KR102010074B1 - Hot dip galvanized steel sheet having good formability and surface appearance and and method for manufacturing the same - Google Patents
Hot dip galvanized steel sheet having good formability and surface appearance and and method for manufacturing the same Download PDFInfo
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C18/00—Alloys based on zinc
- C22C18/04—Alloys based on zinc with aluminium as the next major constituent
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/50—Controlling or regulating the coating processes
- C23C2/52—Controlling or regulating the coating processes with means for measuring or sensing
- C23C2/526—Controlling or regulating the coating processes with means for measuring or sensing for visually inspecting the surface quality of the substrate
Abstract
본 발명의 바람직한 일 측면은 도금원판 및 도금원판 위에 형성된 용융아연도금층을 포함하고, 상기 용융아연도금층의 스팡글 크기가 300㎛이하이고 아연 수지상 사이에 Al-Mn-Zn 정출물이 입자상태로 정출되어 있고, 상기 Al-Mn-Zn 정출물의 평균 크기는 0.5~3㎛이고, 상기 정출물사이의 평균 간격은 1~10 ㎛인 표면외관 및 성형성이 우수한 용융아연도금강판 및 그 제조방법을 제공한다.One preferred aspect of the present invention includes a plating disc and a hot dip galvanizing layer formed on the plating disc, the spangle size of the hot dip galvanizing layer is 300㎛ or less and Al-Mn-Zn crystallized crystallized between the zinc resin phase The average size of the Al-Mn-Zn crystallization is 0.5 ~ 3㎛, the average spacing between the crystallization is 1 ~ 10㎛ provides a hot-dip galvanized steel sheet excellent in surface appearance and formability and a method of manufacturing the same. do.
Description
본 발명은 가전제품 및 자동차용 강판 등에 적용되는 용융아연도금강판 및 그 제조방법에 관한 것으로서, 보다 상세하게는 내골링성 및 성형성이 우수한 용융아연도금강판 및 그 제조방법에 관한 것이다.The present invention relates to a hot-dip galvanized steel sheet and a method for manufacturing the same, which are applied to household electrical appliances and automobile steel plates, and more particularly, to a hot-dip galvanized steel sheet excellent in galling resistance and formability and a method of manufacturing the same.
ASTM A653, DIN EN10346에 의하면 용융아연 도금강판이란 Zn가 99% 이상인 아연도금층을 갖는 강판을 말하며, 이러한 용융아연 도금강판은 제조하기가 용이하고, 제품 가격이 저렴하다. 이에, 상기 용융 아연도금강판은 최근 가전제품 및 자동차용 강판으로 그 적용 범위가 확대되고 있다. According to ASTM A653, DIN EN10346, a hot-dip galvanized steel sheet refers to a steel sheet having a galvanized layer having a Zn of 99% or more. Such hot-dip galvanized steel sheet is easy to manufacture and the product price is low. Thus, the hot-dip galvanized steel sheet has recently been expanded to the extent of the steel sheet for home appliances and automobiles.
자동차용 강판은 스템핑 과정을 거쳐 성형된다. 이때, 강판과 금형과의 마찰이 작을 수록 성형이 잘되며, 이를 위해 윤활피복 용융아연도금강판이 사용되고 있다. 윤활 피복강판은 여러 종류가 있지만 일반적으로 도금 후에 별도의 공정을 거쳐 윤활피막을 도금층 위에 형성되도록 하고 있어 제조가 번거롭다.Automotive steel sheet is formed through a stamping process. At this time, the smaller the friction between the steel plate and the mold, the better the molding, and for this purpose, a lubricated coated hot dip galvanized steel sheet is used. Although there are many kinds of lubricated coated steel sheets, it is generally cumbersome to manufacture a lubricating film on the plating layer through a separate process after plating.
또한, 윤활피막은 차체 조립공정중 도장공정의 인산염 처리시 인산염 피막 불균일을 초래할 가능성이 높으므로 도장 전 탈지단계에서 완전히 제거되어야 하는 등 제약 조건이 많다. In addition, since the lubricating film is highly likely to cause uneven phosphate film during the phosphate treatment of the painting process during the vehicle assembly process, there are many constraints such as to be completely removed in the degreasing step before painting.
본 발명의 바람직한 일 측면은 내골링성 및 성형성이 우수한 용융아연도금강판을 제공하고자 하는 것이다.One preferred aspect of the present invention is to provide a hot-dip galvanized steel sheet excellent in golling resistance and moldability.
본 발명의 바람직한 다른 일 측면은 내골링성 및 성형성이 우수한 용융아연도금강판의 제조방법을 제공하고자 하는 것이다.Another preferred aspect of the present invention is to provide a method for producing a hot-dip galvanized steel sheet excellent in galling resistance and formability.
본 발명의 바람직한 일 측면에 의하면, 도금원판 및 도금원판 위에 형성된 용융아연도금층을 포함하고, 상기 용융아연도금층의 스팡글 크기가 300㎛이하이고 아연 수지상 사이에 Al-Mn-Zn 정출물이 입자상태로 정출되어 있고, 상기 Al-Mn-Zn 정출물의 평균 크기는 0.5~3㎛이고, 상기 정출물사이의 평균 간격은 1~10㎛인 표면외관 및 성형성이 우수한 용융아연도금강판이 제공된다.According to a preferred aspect of the present invention, a plated plate and a hot dip galvanized layer formed on the plated plate, the spun size of the hot dip galvanized layer is 300㎛ or less and the Al-Mn-Zn crystallization between the zinc resin phase The Al-Mn-Zn crystallized product has an average size of 0.5 to 3 µm, and an average spacing between the crystals is 1 to 10 µm, thereby providing a hot dip galvanized steel sheet having excellent surface appearance and formability.
