Manufacturing method of deep sea oil valve body corrosion resistant nickel-based 625 material surfacing inner hole

Abstract

This invention discloses a method for manufacturing an anti-corrosion nickel-based 625 material inner hole for deep-sea oil production valve bodies, comprising the following steps: S1, heat treatment of the blank; S2, shaping of the blank; S3, guide hole treatment of the blank; S4, forging the blank into a valve body blank to obtain a valve body blank with an inner hole; S5, weld overlay treatment of the inner hole wall of the valve body blank. This method for manufacturing an anti-corrosion nickel-based 625 material inner hole for deep-sea oil production valve bodies involves weld overlay on the inner surface of the valve body, giving it bimetallic properties, extending its service life while reducing production costs. Extruding a tapered guide hole onto the blank avoids extrusion deformation during the blank forming process, improving the mechanical properties and corrosion resistance of the valve body itself. The use of two-layer welding ensures the product's corrosion resistance requirements while guaranteeing welding quality.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an anti-corrosion nickel-based 625 material overlay welding inner hole for a deep-sea oil production valve body, belonging to the field of welding technology. Background Technology

[0002] Nickel-based 625 alloy has excellent corrosion resistance and is widely used in the manufacture of aero-engine parts, aerospace structural components, deep-sea oil production and chemical equipment. Deep-sea oil production valves operate in deep-sea environments, up to 3000m deep, and are subjected to erosion by ocean currents and oil and gas flows, as well as external alternating stress. The valve body of deep-sea oil production valves comes into contact with corrosive media such as mud, H2S and CO2. The working environment is harsh and complex, with high working pressure. During oil and gas extraction, the internal pressure is usually as high as 15000psi (103.488kpa) or even higher, and the working temperature is low, with a minimum of about -50℃.

[0003] Due to the special working environment requirements, it must have both corrosion resistance and crack resistance; it is usually made of stainless steel as the base material, and nickel-based 625 alloy is welded onto the inner surface of the valve body to give the valve body bimetallic properties, which extends the service life of the valve body and reduces production costs.

[0004] Production practice has revealed numerous factors contributing to substandard weld overlays in the inner bore of deep-sea oil production valve bodies. These include insufficient strength and density of the valve body itself, inadequate preheating, and untimely welding insulation or tempering. Nickel-based 625 alloys exhibit poor weld metal flowability, shallow penetration, and high susceptibility to hot cracking during inner bore weld overlays. This easily leads to defects such as porosity, incomplete penetration, and hot cracking. During inner bore weld overlays, the molten metal, lacking the constraint of the weld bevel, flows downwards, resulting in uneven weld thickness, deformation, and increased welding difficulty. The high rigidity of the deep-sea oil production valve body leads to significant heat input during inner bore surface weld overlays, easily generating welding stress. The influence of the molten metal from the stainless steel substrate on the weld layer reduces its hardness and wear resistance, rendering it unsuitable for operational requirements.

[0005] Therefore, a manufacturing method for welding the inner hole of the deep-sea oil production valve body with anti-corrosion nickel-based 625 material is needed to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for manufacturing an inner hole of a deep-sea oil production valve body with anti-corrosion nickel-based 625 material overlay welding, so as to solve the problems mentioned in the background art.

[0007] A method for manufacturing an anti-corrosion nickel-based 625 material overlay welding inner hole for a deep-sea oil production valve body includes the following steps:

[0008] S1. Heat treatment of the billet: The billet is placed in a heating furnace and heated to a temperature of 639-700℃ for a holding time of t1. The billet that has undergone one heat treatment is placed in a high-pressure torsion device and pressed downward to a height-to-diameter ratio of 0.85, with radial torsion of 360-720°, and annealed for 1-5 hours. The billet is a bar stock.

[0009] S2. Shaping the billet: Place the billet obtained in step S1 in a heating furnace for secondary heating treatment at a heating temperature of 1270℃. Place the secondary heated billet on a circular arc anvil for rounding and forging operation, with a radial deformation of 15-25%.

[0010] S3. Processing of guide holes for billet: Place the billet obtained in step S2 into a high-pressure torsion device, press it downward to a height-to-diameter ratio of 0.75, torsion radially 360-720° and extrude guide holes on the upper surface of the billet, and anneal for 1-5 hours.

[0011] S4. Forging the billet into a valve body blank: The billet obtained in step S3 is placed in a heating furnace for three heating treatments at a temperature of 639-700℃ and a holding time of t2. The billet after three heating treatments is then placed in a multi-directional forging die for punching to obtain a valve body blank with an inner hole.

