The main characteristics of stainless steel

The main characteristics of stainless steel

weldability

Different uses of products have different requirements for welding performance. A class of tableware welding performance generally do not do requirements, even including part of the pot enterprises. But the vast majority of products need raw materials with good welding performance, 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 require good corrosion resistance, like one or two types of tableware, kitchenware, water heater, water dispenser, etc., some foreign businessmen also do corrosion resistance tests on products: with NACL solution heated to boiling, after a period of time to dump the solution, wash and dry, said weight loss, to determine the degree of corrosion (note: When polishing the product, the emery cloth or sandpaper contains Fe components, which 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 of this process, only a few products such as water heaters, water dispensers and so on do not need polishing. Therefore, this requires the material polishing performance is very good. The main factors affecting polishing properties are as follows:

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

② The problem of raw materials. The hardness is too low, it is not easy to polish 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 property. High hardness BQ sex is relatively good.

(3) After deep stretching, small black spots and RIDGING will appear on the surface of the area with great deformation, which will affect the BQ property. Stainless steel

Heat resistance

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

Carbon influence: Carbon is an element in austenitic stainless steel that strongly forms and stabilizes austenite and enlarges the austenitic region. The capacity of carbon to form austenite is about 30 times that of nickel. Carbon is a kind of interstitial element, which can significantly improve the strength of austenitic stainless steel 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. This is mainly because under some conditions of corrosion resistance of stainless steel (such as welding or heating at 450~850℃), carbon can form high chromium Cr23C6 carbon compounds with chromium in steel, resulting in local chromium depletion, which reduces the corrosion resistance of steel, especially the resistance to intergranular corrosion. So. Since the 60's 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, steel intergranular corrosion sensitivity 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 in the process of austenitic stainless steel smelting should be controlled as low as possible according to the requirements of the carbon content, but also in the subsequent hot and cold processing and heat treatment process in the stainless steel surface carburization, to 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 from negative potential to positive electrode potential. Prevent electrochemical corrosion.