1. What steel is stainless steel? Stainless steel is a type of steel, steel refers to steel containing less than 2% carbon (C), and iron is greater than 2%. The addition of chromium (Cr), nickel (Ni), manganese (Mn), silicon (Si), titanium (Ti), molybdenum (Mo) and other alloying elements in the smelting process improves the properties of the steel and makes the steel resistant to corrosion. (that is, not rust) is the stainless steel we often say.
2. why do stainless steel have different steel numbers? In the process of smelting stainless steel, the amount of addition of different alloys is different due to the different types of alloying elements. The characteristics are also different. In order to distinguish them, different steel name names are attached. The following is a table of the content of "alloying elements" of stainless steel with different steels for common decoration, for reference only:
3. What kind of stainless steel is not easy to rust? There are three main factors affecting the corrosion of stainless steel: 1. The content of alloying elements. In general, steel with a chromium content of 10.5% is less likely to rust. The higher the content of chrome nickel, the better the corrosion resistance. For example, the content of nickel in 304 is 8-10%, and the content of chromium is 18-20%. Such stainless steel will not rust under normal conditions. 2. 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 guarantee the control of alloy elements, the removal of impurities and the control of the cooling temperature of the billet. Therefore, the quality of the product is stable and reliable, and the internal quality is good. Rusty. On the contrary, some small steel mills are very backward and the process is backward. In the process of smelting, impurities cannot be removed, and the products produced will inevitably be rusted. 3. The external environment, the climate is dry and ventilated, the environment is less likely to rust. The air humidity is high, continuous rainy weather, or the environment with large pH in the air is also very easy to rust. 304 stainless steel, if the surrounding environment is too bad, it will rust.
4. stainless steel is not magnetic, without magnetic is good stainless steel? If the microstrip is magnetic, isn't it 304? Many customers can't buy stainless steel in the market, they bring a small magnet, and they suck when they buy it. They think that it is good stainless steel. Without rust, it will not rust. In fact, this is a wrong understanding. The stainless steel belt is not determined by the structure of the magnetic structure. During the solidification process, the molten steel will form stainless steel with different structural structures such as “ferrite”, “austenite” and “martensitic” due to different solidification temperatures. Ferritic "martensitic" stainless steel is magnetic. The "austenitic" stainless steel has good mechanical properties and good weldability, but only the "ferritic" stainless steel with magnetic properties is better than the "austenitic" stainless steel. The so-called 200 series and 300 series stainless steels with high content of manganese and less nickel in the market are not magnetic, but their performance is very different from that of high-nickel 304. 304 is processed by stretching, annealing, polishing and casting. It will also be slightly magnetic, so it is unscientific to use stainless steel belts without magnetism to judge the merits of stainless steel.
5. Why does stainless steel rust? When brown rust spots (points) appeared on the surface of stainless steel, people were amazed: "Stainless steel is not rusted, and rust is not stainless steel. It may be a problem with steel." This is a one-sided misconception that stainless steel is not known. Stainless steel also rusts under certain conditions. Stainless steel has the ability to resist atmospheric oxidation, that is, the rust property, and also has the ability to resist corrosion in a medium containing acid, alkali, and salt, that is, corrosion resistance. However, the corrosion resistance is determined by the chemical composition of the steel itself, the state of each other, the conditions of use, and the type of environmental medium. For example, material 304 has absolutely excellent corrosion resistance in a dry and clean atmosphere, but if it is moved to a coastal area, it will soon rust in a sea fog containing a large amount of salt. Not any kind of stainless steel, it is resistant to corrosion and rust at all times. Stainless steel is a layer of extremely thin and strong and stable chromium-rich oxide film (protective film) on the surface to prevent oxygen atoms from continuing to infiltrate and continue to oxidize to obtain corrosion resistance. For some reason, the film is constantly destroyed, the air or liquid neutralizes the oxygen atoms and the iron atoms in the metal are continuously separated, forming relatively loose iron oxide, and the metal surface is also affected. Constant rust. There are many cases in which the surface film is damaged. The following are common in the daily life:
1.The surface of the stainless steel accumulates the dust containing other metal elements or the attachment of the dissimilar metal particles, in the humid air, the attachments The condensed water between the stainless steel and the stainless steel is connected into a micro-battery, which triggers an electrochemical reaction and the protective film is destroyed, which is called electrochemical corrosion.
2. The surface of the stainless steel is adhered to organic juice (such as melon, noodle soup, etc.), which forms an organic acid in the presence of water and oxygen, and forms an organic acid on the metal surface for a long time.
3. The surface of the stainless steel adheres to acid, alkali, and salt substances (such as alkaline water and lime water sprayed on the wall) to cause local corrosion.
4. In the polluted air (the atmosphere containing a large amount of sulfides, oxides, and hydrogen oxide), in the case of condensed water, sulfuric acid, nitric acid, acetic acid liquid spots, etc. are formed, causing chemical corrosion. All of the above can cause corrosion of the stainless steel surface protective film. In order to ensure that the metal surface is permanently bright and not rusted, we recommend:
1 The decorative stainless steel surface must be cleaned and scrubbed frequently to remove the deposits and eliminate external factors that cause corrosion.
2 There is a kind of 201 and 202 stainless steel on the market that is easy to rust in the coastal area, suitable for use in the environment without industrial pollution and air corrosion.
3 The waterfront area should be made of 304 stainless steel, which is resistant to seawater corrosion.