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KR100368213B1 - Method for preventing widthwise bending deformation of plate - Google Patents

Method for preventing widthwise bending deformation of plate Download PDF

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Publication number
KR100368213B1
KR100368213B1 KR1019960068763A KR19960068763A KR100368213B1 KR 100368213 B1 KR100368213 B1 KR 100368213B1 KR 1019960068763 A KR1019960068763 A KR 1019960068763A KR 19960068763 A KR19960068763 A KR 19960068763A KR 100368213 B1 KR100368213 B1 KR 100368213B1
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KR
South Korea
Prior art keywords
plate
steel sheet
cooling
temperature
hot
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KR1019960068763A
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Korean (ko)
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KR19980050011A (en
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황병원
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주식회사 포스코
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Publication of KR19980050011A publication Critical patent/KR19980050011A/en
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Publication of KR100368213B1 publication Critical patent/KR100368213B1/en

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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B37/00Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/28Control of flatness or profile during rolling of strip, sheets or plates
    • B21B37/44Control of flatness or profile during rolling of strip, sheets or plates using heating, lubricating or water-spray cooling of the product
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B1/00Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B38/00Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product
    • B21B38/006Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product for measuring temperature
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B1/00Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B2001/225Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by hot-rolling
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B2261/00Product parameters
    • B21B2261/02Transverse dimensions
    • B21B2261/04Thickness, gauge
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B2261/00Product parameters
    • B21B2261/20Temperature

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Metal Rolling (AREA)
  • Control Of Metal Rolling (AREA)

Abstract

PURPOSE: A method for preventing widthwise bending deformation of plate is provided to improve product surface quality and productivity at the same time by measuring temperature of upper and lower parts of plate, thereby predicting widthwise bending amount of plate generated after cooling, and performing hot leveling after cooling the upper and lower parts of plate in certain temperature range. CONSTITUTION: In manufacturing plate in hot rolling facility comprising upper and lower thermometers installed in front of hot rolling mill and rear of hot leveling machine, and water cooling unit installed between the hot rolling mill and hot leveling machine, the method for preventing widthwise bending deformation of plate comprises the steps of obtaining deformation amounts (dte,dtc) of the total bending by thermal contraction and dead load of plate in the ordinary temperature state by measuring temperature of upper and lower parts of the plate just before or just after final rolling using the upper and lower thermometers; obtaining an average heat flux (Hm) using the temperature of the upper and lower parts of the plate measured by the upper and lower thermometers; obtaining cooling heat capacity (Qt) of the upper part of the plate and cooling heat capacity (Qb) of the lower part of the plate using the obtained average heat flux; obtaining water quantity of the upper part of the plate (Ft) and water quantity of the lower part of the plate (Fb) using the obtained cooling heat capacities of the upper and lower parts of the plate (Qt,Qb); and performing hot leveling on the cooled plate after cooling the plate correspondingly to the obtained water quantities of the upper and lower parts of the plate (Ft,Fb).

Description

후강판의 폭방향 휨변형 방지방법How to prevent bending deformation in thick steel plate

본 발명은 용접구조용, 선체구조용 및 건축구조용등으로 널리 사용되고 있는 후강판을 제조할 때 자주 발생하는 폭방향 휨변형을 예측하여 제조공정중에 이의발생을 방지하는 방법에 관한 것으로, 보다 상세히는 강판을 가열, 압연 및 냉각할 때 생긴 강판의 상하온도를 열간압이 종료된 직후에 측정하고, 측정된 온도에서 상하부온도편차를 구하여 강판이 상온까지 냉각되었을 때 발생하는 폭방향으로의 휨변형량을 미리 예측하고 이를 방지하는 후강판의 폭방향 휨변형 방지방법에 관한 것이다.The present invention relates to a method of preventing the occurrence of the steel sheet during the manufacturing process by predicting the warpage deformation frequently occurs when manufacturing thick steel sheet widely used for welded structures, hull structures and architectural structures, and more specifically, The upper and lower temperatures of the steel sheets produced during heating, rolling, and cooling are measured immediately after the end of the hot pressure, and the upper and lower temperature deviations are calculated from the measured temperatures to predict the warpage deformation occurring in the width direction when the steel sheet is cooled to room temperature in advance. It relates to a method of preventing the warpage deformation of the thick steel plate to prevent this.

일반적으로, 후강판은 연속주조 또는 강괴의 압연에 의하여 제조한 슬라브 (slab)를 가열로에 장입하여 1150℃∼1250℃로 재 가열한 후 고온상태에서 압연을 하여 소정의 두께, 폭 및 길이를 맞추어 제조한다. 압연이 끝난 강판은 압연시에 발생된 판변형을 제거할 목적으로 열간교정을 행하여 평탄한 강판을 얻는다. 이와 같이 제조된 강판은 냉각대에서 자연냉각으로 상온에 가까운 온도까지 냉각시키고 절단기에서 소정의 폭 및 길이로 분할하여 최종 제품을 만든다.In general, a thick steel sheet is charged into a slab (slab) produced by continuous casting or rolling of a steel ingot in a heating furnace and reheated to 1150 ° C to 1250 ° C, and then rolled at a high temperature to obtain a predetermined thickness, width and length. Manufacture according to The rolled steel sheet is subjected to hot calibration for the purpose of removing the plate deformation generated during rolling to obtain a flat steel sheet. The steel sheet thus manufactured is cooled to a temperature close to room temperature by natural cooling in a cooling zone and divided into predetermined widths and lengths in a cutter to make a final product.

