KR101281236B1 - Method for Manufacturing Pb-Free Free-Cutting Steel Wire Rod - Google Patents
Method for Manufacturing Pb-Free Free-Cutting Steel Wire Rod Download PDFInfo
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- KR101281236B1 KR101281236B1 KR1020090132109A KR20090132109A KR101281236B1 KR 101281236 B1 KR101281236 B1 KR 101281236B1 KR 1020090132109 A KR1020090132109 A KR 1020090132109A KR 20090132109 A KR20090132109 A KR 20090132109A KR 101281236 B1 KR101281236 B1 KR 101281236B1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
- B21B1/18—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section in a continuous process
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/46—Roll speed or drive motor control
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/58—Roll-force control; Roll-gap control
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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
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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
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Abstract
본 발명은 친환경 무연 쾌삭강 선재를 제조하는 방법에 관한 것으로서, 무연 쾌삭강 빌렛의 선재압연조건을 적절히 제어함으로써 선재압연 시 표면결함의 발생을 억제하여 표면품질이 우수한 무연 쾌삭강 선재를 제조할 수 있는 방법을 제공하는 것이다.The present invention relates to a method for manufacturing an environment-friendly lead-free free-cutting steel wire, by controlling the wire rolling conditions of the lead-free free-cutting steel billet appropriately to suppress the occurrence of surface defects during wire-rolling to produce a lead-free free-cutting steel wire with excellent surface quality To provide.
본 발명은 무연 쾌삭강 빌렛을 선재압연공정에서 가열, 조압연, 중간조압연, 중간사상압연 및 사상압연하여 선재를 제조하는 방법으로서, The present invention is a method for producing a wire rod by heating, rough rolling, intermediate rough rolling, intermediate sand rolling and finishing rolling in a wire-free free-cut steel billet process,
상기 선재압연공정의 사상압연 시 사상압연기의 최종스탠드에서의 소재 유출량 속도 차이(ΔV=VExit - VEntry )가 4.7(m/s)미만이 되도록 최종 스탠드에서의 압하량을 제어하고; 그리고 Controlling the amount of rolling down at the final stand such that a difference in material flow rate (ΔV = V Exit -V Entry ) at the final stand of the finishing mill during finishing rolling of the wire rolling process is less than 4.7 (m / s); And
상기 선재압연공정의 사상압연 시 초당 누적 변형(strain)의 절대값이 4.1미만이 되도록 사상압연기의 압하량을 제어하는 것을 특징으로 하는 무연 쾌삭강 선재의 제조방법을 그 요지로 한다.A method of manufacturing a lead-free free-cutting steel wire, characterized in that the rolling reduction of the finishing mill is controlled so that the absolute value of the cumulative strain per second during finishing rolling in the wire rod rolling process is less than 4.1.
무연, 쾌삭강, 표면결함, 선재 Lead free, Free cutting steel, Surface defect, Wire rod
Description
본 발명은 친환경 무연 쾌삭강 선재를 제조하는 방법에 관한 것으로서, 보다 상세하게는 무연 쾌삭강 빌렛의 선재압연공정에서 표면결함의 발생을 억제하여 표면품질이 우수한 선재를 제조할 수 있는 무연 쾌삭강 선재의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing an environmentally friendly lead-free free-cutting steel wire, and more particularly, to a method of manufacturing a lead-free free-cutting steel wire that can produce wire with excellent surface quality by suppressing occurrence of surface defects in the wire-rolling process of lead-free free-cutting steel billets. It is about.
쾌삭강은 기본적으로 우수한 절삭성을 지니며, 이러한 절삭성을 부여하기 위하여 통상적으로, 비금속성 개재물을 강중에 분포시키거나, 여기에 추가로 복합질화물, 복합탄화물, 금속개재물, 단독으로 존재하는 저융점원소 등을 분포시키고 있다. Free-cutting steels basically have excellent machinability, and in order to impart such machinability, a non-metallic inclusion is usually distributed in the steel, or a composite nitride, a composite carbide, a metal inclusion, a low melting point element alone, etc. Is distributed.
쾌삭강에서 이용하는 비금속개재물중의 대표적인 것이 MnS이며, 절삭성은 MnS의 크기, 형상, 분포 등을 제어함으로써 얻어진다. A typical nonmetallic inclusion used in free cutting steel is MnS, and machinability is obtained by controlling the size, shape, distribution, and the like of MnS.
특히, 친환경 무연(Pb-free)쾌삭강은 절삭 가공시 가공품질 및 칩처리성 향상 등을 위하여 저융점 금속인 Bi, Sn 을 추가로 첨가한 강종으로서 환경 유해 원 소인 Pb를 첨가하지 않으면서 유황 쾌삭강 보다 우수한 절삭 가공성을 갖는다.In particular, Pb-free free-cutting steel is a steel grade with the addition of low melting point metals Bi and Sn to improve processing quality and chip processing during cutting, and free sulfur-free cutting without adding environmentally harmful element Pb. It has better cutting workability.