본 발명의 바람직한 다른 일 측면에 의하면, According to another preferred aspect of the present invention,
도금원판을 준비하는 단계;Preparing a plating disc;
상기 도금원판이 용융아연도금욕에 인입되기 전에 도금원판의 표면에 요철을 부여하는 단계;Imparting concavities and convexities to the surface of the plating disc before the plating disc is introduced into the hot dip galvanizing bath;
상기와 같이 표면에 요철이 부여된 도금원판을, 도금욕 온도가 440 ~ 480℃이고 0.1 5~0.3 중량%의 Al 및 0.2~0.5 중량%의 Mn을 포함하는 용융아연도금욕에 침적하여 용융아연도금하는 단계; Plating discs with irregularities applied to the surface as described above were deposited in a hot dip galvanizing bath containing a plating bath temperature of 440 to 480 ° C. and containing 0.1 5 to 0.3% by weight of Al and 0.2 to 0.5% by weight of Mn. Plating;
상기와 같이 용융아연도금된 원판을, 그 도금부착량이 편면당 50~300 g/m2 이 되도록 조절하고, - 4℃/s ~ -10℃/s의 냉각속도로 냉각하는 단계를 포함하고, 상기 요철을 부여하는 단계는 도금원판의 조도가 50배 배율에서 측정시 실제 표면적/투영 표면적의 비율이 1.025~1.030이 되도록 실시되는 표면외관 및 성형성이 우수한 용융아연도금강판의 제조방법이 제공된다.The hot-dip galvanized plate as described above, the plating deposition amount is adjusted to 50 ~ 300 g / m 2 per side, and cooling at a cooling rate of-4 ℃ / s to -10 ℃ / s, The step of imparting the unevenness is provided with a method for producing a hot-dip galvanized steel sheet excellent in surface appearance and formability is carried out so that the ratio of the actual surface area / projection surface area is 1.025 ~ 1.030 when the roughness of the plated plate is measured at 50 times magnification. .
상기 요철을 부여하는 단계는 50메쉬 이상 800 메쉬 이하의 거칠기를 갖는 회전형 휠 브러쉬에 의해 도금원판의 진행 방향에 대해 평행하지 않게 실시될 수 있다.The step of providing the unevenness may be performed not parallel to the traveling direction of the plating disc by the rotary wheel brush having a roughness of 50 mesh or more and 800 mesh or less.
본 발명의 바람직한 측면에 의하면, 도금원판의 미세 조도를 조절하여 도금층의 스팽글을 작게 함과 동시에 Mn을 도금 표면에 균일 분포시킴으로써 표면이 미려하고 가공성이 우수한 용융아연도금강판을 제공할 수 있다. 본 발명에 부합되는 용용도금강판은 자동차용 용융아연도금강판으로 적합하다. According to a preferred aspect of the present invention, it is possible to provide a hot-dip galvanized steel sheet having a beautiful surface and excellent workability by controlling the fine roughness of the plating disc to reduce the sequins of the plating layer and at the same time distribute the Mn uniformly on the plating surface. The hot dip galvanized steel sheet according to the present invention is suitable as a hot dip galvanized steel sheet for automobiles.
도 1은 비교예 및 발명예의 도금원판의 3차원 표면조도 측정결과를 나타내는 것으로, (a)는 비교예 4를 나타내고, (b)는 발명예 1를 나타낸다.
도 2는 냉각속도 - 4℃/s 및 -10℃/s에서의 실시예 1의 비교예 4에 대한 도금표면 EPMA 분석결과를 나타낸다.
도 3은 냉각속도 - 4℃/s 및 -10℃/s에서의 실시예 1의 발명예 1에 대한 도금표면 EPMA 분석결과를 나타낸다. 1 shows the results of measuring the three-dimensional surface roughness of the plating discs of Comparative Examples and Inventive Examples, (a) shows Comparative Example 4, and (b) shows Invention Example 1. FIG.
2 shows the results of plating surface EPMA analysis for Comparative Example 4 of Example 1 at cooling rates of −4 ° C./s and −10 ° C./s.
3 shows the results of plating surface EPMA analysis for Inventive Example 1 of Example 1 at cooling rates of −4 ° C./s and −10 ° C./s.
이하, 본 발명에 대하여 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.
먼저, 본 발명의 바람직한 일 측면에 따르는 표면외관 및 성형성이 우수한 용융아연도금강판에 대하여 설명한다.First, a hot-dip galvanized steel sheet excellent in surface appearance and formability according to a preferred aspect of the present invention will be described.
본 발명의 바람직한 일 측면에 따르는 표면외관 및 성형성이 우수한 용융아연도금강판은 도금원판 및 도금원판 위에 형성된 용융아연도금층을 포함하고, 상기 용융아연도금층의 스팡글 크기가 300㎛이하이고 아연 수지상 사이에 Al-Mn-Zn 정출물이 정출되어 있고, 상기 Al-Mn-Zn 정출물의 평균 크기는 0.5~3㎛ 이고, 상기 정출물사이의 평균 간격은 1~10㎛이다.The hot-dip galvanized steel sheet having excellent surface appearance and formability according to a preferred aspect of the present invention includes a plated plate and a hot dip galvanized layer formed on the plated plate, the spangle size of the hot dip galvanized layer is 300㎛ or less and between the zinc resin phase Al-Mn-Zn crystals were crystallized at, the average size of the Al-Mn-Zn crystals was 0.5 to 3 µm, and the average interval between the crystals was 1 to 10 µm.
