CN116287620A - Production method for producing extra-thick rack steel by adopting composite continuous casting blank - Google Patents

Production method for producing extra-thick rack steel by adopting composite continuous casting blank Download PDF

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CN116287620A
CN116287620A CN202310438970.9A CN202310438970A CN116287620A CN 116287620 A CN116287620 A CN 116287620A CN 202310438970 A CN202310438970 A CN 202310438970A CN 116287620 A CN116287620 A CN 116287620A
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rolling
equal
continuous casting
steel
adopting
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冯赞
刘喜锚
罗登
史术华
廖宏义
张勇伟
高海亮
脱臣德
胡增
金韬
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Hunan Valin Xiangtan Iron and Steel Co Ltd
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Hunan Valin Xiangtan Iron and Steel Co Ltd
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Abstract

A production method for producing extra-thick rack steel by adopting a composite continuous casting blank comprises the following steps of smelting, continuous casting, cogging, vacuum welding, rolling, quick cooling, finishing, quenching and tempering, wherein the steel comprises the following chemical components of, by mass, C=0.12-0.16, si=0.15-0.40, mn=0.9-1.2, P is less than or equal to 0.010, S is less than or equal to 0.003, cr=0.5-1.0, nb=0.005-0.025, V=0.03-0.08, ni=1.8-2.4, mo=0.4-0.6, ti is less than or equal to 0.01-0.025, al=0.03-0.06, B=0.0015-0.0025, and the balance of Fe and unavoidable impurities; according to the invention, a low-carbon alloying component design is adopted, the yield strength of a final steel plate is more than or equal to 690MPa, the tensile strength is more than or equal to 770MPa, the elongation is more than or equal to 16%, the impact at 60 ℃ is more than or equal to 100J, the hardness is more than or equal to 240HBW, and the low-cost production of the extra-thick toothed bar steel with the thickness of 180-250 mm at 690MPa level is realized through a rolling compounding and QT process.

Description

Production method for producing extra-thick rack steel by adopting composite continuous casting blank
Technical Field
The invention belongs to the technical field of metallurgy, and relates to a production method for producing extra-thick rack steel by adopting a composite continuous casting billet.
Background
With the development of wind power and ocean engineering industry, the demands of toothed bar steel are increasing. The toothed bar steel has the characteristics of large thickness, high strength and high toughness. After the steel plate is processed into the rack, when tooth surfaces are meshed, the stress of the core part of the original steel plate is maximum, and the core part is often required to have extremely high strength and toughness, so that the core part of the steel plate is required to be completely quenched into a martensitic structure, and the core part of the steel plate is required to have higher compactness. Thus rack steel 180mm and above in thickness, at 3: with a compression ratio requirement of 1, steel ingots are often required for production. The steel ingot has low solidification speed, obvious ingot segregation and looseness, and air suction is difficult to completely avoid in the casting process, so that the purity of the steel plate is poor, the same plate difference is obvious, and the problems of reduced flaw detection qualification rate and unstable performance exist when the steel plate with the thickness of more than 180mm is rolled.
The application of the continuous casting blank composite technology can well solve the problems. The maximum thickness of the current slab continuous casting is about 470mm, and the maximum thickness of the rolled steel plate is 160mm according to the ship gauge 3:1 compression ratio requirement. Through the composite rolling of a plurality of continuous casting billets, the problems of ingot segregation and high gas content in the die casting process can be well solved. Under the existing mature continuous casting process, the purity of molten steel after refining can be well maintained by the continuous casting blank, and the contents of O, N and H are maintained at the level after RH vacuum degassing, so that the performance stability of the steel plate is ensured. Meanwhile, under the condition of multi-continuous casting billet composite rolling, the loosening in the casting billets can be effectively pressed, the core density of the rolled steel plate is improved, and the good performance of the core of the steel plate is ensured.
