KR20230017462A - Hot work tool steel for Extrusion and forging die with high toughness - Google Patents
Hot work tool steel for Extrusion and forging die with high toughness Download PDFInfo
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- 229910001315 Tool steel Inorganic materials 0.000 title claims abstract description 23
- 238000005242 forging Methods 0.000 title claims abstract description 14
- 238000001125 extrusion Methods 0.000 title claims abstract description 13
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims description 12
- 229910052710 silicon Inorganic materials 0.000 claims description 11
- 229910052804 chromium Inorganic materials 0.000 claims description 10
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052758 niobium Inorganic materials 0.000 claims description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims description 5
- 229910052717 sulfur Inorganic materials 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 229910000831 Steel Inorganic materials 0.000 description 64
- 239000010959 steel Substances 0.000 description 64
- 230000000052 comparative effect Effects 0.000 description 18
- 239000010955 niobium Substances 0.000 description 15
- 239000000203 mixture Substances 0.000 description 12
- 239000011651 chromium Substances 0.000 description 11
- 229910052720 vanadium Inorganic materials 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 150000001247 metal acetylides Chemical class 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 7
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 6
- 239000011572 manganese Substances 0.000 description 6
- 238000005496 tempering Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000011733 molybdenum Substances 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000004512 die casting Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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Abstract
Description
본 발명은 충격인성이 우수한 열간공구강에 대한 것으로, 보다 상세하게는 압출 및 열간단조 공정에 사용 되는 금형소재로 사용되며, 종래의 STD61 열간공구강 보다 충격인성을 개선하기 위한 Si, Mo, V 등을 제어로, 압출 및 열간단조 금형 사용특성이 향상된 열간공구강에 관한 것이다.The present invention relates to hot tool steel with excellent impact toughness, and more specifically, it is used as a mold material used in extrusion and hot forging processes, and Si, Mo, V, etc. are used to improve impact toughness compared to conventional STD61 hot tool steel. As a control, it relates to hot tool steel with improved properties for use in extrusion and hot forging molds.
일반적으로, 열간공구강은 열간단조, 압출 및 다이캐스팅 등에 사용되는 금형용 소재로써, 우수한 내마모성, 내열균열성, 고온강도 및 고인성의 특성이 요구된다.In general, hot tool steel is a material for molds used in hot forging, extrusion and die casting, and requires excellent wear resistance, heat crack resistance, high temperature strength and high toughness.
이러한 열간공구강은 크롬계, 텅스텐계, 그리고 몰리브덴계 열간공구강으로 크게 나뉜다. 이 중 크롬계 열간공구강은 크롬과 탄화물 형성원소의 첨가로 인해 열에 의한 연화저항성이 매우 좋은 것으로 알려져 있다. 일반적으로, 상기 크롬계 열간공구강은 550℃ 부근까지 열 연화(heat softening) 저항성이 유지된다. 또한, 탄소 함량과 총 합금원소 함량이 낮아 일반적인 작업 경도인 40~55 HRC에서의 인성도 우수한 편이므로 공구나 금형뿐만 아니라 열간 구조용으로도 널리 사용되고 있다.These hot tool steels are largely divided into chromium-based, tungsten-based, and molybdenum-based hot tool steels. Among them, chromium-based hot tool steel is known to have very good resistance to softening by heat due to the addition of chromium and carbide forming elements. In general, the chromium-based hot tool steel maintains heat softening resistance up to around 550°C. In addition, since the carbon content and the total alloying element content are low, the toughness at a general working hardness of 40 to 55 HRC is also excellent, so it is widely used not only for tools and molds but also for hot structures.
종래에 주로 사용되는 열간공구강은 한국공업규격(KS)의 5Cr-Mo-V의 STD61이 대부분 사용되고 있으나, 상술한 요구특성과 적용분야를 모두 만족하기에는 어려움이 있다. Conventionally, most of the hot-worked tool steels used are STD61 of 5Cr-Mo-V of the Korean Industrial Standards (KS), but it is difficult to satisfy all of the above-described required characteristics and fields of application.
