The main properties of stainless steel

Weldability
The requirements for welding performance vary depending on the use of the product. A type of tableware generally does not require welding performance, and even includes some pot enterprises. However, the vast majority of products need raw materials with good welding performance, such as second-class tableware, thermos cups, steel pipes, water heaters, water dispensers, etc.

Corrosion resistance
The vast majority of stainless steel products require good corrosion resistance, such as Class I and II tableware, kitchenware, water heaters, water dispensers, etc., and some foreign businessmen also do corrosion resistance tests on products: heat to boiling with NACL aqueous solution, pour out the solution after a period of time, wash and dry, weigh the weight loss, and determine the degree of corrosion (Note: when the product is polished, the abrasive cloth or sandpaper contains Fe components, which 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 abruptly changed, from the negative potential to the positive electrode potential. Prevents galvanic corrosion.

Polishing properties
In today's society, stainless steel products generally go through the polishing process during production, and only a few products such as water heaters and water dispenser liners do not need to be polished. Therefore, this requires that the polishing performance of the raw material is very good. The main factors affecting polishing performance are as follows:
(1) Surface defects of raw materials. Such as scratches, pitting, over-pickling, etc.
(2) The problem of raw materials. If the hardness is too low, it is not easy to polish (BQ is not good), and if the hardness is too low, the orange peel phenomenon is easy to appear on the surface during deep drawing, which affects the BQ property. The BQ with high hardness is relatively good.
(3) After deep drawing, small black spots and RIDGING will also appear on the surface of the area with great deformation, which will affect the BQ properties.

Heat resistance
Heat resistance refers to the fact that stainless steel can still maintain its excellent physical and mechanical properties at high temperatures.
Influence of Carbon: Carbon is an element that strongly forms and stabilizes austenite and expands the austenite region in austenitic stainless steels. Carbon is about 30 times more capable of forming austenite than nickel, a interstitial element that can significantly increase the strength of austenitic stainless steels through solution strengthening. Carbon also improves the stress and corrosion resistance of austenitic stainless steels in highly concentrated chlorides (e.g., 42% MgCl2 boiling solution).

However, in austenitic stainless steel, carbon is often regarded as a harmful element, which is mainly due to the fact that under some conditions in the corrosion-resistant use of stainless steel (such as welding or heating at 450~850 °C), carbon can form a high-chromium Cr23C6 type carbon compound with chromium in steel, which leads to local chromium dilution, so that the corrosion resistance of steel, especially the intergranular corrosion resistance, is reduced. Therefore. Since the 60s, most of the newly developed chromium-nickel austenitic stainless steels are ultra-low-carbon with a carbon content of less than 0.03% or 0.02%, and it can be known that with the reduction of carbon content, the intergranular corrosion sensitivity of steel is reduced, and when the carbon content is less than 0.02%, it has the most obvious effect, and some experiments also point out that carbon will also increase the pitting corrosion tendency of chromium austenitic stainless steel. Due to the harmful effects of carbon, not only should the carbon content be controlled as low as possible in the smelting process of austenitic stainless steel, but also in the subsequent hot, cold working and heat treatment processes to prevent carburization on the surface of stainless steel and avoid the precipitation of chromium carbide.