CN108941494B - Hot-feeding and hot-charging process for medium-thickness plate continuous casting billet - Google Patents
Hot-feeding and hot-charging process for medium-thickness plate continuous casting billet Download PDFInfo
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- CN108941494B CN108941494B CN201811114412.2A CN201811114412A CN108941494B CN 108941494 B CN108941494 B CN 108941494B CN 201811114412 A CN201811114412 A CN 201811114412A CN 108941494 B CN108941494 B CN 108941494B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/20—Controlling or regulating processes or operations for removing cast stock
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
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Abstract
A hot-feeding hot-charging process for a medium-thickness plate continuous casting blank is characterized in that the thickness of a surface chilling layer of the medium-thickness plate continuous casting blank is controlled to be 2-5 mm, then the thickness of a surface oxidation layer is controlled to be larger than or equal to 5mm through heating, and the surface chilling layer of the continuous casting blank is removed through oxidation and descaling, so that the problem of surface star cracks generated in the rolling process after the medium-thickness plate continuous casting blank is hot-fed is successfully solved. The method of the invention enlarges the temperature range of hot charging and hot charging of the continuous casting billet of the medium plate, has wide application range to steel grades, and has operability of the production process, thereby effectively promoting the compact integrated production of the medium plate, reducing the cost and increasing the benefit.
Description
Technical Field
The invention belongs to the technical field of medium plate production, and particularly relates to a hot-conveying and hot-charging process for a continuous casting billet of a medium plate.
Background
In the steel production technology, the hot-conveying hot-charging technology can reduce the energy consumption in the blank reheating process, simplify the production flow, improve the production rhythm, and reduce the area of blank storage plants and the labor input, so the hot-conveying hot-charging technology can obviously reduce the production cost.
However, for some steel grades, especially for Ti and Nb-containing microalloyed steel, after the continuous casting billet is subjected to a hot-feeding and hot-charging process, the problem of surface star cracking is easy to occur in the rough rolling process. It has been found that, when hot charging is carried out in a two-phase region at the surface temperature, after austenitizing heating, pro-eutectoid ferrite films (also called as pseudo-grain boundary ferrite) are still present at austenite grain boundaries in the metal on the surface of a cast slab, and along with the precipitation of a second phase such as carbonitride, the thermoplasticity of the bonding interface is reduced, and cracks are easily formed and spread in these regions during rolling. According to practical experience, when the rolling compression ratio of the medium plate continuous casting billet is 1.5-2.5, star cracks begin to appear on the surface, and the depth of the cracks is generally within 1-2 mm from the surface. According to the flow rule of surface metal during rolling of thick rolled pieces, a weak area generated by star cracks is deduced to be approximately within the range of 2-8 mm of the surface of a continuous casting billet, and the area is remarkably characterized in that fine equiaxial crystals of a chilling layer of the continuous casting billet are transited to coarse columnar crystals of an intermediate layer.
In order to realize hot feeding and hot charging of continuous casting billets, the Chinese patent CN102228968B proposes to rapidly cool the surfaces of the continuous casting billets on a roller way of a continuous casting machine so that the surface temperature of the continuous casting billets is lower than that of the continuous casting billetsA r1Avoiding the two-phase region. Obviously, the method changes the structure states of a chilling layer and an equiaxed direction columnar crystal transition region of the continuous casting billet, thereby avoiding the generation of grain boundary-like ferrite during surface heating and the generation of surface star cracks during rolling, but the method increases the thermal stress and the structure stress of the surface of the casting billet, possibly causes other defects on the surface of the casting billet, causes the temperature return of the casting billet and the deformation during the heating process, also influences the energy-saving effect of hot conveying and hot charging, and needs to add quick cooling equipment on a roller way of a continuous casting machine.
Disclosure of Invention
The invention aims to provide a hot-delivery hot-charging process for a continuous casting blank of a medium plate, which is used for avoiding the star cracks generated on the surface of the blank in the rolling process after the continuous casting blank is hot-delivered and hot-charged.
