KR950004778B1 - Method for making a galvannealed steel sheet with an excellant anti-powdering - Google Patents
Method for making a galvannealed steel sheet with an excellant anti-powdering Download PDFInfo
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- KR950004778B1 KR950004778B1 KR1019920026473A KR920026473A KR950004778B1 KR 950004778 B1 KR950004778 B1 KR 950004778B1 KR 1019920026473 A KR1019920026473 A KR 1019920026473A KR 920026473 A KR920026473 A KR 920026473A KR 950004778 B1 KR950004778 B1 KR 950004778B1
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 59
- 239000010959 steel Substances 0.000 title claims abstract description 59
- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000000227 grinding Methods 0.000 title abstract description 17
- 238000001816 cooling Methods 0.000 claims abstract description 47
- 238000010438 heat treatment Methods 0.000 claims abstract description 32
- 239000011701 zinc Substances 0.000 claims abstract description 18
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 17
- 229910001335 Galvanized steel Inorganic materials 0.000 claims abstract description 9
- 239000008397 galvanized steel Substances 0.000 claims abstract description 9
- 229910052782 aluminium Inorganic materials 0.000 claims abstract 4
- 238000005275 alloying Methods 0.000 claims description 61
- 239000000463 material Substances 0.000 claims description 33
- 238000007747 plating Methods 0.000 claims description 25
- 238000004519 manufacturing process Methods 0.000 claims description 17
- 239000000843 powder Substances 0.000 claims description 15
- 239000000956 alloy Substances 0.000 claims description 7
- 238000005507 spraying Methods 0.000 claims description 7
- 229910045601 alloy Inorganic materials 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 238000005098 hot rolling Methods 0.000 claims 1
- 238000005246 galvanizing Methods 0.000 abstract description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 abstract 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 17
- 229910052742 iron Inorganic materials 0.000 description 6
- 238000012545 processing Methods 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 238000005554 pickling Methods 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 229910007570 Zn-Al Inorganic materials 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 206010027146 Melanoderma Diseases 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 229910001297 Zn alloy Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 229910002056 binary alloy Inorganic materials 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 229910002058 ternary alloy Inorganic materials 0.000 description 1
Classifications
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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
- C23C2/261—After-treatment in a gas atmosphere, e.g. inert or reducing atmosphere
-
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C23C2/04—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
-
- 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
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
- C23C2/29—Cooling or quenching
-
- 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
Abstract
Description
제1도는 본 발명을 적용하기 위한 통상의 용융아연도금 및 합금화 처리장치의 일례를 개략적으로 나타내는 개략도.1 is a schematic diagram schematically showing an example of a conventional hot dip galvanizing and alloying apparatus for applying the present invention.
제2도는 종래의 합금화 처리재를 합금화 열처리하는 공정을 나타내는 공정도.2 is a process chart showing a process of alloying heat treatment of a conventional alloying treatment material.
제3도는 후물재 용융아연 열간압연강판을 종래의 방법에 따라 합금화 열처리하는 공정을 나타내는 공정도.3 is a process chart showing a process of alloying heat treatment of a thick material hot-dip hot rolled steel sheet according to a conventional method.
제4도는 본 발명에 따라 용융압연 열간압연강판을 합금화 열처리하는 공정을 나타내는 공정도.4 is a process chart showing a process of alloying heat treatment of a hot rolled hot rolled steel sheet according to the present invention.
* 도면의 주요부분에 대한 부호의 설명* Explanation of symbols for main parts of the drawings
1 : 아연도금욕 2 : 용융아연 열연강판1: zinc plating bath 2: hot dip galvanized steel sheet
3 : 가열대 4 : 유지대3: heating table 4: holding table
5,6 : 포그냉각대 7 : 상부롤5,6: fog cooling stand 7: upper roll
본 발명은 아연-철 합금도금강판의 제조방법에 관한 것으로, 보다 상세하게는 소재두께가 2.0~4.0mm인 후물재(소재두께가 2.0-4.0mm인 후물재 ; 이하 "후물재"라 칭함) 용융아연 열간압연강판의 합금화 처리에 있어서 내파우더링(anti-powdering)성이 우수한 합금화 용융아연 열연강판(Hot-rolled Galvan-nealed Iron, 이하 Hot-GA라 칭함)을 제조하는 방법에 관한 것이다.The present invention relates to a method for producing a zinc-iron alloy plated steel sheet, and more specifically, a thick material having a material thickness of 2.0 to 4.0 mm (a thick material having a material thickness of 2.0 to 4.0 mm; hereinafter referred to as "thick material") The present invention relates to a method for producing an alloyed hot-dip galvanized steel sheet (hereinafter referred to as Hot-GA) having excellent anti-powdering properties in alloying a hot-dip hot rolled steel sheet.
