WO2004110661A1 - 厚鋼板の制御冷却装置および制御冷却方法 - Google Patents
厚鋼板の制御冷却装置および制御冷却方法 Download PDFInfo
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- WO2004110661A1 WO2004110661A1 PCT/JP2004/008287 JP2004008287W WO2004110661A1 WO 2004110661 A1 WO2004110661 A1 WO 2004110661A1 JP 2004008287 W JP2004008287 W JP 2004008287W WO 2004110661 A1 WO2004110661 A1 WO 2004110661A1
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- Prior art keywords
- cooling
- cooling zone
- zone
- steel plate
- temperature
- Prior art date
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
- B21B37/76—Cooling control on the run-out table
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
- B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2221/00—Treating localised areas of an article
Definitions
- the present invention makes it possible to manufacture a steel plate cooling device, in particular, a steel plate having excellent material uniformity in the thickness direction while cooling at a high speed on average, and to stably produce a low yield ratio steel plate.
- the present invention relates to a cooling device and a controlled cooling method for a thick steel plate that can be realized by the above method. Background art
- controlled cooling is performed after rolling to ensure the mechanical properties required for the steel sheets, especially strength and toughness.
- the cooling rate is often increased from the viewpoint of high strength and high toughness.
- the cooling rate of the surface layer of the thick steel sheet is higher than that of the central part in the thickness direction. It tends to be higher than the core, leaving a problem with the requirement to ensure uniformity of the material.
- Low-yield-ratio steel sheets with such material properties are manufactured by controlled rolling, and are also available in literature such as the 159 * 160th Nishiyama Memorial Lecture by the Iron and Steel Institute of Japan, “Highly functional steel sheets that create a new era”.
- a part of the structure of a thick steel plate can be transformed into a fluoride, and the remaining austenite can be transformed into a bainite or the like by rapid cooling to produce a two-phase structure.
- uneven cooling is likely to occur in the steel sheet ⁇ , causing unevenness and distortion of the material. There is a problem that it is difficult to mass-produce efficiently.
- Patent Document 1 applies a 40-70% cumulative reduction at a temperature of 900 or less in hot rolling. and finish rolling temperature of 3 + 50 ° C or less than Ar 3 transformation point, after rolling the steel sheet table surface temperature Ar 3 - 1.625t (t is thickness, mm) to start water cooling from less than or Ar 3 500 ° C method for producing a high-tensile steel plate is shown open quenching at a cooling rate of 2 ⁇ 50 ° CZs ec to a temperature below.
- Patent Document 2 discloses that when hot rolling a hot steel plate having a temperature deviation in the plate, which is hot-rolled, is cooled with water until the surface temperature of the low-temperature portion becomes 630 to 530 ° C. There is disclosed a method of cooling at a cooling rate of 15 ° C / s or less, followed by cooling at a cooling rate of 25 ° CZs or more.
- a method for producing a high-strength steel sheet having a specific thickness is disclosed.
- Patent Document 4 C 0.18% by weight 0/0, Si: ⁇ 0.55 % N Mn: ⁇ 1.5%, P : Includes ⁇ 0.040%, S ⁇ 0.040% and alloying elements as necessary, and adjusts the carbon equivalent of C + Si / 24 + MnZ6 + ⁇ / 40 + Cr / 5 + Mo / 4 + V / 14 to 0.44 the billet balance the weight percent being Fe ⁇ Pi unavoidable impurities, was heated below 900 ° C or more 1250 e C, Ar.
- Patent Document 1 JP-B-62-4449
- Patent Document 2 JP 2001-164323 A
- Patent Document 3 Japanese Patent Publication No. 7-116504
- Patent Document 4 Japanese Patent Publication No. 7-74379 Disclosure of the Invention
- Each of the means described in Patent Documents 1 to 3 has a method of improving the material uniformity of a thick steel plate in the thickness direction within a certain range.
- the means described in Patent Document 1 increases the rolling reduction at a relatively low temperature of 900 ° C or lower, and lowers the rolling efficiency by lowering the rolling finish temperature to near the Ar 3 transformation point. There's a problem.
- the means described in Patent Document 2 cools the minimum surface temperature in the plate after slow cooling to 530 ° C to 630 ° C, and switches from slow cooling to rapid cooling during cooling. It is difficult to grasp the surface temperature of the steel sheet, and there is a problem in the reproducibility of the effect.
