X65 induction bent pipe with uniform structure and preparation method of X65 induction bent pipe

Abstract

The invention discloses an X65 induction elbow with a uniform structure and a preparation method thereof, and the preparation method comprises the following steps: bending X65 pipeline steel, and spraying water for cooling; then the temperature is increased to 930-950 DEG C, heat preservation is conducted, furnace cooling is conducted to 630-650 DEG C, heat preservation is conducted for 2-4 h, and then air cooling Heating to 890-915 DEG C, preserving heat, performing water cooling, putting into a tempering furnace, preserving heat at 610 + / -15 DEG C, and performing air cooling to obtain the induction elbow with a uniform structure. Preheating treatment is conducted in an isothermal annealing mode, the structure is austenitized through temperature rising, and ferrite and pearlite evenly appear on the structure through isothermal annealing; quenching and tempering heat treatment is carried out in a quenching and tempering mode; through the synergistic effect of the bending process, the preheating treatment and the quenching and tempering heat treatment, the microstructure uniformity of the induction bent pipe product is greatly improved, and then the mechanical property uniformity of the induction bent pipe product is improved.

Description

Technical Field

[0001] The invention relates to the technical field of X65 induction elbow preparation, and in particular to an X65 induction elbow with uniform structure and a preparation method thereof. Background Art

[0002] X65 induction elbow for oil and gas pipeline transportation plays a vital role in oil and gas transportation and is an important component. Its bending angle and bending radius can make the pipeline change direction at a large angle during construction. In terms of materials, induction heating elbows are usually made of high-quality pipeline steel to ensure that they have good mechanical properties and corrosion resistance.

[0003] The process of medium frequency induction heating pipe bending is to put an induction coil on the part of the steel pipe (i.e. the bent mother pipe) to be bent, clamp the end of the steel pipe with a mechanical rotating arm, and pass a medium frequency current through the induction coil to heat the steel pipe. When the temperature of the steel pipe rises to the specified temperature, a mechanical thrust is used at the rear end of the steel pipe to push it forward and bend it. The bent steel pipe part cools down rapidly.

[0004] The elbow is heated at high temperature during the bending process, the tensile wall thickness of the outer arc area is thinned, and the compressive wall thickness of the inner arc area is thickened; since the straight pipe sections at both ends of the elbow are not heated, the mechanical properties of the inner and outer arc areas and the transition area of ​​the elbow have large deviations, which affects the application of the elbow. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an X65 induction bent pipe with uniform structure and a preparation method thereof, adjusts the bending process parameters, and performs preheating treatment and tempering heat treatment after bending, so as to improve the microstructure uniformity of each area of ​​the induction bent pipe product, thereby improving the mechanical properties of the induction bent pipe product.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing a uniformly organized X65 induction elbow, comprising the following steps:

[0007] S1. The part of the X65 pipeline steel to be bent is heated and then bent, and then cooled by spraying water;

[0008] S2. Preheating treatment: heating to 930-950°C, keeping warm for 1-1.5h, furnace cooling to 630-650°C and keeping warm for 2-4h, then air cooling to room temperature;

[0009] S3, perform quenching and tempering heat treatment: heat up to 890-915°C, keep warm for 2-4 hours, water cool, then place in a tempering furnace and keep warm at 610±15°C, then air cool to room temperature to obtain the X65 induction bending pipe with uniform structure.

[0010] The preparation method of the X65 induction bent pipe with uniform structure of the present invention regulates the bending process parameters to ensure the size and losslessness of the bent pipe product after bending; after bending, isothermal annealing is used for preheating treatment, and the temperature is raised to 930-950°C to austenitize the structure, and isothermal annealing is used to make the structure uniformly ferrite and pearlite; finally, quenching + tempering is used for tempering heat treatment; the method of the present invention synergistically improves the microstructure uniformity of the induction bent pipe product through the bending process, preheating treatment and tempering heat treatment, thereby improving the uniformity of the mechanical properties of the induction bent pipe product.

[0011] Furthermore, in S3, the holding time T in the tempering furnace is calculated according to 30 min to 60 min / 25.4 mm pipeline steel wall thickness.

[0012] Furthermore, in S3, the heating rate to 890-915°C is ≤260°C / h.

[0013] Furthermore, in S1, the bending temperature is 960±20°C, and the bending speed is 25±2.5 mm / min.

