KR100431848B1 - Method for manufacturing high carbon wire rod containing high silicon without low temperature structure - Google Patents
Method for manufacturing high carbon wire rod containing high silicon without low temperature structure Download PDFInfo
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- KR100431848B1 KR100431848B1 KR10-1999-0063184A KR19990063184A KR100431848B1 KR 100431848 B1 KR100431848 B1 KR 100431848B1 KR 19990063184 A KR19990063184 A KR 19990063184A KR 100431848 B1 KR100431848 B1 KR 100431848B1
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- cooling
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 14
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 10
- 239000010703 silicon Substances 0.000 title claims abstract description 10
- 238000000034 method Methods 0.000 title abstract description 9
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 24
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000010955 niobium Substances 0.000 claims abstract description 9
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000010949 copper Substances 0.000 claims abstract description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052796 boron Inorganic materials 0.000 claims abstract description 7
- 239000011651 chromium Substances 0.000 claims abstract description 7
- 229910052802 copper Inorganic materials 0.000 claims abstract description 7
- 239000011572 manganese Substances 0.000 claims abstract description 7
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 7
- 238000005507 spraying Methods 0.000 claims abstract description 7
- 239000010936 titanium Substances 0.000 claims abstract description 7
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 6
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 6
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims abstract description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 5
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 5
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 5
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 5
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 5
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 5
- 239000001301 oxygen Substances 0.000 claims abstract description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 5
- 239000011574 phosphorus Substances 0.000 claims abstract description 5
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 5
- 239000011593 sulfur Substances 0.000 claims abstract description 5
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000011733 molybdenum Substances 0.000 claims abstract description 4
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000010937 tungsten Substances 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 238000001816 cooling Methods 0.000 abstract description 54
- 238000005096 rolling process Methods 0.000 abstract description 9
- 229910001563 bainite Inorganic materials 0.000 abstract description 8
- 229910000734 martensite Inorganic materials 0.000 abstract description 8
- 229910000677 High-carbon steel Inorganic materials 0.000 abstract description 7
- 229910001562 pearlite Inorganic materials 0.000 abstract description 5
- 238000010583 slow cooling Methods 0.000 abstract description 5
- 230000002401 inhibitory effect Effects 0.000 abstract description 2
- 229910000831 Steel Inorganic materials 0.000 description 43
- 239000010959 steel Substances 0.000 description 43
- 229910001566 austenite Inorganic materials 0.000 description 25
- 230000000694 effects Effects 0.000 description 19
- 230000003111 delayed effect Effects 0.000 description 13
- 238000010438 heat treatment Methods 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 12
- 229920006395 saturated elastomer Polymers 0.000 description 8
- 230000009466 transformation Effects 0.000 description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 7
- 238000005261 decarburization Methods 0.000 description 7
- 230000006872 improvement Effects 0.000 description 7
- 238000005204 segregation Methods 0.000 description 7
- 239000002131 composite material Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 230000000717 retained effect Effects 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 238000005087 graphitization Methods 0.000 description 4
- 150000004767 nitrides Chemical class 0.000 description 3
- 230000002829 reductive effect Effects 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 229910001567 cementite Inorganic materials 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000019362 perlite Nutrition 0.000 description 1
- 239000010451 perlite Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 230000009772 tissue formation Effects 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 238000005491 wire drawing Methods 0.000 description 1
Classifications
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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
-
- 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
- B21B3/02—Rolling special iron alloys, e.g. stainless steel
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B2015/0057—Coiling the rolled product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B2261/00—Product parameters
- B21B2261/20—Temperature
Abstract
본 발명은 고실리콘 첨가 고탄소강 선재의 제조방법에 관한 것으로, 그 목적은 EDC설비 또는 제어압연설비 등의 설비를 채용하지 않고 통상의 냉각설비에서 선재를 제어냉각함으로써 저온조직(베이나이트+마르텐사이트)의 생성을 억제시켜 균질하고 미세한 페라이트+퍼얼라이트 조직으로 확보할 수 있는 고실리콘 첨가 고탄소 선재의 제조방법을 제공함에 있다.The present invention relates to a method for producing a high silicon-added high carbon steel wire, the purpose of which is to control the cooling of the wire in a conventional cooling equipment without employing equipment such as EDC equipment or controlled rolling equipment (Bainite + Martensite) It is to provide a method for producing a high-silicon-added high carbon wire rod that can be secured as a homogeneous and fine ferrite + pearlite structure by inhibiting the production of).
상기 목적을 달성하기 위한 본 발명은, 중량%로, 탄소:0.65-1.50%, 실리콘:2.0-4.0%, 망간:0.1-0.8%, 크롬:0.1∼0.8%, 인:0.01%이하, 황:0.01%이하, 질소:0.005∼0.01%,산소:0.005% 이하, 여기에 니켈:0.3-2.0%, 보론:0.001∼0.003%,바나듐:0.01∼0.5%, 니오븀:0.01∼0.5%, 몰리브덴:0.01∼0.5%, 티타늄:0.01∼0.2%, 텅스텐:0.01∼0.5%, 구리:0.01∼0.2%로 이루어진 그룹중 선택된 1종 또는 2종이상을 함유하고, 나머지 Fe 및 기타 불순물로 조성되는 빌레트를 1050∼1150℃에서 가열하여 열간선재압연하고 물분사에 의해 860∼950℃까지 급속냉각하여 권취한 다음, 770±30℃까지는 1.8±0.5℃/sec로 공냉하고, 620±50℃까지는 0.4±0.2℃/sec로 서냉한 후 공냉하여 페라이트+퍼얼라이트조직을 확보하는 것을 포함하여 이루어지는 저온조직이 없는 고실리콘 첨가 고탄소 선재의 제조방법에 관한 것을 그 기술적요지로 한다.The present invention for achieving the above object, in weight%, carbon: 0.65-1.50%, silicon: 2.0-4.0%, manganese: 0.1-0.8%, chromium: 0.1 to 0.8%, phosphorus: 0.01% or less, sulfur: 0.01% or less, nitrogen: 0.005 to 0.01%, oxygen: 0.005% or less, nickel: 0.3-2.0%, boron: 0.001 to 0.003%, vanadium: 0.01 to 0.5%, niobium: 0.01 to 0.5%, molybdenum: 0.01 1050 billets containing one or more selected from the group consisting of -0.5%, titanium: 0.01-0.2%, tungsten: 0.01-0.5%, copper: 0.01-0.2%, and consisting of the remaining Fe and other impurities It is heated at ~ 1150 ℃, hot rolled and hot rolled and rapidly cooled to 860 ~ 950 ℃ by water spraying, and then air-cooled at 1.8 ± 0.5 ℃ / sec up to 770 ± 30 ℃, and 0.4 ± 0.2 ℃ up to 620 ± 50 ℃. The technical gist of the present invention relates to a method for manufacturing a high-silicon-added high-carbon wire rod having no low-temperature structure, which includes a slow cooling at / sec and air cooling to secure a ferrite + perlite structure. The.
