Rolling Process Parameters Research Articles

Recrystallization and Related Phenomena. Influence of Hot Rolling and Cooling Conditions on the Grain Refinement of Hot Rolled Extralow-carbon Steel Bands.

In this paper, the effect of various operational parameters in a hot strip rolling process on the grain refinement of hot rolled plain extralow-carbon steel bands has been investigated. The finishing temperature and the onset time of cooling after hot rolling influence the grain refinement significantly. The finishing temperature just above Ar3 is optimum for the grain refinement. The reducing of the onset time of cooling not only refines the grain size, but also decreases the finishing temperature-dependence of grain size. The increase in the reduction of the final hot rolling refines the grain size as well. The cooling rate does not affect the grain size of hot bands in the range between 40 and 120°C/sec significantly. The mechanism of the grain refinement has been discussed with a relation of recrystallization and transformation behavior of austenite and it is concluded that in the case of extralow-carbon steel without Ti and Nb addition, the grain refinement of hot bands is strongly influenced by not only the recrystallization but also grain growth behavior of austenite.

A study of pore closure and welding in hot rolling process

The design of processing conditions to eliminate porosity in steel during hot rolling has become more critical with the advent of continuously cast feed stock. To predict appropriate process parameters, experiments were performed in which holes were drilled in steel slabs, at different depth below the surface perpendicular to the rolling direction. After hot rolling, the state of the deformed holes was examined by optical microscopy. The fracture surfaces of tensile specimens notched in the plane of the closed holes were examined under a scanning electron microscope to investigate the bonding ( welding ) between the surfaces of the closed holes because this bonding is the most important factor indetermining the transverse mechanical properties of the rolled product. The deformation of such holes in the roll gap was modelled as an clastic / plastic plane strain problem using the FE software ABAQUS to investigate the strain and stress around holes and to analyze the conditions required to promote pore closure and welding between the closed surfaces. Experiment results showed that the rate of pore closure was affected by the parameters of rolling process and the position of holes relative to the rolling contact surfaces. FE simulation of pore closure showed a good agreement with experimental results and showed that a certain level of hydrostatic pressure resulted in the closure of pore and that the holding period of the pressure in the compressive state determined the degree of welding of surface of pores; shear is favourable to this welding.

Computer modelling of microstructure during hot flat rolling of aluminium

AbstractPrediction of the evolution of grain size in hot rolling of Al–5Mg alloy (AA 5056) is described in this paper. Published equations that relate microstructure to processing conditions in aluminium are incorporated into a thermomechanical model of hot rolling. Detailed modelling of the distribution of temperature, strain, and strain rate (Zener–Hollomon parameter) allows prediction of through thickness variation in the microstructure. The model described in this paper was developed to examine the effects of rolling process parameters (roll speed, reduction, strip entry temperature, and interpass time) on the extent of recrystallisation and grain size in the resulting microstructure.MST/1439

Geometric and power parameters of the metal powder rolling process. I. Boundaries of the seat of deformation and stress field in the lag and forward slip zones

Geometric and power parameters of the metal powder rolling process. I. Boundaries of the seat of deformation and stress field in the lag and forward slip zones

Finite element investigation of curling in non-symmetric rolling of flat stock

Curling of sheet flat stock during the rolling process can result in damage to equipment and injury to rolling mill operators. Additionally, the resultant curvature leads to poor quality of rolled stock. Curling is primarily due to the non-symmetry in the rolling process parameters—rolling speed mismatch, frictional differences at the two rolls and the differences in the roll radii. This paper presents an investigation of curling due to roll speed mismatch. An explicit time integration elastic-plastic finite element method is used to simulate non-symmetric plane strain rolling; reasonable agreement with experimental results of Kennedy and Slamar is found. The results demonstrate the efficacy of finite element analysis in investigating the effect of individual process parameters on the behavior of multi-variable processes.

Effect of the finish rolling and cooling conditions on the properties of microalloyed plate steels

The processing parameters of finish rolling and cooling of three HSLA steels were varied in a wide range applying the plane strain hot compression simulation test on the hot deformation simulator (Wumsi). Evaluating the flow curves of the deformation steps, some metallurgical phenomena in austenite during hot deformation could be determined. The results of material testing after the simulation experiments exhibit a strong correlation between the finish rolling and cooling conditions and the final mechanical properties of the steels tested. As a way to increase strength, lowering finishing temperatures and/or accelerating cooling after finish rolling proved to be most effective. To improve notch toughness, on the other hand, a high total finishing strain should be applied as well as low finishing temperatures, however, above Ar3.

Macromechanism of powder deformation in the incoherent zone during rolling

Observation of the deformation of a free-flowing material through transparent hopper walls is a technique yielding a great deal of useful information and enabling the deformation behavior of powders to be studied in the lag zone (breaks in the velocity field, formation of arch structures, and the like). A binding link between the geometric and physical parameters of the powder rolling process is the initial powder compressibility. An increase in the intensity of the shear deformation of powders before the commencement of their irreversible densification suggests that impeded deformation zones may not be able to form above the angle of rolling.

Rolling of powder mixtures with a solid lubricant filler

1. It is shown that sheet material can be successfully rolled from powder containing up to 16 wt.% of graphite. 2. To obtain strip with stable properties from a powder mixture with a solid lubricant filler, it is necessary to add glycerin to the charge. The optimum glycerin content depends on the amount of solid lubricant in the charge and the rolling process parameters.