표제지
국문초록
Nomenclature
목차
제1장 서론 26
1.1. 비절삭 기어제조 공정의 개요 26
가. 절삭 가공 26
나. 정밀 단조 26
다. 주조 27
라. 사출 성형 27
마. 분말 단조 27
사. 스탬핑 27
1.2. 연구 현황 분석 29
1.2.1. 기술 현황 29
1.2.2. 국내 현황 분석 33
1.3. 연구의 목적 및 범위 37
1.3.1. 연구 목적 37
1.3.2. 연구의 범위 및 내용 37
제2장 유한 요소법을 이용한 수치해석 40
2.1. 목적 및 방법 40
2.2. 강소성 유한요소법의 수식화 42
2.3. 소결분말금속의 변형해석을 위한 수식화 44
제3장 분말단조에 의한 베벨기어성형 47
3.1. 컴퓨터 시뮬레이션에 의한 성형공정 해석 47
3.2. 분말 합금 설계 49
3.3. 예비성형체 설계 및 제작 50
3.4. 소결시험 54
3.5. 분말단조 금형설계 57
3.6. 성형실험, 특성평가 및 고찰 58
3.6.1. 압하율별 성형품의 특성평가 59
3.6.2. 가열방법 및 냉각법에 따른 특성평가 60
3.6.3. 굴곡강도측정 및 미세조직 관찰 61
3.6.4. 부위별 밀도 측정 62
3.6.5. 표면조도 측정 63
3.7. 침탄열처리 실험 63
3.8. 결론 66
제4장 냉간단조에 의한 베벨기어 성형 68
4.1. 컴퓨터 시뮬레이션에 의한 성형공정 해석 68
4.2. 냉간 단조에 의한 공정설계 73
4.3. 모사 성형 실험 75
4.3.1. 모사 성형 실험의 목적 및 방법 75
4.3.2. 성형실험결과 79
4.4. 금형 설계 및 제작 83
4.5. 성형실험 및 고찰 88
4.6. 결론 90
제5장 복합단조에 의한 베벨기어 성형 92
5.1. 컴퓨터 시뮬레이션에 의한 성형공정 해석 92
5.1.1. 블랭크 형상에 따른 치형성형 94
5.1.2. 복합단조 공정해석 95
5.2. 복합 단조에 의한 공정 설계 99
5.3. 모사 성형 실험 101
5.3.1. 열간 성형 102
5.3.2. 냉간 사이징 103
5.4. 금형 설계 및 제작 104
5.5. 성형실험 및 고찰 107
5.5.1. 블랭크의 준비 107
5.5.2. 단조가열 108
5.5.3. 윤활처리 및 열처리 109
5.6. 결론 111
제6장 비절삭 기어의 비교분석 113
6.1. 공정별 특성 평가 113
6.1.1. 미세조직 113
6.1.2. 메탈 플로우 114
6.1.3. 경도 115
6.1.4. 치굽힘 강도 115
6.1.5. 피로강도시험 116
6.1.6. 기어파면(SEM) 117
6.1.7. 치의 표면조도 117
6.1.8. 기어 맞물림 시험 117
6.1.9. 결론 및 고찰 118
6.2. 비절삭 기어의 경제성 119
6.2.1. 베벨기어의 크기별 최적 공정 및 금형 수명 119
6.2.2. 베벨기어의 단조 기계 용량 선정 119
6.2.3. 기어 성형 공정의 선택 120
6.2.4. 경제성 평가 120
제7장 종합 결론 121
참고문헌 256
ABSTRACT 262
Table 1. Status of non-machined gear manufacturing processes. 126
Table 2. Plant and process features for nonmaterial removing processes 127
Table 3. Specification and chemical composition(in wt%) of Astaloy A 128
Table 4. Results of evaluation with respect to process parameter for the manufacturing of prototype 128
Table 5. Variation of density according to forming amount 130
Table 6. Results of measurement of carbon and oxygen contents 130
Table 7. Results of tooth bending strength test 131
Table 8. Density in the parts after powder forging 131
Table 9. Surface roughness measured at different positions 132
Table 10. Spec. of a straight bevel gear by cold forging 132
Table 11. Chemical compositions of SCM 420H1V 132
Table 12. Optimum lubrication selected by experiment 133
Table 13. Chemical compositions of SKD 11 Steel 134
Table 14. Variables and effects in each step 134
Table 15. Specimen shapes for teeth forming and results 135
Table 16. Experiment variables of spline forming and results 137
Table 17. Blank variables 138
Table 18. Chemical compositions of SCr 420 138
Table 19. Dimensions of blanks used in experiment with lead 138
Table 20. Extruded hone test condition 139
Table 21. Surface roughness of pre and post extruded honing 139
Table 22. Chemical compositions of SCr420 139
Table 23. Chemical compositions of SCM420H1V 140
Table 24. Chemical compositions of "Astaloy A" 140
Table 25. Comparison of tooth surface roughness 140
Table 26. Die life and the optimum process according to bevel gear size 141
Table 27. Press capacity according to bevel gear size 141
Fig. 1. Fe-C phase diagram and range of forging temperature. 142
Fig. 2. Temperature sensitivities of friction coefficient for different lubricants. 143
Fig. 3. Variation of hardness with respect to temperature. 144
Fig. 4. Different temperature ranges for bevel gear forging 145
Fig. 5. Shapes and dimensions of various preforms for computer simulation 146
Fig. 6. Material flow and density distribution of conical preform 147
Fig. 7. Material flow and density distribution of straight cylindrical preform 148
Fig. 8. Material flow and density distribution of straight reverse conical preform 149
Fig. 9. Three different preforms for physical modeling 150
Fig. 10. Comparison of deformation behaviour according to preform shape 150
Fig. 11. Shapes and dimensions of different preforms for physical modeling 151
Fig. 12. Compressive and tensile strain according to the forming amount of each preform shape 151
Fig. 13. Example of surface cracks of prototype 152
Fig. 14. Possible configurations of the preform for forging a straight bevel gear 152
Fig. 15. Flow chart of sintering processes 153
Fig. 16. Variation of oxygen content as a function of distance 154
