{"id":21541,"date":"2023-05-20T11:41:04","date_gmt":"2023-05-20T08:41:04","guid":{"rendered":"https:\/\/fractory.com\/?p=21541"},"modified":"2024-01-26T13:14:43","modified_gmt":"2024-01-26T11:14:43","slug":"case-hardening-explained","status":"publish","type":"post","link":"https:\/\/fractory.com\/case-hardening-explained\/","title":{"rendered":"Case Hardening Explained – How It Works, Benefits & Types"},"content":{"rendered":"

Case hardening is a metallurgical process that allows us to create special parts with unique properties<\/a>. In this article, we explore what it is, its process and its applications.<\/p>\n

What Is Case Hardening?<\/strong><\/h2>\n

Case hardening is a heat treatment process<\/a> that hardens the surface of a metal substrate while maintaining a softer core. This allows to combine the best properties of a soft and hard metal into one part.<\/p>\n

A soft material can handle impact forces much better than a hard material. It is also tougher, more ductile and stronger but it does not have sufficient wear resistance. Good wear resistance is crucial to ensure that the material does not wear away due to abrasion or friction<\/a>. By hardening just the outer surface, we can significantly reduce the wearing of material without compromising other properties.<\/p>\n

We can achieve the thin hardened surface through different means such as altering the crystal structure and\/or the addition of new elements to the surface. But no matter the process, case hardening almost always requires elevated temperatures.<\/p>\n

When Is Case Hardening Used?<\/strong><\/h3>\n

We use case hardening when we need to improve the surface hardness of softer materials such as iron or low-carbon steel<\/a> parts. The standard practice is to do it after all the machining and forming operations as it reduces the machinability of a part. But we may also do it during earlier stages of the manufacturing process. Some of the instances where case hardening procedure is used are as follows:<\/p>\n

Low Budget<\/h4>\n

There is a significant price difference between low-carbon steel and tool steels<\/a> such as high-speed steel. The difference can be more than 20x in some cases. Thus, when the budget is a concern, we can use case-hardened low-carbon steel instead of tool steel.<\/p>\n

Also, case hardening requires less energy and time compared to through hardening as you do not harden the entire cross-section. Thus, along with the raw material cost, we can also save resources in manufacturing.<\/p>\n

Unique Properties<\/h4>\n

The combination of a soft interior core with a hard outer layer provides unique properties as discussed in the earlier section. Case hardening allows us to take advantage of these properties. Case-hardened couplings are examples of parts that provide durability as well as strength. They can handle small misalignments much better than through-hardened parts.<\/p>\n

Reduced Material availability<\/h4>\n

When material availability is an issue, we can opt for case-hardened low-carbon steel; especially in non-critical applications. Many places do not have the required tool steel grades available in different sizes. The only way to obtain it, in that case, is to buy a much bigger size than required. So instead of buying that, we can buy low-carbon steel and get it case-hardened for our applications.<\/p>\n

Application-based use<\/h4>\n

The application sometimes requires only a hard surface. In such cases, instead of through hardening, we can go for just surface hardening. Suitable examples are files, bolts<\/a> and gears.<\/p>\n

In a file, for instance, the teeth are doing all of the work. So it makes sense to use low-carbon steel and just harden the surface. Doing this would be cheaper than using tool steel or even through-hardening.<\/p>\n

Let’s expand on the example of a gear<\/a>. A gear needs high hardness at the tooth to give it wear resistance. But it does not need through-hardening. In fact, it is recommended to keep the core soft to avoid sudden failure under load. A case-hardened gear allows us to integrate flexibility and high surface hardness into the same part.<\/p>\n

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