이러한 후강판의 제조공정에 있어서 슬라브의 가열, 강판의 압연 및 냉각시판의 온도편차가 발생된다. 일반적으로 압연이 종료된 강판에 발생되는 온도편차는 폭방향, 두께방향 및 길이방향의 모든 방향으로 발생하게 되며, 이와같은 각각의 온도 편차는 각기 다른 형태의 판변형을 야기시킨다. 통상, 압연이 종료된 강판의 두께방향 온도분포는 도 1의 (가)또는 (나)와 같이 얻어진다.In the manufacturing process of the thick steel sheet, the slab is heated, the steel sheet is rolled, and the temperature deviation of the commercially available plate is generated. Generally, the temperature deviation generated in the finished steel sheet is generated in all directions in the width direction, the thickness direction, and the longitudinal direction, and such temperature deviations cause different types of plate deformation. Usually, the thickness direction temperature distribution of the steel plate after rolling is obtained as (a) or (b) of FIG.

도 1의 (가)에서 나타난 바와같이 두께방향으로 가열조건과 압연조건이 적절한 경우에는 강판두께 중심부를 기준으로 상하부가 대칭에 가까운 온도구배를 갖게 되며, 도 1의 (나)에 나타난 바와같이 두께방향으로의 가열과 압연조건이 부적절한 경우에는 강판 두께방향으로의 온도구배가 발생함을 알 수 있다.As shown in (a) of FIG. 1, when heating and rolling conditions are appropriate in the thickness direction, the upper and lower parts have a temperature gradient close to symmetrical with respect to the center of the steel sheet thickness, and as shown in (b) of FIG. If the heating and rolling conditions in the direction is inappropriate, it can be seen that a temperature gradient occurs in the thickness direction of the steel sheet.

후강판의 가열과 압연과정에서 도 1의 (가) 및 (나)와 같이 강판이 두께방향으로 각각 다른 온도구배를 갖게되는 이유는 슬라브(slab) 의 상부는 곧바로 버너 (burner)의 화염과 주위온도에 의하여 가열되지만 하부는 슬라브를 이송시키기 위한 이송빔과 지지빔에 의하여 화염의 일부분이 가려지기 때문에 슬라브(slab)의 상부의 입열량이 하부의 입열량보다 크기 때문에 생기는 1차적인 원인이 있고, 이와같이 가열된 슬라브를 추출하여 압연하면 압연과정에서 강판 상부에는 표면산화막을 제거하기 위하여 강판에 투사한 고압수의 체류에 의한 열방출이 생기고 하부는 이송롤의 접촉에 의한 부가적인 열방출이 생기기 때문에 최종적으로 압연이 종료된 강판의 두께방향 온도구배는 가열과 압연조건에 따라 각각 다르게 얻어지게 된다. 따라서 도 1의 (가)의 경우는 가열로에서 생긴 상하온도편차와 압연과정에서 생긴 온도편차가 서로 상쇄될 경우에 얻을 수 있는 온도구배이며, 도 1의(나)는 가열과정에서 발생된 상하온도편차가 압연과정에서 증대 또는 미소멸된 경우에 강판에 잔류하는 온도구배이다.The reason why the steel plate has different temperature gradients in the thickness direction as shown in (a) and (b) of FIG. 1 during the heating and rolling of the thick steel plate is that the upper part of the slab is directly burned with the flames of the burner and the surroundings. Although it is heated by temperature, the lower part of the flame is covered by the transport beam and the support beam for transporting the slab, and the primary cause is that the heat input of the upper part of the slab is larger than that of the lower part. When the heated slabs are extracted and rolled in this way, heat is generated by the retention of high pressure water projected on the steel sheet to remove the surface oxide film on the upper part of the steel sheet during rolling, and additional heat release is caused by the contact of the transfer roll at the lower part. Therefore, the temperature gradient in the thickness direction of the steel sheet finally finished rolling is obtained differently depending on heating and rolling conditions. Therefore, (a) of FIG. 1 is a temperature gradient obtained when the up and down temperature deviation generated in the heating furnace and the temperature deviation generated in the rolling process cancel each other, and FIG. 1 (b) shows the up and down generated in the heating process. It is the temperature gradient that remains in the steel sheet when the temperature deviation increases or disappears during the rolling process.

통상, 후강판 제조시에 도 1의 (나)와 같이 강판 상하부에 온도편차가 발생되면 냉각시 강판이 폭방향 및 길이방향 선후단부에 변형을 하게 된다. 도 2의 (가) 및(나)는 강판이 압연직후에 상하부의 온도편차가 크게 날 경우에 발생되는 강판의 변형형상을 보여주는 모식도로서 도 2의 (가)는 압연직후 하부의 온도가 상부의 온도보다 높은 경우에 발생하는 변형형상이며, (나)는 압연직후 상부의 온도가 하부보다 높을 경우에 발생하는 변형형상이다. 이와같은 변형은 고온의 강판이 냉각될때 발생되는 열수축량이 온도에 따라 다르기 때문에 발생되는 것으로서 온도가 높은 부위는 많이 수축하고 낮은 부위는 적게 수축하게 되어 전체적인 강판의 모양은 휘게된다. 이러한 강판은 사용할 때에 절단 및 용접공정을 어렵게 하기 때문에 변형이 어느 한도 이상으로 크게 발생되면 수요가로 부터 불만제기를 받게 되어 생산공장에서 커다란 손해를 끼치게 된다.In general, when a temperature deviation occurs in the upper and lower steel sheets as shown in Figure 1 (b) during the manufacture of the thick steel sheet, the steel sheet is deformed at the front and rear ends in the width direction and the longitudinal direction during cooling. Figure 2 (a) and (b) is a schematic diagram showing the deformation of the steel sheet generated when the temperature difference of the upper and lower parts immediately after rolling the steel sheet, Figure 2 (a) is the temperature of the lower portion immediately after rolling Deformation occurs when it is higher than the temperature, (b) is a deformation that occurs when the temperature of the upper part immediately after rolling is higher than the lower part. Such deformation occurs because the amount of heat shrinkage generated when the high temperature steel sheet is cooled depends on the temperature. The high temperature portion contracts a lot and the low portion shrinks a little so that the overall shape of the steel sheet is bent. When the steel sheet is difficult to use during the cutting and welding process, if the deformation occurs largely above a certain limit, it will be complained from the demand price and cause great damage in the production plant.

