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What are the main characteristics of stainless steel?
Time: 1662104411

weldability

Different product uses have different requirements for welding performance. A class of tableware generally does not require welding performance, even including 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, drinking fountains and so on.

Corrosion resistance

The vast majority of stainless steel products require good corrosion resistance, such as one or two types of tableware, kitchenware, water heaters, drinking fountains, etc., some foreign businessmen also do corrosion resistance tests on products: warm to boiling with NACL solution, dump the solution after a period of time, wash and dry, call weight loss, to determine the degree of corrosion (note: When polishing the product, because the emery cloth or sandpaper contains Fe components, it will lead to rust spots on the surface of the test.

Polishing property

In today's society, stainless steel products are generally polished in the production process, only a few products such as water heaters, water dispensers, etc., do not need polishing. Therefore, this requires that the polishing properties of raw materials are very good. The main factors that affect the polishing performance are as follows:


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

② Raw material problem. The hardness is too low, and it is not easy to polish when polishing (BQ is not good), and the hardness is too low, and the orange peel phenomenon is easy to appear on the surface when the deep drawing, thus affecting the BQ property. BQ with high hardness is relatively good.

③ After deep stretching of the product, the surface of the area with great deformation will also produce small black spots and RIDGING, thus affecting the BQ property.

Heat resistance

Heat resistance means that stainless steel can still maintain its excellent physical and mechanical properties at high temperatures.

The effect of carbon: Carbon in austenitic stainless steel is an element that strongly forms and stabilizes austenite and expands the austenite region. The ability of carbon to form austenite is about 30 times that of nickel, carbon is a interstitial element, and the strength of austenitic stainless steel can be significantly improved by solution strengthening. Carbon can also improve the stress and corrosion resistance of austenitic stainless steel in highly concentrated chlorides (such as 42%MgCl2 boiling solution).

However, in austenitic stainless steel, carbon is often regarded as a harmful element, mainly because under some conditions in the corrosion resistance of stainless steel (such as welding or heating at 450~850 ° C), carbon can form high-chromium Cr23C6 carbon compounds with chromium in steel, resulting in local chromium depletion, so that the corrosion resistance of steel, especially the resistance to intergranular corrosion, is reduced. Therefore. Since the 1960s, the new development of chromium-nickel austenitic stainless steel is mostly carbon content less than 0.03% or 0.02% ultra-low carbon type, it can be known that with the reduction of carbon content, the intergranular corrosion sensitivity of steel is reduced, when the carbon content is less than 0.02% to have the most obvious effect, some experiments also pointed out that carbon will increase the point corrosion tendency of chromium-austenitic stainless steel. Due to the harmful effect of carbon, not only should the carbon content be controlled as low as possible in the process of austenitic stainless steel smelting as required, but also in the subsequent hot, cold processing and heat treatment process to prevent the surface of stainless steel carburization and avoid chromium carbide precipitation.

Corrosion resistance

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