- Patent Document 3 has a problem that the cooling rate to 400 or more at a temperature lower than 500 ° C is as low as 3 to 12/360, which lowers the processing capacity. However, there is also a problem that sufficient material properties cannot be obtained. '
- Patent Documents 3 and 4 enable the production of a steel sheet with a low yield ratio in principle, but the means disclosed in Patent Document 3, as described above, requires a temperature of 400 ° C at less than 500 ° C. Since the cooling rate to C or higher is as small as 3 to 12 ⁇ / 360, there is a problem that the processing capacity is reduced.On the other hand, the means of Patent Document 4 requires a slow cooling zone to recover heat after cooling. However, since the waiting time for this is required, the time required for rolling is long, and mass production is difficult.
- An object of the present invention is to solve the above-described problems of the conventional technology, and to suppress the occurrence of a difference in hardness between one surface and a center of a steel plate without causing a reduction in rolling efficiency.
- Control cooling equipment for steel plates that enables efficient mass production of low-yield-ratio steel plates, and the use of this manufacturing equipment to produce steel plates while cooling at an average high speed.
- An object of the present invention is to provide an excellent method for manufacturing a thick steel plate.
- the control cooling device for a steel plate according to the present invention has a mild cooling zone on the exit side of a rolling mill for partially transforming a steel structure into a fly, and the remaining austenite is pearlite and vanadium on the rear surface side. And a rapid cooling zone that transforms into a martensite. That is, the control cooling device for a steel plate according to the present invention is provided with a slow cooling zone and a rapid cooling zone which can be independently controlled on the outlet side of the plate rolling mill in that order.
- the slow cooling zone has a cooling capacity for giving a cooling rate of 5 to 15 ° C / .s to a steel plate having a thickness of 25 ⁇ ⁇ .
- Ah is, further in relation to the plate thickness, plate thickness 713 ⁇ 1 2 38 / t L 2 ° C / s or more to the steel sheet t (mm); the cooling capacity to give 1 ⁇ 2 ° Ji 3 following cooling rate
- the equipment can be water passage in 100 ⁇ 500 1 min 'm 2 of water density.
- the rapid cooling zone has a cooling capacity of giving a cooling speed of 30 / s or more to a steel plate having a thickness of 25 mm.
- the steel sheet having a sheet thickness of t (mm) has a cooling capacity of giving a cooling rate of 1425 / t 1 ′ 2 ° CZs or more.
- the equipment be capable of passing water at a water density of 1500 1 min ⁇ m 2 or more.
- control cooling device for the thick steel plate sets a cooling condition for the rapid cooling zone based on a thermometer for measuring the surface temperature of the steel plate passing through the slow cooling zone and a measurement result of the surface temperature of the steel plate by the thermometer.
- Calculation and control device for controlling the rapid cooling zone, and a thermometer installed on the front side of the slow cooling zone to measure the surface temperature of the steel sheet on the exit side of the plate rolling mill, and the measurement results of the steel sheet surface temperature by the thermometer It is preferable to set a cooling condition for the slow cooling zone based on the above, and to provide an arithmetic and control device for controlling the slow cooling zone based on the cooling condition. It is preferable that the arithmetic and control unit controls the cooling stop temperature of the slow cooling zone at a temperature of 600 eC or more.
- control cooling device for the thick steel plate has an air cooling zone between the slow cooling zone and the rapid cooling zone, It is desirable that the air-cooling zone be provided with a thermometer for measuring the surface temperature of the steel sheet passing through the slow cooling zone.
- the steel plate with a thickness of t (mm) is used.
- cooling is performed at a cooling rate of 238 ⁇ ' 2 ° C / s or more and 713 ⁇ ' 2 ° CZs or less in the slow cooling zone, and thereafter, cooling is performed at 1425 t 1 ' 2 ° C / s or more in the rapid cooling zone.
- FIG. 1 is an explanatory view showing a basic mode of a controlled cooling device for a thick steel plate according to the present invention.
- FIG. 2 is an explanatory diagram showing a specific embodiment of a control cooling device for a thick steel plate according to the present invention.
- FIG. 3 is an explanatory diagram showing definitions of temperature and time which are the basis for calculating the cooling rate used in the present invention.
- Fig. 4 is a graph showing the temperature histories of the steel sheet surface and the central part when the required cooling rate is determined by a calculation formula for a thick steel sheet with a thickness of 25mm and a thick steel sheet with a thickness of 40mm.
