What are the Most Common Types of Stainless Steel?

There are countless variations of stainless steel that you could potentially use for a custom wire basket or tray. Each formulation of stainless steel alloy has its own unique properties for tensile strength, melting point, oxidation resistance, and corrosion resistance.

Picking the right grade of stainless steel requires knowing what your options are. To help you better understand your choices, here’s a quick explanation of the most common types of stainless steel and their properties:

The Five Main Categories of Stainless Steel

While there are thousands of different alloys of stainless steel, they can all be divided into three broad categories:

1. Austenitic Stainless Steels. These are the most frequently used types of stainless steels. Austenitic stainless steels tend to have a high chromium content compared to other steel alloys, giving them a higher resistance to corrosion. Another common characteristic of austenitic stainless steel alloys is that they tend to be non-magnetic—though they may become magnetic after cold working.
   
   
2. Ferritic Stainless Steels. The second most common form of stainless steel after austenitic alloys. As the name implies, ferritic stainless steel is magnetic. These alloys can be hardened through cold working. They also tend to be less expensive because of their reduced nickel content.
   
   
3. Martensitic Stainless Steels. The least common category of stainless steel alloy. Their corrosion resistance tends to be lower than either ferritic or austenitic alloys, but they have a high hardness. Martensitic stainless steel alloys are often ideal for applications requiring extraordinarily high tensile strength and impact resistance. When said applications also require corrosion resistance, these alloys may be used with a protective polymer coating.
4. Duplex (Ferritic-Austenitic) Stainless Steels. This category of stainless steel derives its name “duplex” from its composition; it is made of half austenite and half delta-ferrite. These stainless steel alloys have better corrosion resistance, especially against chloride pitting, and higher tensile strength than standard austenitic stainless steels. Due to their physical properties and chemical resistance, duplex stainless steels are used widely in the oil and gas industry for pipework systems or as pipelines and pressure vessels in the petrochemicals industry. 
   
   
5. Precipitation-Hardening (PH) Stainless Steels. This category of stainless steel is comprised of durable, corrosion-resistant alloys with exceptional strength. They can be treated to yield strengths three to four times that of standard austenitic stainless steel. They are most commonly used in the aerospace, nuclear, and oil and gas industries.

There are numerous grades of stainless steel within each category—here are the breakdowns of the most common varieties of each:

Common Types of Austenitic Stainless Steels

Grade 301 Stainless Steel

Grade 301 stainless steel is comprised of additions of chromium and nickel and has exceptionally corrosion resistance. It is both strong and ductile when cold worked. With these properties, grade 301 stainless steel is commonly used in welding, forming and drawing.

Grade 302 Stainless Steel

Grade 302 stainless steel has a composition similar to grade 304, though it contains higher carbon levels. It is especially used for its ability to resist corrosive solvents, chemicals, and acids. Grade 302 stainless steel is commonly used to make conical compression springs and can be found in machines used in kitchens, food processing equipment, and in medical applications.

Grade 303 Stainless Steel

Grade 303 is a non-magnetic alloy and one of the best austenitic stainless steels for machinability. It is not hardenable by heat treatment and has corrosive resistant properties, though not as resistant as grade 304 stainless steel. Grade 303 is commonly used in heavily machined parts, such as gears, aircraft fittings, screws, shafts, and nuts and bolts.

Grade 304 Stainless Steel

The most common variety of stainless steel, and one that is frequently used in Marlin Steel’s custom wire basket designs because of its versatility. Even among steel alloys, grade 304 stainless steel is noteworthy for its high tensile strength—roughly 621 MPa (90 ksi). Like most stainless steel, grade 304 has a high maximum operating temperature (about 870˚C). This combination of high tensile strength, temperature resistance, and corrosion resistance makes grade 304 stainless steel ideal for a wide variety of applications.

Grade 309 Stainless Steel

This nickel-chromium stainless steel has the same machinability characteristics as grade 304, with high tensile strength and chemical resistant properties. Grade 309 can withstand exceptionally high temperatures, which makes it suitable for usage in heat applications. Grade 309 is commonly used for oven lining, aircraft engines, automotive exhaust parts, furnace components, and other applications with high heat. 

Grade 316 Stainless Steel

Another common variety of austenitic stainless steel, grade 316 stainless has a high tensile strength of 579 MPa (84 ksi) and a maximum use temperature of around 800˚C (1,472˚F). While having a lower tensile strength and temperature tolerance than grade 304 stainless steel, grade 316 stainless has a better resistance to chlorides (like salt) than 304 alloy does. This makes it a preferred choice for any application involving exposure to salt or other chlorides.

