Shevchenko Tat'yana Ivanovna

Physic-Metallurgical Faculty

Specialty “Metall Science”

Theme of master's degree work

INFLUNCE OF THE LOW TEMPERATURE HEATINGS TO PHYSICAL AND MECHANICAL PROPERTIES OF HIGH-STRENGT WIRE.

Supervisor –Dr. Sci., Professor Alimov V.I.

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Summary

Question about forming of properties of high-strength during the time of deformation and heat treatment studying comparatively a long ago. The accumulated information allows to establish that  the high-strength wire must have internal tension: to have «normal» distribution of residual tensions, have a high limit of elastisity, it must made from steel with the promoted content of Mn which promotes its resistance to corrosion and abrasion, to have exact sizes and form of section.

As standard methods of test do not give complete information for the estimation of apprasial of making demands of wire  it is important to take into account influence of different factors on its charasterictic and use the different ways of influence for the improvement of quality. Some of them are mechanical, thermal, physical and chemical methods of additional treatment of wire.

At research of additional thermal treatmentr K.F.Starodubov and V.K.Babich establish that at the tempering 200 ⁰C durability of cold-deforming steel  70 became rises with some growth of the tensile strain; this tempering advised for wire which is meant for making steel cabels.I.I. Bakov set that additional tempering of cabel's wire after wire-drawing promoted efficiency of cabel which is in winding from this wire.

At the same time in opinion of other researcher, tempering of cabel's wire is harmful. They consider that negative influence of tempering on quality of cabel's wire is related to the increase of its limit of elastisity and loss of capacity for plastic deformation.

In one of works set that heatings of cabel's wire by 50–100 ⁰С result in the  insignificant changes of mechanical properties: this change is carried by of principle character.

In this work influence of the low temperature heatings on physical and mechanical properties, corrosion stability of high-strength wire of different diameters with coating and without it were studied. For this purpose on the samples of diam. 0,3_br, 0,5_gal, 0,6_gal, 0,65_br, 1,19_br from st. 60 heat treatment with varying of temperatures within the limits of 50–100 ⁰С and duration of retention interval 10-60 min was conducted.

On these samples it was measured specific electrical resistivity (r,Оm*m) by the Tompson's bridge, tested durability of wire which is tie in a bungle (for the wire of diam. 0,3_br) and without him (for other under consideration diameters)  for determination of tensile strength (s, N/mm²), and also to test in torsion.The got results are presented in a table 1.

Table 1. Properties of heat treatment of high-strength  wire

 *) br – bright wire;

     gal – galvanized wire

During the study of corrosion resistance it was determined the index of corrosion  of К^-m, g/m²*h. For this purpose samples exposed to corrosive influence in 4% aqueous solution of NaCl during four weeks.The got values of К^-m are resulted in a table 2.

Table 2. Corrosion resistance of high-strength wire

          *) br – bright wire;

             gal – galvanized wire

So the low temperature heatings can positively influence on physical and mechanical properties of high-strength wire and on its resistance to corrosive effect.