최근 합금화 용융압연 도금강판(Galvannealed Iron, 이하 GA라 칭함)은 도장성, 용접성, 도장후 내식성이 우수하여 건자재용, 가전용 및 자동차용 강판으로 그 수요가 증가하고 있다. 그러나 이들 분야에서 후물재가 요구되는 경우 열연강판을 산세한 후 도장처리만 하여 사용하거나 열간압연강판(이하, "열연강판"이라고도 함)을 산세한 후 연속적으로 도금한 용융아연 열연강판(Hot -rolled Galvanized Iron ; 이하 Hot-GI라 칭함)을 사용하였다. 그러나 이들의 경우 내식성이나 용접성, 도장성등의 문제점이 있기 때문에 후물재로써 이와같은 요구성질을 만족하는 합금화 용융아연 열연강판의 필요성이 대두되고 있다.In recent years, galvannealed iron (GA) is excellent in paintability, weldability, and corrosion resistance after painting, and thus demand for steel sheets for building materials, home appliances, and automobiles is increasing. However, if a thick material is required in these fields, hot-rolled steel sheets (hot-rolled steel plates) are used after pickling the hot rolled steel plate and only by coating or pickling hot rolled steel plate (hereinafter referred to as "hot rolled steel sheet"). Galvanized Iron (hereinafter referred to as Hot-GI) was used. However, in these cases, there is a problem such as corrosion resistance, weldability, paintability, etc., the need for alloyed hot-dip galvanized steel sheet that satisfies these requirements as a thick material has emerged.
일반적으로 합금화 용융아연 도금강판(Galvannealed Iron, 이하 GA라 칭함)은 용융아연 도금설비(Continuous Galvanizing Line, 이하 CGL이라 칭함)내에서 냉연강판을 용융아연도금(Cold-rolled Galvanized Iron ; 이하 CGI라 칭함)한 후, 연속적으로 합금화 가열처리함으로써 용융아연도금층과 강판소지가 상호 확산 반응하여 ξ상, δ1상, Γ상등의 Fe-Zn계 금속간 화합물이 성장하여 합금화 용융아연도금층이 형성된다. 통상 GA재의 품질특성은 점(spot) 용접성, 도장후 내식성 및 도장밀착성이 우수하지만 과합금화재물 프레스(Press) 가공시 도금층이 분말형태로 떨어지는 파우더링(powdering) 현상이 발생하게 되어 사용할 수 없게 되는 문제점이 발생한다.Generally, galvannealed iron (GA) is referred to as cold-rolled galvanized iron (CGI) in a continuous galvanizing line (hereinafter referred to as CGL). After the alloying and heat treatment, the hot dip galvanized layer and the steel sheet are mutually diffused to form Fe-Zn-based intermetallic compounds such as ξ phase, δ 1 phase, and Γ phase to form an alloyed hot dip galvanized layer. In general, the quality characteristics of GA materials are excellent in spot weldability, corrosion resistance and coating adhesion after coating, but powdering phenomenon in which the plating layer falls into powder form during press processing of over alloy material is not available. A problem occurs.
내파우더링성은 합금층이 철(Fe)농도 상승에 따라 비례하여 열화되나, 밀착성 및 용접성은 반대로 개선된다. 이와같이 요구되는 제 특성을 고려할 때 도금층의 최적의 철농도 범위는 8-10%로 비교적 좁게 되며, 주 상(相)으로 δ1상을 갖게 된다.Powder resistance is deteriorated proportionally as the alloy layer is increased in iron (Fe) concentration, but adhesion and weldability are reversely improved. Considering the properties required in this way, the optimum iron concentration range of the plated layer is relatively narrow (8-10%), and has a δ1 phase as the main phase.
