Basic knowledge of stainless steel

Basic knowledge of stainless steel

1、 Introduction to stainless steel:

All metals react with oxygen in the atmosphere to form an oxide film on the surface. Unfortunately, the iron oxide formed on ordinary carbon steel continues to oxidize, resulting in the expansion of corrosion and eventually the formation of holes. Carbon steel surfaces can be guaranteed by electroplating with paint or oxidation resistant metals (e.g., zinc, nickel and chromium), but, as is known, this protection is only a thin film. If the cover is damaged, the steel below will start to rust.

Steel resistant to weak corrosive medium such as air, steam, water and chemical etching medium such as acid, alkali and salt. Also known as stainless acid resistant steel. In practical application, the steel with weak corrosion resistance is often called stainless steel, while the steel resistant to chemical medium corrosion is called acid resistant steel. Due to the difference in chemical composition, the former is not necessarily resistant to chemical medium corrosion, while the latter is generally rust free. The corrosion resistance of stainless steel 2 depends on the alloy elements contained in the steel. Chromium is the basic element to obtain corrosion resistance of stainless steel. When the content of chromium in steel reaches about 12%, a thin oxide film (self passivation film) is formed on the surface of steel by the interaction of chromium and oxygen in corrosive medium, which can prevent further corrosion of steel matrix. In addition to chromium, the common alloy elements are nickel, molybdenum, titanium, niobium, copper, nitrogen, etc., to meet the requirements of various applications on the structure and properties of stainless steel.

2、 Classification of stainless steel stainless steel is usually divided into three types according to the matrix structure:

1. Ferritic stainless steel. The chromium content is 12% - 30%. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its chloride stress corrosion resistance is better than other kinds of stainless steel.

2. Austenitic stainless steel. It contains more than 18% chromium, about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. It has good comprehensive performance and can resist corrosion of various media.

3. Austenitic ferrite duplex stainless steel. It has the advantages of both austenitic and ferritic stainless steels and superplasticity.

4. Martensitic stainless steel. High strength, but poor plasticity and weldability.

3、 Characteristics and applications of stainless steel:

4、 Stainless steel surface process:

5、 Packaging features and main products of each steel plant

Other domestic steel mills: Shandong Taigang, Jiangyin Zhaoshun, Xinghua Dainan, Xi'an Huaxin, southwest and Dongfang special steel. These small plants mainly use waste materials to process rolled plates. The production process is backward, the plate surface is poor, and there is no guarantee of mechanical properties. The element content is almost the same as that of large plants, and the price is cheaper than that of the same model.

Imported steel plants: Shanghai Krupp, South Africa, North America, Japan, Belgium and Finland. The imported plate has advanced production technology, clean and beautiful surface and neat cutting edge, and the price is higher than that of the same model in China.

6、 Specification, model and size of stainless steel: stainless steel plate includes coil and original flat roll:

1. The coil is divided into cold rolling coil and hot rolling coil, trimming coil and rough edge coil.

2. Generally, the thickness of cold rolled coil is 0.3-3 mm, and there are also 4-6 mm cold-rolled sheet with the width of 1 m, 1219 m and 1.5 m, which is represented by 2B.

3. The thickness of hot-rolled coil is generally 3-14mm, and there are also 16mm coils with width of 1250, 1500, 1800 and 2000, which are indicated by No.1.

4. The rolls with width of 1.5m, 1.8m and 2.0m are trimming rolls.

5. The width of burr curl is generally 1520, 1530, 1550, 2200, etc., which is wider than the normal width.

6. In terms of price, there is a general difference of 300-500 yuan between the same model of trimming roll and rough edge roll.

7. The roll can be opened according to the length required by customers, and it is called open plate after being opened and leveled by the flattening machine. Generally speaking, cold rolling is 1.5m * 6m, 1.8m * 6m and 2m * 6m, which is also called 4 * 8ft.

Original plate also known as sheet rolling:

1. The thickness of the original plate is generally between 4mm and 80mm, and there are also 100 mm and 120 mm. This thickness can be fixed rolling.

2. The width is 1.5m, 1.8m and 2m, and the length is more than 6m.

3. Features: the original flat plate has large volume, high cost, difficult pickling and inconvenient transportation.

7、 Thickness differentiation:

1. Because in the rolling process of steel mill machinery, the roller is slightly deformed due to heating, resulting in the thickness deviation of the rolled plate, which is generally thick in the middle and thin on both sides. When measuring the thickness of the board, the middle part of the plate head should be measured according to the national regulations.

2. According to the market and customer demand, tolerance is generally divided into large tolerance and small tolerance.

8、 Specific gravity of each stainless steel material:

1. The specific gravity of 304, 304L, 304j 1, 321, 201, 202 were 7.93.

2. The specific gravity of 316, 316L, 309S and 310S was 7.98.

3. The specific gravity of 400 series is 7.75.

9、 Calculation formula of stainless steel:

Calculation formula:

Stainless steel pipe: (outer diameter wall thickness) × wall thickness × 0.02491 = kg / M

Stainless steel plate; thickness