KR100496540B1 - METHOD FOR MANUFACTURING Ti ADDED HOT ROLLED STEEL SHEET HAVING EXCELLENT PICKLING PROPERTY - Google Patents
METHOD FOR MANUFACTURING Ti ADDED HOT ROLLED STEEL SHEET HAVING EXCELLENT PICKLING PROPERTY Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 35
- 239000010959 steel Substances 0.000 title claims abstract description 35
- 238000005554 pickling Methods 0.000 title claims abstract description 29
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 10
- 238000000034 method Methods 0.000 title claims abstract description 8
- 238000001816 cooling Methods 0.000 claims abstract description 77
- 239000012535 impurity Substances 0.000 claims abstract description 9
- 238000005098 hot rolling Methods 0.000 claims abstract description 7
- 238000004804 winding Methods 0.000 claims description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 239000000463 material Substances 0.000 abstract description 16
- 238000010791 quenching Methods 0.000 abstract description 9
- 230000000171 quenching effect Effects 0.000 abstract description 7
- 239000012467 final product Substances 0.000 abstract description 3
- 230000002542 deteriorative effect Effects 0.000 abstract description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 24
- 229910052799 carbon Inorganic materials 0.000 description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- 239000000654 additive Substances 0.000 description 6
- 238000000137 annealing Methods 0.000 description 6
- 230000000996 additive effect Effects 0.000 description 5
- 238000005097 cold rolling Methods 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 230000009466 transformation Effects 0.000 description 5
- 238000007654 immersion Methods 0.000 description 4
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 4
- 150000004767 nitrides Chemical class 0.000 description 4
- 238000005482 strain hardening Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 229910001567 cementite Inorganic materials 0.000 description 3
- 229910052595 hematite Inorganic materials 0.000 description 3
- 239000011019 hematite Substances 0.000 description 3
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 3
- 238000005297 material degradation process Methods 0.000 description 3
- 238000004451 qualitative analysis Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000000498 cooling water Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000004445 quantitative analysis Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- -1 C: 0.001% Substances 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000005406 washing 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
- 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
- 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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- 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
- B21B2001/225—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 by hot-rolling
-
- 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
-
- 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)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
본 발명은 자동차 외판재 등에 사용되는 Ti-단독 첨가 열연강판의 제조방법에 관한 것이다. 본 발명은, 중량%로 C:0.005%이하, Mn:0.01~0.2%, P:0.015%이하, Si:0.03%이하, Ti:0.03~0.10% 나머지 Fe와 기타 불가피한 불순물로 조성되는 강슬라브를 열간압연하는 것을 포함한 Ti단독 첨가강의 제조방법에 있어서, 상기 열간압연한 후 650~720℃에서 권취하고, 권취코일의 온도가 570℃이하로 강하전 수냉조에 침지하여 냉각하는 것이다. 본 발명에 따르면 최종 제품의 재질열화 없이 산세성이 좋은 스케일을 형성할 수 있어 미산세성 스케일의 발생율을 줄일 수 있다. 또한, 권취코일을 공냉 대신 급냉에 의해 냉각할 수 있어 생산성 향상에도 일조한다. The present invention relates to a method for manufacturing a Ti-only hot rolled steel sheet used in automobile exterior materials and the like. The present invention, by weight percent C: 0.005% or less, Mn: 0.01% to 0.2%, P: 0.015% or less, Si: 0.03% or less, Ti: 0.03 to 0.10% steel slab composed of the remaining Fe and other unavoidable impurities In the method for producing Ti-only steel, including hot rolling, the steel is wound at 650 to 720 ° C. after the hot rolling, and the coiling temperature is immersed in a water-cooling tank before cooling to 570 ° C. or lower to cool. According to the present invention, a good pickling scale can be formed without deteriorating the material of the final product, thereby reducing the incidence of non-pickling scale. In addition, the coiling coil can be cooled by quenching instead of air cooling, thereby contributing to productivity improvement.
