목차

List of tables and figures
제 1 장 서 론
1. 1 연구배경 ????????????????????????????????????????????????????????????????????? 1
1. 2 연구목적 및 내용 ????????????????????????????????????????????????????????? 4
참고문헌 ??????????????????????????????????????????????????????????????????????????? 7
제 2 장 연주기 설계의 이론적 배경 9
2.1 Roll Geometry 설계 고려사항 ??????????????????????????????????????????? 11
2.1.1 주편 품질 측면 ??????????????????????????????????????????????????????? 11
2.1.2 제작성 및 경제성 측면 ????????????????????????????????????????????? 13
2.2 Roll Geometry 설계 이론적 배경 ??????????????????????????????????????? 16
2.2.1 미응고 길이(Metallurgical Length) ???????????????????????????????? 16
2.2.2 Roll Geometry ??????????????????????????????????????????????????????????? 18
2.2.3 2차 냉각대 냉각조건 ????????????????????????????????????????????????? 25
2.2.4 롤 처짐 및 응력과 인발력 ???????????????????????????????????????? 28
2.3 Roll Geometry 개념설계 ??????????????????????????????????????????????????? 38
2.3.1 Roll Geometry 설계 절차 ???????????????????????????????????????????? 38
2.3.2 Roll Geometry 설계 개념 ???????????????????????????????????????????? 36
2.3.3 주편 해석 ??????????????????????????????????????????????????????????????? 48
2.3.4 Roll Geometry 설계결과???????????????????????????????????????????????
참고문헌 ????????????????????????????????????????????????????????????????????????? 50
51
제 3 장 Mold Oscillator의 설계기술 66
3.1 Mold Oscillator 조업 조건에 따른 설계 ?????????????????????????????? 66
3.1.1 Mold 설계 개요 ???????????????????????????????????????????????????????? 66
3.1.2 Oscillator 설계 개요 ?????????????????????????????????????????????????? 69
3.1.3 측면 지지 롤 초기조건 설정방안 ??????????????????????????????? 74
3.1.4 Soft Clamping 초기 조건 설정방안 ??????????????????????????????? 76
3.1.5 Mold Oscillation 하중 조건 및 운전 조건 계산 ??????????????? 80
3.1.6 Oscillator 제어 및 운전 방안 설계 ??????????????????????????????? 87
3.2 폭 가변 장치 운전 방안 및 실험 결과 ????????????????????????????? 92
3.2.1 Mold 제작 개요 ???????????????????????????????????????????????????????? 92
3.2.2 신일철 고속 폭 가변 방법 ???????????????????????????????????????? 93
3.2.3 폭 가변장치 제어기의 현장설치 실험 및 결과 ????????????? 94
3.2.4 시험연주기 적용 시험 ?????????????????????????????????????????????? 95
3.2.5 폭변경 시험결과 ??????????????????????????????????????????????????? 97
3.3 Mold Oscillator 운전 및 조업 결과 ???????????????????????????????????? 98
3.3.1 Oscillator 진동 오차 측정 결과 ??????????????????????????????????? 98
3.3.2 운전영역 결정 ????????????????????????????????????????????????????????? 100
3.3.3 Oscillator 진동 마찰력 측정 및 분석 ???????????????????????????? 100
3.3.4 조업조건에 따른 진동 패턴 분석 ??????????????????????????????? 103
3.3.5 진동 패턴에 따른 주편 표면 품질 분석 ?????????????????????? 104
3.3.6 진동 패턴에 따른 상대속도 평가 ?????????????????????? 106
참고문헌 ??????????????????????????????????????????????????????????????????????????? 108
제 4 장 Pilot Caster 공정 설계기술 156
4.1 공정 설계 개요 ????????????????????????????????????????????????????????????? 156
4.2 Strand 공정 설계 기술 ???????????????????????????????????????????????????? 159
4.2.1 DSR 프로세스 기술 ?????????????????????????????????????????????????? 159
4.2.2 DSR 기계 기술 ???????????????????????????????????????????????????????? 161
4.3 경압하 해석 기술 ?????????????????????????????????????????????????????????? 163
4.3.1 Eulerian 유한 요소 해석 기술 ????????????????????????????????????? 163
4.3.2 Multi Roll 경압하 공정 해석 ??????????????????????????????????????? 166
4.4 몰드 냉각능 설계 기술 ?????????????????????????????????????????????????? 168
4.5 Strand 내에서의 응고 완료점 제어 ??????????????????????????????????? 173
4.5.1 개요 ?????????????????????????????????????????????????????????????????????? 173
4.5.2 열 전달 계수와 몰드 열 전달 보정 ???????????????????????????? 175
4.5.3 표면온도 측정 결과와의 비교 및 보정 ???????????????????????? 177
