Torsion tests allow studying the rheological properties of materials over a wide range of strain and strain rate values, as well as temperature. A key moment in construction of hardening curves is the interpretation of experimental data, which are usually the torque – angle of twist curves. However, there is a number of independent methods to obtain interpretation of experimental data. In addition, there is no single approach to determining the degree of equivalent strain in torsion test. The aim of this paper is to review existing hardening curves definition methods in torsion test and to examine them with the use of finite element modelling.
The article develops one of the main directions of improving the technology of pipe rolling on a reduction-stretching mill, in order to reduce the end crop. The article describes a speed adjustment technique of the reduction mill, when rolling the front end and back end of pipes, the length of which corresponds to the length of the thickness of ends of the finished pipe. A distinctive feature of the technique is the calculation of volume of the thickness end, which must be reduced by an adjusted value, when rolling the end area in the head stands. The sequence of technological calculations and the results of industrial testing of pipe reduction by standard rolling modes, and modes calculated by the proposed technique, are given. An analysis of the results of industrial testing showed the possibility of reducing the mass of the thickness ends by no less than 7%.
Formation of incrassate pipes end is one of main drawbacks of pipes reducing with tensioning method. Therefore, the matter of perfection of reducing mills designs, rollers passes, rolling regimes aimed at end shearing decreasing is very actual. A review of steel pipes hot rolling methods at multi-stand reduction-tensioning mills was carried out, aimed at elaborating of measures for decreasing of end longitudinal different-walled. Techniques of pipe end parts rolling considered, including control of rotary speed regimes of adjacent stands rollers; changing of distance between stands; increasing of pipe end parts temperature to facilitate their tapering; increasing inter-stands tension at the expense of magnetic field application. Also such techniques were considered as application of a short fixed mount in the first mill stand; use of endless reducing; use of idler stands, making breaking down effect and increase of tension. Analysis results of the patent search with utilization of internet-resources showed, that a method of tension increasing at the expense of rollers rotation speed control at pipe end parts rolling is the most acceptable method of pipes incrassate ends length and end shearing decreasing. An actuality of further studies of the elaboration of modified reducing mills speed regimes was noted, aimed at pipes incrassate ends length decreasing depending on their geometry, steels grades, assortment of produced pipes and other technological factors.
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