Description
본 발명은 자동차 외판재 등에 사용되는 Ti-단독 첨가 열연강판의 제조방법에 관한 것으로, 보다 상세하게는 권취코일의 강제수냉각에 의해 재질열화 없이 산세성을 개선하는 Ti단독 첨가 열연강판의 제조방법에 관한 것이다. The present invention relates to a method for manufacturing Ti-only hot-rolled steel sheet used for automobile exterior materials, and more particularly, to a method for manufacturing Ti-only hot-rolled steel sheet which improves pickling properties without deterioration of material by forced water cooling of a winding coil. It is about.
자동차 외판재에는 가공성과 함께 강도가 우수하며 표면성상도 미려한 Ti단독 첨가 냉연강판이 주로 사용되고 있다. Ti단독 첨가강은 결정립내의 탄소를 TiC와 같은 탄화물로서 입계에 석출시키기 위해 Ti를 첨가한 강이다. 표 1에는 초심가공용인 Ti단독 첨가강의 성분이 제시되어 있다. In addition to the workability of the automobile exterior material, the cold-rolled steel sheet added with Ti alone has excellent strength and excellent surface properties. Ti-only steel is a steel to which Ti is added to precipitate carbon in grains as grains such as TiC at grain boundaries. Table 1 shows the components of the Ti-added steel for super-core processing.
Ti단독 첨가강은 도 1과 같은 열연설비에서 열간압연되어 권취된다. 권취후 코일의 냉각은 재질열화를 고려하여 공냉하고 있다. 권취코일의 급냉은 조직내 고용 탄소량을 증가시켜 코일의 가공성을 저하시킨다는 연구보고가 있어 고려되지 않고 있다. Ti-added steel alone is hot rolled and wound in a hot rolling facility as shown in FIG. After winding, the coil is cooled by air in consideration of material degradation. Quenching of coiling coils has not been considered because it increases the amount of dissolved carbon in the tissues and reduces the processability of the coil.
오까모토 등은 0.004중량%C 강을 이용하여 권취후 냉각속도를 변화시키며 열연판에서의 야금학적인 변화와 소둔판의 재질의 변화를 고찰한 연구결과를 보고한 바 있다(A. Okamoto and N.Mizui: Technology of continuously annealed cold rolled sheet steel,Detroit,TMS-AIME,1984,p139). 이 연구결과에는 권취 후 냉각속도가 빠를수록 고용 탄소량이 증가한다고 보고 하였다. 특히, 권취 후 냉각속도가 느릴 경우에는 세멘타이트의 석출과 성장이 조장되어지나 냉각속도가 빠를 경우에는 세멘타이트의 성장과 석출이 억제되고, 조대한 세멘타이트의 성장이 어려우며 고용탄소의 양이 증가하게 된다고 보고하고 있다. Okamoto et al. Reported the results of a study of the metallurgical change in the hot rolled sheet and the change in the material of the annealed sheet. Mizui: Technology of continuously annealed cold rolled sheet steel, Detroit, TMS-AIME, 1984, p139). The study reported that the higher the cooling rate after winding, the higher the amount of dissolved carbon. In particular, if the cooling rate is slow after winding, cementite precipitation and growth are encouraged, but if the cooling rate is fast, growth and precipitation of cementite is suppressed, and the growth of coarse cementite is difficult and the amount of solid carbon is increased. It is reported to be done.
또 후쿠다 미노루(福田 實)는 고용 탄소량이 적어지면 r값(소성 이방성 계수: 재료의 방향에 따라 가공 기계적 성질이 달라지는 것)이 높아 진다고 보고하였다(철과 강 제53년, 1967, p559). 즉 코일을 급냉하면 고용탄소가 입내에 존재하여 가공성에 영향이 있다는 것이다.Fukuda Minoru also reported that when the amount of solid solution carbon decreases, the r-value (plastic anisotropy coefficient: the change in processing mechanical properties depending on the direction of the material) increases (Iron and Steel 53, 1967, p559). In other words, when the coil is quenched, solid carbon exists in the mouth, which affects the processability.