4.5.4 노즐 및 롤의 영향 평가 ??????????????????????????????????????????? 178
4.5.5 주조 조건 변화시의 응고 완료점 변화 ???????????????????????? 180
참고문헌 ??????????????????????????????????????????????????????????????????????????? 181
제 5 장 Pilot caster의 가동결과 199
5.1 Pilot caster의 성능 ?????????????????????????????????????????????????????????? 199
5.1.1 최고 주조속도 ????????????????????????????????????????????????????????? 199
5.1.2 주조속도의 제어 ?????????????????????????????????????????????????????? 200
5.1.3 용강 토출량 ???????????????????????????????????????????????????????????? 201
5.1.4 탕면 제어 ??????????????????????????????????????????????????????????????? 202
5.1.5 Auto start 및 auto stop ???????????????????????????????????????????????? 203
5.1.6 미응고 압하 ???????????????????????????????????????????????????????????? 204
5.2 주편의 품질 ????????????????????????????????????????????????????????????????? 207
5.2.1 주편의 두께 및 폭 ??????????????????????????????????????????????????? 207
5.2.2 주편의 응고 조직 ???????????????????????????????????????????????????? 207
5.2.3 성분편석 ???????????????????????????????????????????????????????????????? 207
5.2.4 주편의 표면온도 ?????????????????????????????????????????????????????? 208
5.2.5 조업조건에 따른 주편의 형상????????????????????????????????????? 209
참고문헌 ??????????????????????????????????????????????????????????????????????????? 212
제 6 장 결 론 230
Abstracts 234
List of Tables and Figures
Tables
Table 2-1 Product mix of pilot caster
Table 2-2 Maximum bending moment and force in the roll
Table 2-3 Steel grade and chemical composition
Table 2-4 Solidification coefficient and unsolidification length
Table 2-5 Strain rate change according to the number of bending roll
Table 2-6 Strain rate change according to the number of unbending roll
Table 2-7 Relation of average roll gap and the roll number of bending part
Table 2-8 Relation of water and temperature in outlet of cooling zone
Table 3-1 Mold thickness of mold top and bottom
Table 3-2 Top width and bottom width of mold
Table 3-3 Taper of mold narrow face by steel group
Table 3.4 Criteria of Oscillating Error
Table 3.5 Oscillation Mark shape data according to the casting condition
Table 3.6 Relative velocity in the low speed and high speed casting
Table 4-1 Soft reduction process design schema
Table 4-2 Mold? High Speed Thin Slab Casters
Table 4-3 Taper of wide face mold
Table 4-4 Cooling condition of mold
Table 4-5 Copper plate of mold
Table 4-6 Heat flux of mold
Table 4-7 Water rate in the 2nd cooling zone
Figures
Fig. 1-1 Schematic drawing of pilot caster
Fig.1-2 3D drawing of pilot caster
Fig.1-3 Schematic drawing of conventional caster
Fig. 2-1 Caster type
Fig. 2-2 Segment extraction
Fig. 2-3 Deformation of slab by ferrostatic pressure of molten steel
Fig. 2-4 Bulging and strain rate model by bulging
Fig. 2-5 Caster radius change in the 1 point un/bending part
Fig. 2-6 Caster radius change in the multi-point un/bending part
Fig. 2-7 Schematic diagram of strain by roll misalignment
Fig. 2-8 Allowable strain of slab according to the carbon content
Fig. 2-9 Component force of slab weight acting to the roll by verticality
Fig. 2-10 Distribution load type acting to the roll
Fig. 2-11 Design process of Roll Geometry
Fig. 2-12 Relation of vertical length and slab quality (Inclusions)
Fig. 2-13 Relation of vertical length and slab quality (Blowholes)
Fig. 2-14 Solidification shell thickness and temperature profile on casting
Fig. 2-15 Results of bulging calculation by the developed program
Fig. 2-16 Results of bulging calculation by the commercial program
Fig. 2-17 Results of strain calculation by the developed program
Fig. 2-18 Results of strain calculation by the commercial program
