SU1731843A1 - Metal-forming device - Google Patents

Abstract

The invention relates to heat treatment of metals by pressure and can be used to change bars of refractory and hard-to-deform metals and alloys, including cast irons, under the action of high-density current. The method consists in heating cast iron billets to 180-590 ° C and subsequent drawing with speed (8.3-10 - 2). 2 ill., 1 tab.

Description

The invention relates to the heat treatment of metals by pressure and can be used to change the bars of refractory and hard-to-deform metals and alloys, including cast iron, under the action of a high-density current.

A known method of thermocyclic treatment of cast iron involves heating to a temperature below Aci and cooling in order to increase the impact strength and lower the cold break threshold of high strength cast iron.

The disadvantage of this method is that high-speed cooling is used to lower the cold break threshold.

The closest in technical essence and the achieved result to the proposed is a method of processing blanks, mainly cast iron, including heating to a predetermined temperature and drawing.

The disadvantage of this method is that due to the slight heating

It is not possible to significantly increase the ductility of cast iron billets during the drawing process.

The purpose of the invention is to increase the plasticity of the blanks.

This goal is achieved by the fact that in the known method of processing workpieces, mainly cast iron, the heating is carried out up to 180-590 ° C, and the drawing is carried out at a speed of 8.3-2.

FIG. 1 shows a scheme for implementing the method; in fig. 2 - characteristic curves of deformation (dependence of deforming stress a on deformation Ј) of samples of cast iron without current (curve 1) and with simultaneous heating with alternating current of industrial frequency (curves 2, 3 and 4),

The method is carried out as follows (Fig. 1). Bar 4 with an initial diameter of dn 9 mm made of gray pearlite or ferritic-pearlitic cast iron with the content of the main alloying elements. 3.3% C, 2.4% Si, obtained by hot pressing, is carried out through the dies 1 with

with

VI WITH

00

Oj

v1

-one

V, varying from 8.3-10 to 2 s. An electric current of power I of the industrial frequency was passed through the working zone with a length of about 50 mm. The current heats the bar to a temperature of 180-590 ° C, determined using thermocouples. The current has increased the technological plasticity of the cast iron rod, which had a level of residual stresses on the order of 600 MPa or more after a large degree of deformation — the line arrangement of graphite inclusions, which does not allow further machining of the rod.

With an increase in current density from 11 A / mm2 (FIG. 2, curve 2), 14 A / mm2 (curve 3) to 20 A / mm2 (curve 4), the ductility of cast iron samples increases significantly (more than 3 times) compared to specimens deformed without current (curve 1), and at a current density of more than 20 A / mm2 it begins to decrease and reaches a value of 1.3% at 22 A / mm (curve 5). It is established that the current current with a density of 9-20 A / mm at a deformation rate of 8, - 2 creates the necessary temperature conditions of 180-590 ° C, which allow processing by drawing a cast iron rod and intensify the processes of plastic flow, lowering the voltage level of the flow and increasing plasticity severely deformed cast iron in more than 2-3 ra

ten

15

20 s

25

thirty

For, get a thin wire of cast iron with a diameter of 2-3 mm.

The table shows the properties of the blanks.

As can be seen from the table, the optimal values of ductility of the cast iron rod Ј from 1.9% to 6.3% are achieved by a combination of the values of j and t ° lying in the indicated intervals. When these intervals are exceeded at low values of j nt °, there is no increase in plasticity (its magnitude is the same as when deformed without current), and when the upper limit values are exceeded, thermal instability occurs, leading to non-uniform plastic deformation and fracture. The rate of deformation in this case should vary within 8,. With slow deformation rates of less than 8.3 1, the bar may overheat and

melting, and at values of more than 2 s, the rod does not have time to be heated to the optimum temperature.

Claims (1)

Claims of the Invention A method of processing blanks, preferably cast iron, which includes heating to a predetermined temperature and drawing, is characterized in that, in order to increase plasticity, heating is carried out to 180-590 ° C, and drawing is carried out at a speed (8.3 - 2). Fig 1 6, MPa 1500 1000 i 2 e, z 9ag.2