냉연강판을 도금소재로 한 CGI를 합금화 처리하는 종래의 방법은 주로 1.0mm 이하 두께의 박물재 및 도금부착량이 45~60g/m2(편면기준)정도의 박도금재의 CGI를 연속적으로 합금화 처리하여 적정 합금화도를 확보한 후, 에어냉각방식으로 강판을 냉각하여 GA재를 제조하였다. 그러나 후물재의 열연강판을 도금소재로 하는 Hot-GI를 기존 CGI의 합금화 공정으로 처리하는 경우, 적정 합금화도를 확보한 후 에어냉각 처리시 후물재의 큰 강판잠열로 인한 냉각능력부족으로 냉각중에 합금화가 계속적으로 일어나게 되어 과합금화가 발생하기 쉽다. 이는 가공시 합금하 도금강판에 있어서 치명적인 파우더링이 발생하는 문제가 있으며, 이를 방지하기 위하여 합금화 온도를 낮출 경우 미합금화로 인하여 가공시 전단응력의 증가로 플레이킹(Flaking) 현상이 발생한다.The conventional method of alloying CGI with a cold rolled steel plate is mainly performed by continuously alloying CGI of a thin metal material having a thickness of 1.0 mm or less and a thin plated material having a plating deposition amount of 45 to 60 g / m 2 (one sided). After securing the appropriate degree of alloying, the steel sheet was cooled by air cooling to produce a GA material. However, when hot-GI, which is made of hot-rolled steel sheet of thick material, is processed by alloying process of existing CGI, it is cooled due to lack of cooling ability due to latent heat of steel plate of thick material during air cooling treatment after securing appropriate alloying degree. Alloying continuously occurs, and superalloying is likely to occur. This is a problem that fatal powdering occurs in the steel plated under the alloy during processing, in order to prevent this, if the alloying temperature is lowered due to unalloyed, flaking occurs due to an increase in shear stress during processing.
따라서, 본 발명은 후물재의 일반 저탄소강 및 구조용 열간압연강판을 용융아연도금한 Hot-GI재를 합금화 열처리시 냉각방법을 개선함으로서 후물재의 잠열최소화에 따른 과합금화를 방지할 수 있을 뿐만 아니라 아연도금욕중의 Al 농도 및 합금화 조건을 적절히 설정하므로 내파우더링이 우수한 합금화 용융아연 열간압연강판의 제조방법을 제공하고자 하는데, 그 목적이 있다.Therefore, the present invention not only prevents over alloying due to the latent heat minimization of thick materials by improving the cooling method during alloying heat treatment of hot-GI materials hot-galvanized on general low carbon steel and structural hot rolled steel sheets of thick materials. Since the Al concentration in the galvanizing bath and the alloying conditions are appropriately set, an object of the present invention is to provide a method for producing an alloyed hot-dip zinc hot rolled steel sheet excellent in powdering.
이하, 본 발명을 제1도를 통해 설명한다.Hereinafter, the present invention will be described with reference to FIG.
본 발명은 연속식 합금화 용융아연 도금강판의 제조방법에 있어서, 0.12~ 0.14wt%의 Al을 함유하는 아연도금욕(1)에서 후물재 열간압연강판(2)을 용융도금한 후, 연속적으로 합금화 가열대(3)에서 용융아연 열연강판 온도가 500~520℃가 되도록 가열하고, 유지대(4)에서 상기 온도범위로 일정시간 유지한 다음, 제 1 및 제 2 포그냉각대(5) 및 (6)에서 공기와 물을 병행하여 고압분사하는 포그냉각방식에 의해 20-40℃/sec의 냉각속도로 급냉하여 상부롤(7)에서의 강판온도가 300℃ 이하가 되도록 합금화 열처리하여 내파우더링성이 우수한 합금화 용융아연 열간압연강판을 제조하는 방법에 관한 것이다.According to the present invention, in the method for producing a continuous alloyed hot-dip galvanized steel sheet, the hot-rolled hot rolled steel sheet (2) is hot-plated in a zinc plating bath (1) containing 0.12 to 0.14 wt% of Al, and then continuously alloyed. Heated so that the hot-dip hot-dip steel sheet temperature is 500 ~ 520 ℃ in the heating table (3), and maintained for a predetermined time in the temperature range in the holding table (4), and then the first and second fog cooling stand (5) and (6 ) Is quenched at a cooling rate of 20-40 ° C./sec by high pressure spraying in parallel with air and water, and the alloying heat treatment is performed so that the steel sheet temperature in the upper roll 7 is 300 ° C. or less. A method for producing an excellent alloyed hot-dip zinc hot rolled steel sheet.