이러한 근거로 인해 자동차 외판에 사용되는 Ti단독 첨가 극저탄소강은 반드시 공냉을 통해 코일을 냉각한 후 냉연공장으로 이송시켜 작업을 행하고 있다. For this reason, the Ti-exclusive ultra low carbon steel used in automobile exteriors is always cooled by air cooling and then transported to a cold rolling mill.
냉각한 열연코일의 표면에는 FeO의 화합물인 스케일이 발생하게 된다. 스케일은 냉연공정에서는 염산으로 세척하는 산세 공정에서 표면 스케일을 제거하고 냉간압연을 행한다. 그러나, 공냉으로 인해 발생하는 스케일 중에 산세공정을 통해 완전히 제거하기 어려운 스케일이 있어, 이로 인해 최종 냉연제품에는 도 2와 같이 미산세성 스케일 결함이 잔존 되는 문제점이 있다.On the surface of the cooled hot rolled coil, scale, which is a compound of FeO, is generated. The scale is subjected to cold rolling by removing the surface scale in the pickling step of washing with hydrochloric acid in the cold rolling step. However, there are scales that are difficult to remove completely through the pickling process among the scales generated by air cooling, and thus, the final cold rolled product has a problem in that the non-pickling scale defects remain as shown in FIG. 2.
본 발명은 상기와 같은 종래의 문제점을 해결하기 위해 안출된 것으로, Ti-단독 첨가강의 산세성을 개선하면서도 최종 제품의 재질 열화가 없도록 하는 Ti단독 첨가강의 제조방법을 제공하는데, 그 목적이 있는 것이다. The present invention has been made to solve the conventional problems as described above, to provide a method of manufacturing Ti-added steel alone to improve the pickling properties of Ti-added steel, but without material degradation of the final product, the object is to .
상기 목적을 달성하기 위한 본 발명의 Ti단독 첨가 열연강판의 제조방법은, 중량%로 C:0.005%이하, Mn:0.01~0.2%, P:0.015%이하, Si:0.03%이하, Ti:0.03~0.10% 나머지 Fe와 기타 불가피한 불순물로 조성되는 강슬라브를 열간압연하는 것을 포함한 Ti단독 첨가강의 제조방법에 있어서, 상기 열간압연한 후 650~720℃에서 권취하고 권취코일의 온도가 570℃이하로 강하하기전 수냉조에 침지하여 냉각하는 것이다. Ti alone-added hot rolled steel sheet of the present invention for achieving the above object is, by weight% C: 0.005% or less, Mn: 0.01% to 0.2%, P: 0.015% or less, Si: 0.03% or less, Ti: 0.03 In the method of manufacturing Ti-additive steel including hot rolling a steel slab composed of the remaining Fe and other unavoidable impurities, the coil is wound at 650 to 720 ° C. after the hot rolling, and the coiling temperature is 570 ° C. or less. It cools by dipping in a water cooling tank before descent.
이하, 본 발명을 상세히 설명한다. Hereinafter, the present invention will be described in detail.
본 발명자들은 Ti단독 첨가 열연코일의 냉각을 수냉각으로 대체하여 스케일의 산세성을 개선하면서도 최종 냉연제품의 재질에는 영향이 없도록 하는데 특징이 있다. The present inventors are characterized by replacing the cooling of the Ti-added hot rolled coil with water cooling to improve pickling properties of the scale while not affecting the material of the final cold rolled product.
본 발명의 대상강종은 자동차 외판재로 사용되는 Ti단독 첨가강으로, 상기 표 1에 제시된 강종이다. 즉, 중량%로 C:0.005%이하, Mn:0.01~0.2%, P:0.015%이하, Si:0.03%이하, Ti:0.03~0.10% 나머지 Fe와 기타 불가피한 불순물로 조성되는 것인데, 편의상 이 강을 간단히 Ti단독 첨가강이라 표기한다. The subject steel grade of the present invention is Ti alone additive steel used as an automobile exterior material, and the steel grades shown in Table 1 above. That is, by weight% C: 0.005% or less, Mn: 0.01 to 0.2%, P: 0.015% or less, Si: 0.03% or less, Ti: 0.03 to 0.10% The remaining Fe and other unavoidable impurities, for convenience Denotes simply Ti addition steel.
