Thread Content
1. Austenitic type (300 series, chromium-nickel): such as 304, 321, 316, 310, etc. 200 is a low-nickel, cost-effective stainless steel that is also austenitic； 2. Martensitic or ferritic type (400 series): such as 430, 420, 410, etc ； Austenitic grades are non-magnetic or weakly magnetic, while martensitic or ferritic grades are magnetic. For hardware products, factors such as rust resistance, hardness, and workability need to be considered; 201, 202, 301, 304, and 316 exhibit progressively better rust resistance, heat resistance, and toughness. The densities corresponding to 202, 304, 316 are: 7.74, 7.93, 7.98. 316 stainless steel plate is a grade under American standards; it is a type of stainless, heat-resistant, and corrosion-resistant steel that belongs to the austenitic category. It is an improved version of 304 stainless steel. Under Chinese standards (GB), it is designated as 0Cr17Ni12Mo2. The commonly used stainless steel sheets are available in 201 and 304 grades; the difference lies in their chemical composition. Among them, 304 stainless steel sheet is the most widely used as a heat-resistant stainless steel; it is an austenitic stainless steel. The 400 series is martensitic stainless steel. 304 stainless steel is non-magnetic, while the 400 series is magnetic. But why can some 304 materials be attracted by magnets? It’s fine for magnets to detect a slight magnetism; austenite can also have a slight magnetism as a result of improper cold working or smelting. Compared to the 400 series, 304 has a higher nickel content, around 8–10%. 400 series stainless steel: This type of stainless steel has a microstructure of tempered martensite, is magnetic, and can be attracted by magnets. Austenitic stainless steels are non-magnetic; 304# stainless steel is a typical example of such materials. However, these stainless steels cannot achieve higher strength through conventional heat treatment. Non-magnetic austenitic stainless steels cannot be made stronger via such treatments, and therefore they are not used for manufacturing blade bodies; instead, they are employed in blade handles, holders, and similar components. Therefore, it’s not possible to simply use the presence or absence of magnetism to determine whether a material is stainless steel. The chromium content in 400 series stainless steels is lower than that in 300 series stainless steels, but it does not suffer from carbon deposition issues like the 300 series; moreover, it can be heat-treated and is suitable for use in environments with temperatures up to 1200°F (about 393 degrees Celsius). Increase its hardness. Ferritic and martensitic stainless steels of the 400 series. 410 is a type of stainless steel in the 400 series. Generally speaking, 304 offers better rust and corrosion resistance. However, in some specific cases, 410 performs better than 304 – for example, in applications where high hardness is required, but neither excellent rust resistance nor corrosion resistance is necessary; in such cases, 410 is a much better choice. Stainless steels in the 400 series can have their hardness increased through heat treatment. Nowadays, 400 series steels are used in lower-end products, while 304 is used in higher-end products. The 300 series consists of chromium-nickel austenitic stainless steels; model 301 has good ductility and is used for molded products. It can also be rapidly hardened through machining. It has good weldability. Its wear resistance and fatigue strength are superior to those of 304 stainless steel. Grade 302—Its corrosion resistance is similar to that of Grade 304; due to its relatively higher carbon content, it has better strength. Model 303—makes it more machinable than 304 by adding small amounts of sulfur and phosphorus. Model 304—General model ； That is, 18/8 stainless steel. The GB grade is 0Cr18Ni9. Model 309—has better temperature resistance than 304. Grade 316 – Following Grade 304, it is the second most widely used steel grade. It is primarily used in the food industry and for surgical instruments. The addition of molybdenum gives it a special corrosion-resistant structure. It is also used as \"marine steel\" because it has better resistance to chloride corrosion compared to 304. SS316 is usually used in nuclear fuel reprocessing facilities. 18/10 stainless steel also generally meets this application level. (Differences between 316L and 316 stainless steel pipes: a. 316L is an ultra-low carbon stainless steel, while 316 stainless steel is a low carbon stainless steel and does not belong to the ultra-low carbon category.) b. Different yield strengths: 316 210 (N/MM2) ； 316L 180(N/MM2). c. Different tensile strength: 316 520 (N/mm²) ； 316L 480(N/MM2). ) Model 321 – has properties similar to 304, except that the addition of titanium reduces the risk of rusting in the welds of the material. 