본 발명에서 도금원판은 용융아연도금강판의 도금원판으로 사용될 수 있는 것이면 그 종류를 한정하지 않는다. In the present invention, the plating disc is not limited as long as it can be used as the plating disc of the hot-dip galvanized steel sheet.
상기 도금원판 위에는 용융아연도금층이 형성되며, 용융아연도금층의 스팡글 크기가 300㎛이하이고 아연 수지상 사이에 Al-Mn-Zn 정출물이 정출되어 있다.A hot dip galvanized layer is formed on the plating disc, and the spangle size of the hot dip galvanized layer is 300 μm or less, and Al-Mn-Zn crystallized crystals are crystallized between zinc resin phases.
상기 스팡글 크기가 300㎛를 초과하는 경우에는 미려한 외관을 확보하기 어려울 수 있다. 바람직한 스팽글 크기는 80 ~ 100 ㎛이다.If the spangle size exceeds 300㎛ it may be difficult to secure a beautiful appearance. Preferred sequin sizes are 80-100 μm.
본 발명자들의 실험에 따르면 도금층 중의 Mn 양이 증가할수록 마찰계수 값이 감소하고, 또한 성형성이 향상되는 것으로 나타났다. 그 이유에 대해서는 명확하지는 않으나, 도금층 중에 포함된 Mn이 마찰 계수를 감소시키는 효과에 기인한 것으로 추정된다. According to the experiments of the present inventors, as the amount of Mn in the plating layer increases, the friction coefficient value decreases, and the moldability is improved. The reason is not clear, but it is assumed that Mn contained in the plating layer is due to the effect of reducing the friction coefficient.
Mn을 포함하는 상기 Al-Mn-Zn 정출물은 마찰계수 값을 감소시키고, 또한 성형성을 향상시키는 작용을 한다.The Al-Mn-Zn crystallized substance containing Mn serves to reduce the coefficient of friction value and also improve formability.
상기 Al-Mn-Zn 정출물의 평균 크기가 너무 작은 경우에는 마찰계수의 감소가 없어 Mn 첨가효과가 나타나지 않을 우려가 있고, 너무 큰 경우에는 강판 표면의 국부적으로 마찰계수가 차이가 나서 성형이 잘 안될 우려가 있다. 따라서, 상기 Al-Mn-Zn 정출물의 평균 크기는 0.5~3㎛로 한정하는 것이 바람직하다.If the average size of the Al-Mn-Zn crystallite is too small, there is no fear of decreasing the coefficient of friction because the coefficient of friction is not reduced. If the Al-Mn-Zn crystallization is too large, the local friction coefficient of the steel sheet surface is different so that molding may not be performed well. There is concern. Therefore, it is preferable to limit the average size of the Al-Mn-Zn crystals to 0.5 to 3 µm.
상기 정출물사이의 평균 간격이 너무 좁은 경우에는 국부적으로 녹이 발생할 우려가 있고, 너무 넓은 경우에는 마찰계수의 감소효과가 적을 우려가 있다. 따라서, 상기 Al-Mn-Zn 정출물사이의 간격은 1~10 ㎛로 한정하는 것이 바람직하다.If the average spacing between the crystals is too narrow, there is a fear that rust occurs locally, if too wide, there is a fear that the effect of reducing the friction coefficient is small. Therefore, the interval between the Al-Mn-Zn crystals is preferably limited to 1 to 10 µm.
상기 용융아연도금층 중의 Al 함량은 0.15~0.3 중량%이고, Mn 함량은 0.2~0.5 중량%이다. Al content of the hot dip galvanized layer is 0.15 to 0.3% by weight, Mn content is 0.2 to 0.5% by weight.
상기 용융아연도금층 중의 Al 함량이 너무 낮을 경우 도금과정중에 도금층이 아연-철 합금상을 형성할 우려가 있고, 너무 높을 경우 용접이 잘 안될 우려가 있다.When the Al content in the hot dip galvanized layer is too low, there is a fear that the plating layer forms a zinc-iron alloy phase during the plating process, and when too high, welding may not be performed well.
상기 용융아연도금층 중의 Mn 함량이 너무 낮을 경우 마찰계수 감소효과를 충분히 얻을 수 없고, 너무 높을 경우 Mn이 드로스 형태로 도금욕에 존재하여 표면외관이 불량해질 수 있다.If the Mn content in the hot-dip galvanized layer is too low, the effect of reducing the friction coefficient cannot be sufficiently obtained. If the Mn content is too high, the surface appearance may be deteriorated because Mn is present in the plating bath in the form of a dross.
본 발명의 바람직한 다른 일 측면에 따르는 표면외관 및 성형성이 우수한 용융아연도금강판의 제조방법에 대하여 설명한다.It will be described a method for producing a hot-dip galvanized steel sheet excellent in surface appearance and formability according to another preferred aspect of the present invention.