특히 최근의 열간공구강 생산에 필수적인 Cr, Mo, V 등의 원료가격 상승으로 인한 금형재 비용의 급등에 따라, STD61의 기본적인 특성의 향상과 동시에 비용 측면에서도 절감 가능한 금형소재의 필요성이 요구되고 있다. In particular, as the cost of mold materials has rapidly increased due to the recent rise in the price of raw materials such as Cr, Mo, and V, which are essential for the production of hot-worked tool steel, there is a need for mold materials that can improve the basic characteristics of STD61 and reduce costs at the same time.
본 발명은 상술한 종래기술의 문제점을 해결하기 위하여 도출된 것으로, 기존 STD61(5Cr-Mo-V)강에 합금원소의 조정 및 첨가를 통하여 새로운 합금 성분계를 도출한 것으로, Mo, V 원소의 첨가를 최적화와 Nb 등의 첨가를 통해 충격인성을 향상 및 제조원가를 절감할 수 있는 압출 및 열간단조 다이스용의 열간공구강을 제공함에 그 목적이 있다.The present invention was derived to solve the problems of the prior art described above, and derived a new alloy composition system through the adjustment and addition of alloy elements to the existing STD61 (5Cr-Mo-V) steel, with the addition of Mo and V elements. Its purpose is to provide hot tool steel for extrusion and hot forging dies that can improve impact toughness and reduce manufacturing costs through optimization and addition of Nb.
또한 본 발명에서 이루고자 하는 기술적 과제들은 이상에서 언급한 기술적 과제들에 한정되지 않으며, 언급하지 않은 또 다른 기술적 과제들은 아래의 기재로부터 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 명확하게 이해될 수 있을 것이다.In addition, the technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned are clearly understood by those skilled in the art from the description below. It could be.
본 발명의 일 측면은, One aspect of the present invention,
중량%로, C: 0.35~0.42%, Si: 0.20~0.50%, Mn: 0.25~0.60%, P: 0.025% 이하, S: 0.025% 이하, Cr: 4.80~5.50%, Mo: 1.00~1.50, V: 0.40~0.60%, Nb: 0.01~0.05%, 잔부 Fe 및 불가피한 불순물로 이루어지는 충격인성이 우수한 압출 및 단조용 열간공구강 소재에 관한 것이다. In % by weight, C: 0.35 to 0.42%, Si: 0.20 to 0.50%, Mn: 0.25 to 0.60%, P: 0.025% or less, S: 0.025% or less, Cr: 4.80 to 5.50%, Mo: 1.00 to 1.50, V: 0.40 to 0.60%, Nb: 0.01 to 0.05% , the balance relates to a hot tool steel material for extrusion and forging with excellent impact toughness consisting of Fe and unavoidable impurities.
상기 Nb 함량이 0.02~0.04% 인 것이 바람직하다.It is preferable that the Nb content is 0.02 to 0.04%.
상술한 구성의 본 발명에 따르면, 종래의 STD61 강종과 비교하여 압출 및 열간단조 공정의 금형사용 과정에서 요구되는 경도의 확보 및 충격인성이 향상이 가능하다. 또한 종래의 STD61과 비교하여 성분 최적화를 통해 제조원가의 절감을 동시에 이룰 수 있다.According to the present invention having the above-described configuration, it is possible to secure hardness and improve impact toughness required in the process of using a mold in the extrusion and hot forging process compared to the conventional STD61 steel grade. In addition, compared to the conventional STD61, it is possible to simultaneously achieve reduction in manufacturing cost through component optimization.
도 1(a-b)은 본 발명의 실시예에 있어서, 발명강 1-4의 템퍼링 온도별 경도(HRC)를 측정하여 종래강에 대비하여 나타낸 그래프이다.
도 2(a-b)는 본 발명의 실시예에 있어서, 비교강 1-6의 템퍼링 온도별 경도(HRC)를 측정하여 종래강에 대비하여 나타낸 그래프이다.
