Transformation textures in hot rolled steels

Abstract

The way in which texture development is affected by hot rolling, intercritical rolling, and warm rolling was studied in a plain carbon, a niobium microalloyed and an interstitial free steel. Three processing parameters were varied: the austenitizing temperature (1250$sp circ$C or 1150$sp circ$C), amount of reduction (90% or 75%) and finish rolling temperature (1020$sp circ$C, 870$sp circ$C, 770$sp circ$C, 730$sp circ$C and 630$sp circ$C for the first two materials, and 1020$sp circ$C, 920$sp circ$C, 870$sp circ$C, 820$sp circ$C, 720$sp circ$C and 620$sp circ$C for the IF steel). It was found that lower reheating temperatures and larger deformations lead to more intense textures. The effect of finish rolling temperature was different for each steel. In the plain carbon, only warm rolling produced a strong texture. In the interstitial free steel, the strongest textures were again produced by rolling in the ferrite range. In the niobium microalloyed steel, the retardation of austenite recrystallization intensifies the fcc deformation texture components; thus, a fairly strong texture is inherited by the ferrite, which is in turn enhanced by further deformation. The experimental textures were compared with the transformation textures predicted by using the Kurdjumov-Sachs relationship. It was found that when most of the reduction was applied in the austenite recrystallization range, the cube texture appeared to form, which transformed preferentially into the rotated cube ${ 001 } langle110 rangle$. When the austenite remained in the pancaked state, the expected transformation products of the fcc rolling texture, i.e. the copper ${ 112 } langle111 rangle$, brass ${ 110 } langle112 rangle$, S ${ 123 } langle634 rangle$ and Goss ${ 110 } langle001 rangle,$ again appeared, with clear preferences for particular variants. The calculations indicate that the final ferrite texture formed from either recrystallized or deformed austenite is significantly modif