Stainless steel is a very important material that plays a vital role in our life. Stainless steel is widely used due to its excellent properties and multiple uses, such as in construction, manufacturing, medical, food processing, and other fields. It is a material that is very resistant to corrosion, high temperature, and easy to clean and maintain, which makes it one of the indispensable materials in many industries. In this article, we will delve into the properties and uses of stainless steel, and take you into stainless steel.
What kind of steel is stainless steel?
Shanghai Huaxiao Take You Into Stainless Steel, Stainless Steel is a type of steel. Steel refers to steel with a carbon (C) content of less than 2% and iron with more 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 performance of the steel and makes the steel corrosion-resistant. (That is, no rust) is what we often call stainless steel.
Why are there different steel grades for stainless steel?
During the smelting process of Shanghai Huaxiao Stainless Steel, due to the different types of alloying elements added, the amount of addition of different varieties is different. Their characteristics are also different, and different steel grade names are given to distinguish them.
What kind of stainless steel is not easy to rust?
There are three main factors that affect stainless steel corrosion:
Stainless Steel Rust
①The content of alloying elements. Generally speaking, the chromium content of 10.5% steel is not easy to rust. The higher the content of chromium and nickel, the better the corrosion resistance. For example, the content of nickel for 304 stainless steel material needs to be 8-10%, and the content of chromium needs to reach 18-20%. Such stainless steel will not rust under normal circumstances.
②The smelting process of the manufacturer will also affect the corrosion resistance of stainless steel. A large stainless steel plant with good smelting technology, advanced equipment, and advanced technology can guarantee the control of alloying elements, the removal of impurities, and the control of the cooling temperature of the billet. Therefore, the product quality is stable and reliable, and the internal quality is good. rust. On the contrary, some small steel plants have very backward equipment and technology. During the smelting process, impurities cannot be removed, and the products produced will inevitably appear to be rusty.
③The external environment, a dry and ventilated environment is less prone to rust. The air humidity is high, and continuous rainy weather or an environment with high pH in the air is also very easy to rust. 304 stainless steel, if the surrounding environment is too bad, it will rust.
Stainless steel is without magnetism, is it good stainless steel without magnetism? If the microstrip is magnetic, isn’t it 304 stainless steel?
Many customers can’t buy stainless steel in the market, so they bring a small magnet and suck it when they buy it. They think that what can’t be sucked is good stainless steel. Without magnetism, there will be no rust. In fact, this is a misunderstanding.
The non-magnetic stainless steel strip is determined by the structure of the structure. During the solidification process, the molten steel will form “ferrite”, “austenite”, “martensite” and other stainless steels with different structures during the solidification process. Ferritic” and “Martensitic” stainless steels are all magnetic. “Austenitic” stainless steel has good comprehensive mechanical properties, process performance, and weldability, but only in terms of corrosion resistance, magnetic “ferritic” stainless steel is better than “austenitic” stainless steel.
At present, the so-called 200 series and 300 series stainless sheets of steel with high manganese content and low nickel content in the market are not magnetic, but their performance is very different from that of 304 with high nickel content. 304 stainless steel is processed by stretching, annealing, polishing, casting, and other processes. It is also slightly magnetic, so it is a misunderstanding and unscientific to judge the quality of stainless steel without magnetism.
Why does stainless steel rust?
When brown rust spots (spots) appear on the surface of stainless steel, people are surprised: “Stainless steel does not rust. If it rusts, it is not stainless steel. It may be that there is a problem with the steel.” This is a one-sided misconception of not understanding stainless steel. Stainless steel also rusts under certain conditions.
Stainless steel has the ability to resist atmospheric oxidation, that is, the performance of non-corrosion, and it also has the ability to resist corrosion in media containing acid, alkali, and salt, that is, corrosion resistance. But the size of its anti-corrosion ability is changed by the chemical composition of the steel itself, the mutual state, the use conditions, and the type of environmental media. Such 304 stainless steel material, in a dry and clean atmosphere, has absolutely excellent corrosion resistance, but if it is moved to a coastal area, it will quickly rust in the sea fog containing a lot of salt. It is not any kind of stainless steel, it is corrosion-resistant and does not rust at all times.
Stainless steel relies on a very thin, strong, dense, and stable chromium-rich oxide film (protective film) on its surface to prevent oxygen atoms from continuing to penetrate and continue to oxidize, thereby gaining corrosion resistance. Once for some reason, this kind of film is constantly destroyed, the oxygen atoms in the air or liquid will continue to infiltrate or the iron atoms in the metal will continue to separate out, forming relatively loose iron oxide, and the metal surface will be affected. Constant corrosion. This kind of surface film is damaged in many situations, and the following are more common in daily life:
①The surface of stainless steel accumulates dust containing other metal elements or attachments of dissimilar metal particles. In humid air, the condensed water between the attachments and stainless steel connects the two to form a micro battery, which initiates an electrochemical reaction. , The protective film is damaged, which is called electrochemical corrosion.
②The surface of stainless steel adheres to organic juices (such as melons, vegetables, noodle soup, etc.), which form organic acids in the presence of water and oxygen and form organic acids to corrode the metal surface for a long time.
③The surface of stainless steel adheres to contain acid, alkali, and salt substances (such as alkali water, and lime water spray test on the decoration wall) causing local corrosion.
④In polluted air (atmosphere containing a large amount of sulfide, oxide, and hydrogen oxide), it will form sulfuric acid, nitric acid, acetic acid liquid spots, etc., causing chemical corrosion when encountering condensed water.
The above conditions can cause damage to the protective film on the surface of the stainless steel and cause corrosion. To ensure that the metal surface is permanently bright and will not be rusted, we recommend:
① The surface of decorative stainless steel must be cleaned and scrubbed frequently to remove the attachments on it and eliminate the external factors that cause rust.
② There is a kind of stainless steel made of 201 and 202 on the market that is easy to rust in coastal areas and is suitable for use in an environment without industrial pollution and air corrosion.
③ Use 304 stainless steel in coastal areas, which can resist seawater corrosion.
What should I do if there are rust spots on the stainless steel?
Chemical methods
Use pickling paste or spray to help re-passivate the rusted parts to form a chromium oxide film to restore corrosion resistance. After pickling, in order to remove the pollutants and acid residues on it, it is very important to rinse with clean water. of. After all, processing, re-polishing with polishing equipment, and sealing with polishing wax. For those with slight rust spots, you can also use a 1:1 gasoline and engine oil mixture to wipe off the rust spots with a clean rag.
Mechanical method
Sandblasting, using glass or ceramic particle shot blasting, brushing, and polishing. Mechanical methods may be able to wipe away the contamination caused by previously removed materials, polishing materials, or oblivious materials. All kinds of pollution, especially foreign iron particles, can become a source of corrosion, especially in humid environments. Mechanical cleaning of the surface is best carried out regularly cleaning in a dry environment.
The use of mechanical methods can only clean the surface, and it is impossible to change the corrosion resistance of the material itself. Therefore, it is recommended to re-polishing with polishing equipment after mechanical cleaning and sealing with polishing wax.