본 발명자들은 상기한 Ti단독 첨가 열연코일에서 발생하는 스케일의 특성을 조사한 결과를 바탕으로, 산세성에 유리하면서도 재질의 영향 즉, 가공성에 열화가 발생하지 않는 제조방법을 도출한 것이다. The present inventors have derived a manufacturing method that does not cause deterioration in workability, that is, material influence, that is, workability, while favoring pickling property, based on the results of the scale characteristics generated in the above-described Ti-added hot rolled coil.
Fe가 산소와 접촉하면 도 3과 같은 FeO산화물이 생성되며 각 조성에 따른 특징은 다음과 같다. 위스타이트(FeO)는 다공질이며 박리가 쉽고 연신이 잘 되어 산세에서 제거도 쉬운 스케일로 알려져 있다. 또한, 마그네타이트(Fe3O4)는 치밀하고 밀착성이 커 산세성이 아주 불량한 난 산세성 스케일로 알려져 있다. 그리고, 헤마타이트(Fe2O3)는 두껍고 상온에서 스케일 박리성이 우수한 성질이 있는 것으로 알려져 있다. 따라서, 스케일의 산세성 측면에서는 위스타이트가 바람직하다.When Fe is in contact with oxygen is produced FeO oxide as shown in Figure 3 and the characteristics according to each composition are as follows. Wisterite (FeO) is known as a scale that is porous, easy to peel off, stretched, and easy to remove from pickling. In addition, magnetite (Fe 3 O 4 ) is known as a poor pickling scale, which is dense and has high adhesiveness and very poor pickling. In addition, hematite (Fe 2 O 3 ) is known to have a thick and excellent property of scale peelability at room temperature. Therefore, Wistat is preferable in view of pickling of the scale.
본 발명자들은 Ti단독 첨가강의 냉각방식에 따른 열연코일의 스케일 특성을 조사하고 그 결과를 도 4와 도 5에 나타내었다. 도 4는 공냉방식으로, 도 5는 권취코일을 수냉조에 침지하여 수냉하는 냉각방식으로 냉각한 열연코일에 대해, 열연코일의 폭, 길이 방향에 형성된 스케일층의 조성을 XRD로 정성 분석한 결과이다. 도 4와 도 5에서 열연코일의 선단에서 1m정도 절단한 코일을 대상으로, 각각 (a)는 코일의 측면 에지로부터 폭방향으로 약 50mm이내의 지점(에지부)의 스케일 층 분석 결과이고, (b)는 코일의 폭방향으로 1/3지점에서의 스케일 층 분석 결과이며, (c)는 코일의 폭방향으로 중심부에서의 스케일 층 분석 결과이다.The present inventors investigated the scale characteristics of the hot rolled coil according to the cooling method of the Ti-only steel added, and the results are shown in FIGS. 4 and 5. 4 is an air cooling method, and FIG. 5 is a result of qualitative analysis of the composition of the scale layer formed in the width and length direction of the hot rolled coil with respect to the hot rolled coil cooled by the cooling method in which the winding coil is immersed in a water cooling tank and water cooled. For the coils cut about 1 m from the tip of the hot rolled coil in FIGS. 4 and 5, (a) is the result of the scale layer analysis of a point (edge portion) within about 50 mm in the width direction from the side edge of the coil, ( b) shows the scale layer analysis result at the 1/3 point in the width direction of the coil, and (c) shows the scale layer analysis result at the center part in the width direction of the coil.
