Production and manufacturing process of Inconel 625 square throttle valve forge piece for deep sea oil and gas exploitation

Abstract

The invention relates to the technical field of manufacturing of square throttle valve forgings, in particular to a production and manufacturing process of Inconel 625 square throttle valve forgings for deep sea oil and gas exploitation, which comprises the following steps: firstly, selecting proper raw materials according to an alloy formula of the square throttle valve forgings, smelting the raw materials into an electroslag ingot through a smelting process, and then treating the surface of the electroslag ingot, oxide skin and defects are removed; secondly, the step forging process is innovated, through the collaborative design of three-heating-number cogging forging and two-heating-number cutting forging and the combination of the large reduction rate and multidirectional deformation of the first pass, the strain penetration depth of the thick section is remarkably increased, compared with a traditional process, the effective strain cumulant is greatly increased, the problem that deformation at the corners of the square valve is not uniform is thoroughly solved, and the yield of the square valve is improved. And a narrow temperature area is accurately controlled, the finish forging temperature is monitored in real time by adopting an infrared thermometer, and a forgeable temperature window is stably controlled within the range of 170-200 DEG C in cooperation with die preheating and graphite lubrication, so that the risk of microcracks caused by the finish forging temperature less than 950 DEG C is avoided.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of square throttle valve forging manufacturing, in particular to a production and manufacturing process of an Inconel 625 square throttle valve forging for deep-sea oil and gas exploitation. BACKGROUND

[0002] With the continuous increase of deep-sea oil exploitation proportion, the service challenge of valves in low-temperature, high-pressure, high-Cl-corrosion and stress corrosion environment is increasingly severe. The traditional austenitic stainless steel (such as F304, F316L) cannot meet the strict requirements of deep-sea valve erosion resistance, thermal cycle resistance and zero leakage due to insufficient high-temperature strength and limited stress corrosion resistance. Under this background, nickel-based alloy has become a key alternative material due to its excellent comprehensive performance.

[0003] Inconel 625, as a solid solution strengthened nickel-based corrosion-resistant alloy, has excellent tensile / fatigue strength, Cl-stress corrosion resistance and oxidation resistance in the temperature range of 0-600 DEG C due to the Mo-Nb composite strengthening mechanism, and has become the core material of deep-sea drilling and production valves. However, the alloy faces significant process bottlenecks in large forging manufacturing:

[0004] Forging process limitation: narrow forgeable temperature window (only about 200 DEG C), high temperature deformation resistance leading to poor forgeability. The traditional forging process has insufficient forging ratio (Y≤6.0), and it is difficult to realize uniform plastic deformation of thick section (>350mm) forgings.

[0005] Organization control problem: insufficient effective strain accumulation in multi-pass deformation, causing abnormal grain coarsening (ASTM 0-2 level), necklace-shaped discontinuous grain boundaries and unrecrystallized regions, directly leading to room temperature strength fluctuation and substandard low-temperature impact toughness.

[0006] Defect risk increases: when the final forging temperature fluctuates by more than 20 DEG C, micro-cracks are easily produced at the corners of the square bar due to strain hardening; the current non-destructive testing standard (ASTM E388) has insufficient detection sensitivity for internal defects of thick-walled parts.

[0007] Although the typical representative of the prior art (such as CN201911405556.8) improves the sulfur resistance by optimizing the F22 steel forging ratio (Y>6) and heat treatment process (normalizing + quenching + tempering), its technical solution has fundamental defects:

[0008] The process parameters are not adapted to the characteristics of Inconel 625, lacking key controls such as upsetting height-diameter ratio (H / D≤0.65), strain rate (0.1-1s -1 ) and so on;

[0009] The temperature control precision (more than ±10 DEG C) is insufficient to suppress delta phase precipitation and grain boundary segregation;

[0010] The lack of raw material purity specification (oxygen content > 30ppm, macrosegregation index > 1.0) aggravates the risk of uneven composition of thick-walled parts.

[0011] Therefore, it is urgent to develop a special manufacturing process for Inconel 625 thick-walled square ring forgings to fundamentally solve the core problems of forging penetration, microstructure uniformity and defect control. SUMMARY

[0012] The purpose of the present application is to provide a production and manufacturing process for Inconel 625 square throttle valve forgings for deep-sea oil and gas development, to solve the above-mentioned deficiencies in the prior art.

