KR100398387B1 - A method of manufacturing high strength wire rods having superior fatigue life for engine valve-spring - Google Patents

A method of manufacturing high strength wire rods having superior fatigue life for engine valve-spring Download PDF

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KR100398387B1
KR100398387B1 KR10-1998-0057103A KR19980057103A KR100398387B1 KR 100398387 B1 KR100398387 B1 KR 100398387B1 KR 19980057103 A KR19980057103 A KR 19980057103A KR 100398387 B1 KR100398387 B1 KR 100398387B1
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fatigue life
less
wire
temperature
strength
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KR10-1998-0057103A
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Korean (ko)
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KR20000041267A (en
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서일권
우용택
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주식회사 포스코
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D41/00Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24Ferrous alloys, e.g. steel alloys containing chromium with vanadium

Abstract

본 발명은 자동차 엔진의 흡·배기 밸브스프링용 선재의 제조방법에 관한 것으로, 그 목적은 제품선의 인장강도가 190kg/mm2이상의 가지면서 피로수명과 인성이 개선되는 엔진밸브스프링용 선재의 제조방법을 제공함에 있다.The present invention relates to a method for manufacturing a wire rod for intake / exhaust valve springs of an automotive engine, and an object thereof is a method for manufacturing a wire rod for an engine valve spring having a tensile strength of 190 kg / mm 2 or more and improving fatigue life and toughness. In providing.
이와 같은 목적을 갖는 본 발명은, 중량%로, C:0.60∼0.70%, Si:1.2∼1.6%, Mn:0.60∼0.90%, Cr:0.60∼0.90%, V:0.15∼0.25%, P:0.025%이하, S:0.025%이하, Al:0.010%이하를 함유하고, 10㎛이내의 크기를 갖는 비연성개재물이 0.05%이내의 분율로 형성되어 있는 빌렛을 1,000∼1,040℃의 온도범위로 재가열한 다음, 중간사상압연전에 수냉을 통해 중간사상압연 출측온도를 900∼950℃로 하는 조건으로 열간선재압연하고, 700∼770℃의 온도에서 권취한 다음, 냉각속도를 0.7∼1.0℃/sec로 하는 것을 포함하여 이루어지는 피로수명이 우수한 고강도 엔진밸브 스프링용 선재의 제조방법에 관한 것을 그 기술적요지로 한다.The present invention having such a purpose is, by weight, C: 0.60 to 0.70%, Si: 1.2 to 1.6%, Mn: 0.60 to 0.90%, Cr: 0.60 to 0.90%, V: 0.15 to 0.25%, and P: Billets containing 0.025% or less, S: 0.025% or less, Al: 0.010% or less, and non-combustible inclusions having a size of 10 μm or less at a fraction of 0.05% are reheated to a temperature range of 1,000 to 1,040 ° C. Next, hot wire is rolled by water cooling before the intermediate sand rolling under the condition that the intermediate sand rolling side temperature is 900 to 950 ° C., and wound at a temperature of 700 to 770 ° C., and then the cooling rate is 0.7 to 1.0 ° C./sec. The technical gist of the present invention relates to a method for producing a high-strength engine valve spring wire rod having excellent fatigue life including the same.
본 발명에 의해 제공되는 선재는 통상의 방법에 따라 제품선(wire)으로 제조되면, 220㎏/㎟ 이상의 인장강도를 가지면서 107회 이상의 피로수명이 확보되는 효과가 있다.When the wire provided by the present invention is manufactured in a wire according to a conventional method, it has an effect of ensuring a fatigue life of 10 7 times or more while having a tensile strength of 220 kg / mm 2 or more.

Description

피로수명이 우수한 고강도 엔진밸브스프링강 선재의 제조방법{A METHOD OF MANUFACTURING HIGH STRENGTH WIRE RODS HAVING SUPERIOR FATIGUE LIFE FOR ENGINE VALVE-SPRING}Manufacturing method of high strength engine valve spring steel wire with excellent fatigue life {A METHOD OF MANUFACTURING HIGH STRENGTH WIRE RODS HAVING SUPERIOR FATIGUE LIFE FOR ENGINE VALVE-SPRING}
본 발명은 자동차 엔진의 흡·배기 밸브스프링용 선재의 제조방법에 관한 것으로, 보다 상세히는 피로수명이 우수하고 강도가 향상된 자동차 엔진밸브스프링강 선재의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a wire rod for intake / exhaust valve springs of an automotive engine, and more particularly, to a method for manufacturing an automotive engine valve spring steel wire with improved fatigue life and strength.