그러나, 무연 쾌삭강은 우수한 절삭 가공성을 보이는 반면, 무연 쾌삭강을 이용하여 선재를 제조하는 경우에는 선재압연공정에서 이들 개재물 및 저융점 금속등에 의해 표면결함이 발생되는 문제점이 있다. However, while lead-free free cutting steel shows excellent cutting processability, when wire rods are manufactured using lead-free free cutting steel, surface defects are caused by these inclusions and low melting point metals in the wire rolling process.
따라서, 무연 쾌삭강을 이용한 선재의 제조시 발생되는 표면결함을 충분히 억제할 수 있는 선재압연기술이 요구되고 있다. Accordingly, there is a demand for a wire rod rolling technology capable of sufficiently suppressing surface defects generated during the production of wire rods using lead-free free cutting steel.
본 발명은 무연 쾌삭강 빌렛의 선재압연조건을 적절히 제어함으로써 선재압연공정에서 표면결함의 발생을 억제하여 표면품질이 우수한 무연 쾌삭강 선재를 제조할 수 있는 무연 쾌삭강 선재의 제조방법을 제공하는 것이다. The present invention provides a method for producing a lead-free free-cutting steel wire rod that can produce lead-free free-cutting steel wire having excellent surface quality by appropriately controlling wire rolling conditions of lead-free free steel billets.
이하, 본 발명에 대하여 설명한다. Hereinafter, the present invention will be described.
본 발명은 무연 쾌삭강 빌렛을 선재압연공정에서 가열, 조압연, 중간조압연, 중간사상압연 및 사상압연하여 선재를 제조하는 방법으로서, The present invention is a method for producing a wire rod by heating, rough rolling, intermediate rough rolling, intermediate sand rolling and finishing rolling in a wire-free free-cut steel billet process,
상기 선재압연공정의 사상압연 시 사상압연기의 최종스탠드에서의 소재 유출량 속도 차이(ΔV=VExit - VEntry )가 4.7(m/s)미만이 되도록 최종 스탠드에서의 압하량을 제어하고; 그리고 Controlling the amount of rolling down at the final stand such that a difference in material flow rate (ΔV = V Exit -V Entry ) at the final stand of the finishing mill during finishing rolling of the wire rolling process is less than 4.7 (m / s); And
상기 선재압연공정의 사상압연 시 초당 누적 변형(strain)의 절대값이 4.1미만이 되도록 사상압연기의 압하량을 제어하는 것을 특징으로 하는 무연 쾌삭강 선재의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a lead-free free cutting steel wire, characterized in that the rolling reduction of the finishing mill is controlled so that the absolute value of the accumulated strain per second during the rolling of the wire rod is less than 4.1.
본 발명에 바람직하게 적용될 수 있는 무연 쾌삭강 빌렛으로는 Lead-free free-cutting steel billets that can be preferably applied to the present invention
중량%로 탄소(C): 0.03~0.30%, 실리콘(Si): 0.01~0.30%, 망간(Mn): 0.2~2.0%, 인(P): 0.02~0.10%, 황(S): 0.06~0.45%, 비스무스(Bi): 0.04~0.20%, 주석(Sn): 0.04~0.20%, 보론(B): 0.001~0.015%, 질소(N): 0.001~0.010%, 전산소(T[O]): 0.002~0.025%, 알루미늄(Al): 10ppm이하 및 칼슘(Ca): 10ppm이하, 잔부 Fe 및 불가피한 불순물로 이루어진 무연 쾌삭강 빌렛을 들 수 있다.By weight% Carbon (C): 0.03-0.30%, Silicon (Si): 0.01-0.30%, Manganese (Mn): 0.2-2.0%, Phosphorus (P): 0.02-0.10%, Sulfur (S): 0.06- 0.45%, Bismuth (Bi): 0.04-0.20%, Tin (Sn): 0.04-0.20%, Boron (B): 0.001-0.015%, Nitrogen (N): 0.001-0.010%, Oxygen (T [O] ): 0.002% to 0.025%, aluminum (Al): 10 ppm or less and calcium (Ca): 10 ppm or less, lead-free free-cutting steel billets composed of residual Fe and unavoidable impurities.
본 발명에 의하면, 무연 쾌삭강 빌렛의 선재압연조건을 적절히 제어하여 선재압연공정에서 표면결함의 발생을 억제할 수 있으므로, 표면품질이 우수한 친환경 무연 쾌삭강 선재를 보다 경제적으로 제공할 수 있다.According to the present invention, it is possible to suppress the occurrence of surface defects in the wire rod rolling process by appropriately controlling the wire rolling conditions of the lead-free free-cutting steel billet, it is possible to more economically provide an eco-friendly lead-free free-cutting steel wire with excellent surface quality.
본 발명에 대하여 상세히 설명한다.The present invention will be described in detail.
