Some range hoods are made of different materials according to different models, such as stainless steel panels, galvanized plates and painted steel plates. Is a relatively corrosion-resistant and easy-to-clean material.
The word "stainless steel" refers not only to one kind of stainless steel, but to 100 kinds of industrial stainless steel, and each developed stainless steel has good performance in its specific application field. The key to success is to find out the purpose first, and then determine the correct steel grade. There are usually only six kinds of steel related to the application field of building construction. They all contain 17 ~ 22% chromium, and the better steel also contains nickel. Adding molybdenum can further improve the atmospheric corrosivity, especially the corrosion resistance to chlorine-containing atmosphere.
Stainless steel is usually divided into martensite steel, ferrite steel, austenite steel, austenite-ferrite (duplex) stainless steel and precipitation hardening stainless steel. In addition, it can also be divided into chromium stainless steel, chromium nickel stainless steel and chromium manganese nitrogen stainless steel.
stainless steel
ferritic stainless steel
Chromium 15% ~ 30%. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its chloride stress corrosion resistance is better than other types of stainless steel, including Crl7, Cr 17Mo2Ti, Cr25, Cr25Mo3Ti and Cr28. Ferritic stainless steel has good corrosion resistance and oxidation resistance because of its high chromium content, but its mechanical properties and technological properties are poor, so it is mostly used in acid-resistant structures with less stress and as oxidation-resistant steel. This kind of steel can resist the corrosion of atmosphere, nitric acid and brine solution, and has the characteristics of good oxidation resistance at high temperature and small thermal expansion coefficient. It can be used in nitric acid and food factory equipment, and can also be used to manufacture parts that work at high temperature, such as gas turbine parts.
austenitic stainless steel
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It contains more than 18% chromium, about 8% nickel and a few elements such as molybdenum, titanium and nitrogen. Good comprehensive performance, corrosion resistance to various media. Commonly used brands of austenitic stainless steel are 1Cr 18Ni9, 0Cr 19Ni9, etc. lavatory
Austenite-ferrite duplex stainless steel
It has the advantages of austenitic and ferritic stainless steel and is superplastic. Austenite and ferrite structure
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About half of each stainless steel. In the case of low C content, Cr content is 18%~28%, and Ni content is 3%~ 10%. Some steels also contain alloying elements, such as molybdenum, copper, silicon, niobium, titanium and nitrogen. This steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferritic steel, it has higher plasticity and toughness, no brittleness at room temperature, significantly improved intergranular corrosion resistance and weldability, and maintained the brittleness, high thermal conductivity and superplasticity of ferritic stainless steel at 475℃. Compared with austenitic stainless steel, it has high strength and obviously improved intergranular corrosion resistance and chloride stress corrosion resistance. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-saving stainless steel.
precipitation hardening stainless steel
The matrix is austenite or martensite, and the commonly used precipitation hardening stainless steel brands are 04Cr 13Ni8Mo2Al, etc. It can be hardened (strengthened) by precipitation hardening (also called age hardening).
Stainless steel disinfection cabinet
Martensite stainless steel
High strength, but poor plasticity and weldability. Commonly used brands of martensitic stainless steel are 1Cr 13, 3Cr 13, etc. Martensite stainless steel has high strength, hardness and wear resistance due to its high carbon content, but its corrosion resistance is slightly poor. Used for some parts with high mechanical performance and general corrosion resistance requirements, such as springs, steam turbine blades, hydraulic machine valves, etc. This kind of steel is used after quenching and tempering. Annealing is required after forging and stamping.
key property
Weldability
Different uses of products have different requirements for welding performance. A kind of tableware generally does not require welding performance, even including some pot enterprises. However, most products need good welding performance of raw materials, such as second-class tableware, thermos cups, steel pipes, water heaters, water dispensers and so on.
Stainless steel sculpture
corrosion resistance
Most stainless steel products require good corrosion resistance, such as first-class and second-class tableware, kitchen utensils, water heaters, water dispensers and so on. There are also foreign businessmen who do corrosion resistance tests on products: boil with NACL aqueous solution, pour out the solution after a period of time, wash and dry, and weigh the weight loss to determine the corrosion degree (note: the abrasive cloth or sandpaper contains Fe when the product is polished, which will lead to rust spots on the surface during testing).
