Stainless steel is an amazing metal that has made possible many modern advancements in all types of industries. Its versatility has allowed for the development of a wide variety of alloys; no matter what the application, there’s usually an appropriate stainless steel. It’s also much more cost effective than most other materials, especially for the level of performance provided.
This diversity is aided by the many different processes that can be used to treat stainless steel. Annealing, cold working and other options all have different effects on the metal; even if you’re dealing with a single alloy, the different ways you treat it give you more possibilities. These processes include what is known as normalization, one of the most popular ways of heat-treating stainless steel and other ferrous metals.
Today, we’ll be discussing normalization and other considerations when heat-treating your stainless steel as part of an effective and affordable production process.
What is normalization?
Before we take a look at normalization specifically, let’s introduce heat treatment in general and what we mean by it. In metallurgy we use the umbrella term annealing, which refers to any heat treatment that alters the physical and/or chemical properties of a metal. The goal is generally to boost the material’s ductility while at the same time reducing its hardness so that it is easier to work with. This goal is accomplished by heating a metal past its recrystallization temperature, followed by a cooling process.
Obviously, there are many different ways of accomplishing heat treatment, each with its specific benefits. Understanding when to use which method is extremely important for anyone working with stainless steel alloys. While process annealing, short cycle annealing and other forms each have their place, one of the most common is known as normalization.
Normalization is recognized as a valuable process when applied to ferrous alloys. Its popularity is due to its ability to imbue steel with a uniform fine-grained structure, while at the same time avoiding too much softening of the steel. This is a tricky balance because while you want to have stainless steel that isn’t too difficult to work with, you don’t want to lose its superior strength.
The process of normalizing stainless steel generally requires heating the metal to anywhere from 20 to 50°C above its highest critical point. The metal will be soaked at that temperature for a short period of time, and then it will be exposed to room temperature air for cooling.
The heating process in this way generates an austenitic grain structure in the metal that is much finer than the ferritic grains. During the cooling, new ferritic grains form that are much more refined. The process of normalization results in a tougher, more ductile stainless-steel alloy, while at the same time removing columnar grains and dendritic segregation that might form during casting. Other benefits include improved machinability and greater dimensional stability. Normalization can also be combined with other heat treatment methods for further refinements.
Why can’t a non-ferrous metal be normalized?
It is technically not true that non-ferrous metals can’t be normalized. The truth is that if you normalize such a metal, nothing much will happen to it in most cases. This is because normalization is a process that specifically affects the grain structure of ferrous metals.
The process can be detrimental to certain non-ferrous metals. When these grades are heated during normalization, a phenomenon known as hot shortness can occur, which will cause the metal to lose its high tensile strength.
What are the Benefits of Normalization?
There are a number of clear benefits to the normalization process. Top of the list is the fact that the process itself is faster than many other forms of annealing. For other types of annealing, there is a lengthy slow cooking of the steel that is necessary to alter its microstructure, and the cooling process is also much longer. Obviously, anything that can shorten your production schedule is a great way of saving both time and money.
In addition, because normalization is the least expensive form of annealing, it has become the most common treatment process for stainless steel. A big reason for this is the fact that normalization involves air cooling, while other annealing methods rely on furnace cooling, a much slower and more energy intensive process.
Another benefit is that normalization can get rid of any dendritic segregation that may have been produced during the casting process. It also is able to generate a harder and stronger metal than the annealing process. It is an important element of improving part quality and controlling dimensional variation; it should be considered any time consistency is important to your production process.
When is normalization needed?
There are many industrial processes involving stainless steel that can benefit from normalization. For instance, when working with hot-rolled steel products, normalization can help make the metal easier to work with and more effective. This can include products such as railroad wheels, bars, axles, and any other forged steel parts.
When dealing with castings requiring many complex shapes, such as you might find in the mining industry, normalization helps to prevent structural irregularities that can have a negative impact on the material.
Overall, because of its many benefits, normalization is a valuable option for boosting the performance of your stainless-steel products. Due to its low cost and ease of processing, it may be beneficial to consider normalization and investigate whether it’s right for your business.
When it comes to normalizing stainless steel, knowing the ins and outs of the process goes a long way to ensuring the success of your project. While you probably understand exactly what you need to make your product effectively, working with experts who are intimately familiar with the materials makes a lot of sense. The dedicated professionals at Clinton Aluminum aim to be true partners to our clients, at their assistance for every step of the procurement process.
Contact us today to speak with one of our knowledgeable and friendly representatives.