• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2002.04a
• /
• pp.1-10
• /
• 2002

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.7
• /
• pp.1301-1306
• /
• 2006

Aluminum alloys are gaining increased acceptance in the automotive and electronic industeries and cold & hot forging is the most efficient method of manufacturing such mass produced parts. This study has been investigated the microstructures and mechanical properties of A6061(Al-1.2Mg-0.8Si) alloy fabricated by cold & hot forging process for development of the future compressor block. The microstructure of cold & hot forginged specimen were composed of eutectic structure aluminum solid solution and $Mg_2Si$ precipitates. The tensile strength of as-solid solution treatment A6061 alloy revealed 291.7MPa. It was fabricated that a trial future compressor cylinder block using cold & hot forging.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.7
• /
• pp.36-43
• /
• 2003

In this paper, the warm forging process sequence has been determined to manufacture the warm forged product for the precision bevel gear used as the differential gear unit of a commercial automobile. The preform shape of bevel gear influences the dimensional accuracy and stiffness of final product. So, the design parameters related preform shape such as aspect ratio and chamfer length having an influence the formability of forged product are analyzed. Then the optimal conditions of design parameters have been selected by artificial neural network (ANN). Finally, to verify the optimal preform shape, the experiments of the warm forging of the bevel gear have been executed. The proposed method can give more systematic and economically feasible means for designing preform shape in metal forming process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1998.03a
• /
• pp.94-99
• /
• 1998

In bulk metal forming processes prediction of tool life is very important for saving production cost and achieving good material properties. Generally the service life of tools in metal forming process is limited to a large extent by wear, fracture and plastic deformation of tools. In case of hot and warm forging processes, tool life depends on wear over 70%. In this study finite element analyses are applied to warm forging and hot forging by adopting suggested wear model. By comparision of simulation and real profile of die, suggested model is verified

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1998.03a
• /
• pp.88-93
• /
• 1998

The service life of tools in metal forming process is to a large extent limited by wear, fatigue fracture and plastic deformation. In warm forging processes wear is the predominant factor for operating lives of tools. To predict tool life by wear, Archard's wear model is generally applied. Usually hardness of die is considered to be a function of temperature in Archard's wear model. But hardness of die is a function of not only temperature but also operating time of die. To consider softening of die by repeated operations, it is necessary to express hardness of dies by a function of temperatures and operating time. By experiment of reheating of dies, die softening curves were obtained. Finally modified Archard's wear model in which hardness of die was expressed as a function of main tempering curve was proposed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.2
• /
• pp.420-425
• /
• 2010

In the process of warm forging, billet is heated up to $800^{\circ}C$ and located in the upper part of die block impression. The scattered oxidized scale may cause workers burn and shortening of die life sticking to the die block impression. The separating materials sprayed in die block cause harmful dust, harmful mist, fume, and bad odor which contaminate workshop environment. The process is classified as one of the avoided jobs and make the planned output achievement difficult. Development of an elimination device to clear out the contaminating materials in the workshop and improvement of the unsatisfactory maintenance method to fix the abrasion of die block impression which delays the dead line, cost increases needs to be developed. In this research, I tried to solve the problems caused in warm forging of bronze pipe joint such as the billet heating process, die maintenance, and manufacturing cost through improvement of warming forging manufacturing method and die maintenance method and eliminating harmful gas which will make the workshop more environment friendly.

• Proceedings of the KSME Conference
• /
• 2001.06c
• /
• pp.525-530
• /
• 2001

As a part of efforts to examine feasibility of warm forging near-net-shape process for non-heat-treated steel to replace quenched and tempered S45C steel, the optimized process condition has been determined to be $820^{\circ}C$ for heating, 10/sec for strain rate of forging and approximately 250MPa for flow stress from observed results such as the $A_{3}$ transformation temperature of about $790^{\circ}C$, the fully dynamic recrystallized behavior between $800^{\circ}C\;and\;850^{\circ}C$ when compressed up to 63% engineering strain at 10/sec strain rate, and the high temperature microsturctural stability. Also, controlled cooling rate of $6.3^{\circ}C/sec$ by water-spraying at a rate of $0.10cc/sec-cm^{2}$ for 60seconds followed by air-cooling right after forging process has been considered in this study as a feasible approach based on examination of the microsturcture of mixed ${\alpha}-ferrite$ and pearlite, the hardness and tensile properties meeting specification, and the reduced total cooling time to room temperature. Successive works would be carried out for the impact strength, machinalility, and forgeability at this process in the near future.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.2
• /
• pp.461-472
• /
• 1996

The relationship between plastic deformation and crystal grain change in warm forging processes of SM10C carbon steel is studied. If the carbon steel is deformed at warm forging temperature(about recrystallization range), material properties are changed due to microstructural chanre of the crystal grain and cementite of the internal part. Some experimental values are investigated in terms of the elliptic degree of cementite, the grain size of cementite and ferrite grain size. When plastic deformation proceeds, the elliptic degree of cementite becomes larger and the grain size of cementite particle becomes small. In addition, the size of ferrite grain becomes fines by recrystallization. The elliptic degree of cementite has a considerable effect on formability. The distribution of effective strain in the forging was calculated by the rigid visco-plastic FEM analysis. The effective strain distribution obtained from the FEM simulation is compared with the experimental result, At the level of effective strain 0.3, dynamic recovery and dynamic recrystallization begin and at the level of over 2.5, the organization of material has better internal structure that is suitable for the following cold forming.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.05a
• /
• pp.833-836
• /
• 2000

The mechanical and thermal load. and thermal softening which is happened by the high temperature of die, in hot and warm forging, cause wear. heat checking and plastic deformation, etc. This study is for the effects of solid lubricants and surface treatments for warm forging die Because cooling effect and low friction are essential to the long lift of dies. optimal surface treatments and lubricants are very important to hot and warm forging Process. The heat that is generated by repeated forging processes. and its transfer are important factors to affect die life. The main factors, which affect die hardness and heat transfer, are surface treatments and lubricants, which are related to thermal diffusion coefficient and heat transfer coefficient, etc. For verifying these. experiments art performed for diffusion coefficient and heat transfer coefficient in various conditions - different initial billet temperatures and different loads. Carbonitriding and ionitriding are used as surface treatments. and oil- base and water-base graphite lubrirants are used. The effects of lubricant and surface treatment for warm forging die lift are explained by their thermal characteristics.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.9
• /
• pp.75-81
• /
• 1998

Simulations of warm and hot forming processes need reliable expressions of flow stress at high temperatures. To get flow stress of the materials usually tension, compression and torsion tests are conducted. In this study, hot compression tests were adopted to get flow stress of medium carbon steel. Experiments have been conducted under both isothermal, near constant strain rate in the temperature ranges 650～100$0^{\circ}C$. Phase transformation takes place by temperature changes for steels in hot and warm forging stage. So Constitutive equation are formulated as the function of strain, strain rate and temperature for isothermal conditions and phase transformation.