength—it sounds counterintuitive, but these processes have been used for centuries to create different effects.

Softening processes include annealing and tempering, which are used for different purposes. Here is an overview of how they work and when you might need to use them.


Annealing is a heat treatment in which a steel part is heated to a specific temperature, then cooled in a slow, controlled manner. This improves the electromagnetic conductivity, softens the metal to increase machinability, increases ductility and makes it suitable for cold working.

The metal is heated in a large oven until recrystallization occurs—this changes the structural properties of the metal, and helps eliminate any defects that are present in the metal. Then the part is cooled very slowly, often in sand or ashes, until it finally reaches room temperature once more. The slow cooling time helps create an interior “microstructure” that is better suited for machining and cold working.

Softening metal by annealing allows the metal to be shaped and worked without fear of cracks. The harder steel is, the more likely it is to experience stress cracks and fractures. Annealing eliminates this possibility by changing the microstructure.


Tempering is the other major softening method in metallurgy. This process increases the toughness of steel and other iron alloys—untempered steel is too brittle for most machining and forming processes, so tempering can eliminate the excess hardness and make it suitable for the desired application. Tempering improves the strength, ductility and structural stability of steel parts.

Tempering slowly heats steel to a specific temperature below the critical point (unlike annealing). When the chosen temperature is reached, it’s held at that point for a predetermined period of time (often about one hour per inch of thickness). Then it’s slowly cooled while in an inert or vacuum environment. This relieves internal stresses and changes the interior microstructure.

The tempering temperature is chosen depending on how much hardness needs to be eliminated from the part. The higher the temperature, the more the hardness is reduced—if you need to increase ductility, you’d opt for a higher temperature, whereas low temperatures are suitable for reducing brittleness.

Whether you need annealing, tempering or other metallurgical services in Gastonia, NC, the team at J. F. Heat Treating Inc. can help you determine which processes are right for your goals. We offer a complete range of metallurgical services, and have been helping locals perfect their metal components for four decades. Reach out to us today to get started or learn more about how we can help with your project.

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