Definition of stainless steel
Stainless steel is a kind of high-alloy steel that can resist corrosion. It has a beautiful surface and does not need to undergo surface treatment such as color plating or paint. Therefore, many machinery factories often do not do any paint treatment to show that they are stainless steel, while black materials ( The so-called black material is the name of general steel) must be anti-rust treatment.
A simple classification of stainless steel
Stainless steel can be roughly divided into three categories: 200 series, 300 series, and 400 series. Among them, the 300 series is the most commonly used, and 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, so it can be attracted by a magnet. The 200 series and 300 series are made of nickel, so they are non-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 contains no nickel, and the 300 series contains the most nickel, so the 300 series is most affected by the price of nickel.
The 300 series can be simply divided into 304, 304L, 316, 316L, 321, 309S, 310S, etc. The basis for the distinction is that the contents of various metal elements are different, and the characteristics of stainless steel with different contents are also different. The difference between 304 and 304L is that The carbon (C) content is different, the one with L means low carbon content, also called low carbon, and the difference between 316 and 316L is the same.
Morphological classification 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. Steel pipe mainly refers to seamless steel pipe, and the opposite of seamless steel pipe is welded pipe. The difference lies in whether it is formed at one time. Components mainly refer to elbows and flanges and other small things.
The coiled material and the plate are the same, but the factory form is different. The coiled material is a roll, and the plate is a sheet. If the factory is a plate, it is also called the original plate. It is usually a thick plate because it is very thick. If it is too large, it cannot be rolled, generally, it cannot be rolled if it is more than 16 mm.
There are rolls and plates, and most of the time it is plated, and the prices of rolls and plates are also different. If you purchase rolls, it is calculated according to the actual weight, so the price is high, and the plate is calculated according to theory, so the price is low. , the reason is that there is a difference. For example, the thickness of 10mm may be 9.6mm, and there will be a price difference in the middle.
Stainless steel plates are divided into hot rolling and cold rolling according to the rolling process of the rolling mill (the rolling mill is the machine name of the rolling plate). Hot rolling is usually marked as NO.1 and cold rolling is marked as 2B or BA (BA is better than 2B surface, To be bright, close to the mirror, the best is the mirror surface, the mirror surface is not in stock, and it needs to be processed), for example, 304 is often a purchased board, which means that the roll must be flattened into a plate by a machine, this machine is a flattening machine. The flattening machine can be opened into different lengths. If it is not a conventional length, it is called a fixed opening, which means that the size is fixed, because customers often ask for different lengths according to actual needs. At this time, the role is very important. Conventional The board does not meet the requirements.
Domestic cold rolling is generally less than 3 mm, hot rolling is generally more than 3 mm, and the thickness of 3 mm includes both hot rolling and cold rolling, but the thickness of imported cold rolled plates can be less than 4 mm or even less than 6 mm. Hot-rolled plates from 3 mm to 12 mm are called medium plates, and those above 12 mm are called thick plates, which can be thicker than 120 mm, and are also called hot-rolled medium plates, while cold-rolled plates are cold-rolled thin plates.
Simple Calculation Method of Theoretical Weight of Stainless Steel Plate
Board weight = specific gravity × thickness (mm) × width (m) × length (m) (mm is the unit of the millimeter, m is the unit of the meter)
In the field of construction machinery, due to the emphasis on precision dimensions, millimeters are used throughout the world. 1000 mm = 1 meter, 1 mm = 100 wires.
The weight obtained according to this formula is kilograms (KG), which must be accurate to two decimal places. Because stainless steel is expensive and the transaction volume is large, the number after the decimal point is also very important, so the money should be accurate to two decimal places. bit.
The specific gravity of stainless steel (KG)
Different stainless steels have different specific gravity:
A specific gravity of the 400 series is 7.75
B, 304.321.304N.201.202.304L..301. Specific gravity is 7.93
C, 310S.309S.316.316L specific gravity is 7.98.
Comparison table for steel-grades
Countries in the world have different names for stainless steel. The markets often come into contact with China and the United States, which are called national standards and American standards. The 200 series, 300 series, and 400 series mentioned above are American standards. American standard is usually called stainless steel because it is easy to understand. All American Standard.
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 appellation generally refers to the middle value of the content, which is a theoretical value, which can be large or small.
What is tolerance?
This is a very important term. Tolerance is the recognized allowable length or thickness deviation. Because of the production process of plates, it is difficult for various reasons. The actual thickness that comes out is often not up to the theoretical thickness. For example, a 6mm board is only 5.6mm. This is tolerance. In China, tolerance is often negative tolerance. When buying and selling boards, it is usually calculated according to the theoretical thickness, which is why the theoretical price is lower than the weighing price. The tolerance is also divided into sizes, and the price is also different. The price of the large tolerance is cheaper. For example, 6mm, if it is below 5.5, it is a large tolerance.
Characteristics and uses of main stainless steel types
304: As a widely used steel, it has good corrosion resistance, heat resistance, low-temperature strength, and mechanical properties, good hot workabilities such as stamping and bending, no heat treatment hardening phenomenon, no magnetism, and the use temperature are minus 193 degrees to Positive 800 degrees.
Uses： tableware, kitchen utensils, 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 similar corrosion resistance to 304 under normal conditions, but after welding and stress relief, it has good intergranular corrosion resistance and can maintain good corrosion resistance without heat treatment. Corrosion resistance, generally used at 400 degrees,
Uses： petrochemical industry, building materials.
321 adds Ti element to 304 steel to prevent intergranular corrosion, suitable for positive 430 to 900 degrees, non-magnetic;
Uses: Automobile exhaust, heat exchangers, containers, and other products that do not undergo heat treatment after welding, due to the addition of Ti element, are not suitable for making food processing equipment.
316 is a low carbon, with MO added, so its corrosion resistance, atmospheric corrosion resistance, and high-temperature strength are particularly good, it can be used under harsh conditions, it is suitable for use below 900 degrees, and it is non-magnetic.
Uses: equipment used in seawater, chemical, dye, paper, acetic acid, fertilizer, and other production equipment, food industry and facilities in coastal areas, products with special requirements for resistance to intergranular corrosion.
309S/310S, these two kinds of materials, the content of nickel and chromium is relatively high, and the content of Si is increased at the same time so that it has high-temperature resistance and corrosion resistance. Among them, 309S can withstand repeated heating below 980 degrees, and 310S can be used at a temperature of 1200 degrees. Continuous use Temperature can be 1150 degrees, non-magnetic.
Uses: Suitable for key parts such as high-temperature electric furnace equipment, drying equipment, furnace materials, aviation, petrochemical, electric power, etc.
The 200 series is similar to the 304 in terms of low cost and economy.
Uses: Food processing utensils, kitchen equipment, food processing equipment, filters, milk tanks, durable consumer goods, washing machine accessories, water heaters, steel furniture, architectural decoration, decoration. In terms of fatigue resistance, 201 has a higher hardness, but its toughness is not as good as 304, and 304 has better fatigue resistance.
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