What Is Stainless Steel

Stainless steel is the abbreviation of stainless acid-resistant steel. It is resistant to air, steam, water and other weakly corrosive media or stainless steel. It is called stainless steel; (Corrosion) The corrosion steel is called acid-resistant steel.

Stainless steel refers to steel that is resistant to weak corrosive media such as air, steam, water, and chemically aggressive media such as acids, alkalis, and salts, and is also known as stainless acid-resistant steel. In practical applications, steel that is resistant to corrosion by weak media is often called stainless steel, and steel that is resistant to chemical media is called acid-resistant steel. Due to the difference in chemical composition of the two, the former is not necessarily resistant to chemical media corrosion, while the latter are generally stainless. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel.

Generally, according to the metallographic structure, ordinary stainless steel is divided into three categories: austenitic stainless steel, ferritic stainless steel, martensitic stainless steel. Based on these three basic metallographic structures, for specific needs and purposes, dual phase steel, precipitation hardening stainless steel and high alloy steel with iron content less than 50% were derived.

According to Metallographic Structure:

01 Austenitic Stainless Steel.

The matrix is dominated by austenite structure (CY phase) with face-centered cubic crystal structure, which is non-magnetic, and is mainly strengthened by cold working (and may cause a certain degree of magnetism) stainless steel. The American Iron and Steel Institute is marked with numbers in the 200 and 300 series, such as 304.

02 Ferritic Stainless Steel.

The matrix is dominated by a body-centered cubic crystal structure of ferrite ((phase a)), which is magnetic and generally cannot be hardened by heat treatment, but cold working can make it slightly strengthened stainless steel. The American Iron and Steel Institute marks 430 and 446.

03 Martensitic Stainless Steel.

The matrix is a martensite structure (body-centered cubic or cubic), magnetic, stainless steel whose mechanical properties can be adjusted by heat treatment. The American Iron and Steel Institute is marked with 410, 420 and 440 numbers. Martensite has an austenite structure at a high temperature, and when cooled to room temperature at an appropriate rate, the austenite structure can be transformed into martensite (ie, hardened).

04 Austenitic-ferrite (duplex) Stainless Steel.

The matrix has both austenite and ferrite two-phase structure. The content of the less-phase matrix is ​generally greater than 15%. It is magnetic and can be strengthened by cold working. 329 is a typical duplex stainless steel. Compared with austenitic stainless steels, dual-phase steels have high strength, and the ability to resist intergranular corrosion and chloride stress corrosion and pitting corrosion have been significantly improved.

05 Precipitation Hardening Stainless Steel.

The matrix is austenitic or martensite structure, and can be hardened by precipitation hardening stainless steel. The American Iron and Steel Institute uses 600 series of numbers, such as 630, that is 17-4PH.

Generally speaking, in addition to alloys, the corrosion resistance of austenitic stainless steel is relatively excellent. In the environment with low corrosion, ferritic stainless steel can be used. For strength or high hardness, martensitic stainless steel and precipitation hardening stainless steel can be used.

