KR20030042798A - Method for hot rolling of high carbon steel in low temperature to prevent coil collapse - Google Patents
Method for hot rolling of high carbon steel in low temperature to prevent coil collapse Download PDFInfo
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- KR20030042798A KR20030042798A KR1020010073579A KR20010073579A KR20030042798A KR 20030042798 A KR20030042798 A KR 20030042798A KR 1020010073579 A KR1020010073579 A KR 1020010073579A KR 20010073579 A KR20010073579 A KR 20010073579A KR 20030042798 A KR20030042798 A KR 20030042798A
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- carbon steel
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- 229910000677 High-carbon steel Inorganic materials 0.000 title claims abstract description 33
- 238000005098 hot rolling Methods 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000001816 cooling Methods 0.000 claims abstract description 24
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 12
- 238000005096 rolling process Methods 0.000 claims description 38
- 241000405070 Percophidae Species 0.000 claims description 19
- 238000004804 winding Methods 0.000 claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 229910000831 Steel Inorganic materials 0.000 claims description 10
- 239000010959 steel Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 8
- 238000005097 cold rolling Methods 0.000 claims description 3
- 230000005496 eutectics Effects 0.000 abstract description 3
- 230000001105 regulatory effect Effects 0.000 abstract 2
- 230000009466 transformation Effects 0.000 description 51
- 229910001562 pearlite Inorganic materials 0.000 description 18
- 239000000463 material Substances 0.000 description 6
- 229910001566 austenite Inorganic materials 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 3
- 230000001965 increasing effect Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 230000003698 anagen phase Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000006355 external stress Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 235000019362 perlite Nutrition 0.000 description 1
- 239000010451 perlite Substances 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000013077 target material Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-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
- B21B1/22—Metal-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
- B21B1/24—Metal-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 in a continuous or semi-continuous process
- B21B1/26—Metal-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 in a continuous or semi-continuous process by hot-rolling, e.g. Steckel hot mill
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
- B21B3/02—Rolling special iron alloys, e.g. stainless steel
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B2015/0057—Coiling the rolled product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B2261/00—Product parameters
- B21B2261/20—Temperature
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
본 발명은 고탄소강 열연코일의 연속식 열간압연 방법에 관한 것으로서, 더욱 상세하게는 열간압연후 냉각중 권취코일의 형상에 있어서 짱구코일의 발생을 방지하기 위하여 마무리 압연온도를 저온으로 하여 열간압연하는 방법에 관한 것이다.The present invention relates to a continuous hot rolling method of a high carbon steel hot rolled coil, and more particularly to hot rolling at a low finishing rolling temperature at a low temperature in order to prevent generation of duckbill coils in the shape of the winding coil during cooling after hot rolling. It is about a method.
일반적으로, 고탄소강은 0.4~1.0% 범위의 탄소를 함유하는 강종으로, 보통 Mn, Si, Cr, Mo, Ni 등을 강도증대 등의 목적으로 2% 미만 소량 함유하며, 최종 미세조직이 펄라이트(pealite)를 주된 조직으로 하는 강을 말한다.In general, high carbon steel is a steel grade containing 0.4 to 1.0% of carbon, and usually contains a small amount of Mn, Si, Cr, Mo, Ni, etc., for the purpose of increasing strength, and the final microstructure is pearlite ( It is a river whose main organization is pealite).
고탄소강은 연속식 열간압연 방법에 의해 열연코일로 제조되는데, 가열된 고탄소강 슬래브(slab)를 열간 압연기에서 소정의 두께로 압연한 뒤 냉각시스템이 구비된 런아웃테이블(Run-Out Table : ROT, 이하, "수냉각대"의 용어와 혼용함)에서 적정 온도까지 수냉각하여 상변태시킨 후, 두루마리 코일형태로 권취하게 된다.High carbon steel is manufactured from a hot rolled coil by a continuous hot rolling method. The heated high carbon steel slab is rolled to a predetermined thickness in a hot rolling mill, and a run-out table equipped with a cooling system (ROT, Hereinafter, mixed with the term "water cooling stand"), the water is cooled to an appropriate temperature to undergo a phase transformation, and then wound into a coil form of a roll.
