Anisotropy of bulk forming limits in hot-rolled steel bars
- PDF / 1,381,756 Bytes
- 6 Pages / 594 x 774 pts Page_size
- 78 Downloads / 214 Views
TURGAY ERTORK is Associate Professor,Department of Metallurgical Engineering,Middle East Technical University,Ankara, Turkey. Manuscript submitted April 14, 1980. METALLURGICALTRANSACTIONSA
orientations.* Upset tests could not generate forming *A distinction must be made between specimen orientations and FLL's correspondingto different directions. The latter are determined by the orientation of critical tensile stresses with respect to principal directions. limit strains in the longitudinal direction. In a later work, Suh and Kuhn ~5obtained complimentary results from bend tests for the same material. These provided the F L L in the longitudinal (rolling) direction. Bend data fell onto the extension of FLL's obtained from upset tests in the other orientations, in conformity with the original findings." Combined results of these investigations ~4.~5are given in Fig. 1. (It should be noted that the compressive strain axis is reversed in all Figures). Workability was poorest in the thickness direction and greatest in the rolling direction. Agreement between the tensile ductilities, as measured by true zero-gage-length fracture strains, and the forming limit strains from upset and bend tests could not be verified for the short-transverse direction, because it was not possible to manufacture tension specimens in plates in this orientation. The purposes of the present study are threefold: i) to explore the anisotropy of bulk forming limits in a different geometry, namely circular cross-sections; ii) to generate tensile data in all three principal directions; and iii) to evaluate further the validity of the tension test in predicting bulk forming limits. EXPERIMENTAL PROCEDURE In order to evaluate mechanical fibering effects in a material with a pronounced inclusion content and alignment, hot-rolled AISI 1040 steel bars 80 mm in diameter were studied. The chemical composition of the bars was determined to be 0.38 pct C, 0.51 pct Mn, 0.08 pct Si, 0.013 pct P, and 0.041 pct S, all in weight percentages. Slight pearlite banding was observed in the direction of rolling, Fig. 2. Alignment of inclusions in this material is shown in Fig. 3; inclusions are elongated in the rolling direction and spread in the circumferential direction. Alignment is symmetrical with respect to the rod axis (in the rectangular geometry, inclusion alignment is symmetrical with respect to the midplane of the
ISSN 0360-2133/81/0511-0743500.75I0 9 1981 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME
VOLUME12A, MAY 1981--743
plate), and includes slight curving in the cross-sectional plane, reflecting the general shape change of the material. Upset test specimens 10 mm in diam were cut from the bars with their axes in the three principal directions: longitudinal (L). circumferential (C), and radial (R). Tension and bent test specimens were also fabricated in these directions. Figure 4 shows the orientations of compression, bend, and tension test specimens, along with critical tensile stresses generated in each specimen (double arrow
Data Loading...
