316 Stainless Steel: Uses, Composition, Properties

SAE 316 stainless steel is a versatile and widely used material known for its excellent corrosion resistance and high strength. It is a member of the austenitic stainless steel family and primarily consists of chromium, nickel, and molybdenum. Due to its exceptional combination of qualities, this steel grade is extensively utilized in various industries, including manufacturing, construction, food processing, and medical equipment.

Type 316 can be applied in harsh environments, such as marine and chemical environments, due to its corrosion resistance. The typical elemental composition of 316 stainless steel is 69% iron, 16–18% chromium, 10–14% nickel, 2–3% molybdenum, 0.08% carbon, and trace amounts of other elements.

This article will delve into the specific features and properties of 316 stainless steel in the following sections.

What Is 316 Stainless Steel?

316 stainless steel has excellent corrosion resistance in many environments. This austenitic stainless steel contains 16–18% chromium, 10–14% nickel, 2–3% molybdenum, 0.08% carbon, and trace amounts of other elements. The addition of molybdenum differentiates it from the most commonly specified stainless steel, 304, and gives 316 much better corrosion resistance than T304. It has a face-centered cubic (FCC) arrangement of atoms and a crystalline structure. Its high strength and toughness are due in part to this configuration. For more information, see our guide on Carbon Metals.

What Is 316 Stainless Steel Used For?

Numerous industries and applications make extensive use of 316 stainless steel. Listed below are some examples:

1. It is often employed in food handling, cooking, and storage equipment due to its durability, ease of cleaning, resistance to bacterial growth, and non-reactivity with food. 
2. It is suitable for handling corrosive chemicals and acids, making it popular in chemical plants and refineries.
3. It is highly corrosion-resistant in marine environments, making it ideal for boat fittings, marine hardware, and offshore structures.
4. It is biocompatible, making it suitable for surgical instruments and implants.

How Is 316 Stainless Steel Made?

The electric arc furnace (EAF) method is the most common way to make 316 stainless steel. Its production primarily uses iron ore, chromium, nickel, and molybdenum as raw materials. The EAF method involves melting the raw materials in an electric arc furnace and modifying the mixture to obtain the desired chemical properties. Following refinement, the molten steel is cast into a variety of shapes, including ingots or continuous casting, and then put through hot rolling, cold rolling, or other shaping procedures to produce the finished product with the desired dimensions and properties.

What Is the Chemical Composition of 316 Stainless Steel?

316 stainless steel typically contains 16 to 18% chromium, 10 to 14 percent nickel, and 2 to 3 percent molybdenum in its chemical makeup. SAE 316 stainless steel's composition  is detailed in Table 1 below:

What Is the Carbon Content of 316 Stainless Steel?

The carbon content in 316 stainless steel is typically ≤ 0.08%.

What Are the Properties of 316 Stainless Steel?

Table 2 highlights the properties of 316 stainless steel:

Is 316 Stainless Steel Magnetic?

No, 316 stainless steel is generally considered non-magnetic. Among non-magnetic steels, 316 stainless steel has the reputation of being the "most nonmagnetic" due to its wide range of nickel content. In fact, the primary phase of 316 stainless steel, austenite, is naturally nonmagnetic. It is possible to introduce magnetism, though, through laborious welding or machining procedures. Cold work can cause austenite to change into ferrite or martensite, both of which have weak magnetic properties. The amount of carbon in the steel affects its ability to undergo martensitic transformation, which in turn affects its magnetic properties. Because of this, 316 stainless steel maintains its reputation as having nonmagnetic properties despite the possibility of magnetic changes in some situations.

Is 316 Stainless Steel a Food-Grade Steel?

Yes, 316 is considered food-grade stainless steel. It is often used in food processing and handling equipment, such as cookware, utensils, and food storage containers. The high corrosion resistance of 316 stainless steel makes it ideal for contact with food, as it is resistant to the acids and chemicals typically found in food and beverages.

