High-strength hydrogen sulfide stress corrosion resistant four-way valve body and manufacturing method thereof

Abstract

The invention provides a high-strength hydrogen sulfide stress corrosion resistant four-way valve body and a manufacturing method thereof, and relates to the field of alloy steel, the four-way valve body is prepared by respectively boring geometric center lines in the length direction and the height direction before hardening and tempering of a solid valve body; steel used by the solid valve body comprises the following elements in percentage by mass: 0.26%-0.33% of C, 0.15%-0.35% of Si, 0.4%-0.9% of Mn, less than or equal to 0.008% of P, less than or equal to 0.004% of S, 1.4%-2.0% of Cr, less than or equal to 0.3% of Ni, 0.6%-1.2% of Mo, less than or equal to 0.3% of Cu, 0.015%-0.035% of Al and the balance of Fe and inevitable impurity elements. According to the four-way valve body produced through the manufacturing method, the yield strength Rp0.2 is larger than or equal to 90 KSI at the same time, and when a hydrogen sulfide stress corrosion resistance test is carried out, when the pre-stress is 80% of the yield strength, the valve body does not break after the test time is longer than 720 hours.

Description

Technical Field

[0001] The present invention relates to the field of alloy steel, and in particular to a high-strength hydrogen sulfide stress corrosion-resistant four-way valve body and a manufacturing method thereof. Background Art

[0002] With the gradual reduction of easily exploitable oil and gas fields, more and more oil and gas wells containing hydrogen sulfide are being developed. At the same time, with the increasing output of oil and gas wells, the requirements for the quenched and tempered steel used in the four-way valve body used in wellhead four-way valves are also becoming higher and higher. It is necessary to meet both high strength (yield strength Rp0.2 meets ≥90KSI) and resistance to hydrogen sulfide stress corrosion (tested according to NACE TM0177 standard). Traditional valve bodies can only meet the use requirements of yield strength below 85KSI. In addition, the cooling effect of the center part of the traditional solid valve body during quenching is poor, and the microstructure cannot be fully converted into martensite, which cannot meet the high strength and hydrogen sulfide stress corrosion resistance requirements.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The object of the present invention is to provide a high-strength hydrogen sulfide stress corrosion-resistant four-way valve body and a manufacturing method thereof to meet the requirements of oil and gas well exploitation. The four-way valve body produced by this method also meets the yield strength Rp0.2≥90KSI, and when undergoing corrosion testing, when the prestress is 80% of the yield strength, the valve body does not break for a test time of >720 hours.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A first aspect of the present invention provides a high-strength hydrogen sulfide stress corrosion resistant four-way valve body, wherein the four-way valve body is prepared by boring the geometric center line of the tempering front length and height direction of a solid valve body respectively;

[0007] The steel used for the solid valve body contains the following elements by mass percentage: C: 0.26%-0.33%, Si: 0.15%-0.35%, Mn: 0.4%-0.9%, P≤0.008%, S≤0.004%, Cr: 1.4%-2.0%, Ni≤0.3%, Mo: 0.6%-1.2%, Cu≤0.3%, Al: 0.015%-0.035%, and the remainder is Fe and unavoidable impurity elements.

[0008] Furthermore, the dimensions of the solid valve body are: 500mm-1500mm in length, 350mm-700mm in width, and 350mm-700mm in height; the boring diameter along the geometric center line in the length direction is 60mm-200mm, and the boring diameter along the geometric center line in the height direction is 120mm-250mm.

[0009] Furthermore, samples are taken from the intersection of 1 / 2 of the wall thickness in the width direction and 1 / 2 of the wall thickness in the height direction of the valve body for testing, and the yield strength Rp0.2 is ≥90KSI, and the longitudinal impact energy at 21°C is ≥100J.

[0010] Furthermore, a hydrogen sulfide stress corrosion resistance test was performed on the valve body. When the prestress was 80% of the yield strength, the valve body did not break when the test time was greater than 720 hours.

