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What is stainless steel ?

In the metallurgical industry, the term stainless steel is used to refer to an iron alloy containing about 10.5% chromium (cr). The name is “stainless steel” but it is actually a steel alloy that is not discolored or corroded as easily as other conventional steels. This material can also be called anti-corrosion steel.

Effect of chrome: (see chart below)

The resistance to atmospheric oxidation at normal temperatures of stainless steel is due to the chromium content of the alloy (min. 10.5% and up to 26% in the case of work). in harsh working environment).

The oxidation state of chromium is usually chromium oxide. When chromium in steel alloys is exposed to air, a very thin layer of chromium III oxide appears on the surface of the material. This layer is so thin that it can not be seen with the naked eye, which means that the metal surface is still shiny. However, they do not completely affect the water and the air should protect the steel layer below. This phenomenon is called anti-rust by means of material technology.

When stainless steel objects are bonded together with force acting like bolts and studs, their oxide layer can fly away at the sites where they are bonded. When disassembled, they can be seen corroded.

Besides chromium, nickel as well as molybdenum and nitrogen also have similar anti-rust properties.

Nickel (Ni) is a common ingredient to enhance the flexibility, ductility, and shaping of stainless steel. Molybdenum (Mo) makes stainless steel highly resistant to corrosion in acidic environments. Nitrogen (N) creates stability for stainless steel at minus temperature (cold).

Different involvement of Chromium, Nickel, Molybdenum, Nitrogen components lead to different crystalline structures that produce different mechanical properties of stainless steel.

Stainless steel has very high oxidation and corrosion resistance, but it is important to choose the right type and specifications to suit your specific situation.
There are four main types of stainless steel:

Austenitic
Ferritic
Austenitic-Ferritic (Duplex)
Martensitic

Austenitic is the most common stainless steel. This category includes SUS 301, 304, 304L, 316, 316L, 321, 310s … These types contain at least 7% nickel, 16% chromium, C 0.08% max. Such components make this type of steel highly resistant to corrosion in the temperature range is quite wide, not magnetic, flexible, flexible, easy solder. This type of steel is used extensively for household appliances, containers, industrial pipes, industrial boats, architectural casing, other constructions …

-Ferritic stainless steel has the same mechanical properties as mild steel, but is more resistant to corrosion than mild steel (black steel). SUS 430, 410, 409, … This type contains about 12% – 17% chromium. Type contains about 12% Chromium is often applied in architecture. The type contains about 17%. Chromium is used to make home appliances, boilers, washing machines, indoor structures …

Austenitic-Ferritic (Duplex): This type of steel has the “middle” type of Ferritic and Austenitic type called DUPLEX. These include the LDX 2101, SAF 2304, 2205, 253MA. Duplex steel contains much less nickel content than Austenitic. DUPLEX is characterized by its high durability and softness. It is used in the petrochemical industry, pulp and paper industry, shipbuilding … In the context of rising stainless steel prices Due to the nickel scarcity, the DUPLEX line is increasingly being used to replace some grades of Austenitic steel such as SUS 304, 304L, 316, 316L, 310s.

– Martensitic: This type contains about 11% to 13% chromium, has good strength and good stiffness, relatively corrosion resistant. Used to make turbine blades, blades.