The technical scheme of the invention is as follows:
the utility model provides a hot-blast hot charging technology of medium plate continuous casting billet, continuous casting billet thickness 180~300mm, width 1870~2280mm, its key process step includes:
1) continuous casting: a straight arc type continuous casting machine is adopted, the steel casting temperature is improved, and the superheat degree is controlled to be 20-40 ℃; reducing the cooling strength of the crystallizer, and controlling the temperature difference of cooling inlet water and cooling outlet water of the crystallizer to be 4-6 ℃; controlling the secondary cooling specific water amount to be 0.6-0.8L/kg; the center segregation is improved by adopting dynamic light pressure and electromagnetic stirring, the light pressure is 3-5%, the stirring current is 450-500A, and the stirring frequency is 5-6 Hz.
2) Hot conveying and hot charging: and when the continuous casting billet enters the heating furnace, the surface temperature of the continuous casting billet is 400-900 ℃.
3) Heating: a walking beam type heating furnace is adopted, the temperature of a hearth of a preheating section is more than or equal to 900 ℃, the temperature of the core part of a continuous casting billet discharged from the furnace is more than or equal to 1200 ℃, and the in-furnace time is more than or equal to 5 hours; controlling the air excess coefficient in the furnace to be 1.3-1.4; the mixed gas is adopted, and the calorific value is 8500-9500 kJ/m 3.
4) Primary descaling: the pressure of the descaling water is more than or equal to 220bar, and the descaling speed is less than or equal to 1 m/s.
According to the invention, the thickness of the surface chilling layer of the medium plate continuous casting billet is controlled to be 2-5 mm, then the thickness of the surface oxidation layer is controlled to be more than or equal to 5mm through heating, so that the chilling layer on the surface of the continuous casting billet is removed through oxidation and dephosphorization, and the problem of surface star crack generated in the rolling process after the medium plate continuous casting billet is subjected to hot charging is successfully avoided. Therefore, the invention has the beneficial effects that: the method has the advantages of enlarging the temperature range of hot charging of the continuous casting billet of the medium plate, along with wide application range to steel grades and operability of the production process, thereby effectively promoting the compact integrated production of the medium plate, reducing the cost and increasing the benefit.
Detailed Description
The present invention is further illustrated by the following examples.
Example 1
The hot-delivery hot-charging process is practiced by a certain medium plate factory, steel is selected to be medium carbon micro alloy steel A32, the thickness of a continuous casting billet is 260mm, the width of the continuous casting billet is 2070mm, and key process steps comprise:
1) continuous casting: adopting a straight arc type continuous casting machine, wherein the superheat degree of cast steel is 30 ℃; cooling temperature difference of inlet and outlet water of the crystallizer: the extrados surface is 4.9 ℃, the intrados surface is 5.0 ℃, and the two narrow surfaces are respectively at 4.9 ℃ and 5.2 ℃; the secondary cooling specific water amount is 0.68L/kg; the dynamic soft reduction is 10mm, the electromagnetic stirring current is 480A, and the frequency is 6 Hz.
2) Hot conveying and hot charging: the surface temperature of the continuous casting billet is 650 ℃ when the continuous casting billet enters the heating furnace.
3) Heating: a walking beam type heating furnace is adopted, the temperature of a hearth of a preheating section is 910-930 ℃, the temperature of a furnace core of a continuous casting billet is 1220 ℃, and the in-furnace time is 350 min; the air excess coefficient in the heating furnace is 1.35; the mixed gas of coke oven gas, converter gas and blast furnace gas is adopted, and the calorific value is 8800-9000 kJ/m3。
4) Primary descaling: the pressure of the descaling water is 230bar, the pressure drop in the descaling process is 5bar at most, and the descaling speed is 0.9 m/s.
The thickness of the rolled steel plate is 25mm, and no star cracks are found on the surface of the steel plate.
Example 2
The hot-delivery hot-charging process is practiced by a certain medium-thickness plate factory, steel is selected to be medium-carbon micro-alloy steel Q370R, the thickness of a continuous casting billet is 180mm, the width of the continuous casting billet is 1870mm, and key process steps comprise:
1) continuous casting: adopting a straight arc type continuous casting machine, wherein the superheat degree of cast steel is 23-25 ℃; cooling temperature difference of inlet and outlet water of the crystallizer: the extrados surface is 5.8 ℃, the intrados surface is 5.6 ℃, and the two narrow surfaces are respectively at 5.9 ℃ and 5.8 ℃; the secondary cooling specific water amount is 0.65L/kg; the dynamic soft reduction is 8mm, the electromagnetic stirring current is 450A, and the frequency is 5 Hz.