Grade 317 Stainless Steel

This stainless steel alloy shares similar properties to all the other austenitic stainless steels, such as high tensile strength, corrosion resistance, and high compositions of nickel and chromium. However, Grade 317 has added molybdenum to improve its resistance to pitting from chlorides. Its ability to resist pitting makes grade 317 ideal for chemical processing and marine industries, although it is more expensive than other similar stainless steels as a result. 

Grade 321 Stainless Steel 

Grade 321 stainless steel has added titanium to withstand corrosion from chemicals and high temperatures. It can resist oxidation up to 1500 degrees fahrenheit and has higher stress rupture properties than grade 304 stainless steel. It is also non-magnetic and can retain its strength at low temperatures.

Grade 347 Stainless Steel

Grade 347 stainless steel has the addition of columbium and tantalum to retain durability at high heat. This non-magnetic stainless steel is ideal for welding or for applicants with intermittent heating between 800 degrees and 1650 degrees fahrenheit. It is also fairly ductile and can be stamped, spun, and drawn when needed.

Ferritic Stainless Steels

Grade 405 Stainless Steel

Grade 405 stainless steel has lower corrosion resistance than grade 430 stainless steel, and so it is suitable for mildly corrosive environments. Due to its additional aluminium content, grade 405 SS does not harden when the material is cooled after welding procedures. It is useful for applications such as steam nozzles and quenching racks. 

Grade 408 Stainless Steel

This stainless steel grade has high heat resistance, though it has poor corrosion resistance. It is made with an 11% chromium and 8% nickel combination.

Grade 409 Stainless Steel

Grade 409 has both high temperature tolerance and corrosion resistance properties. It is especially resistant to exhaust gas and atmospheric corrosion, though not as resistant as grade 430. As a result, grade 409 stainless steel is used for automotive applications, such as exhaust systems.

Grade 420 Stainless Steel

This grade has the highest hardness among all the stainless steel grades with 12% chromium - 50HRC. Grade 420 also offers good ductility and corrosion resistance, especially to alkalis, fresh water, foods, and mild acids. Cutlery is commonly made with grade 420 stainless steel due to its corrosion resistance, though pitting can occur with continued exposure to certain food substances. 

Grade 430 Stainless Steel

While not as strong as either of the austenitic alloys highlighted above, grade 430 stainless steel does have an especially good resistance against nitric acid. Although the tensile strength of 450 MPa (65 ksi) is lower than most austenitic stainless steels, it’s still more than strong enough for many heavy-duty applications.

Grade 434 Stainless Steel

The stronger alternative to grade 430 stainless, 434 stainless steel has a tensile strength of 540 MPa (78 ksi) and a maximum operating temperature of 815˚C (1,499˚F). This makes grade 434 stainless steel slightly better for high-temperature applications than 316 stainless, while being tougher than grade 430 stainless. Grade 434 stainless also has excellent pitting resistance compared to 430 grade stainless steel.

Grade 436 Stainless Steel

A modification of grade 434, 436 stainless steel has added columbium and molybdenum to reduce any roping or riding during stretch forming operations. Grade 436 is highly magnetic and fairly resistant to abrasions. Typical usage ranges from appliance trims and automotive applications. 

Grade 442 Stainless Steel 

One of the most popular precipitation hardening grades of stainless steel in the market, grade 442 stainless is used in various industries. Ductile and soft (for a steel alloy), it can harness high friction and boasts high strength and good corrosion resistance. 

Grade 444 Stainless Steel

Grade 444 is a low carbon stainless steel with added molybdenum to provide good pitting and oxidation resistance. With properties ranging from high strength to good ductility, Grade 444 can be formed with a wide variety of stretch bending operations. However, grade 444 has limited weldability. Applications best suited for grade 444 stainless steel include roofing and coating in marine environment applications and food processing equipment.

Martensitic Stainless Steel

Grade 410 Stainless Steel 

A general purpose martensitic stainless steel, grade 410 offers corrosion resistant abilities which can be further enhanced through hardening, polishing, and tempering. Though not as corrosion resistant as austenitic steels, martensitic stainless steel alloys such as grade 410 still perform well in mild corrosive environments. 