400 series – Ferritic and martensitic stainless steels. Model 408: good heat resistance, moderate corrosion resistance; 11% Cr, 8% Ni. Model 409—the cheapest model (UK and US), typically used for car exhaust pipes; it is a ferritic stainless steel (chromium steel). Model 410—martensite (high-strength chromium steel), good wear resistance, poor corrosion resistance. Model 416 — Sulfur has been added to improve the processability of the material. Model 420 — “cutting tool grade” martensitic steel, similar to the earliest stainless steels such as Brinell high-chromium steel. It is also used for surgical knives, and can be made very shiny. Model 430—ferritic stainless steel, for decorative use, such as in automotive accessories. It has good formability, but poor heat resistance and corrosion resistance. Model 440 – a high-strength cutting tool steel with a slightly higher carbon content; after appropriate heat treatment, it can achieve a high yield strength, with a hardness of up to 58HRC, placing it among the hardest stainless steels. The most common example of application is “shaving blades”. There are three common types: 440A, 440B, and 440C; in addition, there is also 440F (easy-to-machine type). When brown rust spots appear on the surface of stainless steel pipes, people are quite surprised: they think, “Stainless steel doesn’t rust; if it does, it’s no longer stainless steel. There might be something wrong with the steel itself.” In fact, this is a one-sided and mistaken view resulting from a lack of understanding of stainless steel. Stainless steel can also rust under certain conditions. Stainless steel has the ability to resist oxidation in the atmosphere—that is, its rust resistance—and it also possesses the capability to resist corrosion in media containing acids, alkalis, and salts—that is, its corrosion resistance. However, its corrosion resistance varies depending on the chemical composition of the steel itself, its mutual state, operating conditions, and the type of environmental medium. For example, 304 steel pipes have excellent corrosion resistance in a dry and clean atmosphere, but when placed in coastal areas exposed to sea fog containing high levels of salt, they rust very quickly ； The 316 steel pipe, on the other hand, performed well. Therefore, not all stainless steels are resistant to corrosion and do not rust in any environment. Stainless steel gains its rust-resistant properties thanks to an extremely thin, strong, dense, and stable chromium-rich oxide film (protective layer) that forms on its surface, preventing further penetration of oxygen atoms and subsequent oxidation. Once, for some reason, this film is continuously damaged, oxygen atoms from the air or liquid will keep penetrating in, or iron atoms from the metal will continue to separate, forming loose iron oxide; as a result, the metal surface suffers from continuous rusting. There are many ways in which this surface film can be damaged. In daily life, the following are the most common ones: 1. Dust containing other metal elements or particles of foreign metals accumulate on the surface of stainless steel. In humid air, the condensed water between these deposits and the stainless steel forms a micro-battery, triggering an electrochemical reaction that damages the protective film. This phenomenon is known as electrochemical corrosion. 2. Organic juices (such as those from melons and vegetables, noodle soup, phlegm, etc.) adhere to the surface of stainless steel; in the presence of water and oxygen, they form organic acids. Over time, these organic acids corrode the metal surface. 3. Acids, alkalis, and salts adhere to the stainless steel surface (such as alkaline solutions or lime water used in wall decoration that splash onto it), causing localized corrosion. 4. In polluted air (such as air containing large amounts of sulfides, carbon monoxide, and nitrogen oxides), when it comes into contact with condensed water, sulfuric acid, nitric acid, and acetic acid are formed, leading to chemical corrosion. All of the above situations can cause damage to the protective film on the stainless steel surface, leading to rusting. Therefore, to ensure that the metal surface remains bright permanently and is free from rust, we recommend: 1. Regularly clean and scrub the decorative stainless steel surface to remove any deposits and eliminate external factors that could cause damage. 2. In coastal areas, stainless steel of grade 316 should be used, as it can resist corrosion caused by seawater.