이때, 고탄소강 열연코일의 열간압연 공정에서 마무리 압연온도는 통상적으로 880~900℃ 범위이며, 수냉각후 권취온도는 600~650℃ 범위로 관리하고 있다.At this time, the finish rolling temperature in the hot rolling process of the high carbon steel hot rolled coil is usually in the range of 880 ~ 900 ℃, the winding temperature after water cooling is managed in the range of 600 ~ 650 ℃.
이와 같은 열연공정을 거쳐 권취된 권취코일은 코일야적장으로 옮겨져 대기중에 방치되고, 상온까지 냉각되어 제품화된다. 이때, 일반 저탄소강의 경우와는 달리 고탄소강의 경우에는 도 1에 나타낸 바와 같이 열연코일의 형상이 위, 아래로 찌그러져 타원형으로 변하는 소위 짱구코일이 자주 발생되며, 이렇게 권취코일의 형상이 찌그러지면 후공정인 정정공정이나 산세공정 등에서 조업이 매우 어려워지기 때문에 생산성이나 실 수율을 크게 저하시키게 된다.The winding coil wound up through such hot rolling process is transferred to the coil yard, left in the air, cooled to room temperature and commercialized. At this time, unlike in the case of general low carbon steel, in the case of high carbon steel, as shown in FIG. 1, the shape of the hot rolled coil is crushed up and down so that a so-called duckbill coil frequently turns into an elliptical shape. In the process of correction, pickling, etc., the operation becomes very difficult, which greatly reduces productivity and yield.
이를 방지하기 위해, 도 2에 나타낸 바와 같이 쐐기모양의 짱구방지를 위한 코일 적치대를 사용하여 권취코일을 냉각하는 방법이 이용되고 있으나 근본적인 해결책이 되고 있지는 못하다.In order to prevent this, as shown in FIG. 2, a method of cooling the coiling coil using a coil loading stand for preventing wedge-shaped duckbills is used, but it is not a fundamental solution.
본 발명은 상기와 같은 문제점을 해결하기 위하여 창안된 것으로서, 고탄소강의 열간압연 공정에서 마무리 압연온도를 낮춤으로써 펄라이트 변태를 촉진하여 수냉각대에서 일정분율 이상의 펄라이트 변태를 미리 유도하는 것에 의해 짱구코일의 발생을 방지하여 형상이 우수한 고탄소강 열연코일을 제조하는 방법을 제공하는데 그 목적이 있다.The present invention was devised to solve the above problems, by promoting the pearlite transformation by lowering the finish rolling temperature in the hot rolling process of high carbon steel duckbill coil by inducing the pearlite transformation of a certain fraction or more in the water cooling zone in advance It is an object of the present invention to provide a method for manufacturing a high carbon steel hot rolled coil having a superior shape by preventing the occurrence of the carbon dioxide.
본 발명의 다른 목적 및 장점들은 하기에 설명될 것이며, 본 발명의 실시에 의해 알게 될 것이다. 또한, 본 발명의 목적 및 장점들은 첨부된 청구범위에 나타낸 수단 및 조합에 의해 실현될 수 있다.Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. In addition, the objects and advantages of the invention may be realized by the means and combinations indicated in the appended claims.
도 1은 고탄소강 열연코일의 냉각중 짱구코일 발생을 보여주는 도면.1 is a view showing the duckbill coil generation during cooling of the high carbon steel hot rolled coil.
도 2는 종래에 사용된 코일 적치대를 이용하여 짱구코일 발생을 방지하는 방법을 보여주는 도면.Figure 2 is a view showing a method for preventing the duckbill coil generation by using a conventional coil loading stand.
도 3은 고탄소강의 권취시점에서의 변태분율 및 냉각종료 후 코일 에스팩트비(aspect ratio)에 미치는 마무리 압연온도의 효과를 보여주는 그래프.Figure 3 is a graph showing the effect of the finish rolling temperature on the transformation fraction and the coil aspect ratio after the end of cooling at the time of winding of high carbon steel.
