JP2002239750A - Resistance seam welding method excellent in welding part quality and welding equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and equipment for resistance seam welding for avoiding welding failure during welding by any method of grinding/polishing of an electrode surface or welding current control by predicting welding failure caused by a soiled electrode before welding. SOLUTION: This resistance seam welding method for carrying out welding by pressing and energizing an overlapping part of metallic plates with a rolling disc electrode, is characterized in measuring the surface resistance of the disc electrode, and grinding/polishing the disc electrode surface so that the measured value of the resistance does not exceed an upper limit value of the resistance when the measured value of the resistance exceeds the preset upper limit value of the resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to contamination and welding quality of a welding electrode when performing resistance seam welding of a metal plate such as a steel plate, a stainless steel plate, an aluminum alloy plate, etc., which has been subjected to a surface treatment such as plating or an organic film. The present invention relates to a resistance seam welding method and a resistance seam welding device capable of controlling the resistance seam welding.

[0002]

2. Description of the Related Art For example, in the process of manufacturing a fuel tank for a metal automobile, a flange portion of an outer shell formed in advance is overlapped, and the flange portion must be continuously subjected to resistance seam welding without any defect. No. Turn-plated steel sheets containing lead are often used as the metal fuel tank material. Changes to metal plates have been made. Further, the tank shape is required to be difficult to form. For example, an organic film having high lubricity may be applied to the surface of the metal plate in order to ensure excellent formability.

[0003] When performing resistance seam welding of a steel plate, a stainless steel plate, or an aluminum alloy plate that has been subjected to surface treatment such as plating or an organic film, a plating metal and an electrode material are formed on the surface of a welding disk electrode to be used. Alloys and carbides formed by heating and burning of organic coatings and the like form and accumulate and are contaminated.

If such contamination occurs on the surface of the electrode, the conductivity when the electrode and the metal plate are in contact with each other is disturbed and the local current is applied. Current density through the electrode is increased, so that resistance heating between the electrode and the metal plate becomes remarkable. Therefore, when electrode fouling progresses due to an increase in the number of weldings, as shown in FIG. 1, the upper limit current and the lower limit current at which welding can be performed are reduced, and the weldable current range limited by the upper limit current and the lower limit current is narrowed. Problems arise. Here, the upper limit current that can be welded is an upper limit value of a welding current that does not cause severe scattering, pit generation, drilling, and the like, and the lower limit current that can be welded is to obtain a predetermined welding nugget width, In addition, it is the minimum welding current necessary for the welded portion to be continuously connected in the direction of the welding line to ensure airtightness.

Therefore, if welding is continuously repeated using a welding current I0 corresponding to a clean state of the electrode surface after electrode replacement or electrode grinding, electrode contamination gradually progresses with an increase in the number of weldings, and the Welding current I0 set in a proper state deviates from the weldable current range corresponding to the number of weldings,
Poor seam welding quality such as severe scattering, pitting, and perforation.

As a method of solving such poor seam welding quality due to electrode fouling, as shown in FIG. 2, as the number of weldings increases, the welding current is shown in a stepwise solid line (I1). In order to maintain the welding current within the weldable current range corresponding to each welding cycle, or to maintain a clean state after electrode replacement, There is a method of performing grinding or polishing.

[0007] Welding defects such as severe scattering, pit generation, and perforation are phenomena caused by excessive heat generation due to local concentration of welding current. Therefore, a change in resistance between electrodes due to temperature rise due to excessive heat generation or current concentration, or
It is possible to detect a poor welding by a method of managing a contact resistance value between an electrode and a metal plate or the like.
JP-A-2000-1028), although it is spot welding of the same resistance welding or the same resistance welding, the quality of a welded part is judged based on a change in resistance between welding electrodes.
No. 79, etc.) or the contact resistance between the upper and lower seam welding disk electrodes and the metal plate to be welded is measured, the electrode surface state is determined from the measured value, and electrode grinding and electrode polishing are performed according to the electrode surface state. Performing technology (JP-A-4-279287, etc.)
Has been proposed.

[0008]

However, according to the conventional method of changing the welding current stepwise, the welding current range corresponding to each welding number, which changes every moment due to electrode contamination accompanying the increase in the number of weldings, is limited. It is difficult to set the optimum welding current I1, and when rapid electrode fouling proceeds, excessive resistance heat is generated between the electrode and the steel sheet, resulting in poor welding quality such as severe scattering, surface pits, and holes. I can't avoid that. In addition, when performing electrode grinding and electrode polishing for maintaining the same cleanliness of the electrode surface as after electrode replacement, the amount is often performed until the electrode surface is completely free of contamination. Therefore, if grinding and polishing are repeated, the amount of electrode consumption becomes remarkable, and the frequency of electrode replacement increases. Therefore, there is a problem that workability is reduced and manufacturing cost is increased.