[0011] The second aspect of the present invention provides a method for manufacturing the high-strength hydrogen sulfide stress corrosion resistant four-way valve body described in the first aspect, comprising the following steps: electric furnace or converter smelting, LF refining, RH vacuum degassing, continuous casting or die casting, forging into a solid valve body blank, milling, ultrasonic flaw detection, boring, normalizing, austenitizing, quenching, tempering, testing, milling, ultrasonic flaw detection, and precision turning into a valve body of a wellhead four-way valve; wherein,

[0012] The normalizing comprises: performing normalizing pretreatment on the valve body blank after the boring, the normalizing temperature is 870° C.-930° C., and the temperature is kept for 4-6 hours.

[0013] Furthermore, after the RH vacuum degassing, calcium silicon wire is fed to perform inclusion denaturation treatment;

[0014] And / or, the mold casting process adopts argon protection casting;

[0015] And / or, the forging into a solid valve body blank includes placing the blank obtained by continuous casting or die casting into a heating furnace for heating and insulation, the insulation temperature is 1210℃-1230℃, and forging it into a solid valve body blank after taking it out of the heating furnace, the forging temperature is 950℃-1200℃, and after forging, the solid valve body blank is annealed to relieve stress, the annealing temperature is 650℃-690℃.

[0016] Furthermore, the milling is performed on all six surfaces of the solid valve body blank.

[0017] Furthermore, the austenitization holding temperature is 860° C.-900° C., and the holding time is 5-7 hours.

[0018] Furthermore, the quenching is performed by using a PAG polymer quenching liquid to quench and cool the valve body blank after boring.

[0019] Furthermore, the tempering holding temperature is 630° C.-690° C., and the holding time is 8-10 hours.

[0020] The technical solution provided by the present invention has the following beneficial effects:

[0021] (1) The solid valve body is bored along the length and height of the tempering front. The core of the valve body can be in contact with the flowing quenching liquid during the quenching process, so that the core structure can be fully transformed into martensite.

[0022] (2) After boring, the valve body is pre-treated by normalizing to make the structure more uniform and fine, and improve the mechanical properties of the material.

[0023] (3) PAG polymer quenching liquid is used in the quenching process, which effectively prevents the four-way valve body from cracking during the quenching process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a three-dimensional view of the four-way valve body provided by the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The process parameters for which specific conditions are not specified in the following examples are generally in accordance with conventional conditions.

[0027] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0028] According to a first aspect of the present invention, the present invention provides a high-strength hydrogen sulfide stress corrosion resistant four-way valve body, wherein the four-way valve body is prepared by boring the geometric center line of the tempering front length and height direction of a solid valve body respectively;

[0029] The steel used for the solid valve body contains the following elements by mass percentage: C: 0.26%-0.33%, Si: 0.15%-0.35%, Mn: 0.4%-0.9%, P≤0.008%, S≤0.004%, Cr: 1.4%-2.0%, Ni≤0.3%, Mo: 0.6%-1.2%, Cu≤0.3%, Al: 0.015%-0.035%, and the remainder is Fe and unavoidable impurity elements.

[0030] The present invention bores the geometric center line of the length and height directions of the solid valve body in the tempering front respectively so that the core can contact the flowing quenching liquid during the quenching process, so that the core structure can be fully transformed into martensite.

[0031] The steel used in this invention is designed with unique chemical composition, and the functions of each component are as follows:

[0032] C: Improve the hardenability of the material. Too high a value will reduce the impact toughness of the material and reduce the resistance to hydrogen sulfide stress corrosion.

[0033] Mn: Enhances the hardenability of the material. Too high a value will reduce the plasticity and impact toughness of the material and increase the degree of segregation of the material.

[0034] P: The lower the content, the better, because it will cause a significant decrease in plasticity and impact toughness.

[0035] S: The lower the content, the better, because it reduces the ductility and toughness of steel and causes cracks during forging and rolling; sulfur reduces corrosion resistance.

[0036] Cr: An appropriate content of Cr can increase the hardenability of steel, so that the steel has better comprehensive mechanical properties after quenching and tempering; and improve the corrosion resistance of the material.

[0037] Mo: Appropriate content of molybdenum in steel can improve hardenability and thermal strength, prevent temper brittleness, and improve corrosion resistance.

[0038] Al: Aluminum is added to steel as a deoxidizer or alloying element. Its primary role in steel is to refine grains and fix nitrogen, significantly improving the steel's impact toughness and reducing its tendency to cold brittleness and aging. However, its content should not be too high.

