WO2016190467A1 - Hot-rolled steel sheet having excellent composite corrosion resistance to sulfuric acid and hydrochloric acid and manufacturing method therefor - Google Patents

Hot-rolled steel sheet having excellent composite corrosion resistance to sulfuric acid and hydrochloric acid and manufacturing method therefor Download PDF

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Publication number
WO2016190467A1
WO2016190467A1 PCT/KR2015/005381 KR2015005381W WO2016190467A1 WO 2016190467 A1 WO2016190467 A1 WO 2016190467A1 KR 2015005381 W KR2015005381 W KR 2015005381W WO 2016190467 A1 WO2016190467 A1 WO 2016190467A1
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Prior art keywords
steel sheet
rolled steel
sulfuric acid
hydrochloric acid
corrosion resistance
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PCT/KR2015/005381
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French (fr)
Korean (ko)
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윤정봉
이병호
김종화
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주식회사 포스코
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Priority to US15/577,228 priority Critical patent/US20180148811A1/en
Priority to PCT/KR2015/005381 priority patent/WO2016190467A1/en
Priority to KR1020187003152A priority patent/KR102098511B1/en
Priority to CN201580080459.XA priority patent/CN107614721B/en
Priority to EP15893419.0A priority patent/EP3305936B1/en
Priority to JP2017561739A priority patent/JP6549254B2/en
Publication of WO2016190467A1 publication Critical patent/WO2016190467A1/en

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    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/84—Controlled slow cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Definitions

  • the present invention relates to a hot rolled steel sheet excellent in complex corrosion resistance to sulfuric acid and hydrochloric acid that can be preferably applied to materials such as desulfurization of a thermal power plant, denitrification equipment, preheater, and parts thereof, and a manufacturing method thereof.
  • Sulfuric acid or sulfuric acid-hydrochloric acid corrosion resistant steels produce sulfuric acid and hydrochloric acid by producing sulfuric acid and hydrochloric acid by the reaction of sulfur dioxide and chlorine gas exhaust gas generated by burning fossil fuels such as coal or petroleum with water. It is used as a desulfurization and denitrification facility for a serious thermal power plant, or as a heat element material that requires the use of a relatively thick thickness steel plate of a gas gas heater (GGH).
  • GGH gas gas heater
  • Copper (Cu) has a great effect of significantly delaying the corrosion rate of sulfuric acid compared to other additive elements, but if a large amount of copper is added, an appropriate amount of copper (Cu) is added while adding a proper amount of copper (Cu).
  • Steels having a complex addition Japanese Patent Laid-Open No. 1997-025536, Japanese Laid-Open Patent Publication No. 1998-110237, Korean Laid-open Patent Publication No. 2009-0070249, etc. have been developed.
  • One aspect of the present invention is to provide a hot rolled steel sheet having excellent corrosion resistance in a corrosive environment in which sulfuric acid and hydrochloric acid are present in combination and a method of manufacturing the same.
  • C 0.05 ⁇ 0.1%
  • Mn 0.5 ⁇ 1.5%
  • P 0.02% or less
  • S 0.02% or less
  • Al 0.01% ⁇ 0.1%
  • Cu 0.2 ⁇ 0.6 %
  • Sb 0.05-0.1%
  • Cu and Sb are concentrated within 500 nm in the thickness direction from the surface, and the loss of corrosion for the solution of sulfuric acid 16.9% by volume + 0.35% by volume hydrochloric acid is 2.0mg It provides a hot rolled steel sheet having excellent corrosion resistance of sulfuric acid and hydrochloric acid of less than / cm 2 / hr.
  • C 0.05 ⁇ 0.1%
  • Mn 0.5 ⁇ 1.5%
  • P 0.02% or less
  • S 0.02% or less
  • Al 0.01% ⁇ 0.1%
  • Cu 0.2 ⁇
  • Sb 0.05-0.1%
  • balance Fe and other unavoidable impurities at 1100-1300 ° C .
  • the hot rolled steel sheet of the present invention can be suitably applied to materials requiring relatively thick thicknesses of power plant denitrification, desulfurization equipment, flue gas piping of boilers, and preheaters in which complex corrosion of sulfuric acid and hydrochloric acid occurs. It has the effect of greatly extending the life of the.
  • the inventors of the present invention have repeatedly studied in both aspects of the composition and manufacturing method of the steel sheet to minimize the content of copper (Cu) in the sulfuric acid-hydrochloric acid corrosion resistant steel, while ensuring a high composite corrosion resistance,
  • Cu copper
  • Sb is added as a composition and the cooling conditions after hot rolling and the cooling conditions after winding are appropriately controlled, the Cu and Sb concentration layers are formed on the surface of the steel sheet in a sulfuric acid and hydrochloric acid corrosion environment to have an appropriate thickness, thereby providing excellent composite corrosion resistance. It was confirmed that it could be ensured and came to complete this invention.
  • Carbon (C) is an advantageous element for securing the strength of the steel sheet, when the content is less than 0.05% by weight, it is difficult to secure the target strength and there is a problem that the wear resistance is lowered. On the other hand, if the content exceeds 0.1% by weight, weldability is greatly degraded during welding of the steel sheet, so that defects are likely to occur, and corrosion resistance is also greatly reduced. Therefore, in the present invention, the content of carbon is preferably limited to 0.05 to 0.1% by weight.
  • Manganese (Mn) is an element that serves to prevent hot shortness caused by solid solution sulfur by precipitating sulfur dissolved in steel as manganese sulfide and expressing a solid solution strengthening effect.
  • the content of manganese is less than 0.5% by weight, manganese sulfide may not be sufficiently precipitated, causing red brittleness due to solid solution sulfur, and it is difficult to secure a target strength.
  • the content of the manganese is preferably limited to 0.5 to 1.5% by weight.
  • Phosphorus (P) 0.02 wt% or less
  • Phosphorus (P) is an element that is inevitably added in steel, and if its content exceeds 0.02% by weight, there is a problem in that the target composite corrosion resistance is greatly reduced. Therefore, it is desirable to manage the content of P to 0.02% by weight or less.
  • S Sulfur
  • S is an element that is solid-solubilized in steel to cause red-brittle brittleness, so it is desirable to control the content as low as possible. If the content exceeds 0.02% by weight, there is a problem that the possibility of defects due to red-hot brittleness increases, so it is preferable to manage the content of S to 0.02% by weight or less.
  • Aluminum (Al) is an element that is inevitably added during the production of aluminum-killed steel, and preferably 0.01 wt% or more for the deoxidation effect.
  • the content of aluminum exceeds 0.1% by weight, the possibility of causing surface defects of the steel sheet is not only increased, but there is a problem in that weldability is lowered. Therefore, in the present invention, it is preferable to limit the content of Al to 0.01 to 0.1% by weight.
  • Copper (Cu) is an element added in consideration of the complex corrosion characteristics of sulfuric acid and hydrochloric acid, and if the content is too low, it is difficult to secure the target complex corrosion resistance, so it is preferably added at 0.2% or more. It is more preferable to add more than%. Complex corrosion resistance is improved as the content of Cu increases, but if the content is too high, the corrosion resistance increase greatly decreases, the manufacturing cost increases rapidly, and there is a problem of causing surface defects such as radial cracking. Therefore, in this invention, it is preferable that the upper limit of content of Cu is 0.6 weight%, and it is more preferable that it is 0.5 weight%.