Further, Japanese Patent Application Laid-Open Nos. 2000-52052, 2000-102879, and 4-
In the technique proposed in Japanese Patent No. 279287, in order to measure the temperature of the welded portion and the resistance between the electrodes or the contact resistance between the electrode and the metal plate when a welding current is applied, the material to be welded is sandwiched between a pair of electrodes. Even if it is determined from the measured values that the surface condition of the welded portion or the electrode is defective, post-determination is performed, and there is a problem that welding failure cannot be prevented beforehand.

Therefore, the present invention differs from the conventional method of measuring the temperature of the welded portion, the resistance between the electrodes or the contact resistance between the electrode and the metal plate. Provided is a resistance seam welding method and apparatus for predicting welding defects due to electrode contamination before performing the method and avoiding welding defects at the time of welding by any method of grinding / polishing the electrode surface or controlling welding current. That is the task.

[0011]

The present invention solves the above-mentioned problems, and the gist of the invention is as follows.

(1) In a resistance seam welding method in which a superposed portion of a metal plate is welded by pressing and energizing with a rotating disk electrode, the resistance of the disk electrode surface is measured, and the measured value of the resistance is A resistance seam welding method, characterized in that when the resistance exceeds a preset upper limit value of the resistance, the disk electrode surface is ground and polished so that the measured value of the resistance is equal to or less than the upper limit value of the resistance.

(2) In a resistance seam welding method in which a superposed portion of a metal plate is welded by pressing and energizing by a rotating disk electrode, the resistance of the disk electrode surface is measured, and the resistance value is measured. A resistance seam welding method comprising: obtaining a preset upper limit value of a welding current; and controlling a welding current supplied to the disc electrode so as to be equal to or less than the upper limit value of the welding current.

(3) The measured value of the resistance of the surface of the disk electrode is obtained by bringing a pair of detection terminals into contact with the surface of the disk electrode, passing a current for measuring the resistance between the detection terminals, and measuring the resistance between the detection terminals. The resistance seam welding method according to the above (1) or (2), wherein a voltage generated in the step (c) is measured and calculated from the current and the voltage.

(4) A disk electrode capable of rotating and pressurizing and energizing a superposed portion of a metal plate and a resistance of the surface of the disk electrode are measured, and a measured value of the resistance is set in advance. A disk electrode surface contamination state monitoring device that determines whether or not the resistance is equal to or less than an upper limit value, and when the measured value of the resistance of the disk electrode surface exceeds the preset upper limit value of the resistance, A resistance seam welding apparatus comprising a grinding / polishing machine for grinding / polishing a disk electrode surface.

(5) A disk electrode which can rotate and pressurize and energize the superposed portion of the metal plate, and a resistance of the surface of the disk electrode are measured, and a measured value of the resistance is set in advance. When the measured value of the resistance of the disk electrode surface exceeds the predetermined upper limit of the resistance,
A resistance current seam comprising: a welding current control device for adjusting a current flowing through the disk electrode to be equal to or less than an upper limit value of a welding current corresponding to the measured value of the resistance. Welding equipment.

(6) The apparatus for monitoring the state of contamination on the surface of the disk electrode comprises a pair of detection terminals which are in contact with the surface of the disk electrode and which are rotatable or flexible with respect to the rotational movement thereof;
A current generator for generating a current to flow between the detection terminals, a voltage measuring device for measuring a voltage generated between the detection terminals, and a disc from the current flowing between the detection terminals and the voltage generated between the detection terminals Calculation means for calculating the resistance of the electrode surface; storage means for storing a preset upper limit value of the resistance and welding conditions; and whether the measured value of the resistance is equal to or less than the preset upper limit value of the resistance. The resistance seam welding apparatus according to the above (4) or (5), further comprising: determination means for determining whether or not the resistance seam welding is performed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.

In the present invention, a pair of detection terminals 4 are provided on the circumferential surface of each of the rotated or stopped disk electrodes shown in FIG.
a, 4b are brought into contact with each other, when a DC or AC detection current value Ia is applied between the terminals, a voltage value Va generated between the terminals is detected, and an electrode surface resistance value Ra is calculated from Va and Ia.
Detects the status of electrode surface contamination.

A method for detecting the state of contamination of the electrode tip according to the present invention will be described with reference to FIGS. Reference numeral 1 denotes a disk electrode serving as an electrode ring, and reference numeral 2 denotes a stained electrode stained area formed on the surface thereof. Reference numeral 3 denotes a detection device for measuring the resistance and current of the electrode surface, and reference numerals 4a and 4b denote detection terminals. 5 is a current generator for energizing 4a, 4b, 6
Is a voltage measuring device of the voltage obtained from 4a, 4b, 7 is a calculating means for calculating the resistance value Ra from the voltage value Va by the voltage measuring device 6 and the current value Ia for detection by the current generator, 8 is the desired welding condition. Storage means for storing the welding current value and the resistance value, determination means for determining whether or not the electrode surface resistance value and the welding current value are appropriate values; and 10 a fouling state monitoring device. Reference numeral 11 denotes a grinding / polishing machine for grinding / polishing the disk electrode 1, and reference numeral 12 denotes a welding current control device for controlling a welding current.