Fig. 17. Variation of oxygen content as a function of distance from surface in sintered specimens 155
Fig. 18. Variation of oxygen content as a function of distance from surface in sintered specimens 156
Fig. 19. Variation of carbon content as a function of distance from surface in sintered specimens 157
Fig. 20. Variation of carbon content as a function of distance from surface in sintered specimens 158
Fig. 21. Variation of carbon content as a function of distance from surface in sintered specimens 159
Fig. 22. Microstructures of a P/F preform 160
Fig. 23. Change in hardness as a function of distance from surface 161
Fig. 24. Schematic diagram of a powder forging die set 162
Fig. 25. Forging die insert 163
Fig. 26. Change in coating weight according to blank temperature and concentration of lublicant 163
Fig. 27. Changes of product according to different forming amounts 164
Fig. 28. Method of forming amount measurement 164
Fig. 29. Forging load with respect to forging amount 165
Fig. 30. Typical surface cracks on the outer part of prototype 165
Fig. 31. Microstructure of powder forging for the different cooling method 166
Fig. 32. Schematic diagram of a jig and a punch for measurement of bending strength of a tooth 167
Fig. 33. Comparision of tooth bending strength of a prototype with a machined part after finishing heat treatment 168
Fig. 34. SEM microstructures of fractured surface after tooth bending strength test 169
Fig. 35. Observed pore distributions for different forming amounts at different parts of a tooth 171
Fig. 36. Observed of pore distributions for different forming amounts in the full section of a tooth 172
Fig. 37. Volume percentages of pore at different parts of a tooth (Results by image analysis) 173
Fig. 38. Heat treatment cycle 174
Fig. 39. Hardness as a function of distance from surface for a machined part and carburized P/F part 174
Fig. 40. Microstructures of surface and core of a bevel gear produced by powder forging 175
Fig. 41. Forged bevel gear with average cone geometry for (a) axisymmetric cross—section, and... 176
Fig. 42. Initial mesh system for the first trial preform 177
Fig. 43. Loading simulations of the first preform for (a) 0% stroke, (b) 56.1% stroke,... 178
Fig. 44. Effective strain distributions of the final product using the initial preform 179
Fig. 45. Initial mesh system for simulation of the modified preform 180
Fig. 46. Loading simulation with the modified preform for (a) 0% stroke, (b) 34.7% stroke,... 181
Fig. 47. Effective strain distribution in the final product using the modified preform 182
Fig. 48. Backward tracing simulation to get a final preform for (a) 0% stroke, (b) 17.6% stroke,... 183
Fig. 49. Loading simulation of the final preform derived from backward tracing simulation 184
Fig. 50. Effective strain distribution in the final product when the preform obtained from backward tracing... 185
Fig. 51. Forging load vs. stroke when the preform obtained by backward tracing technique is used. 186
Fig. 52. Schematic view of the preform and final product of a spline gear forging. 187
Fig. 53. Schematic view of a spline and a shaft 188
Fig. 54. Schematic view of a preform and die set assembly 189
Fig. 55. Perspective view of distorted meshes at several deformation stages 190
Fig. 56. Top views of distorted meshes at several deformation stages 191
Fig. 57. Strain distribution at several deformation stages 192
Fig. 58. Load versus displacement curve 193
Fig. 59. Dimensions of a straight bevel gear by cold forging 193
Fig. 60. Bevel gear by cold forging 194
Fig. 61. Microstructure of SCM 420H1V 194
Fig. 62. Layout of cold forging process for bevel gear 196
Fig. 63. Flow chart for cold forging of a bevel gear 197
Fig. 64. Spherodized annealing condition 198
Fig. 65. Low temperature annealing condition 198
Fig. 66. Layout of optimum process 199
Fig. 67. Plasticine dies for forming experiments 199
Fig. 68. Lead dies for forming experiments 200
Fig. 69. Appearance of hydraulic press used for experiments 200
Fig. 70. Shape of upsetting blank 201
Fig. 71. Metal flow of optimum forming processes. 202
Fig. 72. Optimum blank for tooth forming 203
Fig. 73. Dies for a bevel gear forming 203
Fig. 74. Typical shape of a gap in EDM 204
