Thermal treatment process for directly-connected sleeve

Abstract

The invention discloses a thermal treatment process for a directly-connected sleeve. The process comprises the following steps of: a, feeding a sleeve with thickened end into a quenching furnace, and heating the whole sleeve to the temperature of between 950 and 1,000 DEG C; b, putting the heated sleeve on a rotary quenching frame, and performing integral water quenching on the sleeve at the temperature of 900 DEG C, wherein the temperature of cooling water is 25 to 30 DEG C; and c, delivering the quenched sleeve to a tempering furnace, heating the sleeve to the temperature of between 600 and 650 DEG C, and performing tempering treatment and air cooling. By the thermal treatment process, the sleeve body and the thickened end have different cooling velocities after being quenched, the thickened end of the sleeve with thickness of more than 25 millimeters is totally quenched, the thickened end and the sleeve body part of the sleeve have the same quenched structure and consistent mechanical properties, and the squeezing damage resistance of the produced sleeve can be over 15 percent higher than the specified value of API 5C2 standard. The process is suitable for thermal treatment of sleeves made of steel with high Mn content and a certain amount of V.

Description

technical field [0001] The invention relates to the technical field of heat treatment, in particular to a heat treatment process of a direct-connected casing. Background technique [0002] The direct-connected casing commonly used in oil and gas well production, because the end part of the pipe is a thickened end, its thickness is quite different from the thickness of the pipe body. When heat treatment is carried out under the same quenching temperature and cooling conditions, the thicker the pipe end, The slower the cooling rate of the pipe end relative to the pipe body, the lower the quenching hardness of the pipe end. After tempering, the mechanical properties of the pipe end are generally about 50 MPa lower than the pipe body, and even lower than 100 MPa in severe cases. , the hardness of the pipe end is also much lower than that of the pipe body. Since the connection between the direct-connected casings is done by processing the internal and external threads on the thi...

AI Technical Summary

Problems solved by technology

Since the connection between the direct-connected casings is done by processing the internal and external threads on the thickened pipe ends, if the mechanical properties of the thickened end of the casing are low, it will affect the overall performance and use of the casing. Safety has a direct impact

Since the design of high-performance casing mainly considers mechanical properties, C and Mn contained in steel are the main materials for improving hardenability during heat treatment. In order to ensure the hardenability of the thickened end of casing, higher C, Mn should be added. Mn, but because the wall thickness of the pipe body is thin, the high hardenability will easily cause the pipe body to be quenched and cracked. Therefore, the hardenability should be appropriately reduced, resulting in a contradiction between the two. However, the existing casing uses Among the steel types, the content of C and Mn is very high, and the hardenability is very good, but in the case of ensuring the hardening of the thickened end of the direct connection casing, the pipe body is prone to quenching cracks

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