일반적으로 엔진의 흡·배기 밸브스프링은 선재를 신선, 냉각, 뜨임(템퍼링)의 공정을 거쳐 제조된 제품선(Wire)을 스프링으로 성형하여 자동차 엔진의 흡·배기밸브 부위에 장착되어진다. 최근, 자동차 산업의 발달에 따라 엔진밸브스프링의 소형화, 고인성화에 의한 컴팩트(COMPACT)엔진, 저소음엔진, 고속출력엔진 등 고기능엔진의 개발 및 사용이 증가하고 있으며, 이에 따라 엔진밸브스프링의 고강도화 및 고내구화(인성향상 및 피로수명확보)가 요구되고 있는 추세이다.In general, the intake / exhaust valve spring of an engine is mounted on the intake / exhaust valve portion of an automobile engine by forming a wire produced by a process of drawing, cooling, and tempering the wire rod with a spring. Recently, with the development of the automobile industry, the development and use of high-performance engines such as compact engines, low noise engines, and high-speed output engines are increasing due to the miniaturization and high toughness of engine valve springs. High durability (improved toughness and fatigue life) are required.
지금까지 엔진밸브스프링용 선재는 제품선 최대 인장강도가 190kg/mm2이 한계로 인식되고 있다. 그 이상의 강도를 확보하기 위해 합금원소를 첨가하면 가능하나, 이 경우에는 합금원소에 의한 변태지연효과로 저온조직의 발생을 피할 수 없고, 또한, 비연성 개재물인 Al계 개재물(약 20㎛)이 고강도에서 피로수명의 저하의 요인으로 작용하여 요구되는 수준(107회 이상)의 피로수명 확보가 불가능하였다.Until now, the maximum tensile strength of the product line for engine valve springs is recognized as 190kg / mm 2 . It is possible to add alloy element to secure more strength, but in this case, low temperature structure is inevitable due to transformation delay effect by alloy element, and Al type inclusion (about 20㎛) which is non-combustible inclusion is high strength. It was not possible to secure the fatigue life of the required level (more than 10 7 times) because it acted as a factor of decreasing fatigue life at.
또한, 종래의 제조기술에 의해 제공되는 엔진밸브스프링용 선재는 20~25㎛수준의 오스테나이트 결정입크기(AUSTENITE GRAIN SIZE, 이하, 간단히 'AGS'라 함)의 확보가능 하였으나, 고인성 확보를 위하여는 더욱 미세한 AGS(15㎛ 이하)가 요구되고 있다.In addition, the wire rod for engine valve spring provided by the conventional manufacturing technology was able to secure the austenite grain size (AUSTENITE GRAIN SIZE, hereinafter simply referred to as 'AGS') of 20 to 25㎛ level, but secured high toughness For this purpose, finer AGS (15 µm or less) is required.
본 발명은 종래기술의 문제점을 해결하기 위하여 끊임없는 연구와 현장실험을 행하고 그 결과에 근거하여 제안된 것으로, 190kg/mm2이상의 고인장강도를 가지면서 피로수명과 인성이 개선되는 엔진밸브스프링용 선재의 제조방법을 제공하는데, 그 목적이 있다.The present invention has been proposed based on the results of the endless research and field experiments to solve the problems of the prior art, for the engine valve spring to improve fatigue life and toughness while having a high tensile strength of 190kg / mm 2 or more To provide a method for producing a wire rod, the purpose is.
