Critical Cooling Rate and Design of Mould Cooling System for Hot Forming of High-Strength Sheet

Abstract:

High-strength sheet including 2MnB5 Boron and magnesium alloy sheet is the material commonly used in modern machinery, which is easy to induce problems such as excessive rebound, cracking, forming force increase, easy mould wear and the like. The heat analysis of 2MnB5 Boron and magnesium alloy sheet hot stamping forming process and experiments indicate that the transition process from Austenite to Martensite by controlling the sheet heating and cooling temperature is the foundation of heat forming. Only when the cooling rate reaches or surpasses the critical cooling rate, Austenite can be transformed to Martensite directly. Critical cooling rate of sheet is related to the elements of critical water flow rate, mould cooling system design, cooling medium, dented mould medium and the like. Under the condition that the elements of mould structure, cooling system, cooling medium and the like are defined, critical cooling rate is a constant value. As a result, through controlling critical water flow rate, hot forming transition process and hot forming requirements can be guaranteed to overcome the excessive rebound, cracking, forming force increase, easy mould wear and the like in hot forming process.

• Periodical: Advanced Materials Research (Volumes 295-297)
• Pages: 1474-1478
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.295-297.1474
• Online since: July 2011
• Authors: You Dan Guo
• Keywords: Cooling System, Critical Cooling Rate, Critical Current Rate, Hot Balance, Hot-Forming, Phase Change Process

References

[1] Youdan Guo. The mould design technique on hot forming of high-strength steel [J].Hot working technology2011,9：17-21

[2] J.Adameczky W.ozgowicz, R.Wusatowski, E.Kalinowska-Ozgowiez and R.Grzyb.Boron-treated microalloyed quenched and tempered plates, their structure and properties.Joumal of Materials Processing Technology.1997, 64

DOI: 10.1016/s0924-0136(96)02548-4

[3] Daxin E. Forming process and mould design[M].Beijing: Beijing institute of technology press, 2007.03

[4] Liyun Shan, Yinghuai Qiang, Yafei Zhang. Engineering Materials[M].Xuzhou: China university of mining and technology press, 2003.01

[5] TURETTA A, BRUSCHI A. GHIOTTI A. Investigation of 22MnB5 formability in hot stamping operations[J]. Mater.Processing Technol, 2006,177:396-400.

DOI: 10.1016/j.jmatprotec.2006.04.041