How was 304 stainless steel named

BS Stainless GmbH

When “stainless steel” was invented, it was an umbrella term that was mainly intended for the cutlery industry for cosmetic reasons. Since then, it has become a description for many different metals referred to as types of stainless steel.

The types of stainless steel fall predominantly into four types, groups or can be referred to as families.

Under "stainless steel types" we categorize the mechanical properties and manufacturing specifications as well as the composition of stainless steel. There is an old three-digit number system that is still used to classify classes, but new classification systems have been developed over time.

Stainless steel families are named after their metallurgical microstructure and are named as follows:


These grades have excellent corrosion resistance and do not become magnetic when annealed. They are ideal for welding and, due to their properties, are extremely hygienic. They cannot be hardened by heat treatment, but they have excellent levels of performance at low temperatures.

Austenitic is arguably the most widely used and popular type of stainless steel. The qualities of this group include 304 (1.4301) and 316 (1.4404); these are designated as A2 (304) and A4 (316) when describing connecting elements. This group of materials has been described in the past as 18/8 due to the combination of chromium and nickel, which normally includes 321 (1.4541), which means that one of these three grades was acceptable. Other popular types are 303 (1.4305), often for round bar-free machining, 310 (1.4845) for heat resistance and variants that increase molybdenum, reduce carbon, etc.


Ferritic - another very popular group of varieties. The ferritic terms come from the fact that there is more iron, with nickel almost always absent. These qualities are often used for indoor applications such as kitchen appliances or areas such as exhaust systems where the appearance of cosmetics may be less important. Ferritic steels are often viewed as a cost-saving variety, but they have some advantages on their own, such as strength, wear resistance, or the fact that they are magnetic. Ferritic stainless steels have moderate corrosion resistance, but are not as great as the austenitic stainless steels. They cannot be hardened by heat treatment and are not so good for welding.

The most common types of stainless steel in this family are 409 (1.4512) and 430 (1.4016).


Martensitic - probably the least known group of stainless steels, most of which can be hardened and hardened by the addition of carbon. The common types are 410 and 420 (1.4021), they contain at least 10.5% chromium. Therefore, these types are popular for products such as blades, knives, scissors, razors and medical devices wherever hardness is important.

Martensitic stainless steels also have moderate corrosion resistance, but this resistance is not as strong as that of the austenitic stainless steels. However, the martensitic stainless steels are heat treatable and magnetic, but very difficult to weld.


This is the youngest group of materials and possibly the fastest growing. The term duplex comes from the structure of the material, which contains elements made of an austenite and a ferrite. The aim is to create types that combine these structures to combine the key elements such as strength and corrosion resistance. The result would be when almost new types of stainless steel were created to provide solutions to industrial problems such as reducing weight and increasing performance in harsh environments.

Duplex stainless steels are very similar to austenitic stainless steels in that they have excellent corrosion resistance, but also have increased resistance to chloride attacks. But it will be better duplex stainless steels have good resistance to stress corrosion cracking. It has a higher tensile strength than austenitic or ferritic grades and is good for welding and formability.

These strains can be the most confusing because, due to brand names, there are often multiple descriptions for the same strain, e.g. B. 1.4462, also UNS 31803, 2205 (1.4462) and sometimes only 318 or 318L. New innovations and applications are constantly being found that are very popular in offshore applications.

Precipitation hardening of steels

Precipitation hardened steels can be martensitic, semi-austenitic as well as austenitic and have good to moderate corrosion resistance and are suitable for welding. These are especially good because they are both high strength and magnetic.