Comprehensive authoritative stainless steel knowledge from China CNC

Classification of stainless steel

Magnetic and non-magnetic stainless steel

Stainless steel can be roughly divided into three categories: 200 series, 300 series, and 400 series. The 300 series is the most commonly used. The 200 series and 400 series are substitutes for the 300 series to a certain extent. Strictly speaking, the 400 series is not called stainless steel. , Called stainless iron, because it does not contain nickel, it can be attracted by a magnet. The 200 series and 300 series have nickel, which is not magnetic and cannot be absorbed by iron.

304 is the most common variety in the 300 series, so generally the price trend of the entire stainless steel can be judged from the price change of 304. The 200 series contains less nickel, the 400 series does not contain nickel, and the 300 series contains the most nickel. Therefore, the 300 series is most affected by nickel prices.

The 300 series can be divided into 304, 304L, 316, 316L, 321, 309S, 310S, etc. The distinction is based on the content of various metal elements, and the characteristics of stainless steel with different content are different. The difference between 304 and 304L is The carbon (C) content is different. The one with L means low carbon content, also called low carbon. The difference between 316 and 316L is the same.

Shape of stainless steel

Stainless steel can be divided into five categories: coils, plates, profiles, steel pipes and parts, the most important being coils and plates. Profiles are materials of various shapes made of plates, including angle steel, flat steel, I-beam, and channel steel. The steel pipe mainly refers to the seamless steel pipe, and the opposite of the seamless steel pipe is the welded pipe. The difference is whether it is formed at one time. Parts mainly refer to elbows and flanges and other small things.

The coil and the sheet are actually the same, and the form of delivery is different. The coil is rolled one by one, and the plates are one by one. If they leave the factory, they are plates, also called original plates, usually thick plates, because they are very thick. If it is, it cannot be rolled, generally it cannot be rolled if it is more than 16 mm.

The price of coil and plate is also different. If it is a purchased coil, it is calculated according to the actual weight. Therefore, the price is high. The plate is calculated according to theory, and the price is low. For example, the actual thickness of 10mm may be 9.6mm. There will be a difference.

Stainless steel plates are divided into hot rolling and cold rolling according to the different rolling processes of the rolling mill (the rolling mill is the machine name of the rolled plate). Hot rolling is usually marked as NO.1; cold rolling is marked as 2B or BA (BA is better than 2B. , To be bright, close to the mirror, the best is the mirror surface, the mirror surface is not in stock, all need to be processed), for example, 304 is often a purchased board, which means that the roll must be flattened by a machine. This machine is a flattening machine .

It can be opened to different lengths by the leveling machine. If it is not a regular length, it is called a fixed opening, which means a fixed opening size. Because customers often ask for different length requirements according to actual needs, the roll becomes important at this time. The board cannot meet the requirements.

Domestic cold rolling is generally below 3 mm, and hot rolling is generally above 3 mm. There are hot rolling and cold rolling for 3 mm thickness, but the thickness of imported cold-rolled plates can reach 4 mm or even 6 mm. Hot-rolled plates of 3 mm to 12 mm are called medium plates, and those of 12 mm or more are called thick plates, which can be thicker than 120 mm and are called hot-rolled medium-thick plates, while cold-rolled plates are cold-rolled sheets.

Calculation of theoretical weight of stainless steel plate

In the field of construction machinery, due to the importance of precision and size, millimeters are used in the world in units of 1000 mm = 1 meter, and 1 mm = 100 silk.

According to this formula the weight is kilogram (KG), to the decimal point to two, because the price of stainless steel, trading volume, the number after the decimal point is very important, so money also to the decimal point to two

Specific gravity of stainless steel (KG)

Different stainless steels have different specific gravity:

The 400 series specific gravity is 7.75

-The specific gravity of 304, 321, 304N, 201, 202, 304L, 301 is 7.93

-The specific gravity of 310S, 309S, 316, 316L is 7.98

Stainless steel number comparison table

Different countries in the world have different names for stainless steel. The market often comes into contact with China and the United States, called the national standard and the American standard. The 200 series, 300 series and 400 series mentioned above are American standards.

National standard============American Standard

1cr17mn6ni5n========201

1cr18mn8ni5n========202

0cr18ni9============304

00cr19ni10==========304L

0cr18ni12mo2t=======316Ti

00cr17ni14mo2=======316L

0cr17ni12mo2========316

1cr18ni9ti==========321

0cr18ni10ti=========321

0cr23ni13===========309S

1cr20ni14===========309S

0cr25ni20===========310S

1cr25ni20===========310s

0cr13===============405

1cr13===============410

2cr13===============420

3cr13===============420

4cr3================430

The element content in the national standard designation generally refers to the intermediate value of the content, which is a theoretical value, which can be large or small.

Characteristics and uses of main stainless steel types

As a widely used steel, 304 has good corrosion resistance, heat resistance, low temperature strength and mechanical properties, good hot work ability such as stamping and bending, no heat treatment hardening phenomenon, non-magnetic, and the use temperature is minus 193 degrees to positive 800 degrees.

Application: tableware, kitchenware, water heaters, boilers, auto parts, medical equipment, food machinery, wine storage, pressure vessels (chemical machinery, chemical equipment).

As a low-carbon 304 steel, 304L has the same corrosion resistance as 304 under normal conditions, but after welding and stress relief, it has good inter granular corrosion resistance and can maintain good performance without heat treatment. Corrosion resistance, generally used at 400 degrees.

Application: petrochemical industry, building materials.

321 adds Ti element to 304 steel to prevent inter granular corrosion. It is suitable for plus 430 to 900 degrees below, non-magnetic.

Application: Automobile exhaust, heat exchangers, containers and other products that do not undergo heat treatment after welding are not suitable for food processing equipment due to the addition of Ti element.

316 has low carbon and added MO elements, so its corrosion resistance, atmospheric corrosion resistance and high temperature strength performance are particularly good. It can be used under harsh conditions and is suitable for use below 900 degrees. It is non-magnetic.

Application: Equipment used in sea water, chemical, dye, paper, acetic acid, fertilizer and other production equipment, food industry and coastal facilities, products that have special requirements for resisting intercrystalline corrosion.

The two materials of 309S/310S have relatively high content of nickel and chromium. At the same time, the content of Si is increased to make it have high temperature resistance and corrosion resistance. Among them, 309S can withstand repeated heating below 980, and the use temperature of 310S reaches 1200 degrees, continuous use The temperature can be 1150 degrees, non-magnetic.

Application: Suitable for key parts of high temperature electric furnace equipment, drying equipment, furnace materials, aviation, petrochemical, electric power, etc.

The 200 series is similar to 304 and the price is cheap and economical.

Application: Food processing utensils, kitchen equipment, food processing equipment, filters, milk cans, consumer durables, washing machine parts, water heaters, steel furniture, building decoration, decoration

In terms of fatigue resistance, 201 has a higher hardness and not as tough as 304, but 304 has better fatigue resistance.

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