F22 forgings for deep sea oil and gas equipment satisfying nace standard requirements and production method thereof

Abstract

The present application belongs to the technical field of forgings production, and relates to a F22 forging for deep-sea oil and gas equipment satisfying NACE standard and a production method thereof; main steps are as follows: controlling initial forging temperature to be 1100-1220 DEG C, final forging temperature to be greater than or equal to 850 DEG C, and forging ratio to be greater than or equal to 4:1; heating to 1210-1250 DEG C, keeping for 5-6 hours, after obtaining the forging, normalizing treatment is carried out, keeping for 3.5-7 hours at 940-960 DEG C, and then air cooling; then quenching treatment is carried out, keeping for 3-6 hours at 930-950 DEG C, and then water cooling; finally, tempering treatment is carried out, keeping for 6-10 hours at 660-665 DEG C, and then air cooling, to obtain the final material. The present application adopts the mode of combining component design with forging process, to realize the purposes of refining grains, improving hardenability and comprehensive mechanical properties; the produced F22 forging not only has good hardness, yield strength and tensile strength, but also has excellent impact toughness, elongation and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of forging production technology, specifically relating to an F22 forging for deep-sea oil and gas equipment that meets NACE standards and its production method. Background Technology

[0002] F22 material forgings are widely used in the deep sea, which requires the forgings to have high hardness, yield strength, tensile strength, as well as good low-temperature impact toughness and elongation.

[0003] Meeting the high strength requirement cannot simultaneously guarantee the impact toughness, elongation, and other indicators. Under existing conventional technical conditions, it is difficult to achieve forgings with such excellent comprehensive performance. Therefore, improving F22 forgings is an urgent technical problem to be solved. In the production process of F22 forgings, strict control must be exercised over the microalloying ratio of raw materials, forging, and heat treatment. Summary of the Invention

[0004] The purpose of this invention is to overcome the technical defects existing in the prior art. This invention provides a development of F22 high-strength forgings for deep-sea oil and gas equipment.

[0005] To achieve the above objectives, the present invention first provides an F22 forging for deep-sea oil and gas equipment that meets NACE standards, and is composed of the following components by weight percentage:

[0006] C: 0.13-0.15%, Si: 0.15-0.30%, Mn: 0.50-0.60%, P: ≤0.010%, S: ≤0.005%, Cr: 2.40-2.50%, Mo: 1.05-1.13%, Ni: 0-0.50%, Al: 0.020-0.05%, Cu: ≤0.25%, Sn: ≤0.010%, As: ≤0.010%, V: 0.01-0.03%, Sb: ≤0.010%, Pb: ≤0.010%, H: ≤2ppm, balance Fe and unavoidable impurities.

[0007] Ingredient design:

[0008] Referencing the F22 material composition in ASTM A182, and controlling the content of alloying elements in the material to reach the required upper limit, while minimizing harmful elements such as arsenic, selenium, and antimony, the hardenability of the material is improved, thereby enhancing mechanical properties such as hardness, yield strength, tensile strength, and impact energy.

[0009] This invention limits the amount of Cr to 2.40-2.50% and the amount of Mo to 1.05-1.13%. Chromium (Cr) can improve the hardenability and wear resistance of steel, and improve its corrosion resistance and oxidation resistance. Mo is a strong carbide-forming element, forming Mo₂C with C, which can inhibit austenite grain growth. At the same time, Mo is also an element that prevents temper embrittlement of type II, and it greatly helps to improve the impact toughness after high-temperature tempering. In addition, V is a strong carbide-forming element. Adding V further refines the grains and improves strength and tempering stability, but the amount should not be too high, so the V content is controlled at 0.01-0.03%.

