Manufacturing method of ultra-deep water jacket watertight partition plate with straight edge splicing

Abstract

The invention discloses a manufacturing method of an ultra-deep water jacket straight edge splicing watertight partition plate, and belongs to the technical field of hardening and tempering process manufacturing. According to the manufacturing method, two steel plates with the diameter of 4 m are spliced and then welded and filled to form a plate with a welded joint; the method comprises the following steps: heating and pressing a plate for multiple times, cooling to room temperature by air cooling, carrying out primary heating and heat preservation according to a normalizing temperature, and carrying out water-cooling quenching for 10-20 minutes to ensure that a watertight partition plate product can be rapidly cooled, carrying out tempering and thermal refining after water-cooling to room temperature, carrying out furnace cooling to 400 DEG C, taking out and carrying out air cooling to room temperature, thereby obtaining the watertight partition plate. By means of the manufacturing method, the abutted seam welding steel plate can be pressed into the ellipsoidal watertight partition plate with the straight edge, the impact toughness is excellent, the yield strength and the tensile strength of a weld joint are effectively improved, the ductility reaches 28%, and the application requirement of the ocean ultra-deep water environment can be well met.

Description

Technical Field

[0001] The present invention relates to the technical field of quenched and tempered steel plate manufacturing, and particularly relates to a manufacturing method for a water-tight partition with straight edges spliced in a ultra-deepwater jacket Background Art

[0003] The environmental conditions in the ultra-deepwater marine environment are harsh and the geological conditions are complex, where the hydrostatic pressure can reach 30 - 40 MPa. In order to meet the service safety and reliability requirements of ultra-deepwater jackets in the ultra-deepwater marine environment, the outer diameter of the jacket legs of existing ultra-deepwater jackets is usually up to 4 meters, which leads to more stringent requirements for the watertightness of ultra-deepwater jackets. The watertight partition (watertight plate) in an ultra-deepwater jacket is a key structural component specifically designed to resist the watertightness of the deep-sea high-pressure environment. The watertight partition adopts a high-strength steel plate screen welding design to form a closed pressure-bearing space with the conduit, so as to improve the watertightness, and at the same time evenly disperse the external high pressure to the entire structure of the jacket to avoid brittle failure caused by local stress concentration. As Figure 1 shown, the feeding thickness of the traditional ellipsoidal watertight partition is usually 19 - 50 mm, which is made by cold stamping or hot stamping, and the diameter usually does not exceed 2 m. At the same time, when the traditional ellipsoidal watertight partition is welded to the conduit, a weld seam with an angle of 45° will be generated, making it difficult to resist the hydrostatic pressure load. In order to solve the problems existing in the application of the traditional ellipsoidal watertight partition in ultra-deepwater jackets, as Figure 2 shown, the watertight partition of a conduit with an outer diameter of 4 m needs to add straight edges on the basis of the traditional ellipsoidal watertight partition to facilitate subsequent in-conduit welding construction reinforcement, so as to better resist the hydrostatic pressure load. The original steel plate material of the watertight partition with straight edges spliced is DH36-Z35, the feeding thickness is generally not less than 50 mm, and the feeding size does not exceed 8 meters. Due to the limitation of the steel plate width, the steel plate needs to be spliced by welding, and then is pressed by multiple external hot stamping at the normalizing temperature and then air-cooled. However, multiple hot stamping will cause loss of the steel plate thickness. At the same time, since welding itself belongs to a casting process, the weld structure has non-uniformity and a large difference from the base metal. After multiple hot stamping and then air-cooling, the weld of the spliced steel plate will be heated multiple times, greatly reducing the mechanical properties of the weld and the heat-affected zone, and making the performance indexes such as the tensile strength, yield strength, and weld elongation rate of the welded joint unable to meet the performance requirements of ultra-deepwater jackets in the ultra-deepwater marine environment.

[0004] In summary, the existing watertight partitions are difficult to resist the hydrostatic pressure load in the ultra-deepwater marine environment, cannot meet the dual requirements of yield strength and tensile strength for application in ultra-deepwater jackets, and severely restrict the economic and efficient development of China's marine oil and gas resources. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a manufacturing method for a super-deepwater jacket with a straight-edge spliced watertight bulkhead. Through this manufacturing method, the spliced steel plates can be welded and then pressed into an ellipsoidal watertight bulkhead with straight edges, which has excellent impact toughness, effectively improves the yield strength and tensile strength, and the elongation rate reaches 28%, and can well meet the application requirements of the marine super-deepwater environment.

