From composition to form, a range of factors impact the characteristics of stainless steel products. One of the most important considerations is which grade of steel to use.
This will determine a range of characteristics and, ultimately, both the cost and lifespan of your stainless steel products.
So how do you know where to start?
While every application is unique, these 7 questions highlight critical considerations to help you narrow down your options and find the grades best suited to your needs or application.
1. What Type of Resistance Does My Steel Need?
When you think of stainless steel, the first things that come to mind are probably resistance to acids and chlorides–such as those found in industrial applications or marine environments. However, temperature resistance is an important consideration as well.
If you need corrosion resistance, you’ll want to avoid ferritic and martensitic steels. Ideal stainless steel grades for corrosive environments include austenitic or duplex alloys such as grades 304, 304L, 316, 316L, 2205, and 904L.
For high-temperature environments, austenitic grades are often best. Finding a grade with high chromium, silicon, nitrogen, and rare earth elements will further alter the steel’s ability to withstand high temperatures. Common grades for high-temperature environments include 310, S30815, and 446.
Austenitic steel grades are also ideal for low-temperature or cryogenic environments. For added resistance, you can look at low carbon or high nitrogen grades. Common grades for low-temperature environments include 304, 304LN, 310, 316, and 904L.
2. Does My Steel Need to be Formable?
A steel with poor formability will become brittle if overworked and offer lower performance. In most cases, martensitic steels are not recommended. Furthermore, steel with low formability might not hold its shape when complex or intricate forming is required.
When choosing a steel grade, you’ll want to consider the form in which you’d like it delivered. Whether you want rods, slabs, bars or sheets will limit your options. For example, ferritic steels are often sold in sheets, martensitic steels are often sold in bars or slabs, and austenitic steels are available in the widest range of forms. Other steel grades available in a variety of forms include 304, 316, 430, 2205, and 3CR12.
3. Will My Steel Require Machining?
Machining isn’t typically a problem. However, work hardening can produce unintended results. The addition of sulfur can improve machinability but reduces formability, weldability and corrosion resistance.
This makes finding a balance between machinability and corrosion resistance a critical consideration for most multistage stainless steel fabrication processes. Depending on your needs, grades 303, 416, 430, and 3CR12 offer a good balance from which to narrow options further.
4. Do I Need to Weld My Stainless Steel?
Welding stainless steel can lead to trouble—including hot cracking, stress corrosion cracking, and intergranular corrosion—depending on the grade of steel used. If you plan to weld your stainless steel, austenitic alloys are ideal.
Low carbon grades can further help with weldability while additives, such as niobium, can stabilize alloys to avoid corrosion concerns. Popular grades of stainless steel for welding include 304L, 316, 347, 430, 439 and 3CR12.
5. Are Heat Treatments Needed?
If your application requires heat treatment, you must consider how the various grades of steel respond. The final characteristics of certain steels are drastically different before and after heat treatment.
In most cases, martensitic and precipitation hardening steels, such as 440C or 17-4 PH, offer the best performance when heat treated. Many austenitic and ferritic stainless steels are non-hardenable once heat treated and therefore are not ideal options.
6. What Strength of Steel is Optimal for My Application?
Steel strength is an essential factor to consider to maximize safety. Yet, overcompensating can lead to unneeded cost, weight, and other wasteful factors. Strength characteristics are loosely set by the family of steel with further variations available in different grades.
- If you need a high-strength stainless steel, martensitic and precipitation hardening grades are likely your best options. Common grades include 440C, 17-4PH, and 15-5PH.
- Austenitic grades, such as the popular 316, offer moderate strength while keeping ductility.
- Duplex steels offer similar ductility while also offering the physical properties of a ferritic stainless steel.
7. What is the Upfront Cost and Lifetime Cost of this Steel in my Scenario?
All of the previous considerations feed into the most important question in choosing a stainless steel grade—lifetime cost. Matching the stainless steel grades to your intended environment, usage and requirements, you can ensure long-lasting performance and exceptional value.
Take care to analyze how the steel will perform over the intended period of use and what costs might be involved in maintenance or replacement before deciding. Limiting costs upfront might result in far more spending over the life of your project, product, structure, or other application.
Of course, if the initial price is too great, you might need to make compromises. Finding a balance is essential to both short-term and long-term success. But by considering these seven points, you’re eliminating potential hazards and setting the foundation for choosing the optimal solution for your needs.
With the sheer number of stainless steel grades and forms available, having an expert to help highlight options and potential pitfalls is an excellent way to ensure you’re getting optimal value for stainless steel investment. As a leading provider of stainless steel across Canada for more than 4 decades, Unified Alloys will leverage our experience to help guide you through the purchasing process. View our extensive list of stainless products online or call to discuss your needs with a member of our team.