KR101560901B1 - Wire rod having excellent low temperature toughness and method for manufacturing the same - Google Patents
Wire rod having excellent low temperature toughness and method for manufacturing the same Download PDFInfo
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- KR101560901B1 KR101560901B1 KR1020130151738A KR20130151738A KR101560901B1 KR 101560901 B1 KR101560901 B1 KR 101560901B1 KR 1020130151738 A KR1020130151738 A KR 1020130151738A KR 20130151738 A KR20130151738 A KR 20130151738A KR 101560901 B1 KR101560901 B1 KR 101560901B1
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- wire rod
- temperature toughness
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- 238000000034 method Methods 0.000 title claims description 14
- 238000004519 manufacturing process Methods 0.000 title abstract description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 46
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 28
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 7
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 7
- 229910000831 Steel Inorganic materials 0.000 claims description 15
- 239000010959 steel Substances 0.000 claims description 15
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 13
- 229910052796 boron Inorganic materials 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000005098 hot rolling Methods 0.000 claims description 5
- PIGFYZPCRLYGLF-UHFFFAOYSA-N Aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 claims description 3
- 239000010960 cold rolled steel Substances 0.000 abstract description 7
- 229910052698 phosphorus Inorganic materials 0.000 abstract description 7
- 229910052760 oxygen Inorganic materials 0.000 abstract description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 18
- 230000000694 effects Effects 0.000 description 12
- 230000032683 aging Effects 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 239000011572 manganese Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 229910052759 nickel Inorganic materials 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 7
- 238000005097 cold rolling Methods 0.000 description 7
- 229910001567 cementite Inorganic materials 0.000 description 6
- 229910017052 cobalt Inorganic materials 0.000 description 6
- 239000010941 cobalt Substances 0.000 description 6
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 6
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000003825 pressing Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 239000011574 phosphorus Substances 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- 238000010273 cold forging Methods 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 229910020630 Co Ni Inorganic materials 0.000 description 1
- 238000003483 aging Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000012669 compression test Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000035755 proliferation Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
저온인성이 우수한 냉간압조용 선재 및 그 제조방법이 개시된다. 본 발명의 일 측면인 저온인성이 우수한 냉간압조용 선재는 중량%로, C: 0.2~0.4%, Mn: 0.4~1.0%, Co: 0.2~2.0%, Ni: 0.5~3.0%, Al: 0.02~0.04%, P: 0.035% 이하, S: 0.040% 이하, O: 0.005% 이하, N: 50ppm 이하, B: 0.001~0.003%, 잔부 Fe 및 기타 불가피한 불순물을 포함하고, 자유 질소량이 10ppm 이하이며, 미세조직은 페라이트와 펄라이트 복합조직인 것을 특징으로 한다.Disclosed is a cold rolled steel wire having excellent low temperature toughness and a method for producing the same. A cold-rolled steel wire rod excellent in low-temperature toughness, which is one aspect of the present invention, contains 0.2 to 0.4% of C, 0.4 to 1.0% of Mn, 0.2 to 2.0% of Co, 0.5 to 3.0% of Ni, And the balance Fe and other unavoidable impurities, and the amount of free nitrogen is not more than 10 ppm, and the content of P is not more than 0.035%, P is not more than 0.035%, S is not more than 0.040%, O is not more than 0.005%, N is not more than 50 ppm, B is from 0.001 to 0.003% , And the microstructure is characterized by being a complex structure of ferrite and pearlite.
Description
본 발명은 저온인성이 우수한 냉간압조용 선재(CHQ: Cold Heading Quality Wire) 및 그 제조방법에 관한 것이다.
The present invention relates to a cold heading quality wire (CHQ) having excellent low temperature toughness and a method of manufacturing the same.
일반적으로 냉간압조 가공을 실시하여 냉간압조용 선재를 생산함에 있어서, 다이의 수명은 생산성과 직결되며 높은 제조 가격으로 인해 냉간단조제품 경쟁력 확보 관점에서 매우 중요한 개선 인자 중 하나이며, 강재의 강도, 변형시효 등에 의해 크게 영향을 받는 것으로 알려져 있다.
Generally, in the production of cold-rolled wire by cold-pressing, the lifetime of the die is one of the important factors in terms of securing the competitiveness of cold forging products due to productivity and high manufacturing cost. It is known that it is greatly influenced by aging.
냉간압조시 다이수명 또는 다이의 마모는 강재의 강도가 클수록 저하되는 경향을 보이며, 이러한 강재의 강도를 낮추는 방법으로는 강재를 구상화 열처리와 같은 연질화 처리하여 펄라이트 내의 경질상인 세멘타이트를 구형으로 만드는 방법이 가장 보편적으로 사용되고 있다. 이 뿐만 아니라, 변형시효는 가공시 소재내부에서 전위의 이동과 증식이 동시에 발생하며, C, N 등의 원소가 이러한 전위를 고착시킴으로써 변형강도를 높이는 현상으로서, 다이의 수명을 감소시키는 한가지 요인이므로 이를 감소시키는 방안도 필요하게 되었으나 현재까지 효과적인 방법은 제시된 바 없는 실정이다.
