Production method for preparing rare earth microalloyed 14Cr1MoR steel plate by adopting continuous casting process and application of rare earth microalloyed 14Cr1MoR steel plate

Abstract

The invention discloses a production method and application for preparing a rare earth microalloyed 14Cr1MoR steel plate by adopting a continuous casting process, and the production method of the steel plate specifically comprises the following steps: electric furnace steelmaking, LF furnace refining, RH furnace refining, continuous casting, heat preservation pit slow cooling, rolling, cooling, flaw detection, normalizing, tempering, cutting, sampling and inspecting. The steel plate is moderately alloyed, the alloy cost is reduced on the premise that the performance of the steel plate is guaranteed, the 14Cr1MoR steel plate produced through the process of normalizing twice and tempering once is superior to a steel plate produced through the process of normalizing and tempering, and the 14Cr1MoR steel plate is excellent in impact toughness at the temperature of 20 DEG C below zero, can meet the requirements of harsh use environments and is suitable for industrial production. The elongation of the 14Cr1MoR steel plate produced by the method is greater than 20%, the impact energy of the steel plate at-20 DEG C can reach more than 170J, and the welding joint crack sensitivity index Pcm is less than 0.30%.

Description

Technical Field

[0001] The present invention relates to the technical field of hot rolling, and particularly to a production method and application of a rare earth microalloyed 14Cr1MoR steel plate prepared by a continuous casting process. Background Art

[0002] In addition to meeting the requirements of GB / T 713-2014, the existing hydrogen-resistant 14Cr1MoR steel plate also needs to ensure that after simulated post-weld heat treatment, the mechanical properties at half of the plate thickness meet the standard requirements, and higher requirements are put forward for the low-temperature impact performance at -18°C, inclusions, harmful elements, gas content, etc.

[0003] The 14Cr1MoR steel plate for hydrogen-resistant equipment is mainly applied to industries or fields such as chemical engineering, coal chemical engineering, and petrochemical engineering. Due to its harsh service conditions, it is required to have high strength, good plasticity and toughness, excellent welding performance, and resistance to temper embrittlement. The 14Cr1MoR type steel belongs to the steel grades of GB713-2014 and is also a representative variety of Cr-Mo steel. It is a heat-resistant steel and hydrogen-resistant steel widely used in the world and is widely used in the manufacture of large-scale devices such as thermal power equipment, nuclear power equipment, and petroleum, chemical, and coal conversion equipment in contact with hydrogen.

[0004] At present, the coal-to-oil industry in China is developing rapidly, with many new project startups and equipment renovation projects, resulting in a large demand for this steel. Since the working environment of this steel is at high temperature, high pressure, and in contact with hydrogen, the service conditions are extremely harsh. Therefore, the design technical conditions generally require this steel to have high strength, good plasticity and toughness, excellent welding performance, and resistance to temper embrittlement. At the same time, with the development of the domestic petrochemical industry, equipment is gradually developing towards large-scale. Therefore, the developed hydrogen-resistant 14Cr1MoR steel plate has a great promoting effect on the development of the domestic petrochemical and coal chemical industries.

[0005] In view of the above factors, in order to meet the actual needs, a production method and application of a rare earth microalloyed 14Cr1MoR steel plate with a thickness of 10-60 mm prepared by a continuous casting process are developed. By adding rare earth, the low welding crack sensitivity is reduced. The produced 14Cr1MoR steel plate is superior to the steel plate produced by the normalizing + tempering process, and has excellent impact toughness at -20°C, which can meet the requirements of a harsh use environment. The elongation of the 14Cr1MoR steel plate prepared by this method is greater than 20%, the impact energy of the steel plate at 20°C can reach more than 170 J, and the welding crack sensitivity index Pcm is less than 0.30%. Summary of the Invention

[0006] In order to make up for the deficiencies of the existing technology, the present invention provides a production method and application of a 10-60 mm rare earth microalloyed 14Cr1MoR steel plate by a continuous casting process, improving the overall quality and market competitiveness of the product.

[0007] The object of the present invention is to provide a production method for preparing a rare earth microalloyed 14Cr1MoR steel plate by continuous casting process. The chemical composition of the steel plate in mass percentage (unit: wt%) is as follows: C: 0.11 - 0.15, Si: 0.50 - 0.65, Mn: 0.40 - 0.60, P: ≤0.012, S: ≤0.015, Als: 0.020 - 0.034, Cr: 1.2 - 1.5, Mo: 0.50 - 0.60, Ce: ≤0.0020, H: ≤1.5 ppm, O: ≤0.0060, N: ≤0.0080, Pcm: ≤0.30, and the rest is iron and inevitable impurities;

[0008] Among them, the welding crack sensitivity index Pcm of the steel plate with low welding crack sensitivity is as follows: Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B - 120Ce;

[0009] The production method of the steel plate includes electric furnace steelmaking → LF furnace refining → RH furnace refining → continuous casting → slow cooling in a holding pit → rolling → cooling → flaw detection → normalizing → tempering → cutting and sampling inspection;

[0010] The production method of the steel plate specifically includes the following steps:

[0011] The tapping temperature of the converter is 1600 - 1660 °C. The single slag process is used for smelting. The converter adopts single slag operation, uses high-quality active lime, controls the basicity of the final slag at 3.2 - 3.6, and uses self-produced high-quality scrap steel 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 at one time as much as possible to reduce the nitrogen increase in the molten steel due to supplementary blowing;

