JPS6149786A - Arc welding method - Google Patents

Abstract

PURPOSE:To know beforehand the generation of an abnormality, to eliminate the cause of the abnormality, and to improve a welding quality by measuring and monitoring a temperature or a temperature distribution of a welding wire which is being fed. CONSTITUTION:When welding is being executed, a temperature measuring device 10 measures a temperature of a welding wire in a contact chip 9 and at outlet of the contact chip 9, and monitors its variation. Accordingly, a degree of a heating effect by heating of a resistance in a wire projecting part is grasped continuously and exactly. In this way, checking and correcting operation can be started before reaching a crucial welding abnormality.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a consumable electrode type arc welding method,
The present invention relates to a welding method that has a function to automatically monitor the welding situation in order to ensure quality more stably than before when putting this welding method into practice.

(Conventional technology) As a typical consumable electrode arc welding method.

This will be explained by taking the submerged arc welding method as an example.

Figure 4 shows the basic configuration of a submerged arc welding machine.
is a welding power source, 2 is a workpiece to be welded (base metal), 4 is a welding wire, 5 is a welding flux socket ξ-16 is a welding wire feeding motor, 7 is a motor control box, 8 is a welding cable,
9 is raining contact tips.

Normally, four bare bath welding wires wound around a wire reel are continuously fed out by a feed motor 6, and the heat of the arc generated between the tip and the base material 2 is heated. melt. (Response current is supplied to the wire from the i6 ground source 1 through the contact tip 9.

Regarding the feeding of the welding wire 4 that is continuously supplied, in order to control the feeding speed, generally the arc voltage is picked up and fed into the drive control circuit of the wire feeding motor 6. As a result, control can be performed so that the arc voltage is kept constant.

However, controlling this arc voltage alone cannot be a condition for obtaining sufficient welding quality, and in actual work,
Many parts of the welding machine are controlled and dependent on the monitoring work of the rotor.

Such conventional methods of controlling welding arc conditions have the following drawbacks.

■ The arc current value, arc voltage value, and welding speed value during welding are generally displayed on instruments on the welding operation panel, and must be constantly visually monitored.

(2) Even if an abnormality occurs in the basic conditions such as the current value, voltage value, welding speed value, etc., no means or method has been adopted to detect and display the cause of the abnormality.

■ Therefore, it is impossible to predict an abnormality until it occurs, and even after an abnormality occurs, the cause of the abnormality cannot be investigated unless it is discovered as a result of the operator's work monitoring, or else the entire cause system is involved. I have no choice but to check. As a result, there is no hope for a quick solution, let alone an accurate investigation of the cause.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned prior art by solving basic elements of welding conditions,
By monitoring the status of the power supply point, which is one of the major causes of fluctuations in welding current and welding voltage, during arcing during welding and judging the results, it is possible to predict the occurrence of abnormalities and eliminate the causes of abnormalities. The purpose is to provide an arc welding method that has the function of improving product quality.

Among these, the present invention aims to improve and stabilize welding quality by quantitatively and quickly determining whether the power supply status from the contact tip is good or bad.

(Means for Solving the Problems) The present invention measures the power supply status in consumable electrode arc welding by measuring the temperature and/or temperature distribution of the welding wire being fed at the outlet side of the power supply contact tip. , and also monitor the temperature and/or temperature of the power supply contact tip itself.
Alternatively, by measuring and monitoring temperature distribution, it is possible to predict the occurrence of an abnormality during welding and eliminate the cause.

Next, the method of the present invention will be explained in detail based on the drawings.

Figure 2 is a view of the area around the contact tip in Figure 4, where 9 is the contact tip, 11 is the nozzle part that guides the wire, 3 is the cap nut for mounting the contact tip, and 4 is the contact tip. indicates welding wire.

The part indicated by the symbol A indicates the arc, and point E is the arc generating end, and power can be supplied from the contact tip to the wire at point P. Also, during welding, the wire is connected from the power feeding point P to the arc generating end. It is shown that the arc is generated in a state where the arc extends by a length t to the workpiece and by a length L to the workpiece to be welded.

Arc welding in progress.

The most obvious phenomenon in which abnormal power supply to the wire is caused is abnormal heating of the protruding length portion of the welding wire (t in FIG. 2).

This phenomenon occurs because the contact status of the welding wire within the power supply contact tip, that is, the power supply state, changes depending on the mechanism and dimensional accuracy of the contact tip (including initial manufacturing accuracy and wear during use). From P in Figure 2 to the arc generation point (
This occurs due to the length of Figure 2 t) changing to Figure 2 E). That is, when an arc is generated during welding, the area from the power feeding point P to the arc generation point E is heated by the resistance heating effect of the welding current.

Generally, the distance from the tip of the contact tip to the workpiece (
L) in Figure 2 is called the wire protrusion length,
The above-mentioned portion t from the feed point P to the arc generation point E is substantially the same.

As the wire protrusion length increases, the effect of resistance heating increases and the wire melting rate increases.

If it is small, the effect of resistance heating will be small, and naturally the melting rate of the wire will be low. These facts are well known experimentally. Therefore, such a movement of the power feeding point that causes a substantial change in the protrusion length immediately causes a change in the wire melting rate, which is the main cause of a change in the set welding conditions.