도 3(a-b)는 본 발명의 실시예에 있어서, 발명강 1-4의 경도(HRC) 조건별 25℃ 충격인성치(J)를 종래강에 대비하여 나타낸 그래프이다.
도 4(a-b)는 도 3(a-b)의 발명의 실시예에 있어서, 비교강 1-6의 경도(HRC) 조건별 25℃ 충격인성치(J)를 종래강에 대비하여 나타낸 그래프이다. 1 (ab) is a graph showing the hardness (HRC) of invention steels 1-4 according to tempering temperature measured in comparison with conventional steels in an embodiment of the present invention.
2 (ab) is a graph showing hardness (HRC) of comparative steels 1-6 according to tempering temperature measured in comparison with conventional steels in an embodiment of the present invention.
Figure 3 (ab) is a graph showing the 25 ℃ impact toughness value (J) for each hardness (HRC) condition of invention steels 1-4 in comparison with conventional steel in an embodiment of the present invention.
Figure 4 (ab) is a graph showing the 25 ℃ impact toughness value (J) for each hardness (HRC) condition of comparative steels 1-6 in comparison with conventional steel in the embodiment of the invention of FIG. 3 (ab).
이하, 본 발명을 설명한다.Hereinafter, the present invention will be described.
본 발명은 기존 STD61 열간공구강 조성에서 Si, Mo, V 및 Nb 함량을 제어함으로서 충격인성이 우수한 열간공구강을 제공함을 특징으로 한다. The present invention is characterized by providing a hot tool steel with excellent impact toughness by controlling the contents of Si, Mo, V and Nb in the composition of the existing STD61 hot tool steel.
본 발명자는 0.40C-1.0Si-5.0Cr-1.2Mo-0.85V의 기본조성을 갖는 열간공구강의 합금조성으로서 충격인성을 개선하기 위한 연구를 행한 결과, 충격인성을 향상을 위한 탄화물 미세분산을 위해 적정량의 Si, Mo 및 V 첨가와 아울러 Nb을 첨가함이 효과적인 것을 발견하고 본 발명을 제시하는 것이다. As a result of research to improve impact toughness as an alloy composition of hot tool steel having a basic composition of 0.40C-1.0Si-5.0Cr-1.2Mo-0.85V, the present inventors have found that an appropriate amount for fine dispersion of carbides to improve impact toughness It is found that the addition of Nb together with the addition of Si, Mo and V of is effective, and the present invention is proposed.
따라서 본 발명의 충격인성이 우수한 열간공구강은 중량%로, C: 0.35~0.42%, Si: 0.20~0.50%, Mn: 0.25~0.60%, P: 0.025% 이하, S: 0.025% 이하, Cr: 4.80~5.50%, Mo: 1.0~1.5%, V: 0.40~0.60%, Nb: 0.01~0.05%, 잔부 Fe 및 불가피한 불순물로 이루어지는 충격인성이 우수한 압출 및 단조용 열간공구강 소재에 관한 것이다. Therefore, the hot tool steel with excellent impact toughness of the present invention contains, by weight, C: 0.35 to 0.42%, Si: 0.20 to 0.50%, Mn: 0.25 to 0.60%, P: 0.025% or less, S: 0.025% or less, Cr: 4.80 to 5.50%, Mo: 1.0 to 1.5%, V: 0.40 to 0.60%, Nb: 0.01 to 0.05%, the balance Fe and unavoidable impurities It relates to a hot tool steel material for extrusion and forging with excellent impact toughness.
이하, 본 발명의 열간공구강의 조성성분 및 그 함량 제한사유를 설명하며, 아래에서 "%"는 달리 규정한 바가 없다면 "중량%"를 의미한다. Hereinafter, the composition of the hot tool steel of the present invention and the reason for limiting the content thereof will be described, and "%" below means "% by weight" unless otherwise specified.