[0012] S5. Welding treatment of the inner hole wall of the valve body blank: The valve body blank obtained in step S4 is placed in a heating furnace for four heating treatments. The heating temperature is 639-700℃ and the holding time is t3. As the heating furnace cools down to 360℃ and holds for 2 hours, the first layer of weld overlay is welded into the inner hole of the valve body blank. After surface treatment of the first layer of weld overlay, the valve body blank is heated to 639℃ and held for 12 hours. After the heating furnace cools down to 380℃, the second layer of weld overlay is welded. Then, it is air cooled and the inner hole is polished.

[0013] Furthermore, in step S1, t1 = a1 * D1 + b1, where D1 is the effective size of the workpiece, a1 is the heating coefficient, and b1 is the additional time. In this invention, b1 is 10-20 minutes.

[0014] Furthermore, in step S4, t2 = a2 * D2 + b2, where D2 is the effective size of the workpiece, a2 is the heating coefficient, and b2 is the additional time. In this invention, b2 is 10-20 minutes.

[0015] Furthermore, in step S5, t3 = a3 * D3 + b3, where D3 is the effective size of the workpiece, a3 is the heating coefficient, and b3 is the additional time. In this invention, b3 is 10-20 minutes.

[0016] Furthermore, in step S1, the billet is F22 stainless steel bar. Using stainless steel as the base material, the composition of F22 stainless steel bar is shown in Table 1 (standard: ASTM A182). It is an improved steel grade based on 12CrMoV steel by adding alloying elements such as Cr and Mo. It belongs to low-alloy chromium-molybdenum heat-resistant steel, equivalent to the national standard 12Cr2Mo1. F22 stainless steel bar has excellent weldability, high hardenability, and good low-temperature impact toughness, meeting the hardness, strength, and impact toughness requirements across the entire thickness of thick workpieces.

[0017] Furthermore, in step S5, a first layer of weld overlay is formed by gas-shielded welding of the inner hole of the valve body blank.

[0018] Furthermore, in step S5, the valve body blank is placed on a chuck, and a first and second overlay layer are welded into the inner hole of the valve body blank. The chuck moves in a circular motion along the center line of the inner hole of the valve body blank. The inner hole of the valve body blank, from the opening to the bottom, includes a cylindrical sidewall region a, an arc surface region b, and a bottom plane region c. When welding the cylindrical sidewall region a, the valve body blank is positioned laterally, with the cylindrical sidewall parallel to the horizontal plane. When welding the arc surface region b, the valve body blank is positioned at an angle, with the arc surface tangent to the horizontal plane. When welding the bottom plane region c, the valve body blank is positioned vertically, with the bottom plane parallel to the horizontal plane. This two-layer, region-specific welding ensures the product's corrosion resistance requirements while also guaranteeing welding quality.

[0019] Furthermore, in step S1, both ends of the bar stock are fixed inside the high-pressure torsion device by claws, and the torsion directions of the lower and upper parts of the high-pressure torsion device are opposite.

[0020] Furthermore, in step S3, the bottom of the blank is fixed to the lower part of the high-pressure torsion device by a chuck, and the upper part of the high-pressure torsion device is provided with a guide hole forming device. The upper part of the high-pressure torsion device moves downward relative to the lower part by rotation.

[0021] Furthermore, the guide hole described in step S3 is a tapered guide hole.

[0022] Furthermore, in step S5, nickel-based 625 alloy welding rods are used for welding. The nickel-based 625 alloy is deposited on the inner surface of the valve body, giving the valve body bimetallic properties, extending its service life while reducing production costs.

[0023] Beneficial Effects: The manufacturing method of the deep-sea oil production valve body using nickel-based 625 material for overlay welding of the inner hole, as described in this invention, involves overlay welding on the inner surface of the valve body, giving it bimetallic properties, extending its service life while reducing production costs. Extruding a tapered guide hole onto the blank avoids extrusion deformation during the blank forming process, improving the valve body's mechanical properties and corrosion resistance. The use of two-layer welding ensures both the product's corrosion resistance requirements and welding quality. Attached Figure Description

[0024] Figure 1 is a process flow diagram of the present invention;

[0025] Figure 2 shows the grain boundary orientation difference of F22 stainless steel matrix after torsion process and subsequent annealing at 1270° for different times; where (a) original; (b) annealed for 10 minutes; (c) annealed for 1 hour; (d) annealed for 3 hours; (e) annealed for 6 hours; (f) annealed for 12 hours;

[0026] Figure 3 is a metallographic image of the forged valve body;

[0027] Figure 4 shows the metallographic image of the second weld overlay layer;

