KR20020036269A - Method for producing high strength hot rolled steel sheet containing phosphorus for hydroforming applications - Google Patents
Method for producing high strength hot rolled steel sheet containing phosphorus for hydroforming applications Download PDFInfo
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- KR20020036269A KR20020036269A KR1020000066376A KR20000066376A KR20020036269A KR 20020036269 A KR20020036269 A KR 20020036269A KR 1020000066376 A KR1020000066376 A KR 1020000066376A KR 20000066376 A KR20000066376 A KR 20000066376A KR 20020036269 A KR20020036269 A KR 20020036269A
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- 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
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- 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
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- 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
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
Abstract
Description
본 발명은 하이드로포밍법이 적용되는 고장력 열연강판의 제조방법에 관한 것으로, 보다 상세하게는 인장강도가 40kg/mm2이상이면서도 연신율이35% 이상으로 연성이 우수한 하이드로포밍용 고장력 열연강판의 제조방법에 관한 것이다.The present invention relates to a method of manufacturing a high tensile strength hot rolled steel sheet to which a hydroforming method is applied, and more particularly, a method of manufacturing a high tensile strength hot rolled steel sheet for hydroforming having excellent ductility with a tensile strength of 40 kg / mm 2 or more and an elongation of 35% or more. It is about.
판재의 성형은 제품의 무게를 낮추고, 강도, 강성을 향상시키면서 원가를 최소화할 수 있는 기술에 관심이 집중되고 있다. 이러한 관심의 결과로 최근 대두된 성형기술이 하이드로포밍(Hydroforming)으로, 크게 튜브 하이드로포밍(tube hydroforming)과 판재 하이드로포밍(sheet hydroforming)으로 구분된다. 판재 하이드로포밍은 다이와 함께 가압용 공구로 펀치를 같이 사용하여 성형하는 기술이며, 튜브 하이드로포밍은 롤포밍으로 제조된 속이 빈 강관의 내부에 액체를 이용하여 압력을 가함으로써 복잡한 형상을 제조하는 기술이다.The molding of sheet materials is focused on technology that can reduce the weight of the product, and minimize the cost while improving strength and rigidity. As a result of this interest, the molding technology that has recently emerged is hydroforming, which is classified into tube hydroforming and sheet hydroforming. Sheet hydroforming is a technique that uses a punch together with a die to form a punch, and tube hydroforming is a technique for manufacturing complex shapes by applying pressure to a liquid inside a hollow steel pipe manufactured by roll forming. .
하이드로포밍 가공기술은 60년대에 개발된 기술로 당시에는 주로 주방용품이나 위생용품에 사용되는 부품을 생산하였다. 이후 큰 발전이 없다가 1994년부터 시작된 초경량 철강차체 제조기술을 개발하면서 동 기술이 자동차의 경량화에 크게 기여할 수 있다는 가능성이 새로이 부각되면서 자동차의 서스페션계, 배기계, 서브프레임, IP빔 등의 부품제조에 활용되고 있으며, 미래 자동차의 제조에 있어 중요한 기술분야가 될 것으로 전망되고 있다.Hydroforming processing technology was developed in the 60's and produced parts used mainly in kitchen or sanitary products at that time. Since there has been no significant development, the development of ultra-light steel body manufacturing technology, which started in 1994, has newly emerged as a possibility that the technology can greatly contribute to the weight reduction of automobiles, resulting in parts such as automobile suspension systems, exhaust systems, subframes and IP beams. It is used for manufacturing and is expected to be an important technical field for manufacturing of future cars.