Description
본 발명은 볼트 등으로 가공되어 사용되는 선재의 제조방법에 관한 것으로, 보다 상세하게는 실리콘 첨가량이 높음에 따른 열간선재압연후의 냉각과정에서 발생하는 저온조직이 없는 고실리콘 첨가 고탄소강 선재의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a wire rod processed and used in bolts, and more particularly, a method for producing a high-silicon-added high carbon steel wire rod without a low-temperature structure generated during cooling after hot wire rolling due to a high amount of silicon addition. It is about.
선재는 일정형상으로 가공되어 다양한 기계부품류에 이용되는데, 그 예로는 볼트, 너트, 스프링 등이 있다. 이러한 기계부품류의 경량화와 고성능화를 위해 선재의 고강도화에 대한 요구는 계속 높아지고 있다. 고강도 소재는 일정하중이 지속적으로 가해지면 수소에 의해 균열이 진전되는 지연파괴가 발생할 수 있다.Wire rod is processed to a certain shape and used for various mechanical parts, for example, bolts, nuts, springs and the like. In order to reduce the weight and performance of such mechanical parts, demand for increasing the strength of wire rods continues to increase. High-strength materials can cause delayed fracture, in which cracks are propagated by hydrogen under constant load.
일례로, 볼트는 지연파괴저항성이 열화되는 문제점으로 현재, 인장강도 130kg/mm2급이상 사용하는 것이 불가능하여 그 사용용도 및 범위가 제한되고 있는 실정이다. 지연파괴저항성이 우수하면서 고강도화가 가능한 볼트용 강을 개발할 경우 기대되는 잇점은 다음과 같다. 즉, 강구조물 측면에서 볼트체결은 용접 접합에 비해 숙련된 기술이 요구되지 않고 취약한 용접부를 대체하는 잇점 등을 고려할 때, 첫째, 볼트체결력 강화에 따른 강구조물의 안정성을 높일 수 있으며 둘째, 볼트체결 갯수의 감소에 의해 강재 사용량을 줄일 수 있다. 또한, 자동차 부품 측면에서는 셋째, 부품의 경량화에 기여하며 넷째, 부품 경량화에 따른 자동차 조립장치의 설계 다양화 및 컴팩트화(compact)가 가능한 잇점이 있다. 따라서, 소재의 지연파괴저항성의 저하없이 고강도화를 달성할 수 있다면, 사용상의 잇점과 산업계에 미치는 영향을 고려할 때 그 파급도는 상당히 클 것으로 예견되고 있다.For example, the bolt is a problem that the delayed fracture resistance deteriorates, it is currently impossible to use more than 130kg / mm 2 grade tensile strength is the situation that the use and range of the use is limited. The followings are the benefits of developing bolt steel with excellent delayed fracture resistance and high strength. That is, in terms of steel structure, bolt fastening does not require skilled skills compared to welding joint, and considering the advantages of replacing weak welds. By reducing the amount of steel used can be reduced. In addition, in terms of automobile parts, third, it contributes to the lightening of parts. Fourth, there is an advantage that the design diversification and compactness of the automobile assembly apparatus according to the lighter parts are possible. Therefore, if the high strength can be achieved without deteriorating the delayed fracture resistance of the material, the spreading degree is expected to be considerably large considering the advantages in use and the effect on the industry.
고강도 소재의 지연파괴저항성은 결정입계에 석출분포하고 있는 석출물이 수소의 트랩 사이트(trapped site)로 작용하여 입계의 강도를 열화시키기 때문에 저하되는 것으로 알려져 있으며, 고강도화를 달성하기 위해서는 열처리후 결정입계에 분포하게 되는 Fe계 석출물들의 분포를 최대한으로 억제시키는 것이 가장 중요하다. 이에 본 발명자는 결정입계에 Fe계 석출물의 석출 가능성이 전혀 없는 페라이트+잔류 오스테나이트의 미세조직을 갖는 고실리콘 첨가 고탄소로 조성되는 강을 개발하였다.The delayed fracture resistance of high-strength materials is known to be lowered because the precipitates distributed at grain boundaries act as trapped sites of hydrogen and degrade the strength of grain boundaries. It is most important to suppress the distribution of Fe-based precipitates to be distributed to the maximum. Accordingly, the present inventors have developed a steel made of high-silicon-added high carbon having a microstructure of ferrite + residual austenite, which has no possibility of precipitation of Fe-based precipitates at grain boundaries.