The cold-rolled steel die life or wear of the die tends to decrease as the strength of the steel increases, and as a method of lowering the strength of such steel, softening the steel to a spheroidizing heat treatment to soften the cementite Methods are most commonly used. In addition, the strain aging is a phenomenon in which displacement and propagation occur simultaneously in the material at the time of processing, and elements such as C and N increase the strain intensity by fixing these dislocations. There has been a need to reduce this, but no effective method has been proposed to date.
본 발명은 변형시효를 효과적으로 억제하여 냉간압조용 다이의 수명을 획기적으로 개선하는 것이 가능하고, 더불어, 저온인성이 우수한 냉간압조용 선재를 제공하고자 하는 것이다.
An object of the present invention is to provide a cold rolled steel wire rod capable of remarkably improving the life of a cold rolling die by effectively suppressing strain aging and having excellent low temperature toughness.
본 발명의 일 측면인 저온인성이 우수한 냉간압조용 선재는 중량%로, C: 0.2~0.4%, Mn: 0.4~1.0%, Co: 0.2~2.0%, Ni: 0.5~3.0%, Al: 0.02~0.04%, P: 0.035% 이하, S: 0.040% 이하, O: 0.005% 이하, N: 50ppm 이하, B: 0.001~0.003%, 잔부 Fe 및 기타 불가피한 불순물을 포함하고, 자유 질소량이 10ppm이하이며, 미세조직은 페라이트와 펄라이트 복합조직인 것을 특징으로 한다.
A cold-rolled steel wire rod excellent in low-temperature toughness, which is one aspect of the present invention, contains 0.2 to 0.4% of C, 0.4 to 1.0% of Mn, 0.2 to 2.0% of Co, 0.5 to 3.0% of Ni, And the balance Fe and other unavoidable impurities, and the amount of free nitrogen is not more than 10 ppm, the content of Fe is not more than 0.04%, P is not more than 0.035%, S is not more than 0.040%, O is not more than 0.005%, N is not more than 50 ppm, B is from 0.001 to 0.003% , And the microstructure is characterized by being a complex structure of ferrite and pearlite.
본 발명의 다른 일 측면인 저온인성이 우수한 냉간압조용 선재의 제조방법은 중량%로 C: 0.2~0.4%, Mn: 0.4~1.0%, Co: 0.2~2.0%, Ni: 0.5~3.0%, Al: 0.02~0.04%, P: 0.035% 이하, S: 0.040% 이하, O: 0.005% 이하, N: 50ppm 이하, B: 0.001~0.003%, 잔부 Fe 및 기타 불가피한 불순물을 포함하는 빌렛을 1150~1300℃로 가열하여 자유 질소량을 10ppm 이하로 제어하는 단계; 및 상기 빌렛을 열간압연하여 선재를 제조하는 단계를 포함한다.
A method for producing cold-rolled steel wire rods having excellent low-temperature toughness, which is another aspect of the present invention, comprises 0.2 to 0.4% of C, 0.4 to 1.0% of Mn, 0.2 to 2.0% of Co, 0.5 to 3.0% of Ni, And a balance containing Fe and other unavoidable impurities at a ratio of 1150 to 1150 at% of Al: 0.02 to 0.04%, P: at most 0.035%, S: at most 0.040%, O: at most 0.005%, N: Controlling the amount of free nitrogen to 10 ppm or less by heating to 1300 캜; And hot rolling the billet to produce a wire rod.
덧붙여 상기한 과제의 해결수단은, 본 발명의 특징을 모두 열거한 것은 아니다. 본 발명의 다양한 특징과 그에 따른 장점과 효과는 아래의 구체적인 실시형태를 참조하여 보다 상세하게 이해될 수 있을 것이다.
In addition, the solution of the above-mentioned problems does not list all the features of the present invention. The various features of the present invention and the advantages and effects thereof will be more fully understood by reference to the following specific embodiments.
본 발명에 따르면, 기존의 냉간압조용 선재의 제조시 다이수명을 저하시키는 주요 원인인 자유 질소를 효과적으로 고정시킴으로써 냉간압조시 변형시효를 억제할 수 있다.According to the present invention, it is possible to effectively suppress cold aging deformation aging by effectively securing free nitrogen, which is a main cause of lowering the die life, when manufacturing a conventional wire rod for cold rolling.
또한, 본 발명에 따르면, -20℃에서의 충격치가 55J 이상으로 저온인성이 우수한 냉간압조용 선재를 제공할 수 있다.
Further, according to the present invention, it is possible to provide a cold rolled steel wire rod excellent in low temperature toughness at an impact value of 55 J or more at -20 캜.
