JP5349560B2 - Welding head for resistance welding machine and welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such problems that a conventional resistance welding system needs to start the discharge of gas such as argon, helium before welding, and to continue to blow the gas for a definite period of time after welding until an electrode is sufficiently cooled, thus wastefully consuming an expensive gas, and also needs a long takt time to obtain a sufficient time until cooling of the electrode. <P>SOLUTION: The welding head for a resistance welder is characterized by comprising: an electrode for the resistance welder; a temperature-measuring unit for measuring the temperature of the electrode; a protection unit which covers the circumference of the electrode and has the inflow port of a gas for blowing to the electrode; and a gas switch for selecting an optional gas out of a plurality of gases. Besides, the welding head is characterized in that the type of the gas to be blown to the electrode is switched according to the measured temperature of the electrode. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

        The present invention relates to a welding head for a resistance welder and a welding method.

In resistance welding, if the work piece is pure copper or silver (or a small amount of a different kind of metal added to them) and the specific resistance is low and the thermal conductivity is large, the welding electrode is Mo (IACS 31%) or W (IACS 30%). For example, a material having a relatively large specific resistance and a low thermal conductivity is used as the resistance welding electrode material. Fe, Ni, stainless steel, etc. In the case of resistance welding of a material having a large specific resistance and a low thermal conductivity compared to pure copper or silver (or a material obtained by adding a trace amount of different metals), Cr—Cu (IACS80 %) Etc. are used.
In recent years, with the increase in electric current of electrical parts, etc., in order to reduce the resistance value and improve the thermal conductivity, it has been replaced with the conventional brass that has been used at relatively low currents. That are added with a small amount of other elements), and use under conditions where Mo and W are red hot is required. When the electrode becomes hot, oxidation in the air and nitridation proceed in the nitrogen atmosphere, and the life of the electrode is remarkably reduced. Therefore, the electrode is protected from the surrounding atmosphere to prevent oxidation exhaustion (scale out) and actively cooled. There is a need to.

For example, molybdenum slightly oxidizes (discolors) at room temperature, begins to oxidize at about 300 ° C., and forms MoO 3 at about 500 ° C. or more to rapidly oxidize. In a nitrogen atmosphere, embrittlement is observed at 600 ° C. or higher, nitrides are formed at about 1500 ° C. or higher, and oxidation begins at about 700 ° C. in the presence of water vapor.
Tungsten is slightly oxidized (discolored) at room temperature, begins to oxidize at about 400 to 500 ° C., forms WO 3 at about 700 ° C. or more, and rapidly oxidizes. In a nitrogen atmosphere, nitrides are formed at about 2300 ° C. or higher, and the presence of water vapor quickly oxidizes in a red hot state.

For this reason, a nozzle has been provided near the tip of the electrode, and a gas such as argon or helium is sprayed shortly before energization to suppress stagnation of oxygen or nitrogen around the electrode so that it does not change even if the electrode becomes hot. To protect.
The sprayed gas is also used for cooling the electrode after the end of bonding. Normally, when welding is performed continuously, the temperature of the electrode at the start of welding energization rises due to heat storage, even if measures such as cooling the folder with water to cool the electrode are used. Since the same amount of energization and energization time as the setting result in excessive melting, it is necessary to set complicated conditions such as appropriately reducing the energization amount and energization time for each number of striking points. By utilizing the cooling effect of the injected gas, the temperature rise of the electrode at the start of welding energization can be suppressed, and the welding conditions can be simplified.

There is also a proposal for shielding the periphery of the electrode as disclosed in Patent Document 1 as a method for preventing the diffusion of the injected gas.

Furthermore, although it is an example of a heat welding apparatus, there also exists a proposal like patent document 2 which controls supply / stop of cooling air with the temperature of a heat generating part.

JP2008-137078 (FIG. 1) JP 2004-90558 (6 pages)

However, in the conventional method, it is necessary to start discharging gas such as argon and helium before bonding and to continue to blow gas for a certain period of time until the electrode sufficiently cools after bonding, resulting in wasted expensive gas. It was. Also, the tact time was long to see the allowance for the electrode to cool down sufficiently.

Even if the gas injection is controlled by the temperature of the electrode as in Patent Document 2, it is necessary to continue to blow an expensive gas such as argon or helium until it becomes lower than the oxidation temperature of the electrode material.

