RU1770408C - Method of wire annealing - Google Patents

Abstract

Usage: the manufacture of steel-copper wire. SUMMARY OF THE INVENTION: a steel-copper wire with a mild steel core is heated to temperatures not exceeding 720 ° C and first cooled at a speed of not more than 35 ° C / s to the temperatures at the end of the core recrystallization process and then at a speed of 270-400 ° amp; C / s

Description

The invention relates to metallurgy, in particular to the manufacture of copper-copper wire with a low carbon steel core

5 Recrystallization annealing of a wire from low carbon steel is known, including its heating to a temperature of no higher than 720 ° C and cooling at a speed of no more than 35 ° C / s, since cooling the wire from a heating temperature at a speed of more than 35 ° C / s leads to a decrease in ductility wire 1.

A disadvantage of the known method, adopted for the prototype, is the increased breakage of the steel-copper wire associated with the slow cooling of the wire during the annealing process. During annealing in continuous furnaces, the breakage is due to the need to use long furnaces. Slow cooling of steel-copper wire in bell-type furnaces causes diffusion of low-melting harmful impurities (lead, bismuth, etc.) from the boundary layers of steel into the copper layer of the shell. Atoms of harmful fusible impurities, located along the grain boundaries of copper, weaken the bond between them, increasing

the fragility of the copper sheath and the bimetallic wire itself. It also increases the breakage of the steel-copper wire.

The aim of the invention is to eliminate the breakage of the steel-copper wire associated with the annealing mode.

This goal is achieved in that in a method of annealing a wire, mainly steel-copper, with a core of low carbon steel, including heating to temperatures no higher than 720 ° C and cooling at a speed of no more than 3 ° C / s, cooling the wire at a speed of no more than 35 ° C / s lead to the temperature of the end of the process of recrystallization of the steel of the core, then at a speed of 270-400 ° C / s.

The studies of the authors found that the temperature limit determining the application of high cooling rates for low carbon steel wire, including steel-copper wire, is the temperature below which the recrystallization process takes an unacceptably long time. In addition, the process of recrystallization proceeds both during heating of the wire and during its cooling.

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denia, i.e. at a constantly changing temperature. Classical threshold temperatures for recrystallization are not observed. Its actual value is indirectly taken into account by the proposed annealing mode and is included in the subject of the invention. At 723 ° C, about 0.02% C is known to dissolve in α-iron, which is in equilibrium with the remaining cementite particles. At lower temperatures, the solubility of carbon decreases and upon cooling it is released as a tertiary cement which does not affect the mechanical properties of the wire. When cooling very rapidly at a speed of 270-400 ° C / s from the heating temperature to the lowest recrystallization temperatures, the recrystallization of the steel takes place under adverse conditions: carbon remains in the supersaturated solution or migrates to the dislocations and blocks them, a heterogeneous structure is formed. This leads to a decrease in the ductility of the wire, primarily relative elongation, and to an increase in their dispersion along the length of the wire. When the wire is cooled at a speed of 270-400 ° C with a temperature lower than the temperature of the steel recrystallization threshold, due to the stabilization of grain boundaries in the steel and the solubility of carbon in it, the ductility of the wire remains high. In addition, in this case, the possibility of embrittlement of the copper sheath due to diffusion of fusible impurities into it is excluded.

The lower limit of the recommended range of cooling rates (270 ° C / s) is defined for cooling steel-copper wire in water heated to a temperature of 35 ° C, the maximum temperature in industrial production conditions. An upper limit (400 ° C / s) has been determined for cooling a steel-copper wire in water having a temperature of 18 ° C.

Examples.

1. A wire with a diameter of 0.8 mm made of low-carbon steel Sv08A, coated with copper, was annealed after cold drawing in a feed furnace in a protective gas medium ПСО-09 (N2 96% + Н2 2% + СО 2%).

From the figure, the steel-copper wire enters sequentially into an electric muffle furnace, a cooling bath, a jet cooling device for water wire, a wire drying device and a winding device. The arrows indicate the inlet and outlet of the shielding gas. Heat treatment mode: heating time 0.8 min (length

working space 9.6 m), working space temperature 900 ° C, cooling time of the wire from 700 ° C to 460 ° C (which corresponds to the temperature of the end of the recrystallization process) 10 s, wire speed 12 m / min. At a working space temperature of 900 ° C and a holding time of 0.8 minutes, the heating temperature of the wire itself was 700 ° C.

The wire exiting the muffle was cooled by water having a temperature of 18 ° C, which corresponded to a cooling rate of 400 ° C / s. There were no wire breaks during heat treatment. Relative extension

finished wire (5 yus 27.4-28.2%, the number of bends n 32-35.

2. Water was drained from the bath and the wire was annealed according to the mode of Example 1. The temperature of the wire exiting the bath muffle

rose to 530 ° C. There were no wire breaks during heat treatment. Plasticity properties of the finished wire: du 18.6-27%, n 30-36.

3. The steel-copper wire with a diameter of about 5 mm was annealed according to the mode of Example 2, providing slow cooling of the wire by stopping the jet cooling of the wire and re-passing the wire through the muffle of the cooling bath.

Heat treatment of the wire is accompanied by breaks. Properties of the finished wire: duo 27.6-29.0%, n 32-34.

4. Keeping the conditions of example 1, from the device for jet cooling the wire

cooled by water heated to a temperature of 35 ° C; cooling rate of 270 ° C / s. There were no wire breaks during heat treatment, plasticity of the finished wire: duo 27.3-28.5%, n 32-34.

5. A steel-copper wire was made according to the conditions of Example 1, but the wire was cooled from a temperature of 460 ° C with water having a temperature of 15 ° C (cooling rate

410 ° C / s). The ductility of the finished wire du Yuo 27.3-28.2%, n 32-35.

6. The steel-copper wire of example 1 from a temperature of 460 ° C was cooled by water having a temperature of 40 ° C (cooling rate

nor 255 ° C / s). The ductility of the finished wire du 27.2-28.4%, n 32-34.

From a comparison of Examples 1 and 5; Figures 4 and 6 show that the ductility of the steel-copper wire remains practically unchanged, but npi /

this additionally introduces a cooling device (example 5) or a heater (example 6) into the feed system. Based on the positive effect, the rate of cooling of the wire at a threshold rate

recrystallization ratios are set in the range 270-400 ° C.

Claims (1)

SUMMARY OF THE INVENTION Method of annealing a wire, mainly steel-copper, with a low-carbon steel core, comprising heating to temperatures not exceeding 720 ° C and cooling at a speed of not more than 35 ° C / s, characterized in that, in order to eliminate wire breakage, cooling at a speed of not more than 35 ° C / s is carried out to the temperatures of the end of the process of recrystallization of the core steel, further - at a speed of 270-400 ° C / s.