The requirements for welding performance vary from product to product. A type of tableware generally does not require welding performance, and even includes some pot enterprises. However, most products require good welding performance of raw materials, such as second-class tableware, vacuum flasks, steel pipes, water heaters, water dispensers, etc.
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 businessmen also do corrosion resistance test on products: use NACL aqueous solution to warm to boiling, after a period of time Drop the solution, wash and dry, weigh the weight loss, to determine the degree of corrosion (Note: when the product is polished, the content of Fe in the abrasive cloth or sandpaper will cause rust on the surface during the test)
In today's society, stainless steel products are generally polished during the production process, and only a few products such as water heaters, water dispenser liners, etc. do not need to be polished. Therefore, this requires a good polishing performance of the raw material. The main factors affecting the polishing performance are as follows:
1 raw material surface defects. Such as scratches, pitting, soaking and so on.
2 raw material problems. The hardness is too low, it is not easy to be polished when polishing (BQ is not good), and the hardness is too low, and the surface is prone to orange peel phenomenon during deep drawing, thereby affecting BQ property. The BQ with high hardness is relatively good.
3 After deep drawing, the surface of the area with a large deformation will also have small black spots and RIDGING, thus affecting BQ
Heat resistance means that stainless steel can maintain its excellent physical and mechanical properties at high temperatures.
Carbon effect: Carbon is strongly formed and stabilized in austenitic stainless steel. Austenite is formed and the elements of the austenite region are enlarged. The ability of carbon to form austenite is about 30 times that of nickel. Carbon is a kind of interstitial element, which can significantly increase the strength of austenitic stainless steel by solid solution strengthening. Carbon also improves the stress and corrosion resistance of austenitic stainless steels in highly concentrated chlorides such as 42% MgCl2 boiling solutions.
However, in austenitic stainless steels, carbon is often considered a harmful element, mainly due to some conditions in the corrosion resistance of stainless steel (such as welding or heating at 450~850 °C), carbon can be used in steel. Chromium forms a high chromium Cr23C6 type carbon compound which leads to partial chromium depletion and a decrease in corrosion resistance of the steel, particularly intergranular corrosion resistance. therefore. The newly developed chromium-nickel austenitic stainless steels since the 1960s are mostly ultra-low carbon with a carbon content of less than 0.03% or 0.02%. It can be known that as the carbon content decreases, the intergranular corrosion sensitivity of steel decreases, when the carbon content is lower than 0.02% has the most obvious effect. Some experiments also pointed out that carbon also increases the tendency of pitting corrosion of chromium austenitic stainless steel. Due to the harmful effects of carbon, not only the lowest possible carbon content should be controlled during the austenitic stainless steel smelting process, but also the carbonation of the stainless steel surface is prevented during the subsequent heat, cold working and heat treatment, and the chromium carbide is avoided. Precipitate.
When the amount of chromium in the steel is not less than 12.5%, the electrode potential of the steel is abruptly changed from a negative potential to a positive electrode potential. Prevent electrochemical corrosion.