A production method for forgings for oil and gas equipment

Abstract

The invention discloses a production method of forgings for oil and gas equipment, comprising sequential steps of upsetting, punching, ring rolling, normal tempering and quenching and tempering; the forgings are made of 12Cr2Mo1V alloy steel, and the element composition of the 12Cr2Mo1V alloy steel comprises, by mass percentage, C: 0.11%-0.15%, Mn: 0.45%-0.6%, P: ≤0.01%, S: ≤0.008%, Si: ≤0.1%, Ni: 0.1%-0.25%, Cr: 2%-2.5%, Mo: 0.9%-1.1%, V: 0.25%-0.35%, Nb: 0.02%-0.05%, B: ≤0.002%, Ti: ≤0.03%, Cu: ≤0.2%, Ca: ≤0.015%, and the main components of the remainder are Fe and inevitable impurities. The forgings for oil and gas equipment produced by this method have good mechanical properties after simulated welding heat treatment at 705°C, especially the impact performance at ‑29°C is in the range of 287~299J.

Description

Technical Field

[0001] The invention relates to the technical field of forging production, and in particular to a production method of forgings for oil and gas equipment. Background Art

[0002] Domestic grade 12Cr2Mo1V alloy steel is a special low-alloy heat-resistant steel with high weldability and low manufacturing cost. It is often used in the manufacture of deep-sea oil and gas equipment. With the increase in energy demand, oil and gas extraction equipment is becoming larger and larger, and the size of pressure vessel forgings made of 12Cr2Mo1V material is gradually increasing. Taking a thick-walled high-cylinder F22V forging as an example, its specific size is Φ1705×Φ985×1310mm. Its thick wall thickness and high height make heat treatment difficult, and its mechanical properties after simulated welding heat treatment at 705℃ are difficult to meet the requirements. The specific mechanical property requirements after welding heat treatment simulation are as follows: The yield strength at 20℃ (Rp0.2) ranges from 415Mpa to 620MPa, the tensile strength at 20℃ (Rm) ranges from 585Mpa to 760MPa, the elongation at 20℃ (δ) ≥17%, the cross-sectional shrinkage at 20℃ (Z) ≥35%, and the impact resistance at -29℃ (KV) ≥55J.

[0003] CN107937831A uses the EBT arc furnace-LF furnace refining-VD vacuum refining-mold casting process route to smelt and pour the steel ingot and adopts annealing, quenching and tempering heat treatment processes. The heat treatment process is easy to implement, and the final alloy steel has high room and high temperature strength and hardness, good low temperature impact toughness, resistance to temper brittleness, and high creep strength and high temperature endurance strength.

[0004] However, the thick-walled high-cylinder F22V forgings are quite different in shape from the forgings in CN107937831A, and it is difficult to use the heat treatment method of CN107937831A to reduce the difficulty of heat treatment, and the solution of CN107937831A does not mention simulated welding heat treatment. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects in the prior art and provide a method for producing forgings for oil and gas equipment, so as to produce thick-walled large forgings whose mechanical properties meet the requirements after simulated welding heat treatment in a 705°C environment.

[0006] In order to achieve the above technical effects, the technical solution of the present invention is: a method for producing forgings for oil and gas equipment, comprising sequential steps of upsetting, punching, ring rolling, normal tempering and quenching and tempering; the forgings are made of 12Cr2Mo1V alloy steel, and the element composition of the 12Cr2Mo1V alloy steel includes, by mass percentage: C: 0.11%~0.15%, Mn: 0.45%~0.6%, P:≤0.01%, S:≤0.008%, Si:≤0.1%, Ni:0.1%~0.25%, Cr:2%~2.5%, Mo:0.9%~1.1%, V: 0.25%~0.35%, Nb:0.02%~0.05%, B:≤0.002%, Ti:≤0.03%, Cu:≤0.2%, Ca:≤0.015%, the balance is mainly composed of Fe and unavoidable impurities. Further, Mn: 0.5%~0.6%, S:≤0.002%, Ni: 0.2%~0.25%.

[0007] The preferred technical solution is that the forging steel further includes elements Al and N, and the Al content is 0.02% to 0.05%, and the N content is 80 to 150 PPM. Furthermore, the N content is 100 to 130 PPM.

[0008] The preferred technical solution is that the upsetting and punching steps are the first fire, and the ring rolling step is the second fire; the initial forging temperature of the first fire and the second fire is not greater than 1120°C; the final forging temperature of the first fire and the second fire is not less than 850°C. Furthermore, the initial forging temperature of the first fire and the second fire is 1120~1200°C.