따라서, 종래에서 가열과 압연공정에서 강판의 상하부 온도편차가 발생되지 않도록 하기 위하여 가열로의 상하부 버너의 화염을 조절하거나 압연시의 고압수의 적용횟수 및 압연시간을 조절하는 방법을 사용하였다. 그러나 후강판은 제조하고자 하는 강판의 두께, 폭 및 길이가 매우 다양하기 때문에 상하부 온도편차가 발생하지 않는 제조조건을 모든 크기의 강재에 대하여 구하기가 어렵고, 특히 고압수의 적용횟수나 압연시간을 조절하는 방법은 제품의 산화막 두께를 두껍게 할 뿐만 아니라 생산성을 저해하는 등 부가적인 손실을 초래하는 문제점이 있다.Therefore, in order to prevent the temperature difference between the upper and lower parts of the steel sheet in the heating and rolling processes, a method of controlling the flames of the upper and lower burners of the heating furnace or adjusting the number of times of application of high pressure water and rolling time during the rolling was used. However, thick steel plates are difficult to obtain manufacturing conditions for steel of all sizes because the thickness, width, and length of the steel sheet to be manufactured vary widely. The method of increasing the thickness of the oxide film of the product as well as the problem of causing additional losses such as inhibiting productivity.

이에, 본 발명자는 상기한 종래방법들의 제반 문제점을 개선시키기 위하여연구 및 실험을 행하고, 그 결과에 의하여 본 발명을 제안하게 된 것으로서, 본 발명은 강판의 압연과정중 마지막 압연 직전에 강판 상하부의 온도를 측정하여 냉각후 발생될 강판 폭방향 휨량을 미리 예측하고 이를 보상하기 위하여 압연기와 열간교정기 사이에 설치된 냉각설비로 상하의 온도가 같게 되도록 강판 상하부를 일정온도구간 냉각한 후 열간교정을 함으로서 강판이 완전히 냉각되었을 때 폭방향으로 곧은 강판을 얻을 수 있을 뿐만 아니라 슬라브의 가열 및 강판압연시 제약조건을 없애므로서 제품의 표면품질 및 생산성 향상도 동시에 얻을 수 있는 후강판의 폭방향 휨변형방지 방법을 제공하고자 하는데, 그 목적이 있다.Thus, the present inventors have conducted research and experiments to improve the above-mentioned problems of the conventional methods, and the present invention has been proposed by the results, and the present invention has the temperature of the upper and lower parts of the steel sheet just before the final rolling of the steel sheet. In order to predict and predict the warpage of the steel plate in the width direction to be generated after cooling, and to compensate for this, the steel sheet is completely heated by cooling the upper and lower parts of the steel sheet at a certain temperature section so that the temperature of the upper and lower sides is the same as the cooling equipment installed between the rolling mill and the hot straightener. When it is cooled, it is possible not only to obtain straight steel plates in the width direction, but also to prevent warping of slabs in the width direction and to improve the surface quality and productivity of the product by simultaneously eliminating the constraints of slab heating. I would like to, but its purpose is.

이하, 본 발명에 대하여 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

본 발명은 열간압연기 전면과 열간교정기 후면에 상하부 온도계가 구비되고, 그리고 상기 열간압연기와 열간교정기 사이에 수냉각장치가 구비되어 있는 열간압연설비에서 후강판을 제조함에 있어서,In the present invention, the upper and lower thermometers are provided on the front of the hot rolling mill and the rear of the hot straightener, and in manufacturing a thick steel sheet in a hot rolling facility having a water cooling device between the hot rolling mill and the hot straightener.

