KR100359500B1 - Rolled steel forging rolls with improved wear resistance and toughness - Google Patents
Rolled steel forging rolls with improved wear resistance and toughness Download PDFInfo
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- KR100359500B1 KR100359500B1 KR10-1998-0041002A KR19980041002A KR100359500B1 KR 100359500 B1 KR100359500 B1 KR 100359500B1 KR 19980041002 A KR19980041002 A KR 19980041002A KR 100359500 B1 KR100359500 B1 KR 100359500B1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B2203/00—Auxiliary arrangements, devices or methods in combination with rolling mills or rolling methods
- B21B2203/18—Rolls or rollers
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Abstract
0.35 내지 0.80 중량%의 탄소, 0.25 내지 0.80 중량%의 규소, 0.35 내지 1.5 중량%의 망간, 0.2 내지 1.5 중량%의 니켈, 4.0% 내지 6.0 중량%의 크롬, 0.5 내지 1.5 중량%의 몰리브덴, 0.05 내지 0.5 중량%의 바나듐, 0.1 중량% 이하의 니오븀을 함유하며, 잔부는 철과 미량의 불순물로 구성되어, 내마모성과 인성이 향상된 압연용 단강 보강롤을 제공한다.0.35 to 0.80 wt% carbon, 0.25 to 0.80 wt% silicon, 0.35 to 1.5 wt% manganese, 0.2 to 1.5 wt% nickel, 4.0 to 6.0 wt% chromium, 0.5 to 1.5 wt% molybdenum, 0.05 To 0.5% by weight of vanadium, 0.1% by weight or less of niobium, the balance is composed of iron and trace impurities, to provide a forged steel reinforcing roll for improved wear resistance and toughness.
Description
본 발명은 압연 판을 제조하는 압연기에 있어서 작업롤을 지지하고 압연 하중을 부여하는데 사용되는 단강 보강롤에 관한 것이며, 특히 내마모성과 인성이 우수한 압연용 단강 보강롤에 관한 것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to forged steel reinforcement rolls used for supporting a work roll and applying a rolling load in a rolling mill for manufacturing a rolled plate, and more particularly, to a forged steel reinforcement roll for rolling excellent in wear resistance and toughness.
종래의 단강 보강롤은, 일반적으로 3%Cr계의 합금이 주로 사용되었으며, 작업롤의 재질 변화에 따라서 합금 원소의 종류와 함량 및 열처리 조건이 변화되었고, 이에 따라 그 기계적 성질이 크게 변화하였다.In the conventional forged steel reinforcing roll, generally 3% Cr-based alloy was mainly used, and the type and content of alloying elements and heat treatment conditions were changed according to the material change of the work roll, and thus the mechanical properties thereof were greatly changed.
종래의 직경 1000㎜∼1600㎜ 크기의 대형 보강롤은, 단조 공정 후 예비 열처리와 차등 열처리를 함으로써 이중의 금속 조직을 갖도록 한 것이 사용되고 있다. 즉, 표면에서 일정한 깊이까지만 경화 열처리를 하여 경도가 높은 조직으로 변태시켜 내마모성과 인성을 부여하고, 내부는 압연 하중에 견디도록 예비 열처리로 일정 강도가 얻어지도록 한 것이다.In the conventional large-sized reinforcing rolls having a diameter of 1000 mm to 1600 mm, those having a double metal structure by preliminary heat treatment and differential heat treatment after the forging process are used. In other words, the hardened heat treatment only to a certain depth on the surface is transformed into a structure of high hardness to give abrasion resistance and toughness, and the inside is to obtain a certain strength by pre-heating to withstand rolling load.
최근에는 압연제품의 표면과 정밀도 향상 요구에 따라서 압연용 작업롤의 재질이, 열간 압연의 경우 고크롬강에서 고속도공구강계로, 냉간 압연의 경우 3Cr계, 5Cr계 및 SHSS(Semi-High Speed Steel)계로 바뀌고 있다. 또한 경도가 높은 바나듐카바이드, 크롬카바이드, 텅스텐카바이드, 몰리브덴카바이드 등의 복합탄화물을 다량 함유시키고 있다.Recently, according to the surface of the rolled product and the demand for improving the accuracy, the material of the rolling work roll is from high chrome steel to high-speed coating oral system for hot rolling, and 3Cr, 5Cr and Semi-High Speed Steel for cold rolling. We are changed to system. Moreover, it contains a large amount of complex carbides such as vanadium carbide, chromium carbide, tungsten carbide and molybdenum carbide with high hardness.
