Precision bright steel pipe is a high-precision steel pipe material that is processed by precision drawing or cold rolling of ordinary seamless steel pipe (or diameter-reduced welded steel pipe). Because there is no oxide layer on the inner and outer walls of precision bright steel pipes, they can withstand high pressure without leakage, has high precision, high smoothness, no deformation in cold bending, no cracks in flaring and flattening, etc., it is mainly used to produce pneumatic or hydraulic components, such as cylinders. Or oil cylinder can be a seamless steel pipe or welded steel pipe.
The chemical composition of precision bright steel pipes is carbon C, silicon Si, manganese Mn, sulfur S, phosphorus P, and chromium Cr. High-quality carbon steel, precision rolling, non-oxidation bright heat treatment (NBK state), non-destructive testing, the inner wall of the steel pipe is brushed with special equipment and washed with high pressure, anti-rust oil is applied to the steel pipe for anti-rust treatment, and both ends are capped for dust-proof treatment. The inner and outer walls of the steel pipe have high precision and high smoothness. After heat treatment, the steel pipe has no oxidation layer and the inner wall is highly clean. The steel pipe can withstand high pressure and does not deform during cold bending. It has no cracks in expanding and flattening. The precision steel pipe provided by Changzhou Rencheng Metal Products Steel Pipe Factory can be used for various complex deformations and mechanical processing. Steel pipe color: white with bright color, high metallic luster.
The main uses of precision bright steel pipes:
Machinery such as automobiles and mechanical parts have very high requirements for the precision and smoothness of steel pipes. Precision steel pipe users are not only those who have relatively high requirements for precision and smoothness. Because precision bright steel pipes have high precision and the tolerance can be maintained at 2-8 wires, many mechanical processing users will Seamless steel pipes or round steel pipes are slowly transforming into precision bright steel pipes.
The effects of elements in precision bright steel pipes on high-temperature temper brittleness are divided into:
(1) Impurity elements such as phosphorus, tin, antimony, etc. that cause high-temperature temper brittleness of precision bright steel pipes.
(2) Alloying elements that promote or slow down high-temperature temper brittleness in different forms and to varying degrees. Chromium, manganese, nickel, silicon, etc. play a promoting role, while molybdenum, tungsten, titanium, etc. play a retarding role. Carbon also plays a contributing role.
Generally, carbon precision bright steel pipes are not brittle to high-temperature tempering. Sensitive. Binary or multi-element alloy steel containing chromium, manganese, nickel, and silicon is very sensitive. The degree of sensitivity varies depending on the type and content of the alloy elements.
There is a significant difference in the sensitivity of the original structure of tempered precision bright steel pipes to the high-temperature temper brittleness of steel. The martensite high-temperature tempered structure is the most sensitive to high-temperature temperature brittleness, the bainite high-temperature tempered structure is the second most sensitive, and the pearlite structure is the least sensitive.
The essence of high-temperature temper brittleness of precision bright steel pipes is generally believed to be the result of the segregation of impurity elements such as phosphorus, tin, antimony, and arsenic at the original austenite grain boundaries, resulting in grain boundary embrittlement. Alloying elements such as manganese, nickel, and chromium co-segregate with the above-mentioned impurity elements at the grain boundaries, promoting the enrichment of impurity elements and aggravating embrittlement. Molybdenum, on the other hand, has a strong interaction with impurity elements such as phosphorus, which can produce a precipitation phase in the crystal and hinder the grain boundary segregation of phosphorus. It can reduce the brittleness of high-temperature tempering. Rare earth elements also have similar effects to molybdenum. Titanium more effectively promotes the precipitation of impurity elements such as phosphorus within the grain, thereby weakening the grain boundary segregation of impurity elements and slowing down high-temperature temper brittleness.
Measures to reduce the high-temperature temper brittleness of precision bright steel pipes include:
(1) Use oil cooling or water rapid cooling after high-temperature tempering to inhibit the segregation of impurity elements at the grain boundaries;
(2) Use molybdenum-containing precision bright steel pipes. When the molybdenum content in the steel increases to 0.7%, the high-temperature temper embrittlement tendency is greatly reduced. Beyond this limit, special molybdenum-rich carbides are formed in the 20# precision steel pipes. As the molybdenum content in the matrix decreases, the embrittlement tendency of precision bright steel pipes increases;
(3) Reduce the content of impurity elements in the 20# precision steel pipe;
(4) For parts that have been working in the high-temperature embrittlement zone for a long time, it is difficult to prevent embrittlement by adding molybdenum alone. The only way is to reduce the content of impurity elements in the 20# precision steel pipe, improve the purity of the precision bright steel pipe, and supplement it with aluminum and rare earth. Composite alloying of elements can effectively prevent high-temperature temper brittleness.
Post time: May-22-2024