JPS6128429B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a single-sided automatic welding method that always provides a predetermined surface bead shape regardless of variations in the groove condition. Single-sided automatic welding is often used for welding large steel plates such as shipbuilding materials because sufficient penetration can be obtained by welding from one side without reversing the material to be welded, and a good bead can be formed. ing. By the way, in order to form a good bead, the shape of the groove of the material to be welded must always be constant, but because the end face of the material to be welded is thermally deformed, for example, when cutting it, the shape of the groove is not necessarily constant. As a result, there was a problem in that the bead shape after welding was irregular. The present inventors have conducted extensive research in order to solve the above-mentioned problems and develop a single-sided automatic welding method that can always form a good bead with a uniform height even when the groove condition fluctuates. . The present inventors previously provided a light amount detector consisting of a plurality of photoelectric light-receiving elements on the side of the backing metal that comes into contact with the backing material in single-sided automatic welding, and used the photoelectric light-receiving elements to detect the welding material during welding. A method of receiving arc light penetrating the back surface and radiant light from the red-hot welding part, converting it into an electrical signal, and controlling the movement speed and horizontal position of the backing metal, as well as current, voltage, welding speed, etc. We have developed a method to control the welding parameters and control the back bead shape and arc drilling force by controlling heat input. Fig. 1 is a longitudinal sectional view of a single-sided automatic welding part showing an example of the above method, and Fig. 2 is a plan view of the backing metal.
is the steel plate that is the material to be welded, 2 is the backing metal, 3 is the steel plate 1
A translucent backing material such as glass fiber tape is interposed between the backing metal 2 and the backing metal 2. 4 is a welding wire, and the arrow indicates the welding direction. A light amount detector consisting of a light receiving element 5 such as a photodiode, phototransistor, CDS, etc. is embedded in the side of the backing metal 2 that is in contact with the backing material 3.
As shown in FIG. 2, four light-receiving elements 5 are embedded in the backing metal 2 at predetermined intervals on the right and left sides of the front and rear sides of the welding wire, respectively, from just below the welding wire in the direction of welding progress. The moving speed and horizontal position of the backing metal 2 are controlled so that the center of the arc generation position 6 is located near the center of the four light receiving elements 5. The present inventors have found that by controlling the welding current so that the amount of light received by the one or more light receiving elements 5 described above is constant, the back bead radius can be made constant regardless of the groove condition. It was found that there is a proportional relationship between the magnitude of this welding current and the height of the surface bead formed within the groove. Figure 7 shows
This is a graph showing the relationship between the amount of arc light (voltage value) received by the one or more light-receiving elements 5 and the back bead width when welding is performed by changing the welding current over a wide range in various groove conditions. be. As shown in the drawings, it was found that there was a good correlation between the amount of arc light (voltage value) and the back bead width, regardless of the groove condition. Therefore, from FIG. 7, it is clear that if the welding current is controlled so that the amount of arc light (voltage value) is constant, the back bead width can be made constant regardless of the groove condition. Figure 8 shows the welding current when the welding current is controlled so that the amount of arc light is constant in various groove conditions.
5 is a graph showing the relationship between the welding current, nugget height, and back bead width. As shown in the drawing,
It was found that if the welding current is controlled so that the amount of arc light is constant, the back bead width will always be constant and there is a proportional relationship between it and the nugget height. The nugget height is the sum of the plate thickness, back bead height, and front bead height, and since the plate thickness and back bead height are given as constant values before welding, from Fig. 8, it can be determined that the welding current is It is clear that there is a proportional relationship between the height of the surface bead formed within the groove. In other words, even if the groove condition changes, if welding is performed so that the welding current is controlled to a predetermined current value depending on the thickness of the material to be welded, a surface bead with a constant height can be obtained. become. This invention was made based on the above knowledge, and includes a light amount detector that detects the amount of arc light and radiation light of the welded part on the back side of the welded material, and In an arc welding method in which welding is performed while a welding machine and the light amount detector are synchronously moved along the welding part, either or both of the arc light and the radiant light that have penetrated the back surface of the welded material are detected by the light amount detection. the welding current of the welding electrode is controlled based on the detected light amount, the controlled welding current value is detected, and the welding current value is set at a predetermined height. To match the set reference current value to form a bead,