[0013] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0014] A production and manufacturing process for Inconel 625 square throttle valve forgings for deep-sea oil and gas development, comprising the following steps:

[0015] Step S1. Material selection and pretreatment: selecting appropriate raw materials according to the alloy formula of square throttle valve forgings, and melting the raw materials into electroslag ingots by melting process, and then treating the surface of the electroslag ingot to remove the oxide scale and defects;

[0016] It should be noted that the composition of the raw material is as follows:

[0017] C≤0.02%、Si≤0.30%、Mn≤0.10%、P≤0.015%、S≤0.015%、Cr:21.00-23.50%、Mo:8.5-10.0%、Fe≤3.0%、Ti≤0.40%、Al≤0.40%、Nb+Ta:3.35-4.05%、Ni≥60.00%;

[0018] The vacuum arc furnace (VAM) + vacuum consumable remelting (VAR) + electroslag remelting (ESR) three-in-one smelting process is used during melting in step S1, and the vacuum degree of the vacuum arc furnace smelting of the three-in-one smelting process is ≤0.1Pa, the slag system of the electroslag remelting is CaF2-Al2O3-CaO (mass ratio 60:30:10), and the melting speed is controlled at 3-5kg / min.

[0019] The macrosegregation index of the ingot is ≤1.0, and the oxygen content is ≤30ppm.

[0020] Step S2. Homogenization treatment: the electroslag ingot is heated to 850℃ at a gradient and kept for ≥4 hours, and then heated to 1180±10℃ and kept for 30-80 hours, so as to eliminate the as-cast dendritic segregation, dissolve the Laves phase and coarse MC carbide, and improve the uniformity of the Nb element distribution of the electroslag ingot;

[0021] It should be noted that the heating rate of homogenization treatment is ≤50℃ / h, and the cooling is furnace cooling to 600℃ and then air cooling.

[0022] Step S3. Upsetting forging: using step heating (300℃-850℃-1170±10℃), holding for ≥5 hours before forging, controlling the open forging temperature ≥1170℃, the final forging temperature ≥1000℃, the total forging ratio >8:1, the first pass reduction >40%; completing in three fires:

[0023] First fire: upsetting - elongation - back to furnace and holding for >3 hours;

[0024] Second fire: upsetting - elongation - furnace temperature drop 20℃ and holding for >2 hours;

[0025] Third fire: upsetting - elongation - air cooling;

[0026] It should be noted that the first pass reduction uses hydraulic machine single deformation ≥45%, and the upsetting height to diameter ratio is controlled at 0.6-0.8;

[0027] The upsetting ratio of each fire is >1.4, and the elongation forging ratio is >1.3;

[0028] The final forging temperature is monitored in real time, not less than 950℃.

[0029] Step S4. Cutting forging: cutting the open upsetting material and gradient heating to 1150±10℃ and holding for ≥4 hours, forging in two fires:

[0030] First fire: elongation - upsetting - back to furnace and holding for ≥3 hours;

[0031] Second fire: elongation - upsetting to target size - air cooling;

[0032] It should be noted that the forging needs to be preheated at 850℃ for ≥2h before forging;

[0033] The final forging temperature is monitored in real time by an infrared temperature measuring instrument, the corner chamfer radius is ≥8mm to avoid stress concentration.

[0034] Step S5. Heat treatment: solution treatment temperature is 970±5℃ and holding for 1 hour, water cooling to room temperature;

[0035] It should be noted that preheating at 650℃ for 1h is needed before reaching the solution temperature;

[0036] The water quenching transfer time of solution treatment is ≤15 seconds, the water temperature is controlled at 20-30℃, and the surface hardness after quenching is ≤300HBW;

[0037] The external thermocouple monitors the surface temperature of the forged piece during solution treatment, and the temperature deviation is controlled within ±5℃.

[0038] Step S6. Rough machining: dry treatment is performed on the room temperature forging, and after the drying is completed, the forging is placed into a machining device, and rough machining is performed according to the drawing;

[0039] It should be noted that the wall thickness of the machined forging is greater than or equal to 350 mm.

[0040] The rough machining allowance is 3-5 mm, and the surface roughness Ra is less than or equal to 6.3 microns.

[0041] Step S7. Non-destructive testing: non-destructive testing is performed on the forging after machining by a detection device, and the forging is sampled, and then tensile, impact, hardness and metallographic structure are tested.

[0042] It should be noted that the non-destructive testing selects ultrasonic testing (UT) and penetration testing (PT), and the ultrasonic testing uses a longitudinal wave straight probe (frequency 2.5 MHz), the sensitivity is Phi 2 mm flat bottom hole, and the penetration testing needs to meet the ASTM E165 standard.

[0043] Further, in steps S3 and S4, the preheating temperature of the forging die is greater than or equal to 300 DEG C, the die material is H13 steel, and the surface is sprayed with a graphite-based lubricant.