[0039] As an optional embodiment of the high-strength hydrogen sulfide stress corrosion resistant four-way valve body of the present invention, the dimensions of the solid valve body are: length 500mm-1500mm (for example, 600mm, 800mm, 1000mm, 1200mm, 1400mm), width 350mm-700mm (for example, 360mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm), height 350mm-700mm (for example, 360mm m, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm); the boring diameter along the geometric center line in the length direction is 60mm-200mm (for example, 100mm, 120mm, 140mm, 160mm, 180mm), and the boring diameter along the geometric center line in the height direction is 120mm-250mm (for example, 140mm, 160mm, 180mm, 200mm, 220mm, 240mm).

[0040] As an optional implementation of the high-strength hydrogen sulfide stress corrosion-resistant four-way valve body of the present invention, samples are taken at the intersection of 1 / 2 of the wall thickness in the width direction and 1 / 2 of the wall thickness in the height direction of the valve body for testing, and its yield strength Rp0.2 is ≥90KSI, and the longitudinal impact energy at 21°C is ≥100J.

[0041] As an optional embodiment of the high-strength hydrogen sulfide stress corrosion resistant four-way valve body of the present invention, a hydrogen sulfide stress corrosion resistance test was performed on the full size of the valve body. When the prestress was 80% of the yield strength, the valve body did not break when the test time was greater than 720 hours.

[0042] According to a second aspect of the present invention, a method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body is provided, comprising the following steps: smelting in an electric furnace or converter, LF refining, RH vacuum degassing, continuous casting or die casting, forging into a solid valve body blank, milling, ultrasonic flaw detection, boring, normalizing, austenitizing, quenching, tempering, testing, milling, ultrasonic flaw detection, and precision turning into a valve body of a wellhead four-way valve; wherein,

[0043] The normalizing includes: performing normalizing pretreatment on the valve body blank after boring, the normalizing temperature is 870℃-930℃ (such as 880℃, 890℃, 900℃, 910℃, 920℃), and keeping the temperature for 4-6 hours (such as 5 hours).

[0044] In the manufacturing method of the present invention, the valve body is bored before heat treatment to ensure that the core structure of the valve body can be fully transformed into martensite during the quenching process, and uniform tempered troostite is formed after tempering, ensuring that the mechanical properties and hydrogen sulfide stress corrosion resistance meet the standard requirements.

[0045] Normalizing pretreatment is used to make the microstructure more uniform and fine, improving the mechanical properties of the material. The normalizing holding temperature should not exceed the range of 870℃-930℃, otherwise it will not only fail to improve the performance, but will actually reduce it. If the normalizing temperature is too high, the grains will become coarse at high temperatures; if the temperature is too low, the microstructure will not be fully austenitized and the grains will not be fully refined.

[0046] As an optional embodiment of the method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body of the present invention, calcium silicon wire is fed into the RH vacuum degassing to perform inclusion denaturation treatment;

[0047] And / or, the mold casting process adopts argon protection casting;

[0048] And / or, the forging into a solid valve body blank includes placing the billet obtained by continuous casting or die casting into a heating furnace for heating and insulation, the insulation temperature is 1210℃-1230℃ (for example, 1215℃, 1220℃, 1225℃), and forging it into a solid valve body blank after taking it out of the heating furnace, the forging temperature is 950℃-1200℃ (for example, 960℃, 970℃, 980℃, 990℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, 1700℃, 1800℃, 1900℃), and after forging, the solid valve body blank is annealed to relieve stress, the annealing temperature is 650℃-690℃ (for example, 670℃).

[0049] As an optional implementation of the method for manufacturing a high-strength hydrogen sulfide stress corrosion-resistant four-way valve body of the present invention, the milling is performed on all six surfaces of the solid valve body blank.

[0050] As an optional embodiment of the method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body of the present invention, the austenitizing temperature is 860°C-900°C (such as 880°C) and the insulation time is 5-7 hours (such as 6 hours).

[0051] As an optional implementation of the method for manufacturing a high-strength hydrogen sulfide stress corrosion-resistant four-way valve body of the present invention, the quenching is to use PAG polymer quenching liquid to quench and cool the solid valve body blank after boring.