본 발명의 바람직한 다른 일 측면에 따르는 표면외관 및 성형성이 우수한 용융아연도금강판의 제조방법은 Method for producing a hot-dip galvanized steel sheet excellent in surface appearance and formability according to another preferred aspect of the present invention
도금원판을 준비하는 단계; Preparing a plating disc;
상기 도금원판이 용융아연도금욕에 인입되기 전에 도금원판의 표면에 요철을 부여하는 단계;Imparting concavities and convexities to the surface of the plating disc before the plating disc is introduced into the hot dip galvanizing bath;
상기와 같이 표면에 요철이 부여된 도금원판을, 도금욕 온도가 440 ~ 480℃이고 0.1 5~0.3 중량%의 Al 및 0.2~0.5 중량%의 Mn을 포함하는 용융아연도금욕에 침적하여 용융아연도금하는 단계; 상기와 같이 용융아연도금된 원판을, 그 도금부착량이 편면당 50~300 g/m2 이 되도록 조절하고, - 4℃/s ~ -10℃/s의 냉각속도로 냉각하는 단계를 포함하고, 상기 요철을 부여하는 단계는 도금원판의 조도가 50배 배율에서 측정시 실제 표면적/투영 표면적의 비율이 1.025~1.030이 되도록 실시된다.Plating discs with irregularities applied to the surface as described above were deposited in a hot dip galvanizing bath containing a plating bath temperature of 440 to 480 ° C. and containing 0.1 5 to 0.3% by weight of Al and 0.2 to 0.5% by weight of Mn. Plating; The hot-dip galvanized plate as described above, the plating deposition amount is adjusted to 50 ~ 300 g / m 2 per side, and cooling at a cooling rate of-4 ℃ / s to -10 ℃ / s, The step of providing the unevenness is carried out so that the ratio of the actual surface area / projection surface area is 1.025 ~ 1.030 when the roughness of the plating disc is measured at 50 times magnification.
도금원판 준비단계Plating Disc Preparation Step
본 발명에서 도금강판은 용융아연도금강판용 원판으로 사용될 수 있는 것이면 그 종류를 한정하지 않는다. In the present invention, the plated steel sheet is not limited as long as it can be used as a disc for hot-dip galvanized steel sheet.
본 발명에서 도금원판을 준비하는 단계는 특별히 한정되는 것은 아니며, 통상적으로 실시되는 공정에 따라 실시될 수 있다. In the present invention, the step of preparing the plating disc is not particularly limited, and may be performed according to a conventionally performed process.
요철 부여 단계Unevenness step
상기 도금원판이 용융아연도금욕에 인입되기 전에 도금원판의 표면에 요철을 부여한다. Unevenness is applied to the surface of the plating disc before the plating disc is introduced into the hot dip galvanizing bath.
원판에 부착된 용융상태의 도금층중에 포함된 Mn은 응고시에 소지철과 도금층 계면에서 Zn 응고핵이 생성된 후에 응고가 진행될 때, Mn 및 Al은 Zn 수지상으로 부터 배출되어 용융금속중의 농도가 높아지게 된다. 본 발명에서 Mn에 의한 마찰계수 감소효과를 얻기 위해서는 Mn이 도금층 표면에 많이 존재하는 것이 바람직하다. 그러나 원판에 부착된 용융상태의 도금층의 냉각 속도가 빠르게 되면 스팽글 크기는 감소하지만 Mn이 도금층 표면으로 확산될 시간이 부족하여 도금층 표면으로 확산되지 못하고 도금층 내부에 갖히게 된다. 한편, Mn이 도금층 표면으로 충분히 확산되게 하기 위해 원판에 부착된 용융상태의 도금층의 냉각 속도를 느리게 하면 Mn은 표면에 많이 존재하지만 아연 스팽글의 크기가 커지게 되고, 이때 Mn은 아연의 수지상 사이에 존재하게 됨에 따라 외관이 불균일해 지게 된다.Mn contained in the molten plating layer adhered to the disc is solidified when Zn coagulation nuclei are formed at the interface between the base iron and the plating layer at the time of solidification, and Mn and Al are discharged from the Zn resin phase to increase the concentration in the molten metal. Will be higher. In the present invention, in order to obtain the effect of reducing the friction coefficient by Mn, it is preferable that a large amount of Mn exists on the surface of the plating layer. However, if the cooling rate of the plating layer in the molten state attached to the disc is increased, the sequin size is reduced, but Mn is not enough time to diffuse to the surface of the plating layer is not spread to the surface of the plating layer and is contained within the plating layer. On the other hand, if the cooling rate of the plating layer in the molten state attached to the disc is slowed down so that Mn is sufficiently diffused to the surface of the plating layer, Mn is present on the surface but the size of the zinc sequins is increased, where Mn is between the dendritic phases of zinc. As it exists, the appearance becomes uneven.
따라서 스팽글 크기와 Mn의 표면 정출 사이에는 상호 모순된다. 즉, 원판에 부착된 용융상태의 도금층의 냉각속도가 빠르게 되면 스팽글 크기가 작아서 외관을 미려하나 Mn 정출물이 도금층 내부에 많이 존재하여 Mn 첨가 효과가 거의 없게 되며, 원판에 부착된 용융상태의 도금층의 냉각속도를 느리게 하면 Mn이 표면에 많이 존재하지만 스팽글 크기가 커지게 되어 미려한 외관을 얻기 힘들며 또한 Mn이 균일하게 분포하지 않아서 마찰계수가 국부적으로 차이가 있어 만족스러운 성형성을 얻기가 힘든 문제가 있다. Thus there is a contradiction between the sequin size and the surface crystallization of Mn. In other words, when the cooling rate of the plated layer in the molten state attached to the disc becomes faster, the sequin size is small and the appearance is beautiful, but there are many Mn crystallizations in the plated layer, so there is almost no effect of Mn addition. If the cooling rate is slow, Mn is present on the surface, but the sequin size increases, making it difficult to obtain a beautiful appearance. Also, because Mn is not uniformly distributed, the friction coefficient is locally different, which makes it difficult to obtain satisfactory formability. have.
