What is precision steel pipe?

Precision steel pipe:

Precision bright pipe (precision steel pipe) is a kind of common seamless steel pipe (or reduced diameter welded steel pipe) through fine drawing or cold rolling processing after a high precision steel pipe material. Because the inner and outer walls of the precision bright tube have no oxide layer, no leakage under high pressure, high precision, high finish, no deformation in cold bending, flaring, flattening and no cracks, it is mainly used to produce pneumatic or hydraulic components, such as cylinders or cylinders, which can be seamless tubes or welded tubes.

The chemical composition of precision bright tube is carbon C, silicon Si, Manganese Mn, sulfur S, phosphorus P, chromium Cr. High quality carbon steel, finished rolling, no oxidation bright heat treatment (NBK state), non-destructive testing, the inner wall of the steel pipe is SCrubbed by special equipment and washed by high pressure, the antirust oil on the steel pipe is used for antirust treatment, and the two ends of the cover is used for dustproof treatment. The inner and outer wall of the steel tube is of high precision, high finish, no oxide layer of the steel tube after heat treatment, high cleanliness of the inner wall, the steel tube is under high pressure, no deformation in cold bending, no cracks in flaring and flattening. The precision steel tube provided by Changzhou Rencheng metal products steel Tube factory can be used for various complex deformation and mechanical processing. Steel pipe color: white with bright, with high metallic luster.

Main uses of precision steel pipe:

Automobile, mechanical parts, such as steel pipe precision, finish has high requirements of machinery. Precision steel pipe users are not only the users with high requirements for precision and finish, because the precision bright pipe is high, the tolerance can be maintained at 2-8 wire, so many mechanical processing users in order to save the loss of labor, material and time, the seamless steel pipe or round steel is slowly transformed into precision bright pipe.

The effect of elements in precision bright tube on high temperature tempering brittleness can be divided into:

(1) High temperature tempering brittle impurity elements such as phosphorus, tin, antimony, etc.

(2) alloying elements that promote or slow down high temperature tempering brittleness in different forms and degrees. Chromium, manganese, nickel, silicon and so on play a promoting role, while molybdenum, tungsten, titanium and so on play a delaying role. Carbon also plays a role.

General carbon precision bright tube is brittle to high temperature tempering. The sensitivity of binary or multiple alloy steels containing chromium, manganese, nickel and silicon is very sensitive. The degree of sensitivity varies with the type and content of alloying elements.

The sensitivity degree of the original structure of the tempered precision bright tube to the high temperature tempering brittleness of steel is significantly different. The high temperature tempering microstructure of martensite is the most sensitive to high temperature tempering brittleness, followed by bainite and pearlite.

The essence of high temperature tempering brittleness of precision bright tubes is generally believed to be the result of grain boundary embrittlement caused by the segregation of impurities such as phosphorus, tin, antimony and arsenic in the original austenite grain boundary. The alloy elements such as manganese, nickel and chromium co-deviate with the impurity elements at grain boundaries, which promotes the enrichment of impurity elements and intensifies the embrittlement. Molybdenum, on the contrary, has a strong interaction with phosphorus and other impurities, which can produce precipitation phase in the grain and hinder the grain boundary segregation of phosphorus, and can reduce the brittleness of high temperature tempering. Titanium can more effectively promote phosphorus and other impurity elements to precipitate in grains, thus weakening the grain boundary segregation of impurity elements and reducing the high temperature tempering brittleness.


The measures to reduce the brittleness of precision bright tube at high temperature are as follows:

(1) Rapid cooling with oil or water after high temperature tempering to inhibit the segregation of impurity elements at grain boundaries;

(2) When the molybdenum content in the steel increases to 0.7%, the high temperature tempering embrittlement tendency is greatly reduced. When the molybdenum content in the steel reaches this limit, special molybdenum-rich carbide is formed in the 20# precision steel pipe, and the molybdenum content in the matrix decreases, and the embrittlement tendency of the precision bright pipe increases.

(3) reduce the content of impurity elements in 20# precision steel pipe;

(4) For the parts working in the high temperature tempering embrittlement area for a long time, it is difficult to prevent embrittlement by adding molybdenum alone. Only by reducing the content of impurities in the 20# precision steel pipe, improving the purity of the precision bright pipe, and assisted by the composite alloying of aluminum and rare earth elements, can the high temperature tempering brittleness be effectively prevented.

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