상기와 같은 목적을 달성하기 위한 본 발명의 고탄소강 열연코일의 짱구코일 발생 방지를 위한 저온압연 방법은, 0.4∼1.0%의 탄소를 함유하는 고탄소강 슬라브를 열연강판으로 열연압연하여 수냉각대(ROT)상에서 냉각한 후 권취하여 열연코일을 제조하는 연속식 열간압연 방법에 있어서, 마무리 압연온도를 탄소함유량에 따라 공석조성 이하의 경우에는 Ae3+30℃∼Ae3+50℃, 공석조성 이상인 경우에는 Acm+30℃∼Acm+50℃의 영역으로 제어하고, 수냉각하여 600~650℃ 범위에서 권취하여 열연코일을 제조하는 것을 특징으로 한다.The low-temperature rolling method for preventing the duckbill coil generation of the high carbon steel hot rolled coil of the present invention for achieving the above object, by hot rolling a high carbon steel slab containing 0.4 to 1.0% of carbon by hot rolled steel sheet In the continuous hot rolling method of producing a hot rolled coil by winding on a roll after cooling on ROT), when the finish rolling temperature is less than or equal to the vacancy composition according to the carbon content, Ae 3 + 30 ° C. to Ae 3 + 50 ° C. In the case, it is characterized in that the hot rolled coil is manufactured by controlling the temperature in the range of Acm + 30 ° C. to Acm + 50 ° C., winding it in water to 600 ° C to 650 ° C.
이하, 본 발명을 상세히 설명하기로 한다.Hereinafter, the present invention will be described in detail.
고탄소강에서 특징적으로 발생하는 짱구코일의 발생원인을 분석하던 중 다음과 같은 현상들이 복합적으로 발생됨이 확인되였다.During the analysis of the cause of the duckbill coil, which is characteristic of high carbon steel, it was confirmed that the following phenomena occur in combination.
첫째, 일반적인 저탄소강의 경우 수냉각 직후 대부분의 상변태가 수냉각대(ROT : Run-Out Table)상에서 완료되는데 반해, 고탄소강의 경우 통상의 압연 및 냉각조건하에서는 수냉각대 상에서 펄라이트 변태(pearlite transformation)가 거의 일어나지 않거나 약간만 일어난 상태로 권취되어 코일형태로 권취된 상태에서 펄라이트 변태가 진행되게 된다.First, in the case of general low carbon steel, most of the phase transformation immediately after the water cooling is completed on the run-out table (ROT), whereas in the case of high carbon steel, pearlite transformation is performed on the water cooling stage under normal rolling and cooling conditions. Is hardly generated or wound in a slight state, and the perlite transformation proceeds in a coiled state.
둘째, 권취된 상태로 펄라이트 변태가 진행될 때, 상변태에 따른 변태발열이 발생되며, 이때 권취된 코일의 강판 사이로 열전달이 원활하지 않아 코일의 내권부의 온도가 권취시의 온도보다 50℃ 이상 크게 상승된다. 특히, 고탄소강의 경우는 주 조직인 펄라이트의 변태 발열량이 일반적인 저탄소강의 주 조직인 페라이트(ferrite)에 비해 상당히 크므로 온도 상승량은 더욱 증가한다.Second, when the pearlite transformation proceeds in the wound state, transformation heat is generated according to the phase transformation. At this time, the heat transfer between the steel sheets of the coil is not smooth, so that the temperature of the inner winding portion of the coil rises more than 50 ° C. above the temperature at the time of winding. do. In particular, in the case of high carbon steel, the transformation calorific value of pearlite, which is the main structure, is considerably larger than that of ferrite, which is the main structure of the low carbon steel.
셋째, 상변태가 진행될 때 외부응력이 가해지는 경우 그 물질의 항복강도보다 낮은 응력이 가해지더라도 영구적인 소성변형(plastic deformation)이 발생하는 변태 초소성(transformation super plasticity) 현상이 발생한다. 따라서, 수냉각대 상에서 펄라이트 변태를 충분히 일으켜 주지 못한 상태에서 권취하는 경우, 상변태는 권취 이후에 서서히 진행하게 되며, 이때 코일의 자중 정도의 응력이 걸리더라도 상변태가 수반되어 변태 초소성 현상에 의해 코일의 형상이 중력방향으로 찌그러지는 소성변형이 일어나게 된다.Third, when external stress is applied when the phase transformation progresses, transformation super plasticity occurs even though a stress lower than the yield strength of the material is applied. Therefore, in the case of winding in a state in which the pearlite transformation has not been sufficiently generated on the water cooling stage, the phase transformation proceeds gradually after the winding. At this time, even if a stress of the coil's own weight is involved, the phase transformation is accompanied by the transformation superplasticity phenomenon The plastic deformation of the shape of the resin is crushed in the direction of gravity.