한편, 종래의 보강롤은, 경화 열처리와 뜨임 처리(tempering)에 의해 베이나이트 조직을 가지게 되는데, 이로서는 상기와 같은 고속도공구강계 및 SHSS계 압연용 작업롤에 대응하기에는 경도가 낮을 뿐만 아니라 작업롤에 함유되어 있는 상기 고경도 합금원소 탄화물에 의하여 쉽게 마모되어 교체 주기가 짧아진다.On the other hand, the conventional reinforcing rolls have a bainite structure by hardening heat treatment and tempering, which is not only low in hardness but also a work roll to cope with the high-speed coating oral and SHSS rolling rolls. It is easily worn by the hard alloy element carbide contained in the and the replacement cycle is shortened.
따라서, 탄소(C), 실리콘(Si), 망간(Mn), 크롬(Cr), 몰리브덴(Mo) 및 바나듐(V) 등을 첨가하고 요구되는 경도에 따라서 탄소함량을 증가시키고 있다.Therefore, carbon (C), silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo), vanadium (V) and the like are added and the carbon content is increased according to the required hardness.
그러나, 탄소함량 증가로 경도를 높이면 내마모성은 향상시킬 수 있으나, 탄화물의 크기와 양이 증가됨으로써 균열 발생의 빈도가 증가되어 내충격성이나 인성이 저하되는 문제점이 있다.However, when the hardness is increased by increasing the carbon content, the wear resistance may be improved, but the size and the amount of the carbide increase, so that the frequency of cracking is increased, thereby reducing the impact resistance or toughness.
또한 조대한 베이나이트 조직은 마르텐사이트 조직보다 인성이 낮기 때문에 압연 하중에 의한 피로로 인하여 롤의 표피가 박리되어 압연사고가 자주 발생한다.In addition, since the coarse bainite structure has lower toughness than the martensite structure, the skin of the roll is peeled off due to the fatigue caused by the rolling load, so that a rolling accident occurs frequently.
이와 같은 이유로, 보강롤의 재질은 내마모성과 인성을 동시에 갖추고 있는 것이 요구된다.For this reason, the material of the reinforcing roll is required to have both wear resistance and toughness at the same time.
그러나, 인성과 내마모성은 서로 상반되는 성질이므로 이들을 동시에 만족시키는 것은 매우 어렵다는 문제가 있다.However, toughness and abrasion resistance are mutually opposite properties, so it is very difficult to satisfy them at the same time.
본 발명은 상기와 같은 문제점을 해결하기 위한 것으로서, 내마모성과 인성을 함께 갖추고 있는 압연용 보강롤을 제공하는 것을 목적으로 한다.The present invention has been made to solve the above problems, and an object of the present invention is to provide a reinforcing roll for rolling having both wear resistance and toughness.
도 1은 본 발명에 의한 보강롤과 종래의 보강롤의 충격값을 비교하는 도면이다.1 is a view comparing the impact value of the reinforcement roll and the conventional reinforcement roll according to the present invention.
상기 목적을 달성하기 위한 본 발명의 압연용 단강 보강롤은, 0.35 내지 0.80 중량%의 탄소, 0.25 내지 0.80 중량%의 규소, 0.35 내지 1.5 중량%의 망간, 0.2 내지 1.5 중량%의 니켈, 4.0% 내지 6.0 중량%의 크롬, 0.5 내지 1.5 중량%의 몰리브덴, 0.05 내지 0.5 중량%의 바나듐, 0.1 중량% 이하의 니오븀을 함유하며, 잔부는 철과 미량의 불순물로 구성되는 것을 특징으로 한다.Forged steel reinforcing rolls of the present invention for achieving the above object, 0.35 to 0.80% by weight of carbon, 0.25 to 0.80% by weight of silicon, 0.35 to 1.5% by weight of manganese, 0.2 to 1.5% by weight of nickel, 4.0% To 6.0% by weight of chromium, 0.5 to 1.5% by weight of molybdenum, 0.05 to 0.5% by weight of vanadium, 0.1% by weight of niobium or less, the balance is characterized by consisting of iron and trace impurities.