Grade 410S Stainless Steel 

This low carbon variation of grade 410 stainless steel is non-hardening, even at high temperatures. It can remain ductile and soft despite rapid temperature changes. This ability prevents grade 410S from cracking during welding or when exposed to high heat. Grade 410S stainless steel is commonly used in thermal processing, petroleum refining, and other petrochemical industry applications. 

Grade 414 Stainless Steel 

Grade 414 stainless steel is essentially grade 410 with the addition of nickel. This additional nickel content makes grade 414 stronger than grade 410 at similar thicknesses. This grade is commonly used to make mining equipment, such as forged shafts and spindles, beater bars, fasteners, and valve seats. 

Grade 416 Stainless Steel 

With a machinability of 85%, grade 416 stainless steel can boast of having the highest machinability of any stainless steel. Due to this property, and its low cost, grade 416 stainless steel is available in a variety of forms such as highly tempered, hardened, or unhardened. Grade 416 has less corrosive resistance than that of austenitic steels, though grade 416 is highly resistant to fresh water, acids, and alkalis. Popular applications include automatic screw-machined components, gears, bolts, and washing machine parts. 

Grade 420 Stainless Steel

If annealed, grade 420 stainless steel has a tensile strength of around 586 MPa (85 ksi). When hardened and stress relieved, this material’s tensile strength jumps to roughly 1,586 MPa (230 ksi). While not as chemically resistant as the austenitic and ferritic stainless steels mentioned above, grade 420 stainless steel does have good resistance to mild acids, water, some alkalis, and food compounds—which is why it is often used for cutlery. When tensile strength and impact resistance are the primary concerns for an application, 420 stainless is a top choice.

Grade 440 Stainless Steel

The high levels of carbon in grade 440 stainless steel allows it to be heat treated, have exceptional wear resistance, and retain a cutting edge. Grade 440 stainless steel is magnetic and has moderate corrosion resistance. Common uses include knives, scissors, and parts that are exposed to oil or gas. 

Duplex (Ferritic-Austenitic) Stainless Steels

Grade 2205 Stainless Steel

Grade 2205 stainless steel is designed to resist stress corrosion cracking, pitting and crevice corrosion with the addition of nitrogen. This enables grade 2205 to have nearly twice the corrosion resistance found in other austenitic steels. Oil and gas, petrochemical, marine, and pulp and page industries find use in grade 2205 in applications requiring high strength and strong corrosion resistance. 

Grade 2304 Stainless Steel 

Though it has the same corrosion resistance of grade 316 austenitic steel, grade 2304  has nearly twice the yield strength of grade 316 and other austenitic steels. It can also perform well in colder temperatures, though with tome exceptions. This material is most suitable for applications in the range of -58°F to 572°F. 

Grade 2507 Stainless Steel 

This duplex stainless steel has high thermal conductivity, strong chloride stress corrosion resistance, and a low coefficient of thermal expansion. Grade 2507 is ideal for applications requiring excellent corrosion resistance and strong tensile strength. Applications which use grade 2507 stainless steel include marine and petrochemical equipment, offshore oil platforms, and a for a variety of mechanical and structural components. 

Precipitation Hardening (PH) Stainless Steels

Grade 17-4 Stainless Steel

This precipitation hardening stainless steel has both exceptional strength and fair corrosion resistance. The degree of strength in grade 17-4 can be manipulated with heat treatment. It also possesses fair machinability and magnetic properties. Common uses for grade 17-4 include applications in the aerospace and petroleum, and chemical industries. 

Grade 15-5 Stainless Steel 

Grade 15-5 boasts of high strength and corrosion resistance, as well as transverse toughness, ductility, and hardness capability. It is not an ideal material for cold working, though it is suitable for hot working. This PH stainless steel is commonly used in high pressure, corrosive environments and is ideal for aerospace parts. 

The Table of Stainless Steel Alloys

Here’s a stainless steel grade chart to break down the characteristics of the alloys listed above:

Marlin Steel's Stainless Steel Solutions

Marlin Steel’s engineers can create and design a large variety of wire forms and baskets to meet your needs, including custom S hooks, swaged pierced wire forms, and eye hooks, among others. These stainless steel forms can be crafted from a variety of the different steel options listed above, depending on your need and application. 

For your choice of stainless steel, it depends on your application. So, be sure to contact an experienced mechanical engineer, as they can take into account other factors that might affect your design needs and can make sure to deliver the best stainless steel solution.