본 발명의 발명자들은 냉간압조용 선재를 제조함에 있어서, 냉간압조시 변형에 의한 변형시효의 증가 및 이로 인한 다이 수명이 저하되는 문제점을 개선할 수 있는 방안에 대하여 연구를 행한 결과, 냉간압조시 변형시효 발생에 원인이 되는 침입형 원소를 고정시킬 경우, 상기 침입형 원소의 이동이 최소화되어 변형시효를 억제할 수 있음을 확인하고, 본 발명에 이르게 되었다.
The inventors of the present invention have made a study on a method for improving the deformation aging due to the cold pressing shrinkage and the problem of deterioration of the die life due to the cold pressing in producing the wire rod for cold rolling, It has been confirmed that when the interstitial elements causing aging are fixed, the movement of the interstitial elements is minimized and the aging of the strain can be suppressed, leading to the present invention.
이하, 본 발명의 일측면인 저온인성이 우수한 냉간압조용 선재에 대하여 상세히 설명한다.
Hereinafter, the wire for cold-press forming having excellent low-temperature toughness, which is one aspect of the present invention, will be described in detail.
먼저, 본 발명 냉간압조용 선재의 합금조성에 대하여 상세히 설명한다.First, the alloy composition of the wire rod for cold-rolling is explained in detail.
탄소(C): 0.2~0.4중량%Carbon (C): 0.2 to 0.4 wt%
탄소는 강도 확보를 위해 필수적으로 포함되는 원소로서, 상기 탄소의 함량이 0.2중량% 미만인 경우에는 충분한 소재강도를 얻기가 어렵고, 최종 QT 열처리 후 충분한 소입성 확보가 용이하지 않다. 반면, 상기 탄소의 함량이 0.4중량%를 초과할 경우에는 높은 소재강도로 인해 본 발명이 확보하고자 하는 냉간압조성 향상 효과를 발현하는데 어려움이 있다.
Carbon is an element that is essential for securing strength. When the content of carbon is less than 0.2% by weight, it is difficult to obtain sufficient material strength and it is not easy to secure sufficient ingotability after the final QT heat treatment. On the other hand, when the content of carbon is more than 0.4% by weight, it is difficult to exhibit the effect of improving the cold rolling composition to be obtained by the present invention due to high material strength.
망간(Mn): 0.4~1.0중량%Manganese (Mn): 0.4 to 1.0 wt%
망간은 강의 강도를 증가시키고 충격특성에 영향을 미치며, 압연성을 증가시키고 취성을 감소시키는 역할을 한다. 상기와 같은 효과를 발현시키기 위해서 0.4중량% 이상의 망간을 포함하는 것이 바람직하다. 반면, 상기 망간의 함량이 1.0중량%를 초과하는 경우에는 강도 증가에 의해 경화현상이 심화되는 문제가 있다.
Manganese increases the strength of the steel, affects the impact properties, increases the rolling property and reduces the brittleness. In order to exhibit the above-mentioned effect, it is preferable to contain 0.4 wt% or more of manganese. On the other hand, when the content of manganese exceeds 1.0 wt%, there is a problem that the hardening phenomenon is intensified by the increase of the strength.
코발트(Co): 0.2~2.0 중량%Cobalt (Co): 0.2 to 2.0 wt%
코발트는 펄라이트(pearlite) 변태를 촉진시키고 세멘타이트(cementite)를 연질화하여 선재의 연성을 향상시키는 역할을 한다. 상기 코발트 함량이 0.2 중량% 미만인 경우에는 세멘타이트의 경도가 높아 세멘타이트 변형능 향상 효과를 기대하기 어렵다. 반면, 상기 코발트 함량이 2.0 중량%를 초과하는 경우에는 최종 QT 열처리 후 충분한 소입성 확보가 용이하지 않다.
Cobalt promotes pearlite transformation and softens cementite to improve the ductility of the wire rod. When the cobalt content is less than 0.2% by weight, the hardness of the cementite is high and it is difficult to expect the effect of improving the cementite deformability. On the other hand, when the cobalt content is more than 2.0 wt%, it is not easy to secure sufficient ingot qualities after the final QT heat treatment.
니켈(Ni): 0.5~3.0 중량%Nickel (Ni): 0.5 to 3.0 wt%
니켈은 오스테나이트 안정화 원소로써, 선재의 저온인성을 향상시키는 역할을 한다. 상기와 같은 효과를 발현시키기 위해서 0.5 중량% 이상의 니켈을 포함하는 것이 바람직하다. 반면, 상기 니켈의 함량이 3.0 중량%를 초과하는 경우에는 세멘타이트의 흑연화가 과도하게 발생하여 QT 열처리시 세멘타이트가 완전히 용해되지 않아 소입강도의 저하가 발생한다.
Nickel is an austenite stabilizing element and plays a role in improving the low temperature toughness of wire rods. In order to exhibit the above-mentioned effect, it is preferable that nickel is contained in an amount of 0.5 wt% or more. On the other hand, when the content of nickel exceeds 3.0% by weight, graphitization of the cementite occurs excessively, and the cementite is not completely dissolved in the QT heat treatment, resulting in a decrease in the quenching strength.
