22nd of March ,2018

How to distinguish stainless steel?

Iron and steel are distinguished by their carbon content. Iron-carbon alloys with a carbon content of less than 2% are steel, and those with a carbon content of more than 2% are called iron. Steel is widely used because of its toughness, elasticity and rigidity. All you come into contact with in life are steel, but people call it differently. For stainless steel, whether the magnet can be attracted or not, as long as it meets the quality standard, it is stainless steel./static/upload/images/2a055636b013640a9c4364d5fe62d2b1.png

Therefore, from the perspective of metallurgy, there is no such thing as stainless steel.

The main element of corrosion resistance of stainless steel is chromium. Steel with chromium content above 10.5% will not rust. The alloying elements added during smelting are different, and there is a difference between magnets that can attract and cannot attract. Stainless steel is generally divided according to the organizational structure, which can be divided into austenite, ferrite, martensite and other categories.

If different proportions of chromium-nickel, etc. are added to molten steel, the austenitic steel produced is stainless steel that cannot be attracted by magnets; if chromium and a small amount of nickel (or no nickel) are added to molten steel, the steel produced is Ferritic stainless steel that magnets can attract; the main alloying elements of martensitic stainless steel are chromium, iron and carbon. There are more than 100 kinds of stainless steel due to different alloy content. Except for austenitic stainless steels, they are all magnetic.

Nickel has very few reserves in the world, and the price is relatively expensive. Therefore, the price of stainless steel with high nickel content is also higher in the market, and the magnet is not attracted. In fact, there is another kind of stainless steel magnet that cannot be attracted. That is stainless steel with high manganese content and low nickel content or no nickel content. The market price of this kind of stainless steel is more than 1,000 yuan per ton lower than that of stainless steel with high nickel content. Some dealers use the misunderstanding that "good stainless steel magnets can't be attracted" to deceive consumers, and the price is as expensive as high nickel stainless steel.

There are more than 100 kinds of stainless steel with different characteristics and functions. Generally, austenitic stainless steel is used for decoration, landscape, and sculpture. Because of the low thermal conductivity of austenitic stainless steel, it is inappropriate to use it as a kettle, wok, and rice cooker. It will waste energy and prolong the time of boiling water for cooking. Using ferritic stainless steel to make woks and rice pots not only has excellent corrosion resistance, but also its thermal conductivity is nearly half higher than that of austenitic stainless steel./static/upload/images/622d7e5ac15b526ed3bd2a75738e3c6a.png

Ferritic stainless steel should be used for the inner tub of washing machine, water heater, vegetable washing basin, etc., as long as the utensils in contact with water should be selected. Some people complain that stainless steel knives are not fast, this is because the wrong stainless steel is selected. Austenitic stainless steel cannot be hardened and is not suitable for cutting tools and cutting tools. Tools made of martensitic stainless steel can change the hardness of stainless steel through heat treatment, such as quenching and tempering.

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