Microstructure and texture of hot-rolled Cb-Ti and V-Cb microalloyed steels with differences in formability and toughnes
- PDF / 1,083,100 Bytes
- 11 Pages / 606.24 x 786 pts Page_size
- 28 Downloads / 190 Views
8/30/04
5:29 PM
Page 2341
Microstructure and Texture of Hot-Rolled Cb-Ti and V-Cb Microalloyed Steels with Differences in Formability and Toughness R.D.K. MISRA, K.K. TENNETI, G.C. WEATHERLY, and G. TITHER The relationship between microstructure and formability (also toughness) of industrially processed Cb-Ti and V-Cb steels with similar yield strength of about 600 MPa and total elongation of 20 pct was examined. The steels were processed under similar conditions and any variations in processing history were unintentional. Cb-Ti steels exhibited superior formability and toughness in relation to V-Cb steels. The improved formability and toughness of Cb-Ti steels is attributed to the cumulative contribution of relatively finer grain size, narrow ferrite grain size distribution, inherently more ductile behavior and microplasticity, the reduced intensity of {100}011 texture, and slightly higher intensity of the desired {332}113 texture.
I. INTRODUCTION
THERE is a strong interest in the use of high-strength “as-hot-rolled” steels in the automotive sector to reduce vehicle weight. Thus, there is a strong drive in the steel industry to enhance the performance of the existing products, particularly, formability and toughness. The improvement of formability[1–4] of high-strength hot-rolled steels is expected to encourage a wide range of applications. Additional benefits associated with some of the newest hot-rolled steels are comparatively low cost of alloy and improved product consistency. Research on steels for automotive applications has emphasized different aspects of formability. Hilton et al.[3] described bulk formability as the “ability of the steel to be stamped into a part without failure occurring within the body of the part from exhaustion of ductility.” The determination of this property is achieved with cup-drawing experiments, forming limit diagrams, and measurement of ductility from conventional tests. Another kind of formability, edge formability, was described as the “ability of the steel to be stamped into a part without failure by fracture or excessive thinning at a sheared edge or hole.”[3] In this case, the property evaluation is achieved with various bend tests and hole expansion tests. In the work discussed here, we are largely concerned with edge formability. Hot-rolled microalloyed steels of yield strength 600 MPa were processed using two different approaches, the vanadiumcolumbium (V-Cb; average V 0.10 wt pct, average Cb 0.07 wt. pct) approach and the columbium-titanium approach (Cb-Ti; average Cb 0.08 wt pct, average Ti 0.07 wt. pct). The carbon and manganese contents were similar in
R.D.K. MISRA, Stuller Endowed Chair in Metallurgy and Professor, and K.K. TENNETI, Graduate Student, are with the Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130. Contact e-mail: [email protected] G.C. WEATHERLY, Professor, formerly with the Department of Materials Science and Engineering, McMaster University, Hamilton, ON Canada L85 4M1, is now d
Data Loading...
