Production method of 15CrMoR steel plate with excellent high-temperature performance for rare earth microalloying hydrogen-contacting equipment

Abstract

The invention discloses a production method of a 15CrMoR steel plate for rare earth microalloying hydrogen-contacting equipment with excellent high-temperature performance. The production method comprises the steps of KR desulfurization, converter smelting, LF refining, RH refining, continuous casting, slow cooling in a heat preservation pit, heating, rolling, cooling, hot straightening, shearing, flaw detection, normalizing and tempering. The steel comprises the following chemical components in percentage by mass: 0.15-0.17% of C, 0.20-0.30% of S i, 0.50-0.60% of Mn, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.019-0.029% of Al s, 0.9-1.1% of Cr, 0.50-0.60% of Mo, less than or equal to 0.0020% of Ce, less than or equal to 1.5 ppm of H, less than or equal to 0.0040% of O, less than or equal to 0.0060% of N and the balance of Fe. And the balance of iron impurities. A normalizing and tempering heat treatment process is adopted, and a low-carbon component design is adopted to ensure that the steel plate obtains excellent high-temperature performance and welding performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot rolling, and particularly relates to a production method of 15CrMoR steel plate for hydrogen-containing equipment with excellent high-temperature performance and rare-earth microalloying. Background Art

[0002] The steel plate for hydrogen-containing equipment of 15CrMoR is mainly applied to industries or fields such as chemical engineering, coal chemical industry, and petrochemical industry.

[0003] The literature "Development of Medium-temperature Pressure Vessel Steel 15CrMoR in Anyang Iron and Steel" analyzed the production process of 15CrMoR steel with a thickness of less than 50. This patent provides a production method of 50-80mm rare-earth microalloyed 15CrMoR steel plate, specifying the specific production process and being suitable for batch production.

[0004] The literature "Research and Production of 15CrMoR Steel Plate with Requirements of Post-weld Heat Treatment by High-temperature Simulation for Large Thickness" provided a production method of 15CrMoR with a thickness of 80-120mm, and the production process adopted quenching + tempering process. This method provides a production method of 50-80mm rare-earth microalloyed 15CrMoR steel plate, and the production process adopts normalizing + tempering process to reduce the process cost. At the same time, adding rare earth reduces the sensitivity to welding cracks. Through the production process of slab quenching + hot charging, the manufacturing cost is reduced. Compared with the above patent, the process is stable, easy to control, and has excellent high-temperature performance and weldability.

[0005] The literature "Research and Development of 15CrMoR(H) Steel for Medium-temperature Pressure Vessel in Hydrogen Environment" provided a process for 15CrMoR steel plate with a thickness of less than 60mm, and Ni and Cu were added to the composition, resulting in a higher cost. This method provides a production method of 50-80mm rare-earth microalloyed 15CrMoR steel plate, adding rare earth to reduce the sensitivity to welding cracks. Through the production process of slab quenching + hot charging, the manufacturing cost is reduced. Compared with the above patent, the process is stable, easy to control, and has excellent high-temperature performance and weldability.

[0006] With the increase in the strength of steel plates, their weldability decreases significantly, and the sensitivity to welding cracks increases. Especially with the increase in the welding line energy, the properties of the heat-affected zone of traditional low-alloy high-strength steel deteriorate during welding. Generally, high-strength plates need to be welded before use. At present, improving welding efficiency and reducing welding costs by means of high-line-energy welding has become a hot trend in the pressure vessel field. In order to improve the properties of the heat-affected zone of thick plates during welding, rare-earth-containing steel plates utilize the fine, dispersed, and composition-controllable oxide inclusions generated during the steelmaking process to change the microstructure and grain size of the steel, thereby improving the weldability of the steel. Rare-earth oxides delay the bainite transformation during welding and inhibit the formation of upper bainite microstructure. On the other hand, the fine rare-earth oxide inclusions inhibit the growth of austenite grains. In addition, previous studies on the effects of different rare-earth, oxygen, and sulfur contents on inclusions in steel and the effects of rare-earth inclusions on austenite grain boundaries have shown that compared with rare-earth oxides, rare-earth aluminates, and rare-earth oxysulfide inclusions, controlling the formation of rare-earth sulfides in steel is more beneficial to improving the toughness of the heat-affected zone during welding. Based on the above principles, through a large number of experimental studies, it is proposed that the welding crack sensitivity index Pcm of steel plates with low welding crack sensitivity be revised as follows:

[0007] Pcm(%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B - 120Ce Summary of the Invention

[0008] The object of the present invention is to provide a production method for 15CrMoR steel plates for hydrogen-containing equipment with excellent high-temperature performance and rare-earth microalloying. The normalizing + tempering heat treatment process is adopted, low-carbon composition design is used, appropriate amounts of Mn, Mo, Cr, Ti, and rare-earth elements are added for microalloying with narrow composition control, and the rolling and heat treatment processes are precisely controlled to ensure that the steel plates obtain excellent high-temperature performance and weldability.