본 발명자들은 무연 쾌삭강 빌렛의 선재압연공정에서 발생되는 표면결함을 억제하기 위하여 연구 및 실험을 행한 결과, 선재압연공정에서의 표면결함은 무연 쾌삭강의 선재압연공정에서 사상압연기의 최종스탠드에서의 소재 유출량 속도 차이(ΔV)(ΔV=VExit - VEntry; VExit: 소재 출측 속도, VEntry: 소재 입측 속도) 및 사상압연 시 초당 누적 변형(strain)의 절대값이 소정의 값 즉, 임계값 미만인 경우에 발생되지 않음을 확인하고, 이러한 연구 및 실험결과를 고려하여 본 발명을 완성하게 이른 것이다.The present inventors have conducted research and experiment to suppress the surface defects generated in the wire rod rolling process of lead-free free-cutting steel billet, the surface defects in the wire rod rolling process is the material outflow in the final stand of the finishing mill in the wire rod rolling process of lead-free free steel Velocity difference (ΔV) (ΔV = V Exit -V Entry ; V Exit : material exit speed, V Entry : material entrance speed) and the absolute value of the cumulative strain per second during finishing rolling are below a predetermined value, i.e. It is confirmed that it does not occur in the case, and completed the present invention in consideration of the results of these studies and experiments.
본 발명에 적용되는 무연 쾌삭강 빌렛의 조성은 특별히 한정되는 것은 아니지만, 본 발명에 바람직하게 적용될 수 있는 무연 쾌삭강의 조성에 대하여 설명한다.Although the composition of the lead-free free cutting steel billet applied to the present invention is not particularly limited, the composition of the lead-free free cutting steel that can be preferably applied to the present invention will be described.
탄소(C) : 0.03~0.30 중량% Carbon (C): 0.03 ~ 0.30 wt%
탄소는 표면조도 및 기계적 성질을 확보하기 위하여 0.03중량% 이상 첨가되어야 한다. 그러나, 탄소의 함량이 0.30 중량%를 초과하게 되면 경한 펄라이트 조직의 증가로 피삭성의 감소를 초래한다.Carbon should be added at least 0.03% by weight to ensure surface roughness and mechanical properties. However, when the content of carbon exceeds 0.30% by weight, the increase in light pearlite structure causes a decrease in machinability.
따라서, 탄소(C)의 함량은 0.03~0.30 중량%로 제한하는 것이 바람직하다.Therefore, the content of carbon (C) is preferably limited to 0.03 to 0.30% by weight.
실리콘(Si) : 0.01-0.30 중량% Silicon (Si): 0.01-0.30 wt%
실리콘은 탈산제로 작용하여 SiO2를 생성하고, 고속 절삭시 열적 확산에 의한 공구의 마모를 최소화 할 수 있는 저융점 복합 산화성 개재물을 형성하기 위하여 0.01 중량% 이상이 첨가되어야 한다. 그러나, 실리콘의 함량이 0.30 중량%를 초과하면 고융점 개재물 또는 SiO2 단독 개재물이 형성되어 오히려 공구의 마모 속도가 현저히 커진다.Silicon should be added at least 0.01% by weight to act as a deoxidizer to produce SiO 2 and form a low melting complex oxidative inclusion that can minimize tool wear due to thermal diffusion during high speed cutting. However, when the content of silicon exceeds 0.30% by weight, high melting point inclusions or SiO 2 alone inclusions are formed, rather the wear rate of the tool is significantly increased.
따라서, 실리콘(Si)의 함량은 0.01-0.30 중량%로 제한하는 것이 바람직하다.Therefore, the content of silicon (Si) is preferably limited to 0.01-0.30% by weight.
망간(Mn): 0.2-2.0 중량% Manganese (Mn): 0.2-2.0 wt%
망간은 MnS 개재물을 형성하여 황(S)에 의한 적열 취성을 방지하고, 또한 탈산제로 작용하여 MnS개재물의 핵으로도 작용하는 MnO를 형성하는 성분으로서 이러한 작용을 발휘하기 위해서는 망간은 0.2 중량% 이상 첨가하는 것이 바람직하다. Manganese forms MnS inclusions to prevent red brittleness due to sulfur (S), and also acts as a deoxidizer to form MnO which also acts as a nucleus of MnS inclusions. It is preferable to add.
그러나, 망간의 함량이 2.0 중량%을 초과하면 페라이트를 고용 강화시키므로 피삭성의 감소를 초래한다. However, if the content of manganese exceeds 2.0% by weight, the ferrite is hardened, resulting in a decrease in machinability.
따라서, 망간의 함량은 0.2-2.0 중량%로 제한하는 것이 바람직하다.Therefore, the content of manganese is preferably limited to 0.2-2.0% by weight.
인(P): 0.02-0.10 중량% Phosphorus (P): 0.02-0.10 wt%
인은 입계에 편석되어 피삭성을 향상시키는 성분으로서, 이를 위해서는 0.02 중량% 이상 함유되는 것이 바람직하나, 기계적 성질과 냉간 가공성을 확보하기 위해서는 0.10 중량%를 초과하지 않아야 한다.Phosphorus is segregated at grain boundaries to improve machinability. For this purpose, phosphorus is preferably contained in an amount of 0.02% by weight or more, but should not exceed 0.10% by weight in order to secure mechanical properties and cold workability.
따라서, 인(P)의 함량은 0.02-0.10 중량%로 제한하는 것이 바람직하다.Therefore, the content of phosphorus (P) is preferably limited to 0.02-0.10% by weight.