Chinese patent CN202011054651 discloses a "low rolling compression ratio rack steel plate and its manufacturing method", which is characterized in that the steel comprises the following chemical components in percentage by mass: c=0.12 to 0.15%, si=0.1 to 0.3%, mn=1.0 to 1.3%, P is less than or equal to 0.02%, S is less than or equal to 0.01%, als=0.01 to 0.03%, ni=2.5 to 3.0%, cr=0.5 to 0.8%, mo=0.5 to 0.8%, cu=0.2 to 0.5%, nb=0.02 to 0.04%, v=0.03 to 0.06%, ti=0.005 to 0.03%, b=0.001 to 0.0015%, the balance being iron and unavoidable impurities. After electroslag remelting and forging, the primary rolling temperature is 1150-1250 ℃, the secondary rolling temperature is 950-1000 ℃, the final rolling temperature is 850-900 ℃, and the rolling compression ratio is less than or equal to 2; and then, carrying out high-temperature quenching, sub-temperature quenching and tempering treatment, wherein the Charpy impact energy single value of the core part of the finished steel plate at 40 ℃ is more than or equal to 90J. The patent utilizes electroslag remelting casting blank production, the purity of the steel plate is high, forging production is adopted, the core is compact, but the electroslag remelting production method has the advantages of high energy consumption, high pollution, special equipment, high investment of heavy forging equipment and inapplicability to most common steelworks. Therefore, the patent is only suitable for a small number of steelworks with special equipment, and is not suitable for general popularization.
Chinese patent CN201710892107 discloses "a 690Mpa grade extra thick toothed bar steel and its production process", the steel comprises the following chemical components in percentage by mass: 0.10 to 0.16 percent of C, 0.15 to 0.35 percent of Si, 0.95 to 1.35 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S, 0.50 to 0.60 percent of Cr, 2.30 to 2.60 percent of Ni, 0.45 to 0.55 percent of Mo, 0.03 to 0.05 percent of V, 0.07 to 0.09 percent of Al, less than or equal to 0.010 percent of Ti, 0.0010 to 0.0020 percent of B, less than or equal to 0.010 percent of N, and the balance of Fe and unavoidable impurities; the carbon equivalent Cep is 0.624-0.755, the welding sensitivity coefficient is 0.2655-0.3404, and the thickness is 152-178 mm. The production scheme adopts steel ingot rolling production, reduces the process of vacuum welding and rolling compounding, but limits the thickness of the produced steel ingot to 178mm, has higher alloy cost, and cannot be used for producing 210mm thick extra-thick toothed bar steel.
Chinese patent CN201610026452 discloses a "large-thickness rack steel plate and its production method", the chemical components of the steel by mass percentage are: c=0.09 to 0.13%, si=0.20 to 0.40%, mn=1.0 to 1.2%, p.ltoreq.0.010%, s.ltoreq.0.003%, ni=3.3 to 3.6%, cr=0.80 to 1.0%, mo=0.70 to 0.80%, cu=0.20 to 0.30%, nb=0.010 to 0.030%, v=0.02 to 0.05%, tal=0.060 to 0.080%, b=0.001 to 0.002%, and the balance Fe and unavoidable impurities. The steel plate is subjected to solid solution strengthening by proper amount of carbon and manganese through reasonable component design; adding a small amount of refined Nb and V grains, wherein the carbonitride of the refined Nb and V grains plays a role in dispersion strengthening; mo, ni and Cr are added to improve the low-temperature toughness and certain hardenability of the steel plate; when the thickness of the steel plate reaches 210mm, the 1/2 part of the plate thickness still has excellent mechanical property of strength and toughness matching. The steel ingot is adopted to roll 210mm extra thick toothed bar steel, so that the alloy addition amount is huge, the cost is high, the uniformity of the same plate is poor, and the economical efficiency is poor in order to ensure the performance of the steel plate.
Disclosure of Invention
The invention aims to provide a production method for producing extra-thick rack steel plates by using composite continuous casting billets, which is characterized in that after the extra-thick continuous casting billets are cut into intermediate billets, multi-layer composite rolling is carried out, and after tempering, the extra-thick rack steel plates with the finished product thickness of 180-250 mm and FH690 are produced, and the extra-thick rack steel plates have the characteristics of high core density, good toughness and excellent lamellar tearing resistance.