  • Antimony (Sb) is an element which is essentially added together with Cu to improve complex corrosion resistance, and is an element that can effectively improve complex corrosion resistance by forming a Cu-Sb composite oxide in a corrosive environment. If the content of the antimony is less than 0.05% by weight it is difficult to obtain the above-described effect, whereas if the content of more than 0.1% by weight not only saturation of the above-described effect, there is a problem that the manufacturing cost rises sharply, in consideration of this, 0.1% by weight or less It is preferable to add by.
  • the remainder consists of Fe and unavoidable impurities.
  • the sum of the content of W, Mo, Co and Ni is more preferably controlled to less than 10ppm. This is because these elements may deteriorate the material properties of the hot rolled steel sheet, such as ductility.
  • the hot-rolled steel sheet of the present invention it is preferable that Cu and Sb are concentrated within 500 nm from the surface thereof. These elements are concentrated on the surface during the production of the steel sheet, but when exposed to the corrosive environment by sulfuric acid and hydrochloric acid, the elements are changed to the form of Cu-Sb composite oxide, thereby improving the corrosion resistance of the hot-rolled steel sheet to a very good level.
  • the content of the concentrated Cu and Sb is not particularly limited, and as described below, it may be sufficient to form an oxide layer having a thickness of 400 nm or more from the surface of the hot-rolled steel sheet in a corrosive environment by sulfuric acid and hydrochloric acid. .
  • the thickness of the oxide layer is less than 400 nm, it is difficult to secure the corrosion resistance targeted by the present invention.
  • the corrosion resistance improves more as the thickness of the said oxide layer becomes thick, in this invention, it does not specifically limit about the upper limit of the thickness of the said oxide layer.
  • the thickness of the oxide layer is more preferably 400 to 500 nm.
  • the hot rolled steel sheet of the present invention has a very good composite corrosion resistance with a loss of corrosion of 16.9% by volume sulfuric acid + 0.35% by volume hydrochloric acid solution of 2.0 mg / cm 2 / hr or less.
  • the reheating temperature is less than 1100 °C, there is a problem that it is difficult to ensure the temperature during the subsequent hot rolling, whereas, if the reheating temperature exceeds 1300 °C, the low melting point Cu is eluted and cracks (crack) on the surface of the slab There is a problem that is likely to occur.
  • the reheated steel slab is hot rolled and finished hot rolled at 850 to 950 ° C. to obtain a hot rolled steel sheet.
  • finish hot rolling temperature is less than 850 °C, there is a problem that the elongation is greatly reduced due to the formation of the drawn grains, the material deviation in each direction is non-uniform, whereas if the finish hot rolling temperature exceeds 950 °C, the austenite grains are coarse to increase the hardenability There is a growing problem.
  • the hot rolled steel sheet is quenched to 120 ⁇ 150 °C / s based on the surface temperature of the steel sheet.
  • the cooling rate is less than 120 °C / s, the surface temperature of the hot-rolled steel sheet is too high, the driving force for the oxide-forming elements existing in the steel to move to the surface, the final oxide is formed when the steel sheet is exposed to the complex corrosive environment There is a difficult problem.
  • the cooling rate is preferably 120 ⁇ 150 °C / s.
  • the cooled hot rolled steel sheet is wound at 650 ⁇ 750 °C. If the coiling temperature is less than 650 °C it may be difficult to ensure the sufficient corrosion resistance since the movement of atoms in the winding process is not easy to form a concentrated layer is difficult to form an oxide layer in a corrosive environment. When the coiling temperature exceeds 750 ° C, defects may occur such that the coiled steel sheet is so high that the reheating temperature is so high that the coiling temperature is preferably in the range of 650 to 750 ° C.
  • the surface of the steel sheet is 720 ⁇ 750 °C by the recuperation phenomenon. Even though the temperature inside the steel sheet is in the range of 650 to 750 ° C. through the cooling process, the surface of the steel sheet has a temperature lower than the temperature range by quenching. Therefore, by going through the recuperation process, the movement of the alloying elements advantageous for forming the oxide layer may be activated, and through this, the concentration layer may be formed to a sufficient thickness. In order to fully acquire the said effect, it is preferable that the surface temperature of the steel plate which passed through this reheating is 720 degreeC or more. However, even after a sufficient recuperation process, the surface temperature of the steel sheet is difficult to exceed 750 °C.
  • the wound steel sheet is slowly cooled to a cooling stop temperature of 350 to 400 ° C. at a rate of 30 to 40 ° C./hr.
  • the cooling rate is preferably in the range of 40 ° C / hr or less. .
  • the cooling rate is preferably in the range of 30 ⁇ 40 °C / hr.
  • the cooling stop temperature is less than 350 °C there is a problem that the material properties of the hot-rolled steel sheet, for example, ductility is deteriorated, productivity is lowered, while if the cooling stop temperature is higher than 400 °C, the thickness of the concentrated layer is not enough to provide corrosion resistance There may be an inferior problem. Therefore, the cooling stop temperature is preferably in the range of 350 ⁇ 400 °C.
  • the steel ingots prepared by dissolving them in the composition of compositions as shown in Table 1 were maintained at 1200 ° C. for 1 hour and then hot rolled. At this time, the finish hot rolling was carried out at 900 °C, to produce a hot rolled steel sheet having a final thickness of 4.5mm. Then, it was maintained after cooling and winding up under the conditions shown in Table 2 below. Then, slow cooling was performed to a cooling end temperature of 380 ° C. at a rate of 35 ° C./h to prepare a final hot rolled steel sheet.
  • each specimen was immersed in a solution of 16.9% sulfuric acid + 0.35% hydrochloric acid at 60 ° C. for 6 hours, and then the corrosion loss of each specimen was measured. Is shown in Table 2 below.
  • the thickness of the oxide layer (corrosion layer) formed on the surface of the steel sheet after the completion of deposition under sulfuric acid-hydrochloric acid complex corrosion conditions was measured and shown in Table 2.
  • Comparative Example 1 satisfies the alloy composition of the present invention, but the coiling temperature is low to 500 ° C, the oxide layer was not sufficiently formed, it can be seen that the corrosion loss is 4.5mg / cm2 / hr very low corrosion resistance.
  • Comparative Examples 2 to 4 satisfy the alloy composition of the present invention, but because the cooling rate is low as 10 °C / s, the oxide layer was not formed sufficiently, which results in corrosion loss of 3.2 mg / cm2 / hr or more as corrosion resistance It can be seen that it is very low.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
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Abstract

Disclosed are: a hot-rolled steel sheet having excellent composite resistance to sulfuric acid and hydrochloric acid; and a manufacturing method therefor. An aspect of the present invention provides a hot-rolled steel sheet having excellent composite corrosion resistance to sulfuric acid and hydrochloric acid, the hot-rolled steel sheet containing, by weight%, 0.05-0.1% of C, 0.5-1.5% of Mn, 0.02% or less of P, 0.02% or less of S, 0.01-0.1% of Al, 0.2-0.6% of Cu, 0.05-0.1% of Sb, the remainder Fe, and inevitable impurities, wherein Cu and Sb are enriched within 500 nm from the surface in the thickness direction, and the mass loss to a solution of 16.9 vol% of sulfuric acid + 0.35 vol% of hydrochloric acid is 2.0 mg/cm2/hr.

