The Influence of a Novel Inorganic-Polymer Lubricant on the Microstructure of Interstitial-Free Steel during Ferrite Rolling

Abstract

A novel polyphosphate lubricant was used and evaluated during hot (ferrite) rolling of an interstitial-free (IF) steel. The texture evolution of these rolled IF steels have been examined by means of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) measurements. The polyphosphate lubricant shows an improved lubrication performance in terms of the texture optimization compared with lubricating oil and with unlubricated conditions. The γ-fiber texture is enhanced, and less shear texture is produced. This microstructure is responsible for enhanced drawability of ferrite rolled IF steels. The very high thermal stability of the polyphosphate enabled its use at very high temperatures (from 700 to 800 °C). Rolling temperature exerted limited influence on the resulting rolling texture evolution. The polyphosphate lubricant stabilizes the surface texture and reduces the gradient of shear texture through the thickness. The in-grain shear bands are reduced significantly (48.5%) compared with the unlubricated condition. Measured grain orientations indicate that the favorable texture of {111}<112> along the γ-fiber is developed while the undesired α-fiber texture of {001}<110> is effectively suppressed.

Texture Evolution with Different Rolling Parameters of Ferritic Rolled IF Steel

“…The usage of lubrication significantly improves the texture along the thickness and reduces the shear strain on the surface. Earlier reports also suggest that the usage of lubrication may reduce the amount of shear band by 32.3% more than the non-lubricated one [22], which may significantly improve the deep drawing performance of the steel plate. If the non-lubricated surface is removed by 1/4th of thickness, the r-value can be increased by 0.3 [25].…”

“…The Goss texture retains during the recrystallization and grain growth. The usage of proper lubrication in the rolling process effectively reduces the friction between the two surfaces, improves the surface quality, changes the surface texture, and promotes the formation of γ texture [22]. However, few scholars have studied the influence of different rolling processing (including reduction rate and deformation temperature) on texture and r-value under non-lubrication rolling.…”