알루미늄(Al): 0.02~0.04중량%Aluminum (Al): 0.02 to 0.04 wt%
알루미늄은 제강 공정에서 탈산제로 많이 사용이 되며, 질소와 반응하여 형성된 AlN에 의해 오스테나이트 결정립을 미세화시키는 효과가 있다. 본 발명에서는 보론을 통한 입계강화 혹은 소입성 향상을 위한 자유보론량의 확보를 위해 질소를 고정시키는 원소로 알루미늄을 활용하였다. 상기 알루미늄의 함량이 0.02중량% 미만인 경우에는 질소를 고정하기에 충분하지 않아 보론에 의한 소입성 향상 효과가 미흡하다. 반면에, 알루미늄의 함량이 0.04중량%를 초과하는 경우에는 알루미나와 같은 비금속개재물의 생성이 과다하여 강재 내 결함발생이 심화된다.
Aluminum is widely used as a deoxidizer in the steelmaking process, and has the effect of making the austenite grains finer by AlN formed by reaction with nitrogen. In the present invention, aluminum is used as an element for fixing nitrogen to secure a free boron amount for enhancing grain boundary strengthening or incombustibility through boron. If the content of aluminum is less than 0.02 wt%, nitrogen is not enough to fix, and the effect of improving boron-boring properties is insufficient. On the other hand, when the content of aluminum exceeds 0.04% by weight, generation of nonmetallic inclusions such as alumina is excessively generated, and the occurrence of defects in the steel is intensified.
산소(O): 0.005중량% 이하Oxygen (O): 0.005 wt% or less
산소는 산화물계 비금속 개재물을 형성하여 피로수명 저하를 유발할 우려가 있으므로, 그 함량의 상한을 0.005중량%로 관리한다.
Oxygen may form an oxide-based non-metallic inclusion and cause fatigue life deterioration. Therefore, the upper limit of the content is controlled to 0.005% by weight.
인(P): 0.035중량% 이하Phosphorus (P): 0.035% by weight or less
상기 인은 불가피하게 함유되는 불순물로써, 결정입계에 편석되어 인성을 저하시키고 지연파괴 저항성을 감소시키는데 주요 원인이 되는 원소이므로, 가능한 한 낮게 제어하는 것이 바람직하다. 이론상 인의 함량은 0%로 제한하는 것이 유리하나, 제조공정상 필연적으로 함유될 수 밖에 없다. 따라서, 상한을 관리하는 것이 중요하며, 본 발명에서는 상기 인 함량의 상한은 0.035중량%로 관리한다.
The phosphorus is inevitably contained and is an element which is segregated at the crystal grain boundaries to decrease the toughness and reduce the delayed fracture resistance. Therefore, it is desirable to control the phosphor as low as possible. Theoretically, it is preferable to limit the phosphorus content to 0%, but it is inevitably contained inevitably in the manufacturing process. Therefore, it is important to manage the upper limit, and in the present invention, the upper limit of the phosphorus content is controlled to 0.035% by weight.
황(S): 0.04중량% 이하Sulfur (S): 0.04% by weight or less
황은 불가피하게 함유되는 불순물로서, 저융점 원소로서 입계에 편석되어 인성을 저하시키고 유화물을 형성시켜 지연파괴 저항성 및 응력이완 특성에 유해한 영향을 미치는 원소이므로, 가능한 한 낮게 제어하는 것이 바람직하다. 이론상의 황의 함량은 0%로 제한하는 것이 유리하나, 제조공정상 필연적으로 함유될 수 밖에 없다. 따라서, 상한을 관리하는 것이 중요하며, 본 발명에서는 상기 황 함량의 상한은 0.04중량%로 관리한다.
Sulfur is an inevitably contained impurity, which is segregated as a low melting point element in the grain boundaries to reduce toughness and form an emulsion, thereby detrimentally affecting the delayed fracture resistance and stress relaxation characteristics. Therefore, it is desirable to control as low as possible. The theoretical sulfur content is advantageous to be limited to 0% but it is inevitably contained in the manufacturing process normally. Therefore, it is important to manage the upper limit, and in the present invention, the upper limit of the sulfur content is controlled to 0.04% by weight.
보론(B): 0.001~0.003중량%Boron (B): 0.001 to 0.003 wt%
보론은 강재의 소입성을 향상시키는 효과가 있다. 본 발명에서는 고용강화원소인 Si 함량의 감소에 따른 강도 저하를 비교적 저렴한 원소인 보론을 통해 보상하기 위해 첨가한다. 상기와 같은 효과를 발현하기 위해서는 보론의 함량이 0.001중량% 이상 포함되는 것이 바람직하다. 반면, 상기 보론의 함량이 0.003 중량%를 초과하는 경우에는 그 효과가 포화되고, 입계가 열화되어 물성저하 등의 원인이 된다.