[0028] Figure 5 shows the metallographic diagram of the first weld overlay layer and the welded part of the forged valve body. Implementation

[0029] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0030] Please see Figure 1 The present invention proposes a method for manufacturing the inner hole of a deep-sea oil production valve body using anti-corrosion nickel-based 625 material for welding, comprising the following steps:

[0031] S1. Heat treatment is performed on 100mm thick F22 stainless steel workpiece bars; the billet is placed in a heating furnace and heated to 639℃ to obtain tempered sorbite, with a holding time t=aD+b, where t is the tempering holding time (min); D is the effective size of the workpiece (mm); a is the heating coefficient (min / mm); and b is the additional time of 10-20 minutes.

[0032] t=aD+b=(1.0-1.5)×100+(10-20)=(110-170)min=(1.8-2.8)h, t takes the median value of 2h.

[0033] The billet is placed in a high-pressure torsion device and pressed downwards to a height-to-diameter ratio of 0.85, then radially torsion 360–720°, and annealed for 2 hours.

[0034] The high-temperature tempering temperature range is 639-700℃, with the median value of 670℃ being preferable. When the tempering temperature is 639℃, the "incubation period" is the shortest, maintaining optimal performance while maximizing energy efficiency.

[0035] The composition of the F22 stainless steel bar is shown in Table 1 (standard: ASTM A182). It is an improved steel grade based on 12CrMoV steel by adding alloying elements such as Cr and Mo. It belongs to low-alloy chromium-molybdenum heat-resistant steel, equivalent to the national standard 12Cr2Mo1. The F22 stainless steel bar has excellent weldability, high hardenability, and good low-temperature impact toughness, meeting the hardness, strength, and impact toughness requirements of thick workpieces throughout their full thickness.

[0036] Table 1 Chemical composition of F22 material

[0037]

[0038] Table 2 Chemical composition of F22 material (continued)

[0039]

[0040] F22 carbon equivalent: Ceq = C + Mn / 6 + (Cr + V + Mo) / 5 + (Cu + Ni) / 15 = 0.97%

[0041] As the high-pressure torsion device applies downward pressure, it applies torque to the cross-section of the billet, causing axial compression deformation and tangential torsion deformation, resulting in plastic deformation. During this process, the internal metal of the billet is squeezed and twisted inward, compacting micro-voids, looseness, and cracks, thus improving the internal density and continuity of the metal. The squeezing and torsion process makes the internal and external cast metal structures of the billet tend to be uniform, significantly improving the mechanical properties. Moreover, the squeezing and torsion process reduces the residual internal stress and eliminates stress concentration caused by internal defects, making the metal structure of the billet more uniform and dense.

[0042] S2. Shape the billet; place the billet processed in step S1 in a heating furnace for reheating at a temperature of 1270℃, and place the billet on a circular arc anvil for rolling and forging operation, with a radial deformation of 15-25%;

[0043] S3. Blank guide hole treatment: The blank treated in step S2 is placed in a high-pressure torsion device, pressed downwards to a height-to-diameter ratio of 0.75, and radially twisted 360-720° to extrude a conical guide hole on the upper surface of the blank. Annealing is then performed for 1-5 hours. This invention uses the method of extruding a conical guide hole on the blank, which can avoid the problem of extrusion deformation during the blank forming process. When the blank is extruded and twisted by the high-pressure torsion device, the density and continuity of the metal microstructure inside the blank are improved, thereby improving its mechanical properties and corrosion resistance.

[0044] like Figure 2 As shown, the high-density dislocations caused by the torsion process form numerous recrystallization nucleation sites. Due to the short 1-hour annealing time, these recrystallization nuclei only form fine austenite grains. The number of fine austenite grains initially increases with annealing time from 10 minutes to 1 hour, reaching a peak at 1 hour, thus improving the intergranular corrosion resistance of the F22 stainless steel billet. Furthermore, the deformation heat treatment forms numerous twin grain boundaries, which further contribute to improved corrosion resistance.

[0045] S4. Place the blank processed in step S3 into a heating furnace and reheat it at a heating temperature of 639-700℃ for 2 hours. Then, place the blank into a multi-directional forging die and punch it to obtain an inner cylindrical valve body blank.