그러나, 고실리콘 첨가 고탄소강은 저실리콘 첨가강 대비 Si성분범위에 따라 차이는 있지만 개략적으로 Ac1및 Acm변태점이 50~100℃ 이상 높으며, 이에 따라 연속냉각곡선(CCT)상의 노이즈(nose)가 단시간측으로 상당히 이동되는 관계로 선재냉각시 쉽게 저온조직(베이나이트 또는 마르텐사이트)이 생성되는 특성이 있다. 선재에 저온조직이 존재하면, 볼트용 선재의 선경조정을 위한 신선가공시 저온조직 주위에 응력이 집중되어 단선의 주원인이 되어 신선성의 저하를 초래하고, 이에 따라 소둔 열처리를 하지 않으면 신선가공이 어려운점이 있다. 또한, 냉간성형을 위한 구상화열처리시 구상화조직의 불균질화를 초래할 수 있어 냉간성형에 요구되어지는 적정 표면경도의 확보가 어렵다는 문제가 있다. 따라서, 고실리콘 첨가 고탄소강을 볼트로 제조하기 위해서는 선재압연공정에서 저온조직의 발생없이 선재를 제조하여야 신선가공성을 확보할 수 있는 것이다.However, although high silicon-added high carbon steels are different depending on the Si component range compared to low silicon-added steels, the Ac 1 and Acm transformation points are generally higher than 50 to 100 ° C., so that the noise on the continuous cooling curve (CCT) is high. Due to the considerable movement to the short time side, the low temperature structure (bainite or martensite) is easily generated during wire cooling. If the low temperature structure exists in the wire rod, stress is concentrated around the low temperature structure during wire drawing for wire diameter adjustment of the wire rod for bolts, which is the main cause of disconnection, which leads to deterioration of freshness. There is a point. In addition, there is a problem that it is difficult to secure the proper surface hardness required for cold forming because the spheroidization heat treatment for cold forming can lead to heterogeneous homogenization of the globular structure. Therefore, in order to manufacture high-silicon-added high carbon steel with bolts, it is necessary to manufacture wire rods without the occurrence of low-temperature structure in the wire rod rolling process to ensure fresh workability.
통상적으로, 선재는 고속열간압연한 후에 스텔모아설비에서 이송되면서 냉각되는데, 이때에는 물분사에 의해 880℃까지 급속냉각을 실시한 후 코일형태로 권취하여 평균 냉각속도 0.8℃/sec로 평균냉각 마무리온도인 720℃부근까지 서냉하여 공냉시킨다. 이러한 종래의 열간선재압연공정에서의 냉각제어기술(냉각온도 및 냉각속도)로는 저온조직이 없는 페라이트+퍼얼라이트 조직을 확보하기가 매우 어려울 뿐만 아니라, 저온조직(베이나이트+마르텐사이트)을 완전히 억제하기가 거의 불가능하다. 이는 스텔모아 설비능력에 기인하는 것으로 스테모아설비에서 선재는 오스테나이트에서 페라이트+퍼얼라이트로 변태할 때 변태 마무리시간의 부족으로 인해 미변태 잔류오스테나이트가 선재 공냉시 저온조직(베이나이트+마르텐사이트)으로 변태하게 되기 때문이다. 물론, 스텔모아(Stelmor)방식 이외의 냉각속도가 아주 느린 EDC(easy drawing conveyor)설비 등을 이용하거나 제어압연설비를 갖춘 압연기에서 제어냉각하여 오스테나이트 입자 미세화로 저온조직의 발생을 억제시킬 수는 있으나, 이는 기존의 스텔모아설비를 완전히 교체해야 가능하다는 단점이 있다.Typically, the wire is cooled while being transferred from the Stelmore facility after high-speed hot rolling, in this case, after the rapid cooling to 880 ℃ by water spraying and winding in the form of a coil, the average cooling finish temperature 0.8 ℃ / sec average cooling finish temperature It cools slowly to near 720 degreeC and air-cools. In the conventional hot wire rolling process, the cooling control technology (cooling temperature and cooling rate) is not only very difficult to secure ferrite + perlite structure without low temperature structure, but also completely suppresses low temperature structure (bainite + martensite). It is almost impossible to do. This is due to the ability of the Stelmoir facility. In the Steamoir facility, when the wire rod is transformed from austenite to ferrite + perlite, the low-temperature structure of the unmodified residual austenite is cooled when the wire rod is air-cooled (bainite + martensite). This is because it is transformed into). Of course, the use of an EDC (easy drawing conveyor) facility, which has a very slow cooling rate other than the Stelmor method, or controlled cooling in a rolling mill equipped with a control rolling facility, can suppress the formation of low temperature tissue by miniaturizing austenite particles. However, this has the disadvantage that it is possible to completely replace the existing Stallmore equipment.
본 발명은 EDC설비 또는 제어압연설비 등의 새로운 설비의 도입 없이 통상의 냉각설비에서 저온조직(베이나이트+마르텐사이트)의 생성을 억제시켜 균질하고 미세한 페라이트+퍼얼라이트 조직으로 확보할 수 있는 고실리콘 첨가 고탄소강 선재의 제조방법을 제공하는데, 그 목적이 있다.The present invention is to suppress the formation of low-temperature structure (bainite + martensite) in a conventional cooling system without introducing new equipment such as EDC equipment or controlled rolling equipment, high silicon that can be secured as a homogeneous and fine ferrite + pearlite structure It is an object of the present invention to provide a method for producing an added high carbon steel wire rod.
