Case Hardening

Case Hardening Process

Case hardening steel in Michigan

Many processes exist to change the properties of steel tools such tempering steel, oil quenching, precipitation hardening, and more. But when it comes to durability, case hardening (also sometimes referred to as surface hardening) is one of the most efficient. The case hardening process adds a thin layer of metal alloy to the outer surface of the metal. This process can minimize wear and tear and increase the strength of the steel parts’ surface. Let’s look at the multiple methods used in the steel heat treatment.

Hardening Methods

Before taking a look at the benefits, take a moment to consider the various ways your steel can be hardened. To transform your steel in this way, some options include:

  • Carburizing (infusion of carbon)
  • Nitriding (using nitrogen rich gas, such as ammonia)

Each of these methods should be chosen based on what you will use your steel for, whether you need to harden the entire piece or a section, and the overall size and shape of your piece. No matter which method you choose, your steel parts will experience a longer lifespan and increased versatility after being treated.

Hardened Steel Lasts Longer

The extra strength that comes from case hardening your steel produces a tough outer layer (called the case) while keeping the inner core (case depth) soft enough to absorb shock. This can increase the lifespan of your object meaning fewer replacements and maintenance costs. This is also useful if you sell products with hardened steel because your customers will come to trust the durability of your product.

Advantages of Case Hardening

Not every metal is created equal. Some metals are sturdy and strong, while others are much more malleable and less durable. Steel parts often require treatment to obtain maximum strength and durability. We can change the mechanical properties of metals through the manufacturing process.

In this process, the metal surface is reinforced through the addition of a thin layer of another metal alloy that increases durability and hardness. Sometimes, this process is called surface hardening. It has many applications, such as producing cooking utensils, reinforcing metal girders and enhancing the functionality of firearms. There are many advantages of the metal case hardening process.

There are many types of case hardening processes. Which one is used will be determined by the metals used in manufacturing and the desired properties of the finished product.


Case hardening metal and steel

In carburizing, the surface hardness of the steel is increased by adding carbon to the component. The component that requires hardening is heated to 9000C and exposed to a carbon environment. The carbon penetrates the surface of the metal and strengthens it. The agent used can be solid, liquid or gas. The initial investment costs are generally higher than other processes. In liquid carburizing, it is difficult to control the depth of hardness and it may not be uniform throughout the object. This process must be carried out in a controlled environment to prevent oxygen from being present in the process which changes the outcome of the metal hardening. Partial vacuum processes shorten the time involved and provide a few economic advantages of case hardening.

Gas Nitriding

With this process, the material is heated to about 5500C and then exposed to atomic nitrogen, which can penetrate the steel or iron. Atomic nitrogen reacts with the metal to increase its hardness and resistance. This process offers a high degree of hardness, but cannot be used with all of the alloy steels.

Following this process, there may additional manufacturing costs in the form of an expensive grinding process to remove the thin white layer which forms on the surface. However, there are no other heat processes which follow nitriding, which means less deformation to the object.

Benefits of Case Hardening

Objects which need to have a hard exterior to endure wear and tear while maintaining a soft interior to withstand shock benefit from this process. The advantages of case hardening are:

  • Creating a more durable product
  • Increases wear-resistance of the metal
  • Increases lifetime of objects
  • Case hardening or surface hardening makes steel easier to weld
  • The metal is more flexible
  • Steel is tougher and stronger

While this can be a beneficial process in many industries, the right process must be used to get the right outcome. Case hardening is not compatible with welding.

It’s important to work with experienced engineers who understand this process to get the desired effect on your final product. When you need solutions that concern it, make sure it’s done right the first time and applied properly to save money down the road.

Subsequent Hardening Applications

Subsequent hardening applications such as these increase strength and wear resistance by diffusing carbon, through a number of different methods, into the surface of steel parts. This creates a casing around the material while retaining a substantially lesser hardness inside the core.

At SST, we’re experts when it comes to mild steel heat treatments, induction hardening, flame hardening and the metallurgy of steels. These intricate processes are applied to low carbon steel parts after machining, as well as high alloy steel bearings, gears and other crucial components. Find out more about how our Case Application heat treating can benefit your business.

Find Out What Else Case Hardening Can Do for You

Whether you want to harden small steel tools or need to improve the durability of large, complex machinery, Specialty Steel Treating, Inc. has the experience to get the job done. Contact us at 586-293-5355 for more information or to request a quote.

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