[0009] To solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A production method for 15CrMoR steel plates for hydrogen-containing equipment with excellent high-temperature performance and rare-earth microalloying according to the present invention includes:

[0011] 1) The tapping temperature of the converter is 1600 - 1660 °C. The single-slag process is used for smelting. The converter adopts single-slag operation, high-quality active lime is used, and the basicity of the final slag is controlled at 3.2 - 3.6; and self-produced high-quality scrap steel is used to reduce the [S] brought in by the scrap steel; the bottom blowing gas of the converter adopts the whole-process argon blowing mode, and the end point is preferably hit once as much as possible to reduce the nitrogen increase in the molten steel due to supplementary blowing;

[0012] 2) Precisely control the composition during refining. The addition amount of white lime is ≥5 kg / ton of steel. During the refining process, the slag sample must be dipped to ensure the rapid formation of white slag and keep the white slag for a certain period of time;

[0013] 3) The molten steel is processed in an RH furnace. The RH vacuum treatment time is not less than 20 minutes, the pure degassing time is not less than 5 minutes, the minimum vacuum degree is 260 Pa, and the off-position hydrogen content is less than or equal to 1.8 ppm.

[0014] 4) To ensure the quality of the slab with a certain compression ratio, continuous casting billets with a thickness of 300 mm are selected. The center segregation of the slab is not greater than B1.0, the center porosity is not greater than grade 2.5, and the middle crack is not greater than grade 1.0. When casting the continuous casting molten steel, the superheat is controlled at 15 - 26 °C, the argon blowing pressure of the long nozzle is ≥ 0.1 Mpa, the flow rate of the argon blowing standby pressure gauge between the submerged nozzles of the tundish reaches 6 - 10 L / min, the pressure of the standby pressure gauge is 0.1 - 0.5 Bar, and the casting machine drawing speed is 0.9 - 1.1 m / min.

[0015] 5) Optimize and adjust the acceleration time of the roller table in the quenching beam to control the surface quenching and cooling time of the slab within 150S - 250S, and design 16 groups of quenching cooling water beams. The cooling time for slow cooling is ≤ 200 min, the slab furnace inlet temperature is 500 - 550 °C, the total time in the furnace is ≥ 180 min. The walking beam reheating furnace with three-stage heating is used when heating the slab. The heating temperature of the first heating section is 1100 - 1160 °C, and the heating time is 40 - 60 minutes. The heating temperature of the second heating section is 1200 - 1260 °C, and the heating time is 40 - 60 min. The soaking temperature is 1230 - 1280 °C, and the heating time is ≥ 40 min. The total heating time is not less than 180 min, and the slab furnace outlet temperature is 1210 - 1250 °C.

[0016] 6) Rolling and cooling process: After the slab is heated, two-stage controlled rolling is carried out. The first-stage rolling is completed on the roughing mill. The starting thickness of the first stage is the slab thickness. The starting temperature of the first stage is 1190 - 1210 °C. When rolling in the first stage, the set torque is 2400 kNm, the set reduction is 35 mm, the rolling speed is 2.0 - 3.4 m / s, and the single-pass reduction rate in the high-temperature elongation stage is not less than 18%. The second-stage rolling is completed on the finishing mill. The starting temperature of the second stage is 900 - 940 °C, the starting thickness of the second stage is 80 - 125 mm, the final rolling temperature of the second stage is 860 - 900 °C. When rolling in the second stage, the set torque is 2200 kNm, the set rolling force is 85 MN, the set reduction is 20 mm, and the reduction rate of the last pass is 12% - 15% to ensure the plate shape. After the steel plate is rolled, laminar flow cooling is carried out. The water temperature of the ACC is 17 - 20 °C, the cooling speed is 7 - 9 °C / s, the final cooling temperature is 620 - 660 °C. Generally, the head shielding is 0 - 2.0 m, the tail shielding is 0 - 2.5 m, and the side shielding is 0 - 2.0 m. Control the overall temperature difference after the steel plate turns red to ≤ 20 °C.

