Recycling of stainless steel bar scrap by radial-shear rolling to obtain an ultrafine-grained gradient structure

This work is devoted to the study of the possibility of recycling bar scrap of stainless metals using radial-shear rolling. In the course of studies on the deformation of bar scrap in the form of pins made of 12X18N9T stainless austenitic steel on a radial-shear rolling mill, the resulting bar was obtained microstructure of two different types: on the periphery an equiaxed ultrafine-grained structure with a grain size of 0.4–0.6 microns was formed; in the axial zone anoriented, banded texture was obtained. This discrepancy in the structure of the peripheral and axial zones, together with the results of cross-section microhardness measurements of samples made of 12X18N9T austenitic stainless steel with a total degree of deformation of 44.4 %, indicates the gradient nature of the resulting microstructure.

Statistical Research of Stainless Austenitic Steel Grain Size Distribution after Screw Rolling

Screw rolling of austenitic stainless-steel billets was conducted in two- and three-high mills. Statistical research results showed that, compared to heated but not rolled conditions, both screw rolling techniques provided a decrease of grain size, variance, grain size distribution asymmetry, and excess in the billet cross-section at the stationary stage of screw rolling. At that stage, grain size distribution after two-high screw rolling is closer to normal in terms of asymmetry and excess values compared to grain-size distribution after three-high screw rolling. A strong negative correlation between strain effective values and grain-size values for the cross-section of the rolled billets at the stationary stage was revealed for both two- and three-high screw rolling.

Characterization of Magnetoelectropolished Stainless Steel Surfaces’ Texture by Using the Angle-Resolved Scattering and Image Processing Analysis Methods

In this article, the results of preliminary experimental studies related to a fast, non-contact assessment of the AISI 316L stainless austenitic steel surfaces after electrochemical polishing in a magnetic field have been presented. The experiments were realized with the use of a modified angle-resolved scattering (ARS) method based on the analysis of angular distribution of the scattered light intensity. Digital images of such distribution were acquired for selected areas of examined samples—base surface and surface after magnetoelectropolishing (MEP) process. Parametric analysis oriented toward the calculation of selected key geo- and photometric parameters carried out in Image Pro®-Plus software allowed for characterization of the surface conditions of the assessed samples in terms of their scattering properties. The obtained experimental results confirmed the usefulness of the ARS method used in the presented studies as well as the possibility of its practical use (after appropriate modifications) on a wider scale, especially in industrial applications.

Impact of radial-shear rolling on the microstructure and mechanical properties of 08Х18Н10Т stainless austenitic steel

Grinding of a structural material microstructure to an ultrafine grain state is a way to increase the strength of it. Intensive plastic deformation is the most perspective method of obtaining ultrafine grain materials. However, with the simultaneous increase in strength properties in ultrafine materials, there is an inevitable decrease in its plastic properties; they are becoming fragile and subject to failure during elongation. The use of metal materials with a gradient structure, having course grain size in the central part of the billet and decreasing to ultrafine grain size at the surface, is an effective way to solve the problem of increasing the plasticity of the metal products in general. Possibilities of forming an ultra-fine grained gradient structure in 08X18N10T stainless austenitic steel by using radial-shear rolling studied. The results of the research showed that the ultra-fine grained structure in the radial-shear rolling rod formed on the mill extends from its surface to a depth of at least a quarter of the radius of the rod. The transition zone is in the region between 0.5R and 0.25R of the bar section. Due to the structural heterogeneity of the cross-section of the bar, there is a smooth drop in the micro-hardness from the surface zone of the bar to its central zone by 10.2 %. All this testifies to the gradient character of the structure formed in the bars of 08X18N10T steel during shaping by radial-shear rolling. Studies of the mechanical properties of the deformed bars of 08X18N10T stainless austenitic steel showed that they monotonously change depending on the number of passes. After 7 passes the strength increased almost 2 times to a value of 1073 MPa, and the elongation, which is one of the indicators of the plasticity of the material, was also reduced by 2 times, reaching 21% from the original value of 40%. The results showed a possibility to obtain the gradient structure with increased level of mechanical properties by radial-shear rolling of long billets of 08Х18Н10Т austenitic stainless steel.

The effect of radial-shear rolling on microstructure and mechanical properties of stainless austenitic steel AISI-321

Improving the quality of metal products by crushing of the microstructure of material is one of the promising areas of modern metallurgy. The basic idea consists in refinement the grain structure of the material to sizes less than a micron, i.e. the obtaining of ultrafine-grained (UFG) materials, offering higher strength properties of the material under preservation or a small loss of ductility. Stainless austenitic steel AISI 321 is widely used in all the above areas as well as in chemical, vacuum and nuclear technology. For the obtaining of UFG structure in this material the method of radial-shear rolling is used. For the purpose of identifying the influence of radial-shear rolling on microstructure and mechanical properties of stainless austenitic steel AISI-321, the experiment was conducted where at the radial-shear rolling mill SVP-08 at 800 °C in several passes of the workpieces with a diameter of 30 mm rolled till a diameter of 13 mm with following cooling in water. The analysis of the microstructure of deformed samples showed the presence of equiaxed ultrafine-grained structure in the peripheral areas of the workpiece and the presence of elongated fibrous texture in the axial zone. The strength characteristics of the workpiece has increased more than 2 times, with a slight decrease of plasticity.