본 발명은 이러한 모순을 해결하기 위하여 도금층의 응고핵 형성단계에서 응고핵이 많이 만들어지게 하면 원판에 부착된 용융상태의 도금층의 냉각 속도를 느리게 하여도 스팽글 크기를 작게 하면서도 Mn을 표면에 균일하게 분포시킬 수가 있으며, 원판에 부착된 용융상태의 도금층의 냉각 속도가 빠를 경우에도 Mn이 표면으로 확산되는 거리가 짧아져서 효과적으로 표면에 존재할 수 있다. 이 경우는 아연의 베이샬 플레인(기저면)이 원판과 평행하지 않고 경사 각도가 큰 스팽글들이 우선적으로 성장하기 때문으로 추정된다. In order to solve this contradiction, when the coagulation nuclei are formed in the coagulation nucleus formation step of the plated layer, Mn is uniformly distributed on the surface while the sequin size is reduced even though the cooling rate of the plated layer in the molten state attached to the disc is decreased. Even if the cooling rate of the plating layer in the molten state attached to the disc is high, the distance at which Mn diffuses to the surface is shortened, so that it can be effectively present on the surface. In this case, it is presumed that the basic plane of zinc (base) is not parallel to the disc, and the sequins with a large inclination angle grow preferentially.
본 발명에서 Zn 응고핵 생성을 촉진시키기 위하여, 도금원판의 조도가 50배 배율에서 측정시 실제 표면적/투영 표면적의 비율이 1.025~1.030이 되도록 도금원판의 표면에 요철을 부여한다. In order to promote the formation of Zn coagulation nuclei in the present invention, the roughness of the plating disc is given irregularities to the surface of the plating disc such that the ratio of the actual surface area / projected surface area is 1.025 to 1.030 when measured at 50 times magnification.
상기 실제 표면적/투영 표면적의 비율이 1.025미만인 경우에는 Zn 응고핵 생성효과가 적고, 1.030을 초과하는 경우에는 표면에 지나치게 요철이 많게 되어 불필요하다. 통상의 냉간압연된 도금원판의 표면적 비율은 1.022이하이다.If the ratio of the actual surface area / projected surface area is less than 1.025, the effect of Zn coagulation nucleation is small, and if it exceeds 1.030, the surface is excessively uneven and unnecessary. The surface area ratio of the conventional cold rolled plating disc is 1.022 or less.
상기 요철 부여는 50메쉬 이상 800 메쉬 이하의 거칠기를 갖는 회전형 휠 브러쉬에 의해 도금원판의 진행 방향(길이방향)에 대해 평행하지 않게 실시될 수 있다.The unevenness may be provided not parallel to the advancing direction (length direction) of the plating disc by the rotary wheel brush having a roughness of 50 mesh or more and 800 mesh or less.
용융아연도금하는Hot dip galvanized 단계 step
상기와 같이 표면에 요철이 부여된 도금원판을, 도금욕 온도가 440 ~ 480℃이고 0.15~0.3 중량%의 Al 및 0.2~0.5 중량%의 Mn을 포함하는 용융아연도금욕에 침적하여 용융아연도금한다.Plating discs with irregularities applied to the surface as described above were deposited in a hot dip galvanizing bath containing a plating bath temperature of 440 to 480 ° C. and containing 0.15 to 0.3% by weight of Al and 0.2 to 0.5% by weight of Mn. do.
상기 도금욕의 온도가 440℃미만인 경우에는 포트내의 용융도금욕의 유동성이 하락하여 표면이 불량해질 우려가 있고, 480℃를 초과하는 경우에는 아연-철 합금이 도금층내에 생성될 우려가 있다.If the temperature of the plating bath is less than 440 ° C., the fluidity of the hot-dip plating bath in the pot may decrease, and the surface may be poor. If the temperature of the plating bath is higher than 480 ° C., the zinc-iron alloy may be formed in the plating layer.
상기 용융아연도금욕 중의 Al 함량이 너무 낮을 경우 도금층 제조과정중에 아연-철 합금상이 도금층내에 포함될 문제가 있고, 너무 높을 경우 도금층의 용접성이 문제가 있다.If the Al content in the hot dip galvanizing bath is too low, there is a problem that the zinc-iron alloy phase is included in the plating layer during the manufacturing process of the plating layer, and if it is too high, there is a problem of weldability of the plating layer.
상기 용융아연도금욕 중의 Mn 함량이 너무 낮을 경우 마찰계수 감소효과를 충분히 얻을 수 없고, 너무 높을 경우 도금욕중에 Mn이 드로스 형태로 존재하여 표면외관이 손상될 수 있다.If the Mn content in the hot dip galvanizing bath is too low, the friction coefficient reduction effect may not be sufficiently obtained. If the Mn content is too high, the surface appearance may be damaged due to the presence of Mn in the form of a dross in the plating bath.
부착량 조절 및 냉각단계Deposition amount adjustment and cooling stage
상기와 같이 용융아연도금된 원판을, 그 도금부착량이 편면당 50~300 g/m2이 되도록 조절하고, - 4℃/s(초) ~ -10℃/s의 냉각속도로 냉각한다.The hot-dip galvanized plate is adjusted as described above so that the plating deposition amount is 50 to 300 g / m 2 per one side, and cooled at a cooling rate of −4 ° C./s (seconds) to −10 ° C./s.
상기와 같이 용융아연도금된 원판을 냉각하면 아연이 응고하여 용융아연도금층을 형성한다.When the hot dip galvanized plate is cooled as described above, zinc coagulates to form a hot dip galvanized layer.