Description

황산 및 염산 복합내식성이 우수한 열연강판 및 그 제조방법Hot rolled steel sheet with excellent corrosion resistance of sulfuric acid and hydrochloric acid and its manufacturing method
본 발명은 화력 발전소 탈황, 탈질설비, 예열기 및 이들의 부품 등의 소재로 바람직하게 적용될 수 있는 황산 및 염산에 대한 복합내식성이 우수한 열연강판 및 그 제조방법에 관한 것이다.The present invention relates to a hot rolled steel sheet excellent in complex corrosion resistance to sulfuric acid and hydrochloric acid that can be preferably applied to materials such as desulfurization of a thermal power plant, denitrification equipment, preheater, and parts thereof, and a manufacturing method thereof.
황산 또는 황산-염산 복합 내식강은 석탄 또는 석유 등 화석 연료를 연소하면서 생성되는 아황산가스 및 염소가스가 함유된 배기가스가 수분과 반응을 하여 황산 및 염산을 생성하여 황산 또는 황산-염산 복합 부식이 심각한 화력발전소 탈황 및 탈질설비 또는 복합 발전소의 배관 및 GGH(Gas Gas Heater)의 비교적 두꺼운 두께의 강판을 사용해야 하는 열소자(heat element) 소재 등으로 이용된다.Sulfuric acid or sulfuric acid-hydrochloric acid corrosion resistant steels produce sulfuric acid and hydrochloric acid by producing sulfuric acid and hydrochloric acid by the reaction of sulfur dioxide and chlorine gas exhaust gas generated by burning fossil fuels such as coal or petroleum with water. It is used as a desulfurization and denitrification facility for a serious thermal power plant, or as a heat element material that requires the use of a relatively thick thickness steel plate of a gas gas heater (GGH).
일반적으로 황산-염산 복합 내식강은 황산 및 염산 복합 분위기에서 일반강 보다 부식속도를 지연시키기 위하여 강중에 구리(Cu)를 다량 첨가하는 것으로 알려져 왔다. In general, sulfuric acid-hydrochloric acid corrosion resistant steel has been known to add a large amount of copper (Cu) in the steel in order to retard the corrosion rate than the general steel in sulfuric acid and hydrochloric acid complex atmosphere.
구리(Cu)는 다른 첨가 원소에 비해 황산 부식속도를 크게 지연시키는 효과가 월등하지만 많이 첨가할 경우 열간압연시 강판의 크랙발생을 유발하는 등의 이유로 적당량의 구리(Cu)를 첨가하면서 다른 원소를 복합 첨가하는 강(일본 공개특허공보 제1997-025536호, 일본 공개특허공보 제1998-110237호, 한국 공개특허공보 제2009-0070249호 등)이 개발되었다.Copper (Cu) has a great effect of significantly delaying the corrosion rate of sulfuric acid compared to other additive elements, but if a large amount of copper is added, an appropriate amount of copper (Cu) is added while adding a proper amount of copper (Cu). Steels having a complex addition (Japanese Patent Laid-Open No. 1997-025536, Japanese Laid-Open Patent Publication No. 1998-110237, Korean Laid-open Patent Publication No. 2009-0070249, etc.) have been developed.
이와 같이, 황산-염산 복합 내식강에서 구리(Cu)의 함량이 높을수록 내식성의 향상이 가능한 반면, 구리(Cu)는 고가의 원소로서 함량이 증가할수록 제조원가가 높아질 뿐만 아니라 융점이 낮은 구리(Cu)가 편석되거나 농도가 높은 부위에서는 약간의 변형에 의해서도 크랙이 발생하기 쉬워, 연속 주조 과정에서 가공을 많이 받는 슬라브의 코너 등에 크랙이 발생하고 열간압연 후에는 표면결함으로 잔존하여 다른 부위보다 먼저 부식하는 문제점이 있다.As such, the higher the content of copper (Cu) in the sulfuric acid-hydrochloric acid corrosion resistant steel, the higher the corrosion resistance is, while copper (Cu) is an expensive element, the higher the content, the higher the production cost and the lower the melting point of copper (Cu). ) In case of segregation or high concentration, cracks are liable to occur even by slight deformation.In the continuous casting process, cracks occur in corners of slabs that are processed a lot, and they remain as surface defects after hot rolling. There is a problem.
이에, 황산-염산 복합 내식강에서 구리(Cu)의 함량은 최소화하면서, 높은 복합내식성을 확보할 수 있는 방안이 요구되고 있는 실정이다.Therefore, there is a demand for a method capable of securing high complex corrosion resistance while minimizing the content of copper (Cu) in the sulfuric acid-hydrochloric acid corrosion resistant steel.
본 발명의 일 측면은, 황산 및 염산이 복합적으로 존재하는 부식환경에서 우수한 내식성을 갖는 열연강판 및 그 제조방법을 제공하고자 하는 것이다.One aspect of the present invention is to provide a hot rolled steel sheet having excellent corrosion resistance in a corrosive environment in which sulfuric acid and hydrochloric acid are present in combination and a method of manufacturing the same.
본 발명의 일 측면은, 중량%로, C: 0.05~0.1%, Mn: 0.5~1.5%, P: 0.02%이하, S: 0.02%이하, Al: 0.01%~0.1%, Cu: 0.2~0.6%, Sb: 0.05~0.1%, 잔부 Fe 및 불가피한 불순물을 포함하고, 표면으로부터 두께 방향으로 500nm 이내에 Cu 및 Sb가 농축되어 있으며, 황산 16.9부피% + 염산 0.35부피% 용액에 대한 부식 감량이 2.0mg/cm2/hr 이하인 황산 및 염산 복합내식성이 우수한 열연강판을 제공한다.One aspect of the present invention, in weight%, C: 0.05 ~ 0.1%, Mn: 0.5 ~ 1.5%, P: 0.02% or less, S: 0.02% or less, Al: 0.01% ~ 0.1%, Cu: 0.2 ~ 0.6 %, Sb: 0.05-0.1%, balance Fe and unavoidable impurities, Cu and Sb are concentrated within 500 nm in the thickness direction from the surface, and the loss of corrosion for the solution of sulfuric acid 16.9% by volume + 0.35% by volume hydrochloric acid is 2.0mg It provides a hot rolled steel sheet having excellent corrosion resistance of sulfuric acid and hydrochloric acid of less than / cm 2 / hr.
본 발명의 다른 일 측면은, 중량%로, C: 0.05~0.1%, Mn: 0.5~1.5%, P: 0.02%이하, S: 0.02%이하, Al: 0.01%~0.1%, Cu: 0.2~0.6%, Sb: 0.05~0.1%, 잔부 Fe 및 기타 불가피한 불순물을 포함하는 강 슬라브를 1100~1300℃에서 재가열하는 단계; 상기 재가열된 강 슬라브를 열간압연하고, 850~950℃에서 마무리 열간압연하여 열연강판을 얻는 단계; 상기 열연강판을 120~150℃/s의 속도로 급냉하는 단계; 상기 냉각된 열연강판을 650~750℃에서 권취하는 단계; 및 상기 권취된 열연강판을 30~40℃/h의 속도로 350~400℃의 냉각정지온도까지 서냉하는 단계를 포함하는 황산 및 염산 복합내식성이 우수한 열연강판의 제조방법을 제공한다.Another aspect of the present invention, in weight%, C: 0.05 ~ 0.1%, Mn: 0.5 ~ 1.5%, P: 0.02% or less, S: 0.02% or less, Al: 0.01% ~ 0.1%, Cu: 0.2 ~ Reheating the steel slab containing 0.6%, Sb: 0.05-0.1%, balance Fe and other unavoidable impurities at 1100-1300 ° C .; Hot rolling the reheated steel slab and finishing hot rolling at 850 to 950 ° C. to obtain a hot rolled steel sheet; Quenching the hot rolled steel sheet at a rate of 120 to 150 ° C./s; Winding the cooled hot rolled steel sheet at 650 to 750 ° C; And slow cooling the wound hot rolled steel sheet to a cooling stop temperature of 350 to 400 ° C. at a rate of 30 to 40 ° C./h.