- Figure 5 is a conceptual diagram showing the relationship between the steel sheet surface temperature and the heat flux (heat removal per unit area and unit time) when cooling a high-temperature steel sheet.
- FIG. 6 is a schematic view of a threading pattern for performing controlled cooling using the controlled cooling device for a thick steel plate according to the present invention.
- FIG. 1 is an explanatory view showing a basic mode of a controlled cooling device for a thick steel plate according to the present invention.
- the slow cooling zone 10 is a zone in which the thick steel plate 1 rolled to the final thickness by the thick steel plate rolling mill 2 is slowly cooled, and a part of the thick steel plate is transformed into ferrite.
- the quenching zone 20 receives the steel plate 1 whose surface layer has undergone ferrite transformation in the gradual cooling zone 10 and quenches it, and transforms the remaining austenite structure into perlite, bainite, martensite, etc. This is the band to be controlled.
- the slow cooling zone 10 is provided with water cooling headers 11 above and below the steel plate 1 pass line, and the water flow 12 flows from a short pipe-shaped nozzle 13 attached to it. It flows out as a laminar flow.
- This slow cooling zone is installed at a position where the thick steel plate that has been rolled is placed relatively close to the thick steel mill and can be cooled immediately.
- the cooling capacity can be 5 to 15 ° CZs in the case of a 25 mm thick steel plate. It should be good. If the temperature is lower than 5 ° CZs, the cooling time will be long, and during that time, it will not be possible to roll with a steel plate rolling mill, and the rolling efficiency will decrease.On the other hand, if it exceeds 15 ° CZs, a hard phase will be formed on the surface layer. This is because there is a risk that some veneer-martensite will be generated.
- the cooling rate is defined by one of the following cooling rates 1 or 2 based on the definition of each temperature and water cooling time shown in FIG.
- Cooling rate 1 (Average cross-sectional temperature at the start of cooling-Average cross-sectional temperature at the end of cooling)
- Cooling rate 2 (Surface temperature just before cooling minus the surface temperature when the surface is regained after cooling is finished) / water cooling time
- cooling rate 1 is easy to use when calculating the temperature history during cooling and determining the cooling time, etc. in the numerical calculation.
- This has the advantage that it is easy to use when quality control is performed by installing thermometers before and after the cooling device in actual operation, and it is practically convenient to use them properly in each of these cases.
- the above cooling rate is based on the water cooling capacity of the slow cooling zone 10 as a function of the thickness t (mm).
- yisZt 1 - 2 ⁇ / ⁇ can be obtained by that given the following cooling rates. This criterion is used to determine the required cooling rate as a function of the sheet thickness and to use this to determine the water cooling capacity according to the sheet thickness.
- the cooling rate and, consequently, the cooling capacity are determined as a function of the sheet thickness.
- heat is transferred from the surface of the steel sheet.
- the same cooling rate is applied to steel sheets of different thicknesses, the temperature difference between the surface and the center increases as the thickness increases, and the material in the thickness direction increases. This is because a difference easily occurs.
- the above function takes into account the effect of the temperature difference due to the plate thickness. The larger the plate thickness, the lower the cooling rate and the smaller the material difference between the surface and the center of the thick steel plate.
- Figure 4 shows the steel plate surface and the central part when the cooling rate obtained from TlS tu ⁇ Zs, which is the upper limit of the cooling rate, was applied to a 25 mm thick steel sheet and a 40 mm thick steel sheet.
- 3 is a graph showing a temperature history of the present invention.
- the cooling rate (according to the above formula) is 15 ° CZs when the thickness is 25 mm
- the cooling rate (according to the above formula) when the thickness is 40 mm. Is 8.5 ° CZs, but the temperature gradients on both steel sheet surfaces are almost the same value.
- the cooling rate for a sheet thickness of 25 mm was used in order to suppress the formation of hard phases such as veneite and martensite on the steel sheet surface and to generate a predetermined amount of ferrite. (According to the above formula) is 15 and 5 or less Good. Accordingly, if determined the maximum 713 ⁇ 'urchin water cooling ability due possible to the 2/3 in accordance with the cooling rate in the thickness, eliminates the waste of the equipment, and also if the thickness 40 mm of a predetermined amount Ferrite can be generated.
