What are the most common types of stainless steel?

In our daily lives, we often encounter various stainless steel products, from cutlery to architectural structures. They have won our favor with their excellent corrosion resistance and enduring beautiful appearance. However, do you truly understand the differences behind these seemingly similar materials? Today, we will explore the most commonly used types of stainless steel together, giving you a deeper understanding of these amazing rust-resistant materials.

What is stainless steel?

In general, stainless steel refers to steel that is not easily rusted. Actually, some stainless steels have both corrosion resistance and acid resistance. The corrosion resistance and acid resistance of stainless steel are due to the formation of a chromium-rich oxide film (passivation film) on its surface. This film isolates the metal from external media, preventing further corrosion, and has the ability to self-repair. Once the film is damaged, the chromium in the steel reacts with oxygen in the medium to generate a new passivation film and continue to protect it.

What are the most common types of stainless steel?

There are five basic types of stainless steel: austenitic, ferritic, martensitic, dual-phase stainless steel, and precipitation-hardening stainless steel.

(1) Austenitic stainless steel is non-magnetic and is a representative grade that adds 18% chromium and contains a certain amount of nickel to increase corrosion resistance. They are widely used grades.

(2) Ferritic stainless steel has magnetic properties, with chromium as its main content at a ratio of 17%. This material has good oxidation resistance.

(3) Martensitic stainless steel also has magnetic properties, with a chromium content of 13% and a carbon content in appropriate proportions. They can be hardened by quenching and tempering.

(4) Dual-phase stainless steel has a mixed structure of ferrite and austenite, with a chromium content between 18% and 28% and a nickel content between 4.5% and 8%. They have good resistance to chloride erosion.

(5) Precipitation-hardening stainless steel has a conventional chromium content of 17% and adds a certain amount of nickel, copper, and niobium. They can be hardened by precipitation and aging.

Classification by metallographic structure:

(1) Ferrite stainless steel (400 series), which is mainly represented by chrome-containing grades such as Gr13, G17, Gr27-30;

(2) Austenitic stainless steel (300 series), chrome-nickel grades, mainly represented by 304, 316, 321, etc.;

(3) Martensitic stainless steel (200 series), chrome-manganese grades with high carbon content, mainly represented by 1Gr13, etc.

Classification by the composition：

There are many types of stainless steel, and their properties and application environments are different. According to the composition, they can be divided into Cr series (SUS400), Cr-Ni series (SUS300), Cr-Mn-Ni series (SUS200), and precipitation hardening series (SUS600).

200 series – chrome-nickel-manganese austenitic stainless steel.

300 series – chrome-nickel austenitic stainless steel.

301 – Good ductility, used for forming products. It can also be quickly hardened by mechanical processing. It has good weldability and its wear resistance and fatigue strength are better than 304 stainless steel.

302 – Corrosion resistance similar to 304, but with higher carbon content, it has better strength.

303 – By adding a small amount of sulfur and phosphorus, it is easier to machine than 304.

304 – That is 18/8 stainless steel. GB brand is 0Cr18Ni9.

309 – Has better temperature resistance than 304.

316 – Following 304, the second most widely used steel grade, mainly used in the food industry and surgical equipment. It adds molybdenum to achieve a special corrosion-resistant structure. It is also used as “ship steel” due to its better corrosion resistance to chlorides compared to 304. SS316 is usually used in nuclear fuel recycling facilities. 18/10 grade stainless steel usually also meets this application level.

321 – Other than adding titanium to reduce the risk of rust in the weld, its other properties are similar to 304.

400 series – Ferritic and martensitic stainless steel.

408 – Good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.

409 – The most inexpensive model (UK and US), usually used as exhaust pipes for automobiles, is ferritic stainless steel (chromium steel).

410 – Martensitic (high-strength chromium steel), wear-resistant, poor corrosion resistance.

416 – Adding sulfur improves processing properties of the material.

420 – “Tool grade” martensitic steel, similar to the earliest stainless steel, such as high-chromium steel. Also used for surgical knives, which can be made very bright.

430 – Ferritic stainless steel, used for decoration, such as automotive ornaments. Good formability, but worse temperature resistance and corrosion resistance.

440 – High-strength tool steel, with slightly higher carbon content. After proper heat treatment, it can achieve higher yield strength, and the hardness can reach up to 58HRC, making it one of the hardest stainless steels. The most common application example is “razor blades”. Common models include 440A, 440B, 440C, and 440F (easy-to-process type).

500 series – Heat-resistant chrome-alloyed steel.

600 series – Martensitic precipitation-hardening stainless steel.

630 – The most commonly used precipitation-hardening stainless steel model, also known as 17-4; 17% Cr, 4% Ni.

Conclusion

Thank you for reading our article and we hope it can help you know the most common types of stainless steel better. If you want to find more information about stainless steel, we would recommend you to visit Sino Stainless Steel.

As a leading supplier of stainless steel products across the world, Sino Stainless Steel provides customers with high-quality stainless steel strips, stainless steel coils, stainless steel plates, stainless steel sheets, stainless steel bars, and stainless steel wires at a very competitive price.