The Control of Texture in Rimmed Steel Strip

Abstract

Through thickness texture segregation has been observed in cold rolled rimmed steel. The effect of rolling draught and lubrication upon the segregation has been recorded. For a constant cold reduction, the mid-plane texture was always the same and was comprised of two partial fibre textures,<110>RD + {111} RP . Texture segregation is associated with deviation from this texture through the rest of the strip. Four types of segregation have been observed and categorised according to rolling draught, i.e. .025 mms for Type I textures and greater than .500 mms for Type IV textures. Type I texture segregation results from variations in {111} RP texture intensity through the strip. Type III textures are characterised by segregation in the extreme surface planes only. In this zone there is a general reduction in texture intensity rather than a change in textural components. Type II texture segregation is a composite of Types I and III. Type IV texture segregation is produced by rolling with heavy draughts and magnesia dusted rolls. The surface texture is described as {110} <UVW> where <UVW> ranges between <001> and <111> Mechanisms are devised to account for texture segregation and, where appropriate, discussed in relation to the literature. Texture segregation is retained after annealing and therefore influences the R value of finished strip. There is a general reduction in R value commensurate with the intensity of segregation. Thus, for a constant cold reduction, RIV< RI < RII< RIII: Also the cold reduction at which the maximum (Romax) occurs in the plot of Ro, value versus percentage reduction is dependent upon texture segregation. Romax is associated with the balancing of {111}RP texture with the detrimental<110>RD texture. This balance is disturbed by texture segregation such that <110>RD texture predominates at variable cold reductions. ‾R and Ro values of strip can be improved by the presence of intragranular cementite approximately 1μ in size. Textural measurements show that the effect is due to the inhibition of the detrimental reorientation of <110>RD textures normally observed during tensile strain.>