[0014] Furthermore, in S1, the portion of the X65 pipeline steel to be bent is heated by an induction coil.

[0015] Furthermore, the water temperature of the water spray cooling is 25±15°C.

[0016] Furthermore, the X65 pipeline steel includes the following components in percentage by mass: C≤0.14%, Si≤0.45%, Mn≤1.60%, P≤0.020%, S≤0.002%, Cr≤0.20%, Ni≤0.30%, Cu≤0.10%, Mo≤0.15%, V≤0.08%, Nb≤0.05%, Ti≤0.04%, B≤0.0005%, Al≤0.06%, Ca≤0.006%, N≤0.012%, Sb≤0.010%, Pb≤0.005%, As≤0.015%, Sn<0.001%, Bi≤0.005%, V+Nb≤0.10%, wherein CEiiw is 0.38%-0.42%, and CEpcm is ≤0.22%. The CEiiw=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15; the CEpcm=C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B). Preferably, the X65 pipeline steel includes the following components, by mass percentage: C: 0.08%, Si: 0.25%, Mn: 1.56%, P: 0.011%, S: 0.001%, Cr: 0.05%, Ni: 0.01%, Cu: 0.01%, Mo: 0.07%, V: 0.05%, Nb: 0.02%, Ti: 0.017%, B: 0.0005%, Al: 0.033%, Ca: 0.001%, N: 0.004%, Sb: 0.003%, Pb: 0.001%, As: 0.01%, Sn: <0.001%, Bi: 0.001%, V+Nb: 0.07%, CEiiw: 0.38%, CEpcm: 0.182%.

[0017] Furthermore, the quenching temperature of the X65 pipeline steel preparation process is 930±10°C, and the tempering temperature is 660±10°C.

[0018] Furthermore, the yield strength / Rt0.5 of the X65 pipeline steel is 450Mpa-570Mpa, the tensile strength is 535Mpa-760Mpa, the elongation is ≥23%, and the yield strength ratio is ≤0.9.

[0019] Furthermore, the hardness of the X65 pipeline steel is ≤230HV10, the impact average value at -20°C is ≥54 joules and the single value is ≥40 joules.

[0020] The second aspect of the present invention provides a uniformly structured X65 induction elbow prepared by the preparation method described in the first aspect.

[0021] Beneficial effects of the present invention:

[0022] The present invention controls the bending process parameters to ensure the size and losslessness of the bent pipe product after bending; after bending, isothermal annealing is used for preheating, the temperature is raised to 930-950°C to austenitize the structure, and isothermal annealing is used to make ferrite and pearlite appear uniformly in the structure; finally, quenching + tempering is used for tempering heat treatment.

[0023] The method of the present invention greatly improves the uniformity of the microstructure of the induction bending pipe product through the synergistic effect of the bending process, preheating treatment and tempering heat treatment, thereby improving the uniformity of the mechanical properties of the induction bending pipe product. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be described clearly and completely below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] This embodiment provides a method for preparing a uniformly textured X65 induction elbow, comprising the following steps:

[0026] S1. The part of the X65 pipeline steel to be bent is heated and then bent, and then cooled by spraying water;

[0027] S2. Preheating treatment: heating to 930-950°C, keeping warm for 1-1.5h, furnace cooling to 630-650°C and keeping warm for 2-4h, then air cooling to room temperature;

[0028] S3, perform quenching and tempering heat treatment: heat up to 890-915°C, keep warm for 2-4 hours, water cool, then place in a tempering furnace and keep warm at 610±15°C, then air cool to room temperature to obtain the X65 induction bending pipe with uniform structure.

[0029] Specifically, in S3, the holding time T in the tempering furnace can be calculated according to 30 min to 60 min / 25.4 mm pipeline steel wall thickness.

[0030] Preferably, in S3, the secondary elbow is heated to 890-915°C at a heating rate of ≤260°C / h.

[0031] As a specific example, in S1, the bending temperature is 960±20°C, and the bending speed is 25±2.5 mm / min; the portion of the X65 pipeline steel to be bent is heated by an induction coil.

[0032] As a specific example, the water temperature of the water spray cooling is 25±15°C.

