Tube product, hollow carrier of perforating gun and method of manufacturing the tube product

Abstract

The present invention relates to a tube product, namely a perforating gun hollow carrier, consisting of a steel alloy with martensitic matrix, characterized in that it has a yield strength Rp0,2 of at least 900 MPa, and that the steel alloy besides iron and impurities caused by melting has the following alloying elements: C 0.15-0.6% Si 1.4-2.6% Cr 2.0-4.0% Mn 0.15-2.0% Mo 0.2-0.6% N<0015% and at least one of the alloying elements Nb, V and Ti in sum of ≥0.01% and the tube product has been subjected to a quenching and partitioning heat treatment. Furthermore, the invention relates to a method of manufacturing such a tube product.

Claims

1. Tube product, namely a perforating gun hollow carrier, consisting of a steel alloy with martensitic matrix, characterized in that it has a yield strength Rp0,2 of at least 900 MPa, and that the steel alloy besides iron and impurities caused by melting has the following alloying elements: C 0.15-0.6% Si 1.4-2.6% Cr 2.0-4.0% Mn 0.15-2.0% Mo 0.2-0.6% N<0015% and at least one of the alloying elements Nb, V and Ti in sum of ≥0.01% and the tube product has been subjected to a quenching and partitioning heat treatment.

2. Tube product according to claim 1, characterized in that the silicon content is in the range from 1.7 to 2.4% and preferably in the range from 1.8 to 2.2.

3. Tube product according to claim 1, characterized in that the chromium content is in the range from 2.5 to 3.5% and preferably in the range from 2.7 to 3.2.

4. Tube product according to claim 1, characterized in that the manganese content is less than 1.5, in particular less than 0.7%.

5. (canceled)

6. Tube product according to claim 1, characterized in that at least one of the following alloying elements is present in the indicated amounts in the steel alloy Nb 0.001-0.1%, preferably 0.015-0.05% V 0.025-0.5% Ti 0.015 to 0.1% Al 0.01-0.1%, preferably 0.015-0.06.

7. Tube product according to claim 1, characterized in that the steel alloy has nickel in an amount of maximum 3%.

8. Tube product according to claim 1, characterized in that the steel alloy has boron in an amount in the range of 0.001-0.004%.

9. Tube product according to claim 1, characterized in that the tube product has a microstructure of martensite and austenite, wherein the portion of austenite is within the range from 5 to 20% and preferably less than 15%.

10. Tube product according to claim 9, characterized in that the amount of austenite in the microstructure, determined in 1 mm depth, measured from the tube outer surface, is more than 5%, in particular at least 10%.

11. Tube product according to claim 9, characterized in that the micro structure has bainite, ferrite and/or perlite in an overall amount of less than 10%, preferably less than 5%.

12. Tube product according to claim 1, characterized in that the tube product has an energy absorption capacity expressed by the product of tensile strength, Rm, and breaking elongation, A, (determined at a round sample with an elongation measurement length of 20 mm) of at least 18,000 MPa %.

13. Tube product according to claim 1, characterized in that the tube product has a notch impact strength of at least 4J at 20° C. (determined on a mini sample 3×4 mm).

14. Tube product according to claim 1, characterized in that the yield strength Rp0.2 is at least 1,050 MPa.

15. Method of manufacturing a tube product, namely perforating gun hollow carrier consisting of a steel alloy with martensitic matrix, characterized in that it has a yield strength Rp0,2 of at least 900 MPa, and that the steel alloy besides iron and impurities caused by melting has the following alloying elements: C 0.15-0.6% Si 1.4-2.6% Cr 2.0-4.0% Mn 0.15-2.0% Mo 0.2-0.6% N<0015% and at least one of the alloying elements Nb, V and Ti in sum of ≥0.01%, the method comprising: a quenching step and a partitioning step, wherein the quenching step has an active cooling phase and optionally a subsequent passive cooling phase.

