What are the 3 grades of stainless steel?

2024-12-23

Stainless steel can generally be divided into austenitic stainless steel, ferritic stainless steel and martensitic stainless steel these three common grades, the following is a detailed introduction

1. Austenitic stainless steel

Composition characteristics

Its chromium (Cr) content is about 16%-26%, nickel (Ni) content is about 6%-22%. This chemical composition makes austenitic stainless steel have good toughness and corrosion resistance. For example, 304 stainless steel is a typical austenitic stainless steel with a chromium content of about 18% and nickel content of about 8%.

Performance characteristics

Corrosion resistance:

It has excellent corrosion resistance to many chemical substances, and can resist the corrosion of atmosphere, water, food and most organic and inorganic acids. In common environments, such as the humid environment of the kitchen, food processing equipment and other use scenarios, it can maintain good condition.

Toughness and ductility:

Excellent toughness and ductility, easy to process and form. It can be made into various products, such as pipes, plates, wires, etc., by cold processing (such as cold rolling, cold drawing) and hot processing (such as forging, hot rolling).

Non-magnetic or weakly magnetic:

In general, it is non-magnetic or weakly magnetic, which makes it advantageous in some applications where magnetism is required (such as electronic device enclosures).

Scope of application

Widely used in food processing equipment, kitchen utensils, building decoration, chemical equipment, medical equipment and other fields. For example, the sink in the family kitchen, tableware, and some medical equipment in the hospital are made of austenitic stainless steel.

2. Ferrite stainless steel

Composition characteristics

The main alloying element of ferritic stainless steel is chromium, the chromium content is usually between 10.5%-30%, and basically nickel free. The high chromium content makes the ferritic stainless steel have good corrosion resistance, such as 430 stainless steel, the chromium content is about 17%.

Performance characteristics

Corrosion resistance:

It has good corrosion resistance to oxidizing acids (such as nitric acid), and can resist the corrosion of atmosphere, fresh water and some chemical media to a certain extent. However, its corrosion resistance is generally slightly lower than that of austenitic stainless steel.

Thermal conductivity:

It has good thermal conductivity, which makes it suitable in some applications that require good heat transfer, such as the bottom of cooking utensils.

Magnetic:

It has obvious magnetic properties, which is an important difference from austenitic stainless steel.

Scope of application

Commonly used in the manufacture of automotive exhaust systems, building decoration materials (such as roofs, curtain walls), kitchen appliances (such as ovens, microwave ovens) and so on. Because its cost is relatively low, it can play a better performance in some occasions where the corrosion resistance requirement is not extremely high.

3.Martensitic stainless steel

Composition characteristics

Martensitic stainless steel contains a high carbon (C) content, generally between 0.1% and 1.0%, and the chromium content is about 11.5% to 18%. The higher carbon content allows it to be strengthened by heat treatment. For example, 410 stainless steel has a chromium content of about 12% and a carbon content of about 0.15%.

Performance characteristics

Strength and hardness:

After proper heat treatment, martensitic stainless steel can obtain higher strength and hardness, and can withstand greater pressure and friction. Its hardness is significantly higher than austenitic and ferritic stainless steel.

Corrosion resistance:

Corrosion resistance is relatively weak, especially in some harsh corrosive environments. However, it can still maintain good performance in the general atmospheric environment and some mildly corrosive media.

Magnetic:

It is magnetic, which is the same as ferritic stainless steel.

Scope of application

It is mainly used for manufacturing tools, mechanical parts, valves, bearings and other parts that require higher strength and certain corrosion resistance. For example, many stainless steel tools in the tool industry are made of martensitic stainless steel, and its high hardness can ensure the sharpness and durability of the tool.