황(S): 0.06-0.45 중량% Sulfur (S): 0.06-0.45 wt%
황은 MnS 개재물을 형성하여 절삭 작업시 구성인선(built up edge)의 생성을 억제하여 절삭공구의 마모를 줄여주고 피삭재의 표면조도를 개선하는 역할을 한다. Sulfur forms MnS inclusions, which inhibits the creation of built up edges during cutting operations, thereby reducing wear of cutting tools and improving the surface finish of the workpiece.
이러한 목적을 위해 황은 0.06 중량% 이상 첨가되어야 한다. 그러나, 황의 양이 많아지면 저융점의 FeS 생성이 용이해져 고온 연성을 떨어뜨려 열간 압연이 어려워지기 때문에 0.45중량%를 초과하지 않아야 한다.Sulfur should be added at least 0.06% by weight for this purpose. However, when the amount of sulfur is large, it should not exceed 0.45% by weight because FeS of low melting point is easily produced and high temperature ductility is degraded, making hot rolling difficult.
따라서, 황의 함량은 0.06-0.45 중량% 로 제한하는 것이 바람직하다.Therefore, the content of sulfur is preferably limited to 0.06-0.45% by weight.
비스무스(Bi): 0.04-0.20 중량% Bismuth (Bi): 0.04-0.20 wt%
비스무스는 강재에 첨가되면 금속개재물로 단독 존재하거나 MnS 개재물에 붙어있는데, 절삭시 가공열에 의해 쉽게 용융되어 절삭 특성을 좋게 하고, 칩과 절삭 공구 사이에서 윤활 피막의 작용을 하여 마찰력을 감소시키고 절삭공구의 마모를 억제하는 작용을 한다. When bismuth is added to steel, it exists as a metal inclusion alone or adheres to MnS inclusions. It is easily melted by the processing heat during cutting to improve cutting characteristics, and acts as a lubricating film between chips and cutting tools to reduce friction and reduce cutting tools. It acts to suppress wear.
비스무스의 함량이 0.04 중량% 보다 적으면 피삭효과가 떨어지고, 반면에 0.20 중량%를 초과하면 주조성과 압연성에 좋지 않기 때문에 비스무스의 함량은 0.04-0.20중량%으로 제한하는 것이 바람직하다.If the content of bismuth is less than 0.04% by weight, the machining effect is inferior. On the other hand, if the content of bismuth is more than 0.20%, the content of bismuth is preferably limited to 0.04-0.20% by weight because it is not good for castability and rollability.
주석(Sn) : 0.04-0.20 중량% Tin (Sn): 0.04-0.20 wt%
주석은 납과 유사한 역할을 수행할 수 있는 원소이다. Tin is an element that can play a role similar to lead.
즉, 주석은 납이 강의 피삭성을 향상시키는 기구 중 하나인 액상 금속 취화와 동일한 역할을 수행할 수 있다. That is, tin may play the same role as liquid metal embrittlement, in which lead is one of the mechanisms for improving the machinability of steel.
구체적으로 이러한 현상은 주석이 페라이트 결정립계로 이동하여 편석되고 입계 결합에너지를 낮춤으로써 입계 파괴를 용이하게 함으로써 나타난다. Specifically, this phenomenon is shown by tin being segregated to ferrite grain boundaries and facilitating grain boundary fracture by lowering grain boundary binding energy.
따라서, 주석에 의한 피삭성 향상효과를 얻기 위해서는 0.04 중량% 이상의 주석이 첨가되어야 한다. Therefore, in order to obtain the machinability improvement effect by tin, 0.04 weight% or more of tin should be added.
그러나, 0.20 중량%를 초과하면 주조, 압연성에 유해한 결과를 초래할 수 있 으므로, 주석의 함량은 0.04-0.20 중량%로 제한하는 것이 바람직하다.However, the content of tin is preferably limited to 0.04-0.20% by weight since the content exceeding 0.20% by weight may cause harmful effects on casting and rolling properties.
보론(B): 0.001-0.015 중량% Boron (B): 0.001-0.015 wt%
보론은 오스테나이트 입계에 편석되어 결정립계를 강화시켜 고온 연성을 향상시킨다. 또한, 흑연을 함유한 강은 피삭성이 우수하다는 것이 알려져 있는데, 강 내부에서 보론이 질소와 반응하여 흑연과 유사한 결정구조와 물리적 특성을 지닌 질화붕소(Boron nitride)(BN)로 생성되면, 흑연을 함유한 강과 동일한 피삭성 향상효과를 기대할 수 있게 된다. Boron segregates at the austenite grain boundaries to strengthen grain boundaries and improve high temperature ductility. In addition, it is known that steel containing graphite is excellent in machinability. When boron reacts with nitrogen in the steel to form boron nitride (BN) having a crystal structure and physical properties similar to that of graphite, graphite The same machinability improvement effect as steel containing can be expected.