또한, 본 발명은 상기한 내파우더링이 우수한 합금화 용융아연 열간압연강판을 제조하는 방법에 있어서, 아연도금욕중의 Al 함량이 0.08~0.12wt%이고, 합금화 열처리시 용융아연 열연강판 온도가 480-500℃이고, 그리고 냉각속도가 30-40℃/sec인 내파우더링성이 우수한 합금화 용융아연 열간압연강판의 제조방법에 관한 것이다.In addition, the present invention is a method for producing an alloyed hot-dip galvanized hot rolled steel sheet excellent in the above-mentioned powder resistance, the Al content of the zinc plating bath is 0.08 ~ 0.12wt%, the hot-dip galvanized steel sheet temperature is 480 during alloying heat treatment The present invention relates to a method for producing an alloyed hot-dip galvanized hot rolled steel sheet having a powder resistance of -500 ° C and a cooling rate of 30-40 ° C / sec.
또한 본 발명은 상기한 내파우더링성이 우수한 합금화 용융아연 열간압연강판을 제조하는 방법에 있어서, 아연도금욕중의 Al 함량이 0.14~0.16wt%이고 합금화 열처리시 열간압연 강판온도가 520~550℃이고, 그리고 냉각속도가 20~30℃/sec인 내파우더링성이 우수한 합금화 용융아연 열간압연가유판의 제조방법에 관한 것이다.In addition, the present invention is a method for producing an alloyed hot-dip galvanized hot rolled steel sheet having excellent powdering resistance, the Al content in the galvanizing bath is 0.14 ~ 0.16wt% and the hot rolled steel sheet temperature during alloying heat treatment is 520 ~ 550 ℃ The present invention relates to a method for producing an alloyed hot-dip galvanized hot rolled sheet having excellent powdering resistance with a cooling rate of 20 to 30 ° C / sec.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
종래의 두꼐 2mm 이하의 냉연강판을 도금소재로 한 CGI를 합금화 처리하는 종래의 GA 열처리 공정은 제2도에 나타난 바와같이, 직화가열방식으로 도금층을 450-550℃로 가열한 다음 균열대에서 5~10초정도 유지하여 적정 합금화도를 확보한 후 상부롤에서의 강판온도가 300℃ 이하가 되게끔, 에어냉각하여 GA재를 제조하는 공정이다.Conventional GA heat treatment process for alloying CGI with a cold rolled steel sheet of 2 mm or less in thickness, as shown in FIG. 2, heats the plating layer to 450-550 ° C. by direct heating, and then It is a process of manufacturing GA material by air cooling so that the steel sheet temperature in the upper roll is 300 ° C. or less after securing the appropriate alloying degree by maintaining about 10 seconds.
그러나 후물재의 열연강판을 사용하여 도금한 Hot-GI재를 종래의 GA 설비와 합금화 조건으로 합금화 처리할 경우 제3도에 나타난 바와같이 후물재인 열연강판의 잠열로 인한 냉각효과 감소로 상부롤에서의 강판온도가 400℃ 이상이 되어 합금화 처리후 냉각과정에서 계속 합금화가 진행되므로 과합금화가 일어나게 된다. 이와같이 과합금화된 Hot-GA재의 도금층은 상부롤에 분말형태로 떨어져 부착되며, 이 분말이 다시 합금화 도금강판에 부착하는 흑점(Black spot)이라는 표면결함을 발생시키게 되며 또한 가공시 파우더링이 심하게 발생하게 된다.However, when the hot-GI material plated using the hot rolled steel sheet of the thick material is alloyed under the alloying conditions with the conventional GA equipment, as shown in FIG. 3, the cooling effect due to the latent heat of the hot rolled steel sheet is reduced as shown in FIG. Since the steel plate temperature of 400 ℃ or more alloying proceeds in the cooling process after the alloying process is over alloying occurs. The plated layer of the superalloyed hot-GA material is attached to the upper roll in a powder form, and this powder generates a surface defect called black spot that is attached to the alloyed steel sheet again, and the powdering occurs badly during processing. Done.
