Main characteristics of stainless steel

weldability

Stainless steel sculpture

Product use of different welding performance requirements are also different. A kind of tableware generally does not require welding performance, even including some pot enterprises. But the vast majority of products need good welding performance of raw materials, such as second class tableware, thermos cup, steel pipe, water heater, water dispenser and so on.

Corrosion resistance

The vast majority of stainless steel products for corrosion resistant performance is good, like a, 2 kinds of tableware, kitchen utensils and appliances, water heaters, water dispensers, etc., some foreign businessmen on corrosion resistance of products also do experiment: in NACL aqueous solution heated to boiling, after a period of time out solution, wash and drying, weight loss, to determine the degree of corrosion (note: When polishing the product, due to the content of Fe in emery cloth or sandpaper, it will lead to rust spots on the surface of the test.

Polishing performance

In today's society, stainless steel products are generally polished in the production of this process, only a few products such as water heater, water dispenser tank do not need polishing. Therefore, the polishing performance of raw materials is very good. The main factors affecting the polishing performance are as follows:

① Surface defects of raw materials. Such as scratches, pitting, pickling and so on.

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

③ For deeply stretched products, small black spots and RIDGING will appear on the surface of the area with great deformation, which will affect the BQ property.

Heat resistant performance

Heat resistance refers to the high temperature stainless steel can still maintain its excellent physical and mechanical properties.

Influence of carbon: Carbon is an element that strongly forms and stabilizes austenite and enlarges austenite zone in austenitic stainless steel. The ability of carbon to form austenite is about 30 times that of nickel. Carbon is an 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 high concentration chloride, such as 42%MgCl2 boiling solution.

But, in the austenitic stainless steel, carbon is often seen as the harmful elements, this is mainly due to the corrosion of stainless steel used in some conditions, such as welding or heating by 450 ~ 850 ℃), carbon steel with chromium in forming high chromium Cr23C6 type carbon compounds which can lead to local chromium depletion, make steel corrosion resistance especially resistant to intergranular corrosion performance degradation. So. Since the 60 s of the development of new cr-ni austenitic stainless steel is mostly carbon content less than 0.03% or 0.02% of the ultra-low carbon type, you can know as the carbon content is reduced, the steel intergranular corrosion sensitivity is reduced, when carbon content less than 0.02% is one of the most obvious effect, some experiments also pointed out that the carbon will also increase the chromium austenitic stainless steel corrosion tendency. Due to the harmful effect of carbon, not only in the process of austenitic stainless steel smelting should be controlled as low as possible carbon content, but also in the subsequent hot, cold processing and heat treatment process to prevent stainless steel surface carburization, to avoid chromium carbide precipitation.

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