[0012] LF refining: Alloy and slag material hoppers are arranged on the furnace cover at the heating station. Through the guiding valves under each hopper, the required alloys or slag materials are quantitatively added, or in the LF furnace with a vacuum system, alloy and slag material feeding devices are arranged on the vacuum cover;

[0013] During LF furnace refining, a powder injection device is often used to carry out desulfurization, purification and microalloying operations on the molten steel. The powder injection device includes a ladle cover, a spray gun for powder injection and a powder distributor with a sliding stroke of 4 m. The distributor is connected to 4 powder bins with a capacity of 500 kg each. When injecting powder, the powder is automatically weighed and mixed first, and then sent to the powder distributor through a screw feeder;

[0014] And according to the different values of the pre-argon temperature, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, so that the activity oxygen in the steel can be reduced to about 15 - 30 ppm, and at the same time, the inclusions in the steel can fully float up, providing qualified molten steel for continuous casting;

[0015] RH refining: The RH vacuum treatment time shall be not less than 20 minutes, the pure degassing time shall be not less than 5 minutes, the minimum vacuum degree shall be 260 Pa, and the off-position hydrogen content shall be less than or equal to 1.8 ppm;

[0016] Continuous casting: During continuous casting, the molten steel volume in the tundish shall be greater than 15 tons. Automatic liquid level control shall be achieved during the casting process, electromagnetic stirring shall be used, and soft reduction shall be used normally. The liquidus temperature of the steel grade is 1469 °C;

[0017] Before rolling, the surface quenching and cooling time of the slab shall be controlled within 150 s. The slab shall be directly warm charged into the heating furnace, with a heating time of 180 minutes and a soaking time of 35 minutes;

[0018] Or before rolling, the surface quenching and cooling time of the slab shall be controlled within 162 s. The slab shall be directly warm charged into the heating furnace, with a heating time of 190 minutes and a soaking time of 40 minutes;

[0019] Or before rolling, the surface quenching and cooling time of the slab shall be controlled within 186 s. The slab shall be directly warm charged into the heating furnace, with a heating time of 204 minutes and a soaking time of 48 minutes;

[0020] Rolling: It is divided into two parts: rough rolling and finish rolling. Among them, the rough rolling mill unit consists of 2 separately arranged rough rolling mills. One of the rough rolling mills is an irreversible rolling mill, and the other is a reversible rolling mill. The slab is rolled through 2 rough rolling mills for a total of 4 - 8 passes to roll into an intermediate strip of a certain thickness, and then enters the finish rolling mill unit for rolling;

[0021] Among them, the finish rolling mill is for continuous irreversible production. The number of finish rolling mills is between 4 and 8. The rolling mill layout form is an alternating arrangement of two-high horizontal rolling mills (H) and vertical rolling mills (V);

[0022] Cooling: After the steel plate is rolled, laminar flow cooling is carried out, which is divided into two stages. The first stage is aerosol cooling, and the second stage is spray cooling. The total length of the first stage and the second stage in the whole plant does not exceed 25 m. Among them, the aerosol cooling in the first stage is at most set to 5 m. 5 groups of nozzles are set in the first stage, and spray-type nozzle spouts are used, with the upper and lower nozzles symmetrically arranged;

[0023] Among them, 8 groups of nozzles are set in the second stage, and flat laminar flow upper nozzle spouts and round tube laminar flow lower nozzle spouts are used, with the upper and lower nozzles configured in a 1:2 ratio;

[0024] Flaw detection: Under the premise of not damaging the working state of the workpiece or raw material, ultrasonic flaw detection is carried out to check the surface and internal quality of the cooled steel plate;

[0025] Heat treatment: Shot peening treatment is required before the normalizing of the steel plate. A process of two normalizings + one tempering is used for treatment, and different temperatures are used for the first normalizing and the second normalizing;

[0026] Inspection: After heat treatment, the steel plate is cut into the required size and leveled to ensure its flatness and accuracy for inspection.

[0027] Furthermore, the total length of the spray gun is 4500 mm, of which 2500 mm is the replaceable part. The spray gun is inserted 100 - 150 mm from the bottom of the ladle for powder spraying. When spraying powder, high-purity argon is used as the carrier gas with a flow rate of 200 - 400 L / min and a treatment time of 5 - 10 min.

[0028] Furthermore, a continuous casting slab with a thickness of 300 mm is 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.

[0029] When pouring molten steel for continuous casting, the argon blowing pressure at 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 speed of the caster is 0.9 - 1.1 m / min.

[0030] Furthermore, the starting rolling thickness is the thickness of the slab. The starting rolling temperature is 1000 - 1150 °C. When rolling, 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 15%.

[0031] The starting rolling temperature for finish rolling is 810 - 850 °C, the finishing rolling temperature is 760 - 790 °C. After rolling, laminar cooling is adopted, and the final cooling temperature is 610 - 630 °C. When rolling, 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%.

[0032] Furthermore, for the first normalizing, the normalizing temperature is 910 - 950 °C, water cooling is used for accelerated cooling, the recrystallization temperature < 300 °C, and the holding time is more than 120 minutes. For the second normalizing, the normalizing temperature is 840 - 860 °C, the holding time is more than 150 minutes, water cooling is used for accelerated cooling, the recrystallization temperature < 200 °C, the tempering temperature is 650 - 700 °C, the tempering holding time is more than 100 minutes, and air cooling is adopted.

