RU2373031C1 - Method of electric contact treatment of metal - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: metal is treated with rotating disk and zone of contact is heated. Also metal in the zone of contact with a rotating disk is heated to temperature of re-crystallising; while feeding of rotating disk is performed at rate depending upon temperature of re-crystallisation, thermo-physical properties of metal and thickness of a treated blank.

EFFECT: reduced specific power consumption at treatment of metal and simplified method of treatment.

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Description

The invention relates to the field of engineering, in particular to methods of electrical contact cutting of metal, and can be used for high-performance processing of workpieces (metal).

One of the most common methods of electrical contact processing of products is the processing of electric arc discharges.

A known method of electrical contact processing, in which the metal in the contact zone with the electrode is heated to the melting temperature and is removed by a rotating disk.

This processing method has high specific energy consumption (for steel 1-2 kW · h / kg) due to heating of the metal to the melting temperature in the contact zone with the rotating disk [Vitlin VB Electrophysical processing methods in metallurgical production / VB Vitlin, A. S. Davydov. M .: Metallurgy, 1979].

The closest to this invention in terms of technical nature and the achieved result is a method by which energy is supplied through a contact tool (rotating disk) - an object. Contact is based on microroughnesses of surfaces. With sufficient input power, heating of the contact zone and the adjacent zone occurs. Dimensional processing is carried out when the workpiece metal in the contact zone is brought to a plastic state, in which the rotating disk mechanically removes the softened metal [Livshits A.L., Kravets A.T., Rogachev I.S., Sosenko AB Electric pulse metal processing. M.: Mechanical Engineering, 1967, 295 pp.].

The disadvantage of this method: the complexity of the technical implementation due to the fact that the temperature of the contact zone is unknown and the processing parameters are not defined.

The objective of the invention is to reduce specific energy consumption during metal processing and simplify the implementation of the processing method.

This is achieved by the fact that the metal in the contact zone with the rotating disk is brought to the recrystallization temperature, which is (0.5 ÷ 0.6) of the melting point of the metal or alloy, and the flow of the rotating tool is determined:

Where

I is the current strength, A;

U is the voltage, V;

η is the efficiency of the installation;

T _p - the temperature of recrystallization of a metal or alloy, K;

δ is the thickness of the workpiece, m;

λ is the coefficient of thermal conductivity of the processed material, W / cm · K;

C is the heat capacity of the processed material, J / kg · K;

ρ is the density of the processed material, kg / m ³ ;

t is the time from the beginning of the action of the heat source to the heating of the selected point of the workpiece to the specified temperature, s.

This method of electrical contact processing is characterized by the following features:

1. heating the metal in the contact zone to a temperature of recrystallization;

2. The rotating disk is fed at a speed depending on the temperature of recrystallization, the thermophysical properties of the metal and the thickness of the workpiece.

The recrystallization temperature is determined for each metal or alloy in the following ratio:

T _p = (0.5 ÷ 0.6) T _pl ,

where T _p is the temperature of recrystallization,

T _PL - melting point

[Evstratov V.A. Theory of metal and alloy processing. Kharkov: Vishka school: Because of Kharkiv. un-te, 1981. - 248 p.].

Together, these features make it possible to reduce energy costs due to the coincidence of the velocity of the heat front and the supply of a rotating electrode tool.

Case Studies

Processing was carried out in air without the use of additional liquid or gaseous media.

The experimental setup is designed on the basis of a manual grinder model IP-2020. The efficiency of the installation is 0.7.

Disc electrode tool made of low carbon steel with a diameter of 150 mm and a thickness of 1.0 mm.

Steel, aluminum and copper cylindrical hollow samples (pipes) were taken as the object of processing. The pipes were cut. The recrystallization temperature was determined by the expression (2), the flow of the rotating disk was calculated by the dependence (1).

Table 1 presents the geometric and thermophysical characteristics of the studied samples, processing modes and experimental results:

Table 1 Characteristics of the studied samples Material I, A U, B δ, mm λ, W / (mK) s, kJ / (kgK) ρ, kg / m ³ V ₃ , m / s Steel (Art. 3) one hundred 35 1.7 37.1 0.591 7800 0,039 Aluminum (D16) 75 25 2.5 238 0.896 2698 0.015 Copper (M1) 75 25 1.9 398 0.386 8690 0.008

Table 2 shows a comparative assessment of the specific energy consumption during processing of the prototype and processing of the proposed method:

table 2 Comparative assessment of specific energy consumption Material of test samples Prototype The proposed method Steel samples St3 0.5-0.8 kWh / kg 0.2-0.4 kWh / kg Aluminum Samples D16 0.75-0.9 kWh / kg 0.3-0.4 kWh / kg Copper samples 0.6-0.75 kWh / kg 0.3-0.37 kWh / kg

Thermal and metallographic analyzes of the samples studied confirm that when cutting steel, aluminum and copper pipes, subject to the electrode-tool (rotating disk) feed calculated by formula (1), the temperature in the cutting zone is equal to the recrystallization temperature.

Figure 1, 2 and 3 presents the structure of steel, aluminum and copper samples, respectively, processed by the proposed method.

In all three cases, there is no dendritic structure over the cross section of the samples (pipes), which means that melting does not occur.

On the surface of the steel sample (Fig. 1), where the strongest heating took place, a pronounced finely dispersed structure is observed. The structure of aluminum and copper samples (figure 2, 3) is more homogeneous. The structure is lamellar, which can be associated with hardening that occurs during cutting.

Claims (1)

A method of electric contact processing of metal, including exposing the metal to a rotating disk and heating the contact zone, characterized in that the metal in the contact zone with the rotating disk is brought to its recrystallization temperature, and the feed rate of the rotating disk is determined by the formula

,
where I is the current strength, A;
U is the voltage, V;
η is the efficiency of the installation;
T _p - recrystallization temperature of the metal or alloy, K;
δ is the thickness of the workpiece, m;
λ is the coefficient of thermal conductivity of the processed material, W / cm · K;
C is the heat capacity of the processed material, J / kg · K;
ρ is the density of the processed material, kg / m ^3;
t is the time from the beginning of the action of the heat source to the heating of the selected point of the workpiece to the specified temperature, s.

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