Fracture Behavior of the Hot Rolled Strip’s Surface Scale Layer from Different Impacts Angles

In order to improve the energy efficiency of shot blasting impact descaling, a three-dimensional finite element impact descaling model was established. Based on the finite element model, the cracking behavior of the scale layer on hot rolled strip from different impacts angles was simulated. The results of finite element calculation and theoretical analysis show that: (1)Under the premise of constant velocity, the descaling area increases with the increase of impact angle, but the increasing rate tends to be moderate. (2)The depth of the impact tunnel and the residual compressive stress surface (-200 MPa) increase as the impact angle goes bigger. The ideal range of impact angle for shot blasting descaling should be 60°-75°.

Preparation features of metal surfaces of machine parts before gluing

The chemical and mechanical methods of preparing metal surfaces before gluing have been examined. The strength test results for shear of adhesive bonds of aluminum and steel samples, the surfaces of which were prepared by grinding, shot-blasting with copper slag and chemical treatment in aqueous solutions of acids before gluing. The best results for shear strength of adhesive bonds are observed for samples whose surfaces were subjected to shot blasting with a copper slag, the worst ones are after chemical method of preparing in aqueous solutions of acids.

Overview of the possibilities of surface modification of materials using energy beam technologies

Along with new trends, the manufacturing industry is also forced to move forward. Therefore, we focused on the use of Waterjet Peening technology - WJP. With the help of this technology, we can strengthen the material (harden) and remove residual stresses. This technology uses high pressure of water jet. Parameters also play an important role, namely the distance of the nozzle from the material being machined, the working pressure is standing, the feed rate, the number of cycles, etc. WJP technology is also promising from an ecological point of view, no harmful substances are formed during machining. Studies have also shown that, there are no heat affected zones during machining. When comparing the mentioned technology on samples made of surgical steel and titanium alloy, it was shown that the sample made of surgical steel showed greater signs of corrosion traces. Based on an experimental comparison of WJP technology and shot blasting technology, it is shown that the technologies achieved relatively the same results in terms of residual stress removal. A significant difference was found on the surface of the material, in the form of the degree of surface damage. With the help of WJP technology, the material did not reach such a roughness level as after shot blasting technology.

FORMATION OF FUNCTIONAL PLASMA SPRAYED COATINGS WITH COMPLEX OF IMPROVED PHYSICAL, MECHANICAL AND OPERATIONAL PROPERTIES

The possibility of increasing the complex of physical, mechanical and operational properties of plasma sprayed coatings from powders of the PG-19M-01 and PRH18N9 grades due to the electric pulse effect on the heterophase high-temperature flow during spraying and next surface plastic deformation of the deposited coatings by shot blasting has been investigated. It is shown that shot blasting provides the formation of a hardening layer with a thickness of up to 180...200 μm, while the maximum level of microhardness is observed at a depth of about 60 μm. The microhardness of the coating from PG-19M-01 powder at the point of maximum hardening increases by 35%; steel coatings from PR-H18N9 powder – by 48% compared to the state after spraying. Experimental studies of the effect of this treatment on the bond strength and wear resistance of the obtained coatings have been carried out. It is shown that after shot-blasting the bond strength of the coatings decreases by 10...15%, and the wear resistance increases by 32...38%.

Dual-frequency ultrasonic cleaning with diluted phosphoric acid solution for removing oxide scale of uncoated steel sheets in hot stamping

Dual-frequency ultrasonic cleaning with a diluted phosphoric acid solution was developed to remove oxide scales on surfaces of hot-stamped parts from uncoated steel sheets, and conventional shot blasting processes are omitted. The removal of the oxide scale by ultrasonic cleaning is accelerated by the phosphoric acid solution and the dual frequency. The removing time for the phosphoric acid solution was shorter than that for a hydrochloric acid solution, and rust appearing for leaving after cleaning was prevented by generating an iron phosphate layer. In dual-frequency ultrasonic cleaning with the diluted phosphoric acid solution, the oxide scale was dissolved, and then the oxide scales were exfoliated from the thin scale and high-pressure portions. The removing time decreased with decreasing pH and oxide scale thickness and with increasing solution temperature. The surface roughness and distortion of an ultrasonic-cleaned hot-stamped part were smaller than those for shot blasting, and the weldability and paintability were similar. The oxide scale of a hot-stamped part having a nonuniform distribution of oxide scale thickness was successfully removed by dual-frequency ultrasonic cleaning with the diluted phosphoric acid solution.

Support with mechanical vibrations of welding processes ‒ review of own research

The article discusses the most important original achievements in the use of high-power mechanical vibrations with low and ultrasonic frequency in various welding processes such as MIG, MAG, TIG, RW, LW, diffusion welding and brazing in relation to various basic materials such as structural steel and aluminum alloys. Mechanical vibrations were introduced by means of ultrasonic vibrating systems and using the shot-blasting process, as well as acoustic influence. As part of the comparative research, the structure and hardness analysis of HV0.1 was presented. The obtained results indicate that both low-frequency and ultrasonic frequency vibrations significantly change the properties of the resulting structures affected by mechanical vibrations. The scale of these changes varies depending on the frequency and parameters specific to each of the welding processes used. The obtained results allow us to conclude that the skillful application of mechanical vibrations accompanying welding processes can contribute to the reduction of grain sizes, to change the depth or width of penetration and to lowering hardness in the sensitive heat affected zone area.

Shot blasting dust as a filler in elastomer composites

The aim of this article was to determine the impact of using shot blasting dust as a filler in natural rubber (NR) composites. Increasing filler contents were used, from 0 to 30 parts by weight per 100 g of rubber. Examination of the wetting characteristics of the dust confirmed its hydrophobic nature. This characteristic makes it easier to introduce dust into the elastomer structure, with better binding to the mixture ingredients. FTIR spectra confirmed the presence of the filler in the elastomer matrix, with changes in absorbency intensity and the absence of peaks at given wave numbers. SEM images were taken to compare the surface topography of the compositions with and without the filler. The compositions with fillers showed the presence of a common spatial network. The functional properties of the obtained elastomer compositions were analyzed. Mechanical examinations demonstrated that the introduction of dust into the elastomer compositions contributed to improve the mechanical properties of the compositions. The conductivity of the elastomer structures increased with the addition of the filler but these changes were minor and allow the vulcanizates to remain classified as insulators. TGA/DSC demonstrated an increase in the thermal stability of the composites after the introduction of shot blasting dust into the elastomer structure. The decomposition temperature shifted toward higher values and an increase in glass transition temperature was observed for the filled compositions. The results of this study indicate that the use of shot blasting dust as a filler in NR improves the functional properties of the vulcanizates and could be competitive with more widely-used methods using fillers such as silica or chalk.