[0033] Furthermore, during the continuous casting process, the average superheat ΔT of the molten steel is controlled between 15 - 30 °C.

[0034] Production method of rare earth microalloyed 14Cr1MoR steel plate by continuous casting process. The chemical composition of the steel plate in mass percentage (unit: wt%) is as follows: C: 0.12, Si: 0.58, Mn: 0.52, P: 0.010, S: 0.003, Als: 0.025, Cr: 1.3, Mo: 0.55, Ce: 0.0003, H: 1.0 ppm, O: 0.0035, N: 0.0042, Pcm: 0.23; the balance is Fe and unavoidable impurities.

[0035] Production method of rare earth microalloyed 14Cr1MoR steel plate by continuous casting process. The chemical composition of the steel plate in mass percentage (unit: wt%) is as follows: C: 0.14, Si: 0.60, Mn: 0.58, P: 0.007, S: 0.002, Als: 0.029, Cr: 1.4, Mo: 0.55, Ce: 0.0002, H: 0.8 ppm, O: 0.0060, N: 0.0051, Pcm: 0.25; the balance is Fe and unavoidable impurities.

[0036] Production method of rare earth microalloyed 14Cr1MoR steel plate by continuous casting process. The chemical composition of the steel plate in mass percentage (unit: wt%) is as follows: C: 0.15, Si: 062, Mn: 0.53, P: 0.008, S: 0.002, Als: 0.030, Cr: 1.45, Mo: 0.57, Ce: 0.0003, H: 1.1 ppm, O: 0.0042, N: 0.0051, Pcm: 0.27; the balance is Fe and unavoidable impurities.

[0037] Application of a production method of rare earth microalloyed 14Cr1MoR steel plate by continuous casting process. The application of the production method of rare earth microalloyed 14Cr1MoR steel plate by continuous casting process is used to prepare steel plates with a thickness of 10 mm - 60 mm in the hot rolling field.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] The present invention reduces the low welding crack sensitivity by adding rare earth. The produced 14Cr1MoR steel plate is superior to the steel plate produced by the normalizing + tempering process, and has excellent impact toughness at -20°C, which can meet the requirements of harsh service environments. The elongation of the 14Cr1MoR steel plate prepared by this method is greater than 20%, the impact energy of the steel plate at -20°C can reach more than 170 J, and the welding crack sensitivity index Pcm is less than 0.30%.

[0040] The method of the present invention requires shot peening treatment before normalizing the steel plate, and adopts a process of two normalizations + one tempering. Different temperatures are used for the first normalization and the second normalization; the two normalizations can ensure the maximum simulated post-weld heat treatment tensile strength and the impact toughness at -20 °C at half of the plate thickness, play the strengthening role of alloying elements, obtain good strength and toughness matching, and can obtain relatively refined structures during the subsequent transformation process, improving the impact toughness of the steel plate.

[0041] The present invention adopts a low-carbon composition design, adds appropriate amounts of Mn, Mo, Cr, Ti and rare earth elements for microalloying with narrow composition control, and precisely controls the rolling and heat treatment processes to ensure that the steel plate obtains excellent high-temperature performance and welding performance. Detailed implementation mode

[0042] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the following further describes the detailed implementation mode of the present invention.

[0043] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0044] A production method for preparing rare earth microalloyed 14Cr1MoR steel plates by continuous casting process. The chemical composition of the steel plates in mass percentage (unit, wt%) is: C: 0.11 - 0.15, Si: 0.50 - 0.65, Mn: 0.40 - 0.60, P: ≤0.012, S: ≤0.015, Als: 0.020 - 0.034, Cr: 1.2 - 1.5, Mo: 0.50 - 0.60, Ce: ≤0.0020, H: ≤1.5 ppm, O: ≤0.0060, N: ≤0.0080, Pcm: ≤0.30, and the rest is iron and unavoidable impurities;

[0045] Among them, the welding crack sensitivity index Pcm of the steel plate with low welding crack sensitivity is as follows: Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B - 120Ce;

[0046] The production method of the steel plate includes electric furnace steelmaking → LF furnace refining → RH furnace refining → continuous casting → slow cooling in a heat preservation pit → rolling → cooling → flaw detection → normalizing → tempering → cutting and sampling inspection. Specific Example 1:

[0048] Production method of rare earth microalloyed 14Cr1MoR steel plate prepared by continuous casting process. The chemical composition of the steel plate in mass percentage (unit: wt%) is as follows: C: 0.12, Si: 0.58, Mn: 0.52, P: 0.010, S: 0.003, Als: 0.025, Cr: 1.3, Mo: 0.55, Ce: 0.0003, H: 1.0 ppm, O: 0.0035, N: 0.0042, Pcm: 0.23; the balance is Fe and unavoidable impurities;

[0049] Among them, the welding crack sensitivity index Pcm of the steel plate with low welding crack sensitivity is as follows: Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B - 120Ce.