덧붙여 상기한 과제의 해결수단은, 본 발명의 특징을 모두 열거한 것은 아니다. 본 발명의 다양한 특징과 그에 따른 장점과 효과는 아래의 구체적인 실시형태를 참조하여 보다 상세하게 이해될 수 있을 것이다.In addition, the solution of the said subject does not enumerate all the characteristics of this invention. Various features of the present invention and the advantages and effects thereof may be understood in more detail with reference to the following specific embodiments.
본 발명에 따르면, 종래 황산-염산 복합 내식강에 비하여 저합금계이면서도 우수한 복합내식성을 가지는 열연강판을 제공할 수 있다. 또한, 본 발명의 열연강판은 황산 및 염산에 대한 복합 부식이 발생하는 발전소 탈질, 탈황설비, 보일러의 배연가스 배관 및 예열기의 비교적 두꺼운 두께를 요구하는 소재에 적합하게 적용할 수 있을 뿐만 아니라, 이들의 수명을 크게 연장하는 효과가 있다.According to the present invention, it is possible to provide a hot-rolled steel sheet having a low corrosion resistance and excellent composite corrosion resistance compared to the conventional sulfuric acid-hydrochloric acid composite corrosion resistant steel. In addition, the hot rolled steel sheet of the present invention can be suitably applied to materials requiring relatively thick thicknesses of power plant denitrification, desulfurization equipment, flue gas piping of boilers, and preheaters in which complex corrosion of sulfuric acid and hydrochloric acid occurs. It has the effect of greatly extending the life of the.
본 발명자들은 황산-염산 복합 내식강에서 구리(Cu)의 함량은 최소화하면서, 높은 복합내식성을 확보할 수 있는 방법에 대하여 강판의 조성 및 제조방법의 양 측면으로 연구를 거듭한 결과, 강판의 일 조성으로 Sb를 첨가함과 동시에, 열간압연 후 냉각 조건 그리고 권취 후 냉각 조건을 적절히 제어할 경우, 황산 및 염산 부식환경에서 강판의 표면에 Cu 및 Sb 농축층이 적절한 두께로 형성되어 우수한 복합내식성을 확보할 수 있음을 확인하고, 본 발명을 완성하기에 이르렀다.The inventors of the present invention have repeatedly studied in both aspects of the composition and manufacturing method of the steel sheet to minimize the content of copper (Cu) in the sulfuric acid-hydrochloric acid corrosion resistant steel, while ensuring a high composite corrosion resistance, When Sb is added as a composition and the cooling conditions after hot rolling and the cooling conditions after winding are appropriately controlled, the Cu and Sb concentration layers are formed on the surface of the steel sheet in a sulfuric acid and hydrochloric acid corrosion environment to have an appropriate thickness, thereby providing excellent composite corrosion resistance. It was confirmed that it could be ensured and came to complete this invention.
이하, 본 발명의 일 측면인 황산 및 염산 복합내식성이 우수한 열연강판에 대하여 상세히 설명한다. Hereinafter, a hot rolled steel sheet excellent in sulfuric acid and hydrochloric acid composite corrosion resistance, which is an aspect of the present invention, will be described in detail.
먼저, 본 발명 열연강판의 합금조성에 대하여 상세히 설명한다.First, the alloy composition of the hot-rolled steel sheet of the present invention will be described in detail.
탄소(C): 0.05~0.1중량%Carbon (C): 0.05-0.1 wt%
탄소(C)는 강판의 강도 확보에 유리한 원소로서, 그 함량이 0.05 중량% 미만이면 목표 강도의 확보가 어려우며 내마모 특성이 저하되는 문제가 있다. 반면 그 함량이 0.1중량%를 초과하게 되면 강판 용접시 용접성이 크게 나빠져 결함이 발생할 가능성이 높고, 내식성도 크게 저하하는 문제가 있다. 따라서, 본 발명에서는 상기 탄소의 함량은 0.05~0.1중량%로 제한함이 바람직하다.Carbon (C) is an advantageous element for securing the strength of the steel sheet, when the content is less than 0.05% by weight, it is difficult to secure the target strength and there is a problem that the wear resistance is lowered. On the other hand, if the content exceeds 0.1% by weight, weldability is greatly degraded during welding of the steel sheet, so that defects are likely to occur, and corrosion resistance is also greatly reduced. Therefore, in the present invention, the content of carbon is preferably limited to 0.05 to 0.1% by weight.
망간(Mn): 0.5~1.5중량%Manganese (Mn): 0.5-1.5 wt%
망간(Mn)은 강중 고용되어 있는 황을 망간황화물로 석출함으로써 상기 고용 황에 의한 적열취성(hot shortness)을 방지하는 역할을 하며, 고용강화 효과를 발현하는 원소이다. 상기 망간의 함량이 0.5중량% 미만인 경우에는 망간황화물이 충분히 석출되지 못하여 고용 황에 의한 적열취성이 발생한 우려가 있으며, 목표 강도의 확보가 어려운 문제가 있다. 반면, 그 함량이 1.5중량%를 초과하는 경우에는 상술한 효과가 포화되며, 제조원가가 급격히 상승하는 문제가 있으므로, 본 발명에서는 상기 망간의 함량은 0.5~1.5중량%로 제한함이 바람직하다.Manganese (Mn) is an element that serves to prevent hot shortness caused by solid solution sulfur by precipitating sulfur dissolved in steel as manganese sulfide and expressing a solid solution strengthening effect. When the content of manganese is less than 0.5% by weight, manganese sulfide may not be sufficiently precipitated, causing red brittleness due to solid solution sulfur, and it is difficult to secure a target strength. On the other hand, when the content is more than 1.5% by weight, the above-mentioned effect is saturated, and manufacturing cost is rapidly increased, so in the present invention, the content of the manganese is preferably limited to 0.5 to 1.5% by weight.
인(P): 0.02 중량% 이하Phosphorus (P): 0.02 wt% or less
인(P)은 강 중 불가피하게 첨가되는 원소이며, 그 함량이 0.02 중량%를 초과하게 되면 목표로 하는 복합내식성이 크게 저하되는 문제가 있다. 따라서, P의 함량을 0.02 중량% 이하로 관리하는 것이 바람직하다.Phosphorus (P) is an element that is inevitably added in steel, and if its content exceeds 0.02% by weight, there is a problem in that the target composite corrosion resistance is greatly reduced. Therefore, it is desirable to manage the content of P to 0.02% by weight or less.
황(S): 0.02 중량% 이하Sulfur (S): 0.02 wt% or less
황(S)은 강 중 고용되어 적열취성을 유발하는 원소이므로, 그 함량을 가능한 낮게 제어하는 것이 바람직하다. 그 함량이 0.02 중량%를 초과하게 되면 적열취성에 의한 결함발생 가능성이 높아지는 문제가 있으므로, S의 함량을 0.02 중량% 이하로 관리하는 것이 바람직하다.Sulfur (S) is an element that is solid-solubilized in steel to cause red-brittle brittleness, so it is desirable to control the content as low as possible. If the content exceeds 0.02% by weight, there is a problem that the possibility of defects due to red-hot brittleness increases, so it is preferable to manage the content of S to 0.02% by weight or less.