일반적으로, 용융아연 도금강판에는 스팡글(spangle) 혹은 꽃무늬라고 불리우는 특유의 도금 조직 형상이 나타나기 쉽다. 이러한 스팡글은 아연의 응고 반응의 특성에 기인하여 일어난다. 즉, 아연이 응고될 때 응고핵을 기점으로 하여 나무 가지 형태의 수지상정(dendrite)이 성장하여 도금조직의 골격을 형성하고, 그 수지상정 사이에 남아 있던 미응고된 용융아연 풀(pool)이 최종적으로 응고되어 도금층 응고가 종료된다. In general, a hot-dip galvanized steel sheet tends to exhibit a unique plating structure called spangle or floral pattern. This spangle occurs due to the nature of the coagulation reaction of zinc. That is, when zinc coagulates, dendrite in the form of tree branches grows from the coagulation nucleus to form a skeleton of plated structure, and an unsolidified molten zinc pool remaining between the dendrites is formed. Finally, it solidifies and the plating layer solidification is completed.
용융아연도금에 있어서, 상기 응고핵은 도금층과 소지철의 계면에서 발생하며, 따라서 상기 계면에서 도금층의 표층부 방향으로 응고가 진행된다. In hot dip galvanizing, the coagulation nuclei are generated at the interface between the plated layer and the base iron, so that coagulation proceeds in the direction of the surface layer portion of the plated layer at the interface.
용융아연도금층에 망간을 포함하는 경우, 도금층의 Zn-Mn 상태도를 살펴보면, Mn의 공정점은 0.5~1중량% 사이에 있고, 공정온도는 410℃ 정도이다. Mn이 첨가된 아연도금욕에서 도금을 실시할 경우 Zn에 대한 Mn의 분배계수는 1보다 작으므로, Mn의 농도가 공정점 이상이 되면 Zn이 응고할 때 수지상정에 고용되지 못한 Mn은 미응고된 용융 Zn 중으로 배출되어, Mn이 정출될 수 있다. In the case of including the manganese in the hot dip galvanized layer, looking at the Zn-Mn state diagram of the plated layer, the process point of Mn is between 0.5 to 1% by weight, the process temperature is about 410 ℃. When the plating is performed in a zinc plating bath containing Mn, the distribution coefficient of Mn to Zn is less than 1. Therefore, when the concentration of Mn is higher than the process point, Mn that is not dissolved in the resin is solidified when Zn solidifies. Into the melted Zn, and Mn can be crystallized.
나아가, 수지상정의 성장속도가 빠를수록 수지상정의 선단에서의 Mn 농도는 높게 되고, 수지상정의 성장 속도가 느릴수록 미응고된 용융아연 중의 Mn은 확산하여 수지상정의 선단에서의 농화 현상이 감소하게 된다. Furthermore, the faster the growth rate of the dendrite, the higher the Mn concentration at the tip of the dendrite, and the slower the growth rate of the dendrite is, the more diffused Mn is in the unconsolidated molten zinc and the thickening phenomenon at the tip of the dendrite is reduced.
즉, 응고 속도가 느리게 진행될수록 수지상정으로부터 배출된 Mn이 용융아연 중으로 확산될 시간이 많아, 수지상정으로 부터 멀리 떨어진 위치에서의 남아 있는 용융아연 중의 Mn 농도가 높아지게 되며, 결과적으로, 도금층의 응고가 끝난 후에 표층부에 존재하는 미량원소가 많아지게 된다. 반면, 수지상정의 응고속도가 빠르게 되면 수지상정의 선단에서의 Mn의 농도가 높게 되고, Mn이 도금층 내부에서 정출될 수 있다. That is, the slower the solidification rate, the more time the Mn discharged from the dendrite will diffuse into the molten zinc, and the higher the Mn concentration in the remaining molten zinc at a position far from the dendrite, resulting in the solidification of the plating layer. After the end, there is a large amount of trace elements present in the surface layer. On the other hand, if the solidification rate of the dendrite is high, the concentration of Mn at the tip of the dendrite is high, and Mn may be crystallized in the plating layer.
본 발명에서는 원판에 부착된 용융상태의 Zn 도금층의 응고현상을 고려하여 용융아연도금된 원판을, 그 도금부착량이 편면당 50~300 g/m2 이 되도록 조절하고, - 4℃/s ~ -10℃/s의 냉각속도로 냉각한다.In the present invention, in consideration of the solidification phenomenon of the Zn plating layer of the molten state attached to the original plate, the hot-dip galvanized base plate is adjusted so that the plating deposition amount is 50 ~ 300 g / m 2 per side,-4 ℃ / s ~- Cool at a cooling rate of 10 ° C / s.
본 발명의 바람직한 다른 일 측면에 따르는 표면외관 및 성형성이 우수한 용융아연도금강판의 제조방법에 의하면, 도금원판 및 도금원판 위에 형성된 용융아연도금층을 포함하고, 상기 용융아연도금층의 스팡글 크기가 300㎛이하이고 아연 수지상 사이에 Al-Mn-Zn 정출물이 정출되어 있고, 상기 Al-Mn-Zn 정출물의 평균 크기가 0.5~3㎛이고, 상기 정출물사이의 평균 간격이 1~10 ㎛인 용융아연도금강판이 제조될 수 있다.According to another preferred aspect of the present invention, there is provided a method for manufacturing a hot-dip galvanized steel sheet having excellent surface appearance and formability, comprising a plated disc and a hot dip galvanized layer formed on the plated disc, wherein the spun size of the hot dip galvanized layer is 300. Melting of Al-Mn-Zn crystals having a thickness of less than or equal to and having an Al-Mn-Zn crystallization crystallized between zinc resin phases, an average size of the Al-Mn-Zn crystallizations being 0.5 to 3 µm, and an average interval between the crystals being 1 to 10 µm Galvanized steel sheet can be produced.