도 4(a)는 위스타이트(FeO)는 검출되지 않고 마그네타이트(Fe304) 및 헤마타이트(Fe203)만 존재 하였다. 그리고 도 4(b)는 마그네타이트와 Fe 만이 검출 되었다. 한편, 수냉조에서 급냉시킨 도 5의 (a)(b)(c)에는 마그네타이트 + 헤마타이트, 마그네타이트 + 위스타이트(FeO), 위스타이트(FeO)가 검출 되었음을 확인하였다. 즉, 공냉재 및 수냉재의 에지부에서는 모두 마그네타이트 + 헤마타이트로 동일한 스케일 조성을 나타내나, 폭방향의 센터부 쪽으로 갈수록 공냉재는 Fe가 검출되고, 급냉재에서는 위스타이트(FeO)가 검출되었다. 이처럼 코일의 냉각속도 변화에 따른 스케일 조성의 변태는 산세 특성 및 기계적 파괴성에 밀접한 영향을 미친다. 즉, 급냉(수냉)할 경우에는 산세성 및 기계적 파괴성이 가장 우수한 위스타이트(FeO) 스케일이 형성되며, 공냉할 경우에는 가장 열악한 산세성과 기게적파괴성을 나타내는 마그네타이트와 Fe가 형성된다.In FIG. 4 (a), wistatite (FeO) was not detected and only magnetite (Fe 3 0 4 ) and hematite (Fe 2 0 3 ) were present. 4 (b), only magnetite and Fe were detected. Meanwhile, it was confirmed that magnetite + hematite, magnetite + wistat (FeO) and wistat (FeO) were detected in (a) (b) (c) of FIG. In other words, both the edge portions of the air-cooling material and the water-cooling material showed the same scale composition as magnetite + hematite, but Fe was detected in the air-cooling material toward the center portion in the width direction, and Wisteite (FeO) was detected in the quenching material. As described above, the transformation of the scale composition due to the change in the cooling rate of the coil has a close influence on pickling properties and mechanical fracture. That is, in the case of quenching (water cooling), the Wistatite (FeO) scale having the best pickling property and mechanical fracture property is formed, and in the case of air cooling, magnetite and Fe which exhibit the worst pickling property and mechanical destruction property are formed.
이와 같이 산세성이 좋은 스케일을 얻기 위해서는 공냉 보다 급냉(수냉)이 바람직하다. 즉, 도 6에서 알 수 있듯이, 고온에서 안정된 산화물인 위스타이트(FeO)가 공석 변태점인 570℃를 통과 하는 경우에는 변태 마그네타이트와 Fe로 공석변태를 하게 되는데, 이때 중요한 인자가 냉각 속도이다. 즉, 임계냉각속도 보다 빠르게 되면 고온에서의 위스타이트(FeO)가 변태 되지 못한 채 상온에서 위스타이트(FeO)로 검출되는 것이다. 다시 말하면, 권취코일을 570℃ 보다 높은 온도에서 수냉조에 침지하는 것과 같이 급냉하면 임계냉각속도 보다 빠른 냉각속도로 냉각되어 위스타이트의 변태가 억제되는 것이다. In order to obtain a good pickling scale in this manner, quenching (water cooling) is more preferable than air cooling. That is, as can be seen in Figure 6, when the high-stabilized oxide Wistatite (FeO) passes through the vacancy transformation point 570 ℃ transforms the vacancy with the transformation magnetite and Fe, the important factor is the cooling rate. In other words, if the critical cooling rate is faster than Wistatite (FeO) at a high temperature is detected as Wistatite (FeO) at room temperature without transformation. In other words, if the winding coil is quenched, such as being immersed in a water cooling bath at a temperature higher than 570 ° C., the transformation of Wistat is suppressed by cooling at a cooling rate faster than the critical cooling rate.