[0006] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0007] A manufacturing method for a super-deepwater jacket with a straight-edge spliced watertight bulkhead, which includes the following steps:

[0008] S1. Welding: Provide two steel plates with a diameter of 4m. After butt joint, weld filling is carried out to form a plate with a welded joint.

[0009] S2. Heating and pressing: Heat the plate in step S1 to 850 - 900 °C, keep it warm, take it out of the furnace for pressing, and the final pressing temperature ≥ 750 °C. Repeat the above process 3 - 5 times.

[0010] S3. Staged heating: Wait for the workpiece in step S2 to air-cool to room temperature, take it out of the furnace for pressing, heat the workpiece to 850 - 900 °C for the first heating, and keep it warm for 30 - 60 min; after air-cooling to room temperature, heat the workpiece to 850 - 950 °C again for the second heating, keep it warm for normalizing for 30 - 60 min, then water-cool and quench for 10 - 20 min, and air-cool to room temperature.

[0011] S4. Tempering treatment: Temper the workpiece obtained in step S3 by heating it to 650 - 700 °C for tempering. After tempering and keeping it warm for 120 - 150 min, cool it in the furnace to 400 °C, and then take it out and air-cool to room temperature to obtain the product.

[0012] As a preferred embodiment of the present invention, in step S2, the holding time t = T × 1 min ± 10 min, where T is the thickness of the plate in mm.

[0013] As a preferred embodiment of the present invention, in steps S2 and S3, the heating rate is 200 - 300 °C / h. Control the heating rate after the temperature of the plate or workpiece reaches 300 °C, 300

[0014] As a preferred embodiment of the present invention, in steps S2 - S4, the allowable temperature difference of the heating temperature is ±20 °C.

[0015] As a preferred embodiment of the present invention, in step S4, the heating rate of tempering is 65 - 85 °C / h.

[0016] As a preferred embodiment of the present invention, in step S4, the cooling rate of furnace cooling is 250 - 280 °C / h.

[0017] As a preferred embodiment of the present invention, the thickness of the steel plate in step S1 is 50-70 mm.

[0018] As a preferred embodiment of the present invention, the material of the steel plate in step S1 is DH36-Z35, and the steel plate is made of a normalized plate produced in accordance with GB 712-2011.

[0019] As a preferred embodiment of the present invention, step S3 includes a step of sizing after being heated once and cooled to room temperature. If the as-furnace size meets the requirements, this step is not required.

[0020] The present invention also provides a super-deepwater jacket with a straight-edge spliced watertight bulkhead, and the straight-edge spliced watertight bulkhead is made by the above manufacturing method.

[0021] As a preferred embodiment of the present invention, the tensile strength of the welded joint of the super-deepwater jacket with a straight-edge spliced watertight bulkhead is 490-620 Mpa, the yield strength ≥ 355 Mpa, the weld elongation ≥ 21%, the impact toughness average value at -20 °C is greater than 50 J, and the single value is greater than 34 J.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The manufacturing method of the present invention obtains an ellipsoidal watertight bulkhead with a straight edge by splicing and welding two steel plates with a diameter of 4 m and then performing hot forming pressing at the normalizing temperature multiple times. Then, it is heated again, and finally, water quenching is used for rapid cooling and tempering treatment. Compared with the existing normalizing technology, for the large-diameter and large-thickness watertight bulkhead, the air-cooling cooling rate is uncertain, and air cooling cannot control the cooling time and the uniformity of the structural parts, so the stability of the weld quality of the welded component products cannot be guaranteed. However, quenching plus tempering can control the cooling rate and the tempering rate, and the process is relatively controllable. The tensile strength of the welded joint of the straight-edge spliced watertight bulkhead can be 490-620 Mpa, the yield strength ≥ 355 Mpa, the weld elongation ≥ 21%, the impact toughness average value at -20 °C is greater than 50 J, the single value is greater than 34 J, the tolerance standard reaches the ASMEⅧ-1 standard, and the product performance meets the requirements of the project specification and AWSD1.1 / D1.1M--2015. Description of the Drawings