[0009] A preferred technical solution is that the upsetting step includes three upsetting steps and three drawing steps which are performed alternately in sequence, and the sum of the upsetting forging ratios of the three upsetting steps and the drawing forging ratios of the three drawing steps is not less than 5.

[0010] The preferred technical solution is that in the three upsetting steps and the three drawing steps: the first upsetting forging ratio is 1.70-1.78; the first drawing forging ratio is 1.54-1.62; the second upsetting forging ratio is 1.7-1.76; the second drawing forging ratio is 1.6-1.68; the third upsetting forging ratio is 1.67-1.75; and the third drawing forging ratio is 1.26-1.34.

[0011] The preferred technical solution is that the ring rolling forging ratio of the ring rolling step is 1.37~1.45.

[0012] The preferred technical solution is that the normalizing and tempering steps are: Normalizing: After the forgings are hot-charged into the furnace, they are kept warm at 640-660℃ for 0.8-1.4h / 100mm according to the effective thickness of the forgings; then the forgings are heated to 940-960℃, kept warm for 2.5-2.8h / 100mm according to the effective thickness of the forgings, then air-cooled, and finally heated again for tempering; Tempering: After cooling, the forging is heated to 670~690℃, kept warm for 4.1~4.5h / 100mm according to the effective thickness of the forging, then furnace cooled at a rate of no more than 40℃ / h, and air cooled after the furnace is cooled to no more than 100℃.

[0013] The preferred technical solution is that the wall thickness of the forging is 300-450 mm, and the heating rate in the normalizing and tempering steps is not greater than 100°C / h. Furthermore, the heating rate in the normalizing and tempering steps is 80-90°C.

[0014] The preferred technical solution is that the quenching and tempering step is divided into quenching and high temperature tempering in sequence, and the quenching step is: The forgings are heated to 670~690℃ at a rate of no more than 100℃ / h, and kept warm for 0.5~0.9h / 100mm according to the effective thickness of the forgings. After the insulation, the temperature is raised to 910~930℃ at a rate of no more than 100℃ / h, and kept warm for 2.2~2.5h / 100mm according to the effective thickness of the forgings, and then cooled by water quenching.

[0015] The preferred technical solution is that the high temperature tempering step is: The forgings are heated to 700-720°C at a rate not exceeding 100°C / h, kept warm for 4.4-4.8h / 100mm according to the effective thickness of the forgings, and finally air-cooled.

[0016] The advantages and beneficial effects of the present invention are: The production method of the forgings for oil and gas equipment is based on 12Cr2Mo1V alloy steel. The cold brittleness phenomenon is alleviated by strictly controlling the contents of residual phosphorus and sulfur in the forging steel. The grains are refined by adding elements of aluminum and nitrogen to the forging steel to improve the toughness of the forgings at low temperatures. The suitable forging ratio enables the forgings to obtain good mechanical properties. The forgings for oil and gas equipment obtained by matching normal tempering heat treatment and quenching and tempering heat treatment are thick-walled large forgings. The mechanical properties of the forgings are good after simulated welding heat treatment under a 705°C environment, especially the impact properties of the forgings at -29°C range from 287 to 299J. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0018] The element composition of alloy steel with grade 12Cr2Mo1V is C: 0.11%~0.15%, Mn: 0.3% ~0.6%, P:≤0.015%, S:≤0.01%, Si:≤0.1%, Ni:≤0.25%, Cr:2% ~2.5%, Mo:0.9% ~1.1%, V: 0.25%~0.35%, Nb:≤0.07%, B:≤0.002%, Ti:≤0.03%, Cu:≤0.2%, Ca:≤0.015%.

[0019] The mass percentage of an element in forging steel is limited to "≤n", which means that the content of the element in the forging steel is 0~n, excluding the minimum endpoint value "0".

[0020] Effective thickness of forgings The effective thickness of forgings is used to calculate the re-melting time of each fire and the holding time of positive tempering heat treatment and quenching and tempering heat treatment. Thick-walled high-cylinder F22V forgings belong to cylindrical workpieces. When the diameter of the inner hole of the forging is greater than or equal to the wall thickness (half of the difference between the outer diameter and the inner diameter), the wall thickness is used as its effective thickness; when the diameter of the inner hole of the forging is less than the wall thickness (half of the difference between the outer diameter and the inner diameter), the outer diameter is used as its effective thickness.

[0021] Maximum simulation of heat treatment process After the forgings are charged into the furnace, they are heated at an average rate of no more than 55°C / h. When the temperature of the forgings reaches 700°C, they are kept warm in the range of 700°C~715°C according to the effective thickness of the forgings at 9.72~9.86h / 100mm. After the insulation, they are cooled at an average rate of no more than 55°C / h.

