If the alloy steel contains a very low proportion of chromium or other elements, it can only form an oxide film on the surface for protection and will still oxidize. It has the same corrosion resistance characteristics as copper or aluminum. This steel is not stainless steel, but weathering steel. Chromium, combined with low carbon content, can show significant corrosion resistance and heat resistance. Nickel, molybdenum, vanadium, titanium, niobium, manganese, tungsten, aluminum, copper, nitrogen, sulfur, phosphorus and selenium can also be added to produce a rust-proof oxide film on its surface to improve corrosion resistance and oxidation resistance to special environments, and give special properties to protect the steel itself from oxidative corrosion by air (especially oxygen), water, certain acids and alkalis in the external environment.

Most stainless steels are first melted in an electric furnace or an oxygen top-blown converter (converter) and then refined in another steelmaking furnace, mainly to reduce the carbon content. In the argon-oxygen decarburization process, a gas mixture of oxygen and argon is sprayed into the molten steel. Changing the ratio of oxygen and argon reduces the carbon content to a controlled level by oxidizing carbon to carbon monoxide without oxidizing and losing expensive chromium. Therefore, cheaper raw materials, such as high-carbon ferrochrome, can be used in the initial melting operation.

1. Weldability

Different product uses have different requirements for welding performance. Class I tableware generally does not require welding performance, even including some pot companies. However, most products require good raw material welding performance, such as Class II tableware, thermos cups, steel pipes, water heaters, water dispensers, etc.

2. Corrosion resistance

Most stainless steel products require good corrosion resistance, such as Class I and Class II tableware, kitchen utensils, water heaters, water dispensers, etc. Some foreign merchants also conduct corrosion resistance tests on their products: use NACL aqueous solution to heat to boiling, pour out the solution after a period of time, wash and dry, weigh the weight loss to determine the degree of corrosion (Note: When polishing the product, because the sandpaper or sandpaper contains Fe, it will cause rust spots on the surface during the test)

When the number of chromium atoms in the steel is not less than 12.5%, the electrode potential of the steel can be suddenly changed from negative potential to positive electrode potential. Prevent electrochemical corrosion.

3. Polishing performance

In today's society, stainless steel products generally go through the polishing process during production. Only a few products such as water heaters and water dispenser tanks do not need polishing. Therefore, this requires the raw material to have good polishing performance. The factors that affect the polishing performance are mainly the following:

① Surface defects of raw materials. Such as scratches, pitting, over-pickling, etc.

② Raw material problems. If the hardness is too low, it is not easy to polish (poor BQ performance), and if the hardness is too low, the surface is prone to orange peel during deep drawing, which affects the BQ performance. The BQ performance of high hardness is relatively good.

③ For products that have undergone deep drawing, small black spots and RIDGING will also appear on the surface of the area with extremely large deformation, which affects the BQ performance.

4. Heat resistance

Heat resistance refers to the ability of stainless steel to maintain its excellent physical and mechanical properties at high temperatures.

The influence of carbon: Carbon is an element that strongly forms and stabilizes austenite and expands the austenite zone in austenitic stainless steel. Carbon has the ability to form austenite about 30 times that of nickel. Carbon is an interstitial element that can significantly improve the strength of austenitic stainless steel through solid solution strengthening. Carbon can also improve the stress corrosion resistance of austenitic stainless steel in high-concentration chlorides (such as 42% MgCl2 boiling solution). However, in austenitic stainless steel, carbon is often regarded as a harmful element. This is mainly because under some conditions in the corrosion-resistant use of stainless steel (such as welding or heating at 450~850℃), carbon can form high-chromium Cr23C6-type carbon compounds with chromium in steel, resulting in local chromium depletion, which reduces the corrosion resistance of steel, especially intergranular corrosion resistance. Therefore. Since the 1960s, the newly developed chromium-nickel austenitic stainless steels are mostly ultra-low carbon types with a carbon content of less than 0.03% or 0.02%. It can be seen that as the carbon content decreases, the intergranular corrosion sensitivity of steel decreases. When the carbon content is less than 0.02%, it has the most obvious effect. Some experiments also point out that carbon will increase the tendency of pitting corrosion of chromium austenitic stainless steel. Due to the harmful effects of carbon, not only should the carbon content be controlled as low as possible during the smelting process of austenitic stainless steel, but also in the subsequent hot, cold working and heat treatment processes, carbon increase on the stainless steel surface should be prevented to avoid the precipitation of chromium carbides.

1. In the field of construction applications, the surface processing of stainless steel is important for many reasons. Corrosive environments require smooth surfaces because smooth surfaces are not prone to fouling. The accumulation of dirt can cause stainless steel to rust and even cause corrosion.

2. In spacious halls, stainless steel is the most commonly used material for elevator decorative panels. Although fingerprints on the surface can be wiped off, they affect the appearance, so it is best to choose a suitable surface to prevent fingerprints from leaving.

3. Sanitary conditions are very important for many industries, such as food processing, catering, brewing and chemical industry. In these application areas, the surface must be easy to clean every day, and chemical cleaning agents are often used. Stainless steel is the best material in this regard. In public places, the surface of stainless steel is often scrawled with graffiti. However, an important feature of it is that they can be washed away. This is a significant feature of stainless steel over aluminum. The surface of aluminum tends to leave marks, which are often difficult to remove. When cleaning the surface of stainless steel, you should clean it along the lines of the stainless steel, because some surface processing lines are one-way. Stainless steel is most suitable for use in hospitals or other areas where hygiene is critical, such as food processing, catering, brewing and chemical industries, not only because it is easy to clean every day, sometimes using chemical cleaning agents, but also because it is less likely to breed bacteria. Tests show that the performance in this regard is the same as that of glass and ceramics.