보론은 0.001 중량% 미만에서는 그 첨가 효과가 미흡하여 0.001중량% 이상 첨가할 필요가 있으며, 반대로 0.015 중량%를 초과하여 첨가할 경우에는 더 이상 효과 상승을 기대할 수 없으며 오스테나이트 결정입계에 보론계 질화물의 석출로 인해 입계강도가 저하되어 열간 가공성이 저하될 수 있으므로 보론의 함량은 0.001-0.015 중량%로 제한하는 것이 바람직하다.When the boron is less than 0.001% by weight, the effect of addition is insufficient, and thus it is necessary to add more than 0.001% by weight.On the contrary, when it is added in excess of 0.015% by weight, the effect can not be expected to increase any more, and the boron nitride at the austenite grain boundary Due to the precipitation of grain boundary strength may be lowered and hot workability may be lowered, the boron content is preferably limited to 0.001-0.015% by weight.
질소(N): 0.001-0.010 중량% Nitrogen (N): 0.001-0.010 wt%
질소는 보론과 함께 BN을 형성하기 위하여 0.001중량% 이상 첨가되어야 한다. Nitrogen should be added at least 0.001% by weight to form BN with boron.
그러나, 0.010중량%를 초과하면 오스테나이트 결정립계에 편석되는 유효 보론의 양을 감소시켜 입계 강화 효과를 떨어뜨린다.However, if it exceeds 0.010% by weight, the amount of effective boron segregated in the austenite grain boundary is reduced, which lowers the grain boundary strengthening effect.
따라서, 질소의 함량은 0.001-0.010 중량%로 제한하는 것이 바람직하다.Therefore, the content of nitrogen is preferably limited to 0.001-0.010% by weight.
전산소(T[O]) : 0.002-0.025 중량% Oxygen (T [O]): 0.002-0.025 wt%
산소는 열간 압연시의 MnS 개재물 연신에 의한 피삭성 저하를 방지하기 위해 0.002 중량% 이상 첨가될 것이 요구된다. 그러나, 절삭 가공시 MnS 개재물의 소성 변형능을 확보하기 위해서는 0.025중량%를 넘지 않아야 한다.Oxygen is required to be added at least 0.002% by weight in order to prevent machinability deterioration due to MnS inclusion stretching during hot rolling. However, in order to ensure the plastic deformation of the MnS inclusions during cutting, it should not exceed 0.025% by weight.
따라서, 전산소(T[O])의 함량은 0.002-0.025 중량%로 제한하는 것이 바람직하다.Therefore, the content of total oxygen (T [O]) is preferably limited to 0.002-0.025% by weight.
알루미늄(Al) 및 칼슘(Ca) : 각각 10ppm이하 Aluminum (Al) and Calcium (Ca): Less than 10ppm each
알루미늄 및 칼슘은 본 발명에서 강중에 형성되는 저융점 복합 산화성 개재물의 형성에 필요하지만, 의도적으로 첨가할 필요는 없으며 슬래그 등에서 자연스럽게 포함되는 양이면 충분하다. 이러한 알루미늄 및 칼슘은 10ppm 이하로 존재하는 것이 바람직하다.Aluminum and calcium are required for the formation of the low melting composite oxidative inclusions formed in the steel in the present invention, but need not be added intentionally, and an amount naturally contained in slag or the like is sufficient. Such aluminum and calcium are preferably present at 10 ppm or less.
이하, 무연 쾌삭강 빌렛을 사용하여 무연 쾌삭강 선재를 제조하는 방법에 대하여 설명한다.Hereinafter, the method of manufacturing a lead-free free cutting steel wire rod using a lead-free free cutting steel billet will be described.
본 발명에서는 선재압연공정에서 상기 빌렛을 가열, 조압연, 중간조압연, 중간사상압연 및 사상압연하여 무연 쾌삭강 선재를 제조한다.In the present invention, the billet is heated, rough rolling, intermediate rough rolling, intermediate sand rolling and finishing rolling to produce a lead-free free-cutting steel wire in the wire rod rolling process.
본 발명에 적용될 수 있는 빌렛의 크기는 통상 사용되는 크기이면, 어느 것 이나 가능하며, 대표적인 빌렛의 일례로는 160mm(폭) ⅹ 160mm(두께) ⅹ 10200mm(길이) 크기의 빌렛을 들 수 있다. The size of the billet which can be applied to the present invention can be any size as long as it is commonly used, and examples of the representative billet include a billet having a size of 160 mm (width) ⅹ 160 mm (thickness) ⅹ 10200 mm (length).
상기 빌렛은 선재압연공정에서 예를 들면, 1200℃ 이상, 바람직하게는 1200~1300℃의 고온에서 재가열된 후, 조압연, 중간조압연, 중간사상압연 및 사상압연의 연속압연을 통해 최종 선재 제품으로 생산된다. The billet is re-heated at a high temperature of, for example, 1200 ° C. or higher, preferably 1200-1300 ° C. in the wire rod rolling process, and then the final wire rod product is subjected to continuous rolling of rough rolling, intermediate rough rolling, intermediate sand rolling, and finishing rolling. Produced as
상기한 빌렛의 조압연, 중간조압연 및 중간사상압연은 특별히 한정되는 것은 아니며, 통상적인 방법에 따라 행하면 된다.The rough rolling, the intermediate rough rolling, and the intermediate sand rolling of the billet described above are not particularly limited, and may be performed according to a conventional method.