알루미늄(Al): 0.01~0.1 중량%Aluminum (Al): 0.01 ~ 0.1 wt%
알루미늄(Al)은 알루미늄 킬드강(Al-killed) 강 제조시 불가피하게 첨가되는 원소로서, 탈산효과를 위해 0.01중량% 이상 첨가됨이 바람직하다. 다만, 상기 알루미늄의 함량이 0.1중량%를 초과하는 경우에는 강판의 표면결함을 유발할 가능성이 높아질 뿐만 아니라 용접성이 저하되는 문제가 있다. 따라서, 본 발명에서는 Al의 함량을 0.01~0.1 중량%로 제한하는 것이 바람직하다.Aluminum (Al) is an element that is inevitably added during the production of aluminum-killed steel, and preferably 0.01 wt% or more for the deoxidation effect. However, when the content of aluminum exceeds 0.1% by weight, the possibility of causing surface defects of the steel sheet is not only increased, but there is a problem in that weldability is lowered. Therefore, in the present invention, it is preferable to limit the content of Al to 0.01 to 0.1% by weight.
구리(Cu): 0.2~0.6 중량%Copper (Cu): 0.2-0.6 wt%
구리(Cu)는 내황산 및 내염산의 복합부식특성을 고려하여 첨가하는 원소로서, 그 함량이 지나치게 낮을 경우 목표로 하는 복합내식성을 확보하기 어려우므로, 0.2% 이상으로 첨가하는 것이 바람직하며, 0.3% 이상으로 첨가하는 것이 보다 바람직하다. 복합내식성은 Cu의 함량이 증가할수록 향상되지만, 그 함량이 지나치게 높을 경우 내식성 증가폭이 크게 저하하고, 제조원가가 급격히 상승하며, 방사형 갈림(star crack)이라는 표면 결함을 유발하는 문제가 있다. 따라서, 본 발명에서는 Cu의 함량의 상한은 0.6 중량%인 것이 바람직하고, 0.5 중량%인 것이 보다 바람직하다.Copper (Cu) is an element added in consideration of the complex corrosion characteristics of sulfuric acid and hydrochloric acid, and if the content is too low, it is difficult to secure the target complex corrosion resistance, so it is preferably added at 0.2% or more. It is more preferable to add more than%. Complex corrosion resistance is improved as the content of Cu increases, but if the content is too high, the corrosion resistance increase greatly decreases, the manufacturing cost increases rapidly, and there is a problem of causing surface defects such as radial cracking. Therefore, in this invention, it is preferable that the upper limit of content of Cu is 0.6 weight%, and it is more preferable that it is 0.5 weight%.
안티몬(Sb): 0.05~0.1중량%Antimony (Sb): 0.05-0.1 wt%
안티몬(Sb)은 상기 Cu와 함께 복합내식성을 향상시키기 위해 필수로 첨가하는 원소로서, 특히 부식환경에서 Cu-Sb 복합산화물을 형성시킴으로써 복합내식성을 효과적으로 향상시킬 수 있는 원소이다. 상기 안티몬의 함량이 0.05중량% 미만이면 상술한 효과를 얻기 어려우며, 반면 0.1중량%를 초과하게 되면 상술한 효과가 포화될 뿐만 아니라, 제조원가가 급격히 상승하는 문제가 있으므로, 이를 고려하여 0.1중량% 이하로 첨가하는 것이 바람직하다.Antimony (Sb) is an element which is essentially added together with Cu to improve complex corrosion resistance, and is an element that can effectively improve complex corrosion resistance by forming a Cu-Sb composite oxide in a corrosive environment. If the content of the antimony is less than 0.05% by weight it is difficult to obtain the above-described effect, whereas if the content of more than 0.1% by weight not only saturation of the above-described effect, there is a problem that the manufacturing cost rises sharply, in consideration of this, 0.1% by weight or less It is preferable to add by.
상기 조성 이외에 나머지는 Fe 및 불가피한 불순물로 이루어진다. 한편, 상기 조성 이외에 다른 조성이 포함될 수 없음을 배제하는 것은 아니나, W, Mo, Co 및 Ni의 함량의 합은 10ppm 미만으로 제어함이 보다 바람직하다. 이들 원소들은 열연강판의 재질 특성, 예컨대 연성 등을 열화시킬 우려가 있기 때문이다.In addition to the above composition, the remainder consists of Fe and unavoidable impurities. On the other hand, it is not excluded that other compositions can not be included in addition to the above composition, the sum of the content of W, Mo, Co and Ni is more preferably controlled to less than 10ppm. This is because these elements may deteriorate the material properties of the hot rolled steel sheet, such as ductility.
한편, 본 발명의 열연강판은 그 표면으로부터 두께 방향으로 500nm 이내에 Cu 및 Sb가 농축되어 있는 것이 바람직하다. 이들 원소들은 강판의 제조시에는 표면에 농화된 상태로 존재하다가 황산 및 염산에 의한 부식환경에 노출될 경우, Cu-Sb 복합산화물의 형태로 변함으로써 열연강판의 내식성을 매우 우수한 수준으로 향상시킨다.On the other hand, in the hot-rolled steel sheet of the present invention, it is preferable that Cu and Sb are concentrated within 500 nm from the surface thereof. These elements are concentrated on the surface during the production of the steel sheet, but when exposed to the corrosive environment by sulfuric acid and hydrochloric acid, the elements are changed to the form of Cu-Sb composite oxide, thereby improving the corrosion resistance of the hot-rolled steel sheet to a very good level.
이때, 농축된 Cu 및 Sb의 함량에 대해서는 특별히 한정하지 아니하며, 하기에서 설명할 바와 같이, 황산 및 염산에 의한 부식환경에서 열연강판의 표면으로부터 400nm 두께 이상의 산화물층을 형성할 수 있을 정도라면 무방하다. 상기 산화물층의 두께가 400nm 미만인 경우에는 본 발명이 목표로 하는 내식성 확보가 곤란하다. 한편, 상기 산화물층의 두께가 두꺼워질수록 내식성이 보다 향상되므로, 본 발명에서는 상기 산화물층 두께의 상한에 대해서는 특별히 한정하지 않는다. 다만, 500nm를 초과하는 경우에는 다량의 합금 첨가 대비 내식성 향상 효과가 낮을 뿐만 아니라, 제조원가가 과도하게 상승하는 문제가 있으므로, 상기 산화물층의 두께는 400~500nm인 것이 보다 바람직하다.At this time, the content of the concentrated Cu and Sb is not particularly limited, and as described below, it may be sufficient to form an oxide layer having a thickness of 400 nm or more from the surface of the hot-rolled steel sheet in a corrosive environment by sulfuric acid and hydrochloric acid. . When the thickness of the oxide layer is less than 400 nm, it is difficult to secure the corrosion resistance targeted by the present invention. On the other hand, since the corrosion resistance improves more as the thickness of the said oxide layer becomes thick, in this invention, it does not specifically limit about the upper limit of the thickness of the said oxide layer. However, in the case of exceeding 500 nm, not only the effect of improving the corrosion resistance is lower than the addition of a large amount of alloy, and there is a problem in that the manufacturing cost is excessively increased, and the thickness of the oxide layer is more preferably 400 to 500 nm.