·탄소 (C): 0.35~0.42%・Carbon (C): 0.35~0.42%
탄소는 열간공구강에서 소입성을 증가시키고 탄화물을 석출시켜 고온강도와 경도를 향상시키는 원소로서, 0.35% 미만에서는 상기 특성을 확보하지 못하며 0.42 를 초과하면 탄소(C)량을 증가시켜도 담금질성이 증가하지 않으므로 0.35∼0.42%의 범위로 한정하는 것이 바람직하다.Carbon is an element that increases hardenability and precipitates carbides in hot tool steel to improve high-temperature strength and hardness. If it is less than 0.35%, the above characteristics cannot be secured, and if it exceeds 0.42, hardenability increases even if the amount of carbon (C) is increased. Since it does not, it is preferable to limit it to the range of 0.35 to 0.42%.
·규소 (Si): 0.20~0.50%Silicon (Si): 0.20 to 0.50%
규소는 내산화성을 향상시키는 효과가 있으나, 0.50%를 초과하면 소성가공을 저하시키며, 함량이 낮을수록 인성은 향상되지만 0.20% 미만에서는 상기 장점 및 기계가공성을 확보할 수 없으므로 0.20∼0.50%가 적당하다.Silicon has the effect of improving oxidation resistance, but if it exceeds 0.50%, it deteriorates plastic working, and the lower the content, the toughness improves, but if it is less than 0.20%, the above advantages and machinability cannot be secured. do.
·망간 (Mn): 0.25~0.60%Manganese (Mn): 0.25~0.60%
망간은 소재의 소입성을 개선하는 효과가 큰 원소로서, 0.25% 미만에서는 원하는 상기 효과를 얻을 수 없고, 0.60%를 초과하게 되면 재질이 지나치게 경해지므로 기계가공성이 저하를 가져 올 수 있으므로 0.25~0.60%가 적당하다.Manganese is an element that has a great effect on improving the hardenability of the material. If it is less than 0.25%, the desired effect cannot be obtained, and if it exceeds 0.60%, the material becomes too hard, which can lead to a decrease in machinability. % is appropriate.
·크롬 (Cr): 4.80~5.50%Chromium (Cr): 4.80~5.50%
크롬은 내산화성을 향상시키고, 탄소와 결합하여 탄화물을 형성을 통해 내마모특성을 향상시킨다. 또한 베이나이트 변태를 지연시켜, 소입성의 향상에 기여하는 원소로서, 4.80% 미만이면 상기 역할을 충분히 수행할 수 없고 5.50%를 초과하면 경화(硬化)되어 가공성이 나빠지므로 4.80∼5.50%의 범위가 적당하다.Chromium improves oxidation resistance and improves wear resistance by combining with carbon to form carbides. In addition, as an element that delays the bainite transformation and contributes to the improvement of hardenability, if it is less than 4.80%, the above role cannot be sufficiently performed, and if it exceeds 5.50%, it is hardened and workability deteriorates, so the range of 4.80 to 5.50% is suitable
·몰리브덴 (Mo): 1.0~1.5%・Molybdenum (Mo): 1.0~1.5%
몰리브덴은 탄소와 결합하여 탄화물 형성을 통해 고온강도 및 인성의 향상에 기여한다. 1.0% 미만에서는 상기의 역할을 충분히 수행할 수 없고, 1.5%를 초과한 함유하면, 고온강도에 기여하지 못하므로, 1.0~1.5%의 범위가 적당하다.Molybdenum combines with carbon to form carbides and contributes to the improvement of high-temperature strength and toughness. If it is less than 1.0%, it cannot sufficiently perform the above role, and if it contains more than 1.5%, it does not contribute to high-temperature strength, so the range of 1.0 to 1.5% is appropriate.
·바나듐 (V): 0.40~0.60%・Vanadium (V): 0.40~0.60%
바나듐은 열처리 과정에서 용해되지 않고, 잔류하여 내마모성을 향상시키며, 결정립 미세화를 통해 인성의 향상에 기여한다. 그러나 0.6% 이상의 함유에서는 미용해 탄화물의 형성으로 충격인성을 저해할 수 있어, 0.6% 이하로 제한이 필요하다. 또한 0.4% 이하의 함유량에서는 상기의 특성을 충분히 확보할 수 없어 조성범위는 0.4~0.6%가 적당하다.Vanadium does not dissolve in the heat treatment process, but remains to improve wear resistance and contribute to improvement of toughness through crystal grain refinement. However, if the content is 0.6% or more, impact toughness may be impaired due to the formation of undissolved carbides, so it is necessary to limit the content to 0.6% or less. In addition, at a content of 0.4% or less, the above characteristics cannot be sufficiently secured, so a composition range of 0.4 to 0.6% is appropriate.