[0010] This invention also provides a method for producing F22 forgings for deep-sea oil and gas equipment that meet NACE standards, comprising the following steps:

[0011] (1) Forging process:

[0012] The initial forging temperature is 1100-1220℃, the final forging temperature is ≥850℃, and the forging ratio is guaranteed to be ≥4:1. During the forging process, the temperature is heated to 1210~1250℃ and held for 5-6 hours. Finally, the forging is taken out of the furnace and forged. After repeated upsetting and drawing by the press and forging hammer, the forging is finally formed and obtained.

[0013] Preferably, the final forging temperature in step (1) is 900℃.

[0014] (2) Post-forging heat treatment: F22 forgings require normalizing treatment after forging;

[0015] The forgings obtained in step (1) are subjected to normalizing treatment. The furnace temperature is ≤350℃, the heating rate is ≤150℃ / h, and the furnace is held at 940-960℃ for 3.5-7 hours before air cooling to obtain the normalized forgings.

[0016] Preferably, the furnace temperature in step (2) is 200-350℃ and the heating rate is 100-150℃ / h.

[0017] (3) Performance heat treatment: quenching followed by high-temperature tempering (quenching and tempering);

[0018] (a) The forgings after normalizing in step (2) are first quenched. The furnace temperature of the forgings is controlled to be ≤350℃, the heating rate is ≤150℃ / h, and the forgings are held at 930-950℃ for 3-6 hours and then water-cooled to obtain the quenched forgings.

[0019] (b) The forgings quenched in step (a) are tempered, and the furnace temperature is controlled to be ≤350℃, the heating rate is ≤150℃ / h, and the forgings are held at 660~665℃ for 6~10 hours and then air-cooled to obtain F22 forgings for deep-sea oil and gas equipment that meet NACE standards.

[0020] Preferably, in step (3) (a), the furnace temperature is 180℃~200℃ and the heating rate is 120~150℃ / h;

[0021] Preferably, in step (3) (b), the furnace temperature is 180℃~200℃ and the heating rate is 120~150℃ / h.

[0022] In step (1) of this invention, the repeated upsetting and drawing processes using a press and forging hammer aim to eliminate internal defects in the raw materials and make the materials more compact, laying the foundation for the performance required by the forgings. In step (2), the material is heated to 30-50 degrees above Ac3, and F22 is held at 940-960 degrees Celsius before air cooling. The main purposes are threefold: firstly, to reduce hardness, improve plasticity, and enhance machinability and pressure processing performance; secondly, to refine the grain size, improve mechanical properties, and prepare for the next process; and thirdly, to eliminate the internal stress generated by forging heat treatment.

[0023] The advantages of quenching and high-temperature tempering in step (3) of this invention:

[0024] Quenching: Heating the steel to a phase transformation temperature Ac3 or Ac1 or higher, F22 is held at 930-950℃ for a period of time, and then rapidly cooled in water to obtain a high-hardness martensitic structure. Quenching can fully utilize the strength and wear resistance potential of steel, but at the same time it will cause great internal stress, reducing the plasticity and impact toughness of steel. Therefore, high-temperature tempering is required to obtain better comprehensive mechanical properties.

[0025] High-temperature tempering: The quenched steel part is reheated to a temperature below Ac1. This temperature needs to be determined based on the different hardness requirements of different materials. Since welding is required after finishing, and stress-relieving heat treatment is also necessary after welding, the higher the tempering temperature of F22 forgings, the better. This ensures that the forgings still meet the requirements after stress-relieving heat treatment. However, excessively high tempering temperatures will lead to a decrease in the hardness of the forgings, which in turn will reduce the yield strength and tensile strength. Therefore, micro-alloying of the material is used to control the tempering temperature while maintaining the hardness value. After tempering, the parts are cooled in air.

[0026] High-temperature tempering after quenching is called tempering, which achieves the desired balance between strength and toughness in steel parts, resulting in high strength as well as excellent toughness, plasticity, and machinability.