본 발명의 열연강판은 황산 16.9부피% + 염산 0.35부피% 용액에 대한 부식 감량이 2.0mg/cm2/hr 이하로서 매우 우수한 복합내식성을 갖는다.The hot rolled steel sheet of the present invention has a very good composite corrosion resistance with a loss of corrosion of 16.9% by volume sulfuric acid + 0.35% by volume hydrochloric acid solution of 2.0 mg / cm 2 / hr or less.
이하, 본 발명의 다른 일측면인 황산 및 염산 복합내식성이 우수한 열연강판의 제조방법에 대하여 상세히 설명한다. Hereinafter, a method for manufacturing a hot rolled steel sheet having excellent sulfuric acid and hydrochloric acid composite corrosion resistance, which is another aspect of the present invention, will be described in detail.
우선, 상술한 조성을 만족하는 강 슬라브를 준비한 뒤, 1100~1300℃에서 재가열한다. 재가열 온도가 1100℃ 미만인 경우에는 후속되는 열간압연시의 온도를 확보하기 어려운 문제가 있으며, 반면, 재가열 온도가 1300℃를 초과하는 경우에는 융점이 낮은 Cu가 용출하여 슬라브 표면에 크랙(crack)이 발생할 가능성이 높다는 문제가 있다.First, after preparing a steel slab that satisfies the above-described composition, it is reheated at 1100 ~ 1300 ℃. If the reheating temperature is less than 1100 ℃, there is a problem that it is difficult to ensure the temperature during the subsequent hot rolling, whereas, if the reheating temperature exceeds 1300 ℃, the low melting point Cu is eluted and cracks (crack) on the surface of the slab There is a problem that is likely to occur.
이후, 상기 재가열된 강 슬라브를 열간압연하고, 850~950℃에서 마무리 열간압연하여 열연강판을 얻는다. 마무리 열간압연 온도가 850℃ 미만인 경우에는 연신된 결정립의 생성으로 인해 연신율이 크게 저하하고, 방향별 재질편차가 불균일해지는 문제가 있으며, 반면 950℃를 초과하게 되면 오스테나이트 결정립이 조대해져 경화능이 크게 증가하는 문제가 있다.Thereafter, the reheated steel slab is hot rolled and finished hot rolled at 850 to 950 ° C. to obtain a hot rolled steel sheet. If the finish hot rolling temperature is less than 850 ℃, there is a problem that the elongation is greatly reduced due to the formation of the drawn grains, the material deviation in each direction is non-uniform, whereas if the finish hot rolling temperature exceeds 950 ℃, the austenite grains are coarse to increase the hardenability There is a growing problem.
이후, 상기 열연강판을 강판의 표면온도를 기준으로 120~150℃/s로 급냉한다. 상기와 같은 급냉을 통하여 권취 후 내식성에 유리한 합금원소가 강판의 표면으로 이동하는데 필요한 추진력을 제공할 수 있다. 냉각속도가 120℃/s 미만이면 열연강판의 표면온도가 너무 높아 강 내부에 존재하는 산화물 형성 원소들이 표면으로 이동하는 추진력이 낮아, 최종적으로 강판이 복합적인 부식환경에 노출되었을 때 충분한 산화물이 형성되기 어려운 문제가 있다. 반면, 냉각속도가 150℃/s를 초과하게 되면 강판내부의 온도가 너무 낮아져 권취 후 목적하는 온도까지 복열이 이루어지지 않아 산화물층 형성에 유리한 합금원소의 이동이 원활하게 이루어지지 않는 문제가 있다. 따라서, 상기 냉각속도는 120~150℃/s이 바람직하다.Then, the hot rolled steel sheet is quenched to 120 ~ 150 ℃ / s based on the surface temperature of the steel sheet. Through such quenching, it is possible to provide the driving force necessary to move the alloying element favorable to the corrosion resistance after the winding to the surface of the steel sheet. If the cooling rate is less than 120 ℃ / s, the surface temperature of the hot-rolled steel sheet is too high, the driving force for the oxide-forming elements existing in the steel to move to the surface, the final oxide is formed when the steel sheet is exposed to the complex corrosive environment There is a difficult problem. On the other hand, if the cooling rate exceeds 150 ° C / s, the temperature inside the steel sheet is too low to rewind to the desired temperature after winding, there is a problem that the smooth movement of the alloying elements to form the oxide layer is not made smoothly. Therefore, the cooling rate is preferably 120 ~ 150 ℃ / s.
이후, 상기 냉각된 열연강판을 650~750℃에서 권취한다. 권취온도가 650℃ 미만일 경우에는 권취공정에서 원자의 이동이 용이하지 않아 농축층의 형성이 곤란하여 부식환경에서 산화물층이 형성되지 않아 충분한 내식성을 확보하기 어려울 수 있다. 상기 권취온도가 750℃를 초과하는 경우에는 복열되는 온도가 너무 높아 권취된 강판이 찌그러지는 등 결함이 발생할 수 있으므로, 상기 권취온도는 650~750℃의 범위를 갖는 것이 바람직하다.Then, the cooled hot rolled steel sheet is wound at 650 ~ 750 ℃. If the coiling temperature is less than 650 ℃ it may be difficult to ensure the sufficient corrosion resistance since the movement of atoms in the winding process is not easy to form a concentrated layer is difficult to form an oxide layer in a corrosive environment. When the coiling temperature exceeds 750 ° C, defects may occur such that the coiled steel sheet is so high that the reheating temperature is so high that the coiling temperature is preferably in the range of 650 to 750 ° C.
한편, 상기 권취시에는 상기 강판의 표면이 복열현상에 의해 720~750℃이 되도록 하는 것이 바람직하다. 상기 냉각 공정을 통해 강판 내부의 온도가 650~750℃의 범위를 갖도록 하더라도 상기 강판의 표면은 급냉에 의해 상기 온도범위보다 낮은 온도를 가지게 된다. 따라서, 상기 복열 과정을 거침으로써 산화물층 형성에 유리한 합금원소의 이동이 활발해지도록 하고, 이를 통해 농축층이 충분한 두께로 형성되도록 할 수 있다. 상기 효과를 충분히 얻기 위해서는 상기 복열을 거친 강판의 표면 온도가 720℃ 이상인 것이 바람직하다. 다만, 충분한 복열 과정을 거치라도 강판의 표면온도가 750℃를 초과하기는 어렵다.On the other hand, during the winding, it is preferable that the surface of the steel sheet is 720 ~ 750 ℃ by the recuperation phenomenon. Even though the temperature inside the steel sheet is in the range of 650 to 750 ° C. through the cooling process, the surface of the steel sheet has a temperature lower than the temperature range by quenching. Therefore, by going through the recuperation process, the movement of the alloying elements advantageous for forming the oxide layer may be activated, and through this, the concentration layer may be formed to a sufficient thickness. In order to fully acquire the said effect, it is preferable that the surface temperature of the steel plate which passed through this reheating is 720 degreeC or more. However, even after a sufficient recuperation process, the surface temperature of the steel sheet is difficult to exceed 750 ℃.