·나이오븀 (Nb): 0.01~0.05%Niobium (Nb): 0.01~0.05%
본 발명에서 Nb은 탄소와 결합을 통한 탄화물의 형성으로 결정립계를 미세화 시키는 중요한 원소이다. 그러나 0.05%를 초과하면 인성에 저해하는 조대한 탄화물을 형성할 수 있어 본 발명에서는 이러한 Nb의 함량을 0.01~0.05% 범위로 제어함이 바람직하다. 보다 바람직하게는, Nb 함량을 0.02~0.04%로 제한하는 것이다. In the present invention, Nb is an important element that refines grain boundaries by forming carbides through bonding with carbon. However, if it exceeds 0.05%, coarse carbides that hinder toughness may be formed. In the present invention, it is preferable to control the Nb content in the range of 0.01 to 0.05%. More preferably, the Nb content is limited to 0.02 to 0.04%.
· 인(P), 황(S): 각 0.025% 이하Phosphorus (P), sulfur (S): less than 0.025% each
인과 황은 제강과정의 불가피하게 잔류하는 불순물 원소로, 그 함유량이 낮을수록 소재의 인성의 향상에 기여하며, 또한 이방성이 현저히 감소하므로 각각 0.025% 이하로 설정한다. Phosphorus and sulfur are impurity elements that inevitably remain in the steelmaking process, and the lower the content, the higher the toughness of the material, and the less anisotropy, so they are each set to 0.025% or less.
기타 본 발명의 열간공구강은 잔여 성분으로서 Fe와 불가피한 불순물을 포함할 수 있다. Other hot tool steels of the present invention may contain Fe and unavoidable impurities as residual components.
이하, 실시예를 통하여 본 발명을 상세하게 설명한다.Hereinafter, the present invention will be described in detail through examples.
(실시예 1)(Example 1)
(STD61강)conventional steel
(STD61 steel)
상기 표 1(성분함량 단위: 중량%)과 같은 조성 성분을 가진 강종들을 진공 유도 용해하였다. 구체적으로, 종래강은 0.40C-1.0Si-5.0Cr-1.2Mo-0.85V을 기본조성으로 하는 STD61강이며, 발명강 1-4는 Si, V 함량 및 Nb 성분을 포함한다는 점에서 상기 종래강과 차이가 있으며, 그리고 비교강 1-6는 Si, V 함량이 벗어나거나, W을 포함하거나, Nb이 첨가되지 않다는 점에서 발명강과 차이가 있다. Steel grades having the composition components shown in Table 1 (component content unit: weight%) were subjected to vacuum induction melting. Specifically, the conventional steel is STD61 steel with a basic composition of 0.40C-1.0Si-5.0Cr-1.2Mo-0.85V, and the invention steel 1-4 is different from the conventional steel in that it contains Si, V content and Nb component. There is a difference, and Comparative Steel 1-6 differs from the inventive steel in that the Si and V contents deviate, contain W, and do not add Nb.
이와 같이 용해된 강종을 이용하여, 잉고트(Ingot)로 주조하고, 이를 소성가공 후 절단하였다. 그리고 절단된 각각의 시편을 ??칭 및 템퍼링 열처리한 후,템퍼링 열처리온도에 따른 경도(HRC)를 측정하여 도 1-2에 나타내었다. 또한 상기 열처리된 시편의 경도(HRC)에 따른 25℃ 충격인성치(J)를 측정하여 도 3-4에 나타내었다. Using the melted steel type, it was cast into an ingot, which was cut after plastic working. And after quenching and tempering heat treatment of each of the cut specimens, the hardness (HRC) according to the tempering heat treatment temperature was measured and shown in FIGS. 1-2. In addition, the 25 ℃ impact toughness value (J) according to the hardness (HRC) of the heat-treated specimen was measured and shown in FIGS. 3-4.