- the condition for giving a temperature gradient of the steel sheet surface equivalent to the cooling rate of 5; Zs at a thickness of 25 mm is determined to be 238 / t 1 ′ 2 ° C in the same manner as described above. Therefore, if the water cooling capacity is determined so that a cooling rate higher than this value can be achieved, a controlled cooling device that does not cause a problem such as a reduction in rolling efficiency can be obtained.
- such a water cooling capacity can be achieved by adjusting the cooling water amount within a range of 50 to 2000 tZh and using a nozzle of a pipe lamina type.
- the nozzle type can be selected from a spray type, a lamina type, a jet type, a mist type, etc., as long as it can achieve the above cooling capacity.
- the water density and 100 1 / min ⁇ m 2 ⁇ 500 1 / in ⁇ m 2 stable slow cooling is obtained, and the this reliably perform ferrite transformation previously described become able to.
- the cooling stop temperature of the slow cooling zone 10 should be controlled within the range of 600 ° C or higher. It is better to be able to set according to. If the cooling stop temperature in the slow cooling zone is 600 ° C or more, stable ferrite transformation becomes possible, and it becomes possible to manufacture thick steel plates with uniform material in the thickness direction and low yield ratio. If it is lower than 600, there is a possibility that veneite-martensite, which is a hard phase, is formed on the surface layer of the steel sheet and the surface is hardened. Therefore, it is preferable to add a function to control the cooling stop temperature to 600 ° C or higher by setting the slow cooling zone 10.
- the cooling stop temperature refers to the average temperature of the cross section at the end of cooling in FIG. 3 or the surface temperature when the surface is double-heated after the end of cooling.
- the cooling stop temperature as in the case of the cooling rate described above, they all indicate the same temperature, and these can be used in the same way as the cooling rate.
- the cooling zone with the above function allows a certain amount of the fluoride phase to be generated on the surface of the thick steel plate during the cooling process.
- the effect is that the plate can be cooled uniformly in its plane.
- FIG. 5 is a conceptual diagram showing the relationship between the steel sheet surface temperature and the heat flux (amount of ripening per unit area and time) when cooling a high-temperature steel sheet.
- the heat flux amount of ripening per unit area and time
- the transition boiling state is a state in which the film boiling ⁇ and the nucleate boiling are mixed.
- the heat flux increases as the steel sheet temperature decreases as shown in the figure. Therefore, if there is uneven temperature in the copper plate surface before cooling, the lower temperature parts are cooled more in the cooling process and the in-plane temperature difference increases.
- the temperature at which transition boiling starts increases as the amount of input water increases, but the cooling rate of 5 to 15 ° CZs, which is the operating condition of the slow cooling zone of the present invention, or the water density of 100 to 500 in . under ni 2, slow when the cooling stop temperature of the cooling zone is above 600 ° C, it is stable and almost completely Makunie Kaga in 9 ⁇ 100M m is a plate thickness range of the water cooling mechanism steel plate In addition to the uniform cooling within the steel sheet surface, stable fluoride transformation is possible and the benefits of stable materials are obtained.
- a rapid cooling zone 20 is provided.
- the quenching zone 20 receives the steel sheet 1 whose surface layer has been transformed into ferrite in the gradual cooling zone 10 and quenched. It is a band to do.
- the quenching zone 20 is provided with water cooling headers 21 above and below the steel sheet 1 pass line, and a high-pressure zipper from a slit nozzle 22 attached to it. The torrent flow is sprayed on thick steel plates.
- This rapid cooling zone 20 is a zone that rapidly cools most of the steel plate and transforms the remaining austenite phase, which was not transformed in the slow cooling zone, to perlite, bainite, martensite, etc.
- the water cooling capacity should be 30 ° CZ s or more based on a 25 mm thick steel plate whose cooling rate on the surface of the steel plate is a reference. If the water cooling capacity is less than 30 ° C / s at 25 mm, cooling at the center of the sheet thickness will be slow and it will be difficult to obtain advantages such as high strength by controlled cooling.
- Such cooling bay degree, slow water cooling capacity of the cooling zone 10, the plate thickness t (mm) as a function of 1425 / t 1 - can be obtained by a 2 t C / s or more.
- This criterion gives the required cooling rate as a function of the sheet thickness, and is used to determine the water cooling capacity according to the sheet thickness.
- the cooling rate is determined as a function of the sheet thickness because heat is transferred from the steel sheet surface when cooling water is applied to cool the steel sheet, but as the sheet thickness increases, the distance between the steel sheet surface and the center part increases.