When there is one welding electrode, at least one of the welding speed and the wire protrusion length of the welding electrode is controlled, and when there are multiple welding electrodes, the welding speed, the wire protrusion length of the welding electrode, and the welding current are controlled. This method is characterized in that at least one of the current values of the welding electrodes that are not used is controlled. Next, an embodiment in which the present invention is applied to a single-sided welding method using two-electrode submerged arc welding will be described based on the block diagram of FIG. In the drawing, 4 is the welding wire of the leading electrode;
4' is a welding wire of a trailing electrode, 13 is a leading electrode nozzle, 13' is a trailing electrode nozzle, and the arrow indicates the welding direction. 11 and 11' are welding power sources whose one ends are connected to the steel plate 1, the leading electrode nozzle 13 is connected to the welding power source 11 by a conductor 15, and the trailing electrode nozzle 13' is connected to the welding power source 11' by a conductor 15', respectively. has been done. Leading electrode nozzle 13 and welding power source 1
A welding current detector 12 is provided in the middle of the conductor 15 connecting the two. The leading electrode nozzle 13 can be moved vertically by an electrode nozzle driving motor 14, and the trailing electrode nozzle 13' can be moved vertically by an electrode nozzle driving motor 14', thereby controlling the protruding length of welding wires 4, 4'. can be controlled. 2 is the backing money, 5
3 is a light-transmitting backing material, and 3 is a light-transmitting backing material. In this invention, the 4
The welding wire 4 of the leading electrode is
The amount of arc light emitted from the welding part and the amount of radiant light from the red-hot welding part are detected, and the detected amount of radiant light is photoelectrically converted into a voltage value and added by adder 7. It is compared with a voltage value for forming a predetermined back bead width set in advance, and a difference voltage is obtained. Next, this differential voltage is input to the welding current controller 10, and the output of the welding power source 11, that is, the welding current of the welding wire 4 of the leading electrode is controlled so that the differential voltage becomes zero. In this way, a back bead of a predetermined shape is formed. Next, the welding current value of the welding wire 4 of the preceding electrode controlled as described above is detected by the welding current detector 12. The detected current value detected by the welding current detector 12 is compared with the set current value set by the front bead height setting device 12' by a comparator 16, as shown in the block diagram of FIG. The voltage difference is output as a voltage difference, and the voltage difference is controlled to be zero by one or more of the following means. (1) The welding speed controller 17 controls the drive of the welding cart drive motor 18, that is, the welding speed. (2) The trailing current controller 19 controls the welding current from the welding electrode 11' of the trailing electrode nozzle to the trailing electrode. (3) The leading electrode wire projection length controller 20 controls the driving of the leading electrode nozzle drive motor 14, that is, the leading electrode welding wire projection length. (4) The trailing electrode wire protrusion length controller 20' drives the trailing electrode nozzle drive motor 14', that is, controls the protrusion length of the welding wire of the trailing electrode. The above control is performed as follows. That is, if the detected current value detected by the welding current detector 12 is smaller than the set current value of the front bead height setting device 12', this means that the amount of weld metal deposited on the front bead is insufficient. Decrease the welding speed or
Increase the current value of the trailing electrode or the welding wire protrusion length of each electrode. On the other hand, if the detected current value is large compared to the set current and others, the amount of weld metal deposited on the front bead is excessive, so either increase the welding speed or
Reduce the current value of the trailing electrode or the welding wire protrusion length of each electrode. If the set current value and the detected current value are the same, the amount of deposited metal on the front bead is appropriate, so welding can be carried out by keeping the welding speed, trailing electrode current value, and wire protrusion length at their current values. Let's do it. Next, specific examples of the present invention will be described. A steel plate with a thickness of 16 mm was welded with a V-groove shape of 50° by two-electrode submerged arc welding under the following conditions. (1) Wire diameter 4.8mmφ x 2 (2) Leading electrode voltage 36V (3) Trailing electrode voltage 42V Set the back bead width to 15 to 16 using the back bead width setting device 8.
mm, and the current value of the leading electrode was controlled. At the same time, the controlled current value is detected, and the welding speed and trailing electrode are adjusted so that the current value becomes 820A, which is the current value that can form the optimal surface bead when welding a steel plate with a thickness of 16 mm. The current value was controlled. Table 1 shows the bead shape when the welding speed and the current value of the trailing electrode are controlled by the gap in the groove according to the method of the present invention, along with a conventional example in which such control is not performed. ing.