[0027] The advantages and technical effects of this invention are:

[0028] (1) The F22 material of this invention is a low alloy steel with a high content of alloying elements. This material has high hardenability. To obtain a product with high comprehensive performance, it is necessary not only to have excellent control of the raw material composition content and reasonable forging process, but also to have reasonable post-forging heat treatment process and performance heat treatment process. Therefore, by combining composition design with forging process, the purpose of refining grains, improving hardenability and improving comprehensive mechanical properties has been achieved. The F22 forgings produced not only have good hardness, yield strength and tensile strength, but also have excellent impact toughness and elongation, and also have good corrosion resistance, meeting the NACE requirements.

[0029] (2) In the present invention, the final forging temperature is controlled to be no less than 850°C. Too low a final forging temperature will cause the parts to crack, while too high a final forging temperature will cause the grains to become coarse. The forging ratio must be ≥4:1, which can ensure that the structure is compact after forging, and can break up the coarse dendrite structure in the raw material and disperse the inclusions to reduce anisotropy. Attached Figure Description

[0030] Figure 1 The image shows the grain size of the material prepared in Example 2.

[0031] Figure 2 The image shows the microstructure of the material prepared in Example 2 under a 100x microscope.

[0032] Figure 3 The image shows the microstructure of the material prepared in Example 2 under a 500x microscope.

[0033] Figure 4 This is a diagram of the non-metallic inclusions in the material prepared in Example 2.

[0034] Figure 5 This is a low-magnification microstructure image of the material prepared in Example 2. Detailed Implementation

[0035] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these embodiments.

[0036] Example 1:

[0037] The forging material composition consists of the following components by weight percentage:

[0038] C: 0.14%, Si: 0.25%, Mn: 0.50%, P: 0.008%, S: 0.001%, Cr: 2.40%, Mo: 1.08%, Ni: 0.20%, Al: 0 .020%, Cu: 0.05%, Sn: ≤0.010%, As: 0.005%, V: 0.013%, Sb: 0.004%, Pb: 0.0002%, H: 0.87ppm.

[0039] The specific steps are as follows:

[0040] (1) Forging process: The raw materials with the above composition are heated and then forged. The initial forging temperature is 1120℃ and the final forging temperature is 900℃. The forging ratio is 23.4:1. During the forging process, the temperature is heated to 1230℃ and held for 5 hours. Finally, the forging is carried out of the furnace and repeatedly upsetting and drawing by the press and forging hammer to eliminate the internal defects of the raw materials and make the material more compact. Finally, the forging is formed.

[0041] (2) Post-forging heat treatment:

[0042] The forgings obtained in step (1) were normalized. The furnace temperature of the forgings was 210℃, the heating rate was 120℃ / h, and the forgings were held at 950℃ for 6 hours before being air-cooled.

[0043] (3) Performance heat treatment:

[0044] Quenching: The forgings after normalizing in step (2) are first quenched. The furnace temperature of the forgings is 180℃, the heating rate is 120℃ / h, and the temperature is held at 940℃ for 4.5 hours before water cooling.

[0045] Tempering: The forgings after quenching are tempered. The forgings are fed into the furnace at a temperature of 180℃, with a heating rate of 120℃ / h. After holding at 663℃ for 10 hours, they are air-cooled.

[0046] Example 2:

[0047] The forging material composition consists of the following components by weight percentage:

[0048] 0.14%, Si: 0.22%, Mn: 0.53%, P: 0.007%, S: 0.002%, Cr: 2.42%, Mo: 1.08%, Ni: 0.20%, Al: 0. 027%, Cu: 0.05%, Sn: 0.0032%, As: 0.006%, V: 0.012%, Sb: 0.0015%, Pb: 0.0006%, H: 0.9ppm.

[0049] The specific steps are as follows:

[0050] (1) Forging process: The raw materials with the above composition are heated and then forged. The initial forging temperature is 1120℃ and the final forging temperature is 900℃. The forging ratio is 42.88:1. During the forging process, the temperature is heated to 1230℃ and held for 6 hours. Finally, the forging is carried out of the furnace and repeatedly upsetting and drawing by the press and forging hammer to eliminate the internal defects of the raw materials and make the material more compact. Finally, the forging is formed.