Boron has an effect of improving the ingotability of the steel material. In the present invention, the decrease in strength due to the decrease in the Si content, which is the solid solution strengthening element, is added to compensate for the relatively inexpensive element boron. In order to exhibit the above-mentioned effect, it is preferable that the boron content is 0.001 wt% or more. On the other hand, when the content of boron exceeds 0.003% by weight, the effect is saturated and the grain boundary is deteriorated, which causes the property deterioration and the like.
질소(N): 50ppm 이하Nitrogen (N): 50ppm or less
질소는 불가피하게 함유되는 불순물로서, 질소 함유량은 다이 수명과 직결되며, 특히, 질소와 같은 침입형 고용원소들은 냉간단조시 발생한 단조열에 의해 소재 내부에 전위의 이동과 증식을 일으키고, 질소와 같은 침입형 고용원소들은 이러한 전위에 고착하여 변형강도를 증가시키게 된다. 따라서, 본 발명에서는 Al 등의 질소 고정원소를 첨가하게 되는데, 상기 질소의 함량이 50ppm을 초과하는 경우에는 Al 등의 질소 고정원소를 첨가하여도 자유 질소를 제어하기 어렵다.
Nitrogen is an impurity inevitably contained. The nitrogen content is directly related to the lifetime of the die. Particularly, the interstitial elements such as nitrogen cause migration and proliferation of dislocation within the material due to forging heat generated during cold forging, Type solid-state elements adhere to these dislocations and increase the deformation strength. Therefore, in the present invention, a nitrogen fixing element such as Al is added. When the nitrogen content exceeds 50 ppm, it is difficult to control free nitrogen even by adding a nitrogen fixing element such as Al.
이외에 잔부 Fe 및 불가피한 불순물을 포함한다. 상기 조성 이외에 유효한 성분의 첨가가 배제되는 것은 아니다.
And the balance Fe and inevitable impurities. Addition of an effective component other than the above-mentioned composition is not excluded.
본 발명의 일 구현예에 따르면, 선재 내 자유 질소량이 10ppm 이하인 것이 바람직하다. 선재 내 자유 질소량을 10ppm 이하로 제어함으로써, 냉간단조시 변형시효에 의한 선재의 변형저항강도 상승이 최소화되며, 보다 구체적으로 상온(RT)~200℃에서 변형량 e=1, 변형속도 ε'=1/s로 변형시, 선재의 변형저항강도는 종래의 Si 첨가강 대비 100MPa 이상 낮은 값을 나타내게 된다.
According to one embodiment of the present invention, it is preferable that the amount of free nitrogen in the wire is 10 ppm or less. By controlling the free nitrogen content in the wire rod to 10 ppm or less, an increase in the deformation resistance strength of the wire rod due to deformation aging during cold forging is minimized. More specifically, the deformation rate e is 1 and the deformation rate ε '= 1 at room temperature (RT) / s, the deformation resistance strength of the wire rod is lower than that of the conventional Si addition steel by 100 MPa or lower.
또한, 본 발명의 일 구현예에 따르면, 선재 내 자유보론량이 10~20ppm인 것이 바람직하다. 선재 내 자유 보론량을 상기의 범위로 제어함으로써, 상기 선재는 소입 후 소입강도가 종래의 Si 첨가강과 유사한 값을 가지게 된다. 상기 자유 보론량이 10ppm 미만인 경우에는 충분한 소입성을 가지지 못하는 문제가 있다. 반면에, 20ppm을 초과하는 경우에는 입계가 열화되어 물성이 저하되는 문제가 있다.
According to an embodiment of the present invention, it is preferable that the amount of free boron in the wire is 10 to 20 ppm. By controlling the amount of free boron in the wire to be within the above range, the wire material has a value similar to that of the conventional Si addition steel after quenching. When the amount of free boron is less than 10 ppm, there is a problem that sufficient incombustibility is not obtained. On the other hand, if it exceeds 20 ppm, there is a problem that the grain boundary is deteriorated and the physical properties are lowered.
또한, 본 발명의 일 구현예에 따른 선재의 미세조직은 페라이트와 펄라이트 복합조직인 것이 바람직하다. 선재의 미세조직이 페라이트와 펄라이트의 복합조직을 가짐으로써, 우수한 냉간압조성을 확보할 수 있다. The microstructure of the wire according to an embodiment of the present invention is preferably ferrite and pearlite composite structure. By having the composite structure of ferrite and pearlite in the microstructure of the wire, excellent cold pressure composition can be secured.
상기와 같은 미세조직을 가짐으로써 발현되는 우수한 냉간압조성을 보다 향상시키기 위해서는 면적분율%로, 10~30%의 페라이트, 잔부 펄라이트의 미세조직을 갖는 것이 바람직하다. 상기 페라이트의 면적분율%이 10% 미만인 경우에는 강도가 높아져 충분한 냉간압조성 확보가 용이하지 않으며, 30%를 초과하는 경우에는 최종 QT 열처리 후 충분한 소입성 확보가 용이하지 않는 문제가 있다.
