The Use of Microstructural Analysis for the Evaluation of Quality of Double-Wall Tubes

Abstract:

Double-wall copper brazed steel tube is an economic alternative of copper and copper nickel tubes, that are used widely in automotive and AC&R applications, offering satisfying rigidity against high pressure, flexibility for bending and flaring, and rather good heat conductibility. When comparing in detail commercially available tubes of such type, significant differences in quality were revealed. This contribution is based on case studies concerning most common causes of failure of double-wall tubes due to several factors. Series of double wall-tubes from different suppliers were studied using light and electron microscopy in order to reveal defects which led to the failure of each set of the tubes. Tubes made of combination of steel and copper were analysed in the initial state and after heat treatment. Heat treatment performed by the suppliers was not further specified and varied between suppliers. Metallographic analysis revealed unsuitable microstructure of steel layers and heterogeneity in Cu layer. More detailed analysis revealed precipitation of Cu-based intermetallic phase on the Cu-steel interface resulting from heat treatment process, but for one set of tubes, precipitates were observed even in the initial state, probably due to higher temperatures used during the fabrication process.

• Periodical: Materials Science Forum (Volume 891)
• Pages: 269-273
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.891.269
• Online since: March 2017
• Authors: Lenka Klakurková, Miroslava Horynová*, Martin Juliš, Pavel Gejdoš
• Keywords: Brake Tube, Compressor Tube, Defects, Double-Wall Copper Brazed Steel Tube, Intermetallics, Microstructure Analysis, Quality

References

[1] M. Mizumura, et al., Behavior of Mechanical-Bonding Double-Wall Pipe Under Various Loading Conditions, Int J Offshore Polar 4 (1994).

[2] H. Suzuki, K. Takiuhi, Fatigue reliability in terms of fatigue fracture under internal pressure of the tube used in brake equipment for automobiles, n: N. Kikai, G. Ronbunshu, A. Hen, Transactions of the Japan Society of Mechanical Engineers, Part A. JSME, 1999, 63(612), 1642-54.

DOI: 10.1299/kikaia.63.1642

[3] S. Abu, A. Albatlan, Effect of hydraulic brake pipe inner diameter on vehicle dynamics, Int J Automot Techn, 16 (2015) 231-237.

DOI: 10.1007/s12239-015-0025-2

[4] K-T. Han and J. S. Park, On the Forming of Brake Tube-End with Double Wall Structure for Automobiles. In: AIP Conference Proceedings, 2004, 712, s. 1178.

DOI: 10.1063/1.1766688

[5] J. Peng, Ch-Y. Zhou, J-L. Xue, Q. Dai a X-H He, Safety assessment of pipes with multiple local wall thinning defects under pressure and bending moment, Nucl Eng Des. 241 (2011) 2758-2765.

DOI: 10.1016/j.nucengdes.2011.06.030

[6] X. Yijian Z, Shengquan, G. Ianzhong, Microstructure and properties of brazed bouble-wall steel tube, Gangtie proceedings, 1993, 1-8.

[7] Y. Chen, J. Liu,Y. Li, J. Wu, M. Lai Mingdao, Composition and microstructure of brazing joint of triple wall brazed tube, Iron & Steel 11 (1997) 98-115.