Different requirements for the use of the product also vary. A class of tableware on the welding performance is generally not required, even including some of the pot-like enterprises. But most of the products require good welding performance, such as two kinds of tableware, thermos flask, steel pipe, water heater, water dispenser and so on.
Most stainless steel products require good corrosion resistance, like one or two kinds of tableware, kitchenware, water heaters, drinking fountains, and some foreign businessmen to the product also do corrosion resistance test: with NaCl aqueous solution heated to boiling, after a period of time after the solution, wash dry, said weight loss, to determine the degree of corrosion (note: Product polishing, Due to the presence of FE in Emery cloth or sandpaper, the surface rust can be caused when testing.
Today's Society of stainless steel products in the production of generally polished this process, only a few products such as water heaters, drinking fountains and so do not need polishing. So this requires that the raw material polishing performance is very good. The factors that affect polishing performance are as follows:
① raw material surface defects. such as scratching, pitting, pickling, etc.
② raw material material problem. Hardness is too low, polishing is not easy to throw bright (BQ), and the hardness is too low, in the deep stretch surface prone to orange peel phenomenon, thus affecting BQ. The BQ of high hardness is relatively good.
③ after the deep stretching of the product, the deformation of the area of a large surface will also be small black spots and ridging, thus affecting the BQ of sex.
Heat resistance is the high temperature of stainless steel can still maintain its excellent physical and mechanical properties.
Carbon impact: Carbon in austenitic stainless steel is strongly formed and stabilized. The austenite and expands the elements of the austenitic area. The ability of carbon to form austenite is about 30 times times that of nickel, carbon is a gap element, and the strength of austenitic stainless steel can be significantly improved by solid solution enhancement. Carbon can also improve the corrosion-resistant properties of austenitic stainless steels in highly concentrated chlorides such as 42%mgcl2 boiling solutions.
However, in austenitic stainless steel, carbon is often regarded as a harmful element, mainly due to some conditions in the corrosion-resistant use of stainless steels (such as welding or 450~850℃ heating), carbon can be formed with chromium in the steel with high chromium $literal type carbon compounds, resulting in local chromium depletion, The corrosion resistance of steels, especially intergranular resistance, is decreased. therefore。 Since the 60 's, the new development of chrome-nickel austenitic stainless steel is mostly carbon content less than 0.03% or 0.02% ultra-low carbon type, you can know that with the reduction of carbon content, steel intergranular corrosion sensitivity reduced, when the carbon content of less than 0.02% has the most obvious effect, some experiments also pointed out that Carbon also increases the point corrosion tendency of chrome austenitic stainless steels. Due to the harmful effects of carbon, not only in the austenitic stainless steel smelting process should be as low as possible to control the carbon content, but also in the subsequent heat, cold processing and heat treatment process to prevent the surface of stainless steel to increase carbon, to avoid chromium carbide precipitation.