도 1은 본 발명의 공정일례도1 is an exemplary process of the present invention
상기 목적을 달성하기 위한 본 발명의 선재제조방법은, 중량%로, C:0.60∼0.70%, Si:1.2∼1.6%, Mn:0.60∼0.90%, Cr:0.60∼0.90%, V:0.15∼0.25%, P:0.025%이하, S:0.025%이하, Al:0.010%이하를 함유하고, 0.05%이내의 분율을 갖는 비연성 개재물이 10㎛이내로 형성되어 있는 빌렛을 1,000∼1,040℃의 온도범위로 재가열한 다음, 중간사상압연전에 수냉을 통해 중간사상압연 출측온도를 900∼950℃로 하는 조건으로 열간선재압연하고, 700∼770℃의 온도에서 권취한 다음, 이송속도를 1.5∼2.0m/sec로 냉각속도를 0.7∼1.0℃/sec로 하는 것을 포함하여 구성된다.Wire rod manufacturing method of the present invention for achieving the above object, in weight%, C: 0.60 to 0.70%, Si: 1.2 to 1.6%, Mn: 0.60 to 0.90%, Cr: 0.60 to 0.90%, V: 0.15 to Billets containing 0.25%, P: 0.025% or less, S: 0.025% or less, Al: 0.010% or less, and non-combustible inclusions having a fraction of 0.05% or less are formed within 10 µm in a temperature range of 1,000 to 1,040 ° C. After reheating, hot-roll re-rolling is carried out under water cooling before the intermediate sand rolling under the condition that the intermediate sand rolling exit temperature is 900 to 950 ° C., and wound at a temperature of 700 to 770 ° C., and then the conveying speed is 1.5 to 2.0 m / sec. Furnace cooling rate is set to 0.7-1.0 degreeC / sec.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
본 발명의 고강도로 피로수명과 인성이 개선되는 엔진밸브스프링용 선재를 제공하기 위하여, (1) 선재의 고강도화를 확보하기 위해 C의 함량을 높이고 합금원소인 V를 첨가하고 (2) 이러한 합금원소첨가로 피로수명의 저하를 막기 위해 비금속개재물의 분율 및 크기를 엄격히 제한하고, (3) 오스테나이트 결정립이 미세화되도록 제반 제조조건을 최적화하여 인성을 개선하는데, 그 특징이 있다. 이러한 본 발명을 강성분과 제조조건으로 구분하여 설명한다.In order to provide an engine valve spring wire rod with improved fatigue life and toughness due to the high strength of the present invention, (1) to increase the content of C and add an alloying element V to secure the high strength of the wire rod, and (2) such an alloy element. In order to prevent fatigue life by addition, the fraction and size of the non-metallic inclusions are strictly limited, and (3) the toughness is improved by optimizing all manufacturing conditions so that the austenite grains can be miniaturized. The present invention will be described by dividing it into steel components and manufacturing conditions.
[강성분][Steel Ingredients]
상기 탄소(C)는 소입, 소려에 의해 요구되는 고강도를 확보하기 위해 0.60중량%이(이하, 단지 '%'라 함)상 첨가하나 0.70% 이상에서는 고강도화에 따른 인성확보가 어렵고, 소입시 판상마르텐사이트의 생성으로 인하 소입균열(Crack)발생이 용이하므로 0.60∼0.70%로 첨가한다.The carbon (C) is added to 0.60% by weight (hereinafter, only referred to as '%') in order to secure the high strength required by quenching and consideration, but at 0.70% or more, it is difficult to secure toughness due to high strength, Since martenite is easily generated due to the generation of martensite, it is added at 0.60 to 0.70%.
상기 규소(Si)는 페라이트에 고용되어 모재의 강도를 향상시키고 변형저항성을 높이는 역할을 하는데, 이를 위해 1.2%이상 첨가하나 1.6% 이상에서는 표면탈탄발생이 커서 피로수명의 급격한 저하 가능성이 크므로 1.2∼1.6%로 첨가한다.The silicon (Si) is dissolved in ferrite to improve the strength of the base material and to increase the deformation resistance. To this end, 1.2% or more is added. However, in 1.6% or more, the surface decarburization is large, which greatly increases the fatigue life. It is added at -1.6%.