[0046] S5. Forging the billet into a valve body blank: The billet processed in step S3 is placed in a heating furnace and reheated at a temperature of 639-700℃ for 2 hours. The billet is then placed in a multi-directional forging die to obtain a cylindrical valve body blank with an inner hole. Maintaining the surface temperature of the valve body blank is consistent with the core temperature, which can eliminate the thermal stress generated by heating during the welding stage and the structural stress generated by the structural transformation. The valve body blank is removed by a robotic arm and installed on a rotating chuck. A first 2.2mm weld overlay layer is welded onto the inner hole of the valve body blank using gas shielded welding. After treating the surface of the weld overlay layer, the valve body blank is heated to 639℃ and held for 12 hours. After the heating furnace cools to 380℃, a second 4.2mm weld overlay layer is welded. Subsequently, it is air-cooled, and the inner hole is ground. The first weld overlay is used to deeply fuse the weld overlay and the valve body substrate. Molten metal components from the valve body substrate will seep into the first weld overlay, which will affect the corrosion resistance of the weld overlay. The second weld overlay, fused with the first weld overlay, is not affected by the molten metal components of the valve body substrate and meets the product's corrosion resistance requirements in terms of thickness.

[0047] Depend on Figure 3-5 As shown, there are no cracks in the valve body and the weld overlay, and there are no defects such as lack of fusion or porosity in the weld overlay, all of which meet the product usage requirements.

[0048] In this embodiment, Ar gas shielded welding is performed on the inner hole of the valve body blank. Nickel-based welding rods with a diameter of 3.2 mm are used. The chuck rotates at a speed of 140 mm / min clockwise, the welding current is 250 A, the wire feed speed is 1800 mm / min, and the shielding gas flow rate is 25 L / min. The welding torch starts at a position 3° from the vertical center line of the bottom of the inner hole. As the inner hole of the valve body blank is welded, the nickel-based welding rod at the starting point is converted into liquid metal and solidifies as the chuck rotates to the horizontal position of the bottom center line. This effectively avoids the molten liquid metal flowing downwards due to the lack of welding groove constraint, which would cause uneven weld thickness and deformation.

[0049] In this embodiment, Ar gas is used for gas shielded welding in step S4, and nickel-based welding rods are used. The valve body blank is taken out by a robot and installed on a rotating chuck. The chuck rotates circumferentially along the center line of the inner hole shaft at a speed of 140 mm / min clockwise. The welding current is 200 A and 25 L / min. The welding torch starts at position 3 of the vertical center line of the bottom of the cross-section. The wire feeding speed is 1800 mm / min, and the shielding gas volume is [missing information]. The circumferential rotation speed of the chuck is proportional to the welding current.

[0050] In this embodiment, during gas-shielded welding in step S4, as the welding progresses to region a of the inner wall of the cylinder, the chuck simultaneously rotates circumferentially along the center line of the inner hole axis, causing the bottom of region a of the inner wall of the cylinder to coincide with the horizontal line. Figure 1 It can be seen that region a is the inner wall of the cylindrical valve body's inner hole. During the welding process in this region, the molten metal in the welding pool is subjected to different forces at different spatial positions, resulting in different flow rates of the molten pool. This causes changes in the thickness of the weld and the shape of the weld. When the local weld thickness is uneven, welding stress is easily generated, affecting product quality.

[0051] In this embodiment, during step S4, as the gas-shielded welding progresses along the arc b region, the chuck rotation angle changes with the welding advance angle, causing the arc b region to be tangent to the horizontal line, while simultaneously rotating circumferentially along the center line of the inner hole axis. Figure 1 It can be seen that during the welding process, the arc b region not only has the issue of the lateral height of the inner wall a region, but also involves the issue of the longitudinal angle. At this time, during the surfacing process, it is necessary to control not only the circumferential rotation of the inner hole axis centerline, but also the angle of the turntable to ensure that the welding point in the arc b region remains tangent to the horizontal line.

[0052] In this embodiment, during step S4, as the gas-shielded welding progresses through the bottom c region of the inner hole, the chuck rotation angle changes with the welding advancement angle to keep the bottom c region aligned with the horizontal line, while simultaneously rotating in a circular motion along the center line of the inner hole axis; Figure 1It can be seen that when welding is performed in the bottom c area, the chuck changes from a horizontal state to a vertical state, so that the bottom c area and the welding torch rotate horizontally and parallel.

[0053] In this embodiment, in step S1, the billet is an F22 stainless steel bar. The stainless steel bar is placed in a 200-ton, 2300 Nm high-pressure torsion device, with both ends fixed inside by jaws. The torsion directions of the lower and upper parts of the high-pressure torsion device are opposite. The high-pressure torsion device applies torque to the cross-section of the billet, causing axial compression deformation and tangential torsion deformation, resulting in plastic deformation. It should be noted that step S1 can be performed once or multiple times, depending on the size of the billet.

