Heat Treatment Technology for Casing Pipe

Sep 28
03:48

2019

Marine Lee

Marine Lee

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The data shows that the 27MnCrV steel pipe is a relatively high-quality high-grade oil casing, and on the other hand, it shows that the sub-temperature quenching process is an excellent method to avoid high-temperature brittleness in the production of steel products.

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27MnCrV is a new type of steel for the production of TP110T steel grade casing pipe. The conventional production of TP110T steel grade oil pipe sets is 29CrMo44 and 26CrMo4. Compared with the latter two,Heat Treatment Technology for Casing Pipe Articles 27MnCrV contains less Mo element, which can greatly reduce the production cost. However, after the production of 27MnCrV by normal austenitizing quenching process, there is obvious high temperature temper brittleness, resulting in low impact toughness and instability.

Solving such problems is usually handled in two ways: First, the method of rapid cooling after tempering avoids high temperature brittleness and obtains toughness. Second, the sub-temperature quenching method improves the toughness by effectively improving the harmful elements and impurities through incomplete austenitization of the steel. The first method requires relative to the heat treatment equipment strict, you need to add extra costs.

27MnCrV steel has AC1=736°C, AC3=810°C, and the heating temperature during sub-temperature quenching is selected between 740-810°C. The sub-temperature quenching selects the heating temperature of 780 ° C, the quenching heating holding time is 15 min; the quenching and tempering selects the temperature of 630 ° C, and the tempering heating and holding time is 50 min. Due to sub-temperature quenching in α + γ two phases.The zone is heated and quenched while retaining a portion of the undissolved ferrite, and the toughness is improved while maintaining high strength.

At the same time, the low temperature quenching is lower than the conventional temperature, which reduces the quenching stress, thereby reducing the quenching deformation, thus the smooth operation of the heat treatment production, and provides a good raw material for the subsequent wire processing.

At present, the process has been applied in the pipe processing plant of Tianjin Steel Pipe. The quality assurance data shows that the yield strength of the steel pipe after heat treatment is 820- 860 MPa, the tensile strength Rm is 910-940 MPa, and the impact toughness Akv is between 65-85 J. The anti-destructive performance is qualified. The data shows that the 27MnCrV steel pipe is a relatively high-quality high-grade oil casing, and on the other hand, it shows that the sub-temperature quenching process is an excellent method to avoid high-temperature brittleness in the production of steel products.

Extended knowledge

Casing Pipe classification:

1. Catheter: It is mainly used for drilling in oceans and deserts to separate seawater and sand to ensure smooth drilling.
2. Surface casing: It is mainly used for drilling and drilling the soft ground to the 
bedrock. In order to seal the part, the formation will not be collapsed, and it needs to be sealed with a surface casing.
3. Technical Casing: When used in the drilling process of complex formations, when 
encountering complex parts such as collapse layer, oil layer, gas layer, water layer, leakage layer, salt paste layer, etc., the technical casing is required to be sealed. Otherwise the drilling will not be possible.
4. Oil casing: When the drilling is drilled to the target layer (oil and gas), the oil layer 
and the upper exposed layer should be sealed with oil casing, and the oil casing is internally oil pipe. The oil casings have deep depths in various types of casings, and their mechanical properties and sealing performance requirements are also high.