Effects of the deep rolling process on the surface roughness and properties of an Al-3vol%SiC nanoparticle nanocomposite fabricated by mechanical milling and hot extrusion

Deep rolling is one of the most widely used surface mechanical treatments among several methods used to generate compressive residual stress. This process is usually used for axisymmetric components and can lead to improvements of the surface quality, dimensional accuracy, and mechanical properties. In this study, we deduced the appropriate deep rolling parameters for Al-3vol%Si C nanocomposite samples using roughness and microhardness measurements. The nanocomposite samples were fabricated using a combination of mechanical milling, cold pressing, and hot extrusion techniques. Density measurements indicated acceptable densification of the samples, with no porosity. The results of tensile tests showed that the samples are sufficiently strong for the deep rolling process and also indicated near 50% improvement of tensile strength after incorporating Si C nanoparticle reinforcements. The effects of some important rolling parameters, including the penetration depth, rotation speed, feed rate, and the number of passes, on the surface quality and microhardness were also investigated. The results demonstrated that decreasing the feed rate and increasing the number of passes can lead to greater surface hardness and lower surface roughness.

Optimization and perfection of the roughing model for ferritic SUS430

Based on the characteristics of ferritic SUS430 heating and deformation,and combined with the features of the 1780 mm hot-rolling mill,a roughing model was introduced in two aspects:optimizing the rough rolling passes and improving the width control precision.Through reducing the rough rolling passes,the rough rolling time can be shortened,the precision rolling startup temperature can be raised and the yield of the hot-rolled products can be increased.Moreover,on the premise that the slab width fluctuation was great,the precision of the width control can be improved through optimizing the parameters of the hot-rolling width control model.The result shows that the optimization and perfection of the original rolling process of the stainless steel 430 series further improved its capacity and product quality.

Study and Application of Camber Control Model of Intermediate Slab in Rough Rolling

In order to solve the camber problem of intermediate slab in a domestic conventional hot rolling mill, a three dimensional elastic-plastic dynamic model was built through finite element method to quantitatively calculate the influence of lateral flow factors in different entry thicknesses, reductions, reduction ratios differences on both sides and width factors. Thus, the extending difference at outlet of intermediate slab in length was transformed into thickness difference on both sides by the results, and then the tilting value of roll gap reduction to control the camber was calculated. Based on the above results, the camber control model of intermediate slab in rough rolling was estab- lished. The practical application on the rough rolling mill obtained a decent control effect, and it proved that this model had a high accuracy.

Linear Integral Analysis of Bar Rough Rolling by Strain Rate Vector

A new linear integral method for bar hot rolling on roughing train was obtained. First, for plastic deformation energy rate, equivalent strain rate about Kobayashi＇s three-dimensional velocity field was expressed by two-dimensional strain rate vector; then, the two-dimensional strain rate vector was inverted into inner product and was integrated term by term. During those processes, boundary equation and mean value theorem were introduced; for friction and shear energy dissipation rate, definite integral was applied to the solution process. Sequentially, the total upper bound power was minimized, and the analytical expressions of rolling torque, separating force, and stress state factor were obtained. The calculated results by these expressions were compared with those of experimental values. The results show that the new linear integral method is available for bar rough rolling analysis and the calculated results by this method are a little higher than those of experimental ones. However, the maximum error between them is less than 10%.

Thermal Scratch on Surface of SUS430 Stainless Steel Strip in Cold Rolling Process

The thermal scratch significantly influences the surface quality of the stainless steel in cold strip rolling. The thermal scratch has a close relation to the rolling parameters, the rolls surface and the emulsions used in rolling. In order to explain the thermal scratch on the strip surface, the cold roiling process of SUS430 stainless steel strip was investigated in the laboratory. The thermal scratch defect occurs frequently in the second rolling pass （maximum reduction in height is 32.3 ~）, especially on the lower surface of strips. When concentration and temperature of the emulsion are the same, the thermal scratch on the surface o{ the strip is aggravated with increasing the roll surface roughness. With the same roll surface roughness and emulsion concentration, the thermal scratch is obviously more severe at an emulsion temperature of 63 ℃ than 55 ℃. With the same roll surface roughness and emulsion tempera- ture, the thermal scratch is distinctly weaker at the emulsion concentration of 6 % than that of 3 %.