지금까지는 금속관의 하이드로포밍 가공방법이나 이에 관련된 장치가 위주를 이루고 있다(일본 공개특허공보 평10-296347, 평11-302862, 평10-175027, 미국특허 5372026호, . 5882039 등). 소재에 관한 기술개발로는 일본 공개특허공보 평 10-176220호에 C:0.02-0.12%, Si:1.5%이하, Mn:1.0-2.5%, P:0.1%이하, S:0.01%이하로 조성되는 강을 냉간가공에 의해 관을 만들고 특정조건에서 열처리하는 기술이 제시되어 있는데, 이 기술은 냉간가공에 의해 얻어진 관의 열처리를 통해 하이드로포밍 성형후에 충분한 강도을 갖는 소재를 제공하고자 하는 것이다.Until now, the method of hydroforming a metal tube and related apparatuses have been mainly oriented (JP-A-10-296347, H11-302862, H10-175027, U.S. Patent 5372026, .5882039, etc.). As for technical development of materials, Japanese Patent Application Laid-Open No. 10-176220 is made of C: 0.02-0.12%, Si: 1.5% or less, Mn: 1.0-2.5%, P: 0.1% or less, and S: 0.01% or less. The technique of forming a tube by cold working and heat-treating under specific conditions has been proposed. The technique is to provide a material having sufficient strength after hydroforming through heat treatment of a tube obtained by cold working.
지금까지는 하이드로포밍에 적합한 소재개발에 적극적으로 대처한 기술은 그다지 많지 않으며, 기본적으로 딥드로잉과 같은 다른 냉간성형기술에 사용되는 재질을 갖는 소재를 그대로 적용하고 있는 실정이다. 그런데, 하이드로포밍은 주로 장출가공에 의하여 성형을 행하기 때문에, 소재의 연신율이 가공성을 좌우하게 되므로, 가공성을 확보하기 위해서는 인장강도 30kg/mm2정도의 낮은 강도의 소재를 사용할 수 밖에 없다. 이에 따라, 다른 냉간성형기술에 사용되는 재질의 열연강판을 그대로 적용하는 방법으로는, 앞으로 자동차 경량화 추세에 적극적으로 대응할 수 없는 문제가 있다.Until now, there are not many technologies that actively cope with the development of materials suitable for hydroforming, and basically the materials having materials used in other cold forming technologies such as deep drawing are applied as they are. By the way, since hydroforming is mainly performed by elongation processing, the elongation of the raw material influences the workability. Therefore, a material having a low strength of about 30 kg / mm 2 has to be used to secure the workability. Accordingly, there is a problem in that the hot rolled steel sheet of a material used for another cold forming technology as it is, as it is, cannot actively cope with the trend of lighter weight in the future.
본 발명에서는 인장강도가 40kg/mm2이상이면서도 연신율이35% 이상으로 연성이 높은 열연강판의 제조방법을 제공하는데, 그 목적이 있다.In the present invention, there is provided a method of manufacturing a hot-rolled steel sheet having a high ductility with an elongation of 35% or more while having a tensile strength of 40 kg / mm 2 or more.
도 1은 시험재의 강도(TS)-연성(El) 그래프1 is a strength (TS) -ductility (El) graph of a test sample
상기 목적을 달성하기 위한 본 발명의 열연강판 제조방법은, 중량%로, C:0.025~0.06%, Mn:0.15~0.45%, P:0.06~0.12%, 나머지 Fe와 기타 불가피한 불순원소로 이루어지는 강슬라브를 Ar3~900℃의 마무리압연온도조건으로 열간압연하고 다음의 조건, 1087*(C+1.1P) + 385 ≤ 권취온도 ≤ 3261*(C+1.1P) + 254에서 권취하는 것을 포함하여 구성된다.Hot-rolled steel sheet manufacturing method of the present invention for achieving the above object, by weight, C: 0.025 ~ 0.06%, Mn: 0.15 ~ 0.45%, P: 0.06 ~ 0.12%, steel consisting of the remaining Fe and other unavoidable impurities The slab was hot rolled at a finish rolling temperature of Ar 3 to 900 ° C and wound at the following conditions: 1087 * (C + 1.1P) + 385 ≤ winding temperature ≤ 3261 * (C + 1.1P) + 254 It is composed.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
본 발명에서는 기본적으로 인장강도가 40kg/mm2이상이면서 하이드로포밍법에 의해 가공이 가능한 소재를 개발하기 위하여 C-Mn-P의 기본 성분계를 조절하면서, 강의 강도와 연성에 미치는 강조성과 열간압연조건의 상관성을 분석한 결과에 입각하여 제조조건을 특정하는데, 그 특징이 있다. 이러한 본 발명을 강조성범위와 그 제조조건으로 구분하여 설명한다.In the present invention, in order to develop a material which can be processed by hydroforming method while having a tensile strength of 40 kg / mm 2 or more, the emphasis and hot rolling conditions on the strength and ductility of the steel are controlled while controlling the basic component system of C-Mn-P. Based on the results of the correlation analysis, the manufacturing conditions are specified. The present invention will be described by dividing it into emphasis range and manufacturing conditions thereof.