[0044] In the above technical solution, the production and manufacturing process of the Inconel 625 square throttle valve forging for deep sea oil and gas development provided by the application has the following beneficial effects:

[0045] (1) The step forging process is innovative, through the collaborative design of three times of blooming forging and two times of cutting forging, combined with a large reduction rate of the first pass and multi-directional deformation, the strain penetration depth of the thick section is significantly improved, the effective strain accumulation is greatly improved compared with the traditional process, the uneven deformation problem at the corner of the square valve is completely solved, and the temperature window is accurately controlled in a narrow temperature range, the final forging temperature is monitored in real time by an infrared temperature measuring instrument, the die is preheated and graphite lubrication is used, the forgeable temperature window is stably controlled in the interval of 170-200 DEG C, and the risk of micro-cracks caused by the final forging temperature being less than 950 DEG C is avoided.

[0046] (2) The gradient heat treatment process is adopted, the original coarse precipitated phase is fully dissolved, the element segregation degree is significantly reduced, the uniform composition condition is created for subsequent dynamic recrystallization, the recrystallization organization proportion and grain refinement degree are all improved to a more optimal level through the synergistic effect of the forging deformation parameter and the step-by-step tempering process, and the brittle phase is effectively inhibited by combining the precise solid solution treatment and the rapid cooling process, so that the material maintains high toughness while the mechanical property index is significantly improved.

[0047] (3) The process system of the application makes breakthroughs in the key performance indicators of material consistency at room temperature, low-temperature impact toughness, etc., and the grain structure uniformity is qualitatively improved compared with the conventional process, which provides a guarantee for the reliability of parts under complex working conditions.

[0048] (4) The application controls the temperature and deformation amount in the forging deformation process, and the actual temperature and time of the product in the heat treatment process, to ensure that the Inconel 625 nickel-based alloy choke valve forgings with a wall thickness of ≥350 mm have uniform metallographic structure and excellent mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0050] Figure 1 The method flowchart provided by the production and manufacturing process embodiment of the Inconel 625 square choke valve forgings for deep-sea oil and gas exploitation of the application is shown.

[0051] Figure 2 The forging breakdown process diagram provided by the production and manufacturing process embodiment of the Inconel 625 square choke valve forgings for deep-sea oil and gas exploitation of the application is shown.

[0052] Figure 3 The square choke valve forging free forging process diagram provided by the production and manufacturing process embodiment of the Inconel 625 square choke valve forgings for deep-sea oil and gas exploitation of the application is shown.

[0053] Figure 4 The Inconel 625 square choke valve forging solution heat treatment diagram provided by the production and manufacturing process embodiment of the Inconel 625 square choke valve forgings for deep-sea oil and gas exploitation of the application is shown.

[0054] Figure 5 The Inconel 625 square choke valve forging T / 4, T / 2 metallographic structure diagram provided by the production and manufacturing process embodiment of the Inconel 625 square choke valve forgings for deep-sea oil and gas exploitation of the application is shown. DETAILED DESCRIPTION

[0055] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the drawings.

[0056] AsFigures 1-5 As shown, the embodiment of the present application provides a production and manufacturing process of Inconel 625 square throttle valve forgings for deep-sea oil and gas exploitation, which comprises the following steps:

[0057] Step S1. Material selection and pretreatment: selecting appropriate raw materials according to the alloy formula of the square throttle valve forgings, and melting the raw materials into electroslag ingots through a melting process, and then treating the surface of the electroslag ingots to remove the oxide skin and defects;

[0058] It should be noted that the composition of the raw materials is as follows:

[0059] C≤0.02%、Si≤0.30%、Mn≤0.10%、P≤0.015%、S≤0.015%、Cr:21.00-23.50%、Mo:8.5-10.0%、Fe≤3.0%、Ti≤0.40%、Al≤0.40%、Nb+Ta:3.35-4.05%、Ni≥60.00%;

[0060] The vacuum arc furnace (VAM) + vacuum consumable remelting (VAR) + electroslag remelting (ESR) three-in-one smelting process is used during melting in step S1, and the vacuum degree of the vacuum arc furnace smelting of the three-in-one smelting process is ≤0.1 Pa, the slag system of the electroslag remelting is CaF2-Al2O3-CaO (mass ratio 60:30:10), and the melting speed is controlled to be 3-5 kg / min.

[0061] The macroscopic segregation index of the ingot is ≤1.0, and the oxygen content is ≤30 ppm.