[0050] The production method of the steel plate specifically includes the following steps:

[0051] The tapping temperature of the converter is 1600 - 1660 °C. The single slag process is used for smelting. The converter adopts single slag operation, uses high-quality active lime, controls the basicity of the final slag at 3.2, and uses self-produced high-quality scrap steel 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 hit as accurately as possible at one time to reduce the nitrogen increase in the molten steel due to supplementary blowing;

[0052] LF refining: Alloy and slag material hoppers are installed on the furnace cover at the heating station. Through the guiding valves under each hopper, the required alloys or slag materials are quantitatively added, or in the LF furnace with a vacuum system, alloy and slag feeding devices are installed on the vacuum cover;

[0053] The LF furnace refining often uses a powder injection device to carry out desulfurization, purification and microalloying operations on the molten steel. The powder injection device includes a ladle cover, a spray gun for powder injection and a powder distributor with a sliding stroke of 4 m. The distributor is connected to 4 powder bins with a capacity of 500 kg each. When injecting powder, the powder is first automatically weighed and mixed, and then sent to the powder distributor through a screw feeder;

[0054] And according to the different values of the pre-argon temperature, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, so that the activity oxygen in the steel can be reduced to about 15 - 30 ppm, and at the same time, the inclusions in the steel can fully float up, providing qualified molten steel for continuous casting;

[0055] RH refining: 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;

[0056] Continuous casting: During continuous casting, the molten steel volume in the tundish is greater than 15 tons. Automatic liquid level control is achieved during the casting process, electromagnetic stirring is used, and soft reduction is used normally. The liquidus temperature of the steel grade is 1469 °C;

[0057] Rolling: It is divided into two parts: rough rolling and finish rolling. Among them, the rough rolling mill consists of 2 separately arranged rough rolling mills. One of the rough rolling mills is an irreversible rolling mill, and the other is a reversible rolling mill. The slab is rolled through the 2 rough rolling mills for a total of 4 - 8 passes to form an intermediate strip of a certain thickness, and then enters the finish rolling mill for rolling;

[0058] Among them, the finish rolling mill is for continuous irreversible production. The number of finish rolling mills is between 4 and 8. The rolling mill layout form is an alternating arrangement of two-high horizontal rolling mills (H) and vertical rolling mills (V);

[0059] Cooling: After the steel plate is rolled, laminar flow cooling is carried out, which is divided into two stages. The first stage is aerosol cooling, and the second stage is spray cooling. The total length of the first stage and the second stage does not exceed 25 m. Among them, the aerosol cooling in the first stage is at most set to 5 m. 5 groups of nozzles are set in the first stage, and spray nozzles are used. The upper and lower nozzles are symmetrically arranged;

[0060] Among them, 8 groups of nozzles are set in the second stage, and flat laminar flow upper nozzle water mouths and round tube laminar flow lower nozzle water mouths are used. The upper and lower nozzles are configured in a 1:2 ratio;

[0061] Flaw detection: Under the premise of not damaging the working state of the workpiece or raw material, ultrasonic flaw detection is carried out to check the surface and internal quality of the cooled steel plate;

[0062] Heat treatment: Shot peening treatment is required before the normalizing of the steel plate. It is processed by the process of two normalizings + one tempering. Different temperatures are used for the first normalizing and the second normalizing;

[0063] Inspection: After heat treatment, the steel plate is cut into the required size and leveled to ensure its flatness and accuracy for inspection;

[0064] The total length of the spray gun is 4500 mm, of which 2500 mm is the replaceable part. The spray gun is inserted 100 - 150 mm from the bottom of the ladle for powder spraying. High-purity argon is used as the carrier gas during powder spraying, with a flow rate of 400 L / min and a treatment time of 10 min.

[0065] For continuous casting, a 300 - mm thick continuous casting billet is selected. The center segregation of the billet 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;

[0066] During the continuous casting of molten steel, the argon blowing pressure at the long nozzle is ≥ 0.1 Mpa, the flow rate of the argon backup pressure gauge between the submerged nozzles in the tundish reaches 10 L / min, the pressure of the backup pressure gauge is 0.1 Bar, and the casting machine drawing speed is 1.1 m / min.

[0067] The rough rolling starting thickness is the slab thickness, the starting rolling temperature is 1150 °C, the set torque during rolling is 2400 kNm, the set reduction is 35 mm, the rolling speed is 3.4 m / s, and the single-pass reduction rate in the high-temperature elongation stage is not less than 15%;

[0068] The finishing rolling starting temperature is 850 °C, the finishing rolling temperature is 790 °C, laminar cooling is adopted after rolling, the final cooling temperature is 630 °C, the set torque during rolling 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 15%.

[0069] For the first normalizing, the normalizing temperature is 950 °C, water cooling is used for accelerated cooling, the recalescence temperature < 300 °C, the holding time is more than 120 minutes. For the second normalizing, the normalizing temperature is 860 °C, the holding time is more than 150 minutes, water cooling is used for accelerated cooling, the recalescence temperature < 200 °C, the tempering temperature is 700 °C, the tempering holding time is more than 100 minutes, and air cooling is adopted.

[0070] During the continuous casting process, the average superheat ΔT of the molten steel is controlled within 24 °C.

[0071] In the above embodiments, before rolling, the surface quenching and cooling time of the slab is controlled within 150 s, the slab is directly warm-loaded into the heating furnace, the heating time is 180 minutes, and the soaking time is 35 minutes.

