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What Is Case Hardening?

March 4th, 2019

Metal must be pliable to be suited to a variety of applications. However, a metal must also be durable, especially when it comes to surface strength. These two characteristics are integral to ensure optimum function and reduce the effect of excessive wear and tear. That’s where case hardening, which is also referred to as surface hardening, comes in. This process enhances surface strength while allowing the core to remain flexible. Specialty Steel Treating offers this and many other essential heat-treating services to clients. Thanks to their extensive knowledge in surface hardening, they’re able to offer the following information so you can make the best decision regarding your metal-treatment needs.

How Does This Process Work?

Case, or surface, hardening increases the surface strength of metal without impacting the inner core of the part. This is accomplished by adding another layer of metal to the surface, which helps decomposition due to repetitive stress. Case hardening steel grades depend on the temperature used during the treatment process. For example, an initial carbon temperature ranging between 1650 to 1700 °F produces an SAE steel grade of 1016. The method and solutions used to cool metals can also have an impact on SAE grading.

Are There Different Types of Surface Hardening?

When increasing the surface strength of steel, you have a few different options at your disposal:

• • Carburizing: This method entails placing metal in a high-temperature environment along with a carbon-based substance, which infuses the surface with carbon. Atmosphere carburizing entails placing metal into a furnace and introducing gases like methane or carbon monoxide. Vacuum carburizing also involves the injection of gases, but in this case the metal is in a vacuum-sealed container.

• • Induction Hardening:  Induction hardening is another type of carburizing. Metal is heated via electromagnetic induction before being rapidly cooled. Cooling agents include water and polymer solution sprays, which are dispersed directly onto the metal. Induction hardening is best for metals containing a carbon content of at least 0.4% or higher.  

• • Nitriding: Surface strength can also be enhanced using nitrogen. In this case, metal is heated using gaseous ammonia at a temperature ranging between 950 and 1,050 °F. How long the metal is treated correlates to how deep nitrogen is diffused into the surface.

• Mechanical Hardening: Some hardening methods don’t require extreme temperatures to increase surface strength. Some types of mechanical hardening utilize cold-working, which involves hammering or rolling metal at room temperature. Metal can also be shot with iron pellets or blasted with air.

What Are the Benefits?

When a metal has a strong outer exterior and a soft inner core it becomes far more durable. These properties make it resistant to wear and tear as well as shock, which will be absorbed by the pliable core. When metal is more resilient it also has a longer lifespan, which prevents the need for frequent parts replacements. Flexible metal is also much easier to weld. As a result, a piece can be molded into a variety of shapes depending on the application in question,

What Are the Applications of Case Hardening?

Case hardening guns is a common practice. Continuous firing of a weapon creates heat, which in turn deforms the gun barrel. When barrels are heat-treated, a gun becomes far more stable. Not only is accuracy improved, but routine maintenance like cleaning is also much easier to perform. Heat-treatment also has applications in the automotive industry. Car parts are often case hardened to withstand repeated stress associated with running a vehicle. This includes universal joints, shafts on water pumps, and pinion gears. Other applications include parts used in the aerospace industry, heavy equipment pieces, railway components, and tooling equipment.

What Are the Next Steps?

Specialty Steel Treating has earned a reputation for quality among its numerous clients occupying many different industries. They can help you select the best hardening process for your needs by using more than six decades of experience. If you’d like more detailed information, feel free to request a quote using their convenient online contact form. You can also learn more about their services by visiting their website.