- the amount of heat transfer due to heat conduction from the inside of the steel sheet decreases as the distance increases according to Fourier's law.Thus, when the sheet thickness increases, the cooling water increases and the cooling capacity from the surface increases, even if the cooling capacity from the surface increases. This is because the cooling rate at the center does not increase due to the internal heat conduction.
- the above function calculates the cooling rate close to the limit in order to enjoy the material benefits of the high cooling rate.
- the cooling water amount can be specifically adjusted in the range of 2000 to 5000 t. Further, from the viewpoint of uniform cooling, it is preferable that the water density be 1500 1 / min 1500m 2 or more in the rapid cooling zone. This is because, as explained earlier with reference to Fig. 5, if cooling is performed in the transition boiling region, the temperature deviation before cooling increases, but if cooling is performed with this amount of water or more, nucleate boiling will occur completely. This is because the temperature difference in the steel sheet surface that existed before the rapid cooling can be reduced.
- 1500 1 When cooling with a water density of / min ⁇ m 2 , a cooling rate of 1425 / t 1 ′ 2 ° CZs or more is obtained when the thickness is t (mm) over the thickness range of 9 to 100 ⁇ ⁇ .
- the nozzle used for the quenching zone has a high impact force when the cooling water collides with the steel sheet, as in the above-mentioned slit jet nozzle.
- it is preferable to have a quantity, a spray type, a lamina type, a jet type, a mist type, etc. can be used if the above conditions are satisfied.
- the cooling stop temperature of this rapid cooling zone must be sufficient to complete the transformation of the steel plate to the microstructure up to its central part. It is better to add a function to set the temperature.
- the austenite phase that was not transformed in the gradual cooling zone can be transformed into perlite, bainite, martensite, etc., and the cooling stop temperature due to the quenching zone Even if the temperature is set to an arbitrary temperature, uniform cooling becomes possible, and it becomes possible to produce a thick steel plate with little distortion.
- the control cooling device for thick steel plates provided with the slow cooling zone 10 and the rapid cooling zone 20 includes thermometers 31, 32, 33 for measuring the surface temperature of the steel sheet 1, and these temperatures.
- the cooling unit is provided with an arithmetic unit 41 and a control unit 42 for controlling the cooling zones 10 and 20 based on signals from the arithmetic unit 41 to set the cooling conditions of the cooling zones 10 and 20 based on the steel sheet surface temperature information from the gauge.
- a control device 40 is provided.
- an air cooling zone 51 is provided between the slow cooling zone and the rapid cooling zone, and a thermometer 32 for measuring the surface temperature of the steel sheet passing through the slow cooling zone is preferably installed in the air cooling zone.
- thermometer 32 is installed on the outlet side of the slow cooling zone 10 so that The temperature can be measured, and based on the result, the cooling conditions such as the passing speed and the cooling water amount are adjusted so that the cooling stop temperature of the rapid cooling zone 20 becomes a predetermined value. It is recommended that the operation is controlled based on the result.
- thermometer 31 is also installed on the front side of the mild cooling zone 10 (or on the exit side of the rolling mill 2) so that the surface temperature of the steel plate 1 immediately after rolling can be measured.
- the cooling conditions such as the passing speed and the amount of cooling water are determined by the arithmetic and control unit 40 (including a slow cooling zone operating condition calculating unit) so that the cooling stop temperature of the cooling water reaches a predetermined value. What is necessary is just to be able to control. This makes it possible to more reliably perform ferrite transformation in the thick steel plate in the moderate cooling zone.
- thermometer 33 can be installed on the outlet side of the rapid cooling zone 20. This measurement result can be used together with the measurement result of the thermometer 32 on the rear surface of the slow cooling zone to analyze the operating conditions of the kibiki device and to feed pack.
- the operation and control device 40 for determining the operating conditions of the slow cooling zone 10 and the rapid cooling zone 20 or the rapid cooling zone 20 in accordance with such temperature measurement results and controlling the operation of each cooling zone (10, 20) is publicly known.
- An existing process computer having a numerical operation function may be used as the operation unit 41.
- an existing control device having a function of inputting and outputting data and controlling devices can be used as the control unit 42.
- a DSC (Distributed Control system) type digital control device can be used suitably.
- thermometer 32 when to define to implement good c such control, thermometer 32 is important to set between the particular slow cooling zone and the quenching zone.