상기 망간(Mn)은 소입성에 의한 강도를 확보하기 위해 0.60%이상 첨가하나 0.90%이상으로 첨가하는 경우 인성이 저하되므로 0.60∼0.90%로 첨가한다.The manganese (Mn) is added at 0.60% or more in order to secure strength due to quenchability, but when added at 0.90% or more, the toughness is decreased, so it is added at 0.60 to 0.90%.
상기 크롬(Cr)은 고강도의 확보를 위한 충분한 소입효과를 위해 0.60%이상 첨가하나 0.90%이상에서는 소재의 변형저항성을 저하시키므로 0.60∼0.90%로 첨가한다.The chromium (Cr) is added at 0.60% or more for sufficient hardening effect to secure high strength, but at 0.90% or more, it is added at 0.60 to 0.90% because it lowers the deformation resistance of the material.
상기 바나듐(V)은 석출강화 효과를 위해 0.15%이상 첨가하나 0.25% 이상에서는 바나듐이 석출하여 강도향상에 기여하는 석출물의 양보다는 모재에 고용되는 양이 증가하여 그 효과가 포화될 뿐 아니라, 오스테나이트 열처리시 모재에 용해되지 않은 조대한 합금 탄화물양이 증가하여 비금속개재물과 같은 작용을 하여서 피로수명을 저하시키므로 0.15∼0.25%로 첨가한다.The vanadium (V) is added to 0.15% or more for the precipitation strengthening effect, but in 0.25% or more, the amount of solid solution dissolved in the base material increases rather than the amount of precipitates contributing to the increase in strength. In the heat treatment of nitrate, the amount of coarse alloy carbide which is not dissolved in the base metal increases, which acts like a non-metallic inclusion, thereby reducing the fatigue life. Therefore, it is added at 0.15∼0.25%.
상기 인(P)과 황(S)은 각각 0.025% 이하로 첨가하는 것이 바람직한데, 그 이유는인의 경우 결정입계에 편석되어 인성을 저하시키기 때문이고, 황의 경우 유화물을 형성시키기 때문이다. 따라서, 일반적인 제강공정에서 인과 황을 가장 엄격하게 제어할 수 있는 수준인 0.025%로 제한한다.The phosphorus (P) and sulfur (S) is preferably added at 0.025% or less, respectively, because phosphorus segregates at grain boundaries to reduce toughness, and sulfur forms emulsions. Therefore, in the general steelmaking process, phosphorus and sulfur are limited to 0.025%, the most strictly controllable level.
상기 알루미늄(Al)은 제강부원료의 투입에 의해 용강중으로 혼입되는데, 그 혼입양이 0.010%이상이 되는 경우 용강중의 산소와 결합하여 알루미나계 개재물의 크기가 10㎛를 초과할 가능성이 높아지므로 0.010%이하로 제한한다.The aluminum (Al) is mixed into the molten steel by the input of steelmaking secondary raw materials, when the mixing amount is more than 0.010%, it is more likely that the size of the alumina inclusions exceeds 10㎛ by combining with oxygen in the molten steel 0.010% It limits to the following.
상기와 같이 조성되는 빌렛에 10㎛이내의 비연성 개재물이 0.05%이내의 분율로 형성되는 것이 좋다. 이는 선재가 고강도의 특성을 갖고 있었도 고응력의 작용하면 개재물에 의해 피로수명이 저하되기 때문에 고강도의 특성에 따른 피로수명을 확보하기 위해서이다. 여기서 비연성 개재물은 대부분 Al2O3계 개재물이고 일부 SiO2계 개재물을 의미한다.It is preferable that the non-combustible inclusions within 10 μm are formed at a fraction within 0.05% on the billet formed as described above. This is to secure the fatigue life according to the characteristics of the high strength because the fatigue life of the wire is reduced by the inclusions even if the wire has a high strength characteristics. Herein, non-flammable inclusions are mostly Al 2 O 3 -based inclusions and mean some SiO 2 -based inclusions.