구체적으로, 도 1(a-b)은 본 발명의 실시예에 있어서, 발명강 1-4의 템퍼링 온도별 경도(HRC)를 측정하여 종래강에 대비하여 나타낸 그래프이다. 또한 도 2(a-b)는 본 발명의 실시예에 있어서, 비교강 1-6의 템퍼링 온도별 경도(HRC)를 측정하여 종래강에 대비하여 나타낸 그래프이다. 그리고 도 3(a-b)는 본 발명의 실시예에 있어서, 발명강 1-4의 경도(HRC) 조건별 25℃ 충격인성치(J)를 종래강에 대비하여 나타낸 그래프이다. 나아가 도 4(a-b)는 도 3(a-b)의 발명의 실시예에 있어서, 비교강 1-6의 경도(HRC) 조건별 25℃ 충격인성치(J)를 종래강에 대비하여 나타낸 그래프이다. 한편 본 발명에서 상기 경도와 충격인성을 측정하는 방법으로, 로크웰 경도 및 샤르피 충격시험을 이용하였다.Specifically, FIG. 1 (a-b) is a graph showing the hardness (HRC) of inventive steels 1-4 according to tempering temperature measured in comparison with conventional steels in an embodiment of the present invention. In addition, FIG. 2 (a-b) is a graph showing the hardness (HRC) of comparative steels 1-6 according to tempering temperature in an embodiment of the present invention, compared to conventional steel. And Figure 3 (a-b) is a graph showing the 25 ℃ impact toughness value (J) for each hardness (HRC) condition of invention steels 1-4 in comparison with conventional steel in an embodiment of the present invention. Further, FIG. 4 (a-b) is a graph showing the 25 ° C. impact toughness value (J) for each hardness (HRC) condition of comparative steels 1-6 in comparison with conventional steel in the embodiment of the invention of FIG. 3 (a-b). Meanwhile, as a method for measuring the hardness and impact toughness in the present invention, Rockwell hardness and Charpy impact test were used.
상기 도면 1-4에 나타낸 바와 같이, 종래강의 성분계에서 합금원소를 일부 를 조정함으써 열간공구강에 필요한 경도가 확보 가능하다는 것을 확인할 수 있다. 또한 발명강 1-4와 비교강 1-6은 모두 종래강 대비 충격인성이 우수하다는 것을 확인할 수 있으며, 특히, 도 3에 나타난 바와 같이, 본 발명강 1-4의 경우가 종래강 및 비교강 대비 가장 우수한 충격인성을 가짐을 알 수 있다. As shown in the drawings 1-4, it can be confirmed that the required hardness of the hot tool steel can be secured by adjusting some of the alloy elements in the composition system of the conventional steel. In addition, it can be seen that both inventive steels 1-4 and comparative steels 1-6 are superior in impact toughness compared to conventional steels. In particular, as shown in FIG. 3, inventive steels 1-4 are conventional steels and comparative steels. It can be seen that it has the best impact toughness in comparison.
(실시예 2)(Example 2)
실시예 1의 종래강, 발명강 1-2 및 비교강 1-2의 조성을 각각 갖는 강종을 전기로에서 용해하고, 이어, 잉고트(Ingot)로 주조하였다. 이어, 주조된 각각의 잉고트(Ingot)를 열간단조, 구상화 열처리를 행한 후, 산업현장에서 사용하는 금형으로 제작 및 열처리하여 수명을 비교 평가하여 하기 표 2에 나타내었다.Steel grades each having the compositions of the conventional steel, invention steel 1-2, and comparative steel 1-2 of Example 1 were melted in an electric furnace, and then cast into ingots. Subsequently, each of the cast ingots was subjected to hot forging and spheroidizing heat treatment, and then manufactured and heat treated with a mold used in an industrial field to compare and evaluate the lifespan, and are shown in Table 2 below.