· 탄소(C)의 함량은 0.025-0.06%로 하는 것이 바람직하다.The content of carbon (C) is preferably 0.025-0.06%.
C는 강의 소입성을 증가 시켜 강도를 상승시키는 원소로 철강소재에서 가장 중요한 원소로, 그 함량이 0.025% 미만으로 극저탄소강의 수준으로 가게 되면 압연조건이 변화하여도 얻을 수 있는 강도가 32kg/mm2정도로 고강도화를 꾀할 수 없다. 첨가량이 많으면 강도의 측면에서는 유리하지만 용접성을 저하시키므로 하이드로포밍과 같이 용접에 의해 금속관을 제조하여야 하는 경우 크게 불리하다. 더욱이 일반적으로 C양이 0.10%가 넘어서면 응고중 mushy zone이 넓어지므로 연속주조시에 크랙의 생성율이 증가되며, 또한 용접성도 크게 저하된다. 그리고 C양의 증가에 의한 강도상승은 강도의 상승과 더불어 연성의 저하를 수반하므로, 0.06%이하로 제한한다.C is an element that increases strength by increasing the hardenability of steel. It is the most important element in steel materials. When the content is less than 0.025% and goes to the level of ultra low carbon steel, the strength obtained even when the rolling conditions change is 32 kg / mm. It is not possible to increase the strength to about 2 degrees. Although the addition amount is advantageous in terms of strength, but the weldability is lowered, it is greatly disadvantageous when the metal tube should be manufactured by welding such as hydroforming. In addition, if the amount of C is more than 0.10%, the mushy zone is widened during solidification, and thus the crack formation rate is increased during continuous casting, and the weldability is also greatly reduced. In addition, the increase in strength due to the increase in the amount of C is accompanied by a decrease in ductility along with the increase in strength, and is therefore limited to 0.06% or less.
· 망간(Mn)은 0.15-0.45%로 관리하는 것이 바람직하다.Manganese (Mn) is preferably managed at 0.15-0.45%.
Mn은 강의 강도 및 인성을 증가시키고 강의 소입성을 증가시키는 원소이다.Mn의 첨가는 일반적으로 C의 첨가보다 강도 상승시 연성의 저하가 적다. 극저탄소강에 Mn양을 0.6%까지 증량하여도 목표로 하는 강도를 얻기 어려웠으며, C양이 높아도 Mn양이 0.1%로 낮으면 강도의 확보가 이루어지지 않는다. 이와 같이 강도의 측면에서는 Mn양을 0.15%이상으로 증가시키는 것이 유리하지만, Mn을 0.45% 보다 과도하게 증가시키면 비금속개재물의 양을 증가시키고 편석도를 증가시켜 용접강관의 재질을 크게 열화시킨다.Mn is an element that increases the strength and toughness of the steel and increases the hardenability of the steel. The addition of Mn generally results in less ductility at the time of strength increase than the addition of C. Even if the Mn amount is increased to 0.6% in the ultra low carbon steel, it is difficult to obtain the target strength. When the C amount is high, the Mn amount is low as 0.1%, and the strength is not secured. In terms of strength, it is advantageous to increase the Mn amount to 0.15% or more, but excessively increasing Mn more than 0.45% increases the amount of non-metallic inclusions and increases segregation, thereby greatly deteriorating the material of the welded steel pipe.
