Stainless steel classification
Stainless steel classification
Stainless Steel Industry Development
Stainless Steel Industry Development

Stainless steel knowledge

Knowledge of Stainless Steel

Knowledge of Stainless Steel

1. Morphological classification of stainless steel

A form of stainless steel classification:

Stainless steel can be divided into five categories: coils, plates, profiles, tubes, and parts. The most important are coils and plates.

Profiles are materials made of various plates, including angles, flat bars, I-beams, and channels.

Steel pipe is mainly a seamless steel pipe. Compared with a seamless steel pipe, it is welded pipe. The difference is whether it is formed at once.

Parts mainly refer to small things such as elbows and flanges

Coil and plate are actually the same, only the delivery form is different. Coil by coil, plate by plate. If the delivery is a plate, also called the original plate, it is usually a thick plate. Because it is very thick, it can not be rolled. Generally, more than 16mm can not be rolled

If there are rolls and plates, they are usually boards. The prices of rolls and plates are also different. If the roll is purchased out, the price is high because it is calculated by actual weight. If you calculate the plate according to the theory, the price is low. The reason is that there is a difference. For example, the actual thickness of 10mm may be 9.6mm, and there will be a price difference in between.

Stainless steel plate is divided into hot-rolled and cold-rolled according to the rolling mill rolling process (the mill is the name of the machine that rolls the plate):

Hot-rolled is usually marked as No.1, cold-rolled is marked as 2B or BA (BA surface is better and brighter than 2B, close to the mirror surface. It is better to be a mirror surface. (Mirror surface is not in stock and needs to be handled). For example, 304 often purchase plates, that is to say, coils must be flattened into plates by machine, which is a flattening machine.

With a flattening machine, the flattening can be opened into different lengths. If it is not a regular length, it is called a fixed opening, that is, fixed opening size, because customers often ask for different lengths according to actual needs. This is when the rolls are important, and the conventional sheet can no longer meet the requirements.

Domestic cold-rolled is generally less than 3mm, and hot-rolled is generally greater than 3mm. There are two kinds of 3mm thickness, hot-rolled and cold-rolled, but the thickness of imported cold-rolled sheets can be less than 4mm, or even less than 6mm.

Hot-rolled 3mm to 12mm plates are called medium plates, and those above 12mm are called thick plates. They can be thicker than 120mm and are called hot rolled medium plates, and cold rolled are cold-rolled thin plates.

2. the characteristics and uses of the main types of stainless steel

as a widely used steel, has good corrosion resistance, heat resistance, low-temperature strength, and mechanical properties, good stamping, bending and another hot workability, no heat treatment hardening phenomenon, non-magnetic, use temperature from negative 193 degrees to positive 800 degrees. Uses tableware, kitchenware, water heaters, boilers, auto parts, medical equipment, food machinery, wine storage, pressure vessels (chemical machinery, chemical equipment).
Knowledge of Stainless Steel
As low carbon 304 steel, the general corrosion resistance is similar to 304, but after welding and stress relief treatment, it has good intergranular corrosion resistance. It can also maintain good corrosion resistance without heat treatment. Generally used at 400℃
Uses petrochemical, building materials.
Ti element is added to 304 steel to prevent intergranular corrosion. Suitable for positive temperatures from 430 to below 900 degrees and non-magnetic.
Applications: automotive exhaust, heat exchangers, containers, and other products that have not been heat-treated after welding and are not suitable for making food processing equipment due to the addition of Ti.
316 low carbon, with the addition of Mo elements, so its corrosion resistance, atmospheric corrosion resistance, and high-temperature strength are particularly good. It can be used in harsh conditions. It is suitable for use below 900 degrees. It is non-magnetic.
Applications: equipment used in seawater, production equipment for chemical, dye, paper, acetic acid, fertilizer, etc., food industry and facilities in coastal areas, products with special requirements for intergranular corrosion resistance.
The content of nickel and chromium in these two materials is relatively high. Also increase the content of Si, so that it has the characteristics of high temperature and corrosion resistance. 309S can withstand repeated heating up to 980. 310S can be used at temperatures up to 1200 degrees and for continuous use up to 1150 degrees. It is non-magnetic.
Application: It is suitable for high-temperature electric furnace equipment and dry equipment, furnace charge, aviation, petrochemical, electric power, and other key parts.

200 series is similar to 304, cheap, and economical.

Applications: food processing utensils, kitchen equipment, food processing equipment, filters, milk cans, durable consumer goods, washing machine parts, water heaters, steel furniture, architectural decoration, and renovation. In terms of fatigue resistance, 201 has higher hardness and toughness than 304, and 304 has better fatigue resistance.

3、Why is stainless steel corrosion resistant?

All metals react with oxygen in the atmosphere to form an oxide film on the surface. Unfortunately, the formation of iron oxide on ordinary carbon steel continues to oxidize, expanding corrosion and eventually forming holes. Carbon steel surfaces can be guaranteed by electroplating with paint or antioxidant metals such as zinc, nickel and chromium, but it is well known that this protection is only a thin film. If the protective layer is damaged, the steel underneath will begin to rust.