[0024] Figure 1 It is a physical diagram of a traditional ellipsoidal watertight bulkhead;

[0025] Figure 2 It is a physical diagram of the straight-edge spliced ellipsoidal watertight bulkhead of the present invention;

[0026] Figure 3The heat treatment curve graph of the manufacturing method of Embodiment 1 of the present invention;

[0027] Figure 4 The heat treatment curve graph of the manufacturing method of Comparative Example 1 of the present invention;

[0028] Figure 5 The tensile comparison graph of the watertight partitions prepared in Embodiment 1 and Comparative Example 1 of the present invention;

[0029] Figure 6 The guiding bending comparison graph of the watertight partitions prepared in Embodiment 1 and Comparative Example 1 of the present invention;

[0030] Figure 7 The metallographic comparison graph of the watertight partitions prepared in Embodiment 1 and Comparative Example 1 of the present invention. Detailed implementation manners

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0032] A manufacturing method for a watertight partition with a straight-edge splicing for a ultra-deepwater jacket specifically includes the following steps:

[0033] S1. Welding: Provide two steel plates DH36-Z35 with a diameter of 4 m and a thickness of 50 - 70 mm. After butt joint, first use manual arc welding, and then weld and fill by submerged arc welding to form a plate with a welded joint;

[0034] S2. Heating and pressing: Heat the plate in step S1 to 850 - 900 °C at a heating rate of 200 - 300 °C / h, with an allowable temperature difference of ±20 °C, keep warm, take out of the furnace for pressing, and the final pressing temperature ≥750 °C. Repeat the above process 3 - 5 times; wherein, the holding time t = T × 1 min ± 10 min, T is the plate thickness, and the unit is mm;

[0035] S3. Staged heating: Wait for the workpiece in step S2 to air-cool to room temperature, take out of the furnace for pressing, heat the workpiece to 850 - 900 °C at a heating rate of 200 - 300 °C / h for the first heating, keep warm for 30 - 60 min, and perform final size trimming; after air-cooling to room temperature, heat the workpiece to 850 - 950 °C at a heating rate of 200 - 300 °C / h again for the second heating, with an allowable temperature difference of ±20 °C. After keeping warm and normalizing for 30 - 60 min, perform water quenching for 10 - 20 min, and then air-cool to room temperature;

[0036] S4, quenching and tempering treatment: Heat the workpiece obtained in step S3 to 650 - 700°C for quenching and tempering at a heating rate of 65 - 85°C / h. The allowable temperature difference is ±20°C. After tempering and holding for 120 - 150 minutes, cool it in the furnace to 400°C at a heating rate of 250 - 280°C / h, then take it out and air-cool it to room temperature to obtain the product.

[0037] The present invention also provides a super-deepwater jacket with a straight-edge spliced watertight bulkhead, and the straight-edge spliced watertight bulkhead is obtained by the above manufacturing method.

[0038] Example 1

[0039] As Figure 3 shown, a manufacturing method of a super-deepwater jacket with a straight-edge spliced watertight bulkhead includes the following steps:

[0040] S1, welding: Provide two steel plates DH36-Z35 with a diameter of 4m and a thickness of 70mm. After butt joint, first use manual arc welding and then perform submerged arc welding to fill and form a plate with a welded joint. Among them, the backing weld uses electrode Tenacito R, the filler weld uses welding wire SA1ACrMo, and the flux is LA436. The welding parameters are shown in Table 1.

[0041] Table 1 Welding parameters

[0042]

[0043] S2, heating and pressing: Place the plate in step S1 in the furnace. The furnace inlet temperature is 40°C. After heating to 300°C, continue to heat the plate to 880 ± 20°C at a heating rate of 300°C / h, hold for 70 minutes, take it out of the furnace for pressing, and the final pressing temperature ≥ 750°C. Repeat the above process 4 times, that is, a total of 3 times of taking it out of the furnace for pressing;

[0044] S3, staged heating: Wait for the workpiece in step S2 to air-cool to room temperature, take it out of the furnace for pressing, heat the workpiece to 880 ± 20°C at a heating rate of 300°C / h for the first heating, and hold for 45 minutes; perform final size trimming. After air-cooling to room temperature, heat the workpiece to 900 ± 20°C again at a heating rate of 300°C / h for the second heating. After holding for normalizing for 45 minutes, perform water quenching for 15 minutes, and then air-cool to room temperature;

[0045] S4, quenching and tempering treatment: Heat the workpiece obtained in step S3 to 650 ± 20°C for quenching and tempering at a heating rate of 85°C / h. After tempering and holding for 145 minutes, cool it in the furnace to 400°C at a heating rate of 280°C / h, then take it out and air-cool it to room temperature to obtain the product.