따라서, 본 발명에서는 Hot-GI재의 합금화의 열처리는 후물재 열연강판의 잠열에 의한 냉각감소를 최대한 줄이기 위하여 적정 합금화후 기존의 에어냉각(Air cooling)에서 공기와 물을 병행하여 고압분사하는 포그냉각(Fog cooling)으로 교체하여 냉각능력을 향상시킴으로써 과합금화에 의한 파우더링 현상을 방지할 수 있는데, 이를 본 발명의 Hot-GA 열처리공정을 나타내는 제4도에 의해 설명하면 다음과 같다. 즉 본 발명은 Al 농도가 0.12~0.14%인 아연도금욕에서 용융도금한 Hot-GI재를 500~520℃로 가열 및 균열처리하여 결정된 합금층내 철농도가 8-10%(δ1상)로 유지되도록 포그냉각을 행하여 상부롤에서의 강판온도가 300℃ 이하가 되도록 냉각시킨 다음 실온까지 에어냉각하므로서, 내파우더링성이 우수한 Hot-GA재가 제조된다.Therefore, in the present invention, the heat treatment of alloying the Hot-GI material is a high temperature spraying fog and air at the same time in the existing air cooling (air cooling) after proper alloying in order to reduce the cooling decrease by the latent heat of the hot-rolled steel sheet By replacing with (fog cooling) it is possible to prevent the powdering phenomenon due to over-alloying by improving the cooling capacity, which will be described with reference to Figure 4 showing the Hot-GA heat treatment process of the present invention. That is, the present invention maintains the iron concentration in the alloy layer determined by heating and cracking the hot-GI material hot-dipped in a zinc plating bath having an Al concentration of 0.12 to 0.14% at 500 to 520 ° C (8-10% (δ1 phase)). Hot-GA material having excellent powdering resistance is produced by performing fog cooling to cool the steel sheet at the upper roll to 300 ° C. or lower and then air cooling to room temperature.
상기 아연도금욕중의 Al은 용융아연도금시 강판표면에서 Fe-Al 2원계 또는 Fe-Zn-Al의 3원계 합금층을 형성하여 취약한 Fe-Zn 합금층의 성장을 억제하므로 도금욕내에 0.18~0.25wt%정도 첨가하고 있으나, 합금화 처리시 이와같은 2,3원계 Al 합금층은 합금화를 방해하는 확산장벽(barrier)으로 작용함으로써 통상 도금욕내 Al 함량은 낮게 관리하고 있다.Al in the galvanizing bath forms Fe-Al binary or Fe-Zn-Al ternary alloy layers on the surface of the steel sheet during hot dip galvanizing to inhibit the growth of the vulnerable Fe-Zn alloy layers. Although 0.25wt% is added, the Al and Ternary Al alloy layer during the alloying process acts as a diffusion barrier (barrier) that hinders the alloying, so that the Al content in the plating bath is usually kept low.
그러나, 본 발명에서는 도금욕중의 Al 함량이 0.08wt% 미만인 경우에는 불균일한 Fe-Al 2원계 또는 Fe-Zn-Al의 3원계 금속간 화합물을 형성하여 국부적인 불균일 합금화(out burst) 조직이 발생하여 과합금화가 일어나게 되고, 0.16wt% 이상인 경우에는 Al 합금층을 두껍게 형성하여 합금화를 지연시키기 때문에 도금액중의 Al 함량은 0.08~0.16wt%로 설정하는 것이 바람직하다.However, in the present invention, when the Al content in the plating bath is less than 0.08 wt%, a nonuniform Fe-Al binary system or a Fe-Zn-Al ternary intermetallic compound is formed to form a localized non-uniform alloying structure. It is preferable that the Al content in the plating solution be set to 0.08 to 0.16 wt% because it is generated and overalloys, and the Al alloy layer is thickened to delay the alloying in the case of 0.16 wt% or more.
한편, 합금화 열처리시 가열온도(합금화 온도) 및 냉각속도는 상기한 도금욕중의 Al 함량에 따라 변화하게 되는데, 도금욕중의 Al 함량이 0.08~0.12wt%인 경우에는 합금화 온도는 480-500℃로, 그리고 냉각속도는 30-40℃/sec로 선정하는 것이 바람직하고, 도금욕중의 Al 함량이 0.12~0.14wt%인 경우에는 합금화 온도는 500~520℃로, 그리고 냉각속도는 20~40℃/sec로 선정하는 것이 바람직하고, 그리고 도금욕중의 Al 함량이 0.14~0.16wt%인 경우에는 합금화 온도는 520~550℃로, 그리고 냉각속도는 20~30℃/sec로 선정하는 것이 바람직하다.On the other hand, during the alloying heat treatment, the heating temperature (alloying temperature) and cooling rate are changed according to the Al content in the plating bath. When the Al content in the plating bath is 0.08 to 0.12 wt%, the alloying temperature is 480-500. It is desirable to select a cooling rate of 30-40 ° C./sec and an alloying temperature of 500-520 ° C. and an cooling rate of 20 ° C. when the Al content in the plating bath is 0.12 to 0.14 wt%. It is preferable to select 40 ° C / sec, and if the Al content in the plating bath is 0.14 to 0.16wt%, the alloying temperature should be selected to 520 ~ 550 ° C and the cooling rate to 20 ~ 30 ° C / sec. desirable.
