SU1583793A1 - Method of determining surface tension of metal melt - Google Patents

Abstract

The invention relates to an instrumentation technique and may find application in measuring the surface tension of molten metals under arc welding conditions. The aim of the invention is to simplify the method by eliminating the need for measuring the height of a crater in a metal melt. To do this, an electric arc is applied to the surface of the melt and the current and voltage of the arc are measured. Additionally, the arc voltage is measured after cooling the melt before solidification at the same current value. The surface tension is calculated from the measured values. 1 il.

Description

The invention relates to instrumentation engineering and can be used in measuring the surface tension of molten metals under conditions of arc fusion welding or plasma arc metal remelting.

The aim of the invention is to simplify the method.

The drawing shows a diagram of the device for implementing the method.

The device consists of a furnace inside of which a crucible 2 is located and with the metal under investigation. Through the wall of the furnace 1, through the seal 3, an electrode holder with a non-consumable electrode 4, provided with a micro-screw, is passed through. An ammeter 5, an arc power source 6, an oscilloscope 7, and an oscillator 8 are included in the electrical circuit between the non-consumable electrode 4 and the crucible 2 with the metal under study. The device is also equipped with a pyrometer 9 for measuring the temperature of the melt, an optical viewing window 10 and a source 11 furnace power 1.

The method is carried out as follows.

In the working space of the furnace 1 under the non-melted electrode 4 is placed the crucible 2 with the preliminary remelted test metal. After that, the non-consumable electrode 4 with a diameter of 2 ... 3 mm is lowered to contact with the surface of the solid metal sample and with the help of a micro-screw it rises to a height H ", the value of which is fixed to an accuracy of hundredths of a millimeter and

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00 SHE

one

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is within 3 ... 4 mm. Then, the working space of the furnace I begins to be flushed with argon or other protective gas, the flow rate of which during the experiment remains constant. After the predetermined protective gaseous medium is created in the working space of furnace 1 using an oscillator 8, an arc is excited between the solid metal in the crucible 2, and e-melting electrode 4. After 0.1 s, when the arc voltage value is set constant, z, using the oscilloscope 7, fix the voltage U0 on the arc at a given arc current strength. In this case, the arc current should not exceed 200 amps of an electrode with a diameter of 2 mm and 250 amps for an electrode with a diameter of 3 mm. Then the current and the arc are turned off.

U0 ratios ---

But

the magnitude of the voltage drop per unit arc length is determined. After that, the power supply 11 of the furnace 1 is turned on and the temperature in the furnace 1 rises to the melting temperature of the metal under study plus 10. 20 ° C. To equalize the temperature in the metal melt, the system is maintained at this temperature for 30 ... 60 s. Then, at the same value of H0, an arc is excited between the non-consumable electrode 4 and the melt using an oscillator 8. In this case, the arc current strength is maintained the same as in the case of the initiation of the arc between the non-consumable electrode 4 and the solid metal. Due to the arc pressure, the magnitude of which depends on the set value of the arc current strength, a trace is formed in the melt, the depth of which is associated with the surface tint of the metallic melt,

The voltage U is measured on the arc in this case. The depth of the trace is determined using the expression

 H „(

Ui

By

- about,

()

h is the depth of the track, m; H0 is the distance from the non-consumable electrode to the surface of the metal melt, m;

U, is the arc stress in the case of a liquid melt, V;

U0 is the arc voltage in the case of

solid melt, V, Surface tension metal- | melt is calculated using the expression

6 i2Ј.) ЈL

2h

(2)

five

0

5 Q

five

0

five

0

five

where 6 P & g is the surface tension, N / m;

arc pressure, determined by arc current, N / m; metal melt density, kg / me; acceleration of free fall, m / s2;

the radius of the anode spot on the surface of the metal melt, determined by the arc current, m

Example. In the furnace 1 under the electrode placed corundum crucible 2 with pre-melted in an argon environment Armco-iron. As a non-melting electrode 4, an EVI-3 tungsten electrode with a diameter of 2 mm is used. After installing the crucible 2, the electrode 4 is lowered with a micro-screw to contact with the surface of the solid metal, and then raised to a height of 4 mm. Argon is then fed to the furnace 1 at a rate of 10-12 L / min. After 4 min, which ensures the creation in the furnace 1 of an argon atmosphere between the electrode 4 and the metal, using an oscillator 8, an arc is excited. After 0.1 seconds, the voltage on the arc, which is fixed with an oscilloscope 7, is set constant and is 200 A at a current of 12.2 V. After that, the arc is interrupted. Then, the power supply 11 of the furnace 1 is turned on and the temperature in it is raised to 1550 ° C. This temperature is measured using a BP-5/20 thermocouple and maintained constant throughout the experiment. After the system has been held for 60 seconds between the molten metal and electrode 4, an arc is also excited with the aid of an oscillator 8. The current strength is maintained at 200 A, 3 seconds after the arc started, the arc voltage becomes 12.7 V.

By expression (1), the value of h is 0.62 mm. Anode radius

51583793

the spot is determined by the current of the arc yoke is the effect that distinguishes

at a current of 200 A, it is 1.55 mm. When the arc current in argon is 200 A, the distance from electrode 4 to the surface of the H0 melt is 4 mm and the diameter of the non melting electrode is 2 mm, the arc pressure is PY 3.1 N / mm2.

Substitute these values as well

n and, in order to simplify the method, the surface of the molten metal is affected by a concentrated electric arc discharge pressure between the surface of the metallic melt and the non-consumable electrode located above the IQ surface of the metallic melt, the voltage and current of the electric melt arc voltage, the voltage of the electric arc discharge is additionally measured after oh

melt density, in the calculated expression (2) we get 6 322 mJ / m,

Claims (1)

Invention Formula this impact, I distinguish n and, in order to simplify the method, the surface of the molten metal is affected by the concentrated pressure of an electric arc discharge between the surface of the metallic melt and the non-consumable electrode located above the Q surface of the metallic melt, the voltage and current of the electric arc are measured discharge, additionally measure the voltage of the electric arc discharge after oh The method of determining the surface of the metal melt its solidification at the same current of the electric discharge, and the surface tension of the metal melt is calculated tension of the metal melt, consisting in the effect of the concentrated pressure on the surface of the metal melt in the liquid state, which ensures the formation of 20 by the difference of measured values of the crater in the metal melt, the voltage of the electric arc dimension of the parameter characteristic of a number. 5-1. . .g: v / g W.-W.-. :: - TL-: D.-: $ / V & " "Q