[0022] Upsetting forging ratio The ratio of the larger value to the smaller value of the forging length before and after upsetting is the upsetting forging ratio.

[0023] Drawing forging ratio The ratio of the larger and smaller lengths of the forging before and after drawing is the drawing forging ratio.

[0024] Ring rolling forging ratio The ratio of the product of the forging wall thickness and length before and after ring rolling is the ring rolling forging ratio. Example

[0025] Example 1

[0026] The measured values ​​of chemical composition mass percentages of the production method of forgings for oil and gas equipment in Example 1 are: C: 0.13%, Mn: 0.52%, P: 0.01%, S: 0.001%, Si: 0.05%, Ni: 0.2%, Cr: 2.15%, Mo: 0.92%, V: 0.29%, Nb: 0.028%, B: 0.0001%, Ti: 0.0028%, Cu: 0.06%, Ca: 0.0001%, N: 120PPM, Al: 0.026%, and the balance is Fe and unavoidable impurities; The production of forgings for oil and gas equipment includes the following steps: forging and post-forging heat treatment. Forging includes the following steps: upsetting, punching, trimming and ring rolling. Post-forging heat treatment includes the following steps: tempering heat treatment and quenching and tempering heat treatment. S1: Heat to 1230℃; S2: The steel ingot with a length of 2080mm is subjected to three-upsetting and three-drawing operations, first upsetting to 1200mm, then drawing to 1900mm, then upsetting to 1100mm, then drawing to 1800mm, then upsetting to 1050mm, and finally rounding and drawing to 1360mm; The first upsetting forging ratio is 1.73; The first drawing and forging ratio is 1.58; The second upsetting forging ratio is 1.73; The second drawing and forging ratio is 1.64; The third upsetting forging ratio is 1.71; The third drawing forging ratio is 1.3; S3: The middle punching hole is Φ465mm, and the punching part has an outer diameter of 1443mm and a height of 1360mm; S4: trimming and forming, returning to the furnace for 6 hours, furnace temperature 1230℃, the surface temperature of the forgings is 900℃, and the core temperature is 950℃; S5: After the forgings are returned to the furnace, the ring rolling machine is used to roll the forgings to an outer diameter of 1705mm, an inner diameter of 985mm, and a length of 1310mm, that is, the ring rolling forging ratio is 1.41.

[0027] S6: Normalizing, after the forging is loaded into the furnace, the temperature is raised to 650℃, kept at this temperature for 3.5h, then raised to 950℃ at a heating rate of 100℃ / h, kept at this temperature for 9.5h, and then air-cooled; Tempering: the temperature in the furnace is raised to 680°C at a heating rate of 100°C / h, kept at this temperature for 15.5h, then cooled at a rate of 38°C / h, and air-cooled after the furnace is cooled to 80°C; S7: Tempering, loading the furnace at room temperature, heating to 680℃ at a rate of 100℃ / h, keeping it at that temperature for 2.5h, heating to 920℃ at a rate of 100℃ / h after the end of the keeping temperature, keeping it at that temperature for 8.5h, then cooling by water quenching, and quenching in water after taking it out of the furnace; The furnace was loaded at room temperature, and the temperature in the furnace was raised to 710°C at a rate of 100°C / h by high-temperature tempering, kept at that temperature for 16.5h, and then air-cooled.

[0028] Example 1 The performance test results and qualification requirements of forgings for oil and gas equipment are as follows: 1. Mechanical properties after quenching and tempering: 20℃ yield strength (Rp0.2) is 537MPa, 20℃ tensile strength (Rm) is 637MPa, 20℃ elongation (δ) is 23.5%, 20℃ section shrinkage (Z) is 83%, -18℃ impact performance (KV) is 292J, 290J, 295J; The qualified requirements of mechanical property test after quenching and tempering are: 20℃ yield strength (Rp0.2) ≥415MPa, 20℃ tensile strength (Rm) ≥585MPa, 20℃ elongation (δ) ≥17%, 20℃ section shrinkage (Z) ≥35%, -18℃ impact performance (KV) ≥55J.

[0029] 2. Austenite grain size results: According to ISO 643 standard (880℃ for 60 minutes), the austenite grain size of the forging is 6.5; Austenite grain size qualification requirement: ≥6.

