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The Knowledge of Stainless Steel
- Dec 05, 2017 -

Stainless steel definition

Stainless steel is a high-alloy steel that can resist corrosion.A beautiful surface, without having to go through the surface treatment of plating or paint, so many machinery factory to show that their own is stainless steel, often without any paint processing, and black material ( The so-called black material is the general name of steel) is the need for anti-rust treatment.


Simple classification of stainless steel

Stainless steel can be divided into superficial 200 series, 300 series and 400 series of three categories, of which 300 series is the most commonly used, 200 series and 400 series is a series of 300 series substitutes, strictly speaking 400 series is not called stainless steel , Called stainless iron, because it does not contain nickel, so the magnet can attract live. The 200 series and 300 series are nickel, so there is no magnetic, iron absorption can not.


304 is the 300 series of the most common species, so the general price change from 304 can determine the price trend of the entire stainless steel. 200 series contains less nickel, 400 series does not contain nickel, 300 series contains the most nickel, so the most affected by the nickel price is the 300 series.


300 series can be simply divided into 304,304L, 316,316L, 321,309S, 310S and so on, the basis for the distinction is a variety of metal elements of different content of different characteristics of stainless steel is not the same, the difference between 304 and 304L is Carbon (C) content is different, with L is low carbon, also known as low-carbon, 316 and 316L the same difference.

Stainless steel morphological classification

Stainless steel can be divided into coils, plates, profiles, steel tubes and parts five categories, the most important is the volume and board. Profile is made from a variety of different shapes of the plate material, angle steel, flat steel, I-beam, channel. Pipe is mainly refers to the seamless steel pipe, and seamless steel pipe is the opposite, the difference is whether a molding. Parts mainly refers to elbows and flanges and other small things.


Coils and plates in fact the same, the factory form is different, the coil is a roll of paper, the sheets are one by one, if the factory is a plate, also called the original board, usually thick, because it is thick , It is impossible to roll, generally 16 millimeters or more can not be rolled up.


Volume, there are plates, plates are often, the volume and the price of the plate is not the same, if the purchase volume, is calculated according to the actual weight, so the price is high, the board is calculated in accordance with the theory, the price is low , Because there are under the poor, such as the actual thickness of 10mm may be 9.6mm, there will be a spread between the middle.


Stainless steel is divided into hot-rolled and cold-rolled according to the rolling process of the rolling mill (the rolling mill is the name of the rolling mill). Hot rolling is usually designated 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, the mirror is out of stock, need to be processed), such as the 304 is often purchasing board, it means the volume must pass through the machine Kaiping into a plate, this machine is Kaiping machine. Through the Kaiping Kaiping can be opened into different lengths, if not the conventional length is called open, the meaning is to open the size, because customers according to actual needs, often put forward different length requirements, this time the volume becomes important, the conventional Board can not meet the requirements.


Domestic cold-rolled generally less than 3 mm, hot-rolled generally more than 3 mm, 3 mm thickness of both hot and cold rolled, but the imported cold-rolled plate thickness can reach 4 mm below or even 6 mm below. Hot rolled 3 mm to 12 mm plate called the plate, 12 mm thick plate called, can be thick to 120 mm above, and said hot plate, and cold-rolled sheet is cold-rolled.

Simple calculation method of the theoretical weight of stainless steel plate

Plate Weight = Specific Gravity × Thickness (mm) × Width (m) × Length (m) (mm is a unit of millimeter and m is a unit of meter)

In the field of construction machinery due to precision dimensions, the world uses the millimeter as a unit 1000 mm = 1 m, 1 mm = 100 wire.


Calculated according to this formula is the weight of kilograms (KG), to be accurate to two decimal places, because stainless steel expensive, trading volume, the figure after the decimal point is also very important, so the money must be accurate to two decimal places Bit.

The proportion of stainless steel (KG)

Different stainless steels have different proportions:

A, 400 series proportion is 7.75

B, 304.321.304N.201.202.304L..301, the specific gravity is 7.93

C, 310S.309S.316.316L The specific gravity is 7.98.

Steel reference table

The countries in the world call different stainless steel, the market is often in contact with China and the United States, called the national standard and the American standard, said 200 series 300 series 400 series is the American standard, the American standard as easy to understand, so commonly called Are 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 content of the elemental content in the national standard generally refers to the median of the content, which is the theoretical value.