·인(P)은 0.06-0.12%의 범위로 첨가하는 것이 바람직하다.Phosphorus (P) is preferably added in the range of 0.06-0.12%.
P는 페라이트의 형성을 조장하는 원소로 강의 강도를 해치지 않고 연성을 증가시킬 수 있으며, 특히 소성이방성을 낮추지 않으면서 강도를 높일 수 있어 스탬핑 가공용으로 사용되는 경우 좋은 성능을 발휘할 수 있다. 이러한 P를 적극적으로 활용함으로서 고강도와 더불어 고연성을 확보하는데, 이를 위해 P은 0.06% 이상으로 한다. 그런데, P은 강재의 제조시 편석가능성이 큰 원소로서 중심편석은 물론 미세편석도 형성하여 두께가 두꺼운 소재로 사용되는 경우에는 재질에 좋지 않은 영향을 주므로 그 첨가량을 0.12%이하로 한다P is an element that promotes the formation of ferrite and can increase ductility without harming the strength of the steel, and in particular, can increase the strength without lowering the plastic anisotropy, thereby exhibiting good performance when used for stamping. By actively using such P, high strength and high ductility are secured. For this purpose, P is set to 0.06% or more. By the way, P is a high segregation element in the production of steel, and forms a central segregation as well as fine segregation, and when used as a thick material, adversely affects the material, so the amount of addition should be 0.12% or less.
상기와 같이 조성되는 강을 제조하기 위해서는 탈산을 하게 되는데, 탈산제로는 Si 또는 Al이 사용된다. Si을 Al과 복합 탈산제로 이용하는 경우 Si의 양은 약 0.03% 내외가 되며, Si 만에 의한 탈산의 경우 0.25% 내외가 첨가된다. 본 발명에서는 Si의 양에 대해서는 특별한 제한을 두지 않으나, 일반적인 탈산의 목적으로 첨가되는 수준으로 관리하는 것이 바람직하다.In order to manufacture the steel composition as described above is deoxidized, Si or Al is used as the deoxidizer. When Si is used as a complex deoxidizer with Al, the amount of Si is about 0.03%, and in case of deoxidation by only Si, about 0.25% is added. In the present invention, there is no particular limitation on the amount of Si, but it is preferable to control the added amount for the purpose of general deoxidation.
본 발명에서는 상기와 같이 조성되는 강슬라브를 열간압연하고 이어 권취하여 열연강판으로 제조한다. 열연강판의 강도와 연성을 확보하기 위해서는 미세조직의 제어가 필수적이며 이를 위한 마무리압연온도 및 권취온도의 설정이 매우 중요하다.In the present invention, the steel slab formed as described above is hot rolled and then wound to produce a hot rolled steel sheet. In order to secure the strength and ductility of the hot rolled steel sheet, it is essential to control the microstructure, and the setting of the finish rolling temperature and the winding temperature is very important.
·열간압연공정(무리압연온도: Ac3-900℃)Hot rolling process (Flock rolling temperature: A c3 -900 ℃)
열간압연공정에서 압연 마무리온도가 너무 높으면 압연후의 오스테나이트의 결정립이 증대되며, 이에 따라 변태후의 페라이트의 결정립도 증가되어 인성을 저하시키고 강도에도 불리하게 작용한다. 따라서, 마무리압연온도는 900℃ 이하로 제한하는 것이 바람직하다. 그러나, 압연 마무리 온도가 너무 낮으면 이상역 압연에 의한 혼립조직의 발생등의 문제가 발생되므로 압연 마무리 온도는 Ar3온도 이상으로 하는 것이 바람직하다.In the hot rolling process, if the rolling finish temperature is too high, the grain size of austenite after rolling increases, thereby increasing the grain size of ferrite after transformation, thereby degrading toughness and adversely affecting strength. Therefore, the finish rolling temperature is preferably limited to 900 ° C or less. However, if the rolling finish temperature is too low, problems such as generation of a mixed structure due to abnormal reverse rolling occur, so that the rolling finish temperature is preferably at least Ar 3 temperature.
