High-quality Rolling Research Articles

Effect of laser shock peening on the retention ability of surface roughness in forged Cr5 steel

The roughness retention ability of the work roll surface during the cold rolling process is of great significance, especially in the production of the high-quality rolling section. Laser shock peening (LSP) is an advanced and effective surface treatment technique to improve the fatigue life, wear resistance, and other mechanical characteristics of metal components. Current studies commonly examined the reinforcement effect of single and multiple LSP treatments on Cr5 steel samples through XRD analysis, hardness testing, and residual stress measurements of different parameters. In addition, the abrasion test is widely conducted to determine the wear resistance. Compared to unprocessed samples, LSP could promote grain refinement and thus significantly increase the hardness and residual stress. Furthermore, the slight decrease in surface roughness shows that LSP treatment is an effective approach to slowing down the roughness decline rate and prolonging the roller service life. It is also found that multiple LSP impacts could remarkably improve the surface roughness retention of Cr5 steel, in which the optimal laser power density was around 23 GW/cm2.

Field studies of the wave roller

The article presents a description of a fundamentally new design of a soil-cultivating wave roller and presents the results of its research. Adequate mathematical models of the soil rolling process are presented from the standpoint of compliance with the reference values of its density and aggregate composition. Thanks to the research, it was found that the quality of rolling by the developed wave roller is 20.9% better than that of the KKZ-6 roller commercially produced by the industry. To obtain the most high-quality rolling result, the developed wave roller determined its main design and operating parameters optimized for the process of surface tillage, namely: the speed of movement and the distance from the edge of the hollow cylinder to the inner surface of the compactor.

Silicon nitride ceramics with sintering oxide additives obtained from organoyttriumoxanealumoxane

Sintered blanks for spherical bodies of rolling from silicon nitride ceramics were obtained using the addition of an yttrium-containing organoalumoxane ― element organic oligomer, soluble in traditional organic solvents and rolling in pyrolysis into an oxide aluminum-sintering additive in a given mass ratio Al2O3/Y2O3 = 3/1. Studies conducted using thermogravimetry, X-ray phase analysis, optical and electron scanning microscopy showed that the feature of the use of elementoxane instead of the sintering additives of aluminum and yttrium oxides powder is a uniform distribution of aluminum and yttrium oxides in Si3N4- ceramics and the chemical activity of pyrolysis products of organoyttriumoxanealumoxane (OYA), Including amorphous nanoscale oxides on the surface of the Si3N4 powder. Density, porosity, microstructure and the degree of purity of the polished surface of the obtained ceramics indicate its prospects for use as a blank of high-quality rolling bodies. Ill. 6. Ref. 16. Tab. 1.

Theoretical Substantiation of the Traction Resistance of the Ridge Seeder

The analysis of the current state of the enterprises of the agro-industrial complex of Russia has shown that various energy-saving cultivation technologies of agricultural crops, including row crops on ridges, are being applied on a large scale. Mainly, such technologies imply a reduction in the number of technological operations performed, the replacement of sowing on pre-treated soil with sowing according to minimal technology or no-till at all. When implementing comb sowing of row crops, the problem of energy saving remains relevant. Keeping in mind the design features and the operation principle of tillage rollers, it can be stated that they are designed mainly for the destruction of soil lumps and compaction of soil on a flat field before or after sowing. There is a problem of high-quality rolling of soil ridges formed simultaneously with the sowing of row crops. (Research purpose) The research purpose is to substantiate the traction resistance of a roller aggregated with a combed roller theoretically. (Materials and methods) The algorithms used to assess the quality of the rollers are imperfect, for reliable justification of the optimization parameter, it is necessary to solve a number of issues, in particular, the methodology for determining the traction resistance of rollers designed for the final creation of soil ridges by simultaneous action of spherical disks and conical wheels on their sides. A skating roller has been developed for the finishing operation of forming a soil ridge with the required parameters and density simultaneously with sowing, the novelty of which is confirmed by patents of the Russian Federation No. 194330, No. 194348, No. 196712. (Results and discussion) The article presents the process of forming a soil ridge by a roller, and the justification of the traction resistance of a ridge drill roller. A vertical load artificially created by a spring additionally acts on the roller of the comb seeder, this load evenly spreads to the conical core and spherical disks of the roller. (Conclusions) The total traction resistance of the roller of the comb seeder is affected by the weight of the conical wheel, frame, additional spring compression load, the size of the rolling wheel and spherical discs, the speed of the roller, as well as the physical and mechanical properties of the soil.