[0062] Step S2. Homogenization treatment: the electroslag ingot is heated to 850℃ at a gradient and kept for ≥4 hours, and then heated to 1180±10℃ and kept for 30-80 hours, so as to eliminate the as-cast dendritic segregation, dissolve the Laves phase and coarse MC carbide, and improve the uniformity of the Nb element distribution of the electroslag ingot;

[0063] It should be noted that the heating rate of the homogenization treatment is ≤50℃ / h, and the cooling is carried out by furnace cooling to 600℃ and then air cooling.

[0064] Step S3. Open-die forging: using stepwise heating (300℃-850℃-1170±10℃), keeping for ≥5 hours, and then forging, controlling the open-die forging temperature to be ≥1170℃, the finish forging temperature to be ≥1000℃, the total forging ratio to be >8:1, and the first pass reduction to be >40%; and completing in three heats:

[0065] First heat: upsetting - elongating - reheating and keeping for >3 hours;

[0066] Second heat: upsetting - elongating - reducing the furnace temperature by 20℃ and keeping for >2 hours;

[0067] Third fire: upsetting - elongation - air cooling;

[0068] It should be noted that the first pass reduction rate is greater than or equal to 40% of the single deformation of the hydraulic machine, and the upsetting height to diameter ratio is controlled at 0.6-0.8;

[0069] The upsetting ratio of each fire is greater than 1.4, and the elongation forging ratio is greater than 1.3;

[0070] The final forging temperature is monitored in real time and is not less than 950℃.

[0071] Step S4. Cutting forging: after cutting the cogging material, gradually heat to 1150±10℃ and keep for ≥4 hours, forge in two fires:

[0072] First fire: elongation - upsetting - return to furnace and keep for ≥3 hours;

[0073] Second fire: elongation - upsetting to target size - air cooling;

[0074] It should be noted that the forging needs to be preheated at 850℃ for ≥2h before forging;

[0075] The final forging temperature is monitored in real time by an infrared temperature measuring instrument, the corner chamfer radius is ≥8mm to avoid stress concentration.

[0076] Step S5. Heat treatment: solution treatment temperature is 970±5℃ for 1 hour, water cooling to room temperature;

[0077] It should be noted that the solution treatment needs to be preheated at 650℃ for 1h before solution treatment;

[0078] The water quenching transfer time of solution treatment is ≤15 seconds, the water temperature is controlled at 20-30℃, and the surface hardness after quenching is ≤300HBW;

[0079] The external thermocouple monitors the surface temperature of the forged piece during solution treatment, and the temperature deviation is controlled within ±5℃.

[0080] Step S6. Rough machining: dry the room temperature forged piece, after drying, put the forged piece into the machining equipment, and rough machining according to the drawing;

[0081] It should be noted that the wall thickness of the forged piece after machining is ≥350mm;

[0082] The rough machining allowance is reserved for 3-5mm, and the surface roughness Ra is ≤6.3μm.

[0083] Step S7. Non-destructive testing: non-destructive testing of the forged piece after machining is carried out by detection equipment, and the forged piece is sampled, and then tensile, impact, hardness and metallographic structure are tested;

[0084] It should be noted that the non-destructive testing selects ultrasonic testing (UT) and penetration testing (PT), and the ultrasonic testing adopts longitudinal wave straight probe (frequency 2.5 MHz), the sensitivity is Phi 2mm flat bottom hole, and the penetration testing needs to meet the ASTM E165 standard.

[0085] In another embodiment provided by the application, in steps S3 and S4, the preheating temperature of the forging die is greater than or equal to 300 DEG C, the die material is H13 steel, and the surface is sprayed with a graphite-based lubricant.

[0086] The Inconel 625 nickel-based alloy square throttle valve forgings for deep-sea oil and gas exploitation produced by the production process have the performance and organization test as shown in Table 1, and T represents the part wall thickness:

[0087] Table 1: Anatomical organization and performance of Inconel 625 square throttle valve forgings after heat treatment

[0088]

[0089] Compared with the prior art, it can be seen that the forgings produced by the embodiment have the best quality. The above only describes some exemplary embodiments of the application by way of illustration, and it is needless to say that the described embodiments can be modified in various ways without departing from the spirit and scope of the application for ordinary skilled in the art. Therefore, the above drawings and descriptions are illustrative in nature and should not be understood as limiting the scope of protection of the claims of the application.