Machinability Rating of 316 Stainless Steel

In comparison to other stainless steel grades like 303 stainless steel, 316 stainless steel has a lower machinability rating. The American Iron and Steel Institute (AISI) scale, which evaluates a material's ease of machining, gives it a rating of 60%. This rating means that it is either relatively easier to machine or relatively more difficult to machine when compared to other stainless steel grades with higher percentages or lower percentages, respectively. While the presence of molybdenum and nickel in 316 stainless steel improves its corrosion resistance properties, these alloying components also increase the hardness of the material. As a result, machining 316 stainless steel becomes more challenging because it leads to increased tool wear and slower machining speeds.

What Are the Thermal Properties of 316 Stainless Steel?

316 stainless steel exhibits several important thermal properties. It has a thermal conductivity that is approximately 16.3 W/m·K ( watt per meter per Melvin) at room temperature. Ferritic stainless steel has a higher thermal conductivity than austenitic stainless steel, such as 316 stainless steel. Stainless steel's thermal conductivity can change depending on its structure and composition. Compared to metals like copper or aluminum, which have thermal conductivities as high as 400 W/mK, stainless steel has a much lower thermal conductivity. 

The coefficient of thermal expansion for 316 stainless steel between 20 °C and 200 °C is around 16.5 x 10-6/°C. This means that it expands and contracts relatively more than some other materials when exposed to temperature changes. The melting point of 316 stainless steel ranges from approximately 1370 to 1400 °C. The high melting temperature of this stainless steel grade is a desirable characteristic as it contributes to improved creep resistance. Creep resistance refers to the material's ability to withstand deformation under prolonged exposure to high temperatures, making it suitable for applications requiring stability and strength at elevated temperatures.

What Are the Common Forms of 316 Stainless Steel Material?

316 Stainless steel comes in a number of forms, including:

Sheet

Sheet metal encompasses metal objects that have a width ranging from 0.5 to 6mm, and it is the width that determines the thickness. Among the versatile options, stainless steel sheets, also known as cold-rolled products, stand out. These sheets can be molded into various shapes, making them ideal for cookware applications like grills, pots, and sinks. Furthermore, they are commonly used as finishes for appliances such as countertops, refrigerators, freezers, and dishwashers. Stainless steel sheet metal also finds utility in manufacturing light bulb bases and automobile license plates.

Bar

316 stainless steel bars are rods available in various sizes. They may be cylindrical or rectangular, depending on the specific requirements of the application. SAE 316 stainless steel bar stock has the same properties and composition as sheets. Because of its shape, bar stock is more rigid and can support higher loads than sheet metal. Bar stock is often used in construction, architectural applications, shafts, fasteners, and marine hardware.  316L stainless steel sheet with a 2B finish exhibits a mill finish, characterized by its smooth surface. Unlike the brushed finish commonly found on kitchen appliances, the mill finish of 316L stainless steel sheet is free from any visible texture or pattern. This smooth and uniform surface lends a clean and sleek appearance to the sheet, making it suitable for various applications that require a polished and refined look.

Plate

316 stainless steel plates are larger, thicker flat plates typically over 6 mm in thickness. Plate offers the same properties as a sheet but the additional thickness makes 316 plate suitable for heavy-duty applications. Common uses include structural components, pressure vessels, and chemical processing equipment.

Hot Rolled

Hot-rolled 316 stainless steel products undergo a production process that involves heating the metal above its recrystallization temperature. Once heated, the stainless steel is shaped and formed at an elevated temperature, allowing it to take on the desired dimensions and characteristics. After the forming process, the hot-formed stainless steel is allowed to cool. The production of hot-formed stainless steel may appear straightforward, but the current method used for approximately 95% of production involves decanting the molten metal from the Argon Oxygen Decarburization (AOD) vessel into a cooled continuous caster. As the metal emerges from the caster horizontally, it solidifies into a slab shape. The microstructure of the slab exhibits columnar characteristics on the outer sides due to the cooling effect from the caster walls. In contrast, the center of the slab maintains a relatively uniform equiaxed microstructure. Hot-rolled 316 stainless steel is used in construction, automotive applications, and industrial equipment.