따라서, 본 발명에서는 권취한 코일을 570℃이하로 온도강하전에 수냉조에 침지하여 냉각하는 것이 바람직하다. 도 7에는 권취완료후 공냉에 의한 온도강하 커브가 나타나 있는데, 이 냉각커브는 화상온도계를 이용한 결과이다. 700℃에서 권취할 경우에 150분(2.5H)을 초과할 경우에 권취코일의 온도가 570℃이하로 떨어지는 것을 확인할 수 있다. 따라서, 권취온도에 따라 수냉조의 침지 대기시간을 설정하는 것이 바람직하다. Therefore, in this invention, it is preferable to immerse and cool the coil wound up to 570 degreeC or less in water cooling tank before temperature fall. 7 shows the temperature drop curve by air cooling after the winding is completed, and this cooling curve is the result of using an image thermometer. When winding at 700 ° C it can be seen that the temperature of the winding coil drops below 570 ° C when it exceeds 150 minutes (2.5H). Therefore, it is preferable to set the immersion waiting time of the water cooling tank according to the coiling temperature.
만일, 냉각대기시간이 길어져 권취코일의 온도가 공냉으로 570℃이하로 직하가 되는 경우에는 산소의 산화 반응인 FeO의 분해 반응이 길어져 FeO가 전량 Fe3O4+Fe로 분해되는 결과가 나타낸다. 결국 반응식 1과 같이 산세성이 양호한 FeO의 감소와 산세시 H2를 형성시켜 산세성을 저하시키는 Fe의 형성원인이 된다. 그러므로, 권취후 570℃이상에서 수냉이 시작 되도록 되도록 조업조건을 설정하는 것이 바람직하다.If the cooling waiting time is long and the temperature of the winding coil is directly below 570 ° C. by air cooling, the decomposition reaction of FeO, which is an oxidation reaction of oxygen, becomes long, resulting in the decomposition of FeO into the total amount of Fe 3 O 4 + Fe. Eventually, as shown in Scheme 1, FeO having good pickling property and H 2 is formed during pickling, thereby reducing pickling property. Causes of Fe formation. Therefore, it is preferable to set operating conditions so that water cooling starts at 570 degreeC or more after winding.
[반응식 1]-서냉Scheme 1-slow cooling
4FeO→Fe304 + Fe4FeO → Fe 3 0 4 + Fe
2HCl + Fe → FeCl2 + [H2]↑2HCl + Fe → FeCl 2 + [H 2 ] ↑
[반응식 2]-급냉Scheme 2-quenching
4FeO→FeO + Fe304 4FeO → FeO + Fe 3 0 4
도 8은 코일의 길이방향에 따른 스케일층 조성의 정량적 분석 결과이다. 즉, 코일의 선단으로부터 1m의 지점인 탑부(top)와 선단으로부터 15m의 지점인 탑부+15m지점, 코일 길이방향 최후단 지점인 테일부(tail)에 대해 조사한 것이다. 도 8을 보면 냉각조건에 따라 스케일의 조성이 달라지고 급냉시에 산세성이 우수한 스케일이 조성되는 것을 확인할 수 있다. 8 is a quantitative analysis result of the scale layer composition along the longitudinal direction of the coil. That is, the survey was conducted on the top part (1m) from the tip of the coil, the top part + 15m point (15m) from the tip, and the tail part (tail) of the last point in the longitudinal direction of the coil. Referring to Figure 8 it can be seen that the composition of the scale is changed according to the cooling conditions and the scale is excellent in pickling properties during quenching.
이와 같이, 본 발명에 따라 열연코일을 수냉각하면 코일의 중심부 표면에는 위스타이트의 스케일이 존재하여 산세성이 개선된다. As such, when the hot rolled coil is water cooled according to the present invention, a scale of Wistat is present on the central surface of the coil to improve pickling properties.
본 발명에 따라 Ti단독 첨가 열연코일을 급냉 하더라도 재질열화는 발생하지 않는 것으로 확인되었다. 권취 후 냉각속도가 빠를수록 탄,질화물들의 석출과 성장이 억제되어 고용 탄소량이 증가하나, 냉연 후 소둔 과정에서 탄,질화물의 석출이 추가적으로 발생하여 입내 고용탄소의 양에서는 차이가 미미한 것으로 확인되었다. According to the present invention, even if the Ti alone added hot rolled coil was quenched, it was confirmed that material degradation did not occur. The higher the cooling rate after the winding, the more the carbon content increased due to the suppression of the precipitation and growth of carbon and nitride, but the precipitation of carbon and nitride was additionally generated during the annealing process after cold rolling.