Fig. 2-19 Results of stress calculation by the developed program
Fig. 2-20 Strain and strain rate calculation by the commercial program
Fig. 2-21 Comparison of strain in the other caster (Algoma, Mini-mill, Pilot caster)
Fig. 2-22 Layout of pilot caster (side view)
Fig. 3-1 Taper of wideface mold
Fig. 3-2 Mold oscillator of pilot caster
Fig. 3-3 Foundation frame
Fig. 3-4 Intermediate stand
Fig. 3-5 Base frame
Fig. 3-6 Oscillating frame
Fig. 3-7 Cassette frame
Fig. 3-8 Width adjustment mold (WAM)
Fig. 3-9 Mold
Fig. 3-10 Soft clamp
Fig. 3-11 Cylinder and rod
Fig. 3-12 Section drawing of cylinder and rod
Fig. 3-13 Schematic drawing of Base frame extraction
Fig. 3-14 Schematic drawing of Cassette extraction
Fig. 3-15 Schematic diagram of ferostatic force
Fig. 3-16 Disk spring
Fig. 3-17 Schematic diagram of soft clamping
Fig. 3-18 Load diagram of disk spring (100x51x7)
Fig. 3-19 Load diagram of disk spring (100x51x5)
Fig. 3-20 Dynamic simulation of mold oscillator
Fig. 3-21 Flow rate of the reciprocating action
Fig. 3-22 Operating Window
Fig. 3-23 Waveform Profile
Fig. 3-24 Velocity Profile
Fig. 3-25 Schematic diagram of Negative Strip Time (Tn)
Fig. 3-26 Parallel pattern
Fig. 3-27 Stepwise pattern
Fig. 3-28 Z-mode pattern
Fig. 3-29 Schematic diagram of high speed motion of NSC
Fig. 3-30 Schematic diagram of the WAM controller
Fig. 3-31 Comparison of velocity profile
Fig. 3-32 Modified profile for the physical application
Fig. 3-33 Off-line test results of WAM
Fig. 3-34 Parallel pattern test results
Fig. 3-35 Deformation force of narrow face
Fig. 3-36 Parallel pattern test
Fig. 3-37 Stepwise pattern test
Fig. 3-38 Z mode pattern test(Taper gap 5mm)
Fig. 3-39 Fast mode pattern test(Taper gap 2.5/0 mm)
Fig. 3-40 Fast mode pattern test(Taper gap 5/-2 mm)
Fig. 3-41 Comparison of force according to pattern type
Fig. 3-42 Comparison of force by taper in Z mode
Fig. 3-43 Operating Window and oscillation pattern
Fig. 3-44 Operating test of mold oscillator
Fig. 3-45 Test stand for mold oscillator
Fig. 3-46 Oscillating Error check method
Fig. 3-47 Oscillating Position Error by stroke and frequency
Fig. 3-48 Oscillating Error on Waveform
Fig. 3-49 Oscillating Error on Asymmetry
Fig. 3-50 Flow diagram of servo valve (Rexroth NS 16 model)
Fig. 3-51 Test result of the operating window
Fig. 3-52 Force by oscillating error on the Break-Out casting
Fig. 3-53(a) Friction force at the speed 2.5 mpm (LCR 20mm)
Fig. 3-53(b) Friction force at speed 2.5 mpm (LCR 30mm)
Fig. 3-54 Powder consumption at Asymmetry 50%
Fig. 3-55 Powder consumption at Asymmetry 60%
Fig. 3-56 Powder consumption at Asymmetry 70%
Fig. 3-57 Negative Strip Distance according to stroke and asymmetry
Fig. 3-58 Negative Strip Ratio according to stroke and asymmetry
Fig. 3-59 Oscillation Mark Depth in Left Side of Slab
Fig. 3-60 Oscillation Mark Depth in Right Side of Slab
Fig. 3-61 Oscillation Mark Mean Depth of Slab
Fig. 3-62 OSM Hook Shape in Cast Speed 2.2mpm
Fig. 3-63 OSM Hook Shape in Cast Speed 2.5mpm
& Frequency 50cpm and BreakOut Status
Fig.3-64 Oscillation pattern for the low speed casting
Fig.3-65 Velocity profile and waveform for the low speed casting
Fig.3-66 Oscillation pattern for the high speed casting
Fig.3-67 Velocity profile and waveform for the high speed casting
Fig. 4-1 Technical issue in the strand of caster
Fig. 4-2 Measuring technology of crater end
Fig. 4-3 Optimizing technology for roll gap control
Fig. 4-4 Conventional roll gap control type
Fig. 4-5 Developed segment in the pilot caster
Fig. 4-6 Joint condition in the dynamic analysis of segment
Fig. 4-7 Load condition in the dynamic analysis of segment