系列 美标(ASTM) 国标(GB) 日表(SUS) 性质 用途
200 201 ICr17Mn6Ni5N SUS201 It has the characteristics of acid resistance, alkali resistance, high density, no bubbles, no pinholes, etc. It is used to produce various high-quality materials such as watch cases and strap bottom covers. Mainly used to make decorative tubes. Some shallow stretch products for industrial tubes
202 ICr18Mn8Ni5N SUS202 Part of nickel is replaced with Mn and N, thus obtaining good mechanical properties and corrosion resistance. It is a new type of nickel-saving stainless steel. Its room temperature strength is higher than 304, and it has better oxidation resistance and less than 800 degrees. Medium temperature intensity Mainly used to make decorative tubes. Some shallow stretch products for industrial tubes
2205 OOCr22NiMo3N SUS2205 Its Cr, Mo and N element intervals are relatively narrow, and it is easy to achieve phase balance (that is, two phases account for about half of each), which improves the strength, corrosion resistance and welding performance of steel. Materials, such as oil and gas pipelines, etc. Used in heat exchangers and cold showers and devices for oil refining, chemical fertilizers, papermaking, petroleum, chemical industry, etc. which are resistant to seawater and high temperature concentrated nitric acid.
300 304 ICr18Ni9 SUS304 As a versatile steel, it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties. Good hot workability, such as stamping and bending, without heat treatment hardening (non-magnetic, use temperature -196 ℃ -800 ℃) Food industry, household products 1.2 class tableware, kitchen cabinets, indoor pipelines, water heaters, boilers, melting tanks)
304JI SUS304JI Cu should be added, its formability, especially wire drawing and aging crack resistance is good, and can form products with complex shapes, and its corrosion resistance is the same as 304 steel Vacuum flasks, kitchen sinks, pots, pots, thermal insulation, door handles, textile processing machines
304L OOCr19Ni10 SUS304L As a low-C 304 steel, under normal conditions, the corrosion resistance of E is similar to that of 304 steel, but after welding or after stress relief, its resistance to grain boundary corrosion is excellent, and it can also be used without heat treatment. Baote has good corrosion resistance, generally used below 400 (non-magnetic, use temperature -196 ℃ -800 ℃) Used in the field of chemical, coal and petroleum industries that require high corrosion resistance in the industry
321 ICr18Ni9Ti SUS321 Add T element to 304 steel to prevent grain boundary corrosion. Suitable for use at 430 ℃ -900 ℃ cover Agriculture, ship parts, atomic energy industry, aircraft, takeover, boiler drum auto parts (windshield wipers, muffler, molded products)
316 OCr17Ni12Mo2 SUS316 Mo should be added, so its corrosion resistance, atmospheric corrosion resistance and high temperature strength are particularly good, can be used under harsh conditions, and has excellent work hardening (non-magnetic) Production equipment for sea water, chemical, dyes, papermaking, oxalic acid, fertilizers, etc .: photographs, food industry, coastal area facilities, ropes, CD rods, bolts, nuts
316L OOCr17Ni14Mo2 SUS316L As the low-C series of 316 steel, in addition to having the same characteristics as 316 steel, its anti-grain boundary corrosion is excellent In 316 iron and steel applications, products that have special requirements to resist grain boundary corrosion
309S OCr23Ni13Mo2 SUS309S 23Cr-13Ni high alloy steel stainless steel has excellent corrosion resistance and strength, suitable for parts with working temperature of 1000 ℃ Exhaust machines, heat treatment furnaces, heat exchangers, etc.
310S OCr25Ni20Si2 SUS310S Very good oxidation resistance, corrosion resistance, high temperature resistance, because a higher percentage of chromium and nickel, 310s has much better creep strength, can continue to operate at high temperatures, and has good high temperature resistance. Boilers, exhaust equipment, heat treatment furnaces and heat exchangers, etc.
400 409L OOCr12Ti SUS409L The cheapest model, because of the addition of Ti element, so its high temperature corrosion resistance and high temperature strength are better. Ferrite stainless steel (chrome steel) Automotive exhaust pipes, heat exchangers, containers and other products that are not heat-treated after welding
410 ICr13 SUS410 It is a representative steel of martensitic steel. Although it has high strength, it is not suitable for use in harsh corrosive environments.It has good workability and hardened heat treatment surface (magnetic) Blade, mechanical writing, petroleum refining device, bolt, nut, pump rod, class 1 tableware (knife and fork)
410S OCr13 SUS410S
420JI 2Cr13 SUS420JI High hardness after quenching, good corrosion resistance (magnetic) Cutlery (knife), turbine blades
420J2 2Cr13 SUS420J2 After quenching, the hardness of the steel is higher than 420JI (magnetic) Blades, nozzles, valves, rulers, tableware (scissors, knives)
430 ICr17 SUS430 The representative steel type of ferritic steel, low thermal expansion rate, excellent formability and oxidation resistance Heat-resistant appliances, burners, room electrical products, type 2 tableware, kitchen sinks, exterior decoration materials, bolts, nuts, CD rods, screens
444 Water tank special board
surface feature Summary of Manufacturing Method 用途
NO.1 Silvery white matte Hot rolled to a specified thickness, on a rough, matte surface that has been annealed and dephosphorized Uses that do not require surface gloss
NO.2D silver white After cold rolling, heat treatment and pickling are carried out, and sometimes a matte surface processing of the final light rolling is performed on the matte silver roller 2D products are used for applications that do not have strict surface requirements, generally used for deep drawing materials
NO.2B Gloss is stronger than NO, 2D After No.2D treatment, it is used in the final light cold rolling through the polishing roller to obtain a suitable gloss. This is the most commonly used surface processing, and this processing can also be used as the first step of polishing General materials
BA As bright as a mirror No standard, but usually bright annealed surface processing, the surface is highly reflective Building materials, kitchen utensils
NO.3 Coarse grinding Grind NO.2D and NO.2B materials with 100-200 # (unit) whetstone grinding belt Building materials, kitchen utensils
NO.4 Intermediate grinding The polished surface obtained by grinding N0.2D and NO.2B with 150-180 # grain grinding belt, which is universal, with a specular reflection and a bright surface with visible, grain Building materials, kitchen utensils

Thickness Distinction

  1. Because of the slight deformation of the heating roller during the rolling process of the steel mill machinery, the thickness of the rolled board is deviated, and the middle is generally thick and thin on both sides. When measuring the thickness of the board, the national regulations should measure the middle part of the board head.
  2. The reason for the tolerance is based on the market and customer needs, generally divided into large tolerances and small tolerances: for example
厚度(thickness 大差 小差
冷轧 0.4 0.31 0.36以上
0.5 0.41 0.45以上
0.6 0.51 0.56以上
0.7 0.61 0.65以上
0.8 0.71 0.75以上
0.9 0.81 0.85以上
1 0.89 0.93以上
1.2 1.08 1.12以上
1.5 1.27 1.43以上
2 1.83 1.9以上
3 2.8 2.85以上
热扎 3 2.75 2.85以上
4 3.5 3.65以上
5 4.5 4.65以上
6 5.55 5.65以上
8 7.3 7.50以上
10 9.3 9.50以上
12 11.3 11.5以上
14 13.4 13.5以上

 

What Kind of Stainless Steel Is Not Easy to Rust ?