따라서, 고탄소강에서 발생하는 짱구코일 현상을 근본적으로 해결하기 위해서는 수냉각대 상에서 펄라이트의 상변태를 적어도 60% 이상 진행시킨 후 권취해야 함이 밝혀졌으며, 이를 위해 저온압연법을 채택하게 이르렀다.Therefore, in order to fundamentally solve the duckbill coil phenomenon occurring in high carbon steel, it was found that the phase transformation of pearlite on the water cooling stage should be carried out after at least 60% or more, and the cold rolling method was adopted.
본 발명에서 제시하는 저온압연법에 의하여 짱구코일 발생을 방지하는 원리 및 효과는 다음과 같이 설명될 수 있다.The principle and effect of preventing duckbill coils by the low temperature rolling method proposed in the present invention can be described as follows.
즉, 압연온도(마무리 압연온도)를 낮춤에 따라 오스테나이트(austenite)의 재결정을 억제하고 압연에 의한 잔류변형이 축적되도록 하여, 오스테나이트의 내부에너지를 증가시켜 상변태의 구동력을 크게 해준다. 한편, 상변태의 핵생성은 오스테나이트 결정입계 및 변형대에서 일어나는데, 압연온도 저하에 따라 재결정이 억제되어 단위체적당 오스테나이트 결정입계 면적 및 변형대가 크게 증가되어 펄라이트 핵생성장소가 많아져 상변태가 촉진되게 된다. 즉, 펄라이트 상변태의 노즈(nose)가 단시간 축으로 이동하여 동일한 냉각조건 하에서 펄라이트 상변태가 빠른 시간 내에 쉽게 일어나게 된다. 따라서, 저온압연을 하게 되면, 통상 마무리 압연온도를 880~900℃로 열간압연한 경우에 비해 수냉각대 상에서 상당량의 펄라이트 변태를 유도할 수 있으므로, 권취시점에서는 이미 펄라이트 상변태량이 상대적으로 커져 권취 이후의 상변태량 및 변태발열량이 작아 짱구코일의 발생이 근본적으로 방지되게 된다.That is, as the rolling temperature (finishing rolling temperature) is lowered, the recrystallization of austenite is suppressed and residual strain due to rolling is accumulated, thereby increasing the internal energy of austenite to increase the driving force of the phase transformation. On the other hand, the nucleation of phase transformation occurs at the austenite grain boundaries and strain bands, and recrystallization is suppressed as the rolling temperature decreases, so that the austenite grain boundary area and strain bands per unit volume are greatly increased to increase the pearlite nucleus growth phase to promote phase transformation. do. That is, the nose of the pearlite phase transformation moves to the short time axis, so that the pearlite phase transformation occurs easily within a short time under the same cooling condition. Therefore, the low temperature rolling can induce a significant amount of pearlite transformation on the water cooling stage compared to the case of hot rolling of the finishing rolling temperature of 880 ~ 900 ℃, since the phase of the pearlite phase transformation is already relatively large at the time of winding, Phase transformation amount and transformation calorific value of the duckbill coil is fundamentally prevented.