상기 상하부 온도계로 마지막 압연 직전 또는 직후에 강판의 상하온도를 측정하여 상온상태에서 강판의 열수축과 자중에 의한 총휨량 변형량(dte),(dtc)을 상부 온도가 높을 경우에는 식(1a)에 의해 하부온도가 높을 경우에는 식(1b)에 의하여 구하는 단계:The upper and lower thermometers measure the upper and lower temperatures of the steel sheet immediately before or after the last rolling, and when the upper temperature is high, the total amount of deformation (dte) and (dtc) due to heat shrinkage and self-weight of the steel sheet at room temperature is expressed by Equation (1a). If the lower temperature is high, the step obtained by equation (1b):

(여기서,α:강의 열팽창계수, W:강판폭(mm), h:강판두께(mm), q:강판 단위폭당단중 E:강의 탄성계수 I:단면 2차 모우멘트, △T:상하온도 편차)(Where α is the coefficient of thermal expansion of steel, W is the width of steel sheet (mm), h is the thickness of steel sheet (mm), and q is the unit width per unit width of steel E: elastic modulus of steel I: cross-sectional secondary moment, ΔT: up and down temperature) Deviation)

상기 상, 하부 온도계로 측정한 강판의 상, 하온도를 이용하여 하기 식(2)로 평균 열유속(Hm)을 구하는 단계;Obtaining an average heat flux (Hm) by using the upper and lower temperatures of the steel sheet measured by the upper and lower thermometers in the following formula (2);

(여기서,ρ:강의 밀도, C:강의 오스테나이트 상태의 비열,τ:냉각시간)Where ρ is the density of the steel, C is the specific heat in the austenite state of the steel, and τ is the cooling time.

상기에서 구한 평균열유속을 이용하여 강판 상부의 냉각열량(Qt) 및 하부의 냉각열량(Qb)을 하기식(3a) 및 식(3b)로 구하는 단계;Calculating the amount of cooling heat (Q t ) of the upper part of the steel sheet and the amount of cooling heat of the lower part (Q b ) by using the average heat flux obtained in the following formulas (3a) and (3b);

상기에서 구한 상, 하부의 냉각열량(Qt),(Qb)을 이용하여 하기식(4a),(4b)에 의해 상부수량(Ft) 및 하부 수량(Fb)을 구하는 단계; 및Obtaining the upper quantity (F t ) and the lower quantity (F b ) by the following formulas (4a) and (4b) using the above-obtained upper and lower cooling calories (Q t ) and (Q b ); And

상기 식에서 상수 Bt및 Bb는 수량의 증가에 따라 강판 표면으로 부터 빠져나가는 열량의 비를 나타내는 계수이며, Ct및 Cb는 공냉에 의한 영향을 나타내는 계수, At및 Ab는 냉각수를 강판에 분사할 때 강판에 접촉하는 시간에 따라 냉각을 촉진시키는 정도를 나타내는 계수임)In the above formula, the constants B t and B b are coefficients representing the ratio of heat released from the surface of the steel sheet with increasing quantity, C t and C b are coefficients indicating the influence of air cooling, and A t and A b are cooling water. Coefficient to indicate the degree to promote cooling according to the time of contact with the steel sheet when spraying the steel sheet)

상기에서 구한 상, 하부 냉각수량(Ft),(Fb)에 상응하게 강판을 냉각한후, 열간교정하는 단계를포함하여 구성되는 후강판의 폭방향 휨변형 방지방법에 관한 것이다.It relates to a method for preventing warpage in the width direction of a thick steel plate comprising the step of cooling the steel sheet correspondingly to the upper, lower cooling water (F t ), (F b ) obtained in the above, followed by hot calibration.

이하 본 발명을 보다 상세히 설명한다.Hereinafter, the present invention will be described in more detail.

본 발명에 따라 강판을 상온까지 공냉한 후 폭방향 휨변형이 거의 발생되지 않도록하기 위해서는 도 3에 나타낸 바와같이, 열간압연기(1)전면에 설치된 상하온도측정기(1a,1b)를 이용하여 강판의 상하부 온도를 측정하여야 한다.In order to hardly generate the warpage deformation in the width direction after air cooling the steel sheet to room temperature according to the present invention, as shown in FIG. 3, the steel sheet is heated by using the upper and lower temperature measuring devices 1a and 1b installed on the front surface of the hot rolling mill 1. Upper and lower temperature shall be measured.

다음에, 하기식(1aa)와 같이 상기에서 측정된 상, 하온도의 편차(△T)를 구한다.Next, the deviation (ΔT) of the up and down temperatures measured above is calculated as in the following formula (1aa).

(여기서 Tt:측정된 상부온도의 평균값Where T t is the average value of the measured upper temperature

Tb:측정된 하부온도의 평균값)T b : average value of the measured lower temperature)

상기 수식에서 사용되는 측정된 상, 하부 온도는 길이방향으로 측정된 온도를 평균하는 것이 바람직하다. 이는 강판 길이방향으로 측정된 온도는 매우 좁은 간격으로 측정되기 때문에 냉각시 이들 모든 온도 측정점에 대하여 냉각제어를 하기기 불가능하고 온도측정시 강판 표면의 상태에 따라 부위별 온도편차가 크게 발생할 우려가 있기 때문이다.The measured phase and lower temperature used in the above formula is preferably to average the temperature measured in the longitudinal direction. This is because the temperature measured in the longitudinal direction of the steel sheet is measured at very narrow intervals, so it is impossible to control the cooling of all these temperature measuring points during cooling, and there is a possibility that there is a large temperature deviation for each part depending on the state of the steel sheet surface during temperature measurement. Because.