이와같이 도금욕중의 Al 함량에 따라 합금화 열처리 온도 및 냉각속도를 조절하므로서, 8-10%의 Fe(δ1상)이 확보되어 도금층의 밀착성이 유지되는 동시에 내파우더링성이 개선될 수 있다.Thus, by controlling the alloying heat treatment temperature and cooling rate according to the Al content in the plating bath, 8-10% of Fe (δ1 phase) is secured to maintain the adhesion of the plating layer and at the same time improve the powdering resistance.
이때, 합금화 온도가 상기한 각각의 합금화 온도의 하한 온도보다 낮은 경우에는 Fe의 아연도금층으로의 확산이 느리고, 불균일하게 되어 미합금화 현상이 발생되고, 합금화 온도가 상기한 상한값보다 높은 경우에는 Fe의 아연도금층으로의 확산이 너무 빨라져 과합금화 현상이 일어나 내파우더링성을 저해하게 된다.At this time, when the alloying temperature is lower than the lower limit temperature of each alloying temperature described above, the diffusion of Fe into the galvanized layer becomes slow and uneven, so that an unalloyed phenomenon occurs, and when the alloying temperature is higher than the above upper limit, Diffusion into the galvanized layer is so fast that overalloying occurs, impairing powder resistance.
또한, 냉각속도가 상기한 각각의 냉각속도의 하한값보다 더 느린 경우에는 포그방식이라 하더라도 강판의 냉각시간이 길어져 강판의 잠열이 존재하여 Fe의 확산이 합금화 처리이후에도 계속 일어나 과합금화되므로 내파우더링성이 나빠지고, 냉각속도가 상한값보다 더 빠른 경우에는 Fe의 확산시간이 짧아 미합금화 현상이 발생되어 가공시 플레이킹 현상이 발생하게 된다.In addition, when the cooling rate is slower than the lower limit of each cooling rate described above, even in the fog method, the cooling time of the steel sheet is long, and the latent heat of the steel sheet is present. When the cooling rate is worse than the upper limit, the diffusion time of Fe is short, so that the alloying phenomenon occurs and the flaking phenomenon occurs during processing.
본 발명에 있어서, 합금화 열처리시 각 합금화 온도에서의 유지시간은 라인속도(Line speed)등의 작업조건에 따라 변화될 수 있으나, 8~10%의 합금화도(Fe)를 확보하기 위하여 6-8초가 바람직하다.In the present invention, the holding time at each alloying temperature during the alloying heat treatment may be changed depending on the working conditions such as line speed, but in order to secure an alloying degree (Fe) of 8 to 10%. Candles are preferred.
한편, 본 발명에서는 냉각방식으로 공기와 물을 병형하여 고압분사하는 포그냉각방식을 채택하고 있는데, 그 이유는 후물재인 융용아연 열연강판을 냉각할시 발생되는 잠열을 최소화하여 과합금화를 방지하므로서 내파우더링성을 향상시키기 위함이다.On the other hand, the present invention adopts a fog cooling method of spraying high-pressure spraying the air and water as a cooling method, the reason is that by minimizing the latent heat generated when cooling the molten zinc hot-rolled steel sheet as a thick material to prevent over alloying This is to improve the powdering property.
이하, 실시예를 통하여 본 발명을 보다 상세히 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.
