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.
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.
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.
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.
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.
Stainless steel is a commonly used material in applications ranging from medical instruments or chemical storage to transport or power generation because of its high corrosion resistance, hygiene, and strength. While there are more than 3,500 grades of steel, not all stainless steel grades are created equally.
With so many options, how can you ensure you’re selecting the appropriate grade for your specific needs?
To determine which grade of steel will uphold best in a given environment, think about the conditions your final product will face. Extremely low pH, high stresses and high temperatures, and crevice corrosion negatively impact stainless steel performance. Steels in the austenitic T3XX series, like the common types 316 and 304 alloys, retain their strength, toughness, and corrosion-resistant properties over the broadest temperature range.
Corrosion resistance is the main reason for choosing austenitic stainless grades. Type 316, with its molybdenum addition, even resists chloride ions found in marine and chemical processing applications. With any steel grade, high-quality structural design is the best defense against corrosion.
Next, consider these three top mechanical qualities:
Stainless steel contains 10–30% chromium as its alloying element, which is what helps it resist corrosion. The nickel addition in austenitic grades provides the highest toughness and ductility among stainless grades. Grades high in chromium, molybedenum, and nickel are the most resistant to corrosion.
Alloy content is not the only aspect to consider when choosing a grade of stainless steel; the material’s processing also affects the mechanical response. The duration of time steel is held at different temperatures as part of its cooling process, as well as the total speed at which it is cooled can affect its overall quality.
While the hardness of carbon steels can be increased by heat treatment, austenitic stainless is hardened by cold working operations like rolling, bending, swaging, or drawing at temperatures below the recrystallization temperature. Be aware that increased hardness by cold working operations decreases other properties like elongation and impact resistance.
Austenitic stainless steel is widely available in bar, wire, tube, pipe, sheet, and plate forms; Most products require additional forming or machining before they can be used for their specific application.
Stainless steel tubing, for instance, may need bending or coiling, re-drawing, machining, welding, or end forming. If your stainless steel will see machining processes like CNC machining, drilling, reaming, bevel cutting, chamfering, knurling, or threading, choose a machining rate that mitigates the risk of work hardening or select a “free-machining” grade containing sulfur.
When welding any stainless steel parts, embrittlement in the weld area is a top concern. Choose a lower carbon grade like 304, 304L, or 316L to reduce carbide formation.
Many designers choose stainless steel for its aesthetic appearance, whether that appearance is a shiny, electropolished “bright” finish, a dull “pickled” finish, a matte surface polished to a specific RMS, or a light-absorbing black oxide coating. Austenitic stainless steel grades can take any of these finishes plus the common addition of passivation.
Customers may also need certification for application-specific specifications. For instance, ASTM A213 and A249 should be used for boiler, superheater, and heat-exchanger tubes, while ASTM A908 should be used for hard-drawn austenitic stainless steel industrial needle tubing. There are more than 12,000 ASTM standards, and each addresses a specification so customers know the technical standards tested for chemical composition, heat treatment or temper, and other physical and mechanical attributes.
Although high-performing austenitic stainless steels are the most expensive stainless steels upfront, they are well worth the investment. Choosing a corrosion-resistant material well-suited to its application reduces maintenance, downtime, and replacement costs. Life-cycle costing methods can quantify current and future costs and create an “apples-to-apples“ comparison of different materials.
At Eagle Stainless we can help you prioritize your material requirements and guide you toward choosing the perfect stainless steel grades for your application. With quality management certifications in place since 1998, our commitment to quality is evident at every step of the process and designed to help you make the best steel selection for your industrial application.
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