What do you dont know about stainless steel?

Stainless steel is a kind of high alloy steel, which can resist corrosion in the air chemical corrosion. The main reason of corrosion resistance of stainless steel pipe is that chromium plays a role in its composition. On the one hand, a very thin chromium film is formed on the steel surface to separate the oxygen the steel. On the other hand, the addition of chromium increases the potential of iron-based solid solution electrode. Generally, in order to maintain the inherent corrosion resistance of stainless steel, it contains more than 12% chromium.

"Stainless steel" is just a general term, it can represent more than 100 kinds of industrial stainless steel. According to the structure, it can be divided into austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, duplex stainless steel precipitation hardening stainless steel.

In recent years, in order to solve the problems of intergranular corrosion stress corrosion of austenitic stainless steel, ultra-low carbon stainless steel ultra pure ferritic stainless steel were developed respectively. At present, there are more than 230 kinds of stainless steel on the market, nearly 50 kinds of stainless steel are often used. About 80% of them are derivatives of austenitic stainless steel the remaining 20% are made of Cr13. Continuous development. The main research development of stainless steel grades mainly focus on the development of corrosion resistance high strength stainless steel.

Due to the different uses of various types of stainless steel, the processing technology quality requirements of raw materials are also different. The following is a representative description of the material, surface treatment grade, thickness tolerance, weldability corrosion resistance.

Generally speaking, ordinary stainless steel pipe hot rolled coil go through the following important processes:

(1) Material (1) DDQ material: refers to the material used for deep drawing, we call it soft material. The main characteristics of this material are its high elongation low hardness. The internal grain size is between 7.0 8.0, the deep drawing performance is excellent. If the expansion of raw materials can be realized, cracking pulling will easily occur in the processing of deep drawing products, which will affect the yield. ② General materials: mainly used for materials other than DDQ. It is characterized by low elongation. Compared with DDQ material, its deep drawing property is relatively poor. It is mainly used for products that can be obtained without stretching, such as tableware, electrical appliances, etc.

(2) Surface treatment grade stainless steel sheet is a very expensive material, customers have high requirements for its surface quality. However, stainless steel plate in the production process will inevitably produce a variety of defects, such as scratches, pits, creases, pollution so on, which will affect its surface quality. Generally, the surface treatment grades of stainless steel can be divided into No. 1 (original surface), No. 2D (blunt surface), No. 2B (ground surface), No. 3 (coarse grinding), No. 4 (fine grinding), etc. the surface roughness decreases in turn. Among them, the surface treatment level of Ba plate is high, the reflectivity is high, so it can be used as a mirror.

(3) Stainless steel products with different thickness tolerances require different thickness tolerances of raw materials. The thickness tolerance of second-class tableware thermos cup is high, which is - 3-5%, while the thickness tolerance of first-class tableware is generally - 5%, the requirement of steel pipe is - 10%, the thickness tolerance of hotel refrigerator is - 8%, the thickness tolerance of dealers is between - 4% 6%.

(4) Different products with different weldability have different requirements on welding performance. A kind of tableware usually does need welding performance, even includes some pot enterprises. However, most products require good welding properties of raw materials, such as second-class tableware, heat preservation cup, steel pipe of power plant boiler, water heater, water heater, etc.

(5) Corrosion resistance most stainless steel products require good corrosion resistance, such as class I II tableware, kitchen utensils, water heaters, water dispensers, etc. Some foreign merchants also test the corrosion resistance of the products: boiling, pouring out the solution for a period of time, washing drying, then weighing to determine the degree of corrosion.