본 발명에서는 이러한 관점에서 마무리 압연온도를 가능한 저온으로 하는 것이 바람직하나 마무리 압연온도를 너무 낮추면 열간압연시 상변태가 일어나 혼립조직이 발생하므로, 상변태 개시온도보다 높은 오스테나이트 영역에서 마무리 압연을 종료하는 것이 바람직하다. 통상적으로, 상변태가 개시되는 온도는 평형 상변태 온도보다 낮은 온도이며, 소재의 성분에 따라 변화한다. 본 발명의 대상 소재인 0.4~1.0%의 탄소를 함유하는 고탄소강은 평형 상변태 온도보다 약 50℃정도 낮은 온도에서 상변태를 개시하므로, 압연종료온도를 그 온도 직상까지 낮추는 것이 가장 바람직하다. 그러나, 열간압연중 열연강판에는 폭방향으로 온도의 불균일이 존재하며, 따라서 에지(edge)부의 온도는 통상 온도측정 부위인 폭방향 중심부보다 약 80℃정도 낮기 때문에, 이를 감안하여 에지부에서 압연중 상변태가 개시되지 않도록 하기 위해서 온도제어의 기준이 되는 폭방향 중심부의 마무리 압연온도를 평형 상변태 온도를 기준으로 하여 이보다 30~50℃ 높은 온도영역에서 행하도록 하는 것이 가장 바람직하다.In the present invention, it is preferable to make the finish rolling temperature as low as possible, but if the finish rolling temperature is too low, phase transformation occurs during hot rolling, and a mixed structure occurs, so that finishing rolling is finished in the austenite region higher than the phase transformation start temperature. desirable. Typically, the temperature at which phase transformation is initiated is lower than the equilibrium phase transformation temperature and varies depending on the composition of the material. High carbon steel containing 0.4 to 1.0% of carbon, which is the target material of the present invention, initiates phase transformation at a temperature about 50 ° C. lower than the equilibrium phase transformation temperature, and thus, it is most preferable to lower the rolling end temperature to just above the temperature. However, there is a temperature nonuniformity in the width direction of the hot rolled steel sheet during hot rolling, and therefore the temperature of the edge portion is about 80 ° C. lower than the central portion in the width direction, which is a temperature measuring part, and thus the rolling is performed at the edge portion. In order to prevent the phase transformation from being initiated, it is most preferable that the finish rolling temperature of the central portion in the width direction, which is a reference for temperature control, is performed in a temperature range of 30 to 50 ° C. higher than this based on the equilibrium phase transformation temperature.
즉, 탄소함량이 공석(eutectoid)조성 이하인 고탄소강의 경우, 페라이트의 평형상변태 온도(Ae3)보다 30∼50℃ 높은 온도에서 마무리 압연하고, 탄소함량이 공석조성 이상인 고탄소강의 경우에는, 세멘타이트(cementite)의 평형상변태 온도(Acm)보다 30∼50℃ 높은 온도구간에서 마무리 압연하는 것이 좋다.That is, in the case of high carbon steel having a carbon content of less than eutectic composition, finish rolling at a temperature of 30 to 50 ° C. higher than the equilibrium transformation temperature (Ae 3 ) of ferrite, and in the case of high carbon steel having a carbon content of more than vacancy composition, It is better to finish-roll at a temperature range of 30 to 50 ° C. higher than the equilibrium transformation temperature (Acm) of cement.
열간압연 후에는 이어서 수냉각을 하는데, 이때의 냉각량은 권취온도가 600∼650℃가 되도록 조절하여 강판의 온도를 펄라이트 상변태의 노즈 온도로 유지되도록 함이 바람직하다. 만약, 권취온도가 600℃ 미만으로 낮아질 경우에는 베이나이트(bainite) 등의 저온조직이 발생하여 경도과다, 인성저하 등 재질을 열화시킬 수 있으며, 권취온도가 650℃를 초과하면 수냉각대에서 상변태가 완전히 일어나지 못하여 짱구코일이 발생할 가능성이 있기 때문에 바람직하지 않다.After hot rolling, water cooling is performed, and the amount of cooling at this time is preferably adjusted to a coiling temperature of 600 to 650 ° C. to maintain the temperature of the steel sheet at a nose temperature of pearlite phase transformation. If the winding temperature is lower than 600 ℃, low-temperature structure such as bainite (bainite) may occur to deteriorate the material such as excessive hardness, toughness degradation, etc. If the winding temperature exceeds 650 ℃, the phase transformation in the water cooling stand Is not desirable because it may not occur completely and duckbill coils may occur.
이하, 본 발명에 따른 실시예를 구체적으로 설명한다.Hereinafter, embodiments according to the present invention will be described in detail.
실시예 1Example 1
고탄소강 열연강판의 대표적인 강종이며, 하기의 표 1과 같은 조성을 갖는 SK5재를 대상으로 통상의 열간압연법과 본 발명에 따른 저온압연법으로 최종제품의 두께가 4.0mm인 열연강판을 생산하였다.Representative steel grade of high carbon steel hot-rolled steel sheet, and produced a hot-rolled steel sheet having a thickness of the final product 4.0mm by using the conventional hot rolling method and the low temperature rolling method according to the present invention for the SK5 material having a composition as shown in Table 1 below.