상기 권취된 강판을 30~40℃/hr의 속도로 350~400℃의 냉각정지온도까지 서냉한다. 상기 냉각속도가 과도하게 빠른 경우에는 농축층을 형성하는 원소인 Cu의 이동이 충분하지 못하여 충분한 두께의 농축층 형성이 곤란할 수 있으므로, 상기 냉각속도는 40℃/hr 이하의 범위를 갖는 것이 바람직하다. 반면, 30℃/hr미만일 경우에는 결정립의 크기가 과도하게 커져 강도가 낮아질 수 있으므로, 상기 냉각속도는 30~40℃/hr의 범위를 갖는 것이 바람직하다. 한편, 상기 냉각정지온도가 350℃ 미만일 경우에는 열연강판의 재질 특성, 예컨대 연성이 열화되고, 생산성이 저하되는 문제가 있으며, 반면 400℃를 초과하는 경우에는 농축층의 두께가 충분하지 못하여 내식성이 열위하는 문제가 있을 수 있다. 따라서, 상기 냉각정지온도는 350~400℃의 범위인 것이 바람직하다.The wound steel sheet is slowly cooled to a cooling stop temperature of 350 to 400 ° C. at a rate of 30 to 40 ° C./hr. When the cooling rate is excessively fast, since the movement of Cu, which is an element forming the concentrated layer, may not be sufficient, it may be difficult to form a concentrated layer having a sufficient thickness. Therefore, the cooling rate is preferably in the range of 40 ° C / hr or less. . On the other hand, if less than 30 ℃ / hr because the size of the crystal grains is excessively large, the strength can be lowered, the cooling rate is preferably in the range of 30 ~ 40 ℃ / hr. On the other hand, when the cooling stop temperature is less than 350 ℃ there is a problem that the material properties of the hot-rolled steel sheet, for example, ductility is deteriorated, productivity is lowered, while if the cooling stop temperature is higher than 400 ℃, the thickness of the concentrated layer is not enough to provide corrosion resistance There may be an inferior problem. Therefore, the cooling stop temperature is preferably in the range of 350 ~ 400 ℃.
이하, 실시예를 통하여 본 발명을 보다 구체적으로 설명하고자 한다. 다만, 하기의 실시예는 본 발명을 예시하여 보다 상세하게 설명하기 위한 것일 뿐, 본 발명의 권리범위를 한정하기 위한 것이 아니라는 점에 유의할 필요가 있다. 본 발명의 권리범위는 특허청구범위에 기재된 사항과 이로부터 합리적으로 유추되는 사항에 의해 결정되는 것이기 때문이다.Hereinafter, the present invention will be described in more detail with reference to Examples. However, it is necessary to note that the following examples are only for illustrating the present invention in more detail, and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the claims and the matters reasonably inferred therefrom.
(실시예)(Example)
하기 표 1에 나타낸 바와 같은 성분조성으로 용해하여 제조한 강괴를 1200℃ 가열로에서 1시간 유지한 후 열간압연하였다. 이때, 마무리 열간압연은 900℃에서 실시하였으며, 최종 4.5mm의 두께를 갖는 열연강판을 제조하였다. 이후, 하기 표 2에 나타낸 조건으로 냉각 및 권취한 후 유지하였다. 그 다음, 35℃/h의 속도로 380℃의 냉각종료온도까지 서냉하여, 최종 열연강판을 제조하였다.The steel ingots prepared by dissolving them in the composition of compositions as shown in Table 1 were maintained at 1200 ° C. for 1 hour and then hot rolled. At this time, the finish hot rolling was carried out at 900 ℃, to produce a hot rolled steel sheet having a final thickness of 4.5mm. Then, it was maintained after cooling and winding up under the conditions shown in Table 2 below. Then, slow cooling was performed to a cooling end temperature of 380 ° C. at a rate of 35 ° C./h to prepare a final hot rolled steel sheet.
상기에 따라 제조된 열연강판의 부식특성을 관찰하기 위하여, 각각의 시편을 60℃의 황산 16.9부피% + 염산 0.35부피% 용액에 6시간 동안 침적한 후 각 시편의 부식감량을 측정하고, 그 결과를 하기 표 2에 나타내었다. In order to observe the corrosion characteristics of the hot-rolled steel sheet prepared according to the above, each specimen was immersed in a solution of 16.9% sulfuric acid + 0.35% hydrochloric acid at 60 ° C. for 6 hours, and then the corrosion loss of each specimen was measured. Is shown in Table 2 below.
또한, 황산-염산 복합부식조건에서의 침적 완료 후 강판 표면에 형성된 산화물층(내식층)의 두께를 측정하여 표 2에 나타내었다.In addition, the thickness of the oxide layer (corrosion layer) formed on the surface of the steel sheet after the completion of deposition under sulfuric acid-hydrochloric acid complex corrosion conditions was measured and shown in Table 2.
표 1
강종 성분조성 (중량%)
C Mn P S Al Cu Sb
발명강 1 0.075 0.69 0.012 0.009 0.033 0.32 0.08
발명강 2 0.068 0.67 0.011 0.009 0.029 0.39 0.06
발명강 3 0.074 0.75 0.009 0.01 0.029 0.44 0.05
비교강 1 0.069 0.74 0.012 0.011 0.035 0.28 -
Table 1
Steel grade Composition of Composition (wt%)
C Mn P S Al Cu Sb
Inventive Steel 1 0.075 0.69 0.012 0.009 0.033 0.32 0.08
Inventive Steel 2 0.068 0.67 0.011 0.009 0.029 0.39 0.06
Inventive Steel 3 0.074 0.75 0.009 0.01 0.029 0.44 0.05
Comparative Steel 1 0.069 0.74 0.012 0.011 0.035 0.28 -
표 2
강종 냉각속도(℃/s) 권취온도(℃) 부식감량 (mg/cm2/hr) 산화물층 두께 (nm) 구분
발명강 1 130 700 1.8 420 발명예 1
130 500 4.5 57 비교예 1
10 700 3.8 63 비교예 2
발명강 2 130 700 1.6 440 발명예 2
10 700 3.6 69 비교예 3
발명강 3 130 700 1.4 460 발명예 3
10 700 3.2 75 비교예 4
비교강 1 130 700 8.8 220 비교예 5
TABLE 2
Steel grade Cooling rate (℃ / s) Winding temperature (℃) Corrosion loss (mg / cm 2 / hr) Oxide layer thickness (nm) division
Inventive Steel 1 130 700 1.8 420 Inventive Example 1
130 500 4.5 57 Comparative Example 1
10 700 3.8 63 Comparative Example 2
Inventive Steel 2 130 700 1.6 440 Inventive Example 2
10 700 3.6 69 Comparative Example 3
Inventive Steel 3 130 700 1.4 460 Inventive Example 3
10 700 3.2 75 Comparative Example 4
Comparative Steel 1 130 700 8.8 220 Comparative Example 5
상기 표 1 및 2에서 알 수 있듯이, 본 발명이 제안하는 합금조성과 제조조건을 만족하는 발명예 1 내지 3의 경우에는 400nm 이상의 산화물층이 형성됨으로써 황산 및 염산에 의한 부식환경하에서 부식감량이 2.0mg/㎠/Hr이하로 매우 우수한 내식특성을 가지고 있음을 알 수 있다. As can be seen from Tables 1 and 2, in the case of Inventive Examples 1 to 3 satisfying the alloy composition and manufacturing conditions proposed by the present invention by forming an oxide layer of 400nm or more, the corrosion loss in the corrosion environment by sulfuric acid and hydrochloric acid 2.0 It can be seen that the corrosion resistance is very good at less than mg / ㎠ / Hr.