2) Hot conveying and hot charging: the surface temperature of the continuous casting billet is 580 ℃ when the continuous casting billet enters the heating furnace.
3) Heating: a walking beam type heating furnace is adopted, the temperature of a hearth of a preheating section is 910-930 ℃, the temperature of a furnace core of a continuous casting billet is 1210 ℃, and the in-furnace time is 320 min; the air excess coefficient in the heating furnace is 1.35; the mixed gas of coke oven gas, converter gas and blast furnace gas is adopted, and the calorific value is 9000-9200 kJ/m3。
4) Primary descaling: the pressure of the descaling water is 230bar, the pressure drop in the descaling process is 2bar at most, and the descaling speed is 1.0 m/s.
The thickness of the rolled steel plate is 10mm, and no star cracks are found on the surface of the steel plate.
Example 3
The hot-delivery hot-charging process is practiced by a certain medium plate factory, the steel grade is selected to be low-carbon weathering steel Q420qENH, the thickness of a continuous casting billet is 220mm, the width of the continuous casting billet is 2070mm, and the key process steps comprise:
1) continuous casting: adopting a straight arc type continuous casting machine, wherein the superheat degree of cast steel is 27-28 ℃; cooling temperature difference of inlet and outlet water of the crystallizer: the extrados surface is 5.3 ℃, the intrados surface is 5.3 ℃, and the two narrow surfaces are respectively at 5.8 ℃ and 5.7 ℃; the secondary cooling specific water amount is 0.70L/kg; the dynamic soft reduction is 8mm, the electromagnetic stirring current is 460A, and the frequency is 5.5 Hz.
2) Hot conveying and hot charging: the surface temperature of the continuous casting billet is 750 ℃ when the continuous casting billet enters the heating furnace.
3) Heating: a walking beam type heating furnace is adopted, the temperature of a hearth of a preheating section is 915-930 ℃, the temperature of the core part of a continuous casting billet discharged from the furnace is 1225 ℃, and the in-furnace time is 325 min; the air excess coefficient in the heating furnace is 1.35; adopts coke oven gas, converter gas and blast furnace coalThe heat value of the mixed gas of the gas is 8950-9120 kJ/m3。
4) Primary descaling: the pressure of the descaling water is 230bar, the pressure drop in the descaling process is 4bar at most, and the descaling speed is 0.9 m/s.
The thickness of the rolled steel plate is 24mm, and no star cracks are found on the surface of the steel plate.
Example 4
The hot-conveying hot-charging process is practiced by a certain medium plate factory, the steel type is selected to be ultra-low carbon pipeline steel X70, the thickness of a continuous casting billet is 300mm, the width of the continuous casting billet is 2280mm, and the key process steps comprise:
1) continuous casting: adopting a straight arc type continuous casting machine, wherein the superheat degree of cast steel is 25 ℃; cooling temperature difference of inlet and outlet water of the crystallizer: the outer arc surface is 4.5 ℃, the inner arc surface is 4.6 ℃, and the two narrow surfaces are both 4.2 ℃; the secondary cooling specific water amount is 0.75L/kg; the dynamic soft reduction is 12mm, the electromagnetic stirring current is 500A, and the frequency is 6 Hz.
2) Hot conveying and hot charging: when the continuous casting billet enters the heating furnace, the surface temperature of the continuous casting billet is 680 ℃.
3) Heating: a walking beam type heating furnace is adopted, the temperature of a hearth of a preheating section is 920-935 ℃, the temperature of a discharging core of a continuous casting billet is 1210 ℃, and the in-furnace time is 360 min; the air excess coefficient in the heating furnace is 1.35; the mixed gas of coke oven gas, converter gas and blast furnace gas is adopted, and the calorific value is 8550-8650 kJ/m3。
4) Primary descaling: the pressure of the descaling water is 230bar, the pressure drop in the descaling process is 5bar at most, and the descaling speed is 0.8 m/s.
The thickness of the rolled steel plate is 29.7mm, and no star cracks are found on the surface of the steel plate.