다음에, 상기와 같이 구한 상하부 온도편차(△T)를 이용하여 강판이 상온으로 냉각되었을 때의 강판 상하부 열수축 차이에 의하여 발생되는 폭방향 최대 휨변형량(dth)을 하기식(1ab)를 이용하여 구한다.Use Next, the upper and lower temperature difference (△ T) steel sheet to a width direction of the maximum bending amount of deformation (d th) generated by the upper and lower heat shrinkage difference formula (1ab) of when the steel sheet is cooled to ambient temperature by using the determined as described above Obtain it by

상기 (1ab)식은 강판 상하부에 온도편차 △T가 있는 강판이 냉각될 때 상하부 열수축의 차이에 의하여 발생되는 휨변형량중 최대치이며, 만약 강판의 변형이 발생되면 강판의 중량에 의하여 자중완화가 생기게 된다. 통상 강판의 자중완화는 강판의 상부온도가 높아 냉각시 강판의 폭방향 중심이 오목하게 휠 경우 하기식 (1ac)와 같이 구하여지며, 하부온도가 높아 냉각시 중심이 볼록하게 휠 경우 하기식(1ad)과 같이 구할 수 있다.Equation (1ab) is the maximum value of the bending deflection caused by the difference between the upper and lower heat shrinkage when the steel sheet having the temperature deviation ΔT is cooled in the upper and lower parts of the steel sheet, and if deformation of the steel sheet occurs, self-weight relaxation is caused by the weight of the steel sheet. . In general, the self-weight relaxation of a steel sheet is obtained as shown in the following formula (1ac) when the center of the width direction of the steel sheet is concave when cooling due to the high temperature of the steel sheet, and when the center is convexly curved when cooling due to the lower temperature (1ad). Can be obtained as

상기와 같이 구하여진 열변형량과 자중완하량을 중첩하면 강판에 최종적으로발생되는 총 휨 변형량(dte,dtc)을 구할 수 있다. 이는 측정온도중 상부온도가 높을 경우는 하기식(1a)로 구할수 있으며, 하부온도가 높은 경우는 하기식(1b)로 구할 수 있다.By superimposing the thermal strain and the self-weighting amount obtained as described above, the total amount of deflection deformation (d te , d tc ) finally generated in the steel sheet can be obtained. This can be obtained by the following equation (1a) when the upper temperature of the measured temperature is high, and by the following equation (1b) when the lower temperature is high.

상기 식(1a) 및 식(1b)을 이용하면 압연직후 상하부 온도측정치만으로도 상온시 강판의 휨변형량을 미리 예측할 수 있다.By using the above formulas (1a) and (1b), it is possible to predict the amount of warpage of the steel sheet at room temperature in advance even with the upper and lower temperature measurements immediately after rolling.

다음은 이러한 휨변형량이 과다하게 크게 발생될 경우, 휨변형을 방지하기 위한 냉각방법에 대하여 설명한다.Next, a description will be given of a cooling method for preventing bending deformation when such bending deformation is excessively large.

압연직후 상하부 온도편차가 크게 발생될 경우 열간교정전 수냉각으로 강판의 상하부온도를 같게 만들어 주면 최종적으로 상온까지 냉각된 강판에서는 휨변형이 없게된다. 이를 위하여 강판 상하부에 수냉각으로 빼앗을 열량을 구하기 위하여 강판내부의 에너지 변화량과 강판 상하부 표면에서 외부로 빠져나가는 열량을 같게놓아 수냉각시 강판 상하부로 빠져나가는 평균열유속계수(Hm)을 하기 식(2)와 같이 구한다.If the upper and lower temperature deviation occurs immediately after rolling, if the upper and lower temperatures of the steel sheet are equalized by water cooling before hot calibration, there is no bending deformation in the steel sheet finally cooled to room temperature. For this purpose, the average heat flux coefficient (Hm) exiting the upper and lower steel plates during water cooling is given by equalizing the energy change inside the steel sheet with the amount of heat flowing out from the upper and lower surfaces of the steel sheet to obtain the heat amount to be taken by water cooling in the upper and lower steel sheets. )

상기식(2)를 이용하여 강판 상부에서 빼앗을 열량(Qt) 및 하부에서 뺏앗을열량(Qb)을 구하면 하기식(3a) 및 식(3b)와 같게 된다.By using the above formula (2) to obtain the amount of heat (Q t ) to take away from the top of the steel sheet and the amount of heat (Q b ) to take away from the lower portion is the same as the following formula (3a) and formula (3b).

상기 식(3a) 및 (3b)에서 수냉각 종료온도 T0는 냉각시 저온 변태조직의 발생을 방지하기 위하여 상하부 온도중 낮은 온도보다 100℃정도 낮은 온도로 설정하는 것이 바람직하다.In the above formulas (3a) and (3b), the water cooling end temperature T 0 is preferably set to about 100 ° C. lower than the lower temperature of the upper and lower temperatures in order to prevent the occurrence of low temperature transformation tissue during cooling.

다음에,상기에서 구한 상, 하부의 냉각열량(Qt),(Qb)을 이용하여 하기식 (4a),(4b)에 의해 상부수량(Ft) 및 하부 수량(Fb)을 구하는 단계; 및Next, the upper quantity F t and the lower quantity F b are obtained by the following formulas (4a) and (4b) using the above-obtained upper and lower amounts of cooling heat Q t and Q b . step; And

상기 식에서 상수 Bt및 Bb는 수량의 증가에 따라 강판 표면으로 부터 빠져나가는 열량의 비를 나타내는 계수이며, Ct및 Cb는 공냉에 의한 영향을 나타내는 계수, At및 Ab는 냉각수를 강판에 분사할 때 강판에 접촉하는 시간에 냉각을 촉진시키는 정도를 나타내는 계수이다.In the above formula, the constants B t and B b are coefficients representing the ratio of heat released from the surface of the steel sheet with increasing quantity, C t and C b are coefficients indicating the influence of air cooling, and A t and A b are cooling water. It is a coefficient which shows the degree which accelerates cooling at the time of contacting a steel plate, when spraying on a steel plate.