[0017] 7) Heat treatment process: Shot peening treatment is required before normalizing the steel plate. The normalizing holding temperature is 880 - 940 °C, the holding time is more than 100 - 140 minutes, and air cooling is used; the tempering holding temperature is 620 - 700 °C, the tempering holding time is more than 100 minutes, and air cooling is used;

[0018] The chemical composition of the steel plate by mass percentage is: C: 0.15 - 0.17, Si: 0.20 - 0.30, Mn: 0.50 - 0.60, P: ≤0.012, S: ≤0.005, Als: 0.019 - 0.029, Cr: 0.9 - 1.1, Mo: 0.50 - 0.60, Ce: ≤0.0020, H: ≤1.5 ppm, O: ≤0.0040, N: ≤0.0060, Pcm: ≤0.30; the rest is iron and inevitable impurities.

[0019] Furthermore, the chemical composition of the steel plate by mass percentage is: C: 0.16, Si: 0.25, Mn: 0.55, P: 0.009, S: 0.001, Als: 0.024, Cr: 1.0, Mo: 0.55, Ce: 0.0002, H: 0.8 ppm, O: 0.0021, N: 0.0042, Pcm: 0.26; the balance is Fe and inevitable impurities.

[0020] Furthermore, the chemical composition of the steel plate by mass percentage is: C: 0.15, Si: 0.22, Mn: 0.54, P: 0.008, S: 0.002, Als: 0.025, Cr: 0.9, Mo: 0.57, Ce: 0.0003, H: 0.8 ppm, O: 0.0018, N: 0.0038, Pcm: 0.23; the balance is Fe and inevitable impurities.

[0021] Furthermore, the chemical composition of the steel plate by mass percentage is: C: 0.17, Si: 0.28, Mn: 0.55, P: 0.008, S: ≤0.003, Als: 0.026, Cr: 1.0, Mo: 0.55, Ce: 0.0002, H: 1.1 ppm, O: 0.0020, N: 0.0049, Pcm: 0.27; the balance is Fe and inevitable impurities.

[0022] Furthermore, control the surface quenching cooling time of the slab at 160S, directly warm-load the slab into the heating furnace, the heating time is 200 minutes, and the soaking time is 45 minutes; roll it into a steel plate with a thickness of 60 mm.

[0023] Furthermore, control the surface hardening and cooling time of the slab at 172S, directly warm-charge the slab into the heating furnace, with a heating time of 196 minutes and a soaking time of 42 minutes; roll it into a steel plate with a thickness of 70mm.

[0024] Furthermore, control the surface hardening and cooling time of the slab at 180S, directly warm-charge the slab into the heating furnace, with a heating time of 209 minutes and a soaking time of 49 minutes; roll it into a steel plate with a thickness of 80mm.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are:

[0026] (1) The thickness of the steel plate is 50mm - 80mm;

[0027] (2) Appropriate alloying of the steel plate reduces the alloy cost while ensuring the performance of the steel plate;

[0028] (3) The slab adopts a hardening process and is directly warm-charged, reducing energy consumption and improving performance stability;

[0029] (4) The addition of an appropriate amount of rare earth elements reduces the sensitivity coefficient of welding cracks and improves the welding performance of the steel plate;

[0030] (5) The steel plate has excellent high-temperature performance and thickness-direction performance.

[0031] The prominent advantage of the present invention is the use of a C-Mn composition design, adding appropriate amounts of Mo, Cr elements and rare earth elements for microalloying and narrow composition control, which improves the performance stability of the steel plate for hydrogen-containing equipment, reduces the sensitivity of welding cracks, improves the welding performance of the steel plate, broadens the process design window, improves the batch production efficiency, and stably mass-produces 15CrMoR steel plates with a thickness of 50mm - 80mm. Through actual production and inspection, its mechanical properties are excellent, the strength of the steel plate in each embodiment meets the standard requirements, the elongation rate is greater than 20%, the impact energy of the steel plate at 20°C can reach more than 170J, and the welding crack sensitivity index Pcm is less than 0.30%. Detailed implementation manners

[0032] The following further describes the present invention in combination with embodiments.