상기 목적을 달성하기 위한 본 발명의 선재제조방법은, 중량%로, 탄소:0.65-1.50%, 실리콘:2.0-4.0%, 망간:0.1-0.8%, 크롬:0.1∼0.8%, 인:0.01%이하, 황:0.01%이하, 질소:0.005∼0.01%, 산소:0.005% 이하, 여기에 니켈:0.3-2.0%, 보론:0.001∼0.003%, 바나듐:0.01∼0.5%, 니오븀:0.01∼0.5%, 몰리브덴:0.01∼0.5%, 티타늄:0.01∼0.2%, 텅스텐:0.01∼0.5%, 구리:0.01∼0.2%로 이루어진 그룹중 선택된 1종 또는 2종이상을 함유하고, 나머지 Fe 및 기타 불순물로 조성되는 빌레트를 1050∼1150℃에서 가열하여 열간선재압연하고 물분사에 의해 860∼950℃까지 급속냉각하여 권취한 다음, 770±30℃까지는 1.8±0.5℃/sec로 공냉하고, 620±50℃까지는 0.4±0.2℃/sec로 서냉한 후 공냉하여 페라이트+퍼얼라이트조직을 확보하는 것을 포함하여 구성된다.Wire rod manufacturing method of the present invention for achieving the above object, in weight%, carbon: 0.65-1.50%, silicon: 2.0-4.0%, manganese: 0.1-0.8%, chromium: 0.1-0.8%, phosphorus: 0.01% Sulfur: 0.01% or less, Nitrogen: 0.005 to 0.01%, Oxygen: 0.005% or less, Nickel: 0.3-2.0%, Boron: 0.001 to 0.003%, Vanadium: 0.01 to 0.5%, Niobium: 0.01 to 0.5% , Molybdenum: 0.01% to 0.5%, titanium: 0.01% to 0.2%, tungsten: 0.01% to 0.5%, copper: 0.01% to 0.2%, selected from the group consisting of remaining Fe and other impurities The heated billet is heated at 1050∼1150 ℃, hot rolled to hot wire, rapidly cooled to 860∼950 ℃ by water spraying, and then air cooled at 1.8 ± 0.5 ℃ / sec up to 770 ± 30 ℃, and then cooled to 620 ± 50 ℃. It consists of securing the ferrite + pearlite structure by slow cooling at 0.4 ± 0.2 ℃ / sec and then air cooling.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
본 발명은 선재를 볼트 등의 강가공물로 가공한 다음 이를 열처리하여 최종미세조직을 페라이트와 잔류오스테나이트의 복합조직을 형성할 수 있는 고실리콘 첨가 고탄소강을 대상강종으로 하여, 이 강종을 선재압연과정에서 제어냉각에 의해 저온조직의 발생없이 제조할 수 있는 방법을 제안한다는데, 그 특징이 있다. 이러한 본 발명의 대상강종인 고실리콘 첨가 고탄소강의 강성분계를 먼저, 설명한 다음에 이 강을 선재압연하는 방법을 설명한다.The present invention is a high-silicon-added high carbon steel that can form a composite structure of ferrite and residual austenite by processing the wire rod into a steel workpiece such as bolt and then heat-treating it, and the steel rod is rolled. It proposes a method that can be manufactured without the occurrence of low-temperature tissue by controlled cooling in the process, there is a feature. The steel component system of the high silicon-added high carbon steel which is the target steel grade of this invention is demonstrated first, and then the method of wire-rolling this steel is demonstrated.
[고실리콘 첨가 고탄소강][High silicon-added high carbon steel]
본 발명의 강에서 탄소(C)의 함량은 0.65-1.5%으로 하는 것이 바람직하다. 탄소의 함량이 0.65%미만에서는 페라이트+잔류오스테나이트 복합조직강 제조를 위한 열처리후 페라이트+잔류오스테나이트내에 적정한 잔류 오스테나이트양, 형상 및 크기를 얻기가 곤란하고 또한, 기계적, 열적 안정성과 고강도 볼트용강으로서의 충분한 인장강도와 항복강도를 확보하기 어렵기 때문이다. 또한, 탄소의 함량이 1.50% 보다 많아지면 열처리후 단면감소율, 연신율과 충격인성 등의 특성이 저하되고, 선재제조시 편석 및 표면흠이 발생하며, 가열로 장입시 표면탈탄이 심화되고, 볼트 체결시 영구변형성 및 정적 피로특성이 열화하며, 미세복합 조직의 적절한 형상과 크기 그리고, 페라이트+잔류오스테나이트 복합조직을 확보하기 위한 변태 소요시간이 길어지며, 잔류 오스테나이트내의 탄소농도 및 계면농도구배 등에 좋지않은 영향을 미치기 때문이다.In the steel of the present invention, the content of carbon (C) is preferably 0.65-1.5%. If the carbon content is less than 0.65%, it is difficult to obtain an adequate amount of retained austenite, shape and size in the ferritic + residual austenite after heat treatment for the production of ferritic + residual austenite composite steel. This is because it is difficult to secure sufficient tensile strength and yield strength as molten steel. In addition, when the carbon content is more than 1.50%, characteristics such as cross-sectional reduction rate, elongation rate and impact toughness decrease after heat treatment, segregation and surface flaws occur during wire rod manufacturing, and surface decarburization deepens when charging furnace, and bolts are fastened. Permanent deformation and static fatigue characteristics deteriorate, the appropriate shape and size of microcomposite tissues, the transformation time required to secure ferrite + residual austenite complex tissues, carbon concentration in residual austenite, and interfacial tool distribution Because it has a bad effect.
실리콘(Si)의 함량은 2.0-4.0%로 한정하는 것이 바람직하다. 실리콘이 2.0%미만에서는 페라이트 변태후 잔류 오스테나이트의 기계적, 열적 안정성이 저하되어 페라이트+잔류오스테나이트 복합조직과 적정 잔류 오스테나이트양을 확보하기 어렵고, 페라이트의 고용강화 효과가 미흡하여 강도확보에 어려움이 있으며, 또한 지연파괴저항성, 표면 부식특성, 충격인성, 볼트 체결시 영구변형성 등에 영향을 미치고, 선재 탈탄제어를 위한 선재가열로내에서의 표면 페라이트 탈탄층의 균일성 및 적정두께를 확보하기가 어려워 탈탄이 심화되고, 선재냉각시 소입성 증가로 표면 스케일 특성의 제어가 어려운 단점이 있다. 실리콘이 4.0%를 초과하는 경우에는 상기 언급한 효과가 포화되고 소입성, 복합조직강의 구성, 충격인성, 피로특성 등에 좋지 않은 영향을 미치며, 선재제조를 위한 부룸(bloom) 또는 빌레트(billet)제조시 실리콘 편석에 의한 미세조직의 불균질화를 초래하여 최종 제품에서의 품질특성이 저하되기 때문이며, 또한 열처리시 표면 페라이트층의 두께가 증가하여 균질 표면 탈탄제어가 어렵기 때문이다.The content of silicon (Si) is preferably limited to 2.0-4.0%. If the silicon is less than 2.0%, the mechanical and thermal stability of the retained austenite after ferrite transformation decreases, making it difficult to secure the ferrite + residual austenite composite structure and the appropriate amount of retained austenite. It also affects delayed fracture resistance, surface corrosion characteristics, impact toughness, permanent deformation during bolting, and ensures uniformity and proper thickness of the surface ferrite decarburized layer in the wire heating furnace for wire decarburization control. It is difficult to further decarburize, and it is difficult to control surface scale characteristics due to increased hardenability during wire cooling. If the silicon exceeds 4.0%, the above-mentioned effect is saturated and adversely affects the hardenability, the composition of the composite tissue steel, the impact toughness, the fatigue characteristics, and the production of bloom or billet for wire rod manufacturing. This is because the quality characteristics in the final product are deteriorated due to the inhomogeneity of the microstructure due to the segregation of silicon at the same time, and it is difficult to control the homogeneous surface decarburization because the thickness of the surface ferrite layer increases during heat treatment.