이하, 본 발명을 실시 예를 통하여 보다 구체적으로 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.
[실시예 1]Example 1
중량%로, C:0.0015%, Mn:0.07%, P:0.0013%, Si:0.02%, Ti:0.03% 나머지 Fe 및 기타 불가피한 불순물로 조성되는 Ti-단독 첨가강(EDDQ강재)와 중량%로, C:0.001%, Mn:0.05%, P:0.009%, Si:0.02%, Ti:0.08% 나머지 Fe 및 기타 불가피한 불순물로 조성되는 Ti-단독 첨가강(SEDDQ강재)을 대상으로 권취후의 냉각조건을 공냉 또는 수냉(수냉조 침지)하여 미산세성 스케일의 발생율을 조사하고 그 평균치를 표 2에 나타내었다. In weight%, C: 0.0015%, Mn: 0.07%, P: 0.0013%, Si: 0.02%, Ti: 0.03% by weight of Ti-only additive steel (EDDQ steel) composed of the remaining Fe and other unavoidable impurities , C: 0.001%, Mn: 0.05%, P: 0.009%, Si: 0.02%, Ti: 0.08% Cooling condition after winding on Ti-only additive steel (SEDDQ steel) composed of remaining Fe and other unavoidable impurities The incidence of the micro-acid scale was investigated by air cooling or water cooling (immersion in water cooling bath), and the average is shown in Table 2.
표 2에 나타난 바와 같이, 본 발명에 따라 급냉한 열연코일에서 미산세성 스케일 발생율이 현격히 줄어든 것을 확인할 수 있었다. As shown in Table 2, it was confirmed that the incidence of micro-acid scales was significantly reduced in the hot-rolled coil quenched according to the present invention.
[실시예 2]Example 2
중량%로, C:0.0015%, Mn:0.07%, P:0.0013%, Si:0.02%, Ti:0.03% 나머지 Fe 및 기타 불가피한 불순물로 조성되는 Ti-단독 첨가강(EDDQ강재)을 대상으로 권취후의 냉각조건을 공냉 또는 수냉(수냉조 침지)한 열연판을 소둔처리하여 기계적특성에 대해 조사하였다. 열연판의 두께는 0.7~0.9mm이고, 폭은 1496~1539mm 였다. By weight%, C: 0.0015%, Mn: 0.07%, P: 0.0013%, Si: 0.02%, Ti: 0.03% Coated Ti-alone additive steel (EDDQ steel) composed of the remaining Fe and other unavoidable impurities The subsequent cooling conditions were investigated by annealing the hot-rolled sheet subjected to air-cooling or water-cooling (immersion of water-cooling bath). The hot rolled sheet had a thickness of 0.7-0.9 mm and a width of 1496-1539 mm.
시험결과 냉각조건에 따른 미 산세성 스케일의 발생실적이 공냉 조건에서는 5매로 (71%), 수냉 조건에서 0% 발생하였으며 재질 영향도는 다음과 같았다.According to the test results, the occurrence of micro pickling scale according to the cooling conditions was 5 sheets (71%) in the air-cooled condition and 0% in the water-cooled condition.