비교예 1은 본 발명의 합금조성을 만족하나, 권취온도가 500℃로 낮아 산화물층이 충분히 형성되지 않았으며, 이로 인해 부식감량이 4.5mg/㎠/hr로서 내식성이 매우 낮은 것을 알 수 있다.Comparative Example 1 satisfies the alloy composition of the present invention, but the coiling temperature is low to 500 ° C, the oxide layer was not sufficiently formed, it can be seen that the corrosion loss is 4.5mg / ㎠ / hr very low corrosion resistance.
비교예 2 내지 4는 본 발명의 합금조성을 만족하나, 냉각속도가 10℃/s로서 낮은 수준이어서, 산화물층이 충분히 형성되지 않았으며, 이로 인해 부식감량이 3.2mg/㎠/hr 이상으로서 내식성이 매우 낮은 것을 알 수 있다.Comparative Examples 2 to 4 satisfy the alloy composition of the present invention, but because the cooling rate is low as 10 ℃ / s, the oxide layer was not formed sufficiently, which results in corrosion loss of 3.2 mg / ㎠ / hr or more as corrosion resistance It can be seen that it is very low.
비교예 5의 경우에는 본 발명의 제조조건을 만족하나, Sb가 첨가되지 않아 황산 및 염산에 의한 부식환경에서 부식감량 8.8 mg/cm2/hr로서 내식성이 매우 낮은 수준임을 알 수 있다. 이는 산화물층 내 내식성이 우수한 Cu-Sb 복합 산화물이 존재하지 않기 때문이다. In the case of Comparative Example 5, but satisfying the manufacturing conditions of the present invention, it can be seen that corrosion resistance is very low as corrosion loss 8.8 mg / cm 2 / hr in the corrosion environment by sulfuric acid and hydrochloric acid because Sb is not added. This is because there is no Cu-Sb composite oxide having excellent corrosion resistance in the oxide layer.
이상 실시예를 참조하여 설명하였지만, 해당 기술 분야의 숙련된 통상의 기술자는 하기의 특허 청구의 범위에 기재된 본 발명의 사상 및 영역으로부터 벗어나지 않는 범위 내에서 본 발명을 다양하게 수정 및 변경시킬 수 있음을 이해할 수 있을 것이다.Although described with reference to the above embodiments, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the invention described in the claims below. You will understand.

Claims (6)

  1. 중량%로, C: 0.05~0.1%, Mn: 0.5~1.5%, P: 0.02% 이하, S: 0.02% 이하, Al: 0.01~0.1%, Cu: 0.2~0.6%, Sb: 0.05~0.1%, 잔부 Fe 및 불가피한 불순물을 포함하고, 표면으로부터 두께 방향으로 500nm 이내에 Cu 및 Sb가 농축되어 있으며, 황산 16.9부피% + 염산 0.35부피% 용액에 대한 부식 감량이 2.0mg/cm2/hr 이하인 황산 및 염산 복합내식성이 우수한 열연강판.By weight%, C: 0.05-0.1%, Mn: 0.5-1.5%, P: 0.02% or less, S: 0.02% or less, Al: 0.01-0.1%, Cu: 0.2-0.6%, Sb: 0.05-0.1% Sulfuric acid containing residual Fe and unavoidable impurities, wherein Cu and Sb are concentrated within 500 nm from the surface in a thickness direction, and the loss of corrosion of a solution of 16.9% by volume sulfuric acid + 0.35% by volume hydrochloric acid is 2.0 mg / cm 2 / hr or less; Hot rolled steel with excellent hydrochloric acid composite corrosion resistance.
  2. 제1항에 있어서,The method of claim 1,
    상기 불가피한 불순물은 W, Mo, Co 및 Ni를 포함하고, 이들 함량의 합은 10ppm 미만인 황산 및 염산 복합내식성이 우수한 열연강판.The inevitable impurities include W, Mo, Co and Ni, and the sum of these contents is less than 10 ppm sulfuric acid and hydrochloric acid composite corrosion resistance excellent hot rolled steel sheet.
  3. 제1항에 있어서,The method of claim 1,
    상기 농축된 Cu 및 Sb는 황산 및 염산 부식환경에서 Cu-Sb 복합 산화물을 포함하는 산화물층을 형성하는 것을 특징으로 하는 황산 및 염산 복합내식성이 우수한 열연강판.The concentrated Cu and Sb is a hot rolled steel sheet excellent in sulfuric acid and hydrochloric acid composite corrosion resistance, characterized in that to form an oxide layer containing a Cu-Sb composite oxide in a sulfuric acid and hydrochloric acid corrosion environment.
  4. 제3항에 있어서,The method of claim 3,
    상기 산화물층은 상기 열연강판 표면으로부터 두께 방향으로 400~500nm의 두께로 형성되는 것을 특징으로 하는 황산 및 염산 복합내식성이 우수한 열연강판.The oxide layer is hot-rolled steel sheet excellent sulfuric acid and hydrochloric acid composite corrosion resistance, characterized in that formed from a thickness of 400 ~ 500nm in the thickness direction from the surface of the hot rolled steel sheet.
  5. 중량%로, C: 0.05~0.1%, Mn: 0.5~1.5%, P: 0.02% 이하, S: 0.02% 이하, Al: 0.01~0.1%, Cu: 0.2~0.6%, Sb: 0.05~0.1%, 잔부 Fe 및 기타 불가피한 불순물을 포함하는 강 슬라브를 1100~1300℃에서 재가열하는 단계;By weight%, C: 0.05-0.1%, Mn: 0.5-1.5%, P: 0.02% or less, S: 0.02% or less, Al: 0.01-0.1%, Cu: 0.2-0.6%, Sb: 0.05-0.1% Reheating the steel slab containing the balance Fe and other unavoidable impurities at 1100-1300 ° C .;
    상기 재가열된 강 슬라브를 열간압연하고, 850~950℃에서 마무리 열간압연하여 열연강판을 얻는 단계;Hot rolling the reheated steel slab and finishing hot rolling at 850 to 950 ° C. to obtain a hot rolled steel sheet;
    상기 열연강판을 120~150℃/s의 속도로 급냉하는 단계;Quenching the hot rolled steel sheet at a rate of 120 to 150 ° C./s;
    상기 냉각된 열연강판을 650~750℃에서 권취하는 단계; 및Winding the cooled hot rolled steel sheet at 650 to 750 ° C; And
    상기 권취된 열연강판을 30~40℃/h의 속도로 350~400℃의 냉각정지온도까지 서냉하는 단계를 포함하는 황산 및 염산 복합내식성이 우수한 열연강판의 제조방법.Method of producing a hot-rolled steel sheet excellent in sulfuric acid and hydrochloric acid composite corrosion resistance comprising the step of slowly cooling the wound hot rolled steel sheet to a cooling stop temperature of 350 ~ 400 ℃ at a rate of 30 ~ 40 ℃ / h.
  6. 제5항에 있어서,The method of claim 5,
    상기 권취시, 상기 강판의 표면이 복열 현상에 의해 720~750℃이 되도록 하는 황산 및 염산 복합내식성이 우수한 열연강판의 제조방법.The method of manufacturing a hot rolled steel sheet having excellent corrosion resistance of sulfuric acid and hydrochloric acid such that the surface of the steel sheet is 720 to 750 ° C by reheating during winding.
PCT/KR2015/005381 2015-05-28 2015-05-28 Hot-rolled steel sheet having excellent composite corrosion resistance to sulfuric acid and hydrochloric acid and manufacturing method therefor WO2016190467A1 (en)

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