The invention is realized by the following technical scheme:
a production method for producing extra-thick rack steel by adopting a composite continuous casting blank comprises the production process route of smelting, continuous casting, cogging, vacuum welding, rolling, quenching, tempering and finishing; the steel comprises the following chemical components, by mass, C=0.12-0.16, si=0.15-0.40, mn=0.9-1.2, P.ltoreq.0.010, S.ltoreq.0.003, cr=0.5-1.0, nb=0.005-0.025, V=0.03-0.08, ni=1.8-2.4, mo=0.4-0.6, ti=0.01-0.025, al=0.03-0.06, B=0.0015-0.0025, and the balance Fe and unavoidable impurities; the thickness of the finished steel product is 180-250 mm, the yield strength is more than or equal to 690MPa, the tensile strength is more than or equal to 770MPa, and the impact absorption energy at minus 60 ℃ is more than or equal to 100J; the key process steps comprise:
(1) Smelting: adopting a BOF-LF-RH production process path, adopting high-alkalinity slag for converter smelting and refining LF furnace, and controlling P, S content; the RH furnace production adopts a deep degassing process, the total vacuum treatment time is more than or equal to 18min, and deep calcium treatment is performed before the RH furnace is out of the station;
(2) Continuous casting: adopting a 450mm extra-thick continuous casting blank, controlling the superheat degree to be 6-20 ℃, casting at a constant pulling speed, adopting forced cooling for secondary cooling, and controlling the low-power segregation to be below national standard class C1.5;
(3) Cogging: heating the continuous casting blank to 1150 ℃ and preserving heat for 20-40 minutes, rolling to 140-200 mm by a roughing mill, and cooling to room temperature by air after rolling;
(4) Vacuum welding: grinding the butt joint surface of 2-3 base materials after cogging to be bright, stacking, placing the base materials into a vacuum welding chamber, and welding and sealing the periphery of the butt joint surface in a vacuum environment;
(5) Rolling: the stacked and welded base materials are reheated to 1150-1220 ℃, rolled into finished product thickness through two stages of rolling, rough rolling is carried out at a low speed and under a large pressure, the maximum rolling reduction is more than or equal to 45mm, and air cooling is carried out to room temperature;
(6) Tempering: the steel plate is quenched to room temperature on a rolling quenching machine after being reheated to 900-930 ℃, and the quenching time is more than or equal to 40 minutes according to the thickness;
(7) Tempering: tempering at 600-630 ℃ on a roller hearth furnace, preserving heat for 200-300 minutes, discharging, and air-cooling to room temperature;
(8) Finishing: and (5) carrying out hot cutting at the temperature after the heat treatment of the steel plate, and checking the rolling composite quality.
The invention adopts the design of low-carbon alloying components, the yield strength of the produced steel plate is more than or equal to 690MPa, the tensile strength is more than or equal to 770MPa, the elongation is more than or equal to 16 percent, the impact at minus 60 ℃ is more than or equal to 100J, the hardness is more than or equal to 240HBW, and the production of 690 MPa-level low-cost extra-thick rack steel is realized through rolling compounding and QT technology. Can meet the production requirement of the rack plate with the thickness less than or equal to 250 mm. The method is suitable for producing 180-250 mmEH690 extra-thick rack steel plates, and the produced steel has excellent low-temperature toughness and low production cost. The method has the outstanding characteristics that the ultra-thick toothed bar is produced by adopting a homogeneous composite process, the steel plate has the characteristics of uniform performance and excellent quality, the metal utilization rate is high, and the requirements of low consumption and low emission of steel enterprises are met.
Drawings
FIG. 1 is a structural golden phase diagram of a 250mmEH690 rack steel plate.
Detailed Description
The following will further explain the main matters of the present invention, such as the control range of components and the preferred embodiments, by referring to examples.
Smelting example 1
The production process of super thick rack steel with composite continuous casting includes smelting, continuous casting, cogging, vacuum welding, rolling, quenching, tempering and finishing. The converter smelting and refining LF furnace adopts high-alkalinity slag, and the residual element content P=0.009 and S=0.002; the RH furnace production adopts a deep degassing technology, the total vacuum treatment time is 18min, and the pure calcium wire is calcified for 200 meters before the RH furnace is out; the continuous casting adopts 450 super-thick continuous casting blanks, the superheat degree is controlled to be 10-15 ℃, the constant-pulling speed casting is carried out, the secondary cooling water ratio is 0.45L/kg, and the low-segregation national standard C class is 1.5; heating the continuous casting blank to 1150 ℃ or above, preserving heat for 20 minutes, rolling to 200mm by a roughing mill, and cooling to room temperature by air after rolling. Grinding the butt joint surface of the 2 base materials after the cogging until the butt joint surface is bright, cleaning, stacking, placing the base materials into a vacuum welding chamber, and welding and sealing the periphery of the butt joint surface in a vacuum environment; the stacked and welded base materials are reheated to 1180 ℃, rolled into a finished product with the thickness of 180mm through two-stage rolling, wherein rough rolling adopts the rolling speed of 2m/s, the maximum rolling reduction is 48mm, and the base materials are cooled to room temperature through air. The rolled steel plate is re-heated to 900 ℃ and then quenched to room temperature on a rolling quenching machine, and the quenching time is 45 minutes; tempering at 630 ℃ on a roller hearth furnace, preserving heat for 200 minutes, and air cooling to room temperature after discharging; after the heat treatment of the steel plate, performing fire cutting inspection at 50 ℃ for normal warehouse entry.
