Papers by Keyword: Controlled Rolling

Abstract: The work introduces an improved mode of production of steel sheets of the C355Zh2 type recommended for industrial use in factory conditions in Ukraine; this contributed to reducing the dispersion of the values of the strength and plasticity indicators of the finished product and increasing the yield of suitable products obtained using the proposed mode of controlled rolling.

Abstract: A microstructure consisted of granular bainite, upper bainite, acicular ferrite, polygonal ferrite, and a little of pearlite was obtained by controlling rolling and cooling in marine steel. The grain size of the two steels was refined to 5-9 μm. The size of the MA island was about 3-6 μm. Both steels had higher tensile strength, yield strength, elongation and hardness, and the performance of steel B was better than that of steel A. Both steels exhibited large and deep dimples at -80 °C impact fracture. The longitudinal impact energy of the specimens was above 250J, and the steel B even exceeded 300J. Its longitudinal impact performance was better than lateral impact performance. Both steels had achieved good performance due to fine grain strengthening, MA island strengthening, precipitation strengthening and dislocation strengthening caused by controlled rolling and cooling. The alloying element nickel effectively improved the low temperature impact toughness of the experimental steel. Excellent impact energy of both steels was attributed to higher texture strength for RD specimens.

Abstract: To obtain reliable joints in the conditions of open construction is complicated or impossible to use stationary machines and apparatuses, so requirements to welding processes are of special interest. The most interest concerning the support of strength and reliability of welded joint is specific processes developed after the crystallization of weld at weld zone. The value of the zone of thermal influence depends on the welding conditions and properties of metal that is welded. That is why the research on the influence of welding conditions on the formation of the structure of welded zone and thermal influence zone is actual.

Abstract: Under industrial conditions, it is common to avoid undesirable costly modernization of the existing equipment and increase the production efficiency. That is why as a basis of the solution to the scientific-applied problem, the authors took the idea of the adjustment of temperature-deformation regimes of metal-roll thick plate rolling for building constructions of the certain assignment in the way to initiate heterogeneous origination of ferrite on the polygonal boundaries of austenite as well as to form, before the finish rolling, as much as possible dispersed grain of hypoeutectoid ferrite. It must guarantee the formation of highly-dispersed final ferrite-perlite structure and the high level of strength and plasticity of the thick plate.

Abstract: Using the laboratory rolling mill with smooth rolls, piercing, as well as rolling in a pilger mill of the seamless tubes with diameter 273 mm from the HSLA steel microalloyed with vanadium steel was simulated. Influence of the wall thickness (6.3 – 40 mm) and finish rolling temperature on the final structural and mechanical properties was investigated. Necessary temperatures of the phase transformations in the course of cooling were determined by dilatometric tests. Based on the dilatometry results, finish rolling temperatures were reduced. Lower rolling temperatures yielded in a relative grain refinement. Effect of the finish rolling temperature did not have any marked impact on the tensile tests results. Strength properties decreased only slightly with the increasing wall thickness and the plastic properties were not influenced significantly by this parameter. The positive effect of the reduced finishing temperature appeared markedly in the results of impact tests performed at room temperature only. Notch toughness was increased by approx. 25 % in the case of the wall thickness of not less than 20 mm.

Abstract: The research presented in the paper was carried out for the experimental steels with modified chemical composition allocated to pipelines for 760÷1180 °C range, strain rate s^–1 s^–1 and different distributions of particular reductions between passes were presented. Physical modeling of the rolling process was carried out upon using the GLEEBLE 3800 simulator. The research was based on the findings of the paper [1].

Abstract: Nowadays, the strategy for improving of mechanical properties in metals is not oriented to alloying followed by heat treatment. An effective way how to improve the mechanical properties of metals is focused on the research looking for some additional structural abilities of steels. Structural refinement is one of the ways. Refinement of the austenitic grain size (AGS) carried out through plastic deformation in a spontaneous recrystallization region of austenite, formation of AGS by plastic deformations in a non-recrystallized region of austenite will be considered as potential ways for AGS refinement. After classic methods of plastic deformations, next structure refinement can be obtained by an application of severe plastic deformation (SPD) methods.

Abstract: The numerical simulation method was adopted to study the multi-pass controlled rolling deformation process of the 400mm thick slab and the changing rule of the internal strain field. It was tried to simulate the center strain changes of the thick slab by two deformation processes which were the first rolling deformation process under a uniformed temperature and the second rolling deformation process after the waiting. It was shown that in the rolling process of super-thick steel plate both the first rolling process and the second rolling process could control the deformation of the central region. When the macro pressure rate was the same, the thinner was the slab, the greater pressure rate in the central region. The amount of deformation of both the first process and the second one was the same as 20%. The maximum strain was located in nearly one-tenth thickness of the surface layer and the minimum was in the center.

Abstract: The numerical simulation method was adopted to study the single-pass controlled rolling deformation process of the 400mm thick slab .Two forms of the rolling deformation which are uniform temperature rolling and rolling of temperature waiting under air cooling have been used to simulate the center strain changes of the thick slab. It was shown that: increasing the deformation of single-pass can significantly increase center strain of the thick slab; temperature waiting under air cooling can lead to a large temperature range between surface and center, which can increase center strain of thick slab during subsequent rolling.

Abstract: Development of industries in recent years reveals the essential need to the microalloyed steels with high strength and good ductility. Refinement of Ferrite grains by thermomechanical Treatment is the only lower cost effective method to improve strength and toughness spontaneously in this type of steels. API X70 steel belongs to high strength microalloyed steel group. The manufacturing process of this steel is controlled rolling which is a kind of thermomechanical treatment and it is considered as a grain refining method. In this research, three specimens of API X70 steel were experimentally rolled in order to achieve ultrafine grained microstructure. Rolling operations are designed in such a way that the rolling of these specimens finished at 846, 823 and 800°C. Results of the experiments were analyzed by mechanical tests and microstructures observations. The microstructure observations show that decreasing of finish rolling temperature causes decrease in Ferrite grain size. Results also show that rolling of API X70 steel in the vicinity of A_r3 temperature and high strain rates lead to ultrafine Ferrite grains in microstructure. This is due to the transformation of work hardened austenite to Ferrite. On the other side, Tensile and impact tests show that decreasing of finish rolling temperature causes increasing in yield and tensile strength and also improves the toughness.