상기와 같은 구성의 보강롤은, 종래에 비하여 니켈, 크롬, 몰리브덴, 바나듐 등의 첨가량을 높이고 니오븀을 새로이 첨가하여 소재의 경화능을 높여 내마모성을 향상시키고, 경화시에 마르텐사이트 조직을 얻음으로써 인성 및 피로강도를 향상시키며, 동시에 니오븀은 탄화물을 형성하여 오스테나이트 온도영역에서 용융되지 않고 잔존하여, 오스테나이트의 결정립 성장을 억제하여 내충격성과 인성을 향상시킴으로써 롤의 표피가 박리되는 사고를 방지할 수 있다. 더욱이, 크롬량이 크게 증가됨으로써 페라이트 기지를 고용강화하여 경도를 향상시킨다. 고용강화에 의한 경도 향상은 탄소량 증가에 의한 경도 향상에 수반하는 인성 저하 문제를 효과적으로 해결할 뿐 아니라 뜨임 시에 미세한 합금 탄화물의 석출로 내마모성과 인성의 향상을 가져온다.The reinforcement rolls having the above-described structure have higher toughness by increasing the addition amount of nickel, chromium, molybdenum, vanadium and the like and adding niobium to increase the hardenability of the material, thereby improving wear resistance and obtaining martensitic structure during hardening. And fatigue strength, and at the same time, niobium forms carbide and remains unmelted in the austenite temperature range, and inhibits grain growth of austenite to improve impact resistance and toughness, thereby preventing the peeling of the skin of the roll. have. In addition, the amount of chromium is greatly increased, so that the ferrite matrix is hardened to improve the hardness. The hardness improvement by solid solution strengthening not only effectively solves the problem of toughness accompanying the increase of the carbon content, but also improves wear resistance and toughness by precipitation of fine alloy carbides during tempering.
이하, 본 발명에서 단강 보강롤의 성분을 상기와 같이 한정한 이유에 대하여설명한다.Hereinafter, the reason for limiting the components of the forged steel reinforcement roll as described above will be described.
탄소는 경도 및 내마모성을 증가시키는 대표적인 원소로서 합금 원소와 결합하여 탄화물을 형성하는데 0.35 중량% 이하이면 경화능이 감소하고 석출 탄화물의 양이 감소하여 기지 경도와 내마모성이 저하되므로 이를 하한으로 설정하였다. 반면, 0.80 중량% 이상이 되면 다량의 조대한 탄화물이 생성되어 내충격성이 저하되므로 0.80 중량%를 상한으로 설정하였다.Carbon is a representative element for increasing hardness and wear resistance, and carbides are combined with alloying elements to form carbides. When the carbon content is less than 0.35% by weight, the hardenability decreases and the amount of precipitated carbides decreases the hardness and wear resistance. On the other hand, if it is more than 0.80% by weight, a large amount of coarse carbides are generated and impact resistance is lowered, so 0.80% by weight was set as an upper limit.
규소는 제강 과정에서 탈산 작용을 할뿐만 아니라 페라이트 기지에 완전 고용되어 강의 기지 강도를 높이는 합금 원소로서, 0.25 중량% 이하이면 탈산이 부족하고 강의 기계적 성질을 감소시키므로 0.25 중량%를 하한으로 하였다. 반면, 0.80 중량% 이상이 되면 강의 단조성을 감소시키고 결정립계에 개재물로 존재할 수 있기 때문에 0.80 중량%를 상한으로 설정하였다.Silicon is an alloying element that not only deoxidizes during the steelmaking process but also is completely dissolved in the ferrite matrix to increase the steel sheet's known strength. If the content is less than 0.25% by weight, silicon is deoxidized and the mechanical properties of the steel are reduced. On the other hand, if it is more than 0.80% by weight, the forging of steel is reduced and may be present as an inclusion at the grain boundary, so 0.80% by weight is set as an upper limit.