Rolling bearing performance rating parameters: Review and engineering assessment

The choice of a rolling bearing for a particular application relies on performance rating parameters as the static, the dynamic, and the fatigue limit load of bearings. The values of these parameters define the calculated performance of the bearing. Endurance testing of high-quality rolling bearings has been used for the development of rolling bearing performance standards like the ISO 281 and ISO 76 that are commonly used throughout the industry. However, standard test methods for the measurement and validation of load ratings of rolling bearings are not available in the standards. This leads to the undifferentiated use of the “status of the art” standardized performance to the very large variety of rolling bearing types and qualities that are produced today. The current paper revisits the origin, definition, and development of rolling bearing performance parameters. A numerical study for the determination process of bearing load ratings is carried out. The results are compared with standardized values and values quoted by bearing manufacturers. This provides an overview of the load rating practices that are in use. The limitations and possible improvements of the present methodology are discussed.

ДОСЛІДЖЕННЯ ВПЛИВУ ГАРЯЧОЇ НЕСИМЕТРИЧНОЇ СОРТОВОЇ ПРОКАТКИ НА ФОРМУВАННЯ МІКРОСТРУКТУРИ, МЕХАНІЧНИХ ВЛАСТИВОСТЕЙ ТА СЛУЖБОВИХ ХАРАКТЕРИСТИК ГОТОВОГО ПРОКАТУ

The aim of the work is to study the influence of the process of hot asymmetric rolling on the structural state, mechanical properties and operational characteristics of long products of simple form from ordinary carbon steel. To simulate the process of asymmetric high-quality rolling, the mathematical model previously developed in the ISI added the possibility of taking into account cases of rolling in a pair of rolls of different diameters, rolling in a pair of rolls of different materials, rolling with one drive and one non-drive rolls, rolling at different speeds in a pair of rolls and other. The calculations showed a reduction in rolling force to 10 % with an asymmetric rolling process compared to the traditional rolling process. The study of the features of the process of hot asymmetric rolling (shear rolling) compared with the traditional rolling process was carried out under industrial conditions in the production of a 12x12 mm square profile from ordinary low-carbon steel St3sp. It was found that the average values of HRB, σВ, and σТ in the studied samples practically do not differ, and the average values of δ5 are higher by 8 % (abs.) or ~ 27 % (rel.) In samples that were rolled using the asymmetric rolling technology than in samples that were rolled using traditional rolling technology. The estimation of dislocation density by the X-ray diffraction method showed that during hot asymmetric rolling, the dislocation density is reduced by ~ 46% due to the active flow of in-situ polygonization and recrystallization processes during deformation. In this case, the average values of the microfractures of the crystalline lattice of ferrite are 21% lower in the samples obtained by the method of asymmetric rolling than in the samples obtained by traditional rolling. For the first time, a decrease in the total atmospheric corrosion rate was found in samples that were rolled using asymmetric rolling technology (0.39 g/m2xh) compared to samples that were rolled using traditional rolling technology (0.445 g/m2xh).

The mechanism of grain refinement and plasticity enhancement by an improved thermomechanical treatment of 7055 Al alloy

An improved double step hot rolling (DTR) processing was proposed to manufacture fine grained Al–Zn–Mg–Cu alloys based on pre-deformation, short-period annealing and final hot rolling. The DTR processing can produce high-quality rolling sheets with much finer recrystallized structures and significantly improved mechanical properties when compared with the conventional hot rolling (CTR). The main differences between the two TMTs (thermomechanical treatments) were investigated and the specific grain refining procedure of DTR was carefully characterized. The results show that the grain refinement is mainly proceeded via dislocation rearrangement and low angle grain boundaries transition, which can be attributed to the pinning effect of deformation induced precipitates (DIPs). Pre-deformation can accelerate the formation and spheroidization of fine DIPs which prohibit the migration of grain boundaries and the movement of dislocations. As a result, high density dislocation cells are formed and turn into polygon sub-grains after short-period intermediate annealing. During the final hot rolling, low angle grain boundaries gradually transferred into high angle grain boundaries which contributes to the final fine grained structures. The initiation and propagation of cracks were also delayed by grain refinement.