[Table] As is clear from Table 1 above, as a result of controlling the welding speed and trailing electrode current according to the dimensions of the groove gap using the method of the present invention, the results are compared with the conventional example in which such control is not performed. However, a uniform front bead shape was obtained, and the back bead shape was also uniform. Figure 5 shows 600A, 700A using 4.0mmφ wire at 32V arc voltage and 35cm/min speed.
This graph shows the wire melting speed when welding with a welding current of 800A and varying wire protrusion lengths.The wire melting speed increases as the wire protrusion length increases. Therefore, it can be seen that the desired surface bead shape can be obtained by changing the wire protrusion length according to the change in the welding current of the preceding electrode according to the method of the present invention. Although the above-described embodiments have been described with reference to two welding electrodes, the same method can be used even with one welding electrode. In addition, when there is only one welding electrode, the welding speed and the protrusion length of the welding electrode are used as control factors, and control is performed using at least one of them. In addition, when there are a plurality of welding electrodes, at least one of the welding speed, the wire protrusion length of the welding electrode, and the current value of the welding electrode whose welding current is not controlled is controlled. Note that normally, the welding current control is performed for the preceding electrode based on the above-mentioned light amount. This invention is effective not only for the single-sided arc welding method that forms a back bead, but also for the arc welding method that does not form a back bead at the welded portion of the steel plates 1 and 1, as shown in Fig. 6 A and B. Moreover, it can be widely applied not only to submerged arc welding but also to gas shielded arc welding using consumable electrodes and other various types of welding. As described above, according to the method of the present invention, a constant back bead shape can be obtained in single-sided arc welding regardless of variations in the groove condition, and at the same time,
The height of the surface bead can be automatically kept constant, and in arc welding that does not form a uranami bead, a constant penetration depth and constant bead height can be obtained regardless of fluctuations in the groove condition. etc., bring about excellent industrial effects.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a single-sided automatic welding part showing control means using a photoelectric light receiving element, Fig. 2 is a plan view of the backing metal, and Fig. 3 shows a single-sided welding method using two-electrode submerged arc welding. FIG. 4 is a block diagram of the control of the amount of welded metal on the front bead according to the present invention, FIG. 5 is a diagram showing the relationship between wire protrusion length and wire melting rate, and FIG.
The figure is a longitudinal cross-sectional view of a welded part where no back bead is formed.
FIG. 7 is a graph showing the relationship between the amount of arc light and the back bead width, and FIG. 8 is a graph showing the relationship between the welding current, the back bead width, and the nugget height. In the drawings, 1... Steel plate, 2... Backing metal, 3... Backing material,
4, 4'... Welding wire, 5... Light receiving element, 6...
...Arc generation position, 6'...Red hot part of welding, 7...
Adder, 8... Back bead width setting device, 9... Comparator, 10... Welding current controller, 11, 11'...
Welding power source, 12... Welding current detector, 12'...
Front bead height setting device, 13, 13'... Electrode nozzle, 14, 14'... Electrode nozzle driving motor,
15, 15'... conductor, 16... comparator, 17...
...Welding speed controller, 18... Welding cart drive motor, 19... Trailing current controller, 20, 20'...
Wire protrusion length controller.

Claims (1)

[Scope of Claims] 1. A light amount detector for detecting the amount of arc light and radiation light of the welding part is arranged on the back side of the material to be welded, and the welding machine and the light amount detector are arranged along the groove of the material to be welded. In the arc welding method in which welding is carried out while moving the welding device in synchronization with the workpiece, either or both of the arc light and the radiation light that penetrate the back surface of the welded material is received by the light amount detector, and the amount of light is detected. The welding current value is controlled so that the difference becomes zero by comparing the light amount set in advance with a reference light amount that can form the back bead width, and this controlled welding current value is detected. so that the welding current value matches a set reference current value that can form a surface bead of a predetermined height,
When there is one welding electrode, at least one of the welding speed and the wire protrusion length of the welding electrode is controlled, and when there are a plurality of welding electrodes, the welding speed, the wire protrusion length of the welding electrode, and an arc welding method, characterized in that at least one of the current values of the welding electrodes in which the welding current is not controlled is controlled. 2. The arc welding method according to claim 1, characterized in that the amount of arc light that penetrates the back surface of the material to be welded is mainly detected and controlled. 3. The arc welding method according to claim 1, characterized in that the amount of radiation light from a molten pool of the material to be welded is mainly detected and controlled. 4. The arc welding method according to claim 1, characterized in that the amount of radiation light from a weld bead of the material to be welded is mainly detected and controlled.