Vacuum coating of stainless steel objects with vacuum coating equipment
Stainless steel is the abbreviation of stainless and acid resistant steel. Stainless steel is resistant to weak corrosive media, such as air, steam and water or stainless steel. The steel that is resistant to chemical corrosion media (such as acid, alkali and salt) is called acid resistant steel.
Stainless steel refers to steel that is resistant to weak corrosive media such as air, steam and water and chemical corrosive media such as acid, alkali and salt, also known as stainless acid resistant steel. In practice, steel resistant to weak corrosion medium is often called stainless steel, and steel resistant to chemical medium is called acid resistant steel. Due to the different chemical composition of the two, the former is not necessarily resistant to the corrosion of chemical media, and the latter is generally stainless. The corrosion resistance of stainless steel depends on the alloy elements contained in the steel.
Generally speaking, according to the metallographic structure, ordinary stainless steel can be divided into three categories: austenitic stainless steel, ferritic stainless steel and martensitic stainless steel. On the basis of these three basic metallographic structures, duplex steel, precipitation hardening stainless steel and high alloy steel with iron content less than 50% are derived for specific requirements and applications.
1. Austenitic stainless steel. Stainless steel with austenite structure (CY phase) of matrix face centered cubic crystal structure is non-magnetic, which is mainly strengthened by cold working (and may lead to certain magnetism). Aisa is marked with 200 and 300 series numbers, such as 304.
2. Ferritic stainless steel. Stainless steel with ferrite structure (phase a) - core cubic crystal structure, which is magnetic, generally cannot be hardened by heat treatment, but can be slightly strengthened by cold working. Aisa is marked by 430 and 446.
3. Martensitic stainless steel. The mechanical properties of stainless steel with martensitic matrix (body centered cubic or cubic) and magnetism can be adjusted by heat treatment. The American Iron and Steel Association is marked with the numbers 410, 420, and 440. Martensite has austenite structure at high temperature. When it is cooled to room temperature at an appropriate rate, the austenite structure can be transformed into martensite (i.e. hardening).
4. AUSTENITIC FERRITIC (duplex) stainless steel. 329 is a typical duplex stainless steel, which has both austenite and ferrite matrix, and the content of rare phase matrix is generally more than 15%. It is magnetic and can be strengthened by cold working. Compared with austenitic stainless steel, duplex steel has high strength, intergranular corrosion resistance, chloride stress corrosion resistance and pitting corrosion resistance.
5. Precipitation hardening stainless steel. Stainless steel with austenitic or martensitic matrix can be hardened by precipitation hardening. The American Iron and Steel Association is marked with a 600 series number, such as 630, which is 17-4PH. Generally speaking, except for alloys, austenitic stainless steel has very good corrosion resistance. Ferritic stainless steel can be used in low corrosion environment. In mild corrosive environment, martensitic stainless steel and precipitation hardening stainless steel can be used if the material is required to have high strength or hardness.
There are three main factors affecting the corrosion of stainless steel:
1. Content of alloy elements. Generally speaking, steel containing 10.5% chromium is not easy to rust. The higher the chromium content, the better the corrosion resistance. For example, 304 material requires 8-10% nickel and 18-20% chromium. This kind of stainless steel generally does not rust.
2. The smelting process of the manufacturer will also affect the corrosion resistance of stainless steel. Large stainless steel plants with good smelting technology, advanced equipment and advanced technology can ensure the control of alloy elements, the removal of impurities and the control of billet cooling temperature. Therefore, the product quality is stable and reliable, the internal quality is good, and it is not easy to rust. On the contrary, some small steel mills are backward in equipment and technology. In the smelting process, impurities cannot be removed, and the products produced will inevitably rust.
3. The external environment, dry and well ventilated environment, is not easy to rust. However, areas with high air humidity, continuous rainy weather or high air pH are prone to rust. 34 stainless steel will rust if the surrounding environment is too poor.
A good way to make the surface of stainless steel brighter, stronger, more durable and not corroded is vacuum coating, that is, a kind of equipment called vacuum coating is used to treat the surface of stainless steel. Using vacuum coating equipment to coat metal surface will be better than traditional technology!
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