What is tolerance

This is a very important term, and tolerances are accepted as length or thickness deviations, which are difficult for a variety of reasons in the production of sheet metal. Actual thickness is often out of the theoretical thickness, such as 6 mm plate, only 5.6 mm, which is the tolerance, the domestic tolerance is often negative tolerance, of course, there are positive tolerances, but rarely. In buying and selling boards, usually based on the theoretical thickness to calculate, which is why the theoretical price Weighing the reasons for the low price, the size of the tolerance there are points, the price is not the same, the price of large tolerances cheap.For example, 6 mm , If it is 5.5 the following is a big tolerance.

1,304 / 2B tolerance range in the table below (for reference only)

specification

Big difference

normal

Small difference

No tolerances

0.4MM

0.3-0.32

0.33-0.37

0.37-0.39

0.39 and above

0.5MM

0.4-0.42

0.43-0.47

0.47-0.49

0.49 or more

0.6MM

0.5-0.52

0.53-0.57

0.57-0.59

0.59 above

0.7MM

0.6-0.62

0.63-0.67

0.67-0.69

Above 0.69

0.8MM

0.7-0.72

0.73-0.77

0.77-0.79

Above 0.79

0.9MM

0.8-0.82

0.83-0.87

0.87-0.89

0.89 or more

1.0MM

0.89-0.91

0.91-0.94

0.94-0.99

Above 0.99

1.2MM

1.01-1.08

1.09-1.15

1.16-1.18

Above 1.18

1.5MM

1.32-1.38

1.39-1.45

1.46-1.48

Above 1.48

2.0MM

1.71-1.79

1.8-1.86

1.87-1.9

1.9 or more

2.5MM

2.23-2.38

2.39-2.42

2.42-2.47

Above 2.47

3.0MM

2.7-2.77

2.78-2.85

2.85-2.9

2.9 or more

2, hot-rolled sheet tolerance table in the table below (for reference)

specification

Big difference

normal

Small difference

No tolerances

3.0MM

2.6-2.75

2.75-2.85

2.86-2.9

2.9 or more

4.0MM

3.2-3.6

3.6-3.75

3.75-3.95

Above 3.95

5.0MM

4.2-4.6

4.6-4.75

4.75-4.95

Above 4.95

6.0MM

5.1-5.5

5.5-5.75

5.75-5.9

5.9 above

8.0MM

7.2-7.5

7.5-7.75

7.75-7.95

7.9 or more

10.0MM

9.1-9.3

9.3-9.6

9.6-9.85

9.85 above

12.0MM

11.1-11.2

11.2-11.6

11.6-11.85

Above 11.85

14.0MM

13.1-13.2

13.2-13.6

13.6-13.85

Above 13.85

The characteristics and uses of the main stainless steel types

304: As a widely used steel, has good corrosion resistance, heat resistance, low temperature strength and mechanical, stamping, bending and other hot workability, no heat treatment hardening phenomenon, non-magnetic, the use temperature of minus 193 degrees to It is 800 degrees.

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


304L as a low-carbon 304 steel, corrosion resistance and 304 in the general state is similar, but after welding and stress relief, it is good anti-intergranular corrosion resistance, without heat treatment, but also to maintain good Corrosion resistance, generally used at 400 degrees,

Uses: petrochemical industry, building materials.


321 added Ti element in 304 steel to prevent intergranular corrosion, for positive 430 to 900 degrees below, non-magnetic;

Uses: Automotive exhaust, heat exchangers, containers and other products after welding without heat treatment, due to the addition of Ti elements, it is not suitable for the production of food processing equipment.


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

Uses: Seawater used in equipment, chemicals, dyes, paper, acetic acid, fertilizers and other production equipment, food industry and coastal facilities, the fight against the special requirements of the corrosion products.


309S / 310S these two kinds of materials, nickel and chromium content is relatively high, while increasing the content of Si, which has high temperature and corrosion resistance, which 309S can withstand repeated heating below 980, 310S temperature of 1200 degrees, continuous use Temperature can be 1150 degrees, non-magnetic.

Uses: Suitable for high temperature electric furnace equipment, drying equipment and other key parts, furnace materials, aviation, petrochemical, electricity and so on.


200 series is similar to 304 cheap economy.

Uses: food processing utensils, kitchen equipment, food processing equipment, filters, milk cans, consumer durables, washing machine parts, water heaters, steel furniture, building decoration, decoration. Fatigue resistance, 201 greater hardness, toughness 304, 304 or better fatigue resistance.