망간(Mn)은 기지조직내에 치환형 고형체를 형성하여 고용강화하는 원소로 고장력볼트 특성에 매우 유용하므로 그 함량은 모재의 강도, 열처리시 소입성, 응력이완성, 편석대 생성에 따른 유해한 영향 등을 고려하여 0.1-0.8%로 하는 것이 바람직하다. 이는 망간의 함량이 0.1% 미만의 경우 망간편석에 의한 편석대의 형성은거의 없으나, 고용강화효과의 미흡으로 소입성, 영구변형저항성개선이 미흡하고, 0.8%를 초과할 경우에는 주조시 망간편석으로 인한 국부소입성이 증대하고 편석대의 형성으로 조직이방성이 심화되어 조직이 불균질하게 되어 볼트특성이 저하되기 때문이다.Manganese (Mn) is an element that forms solid solids in the matrix and strengthens solid solution, which is very useful for the characteristics of high-strength bolts. It is preferable to set it as 0.1-0.8% in consideration of these. In case of less than 0.1% of manganese, segregation zones are rarely formed by manganese segregation. However, due to insufficient solidification effect, hardenability and improvement of permanent deformation resistance are insufficient. This is because the local quenchability due to the simple stone increases and the anisotropy of the tissue deepens due to the formation of the segregation zone, resulting in the inhomogeneity of the tissue and deteriorating the bolt characteristics.
크롬(Cr)의 함량은 0.1∼0.8%로 하는 것이 바람직하다. 크롬의 함량이 0.1%미만에서는 고실리콘 첨가강의 열처리시 표면탈탄제어를 위한 표면 페라이트층의 형성이 어려워 탈탄억제 효과가 거의 없고, 소입성 개선을 기대하기 어렵기 때문이다. 또한, 0.8%를 초과하면 등온열처리시 페라이트+잔류오스테나이트 복합조직의 변태 소요시간이 길어지기 때문에 바람직하지 않으며, 선재 탈탄층 제어를 위한 선재 가열로 장입시 표면 적정 페라이트층의 생성이 어려워 균질 탈탄제어에 영향을 미치기 때문이다.It is preferable to make content of chromium (Cr) into 0.1 to 0.8%. If the content of chromium is less than 0.1%, it is difficult to form a surface ferrite layer for surface decarburization control during heat treatment of high silicon-added steel, so that there is almost no decarburization inhibitory effect, and it is difficult to expect quenchability improvement. In addition, if it exceeds 0.8%, it is not preferable because the transformation time of the ferrite + residual austenite composite structure becomes longer during isothermal heat treatment, and it is difficult to generate a surface titration ferrite layer when charging the wire rod for controlling the wire decarburization layer. This affects control.
인(P) 및 황(S)의 함량은 0.01%이하로 하는 것이 바람직하다. 인은 결정입계에 편석되어 인성을 저하시키므로 그 상한을 0.01%로 제한하는 것이며, 황은 저융점 원소로 입계 편석되어 인성을 저하시키고 유화물을 형성시켜 지연파괴저항성 및 응력이완특성에 유해한 영향을 미치므로 그상한을 0.01%로 제한하는 것이다.The content of phosphorus (P) and sulfur (S) is preferably 0.01% or less. Phosphorus segregates at grain boundaries and lowers its toughness, limiting its upper limit to 0.01%. Sulfur is a low melting point element that segregates grains to reduce toughness and form an emulsion, which has a detrimental effect on delayed fracture resistance and stress relaxation characteristics. The upper limit is limited to 0.01%.
질소(N)의 함량은 0.005-0.01%로 하는 것이 바람직하다. 질소의 함량이 0.005%미만에서는 비확산성 수소 트랩 사이트로 작용하는 바나듐 및 니요븀계 질화물의 형성이 어렵기 때문이며, 0.01%를 초과하는 경우에는 그 효과가 포화되기 때문이다.The content of nitrogen (N) is preferably made 0.005-0.01%. This is because when the nitrogen content is less than 0.005%, it is difficult to form vanadium and niobium-based nitrides that act as non-diffusion hydrogen trap sites, and when the content exceeds 0.01%, the effect is saturated.
산소(O)의 함량은 0.005%이하로 하는 것이 바람직하다. 산소의 함량이 0.005%를 초과하면 조대한 산화물계 비금속개재물이 용이하게 형성되어 피로수명이 저하되기 때문이다.The content of oxygen (O) is preferably made 0.005% or less. This is because when the content of oxygen exceeds 0.005%, coarse oxide-based nonmetallic inclusions are easily formed and fatigue life is reduced.
바나듐(V) 또는 니요븀(Nb)은 지연파괴저항성 및 응력이완성 개선원소로서, 각각 0.05-0.5%로 하는 것이 바람직하다. 이들의 함량이 0.05%미만에서는 모재내 바나듐 또는 니요븀계 석출물들의 분포가 적어짐에 따라 비확산성 수소 트랩사이트(trap site)로의 역할이 미흡하여 지연파괴저항성 개선효과를 기대하기 어려우며, 또한 석출강화를 기대하기 어려워 응력이완저항성에 대한 개선효과가 충분하지 못하며, 오스테나이트 결정립 미세화를 기대하기 어려워 페라이트+잔류 오스테나이트 복합조직의 구성시 조직 미세화에 영향을 미치기 때문이다. 또한, 0.5%를 초과하면 V 또는 Nb계 석출물들에 의한 지연파괴저항성 및 응력이완저항성에 대한 개선 효과가 포화하고 오스테나이트 열처리시 모재에 용해되지 않은 조대한 합금 탄화물양이 증가하여 비금속 개재물과 같은 작용을 하므로 피로특성의 저하를 초래하기 때문이다.Vanadium (V) or niobium (Nb) is an element that improves delayed fracture resistance and stress relaxation resistance, and is preferably set to 0.05 to 0.5%, respectively. If the content is less than 0.05%, the distribution of vanadium or niobium-based precipitates in the base material decreases, and thus the role of the non-diffusible hydrogen trap site is insufficient. This is because it is difficult to improve the stress relaxation resistance is not sufficient, and it is difficult to expect attenuation of austenite grains, which affects the microstructure of the ferrite + residual austenite composite. In addition, when it exceeds 0.5%, the improvement effect on delayed fracture resistance and stress relaxation resistance by V or Nb-based precipitates is saturated, and the amount of coarse alloy carbides which are not dissolved in the base metal during austenite heat treatment increases, such as nonmetallic inclusions. This is because it causes a decrease in fatigue characteristics.