[0072] The mechanical properties of Example 1 are shown in the following table:

[0073] Specific Example Two:

[0075] A production method for preparing a rare earth microalloyed 14Cr1MoR steel plate by continuous casting process. The chemical composition of the steel plate in mass percentage (unit, wt%) is: C: 0.14, Si: 0.60, Mn: 0.58, P: 0.007, S: 0.002, Als: 0.029, Cr: 1.4, Mo: 0.55, Ce: 0.0002, H: 0.8 ppm, O:: 0.0060, N: 0.0051, Pcm: 0.25; the balance is Fe and unavoidable impurities;

[0076] Among them, the welding crack sensitivity index Pcm of the steel plate with low welding crack sensitivity is as follows: Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B - 120Ce.

[0077] The production method of the steel plate specifically includes the following steps:

[0078] The tapping temperature of the converter is 1600 - 1660°C. The single slag process is adopted for smelting, and the converter uses single slag operation. High-quality active lime is used, and the basicity of the final slag is controlled at 3.6. 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 to reduce the nitrogen increase in the molten steel due to supplementary blowing;

[0079] LF refining: Alloy and slag material hoppers are arranged on the furnace cover at the heating station. Through the guiding valves under each hopper, the required alloys or slag materials are quantitatively added, or in the LF furnace with a vacuum system, alloy and slag feeding devices are arranged on the vacuum cover;

[0080] During LF furnace refining, a powder injection device is often used to perform desulfurization, purification and micro-alloying operations on the molten steel. The powder injection device includes a ladle cover, a lance for powder injection and a powder distributor with a sliding stroke of 4m. The distributor is connected to 4 powder bins with a capacity of 500kg each. During powder injection, the powder is automatically weighed and mixed first, and then sent to the powder distributor through a screw feeder;

[0081] According to the different values of the pre-argon temperature, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, so that the active oxygen in the steel can be reduced to about 15 - 30ppm, and at the same time, the inclusions in the steel can fully float up, providing qualified molten steel for continuous casting;

[0082] RH refining: 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-position hydrogen content is less than or equal to 1.8ppm;

[0083] Continuous casting: During continuous casting, the molten steel volume in the tundish is greater than 15 tons. The liquid level is automatically controlled during the casting process, electromagnetic stirring is used, and soft reduction is used normally. The liquidus temperature of the steel grade is: 1469°C;

[0084] Rolling: It is divided into rough rolling and finish rolling. Among them, the rough rolling mill unit consists of 2 separately arranged rough rolling mills. One of the rough rolling mills is an irreversible rolling mill, and the other rough rolling mill is a reversible rolling mill. The slab is rolled through 2 rough rolling mills for a total of 4 - 8 passes, rolled into an intermediate strip of a certain thickness, and then enters the finish rolling mill unit for rolling;

[0085] Among them, the finish rolling mill is for continuous irreversible production. The number of finish rolling mills is between 4 and 8. The arrangement form of the rolling mills is the alternating arrangement of two-high horizontal rolling mills (H) and vertical rolling mills (V);

[0086] Cooling: After the steel plate is rolled, laminar cooling is carried out in two stages. The first stage is air mist cooling, and the second stage is water spraying cooling. The total length of the first stage and the second stage does not exceed 25 m. Among them, the air mist cooling in the first stage is set at most 5 m, and 5 groups of nozzles are set in the first stage. Spray nozzles are used, and the upper and lower nozzles are symmetrically arranged.

[0087] Among them, 8 groups of nozzles are set in the second stage. Flat laminar flow upper nozzle water inlet and round tube laminar flow lower nozzle water inlet are used, and the upper and lower nozzles are configured in a 1:2 ratio.

[0088] Flaw detection: Under the premise of not damaging the working state of the workpiece or raw material, ultrasonic flaw detection is carried out to check the surface and internal quality of the cooled steel plate.

[0089] Heat treatment: Shot peening treatment is required before the normalizing of the steel plate. The process of two normalizings + one tempering is adopted, and different temperatures are used for the first normalizing and the second normalizing.

[0090] Inspection: After heat treatment, the steel plate is cut into the required size and leveled to ensure its flatness and accuracy for inspection.

[0091] The total length of the spray gun is 4500 mm, of which 2500 mm is the replaceable part. The spray gun is inserted 100 mm from the bottom of the ladle for powder spraying. High-purity argon is used as the carrier gas during powder spraying, with a flow rate of 200 L / min and a treatment time of 5 min.

[0092] For continuous casting, a continuous casting billet with a thickness of 300 mm is selected. The center segregation of the billet 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.

[0093] When pouring molten steel for continuous casting, the argon blowing pressure of the long nozzle ≥ 0.1 Mpa, the flow rate of the argon blowing standby pressure gauge between the submerged nozzles of the tundish reaches 6 L / min, the pressure of the standby pressure gauge is 0.1 Bar, and the casting speed of the casting machine is 0.9 m / min.

[0094] The starting rolling thickness for rough rolling is the slab thickness, the starting rolling temperature is 1000 °C, the set torque during rolling is 2400 kNm, the set reduction is 35 mm, the rolling speed is 2.0 m / s, and the single-pass reduction rate in the high-temperature elongation stage is not less than 15%.

[0095] The starting rolling temperature for finish rolling is 810 °C, the finishing rolling temperature is 760 °C, laminar cooling is adopted after rolling, the final cooling temperature is 630 °C, the set torque during rolling 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%.

[0096] For the first normalizing, the normalizing temperature is 910 °C, water cooling is used for accelerated cooling, the return red temperature < 300 °C, the holding time is more than 120 minutes. For the second normalizing, the normalizing temperature is 840 °C, the holding time is more than 150 minutes, water cooling is used for accelerated cooling, the return red temperature < 200 °C. The tempering temperature is 650 °C, the tempering holding time is more than 100 minutes, and air cooling is adopted.