이하, 실시예를 통해 본 발명을 보다 구체적으로 설명한다. 그러나, 이하의 실시예는 본 발명의 일 예로서, 이에 의해 본 발명이 한정되는 것은 아니다. Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are examples of the present invention, and the present invention is not limited thereto.
(실시예 1)(Example 1)
도금원판이 도금욕에 인입되기 전에, 도금원판의 표면에 하기 표 1의 조건으로 요철을 부여한 다음, 도금욕 온도가 455℃이고 Al의 함량 및 Mn의 함량이 하기 표 1과 같은 아연도금욕에 침지하여 용융아연도금한 후, 140g/m2 의 부착량으로 도금부착량을 조절하고 하기 표 1과 같은 냉각속도로 냉각하여 용융아연도금강판을 제조하였다. 도금부착량은 가스와이핑에 의해 조절하고, 냉각속도는 공기의 풍량에 의해 조절하였다.Before the plating plate is introduced into the plating bath, the surface of the plating plate is provided with unevenness under the conditions shown in Table 1, and then the plating bath temperature is 455 ° C, and the Al content and Mn content are added to the zinc plating bath as shown in Table 1 below. After immersion by hot dip galvanizing, the coating weight was adjusted to a deposition amount of 140 g / m 2 and cooled at a cooling rate as shown in Table 1 to prepare a hot dip galvanized steel sheet. The coating amount was controlled by gas wiping, and the cooling rate was controlled by the air volume of the air.
여기서, 요철 부여(미세 표면조도 부여)는 50메쉬에서 600 메쉬까지의 샌드페이퍼를 여러 번 강판과 마찰시켜서 표면조도를 변화시켰다. 도금전 소재원판의 표면 미세 조도의 부여효과는 ISO 4287에 의거하여 표면 조도를 측정하여 실제 표면적과 투영 표면적의 비율로 표시하였다. 즉 미세 요철이 많을수록 실제 표면적이 증가하여 비율값이 증가하게 된다. Here, the roughness provision (fine surface roughness imparting) was made by rubbing the sandpaper from 50 mesh to 600 mesh several times with the steel sheet to change the surface roughness. The effect of imparting surface fine roughness of the raw material before plating was expressed by the ratio of the actual surface area and the projected surface area by measuring the surface roughness according to ISO 4287. That is, the more the fine concavo-convex, the more the actual surface area is increased, the ratio value is increased.
상기와 같이 제조된 용융아연도금강판에 대하여 도금층 중의 Al 및 Mn 함량, 가공성 및 스팡글 크기, Al-Mn-Zn 정출물의 크기 및 간격을 측정하고, 그 결과를 하기 표 2에 나타내었다.For the hot-dip galvanized steel sheet prepared as described above, Al and Mn content, processability and spangle size, Al-Mn-Zn crystallite size and spacing in the plating layer were measured, and the results are shown in Table 2 below.
여기서, 가공성은 연속마찰 시험시 마찰계수가 0.25를 초과하는 마찰 횟수로 표시하고, 스팽글 크기는 광학현미경으로 측정하였다.Here, the workability is expressed by the number of friction of the friction coefficient is greater than 0.25 in the continuous friction test, the sequin size was measured by an optical microscope.
한편, 비교예 4 및 발명예 1의 도금원판의 3차원 표면조도 측정결과를 도 1에 나타내었으며, 도 1에서 (a)는 비교예 4를 나타내고, (b)는 발명예 1를 나타낸다.On the other hand, the measurement results of the three-dimensional surface roughness of the plating discs of Comparative Example 4 and Inventive Example 1 are shown in Figure 1, in Figure 1 (a) shows Comparative Example 4, (b) shows Inventive Example 1.
(℃/s)Cooling rate
(℃ / s)
(연속마찰시험횟수)Machinability
(Number of continuous friction tests)
(㎛)Sequin Size
(Μm)
상기 표 1 및 표 2로부터 알 수 있는 바와 같이, 비교예 1은 Mn을 첨가하지 않고 도금원판의 미세 조도를 부여하지 않은 경우로 15회 연속 마찰 시험시 마찰계수값이 0.25로 증가하였다. 또, 비교예 2는 Mn을 첨가하지 않고 미세 요철을 부여하여 면적비가 1.025가 되도록 한 후에 냉각속도를 -15/s로 급냉한 경우로서 스팽글 크기는 250㎛로 표면은 미려하지만 가공성은 25회로 불량하였다. 비교예 3은 미세 요철을 형성하지 않은 원판을 사용하여 도금층 중 Mn이 0.2% 포함되고 냉각속도가 -4/s인 경우로 표면 Mn 정출물에 의해 비교예 1 및 2보다 높은 42 정도였지만 스팽글 크기가 600㎛로 조대하여 외관이 불량하였다. 비교예 4는 도금층중 Mn 함량이 0.4%이며, 표면 조도가 면적비율이 1.024로 본 발명에서 제안한 범위보다 낮으며 냉각속도가 -15/s로 빠른 경우로 스팽글 크기는 250㎛ 로 작아서 표면외관은 미려하나 표면에 Mn 정출물이 정출되지 않아 가공성은 30회로 불량하였다. 비교예 5는 Mn 함량이 0.7%인 경우로 표면에 드로스가 많이 부착되어 평가가 곤란하였다. 발명예 1~3은 본 발명에서 제안한 범위로 제조된 도금층을 갖는 것으로 스팽글 크기가 모두 150㎛이하로 미려하고, 가공성도 60회 이상으로 매우 우수하였다.As can be seen from Table 1 and Table 2, in Comparative Example 1, the coefficient of friction increased to 0.25 during 15 consecutive friction tests in the case where Mn was not added and the fine roughness of the plating disc was not given. In addition, Comparative Example 2 is a case where the cooling rate is quenched at -15 / s after adding the fine concavities and convexities without adding Mn so that the area ratio is 1.025. It was. Comparative Example 3 is about 42% higher than Comparative Examples 1 and 2 by the surface Mn crystallization case where Mn is included in the plating layer and the cooling rate is -4 / s using a disc that does not form fine irregularities, but the sequin size Was coarse to 600 µm, and the appearance was poor. In Comparative Example 4, the Mn content in the plating layer was 0.4%, the surface roughness was 1.024, which was lower than the range proposed by the present invention, and the cooling rate was -15 / s. The sequin size was 250 µm. Beautiful but Mn crystallization was not crystallized on the surface, the workability was poor 30 times. In Comparative Example 5, when the Mn content was 0.7%, a lot of dross was attached to the surface, and evaluation was difficult. Inventive Examples 1 to 3 had a plating layer prepared in the range proposed by the present invention, all of which had a sequin size of less than 150 μm, and were excellent in workability of 60 or more times.