따라서, 냉각수량이 동일할 때에 상부에 분사된 냉각수가 하부에 비하여 접촉하는 시간이 길기 때문에 열유속이 하부에 비하여 크다. 이러한 상하부 냉각거동은 냉각노즐의 형상과 냉각방식에 따라 각각 다르다.Therefore, when the amount of cooling water is the same, the heat flow rate is larger than that of the lower part because the cooling water sprayed on the upper part takes longer to contact the lower part. The upper and lower cooling behaviors are different depending on the shape of the cooling nozzle and the cooling method.

다음에, 상기에서 구한 상, 하부 냉각수량(Ft) 및 (Fb)에 상응하여 냉각장치 (3)의 상, 하부 냉각노즐(5a)(5b)을 통해 냉각수를 분사하여 이송롤(7)상을 이송하는 강판(4)을 냉각한후, 열간교정기(6)에서 열간교정한다.Next, the coolant is sprayed through the upper and lower cooling nozzles 5a and 5b of the cooling apparatus 3 corresponding to the above-described upper and lower cooling water amounts F t and F b to transfer the roll 7. After cooling the steel plate 4 to convey the phase, it is hot-calibrated by the hot-calibrator 6.

즉, 상기에서 구한 수량으로 냉각을 하면, 수냉각 종료시점에서 상하부 온도가 거의 같게되고 그후 열간 교정을 하면 강판은 상온까지 냉각되어도 변형을 발생시키지 않게 된다.In other words, when cooling by the above-mentioned water quantity, the upper and lower temperatures are almost the same at the end of the water cooling, and if hot calibration is performed thereafter, the steel sheet does not generate deformation even when cooled to room temperature.

즉, 본 발명에서는 도 3과 같이 열간압연기 전면에 강판(4)의 상하부 온도분포를 측정할 수 있는 상하 온도측정기(1a)(1b)를 설치하여 마지막 압연직전 또는 직후에 강판의 상하부 온도를 측정하고 이 온도에서 강판 전체의 온도가 상온으로 되었을때 발생시키는 열수축에 의한 휨량을 컴퓨터등에서 계산하여 휨량의 크기가 허용범위 보다 크게 될 경우에는 열간압연기의 열간교정기 사이에 설치된 냉각장치 (3)의 상하부 노즐(5a,5b)를 이용하여 편차냉각을 함으로써 상하부 온도를 거의 같게 되도록 냉각하는 방법으로 냉각 및 열간교정후 최종적으로 냉각되었을 때 얻어지는 강판은 폭방향으로 휨이 거의 발생되지 않는 강판이 제조된다.That is, in the present invention, the upper and lower temperature measuring instruments (1a) (1b) that can measure the upper and lower temperature distribution of the steel sheet 4 on the front of the hot rolling mill as shown in Figure 3 to measure the upper and lower temperatures of the steel sheet immediately before or immediately after the last rolling At this temperature, the amount of deflection due to heat shrinkage generated when the temperature of the whole steel sheet reaches room temperature is calculated by a computer, and when the magnitude of the deflection is greater than the allowable range, the upper and lower parts of the cooling device (3) installed between the hot straighteners of the hot rolling mill. The steel sheet obtained when cooling is finally made after cooling and hot correction by cooling by deviation cooling using the nozzles 5a and 5b so that the upper and lower temperatures are almost the same is produced.

이하 실시예를 통하여 본 발명을 구체적으로 설명한다.Hereinafter, the present invention will be described in detail through examples.

실시예Example

열간압연강판의 압연후 상하부 온도편차에 의하여 발생되는 냉각중 열수축 차이에 의한 휨변형의 방지효과를 보기 위하여 열간압연기 전면과 열간교정기 후면에 강판상부와 하부의 온도를 측정할 수 있도록 온도계를 각각 설치하여 본 발명과 종래의 방법으로 압연을 하였다. 종래의 방법으로는 가열로에서 1250℃근방으로 가열한 스라브를 압연하고 수냉각을 거치지 않고 냉각대에서 공냉하여 폭방향 휨변형량을 측정하고 이를 계산치와 비교하였다. 본 발명의 방법에서는 마지막 압연 직후에 강판의 상하부 온도를 길이방향으로 측정하고 이들을 각각 평균하여 상하부의 온도 편차를 구한 후 본 발명에 의해 휨변형량을 예측하고 이를 방지하기 위한 수냉각량을 구하고, 그 결과를 도 4에 나타내었으며, 도 4에 나타난 바와 같이 상, 하부 노즐의 수량비로 냉각대에서 충분히 냉각하여 휨변형량을 측정하였고, 그 결과를 하기표 1에 나타내었다.Thermometers are installed on the front of the hot rolling mill and on the rear of the hot caliper to measure the temperature of the upper and lower parts of the hot rolled steel sheet in order to prevent the bending deformation caused by the difference in heat shrinkage during cooling caused by the upper and lower temperature deviations of the hot rolled steel sheet. By the present invention and a conventional method. In the conventional method, the slab heated at 1250 ° C. in a heating furnace was rolled and air cooled in a cooling zone without undergoing water cooling to measure the warpage in the width direction and compared with the calculated value. In the method of the present invention, immediately after the last rolling, the temperature of the upper and lower parts of the steel sheet is measured in the longitudinal direction and averaged, respectively, to obtain the temperature deviation of the upper and lower parts, and then the amount of water cooling to predict and prevent the deflection deformation is calculated by the present invention. The results are shown in FIG. 4, and as shown in FIG. 4, the amount of deflection of the upper and lower nozzles was sufficiently cooled in the cooling zone to measure the amount of deflection. The results are shown in Table 1 below.

