SU1341563A1 - Method of determining tolerable current for graphite coating of electrodes - Google Patents

Abstract

The invention relates to a measurement technique and can be used in the operation of graphitized electrodes in arc steelmaking furnaces. The purpose of the invention is to improve accuracy and simplify the method. The dependences of the permissible current for the reference groups of electrodes on the ratio of the mechanical strength of the diametric compression to the elastic modulus are constructed. Measured for the tested electrodes, the electrical resistivity, the mechanical strength for diametric compression, the modulus of elasticity of the test electrodes. The permissible current for test electrodes of electrodes is determined by the aforementioned ratio, electrical resistivity and the previously constructed dependence for reference electrode groups. 1 ilt i O) 4: d with DO

Description

The invention relates to a measurement technique and can be used in the operation of graphitized electrodes in arc steel-smelting furnaces.

The aim of the invention is to improve the accuracy and simplify the method for determining the permissible value of current.

For the reference electrode groups, the mechanical compressive strength, modulus of elasticity, and electrical resistivity are measured. The ratio of the mechanical strength to diametric compression to the elastic modulus for the reference electrode groups is found. The dependencies of permissible current values, obtained experimentally, during operation for reference groups of electrodes, from the ratio of mechanical strength for diametric compression to the modulus of elasticity of reference groups of electrodes are constructed from their specific electrical resistance.

μOM-m: I group 6.1-9; Group II 25 mm samples. Samples tested

on the device Super-Rockwell type TKS-1, having a device for compression. Samples are compressed pre

35

40

 9.1-12.5.

For the tested electrodes, the mechanical strength for diametrical compression, modulus of elasticity, electrical resistivity is measured, and the ratio of the mechanical strength for diametrical compression to the modulus of elasticity is calculated. Then, based on the previously constructed dependences of the permissible current values on the ratios of the mechanical strength for diametric compression to the elastic modulus of the reference electrode groups and the ratio of the mechanical strength for diametric compression to the elastic modulus of the test electrodes, the current for the test electrodes is determined during their operation.

Example. In order to determine the allowable current value for graphitized electrodes during their operation in an electric arc furnace DSP-80A when melting steel grade 12X18H10T for a reference group of electrodes with a diameter of 555 mm, 50 values of electrical resistivity (p, μm m) in a direction parallel to the axis are measured pressing. The electrical resistivity is measured by the probe method and is calculated using the formula

U-S

R GG

load P 3 kgf, establish the initial position of the displacement indicator. Load the full force P equal to 15 or 30 kgf, fix the readings of ° C, movement indicator. Unload the sample to P 3 kgf, fix the position of the movement indicator.

(P - PJ

E

S C (oi, -Y-4) kgf / mm,

where 1 is the sample length;

S is the sample section area,

mm;

C is the cost of dividing the displacement indicator scale, mm. Then, for the electrodes of the reference groups (group I with a specific resistance of 6.1–9 μΩ M and group II with a specific resistance of 9.1–12.5 μOhm), the ratio of mechanical strength is found on rupture (diametric compression) Op, Z to the modulus of elasticity MPa t, e. and / p, / E,%.

The allowable current for reference electrode groups is found experimentally. To do this, IZ-ISHIOT steels were smelted from the electrode1-g reference groups on a 100-ton arc furnace

Where

and - voltage drop between

potential probes, B; I - current strength. BUT; S is the cross-sectional area, m;

1 - distance between potential probes, m

Also measured at the electrodes of the reference groups is the mechanical strength for diametrical compression (tensile strength - diametrical compression).

The mechanical strength of the electrodes for diametric compression (Gp) is measured on samples with a diameter of 50 mm and a height of 50 mm ± 0.1, the axis of symmetry of cylindrical samples coincides with the direction of the pressing axis, the destruction of the sample occurs along the diametral plane, which indicates the direction of the load.

The electrodes of the reference groups measure the elastic modulus (E, MPa) at about

load P 3 kgf, establish the initial position of the displacement indicator. Load the full force P, avnoy 15 or 30 kgf, record readings of ° C, movement indicator. Unload the sample to P 3 kgf, fix the position of the movement indicator.

(P - PJ

E

S C (oi, -Y-4) kgf / mm,

where 1 is the sample length;

S is the sample section area,

mm;

C is the cost of dividing the displacement indicator scale, mm. Then, for the electrodes of the reference groups (group I with a specific resistance of 6.1–9 μΩ M and group II with a specific resistance of 9.1–12.5 μOhm), the ratio of mechanical strength is found on rupture (diametric compression) Op, Z to the modulus of elasticity MPa t, e. and / p, / E,%.