- so-called radiation thermometers that detect radiant energy on the surface of steel sheets are often used. If an object that absorbs radiant energy exists between the thermometer and the steel plate, accurate measurement is impossible.
- an air cooling zone 51 is provided between the slow cooling zone 10 and the rapid cooling zone 20, and a thermometer 32 on the rear surface of the slow cooling zone is provided in the air cooling zone 51.
- the length of the air-cooled zone 51 must be long enough to mount the thermometer 32, and for accurate temperature measurement, make sure that water vapor and cooling water do not enter the front and rear zones.
- the radiation thermometer which is generally used, uses a lens to condense the light energy emitted from the steel sheet. Considering that the condensed spot size is about 200 mm, air-cooled Belt 51 must be at least 200 mm long. Furthermore, in the actual process, there is a possibility that the effective measuring section may be limited because steam leaks or enters from the slow cooling zone or the rapid cooling zone to the air cooling zone. Considering the necessity of installing the above-mentioned leak steam purging equipment and a turbo fan, it is preferable that the length of the air-cooled zone is about 2 m or more.
- the productivity is excellent and the stability of the material is extremely excellent.
- the processes of pattern 1 to pattern 4 shown in FIG. 6 can be adopted.
- the steel sheet that has been finish-rolled is cooled while passing through the slow cooling zone and the rapid cooling zone.
- the length of the air cooling zone 51 provided between the slow cooling zone 10 and the rapid cooling zone 20 is preferably set to be equal to or longer than the maximum length of the steel sheet to be processed.
- the steel sheet coming out of the slow cooling zone 10 can be guided to the air cooling zone 51, and the sheet passing speed can be changed in the air cooling zone 51 to be introduced into the rapid cooling zone 20.
- High-precision controlled cooling that gives a predetermined cooling rate and cooling stop temperature in each cooling zone by making the passing speed of zone 20 different is possible.
- Patterns 2 to 4 are cases in which oscillation cooling is performed in the slow cooling zone 10 and / or the rapid cooling zone 20. By employing such a passing plate pattern, the apparatus of the present invention can be effectively used even when the length of the air cooling zone 51 is shorter than, for example, the length of the treated steel sheet.
- Pattern 2 After the steel sheet enters the slow cooling zone 10, the steel sheet is cooled by oscillation in the slow cooling zone 10 for a predetermined time, and then the surface temperature of the steel sheet is measured by the thermometer 32 on the exit side of the slow cooling zone 10. It measures the temperature, accelerates to the required sheeting speed in the rapid cooling zone 20 based on the temperature results, and performs pass cooling in the rapid cooling zone 20.
- Pattern 3 is to perform oscillation cooling in the rapid cooling zone 20, so that even if the steel sheet thickness is extremely large and the cooling time in the rapid cooling zone 20 takes a long time, the rolling speed, the speed of the slow cooling zone 10, The required cooling speed can be ensured regardless of the control range of the transfer speed.
- Pattern 4 is a case where oscillation cooling is performed in the slow cooling zone 10 and the rapid cooling zone 20. In this pattern, the advantages obtained by the above patterns 2 and 3 can be obtained at the same time.
- the pattern with the highest efficiency can be selected according to the plate thickness, cooling rate in the slow cooling zone, cooling stop temperature, cooling rate in the rapid cooling zone, and cooling stop temperature. Just fine. For example, all patterns may be made available in accordance with the type of steel, equipment and product to be manufactured, or only some of the patterns may be made available.
- Comparative Example 1 is a case in which a cooling device having only a rapid cooling zone is used, and Comparative Example 2 is, as described in Patent Document 1, at an Ar 3 temperature or higher and an Ar 3 temperature + 50 ° C or lower. rolling exit, the cooling start Ar 3 temperature or less, subject to there upon cooling as Ar 3 temperature one 1. least 625t e C, finishing rolling temperature 780 ° C, by rapid cooling zone as a cooling start temperature 740 ° C The cooling was performed.
- Comparative Example 3 is a case where only a slow cooling zone is used as in Patent Document 3.
- the material difference (ATS, ⁇ ) between the tensile strength TS and the hardness Hv in the thickness direction of the product is small.
- Comparative Example 1 although the time required from the start of rolling to the end of cooling is short, the material difference in the thickness direction of the product is large.