[0033] Preferably, the X65 pipeline steel comprises the following components, measured by mass percentage: C≤0.14%, Si≤0.45%, Mn≤1.60%, P≤0.020%, S≤0.002%, Cr≤0.20%, Ni≤0.30%, Cu≤0.10%, Mo≤0.15%, V≤0.08%, Nb≤0.05%, Ti≤0.04%, B≤0.0005%, Al≤0.06%, Ca≤0.006%, N≤0.012%, Sb≤0.010%, Pb≤0.005%, As≤0.015%, Sn<0.001%, Bi≤0.005%, V+Nb≤0.10%, wherein CEiiw 0.38%~0.42%, CEpcm≤0.22%.

[0034] Preferably, the quenching temperature in the preparation process of the X65 pipeline steel is 930±10°C, and the tempering temperature is 660±10°C.

[0035] Preferably, the yield strength / Rt0.5 of the X65 pipeline steel is 450Mpa-570Mpa, the tensile strength is 535Mpa-760Mpa, the elongation is ≥23%, and the yield strength ratio is ≤0.9.

[0036] Preferably, the hardness of the X65 pipeline steel is ≤230HV10, the average impact value at -20°C is ≥54 joules and the single value is ≥40 joules.

[0037] Another embodiment provides a uniformly textured X65 induction elbow prepared by the preparation method described in the above embodiment.

[0038] Example 1

[0039] This embodiment provides a method for preparing a uniformly textured X65 induction elbow, comprising the following steps:

[0040] S1. The part of the X65 pipeline steel to be bent is heated to 962°C by an induction coil for bending at a bending speed of 25 mm / min and cooled by spraying water at 30°C;

[0041] Among them, X65 pipeline steel includes the following components: C: 0.08%, Si: 0.25%, Mn: 1.56%, P: 0.011%, S: 0.001%, Cr: 0.05%, Ni: 0.01%, Cu: 0.01%, Mo: 0.07%, V: 0.05%, Nb: 0.02%, Ti: 0.017%, B: 0.0005%, Al: 0.033%, Ca: 0.001%, N: 0.004%, Sb: 0.003%, Pb: 0.001%, As: 0.01%, Sn: <0.001%, Bi: 0.001%, V+Nb: 0.07%, CEiiw: 0.38%, CEpcm: 0.182%;

[0042] S2, preheating treatment: heating to 950 ° C, keeping warm for 1.5 hours, furnace cooling to 650 ° C and keeping warm for 2 hours, and then air cooling to room temperature;

[0043] S3, perform quenching and tempering heat treatment: heat up to 890°C, keep warm for 2h, water cool (quench), then place in a tempering furnace and keep warm at 620°C, then air cool to room temperature, to obtain the X65 induction bending pipe with uniform structure.

[0044] Comparative Example 1

[0045] This comparative example provides a method for preparing an X65 induction elbow, comprising the following steps:

[0046] S1. The part of the X65 pipeline steel to be bent is heated to 962°C by an induction coil for bending at a bending speed of 25 mm / min and cooled by spraying water at 30°C;

[0047] Among them, X65 pipeline steel includes the following components: C: 0.08%, Si: 0.25%, Mn: 1.56%, P: 0.011%, S: 0.001%, Cr: 0.05%, Ni: 0.01%, Cu: 0.01%, Mo: 0.07%, V: 0.05%, Nb: 0.02%, Ti: 0.017%, B: 0.0005%, Al: 0.033%, Ca: 0.001%, N: 0.004%, Sb: 0.003%, Pb: 0.001%, As: 0.01%, Sn: <0.001%, Bi: 0.001%, V+Nb: 0.07%, CEiiw: 0.38%, CEpcm: 0.182%;

[0048] S2. Perform quenching and tempering heat treatment: heat up to 950°C, keep warm for 1 hour, water cool (quench), then place in a tempering furnace and keep warm at 640°C, then air cool to room temperature to obtain an X65 induction bending pipe.

[0049] According to ISO 15590-1 standard, the straight section, outer arc, inner arc, starting area and ending area of ​​the X65 induction bending pipe obtained in Example 1 and Comparative Example 1 were sampled and the mechanical properties were tested. The tensile test results are shown in Table 1, and the impact force (J) results obtained in each area of ​​the impact test are shown in Table 2.