Fig. 75. Shapes at before and after erosion with high intensity acid 204
Fig. 76. Specimen and equipment for the first erosion experiment 205
Fig. 77. Specimen for the second erosion experiment 205
Fig. 78. Relation between erosion time and average surface roughness 206
Fig. 79. Relation between erosion time and maximum surface roughness 206
Fig. 80. SEM micrograph of specimen surface erosed for 5 min 207
Fig. 81. SEM micrograph of specimen surface erosed for 10 min 207
Fig. 82. Erosion of a bevel gear electrode 208
Fig. 83. EDM electrode for bevel gear forming dies 208
Fig. 84. Objectives of annealing 209
Fig. 85. Upper and lower die inserts used for forging in practice 209
Fig. 86. Formed shapes of bevel gear in each stroke. 209
Fig. 87. Schematic diagrams of a bevel gear for (a) a plane view, and (b) a cross-section view 210
Fig. 88. Dimensions of a bevel gear I 210
Fig. 89. Deformation predictions of gear no.1 ; D=26㎜, H=42.3㎜, pitch circle angle 211
Fig. 90. Deformation predictions of gear no.2 ; D=29㎜, H=34㎜, pitch circle angle 212
Fig. 91. Deformation predictions of gear no.3 ; D=32㎜, H=27.9㎜, pitch circle angle 213
Fig. 92. Load curves of hot forging; pitch circle angle, axisymmetric deformation 214
Fig. 93. Strain distributions of hot forging 215
Fig. 94. Deformation predictions ; D=26㎜, H=42.3㎜, outside diameter angle 216
Fig. 95. Deformation predictions ; D=32㎜, H=27.9㎜ outside diameter angle 217
Fig. 96. A complex forging process of a bevel gear 218
Fig. 97. Model for F.E.M analysis 218
Fig. 98. Metal flow in hot forging (outside diameter, plane strain)... 219
Fig. 99. Deformation analysis of small inner depth for cold sizing (outside dia. , A=3.5) 220
Fig. 100. Deformation analysis of large inner depth for cold sizing (outside dia. , A=3.5) 221
Fig. 101. Strain distribution in hot forging (a) A=3.5 (b) A=10.5 223
Fig. 102. Elastic deformation of workpiece during cold forging(bevel gear II) 224
Fig. 103. Elastic deformation of dies during cold forging (bevel gear III) 225
Fig. 104. Elastic deformation of workpiece during cold forging(bevel gear III) 226
Fig. 105. Location of workpiece in dies in cold forging (bevel gear II)... 227
Fig. 106. Deformation analysis results of A-A section in cold forging (bevel gear II) 228
Fig. 107. Deformation analysis results of B-B section in cold forging (bevel gear II) 229
Fig. 108. Deformation analysis results of C-C section in cold forging (bevel gear II) 230
Fig. 109. Model for bevel gear forging by the complex forging 231
Fig. 110. Process layouts of a bevel gear complex forging 232
Fig. 111. Methods of cold sizing 233
Fig. 112. Length orientation of cold sizing and its variables 233
Fig. 113. Condition of size selection of optimum blank size 234
Fig. 114. Results of cold sizing experiment 236
Fig. 115. Copper electrode of a bevel gear 237
Fig. 116. Upper punch drawings for cold sizing of a bevel gear 238
Fig. 117. Drawings of lower die for cold sizing of a bevel gear 238
Fig. 118. Dies for hot forging of a bevel gear 239
Fig. 119. Dies for cold sizing of a bevel gear 239
Fig. 120. Extruded hone machine 240
Fig. 121. A bevel gear extruded hone process layout 240
Fig. 122. A extruded hone jig 241
Fig. 123. Deformation mode of a bevel gear in each step 242
Fig. 124. Final product 242
Fig. 125. Microstructures of wrought materials 243
Fig. 126. Microstructures at gear surface and inside 245
Fig. 127. Metal flow of a bevel gear in each process 246
Fig. 128. Change in hardness as a function of distance from surface for different gear manufacturing processes 247
Fig. 129. Comparision of tooth bending strength 248
Fig. 130. A jig for strength test 248
Fig. 131. Tooth bending fatigue strength test 249
Fig. 132. Results of tooth bending fatigue strength test 250
Fig. 133. SEM microstructure of fatigue failure surface 251
Fig. 134. Examples of contact marking test 252
Fig. 135. Tooth contact marking test of bevel gear 252
Fig. 136. Sequence of process selection in producing a bevel gear by net shape manufacturing 253
Fig. 137. Suggestion of forming process selection by a basis of gear size 253
Fig. 138. Product quality of a bevel gear according to manufacturing process 254
Fig. 139. Relative cost of a bevel gear according to manufacturing process 255