The more common types of stainless steel:

1.201 stainless steel

201 stainless steel has the characteristics of certain acid and alkali resistance, high density, no bubbles and no pinholes in polishing. Mainly used for decorative pipes, industrial pipes, and some shallow-stretched products.

200 series stainless steel was first developed successfully in the United States as a substitute for 300 series stainless steel during World War II. At that time, due to the war, nickel as a strategic material was strictly controlled by the relevant countries, and the supply of nickel in the United States was seriously insufficient. In order to solve the production and supply problems of stainless steel in the case of a serious shortage of nickel supply, the United States has developed this new series of austenitic stainless steels that replace nickel with manganese.

After the end of World War II, the supply of nickel in the United States gradually improved. Therefore, the production of 300 series stainless steel is no longer restricted by the shortage of raw materials, so the 200 series has not been greatly developed. Several Indians who participated in the development of 200-series stainless steel at the beginning brought back to India the 200-series stainless steel developed in the United States from the fact that India is relatively rich in manganese resources and lacking in nickel resources after returning to India.

The successful application of 200 series stainless steel in India is due to the possibility of replacing 304 stainless steel in some specific applications.

The disadvantage of this series of materials is: the chromium content below 18% and the low nickel content cannot reach a balance and form ferrite. For this reason, the chromium content in the 200 series stainless steel is reduced to 13.5%~15%, some The situation has dropped to 13%~14%, and its corrosion resistance cannot be compared with 304 and other similar steels. In addition, manganese and in some cases copper reduce the effect of repassivation under acidic conditions common to corrosion sites in deposition zones and crevices. 200 series steel will fail at these conditions approximately 10-100 times faster than 304 stainless steel. Residual sulphur and carbon content in these steels are often not controlled in production, and the material cannot be traced back to its origin, even when the material is recycled. If Cr-Mn steels are not specified, they can be a dangerous mix of scrap, resulting in castings with unexpectedly high levels of manganese.

201 stainless steel itself is non-toxic.

But 201 is easy to rust, and it is harmful to the body after rusting. The Mn content in the 201 material is very high, and element ions that are harmful to health will be precipitated during the heating and use of food. The corrosion resistance of 201 stainless steel is not good, and it is generally used in a low-corrosion environment.

201 stainless steel is a low-nickel stainless steel, and its anti-rust performance is relatively poor. It is generally used for products with relatively dry contact environments, while tableware generally uses 304. This stainless steel is a high-nickel stainless steel with strong anti-rust performance. If 201 stainless steel is used as living utensils , It is recommended not to be used for high temperature and oil products.

2. 304 stainless steel:

304 stainless steel is a common material in stainless steel, with a density of 7.93 g/cm³; it is also called 18/8 stainless steel in the industry, meaning it contains more than 18% chromium and more than 8% nickel; high temperature resistance of 800 ℃, with good processing performance , With the characteristics of high toughness, it is widely used in industry and furniture decoration industry and food and medical industry. However, it should be noted that food-grade 304 stainless steel has stricter content indicators than ordinary 304 stainless steel. For example: the international definition of 304 stainless steel is basically 18%-20% of chromium and 8%-10% of nickel, but food-grade 304 stainless steel is 18% of chromium and 8% of nickel, which is allowed to fluctuate within a certain range, and Limit the content of various heavy metals.

For 304 stainless steel, the Ni element in its composition is very important, which directly determines the corrosion resistance and value of 304 stainless steel.

The most important elements in 304 are Ni and Cr, but they are not limited to these two elements. Specific requirements are specified by product standards. The common judgment in the industry is that as long as the Ni content is greater than 8% and the Cr content is greater than 18%, it can be considered as 304 stainless steel. This is why the industry calls this type of stainless steel 18/8 stainless steel.

304 stainless steel is the most widely used chromium-nickel stainless steel. As a widely used steel, it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties; good hot workability such as stamping and bending, no heat treatment Hardening phenomenon (use temperature -196℃~800℃). Corrosion resistance in the atmosphere, if it is an industrial atmosphere or heavily polluted area, it needs to be cleaned in time to avoid corrosion. Suitable for food processing, storage and transportation. Has good processability and weldability. Plate heat exchangers, bellows, household products (Class 1 and 2 tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs), auto parts (windshield wipers, mufflers, molded products), medical appliances, building materials, chemicals, food industry , agriculture, ship parts, etc. 304 stainless steel is a nationally recognized food grade stainless steel.

Most of the usage requirements are to maintain the original appearance of the building for a long time. When determining the type of stainless steel to choose, the main considerations are the required aesthetic standards, the corrosiveness of the local atmosphere, and the cleaning system to be used. However, other applications increasingly seek only structural integrity or water impermeability. For example, roofs and side walls of industrial buildings. In these applications, the owner's construction cost may be more important than aesthetics, and the surface is not very clean. 304 stainless steel works reasonably well in dry indoor environments. However, in rural and urban areas, to maintain its appearance outdoors, frequent cleaning is required. In heavily polluted industrial and coastal areas, the surface can be very dirty and even rust.

However, for an aesthetic effect in an outdoor environment, nickel-containing stainless steel is required. Therefore, 304 stainless steel is widely used in curtain walls, side walls, roofs and other construction purposes, but in severely corrosive industrial or marine atmospheres, 316 stainless steel is preferred. Stainless steel sliding doors, people have fully realized the advantages of using stainless steel in structural applications. 304 and 316 stainless steels are included in several design guidelines. Because the "duplex" stainless steel 2205 combines good atmospheric corrosion resistance with high tensile and elastic strengths, this steel is also included in European guidelines. Product Shapes Stainless steel is actually manufactured in a full range of standard metal shapes and sizes, and many special shapes are also available. The most commonly used products are made from sheet and strip, but also special products are produced from medium and heavy plates, for example, in the production of hot-rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular and hexagonal welded or seamless pipes and other forms, including profiles, bars, wires and castings.