Manufacturing processes of metal ware production are based on different methods of deformational processing. It is evident that during such kind of processing metal microstructure changes causing the change of its mechanical properties. One of the important tasks of state-of the-art material science is to find effective ways to increase strength of metals. It is well known that in order to improve metals’ strength it is necessary to choose the complex effect on microstructure combining methods of different physical nature: to use alloying elements, to apply any kind of thermal treatment or deformational processing.
When analyzing the existing approaches to increase of mechanical properties in metals [1] one can make the following conclusions. Firstly, at present time it is not enough to use any method which is based on the only one strengthening mechanism for steels. Secondly, choice of the grade of steel or alloying elements for it should be based on the prediction of the effects which can be probably occur on every stage of steel treatment. In order to implement different strengthening mechanisms during processing high carbon steel are preferable. Eutectoid steel in cooling has the only one critical point and at ambient temperature microstructure consists only from pearlite. It proves that properties of this steel will be uniform all over the whole volume of the processed workpiece. It makes it possible to deform this kind of steel with high values of deformation degree and to store the definite value of its ductility. Thirdly, the most effective way to increase strength properties in steel is to use the deformational processing. It leads to the decrease of grain size of the processed metals. In this case Hall-Petch equation makes it possible to predict the level of mechanical properties after deformational processing.
Existing methods of metal processing are based on different kinds of plastic deformation: tensile, compression, bending, and torsion. Every kind of plastic deformation causes peculiar changes in microstructure to its deformation scheme and stress-strain state in the processed metal.
Drawing is the main operation for wire production. At drawing the wire is processed by tensile and compression deformation which result in specific texture formation. In [2–5] the results of pearlitic steels microstructure evolution during drawing are presented. Influence of microstructure formation on mechanical properties of carbon steel wire with different carbon content was studied as well.
Bending as the kind of plastic deformation which is the basic one at wire descaling operation. During bending different parts of wire are deformed by tensile and compression deformation. Alternate bending is widely used in different technological processes both as auxiliary (coiling and recoiling) and separate (sheet forging, strengthening) operation. In contrast to traditional methods of metal processing in which total deformation is limited by dimensions of workpiece or the part the total deformation in bending actually in not limited at all. It increases the efficiency of the process. Peculiarities of wire bending are presented in [6, 7].
Twisting makes it possible to arrange several wires into one metal part – cable or rope. Torsion deformation is characterized by very complicated scheme. There is no consistent opinion about stress-strain state of the processed metal under torsion deformation. One of the point of view is based on the hypothesis that torsion deformation is maximum on the surface. Tangential stresses are considered to change in different ways from maximum values on the surface to the zero in the center of the processed workpiece [8]. Influence of torsion deformation on microstructure of pearlitic steel wire is presented in [9, 10].
It is the well known fact that methods of severe plastic deformation (SPD) allow to increase strength properties while ductility of metals does not decrease. At present time plenty of investigations are devoted to different aspects, both theoretical and experimental, of this kind of processing [11–17 and others]. But it is mentioned by different researchers [18, 19 and others] that at present time there are some difficulties in implementation of the existing SPD methods in the operating metal ware industrial technological manufacturing processes. It can be explained by their low processability, limits in workpiece dimensions, the necessity to design new equipment and tools. Traditional methods of improving mechanical properties of metals and alloys have already exhausted their technical and technological performance capabilities to a great extent. From this point of view, metal ware manufacturing technologies based on combination and integration of different operations in one continuous line, which result in refining the microstructure of processed metals and alloys are very promising.
One of the important aspects of any method of deformational processing is the contact interaction between the workpiece and a tool. Stress-strain state of the workpiece in the contact area with a tool depends on hard friction conditions, increase of temperature in the contact zone and as a result can cause damage and fracture of the workpiece [20–22 and others]. It can limit the possibility of implementation of SPD methods into industrial manufacturing technologies.
The aim of this study is to compare the level of deformation on the contact surface between a workpiece and a tool in different SPD processes in order to estimate their possibility to be applied at large scale production. For the comparison following methods based on different kinds of deformation were chosen: method based on simple shear in one deformation zone, method based on simple shear with torsion, method based on simple shear in two deformation zones with torsion, and continuous method of combined deformational processing by drawing with torsion.