Polishing performance
In today's society, stainless steel products are generally polished during production, and only a few products, such as water heaters and drinking fountains, do not need polishing. Therefore, this requires that the polishing performance of raw materials is very good. The main factors affecting polishing performance are as follows:
① Surface defects of raw materials. Such as scratches, pits, pickling, etc.
② Material problems of raw materials. If the hardness is too low, it will not shine easily during polishing (BQ performance is not good), and if the hardness is too low, orange peel will easily appear on the surface during drawing, which will affect BQ performance. BQ with high hardness has relatively good performance.
③ After deep drawing, small black spots and ridges will appear on the surface of the area with large deformation, which will affect the performance of BQ.
Heat-resistant effect
Heat resistance means that stainless steel can still maintain its excellent physical and mechanical properties at high temperature.
Influence of carbon: carbon is strongly formed and stable in austenitic stainless steel. An element that defines austenite and expands the austenite region. The ability of carbon to form austenite is about 30 times that of nickel. Carbon is a interstitial element, and the strength of austenitic stainless steel can be significantly improved by solid solution strengthening. Carbon can also improve the stress resistance and corrosion resistance of austenitic stainless steel in high concentration chloride (such as 42%MgCl2 boiling solution).
However, in austenitic stainless steel, carbon is often regarded as a harmful element, which is mainly due to the fact that carbon and chromium in steel can form high chromium Cr23C6-6 carbon compound under some corrosion-resistant conditions (such as welding or heating at 450~850℃), which leads to local chromium depletion and reduces the corrosion resistance of steel, especially the intergranular corrosion resistance. Therefore. Most of the newly developed Cr-Ni austenitic stainless steels since 1960s are ultra-low carbon stainless steels with carbon content less than 0.03% or 0.02%. It can be seen that with the decrease of carbon content, the intergranular corrosion sensitivity of steel decreases, and the effect is most obvious when the carbon content is less than 0.02%. Some experiments also point out that carbon will also increase the pitting tendency of Cr-Ni austenitic stainless steel. Due to the harmful effect of carbon, in the process of smelting and tempering of austenitic stainless steel, not only should the carbon content be controlled as low as possible, but also the increase of carbon on the surface of stainless steel and the precipitation of chromium-free carbide should be prevented in the subsequent hot, cold and heat treatments.
corrosion resistance
When the number of chromium atoms in steel is not less than 12.5%, the electrode potential of steel will suddenly change from negative potential to positive potential. Prevent electrochemical corrosion.
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Antibacterial stainless steel
Tested by authoritative units, antibacterial stainless steel has a killing rate of more than 99% for Escherichia coli and Staphylococcus aureus, and also has a significant killing effect on other bacteria such as Candida albicans and Rhizoctonia solani, showing excellent broad-spectrum antibacterial performance and antibacterial durability. Tested by the National Institute of Pharmaceutical and Biological Products, the antibacterial stainless steel fully meets the national technical standards in terms of toxicity and human safety. While endowing stainless steel with antibacterial properties, the mechanical properties, corrosion resistance, cold and hot working properties and welding properties of the material are equivalent to those of the original stainless steel.
The successful development of antibacterial stainless steel provides a broad space for the development of antibacterial products. Antibacterial stainless steel products have great development potential and broad market prospects. In today's society, many domestic manufacturers have expressed strong interest in antibacterial stainless steel, and the research group is actively seeking support to carry out pilot tests in order to turn the results into commodities as soon as possible.
precipitation hardening stainless steel
It has good formability and weldability, and can be used as ultra-high strength material in nuclear industry and aerospace industry.
It can be divided into Cr series (400 series), Cr-Ni series (300 series), Cr-Mn-Ni series (200 series), heat-resistant chromium alloy steel (500 series) and precipitation hardening series (600 series).
200 series: Cr-Mn-Ni alloy
20 1, 202, etc. Manganese replaces nickel, which has poor corrosion resistance and is widely used as a cheap substitute for 300 series in China.
300 series: Cr-Ni austenitic stainless steel
30 1: Good ductility, used for molding products. It can also be rapidly hardened by machining. Good weldability. Wear resistance and fatigue strength are better than 304 stainless steel.