니켈(Ni)은 열처리시 표면에 니켈 농화층을 형성하여 외부수소의투과(permeation)를 억제하여 지연파괴저항성을 개선하는 원소로, 그 함량은 0.3-2.0%로 하는 것이 바람직하다. 니켈의 함량이 0.3%미만에서는 표면농화층 형성이 불완전하여 지연파괴저항성의 개선효과를 기대하기 어려우며, 또한 탈탄제어, 인성 및 냉간성형성 향상을 위한 구상화 또는 흑연화처리시 열처리시간이 길어지며, 볼트성형시의 냉간성형성의 개선효과가 없기 때문이다. 2.0%를 초과하는 경우에는 그 효과가 포화되고 잔류 오스테나이트량의 적정한 양, 크기 및 형상 등에 부정적인 영향을 미치기 때문이다.Nickel (Ni) is an element that improves the delayed fracture resistance by forming a nickel thickened layer on the surface during heat treatment to suppress permeation of external hydrogen, and the content thereof is preferably 0.3-2.0%. If the nickel content is less than 0.3%, the formation of the surface thickening layer is incomplete, so it is difficult to expect the effect of improving the delayed fracture resistance, and the heat treatment time is increased during the spheroidization or graphitization treatment to improve the decarburization control, toughness and cold forming. This is because there is no improvement effect of cold forming during bolt forming. If it exceeds 2.0%, the effect is saturated and negatively affects the appropriate amount, size and shape of the amount of retained austenite.
붕소(보론,B)는 본 발명에서 소입성 및 지연파괴저항성 개선을 위한 입계강화원소로, 그 함량은 0.0010∼0.003%로 하는 것이 바람직하다. 붕소의 함량이 0.0010%미만에서는 열처리시 보론원자들의 입계편석에 따른 입계강화에 따른 입계강도 개선효과가 미흡하고, 또한 냉간성형성 개선을 위한 흑연화 처리시 흑연화 촉진 효과가 미흡하기 때문이다. 붕소의 함량이 0.003%를 초과할 경우에는 그 효과가 포화되고 오히려 입계에 보론계 질화물의 석출로 입계강도의 저하를 초래하기 때문이다.Boron (boron, B) is a grain boundary strengthening element for improving the hardenability and delayed fracture resistance in the present invention, the content is preferably 0.0010 to 0.003%. If the content of boron is less than 0.0010%, the effect of improving grain boundary strength due to grain boundary strengthening due to grain boundary segregation of boron atoms during heat treatment is insufficient, and the graphitization promoting effect is insufficient during graphitization treatment for improving cold forming. If the content of boron exceeds 0.003%, the effect is saturated, rather, the precipitation of boron nitride at the grain boundary leads to a decrease in grain boundary strength.
몰리브덴(Mo) 및 텅스텐(W)의 함량은 0.01-0.5%로 하는 것이 바람직하다. 이들의 함량이 0.01%미만에서는 페라이트와 잔류 오스테나이트의 입계강화 효과가 미흡하고 또한 열처리시 소입성, 페라이트의 고용강화, Mo 및 W계 석출강화 효과가 미흡하기 때문이다. 0.5%를 초과할 경우에는 그 효과가 포화되고, 소입성의 증가로 선재제조시 저온조직(마르텐사이트+베이나이트)의 생성이 용이하고 냉간성형성 개선을 위한 구상화 또는 흑연화처리시 열처리 시간이 길어지는 단점이 있기 때문이다.The content of molybdenum (Mo) and tungsten (W) is preferably 0.01-0.5%. If the content is less than 0.01%, the grain boundary strengthening effect of the ferrite and the retained austenite is insufficient, and the hardenability during the heat treatment, the solid solution strengthening of the ferrite, and the Mo and W system precipitation strengthening effects are insufficient. If it exceeds 0.5%, the effect is saturated, and as the hardenability is increased, it is easy to form low-temperature structure (martensite + bainite) during wire rod manufacturing, and the heat treatment time during spheroidization or graphitization treatment to improve cold formability This is because there is a disadvantage.
구리(Cu)의 함량은 0.01-0.2%로 하는 것이 바람직하다. 구리의 함량이 0.01%미만에서는 부식저항에 대한 개선효과가 미흡하며, 0.2%초과할 경우에는 그 개선효과가 포화되고 입계 편석시 녹는점(melting point)이 낮아져 선재압연을 위한 가열로 장입시 결정입계 취화에 따른 표면흠 발생 가능성이 높고, 최종 제품에서의 충격인성이 저하되기 때문이다.The content of copper (Cu) is preferably made 0.01-0.2%. When the copper content is less than 0.01%, the improvement effect on the corrosion resistance is insufficient. When the copper content is over 0.2%, the improvement effect is saturated and the melting point is lowered at the grain boundary segregation. This is because surface flaws are more likely to occur due to grain boundary embrittlement and impact toughness in the final product is lowered.