In order to further improve the excellent cold-rolling composition expressed by having such a microstructure, it is preferable to have a microstructure of ferrite and remainder pearlite of 10 to 30% in area fraction%. If the percentage of the area percentage of the ferrite is less than 10%, the strength becomes high and the sufficient cold-rolling composition can not be secured easily. When the area fraction is more than 30%, sufficient entrapmentability after the final QT heat treatment is not easily secured.
또한, 본 발명의 일 구현예에 따르면, 선재 내 니켈 함량이 적절히 제어되어 우수한 저온인성을 나타내게 되며, 구체적으로 -20℃에서 55J 이상의 충격치를 나타낸다.
In addition, according to one embodiment of the present invention, the nickel content in the wire rod is appropriately controlled to exhibit excellent low-temperature toughness, specifically showing an impact value of 55 J or more at -20 캜.
이하, 본 발명의 다른 일측면인 저온인성이 우수한 냉간압조용 선재의 제조방법에 대하여 상세히 설명한다.
Hereinafter, a method of manufacturing a wire rod for cold-pressing that is excellent in low-temperature toughness, which is another aspect of the present invention, will be described in detail.
상술한 조성을 만족하는 빌렛을 1150~1300℃의 온도영역에서 1시간 이상 가열한다. 상기와 같이 1150~1300℃의 온도영역에서 가열하는 것은 강내 자유 질소(free N)량을 제어하기 위한 것으로서, 형성된 AlN이 고온 가열에 의해 분해되지 않도록 함으로써 강 내 N가 자유 질소로 존재하는 것을 제어할 수 있다. The billet satisfying the above composition is heated in a temperature range of 1150 to 1300 캜 for 1 hour or more. As described above, heating in the temperature range of 1150 to 1300 ° C is for controlling the amount of free N in the steel, so that the formed AlN is not decomposed by heating at high temperature, can do.
본 발명에서 의미하는 자유 질소(free N)란 강 내에서 알루미늄(Al)과 결합하지 못하고 잔류하고 있는 상태의 질소를 의미한다. Free nitrogen (N) as used in the present invention means nitrogen in a state in which the aluminum does not bond with aluminum (Al) in the steel.
빌렛의 가열온도가 1150℃ 미만일 경우, 결정립이 비정상적으로 성장하여 불균일한 미세조직이 형성되는 문제가 있으며, 반면, 1300℃를 초과할 경우, 탈탄현상이 심화되는 문제가 있다.
When the heating temperature of the billet is less than 1150 ° C, the crystal grains grow abnormally and uneven microstructures are formed. On the other hand, when the temperature exceeds 1300 ° C, there is a problem that the decarburization phenomenon is intensified.
상기에 의해 가열된 빌렛을 선재 형상으로 열간압연한 후 냉각한다. 이때, 열간압연 및 냉각은 통상의 선재압연 방법에 의할 수 있다.
The billet heated by the above is hot rolled into a wire form and then cooled. At this time, hot rolling and cooling can be performed by a conventional wire rolling method.
상기한 방법에 의해 제조된 선재는 알루미늄 질화물(AlN)을 함유하는 선재로서, 자유 질소량을 10ppm 이하로 함유함에 특징이 있다. 이와 같은 선재를 냉간압조하게 되면, 전위를 고착시키는 N가 Al과 결합하여 고정됨에 따라 자유 N에 의한 전위 고착 등의 현상이 발생되지 않아 강재의 변형저항강도 상승이 억제된다. 따라서, 다이수명의 개선에 효과적인 영향을 미칠 수 있다.
The wire rod produced by the above method is characterized by containing a free nitrogen content of 10 ppm or less as a wire rod containing aluminum nitride (AlN). When such a wire rod is cold-pressed, N, which fixes the potential, is fixed by bonding with Al, so that a phenomenon such as dislocation adhesion by free N does not occur and the increase of the deformation resistance strength of the steel is suppressed. Therefore, it is possible to effectively influence the improvement of the die life.
이하, 실시예를 통하여 본 발명을 보다 구체적으로 설명하고자 한다. 다만, 하기의 실시예는 본 발명을 예시하여 보다 상세하게 설명하기 위한 것일 뿐, 본 발명의 권리범위를 한정하기 위한 것이 아니라는 점에 유의할 필요가 있다. 본 발명의 권리범위는 특허청구범위에 기재된 사항과 이로부터 합리적으로 유추되는 사항에 의해 결정되는 것이기 때문이다.
Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred from them.
(( 실시예Example ))
하기 표 1과 같은 성분조성을 갖는 각각의 강재를 준비한 후, 상기 강재를 시료로 하여 50Kg 잉곳을 주조한 후, 이를 1200℃에서 6시간 균질화 열처리하고, 두께 15㎜로 열간압연 하였다. 열간압연시 열간 마무리 압연 온도는 900℃ 이상으로 하였으며, 압연비는 80% 이상으로 실시하였다. 그 후, 공냉하였다.