Annealed

Annealing or solution treatment is a crucial process employed to crystallize work-hardened stainless steel and disperse chromium carbides that have precipitated around the work-hardened stainless steel. This treatment effectively removes residual stresses and homogenizes dendritic stainless steel welds. Annealing is typically conducted at temperatures above 1040 °C, although specific steel types can be annealed at controlled temperatures below 1010 °C to achieve fine grain size. To prevent surface scaling and control grain growth, the annealing process is carefully controlled for a short duration, ensuring optimal results without compromising the material's surface integrity.

Cold Drawn

Cold drawing (also cold working and cold rolling) involves pulling 316 stainless steel through a die to reduce its diameter and improve its surface finish. This process increases the material's strength and hardness while maintaining good dimensional accuracy. Cold-drawn 316 stainless steel is commonly used in precision components, shafts, and fasteners where strength and tight tolerances are required.

What Are Equivalents of 316 Stainless Steel?

Table 3 lists some equivalents of 316 stainless steel in different countries:

What Are the Advantages of Using 316 Stainless Steel?

SAE 316 stainless steel offers several advantages that make it a popular choice in various industries:

1. It has superior corrosion resistance, particularly in aggressive environments and exposure to chlorides, acids, and marine conditions.
2. It can withstand elevated temperatures without significant loss of corrosion resistance or strength.
3. It possesses excellent strength and toughness for structural applications.
4. It can be easily fabricated, welded, and formed into various shapes and sizes.
5. It is non-toxic, easy to clean, and resistant to bacterial growth, which is important for food processing and medical applications.
6. Its potential for a polished surface finish and high luster enhances its visual appeal in architectural and decorative applications.

What Are the Disadvantages of Using 316 Stainless Steel?

While 316 stainless steel offers numerous benefits, there are a few potential disadvantages to consider:

1. The higher cost of 316 stainless steel compared to other stainless steel grades can be attributed to its higher alloy content. For instance, the scrap price of 316 stainless steel, at $0.78 per pound, is higher than that of 304 stainless steel, which stands at $0.56 per pound. This price disparity reflects the increased expenses associated with the production and composition of 316 stainless steel.
2. Compared to some other stainless steel grades, 316 stainless steel has lower machinability, which can lead to increased tool wear and slower machining speeds.
3. Compared to 304 stainless steel, 316 stainless steel exhibits lower formability and machinability.

What Is the Difference Between 316 Stainless Steel and 304 Stainless Steel?

The primary difference between 304 and 316 stainless steels is that 316 contains 20-3% molybdenum, while 304 contains none at all. AISI 316 also contains more nickel and a little less chromium than 304. These differences give 316 better overall corrosion resistance, especially in chloride-containing environments. Type 304 is less expensive than 316, and is used in about 60% of austenitic stainless steel applications.

What Is the Difference Between 316 Stainless Steel and 18-8 Stainless Steel?

SAE 304 stainless steel is sometimes referred to as "18-8 stainless, with the "18" denoting the amount of chromium it contains, and the "8" indicating the amount of nickel. The main difference between 316 stainless steel and 18-8 (or 304) stainless steel is that 316 stainless steel contains 2-3%molybdenum. The addition of molybdenum increases the corrosion resistance of 316 stainless steel, making it more suitable for applications where corrosion resistance is critical. 

What Is the Difference Between 316 Stainless Steel and A2 Stainless Steel?

A2 is simply another name for AISI 304 stainless steel, also known as "18-8."  A2 (or 304) stainless contains 18-20% chromium, 8-10% nickel, and no molybdenum, unlike 316, which contains 2-3% molybdenum. The molybdenum added to 316 gives it better corrosion resistance than A2, especially in chloride-containing environments.

Summary

This article presented 316 stainless steel, explained it, and discussed its composition and properties. To learn more about 316 stainless steel, contact a Xometry representative.

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