Precision bright pipe is a kind of ordinary seamless steel pipe (or de-diameter welded steel pipe) through fine drawing or cold rolling processing of a high-precision steel pipe material. Because there is no oxide layer on the inner and outer walls of the precision bright pipe, no leakage under high pressure, high precision, high finish, cold bending without deformation, flaring, flattening without cracks, etc., it is mainly used to produce products of pneumatic or hydraulic components, such as cylinders or cylinders, which can be seamless pipes and welded pipes.
The chemical composition of the precision bright tube is carbon C, silicon Si, manganese Mn, sulfur S, phosphorus P, chromium Cr. The inner wall of the steel pipe is cleaned by special equipment and washed under high pressure, the anti-rust oil on the steel pipe is treated as anti-rust, and the caps at both ends are treated as dustproof. High precision and high finish of the inner and outer walls of the steel pipe, no oxide layer after heat treatment, high cleanliness of the inner wall, steel pipe under high pressure, cold bending without deformation, flaring, flattening without cracks. Precision steel pipe can be used for a variety of complex deformation and mechanical processing. Steel pipe color: white with bright, with high metallic luster.
Precision bright pipe main application:
Automobiles, mechanical parts, etc., have high requirements for the precision and finish of steel pipes. Precision steel pipe users are not only users with high precision and finish requirements, because of the high precision of the precision bright pipe, the tolerance can be maintained at 2-8 wires.
The influence of elements in precision bright tubes on high temperature tempering brittleness:
(1) Impurity elements such as phosphorus, tin, antimony, etc. that cause high temperature tempering brittleness of precision bright tubes.
(2) Alloying elements that promote or slow down high-temperature tempering brittleness in different forms and to different 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 catalytic role.
General carbon precision bright tubes are not sensitive to high temperature tempering brittleness, and binary or multiple alloy steels containing chromium, manganese, nickel and silicon are very sensitive, and their sensitivity varies according to the type and content of alloying elements.
The sensitivity of the original structure of the tempered precision bright pipe to the high temperature tempering brittleness of steel is significantly different. The sensitivity of martensite high-temperature tempering structure to high-temperature tempering brittleness is the highest, followed by bainite high-temperature tempering structure, and pearlite structure is the least.
The nature of high temperature tempering brittleness of precision bright pipes is generally believed to be the result of the segregation of impurity elements such as phosphorus, tin, antimony and arsenic at the grain boundaries of the original austenite, resulting in the embrittlement of the grain boundaries. The co-segregation of manganese, nickel, chromium and other alloying elements at the grain boundary promotes the enrichment of impurity elements and intensifies the embrittlement. Molybdenum, on the contrary, has a strong interaction with impurity elements such as phosphorus, which can produce a precipitated phase in the crystal and hinder the grain boundary segregation of phosphorus, and can reduce high temperature tempering brittleness rare earth elements also have a similar effect with molybdenum. Titanium can more effectively promote the precipitation of impurity elements such as phosphorus in the crystal, thus weakening the grain boundary segregation of impurity elements and slowing down the high temperature tempering brittleness.
The measures to reduce the high temperature tempering brittleness of precision bright pipe are:
(1) Oil cooling or water rapid cooling after high temperature tempering to inhibit the segregation of impurity elements in the grain boundary;
(2) The use of molybdenum containing precision bright tube species, when the molybdenum content in the steel increases to 0.7%, the high temperature tempering embrittlement tendency is greatly reduced, more than this limit 20# precision steel pipe formed a special carbide rich in molybdenum, molybdenum content in the matrix decreases, the embrittlement tendency of precision bright tube increases;
(3) Reduce the content of impurity elements in the precision steel pipe;
For the parts working in the high-temperature tempering embrittlement zone for a long time, it is difficult to prevent embrittlement with molybdenum alone. Only by reducing the content of impurity elements in the precision steel pipe, improving the purity of the precision bright pipe, and supplemented by the composite alloying of aluminum and rare earth elements, can the high-temperature tempering embrittlement be effectively prevented.
Precision bright pipe standards:
China: GB/T3639, Germany: DIN2391, DIN2393, DIN2445, EU: EN10305, Germany: DIN1630, DIN1629, USA: ASTM A519, Japan: JIS G3445.....
Steel grade:
10#, 20#, 35#, 45#, 40Cr, 25Mn, 37Mn5, St35(E235), St37.4, St45(E255), St52(E355) 30CrMo, 42CrMo, 4130, 4140.......
Main delivery status:
NBK(+N), GBK(+A), BK(+C), BKW(+LC), BKS(+SR)
After the martensitic structure is obtained by quenching the precision bright tube, it is tempered in the temperature range of 450 ~ 600℃; Or at 650℃ after tempering at a slow cooling rate of 350 ~ 600℃; Or after tempering at 650 ° C, long-term heating in the temperature range of 350 ~ 650 ° C will cause embrittlement of the precision bright tube. If the already brittle precision steel pipe is reheated to 650 ° C and then quickly cooled, the toughness can be restored. The high temperature tempering brittleness is manifested as the increase of the toughness and brittleness transformation temperature of the precision bright pipe. Sensitivity is generally expressed as the difference between the toughness and brittleness transition temperature of the toughening state and the embrittlement state. The more serious the tempering brittleness at high temperature, the higher the proportion of the fracture of the precision bright pipe is.
Email: sale@galaxy-steel.com
Wechat: LXF13931739696. Whatsapp: 008613931739696
Website: www.friend-steelpipes.com www.cz-steelpipe.com
CANGZHOU GALAXY STEEL PIPE CO., LTD
No comments:
Post a Comment