302: Corrosion resistance is the same as that of 304, and its strength is better because of its relatively high carbon content.
303: Adding a small amount of sulfur and phosphorus makes it easier to cut than 304.
304: universal model; Namely 18/8 stainless steel. Products such as: corrosion resistant containers, tableware, furniture, railings, medical equipment. The standard components are 18% chromium and 8% nickel. It is a non-magnetic stainless steel, and its metallographic structure will not be changed by heat treatment. GB brand is 0Cr 18Ni9.
304 L: It has the same characteristics as 304, but it is more corrosion-resistant and easy to heat-treat, but its mechanical properties are poor. It is suitable for welding and products that are difficult to heat treat.
304 N: It has the same characteristics as 304. It is a stainless steel containing nitrogen. Nitrogen is added to improve the strength of steel.
309: Compared with 304, it has better temperature resistance, and the temperature resistance is as high as 980℃.
309 S: contains a lot of chromium and nickel, so it has good heat resistance and oxidation resistance. Products such as heat exchangers, boiler parts and jet engines.
3 10: Excellent oxidation resistance at high temperature, with the highest service temperature of 1200℃.
3 16: After 304, the second most widely used steel is mainly used in food industry, watch accessories, pharmaceutical industry and surgical instruments. Adding molybdenum element makes it obtain a special corrosion-resistant structure. Because it has better chloride corrosion resistance than 304, it is also used as "marine steel". SS3 16 is usually used in nuclear fuel recovery devices. 18/ 10 stainless steel usually meets this application level.
3 16 L: low carbon makes it more corrosion resistant and easy to heat treat. Chemical processing equipment, nuclear power generator, refrigerant storage tank and other products.
32 1: Its performance is similar to that of 304, except that the risk of weld corrosion is reduced by adding titanium.
347: Adding stable element niobium is suitable for welding aviation equipment parts and chemical equipment.
Series 400: ferritic and martensitic stainless steel without manganese, which can replace 304 stainless steel to some extent.
408: Good heat resistance and weak corrosion resistance, 1 1% Cr, 8% Ni.
409: The cheapest model (British and American), usually used as automobile exhaust pipe, belongs to ferritic stainless steel (chrome steel).
4 10: Martensite (high-strength chromium steel) with good wear resistance and poor corrosion resistance.
4 16: adding sulfur can improve the processability of materials.
420: "Blade-grade" martensitic steel, similar to Brinell high chromium steel, the earliest stainless steel. It can also be used for scalpels, which can be made very bright.
430: ferritic stainless steel, used for decoration, such as automobile parts. Good formability, but poor temperature resistance and corrosion resistance.
440: High-strength cutting tool steel, with slightly higher carbon content, can obtain higher yield strength after proper heat treatment, and the hardness can reach 58HRC, which is one of the hardest stainless steels. The most common application example is "shaving blade". There are three commonly used models: 440A, 440B, 440C and 440F (easy to process).
500 series: heat-resistant chromium alloy steel.
Series 600: martensitic precipitation hardening stainless steel.
wrought stainless steel wire
Stainless steel mesh is mainly used for filtering products, also known as stainless steel filter mesh.
Materials: SUS20 1, 202,302,304,31304L, 3 16L, 32 1 stainless steel wire, etc.
Weaving: plain weave, twill weave and dense weave.
Screen: stainless steel screen with the specification of 1 mesh -635 mesh. Mat weaving can reach 2800 mesh.
Uses: Stainless steel mesh and other wire woven mesh are mainly used for filtration in acid-base environment, mud mesh in petroleum industry, screen mesh in chemical fiber industry, pickling mesh in electroplating industry, gas and liquid filtration and other media separation.
Reticular belt
Classification by appellation: stainless steel mesh belt, conveyor belt, metal conveyor belt, stainless steel conveyor belt, metal mesh belt, metal conveyor belt, stainless steel transmission belt, metal transmission mesh belt, etc.
Classification by use: widely used in annealing furnace mesh belt and grid furnace mesh belt in glass products industry. Food processing industry, dehydrated vegetables, quick-frozen food single cabinet pretreatment mesh belt, chain mesh belt. Powder metallurgy, metal heat treatment, quenching, sintering, brazing, roasting, polishing, blackening, bearing, carburizing high-temperature furnace mesh belt, baffle mesh belt, coating and drying line mesh belt conveyor, foam nickel reduction production line mesh belt, cleaning machine, elevator, dryer, drying cylinder, curing furnace mesh belt. Chain mesh and mesh belt in each conveying process.
