Measurement and prediction of plastic anisotropy in deep-drawing steels

R-values and yield stresses were measured as a function of inclination with respect to the rolling direction on 15 steels selected from four basic types [high-strength low-alloy (HSLA), Al-killed drawing quality (AKDQ), interstitial-free (IF), and rimmed]. Orientation distribution functions (ODF’s) were also determined for these steels, using both X-ray and neutron diffraction techniques. The series expansion method was employed for predicting the plastic anisotropy of the rolled sheets. Comparison with the experimental measurements indicates that the “pancake” relaxed constraint model is a more accurate predictor of behavior than the Taylor, Sachs-Kochendörfer, or two other relaxed constraint models. The best quantitative agreement is obtained when the critical resolved shear stress (CRSS) ratio for glide on the {112} (111) and {110} (111) slip systems (t₁₁₂/t₁₁₀) is 0.95. A “lath” relaxed constraint model (with ?₂₃ relaxed), associated with the same CRSS ratio, leads to good results for steels with elongated microstructures.     

Production of cold-rolled steel coils

The aspects of cold rolling and subsequent coiling that affect the quality of the steel strip produced are identified on the basis of theoretical and experimental research and production experience at various steel plants. The influence of the strip width and thickness, the surface temperature, the temperature of the rolled metal, and other factors on the stress-strain state of the coils is established. Rational rolling and coiling conditions at continuous and reversible mills are recommended.     

Improving the production of cold-rolled steel

The influence of the basic technological factors on the loss of strip width in cold rolling is considered. The influence of technological factors and the state of the working rollers on the formation of light bands (impressions) at each working roller in the first cell of the old-rolling mill is investigated. Means of eliminating these problems in the production of cold-rolled steel are proposed.     

Properties of cold-rolled high-strength steel sheets

For high-strength steel sheets, a new concept has become necessary,viz, the relation between strength and formability. When the relation between tensile strength and elongation is appraised for ranking in terms of the strengthening mechanism, it is found that the substitutional solid-solution hardening type is excellent and the precipitation hardening type is inferior. In batch annealing, the phosphorus-added aluminum-killed steel sheets are representative of the former type having excellent formability as indicated by a highr values despite their tensile strength of 450 N/mm². The titanium-added aluminum-killed steel sheets, which are representative of the latter type, have a tensile strength of 600 N/mm² and a relatively highr value. Continuous annealing of the highstrength steel sheets of the same chemical composition causes higher yield stresses and combinations of yield stress and elongation. Alternatively with continuous annealing the same level of strength can be achieved with smaller additions of alloying elements than with batch annealing. An additional advantage of continuous annealing is the uniformity of properties along the length of the coil. The rapid cooling possible after continuous annealing allows production of high strength steel sheets having excellent mechanical properties that are unobtainable in the batched annealed steels. For example, steel sheets of 0.4 pet Si and 1.4 pet Mn after continuous annealing, haven values and Erichsen values as higher than conventional low-carbon rimmed or capped steel sheets even while they have a tensile strengths of 550 N/mm².      

Through-thickness texture gradients in cold-rolled aluminum

The through-thickness texture variations in ∼40 pct cold-rolled polycrystalline aluminum were studied using X-ray diffraction and the electron backscattering pattern (EBSP) technique. The influence of the roll-gap geometry and of sequences of small and intermediate draughts on the development of deformation textures in multipass rolling was considered. It was found that similar textures were formed near the surface and in the central layers of all specimens, while, in the intermediate layers of different plates, different textures were observed. Small draughts gave rise to the shear texture in the intermediate layers, while no pronounced shear texture was revealed anywhere through the thickness of plates rolled with intermediate draughts. It was found that small-draught rolling only has a pronounced effect on the texture if it accounts for a significant strain in the rolling schedule. It was found, furthermore, that nonuniformity of the initial recrystallization texture may be retained in the texture after ∼40 pct rolling.     

Properties of cold-rolled high-strength steel sheets

For high-strength steel sheets, a new concept has become necessary,viz, the relation between strength and formability. When the relation between tensile strength and elongation is appraised for ranking in terms of the strengthening mechanism, it is found that the substitutional solid-solution hardening type is excellent and the precipitation hardening type is inferior. In batch annealing, the phosphorus-added aluminum-killed steel sheets are representative of the former type having excellent formability as indicated by a highr values despite their tensile strength of 450 N/mm². The titanium-added aluminum-killed steel sheets, which are representative of the latter type, have a tensile strength of 600 N/mm² and a relatively highr value. Continuous annealing of the highstrength steel sheets of the same chemical composition causes higher yield stresses and combinations of yield stress and elongation. Alternatively with continuous annealing the same level of strength can be achieved with smaller additions of alloying elements than with batch annealing. An additional advantage of continuous annealing is the uniformity of properties along the length of the coil. The rapid cooling possible after continuous annealing allows production of high strength steel sheets having excellent mechanical properties that are unobtainable in the batched annealed steels. For example, steel sheets of 0.4 pet Si and 1.4 pet Mn after continuous annealing, haven values and Erichsen values as higher than conventional low-carbon rimmed or capped steel sheets even while they have a tensile strengths of 550 N/mm².