The Oxide Inclusion and Heat-Affected-Zone Toughness of Low Carbon Steels

Abstract:

The relationship between the oxide inclusions and the Heat-affected-zone (HAZ) toughness of microalloying steels has been investigated. The low carbon steels are smelted with special oxide introduction technique and the properties of HAZ has been studied with thermo-simulation. The optical microscope and SEM were used to analyze the size, composition and distribution of the inclusions, the mechanical properties after thermo-simulation was also analyzed. The results show that the inclusions in steel are mainly Ti and Al oxide with MnS, these complex inclusions are well distributed and the size is less than 3 micron. Microstructure of HAZ consists of intragranular acicular ferrite (IAF), intergranular ferrite and small amount of lath bainite while the cooling time during the phase formation is short. After the thermo simulation with the cooling time between 800°C and 500°C (t8/5) increasing the toughness of HAZ decreased and the size of prior austenite grain increased. Inclusions which located near the prior austenite grain boundary couldn’t induce the nucleation of IAF, only the ones inside the prior austenite grain can promote IAF’s growth.

• Periodical: Materials Science Forum (Volumes 654-656)
• Pages: 358-361
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.654-656.358
• Online since: June 2010
• Authors: Wei Shu, Xue Min Wang, Shu Rui Li, Xin Lai He
• Keywords: Heat Affected Zone (HAZ), Intragranular Acicular Ferrite, Oxide Inclusion, Phase Change Cooling Time

References

[1] Homma H, Ohkita S, Matsuda S, et al: Welding J. Vol. 66 (1987), p.301.

[2] Shim J H, Cho Y W, Chunq S H, et al: Acta Materialia. Vol. 47 (1999), p.2751.

[3] Yamamoto K, Haseqawa T, Takamura J: ISIJ int. 1996, Vol. 36(1996), p.80.

[4] Al Hajeri K F, Garcia C I, Hua M J, et al: ISIJ int. Vol. 46 (2006), p.1233.

[5] Barbaro F J, Krauklis P, Easterling K E: Mater Sci Techn. Vol. 5 (1989), p.1057.

[6] Hong S G, Kang K J, Park C G: Scr Mater. Vol. 46 (2002), p.163.

[7] Jye-Long Lee: Acta Metallurgica Materialia. Vol. 42 (1994), p.3291.

[8] Kojima A, Kiyose A, Uemori R: Nippon Steel Technical Report. Vol. 90 (2004), p.2.

[9] Byun J S, Shim J H, Cho Y W, et al: Acta Materialia. Vol. 51 (2003), p.1593.

[10] Vega M I, Medina S F, Quispe A, et al: ISIJ int. Vol. 45 (2005), p.3291 (a) (b) (c) 50µm 10µm 25µm (e) (f) (d) 25µm.