There are three main factors affecting stainless steel corrosion:
The Content Of Alloy Elements.
Generally speaking, steel with chromium content of 10.5% is not easy to rust. The higher the chromium-nickel content, the better the corrosion resistance. For example, the content of 304 nickel is 8-10%, and the chromium content is 18-20%. Such stainless steel will not rust under normal circumstances.
The Smelting Process of The Production Enterprise Will Also Affect the Corrosion Resistance of Stainless Steel.
The large stainless steel plant with good smelting technology, advanced equipment and advanced technology can be guaranteed both in the control of alloy elements, the removal of impurities, and the control of the cooling temperature of the billet. Therefore, the product quality is stable and reliable, the internal quality is good, and it is not easy to rust. On the contrary, some small steel mills are backward in equipment and technology, and impurities cannot be removed during the smelting process, and the products produced will inevitably rust.
The External Environment, Dry Climate And Good Environment Are Not Easy to Rust.
And the humidity of the air is high, and it is easy to rust in the continuous rainy weather or the environment area with large pH in the air. 304 stainless steel, it will rust if the surrounding environment is too bad.

How to deal with stainless steel rust spots?
Chemical Methods
Use pickling paste or spray to assist in the re-passivation of its rusted parts to form a chromium oxide film to restore its corrosion resistance. After pickling, in order to remove all contaminants and acid residues, it is very important to properly rinse with water. After everything is processed, use the polishing equipment to re-polish and close with polishing wax. For those with slight rust spots, use a 1: 1 mixture of gasoline and engine oil to wipe off the rust spots with a clean cloth.
Mechanical Methods
Sandblasting, shot blasting with glass or ceramic particles, annihilation, scrubbing and polishing. It is possible to use mechanical methods to wipe out the contamination caused by the previously removed materials, polished materials or annihilated materials. All kinds of pollution, especially foreign iron particles, can become a source of corrosion, especially in humid environments. Therefore, mechanically cleaned surfaces should preferably be cleaned regularly under dry conditions. The mechanical method can only clean the surface, and cannot change the corrosion resistance of the material itself. Therefore, it is recommended to re-polish with polishing equipment after mechanical cleaning and close with polishing wax.

Stainless steel
Commonly Used Stainless Steel Grades And Performance:
1.304 Stainless Steel.
It is one of the austenitic stainless steels with large application and widest scope of application. It is suitable for the manufacture of deep-drawn molded parts and acid pipelines, containers, structural parts, various instrument bodies, etc. component.
2.304L Stainless Steel.
In order to solve the problem that the precipitation of Cr23C6 causes 304 stainless steel to have a severe tendency to intergranular corrosion under some conditions, the ultra-low carbon austenitic stainless steel developed in its sensitized state is significantly better than 304 stainless steel. Except for the slightly lower strength, the other properties are the same as 321 stainless steel. It is mainly used for corrosion-resistant equipment and components that cannot be solution treated after welding, and can be used to manufacture various instrument bodies.
304H Stainless S
The internal branch of 304 stainless steel, the carbon mass fraction is 0.04%-0.10%, the high temperature performance is better than 304 stainless steel.
316 Stainless S
Adding molybdenum on the basis of 10Cr18Ni12 steel makes the steel have good resistance to reducing media and pitting corrosion resistance. In seawater and other various media, corrosion resistance is better than 304 stainless steel, mainly used for pitting corrosion resistant materials.
316L Stainless S
Ultra-low carbon steel has good resistance to sensitized intergranular corrosion and is suitable for manufacturing welded parts and equipment with thick cross-sectional dimensions, such as corrosion-resistant materials in petrochemical equipment.
316H Stainless S
The internal branch of 316 stainless steel, the carbon mass fraction is 0.04%-0.10%, high temperature performance is better than 316 stainless steel.
317 Stainless S
The pitting corrosion resistance and creep resistance are better than 316L stainless steel, which is used to manufacture petrochemical and organic acid corrosion resistant equipment.
8.321 Stainless Steel.
Titanium stabilized austenitic stainless steel, adding titanium to improve intergranular corrosion resistance, and has good high temperature mechanical properties, can be replaced with ultra-low carbon austenitic stainless steel. Except for spec

 

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