상기 빌렛의 조압연, 중간조압연 및 중간사상압연의 바람직한 일례로서는 조압연은 패스당 10~40%의 감면율로 2~10패스 압연하고, 중간조압연은 패스당 10~40%의 감면율로 4~10패스 압연하고, 그리고 중간사상압연은 패스당 10~40%의 감면율로 4~10패스 압연하는 것을 들수 있다.As a preferable example of rough rolling, intermediate rough rolling and intermediate sand rolling of the billet, rough rolling is rolled 2 to 10 passes at a reduction rate of 10 to 40% per pass, and intermediate rough rolling is performed at a reduction ratio of 10 to 40% per pass. Rolling of ~ 10 pass, and intermediate sand rolling is 4 to 10 pass rolling with a reduction rate of 10 to 40% per pass.
상기 사상압연은 패스당 10~40%의 감면율로 2~10패스 압연한다.The finishing rolling is rolled 2 to 10 passes at a reduction rate of 10 to 40% per pass.
그리고, 상기 사상압연에서는 사상압연기의 최종스탠드에서의 소재 유출량 속도 차이(ΔV=VExit - VEntry ; VExit: 소재 출측 속도, VEntry: 소재 입측 속도)가 4.7(m/s)미만이 되도록 최종 스탠드에서의 압하량을 제어하여야 한다.In the finishing rolling, the difference in material flow rate in the final stand of the finishing mill (ΔV = V Exit -V Entry ; V Exit : material exit speed, V Entry : material entrance speed) is less than 4.7 (m / s). The amount of reduction in the final stand shall be controlled.
소재 유출량 속도 차이(ΔV=VExit - VEntry )는 VExit{1- 1/(1+감면율/100)} 로 나타낼 수 있다.The material flow rate difference (ΔV = V Exit -V Entry ) can be expressed as V Exit {1−1 / (1 + Reduction Rate / 100)}.
본 발명에서는 무연 쾌삭강 빌렛의 선재압연공정의 사상압연공정에서 최종 스탠드에서의 감면율과 압연 속도 조건과 표면결함발생과의 관계를 조사하고, 그 결과의 일례를 도 1에 나타내었다.In the present invention, the relationship between the reduction rate at the final stand, the rolling speed condition, and the occurrence of surface defects in the filament rolling step of the wire rod rolling step of the lead-free free cutting steel billet was examined, and an example of the result is shown in FIG. 1.
도 1에서 점선의 아래 영역은 표면결함이 발생되지 않는 영역이고, 그 점선의 윗 영역은 표면결함이 발생되는 영역이다.In FIG. 1, the area under the dotted line is an area where no surface defects occur, and the area above the dotted line is an area where the surface defects occur.
도 1에 나타난 바와 같이, 선재압연시 표면결함의 발생은 최종 스탠드에서의 감면율과 압연 속도에 영향을 받음을 알 수 있다.As shown in Figure 1, it can be seen that the occurrence of surface defects during the wire rolling is affected by the reduction rate and the rolling speed at the final stand.
본 발명자들은 이러한 선재압연시 표면결함의 발생이 압연과정 중에 발생하는 인장력과 관련성이 크다는 것을 인식하고, 선재압연시 인장력을 일정값 보다 작게 발생되는 조건으로 압연한 결과, 표면결함의 발생을 억제할 수 있었다.The present inventors have recognized that the occurrence of surface defects during the rolling of the wire is related to the tensile force generated during the rolling process. Could.
선재압연시 인장력은 압연중 소재 출측 속도와 입측 속도차이에 의해 발생하므로, 본 발명에서는 선재압연시 최종 스탠드에서의 소재 출측 속도와 입측 속도의 차이(ΔV)가 4.7(m/s)미만이 되도록 최종 스탠드에서의 압하량을 제어한다.Since the tensile force at the time of rolling is generated by the difference between the exit and exit speeds during rolling, in the present invention, the difference (ΔV) between the exit and exit speeds of the final stand at the wire rod is less than 4.7 (m / s). Control the amount of rolling down on the final stand.
상기와 같이 선재압연시 최종 스탠드에서의 소재 출측 속도와 입측 속도의 차이(ΔV)가 4.7(m/s)미만이 되도록 하면, 선재압연시 발생되는 인장력이 표면결함의 발생을 억제할 수 있는 인장력내에 있게 되어 표면결함의 발생이 억제된다.As described above, if the difference (ΔV) between the material exit speed and the entrance speed at the final stand during the wire rod is less than 4.7 (m / s), the tensile force generated during the wire rod rolling can suppress the occurrence of surface defects. The surface defects are suppressed.
즉, 본 발명에서는 사상압연기의 최종스탠드에서의 소재 유출량 속도 차이(ΔV)가 4.7(m/s)미만이 되도록 압하량을 제어함으로써 표면결함의 발생을 방지할 수 있다.That is, in the present invention, it is possible to prevent the occurrence of surface defects by controlling the amount of reduction so that the difference in material flow rate (ΔV) in the final stand of the finishing mill is less than 4.7 (m / s).