이러한 비연개재물의 분율 및 크기는 제강조건에 따라 달라지는데, 이는 제강조건을 적절히 설정하면 달성된다. 일례로, 본 발명의 일실시예에서는 전로 취련종점의 탄소를 0.20∼0.35%로 하고 레이들로 출강하여 염기도(CaO/SiO2)가 0.95∼1.05로 하는 조건으로 정련한 용강을 연속주조함으로써, 비연성 개재물의 분율 및 크기를 요구수준으로 관리할 수 있었다. 그 이유는 첫째, 전로 취련종점의 탄소를 하향화(C:0.20∼0.35%)함에 따라 산소의 용해도가 낮아지고 결국, 비금속개재물의형성원인 산소가 적어져 비금속개재물의 생성이 억제되며, 둘째, 슬래그의 염기도를 0.95∼1.05로 조정하면 슬래그의 유동성이 최상으로 되어 개재물의 포집능이 극대화되기 때문이다. 여기서, 비연성 개재물의 분율은, 빌렛에서 단위시야(100배 확대, 200시야 이상)내 개재물 점유비를 계산한 것이다.The fraction and size of these non-lead inclusions depend on the steelmaking conditions, which are achieved by properly setting the steelmaking conditions. For example, in one embodiment of the present invention by continuously casting a molten steel refined under the condition that the carbon at the converter termination point is 0.20 to 0.35% and the steel is laid down with a ladle and the basicity (CaO / SiO 2 ) is 0.95 to 1.05. The fraction and size of non-flammable inclusions could be managed at the required level. The reason for this is as follows: First, as the carbon at the termination point of the converter is lowered (C: 0.20 to 0.35%), the solubility of oxygen is lowered, and as a result, the oxygen, which is a source of formation of nonmetallic inclusions, is reduced, thereby suppressing the formation of nonmetallic inclusions. If the basicity of is adjusted to 0.95 to 1.05, the fluidity of the slag is the best, and the trapping ability of the inclusions is maximized. Here, the fraction of non-combustible inclusions calculates the occupancy ratio of inclusions in a unit field of view (100 times magnification, 200 fields or more) by billet.
[제조조건][Production conditions]
상기와 같이 조성되는 빌렛으로 선재를 제조하는 방법은 도 1의 선재압연공정을 통해 설명한다. 빌렛을 가열로에서 1,000-1040℃의 온도범위로 재가열하는 것이 바람직한데, 그 이유는 선재가열로 온도가 1,000℃이하인 경우 온도가 낮아서 선재압연이 어려고 1,040℃이상인 경우 고규소강으로 표면탈탄이 발생하기 때문이다.The method of manufacturing the wire rod with the billet formed as described above will be described through the wire rod rolling process of FIG. 1. It is preferable to reheat the billet in the temperature range of 1,000-1040 ℃ in the heating furnace, because the wire degassing occurs in high-silicon steel when the temperature is lower than 1,000 ℃ due to the wire heating. Because.
상기와 같이 재가열하고 이어 조압연, 중간사상압연, 사상압연으로 이루어지는 선재압연하는데, 본 발명에서는 중간사상압연 출측온도의 제어로 오스테나이트 결정립의 미세화를 도모한다. 구체적으로 중간사상압연의 출측온도는 900∼950℃로 하는데, 그 이유는 900℃미만의 경우 온도가 낮아 사상압연이 어렵고 950℃를 초과한 경우는 오스테나이트 입도(AGS)의 미세화가 불가능하기 때문이다. 중간사상압연의 출측온도의 제어는 중간사상압연전에 인위적으로 냉각하여 조절하여야 한다. 왜냐하면, 중간사상압연동안에 소성변형열에 의해 소재온도가 증가하므로 이 소성변형열을 감안하여 중간사상압연 출측온도가 900∼950℃가 되도록 사전에 냉각하여 중간사상압연을 행하면 된다. 본 발명에서는 중간사상압연전에 설치된 수냉각장치에서 수냉각(Pre-cooling)하여 중간사상압연 출측온도를 제어하였다.The wire is reheated as described above, followed by wire rolling consisting of rough rolling, intermediate sand rolling, and filament rolling. In the present invention, the austenitic grains are refined by controlling the intermediate sand rolling exit temperature. Specifically, the exit temperature of intermediate sand rolling is set to 900 to 950 ° C., because the temperature is low at temperatures lower than 900 ° C., which makes it difficult to finish the rolling. If the temperature exceeds 950 ° C., the austenite grain size (AGS) cannot be refined. to be. Control of the exit temperature of intermediate rolling must be controlled by artificial cooling before intermediate rolling. Because the temperature of the material increases due to the plastic deformation heat during the intermediate sand rolling, in consideration of the heat of plastic deformation, the intermediate sand rolling may be cooled in advance so that the intermediate sand rolling side temperature is 900 to 950 ° C. In the present invention, water cooling (pre-cooling) in the water cooling apparatus installed before the intermediate sand rolling to control the intermediate sand rolling side temperature.