[0054] In this embodiment, in step S3, the bottom of the bar stock is fixed by the jaws and the lower part of the high-pressure torsion device, while the upper part of the high-pressure torsion device rotates downwards relative to the bottom. This downward rotation of the upper part of the high-pressure torsion device relative to the bottom causes the inner hole to be formed by extrusion molding, avoiding metal cracking caused by punching. Figure 1 It can be seen that the inner hole becomes larger during the stamping process of the bar stock, and is used as the inner hole of the valve body. The excess part at the lower end of the inner hole is used to facilitate chuck fixation during welding. After the inner hole is welded, the excess part is cut off.

Claims

1. A method for manufacturing a deep-sea oil extraction valve body corrosion-resistant nickel-based 625 material surfacing inner hole, characterized in that, It comprises the following steps: S1, heating treatment of the blank: the blank is placed in a heating furnace for heating, the heating temperature is 639-700℃, the holding time is t1, the once heated blank is placed in a high-pressure torsion device to be pressed to a high-diameter ratio of 0.85, radially twisted by 360-720°, and annealed for 1-5h, the blank is a bar; S2, shaping treatment of the blank: the blank obtained in step S1 is placed in a heating furnace for secondary heating treatment, the heating temperature is 1270℃, the twice heated blank is placed on a circular arc anvil for round-punching forging operation, the radial deformation is 15-25%; S3, blank guide hole treatment: the blank obtained in step S2 is put into a high-pressure torsion device, pressed to a high-diameter ratio of 0.75, radially twisted by 360-720° and extruded to guide holes on the upper surface of the blank, and annealed for 1-5h; S4, blank forging into valve body blank treatment: the blank obtained in step S3 is put into a heating furnace for thrice heating treatment, the heating temperature is 639-700℃, the holding time is t2, the thrice heated blank is put into a multi-directional die forging for die punching to obtain a valve body blank with an inner hole; S5, valve body blank inner hole wall surfacing treatment: the valve body blank obtained in step S4 is put into a heating furnace for four times heating treatment, the heating temperature is 639-700℃, the holding time is t3, the first layer of surfacing layer is welded on the inner hole of the valve body blank as the heating furnace cools to 360℃ and is held for 2h, after the surface treatment of the first layer of surfacing layer, the valve body blank is heated to 639℃ and held for 12h, the second layer of surfacing layer is welded as the heating furnace cools to 380℃, and then air-cooled, the inner hole is polished.

2. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. In step S1, t1=a1*D1+b1, D1 is the effective size of the workpiece, a1 is the heating coefficient, and b1 is the additional time.

3. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. In step S4, t2=a2*D2+b2, D2 is the effective size of the workpiece, a2 is the heating coefficient, and b2 is the additional time.

4. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. In step S5, t3=a3*D3+b3, D3 is the effective size of the workpiece, a3 is the heating coefficient, and b3 is the additional time.

5. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. In step S1, the blank is F22 stainless steel bar.

6. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. In step S5, the first layer of surfacing layer is welded on the inner hole of the valve body blank by gas shielded welding.

7. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. In step S5, the valve body blank is set on a chuck to weld the first layer of surfacing layer and the second layer of surfacing layer on the inner hole of the valve body blank, the chuck makes circumferential motion along the axial center line of the inner hole of the valve body blank, the inner hole of the valve body blank sequentially comprises a cylindrical side wall a region, a circular arc surface b region and a bottom plane c region from the opening to the bottom, when welding the cylindrical side wall a region, the valve body blank is transversely arranged, the cylindrical side wall is parallel to the horizontal plane; when welding the circular arc surface b region, the valve body blank is obliquely arranged, the circular arc surface is tangent to the horizontal plane; when welding the bottom plane c region, the valve body blank is vertically arranged, the bottom plane is parallel to the horizontal plane.

8. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. In step S1, the two ends of the bar are fixed in the high-pressure torsion device by clamping jaws, and the twisting directions of the lower part and the upper part of the high-pressure torsion device are opposite.

9. The method of claim 1, wherein the nickel-based 625 material is a corrosion resistant nickel-based 625 material. The bottom of the blank in step S3 is fixed by a jaw under the high-pressure twisting device, and the upper part of the high-pressure twisting device is provided with a guide hole forming device, and the upper part of the high-pressure twisting device is moved downward by rotating relative to the lower part.

10. The manufacturing method of the inner hole of the deep-sea oil production valve body with anti-corrosion nickel-based 625 material overlay welding as described in claim 1, characterized in that, In step S5, the welding adopts a nickel-based 625 alloy welding rod.

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