What is the difference between stainless steel 30403, 30408 and 30409
The three stainless steel materials 30408, 30403 and 30409 are the domestic names of stainless steel for pressure equipment. They are produced according to the standard of GB-T 24511-2017 "Stainless Steel and Heat-resistant Steel Plates and Strips for Pressure Equipment" and are mainly used for pressure vessels. and other pressure equipment.
30408 stainless steel is the most widely used steel among many stainless steels. It also has two well-known nicknames, that is, food-grade stainless steel and 18/8 stainless steel. However, it must be produced in strict accordance with relevant national standards. Its digital code is S30408, and the corresponding national standard grade is 06Cr19Ni10 (304).
30403 stainless steel is a low-carbon material of 304 stainless steel, its digital code is S30403, the corresponding national standard grade is 022Cr19Ni10 (304L), and its carbon content is 0.03%. Lower carbon content gives better corrosion resistance and weldability.
30409 stainless steel is a high-carbon material of 304 stainless steel, its digital code is S30409, the corresponding national standard grade is 07Cr19Ni10 (304H), and its carbon content is 0.04-0.1%. It has better high temperature strength and oxidation resistance.
Under what circumstances will stainless steel rust?
Stainless steel relies on an extremely thin, firm, dense and stable chromium-rich oxide film (protective film) formed on its surface to prevent the infiltration and oxidation of oxygen atoms and obtain the ability to resist corrosion. Once for some reason, the film is continuously damaged, the oxygen atoms in the air or liquid will continuously infiltrate or the iron atoms in the metal will continuously separate out to form loose iron oxide, and the metal surface will be continuously rusted.
The cause of stainless steel rust
1. When there are other metal elements, dust, or metal particles attached to the surface of the stainless steel plate, it is prone to chemical corrosion and rust. The most common is that some processing plants are producing products, such as pull In the process of stretching and stamping, the mold on the punching machine contains iron particles attached to the stainless steel surface
2. In the process of polishing and drawing, because the sand grains contain a certain amount of iron elements, they are attached to the surface of stainless steel for a long time, and when they encounter chlorine ions in the air, sulfur ions will react chemically and cause rust.
3. The stainless steel plate will also rust during the return to the south sky. The reason is that the air is humid when the stainless steel plate or stainless steel coil is back to the south sky. There is a certain gap between the stainless steel plate and the plate. Alternating temperature The moisture in the air, especially in the southern coastal cities, contains relatively high chloride ions and sulfur ions. It enters the gap between the stainless steel plate and the plate along with the air, causing the stainless steel to rust quickly.
4. Side effects of stainless steel surface, acid-base salt, such as acid-base water, lime and so on. Over time, local corrosion and rust are caused by chemical action
5. In the usual stainless steel storage environment, the air contains a lot of sulfide, carbon dioxide, etc. If polluted air or chemical plants encounter condensed water, it will also form sulfuric acid, nitric acid, etc., and will also produce some chemical corrosion, resulting in rust spots on the surface of stainless steel.
Stainless Steel Suppliers
Shangyi International Trade Co., Ltd. specializes in the production of stainless steel products for many years. The Stainless Steel produced by our company has excellent performance and is well recognized by the market. If you have this demand, please contact us.