[0097] During the continuous casting process, the average superheat ΔT of the molten steel is controlled between 24 °C.

[0098] In the above embodiments, before rolling, the surface quenching and cooling time of the slab is controlled at 162 s, the slab is directly hot charged into the heating furnace, the heating time is 190 minutes, and the soaking time is 40 minutes.

[0099] The mechanical properties of Example 2 are shown in the following table:

[0100] Specific Embodiment Three

[0102] A production method for preparing a rare earth microalloyed 14Cr1MoR steel plate by continuous casting process. The chemical composition (unit, wt%) of the steel plate includes: C: 0.15, Si: 0.62, Mn: 0.53, P: 0.008, S: 0.002, Als: 0.030, Cr: 1.45, Mo: 0.57, Ce: 0.0003, H: 1.1 ppm, O: 0.0042, N: 0.0051, Pcm: 0.27; the balance is Fe and inevitable impurities;

[0103] Among them, the welding crack sensitivity index Pcm of the steel plate with low welding crack sensitivity is as follows: Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B - 120Ce.

[0104] The production method of the steel plate includes electric furnace steelmaking → LF furnace refining → RH furnace refining → continuous casting → slow cooling in a heat preservation pit → rolling → cooling → flaw detection → normalizing → tempering → cutting and sampling inspection;

[0105] The production method of the steel plate specifically includes the following steps:

[0106] 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, the basicity of the final slag is controlled at 3.5, 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 to reduce the nitrogen increase in the molten steel due to supplementary blowing;

[0107] LF refining: Alloy and slag material hoppers are installed on the furnace cover at the heating station. Through the guiding valves under each hopper, the required alloys or slag materials are quantitatively added. Or in the LF furnace with a vacuum system, a feeding device for alloys and slag materials is installed on the vacuum cover;

[0108] During LF furnace refining, powder injection equipment is often used to desulfurize, purify and micro-alloy the molten steel. The powder injection equipment includes a ladle cover, a spray gun for powder injection, and a powder distributor with a sliding stroke of 4m. The distributor is connected to 4 powder bins with a capacity of 500kg each. During powder injection, the powder is automatically weighed and mixed first, and then sent to the powder distributor through a screw feeder;

[0109] According to the different values of the temperature before argon blowing, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, so that the active oxygen in the steel can be reduced to about 15 - 30ppm, and at the same time, the inclusions in the steel can fully float up, providing qualified molten steel for continuous casting;

[0110] RH refining: 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;

[0111] Continuous casting: During continuous casting, the molten steel volume in the tundish is greater than 15 tons. During the casting process, automatic liquid level control is achieved, electromagnetic stirring is used, and soft reduction is used normally. The liquidus temperature of the steel grade is 1469℃;

[0112] Rolling: It is divided into two parts: rough rolling and finish rolling. Among them, the rough rolling mill unit consists of 2 separately arranged rough rolling mills. One of the rough rolling mills is an irreversible rolling mill, and the other is a reversible rolling mill. The slab is rolled through 2 rough rolling mills for a total of 4 - 8 passes, rolled into an intermediate strip with a certain thickness, and then enters the finish rolling mill unit for rolling;

[0113] Among them, the finish rolling mill is for continuous irreversible production. The number of finish rolling mills is between 4 and 8. The rolling mill layout form is an alternating arrangement of two-high horizontal rolling mills (H) and vertical rolling mills (V);

[0114] Cooling: After the steel plate is rolled, laminar flow cooling is carried out, which is divided into two stages. The first stage is aerosol cooling, and the second stage is spray cooling. The total length of the first stage and the second stage does not exceed 25m. Among them, the aerosol cooling in the first stage is at most 5m. 5 groups of nozzles are set in the first stage. Spray-type nozzle holders are used, and the upper and lower nozzles are symmetrically arranged;

[0115] Among them, 8 groups of nozzles are set in the second stage. Flat laminar flow upper nozzle holders and round tube laminar flow lower nozzle holders are used, and the upper and lower nozzles are configured in a 1:2 ratio;

[0116] Flaw detection: Under the premise of not damaging the working state of the workpiece or raw material, ultrasonic flaw detection is carried out to check the surface and internal quality of the cooled steel plate;

[0117] Heat treatment: Shot peening treatment is required before normalizing the steel plate. The process of two normalizations + one tempering is adopted, and different temperatures are used for the first normalization and the second normalization;

[0118] Inspection: After heat treatment, the steel plate is cut into the required size and leveled to ensure its flatness and accuracy for inspection.

[0119] The total length of the spray gun is 4500 mm, of which 2500 mm is the replaceable part. The spray gun is inserted 100 - 150 mm from the bottom of the ladle for powder spraying. High-purity argon is used as the carrier gas during powder spraying, with a flow rate of 300 L / min and a treatment time of 5 - 10 min.

[0120] For continuous casting, a 300-mm-thick continuous casting billet is selected. The center segregation of the billet 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;

[0121] During the continuous casting of molten steel, 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 8 L / min, the pressure of the standby pressure gauge is 0.1 Bar, and the casting speed of the casting machine is 1.0 m / min.