이 결과에 의하면 급냉재 및 공냉재간 재질실적 차이는 무시 할 정도임을 알 수 있었다. 표 4에 나타난 바와 같이, 공냉과 수냉의 냉각조건에 따른 항복강도(YP), 인장강도(TS), 연신율(EL), 가공경화지수(N) 등의 값에서 큰 차이가 없었다. 그것은 권취 후 냉각속도가 빠를수록 탄,질화물들의 석출과 성장이 억제되어 고용 탄소량이 증가하나 냉연 후 소둔과정에서 탄,질화물의 석출이 추가적으로 발생하여 입내 고용탄소의 양에서는 차이가 미미함을 알 수 있었다.The results show that the difference in material performance between quench and air coolant is negligible. As shown in Table 4, there were no significant differences in yield strength (YP), tensile strength (TS), elongation (EL), and work hardening index (N) according to the cooling conditions of air cooling and water cooling. that is The faster the cooling rate after winding, the more the carbon and nitrides are inhibited from the precipitation and growth of carbon dioxide. However, the carbon and nitride precipitated in the annealing process after cold rolling. .
[실시예 3]Example 3
중량%로, C:0.001%, Mn:0.05%, P:0.009%, Si:0.02%, Ti:0.08% 나머지 Fe 및 기타 불가피한 불순물로 조성되는 Ti-단독 첨가강(SEDDQ강재)을 대상으로 권취후의 냉각조건을 공냉 또는 수냉(수냉조 침지)한 열연판을 소둔처리하여 기계적특성에 대해 조사하였다. 열연판의 두께는 0.7~0.9mm이고, 폭은 1496~1539mm 였다. By weight%, C: 0.001%, Mn: 0.05%, P: 0.009%, Si: 0.02%, Ti: 0.08% Winding on Ti-only additive steel (SEDDQ steel) composed of the remaining Fe and other unavoidable impurities The subsequent cooling conditions were investigated by annealing the hot-rolled sheet subjected to air-cooling or water-cooling (immersion of water-cooling bath). The hot rolled sheet had a thickness of 0.7-0.9 mm and a width of 1496-1539 mm.
표 6에 나타난 바와 같이, 공냉과 수냉의 냉각조건에 따른 항복강도(YP), 인장강도(TS), 연신율(EL), 가공경화지수(N) 등의 값에서 큰 차이가 없었다. As shown in Table 6, there were no significant differences in yield strength (YP), tensile strength (TS), elongation (EL), and work hardening index (N) according to the cooling conditions of air cooling and water cooling.
상술한 바와 같이, 본 발명에 따르면 최종 제품의 재질열화 없이 산세성이 좋은 스케일을 형성할 수 있어 미산세성 스케일의 발생율일 줄일 수 있다. 또한, 권취코일을 공냉 대신 급냉에 의해 냉각할 수 있어 생산성 향상에도 일조한다. As described above, according to the present invention, it is possible to form a good pickling scale without deteriorating the material of the final product, thereby reducing the occurrence rate of the non-pickling scale. In addition, the coiling coil can be cooled by quenching instead of air cooling, thereby contributing to productivity improvement.
도 1은 열간압연 설비의 개략도이고1 is a schematic view of a hot rolling facility
도 2는 미산세성 스케일의 결함을 나타내는 사진이며2 is a photograph showing a defect of the non-pickling scale.
도 3은 열연강판 표면 스케일의 특징을 나타내는 개략도이며3 is a schematic view showing the characteristics of the hot-rolled steel sheet surface scale
도 4는 공냉시킨 열연코일의 스케일층 XRD 정성분석 결과도이며4 is a result of scale layer XRD qualitative analysis of air-cooled hot rolled coil.
도 5는 수냉시킨 열연코일의 스케일층 XRD 정성분석 결과도이고5 is a scale layer XRD qualitative analysis result of a water-cooled hot rolled coil.
도 6은 FeO의 CCT 곡선을 나타내는 그래프이며,6 is a graph showing a CCT curve of FeO,
도 7은 열연코일의 공냉시간에 따른 온도강하 그래프7 is a graph of temperature drop according to the air cooling time of the hot rolled coil
도 8은 Ti 단독 첨가 열연코일의 위치별 냉각조건에 따른 위스타이트의 정량적 분석 결과를 나타내는 그래프이다. 8 is a graph showing the results of quantitative analysis of Wistatite according to cooling conditions for each position of Ti-added hot rolled coils.
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