Each of the steel materials having the composition shown in Table 1 below was prepared, and a 50 kg ingot was cast using the steel material as a sample. The ingot was homogenized at 1200 ° C for 6 hours and hot-rolled to a thickness of 15 mm. The hot rolling temperature during hot rolling was 900 ℃ or higher and the rolling ratio was over 80%. Thereafter, it was air-cooled.
이후, 글리블 압축 시험편을 이용하여 볼트 냉간압조 모사를 실시하였다. 변형량과 변형속도는 각각 e=1, ε'=1/s로 하였으며, 변형온도는 각각 상온(25℃)과 볼트 단조시 최대 상승온도이자 시효경화 효과가 가장 크게 나타나는 온도인 200℃로 하였다. 상기와 같이 볼트 냉간압조 모사 후, 변형저항강도의 변화를 측정하였으며, 이를 하기 표 2에 나타내었다. 한편, 괄호 안의 값은 종래예의 강도값을 기준으로 상승분(+) 또는 저하분(-)을 나타낸다.
Thereafter, a bolt cold pressing simulation was performed using a Griple compression test specimen. The deformation and deformation rates were set to e = 1 and ε '= 1 / s, respectively. The deformation temperatures were set at room temperature (25 ° C) and 200 ° C, which is the maximum rising temperature for bolt forging and the maximum age hardening effect. After the bolt cold stamping simulation as described above, the change in the deformation resistance strength was measured, and it is shown in Table 2 below. On the other hand, the values in parentheses indicate an increase (+) or a decrease (-) based on the intensity value of the conventional example.
이후, 제조된 선재의 소입강도를 측정하기 위하여, 상기 선재를 950℃로 가열한 뒤, 60℃의 오일(Oil)에서 유냉한 후 강도를 측정하였으며, 이를 하기 표 2에 함께 나타내었다. 한편, 괄호 안의 값은 종래예의 소입강도값을 기준으로 상승분(+) 또는 저하분(-)을 나타낸다.
Then, in order to measure the crush strength of the manufactured wire rod, the wire rod was heated to 950 ° C and then cooled in oil at 60 ° C to measure the strength. The results are shown in Table 2 below. On the other hand, the values in parentheses indicate an increase (+) or a decrease (-) based on the value of the intrinsic strength of the conventional example.
한편, 충격값은, ASTM Standard E8m-04 규격을 기준으로 시험하여 얻은 결과이며, 이 때 충격시험편은 압연방향의 수직방향으로 채취하였으며, -20℃의 온도에서 측정하였다.
On the other hand, the impact value was obtained by testing according to the ASTM Standard E8m-04 standard. In this case, the impact specimen was taken in the vertical direction in the rolling direction and measured at a temperature of -20 ° C.
(ppm)Free boron amount
(ppm)
(MPa)Intrinsic strength
(MPa)
(U-notch)Impact value (-20 ℃)
(U-notch)
Si가 포함되어 있는 종래예와 Si가 포함되어 있지 않은 발명예 1, 2, 비교예 1 내지 6을 대비하여 보면, Si이 포함되지 않은 발명예 1, 2, 비교예 1 내지 6은 모두 상온 및 고온 압축강도가 감소하여 고용강화 효과가 감소한 것을 확인할 수 있다.
Compared with the conventional example in which Si is contained and the case of Inventive Examples 1 and 2 and Comparative Examples 1 to 6 in which Si is not contained, in Inventive Examples 1 and 2 and Comparative Examples 1 to 6 not containing Si, It can be confirmed that the high temperature compressive strength is decreased and the solid solution strengthening effect is reduced.
비교예 1 및 2는 니켈의 미첨가로 -20℃에서의 충격값이 55J 미만으로 저온인성이 열위하게 나타났고, 비교예 3은 코발트 첨가량 부족으로 변형저항강도가 충분히 낮아지지 않았으며, 비교예 4는 코발트 첨가량 과다로 소입 후 소입강도가 지나치게 열위하게 나타났다. 비교예 5는 니켈 첨가량 부족으로 저온인성이 열위하게 나타났고, 비교예 6은 니켈 첨가량 과다로 소입 후 소입강도가 지나치게 열위하게 나타났다.
Comparative Examples 1 and 2 showed low temperature toughness at an impact value of less than 55 J at -20 캜 due to no addition of nickel and Comparative Example 3 did not sufficiently lower the deformation resistance strength due to insufficient addition of cobalt, 4 showed excessively low sintering intensity after cobalt addition. In Comparative Example 5, the low-temperature toughness was low due to the insufficient amount of nickel, and in Comparative Example 6, the superficial strength was excessively weak after the excessive addition of nickel.
반면, 발명예 1 및 2는 합금원소의 첨가량이 본 발명이 제안한 범위를 만족함으로써, 변형저항강도가 종래예 대비 100MPa 이상 낮으며, 소입 후 소입강도가 종래예와 유사한 값을 나타내며, 나아가 -20℃에서의 충격값이 55J 이상으로 저온인성이 우수함을 확인할 수 있다.