(실시예 2)(Example 2)
냉각속도 - 4℃/s 및 -10℃/s로 변화시킨 것을 제외하고, 실시예 1의 비교예 4와 동일하게 제조된 도금강판에 대한 도금표면 EPMA 분석을 실시하고 그 결과를 도 2에 나타내었다.Except for changing the cooling rate-4 ℃ / s and -10 ℃ / s, the plating surface EPMA analysis of the plated steel sheet prepared in the same manner as in Comparative Example 4 of Example 1 was carried out and the results are shown in Figure 2 It was.
냉각속도 - 4℃/s 및 -10℃/s에서의 실시예 1의 발명예 1에 대한 도금표면 EPMA 분석을 실시하고, 그 결과를 도 3에 나타내었다. Plating surface EPMA analysis of Inventive Example 1 of Example 1 at cooling rates −4 ° C./s and −10 ° C./s was carried out, and the results are shown in FIG. 3.
도 2에 나타난 바와 같이, 냉각속도가 느릴 경우에는 표면에 Mn 이 정출하게 되며 냉각속도가 빠르게 되면 Mn의 표면정출은 감소하게 됨을 알 수 있다. 이러한 경우, 조대한 스팽글이 생성되어 외관이 불량해지고, 수지상정의 크기가 증가하여 Mn 분포가 불균일해지는 문제가 있다.As shown in FIG. 2, when the cooling rate is low, Mn is crystallized on the surface, and when the cooling rate is high, surface crystallization of Mn is reduced. In such a case, coarse sequins are generated to deteriorate the appearance, and the size of the dendrite is increased, resulting in a nonuniform Mn distribution.
도 3에 나타난 바와 같이, 본 발명에 따라 제조된 도금강판은 도 2의 비교예 4에 비하여 Mn의 정출이 균일하며 또한 냉각속도의 영향을 적게 받음을 알 수 있다.As shown in Figure 3, the plated steel sheet produced according to the present invention can be seen that the crystallization of Mn is uniform and less affected by the cooling rate compared to Comparative Example 4 of FIG.
Claims (4)
A plated disc and a hot dip galvanized layer formed on the plated disc, the spangle size of the hot dip galvanized layer is 300 μm or less (excluding 0), and Al-Mn-Zn crystallized crystals are crystallized between zinc resin phases. The hot-dip galvanized steel sheet having excellent surface appearance and formability, wherein the average size of the Al-Mn-Zn crystals is 0.5 to 3 μm, and the average spacing between the crystals is 1 to 10 μm.
The hot-dip galvanized steel sheet having excellent surface appearance and formability according to claim 1, wherein the spangle size is 80 to 100 µm.
상기 도금원판이 용융아연도금욕에 인입되기 전에 도금원판의 표면에 요철을 부여하는 단계;
상기와 같이 표면에 요철이 부여된 도금원판을, 도금욕 온도가 440 ~ 480℃이고 0.15~0.3 중량%의 Al 및 0.2~0.5 중량%의 Mn을 포함하는 용융아연도금욕에 침적하여 용융아연도금하는 단계; 및
상기와 같이 용융아연도금된 원판을, 그 도금부착량이 편면당 50~300g/m2 이 되도록 조절하고, - 4℃/s ~ -10℃/s의 냉각속도로 냉각하는 단계를 포함하고, 상기 요철을 부여하는 단계는 도금원판의 조도가 50배 배율에서 측정시 실제 표면적/투영 표면적의 비율이 1.025~1.030이 되도록 실시되는 표면외관 및 성형성이 우수한 용융아연도금강판의 제조방법.
Preparing a plating disc;
Imparting concavities and convexities to the surface of the plating disc before the plating disc is introduced into the hot dip galvanizing bath;
Plating discs with irregularities applied to the surface as described above were deposited in a hot dip galvanizing bath containing a plating bath temperature of 440 to 480 ° C. and containing 0.15 to 0.3% by weight of Al and 0.2 to 0.5% by weight of Mn. Making; And
The hot-dip galvanized plate as described above, the plating deposition amount is adjusted to 50 ~ 300g / m 2 per side, and cooling at a cooling rate of-4 ℃ / s to -10 ℃ / s, the The step of imparting unevenness is a method of manufacturing a hot-dip galvanized steel sheet excellent in surface appearance and formability is carried out so that the ratio of the actual surface area / projection surface area is 1.025 ~ 1.030 when the roughness of the plated plate is measured at 50 times magnification.
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