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Device For Quality Control Of Steel Wire

[Category : - MECHANICAL ENGINEERING]
[Viewed 2287 times]

Abstract.

Manufacturing structural components from steel wire often requires that the wire strands are straight and lack any inherent curvature.We create the device for non-destructive methods of testing steel wire straightness while the wire is being produced.
We made a conclusions about the reasons of bending moment appearance. The asymmetry in the density of microcracks on the left and right of the axis of symmetry of the wire leads to the asymmetry of stress in the metal. Also, asymmetry of stress could be the consequence of different mechanical properties of different section of steel wire. This difference in mechanical properties could be the consequence of different concentration of micro defects. Another possible reason of this effect could be the difference in chemical composition of neighbouring wire arrears. So, it was necessary to construct simple devise, which could indicate all that factors. It was suggested to measure the concentration of microcracks by indirect method. Concentration of microcracks affect the number of physical properties of the metal. First of all they are electrical conductivity and magnetic properties. We decide, that the simplest solution is to control the asymmetry of stress in the wire by the asymmetry of the magnetic properties of the wire. The devise for such control was developed. This devise contains the magnetizing node, measuring node with magnetic sensors and signal processing unit.

Introduction.

Steel wire is a component used in many structural applications due to its high tensile strength and hardness. Manufacturing structural components from steel wire often requires that the wire strands are straight and lack any inherent curvature. Manufacturing the steel wire filaments is a complex process that involves routing the wire under tension over many pulleys at high speeds. Any misalignment during the wire routing, or a number of other factors, can cause asymmetric stresses within the wire structure and result in curvature along the length of the wire. Wire curvature is difficult to detect while the wire is under tension and also when the wire is spooled as a finished product. Curvatures are usually only detected when the wire is wire is free of stress (tension, bending, or torsion; e.g. when removed from spool).

Mechanisms of asymmetry stress formation
The aim of our work was to create non-destructive methods of testing steel wire straightness while the wire is being produced. We have considered only the low-temperature process of drawing.
Drawing process, as well as all other methods of metal forming, always accompanied by uneven deformation. The main reasons of uneven deformation are:
geometrical factor; external (contact) and interlayer friction; crystallographic orientation of sliping; inequality of metal properties in its separate microvolumes. In addition, the peripheral layers have greater resistance to change in shape due to contact friction. As a result, the proportion of longitudinal tensile stress in the peripheral layers is higher than in the central.

Drawing process is accompanied not only by changing the geometric shape and size of the workpiece, but also significant changes in the physical and mechanical properties and structure of the treated metal. These changes depend on the properties of the metal, the magnitude of this strain and other reasons. But general trends can be identified: strength properties are increasing; plastic properties are reduced;metal density slightly changes (0.5-1.0%); corrosion resistance is reduced; electrical resistance increases; magnetic properties of metal are change.

What are the internal mechanisms of these changes? Defects, indused by drowing proces, could lead to this changes. There are two mechanisms of defect indusing in drowing process. Defects could be indused by mechanical action. Also they could be indused by thermal action. Even in the process of cold drawing the temperature of wire could resch 180 degrees Celsius becouse of friction. It is necessary to add, that process of heating is very quick. Large amount of heat released in a relatively small volume of the deformation zone. Removal of heat through the instrument is difficult and overwhelming amount of evolved heat is carried away with the metal. An increase in temperature causes a rapid development of dynamic and static processes of aging. The phenomenon of strain aging due to the interaction of impurity atoms (mainly carbon, nitrogen and hydrogen) with dislocation cores. The stress field around the dislocations is uniform. Impurity atoms are attracted to the dislocations. Impurity atoms diffuse into the areas of dislocation cores. Diffusion is accelerated by increasing the temperature. Clusters of impurity atoms are formed around the nucleus when a certain temperature is reached. The result of this is to limit the mobility of the moving dislocations. The accumulation of such defects alter the mechanical properties of the metal.

So, we can make a conclusions about the reasons of bending moment appearance. The asymmetry in the density of microcracks on the left and right of the axis of symmetry of the wire leads to the asymmetry of stress in the metal. Also, asymmetry of stress could be the consequence of different mechanical properties of different section of steel wire. This difference in mechanical properties could be the consequence of different concentration of micro defects. And also one possible reason of this effect is different chemical composition of different wire arrears. So, it was necessary to construct simple devise, which could indicate all that factors.

Device for non-destructive control of steel wire quality

So, we decide, that the simplest solution is to control the asymmetry of stress in the wire by the asymmetry of the magnetic properties of the wire. The devise for such control was developed. This devise contains the magnetizing node, measuring node with magnetic sensors and signal processing unit. Devices with similar design are used for quality control of the steel wire ropes. A constant magnetic field is used there and the signal is received from the whole volume of the sample. We need to get a signal only from the surface of the sample, therefore, we use the variable magnetic field of high frequency. Thanks to the skin-effect it does not penetrate deep into the metal.
Thus, the process of work of our detector is similar to the work of the tape recorder. First, a moving wire is magnetizing by the variable magnetic field. Then we get a signal using sensors located on either side of the wire. The sensors are analog of tape playback magnetic heads. The difference signals from the right and left sensor indicates the asymmetry of stress in the wire, so, it helps to test steel wire straightness while the wire is being produced.

Financial information

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This device has not been previously sold or marketed.

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Asking price:

30,000 USD

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sergeiv (Russian Federation)

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