[0052] The quenching process of the present invention adopts PAG polymer quenching liquid for quenching, which can effectively prevent the problem of cracking of the four-way valve body during the quenching process.

[0053] As an optional embodiment of the method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body of the present invention, the tempering temperature is 630°C-690°C (for example, 660°C) and the insulation time is 8-10 hours (for example, 9 hours).

[0054] The process not described in detail in the present invention is a conventional process in the art.

[0055] The present invention will be further described in detail below with reference to specific examples and comparative examples.

[0056] Example

[0057] The steel used for the solid valve body in this embodiment contains, by mass percentage, the following: C: 0.32%, Si: 0.30%, Mn: 0.8%, P: 0.007%, S: 0.004%, Cr: 1.6%, Ni: 0.05%, Mo: 1.0%, Cu: 0.04%, Al: 0.020%, and the remainder is Fe and unavoidable impurity elements.

[0058] The dimensions of the four-way valve body are as follows: length 1200mm, width 500mm, height 500mm, the diameter of the through hole along the geometric center line in the length direction is 160mm, and the diameter of the through hole along the geometric center line in the height direction is 200mm.

[0059] The manufacturing process of the four-way valve body is as follows: electric furnace smelting, LF refining, RH vacuum degassing, die casting, forging into valve body, milling, ultrasonic testing, boring, normalizing, austenitizing, quenching and cooling, tempering, testing, milling, ultrasonic testing, and valve body precision turning into the valve body of the wellhead four-way valve.

[0060] The specific manufacturing process of the four-way valve body is as follows: the smelting raw materials required to prepare the chemical composition steel materials mentioned above are sequentially subjected to electric furnace smelting, LF furnace refining, RH vacuum degassing to remove harmful gases oxygen and hydrogen, and silicon calcium wire is fed after RH refining to perform inclusion modification treatment. The die casting process adopts argon protection casting. After annealing, the steel ingot is sent to the forging workshop heating furnace to be heated to 1210℃~1230℃. After keeping warm for 2 hours, it is taken out of the furnace and forged into a solid valve body blank (length × width × height is 1200mm×500mm×500mm). The forging temperature is between 950℃~1200℃. After forging, the valve body blank is annealed to relieve stress at an annealing temperature of 670℃ and kept warm for 26 hours. Then the 6 faces of the valve body blank are milled, followed by ultrasonic flaw detection. After passing the flaw detection, it is pressed Figure 1 Boring is performed in the length and height directions shown. The diameter of the bore in the length direction is The diameter of the hole in the height direction is The bored valve body blank is then normalized at 900°C for 5 hours. It is then austenitized at 880°C for 6 hours before being removed from the furnace and quenched in PAG coolant (Dejieli). Finally, it is tempered at 660°C for 9 hours. After tempering, samples are taken at the 1 / 2T (wall thickness) intersection, where 1 / 2 the width and 1 / 2 the height meet, to test mechanical properties and hydrogen sulfide stress corrosion resistance.

[0061] Comparative Example 1

[0062] The only difference between the comparative example and the embodiment is that the solid valve body is directly heat treated, that is, the boring is arranged after the tempering process and before the detection.

[0063] Comparative Example 2

[0064] The only difference between the comparative example and the embodiment is that no normalizing heat treatment is performed before quenching in the manufacturing process of the four-way valve body.

[0065] Comparative Example 3

[0066] The only difference between the comparative example and the embodiment is that the quenching liquid for the four-way valve body is water quenching instead of PAG quenching liquid.

[0067] Result: The valve body cracked during the quenching process and the mechanical properties were not tested.

[0068] Comparative Example 4

[0069] The steel used in the four-way valve body contains the following elements by mass: C: 0.35%, Si: 0.25%, Mn: 1.0%, P: 0.012%, S: 0.005%, Cr: 1.3%, Ni: 0.10%, Mo: 0.5%, Cu: 0.08%, Al: 0.025%, with the remainder being Fe and unavoidable impurities. This comparative example differs from the example in chemical composition, but the remaining processes are identical.