The allowable current for reference electrode groups is found experimentally. To do this, IZ-ISHIOT steels were smelted from the electrode1-g reference groups on a 100-ton arc furnace

12-18119 and determined the optimal level of specific consumption of the electrodes with the smallest number of failures and corresponding to this specific consumption. electric current (1dop, kA) for each group of electrodes.

The dependencies of permissible values obtained experimentally during the operation of reference groups of Q electrodes on the ratios of mechanical strength for diametric compression to elastic modulus (G p / E (,%) for these reference groups of electrodes are constructed.

The drawing shows the dependence of the allowable currents on the ratio G p / Ej,% for reference groups of electrodes, where curve 1 is the dependence of dop on% for the 1st reference group (specific resistivity is from 6.1 to 9.0 μOM m), curve 2 dependence I

AOP

from G p / Ej,% for

From the obtained point, perpendicular conductors are drawn to the ordinate axis, on which the value of the permissible current d of the given electrode under test is found.

For one of the tested electrodes, the ratio of the mechanical strength for diametric compression to the elastic modulus GP / Ej. 0.125%, and the electrical resistivity of about 8.0 µOhm-m. Therefore, the allowable current for a given test electrode should be found on curve 1.

By setting the perpendicular to the abscissa from the point corresponding to the value of G p / Ej 0.125%, before intersecting curve 1, a point 3 is obtained. From the point 3, perpendicular to the ordinate axis is taken, the value of L is determined — the idle current I ddr 46.0 ka.

11th reference group (electrical resistivity 9.1-12.5 µOm.m)

The permissible current for graphitized electrodes with a diameter of 555 mm is determined from the previously constructed dependences of the permissible current - the maximum mechanical ratios, and similarly, the permissible currents for other tested electrodes 25 are found (see drawing, points 4.5).

Claims (1)

The invention method for determining permissible 35 diametrically compressed to modulus for graphitized electrodes, for elasticity Gp / Ej,% for reference electrode groups (reference curves 1 and 2) as follows. For the studied electrodes with a diameter of 555 mm, the mechanical strength for diametrical compression Cj pj and the elastic modulus E in the direction perpendicular to the pressing axis, as well as the electrical resistivity p in the direction parallel to the pressing axis are determined. Find the ratio of mechanical strength diametrically compressive G pj 40 to modulus of elasticity E when operating in arc steel-making furnaces, including measuring physical points of the reference electrode group, building up the allowable current of the reference electrode group from these values, measuring physical quantities for the test electrodes, and finding the allowable current from the dependencies for the test electrodes, differing from that, in order to improve the accuracy and simplify the method, the mechanical strength is measured for the diametrical compression and the elastic modulus of the electrical device, then according to the drawing on the x-axis lay off the ratio,%, of the agents; find the ratio of the mechanical Pi perpendicular to the intersection with the curve corresponding to the value of electrical resistivity for the given electrode to be used. strength to diametric compression to the modulus of elasticity of the electrodes, which determine the permissible operating current, From the obtained point, perpendicular is led to the ordinate axis, on which the value of the permissible current d of the given electrode under test is found. For one of the tested electrodes, the ratio of the mechanical strength for diametric compression to the elastic modulus GP / Ej. 0.125%, and the electrical resistivity of about 8.0 µOhm-m. Therefore, the allowable current for a given test electrode should be found on curve 1. By setting the perpendicular to the abscissa from the point corresponding to the value of G p / Ej 0.125%, before intersecting curve 1, a point 3 is obtained. From the point 3, perpendicular to the ordinate axis is taken, the value of L is determined — the idle current I ddr 46.0 ka. Similarly, the allowable currents for the other test electrodes 25 are found (see drawing, points 4.5). The invention method for determining permissible ka for graphite electrodes when operating in arc steel-making furnaces, including measuring physical indexes of the reference electrode group, plotting the allowable current of the reference electrode group on these values, measuring physical quantities for the test electrodes, and finding the allowable current from the dependencies for the test electrodes, characterized in that In order to improve accuracy and simplify the method, the mechanical strength for diametric compression and the modulus of elasticity of electrical strength for diametric compression are measured. the modulus of elasticity of the electrodes, which determine the permissible operating current, 0,2S Editor E. Sligan Compiled by V.Ekaev Tehred M.Didyk Order 4431/49 Circulation 776 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab, 4/5 Production and printing company, Uzhgorod, st. Project, 4  0 Corrector G, Reshetnik