The present invention proposes a resistance welding head and a welding method that efficiently use these expensive gases and realize reduction of the unit cost and time of joining.

A welding head for a resistance welding machine according to the present invention includes an electrode for resistance welding, temperature measuring means for measuring the temperature of the electrode, protective means for covering the periphery of the electrode and having a gas inlet for spraying the electrode. , possess a gas switching means for selecting an arbitrary gas among the plurality of kinds of gases, and it is characterized in that performed based decision to switch the gas sprayed on the electrode in the measurement temperature of the temperature measuring means.

In addition, the measurement temperature of the electrode for performing the determination to switch the gas sprayed onto the electrode is a nitriding temperature or an oxidation temperature of the electrode material.
In other words, the electrode in the high temperature state after welding is cooled to a nitriding temperature or oxidation temperature of the electrode material with a gas that has an effect of suppressing nitriding or oxidation, so that the electrode temperature is less than the nitriding temperature or the oxidation temperature of the electrode material. After lowering, switch to an inexpensive gas such as nitrogen or compressed air for cooling.

Usually, argon or helium gas is used as a gas to suppress nitriding. When suppressing vaginalization, the gas to be sprayed is one of argon or helium and the other is nitrogen, and the electrode temperature after welding is the electrode material. Argon or helium is sprayed until the temperature is lower than the nitriding temperature of the electrode, and the temperature is switched to nitrogen at a temperature lower than the nitriding temperature of the electrode material.

In order to further suppress oxidation, the gas to be sprayed is argon, helium or nitrogen on one side and compressed air on the other side, and argon, helium or nitrogen is blown until the electrode temperature after welding is lower than the oxidation temperature of the electrode material. It is characterized by switching to compressed air below the oxidation temperature of the material.

Furthermore, the gas to be blown is made of argon or helium, nitrogen and compressed air, and argon or helium is blown until the electrode temperature after welding becomes lower than the nitriding temperature of the electrode material. Switching to nitrogen, nitrogen is blown until the electrode temperature falls below the oxidation temperature of the electrode material, and when the electrode temperature falls below the oxidation temperature of the electrode material, switching to compressed air is performed.

Further, the present invention is a welding method using a resistance welder,
1) while spraying step and 2) before SL gas to be injected toward the nitriding or gas the electrodes to inhibit oxidation, steps and 3 perform welding by controlling the power supplied to the electrode) the after welding while spraying the gas, electrodes temperature measurements resistance welding with a step of changing the gas to be injected by the gas body switching means to a compressed air or nitrogen when the lower than nitriding or oxidation temperature of the members constituting the electrodes It features a welding method using a machine.

Provided are a welding head and a welding method for a resistance welding machine that efficiently use expensive gas and realize a reduction in joining unit cost and joining time.

It is a lineblock diagram of a welding head using a bubble for gas change concerning one embodiment of the present invention. It is a lineblock diagram of a welding head using a gas kind change part which consists of a plurality of solenoid valves etc. for gas change concerning one embodiment of the present invention. It is a block diagram of the welding head which added the inflow adjustment parts, such as a speed controller, to the form of FIG. It is a block diagram of the welding head which has arrange | positioned the gas kind switching part and inflow adjustment part of the form of FIG. 3 independently for every protection head. It is a block diagram of a welding head when the gas type is made into three types with the welding head of the form of FIG. It is a flowchart which shows an example of the joining method of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view showing an example of the configuration of a welding head of a resistance welding machine according to an embodiment of the present invention.
An electrode 12 provided with a thermometer 17 such as a thermocouple thermometer as temperature measuring means is covered with a protective cover 11 as protective means. The protective cover 11 is provided with a plurality of suction ports 18 for introducing gas into the protective cover 11. The suction port 18 is connected by a tube to valves 14 (a) and 14 (b) for performing gas ON / OFF by a signal from a control unit (not shown), and the valves 14 (a) and 14 (b) are different types of gases. (Gas 15 and gas 16) are supplied. Assuming that the gas 15 is a relatively expensive helium or argon gas that suppresses nitriding, and the gas 16 is an inexpensive nitrogen gas.

At the time of joining, first, 14 (b) is turned OFF and 14 (a) is turned ON, and the inside of the protective cover 11 is filled with the gas 15. The time to allow the gas 15 to overflow from the protective cover 11 is set, and the object to be joined is moved between the electrodes 12 by a moving means (not shown). Next, the electrode 12 is brought into contact with an object to be joined by a moving means (not shown) and then energized to perform welding.