[실시예]EXAMPLE
두께 3.0mm인 일반 저탄소강 및 구조용 강의 열연강판을 산세한 후 가열대 강판온도 550℃, 강판인입온도 460℃로 열처리한 다음, 하기 표 1과 같이 Al 농도를 변화시킨 용융아연도금욕에 5초동안 침적하여 도금부착량이 편면기준 70~80g/m2이 되도록 용융아연도금을 행한 Hot-GI재를 하기 표1과 같이 합금화 열처리 조건을 변화시켜 가면서 합금화 열처리를 행하여 Hot-GA재를 제조한 다음, 합금화도 및 내파우더링성을 조사하고, 그 조사결과를 하기 표 1에 나타내었다.After pickling hot rolled steel sheets of general low carbon steel and structural steel with a thickness of 3.0 mm, heat-treated at a heating table steel plate temperature of 550 ° C. and a steel sheet drawing temperature of 460 ° C., and then for 5 seconds in a molten zinc plating bath having an Al concentration changed as shown in Table 1 below. The hot-GI material which was hot dip galvanized so that the plating deposition amount was deposited by 70 ~ 80g / m 2 on one side was prepared by performing the alloying heat treatment while changing the alloying heat treatment conditions as shown in Table 1 below. Alloying degree and powder resistance were investigated, and the results of the investigation are shown in Table 1 below.
상기 표 1에서 내파우더링 시험은 60° 굽힘시험(bending)후 압축응력을 받은 부분에서 탈락된 분말이 테이프에 묻어나오는 량으로 상대평가한 등급으로 나타낸 것으로서, 여기서 1등급은 거의 파우더링이 없는 미합금화 상태이며, 3등급까지는 비교적 양호한 상태를 나타내고, 4등급 이하는 과합금화로 파우더링이 상당히 일어나거나 도금층 박리가 일어나는 경우를 나타낸다.In Table 1, the powder resistance test is expressed as a grade evaluated relative to the amount of powder dropped on the tape from the compressive stress after 60 ° bending test, where the first grade is almost no powdering. Unalloyed state, up to grade 3 is relatively good, and grade 4 or less represents a case where powdering occurs considerably due to over alloying or plating layer peeling occurs.
[표 1]TABLE 1
상기 표 1에 나타난 바와같이, 후물재의 Hot-GI재를 합금화 처리한 후 냉각방법을 에어냉각으로 하는 경우 [비교재(9-14)]에는 후물재의 잠열로 인하여 최대냉각속도가 20℃/sec 이하로 되기 때문에 모든 도금욕의 Al 농도 및 합금화 가열대 강판온도조건에서 과합금화가 발생하여 파우더링이 심하게 나타남을 알 수 있다.As shown in Table 1, when the cooling method is air-cooled after alloying the hot-GI material of the thick material [Comparative material (9-14)], the maximum cooling rate is 20 ℃ due to the latent heat of the thick material Since it becomes less than / sec, it can be seen that over alloying occurs under Al concentration and alloy heating zone steel plate temperature conditions of all plating baths, so that powdering appears severely.
한편, 냉각방식이 포그냉각방식이라 하더라도 도금욕중의 Al 농도, 가열대 강판온도 및 냉각온도중 어느 하나 또는 둘이상의 조건이 본 발명의 범위를 벗어나는 경우 [비교재(1-8)]에는 미합금화 또는 내파우더링성이 불량하게 나타남을 알 수 있다.On the other hand, even if the cooling method is fog cooling method, if any one or two or more conditions of the Al concentration in the plating bath, heating zone steel plate temperature and cooling temperature is outside the scope of the present invention [Comparative Material (1-8)] is unalloyed Or it can be seen that the powder resistance is poor.
반면에, 도금욕의 Al 농도, 합금화 온도, 냉각속도 및 냉각방식이 본 발명에 부합되는 경우 [발명재(a-j)]에는 내파우더링성이 우수한 Hot-GA재가 얻어짐을 알 수 있다.On the other hand, when the Al concentration, alloying temperature, cooling rate and cooling method of the plating bath are in accordance with the present invention, it can be seen that Hot-GA material having excellent powdering resistance is obtained in the invention (a-j).
상술한 바와같이, 본 발명은 종래의 합금화 열처리과정중 냉각능력을 강화하여 잠열에 의한 과합금화를 방지함으로써 내파우더링성이 우수한 후물재의 합금화 용융아연 열간압연강판을 제조할 수 있는 효과가 있는 것이다.As described above, the present invention is to enhance the cooling capacity of the conventional alloying heat treatment process to prevent over alloying due to latent heat, thereby producing an alloyed hot-dip galvanized hot rolled steel sheet having excellent powder resistance. .
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