Intercritical Quench Hardening of Structural Pipeline Steels

Abstract:

The paper considers the effect of low-carbon pipeline steels initial condition on their mechanical properties and structure after quench hardening at different temperatures in the intercritical temperature range Ac₁–Ac₃ (ITR) followed by tempering at 600 °C. If the prior heat treatment is annealing or normalizing , which produces the ferrite-pearlite structure, then quenching from temperatures just above Ac₁ causes very strong embrittlement due to the formation of a high-carbon austenite film at ferrite/pearlite boundaries. Increasing quenching temperature in the intercritical range increases impact toughness and ductile fracture fraction for both types of prior treatment, though normalizing provides higher impact toughness than annealing. On the contrary, if the prior heat treatment is quench hardening, then the highest impact toughness is observed when the second quenching temperature lies a little above Ac₁. Impact toughness and ductile fraction for preliminarily quenched samples gradually decreases along with the increase in austenitization temperature in the intercritical range.

• Periodical: Materials Science Forum (Volume 843)
• Pages: 248-252
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.843.248
• Online since: February 2016
• Authors: D.A. Mirzaev*, A.N. Makovetskii
• Keywords: Austenite, Bainite, Impact Toughness, Intercritical Quench Hardening, Low-Carbon Steels, Martensite, Pipeline Steels, Tempering

References

[1] V.M. Schastlivtsev, D.A. Mirzaev, I.L. Yakovleva, Structure of Heat Treated Steel, Metallurgiya Publ., Moscow, (1994).

[2] V.D. Sadovskii, Structural Inheritance in Steel, Metallurgiya Publ., Moscow, (1973).