Example 5
The hot-delivery hot-charging process is practiced by a certain medium plate factory, the steel grade is high-carbon weather-resistant die steel P20, the thickness of a continuous casting billet is 300mm, the width of the continuous casting billet is 2070mm, and the key process steps comprise:
1) continuous casting: adopting a straight arc type continuous casting machine, wherein the superheat degree of cast steel is 35-38 ℃; cooling temperature difference of inlet and outlet water of the crystallizer: the extrados surface is 4.3 ℃, the intrados surface is 4.6 ℃, and the two narrow surfaces are respectively 4.4 ℃ and 4.7 ℃; the secondary cooling specific water amount is 0.64L/kg; the dynamic soft reduction is 12mm, the electromagnetic stirring current is 500A, and the frequency is 6 Hz.
2) Hot conveying and hot charging: when the continuous casting billet enters the heating furnace, the surface temperature of the continuous casting billet is 800 ℃.
3) Heating: a walking beam type heating furnace is adopted, the temperature of a hearth of a preheating section is 925-940 ℃, the temperature of a discharging core of a continuous casting billet is 1240 ℃, and the in-furnace time is 365 min; the air excess coefficient in the heating furnace is 1.35; the mixed gas of coke oven gas, converter gas and blast furnace gas is adopted, and the heat value is 8650-8800 kJ/m3。
4) Primary descaling: the pressure of the descaling water is 230bar, the pressure drop in the descaling process is 4bar at most, and the descaling speed is 0.8 m/s.
The thickness of the rolled steel plate is 68mm, and no star cracks are found on the surface of the steel plate.
Claims (1)
1. The utility model provides a hot-blast hot charging technology of medium plate continuous casting billet, continuous casting billet thickness 180~300mm, width 1870~2280mm, its characterized in that key process step includes:
1) continuous casting: a straight arc type continuous casting machine is adopted, the steel casting temperature is improved, and the superheat degree is controlled to be 20-40 ℃; reducing the cooling strength of the crystallizer, and controlling the temperature difference of cooling inlet water and cooling outlet water of the crystallizer to be 4-6 ℃; controlling the secondary cooling specific water amount to be 0.6-0.8L/kg; the center segregation is improved by adopting dynamic light pressure and electromagnetic stirring, the light pressure is 3-5%, the stirring current is 450-500A, and the stirring frequency is 5-6 Hz; controlling the thickness of a chilling layer on the surface of a continuous casting blank of a medium plate to be 2-5 mm in continuous casting;
2) hot conveying and hot charging: when the continuous casting billet enters a heating furnace, the surface temperature of the continuous casting billet is 400-900 ℃;
3) heating: a walking beam type heating furnace is adopted, the temperature of a hearth of a preheating section is more than or equal to 900 ℃, the temperature of the core part of a continuous casting billet discharged from the furnace is more than or equal to 1200 ℃, and the in-furnace time is more than or equal to 5 hours; controlling the air excess coefficient in the furnace to be 1.3-1.4; mixed gas with a heat value of 8500-9500 kJ/m is adopted3(ii) a Controlling the thickness of the surface oxidation layer to be more than or equal to 5mm during heating;
4) primary phosphorus removal: the dephosphorization water pressure is more than or equal to 220bar, and the descaling speed is less than or equal to 1 m/s.
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| CN115194114A (en) * | 2022-06-02 | 2022-10-18 | 南京钢铁股份有限公司 | Continuous casting billet surface heat treatment method |
| CN115341129A (en) * | 2022-08-01 | 2022-11-15 | 南京钢铁股份有限公司 | Micro-alloyed low-alloy structural steel hot-feeding and hot-charging production method |
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| JPH0642979B2 (en) * | 1989-02-20 | 1994-06-08 | 新日本製鐵株式会社 | Manufacturing method of high strength steel for welding and low temperature containing titanium oxide |
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Patent Citations (8)
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| JPH0255606A (en) * | 1988-08-18 | 1990-02-26 | Nippon Steel Corp | Manufacture of very thick steel plate of excellent internal quality |
| JPH0642979B2 (en) * | 1989-02-20 | 1994-06-08 | 新日本製鐵株式会社 | Manufacturing method of high strength steel for welding and low temperature containing titanium oxide |
| CN1640569A (en) * | 2004-01-12 | 2005-07-20 | 鞍钢集团新钢铁有限责任公司 | Direct rolling process for heavy-medium plate billet continuous casting-rolling mill set |
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