[0046] Comparative Example 1

[0047] This comparative example provides a manufacturing method for a super-deepwater jacket with a straight-edge watertight bulkhead. As Figure 4 shown, steps S1 and S2 in this manufacturing method are exactly the same as those in Example 1. The differences between this comparative example and Example 1 lie in steps S3 and S4, which are specifically as follows:

[0048] S3. Stage heating: After the workpiece in step S2 is air-cooled to room temperature and taken out of the furnace for pressing, the workpiece is heated to 880 ± 20 °C at a heating rate of 300 °C / h for the first heating and held for 45 min; after air-cooling to room temperature, final size trimming is carried out, and then the workpiece is heated to 900 ± 20 °C at a heating rate of 300 °C / h for the second heating. After normalizing and holding for 45 min, it is air-cooled to room temperature;

[0049] S4. Tempering treatment: The workpiece obtained in step S3 is tempered and heated to 650 ± 20 °C at a heating rate of 85 °C / h for tempering. After tempering and holding for 145 min, it is furnace-cooled to 400 °C at a cooling rate of 280 °C / h and then taken out and air-cooled to room temperature to obtain the product.

[0050] I. Mechanical property test

[0051] Simulate the production construction process of the ellipsoidal straight-edge spliced watertight bulkhead, including welding, heat treatment, and cooling treatment. Mechanical property test comparisons were carried out on specimens using the modulation process of Example 1 and the normalizing process of Comparative Example 1. The test method comprehensively tested various positions of the welded joint, including: tensile strength, yield strength, elongation, bending, impact, tensile strength of the weld metal, yield strength, elongation, transverse and longitudinal tensile strength of the base material, and yield strength. The test standards refer to the project welding specification and AWS D1.1 / D1.1M—2015. The results are shown in Table 2.

[0052] Table 2 Mechanical property data of the straight-edge watertight bulkhead in Example 1 and Comparative Example 1

[0053]

[0054] As can be seen from the data in Table 2, compared with the traditional normalizing method, the present invention can effectively improve the yield strength of the welded joint, the yield strength of the weld metal, and the yield strength of the base material by using the tempering method, and all of them meet the standard requirement range.

[0055] II. Tensile test

[0056] As Figure 5 can be seen, after the tensile test using the latest tempering method, its strength is 517 / 516 Mpa, and the fracture position of the tensile specimen is the base material. The strength of the specimen by the normalizing method is 460 / 465 Mpa, and the fracture position of the tensile specimen is the center of the weld. The properties after tempering all meet the standard requirements.

[0057] III. Guided Bending Test

[0058] As can be seen from Figure 6 it, according to the standards and specifications, the bending test should adopt the side bending method, the bending shaft diameter should be 50.8 mm, and the bending angle should be 180°. After the bending tests of Example 1 and Comparative Example 1, there were no cracks and fissures. The results of the bending test showed that both states met the standard requirements.

[0059] IV. Impact Toughness Test

[0060] The impact toughness tests were carried out on Example 1 and Comparative Example 1. The test temperature was -20 °C, and the test method referred to AWSD1.1 / D1.1M--2015 and ASTM A370--19el. The results are shown in Tables 3 and 4.

[0061] Table 3 Impact Toughness Data of Welded Joints

[0062]

[0063] As can be seen from Table 3, all the results of Example 1 after testing met the requirements of the standards and specifications, and the impact toughness values were stable without abnormalities. The average impact toughness value at the center of the weld in Comparative Example 1 was lower than the requirements of the standards and specifications, and the experimental results were unqualified.

[0064] Table 4 Impact Toughness Data of Base Metal

[0065]

[0066]

[0067] As can be seen from Table 4, both Example 1 and Comparative Example 1 met the requirements, proving that the influence on the base metal was small.