티타늄의 함량은 0.01-0.2%로 하는 것이 바람직하다. 티타늄의 함량이 0.01%미만에서는 오스테나이트 결정립 미세화 효과가 미흡하며, 지연파괴저항성에 유효한 결정입계내의 티타늄계 탄,질화물의 석출분포가 미흡하여 그 개선효과를 기대하기 어렵기 때문이며, 0.2%를 초과할 경우에는 그 첨가효과가 포화되고 조대한 티타늄계 탄, 질화물을 형성하여 기계적 성질에 영향을 미치기 때문이다.The content of titanium is preferably 0.01-0.2%. If the titanium content is less than 0.01%, the austenite grain refining effect is insufficient, and the precipitation distribution of titanium-based carbon and nitride in the grain boundary effective for delayed fracture resistance is insufficient, so that the improvement effect is difficult to be expected. If exceeded, the effect of saturation is saturated and coarse titanium-based carbon and nitride are formed to affect the mechanical properties.
[선재의 제조방법][Manufacturing method of wire rod]
상기와 같이 조성되는 강편(billet)을 선재상태로 고속열간압연한 후 물분사에 의해 860∼950℃까지 급속냉각을 실시한다. 이때 선재의 선경은 지름 30mm이하로 하여 제조하는 것이 바람직하다. 상기 온도 범위는 오스테나이트와 세멘타이트의 이상 구역으로 미세한 오스테나이트 결정립을 유지할 수 있고 CCT(ContinuousCooling Transformation)곡선상으로 볼 때 변태개시 온도 및 시간이 통상 냉각개시온도 850℃ 대비 고온 및 단시간 방향 이동하기 때문에 소재의 경화능 저하에 따른 저온조직의 발생 가능성을 억제하는데 유리하다. 이는 이상구역에서 세멘타이트 석출에 의한 오스테나이트의 탄소농도가 감소하기 때문이다.After the high-speed hot rolling of the steel sheet (billet) formed as described above in a wire rod state, rapid cooling to 860 ~ 950 ℃ by water spraying. At this time, the wire diameter of the wire rod is preferably manufactured to a diameter of 30mm or less. The temperature range can maintain fine austenite grains as an abnormal region of austenite and cementite, and the transformation start temperature and time are shifted in high temperature and short time direction compared to the cooling start temperature of 850 ° C. in the view of the Continuous Cooling Transformation (CCT) curve. Therefore, it is advantageous to suppress the possibility of low-temperature tissues caused by lowering the hardenability of the material. This is because the carbon concentration of austenite is reduced by cementite precipitation in the abnormal zone.
상기와 같이 860∼950℃까지 급속냉각시킨 이후 코일형태로 권취하여 770±30℃ 까지 1.8±0.5℃/sec로 냉각시킨다. 여기서 냉각온도를 770℃기준으로 ±30℃로 하고 냉각속도를 1.8℃sec기준으로 ±0.5℃/sec의 범위로한 것은 선재가 코일형태로 권취 된 이후 컨베아 위에서의 선재집적상태 즉, 겹침부와 비겹침부위의 냉각정도의 차이를 고려한 범위이다. 이러한 냉각온도 및 냉각속도의 조건은 신선성이 양호한 미세 페라이트+퍼얼라이트조직을 확보하기 위한 것으로 CCT곡선상의 노이즈(nose)의 상향 위치에 해당된다. 그러나, 1.8±0.5℃/sec의 냉각속도로 770+30℃보다 높은 온도로 냉각이 될 경우 냉각대에서의 적정 변태소요시간이 불충분하게 되어 저온조직의 발생 가능성이 높으며 또한 770-30℃ 미만의 온도로 냉각이 될 경우에서도 저온조직의 발생가능성이 매우 높다.After the rapid cooling to 860 ~ 950 ℃ as described above it is wound in a coil form and cooled to 1.8 ± 0.5 ℃ / sec to 770 ± 30 ℃. In this case, the cooling temperature is ± 30 ℃ based on 770 ℃ and the cooling rate is within ± 0.5 ℃ / sec based on 1.8 ℃. The wire rod is accumulated on the conveyor after the coil is wound in coil form. It is the range that considers the difference in cooling degree between and non-overlapped part. The conditions of the cooling temperature and the cooling rate are to secure a fine fresh ferrite + perlite structure and correspond to an upward position of noise on the CCT curve. However, when cooling to a temperature higher than 770 + 30 ℃ at a cooling rate of 1.8 ± 0.5 ℃ / sec, the proper transformation time in the cooling zone is insufficient, which is highly likely to cause low temperature tissue and also lower than 770-30 ℃. Even when cooled to temperature, the occurrence of low temperature tissue is very high.
상기와 같이 냉각하고 이어 620±50℃까지 0.4±0.2℃/sec로 서냉시킨다. 냉각온도를 620±50℃한 것은, 620＋５０℃보다 높은 온도로 냉각할 경우 미변태 오스테나이트의 잔존으로 공냉시 저온조직의 발생할 가능성이 높으며， ６２０－５０℃미만으로 냉각할 경우에는 본 발명의 서냉 냉각속도인 0.4±0.2℃/sec이상의 냉각속도가 되기 때문에 적정조직인 페라이트+퍼얼라이트조직이 확보가 불가능하다 또한， 서냉 냉각속도를 0.4±0.2℃/sec으로 한 것은 620±50℃까지 0.6℃/sec 보다 빨리 냉각할 경우 저온조직의 발생 가능성이 높으며 0.2℃／sec미만으로 냉각할 경우 냉각설비의 한계로 인해 적정냉각온도인 620±50℃범위를 확보하기가 어려워 저온조직이 생성하기 때문다． Cool as above, followed by slow cooling at 0.4 ± 0.2 ° C / sec to 620 ± 50 ° C. The cooling temperature of 620 ± 50 ° C is more likely to occur at low temperatures than 620 + 500 ° C due to the presence of unmodified austenite. It is impossible to secure ferrite + perlite structure, which is an appropriate structure because the cooling rate is higher than 0.4 ± 0.2 ℃ / sec. Also, the slow cooling rate of 0.4 ± 0.2 ℃ / sec is 0.6 ℃ / to 620 ± 50 ℃. If cooling faster than sec, there is a high possibility of low temperature tissue. If cooling less than 0.2 ℃ / sec, it is difficult to secure the proper cooling temperature range of 620 ± 50 ℃ due to the limitation of the cooling equipment.