·권취공정(1087*(C+1.1P) + 385 ≤ 권취온도 ≤ 3261*(C+1.1P) + 254)Winding process (1087 * (C + 1.1P) + 385 ≤ winding temperature ≤ 3261 * (C + 1.1P) + 254)
상기와 같이 열간압연하고 권취하는데, 이때의 권취온도는 40kg/mm2이상의 강도와 연신율이35% 이상의 연성을 확보할 수 있는 조건을 설정하여야 한다. 권취온도가 너무 높으면 페라이트의 입경이 증가되며 페라이트내의 C고용도가 낮아져강도가 낮아지고 연신율은 증가된다. 그러나, 권취온도가 너무 높아지면 입경의 매우 커지게 되어 강도의 저하와 더불어 연신율도 감소하는 결과가 나타난다. 반대로, 권취온도가 낮아지면 페라이트의 입경감소와 더불어 페라이트내의 C고용도도 증가되고 또한, 미세립의 형상도 acicular type으로 바뀌면서 강도가 증가된다. 이에 따라 연신율은 강도에 반비례하여 변하게 된다.Hot rolling and winding as described above, the winding temperature at this time should be set to the conditions to ensure the strength and elongation of 35% or more of 40kg / mm 2 or more. If the coiling temperature is too high, the grain size of the ferrite is increased, the C employment in the ferrite is lowered, the strength is lowered, and the elongation is increased. However, if the coiling temperature is too high, the particle size becomes very large, resulting in a decrease in strength and an elongation. On the contrary, when the coiling temperature is lowered, the C employment in the ferrite increases with the decrease of the particle size of the ferrite, and the strength increases as the shape of the fine grain changes to the acicular type. As a result, the elongation changes in inverse proportion to the strength.
이와 같이 강의 강도와 연성은 권취온도에 따라 변하지만, 강의 강도와 연성에는 C의 함량도 영향을 미친다. 본 발명에서는 이러한 점을 감안하여 강의 성분과 권취온도가 강의 강도와 연성에 미치는 영향을 분석한 결과, C 및 P의 함량이 강도에 미치는 영향도로부터 C+1.1P라는 인자를 구해내고 이 인자를 고려하여 아래 관계식 1과 같은 권취온도식을 구할 수 있었다.In this way, the strength and ductility of the steel is changed depending on the winding temperature, but the content of C also affects the strength and ductility of the steel. In view of the above, the present invention analyzes the effects of steel composition and winding temperature on the strength and ductility of the steel. In consideration of the following winding temperature equation,
[관계식 1][Relationship 1]
1087*(C+1.1P) + 385 ≤ 권취온도 ≤ 3261*(C+1.1P) + 2541087 * (C + 1.1P) + 385 ≤ winding temperature ≤ 3261 * (C + 1.1P) + 254
본 발명에 따라 열간압연하고 상기 관계식 1로부터 구한 권취온도에서 열연강판을 권취하기 위해서는 열간압연직후에 열연강판을 급냉(수냉)하여 권취온도를 관리한다.According to the present invention, in order to wind the hot rolled steel sheet at the coiling temperature obtained from the above equation 1, the hot rolled steel sheet is quenched (water cooled) and then the coiling temperature is managed.
이하, 본 발명을 실시예를 통하여 보다 구체적으로 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.