또한, 상기 사상압연 시 초당 누적 변형(strain)의 절대값이 4.1미만이 되도록 사상압연기의 압하량을 제어하여야 한다.In addition, the rolling reduction of the finishing mill must be controlled so that the absolute value of the cumulative strain per second during the finishing rolling is less than 4.1.
쾌삭강과 같은 고 개재물, 고합금 첨가강 작업시 사상압연 구간에서 고감면/고속 압연으로 인해 개재물과 합금원소의 입계 편석에 의해 입계파단형 결함이 발생할 수 있는데, 본 발명에서는 결함이 발생되지 않는 초당 누적 변형(strain)의 임계값을 도출한 것으로서, 초당 누적 변형의 절대값이 4.1 을 초과하면 결함이 발생하게 된다. In case of high inclusions such as free cutting steel and high alloying steel, grain boundary fracture may occur due to grain boundary segregation of inclusions and alloying elements due to high reduction / high speed rolling in the finishing rolling section. The threshold value of the cumulative strain is derived. If the absolute value of the cumulative strain per second exceeds 4.1, a defect occurs.
따라서, 사상압연에서 결함을 방지하기 위하여 초당 누적 변형의 절대값이 4.1 미만이 되도록 사상압연기의 압하량을 제어하여야 한다.Therefore, in order to prevent defects in finishing rolling, the rolling reduction of the finishing mill should be controlled so that the absolute value of cumulative deformation per second is less than 4.1.
이하, 실시예를 통하여 본 발명을 보다 구체적으로 설명한다.Hereinafter, the present invention will be described more specifically by way of examples.
(실시예)(Example)
중량%로, 탄소(C): 0.07%, 실리콘(Si): 0.05%, 망간(Mn): 1.4%, 인(P): 0.05%, 황(S): 0.4%, 비스무스(Bi): 0.1%, 주석(Sn): 0.05%, 보론(B): 0.005%, 질소(N): 0.007%, 전산소(T[O]): 0.015%, 알루미늄(Al): 1ppm 및 칼슘(Ca): 1ppm, 잔부 Fe 및 불가피한 불순물로 이루어진 160mm(폭) ⅹ 160mm(두께) ⅹ 10200mm(길이)크기의 무연 쾌삭강 빌렛을 1250℃이상의 온도에서 가열하고 패스당 21%의 감면율로 5패스 조압연하고, 패스당 28%의 감면율로 6패스 중간조압연하고, 패스당 22%의 감면율로 6패스 중간사상압연한 다음, 하기 표 1과 같이 각각 2패스, 4패스, 6패스 및 8패스 사상압연하여 선경 15mmφ, 12mmφ, 10mmφ 및 8mmφ인 선재를 제조하고 표면결함By weight, carbon (C): 0.07%, silicon (Si): 0.05%, manganese (Mn): 1.4%, phosphorus (P): 0.05%, sulfur (S): 0.4%, bismuth (Bi): 0.1 %, Tin (Sn): 0.05%, Boron (B): 0.005%, Nitrogen (N): 0.007%, Oxygen (T [O]): 0.015%, Aluminum (Al): 1 ppm and Calcium (Ca): 160mm (width) ⅹ 160mm (thickness) ⅹ 10200mm (length) lead-free free-cut steel billets of 1ppm, balance Fe and unavoidable impurities are heated at a temperature of 1250 ℃ or more, 5 pass rough rolling with 21% reduction per pass, 6 pass intermediate rough rolling with 28% reduction rate per step, 6 pass intermediate rolling with 22% reduction rate per pass, followed by 2 pass, 4 pass, 6 pass and 8 pass finishing rolling, respectively, as shown in Table 1 below. , Surface defects of wire rods of up to 12 mmφ, 10 mmφ and 8 mmφ
발생여부를 조사하고 그 결과를 하기 표 1에 나타내었다.It was investigated whether the occurrence and the results are shown in Table 1 below.
하기 표 1에는 초당 누적 변형량이 표시되어 있으며, 표면결함발생여부는 표면결함이 발생되지 않은 경우에는 양호로 표시하고 결함이 발생되는 경우에는 결함발생이라고 표시하였다.Table 1 shows the cumulative deformation amount per second, and the occurrence of surface defects was marked as good when no surface defects occurred, and marked as defects when the defects occurred.