[0030] 3. Maximum simulated heat treatment test results: 20℃ yield strength (Rp0.2) is 500 Mpa, 20℃ tensile strength (Rm) is 615 Mpa, 20℃ elongation (δ) is 28.5%, 20℃ section shrinkage (Z) is 81%, -29℃ impact performance (KV) is 290J, 287J, 299J; The qualified requirements for the maximum simulated heat treatment are as follows: the yield strength at 20℃ (Rp0.2) ranges from 415Mpa to 620MPa, the tensile strength at 20℃ (Rm) ranges from 585Mpa to 760MPa, the elongation at 20℃ (δ) ≥17%, the cross-sectional shrinkage at 20℃ (Z) ≥35%, and the impact resistance at -29℃ (KV) ≥55J.

[0031] Comparative Example 1 Comparative Example 1 The measured values ​​of the chemical composition mass percentages of the production method for oil and gas equipment forgings are: C: 0.13%, Mn: 0.5%, P: 0.014%, S: 0.009%, Si: 0.08%, Ni: 0.24%, Cr: 2.3%, Mo: 1%, V: 0.28%, Nb: 0.05%, B: 0.001%, Ti: 0.01%, Cu: 0.19%, Ca: 0.013%, N: 110PPM, Al: 0.025%, and the balance is Fe and unavoidable impurities; The forging process of Comparative Example 1 is the same as that of Example 1.

[0032] Comparative Example 1 cracked during the water quenching process in S7 and was a defective product.

[0033] The increase in the phosphorus and sulfur contents in Comparative Example 1 indicates that the phosphorus and sulfur contents affect the quenching stability of the forgings to a certain extent, and the presence of phosphorus and sulfur will increase the internal stress during the quenching process. These internal stresses are generated during the quenching process due to the rapid cooling of the material, and when the internal stress exceeds the fracture strength of the material, it will cause cracking.

[0034] Example 2

[0035] The measured values ​​of chemical composition mass percentages of the production method of forgings for oil and gas equipment in Example 2 are: C: 0.14%, Mn: 0.5%, P: 0.003%, S: 0.003%, Si: 0.07%, Ni: 0.22%, Cr: 2.4%, Mo: 1%, V: 0.3%, Nb: 0.05%, B: 0.001%, Ti: 0.01%, Cu: 0.06%, Ca: 0.01%, N: 80PPM, Al: 0.013%, and the balance is Fe and unavoidable impurities; The forging process of Example 2 is the same as that of Example 1.

[0036] The performance test results of the forgings for oil and gas equipment in Example 2 are as follows: 1. Mechanical properties after quenching and tempering: 20℃ yield strength (Rp0.2) is 470MPa, 20℃ tensile strength (Rm) is 601MPa, 20℃ elongation (δ) is 21%, 20℃ section shrinkage (Z) is 81%, -18℃ impact performance (KV) is 240J, 251J, 255J; 2. Austenite grain size results: According to ISO 643 standard (880℃ for 60 minutes), the austenite grain size of the forging is grade 6; 3. Maximum simulated heat treatment test results: 20℃ yield strength (Rp0.2) is 420 Mpa, 20℃ tensile strength (Rm) is 590 Mpa, 20℃ elongation (δ) is 23%, 20℃ section shrinkage (Z) is 71%, -29℃ impact performance (KV) is 220J, 226J, 234J; In Example 2, the aluminum content of the forging is reduced and the nitrogen content is controlled to be small, and the mechanical properties of the forging and the mechanical properties after the maximum simulated heat treatment test are all reduced, indicating that the additional addition of aluminum and nitrogen elements to the forging is beneficial to improving the mechanical properties of the forging, and aluminum is beneficial to improving the tempering resistance of the forging.

[0037] Example 3

[0038] Based on the forging steel of Example 1, the forging process of Example 3 is the same as that of Example 1, except that S7: After quenching and tempering, load the furnace at room temperature, heat up to 680℃ at a rate of 100℃ / h, keep warm for 2.5h, and after the end of the heat preservation, heat up to 920℃ at a rate not exceeding 100℃ / h, keep warm for 8.5h, then cool down by water quenching, and quench in water after taking out of the furnace; The furnace was loaded at room temperature, and the temperature in the furnace was raised to 750°C at a rate of 100°C / h by high-temperature tempering, kept at that temperature for 16.5h, and then air-cooled.

