Influence of TiN particles and microstructure on cleavage fracture in simulated HAZ

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:293134

Zhang, L P; Davis, C L; Strangwood, M ^[1]

---

1. Univ. of Birmingham, Edgbaston, (United Kingdom). School of Metallurgy and Materials

Thermally stable TiN particles can effectively pin austenite grain boundaries in weld heat affected zones (HAZs), thereby improving toughness, but can also act as cleavage initiators. The effects of prior austenite grain size and matrix microstructure on the cleavage fracture of simulated HAZs in steels with two Ti levels (0.045 and 0.1 wt%) have been investigated using two peak temperatures (T{sub p}) and three cooling times by a Gleeble 1500TCS. Coarse (1--6 {micro}m) and fine (35--400 nm) TiN particles were identified in both steels and it was found that the mean size in both ranges increased with increasing Ti content at a constant number density. Higher T{sub p} (1350 C vs. 1100 C) for the same cooling time gave austenite grain growth and decreased toughness significantly. However, increasing cooling time from 8s to 90s changed the matrix microstructure from bainite to ferrite-pearlite with little variation in toughness. For both steels cleavage initiation was observed to occur at large TiN particles. For this range of variables, austenite grain size dominates toughness, although further investigation is required on steels with a lower Ti level, thereby avoiding coarse TiN particles, to determine the relative role of TiN particles on grain size and cleavage initiation and hence on toughness.

• OSTI ID: 293134
• Report Number(s): CONF-970980--; ISBN 0-87339-381-3
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
FRACTURE PROPERTIES
GRAIN SIZE
HEAT AFFECTED ZONE
MICROSTRUCTURE
NUCLEATION
STEELS
TITANIUM NITRIDES