[0051] (2) Post-forging heat treatment:

[0052] The forgings obtained in step (1) were normalized. The furnace temperature of the forgings was 210℃, the heating rate was 120℃ / h, and the forgings were held at 955℃ for 3.5 hours before being air-cooled.

[0053] (3) Performance heat treatment:

[0054] Quenching: The forgings after normalizing in step (2) are first quenched. The furnace temperature of the forgings is 180℃, the heating rate is 120℃ / h, and they are held at 940℃ for 3.0 hours before being water cooled.

[0055] Tempering: The forgings after quenching are tempered. The forgings are fed into the furnace at a temperature of 180℃, with a heating rate of 120℃ / h. They are held at 665℃ for 6.0 hours and then air-cooled.

[0056] Example 3:

[0057] The forging material composition consists of the following components by weight percentage:

[0058] 0.135%, Si: 0.20%, Mn: 0.51%, P: 0.010%, S: 0.001%, Cr: 2.40%, Mo: 1.07%, Ni: 0.25%, Al: 0. 024%, Cu: 0.05%, Sn: 0.0027%, As: 0.006%, V: 0.017%, Sb: 0.0009%, Pb: 0.0004%, H: 0.52ppm.

[0059] The specific steps are as follows:

[0060] (1) Forging process: The raw materials with the above composition are heated and then forged. The initial forging temperature is 1120℃ and the final forging temperature is 900℃. The forging ratio is 23.7:1. During the forging process, when the temperature is heated to 1230℃, it is held for 5 hours. Finally, the forging is carried out of the furnace and repeatedly upsetting and drawing by the press and forging hammer to eliminate the internal defects of the raw materials and make the material more compact. Finally, the forging is formed.

[0061] (2) Post-forging heat treatment:

[0062] The forgings obtained in step (1) were normalized. The furnace temperature of the forgings was 210℃, the heating rate was 120℃ / h, and the forgings were held at 950℃ for 7.0 hours before being air-cooled.

[0063] (3) Performance heat treatment:

[0064] Quenching: The forgings after normalizing in step (2) are first quenched. The furnace temperature of the forgings is 180℃, the heating rate is 120℃ / h, and the temperature is held at 940℃ for 6.0 hours before water cooling.

[0065] Tempering: The forgings after quenching are tempered. The forgings are fed into the furnace at a temperature of 180℃, with a heating rate of 120℃ / h. They are held at 660℃ for 8.0 hours and then air-cooled.

[0066] Mechanical properties were tested on the products produced in Examples 1-3, and the results are shown in Table 1.

[0067] Table 1 Results of Mechanical Property Tests

[0068]

[0069] This invention improves the steel forging process in three aspects: formulation, forging process, and heat treatment process. First, it strengthens the grains by refining the formulation. Second, it eliminates cracks by forging. When the forging temperature is close to the final forging temperature, a light-hammering and fast-forging process is used to make the grains even finer. Finally, it combines the heat treatment process to achieve excellent mechanical properties, thus solving the current technical problems and obtaining F22 material with excellent performance.

[0070] According to API 6A requirements, the hardness of forgings with NACE requirements cannot exceed 237 HBW. The hardness control range of this invention is 217-237 HBW, which meets the NACE requirements. Since hardness and strength are interrelated, increasing hardness can increase strength. At the same time, it is necessary to consider improving the overall performance of the material. This requires comprehensive consideration from three aspects: material composition, forging, and heat treatment. This invention effectively controls these three aspects, meeting the NACE requirements while significantly improving indicators such as elongation, reduction of area, and impact toughness. This results in excellent overall performance of the forgings and solves the current technical problems.

[0071] Further testing was conducted on the forging material prepared in Example 2:

[0072] Figure 1 The image shows the grain size of the material, tested according to the ASTM E112-13(2021) comparative method. The image shows that the grain size is very fine, at grade 9. Grain size reflects the quality of the forging during actual heat treatment and hot working, and directly affects the microstructure and properties of the product obtained after the steel is cooled.