To detect the state of contamination of the electrode tip, the detection terminals 4a and 4b are brought into contact with the electrode wheel when the electrode wheel composed of the disk electrode 1 is rotating or stopped, and the current generator 5 is used to detect the detection terminal 4a. By supplying the detection current Ia between the detection terminals 4a and 4b, a voltage generated in the electrode contamination area 2 on the electrode surface is detected between the detection terminals 4a and 4b. At this time, the contamination state monitoring device 10
Is used to calculate the resistance value Ra from the voltage value Va between the detection terminals measured by the voltmeter 6 and the detection current value Ia.

The calculated resistance value Ra is compared with the welding conditions stored in the storage means 8 and the upper limit value of the resistance to determine whether or not the measured value Ra of the resistance is equal to or less than a predetermined upper limit value of the resistance. When the discrimination is made using the means 9 and the resistance exceeds a preset upper limit value of the resistance, the disc electrode 1 is ground.
The grinding and polishing are repeatedly performed using the polishing machine 11 until the electrode surface resistance falls below a preset upper limit.

That is, according to the present invention, the resistance value obtained by measuring the fouling state of the electrode surface using the fouling state monitoring device is compared with the welding conditions and the upper limit value of the resistance stored in the storage means, and the measured resistance value is obtained. Is determined using a determination means to determine whether or not the resistance value is equal to or less than a predetermined upper limit value of the resistance. If the resistance value exceeds the predetermined resistance value, the grinding for grinding / polishing the disk electrode surface is performed. Using a polishing machine, the grinding and polishing are repeatedly performed until the electrode surface resistance falls below a preset upper limit.

As described above, by constantly maintaining and securing the resistance value Ra below the preset upper limit value, it is possible to control the amount of grinding of the electrode, and to perform welding such as severe scattering, surface pits and holes. It is possible to prevent the occurrence of quality defects and suppress excessive grinding.

Alternatively, the calculated resistance value Ra is compared with the welding conditions stored in the storage means 8 and the upper limit value of the resistance, and the current welding current is set to a predetermined upper limit of the welding current corresponding to the resistance value. If it exceeds the value, the judgment means 9
Is used to determine an appropriate current value, and the welding current control device 12
To prevent the welding current from exceeding the upper limit of the welding current.
Is energized.

That is, the resistance value obtained by measuring the state of the electrode surface contamination using the electrode contamination monitoring device is compared with the welding conditions and the upper limit value of the resistance stored in the storage means, and the current welding current is compared with the resistance value. If the value exceeds the corresponding preset upper limit of the welding current, an appropriate current value is determined using the determination means, and the disc is controlled so as not to exceed the upper limit of the welding current using the welding current control device. Apply current to the electrodes.

[0027] Therefore, even if rapid electrode fouling progresses, it is possible to prevent the occurrence of poor welding quality such as severe scattering, surface pits, and holes due to excessive resistance heating between the electrode and the steel sheet.

[0028]

Next, embodiments of the present invention will be described. According to the method of the present invention, the electrode surface resistance value with respect to the number of times of resistance seam welding of an aluminum-plated steel sheet and the quality of the welded portion at that time were evaluated.

FIG. 5 shows the change in electrode surface resistance with the number of weldings. When the surface resistance value exceeds the threshold value Rc,
Poor welding occurred.

FIG. 6 shows a change in the electrode surface resistance when the electrode grinding is controlled. By maintaining the surface resistance value below the threshold value Rc, poor welding did not occur. As a result, in the present embodiment, the resistance of the disk electrode surface is measured, and the electrode surface is ground or controlled so that the resistance value does not exceed the threshold value Rc, or the current value is controlled. By performing electrode management so as to maintain the electrode surface resistance within the range, it was possible to reliably maintain excellent welding quality. Therefore, according to the present invention, resistance seam welding can be performed with stable welding quality.

[0031]

[Effects of the Invention] When performing lap resistance seam welding of a metal plate such as a steel plate, a stainless steel plate, an aluminum alloy plate or the like that has been subjected to surface treatment such as plating or an organic film, the plated metal and the electrode are used on a welding electrode wheel used. An alloy with the material, carbides and the like formed by heating and burning of the organic film and the like are formed, and the electrode surface is contaminated.

According to the present invention, it is possible to select the optimum value of the welding current with respect to the electrode contamination level by judging the electrode surface contamination state before welding by the resistance value Ra. However, since an optimal welding current can be applied, it is possible to prevent the occurrence of severe scattering, surface pits and holes due to excessive resistance heating between the electrode and the steel sheet.