[실시예]EXAMPLE
표1에서 보이는 바와 같이 화학성분이 다른 10가지 강종을 진공용해로에서 용해하여 잉곳트로 제작한 후, 슬라브를 만들기 위하여 두께 20mm로 사이징 압연을 행하였다. 슬라브는 길이 170mm, 폭 200mm, 두께 20mm의 직육면체로 만들었으며, 이 슬라브를 이용하여 열간압연을 행하였다. 열간압연중 가장 중요한 인자는 압연 마무리 온도 (Finishing Temperature, FT)와 권취온도 (Coiling Temperature, CT)이며, 따라서 본 실험에서도 표2에 보이는 바와 같이 압연 마무리 온도 및 권취온도를 변화하여 가면서 열간압연을 행하였다.As shown in Table 1, ten different steel species having different chemical components were dissolved in a vacuum melting furnace to produce an ingot, and then sizing rolling was performed to a thickness of 20 mm to make a slab. The slab was made of a cuboid of 170 mm in length, 200 mm in width and 20 mm in thickness, which was hot rolled. The most important factors during the hot rolling are the finishing temperature (FT) and the coiling temperature (CT). Therefore, in this experiment, as shown in Table 2, the hot rolling is performed by changing the rolling finish temperature and the coiling temperature. It was done.
상기와 같이하여 제조된 열연강판의 압연온도별 인장특성을 표3에 나타내었다.Table 3 shows the tensile properties of the hot rolled steel sheets manufactured as described above according to rolling temperatures.
표3에서 알 수 있듯이, 적정한 화학성분과 압연조건에 대해서만 목표로 하는 인장강도 40kg/mm2이상, 연신율 35% 이상의 재질이 얻어진다.As can be seen from Table 3, a material with a tensile strength of 40 kg / mm 2 or more and an elongation of 35% or more can be obtained only for the appropriate chemical composition and rolling conditions.
발명강인 H5강의 FT3 및 FT4 조건의 경우 압연 마무리 온도가 너무 높아 인장강도 및 연신율이 목표치에 미달하는 결과를 볼 수 있으며, 이를 통해 볼 때, 압연 마무리 온도는 900℃ 이하로 제한하는 것이 바람직함을 알 수 있다.In the case of the FT3 and FT4 conditions of the inventive steel H5, the rolling finish temperature is too high, and thus the tensile strength and elongation are less than the target value. From this, the rolling finish temperature is preferably limited to 900 ° C or less. Able to know.
또한, 발명강 H5에서 권취온도가 600℃ 이상이 되면 강도가 목표보다 낮아지게 되며, 발명강 H10에서는 첨가원소의 함량이 높아서 시험한 모든 권취온도에서 강도는 확보가 되지만, 권취온도가 500℃로 낮아지게 되면 연신율이 목표보다 낮아지기 때문에 본 발명에서는 권취온도를 아래와 같이 화학성분에 대한 식에 의해 제한토록 한다. 즉, 실험데이터로부터 구한 C 및 P의 강도에 미치는 영향도로부터 성분계 인자로서 C+1.1P을 설정할 수 있고, 따라서,In addition, when the coiling temperature is higher than 600 ℃ in the invention steel H5, the strength is lower than the target, in the invention steel H10 the strength is secured at all the coiling temperature tested because the content of the added element is high, but the coiling temperature is 500 ℃ When lowering, the elongation is lower than the target, in the present invention, the winding temperature is limited by the formula for the chemical composition as follows. That is, C + 1.1P can be set as a component factor based on the influence on the strength of C and P obtained from the experimental data.
1087*(C+1.1P) + 385 ≤ CT ≤ 3261*(C+1.1P) + 2541087 * (C + 1.1P) + 385 ≤ CT ≤ 3261 * (C + 1.1P) + 254
의 범위로 권취온도를 설정할 수 있다.The winding temperature can be set within the range of.
상기한 바와 같이, 본 발명에서는 가공성이 우수한 하이드로포밍용 강재를 제공할 수 있어 자동차부품의 경량화에 기여할 수 있는 유용한 효과가 있는 것이다.As described above, in the present invention, it is possible to provide a hydroforming steel having excellent workability, which has a useful effect of contributing to the weight reduction of automobile parts.
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