Three properties of 20cr seamless steel tube

　　(I) Chemical stability of 20cr seamless steel pipe

　　Refers to the general term for the corrosion resistance and oxidation resistance of 20cr seamless steel pipe materials. The chemical stability of the material at high temperatures is called thermal stability.

　　(II) the oxidation resistance of 20cr seamless steel pipe

　　The ability of 20cr seamless steel pipe to resist oxidation at room temperature or high temperature, the oxidation process is actually a form of chemical corrosion. It can directly use the amount of heavy loss after the surface of the pipe is corroded within a certain period of time, which is expressed by the speed of metal weight loss.

　　(III) the corrosion resistance of 20cr seamless steel pipe

　　The ability of a material to resist the corrosive effects of surrounding media. The corrosion resistance of metals is related to many factors, such as the chemical composition of metals, processing properties, heat treatment conditions, microstructure, and media and temperature. Chemical corrosion is the result of direct chemical interaction between metals and surrounding media. It includes two forms of gas corrosion and metal corrosion in non-electrolyte. Its characteristics are: no current is generated during the corrosion process; and corrosion products are deposited on the surface of the 20cr seamless steel pipe. To understand the corrosion resistance of 20cr seamless steel pipes, we should first grasp the following points:

　　(1) General corrosion: This kind of corrosion is evenly distributed on the entire inner and outer surfaces, which continuously reduces the cross-section, and finally causes the force parts to be destroyed.

　　(2) Pitting corrosion: The corrosion is concentrated in a small area of the surface of the 20Cr seamless steel pipe, and it develops rapidly to the deep, and finally penetrates the metal, which is a relatively harmful corrosion damage.

　　(3) Corrosion fatigue: refers to the damage caused by the material in the corrosive medium under the action of alternating stress.

　　(4) Corrosion rate: The depth of material that a metal material corrodes in a unit time is called the corrosion rate.

　　(5) Electrochemical corrosion: The corrosion caused by the action of 20cr seamless steel pipe when it comes into contact with electrolyte solutions such as acid, alkali and salt is called electrochemical corrosion. Its characteristic is that current is generated during the corrosion process, and its corrosion products (rust) are not covered on the metal surface as the anode, but at a certain distance from the anode metal.

　　(6) Intergranular corrosion: Corrosion takes place inside the metal along the edges of the grains, usually does not cause any change in the shape of the metal, and often causes sudden damage to equipment or machinery.

　　(7) Stress corrosion: refers to the damage caused by metals in corrosive media under the effect of static stress. The damage caused by this corrosive medium is also a type of transgranular corrosion.

　　(8) Corrosion rate: The weight loss of 20cr seamless steel pipe material per unit area after corrosion in a unit time is called the corrosion rate.