도 4에 있어서, 상기식(4a)에서의 At는 8.6781, Bt는 9.2979, Ct는 0.0967이며, 상기 식(4b)에서의 Ab는 8.4694, Bb는 12.8720, Cb는 -0.1671이다.In Figure 4, A t in the formula (4a) is 8.6781, B t is 9.2979, C t is 0.0967, A b in the formula (4b) is 8.4694, B b is 12.8720, C b is -0.1671. to be.

상기 표 1에 나타난 바와같이, 본 발명에 따라 휨변형량을 예측하고 냉각하는 발명예(1-7)의 경우에는 종래예에 비하여 폭방향 휨변형괴 대폭감소됨을 알 수 있다. 본 발명의 냉각 효과는 압연과 열간교정과정 사이에 강판의 상하부 온도를 같게하는 냉각방법이 적절하여 상하부 온도를 거의 같게 만들기 때문으로 강판이 상온상태에 이르렀을 때 휨변형이 거의 발생되지 않는 것이다.As shown in Table 1, it can be seen that in the case of Inventive Example (1-7), which predicts and cools the deflection amount according to the present invention, the widthwise warpage strain band is greatly reduced as compared with the conventional example. The cooling effect of the present invention is that the cooling method of equalizing the upper and lower temperatures of the steel sheet between the rolling and the hot calibration process is appropriate to make the upper and lower temperatures almost the same, so that the bending deformation hardly occurs when the steel sheet reaches the normal temperature state.

상술한 바와같이, 본 발명은 종래의 압연방법에서 발생될 수 있는 폭방향 휨변형을 방지할 수 있을 뿐만 아니라 후공정에서 교정부하를 감소시킬 수 있기 때문에 형상 품질 향상의 도모 뿐만 아니라 생산비 절감도 동시에 얻을 수 있은 후강판의 제조방법을 제공하는 효과가 있는 것이다.As described above, the present invention not only prevents the warping in the width direction that may occur in the conventional rolling method, but also reduces the calibration load in the post-process, thereby improving shape quality and reducing production costs. It is effective to provide a method for producing a thick steel sheet can be obtained.

도 1 (가)는 상하부의 가열, 압연 및 냉각조건이 적절할 때 얻어지는 열간압연 강판의 두께방향 온도분포의 일예를 나타내는 온도 분포도1 (a) is a temperature distribution diagram showing an example of a temperature distribution in the thickness direction of a hot rolled steel sheet obtained when heating, rolling and cooling conditions of the upper and lower parts are appropriate;

(나)는 상하부의 가열, 압연 및 냉각조건이 부적절 할 때 발생되는 강판의 두께방향 온도분포의 일예를 나타내는 온도 분포도(B) is a temperature distribution diagram showing an example of temperature distribution in the thickness direction of a steel sheet generated when heating, rolling and cooling conditions of the upper and lower parts are inadequate;

도 2 (가)는 압연후 하부 온도가 상부 온도보다 높은 경우의 강판이 상온으로 냉각되었을 때 열수축차이에 의하여 강판이 위로 볼록한 휨변형 형상을 보여주는 모식도Figure 2 (a) is a schematic diagram showing the bending deformation shape of the steel plate convex upward due to the heat shrinkage difference when the steel sheet is cooled to room temperature when the lower temperature is higher than the upper temperature after rolling.

(나)는 압연후 상부 온도가 하부 온도보다 높은 경우의 강판이 상온으로 냉각되었을 때 열수축 차이에 의하여 강판이 아래로 볼록한 휨변형 형상을 보여주는 모식도(B) is a schematic diagram showing the bending deformation shape of the steel sheet convex downward due to the heat shrinkage difference when the steel sheet is cooled to room temperature when the upper temperature is higher than the lower temperature after rolling.

도 3은 본 발명에 따라 강판을 열간압연하고 냉각하는 순서를 나타내는 구성도3 is a block diagram showing a procedure of hot rolling and cooling a steel sheet according to the present invention.

도 4는 본 발명에서 수냉각시 상하부에서 냉각하여야 하는 열량에 따른 수량 밀도의 관계를 나타내는 그래프Figure 4 is a graph showing the relationship between the water density according to the amount of heat to be cooled in the upper and lower parts during water cooling in the present invention

*도면의 주요 부분에 대한 부호의 설명** Description of the symbols for the main parts of the drawings *

1a,1b ... 상하부 온도측정기 2 ... 열간압연기1a, 1b ... upper and lower temperature measuring instruments 2 ... hot rolling mill

3 ... 냉각장치 4 ... 열간압연강판3 ... chiller 4 ... hot rolled steel sheet

5a,5b ... 상하부 냉각노즐 6 ... 열간교정기5a, 5b ... upper and lower cooling nozzle 6 ... hot calibrator

7 ... 이송롤7 ... feed roll

Claims (2)