- Comparative Examples 2 and 3 the difference in material in the thickness direction of the product is small, but the time required from the start of rolling to the end of cooling is long. This is because in the case of Comparative Example 2, rolling was performed to a temperature lower than that of the invention example, and after the finish rolling, it was waited until the cooling start temperature was reached. In the case of Comparative Example 3, the required cooling time was longer in the slow cooling zone, and the required time was longer.
- ATS is the difference in tensile strength between the 1Z2 sheet thickness position and the 1st-4th sheet thickness position
- ⁇ Hv is the difference in the surface hardness between the 1Z2 position and the surface layer position (0.5 0 ⁇ below the surface).
- the cooling rate and cooling stop temperature are calculated using the values defined by the average cross-sectional temperature at the end of cooling, calculated by the process computer based on the temperatures measured by the thermometers 31, 32, and 33. I have.
- Table 3 shows the properties and treatment patterns of the materials to be treated.
- Table 4 shows the operation results when controlled cooling is performed in accordance with this method (Examples 4 to 5) in comparison with the case of the comparative example.
- Comparative Example 4 is a case in which the steel plate was allowed to stand by and cooled to 740 ° C, which is the Ar 3 transformation point, and then cooled to around 450 ° C in the rapid cooling zone.
- Comparative Example 5 In accordance with Patent Document 3, a case carrying out the cooling to near 450 e C only moderate cooling zone.
- Comparative Example 7 is a case where cooling was performed to around 450 ° C. in the rapid cooling zone as it was after the end of rolling. As shown here, in the case of the present invention, the predetermined yield ratio YR is a value close to 70%, and the time required from the start to the end of rolling is shortened.
- Example 2 Using the same control cooling device as used in Example 1, the temperature of the slow cooling zone was measured, and the cooling conditions for the rapid cooling zone were changed based on the measured values to perform controlled cooling of the thick steel plate. Natsu The properties and treatment conditions of the material to be treated are as shown in Table 5.
- Table 6 shows the actual operating parameter results for the controlled cooling of thick steel plates in which the cooling conditions in the rapid cooling zone are changed based on the measured temperature on the exit side of the slow cooling zone in the above operation. It is shown in comparison with.
- the actual cooling stop temperature of the slow cooling zone is about 40 higher than the target. For this reason, if cooling is performed at the rapid cooling zone passing speed determined by the initial calculation, there is a risk that the cooling stop temperature will increase and the required strength will not be obtained.
- the cooling was performed by changing the belt passing speed of the belt, and the cooling stop temperature of the rapid cooling zone could be set to the target cooling stop temperature. As a result, a controlled cooling structure having a fine structure up to the center could be obtained.
- TS is the value at the position of thickness 1-2.
- the cooling rate and the cooling stop temperature are calculated using the values defined by the average cross-sectional temperature at the end of cooling calculated by the process computer based on the temperatures measured by the thermometers 31, 32, and 33. I have.
- Example 5 shows the properties of the materials to be treated and the processing conditions.
- the operation results are as shown in Table 7.
- the actual cooling start temperature is about 40 ° C higher than the target, so if the cooling is performed at the slow cooling zone passing speed determined by the initial calculation, the slow cooling zone cooling will be performed. There was a risk that the stop temperature would increase and the desired fly transformation would not be possible in the slow cooling zone. Therefore, based on the actual results, cooling was performed with the passing speed of the slow cooling zone changed, and the cooling stop temperature of the slow cooling zone could be set to the target cooling stop temperature. As a result, a predetermined strength deviation was achieved in the thickness direction.
- ATS is the difference in tensile strength between the plate thickness 12 position and the plate thickness 1/4 position.
- values defined by the cross-sectional average temperature at the end of cooling calculated by the process computer based on the temperatures measured by the thermometers 31, 32, and 33 are used. Industrial applicability
- the apparatus which concerns on this invention, it becomes possible to manufacture the thick steel plate which has a small difference in hardness between one surface and a center, and is uniform in material, without lowering rolling efficiency.
- the reproducibility of the material can be maintained high while maintaining a high cooling rate as a whole, and efficient mass production of the steel sheet becomes possible.
- the present invention makes the temperature distribution after cooling uniform and makes it possible to produce steel plates without distortion.
- the present invention is capable of controlling the operating conditions in the quenching wholesale zone by actually measuring the surface temperature of the steel plate after slow cooling, and quenching quickly thereafter, so that the productivity is extremely high. Also, based on the measured temperature in the slow cooling zone, Since the operating conditions can be controlled, the amount of second phase structure generated in the quenching zone can be controlled with good reproducibility.
