臺灣博碩士論文加值系統

自 1984 年 Saab 汽車 AB 首次將熱沖壓技術應用於汽車行業，這種加工經過多次改進後逐漸成為汽車行業的一項重要技術。熱沖壓鋼主要用於汽車門梁、隧道、立柱、保險桿，這些部件需要輕量化以減輕車輛重量，同時確保高抗拉強度。為了滿足這些技術要求，產品在經過熱沖壓工藝後必須快速冷卻，以達到麻田散鐵組織。因此，熱沖壓技術的基本要求之一為熱沖壓模具中冷卻系統的設計。雖然目前在大多數熱沖壓工藝中都使用水作為冷卻，但它也有一些缺點，例如在模具中容易形成沉積物，在高溫下與水接觸時容易氧化模具。在本論文中，使用空氣作為冷卻的新方法成為一種對環境友善的冷卻方法，並解決使用水作為冷卻劑的缺點。在這項研究中，使用 CSC-15B22 和 S45C 鋼的實驗來測試和比較空氣和水冷卻的可能性。然後，使用 Fluent 分析冷卻系統在熱沖壓中的有效性。工件尺寸為 150x100x1.5 mm ，並使用馬弗爐中 5 分鐘內加熱至約 900°C 的沃斯田鐵溫度。然後將工件快速轉移到熱沖壓模具中，並藉由模具內部的冷卻通道通過的水和壓縮空氣進行冷卻。下一步，當比較上述實驗和模擬結果的效率時，將再重新設計模具，從模具表面到冷卻通道鑽出一排小孔，每個孔的直徑為1毫米，以提高冷卻效率的工件。結果表明，通過重新設計的模具從微小孔中出來的壓縮空氣直接冷卻後，工件有顯著的變化效率。 CSC-15B22鋼的抗拉強度高達1350 MPa，相比原來的545 MPa，S45C鋼的抗拉強度高達1385 MPa，相比原來的518 MPa。結果還表明，工件也能直接藉由空氣噴孔噴出的冷卻空氣得到麻田散鐵組織。

Since the first time hot stamping technology was utilized in the automotive industry by Saab Automobile AB in 1984, this processing gradually became an important technology in the automotive industry after many enhancements. Hot stamping steel is mainly employed for automotive door beams, tunnels, pillars, bumpers, these parts need to be lightweight to reduce the weight of the vehicle while ensuring high tensile strength. To meet these technological requirements, the products must be rapidly cooled after passing through the hot stamping steel process to achieve the martensite microstructure. As a result, one of the essential requirements in hot stamping technology is the design of the cooling system in the hot stamping die. Although water is currently used as a coolant in most hot stamping processes, it also has some disadvantages, such as easy deposit formation in the die, making it easy to oxidize the die when in contact with water at high temperatures. In this thesis, a new cooling method using air as the coolant is expected to become an environmentally friendly cooling method and limit the disadvantages of using water as a coolant. In this study, experiments with CSC-15B22 and S45C steel were used to test and compare air and water cooling possibilities. After that, the Fluent was used to analyze the effectiveness of the cooling system in hot stamping. The workpiece with size 150x100x1.5 mm will be first heated up in a muffle furnace to its austenitizing temperature of about 900°C within 5 mins. Then the workpiece is quickly transferred to a hot stamping die and cooled by water and compressed air with a cooling channel inside the die. In the next step, when comparing the efficiency from experimental and simulation results above, the die will be redesigned by drilling an array of tiny holes with a diameter of each hole of 1 mm from the die surface to the cooling channel to increase the cooling efficiency of the workpiece. The results reveal that it shows a marked change efficiency after being cooled directly by compressed air coming out of tiny holes with a redesigned die. CSC-15B22 steel has a tensile strength of up to 1350 MPa, compared to 545 MPa originally, and S45C steel has a tensile strength of up to 1385 MPa, compared to 518 MPa originally. The results also show that the workpiece was transformed to martensite after cooling directly from the air-jet impingement.

摘要 i
Abstract ii
Acknowledgments iv
Contents v
List of Tables vii
List of Figures viii
Symbol Description xii
Chapter 1 Introduction 1
1.1 Research Purpose 1
1.2 Research Method and Process 2
1.3 Literature Review 4
1.3.1 Hot Stamping Technology 4
1.3.2 CAE Technology for Hot Stamping 5
1.3.3 Cooling Water Channels Design 5
1.3.4 Air Cooling Technology for Hot Stamping Die 6
Chapter 2 Theoretical Framework 8
2.1 Principle of Hot Stamping 8
2.2 Material Properties of CSC – 15B22 Steel 10
2.2.1 Stress-Strain Characteristic Curve 10
2.2.2 Heat Transfer Parameters 12
2.2.3 The Continuous Cooling Transformation (CCT) Curves 14
2.3 Material Properties of S45C Carbon Steel 15
2.4 Material Properties of SKD61 Steel 17
2.5 Design of Cooling Channel 19
2.5.1 Water Cooling Channel 19
2.5.2 Direct Cooling Under the Cction of Air-Jet Impinging 19
2.5.3 Turbulence Intensity 21
2.6 Principle of Heat Transfer 22
2.6.1 Conduction Heat Transfer 22
2.6.2 Convection Heat Transfer 23
2.6.3 Radiation Heat Transfer 25
2.7 Basic Principles of Finite Element Method 25
2.8 Solver k-epsilon 27
Chapter 3 Research Methodology 29
3.1 Fluid Simulation Software Ansys Fluent 29
3.2 Die Design and Simulation Parameter 31
3.2.1 Die Design 31
3.2.2 Simulation Paremeters 33
3.2.3 Experimental Parameter Setting 37
3.3 Hot Stamping Experimental 37
3.3.1 Introduction of Experiment Equipment 37
3.3.2 Temperature Measuring Instrument 38
3.3.3 Flow Meter 39
3.3.4 Experimental Procedure 40
3.4 Microstructure Examination and Hardness Test 44
3.4.1 Microstructure Examination 44
3.4.2 Hardness Test 47
Chapter 4 Results and Discussion 50
4.1 Simulation Results 50
4.1.1 Mesh Convergence Analysis 50
4.1.2 Comparison Between Experiment and Simulation Result 52
4.1.3 Investigation of Heat Transfer by Fluent 69
4.2 Experimental Results 77
4.2.1 Hardness Test 77
4.2.2 Microstructure Inspection of Workpiece After Hot-Stamping Experiment 82
Chapter 5 Conclusions and Development Direction 86
5.1 Conclusions 86
5.2 Development Direction 87
References 88
Extended Abstract 91

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