상기와 같이 선재압연한 다음, 700-770℃의 온도범위에서 권취하는 것이 바람직하다. 그 이유는 700℃미만에서는 변태개시온도가 낮아 마르텐사이트발생영역을 통과하여 양호한 조직의 확보가 불가하고, 770℃를 초과할 경우는 급냉에 의한 마르텐사이트가 발생되기 때문이다.After the wire is rolled as described above, it is preferable to wind in a temperature range of 700-770 ℃. The reason is that below 700 ° C, the transformation start temperature is low, so that it is impossible to secure a good structure through the martensite generation region, and when it exceeds 770 ° C, martensite is generated by quenching.
상기와 같이 권취한 다음 냉각속도를 0.7-1.0℃/sec로 하는 것이 바람직한데, 그 이유는 1.0℃/sec 초과시는 급냉에 의해 마르텐사이트 발생영역을 지나기 때문이며, 0.7℃/sec 미만일 경우는 공냉대 구간내에서 변태완료가 불가능하기 때문이다.After winding as described above, the cooling rate is preferably 0.7-1.0 ° C./sec, because when it exceeds 1.0 ° C./sec, it passes through the martensite generation zone by quenching. This is because metamorphosis is not possible within the interval.
상기와 같이 냉각속도는 권취된 선재의 이송속도를 1.5-2.0m/sec로 하여 확보한다. 이송속도가 1,5m/min 이하에서는 냉각속도가 0.7℃/sec이상을 확보할 수 없으며, 2.0m/min이상의 속도에서는 선재의 겹침에 의한 현열의 효과가 미흡하여 냉각속도가 1.0℃/sec를 초과하기 때문이다.As described above, the cooling rate is secured by transferring the wound wire to 1.5-2.0 m / sec. If the feed speed is less than 1,5m / min, the cooling rate cannot secure more than 0.7 ℃ / sec. If the speed is more than 2.0m / min, the effect of sensible heat due to the overlapping of wire rods is insufficient. Because it exceeds.
이하, 본 발명을 실시예를 통해 구체적으로 설명한다.Hereinafter, the present invention will be described in detail through examples.
[실시예]EXAMPLE
전로 취련종점의 탄소를 0.20∼0.35%로 하고 레이들로 출강하여 염기도(CaO/SiO2)가 0.95∼1.05로 하는 조건으로 정련한 용강을 연속주조하여 아래 표 1과 같이 조성되는 250x330mm의 블룸을 얻고 이를 160㎜의 빌렛으로 강편압연한 다음, 이 빌렛을 아래 표 2의 조건으로 압연하여 직경이 8mm의 선재(wire rods)로 제조한 후, 신선하여 제품선(wire)으로 제조한 다음, 강도를 측정하고 그 결과를 표 2에 나타내었다. 한편, 종래강의 경우는 전로취련종점이 약 0.06%이고 염기도는 특별히 관리하지 않고 정련한 용강을 연속주조하여 얻은 블룸으로 선재를 제조한 것이다.The carbon of the converter termination point is 0.20 to 0.35%, and the steel is cast in a ladle to continuously cast molten steel refined under the condition of basicity (CaO / SiO 2 ) of 0.95 to 1.05. The steel sheet was rolled into a billet of 160 mm, and then rolled under the conditions of Table 2 below to manufacture wire rods having a diameter of 8 mm, and then freshly manufactured into a wire, followed by strength. Was measured and the results are shown in Table 2. On the other hand, in the case of conventional steel, the converter termination point is about 0.06%, and basicity is not produced, and wire rods are manufactured by BLUM obtained by continuous casting of refined molten steel.