- Thickness 50 halls, width: 3000mm, length: 15000mm male material Material & (70% yield ratio target)
- Pattern 1 (Fig. 6) After passing through the slow cooling zone, change 3 ⁇ 4g to perform cooling in the rapid cooling zone.
- Cooling stop temperature Cooling rate Mechanical properties .1st cold 2nd cold rolling open
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Abstract
Description
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KR (1) | KR100715264B1 (ja) |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8051695B2 (en) | 2006-10-30 | 2011-11-08 | Jfe Steel Corporation | Method for cooling hot strip |
CN103962385A (zh) * | 2014-04-21 | 2014-08-06 | 河北工程大学 | 一种细化scm435钢奥氏体晶粒的轧制工艺 |
CN106424160A (zh) * | 2016-11-14 | 2017-02-22 | 北京京诚瑞信长材工程技术有限公司 | 可实现多种合金钢棒材轧后控冷要求的轧钢生产线 |
CN109234495A (zh) * | 2018-10-16 | 2019-01-18 | 江阴兴澄特种钢铁有限公司 | 一种低圧缩比高探伤要求SM4Gr2MnNi模具钢板的连铸生产工艺 |
Families Citing this family (3)
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KR101583899B1 (ko) | 2014-01-02 | 2016-01-13 | 한양대학교 에리카산학협력단 | 열연 강판, 그 제조 방법, 및 제조 설비 |
KR101628628B1 (ko) * | 2015-08-03 | 2016-06-09 | 한양대학교 에리카산학협력단 | 열연 강판, 그 제조 방법, 및 제조 설비 |
KR102166607B1 (ko) * | 2018-11-26 | 2020-10-16 | 현대제철 주식회사 | 후판의 스탭냉각 제어 장치 및 방법 |
Citations (3)
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JPS6244529A (ja) * | 1985-08-22 | 1987-02-26 | Kobe Steel Ltd | 被冷却材の強制水冷却停止温度の推定方法 |
JP2000084612A (ja) * | 1998-09-08 | 2000-03-28 | Nkk Corp | 熱間圧延鋼板の制御冷却方法 |
JP2001164323A (ja) * | 1999-12-08 | 2001-06-19 | Nippon Steel Corp | 厚鋼板の冷却方法 |
-
2004
- 2004-06-08 WO PCT/JP2004/008287 patent/WO2004110661A1/ja active Application Filing
- 2004-06-08 KR KR1020057023487A patent/KR100715264B1/ko active IP Right Grant
- 2004-06-11 TW TW093116859A patent/TWI294796B/zh not_active IP Right Cessation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6244529A (ja) * | 1985-08-22 | 1987-02-26 | Kobe Steel Ltd | 被冷却材の強制水冷却停止温度の推定方法 |
JP2000084612A (ja) * | 1998-09-08 | 2000-03-28 | Nkk Corp | 熱間圧延鋼板の制御冷却方法 |
JP2001164323A (ja) * | 1999-12-08 | 2001-06-19 | Nippon Steel Corp | 厚鋼板の冷却方法 |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8051695B2 (en) | 2006-10-30 | 2011-11-08 | Jfe Steel Corporation | Method for cooling hot strip |
CN103962385A (zh) * | 2014-04-21 | 2014-08-06 | 河北工程大学 | 一种细化scm435钢奥氏体晶粒的轧制工艺 |
CN106424160A (zh) * | 2016-11-14 | 2017-02-22 | 北京京诚瑞信长材工程技术有限公司 | 可实现多种合金钢棒材轧后控冷要求的轧钢生产线 |
CN109234495A (zh) * | 2018-10-16 | 2019-01-18 | 江阴兴澄特种钢铁有限公司 | 一种低圧缩比高探伤要求SM4Gr2MnNi模具钢板的连铸生产工艺 |
CN109234495B (zh) * | 2018-10-16 | 2020-07-31 | 江阴兴澄特种钢铁有限公司 | 一种低圧缩比高探伤要求SM4Gr2MnNi模具钢板的连铸生产工艺 |
Also Published As
Publication number | Publication date |
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KR20060018246A (ko) | 2006-02-28 |
KR100715264B1 (ko) | 2007-05-04 |
TWI294796B (en) | 2008-03-21 |
TW200534936A (en) | 2005-11-01 |
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