The corrosion resistance of stainless steel depends on chromium, but since chromium is one of the components of steel, the protection method is different.

When chromium is added at 10.5%, the steel’s resistance to atmospheric corrosion increases significantly, but when the chromium content is higher, it still improves the corrosion resistance, but not significantly. The reason is that when the steel is alloyed with chromium, the type of surface oxide changes to one similar to that formed on pure chromium metal. This closely adhering chromium-rich oxide prevents further oxidation of the surface. This oxide layer is very thin. Through it, you can see the natural luster of the steel surface, which gives stainless steel its unique surface. Moreover, if the surface layer is damaged, the exposed steel surface will react with the atmosphere to repair itself and re-form this “passivation film” to continue to play a protective role.

Therefore, all stainless steel has a common characteristic, that is, the chromium content of 10.5% or more.

Knowledge of Stainless Steel

4、Stainless steel surface treatment.



Summary of manufacturing methods



Silver white matte

Hot rolled to specified thickness, on a rough, matte surface annealed and dephosphorized

Use without surface gloss


Silvery white

A matte finish in which heat treatment and pickling are carried out after cold rolling, and sometimes the final light rolling is carried out on the rough roller

2D products are used for purposes with lax surface requirements, general materials and deep drawing materials


Gloss stronger than No.2D

After No.2D treatment, the polishing roller is used for the final light cold rolling to obtain suitable gloss. This is the most commonly used surface processing, which can also be used as the first step of polishing

General timber


Bright as a mirror

There is no standard, but it is usually bright annealed surface processing, with high surface reflectance

Building materials, kitchen utensils


Rough grinding

Grind No.2D and no.2b materials with 100 ~ 200# (unit) abrasive belt

Building materials, kitchen utensils


Intermediate grinding

The polished surface obtained by grinding No.2D and no.2b materials with 150 ~ 180# abrasive belt, which is a general, specular and bright surface with visible ‘grains’

Building materials, kitchen utensils

Knowledge of Stainless Steel

5.the interpretation of some terms in the stainless steel industry

(1)Superheavy plate:

Reason: It should be the technical reason of the steel mill. When rolling thick plates, the actual thickness is thicker than the standard thickness, or the length and width are longer than the standard, resulting in a heavier weight than the adjusted weight.

(2)Modified rolled plate:

The modified rolled plate is generally made from small mill scrap and billets. The processing technology is backward, the plate is poor, quality and mechanical properties are not guaranteed, nickel content does not meet the formal requirements. The processing is difficult to punch holes and archwire. It has the advantage that the price is about 1500-2000 cheaper than the big mills.

(3)Calendered plate:

Reasons for producing calendered sheet: Because the price difference between hot rolled sheet coils and cold rolled sheet coils is great, and the price of exchange rolled sheet coils is cheaper than cold rolled sheet coils, the calendered sheet has both price advantage and great profit margin, so many manufacturers produce calendered sheet.

Production process: As the calendered plate manufacturers themselves do not have the ability to produce cold-rolled plates, their production process can not meet the requirements of the production of the cold plates, they buy hot-rolled coils from large steel mills, surface treatment. Annealing treatment, and then rolled into cold-rolled coils of other thicknesses.

Knowledge of Stainless Steel

6、Stainless steel specifications size: stainless steel plate including rolled plate and original plate


(1) coil is also divided into cold-rolled coil and hot-rolled coil, trimmed coil and burr coil
(2) cold rolled coil thickness is generally 0.3-3mm, there are also 4-6mm thickness of cold rolled sheet. Width of 1m, 1219m and 1.5m, expressed in 2B.
(3) hot-rolled coil thickness is generally 3-14mm, there are also 16mm volume, width of 1250, 1500, 1800, 2000, with No. 1
(4) width of 1.5m, 1.8m, 2.0m volume for cutting edge volume
(5)The width of burr roll is usually 1520, 1530, 1550, 2200, etc., which is wider than the normal width.
(6)In the price, the difference between trimming roll and burr roll of the same model is usually about 300-500 yuan.
(7) It can be unrolled according to the length requested by customers. After leveling by leveling machine, it is called open plate. Cold rolled is generally flattened by 1m*2M and 1219*2438, also called 4*8 feet. Hot rolled is generally leveled at 1.5m*6m, 1.8m*6m and 2m*6m. Those opened according to these dimensions are called standard plates or sizing plates.

Raw flat plate, also known as rolled plate:

(1) The thickness of the original plate is generally 4mm-80mm, but also 100mm and 120mm. This thickness can be rolled at a fixed time.
(2) The width is 1.5m, 1.8m, 2m, and the length is greater than 6m.
(3) Characteristics: The original flat plate is large, high cost, difficult to pickle, and inconvenient to transport.

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