[0033] Embodiment 1

[0034] Control the surface hardening cooling time of the slab at 160 s, directly warm-charge the slab into the heating furnace, with a heating time of 200 minutes and a soaking time of 45 minutes. The mass percentage content of the chemical composition of the slab is: C: 0.16, Si: 0.25, Mn: 0.55, P: 0.009, S: 0.001, Als: 0.024, Cr: 1.0, Mo: 0.55, Ce: 0.0002, H: 0.8 ppm, O: 0.0021, N: 0.0042, Pcm: 0.26; the balance is Fe and unavoidable impurities. Roll it into a steel plate with a thickness of 60 mm. The detailed rolling process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0035] Example 2

[0036] Control the surface hardening cooling time of the slab at 172 s, directly warm-charge the slab into the heating furnace, with a heating time of 196 minutes and a soaking time of 42 minutes. The mass percentage content of the chemical composition of the slab is: C: 0.15, Si: 0.22, Mn: 0.54, P: 0.008, S: 0.002, Als: 0.025, Cr: 0.9, Mo: 0.57, Ce: 0.0003, H: 0.8 ppm, O: 0.0018, N: 0.0038, Pcm: 0.23; the balance is Fe and unavoidable impurities. Roll it into a steel plate with a thickness of 70 mm. The detailed rolling process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0037] Example 3

[0038] Control the surface hardening cooling time of the slab at 180 s, directly warm-charge the slab into the heating furnace, with a heating time of 209 minutes and a soaking time of 49 minutes. The mass percentage content of the chemical composition of the slab is: C: 0.17, Si: 0.28, Mn: 0.55, P: 0.008, S: ≤0.003, Als: 0.026, Cr: 1.0, Mo: 0.55, Ce: 0.0002, H: 1.1 ppm, O: 0.0020, N: 0.0049, Pcm: 0.27; the balance is Fe and unavoidable impurities. Roll it into a steel plate with a thickness of 80 mm. The detailed rolling and heat treatment processes are shown in Table 1, and its mechanical properties are shown in Table 2.

[0039] The 50 - 80 mm rare earth steel plate with low welding crack sensitivity produced by using this composition and process design has chemical composition and mechanical properties meeting the national standard requirements of GB / T 713 - 2023 Steel Plates for Pressure Equipment. It has appropriate strength, a low yield ratio, excellent elongation, especially outstanding high-temperature performance, and good welding performance as feedback from users.

[0040] Table 1 Process Parameters of Examples 1 - 4

[0041]

[0042] Table 2 Mechanical properties of Examples 1-4

[0043]

[0044]

[0045] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing 15CrMoR steel plate with excellent high temperature performance and rare earth microalloying for hydrogenation equipment, characterized in that: include: 1) The tapping temperature of the converter is 1600-1660℃, and the single slag process is adopted for smelting. The converter adopts single slag operation, uses high-quality active lime, and the final slag basicity is controlled at 3.2-3.6; and self-produced high-quality scrap steel is used to reduce the [S] brought in by scrap steel; the bottom blowing gas of the converter adopts the full-process argon blowing mode, and the end point is hit as much as possible in one time to reduce the increase of nitrogen in the molten steel due to supplementary blowing; 2) Refining accurately controls the composition, the amount of lime added is ≥5kg / ton of steel, and the slag sample must be dipped during the refining process to ensure that the white slag is quickly formed and kept for a certain period of time; 3) The molten steel is subjected to RH furnace treatment, the RH vacuum treatment time is not less than 20 minutes, the pure degassing time is not less than 5 minutes, the minimum vacuum degree is 260Pa, and the off-site hydrogen content is less than or equal to 1.8ppm; 4) In order to ensure the quality of slabs with a certain compression ratio, 300mm thick continuous casting slabs are selected, the center segregation of the slab is not greater than B1.0, the center looseness is not greater than 2.5, and the middle crack is not greater than 1.0; the superheat during continuous casting molten steel casting is controlled at 15-26℃, the argon blowing pressure of the long nozzle is ≥0.1Mpa, the argon blowing standby pressure gauge flow rate of the tundish submerged nozzle plate reaches 6-10L / min, the standby pressure gauge pressure is 0.1-0.5Bar, and the casting machine pulling speed is 0.9-1.1m / min; 5) Optimize and adjust the acceleration time of the roller in the quenching beam, so that the slab surface quenching cooling time is controlled at 150S-250S, and design 16 sets of quenching cooling water beams; the cooling time is slow cooling time ≤200min, the slab furnace temperature is 500-550℃, the total furnace time is ≥180min, and the slab is heated in a three-stage walking beam heating furnace. The heating temperature of the first heating section is 1100-1160℃, and the heating time is 40-60 minutes; the heating temperature of the second heating section is 1200-1260℃, and the heating time is 40-60min; the ambulation temperature is 1230-1280℃, the heating time is ≥40min, the total heating time is not less than 180min, and the slab furnace temperature is 1210-1250℃; 6) Rolling and cooling process: After the slab is heated, two-stage controlled rolling is carried out. The first stage rolling is completed on the rough rolling mill. The first stage rolling thickness is the slab thickness. The first stage rolling temperature is 1190-1210°C. The set torque during the first stage rolling is 2400kNm, the set reduction is 35mm, the rolling speed is 2.0-3.4m / s, and the single pass reduction rate in the high temperature extension stage is not less than 18%; the second stage rolling is completed on the finishing mill. The second stage rolling temperature is 900-940°C, and the second stage rolling thickness is 80-1 25mm, the second stage final rolling temperature is 860-900℃, the second stage rolling torque is set to 2200kNm, the rolling force is set to 85MN, the reduction is set to 20mm, and the final reduction rate is 12%-15% to ensure the plate shape; after the steel plate is rolled, laminar cooling is carried out, the ACC water temperature is 17-20℃, the cooling rate is 7-9℃ / s, the final cooling temperature is 620-660℃, generally the head is shielded by 0-2.0m, the tail is shielded by 0-2.5m, and the edge is shielded by 0-2.0m, and the overall temperature difference of the steel plate after returning to red is controlled to be ≤20℃; 7) Heat treatment process: Shot blasting is required before normalizing the steel plate. The normalizing holding temperature is 880-940°C, the holding time is greater than 100-140 minutes, and air cooling is performed. Tempering and holding temperature is 620~700℃, tempering and holding time is more than 100 minutes, and air cooling; The chemical composition of the steel plate in mass percentage is: C: 0.15-0.17, Si: 0.20-0.30, Mn: 0.50-0.60, P: ≤0.012, S: ≤0.005, Als: 0.019-0.029, Cr: 0.9-1.1, Mo: 0.50-0.60, Ce: ≤0.0020, H: ≤1.5ppm, O: ≤0.0040, N: ≤0.0060, Pcm: ≤0.30; the rest is iron and unavoidable impurities.