Classification by materials: 1cr 13 belt, 20 1 belt, 304 belt, 3 16 belt, etc.
Classification by shape: herringbone mesh belt, B mesh belt, diamond mesh belt, horseshoe mesh belt, chain conveyor belt, glasses mesh belt, chain plate mesh belt and spherical mesh belt.
Stainless steel product development: stainless steel mesh belt, mesh belt, mesh belt conveyor, metal mesh belt, high temperature mesh belt, Great Wall mesh belt, B mesh belt and stainless steel ornaments. All products in the expansion are made of stainless steel wire and stainless steel plate.
attraction
Austenite is nonmagnetic or weakly magnetic, while martensite and ferrite are magnetic. After cold working, the structure of austenite will also be transformed into martensite, and then the magnetism will become larger. Therefore, the method of distinguishing the quality and authenticity of stainless steel by magnet adsorption in life is one-sided and wrong.
Stainless steel surface treatment grade
Original surface: 1 surface after hot rolling, heat treatment and pickling. Generally used in cold-rolled materials, industrial storage tanks, chemical devices, etc. , thickness from 2.0 mm to 8.0 mm.
Blunt surface: 2D cold rolling, heat treatment and pickling. Its material is soft and its surface is silvery white. Used for deep drawing, such as automobile parts, water pipes, etc.
Fog surface: 2B cold-rolled, heat-treated, acid-washed, and then finish-rolled to make the surface moderately bright. Because the surface is smooth and easy to grind, it makes the surface brighter and has a wide range of uses, such as tableware and building materials. After surface treatment to improve mechanical properties, it can meet almost all purposes.
No.3 coarse sand is a product ground with 100- 120 abrasive belt. It has good luster and discontinuous coarse grains. Used in building interior and exterior decoration materials, electrical products and kitchen equipment.
Fine sand: No.4 is a product of abrasive belt grinding, and its particle size is 150- 180. Good gloss, discontinuous coarse grains, and the stripes are thinner than those of No.3 used in bathhouses, interior and exterior decoration materials, electrical products, kitchen equipment and food equipment.
No.320 product ground with No.320 abrasive belt. Good gloss, discontinuous coarse grains, and the stripes are finer than those of No.4 used in baths, interior and exterior decoration materials, electrical products, kitchen equipment and food equipment.
Hairline: HLNo. 4. The product with grinding pattern (subdivision number 150-320) is polished with a suitable abrasive belt and continuously ground. Mainly used in building decoration, elevators, doors and panels of buildings.
Bright surface: the product after cold rolling, bright annealing and leveling of BA. Excellent surface gloss and high reflectivity. Like the surface of a mirror. Used in household appliances, mirrors, kitchen equipment, decorative materials, etc.
application area
In the field of building application, the surface treatment of stainless steel is important for many reasons. The corrosive environment requires a smooth surface, because it is not easy to accumulate scale. The deposition of dirt will make stainless steel rust and even cause corrosion.
In the spacious hall, stainless steel is the most commonly used material for elevator decorative plates. Although the fingerprints on the surface can be erased, it affects the appearance, so it is best to choose a suitable surface to prevent fingerprints from leaving.
Sanitary conditions are important for many industries, such as food processing, catering, brewing and chemical industry. In these applications, the surface must be easy to clean every day and chemical cleaning agents are often used.
Stainless steel is the best material in this field. In public places, stainless steel surfaces are often scribbled. But one of its important features is that it can be washed away, which is a remarkable feature that stainless steel is superior to aluminum. The surface of aluminum is easy to leave traces and often difficult to remove. When cleaning the surface of stainless steel, it should be cleaned along the lines of stainless steel, because some lines of surface processing are unidirectional.
Stainless steel is most suitable for hospitals or other areas where sanitary conditions are crucial, such as food processing, catering, brewing, chemical industry, etc., not only because it is easy to clean every day, but also because it is not easy to breed bacteria. Experiments show that the performance of this aspect is the same as that of glass and ceramics.