Application of combined casting–pressing for the fabrication of aluminum wire for soldering waveguides

Technical and process features of a flowsheet for fabricating the wire of casting aluminum alloys intended to solder waveguides with the use of the combined continuous casting–pressing of nonferrous metals are considered. The dependences necessary and sufficient to design the constructive elements of equipment and process modes providing the implementation of conditions for the stable run of processes of continuous supply of the metal melt into the stream of the carousel molding laboratory machine, its solidification, and extrusion into the die opening similarly to Conform technology are established. The magnitude of the cross section of the hole in the supply dispenser of the metal melt into the stream of the crystallizer wheel is calculated. The process modes of the continuous casting–pressing using a laboratory installation of a billet 3 mm in diameter and its subsequent treatment by high-quality rolling and drawing in combination with intermediate annealing procedures to the final sizes are presented. According to this flowsheet, a pilot batch of round and square wire of alloys AK12Ts10 and AK12Ts15 has been produced in the amount of 3 kg and delivered to the AO ISS enterprise for industrial test soldering of waveguides.

THEORY AND PRACTICE OF RESOURCE-SAVING TECHNOLOGIES OF MILL BAR PRODUCTION AT THE OPERATING CONTINUOUS ROLLING MILLS

Based on the modeling results of the processes of high-quality rolling in calibers of a simple form, the flow patterns of surface layers of the blanks and their influence on the formation of stress-strain state of the metal in the rolling process have been determined and confirmed experimentally. Subject to the formed recommendations a new calibration of rolls of roughing mill of continuous light-section mill 250-2 of OJSC «EVRAZ ZSMK» has been developed and passed the trial approbation. Its use has increased the yield in the production of high-quality rolled structural steel by 3 %. The evaluation to improve the production efficiency by increasing productivity in the implementation process of rolling-separation under the existing continuous light-section mill 250-1 of OJSC «EVRAZ ZSMK» has been conducted. A technique for determining the multiplicity of separation depending on the desired performance increments has been offered, as well as provided the guidance on the calculation of the speed limit in the roughing and finishing stand continuous mill, the actual data on the change of the total reduction ratio and speed conditions on groups stands in the preparation of rebars no. 10, no. 12, no. 14.

Improved thermo-mechanical processing for effective grain refinement of high-strength AA 7050 Al alloy

An improved thermo-mechanical processing (N-ITMT) was proposed for manufacturing fine-grained precipitation-hardening Al–Zn–Mg–Cu alloy based on cold rolling, short-period annealing and continuous rolling, and the corresponding microstructure evolution and mechanical properties were investigated. The N-ITMT processing can produce high-quality rolling sheets without edge cracks compared with the traditional RI-ITMT. The recrystallized fine-grained structures of N-ITMT samples are similar to those of RI-ITMT when the total reduction of N-ITMT reached 85% and exhibited high stability during long-period solution treatment. Moreover, the mechanical properties of N-ITMT samples are almost the same as those of RI-ITMT after peak aging (T6). It shows that cold deformation plus short-period annealing can acquire large quantities of MgZn2 particles with diameter ≥0.2μm, which can perform as nucleation sites for new recrystallized grains during subsequent solution treatment. It is greatly indicated that the static long-period overaging used by RI-ITMT can be replaced by cold deformation plus shot-period annealing, and the continuous rolling after short-period annealing would benefit the crack-free rolling sheets. Thus, N-ITMT would be a good alternative to RI-ITMT for efficient commercial production of different heat-treatable Al alloys to acquire fine grains.