2. The method for producing the rare earth microalloyed 15CrMoR steel plate for hydrogenation equipment with excellent high temperature performance according to claim 1, characterized in that: The chemical composition of the steel plate in mass percentage is: C: 0.16, Si: 0.25, Mn: 0.55, P: 0.009, S: 0.001, Als: 0.024, Cr: 1.0, Mo: 0.55, Ce: 0.0002, H: 0.8ppm, O: 0.0021, N: 0.0042, Pcm: 0.26; the remainder is Fe and unavoidable impurities.

3. The method for producing the rare earth microalloyed 15CrMoR steel plate for hydrogenation equipment with excellent high temperature performance according to claim 1, characterized in that: The chemical composition of the steel plate in mass percentage is: C: 0.15, Si: 0.22, Mn: 0.54, P: 0.008, S: 0.002, Als: 0.025, Cr: 0.9, Mo: 0.57, Ce: 0.0003, H: 0.8ppm, O: 0.0018, N: 0.0038, Pcm: 0.23; the remainder is Fe and unavoidable impurities.

4. The method for producing the rare earth microalloyed 15CrMoR steel plate for hydrogenation equipment with excellent high temperature performance according to claim 1, characterized in that: The chemical composition of the steel plate in mass percentage is: C: 0.17, Si: 0.28, Mn: 0.55, P: 0.008, S: ≤0.003, Als: 0.026, Cr: 1.0, Mo: 0.55, Ce: 0.0002, H: 1.1ppm, O: 0.0020, N: 0.0049, Pcm: 0.27; the remainder is Fe and unavoidable impurities.

5. The method for producing the rare earth microalloyed 15CrMoR steel plate for hydrogenation equipment with excellent high temperature performance according to claim 2, characterized in that: The slab surface quenching cooling time is controlled at 160S, the slab is directly placed in a heating furnace with a warm temperature, the heating time is 200 minutes, and the soaking time is 45 minutes; and the slab is rolled into a steel plate with a thickness of 60mm.

6. The method for producing the rare earth microalloyed 15CrMoR steel plate for hydrogenation equipment with excellent high temperature performance according to claim 3, characterized in that: The slab surface quenching cooling time is controlled at 172S, the slab is directly warm loaded into a heating furnace, the heating time is 196 minutes, and the soaking time is 42 minutes; and the slab is rolled into a steel plate with a thickness of 70mm.

7. The method for producing the rare earth microalloyed 15CrMoR steel plate for hydrogenation equipment with excellent high temperature performance according to claim 4, characterized in that: The slab surface quenching cooling time is controlled at 180S, the slab is directly placed in a heating furnace with a warm load, a heating time of 209 minutes, and a soaking time of 49 minutes; and the slab is rolled into a steel plate with a thickness of 80mm.

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