Welding control methods include constant current control, constant power control, and welding heat control. The thermometer 17 may be used for temperature measurement in the case of welding heat control, or may be measured by another method.

When the object to be joined is made of a copper-based metal and has a thickness, the electrode 12 is energized for a long time, and the electrode 12 has a low thermal conductivity, so the heat generation is large. It becomes hot enough to cause the phenomenon. For this reason, it is necessary to spray gas for cooling even after the welding is completed and the energization is stopped.

During cooling with the gas 15, the measured value of the thermometer 17 is observed, and after the measured value falls below the nitriding temperature of the material of the electrode 12, the valve 14 (b) is opened to start the injection of the gas 16. 14 (a) is closed to stop the spraying of the gas 15, and the gas to be cooled is switched to the gas 16.

For example, when the material of the electrode 12 is tungsten, it is nitrided at about 2300 ° C. or more, and in the case of molybdenum, it is nitrided at about 600 ° C. or more, so the measured value of the thermometer 17 is not nitrided, that is, about 2200 ° C. in the case of tungsten. In this case, when the temperature falls to about 500 ° C., switching from the gas 15 to the gas 16 is performed.

Further, when the gas 15 is helium or argon gas or nitrogen, and the gas 16 is normal compressed air containing oxygen, the electrode 12 is oxidized at a temperature of about 400 ° C. or higher when the material is tungsten, and when it is molybdenum, it is oxidized at a temperature of about 300 ° C. or higher. Therefore, when the measured value of the thermometer 17 falls to a temperature at which it does not oxidize, that is, about 300 ° C. for tungsten and about 200 ° C. for molybdenum, switching from gas 15 to gas 16 is performed.

Further, the measured value of the thermometer 17 is monitored, and after the temperature of the electrode 12 has sufficiently decreased, the gas injection is stopped and the joining operation is completed.

In FIG. 1, the protective cover 11 is provided with the number of inlets corresponding to the gas, but this makes the piping around the head with many operating parts complicated. For this reason, there are restrictions on the movement of the object to be joined, and there is a risk of contact. FIG. 2 shows an improved form of these. In a mode in which the inlet 18 of the protective cover 11 corresponding to the number of types of gas is provided in one place, the valves 14 (a) and 14 (b) are deleted, and a gas type switching device 19 as a gas switching unit is added instead. is there. The gas type switch 19 includes a combination of a plurality of solenoid valves, and performs gas selection and output / stop control by a signal from a control unit (not shown). In FIG. 2, two types of gases are selected.

The present bonding head uses two electrodes 12 as one pair, but the electrodes are usually mounted so that the electrodes face each other vertically. At this time, depending on the gas density (specific gravity) of the gas used, the filling condition of the gas in the upper and lower protective covers 11 is different, and if the amount of ejection is the same, the gas in the protective cover on one side overflows first. Unevenness occurs in quantity and filling time. In FIG. 3, an inflow adjusting portion 13 such as a speed controller for adjusting the gas flow rate is provided between the protective cover 11 and the gas type switch 19 so that the gas in the upper and lower protective covers 11 is filled with a good balance. adjust.

When it is desired not only to adjust the filling amount in the two protective covers 11 but also to change the filling amount depending on the type of gas, a gas type switch 19 is provided for each protective cover as shown in FIG. What is necessary is just to provide in the input part of each kind switch.

Although the example shown above is control which switches two types of gas, this invention does not determine the number of types of gas. For example, as shown in FIG. 5, when the gas type is three and the gas 15 is helium or argon, the gas 16 is nitrogen, and the gas 20 is compressed air, when the electrode 12 is made of tungsten, the temperature is about 2300 ° C. or more. In the case of molybdenum, nitriding is performed at about 600 ° C. or higher, so the temperature measured by the thermometer 17 is not nitrided, that is, about 2200 ° C. in the case of tungsten and about 500 ° C. in the case of molybdenum. Switch to. Next, when the material of the electrode 12 is tungsten, it is oxidized at about 400 ° C. or more, and in the case of molybdenum, it is oxidized at about 300 ° C. or more. Therefore, the measured value of the thermometer 17 is not oxidized, that is, about 300 ° C. in the case of tungsten. In the case of molybdenum, when the temperature falls to about 200 ° C., switching from the gas 16 to the gas 20 is performed.