[0068] V. Metallographic Comparison Diagram

[0069] As can be seen from Figure 7 it, by comparing Example 1 and Comparative Example 1, it can be known that after the water-tight partition was formed, due to normalizing and pressing to weld and join the water-tight partition, the weld was heated multiple times. In Comparative Example 1, the normalized structure formed a hypoeutectoid steel microstructure after hot working, with a banded structure in which ferrite and pearlite were alternately layered along the rolling deformation direction. This was due to the difference in the cooling and solidification rates of the surface and the core of the steel plate, which easily formed a central structure with porosity. The banded structure would cause anisotropy in the mechanical properties of the welded joint.

[0070] It can be seen from the metallographic structure photos that the structure obtained after the quenching and high-temperature tempering treatment of Example 1 is fine and uniform, the banded structure is basically eliminated, and its cementite is dispersed in a spheroidal shape, making the material properties tend to be homogenized. It can be seen that compared with the normalized state of Comparative Example 1, the quenched and tempered state of Example 1 not only has higher strength, but also has higher plasticity and toughness than the normalized state.

[0071] The above-mentioned implementation manners are only the preferred implementation manners of the present invention, and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of protection required by the present invention.

Claims

1. A manufacturing method of a super-deepwater jacket with a straight-edge spliced watertight bulkhead, characterized in that: It includes the following steps: S1. Welding: Provide two steel plates with a diameter of 4m. After splicing, fill them by welding to form a plate with a welded joint. S2. Heating and pressing: Heat the plate obtained in step S1 to 850 - 900 °C, keep it warm, take it out of the furnace for pressing, and the final pressing temperature ≥ 750 °C. Repeat the above process 3 - 5 times. S3. Staged heating: Wait for the workpiece obtained in step S2 to be air-cooled to room temperature, take it out of the furnace for pressing, heat the workpiece to 850 - 900 °C for the first heating and keep it warm for 30 - 60 min; after air-cooling to room temperature, heat the workpiece to 850 - 950 °C again for the second heating. After normalizing and keeping it warm for 30 - 60 min, quench it in water for 10 - 20 min and then cool it to room temperature. S4. Tempering treatment: Temper the workpiece obtained in step S3 by heating it to 650 - 700 °C. After tempering and keeping it warm for 120 - 150 min, cool it in the furnace to 400 °C, and then air-cool it to room temperature to obtain the product.

2. The manufacturing method of the ultra-deepwater jacket with straight-edge watertight partitions according to claim 1, wherein: In step S2, the holding time t = T × 1 min ± 10 min, where T is the thickness of the plate.

3. The manufacturing method of the ultra-deepwater jacket with a watertight partition having a straight-edge splice according to claim 1, wherein: In steps S2 and S3, the heating rate is 200 - 300 °C / h.

4. The manufacturing method of the ultra-deepwater jacket with a watertight partition having a straight-edge splicing according to claim 1, wherein: In steps S2 - S4, the allowable temperature difference of the heating temperature is ±20 °C.

5. The manufacturing method of the ultra-deepwater jacket with a watertight partition having a straight-edge splicing according to claim 1, characterized in that: In step S4, the heating rate of the tempering heating is 65 - 85 °C / h.

6. The manufacturing method of the ultra-deepwater jacket with a watertight partition having a straight-edge splicing according to claim 1, characterized in that: In step S4, the cooling rate of the furnace cooling is 250 - 280 °C / h.

7. The manufacturing method of the ultra-deepwater jacket with a watertight bulkhead having a straight-edge splicing according to claim 1, wherein: In step S1, the thickness of the steel plate is 50 - 70 mm.

8. The manufacturing method of the ultra-deepwater jacket with a watertight bulkhead having a straight-edge splicing according to claim 1, wherein: In step S1, the material of the steel plate is DH36-Z35.

9. The manufacturing method of the ultra-deepwater jacket with a watertight partition having a straight-edge splicing according to claim 1, characterized in that: In step S3, it also includes a step of sizing after the first heating and cooling to room temperature.

10. A super-deepwater jacket with a straight-edge spliced watertight bulkhead, characterized in that: The straight-edge splicing watertight bulkhead is made by the manufacturing method according to any one of claims 1 - 9.

Images