이때, 마무리 압연온도를 890℃로 제어하는 종래의 방법과 본 발명에 따라 마무리 압연온도를 80℃ 낮춘 810℃로 제어하는 두가지 방법으로 열연강판을 제조하였다. 본 발명에 따라 적용된 마무리 압연온도인 810℃는 이 조성에서의 평형상변태 온도인 약 770℃보다 40℃ 높은 조건이다.At this time, the hot-rolled steel sheet was manufactured by the conventional method of controlling the finishing rolling temperature to 890 ° C and the two methods of controlling the finishing rolling temperature to 810 ° C lowering the finishing rolling temperature by 80 ° C. The finishing rolling temperature applied in accordance with the present invention, 810 ° C., is 40 ° C. higher than about 770 ° C., the equilibrium transformation temperature in this composition.
이때, 마무리 압연온도 저하에 따른 압연하중의 변화를 측정한 결과, 통상의 압연하중 허용범위내로서 전혀 문제가 없었으며, 폭 적중율 및 두께 적중율도 커다란 차이가 없었다.At this time, as a result of measuring the change in the rolling load according to the reduction of the finish rolling temperature, there was no problem at all within the allowable range of the rolling load, and the width hit ratio and the thickness hit ratio did not show a big difference.
나아가, 두 방법에서 권취온도는 공히 650℃로 하였다.Furthermore, the winding temperatures were both 650 ° C in both methods.
이와 같은 조건으로 제조된 열연코일을 대기중에 적치하여 상온까지 냉각한 후 짱구발생 정도를 조사하고, 그 결과를 다음의 표 2에 나타낸다.The hot rolled coils prepared under such conditions were loaded in the air, cooled to room temperature, and then the degree of cranial development was investigated. The results are shown in Table 2 below.
여기서, 에스팩트비(aspect ratio)는 코일단축경을 코일장축경으로 나눈 값으로 구해진다.Here, the aspect ratio is obtained by dividing the coil short diameter by the coil long diameter.
표 2를 참조하면, 종래 방법으로 열연코일을 제조한 경우 권취코일 수직방향의 코일직경(코일단축경)이 코일 수평방향의 코일직경(코일장축경)보다 평균 18cm나 작게 측정되어 짱구코일 현상이 심하게 발생한 반면, 본 발명의 저온압연으로 열연코일을 제조한 경우에는 코일단축경과 코일장축경의 차이가 4cm 이내로 거의짱구코일 현상이 발생하지 않았음을 알 수 있다.Referring to Table 2, when the hot rolled coil is manufactured by a conventional method, the coil diameter (coil shorter diameter) in the winding coil vertical direction is measured to be 18 cm smaller than the coil diameter (coil long axis diameter) in the coil horizontal direction, so that On the contrary, when the hot rolled coil is manufactured by cold rolling of the present invention, it can be seen that the difference between the coil short axis diameter and the coil long axis diameter is almost 4 cm.
실시예 2Example 2
상기 실시예 1에서와 동일한 방법으로 0.4%~1.0%의 탄소를 포함하는 다양한 성분계의 고탄소강에 대하여 마무리 압연온도를 다양하게 변화시켜 열연코일을 생산한 후, 각 조건에서의 짱구발생 정도를 측정하고, 권취시점에서의 펄라이트 상변태율과 짱구발생 정도를 나타내는 에스팩트비를 분석하여, 그 결과를 마무리 압연온도에서 평형변태 온도를 뺀 값에 대하여 도 3과 같이 나타낸다.In the same manner as in Example 1 after producing a hot-rolled coil by varying the finish rolling temperature for a high carbon steel of various components containing 0.4% to 1.0% of carbon, and measuring the degree of duckbill in each condition In addition, an analysis of the percentage ratio indicating the pearlite phase transformation rate and the degree of duckbill occurrence at the time of winding, and the results are shown in Figure 3 with respect to the value obtained by subtracting the equilibrium transformation temperature from the finish rolling temperature.
이를 참조하면, 권취시점에서의 펄라이트 상변태율과 코일 에스팩트비는 마무리 압연온도에 크게 의존함을 알 수 있다.Referring to this, it can be seen that the pearlite phase transformation rate and coil aspect ratio at the time of winding depend greatly on the finish rolling temperature.