화학성분(단위:중량%)Chemical composition (unit: weight%)
구분division CC SiSi MnMn PP SS CrCr VV AlAl 비연성개재물Non-flammable inclusions
크기size 분율Fraction
발명강1Inventive Steel 1 0.610.61 1.251.25 0.700.70 0.0200.020 0.0100.010 0.700.70 0.200.20 0.0080.008 9㎛9㎛ 0.030.03
발명강2Inventive Steel 2 0.670.67 1.321.32 0.800.80 0.0190.019 0.0120.012 0.820.82 0.190.19 0.0090.009 9㎛9㎛ 0.020.02
종래강AConventional Steel A 0.53* 0.53 * 1.221.22 0.710.71 0.0230.023 0.0090.009 0.710.71 -* - * 0.020* 0.020 * 20㎛* 20 μm * 0.030.03
종래강BConventional Steel B 0.57* 0.57 * 1.341.34 0.810.81 0.0200.020 0.0120.012 0.810.81 -* - * 0.021* 0.021 * 21㎛* 21 μm * 0.040.04
*는 본 발명의 조건을 벗어나는 것임* Is outside the conditions of the present invention
구분division 제조조건Manufacture conditions 선재의 성질Wire Rod Properties
중간사상출측온도Middle frost exit temperature 권취온도Coiling temperature 냉각속도Cooling rate 제품선강도(kg/mm2)Product strength (kg / mm 2 ) 피로수명(회)Fatigue Life (times) AGSAGS 조직group
발명재 1Invention 1 발명강1Inventive Steel 1 900℃900 ℃ 738℃738 ℃ 0.8m/sec0.8 m / sec 230230 1.7x107 1.7 x 10 7 5㎛5㎛ 펄라이트Pearlite
발명재 2Invention Material 2 발명강2Inventive Steel 2 945℃945 ℃ 750℃750 ℃ 1.0m/sec1.0 m / sec 221221 1.2x107 1.2 x 10 7 15㎛15 μm 펄라이트Pearlite
종래재 AConventional material A 종래강1Conventional Steel 1 1002℃* 1002 ℃ * 790℃* 790 ℃ * 1.9m/sec* 1.9 m / sec * 187187 1.1x107 1.1 x 10 7 19㎛19 μm 마르텐사이트Martensite
종래재 BConventional material B 종래강2Conventional Steel 2 1051℃* 1051 ℃ * 792℃* 792 ℃ * 2.4m/sec* 2.4 m / sec * 191191 1.2x107 1.2 x 10 7 26㎛26 μm 마르텐사이트Martensite
*는 본 발명의 조건을 벗어나는 것임* Is outside the conditions of the present invention
표 1 및 2에 나타난 바와 같이, 종래재(A,B)는 중간사상 출측온도가 950℃를 초과하여 오스테나이트 입도(AGS)의 미세화가 불가능한 상태에서 770℃의 고온에서 권취하고 냉각속도도 빨라서 급냉에 의해 마르텐사이트 조직이 얻어졌다. 이에 반해, 본 발명의 강을 적절한 조건으로 제조한 발명재(1,2)는 펄라이트 조직이 얻어졌으며, 피로수명도 우수하고 제품선강도 또한 우수함을 알 수 있었다.As shown in Tables 1 and 2, the conventional materials (A, B) are wound at a high temperature of 770 ℃ in the state that the medium exit exit temperature exceeds 950 ℃, it is impossible to refine the austenite grain size (AGS) Martensite structure was obtained by quenching. On the contrary, it was found that the inventive materials (1, 2), which produced the steel of the present invention under appropriate conditions, had a pearlite structure, excellent fatigue life, and excellent product line strength.
상술한 바와 같이, 본 발명은 고강도 확보를 위한 적절한 합금성분 갖으면서 일정크기의 비연성개재물을 일정분율로 형성한 강편을 적절한 조건으로 제조하여 선재의 강도와 오스테나이트 결정립 미세화에 의한 인성확보로 피로수명이 개선되는 선재를 제공하는 유용한 효과가 있다.As described above, the present invention is manufactured by producing a steel sheet having a certain fraction of non-combustible inclusions of a certain size while having a suitable alloy component for securing high strength under appropriate conditions to ensure the fatigue life by securing the strength of the wire rod and toughness due to the refinement of austenite grains There is a useful effect of providing this improved wire rod.