[0122] The starting rolling thickness is the slab thickness. The starting rolling temperature is 1100 °C. When rolling, the set torque is 2400 kNm, the set reduction is 35 mm, the rolling speed is 3.0 m / s, and the single-pass reduction rate in the high-temperature elongation stage is not less than 13%;

[0123] The starting rolling temperature for finish rolling is 830 °C, the final rolling temperature is 780 °C. After rolling, laminar cooling is adopted, and the final cooling temperature is 610 - 630 °C. When rolling, 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 13%.

[0124] For the first normalization, the normalization temperature is 930 °C, water cooling is used for accelerated cooling, the return red temperature < 300 °C, and the holding time is more than 120 minutes. For the second normalization, the normalization temperature is 850 °C, the holding time is more than 150 minutes, water cooling is used for accelerated cooling, the return red temperature < 200 °C, the tempering temperature is 680 °C, and the tempering holding time is more than 100 minutes, with air cooling.

[0125] During continuous casting, the average superheat ΔT of the molten steel is controlled within 23 °C.

[0126] In the above embodiments, before rolling, the surface quenching and cooling time of the slab is controlled at 186 s, the slab is directly warm-charged into the heating furnace, the heating time is 204 minutes, and the soaking time is 48 minutes.

[0127] The mechanical properties of Example 3 are shown in the following table:

[0128] Specific Embodiment 4

[0130] An application of a production method for preparing rare earth microalloyed 14Cr1MoR steel plates by continuous casting process is to prepare steel plates with a thickness of 10 mm - 60 mm in the hot rolling field by using the production method for preparing rare earth microalloyed 14Cr1MoR steel plates by continuous casting process.

[0131] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0132] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A production method of rare earth microalloyed 14Cr1MoR steel plate by continuous casting process, characterized in that; The chemical components of the steel plate by mass percentage (unit: wt%) are as follows: C: 0.11 - 0.15, Si: 0.50 - 0.65, Mn: 0.40 - 0.60, P: ≤0.012, S: ≤0.015, Als: 0.020 - 0.034, Cr: 1.2 - 1.5, Mo: 0.50 - 0.60, Ce: ≤0.0020, H: ≤1.5 ppm, O: ≤0.0060, N: ≤0.0080, Pcm: ≤0.30, and the rest is iron and inevitable impurities; Among them, the welding crack sensitivity index Pcm of the steel plate with low welding crack sensitivity is as follows: Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B - 120Ce; The production method of the steel plate includes electric furnace steelmaking → LF furnace refining → RH furnace refining → continuous casting → slow cooling in a heat preservation pit → rolling → cooling → flaw detection → normalizing → tempering → cutting and sampling inspection; The production method of the steel plate specifically includes the following steps: The tapping temperature of the converter is 1600 - 1660 °C. The single slag process is used for smelting. The converter adopts single slag operation, uses high-quality active lime, controls the basicity of the final slag at 3.2 - 3.6, and uses self-produced high-quality scrap steel 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 in one time as much as possible to reduce the nitrogen increase in the molten steel due to supplementary blowing; LF refining: Alloy and slag material hoppers are arranged on the furnace cover at the heating station. Through the guiding valves under each hopper, the required alloys or slag materials are quantitatively added, or in the LF furnace with a vacuum system, alloy and slag feeding devices are arranged on the vacuum cover; The LF furnace refining often uses a powder injection device to carry out desulfurization, purification and microalloying operations on the molten steel. The powder injection device includes a ladle cover, a spray gun for powder injection and a powder distributor with a sliding stroke of 4 m. The distributor is connected to 4 powder bins with a capacity of 500 kg each. When spraying powder, the powder is automatically weighed and mixed first, and then sent to the powder distributor through a screw feeder; And according to the different values of the pre-argon temperature, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, so that the active oxygen in the steel can be reduced to about 15 - 30 ppm, and at the same time, the inclusions in the steel can fully float up to provide qualified molten steel for continuous casting; RH refining: 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; Continuous casting: During continuous casting, the molten steel amount in the tundish is greater than 15 tons. The liquid level is automatically controlled during the casting process, electromagnetic stirring is used, and soft reduction is used normally. The liquidus temperature of the steel grade is 1469 °C; Before rolling, the surface quenching and cooling time of the slab is controlled at 150 S, the slab is directly warm-charged into the heating furnace, the heating time is 180 minutes, and the soaking time is 35 minutes; Or before rolling, the surface quenching and cooling time of the slab is controlled at 162 S, the slab is directly warm-charged into the heating furnace, the heating time is 190 minutes, and the soaking time is 40 minutes; Or, before rolling, control the surface quenching and cooling time of the slab at 186 s, directly warm-charge the slab into the heating furnace, with a heating time of 204 minutes and a soaking time of 48 minutes; Rolling: It is divided into rough rolling and finish rolling. Among them, the rough rolling mill consists of 2 separately arranged rough rolling mills. One of the rough rolling mills is an irreversible rolling mill, and the other is a reversible rolling mill. The slab is rolled through 2 rough rolling mills for a total of 4 - 8 passes to form an intermediate strip billet of a certain thickness, and then enters the finish rolling mill for rolling; Among them, the finish rolling mill is in continuous irreversible production, the number of finish rolling mills is between 4 and 8, and the rolling mill layout form is an alternating arrangement of two-high horizontal mills (H) and vertical mills (V); Cooling: After the steel plate is rolled, laminar flow cooling is carried out in two stages. The first stage is aerosol cooling, and the second stage is spray cooling. The total length of the first stage and the second stage does not exceed 25 m. Among them, the aerosol cooling in the first stage is at most set at 5 m. 5 groups of nozzles are set in the first stage, and spray nozzles are used. The upper and lower nozzles are symmetrically arranged; Among them, 8 groups of nozzles are set in the second stage, and flat laminar flow upper nozzle water mouths and round tube laminar flow lower nozzle water mouths are used. The upper and lower nozzles are configured in a 1:2 ratio; Flaw detection: Under the premise of not damaging the working state of the workpiece or raw material, ultrasonic flaw detection is carried out to check the surface and internal quality of the cooled steel plate; Heat treatment: Shot peening treatment is required before normalizing the steel plate. The process of two normalizations + one tempering is adopted, and different temperatures are used for the first normalization and the second normalization; Inspection: After heat treatment, the steel plate is cut into the required size and leveled to ensure its flatness and accuracy for inspection treatment.