(압출본)Extrusion mold life
(extruded copy)
(사용타수)Forging die life
(number of strokes used)
상기 표 2에서 나타난 바와 같이, 0.40C-1.0Si-5.0Cr-1.2Mo-0.85V 을 종래강 기본 조성의 Si, Mo 및 V 함량을 조절함과 아울러, Nb 성분을 적정량 함유시킨 발명강 1-2의 경우, 종래 STD61강 대비 금형 수명에 있어 우수한 것을 알 수 있다. As shown in Table 2, 0.40C-1.0Si-5.0Cr-1.2Mo-0.85V was used to adjust the Si, Mo, and V contents of the basic composition of the conventional steel, and the inventive steel 1- containing an appropriate amount of Nb component In the case of 2, it can be seen that it is superior in mold life compared to conventional STD61 steel.
이에 대하여, 비교강 1-2는 W 함량이 과다한 경우로서, 실질적인 사용 금형수명은 향상되지 않는 것을 알 수 있다In contrast, comparative steel 1-2 is a case where the W content is excessive, and it can be seen that the actual use mold life is not improved.
한편 표 2 결과를 보면 0.40C-0.3Si-5.0Cr-0.80Mo-0.50V를 기본조성으로 하고, 여기에 Nb이 적정량 함유된 발명강 1-2의 경우, 종래 STD61강 대비 충격인성의 향상 및 금형수명이 확보가 가능한 것을 확인할 수 있다. 이러한 발명강이 종래의 STD61 강 보다 충격인성이 우수한 이유는, V 하향으로 입계에 VC 형성을 줄이고, Si 하향으로 미세한 탄화물의 석출로 인한 것으로 판단된다. 그런데 본 발명 보다 W이 첨가된 비교강 1-2의 경우, 상대적으로 조대한 탄화물을 형성하는 W의 함유로 충격인성의 개선이 충분치 않아 결과적으로 고온 수명의 확보에는 좋지 않았다.On the other hand, looking at the results of Table 2, in the case of invention steel 1-2 containing 0.40C-0.3Si-5.0Cr-0.80Mo-0.50V as a basic composition and containing an appropriate amount of Nb, improved impact toughness compared to conventional STD61 steel and It can be confirmed that the mold life can be secured. The reason why the inventive steel has better impact toughness than the conventional STD61 steel is considered to be due to the reduction of VC formation at the grain boundary in the V downward direction and the precipitation of fine carbides in the Si downward direction. However, in the case of Comparative Steel 1-2 to which W was added than in the present invention, the improvement in impact toughness was not sufficient due to the inclusion of W forming relatively coarse carbides, and as a result, it was not good for securing high-temperature life.
이상에서 설명한 바와 같이, 본 발명의 상세한 설명에서는 본 발명의 바람직한 실시 예에 관하여 설명하였으나 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자라면 본 발명의 범주에서 벗어나지 않는 한도 내에서 여러 가지 변형이 가능함은 물론이다. 따라서 본 발명의 권리 범위는 설명된 실시 예에 국한되어 정해져서는 안 되며, 후술하는 청구범위뿐만 아니라, 이와 균등한 것들에 의해 정해져야 한다.As described above, the detailed description of the present invention has been described with respect to the preferred embodiments of the present invention, but those skilled in the art to which the present invention belongs may make various modifications without departing from the scope of the present invention. Of course it is possible. Therefore, the scope of the present invention should not be limited to the described embodiments and should not be defined, and should be defined by not only the claims described later, but also those equivalent thereto.
Claims (2)
In % by weight, C: 0.35 to 0.42%, Si: 0.20 to 0.50%, Mn: 0.25 to 0.60%, P: 0.025% or less, S: 0.025% or less, Cr: 4.80 to 5.50%, Mo: 1.0 to 1.5% , V: 0.40 ~ 0.60%, Nb: 0.01 ~ 0.05%, a hot tool steel for extrusion and forging with excellent impact toughness consisting of Fe and unavoidable impurities.
The hot tool steel for extrusion and forging according to claim 1, wherein the Nb content is 0.02 to 0.04%.
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