이어 상기와 같이 620±50℃의 범위까지 서냉한 다음， 공냉하는데， 이는 변태가 완료된 상태로 냉각속도의 변화가 조직에 미치는 영향이 없기 때문이다.Then, as described above, it cools slowly to the range of 620 ± 50 ° C and then air-cooled because the change of cooling rate does not affect the tissue with the transformation completed.
이하， 본 발명을 실시예를 통하여 보다 구체적으로 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.
[실시예]EXAMPLE
아래 표 1로 조성되는 빌레트(160×160)를 1100℃에서 2시간 유지한 후 고속압연하여 지름 14mm선재로 만들고 발명재와 비교재의 냉각조건은 각각 달리하여 선재를 제조하였다.The billet (160 × 160) formed in Table 1 below was maintained at 1100 ° C. for 2 hours, and then rolled at high speed to a 14 mm diameter wire rod, and wire rods were manufactured by different cooling conditions of the invention and the comparative material.
표 2의 발명예(1-9)는 표 2에 나타난 바와 같이, 열간압연한 후 760-900℃의 범위내로 물분사에 의해 급속 냉각하여 권취하고 860-950℃범위까지 1.3-2.3℃/sec 범위의 냉각속도로 냉각시키고 570-700℃ 범위까지 0.2-0.6℃/sec의 냉각속도 범위로 서냉한 후 상온까지 공냉하여 제조하였다. 또한, 표 2에서비교예(1-10)은 열간압연한 후 860℃ 이하 또는 950℃ 이상의 범위로 물분사에 의해 급속 냉각하여 권취하고 740℃이하 또는 800℃이상에서 1.3℃/sec이하 또는 2.3℃/sec 냉각속도 이상의 범위로 냉각시키고 570℃이하 또는 700℃이상까지 1.0-5.3℃/sec로 서냉한 후 상온까지 공냉하여 제조하였다.Inventive Example (1-9) of Table 2, as shown in Table 2, is hot-rolled and then rapidly cooled by water spraying in the range of 760-900 ° C., and then 1.3-2.3 ° C./sec to the range of 860-950 ° C. It was prepared by cooling at a cooling rate in the range and slowly cooling to a cooling rate range of 0.2-0.6 ° C./sec to a range of 570-700 ° C. and then air cooling to room temperature. In addition, in Table 2, Comparative Example (1-10) is hot-rolled and then rapidly cooled by water spraying in the range of 860 ° C or less or 950 ° C or more, and wound up to 1.3 ° C / sec or less at 740 ° C or less or 800 ° C or 2.3 or less. It was prepared by cooling to a range above the cooling rate of ℃ / sec and slow cooled to 1.0-5.3 ℃ / sec to 570 ℃ or less or 700 ℃ or more and air cooled to room temperature.
상기와 같이 제조된 선재들의 저온조직 생성율은 화상분석기(image analyze)를 이용하여 측정하였으며, 이때 피검면은 300mm2를 기준으로 하였다.The low temperature tissue generation rate of the wire rods prepared as described above was measured using an image analyzer, and the test surface was based on 300 mm 2 .
표 2에 나타난 바와 같이, 발명예(1-9)들은 선재상태에서의 미세조직이 기지조직내에 저온조직(베이나이트 또는 마르텐사이트)이 없는 미세 페라이트+퍼얼라이트 조직을 확보할 수 있는 반면, 비교예(1-10)은 저온조직의 상분율이 10-60% 범위로 분포하는 것으로 볼때 본 발명의 선재냉각제어법에 저온조직이 매우 효과적으로 제어됨을 잘 알 수 있다.As shown in Table 2, Inventive Examples (1-9), while the microstructure in the wire rod state can secure a fine ferrite + pearlite structure without low-temperature tissue (bainite or martensite) in the matrix structure, compared Example (1-10) it can be seen that the low temperature structure is very effectively controlled by the wire cooling control method of the present invention when the percentage of low temperature structure is distributed in the range of 10-60%.
상술한 바와 같이, 본 발명은 EDC설비 또는 제어압연설비에 의해 오스테나이트입자 미세화법에 의하지 않고 통상의 냉각설비에서 단지 선재를 제어냉각시켜 줌으로서 저온조직(베이나이트+마르텐사이트)의 생성을 억제시켜 균질하고 미세한 페라이트+퍼얼라이트 조직으로 구성된 고실리콘 첨가 고탄소 볼트용강 선재를 제공할 수 있는 것이다.As described above, the present invention suppresses the formation of low-temperature structure (bainite + martensite) by controlling and cooling only the wire rod in an ordinary cooling facility by the EDC facility or the control rolling facility without using austenite particle refining method. It is possible to provide a high silicon-added high-carbon bolted steel wire composed of a homogeneous and fine ferrite + pearlite structure.
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| KR10-1999-0063184A KR100431848B1 (en) | 1999-12-28 | 1999-12-28 | Method for manufacturing high carbon wire rod containing high silicon without low temperature structure |
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| KR100900646B1 (en) * | 2002-12-20 | 2009-06-02 | 주식회사 포스코 | Method of manufacturing high Si added high carbon wire rod |
| KR100920567B1 (en) * | 2002-12-26 | 2009-10-08 | 주식회사 포스코 | Method of manufacturing high Si added high carbon wire rod |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61133326A (en) * | 1984-12-04 | 1986-06-20 | Kawasaki Steel Corp | Production of middle-and high-carbon steel material for directly heat treated wire |
| JPS63118013A (en) * | 1986-11-04 | 1988-05-23 | Kobe Steel Ltd | Production of hot rolled wire rod of high-si steel |
| JPH10280051A (en) * | 1997-04-02 | 1998-10-20 | Nippon Steel Corp | Wire rod or steel wire excellent in wire drawability and its production |
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1999
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61133326A (en) * | 1984-12-04 | 1986-06-20 | Kawasaki Steel Corp | Production of middle-and high-carbon steel material for directly heat treated wire |
| JPS63118013A (en) * | 1986-11-04 | 1988-05-23 | Kobe Steel Ltd | Production of hot rolled wire rod of high-si steel |
| JPH10280051A (en) * | 1997-04-02 | 1998-10-20 | Nippon Steel Corp | Wire rod or steel wire excellent in wire drawability and its production |
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