2. The production method of rare earth microalloyed 14Cr1MoR steel plate prepared by continuous casting process according to claim 1, characterized in that; The total length of the spray gun is 4500 mm, of which 2500 mm is the replaceable part. The spray gun is inserted 100 - 150 mm from the bottom of the ladle for powder spraying. High-purity argon is used as the carrier gas during powder spraying, with a flow rate of 200 - 400 L / min and a treatment time of 5 - 10 min.

3. The production method of rare earth microalloyed 14Cr1MoR steel plate prepared by continuous casting process according to claim 2, characterized in that; For continuous casting, a 300 - mm thick continuous casting billet is selected. The center segregation of the billet 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 pouring molten steel for continuous casting, the argon blowing pressure of the long nozzle is ≥0.1 Mpa, the argon blowing standby pressure gauge flow rate between the plates of the submerged nozzle in the tundish reaches 6 - 10 L / min, the standby pressure gauge pressure is 0.1 - 0.5 Bar, and the casting machine casting speed is 0.9 - 1.1 m / min.

4. The production method of the rare earth micro-alloyed 14Cr1MoR steel plate prepared by continuous casting process according to claim 3, characterized in that; The starting rolling thickness of rough rolling is the slab thickness, the starting rolling temperature is 1000 - 1150 °C, the set torque during rolling 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 15%; The starting rolling temperature of finish rolling is 810 - 850 °C, the finishing rolling temperature is 760 - 790 °C, laminar flow cooling is adopted after rolling, the final cooling temperature is 610 - 630 °C, the set torque during rolling 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%.

5. The production method of the rare earth microalloyed 14Cr1MoR steel plate prepared by continuous casting process according to claim 4, characterized in that; For the first normalizing, the normalizing temperature is 910 - 950 °C, water cooling is adopted for accelerated cooling, the return red temperature < 300 °C, and the holding time is more than 120 minutes. For the second normalizing, the normalizing temperature is 840 - 860 °C, the holding time is more than 150 minutes, water cooling is adopted for accelerated cooling, the return red temperature < 200 °C, the tempering temperature is 650 - 700 °C, the tempering holding time is more than 100 minutes, and air cooling is used.

6. The production method of rare earth microalloyed 14Cr1MoR steel plate prepared by continuous casting process according to claim 5, characterized in that; During the continuous casting process, the average superheat ΔT of the molten steel is controlled between 15 - 30 °C.

7. The production method of preparing rare earth microalloyed 14Cr1MoR steel plate by continuous casting process according to claim 6, characterized in that; The chemical composition of the steel plate in mass percentage (unit, wt%) is as follows: C: 0.12, Si: 0.58, Mn: 0.52, P: 0.010, S: 0.003, Als: 0.025, Cr: 1.3, Mo: 0.55, Ce: 0.0003, H: 1.0 ppm, O: 0.0035, N: 0.0042, Pcm: 0.23; the balance is Fe and unavoidable impurities.

8. The production method of rare earth microalloyed 14Cr1MoR steel plate prepared by continuous casting process according to claim 7, characterized in that; The chemical composition of the steel plate in mass percentage (unit, wt%) is as follows: C: 0.14, Si: 0.60, Mn: 0.58, P: 0.007, S: 0.002, Als: 0.029, Cr: 1.4, Mo: 0.55, Ce: 0.0002, H: 0.8 ppm, O: 0.0060, N: 0.0051, Pcm: 0.25; the balance is Fe and unavoidable impurities.

9. The production method of preparing rare earth microalloyed 14Cr1MoR steel plate by continuous casting process according to claim 8, characterized in that; The chemical composition of the steel plate in mass percentage (unit, wt%) is as follows: C: 0.15, Si: 0.62, Mn: 0.53, P: 0.008, S: 0.002, Als: 0.030, Cr: 1.45, Mo: 0.57, Ce: 0.0003, H: 1.1 ppm, O: 0.0042, N: 0.0051, Pcm: 0.27; the balance is Fe and unavoidable impurities.

10. Application of a production method for preparing a rare earth microalloyed 14Cr1MoR steel plate by continuous casting process according to any one of claims 1-9, characterized in that; The application of the production method of the rare earth microalloyed 14Cr1MoR steel plate prepared by the continuous casting process according to any one of claims 1 - 9 is used to prepare steel plates with a thickness of 10 mm - 60 mm in the hot rolling field.

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