본 발명은 열간압연기 전면과 열간교정기 후면에 상하부 온도계가 구비되고, 그리고 상기 열간압연기와 열간교정기 사이에 수냉각장치가 구비되어 있는 열간압연설비에서 후강판을 제조함에 있어서,In the present invention, the upper and lower thermometers are provided on the front of the hot rolling mill and the rear of the hot straightener, and in manufacturing a thick steel sheet in a hot rolling facility having a water cooling device between the hot rolling mill and the hot straightener. 상기 상하부 온토계로 마지막 압연 직전 또는 직후에 강판의 상하온도를 측정하여 상온상태에서 강판의 열수축과 자중에 의한 총휨량 변형량(dte),(dtc)을 상부 온도가 높을 경우에는 식(1a)에 의해 하부온도가 높을 경우에는 식(1b)에 의하여 구하는 단계;Measure the upper and lower temperatures of the steel sheet immediately before or after the last rolling with the upper and lower thermomechanical system, and the total amount of deformation (d te ), (d tc ) due to heat shrinkage and self-weight of the steel sheet at room temperature, the formula (1a) When the lower temperature is high by the step of obtaining by the formula (1b); (여기서,α:강의 열팽창계수, W:강판폭(mm), h:강판두께(mm), q:강판 단위폭당 단중 E:강의 탄성계수 I:단면 2차 모우멘트, △T:상하온도 편차)(Where α is the coefficient of thermal expansion of steel, W is the width of steel sheet (mm), h is the thickness of steel sheet (mm), and q is the unit weight per unit width of steel sheet E: modulus of elasticity of steel I: cross-sectional secondary moment, ΔT: vertical temperature deviation) ) 상기 상, 하부 온도계로 측정한 강판의 상, 하온도를 이용하여 하기 식(2)로 평균 열유속(Hm)을 구하는 단계;Obtaining an average heat flux (Hm) by using the upper and lower temperatures of the steel sheet measured by the upper and lower thermometers in the following formula (2); (여기서,ρ:강의 밀도, C:강의 오스테나이트 상태의 비열,τ:냉각시간)Where ρ is the density of the steel, C is the specific heat in the austenite state of the steel, and τ is the cooling time. 상기에서 구한 평균열유속을 이용하여 강판 상부와 냉각열량(Qt) 및 하부의냉각열량(Qb)을 하기식(3a) 및 식(3b)로 구하는 단계:Using the average heat flux obtained above to obtain the calorific value of the upper and the cooling heat (Q t ) and the cooling heat amount (Q b ) of the lower portion by the following formula (3a) and formula (3b): 상기에서 구한 상, 하부의 냉각열량(Qt),(Qb)을 이용하여 하기식(4a),(4b)에 의해 상부수량(Ft) 및 하부 수량(Fb)을 구하는 단계; 및Obtaining the upper quantity (F t ) and the lower quantity (Fb) by the following formulas (4a) and (4b) using the above-obtained upper and lower cooling calories (Q t ) and (Q b ); And 상기 식에서 상수 Bt및 Bb는 수량의 증가에 따라 강판 표면으로 부터 빠져나가는 열량의 비를 나타내는 계수이며, Ct및 Cb는 공냉에 의한 영향을 나타내는 계수, At및 Ab는 냉각수를 강판에 분사할 때 강판에 접촉하는 시간에 따라 냉각을 촉진시키는 정도를 나타내는 계수임)In the above formula, the constants B t and B b are coefficients representing the ratio of heat released from the surface of the steel sheet with increasing quantity, C t and C b are coefficients indicating the influence of air cooling, and A t and A b are cooling water. Coefficient to indicate the degree to promote cooling according to the time of contact with the steel sheet when spraying the steel sheet) 상기에서 구한 상, 하부 냉각수량(Ft),(Fb)에 상응하게 강판을 냉각한후, 열간교정하는 단계를포함하여 구성되는 후강판의 폭방향 휨변형 방지방법Method for preventing the warpage in the width direction of the thick steel plate comprising the step of cooling the steel sheet in accordance with the upper, lower cooling water (F t ), (F b ) obtained in the above, followed by hot calibration 제 1항에 있어서, At는 8.6781, Bt는 9.2979, Ct는 0.0967이고, Ab는 8.4694, Bb는 12.8720, Cb는 -0.1.671인 것을 특징으로 하는 후강판의 폭방향 휨변형 방지방법The widthwise deflection of the thick steel sheet according to claim 1, wherein A t is 8.6781, B t is 9.2979, C t is 0.0967, A b is 8.4694, B b is 12.8720, and C b is -0.1.671. How to prevent deformation
KR1019960068763A 1996-12-20 1996-12-20 Method for preventing widthwise bending deformation of plate KR100368213B1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100623764B1 (en) * 2004-06-15 2006-09-19 현대자동차주식회사 Apparatus for automatically correcting deformation of structures welded for cantilever
KR101428318B1 (en) * 2012-12-26 2014-08-07 주식회사 포스코 Apparatus for guiding approach of strip

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Publication number Priority date Publication date Assignee Title
KR100874054B1 (en) * 2006-10-26 2008-12-12 현대제철 주식회사 Apparatus and method for controlling length and weight of manufactured goods
CN115446153B (en) * 2022-08-10 2024-06-11 沪东中华造船(集团)有限公司 Jumping type water and fire correction method for welding deformation of marine thin steel plate

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100623764B1 (en) * 2004-06-15 2006-09-19 현대자동차주식회사 Apparatus for automatically correcting deformation of structures welded for cantilever
KR101428318B1 (en) * 2012-12-26 2014-08-07 주식회사 포스코 Apparatus for guiding approach of strip

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