Stainless steel has a chromium content of more than 12.5% in steel and has a high resistance to corrosion of external media (acid, alkali salt), called stainless steel in stainless steel pipe factory. According to the microstructure of steel, stainless steel can be divided into martensite type, ferrite type, austenite type, ferrite-austenite type, precipitation hardening type stainless steel. According to national standard GB3280-92, there are 55 regulations. . In daily life, we contact a lot of austenitic stainless steel (some people call it nickel stainless) and Martensitic stainless steel (some people call it stainless iron, but it is not scientific, easy to misunderstand, should be avoided) .
Typical grades for austenitic stainless steels are 0Cr18Ni9, namely “304” and 1Cr18Ni9Ti. Martensitic stainless steel is the stainless steel we make knife and scissors. The grades are mainly 2Cr13, 3Cr13, 6Cr13, 7Cr17 and so on. Due to the difference in the composition of the two types of stainless steel, the microstructure of the built-in metal is also different. Austenitic stainless steel due to the addition of higher chromium and nickel in steel (containing about 18% chromium and more than 4% Ni), the internal structure of steel presents a state of austenite, which is Without magnetic permeability, it cannot be attracted by magnets. Often used as decorative materials, such as stainless steel tubes, towel racks, tableware, stoves, etc. Martensitic stainless steel is used for making stainless steel for knife and scissors. Because the knife and scissors have the function of cutting objects, they must have sharpness. To have sharpness, they must have a certain hardness. This type of stainless steel must undergo a heat transfer to cause internal structural transformation. Only when the hardness is increased can the knife be cut. However, the internal structure of this type of stainless steel is tempered martensite, which is magnetically permeable and can be attracted by magnets. Therefore, it is not possible to simply describe the stainless steel with or without magnetic properties.
Why is stainless steel material not easy to rust?
“rust” is essentially corrosion or rust, which is caused by the chemical or electrochemical action of the surface of the steel and the oxygen, water and acid, alkali, salt and other substances in the atmosphere. . The substance produced on the surface is “rust” which is an oxide of iron.
Why is stainless steel not easy to rust, it is related to the addition of more than 12.5% of chromium in the matrix. In oxidatively corrosive and non-erodible media, chromium can quickly form a dense passivation film on the steel surface to prevent the metal matrix from being destroyed. When the chromium content is above 12.5%, a dense and stable passivation film is formed, and the rust-proof property undergoes a leap-type consolidation, and the rust resistance is greatly enhanced, which is why the chromium content in the stainless steel is 12%. The above reasons.
Stainless steel, as its name suggests, is stainless steel. Here, “rust” is relative, not absolute, relative to carbon steel. Stainless steel is not prone to rust, but it is not absolutely rust-free, but it is not easily corroded and rusted than carbon steel under the same conditions and environment.2.5 inch stainless steel pipe
The stainless steel material is added with chromium, and after adding an appropriate amount of alloying elements such as Ni, Mo, V, etc., the anti-rust performance is stronger. Therefore, in the rust prevention performance, the austenitic stainless steel is stronger than the martensitic stainless steel. Secondly, the corrosion resistance grade of stainless steel is also related to the amount of carbon, the amount of chromium, and the surface treatment state. With the increase of carbon content, the anti-rust performance of stainless steel decreases, and the anti-rust performance of 3Cr13 is inferior to that of 2Cr13. As the content of steel increases, the rust resistance increases. The surface treatment method and state simultaneously affect the rust prevention ability. The rust-proof performance of the knife-cut surface is chrome-plated, electropolishing, mirror polishing, abrasive belt and hand polishing.
To prevent rust of stainless steel products, the main thing is not to damage the passivation film of the stainless steel surface layer. Wash it as soon as possible after use. Dry it. Try not to touch acid and alkali salts.