On the other hand, in Inventive Examples 1 and 2, the deformation resistance strength is lower than that of the conventional example by lowering the addition amount of the alloying element to the range proposed by the present invention, and the quenching strength after quenching is comparable to that of the conventional example. It is confirmed that the impact value at 55 DEG C is more than 55 J, which is excellent in low temperature toughness.
상기 각 강종들의 변형저항강도의 변화는 종래예와 비교해 보았을 때, 큰 차이가 없는 것으로 보여지지만, 실제로 수천 또는 수만회 이상의 냉간압조 공정을 실시할 경우 매우 큰 차이이며, 따라서, 이러한 차이는 냉간압조시 다이수명에 큰 영향을 미치게 된다.
Although the change in the deformation resistance strength of each of the above steel types is not significantly different when compared with the conventional example, it is a very large difference when a cold stamping process is actually carried out several thousands or tens of thousands times, It has a great influence on the life of the Joshidai.
이상 실시예를 참조하여 설명하였지만, 해당 기술 분야의 숙련된 통상의 기술자는 하기의 특허 청구의 범위에 기재된 본 발명의 사상 및 영역으로부터 벗어나지 않는 범위 내에서 본 발명을 다양하게 수정 및 변경시킬 수 있음을 이해할 수 있을 것이다.While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. .
Claims (8)
0.2 to 2.0% of Co, 0.5 to 3.0% of Ni, 0.02 to 0.04% of Al, 0.035% or less of P, 0.040% or less of S , O: not more than 0.005%, N: not more than 50 ppm, B: 0.001 to 0.003%, the balance Fe and other unavoidable impurities and having a free nitrogen content of 10 ppm or less, Cho Sun - Jae.
상기 선재의 자유 보론량은 10~20ppm인 저온인성이 우수한 냉간압조용 선재.
The method according to claim 1,
Wherein the wire rod has a free boron content of 10 to 20 ppm and is excellent in low temperature toughness.
상기 미세조직은 면적분율로, 10~30%의 페라이트, 잔부 펄라이트인 저온인성이 우수한 냉간압조용 선재.
The method according to claim 1,
Wherein the microstructure has an area fraction of 10 to 30% of ferrite, the balance pearlite being excellent in low temperature toughness.
상기 선재는 알루미늄 질화물(AlN)을 함유하는 저온인성이 우수한 냉간압조용 선재.
The method according to claim 1,
Wherein said wire rod contains aluminum nitride (AlN) and has excellent low-temperature toughness.
상기 선재는 -20℃에서의 충격값이 55J 이상인 저온인성이 우수한 냉간압조용 선재.
The method according to claim 1,
Wherein said wire rod has an impact value of 55 J or more at -20 캜 and is excellent in low temperature toughness.
상기 빌렛을 열간압연하여 선재를 제조하는 단계를 포함하는 저온인성이 우수한 냉간압조용 선재의 제조방법.
The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.2 to 0.4% of C, 0.4 to 1.0% of Mn, 0.2 to 2.0% of Co, 0.5 to 3.0% of Ni, 0.02 to 0.04% of Al, 0.001 to 0.003% Heating the billet containing N: 50 ppm or less, P: 0.035% or less, S: 0.04% or less, the balance Fe and other unavoidable impurities to 1150 to 1300 캜 to control the amount of free nitrogen to 10 ppm or less; And
And a step of hot-rolling the billet to produce a wire rod.
상기 선재의 자유 보론량은 10~20ppm인 저온인성이 우수한 냉간압조용 선재의 제조방법.
The method according to claim 6,
Wherein the amount of free boron in the wire is 10 to 20 ppm, and the low-temperature toughness is excellent.
상기 선재는 알루미늄 질화물(AlN)을 함유하는 저온인성이 우수한 냉간압조용 선재의 제조방법.The method according to claim 6,
Wherein the wire rod contains aluminum nitride (AlN) and has excellent low-temperature toughness.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2002155344A (en) | 2000-09-11 | 2002-05-31 | Koji Onoe | High strength screw steel and high strength screw |
| JP2005133152A (en) | 2003-10-30 | 2005-05-26 | Kobe Steel Ltd | High-strength wire rod to be induction-hardened superior in cold workability and impact resistance, and steel component using the wire rod |
| JP2009155686A (en) | 2007-12-26 | 2009-07-16 | Kobe Steel Ltd | Steel for cold working, method for producing the same, and cold-worked steel component |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002155344A (en) | 2000-09-11 | 2002-05-31 | Koji Onoe | High strength screw steel and high strength screw |
| JP2005133152A (en) | 2003-10-30 | 2005-05-26 | Kobe Steel Ltd | High-strength wire rod to be induction-hardened superior in cold workability and impact resistance, and steel component using the wire rod |
| JP2009155686A (en) | 2007-12-26 | 2009-07-16 | Kobe Steel Ltd | Steel for cold working, method for producing the same, and cold-worked steel component |
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