Smelting example 2
The production process of super thick rack steel with composite continuous casting includes smelting, continuous casting, cogging, vacuum welding, rolling, quenching, tempering and finishing. The converter smelting and refining LF furnace adopts high-alkalinity slag, and the residual element content P=0.008 and S=0.0022; the RH furnace production adopts a deep degassing process, the total vacuum treatment time is 20min, and a 200-meter pure calcium wire is calcified before the RH furnace is out; the continuous casting adopts 450 extra thick continuous casting blanks, the superheat degree is controlled to be 10-13 ℃, the constant-pulling speed casting is carried out, the secondary cooling water ratio is 0.46L/kg, and the low-segregation national standard C class is 1.5; heating the continuous casting blank to 1170 ℃, preserving heat for 20 minutes, rolling to 200mm by a roughing mill, and cooling to room temperature by air after rolling. Grinding the butt joint surface of the 2 base materials after the cogging until the butt joint surface is bright, cleaning, stacking, placing the base materials into a vacuum welding chamber, and welding and sealing the periphery of the butt joint surface in a vacuum environment; the stacked and welded base materials are reheated to 1180 ℃, rolled into a finished product with the thickness of 200mm through two-stage rolling, wherein rough rolling adopts the rolling speed of 2m/s, the maximum rolling reduction is 47mm, and the base materials are cooled to room temperature through air. The rolled steel plate is re-heated to 910 ℃ and then quenched to room temperature on a rolling quenching machine, and the quenching time is 50 minutes; tempering at 630 ℃ on a roller hearth furnace, preserving heat for 220 minutes, and air cooling to room temperature after discharging; and after the heat treatment of the steel plate, performing fire cutting inspection at 55 ℃ for normal warehouse entry.
Smelting example 3
The production process of super thick rack steel with composite continuous casting includes smelting, continuous casting, cogging, vacuum welding, rolling, quenching, tempering and finishing. The converter smelting and refining LF furnace adopts high-alkalinity slag, and the residual element content P=0.007 and S=0.0018; the RH furnace production adopts a deep degassing technology, the total vacuum treatment time is 22min, and a 300-meter pure calcium line is calcified before the RH furnace is out; the continuous casting adopts 450 super-thick continuous casting blanks, the superheat degree is controlled to be 10-13 ℃, the constant-pulling speed casting is carried out, the secondary cooling water ratio is 0.47L/kg, and the low-segregation national standard C class is 1.0; the continuous casting billet is heated to 1170 ℃, kept for 30 minutes, rolled to 140mm by a roughing mill, and cooled to room temperature by air after rolling. Grinding the butt joint surface of the 3 base materials after the cogging until the butt joint surface is bright, cleaning, stacking, placing the base materials into a vacuum welding chamber, and welding and sealing the periphery of the butt joint surface in a vacuum environment; the stacked and welded substrates were reheated to 1180 ℃, rolled to a finished thickness of 230mm by two-stage rolling, wherein the rough rolling was performed at a rolling speed of 1.5m/s, a maximum reduction of 48mm, and air cooled to room temperature. The rolled steel plate is re-heated to 920 ℃ and then quenched to room temperature on a rolling quenching machine, and the quenching time is 55 minutes; tempering at 620 ℃ on a roller hearth furnace, preserving heat for 250 minutes, and air cooling to room temperature after discharging; and after the heat treatment of the steel plate, performing fire cutting inspection at 60 ℃ for normal warehouse entry.
Smelting example 4
The production process of super thick rack steel with composite continuous casting includes smelting, continuous casting, cogging, vacuum welding, rolling, quenching, tempering and finishing. The converter smelting and refining LF furnace adopts high-alkalinity slag, and the residual element content P=0.008 and S=0.0022; the RH furnace production adopts a deep degassing technology, the total vacuum treatment time is 20min, and a 300-meter pure calcium line is calcified before the RH furnace is out; the continuous casting adopts 450 super-thick continuous casting blanks, the superheat degree is controlled to be 10-13 ℃, the constant-pulling speed casting is carried out, the secondary cooling water ratio is 0.47L/kg, and the low-segregation national standard C class is 1.5; the continuous casting billet is heated to 1180 ℃, kept for 40 minutes, rolled to 150mm by a roughing mill, and cooled to room temperature by air after rolling. Grinding the butt joint surface of the 3 base materials after the cogging until the butt joint surface is bright, cleaning, stacking, placing the base materials into a vacuum welding chamber, and welding and sealing the periphery of the butt joint surface in a vacuum environment; the stacked and welded substrates were reheated to 1180 ℃, rolled to a finished thickness of 250mm by two-stage rolling, wherein the rough rolling was performed at a rolling speed of 1.5m/s, a maximum reduction of 50mm, and air cooled to room temperature. The rolled steel plate is reheated to 930 ℃ and then quenched to room temperature on a rolling quenching machine, and the quenching time is 60 minutes; tempering at 600 ℃ on a roller hearth furnace, preserving heat for 300 minutes, and air cooling to room temperature after discharging; and after the heat treatment of the steel plate, performing fire cutting inspection at 60 ℃ for normal warehouse entry.