[0039] The performance test results of the forgings for oil and gas equipment in Example 3 are as follows: 1. Mechanical properties after quenching and tempering: 20℃ yield strength (Rp0.2) is 450MPa, 20℃ tensile strength (Rm) is 600MPa, 20℃ elongation (δ) is 18%, 20℃ section shrinkage (Z) is 40%, -18℃ impact performance (KV) is 180J, 184J, 190J; 2. Austenite grain size results: According to ISO 643 standard (880℃ for 60 minutes), the austenite grain size of the forging is 6.1; 3. Maximum simulated heat treatment test results: 20℃ yield strength (Rp0.2) is 430 Mpa, 20℃ tensile strength (Rm) is 590 Mpa, 20℃ elongation (δ) is 19%, 20℃ section shrinkage (Z) is 38%, -29℃ impact performance (KV) is 165J, 167J, 181J; In Example 3, the high-temperature tempering temperature of the forgings is increased, and the mechanical strength of the forgings after quenching and tempering and the mechanical strength after the maximum simulated heat treatment test are reduced.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for producing forgings for oil and gas equipment, comprising the steps of upsetting, punching, ring rolling, normal tempering and quenching and tempering in sequence; characterized in that: The forging is made of 12Cr2Mo1V alloy steel, and the element composition of the 12Cr2Mo1V alloy steel includes, by mass percentage: C: 0.11%~0.15%, Mn: 0.45%~0.6%, P: ≤0.01%, S: ≤0.008%, Si: ≤0.1%, Ni: 0.1%~0.25%, Cr: 2%~2.5%, Mo: 0.9%~1.1%, V: 0.25%~0.35%, Nb: 0.02%~0.05%, B: ≤0.002%, Ti: ≤0.03%, Cu: ≤0.2%, Ca: ≤0.015%, the remainder is mainly composed of Fe and unavoidable impurities.

2. The method for producing forgings for oil and gas equipment according to claim 1, characterized in that: The forging steel also includes elements Al and N, and the content of the Al element is 0.02% to 0.05%, and the content of the N element is 80 to 150 PPM.

3. The method for producing forgings for oil and gas equipment according to claim 1, characterized in that: The upsetting and punching steps are the first firing, and the ring rolling step is the second firing; the initial forging temperature of the first firing and the second firing is no more than 1120°C; the final forging temperature of the first firing and the second firing is no less than 850°C.

4. The method for producing forgings for oil and gas equipment according to claim 1, characterized in that: The upsetting step includes three upsetting steps and three drawing steps which are performed alternately in sequence, and the sum of the upsetting forging ratios of the three upsetting steps and the drawing forging ratios of the three drawing steps is not less than 5.

5. The method for producing forgings for oil and gas equipment according to claim 4, characterized in that: In the three upsetting steps and the three drawing steps: The first upsetting forging ratio is 1.70~1.78; The first drawing forging ratio is 1.54~1.62; The second upsetting forging ratio is 1.7~1.76; The second drawing forging ratio is 1.6~1.68; The third upsetting forging ratio is 1.67~1.75; The third drawing forging ratio is 1.26~1.

34.

6. The method for producing forgings for oil and gas equipment according to claim 1, characterized in that: The ring rolling forging ratio of the ring rolling step is 1.37~1.

45.

7. The method for producing forgings for oil and gas equipment according to claim 1, characterized in that: The normalizing and tempering steps are: Normalizing: After the forgings are hot-charged into the furnace, they are kept warm at 640-660℃ for 0.8-1.4h / 100mm according to the effective thickness of the forgings; then the forgings are heated to 940-960℃, kept warm for 2.5-2.8h / 100mm according to the effective thickness of the forgings, then air-cooled, and finally heated again for tempering; Tempering: After cooling, the forging is heated to 670~690℃, kept warm for 4.1~4.5h / 100mm according to the effective thickness of the forging, then furnace cooled at a rate of no more than 40℃ / h, and air cooled after the furnace is cooled to no more than 100℃.

8. The method for producing forgings for oil and gas equipment according to claim 7, characterized in that: The wall thickness of the forging is 300-450 mm; the heating rate in the normalizing and tempering steps is not greater than 100° C. / h.

9. The method for producing forgings for oil and gas equipment according to claim 1, characterized in that: The quenching and tempering process is divided into quenching and high temperature tempering in sequence, and the quenching step is: The forgings are heated to 670~690℃ at a rate of no more than 100℃ / h, and kept warm for 0.5~0.9h / 100mm according to the effective thickness of the forgings. After the insulation, the temperature is raised to 910~930℃ at a rate of no more than 100℃ / h, and kept warm for 2.2~2.5h / 100mm according to the effective thickness of the forgings, and then cooled by water quenching.

10. The method for producing forgings for oil and gas equipment according to claim 9, characterized in that: The high temperature tempering step is: The forgings are heated to 700-720°C at a rate not exceeding 100°C / h, kept warm for 4.4-4.8h / 100mm according to the effective thickness of the forgings, and finally air-cooled.