Fig. 4-8 Lateral load condition acting on the hydraulic cylinder
Fig. 4-9 Lateral load acting on the Reduction Pivot Wheel
Fig. 4-10 Casting process model by the single roll
Fig. 4-11 Soft reduction process model by the single roll
Fig. 4-12 Solidification region for analysis
Fig. 4-13 Boundary condition for the analysis by 5 roll
Fig. 4-14 Analysis mesh and stress profile
Fig. 4-15 (a) Strain profile, (b) Profile change of slab surface
Fig. 4-16 Mold heat flux according to the casting speed
Fig. 4-17 Mold heat flux at casting speed 1 mpm
Fig. 4-18 Mold heat flux at casting speed 3.5 mpm
Fig. 4-19 Mold heat flux at NF and WF by casting speed (950 x 140 mold)
Fig. 4-20 Mold heat flux at NF and WF by casting speed (1100 x 100 mold)
Fig.4-21 Return time to the same crater end after casting condition change
Fig. 4-22 Crater end change by casting speed and cooling rate
Fig. 4-23 Crater end change when the casting speed is changed after cooling water change
Fig. 4-24 Crater end change by heat transfer coefficient adjusting
Fig. 4-25 Slab surface temperature by the mold heat flux
Fig. 4-26 Slab surface temperature measured by Pyrometer and TC
Fig. 4-27 Effect on to the crater end by the nozzle water rate
Fig. 4-28 Effect on to the crater end by nozzle excepting the roll cooling
Fig. 4-29 Crater end change by the casting condition change
Fig. 5-1 The variation of casting speed determined at top driven motor of segment #1 when the casting speed is increased up to 0.97 m/min
Fig. 5-2 The variation of casting speed determined at a top driven motor of segment #1 when the casting speed is controlled by 0.97 m/min
Fig. 5-3 Variation of casting speed, stopper opening and mold level when the casting speed is 1.0 m/min
Fig. 5-4 Schematic diagram showing the opening pattern of stopper at the first operation stage
Fig. 5-5 Photo showing the shape of slab cross section cast at pilot caster
Fig. 5-6 Relationship between the reduction depth and the increased width of slab when liquid core reduction technology is applied
Fig. 5-7 Photos showing the microstructure of slab cross section when liquid core reduction is applied to 40 mm
Fig.5-8 3 dimensional drawing showing a segment #0 of pilot caster
Fig.5-9 Pressure change determined by hydraulic cylinders at segment #0 of pilot caster during casting.
Fig.5-10 Maximum and normal pressure change determined by hydraulic cylinders at segment #0 of pilot caster during casting
Fig. 5-11 Stress and strain curve for 0.096 % C 1.49% Mn 0.009 % S steel at strain rate=8 X 10-4 s-1, using a compression tester.
Fig. 5-12 The variation of thickness and width determined at a pilot caster slab
Fig. 5-13 The microstructure of pilot caster slab at casting speed 2.2 m/min
Fig.5-14 Mapping results showing manganese and phosphorus concentration distribution of pilot caster slab at casting speed 2.2 m/min
Fig.5-15 Photos showing the difference of slab surface color according to the casting speed at pilot caster
Fig. 5-16 Schematic diagram showing the cooling mechanism of slab
Fig. 5-17 Surface temperature variation of slab cast at pilot caster according to the casting speed
Fig. 5-18 Width of slab on cast condition
Fig. 5-19 Thickness of drive side
Fig. 5-20 Thickness of non drive side
Fig. 5-21 Width change of slab on condition(140t x 800w)
Fig. 5-22 Thickness of drive side under LCR (2.5 mpm)
Fig. 5-23 Thickness of non drive side under LCR (2.5 mpm)
Fig. 5-24 Width change of slab on condition(100t x 1000w, 2.5~4.0mpm)
Fig. 5-25 Thickness of drive side under LCR10(100t, 2.5~4 mpm)
Fig. 5-26 Thickness of non drive side under LCR10(100t, 2.5~4mpm)