Further, by measuring the resistance value Ra before welding and constantly maintaining and securing the resistance value Ra at or below a preset upper limit value, it is possible to control the amount of electrode grinding and to sharply disperse. In addition, it is possible to prevent the occurrence of poor welding quality such as surface pits and holes, and to suppress excessive grinding.

Therefore, it is possible to reliably prevent the quality of the welded portion from being deteriorated due to electrode fouling before welding, and to provide high productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship of a change in a weldable current range with the number of times of welding.

FIG. 2 is a diagram showing an example of a welding current setting method with respect to the number of times of welding.

FIG. 3 is a model diagram of electrode surface resistance measurement.

FIG. 4 is a diagram showing a main part of a resistance seam welding apparatus having an electrode surface resistance measurement function.

FIG. 5 is a diagram showing a change in electrode surface resistance and a state of occurrence of poor welding when welding is repeated at a constant current by a conventional method (without electrode grinding control).

FIG. 6 is a diagram showing a change in electrode surface resistance and a state of occurrence of poor welding when welding is repeated at a constant current according to the present invention (with electrode grinding control).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc electrode 2 Electrode contamination area 3 Detecting device 4a, 4b Detection terminal 5 Current generator 6 Voltage measuring device 7 Calculation means 8 Storage means 9 Judging means 10 Soil condition monitoring device 11 Grinding / polishing machine 12 Welding current control device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 11/06 520 B23K 103: 06 B23K 103: 06 103: 10 103: 10 103: 16 103: 16 B60K 15/02 Z (72) Inventor Takashi Tanaka 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Headquarters (72) Inventor Masahiro Ohara No. 1 Nishinoshu, Oita City Nippon Steel Corporation In the Oita Works (72) Inventor Masanori Kondo 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3D038 CA05 CC19

Claims (6)

[Claims] In a resistance seam welding method in which a superposed portion of a metal plate is welded by pressing and energizing a rotating plate electrode, the resistance of the surface of the disk electrode is measured, and the measured value of the resistance is determined in advance. A resistance seam welding method, characterized in that the disk electrode surface is ground and polished so that the measured value of the resistance becomes equal to or less than the upper limit of the resistance when the resistance exceeds the set upper limit of the resistance. 2. A resistance seam welding method in which a superposed portion of a metal plate is welded by pressing and energizing a rotating plate electrode by means of a rotating disk electrode, the resistance of the disk electrode surface is measured, and the resistance is measured in advance. A resistance seam welding method, wherein an upper limit value of a set welding current is obtained, and a welding current applied to the disk electrode is controlled so as to be equal to or less than the upper limit value of the welding current. 3. A measured value of the resistance of the surface of the disk electrode is obtained by bringing a pair of detection terminals into contact with the surface of the disk electrode, passing a current for measuring the resistance between the detection terminals, and detecting the resistance between the detection terminals. The resistance seam welding method according to claim 1, wherein a generated voltage is measured and calculated from the current and the voltage. 4. A disk electrode capable of rotating and pressurizing and energizing a superposed portion of a metal plate, and measuring the resistance of the surface of the disk electrode, and measuring the resistance with a predetermined resistance. A contamination state monitoring device for the disc electrode surface to determine whether or not it is less than or equal to the upper limit value, and when the measured value of the resistance of the disc electrode surface exceeds the preset upper limit value of the resistance, the circle A resistance seam welding apparatus comprising: a grinding / polishing machine for grinding / polishing a surface of a plate electrode. 5. A disk electrode which can rotate and pressurize and energize a superposed portion of a metal plate, and a resistance of the disk electrode surface is measured, and the measured value of the resistance is set in advance. A disk electrode surface contamination state monitoring device that determines whether the resistance is equal to or less than an upper limit value of the resistance, and when the measured value of the resistance of the disk electrode surface exceeds the preset upper limit value of the resistance, A resistance current welding device comprising: a welding current control device for adjusting a current flowing through the disc electrode to be equal to or less than an upper limit value of a welding current corresponding to the measured value of the resistance. apparatus. 6. A device for monitoring the state of contamination of a surface of a disk electrode, comprising: a pair of detection terminals that are in contact with the surface of the disk electrode and that are rotatable or flexible with respect to the rotational movement thereof; A current generator for generating a current for supplying current to the detection electrode, a voltage measuring device for measuring a voltage generated between the detection terminals, and a voltage between the detection terminal and the current flowing between the detection terminals. Calculating means for calculating the resistance; storage means for storing a preset upper limit value of the resistance and welding conditions; and determining whether the measured value of the resistance is equal to or less than the preset upper limit value of the resistance. The resistance seam welding apparatus according to claim 4, further comprising a determination unit configured to perform the determination.