Claims (1)

  1. 전로 취련종점의 탄소를 0.20∼0.35%로 하고 레이들로 출강하여 염기도(CaO/SiO2)를 0.95∼1.05로 하는 조건으로 정련하고, 연속주조한 후, 중량%로, C:0.60∼0.70%, Si:1.2∼1.6%, Mn:0.60∼0.90%, Cr:0.60∼0.90%, V:0.15∼0.25%, P:0.025%이하, S:0.025%이하, Al:0.010%이하를 함유하고, 10㎛이내의 크기를 갖는 비연성개재물이 0.05%이내의 분율로 형성되어 있는 빌렛을 얻는 단계,The carbon at the converter termination point was 0.20 to 0.35%, and the steel was laid down in a ladle, and refined under the condition of basicity (CaO / SiO 2 ) at 0.95 to 1.05, and after continuous casting, at a weight% of C: 0.60 to 0.70% , Si: 1.2 to 1.6%, Mn: 0.60 to 0.90%, Cr: 0.60 to 0.90%, V: 0.15 to 0.25%, P: 0.025% or less, S: 0.025% or less, Al: 0.010% or less, and Obtaining a billet in which a non-flammable inclusion having a size within 10 μm is formed at a fraction within 0.05%,
    이 빌렛을 1,000∼1,040℃의 온도범위로 재가열한 다음, 중간사상압연전에 수냉을 통해 중간사상압연 출측온도를 900∼950℃로 하는 조건으로 열간선재압연하고, 700∼770℃의 온도에서 권취한 다음, 냉각속도를 0.7∼1.0℃/sec로 하는 것을 포함하여 이루어지는 피로수명이 우수한 고강도 엔진밸브 스프링용 선재의 제조방법.The billet was reheated to a temperature range of 1,000 to 1,040 ° C, and then hot-rolled at a temperature of 700 to 770 ° C, followed by water cooling before the intermediate rolling, to condition that the exiting temperature of intermediate rolling was 900 to 950 ° C. Next, the manufacturing method of the wire rod for high strength engine valve spring excellent in fatigue life which consists of setting a cooling rate to 0.7-1.0 degreeC / sec.
KR10-1998-0057103A 1998-12-22 1998-12-22 A method of manufacturing high strength wire rods having superior fatigue life for engine valve-spring KR100398387B1 (en)

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KR101091934B1 (en) 2004-03-13 2011-12-09 주식회사 포스코 Method for manufacturing the wire rod of high silicone steel containing fine inclusion

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KR100723187B1 (en) * 2005-12-26 2007-05-29 주식회사 포스코 Steel for high strength suspension spring having excellent impact properties and method of producing high strength suspension spring by using the same

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JPS59170241A (en) * 1983-03-18 1984-09-26 Daido Steel Co Ltd Steel for high-strength and high-toughness spring
JPH046211A (en) * 1990-04-25 1992-01-10 Kobe Steel Ltd Production of steel wire for spring having excellent fatigue strength
JPH05214484A (en) * 1992-02-03 1993-08-24 Daido Steel Co Ltd High strength spring steel and its production
JPH06122052A (en) * 1992-10-14 1994-05-06 Nippon Steel Corp Continuous casting method for steel
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JPS59170241A (en) * 1983-03-18 1984-09-26 Daido Steel Co Ltd Steel for high-strength and high-toughness spring
JPH046211A (en) * 1990-04-25 1992-01-10 Kobe Steel Ltd Production of steel wire for spring having excellent fatigue strength
JPH05214484A (en) * 1992-02-03 1993-08-24 Daido Steel Co Ltd High strength spring steel and its production
JPH06122052A (en) * 1992-10-14 1994-05-06 Nippon Steel Corp Continuous casting method for steel
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101091934B1 (en) 2004-03-13 2011-12-09 주식회사 포스코 Method for manufacturing the wire rod of high silicone steel containing fine inclusion

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