Determination of Heat Transfer Coefficients for Different Initial Tool Temperatures and Closed Loop Controlled Constant Contact Pressures

Abstract:

The boron steel quenching requirement on hot forming manufacturing processes allows the industry to create tailored parts to improve their mechanical functionality. During the cooling, the microstructure of the material changes depending on the imposed cooling rate. However, an accurate prediction of the cooling ratios is needed in order to correctly design the process. In this work the interfacial heat transfer coefficient (HTC) has been determined at different contact conditions, varying the initial die temperature. Experimental tests have been realized in a SCHMIDT micro servo-press, which is able to compensate the thermal contraction of the blank and tools to precisely keep constant the contact pressure. Temperature evolution of the tools and the blank has been monitored with nine thermocouples. For the determination of the heat transfer coefficient (HTC) an analytical-numerical method has been used leading to a fast and reliable calculation method able to determine the HTC value for each process time. This methodology allows relating the HTC to the blank temperature, difference on temperature on the interface to improve the tailor tempering of boron alloys simulation.

• Periodical: Key Engineering Materials (Volumes 651-653)
• Pages: 1537-1542
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.651-653.1537
• Online since: July 2015
• Authors: Joseba Mendiguren*, Rafael Ortubay, Xabier Agirretxe, José Miguel Martín, Lander Galdos, Eneko Sáenz de Argandoña
• Keywords: Heat Transfer Coefficient, Hot Stamping

References

[1] Abdulhay B, Bourouga B, Dessain C, Brun G, Wilsius J. Development of estimation procedure of contact heat transfer coefficient at the Part–Tool interface in hot stamping process. Heat Transfer Eng. 2011; 32(6): 497-505.

DOI: 10.1080/01457632.2010.506362

[2] Abdulhay B, Bourouga B, Dessain C. Experimental and theoretical study of thermal aspects of the hot stamping process. Appl Therm Eng. 2011 4; 31(5): 674-85.

DOI: 10.1016/j.applthermaleng.2010.11.010

[3] Bai Q, Lin J, Zhan L, Dean TA, Balint DS, Zhang Z. An efficient closed-form method for determining interfacial heat transfer coefficient in metal forming. Int J Mach Tools Manuf. 2012 5; 56(0): 102-10.

DOI: 10.1016/j.ijmachtools.2011.12.005

[4] Caron E, Daun KJ, Wells MA. Experimental characterization of heat transfer coefficients during hot forming die quenching of boron steel. Metallurgical and Materials Transactions B. 2013; 44(2): 332-43.

DOI: 10.1007/s11663-012-9772-x

[5] Chang C, Bramley AN. Determination of the heat transfer coefficient at the workpiece—die interface for the forging process. Proc Inst Mech Eng Pt B: J Eng Manuf. 2002; 216(8): 1179-86.

[6] Hay BA, Bourouga B, Dessain C. Thermal contact resistance estimation at the blank/tool interface: Experimental approach to simulate the blank cooling during the hot stamping process. International journal of material forming. 2010; 3(3): 147-63.

DOI: 10.1007/s12289-010-0687-2

[7] Koistinen DP, Marburger RE. A general equation prescribing the extent of the austenite-martensite transformation in pure iron-carbon alloys and plain carbon steels. Acta Metallurgica. 1959 1; 7(1): 59-60.

DOI: 10.1016/0001-6160(59)90170-1

[8] Lenard J, Davies M. An experimental study of heat transfer in metal-forming processes. CIRP Annals-Manufacturing Technology. 1992; 41(1): 307-10.

DOI: 10.1016/s0007-8506(07)61210-4

[9] Malinowski Z, Lenard J, Davies M. A study of the heat-transfer coefficient as a function of temperature and pressure. J Mater Process Technol. 1994; 41(2): 125-42.

[10] Merklein M, Lechler J. Determination of material and process characteristics for hot stamping processes of quenchenable ultra high strength steels with respect to a FE-based process design. (2008).

DOI: 10.4271/2008-01-0853

[11] Merklein M, Lechler J. Investigation of the thermo-mechanical properties of hot stamping steels. J Mater Process Technol. 2006; 177(1): 452-5.

DOI: 10.1016/j.jmatprotec.2006.03.233

[12] Salomonsson P, Oldenburg M, Åkerström P, Bergman G. Experimental and numerical evaluation of the heat transfer coefficient in press hardening. steel research international. 2009; 80(11): 841-5.

[13] Tondini F, Bosetti P, Bruschi S. Heat transfer in hot stamping of high-strength steel sheets. Proc Inst Mech Eng Pt B: J Eng Manuf. 2011; 225(10): 1813-24.

DOI: 10.1177/0954405411413987

[14] Wang C, Zhang Y, Tian X, Zhu B, Li J. Thermal contact conductance estimation and experimental validation in hot stamping process. Science China Technological Sciences. 2012; 55(7): 1852-7.

DOI: 10.1007/s11431-012-4871-0