Stainless steel

Definition of stainless steel

In the air or chemical corrosion medium can resist corrosion of a high alloy steel, stainless steel is a beautiful surface and good corrosion resistance, do not have to be plated and other surface treatment, and play the inherent surface properties of stainless steel, used in many aspects of a kind of steel, usually called stainless steel. On behalf of the performance of 13 chromium steel, 18- chromium – nickel steel and other high alloy steel.
From the metallographic point of view, because stainless steel contains chromium and the surface of the formation of a very thin chromium film, the film separated from the oxygen in the steel invasion of corrosion resistance. To maintain the corrosion resistance inherent in stainless steel, steel must contain more than 12% chromium.

The development history of stainless steel

The reason why iron and steel materials are so widely used is because of the concentration of iron ore deposits, large storage, relatively economic mining and smelting, and strong cold and hot deformation capacity of semi-finished iron and steel. The finished products have excellent mechanical properties (strength, plasticity and impact resistance) and machining properties (cutting, welding, cold deformation, etc.). But compared with silicic acid materials, polymer synthetic materials and some non-ferrous metals, its biggest disadvantage is: in the atmosphere or acid, alkali, salt and other media conditions, easy to lose weight due to corrosion, and even complete destruction.

Types of stainless steel

Stainless steel can be classified by use, chemical composition and metallographic structure.
The austenitic steel is composed of 18% chromium -8% nickel, and the amount of each element is different, so as to develop various kinds of steel.
Classification by chemical composition: ①Cr series: ferrite series, Martensite system series ②Cr-Ni series: Austenite system series, abnormal series, precipitation hardening series.
Classification of metallographic structure: (1) austenitic stainless steel, (2) ferritic stainless steel, (3) martensitic stainless steel, (4) duplex stainless steel, (5) precipitation hardening stainless steel