800
Good
Defect
상기 표 1에 나타난 바와 같이, 사상압연시 초당 누적 변형의 절대값이 본 발명의 범위인 4.1미만인 경우, 즉 초당 누적 변형의 절대값이 3.2인 선경 15 mmφ의 선재 및 초당 누적 변형의 절대값이 4.0인 12mmφ의 선재를 제조하는 경우에는 표면결함이 발생되지 않음을 알 수 있다.As shown in Table 1, when the absolute value of the cumulative strain per second during finishing rolling is less than 4.1, which is the scope of the present invention, that is, the absolute value of the
또한, 상기한 160mm(폭) ⅹ 160mm(두께) ⅹ 10200mm(길이)크기의 무연 쾌삭강 빌렛을 1250℃이상의 온도에서 가열하고 패스당 23%의 감면율로 10패스 조압연하고, 패스당 21%의 감면율로 4패스 중간조압연하고, 패스당 16%의 감면율로 6패스 중간사상압연한 다음, 하기 표 2와 같이 각각 2패스, 4패스, 6패스 및 8패스 사상압연하여 선경 15mmφ, 12mmφ, 10mmφ 및 8mmφ인 선재를 제조하고 표면결함 발생여부를 조사하고 그 결과를 하기 표 2에 나타내었다.In addition, the above-mentioned lead-free free-cut steel billets of 160 mm (width) ⅹ 160 mm (thickness) ⅹ 10200 mm (length) are heated at a temperature of 1250 ° C. or higher and roughly rolled in 10 passes with a 23% reduction rate per pass, and 21% reduction ratio per pass. 4 pass intermediate rough rolling, and 6 pass intermediate rolling with 16% reduction rate per pass, and then 2 pass, 4 pass, 6 pass and 8 pass finishing rolling, respectively, as shown in Table 2 below, and the diameters of 15mmφ, 12mmφ, 10mmφ and A wire rod of 8 mm phi was prepared and the occurrence of surface defects was investigated and the results are shown in Table 2 below.
하기 표 2에는 초당 누적 변형량이 표시되어 있으며, 표면결함발생여부는 표면결함이 발생되지 않은 경우에는 양호로 표시하고 결함이 발생되는 경우에는 결함발생이라고 표시하였다.Table 2 shows the cumulative deformation amount per second, and the occurrence of surface defects is indicated as good when no surface defects are generated and marked as defects when a defect is generated.
920
Good
Defect
상기 표 2에 나타난 바와 같이, 사상압연시 초당 누적 변형의 절대값이 본 발명의 범위인 4.1 미만인 경우, 즉 초당 누적 변형의 절대값이 2.8인 선경 15mmφ의 선재, 초당 누적 변형의 절대값이 3.9인 선경 12mmφ의 선재 및 초당 누적 변형의 절대값이 4.0인 선경 10mmφ의 선재를 제조하는 경우에는 표면결함이 발생되지 않음을 알 수 있다.As shown in Table 2 above, when the absolute value of the cumulative strain per second during finishing rolling is less than 4.1, which is the scope of the present invention, that is, the wire rod having a diameter of 15 mmφ and the absolute value of the cumulative strain per second is 3.9. It can be seen that surface defects do not occur when a wire having a diameter of 12 mmφ and a wire having a diameter of 10 mmφ having an absolute value of cumulative strain per second are 4.0.
또한, 상기 표 1 및 2의 선경을 갖는 선재의 제조시 사상압연의 최종 패스(스탠드)에서의 압연조건을 하기 표 3과 같이 조절하여 선재를 제조한 후, 표면결함 발생여부를 조사하고 그 결과를 하기 표 3에 나타내었다.In addition, after manufacturing the wire by adjusting the rolling conditions in the final pass (stand) of finishing rolling in the manufacture of the wire having the wire diameters of Tables 1 and 2 as shown in Table 3, and investigates the occurrence of surface defects It is shown in Table 3 below.
(mmφ)fairyland
(mmφ)
(%)Reduction rate
(%)
Table 2 Manufacturing Process
상기 표 3에 나타난 바와 같이, 사상압연기의 최종스탠드에서의 소재 유출량 속도 차이(ΔV)가 본 발명의 범위인 4.7(m/s)미만인 경우에는 표면결함이 발생되지 않음을 알 수 있다.As shown in Table 3, it can be seen that the surface defect does not occur when the difference in material flow rate (ΔV) in the final stand of the finishing mill is less than 4.7 (m / s) of the present invention.
도 1은 최종 스탠드에서의 압연속도 및 감면율에 대한 결합발생 영역의 일례를 나타내는 그래프1 is a graph showing an example of the bond generation area against the rolling speed and reduction rate at the final stand;
Claims (3)
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KR19980051160A (en) * | 1996-12-23 | 1998-09-15 | 김종진 | Method for manufacturing bismuth (Bi) -sulfur (S) -based free-cutting steel wire with excellent surface finish |
KR100306138B1 (en) | 1997-12-26 | 2001-11-02 | 이구택 | METHOD FOR MANUFACTURING Bi-S FREE CUTTING STEEL ROD WIRE WITH NO SURFACE DEFECTS |
KR20090066638A (en) * | 2007-12-20 | 2009-06-24 | 주식회사 포스코 | Eco-friendly pb-free free cutting steel with excellent machinability and hot workability |
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KR19980051160A (en) * | 1996-12-23 | 1998-09-15 | 김종진 | Method for manufacturing bismuth (Bi) -sulfur (S) -based free-cutting steel wire with excellent surface finish |
KR100306138B1 (en) | 1997-12-26 | 2001-11-02 | 이구택 | METHOD FOR MANUFACTURING Bi-S FREE CUTTING STEEL ROD WIRE WITH NO SURFACE DEFECTS |
KR20090066638A (en) * | 2007-12-20 | 2009-06-24 | 주식회사 포스코 | Eco-friendly pb-free free cutting steel with excellent machinability and hot workability |
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