JPH0921780A - Oxygen probe and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily and effectively connect a measuring electrode to a lead wire by welding the electrode to the lead by percussion welding. SOLUTION: A percussion welding is used to connect a measuring electrode 32 to a lead wire 34, and a duplex energy storage system is preferably used as an excuting welding machine. In this case, the electrode 32 is mounted at one welding head of the machine, and the lead wire 34 is mounted at the other welding head. Then, after charge is stored in a capacitor, the electrode 32 is made to relatively come close to the lead wire 34. An arc is generated by this approach, and the opposed ends of the electrodes 32 and the lead wire 34 exposed to the arc are melted. The both are butted to each other from this state, and brought into pressure contact with each other to complete the welding of the connecting parts 36 of both the members. The welding conditions such as the welding voltage, the moving speed of the welding head are suitably decided in accordance with the materials and shapes of the electrode 32 and the lead wire 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen probe used in a metal refining process, which mainly measures an oxygen activity in a molten metal such as molten steel or molten copper.

[0002]

2. Description of the Related Art In recent years, an oxygen probe which plays an important role in the field of steelmaking includes, for example, a zirconia solid electrolyte whose principle is an oxygen concentration battery, and a measuring electrode. Molybdenum, iron, etc. are often used as the material of this measuring electrode, and copper is often used as the lead wire connecting the measuring electrode and the connector. At present, either a silver brazing method or a method of directly winding the lead wire around the measurement electrode is used for joining the measurement electrode and the lead wire.

[0003]

However, in the method by silver brazing, the oxide on the joint surface must be removed by flux before the measuring electrode is preheated before the silver brazing is poured. The efficiency is poor, and on the other hand, the method of directly winding the lead wire has many problems such as it is difficult to securely bond the both.

Therefore, the present invention is to provide an inexpensive oxygen probe capable of easily and surely joining a measuring electrode and a lead wire, and a method for producing the same.

[0005]

In order to achieve the above object, the present invention is an oxygen probe for measuring the oxygen activity in molten metal, which comprises a measuring electrode and a lead connecting the measuring electrode and a connector. An oxygen probe comprising a wire and a measurement electrode and a lead wire welded by percussion welding.

The present invention also includes the steps of attaching the measuring electrode to the first welding head of the welding machine and the lead wire to the second welding head, accumulating electric charge in the capacitor of the welding machine, and measuring electrode. And the lead wire are relatively brought close to each other to generate an arc to melt opposite ends of both members, and oxygen is connected to the measuring electrode and the lead wire to perform percussion welding of both members. A method for manufacturing a probe is provided.

[0007]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the oxygen probe 10 of the present invention comprises a cylindrical housing 12 and a protective tube 14 provided around the housing 12. The protection tube 14 is
It is composed of a heat resistant member such as ceramic fiber and a paper tube. Various measuring elements are attached to the tip of the housing 12 via a mounting block 16 made of refractory cement. One of the measuring elements is a zirconia solid electrolyte 20, which is connected to the connector 2 via a reference electrode lead wire 22.
4 is connected. The zirconia solid electrolyte 20 is filled with a substance serving as a reference of oxygen, for example, a mixed powder of chromium and chromium oxide. Next to the electrolyte is a thermocouple 26, which is another probe protected by a quartz tube, and is connected to the connector 24 by a support pin 28, which is a compensating lead wire. The connector 24 has a plurality of connector pins 30 that send an electric signal from each of the measuring elements to a measuring instrument (not shown).

Next to the thermocouple 26, another measuring electrode 32, which is a measuring element, is provided and is connected to the connector 24 via a lead wire 34. In the present invention, the measurement electrode 3
Percussion welding is used to join the 2 and the lead wire 34. The percussion welding machine (not shown) for carrying out this welding is preferably of the dual energy storage type. In this case, first, the measurement electrode 32 is provided on one of the welding heads of the welding machine
Attach the lead wire 34 to the other welding head. Next, after accumulating electric charge in the capacitor, the lead wire 34 is brought relatively close to the measurement electrode 32. This approach causes an arc. When an arc is generated, the opposing ends of the measurement electrode 32 and the lead wire 34 exposed to the arc are melted. Then, when the two members are made to collide with each other and are pressed against each other in this state, the welding of the joint portion 36 of both members is completed. The welding conditions such as the welding voltage and the moving speed of the welding head may be appropriately determined according to the materials and shapes of the measurement electrode and the lead wire.
Further, the system of the percussion welding machine is not limited to the double energy storage system.