An example of the welding method of the resistance welder using the welding head shown in FIG. 5 will be described with reference to FIG. The welding head includes an electrode for resistance welding, temperature measuring means for measuring the temperature of the electrode, protective means for covering the periphery of the electrode and having a gas inlet for spraying the electrode, and a plurality of types of gas. Gas switching means for selecting an arbitrary gas.
Prior operations will not be described, but will be described after the workpiece is in contact with the electrodes in a weldable state.
First, injection of helium or argon gas, which is the gas 15, is started (S601).
After the gas 15 is filled in the protective means, energization of the electrode is started, and the temperature of the electrode is controlled to be a predetermined temperature within a predetermined time according to the information of the temperature measuring means, and joining of the workpieces is performed. Perform (S602, S603).
Next, temperature information from the temperature measuring means is monitored, and cooling is performed with helium or argon gas until the electrode temperature falls below the nitriding temperature of the electrode material (S604, S605).
When the temperature of the electrode becomes lower than the nitriding temperature of the electrode material, the gas switching unit stops the spraying of the gas 15 and the spraying of the nitrogen gas as the gas 16 is started (S606).
Next, temperature information from the temperature measuring means is monitored, and cooling is performed with nitrogen gas until the electrode temperature falls below the oxidation temperature of the electrode material (S607, S608).
When the temperature of the electrode becomes lower than the oxidation temperature of the electrode material, the gas switching means stops the injection of the gas 16 and the injection of the compressed air as the gas 20 is started (S609).
Next, temperature information from the temperature measuring means is monitored, cooling with compressed air is performed until the temperature of the electrode falls below a predetermined temperature, and then the blowing of compressed air is stopped by the gas switching means. (S610, S611, S102).
With the above method, it is possible to prevent deterioration of the electrode while eliminating waste of expensive gas.

11: Protective cover 12: Electrodes 15, 16, 20: Gas 17: Thermometer 19: Gas type switch

Claims (6)

Electrodes for resistance welding;
Temperature measuring means for measuring the temperature of the electrode and protective means covering the periphery of the electrode and having a gas inlet for spraying the electrode;
Have a, and the gas switching means for selecting an arbitrary gas among the plurality of types of the gas, and wherein a decision to switch the gas sprayed on the electrode be performed based on the measured temperature of the temperature measuring means resistance Welding head for welding machine. The welding head for a resistance welder according to claim 1, wherein the measurement temperature of the electrode that determines to switch the gas sprayed to the electrode is less than the nitriding temperature or the oxidation temperature of the electrode material. One of the gases to be sprayed onto the electrode is argon or helium and the other is nitrogen, and argon or helium is sprayed until the measurement temperature of the electrode after welding is lower than the nitriding temperature of the electrode material. resistance welding machine for welding head according to claim 1 or 2, characterized in that switching to nitrogen below the nitriding temperature. One of the gases to be sprayed on the electrode is argon, helium or nitrogen, and the other is compressed air, and argon, helium or nitrogen is sprayed until the measurement temperature of the electrode after welding becomes lower than the oxidation temperature of the electrode material, and measurement of the electrode is performed. resistance welding machine for welding head according to claim 1 or 2 temperature and switches to the compressed air below the oxidation temperature of the electrode material. The gas to be sprayed onto the electrode is three types of argon or helium, nitrogen and compressed air, and argon or helium is blown until the measurement temperature of the electrode after welding becomes lower than the nitriding temperature of the electrode material, and the measurement temperature of the electrode features There switched to nitrogen below the nitriding temperature of the electrode material, blowing nitrogen until the measured temperature of the electrode is less than the oxidation temperature of the electrode material, a switch are archives air measured temperature of the electrode is less than the oxidation temperature of the electrode material resistance welding machine for welding head according to claim 1 or 2,. In the resistance welding machine welding method,
1) while spraying step and 2) before SL gas to be injected toward the nitriding or gas the electrodes to inhibit oxidation, steps and 3 perform welding by controlling the power supplied to the electrode) the after welding while spraying the gas, electrodes temperature measurements resistance welding with a step of changing the gas to be injected by the gas body switching means to a compressed air or nitrogen when the lower than nitriding or oxidation temperature of the members constituting the electrodes Machine welding method.

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