Kevin Banks

Influence of Ti on hot ductility of Nb containing HSLA steels

Abstract The influence of a low Ti addition (∼0·01%) on the hot ductility of Nb containing HSLA steels has been examined. For conventional cooling conditions in which an average cooling rate from the melting point to the test temperature was used, the ductility decreased markedly with the addition of Ti. However, when cooling conditions after melting were more in accord with the thermal heat treatment undergone by the strand during continuous casting, i.e. cooling is fast to begin with, reaches a minimum and then reheats, after which the temperature falls more slowly to the test temperature, the Ti addition was found to be beneficial.

Regression equation for Ar3 temperature for coarse grained as cast steels

Abstract A regression equation for the Ar3 temperature for as cast ferrite/pearlite steels has been obtained. At these coarse grain sizes, very little influence of grain size on the Ar3 is observed. Out of all the elements examined, C, Mn and Nb had the major influence in decreasing the Ar3. A change in cooling rate from 10 to 200 K min−1 results in only a small decrease of around 20°C. Of particular interest is the very marked effect of Nb in reducing the Ar3, an addition of 0·03%Nb causing a decrease in the Ar3 of 50°C.

Hot Strength During Coiling of Low C and Nb‐Microalloyed Steels

The flow stress under typical hot coiling conditions has been quantified for low C and Nb-Ti (V) microalloyed steels. The equation is intended for calculating the amount of bending torque required during coiling, particularly for thick, microalloyed skelp, so as to optimally adjust the coiler tension settings. Simplified rolling, runout table (ROT), and coiling simulations, typical for 10mm strip were performed. A small plastic strain was applied during the coiling stage to study flow behaviour in the ferrite and two-phase regions. The flow stress equation developed is applicable for the following chemistry limits: 0–0.09%Nb, 0.25–1.59%Mn, 0.06–0.16%C, 0–0.25%Si, 0–0.02%Ti and 0–0.07%V. Dilatometry measurements showed that, at high coiling temperatures, a significant fraction of untransformed austenite was often present during coiling. The most significant variables contributing to flow stress in the coiling region in decreasing order are: strain, Nb content, temperature and Mn content.

Influence of chemistry and runout table parameters on hot coil collapse in C–Mn steels

Abstract The key metallurgical parameters affecting the incidence of coil collapse (soft slump) of C–Mn steels has been investigated using industrial data and laboratory simulation. Runout table (ROT) cooling/coiling simulations were performed on a Gleeble 1500D to study transformation before and during coiling of thin strip. For low C (<0·07%) grades, coiling temperatures above 650°C coupled with high nitrogen contents decreased the transformation end temperature Ar1 and increased collapse. Coiling temperatures above the Ar1 for ROT cooling increased both dilation and the time to complete transformation during coiling. These effects correlated with industrial conditions where a high frequency of coil collapse was observed.