16. Method according to claim 15, characterized in that in the active cooling phase the tube product is cooled at a cooling rate, which is higher than the critical cooling speed, to a temperature T1, which is martensite start temperature +/−100° C., and in a second, passive cooling phase is cooled at air to a temperature T2, which is preferably higher than 150° C. and lower than the martensite start temperature.

17. Method according to claim 15, characterized in that in the partitioning step the tube product is heated to and held at a temperature T3, which is higher than the martensite start temperature and preferably lower than 500° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] One embodiment of the invention is described in more detail by the following description of the figures. Therein:

[0053] FIG. 1: shows a schematic depiction of a steel tube product in one embodiment as hollow carrier of a perforating gun;

[0054] FIG. 2: shows a schematic depiction of the heat treatment according to one embodiment of the invention;

[0055] FIG. 3: shows a schematic depiction of the heat treatment according to a further embodiment of the invention; and

[0056] FIG. 4: shows a tube wall section of an inventive tube product according to two embodiments of the invention with associated diagram of the austenite content in the tube wall.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] In FIG. 1, one embodiment of the steel product 1 is schematically shown, which is a perforation gun. The perforation gun 1 comprises a tube element 10, which can also be referred to as hollow carrier. The tube element 10 preferably is a seamless tube element. In the tube element 10 locally limited sections 100 with reduced wall thickness are introduced. The locally limited areas 100 each have a circular area. The areas 100 are distributed over the length of the tube element 10. In the tube element 10 an ignition unit 18 with ignition charges is inserted. By the ignition unit 11 an explosive material of the ignition charge is ignited and thereby on one hand the areas 100 of the tube element 10 are opened and on the other hand the surrounding material, for example rock, is perforated.

[0058] In FIG. 2 it is shown that the tube product is heated in a first step to a temperature, which is higher than the Ac3 temperature of the material of the tube product. In a first quenching step, the tube product is cooled down at a high cooling rate to a temperature T1, which in the depicted embodiment lies above the martensite start temperature, Ms. Thereby, the quenching temperature can be achieved with process reliability. In a second cooling step, the tube product is cooled by passive cooling, for example by the transport of the tube product during manufacturing to a temperature T2, which is lower than the Ms temperature. In the partitioning step subsequently the tube product is heated to a temperature T3, which is higher than the Ms temperature, and is held at this temperature.

[0059] The process in FIG. 3 differs from the embodiment of FIG. 2 in that in the embodiment in FIG. 3 the quenching step only comprise an active cooling step. Therein the tube product is cooled in the active cooling phase with a cooling rate which is higher than the critical cooling speed to a temperature T1, which is between the martensite start temperature and the martensite start temperature minus 150° C. A passive cooling step is not carried out. Instead, the tube product is immediately heated from the temperature T1 to a temperature T3, which is higher than the martensite start temperature and which is preferably lower than or equal to 500° C.

[0060] FIG. 4 shows the tube wall section of an inventive tube product with two phase cooling. The corresponding diagram shows on the horizontal axis the distance D or the measuring points, respectively, measured from the tube outer side 103, and on the vertical axis the austenite portion A. In curve K1 an overall degressively increasing austenite portion A1.1 over the tube wall from the tube outer side to the tube inner side 104 and a distinct, nearly constant austenite portion A1.2 already at less than half of the tube wall thickness WD is apparent. In comparison thereto, curve K2 shows a tube product with only one active cooling. Therein, both a comparatively lower austenite portion of the tube outer side as well as a clearly flatter increase is apparent.

[0061] Since the hollow carrier consists of the novel alloy and is manufactured by a manufacturing process with Q&P heat treatment, the hollow carrier has a higher resistance against adiabatic shearing as well as a high notch impact value. The performance of the alloy can be expressed by the ability to withstand increasing explosive amounts without being destroyed.

LIST OF REFERENCE NUMBERS

[0062] 1 steel tube product [0063] 10 tube element [0064] 100 area of smaller wall thickness [0065] 103 tube outer side [0066] 104 tube inner side [0067] 11 charging unit [0068] A austenite portion [0069] D distance [0070] WD wall thickness