In the automatic arc welding machines currently in use, the wire feeding speed is controlled by the arc voltage in this example, as illustrated as a conventional technology, but in reality the arc voltage simply picks up the arc voltage. Since this is impossible, the detection end is taken from between the workpiece 2 and a location as close as possible to the contact tip 9, which is close to the connection point of the ζ welding power source, as illustrated in FIG. is common.

Therefore, in addition to the pure arc voltage, this voltage includes the voltage drop at the protruding length of the wire, etc., and includes the arc current (welding current), arc voltage (welding In order to keep the voltage constant, fluctuations in melting speed and reaction caused by changes in the feeding point are extremely unfavorable.

In the present invention, in order to detect and eliminate this kind of disturbance phenomenon, the surface temperature of the wire being fed is continuously measured and monitored,
Abnormalities can be detected immediately and welding quality can be stabilized.

FIG. 1 is an explanatory diagram of the nature of the welding device, and shows a state in which a temperature measuring device 10 is added to the configuration of the basic welding device shown in FIG. 2 is the object to be welded, 1 is the welding power source, 4 is the welding wire,
Reference numeral 6 indicates a feeding device and a control device for feeding this, and 7.10 indicates a temperature measuring device added in the present invention. In this example, a non-contact type temperature measuring device is illustrated, but a contact type can also be used.

10 is a temperature measuring device using an infrared detection method, for example;
The temperature distribution in the direction of the wire feeding axis can be determined using a thermography device. With this device, it is possible to obtain information regarding the temperature of the welding wire at the outlet of the contact tip and the temperature of the contact tip itself. Infrared detection type temperature measuring devices and thermography devices are
Generally, commercially available ones are sufficient. That is, this makes it possible to grasp the magnitude of the resistance heating effect of the wire, which is one of the factors that change the wire melting rate, and to use this as a means of solving problems in keeping the welding conditions constant.

(Function of the invention) With the device configuration according to the method of the present invention shown in FIG. 1, when bath welding is performed, the temperature measuring device 10 measures the temperature of the contact tip and the welding wire 3 at the outlet of the contact tip. Monitor its changes. FIG. 3 shows an enlarged view of the inside of the contact tip, where current from the power source is transferred to the wire through the sliding contact point between the tip and the wire. The tip is usually straight, and its inner diameter is larger than the inner diameter of the wire.

Therefore, the point at which the wire and the chip come into contact changes depending on various conditions. A point PI or Q in the figure indicates that this contact point changes depending on the situation, 9 indicates a contact tip, and 4 indicates a welding wire. Figure 5 explains how the temperature of the wire sent out from the contact tip changes. In the figure, the horizontal axis shows the temperature and the vertical axis shows the distance from the outlet to the arc generating end E. Curve I
This figure shows the temperature distribution in two states in which the positions of the power feeding points and (1) are different.

Curve I shows the temperature distribution when the feeding point is at the tip position within the contact tip (point P in Figure 2, and on the point P side in Figure 3), and curve ■ shows the temperature distribution when the feeding point is under some conditions. Move and 3rd
Moving to point Q illustrated in the figure, the substantial wire protrusion length t becomes larger, indicating that the temperature rise due to resistance heating becomes higher.

In FIG. 5, the temperature at the contact tip exit, which was initially To, becomes Tl [-1, and at any point on the wire 4 during feeding, the temperature that was initially Tl-2 changes to , T
In other words, by monitoring the temperature of the wire at the outlet of the contact tip, changes in the power supply state can be accurately determined.

(Effect of the invention) According to the method of the present invention, the following effects can be expected.

■ By monitoring the temperature of the contact tip, it is possible to know whether the device setup at the power supply is good or not. With the configuration of the tip portion illustrated in FIG. 2, it is possible to accurately determine whether overheating is due to poor tightening of the tip, or whether the tip is at the end of its lifespan, ie, when it is time to replace it.

■ By monitoring the temperature of the welding wire at the contact tip, it is possible to continuously and accurately grasp the degree of heating effect due to resistance heat generation at the wire protrusion. That is, in the power feeding system with the illustrated structure, changes in the tip hole diameter during use - an increase in the inner diameter of the stone due to wear, a change in the power feeding point due to a change in the wire straightening condition, a replaced contact tip, a wire hole diameter or a wire diameter, Or, it is possible to accurately monitor the suitability or nonconformity of both of them, and it is possible to take inspection and corrective actions before a definitive welding abnormality occurs.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the configuration of a welding device according to the present invention, Fig. 2 is an enlarged sectional view of the area around the contact tip, Fig. 3 is an enlarged sectional view of the contact tip, and Fig. 4 is a conventional general welding method. FIG. 5, which is a diagram showing the configuration of the device, is an explanatory diagram showing changes in the temperature of the wire according to the feed ratio from the contact tip. 1... Welding power source 2... Work to be welded 3...
Cap nut 4... Welding wire 5... Flux hopper 6... Wire feeding motor 7... Motor control box 8... Welding cable 9,... Contact tip 10... Temperature measuring device 11...Guide nozzle

Claims (1)

[Claims] By measuring and monitoring the temperature and/or temperature distribution of the welding wire being fed at the power supply contact tip and/or the outlet side of the contact tip in consumable electrode arc welding, it is possible to determine whether the conditions during welding are good or not. An arc welding method characterized by determining.