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Things To Consider When Choosing A Stainless Steel Grade

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There are a lot of variables that go into a successful operation and it can be hard for manufacturers to keep track of all of them. But when it comes to choosing materials for the job, it pays to take your time and get it right. Stainless steel is an amazing metal that offers a great deal of variety in terms of its many alloys. Choosing the right one can go a long way to ensuring that you can stay ahead of your competitors.

If you need help picking out the perfect stainless steel grade for a particular job, the experienced technical professionals at Clinton Aluminum can help. Our priority is to support the success of clients and we’re standing ready to advise you through every step of the production process.

The Magic of Stainless Steel

Stainless steel is obviously best known for its corrosion resistance, but there is a lot more to the metal than just a single attribute. Its popularity also derives from many other advantages, including a high strength-to-weight ratio, excellent formability, and low maintenance requirements. Another major benefit is its ability to be recycled and reused, making it very efficient as a production material.

The tremendous versatility of stainless steel stems from the great diversity of grades and alloys that have been developed over the last century. By experimenting with the different alloying agents that get added to the steel, researchers have accentuated the positive attributes of the metal and created very specific grades that are suitable for very specific scenarios.

All of this variety means that it’s very important for engineers and manufacturers to carefully select the alloy that best matches with the end use it is intended for.

The Five Main Categories of Stainless Steel

Before picking a specific grade, it helps to know which category of stainless steel you want. Each of the five families is noted for its particular characteristics. Probably the most popular family of stainless steels is known as austenitic, which has the primary alloying agents of chromium and nickel. These nonmagnetic grades generally have the highest corrosion resistance and cannot be hardened via heat treatment. The 200 and 300 series, including grade 304, which is the most common alloy currently on the market, are in the austenitic family.

Next up are the ferritic stainless steels. They have lower chromium and nickel content than austenitic steels, but they also have molybdenum, aluminum, and titanium added. They are highly recognized for having good ductility and a relatively high resistance to stress corrosion cracking. These alloys include many of the 400 series of stainless steels, and are popular in automobiles and kitchenware, among other applications.

It’s important to know that martensitic stainless steels also fall into the 400 series, making it difficult to distinguish them from ferritic steels. The primary difference is that they have higher levels of carbon and lower levels of chromium, which allows for hardening via heat treatment. Specific martensitic alloys include 403, 410, 416, and 420.

Duplex stainless steel is the most recently developed family. Its metallurgic structure combines the properties of ferritic and austenitic alloys. They contain 24% chromium and 5% nickel, which results in a greater yield strength and improved resistance to stress corrosion in chloride environments, such as seawater.

The final family is known as precipitation-hardening stainless steel. They include aluminum, copper, and titanium as alloying agents and they can be hardened via a process that involves a solution and aging heat treatment. These alloys, which feature high tensile strengths, all fall into the 600 series.

Factors to Consider When Selecting A Grade

Once you know which family you want, you can start to pick out a specific grade. During this process, you’ll want to consider a number of factors. Perhaps most important is examining what type of environment your product or structure will most frequently encounter. For example, if you are building an application that will be in a marine environment, then corrosion resistance is of the utmost importance. While all stainless steels offer adequate anti-corrosion properties, not all are up to the task of dealing with seawater.

Another critical consideration is whether or not the metal will need to be welded. As a general rule, it’s more difficult to weld stainless steel compared to traditional carbon steel. The austenitic family is most well suited for welding applications, in particular alloys such as 347, which has niobium stabilizers added. Because they share many of the properties of the austenitic family, duplex stainless steels also work well with welding.

Formability is also of primary importance when choosing which grade of stainless steel. Besides welding, other processes that will shape or stress the metal include machining or bending. You’ll want to avoid any grade that is too brittle and will not respond well to being manipulated in certain ways. For example, martensitic stainless steels are not easily formed and should be avoided.

Of course, when we’re talking about steel, strength is also a factor. In recent years, certain grades have been developed with extremely high strengths. For instance, when nickel gets added to stainless steel, it boosts the toughness and ductility. But for even greater strength, the martensitic and precipitation hardened families may be what you are looking for.

Of course, no discussion of stainless steel would be complete without mentioning its corrosion resistance. Different alloys are able to withstand different conditions, so it’s best to check the particulars of each grade to find the combination of properties right for your application. The reason why grade 304 is so popular is that it has a high corrosion resistance thanks to its high level of chromium. Of course, for even greater resistance, grade 316, with its high molybdenum, is your answer.

Summary

Whatever your application, it’s likely that there’s a grade of stainless steel that’s perfect for you. Rather than try and make the choice on your own, why not consult with the friendly and dedicated experts at Clinton Aluminum. Our mission is to make sure our clients always have the perfect material for the job. Contact us today to learn how we can help your business succeed.

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