[0070] Performance Testing

[0071] Test methods for yield strength, tensile strength, elongation, and shrinkage: ASTM E8;

[0072] 21℃ longitudinal impact energy test method: ASTM E23;

[0073] Impact specimen hardness test method: ASTM E18;

[0074] Testing methods for hydrogen sulfide stress corrosion resistance: NACE TM0177 Method A, API Spec5CT "Casing and Tubing".

[0075] Performance data

[0076]

[0077] Note: The specifications for the embodiment are: length × width × height: 1200mm × 500mm × 500mm, with a bore diameter of 160mm in the longitudinal direction and a bore diameter of 200mm in the height direction. For Comparative Example 1, the dimensions for the solid valve body are 1200mm × 500mm × 500mm, with no bore being bored and the valve body being directly normalized and tempered. For Comparative Example 2, the dimensions for the solid valve body are 1200mm × 500mm × 500mm, with a bore diameter of 160mm in the longitudinal direction and a bore diameter of 200mm in the height direction, with no normalizing and the valve body being directly tempered (tempering includes austenitizing heating, quenching, and tempering). The valve body dimensions for Comparative Examples 3 and 4 are the same as those for the embodiment.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength hydrogen sulfide stress corrosion resistant four-way valve body, characterized in that: The four-way valve body is prepared by boring the geometric center line of the length and height direction of the tempering front of the solid valve body respectively; The steel used for the solid valve body contains the following elements by mass percentage: C: 0.26%-0.33%, Si: 0.15%-0.35%, Mn: 0.4%-0.9%, P≤0.008%, S≤0.004%, Cr: 1.4%-2.0%, Ni≤0.3%, Mo: 0.6%-1.2%, Cu≤0.3%, Al: 0.015%-0.035%, and the remainder is Fe and unavoidable impurity elements.

2. The high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 1, characterized in that: The dimensions of the solid valve body are: 500mm-1500mm in length, 350mm-700mm in width, and 350mm-700mm in height; the boring diameter along the geometric center line in the length direction is 60mm-200mm, and the boring diameter along the geometric center line in the height direction is 120mm-250mm.

3. The high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 1, characterized in that: Samples are taken from the intersection of 1 / 2 of the wall thickness in the width direction and 1 / 2 of the wall thickness in the height direction of the valve body for testing, and the yield strength Rp0.2 is ≥90KSI, and the longitudinal impact energy at 21°C is ≥100J.

4. The high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 1, characterized in that: The valve body is subjected to a hydrogen sulfide stress corrosion resistance test. When the prestress is 80% of the yield strength, the valve body does not break when the test time is greater than 720 hours.

5. A method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to any one of claims 1 to 4, characterized in that: The following steps are involved: Electric furnace or converter smelting, LF refining, RH vacuum degassing, continuous casting or die casting, forging into solid valve body blank, milling, ultrasonic flaw detection, boring, normalizing, austenitizing, quenching, tempering, testing, milling, ultrasonic flaw detection, and precision turning into the valve body of the wellhead four-way valve; among which, The normalizing comprises: performing normalizing pretreatment on the valve body blank after the boring, the normalizing temperature is 870° C.-930° C., and the temperature is kept for 4-6 hours.

6. The method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 5, characterized in that: After the RH vacuum degassing, calcium silicon wire is fed to perform inclusion denaturation treatment; And / or, the mold casting process adopts argon protection casting; And / or, the forging into a solid valve body blank includes placing the blank obtained by continuous casting or die casting into a heating furnace for heating and insulation, the insulation temperature is 1210℃-1230℃, and forging it into a solid valve body blank after taking it out of the heating furnace, the forging temperature is 950℃-1200℃, and after forging, the solid valve body blank is annealed to relieve stress, the annealing temperature is 650℃-690℃.

7. The method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 5, characterized in that: The milling is performed on all six surfaces of the solid valve body blank.

8. The method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 5, characterized in that: The austenitization holding temperature is 860° C.-900° C., and the holding time is 5-7 hours.

9. The method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 5, characterized in that: The quenching is to use PAG polymer quenching liquid to quench and cool the valve body blank after boring.

10. The method for manufacturing a high-strength hydrogen sulfide stress corrosion resistant four-way valve body according to claim 5, characterized in that: The holding temperature of the tempering is 630° C.-690° C., and the holding time is 8-10 hours.

Images