망간은 오스테나이트 상(相)의 안정화 원소로 보강롤의 경화깊이를 증가시키는 원소이다. 그러나, 첨가량이 0.35 중량% 미만이면, 소입능(경화능)이 저하되어 요구되는 경화 깊이를 얻지 못한다. 반면, 1.5 중량% 이상으로 첨가하면 상온에 잔류 오스테나이트가 존재하여 조직을 취약하게 하거나 변형을 유발시키므로 1.5 중량%를 상한으로 설정하였다.Manganese is an element that increases the hardening depth of the reinforcement roll as a stabilizing element in the austenite phase. However, when the addition amount is less than 0.35% by weight, the quenching capacity (curing ability) is lowered and the required curing depth cannot be obtained. On the other hand, when added in more than 1.5% by weight, the residual austenite is present at room temperature to weaken the tissue or cause deformation, so 1.5% by weight was set as the upper limit.
니켈은 인성과 경화능을 향상시키고 보강롤과 같은 대형 롤에 있어서 질량 효과를 경감시킨다. 다만, 첨가량이 0.2 중량% 이하이면 크롬, 몰리브덴, 바나듐의 첨가에 의한 인성 감소를 보상하지 못하므로 0.2 중량% 하한으로 설정하였고, 1.5 중량% 이상으로 되면 비경제적이며 잔류 오스테나이트를 형성시켜 조직을 취화시키므로 1.5 중량%를 상한으로 설정하였다.Nickel improves toughness and hardenability and reduces mass effects in large rolls such as reinforcement rolls. However, if the added amount is less than 0.2% by weight, the reduction in toughness due to the addition of chromium, molybdenum and vanadium cannot be compensated, so the lower limit is set to 0.2% by weight. As embrittlement, 1.5% by weight was set as the upper limit.
크롬은 경화능을 향상시키고 석출 탄화물을 형성하는 원소로써 내마모성을 향상시킨다. 다만, 함유량이 4.0 중량% 이하로 되면 크롬탄화물 형성이 급감하고 몰리브덴, 바나듐 등과 복합탄화물을 형성하여 뜨임 저항을 증대시키는 효과가 저하되므로 하한을 4.0 중량%로 설정하였다. 반면, 함유량이 6.0 중량% 이상으로 되면 탄화물 양이 증가하여 인성이 저하되므로 6.0 중량%를 상한으로 설정하였다.Chromium is an element that improves hardenability and forms precipitated carbides, thereby improving wear resistance. However, when the content is 4.0% by weight or less, the formation of chromium carbide is drastically reduced, and the effect of increasing the tempering resistance by forming a composite carbide with molybdenum, vanadium and the like is lowered, so the lower limit is set to 4.0% by weight. On the other hand, when the content is 6.0% by weight or more, the amount of carbide is increased and toughness is lowered, so 6.0% by weight is set as an upper limit.
몰리브덴은 탄화물을 형성하여 고온 경도와 강도를 부여하고 뜨임 저항을 증대시키며 뜨임 2차 경화성을 크게 향상시키나, 그 함유량이 0.5 중량% 이하이면 상기 효과가 저하되므로 0.5 중량%를 하한으로 설정하였다. 반면 1.5 중량% 이상으로 되면 충격 인성을 감소시키고 비경제적이므로 1.5 중량%를 상한으로 설정하였다.Molybdenum forms carbide to impart high temperature hardness and strength, increase tempering resistance, and greatly improve tempering secondary curability, but if the content is 0.5 wt% or less, the effect is lowered, so 0.5 wt% is set as the lower limit. On the other hand, if more than 1.5% by weight, impact toughness is reduced and is economical, so 1.5% by weight was set as an upper limit.