Claims

1. A manufacturing process for producing an Inconel 625 square choke valve forging for deep sea oil and gas exploration, characterized in that, It comprises the following steps: Step S1. Selection and pretreatment: selecting appropriate raw materials according to the alloy formula of the square throttle forging and melting the raw materials into electroslag ingots through a melting process, and then treating the surface of the electroslag ingots to remove the oxide skin and defects; Step S2. Homogenization treatment: the electroslag ingot is heated at a gradient to 850 DEG C for ≥4 hours, and then heated to 1180±10 DEG C for 30-80 hours to eliminate as-cast dendritic segregation, dissolve Laves phase and coarse MC carbide, and improve the uniformity of the distribution of Nb element in the electroslag ingot; Step S3. Open-die forging: using step-up heating (300 DEG C-850 DEG C-1170±10 DEG C), and then forging after ≥5 hours of heat preservation, controlling the open-die forging temperature ≥1170 DEG C, the finish-forging temperature ≥1000 DEG C, the total forging ratio >8:1, and the first-pass reduction rate >40%; and completing in three heats: First heat: upsetting - elongating - reheating and heat preservation >3 hours; Second heat: upsetting - elongating - reducing the furnace temperature by 20 DEG C and heat preservation >2 hours; Third heat: upsetting - elongating - air cooling; Step S4. Cutting and forging: cutting the open-die forging stock, heating at a gradient to 1150±10 DEG C for ≥4 hours, and then forging in two heats: First heat: elongating - upsetting - reheating and heat preservation ≥3 hours; Second heat: elongating - upsetting to the target size - air cooling; Step S5. Heat treatment: solid solution treatment at 970±5 DEG C for 1 hour, and then water cooling to room temperature; Step S6. Rough machining: drying the room-temperature forging, and then putting the forging into a machining device after the drying is completed, and rough machining according to the drawing; Step S7. Non-destructive testing: non-destructively testing the forging after the machining is completed through a testing device, sampling the forging, and then testing the tensile strength, low-temperature impact, hardness, and metallographic structure.

2. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S1: The composition of the raw material is as follows: C≤0.02%, Si≤0.30%, Mn≤0.10%, P≤0.015%, S≤0.015%, Cr: 21.00-23.50%, Mo: 8.5-10.0%, Fe≤3.0%, Ti≤0.40%, Al≤0.40%, Nb+Ta: 3.35-4.05%, Ni≥60.00%; The vacuum arc furnace (VAM) + vacuum consumable remelting (VAR) + electroslag remelting (ESR) three-in-one smelting process is used in the melting in the step S1, the vacuum degree of the vacuum arc furnace smelting in the three-in-one smelting process is ≤0.1 Pa, the electroslag remelting slag system is CaF2-Al2O3-CaO (mass ratio 60:30:10), and the melting speed is controlled to be 3-5 kg / min.

3. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S1, the macrosegregation index of the ingot is ≤1.0, and the oxygen content is ≤30 ppm.

4. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S2: The heating rate of the homogenization treatment is ≤50 DEG C / h, and the cooling is furnace cooling to 600 DEG C and then air cooling.

5. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S3: The first-pass reduction rate uses the single deformation amount of the hydraulic press ≥40%, and the upsetting height to diameter ratio is controlled to be 0.6-0.8; The upsetting ratio of each heat is >1.4, and the elongating forging ratio is >1.3; The finish-forging temperature is monitored in real time, and is not lower than 950 DEG C.

6. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S4: The preheating at 850℃ is required for ≥2h before reaching the forging temperature; The final forging temperature is monitored by infrared thermometer in real time, and the chamfer radius of the corners is ≥8mm to avoid stress concentration.

7. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the steps S3 and S4, the preheating temperature of the forging die is ≥300℃, the die material is H13 steel, and the surface is sprayed with graphite-based lubricant.

8. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S5: The preheating at 650℃ is required for 1h before reaching the solution temperature; The water quenching transfer time of the solution treatment is ≤15s, the water temperature is controlled at 20-30℃, and the surface hardness after quenching is ≤300HBW; The surface temperature of the forging is monitored by an external thermocouple during the solution, and the temperature deviation is controlled within ±5℃.

9. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S6: The wall thickness of the forging after processing is ≥350mm; The rough machining allowance is reserved for 3-5mm, and the surface roughness Ra is ≤6.3μm.

10. A process for manufacturing an Inconel 625 square choke valve forging for deep sea oil and gas exploration as claimed in claim 1 wherein, In the step S7: The non-destructive testing is selected from ultrasonic testing (UT) and penetration testing (PT), the ultrasonic testing adopts longitudinal wave straight probe (frequency 2.5MHz), the sensitivity is Φ2mm flat bottom hole, and the penetration testing needs to meet the ASTM E165 standard.

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