The chemical composition control of each smelting example is shown in Table 1, and the detection performance of the steel is shown in Table 2.
Table 1 example control of chemical composition (wt%) of Steel
Figure SMS_1
。
Table 2 results of various test properties of example steels
Figure SMS_2
。
As can be seen from Table 2, the invention can produce the rack steel with the strength below 180-250 mm and the toughness and Z-direction performance which meet the requirements of the rack steel on the core toughness. The steel plates with various thicknesses have stable performance, good toughness matching and excellent lamellar tearing resistance. As the steel plate is rolled by adopting the continuous casting billet, the steel plate has high purity and good uniformity, and is worth popularizing.
As can be seen from FIG. 1, after the steel plate is quenched and tempered, the whole plate generates fine and uniform sorbite and bainite tissues, the tissues are good, and the requirements of the tissues of the steel grade are met.

Claims (1)

1. A production method for producing extra-thick rack steel by adopting a composite continuous casting blank comprises the following production process routes of smelting, continuous casting, cogging, vacuum welding, rolling, quenching, tempering and finishing, and is characterized in that: the steel comprises the following chemical components, by mass, C=0.12-0.16, si=0.15-0.40, mn=0.9-1.2, P.ltoreq.0.010, S.ltoreq.0.003, cr=0.5-1.0, nb=0.005-0.025, V=0.03-0.08, ni=1.8-2.4, mo=0.4-0.6, ti=0.01-0.025, al=0.03-0.06, B=0.0015-0.0025, and the balance Fe and unavoidable impurities; the thickness of the finished steel product is 180-250 mm, the yield strength is more than or equal to 690MPa, the tensile strength is more than or equal to 770MPa, and the impact absorption energy at minus 60 ℃ is more than or equal to 100J; the key process steps comprise:
(1) Smelting: adopting a BOF-LF-RH production process path, adopting high-alkalinity slag for converter smelting and refining LF furnace, and controlling P, S content; the RH furnace production adopts a deep degassing process, the total vacuum treatment time is more than or equal to 18min, and deep calcium treatment is performed before the RH furnace is out of the station;
(2) Continuous casting: adopting a 450mm extra-thick continuous casting blank, controlling the superheat degree to be 6-20 ℃, casting at a constant pulling speed, adopting forced cooling for secondary cooling, and controlling the low-power segregation to be below national standard class C1.5;
(3) Cogging: heating the continuous casting blank to 1150 ℃ and preserving heat for 20-40 minutes, rolling to 140-200 mm by a roughing mill, and cooling to room temperature by air after rolling;
(4) Vacuum welding: grinding the butt joint surface of 2-3 base materials after cogging to be bright, stacking, placing the base materials into a vacuum welding chamber, and welding and sealing the periphery of the butt joint surface in a vacuum environment;
(5) Rolling: the stacked and welded base materials are reheated to 1150-1220 ℃, rolled into finished product thickness through two stages of rolling, rough rolling is carried out at a low speed and under a large pressure, the maximum rolling reduction is more than or equal to 45mm, and air cooling is carried out to room temperature;
(6) Tempering: the steel plate is quenched to room temperature on a rolling quenching machine after being reheated to 900-930 ℃, and the quenching time is more than or equal to 40 minutes according to the thickness;
(7) Tempering: tempering at 600-630 ℃ on a roller hearth furnace, preserving heat for 200-300 minutes, discharging, and air-cooling to room temperature;
(8) Finishing: and (5) carrying out hot cutting at the temperature after the heat treatment of the steel plate, and checking the rolling composite quality.
CN202310438970.9A 2023-04-23 2023-04-23 Production method for producing extra-thick rack steel by adopting composite continuous casting blank Pending CN116287620A (en)

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