[0073] Microstructural testing is based on: ASTM E407-07(2015)e1; Figure 2 The image shows the microstructure of the material under a 100x microscope, which demonstrates that the tissue distribution is uniform under 100x magnification. Figure 3 The image shows the microstructure of the material under a 500x microscope, which reveals that it consists of granular bainite and ferrite.

[0074] Figure 4Table 2 shows the non-metallic inclusions in the material (testing standard: ASTM E45-18a Method A). As can be seen from the figures, the non-metallic inclusions in the material of this invention are well controlled, and the test results are excellent.

[0075] Table 2 Results of Non-metallic Inclusion Detection

[0076]

[0077] Figure 5 The image shows the low-magnification microstructure of the material (testing standard: ASTM E381-20). Combined with Table 3, it can be seen that the forging ratio of the present invention is appropriate, and the low-magnification microstructure of the material is very dense.

[0078] Table 3. Results of low-magnification tissue analysis

[0079]

[0080] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for producing F22 forgings for deep-sea oil and gas equipment that meet NACE standards, characterized in that, F22 forgings consist of the following components by mass percentage composition: C: 0.13-0.15%, Si: 0.15-0.30%, Mn: 0.50-0.60%, P: ≤0.010%, S: ≤0.005%, Cr: 2.40-2.50%, Mo: 1.05-1.13%, Ni: 0-0.50%, Al: 0.020-0.05%, Cu: ≤0.25%, Sn: ≤0.010%, As: ≤0.010%, V: 0.01-0.03%, Sb: ≤0.010%, Pb: ≤0.010%, H: ≤2ppm, with the balance being Fe and unavoidable impurities; the method includes the following steps: (1) Forging process: The initial forging temperature is 1100-1220℃, the final forging temperature is ≥850℃, and the forging ratio is 23.7~42.88:

1. During the forging process, the temperature is heated to 1210~1250℃ and held for 5-6 hours. Finally, the forging is carried out after being taken out of the furnace and repeatedly upsetting and drawing by the press and forging hammer to finally form the forging. (2) Normalizing treatment: The forgings obtained in step (1) are subjected to normalizing treatment. The furnace temperature is ≤350℃, the heating rate is ≤150℃ / h, and the furnace is held at 940-960℃ for 3.5-7 hours before air cooling to obtain the normalized forgings. (3) Performance heat treatment: (a) The forgings after normalizing in step (2) are first quenched. The furnace temperature of the forgings is controlled to be ≤350℃, the heating rate is ≤150℃ / h, and the forgings are held at 930-950℃ for 3-6 hours and then water-cooled to obtain the quenched forgings. (b) The forgings quenched in step (a) are tempered, and the furnace temperature is controlled to be ≤350℃, the heating rate is ≤150℃ / h, and the forgings are held at 660~665℃ for 6~10 hours and then air-cooled to obtain F22 forgings for deep-sea oil and gas equipment that meet NACE standards; wherein the hardness of the F22 forgings is controlled within the range of 217-237HBW.

2. The method for producing F22 forgings for deep-sea oil and gas equipment that meet NACE standards according to claim 1, characterized in that, The final forging temperature in step (1) is 900℃.

3. The method for producing F22 forgings for deep-sea oil and gas equipment that meet NACE standards according to claim 1, characterized in that, In step (2), the furnace temperature is 200~350℃ and the heating rate is 100~150℃ / h.

4. The method for producing F22 forgings for deep-sea oil and gas equipment that meet NACE standards according to claim 1, characterized in that, In step (3) (a), the furnace temperature is 180℃~200℃ and the heating rate is 120~150℃ / h.

5. The method for producing F22 forgings for deep-sea oil and gas equipment that meet NACE standards according to claim 1, characterized in that, In step (3) (b), the furnace temperature is 180℃~200℃ and the heating rate is 120~150℃ / h.

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