바나듐은 불용성 바나듐탄화물을 형성하고 결정립을 미세화시켜 인성을 향상시킨다. 다만, 함유량이 0.05 중량% 이하이면 페라이트 기지에 모두 고용되어 탄화물에 의한 효과를 나타낼 수 없으므로 0.05 중량%를 하한으로 설정하였다. 반면, 0.5 중량% 이상이 되면 가열온도에서 오스테나이트에 고용되지 않는 불용성 바나듐탄화물의 양이 증가하여 인성을 저하시키므로 0.5 중량%를 상한으로 설정하였다.Vanadium forms insoluble vanadium carbides and refines grains to improve toughness. However, if the content is 0.05% by weight or less, all of the solid solution in the ferrite matrix can not exhibit the effect of carbide, so 0.05% by weight was set as the lower limit. On the other hand, when 0.5 wt% or more is increased, the amount of insoluble vanadium carbide that is not dissolved in austenite at the heating temperature is increased, thereby decreasing toughness, and thus 0.5 wt% is set as an upper limit.
니오븀은 미세한 니오븀탄화물을 석출시켜 오스테나이트화 온도영역에서 결정립의 성장을 억제하여 합금의 파괴인성값을 향상시키고 뜨임 열처리시 2차 경화 효과를 나타내는 합금원소이다. 그러나, 0.1 중량% 이상으로 첨가되면 초기에 형성된 조대화 니오븀탄화물이 오스테나이트화 온도영역에서는 용해되지 못하고 잔류하여 합금의 소입성을 감소시킬 뿐만 아니라 경도가 높은 작업롤과의 마찰시 보강롤의 마모를 촉진시키는 연삭제로 작용할 수 있다. 따라서, 그 상한을 0.1 중량%로 설정하였다.Niobium is an alloying element that precipitates fine niobium carbide and suppresses grain growth in the austenitization temperature range, thereby improving the fracture toughness of the alloy and exhibiting a secondary curing effect during tempering heat treatment. However, when added at 0.1% by weight or more, the coarsened niobium carbide initially formed does not dissolve in the austenitization temperature range and remains to reduce the hardenability of the alloy and wear of the reinforcement roll when friction with a high hardness work roll. It can act as a softener to promote. Therefore, the upper limit was set to 0.1 weight%.
표 1에 종래의 압연용 보강롤로 사용되던 소재의 일반적인 화학조성과 본 발명의 내마모성과 인성이 향상된 압연용 단강 보강롤의 화학조성을 각각 나타내었다.Table 1 shows the general chemical composition of the material used as a conventional reinforcement roll for rolling and the chemical composition of the forged steel reinforcing roll for improved wear resistance and toughness of the present invention.
[표 1]TABLE 1
한편, 보강롤의 조성을 상기와 같이 구성할 경우, 종래의 보강롤에 대하여 실시하는 것과 동일한 조건으로 열처리를 하여도 그 조직이 베이나이트가 아닌 마르텐사이트로 된다. 따라서, 열처리 조건을 종래에 비하여 특별히 바꾸어주지 않고도 기계적 성질이 우수한 보강롤을 얻을 수 있다.On the other hand, when the composition of the reinforcement roll is constituted as described above, the structure becomes martensite instead of bainite even if the heat treatment is performed under the same conditions as for the conventional reinforcement roll. Therefore, it is possible to obtain a reinforcing roll having excellent mechanical properties without changing the heat treatment conditions as compared with the conventional one.
도 1은 종래의 합금과 본 발명의 합금을 충격값으로 비교한 도면이다. 도면에서 본 발명에 의한 보강롤의 충격값이 종래 보강롤의 충격값에 비하여 한층 우수한 것을 알 수 있다.1 is a view comparing the conventional alloy and the alloy of the present invention with an impact value. In the drawings it can be seen that the impact value of the reinforcement roll according to the present invention is much better than the impact value of the conventional reinforcement roll.
본 발명에 의한 합금조성의 보강롤에 의하면 내마모성과 인성이 향상된 보강롤을 얻을 수 있다.According to the reinforcing roll of the alloy composition according to the present invention can be obtained a reinforcing roll with improved wear resistance and toughness.
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| KR10-1998-0041002A KR100359500B1 (en) | 1998-09-30 | 1998-09-30 | Rolled steel forging rolls with improved wear resistance and toughness |
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