[0050] Table 1

[0051]

[0052] It can be seen from Table 1 that the mechanical properties of different areas of the induction bending pipe prepared in Comparative Example 1 have great differences, especially in terms of yield strength and tensile strength. The difference in yield strength and tensile strength between the starting area and the outer arc area reaches 55 MPa, and the uniformity of the product is poor.

[0053] However, the difference in mechanical properties of each area of ​​the induction bending pipe prepared in Example 1 is significantly reduced, among which the yield strength difference between the starting area and the outer arc area is only 15MPa, and the tensile strength difference is only 10MPa, and they have very similar or even the same elongation, cross-sectional shrinkage and yield strength ratio; this is because in Example 1, the bent pipe is preheated by isothermal annealing, the temperature is raised to 950°C to austenitize the structure, and ferrite and pearlite are uniformly present in the structure through isothermal annealing, and finally quenching + tempering is used for tempering heat treatment. The obtained product has excellent structural uniformity and therefore has mechanical properties with small deviations.

[0054] Table 2

[0055] Group Starting area / joule Outer arc area / Joule Inner arc area / joule End Zone / Joule Example 1 ＞300 ＞300 ＞300 ＞300 Comparative Example 1 13 33 17 19

[0056] It can be seen from Table 2 that each region of the bent pipe product prepared in Example 1 of the present invention has excellent impact resistance, however, the impact resistance of each region in Comparative Example 1 is significantly different, and the impact resistance is poor, which cannot meet product requirements.

[0057] In summary, the present invention controls the bending process parameters to ensure the size and losslessness of the bent pipe product after bending; after bending, isothermal annealing is used for preheating, and the temperature is raised to 930-950°C to austenitize the structure, and isothermal annealing is used to make the structure uniformly ferrite and pearlite; finally, quenching + tempering is used for tempering heat treatment; through the synergistic effect of bending process, preheating treatment and tempering heat treatment, the uniformity of the microstructure of the induction bent pipe product is greatly improved, thereby improving the uniformity of the mechanical properties of the induction bent pipe product.

[0058] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a uniformly organized X65 induction elbow, characterized in that: The steps include: S1. The part of the X65 pipeline steel to be bent is heated and then bent, and then cooled by spraying water; S2. Preheating treatment: heating to 930-950°C, keeping warm for 1-1.5h, furnace cooling to 630-650°C and keeping warm for 2-4h, then air cooling to room temperature; S3, perform quenching and tempering heat treatment: heat up to 890-915°C, keep warm for 2-4 hours, water cool, then place in a tempering furnace and keep warm at 610±15°C, then air cool to room temperature to obtain the X65 induction bending pipe with uniform structure.

2. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: In S3, the holding time T in the tempering furnace is calculated according to 30 min to 60 min / 25.4 mm pipeline steel wall thickness.

3. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: In S1, the bending temperature is 960±20°C, and the bending speed is 25±2.5 mm / min.

4. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: In S1, the portion of the X65 pipeline steel to be bent is heated by an induction coil.

5. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: The water temperature of the water spray cooling is 25±15°C.

6. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: The X65 pipeline steel includes the following components by mass percentage: C≤0.14%, Si≤0.45%, Mn≤1.60%, P≤0.020%, S≤0.002%, Cr≤0.20%, Ni≤0.30%, Cu≤0.10%, Mo≤0.15%, V≤0.08%, Nb≤0.05%, Ti≤0.04%, B≤0.0005%, Al≤0.06%, Ca≤0.006%, N≤0.012%, Sb≤0.010%, Pb≤0.005%, As≤0.015%, Sn<0.001%, Bi≤0.005%, V+Nb≤0.10%, wherein CEiiw is 0.38%-0.42%, and CEpcm is ≤0.22%.

7. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: The quenching temperature of the X65 pipeline steel preparation process is 930±10°C, and the tempering temperature is 660±10°C.

8. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: The X65 pipeline steel has a yield strength / Rt0.5 of 450Mpa-570Mpa, a tensile strength of 535Mpa-760Mpa, an elongation of ≥23%, and a yield strength ratio of ≤0.

9.

9. The method for preparing the uniformly organized X65 induction elbow according to claim 1, characterized in that: The hardness of the X65 pipeline steel is ≤230HV10, the impact average value at -20°C is ≥54 joules and the single value is ≥40 joules.

10. An X65 induction elbow with uniform structure obtained by the preparation method according to any one of claims 1 to 9.

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