The tip of the housing 12 provided with a measuring element such as a measuring electrode is protected by a protective cap 38, which melts and disappears when the oxygen probe 10 is inserted into the molten metal.

Next, the procedure for measuring the oxygen activity in the molten metal using the oxygen probe having such a constitution will be described.

First, a holder (not shown) is attached to the other end of the housing. At this time, the external measuring instrument and the connector pin 30 are electrically connected. Then, the oxygen probe is immersed in a predetermined molten metal. When immersed, as described above, the protective cap 38 melts and disappears, and
The electrolyte 20 and thermocouple 26 reach thermal equilibrium with the molten metal,
The oxygen potential of the substance serving as a reference for oxygen in the electrolyte becomes constant. Then, an electromotive force is generated between the measurement electrode and the reference electrode lead according to the acidity potential difference between the oxygen potential of the oxygen reference substance and the oxygen potential of the molten metal. Then, based on the electromotive force and the temperature obtained from the thermocouple, the oxygen activity in the molten metal can be calculated from the following equation (1).

[0012]

[Equation 1] Here, ΔG ° is the standard free energy of formation reaction of oxygen in molten metal, R is the gas constant, T is the temperature (K) of the molten metal, F is the Faraday constant, Pe ′ is the electron conductivity parameter, and Po ′ is the electron conductivity parameter. ₂ is the oxygen partial pressure of the reference substance.

[0013]

EXAMPLES Table 1 shows the experimental results of welding the measuring electrode and the lead wire in accordance with the present invention using a double energy storage type percussion welding machine.

[0014]

[Table 1]

Two sets of measuring electrodes and lead wires were prepared for this experiment. One set was a molybdenum measuring electrode with an outer diameter of 2 mm and a copper-nickel alloy lead wire with an outer diameter of 0.65 mm, and the other set was a molybdenum measuring electrode with an outer diameter of 3 mm. , A copper lead wire having an outer diameter of 1.2 mm. The capacitor capacity of the percussion welding machine was 40 μF for pilot arc, 3000 μF for melting, and the welding gap was 1.5 mm.

As a result of the experiment, the time required for one welding operation was about 5 seconds, and it was proved that it was significantly more efficient than the conventional silver brazing (about 60 seconds). It was also found that the tensile strength of the welded portion between the measuring electrode and the lead wire is slightly weaker than the tensile strength (9.3 Kg / f) of the lead wire itself, and it has sufficient tensile strength.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an oxygen probe according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a connection state between a measurement electrode and a lead wire.

[Explanation of symbols]

 10 Oxygen probe 12 Housing 14 Protective tube 16 Mounting block 20 Solid electrolyte 22 Reference electrode lead wire 24 Connector 26 Thermocouple 28 Support pin 30 Connector pin 32 Measuring electrode 34 Lead wire 36 Joint part 38 Protective cap

Claims (3)

[Claims] 1. An oxygen probe for measuring oxygen activity in a molten metal, comprising a measuring electrode and a lead wire connecting the measuring electrode and a connector, the measuring electrode and the lead wire being connected by percussion welding. An oxygen probe characterized by being welded. 2. The measuring electrode is made of molybdenum or iron,
The oxygen probe according to claim 1, wherein the lead wire is made of copper or an alloy of copper and nickel. 3. A method for producing an oxygen probe for measuring oxygen activity in molten metal, comprising: (a) a measuring electrode on a first welding head of a welding machine and a lead wire on a second welding head. Respectively, (b) accumulating electric charge in the capacitor of the welding machine, and (c) making the measuring electrode and the lead wire relatively close to each other to generate an arc, thereby facing opposite ends of both members. And a step of: (d) causing the measurement electrode and the lead wire to collide with each other to perform percussion welding of both members.