Different types of stainless steel grades

All stainless steel alloys have distinct physical properties such as tensile strength, corrosion resistance, melting points, and oxidation resistance. This article aims to give you the awareness to choose the best quality stainless steel and grade suited for your end applications. Here is a summary of the most popular types of stainless steel and their characteristics. 

Five main categories of stainless steel: -

1. Austenitic stainless steel: this is the most commonly used stainless steel variant. Compared to other steel alloys, austenitic stainless steels typically have a higher chromium concentration, which increases their corrosion resistance. The tendency for austenitic stainless steel alloys to lack magnetic properties, though possible after cold treatment, is another shared feature of these materials.

2. Ferritic stainless steel: this is the second most commonly used variant after austenitic stainless steel. Ferritic stainless steel is magnetic, as the name suggests. Cold working can be used to harden these alloys. Due to their lower nickel content, they are also less expensive.

3. Duplex (ferritic-austenitic) stainless steels: the name "duplex" for this subcategory of stainless steel comes from its composition of equal amounts of austenite and delta-ferrite. These stainless steel alloys outperform austenitic stainless steels in terms of tensile strength and corrosion resistance, particularly regarding chloride pitting. Duplex stainless steels are frequently used for pipelines and pressure vessels in the petrochemicals industry and pipework systems in the oil and gas sector due to their physical characteristics and chemical resistance.

4. martensitic stainless steels: this is the least common category of stainless steel. Despite having a higher hardness than ferritic or austenitic alloys, its corrosion resistance is typically lower. Martensitic stainless steel alloys are often the best choice for applications requiring extremely high tensile strength and impact resistance. 

Within each of the above categories, there are various grades of stainless steel; the most popular types of each are broken down below:

Austenitic stainless steels

Grade 301 –  301 steel is made with additives of nickel and chromium. It is both robust and ductile when cold worked. Grade 301 stainless steel is frequently used in welding, forming, and drawing thanks to these qualities.

Grade 302 – grade 302 stainless steel is very similar to grade 304 stainless steel, except that it contains higher carbon levels. It is particularly used for its capacity to withstand caustic chemicals, solvents, and acids. Conical compression springs made of grade 302 stainless steel are often used in kitchen appliances, food processing machinery, and medical applications.

 Grade 303 – This grade is not as resistant to corrosion as grade 304; it cannot be hardened by heat treatment. Heavy-duty machined components, including gears, aviation fittings, screws, shafts, nuts, and bolts, frequently employ grade 303.

Grade 304 – grade 304 is the most versatile variant of austenitic stainless steel. Grade 304 stainless steel stands out even among steel alloys for its high tensile strength, approximately 621 MPa (90 ksi). Because of its tensile strength, temperature, and corrosion resistance, 304 stainless steel is used for various applications.

Grade 309 – this nickel-chromium stainless steel's higher tensile strength and chemical resistance are similar to those of grade 304. Grade 309 is suitable for heat applications because it can tolerate extremely high temperatures. For high-heat applications such as furnace parts, aircraft engines, automotive exhaust systems, and oven liners, grade 309 is frequently utilised.

Ferritic stainless steel

Grade 405 - due to its weaker corrosion resistance, grade 405 stainless steel is appropriate for mild corrosive applications. Grade 405 SS does not harden when the material is cooled after welding procedures because of the additional aluminium it contains. It is used for applications like steam nozzles and quenching racks.

Grade 408 - although this type of stainless steel has weak corrosion resistance, it has good heat resistance. It is made from a combination of 8% nickel and 11% chromium.

Grade 409 -  both high-temperature tolerance and corrosion resistance characteristics are present in grade 409. It is particularly resistant to exhaust gas and atmospheric corrosion and is consequently used in automobile applications, including exhaust systems.

 Grade 420 - With 12% chromium and a 50HRC hardness, this grade of stainless steel is the hardest of all the grades. It also has good ductility and corrosion resistance, particularly against alkalis, fresh water, foods, and mild acids. Grade 420 stainless steel is often used to make cutlery, though prolonged exposure to certain food substances can cause pitting.

Duplex stainless steel

Grade 2205 - with the addition of nitrogen, grade 2205 stainless steel is intended to withstand stress corrosion cracking, pitting, and crevice corrosion. As a result, grade 2205 has corrosion resistance that is over two times greater than that of other austenitic steels. Applications needing high strength and great corrosion resistance are used grade 2205 in the oil and gas, petrochemical, maritime, and pulp and paper sectors.

 Grade 2304 -  grade 2304 has over twice the yield strength of grade 316 and comparable austenitic steels yet has the same level of corrosion resistance. It can also function well in cooler climates, with few exceptions. Most uses for this material fall between -58°F and 572°F.

 Grade 2507 - this duplex stainless steel has a low coefficient of thermal expansion, strong chloride stress corrosion resistance, and high thermal conductivity. Applications requiring exceptional corrosion resistance and high tensile strength are best served by grade 2507. Applications for grade 2507 stainless steel include offshore oil platforms, marine and petrochemical equipment, and various mechanical and structural parts.

 Martensitic stainless steel

 Grade 410: grade 410 is a general-purpose martensitic stainless steel that offers corrosion resistance properties that can be enhanced through hardening, polishing, and tempering. Even though martensitic stainless steel alloys like grade 410 perform well in mild corrosive settings, they are not as corrosion-resistant as austenitic steels.

 Grade 414: grade 410 stainless steel is essentially grade 410 with nickel added. Nickel addition also makes it more robust than grade 410. This steel is frequently used to create valve seats, beater bars, forged shafts and spindles, fasteners, and mining equipment.

 Grade 416: grade 416 stainless steel boasts the highest machinability of any stainless steel with a rating of 85 %. Considering this property and its affordability, grade 416 stainless steel is available in a range of finishes, including severely tempered, hardened, and unhardened. Although grade 416 is extremely resistant to fresh water, acids, and alkalis, it has less corrosion resistance than austenitic steels. Automatic screw-machined parts, gears, bolts, and washing machine parts are common uses.

Your choice of stainless steel depends on your application. Make sure you contact a trusted supplier acclaimed for making on-time deliveries at the most transparent prices. Contact JSW One MSME to get the best quality stainless steel and experience punctuality with every purchase.