그리고, 짱구발생 정도가 에스팩스트비를 기준으로 0.95 이상으로 얻어져야만 후공정에 영향이 없다는 점을 감안할 때, 압연온도를 평형변태 온도의 +50℃ 이하로 제어해야 하며, 이 경우 권취시점에서의 변태분율은 약 60% 이상이 됨을 알 수 있다.In addition, considering that the inherent degree of duckbill should be obtained at 0.95 or more on the basis of the S-FAX ratio, there is no influence on the post-process. It can be seen that the transformation fraction is about 60% or more.
한편, 압연온도를 평형변태 온도의 +30℃ 이하로 한 경우 짱구코일 발생은 거의 없으며, 권취시점에서의 변태분율은 80% 이상이 되나 폭방향 에지부에서 부분적으로 혼립조직이 발생하여 바람직하지 않음을 알 수 있다.On the other hand, when the rolling temperature is lower than + 30 ° C of equilibrium transformation temperature, there is almost no duckbill coil. It can be seen.
이상의 결과를 종합하면, 고탄소강의 짱구코일 발생을 방지하기 위한 적절한 제조조건으로는 수냉각대 상에서 적어도 상변태를 60% 이상 진행시킨 후 권취해야 하며, 이를 위해서는 마무리 압연온도를 평형변태 온도의 +30~50℃ 영역으로 설정해야 한다.Taken together, the proper manufacturing conditions to prevent the development of high-carbon steel duckbill coils should be wound after at least 60% of phase transformation on the water cooling stage.To this end, the finish rolling temperature is +30 of the equilibrium transformation temperature. It should be set in the range of ~ 50 ° C.
이상과 같이, 본 발명은 비록 한정된 실시예와 도면에 의해 설명되었으나, 본 발명은 이것에 의해 한정되지 않으며 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에 의해 본 발명의 기술사상과 아래에 기재될 청구범위의 균등범위 내에서 다양한 수정 및 변형이 가능함은 물론이다.As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.
본 발명에 따르면, 열간압연시 마무리 압연온도를 낮추어 압연함으로써 수냉각대 상에서의 펄라이트 변태를 촉진하여 권취 이후의 펄라이트 변태량을 감소시킴으로써, 이에 따른 변태발열에 의한 복열 효과 및 변태초소성을 근본적으로 방지하여 고탄소강 제조시 고질적으로 문제가 되는 짱구코일의 발생을 방지할 수 있게 되어, 이에 따른 실 수율 및 생산성의 저하를 방지할 수 있는 유용한 효과가 있다.According to the present invention, by lowering the finish rolling temperature during hot rolling to promote the pearlite transformation on the water cooling stage to reduce the amount of pearlite transformation after winding, thereby reducing the reheating effect and the transformation superplasticity caused by the transformation heat. By preventing it is possible to prevent the generation of the duckbill coil, which is a problem in the manufacture of high carbon steel, there is a useful effect that can prevent the decrease in yield and productivity.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101277923B1 (en) * | 2011-08-29 | 2013-06-26 | 현대제철 주식회사 | An apparatus for preventing deformation from strip coil |
| CN107904376A (en) * | 2017-10-31 | 2018-04-13 | 首钢京唐钢铁联合有限责任公司 | A kind of method and device for preventing the flat volume of dual phase steel |
| CN114669612A (en) * | 2022-03-25 | 2022-06-28 | 德龙钢铁有限公司 | Method for controlling flat rolling of hot-rolled strip steel |
-
2001
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101277923B1 (en) * | 2011-08-29 | 2013-06-26 | 현대제철 주식회사 | An apparatus for preventing deformation from strip coil |
| CN107904376A (en) * | 2017-10-31 | 2018-04-13 | 首钢京唐钢铁联合有限责任公司 | A kind of method and device for preventing the flat volume of dual phase steel |
| CN114669612A (en) * | 2022-03-25 | 2022-06-28 | 德龙钢铁有限公司 | Method for controlling flat rolling of hot-rolled strip steel |
| CN114669612B (en) * | 2022-03-25 | 2024-04-26 | 德龙钢铁有限公司 | Method for controlling hot rolled strip steel flat coil |
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