JPH05293645A - Method for deciding welding speed in multilayer filling arc welding - Google Patents

Abstract

PURPOSE:To provide an excellent weld joint free from weld defects by estimating a groove width from the average welding speed of the rear bead of a 1st layer and determining the optimum welding speed after a corresponding 2nd layer from the relation to the optimum welding speed obtained in advance. CONSTITUTION:When the 1st layer is welded in the welding after the 2nd layer on in the multilayer filling arc welding, the rear bead is brought under control under control of the welding speed and the groove width is estimated from the average welding speed of that time. The optimum welding speed after the 2nd layer corresponding to the estimated groove width is decided from the relation between the groove width obtained in advance and the optimum welding speed. In such a way, the excellent weld joint free from weld defects can be obtained and the rear bead in a welding time of the 1st layer can be performed under simple control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the optimum welding speed for the second and subsequent layers in multi-layer arc welding.

[0002]

2. Description of the Related Art In the case of multi-layer arc welding using an automatic welding machine, for example, in the case of automatically welding butt joints such as rails and pressure vessels, the narrow groove must be welded in multiple layers. The groove width is usually set to a constant width, but it often changes depending on the set state of the base material, thermal deformation, groove accuracy, and the like. In the case of rails, the change in groove width is about 12 mm to 18 mm. Therefore, in the conventional method, the groove width is measured in advance, and the welding conditions such as the welding speed are determined from the measurement result of the groove width. Further, since it is necessary to form the back bead satisfactorily during the initial layer welding, it is necessary to strictly control the welding speed during the welding conditions. An example of such a back bead control method is disclosed in Japanese Patent Laid-Open No. 64-15278.

The back bead control method disclosed in the above publication is shown in FIGS.
As shown in 0, the voltage Vd generated between the conductive material 6 attached to the insulating backing material 4 and the base materials 1 and 2 is detected during welding, and this Vd is a preset reference value. The welding speed is controlled so as to match V0. That is, when Vd> V0, the welding speed is reduced and Vd <V0
If, increase the welding speed. As a result, the welding speed is increased when the groove width is narrowed, and the welding speed is decreased when the groove width is increased, so that the back bead can be favorably formed with substantially the same bead thickness. In the figure, 3 is a narrow groove, 7 is a voltmeter, 10 is an electrode wire, 11 is an arc, 12 is a welding bead of the first layer, 13 is a molten pool, and 14 is a back bead.

Further, since it is not necessary to strictly control the welding speed in the second layer and thereafter, welding is performed at a welding speed higher than that in the first layer. Since the groove width G is measured first, the welding speed for the second and subsequent layers is set according to the first groove width without measuring the groove width for the second and subsequent layers. In this way, when welding the first layer, the welding speed is controlled by the back bead control method as described above in response to changes in the groove width. On the other hand, when welding the second and subsequent layers, it is necessary to control the bead thickness of each layer in the same way. Therefore, if the groove width is narrow, the welding speed is increased, and if the groove width is wide, the welding speed is increased. I have to be late.

[0005]

However, when determining the welding speed, the groove width at the time of the first measurement and the actual groove width at the time of welding the second and subsequent layers may be slightly different from each other. When the groove width is regarded as invariable and welding is performed at a constant welding speed, welding defects as shown in FIG. 11 occur. That is, when the groove width is narrow and the welding speed is slower than the predetermined speed, the bead W2 of the second layer becomes thick due to excessive melting as shown in FIG. It becomes a so-called angle shape, and the insufficient penetration portion 16 is generated between the bead W1 of the first layer. On the contrary, when the groove width is wide and the welding speed is faster than the predetermined speed,
As shown in FIG. 1 (c), the bead W2 of the second layer becomes thin due to insufficient melting, and the bead cross section becomes dish-shaped to form the undercut portion 17. On the other hand, when the welding speed is appropriate with respect to the groove width, the bead W2 of the second layer is also formed favorably with substantially the same thickness as shown in FIG. 11 (b).

Further, it is extremely inconvenient and inefficient to measure the groove width each time each layer is welded and set the welding speed based on the measurement result.

Therefore, the object of the present invention is to prevent the occurrence of the above-mentioned welding defects in the welding of the second and subsequent layers in the multi-layer arc welding, without measuring the groove width at all. The purpose is to obtain a method for determining the optimum welding speed for the second and subsequent layers by utilizing the controlled welding speed during layer welding.

[0008]

In order to achieve the above object, the method for determining the welding speed in the multi-layer arc welding according to the present invention is such that during the first layer welding, the welding speed is controlled as described above and the back bead is controlled. Is controlled, and the groove width is estimated by calculating the average welding speed at that time.
The optimum welding speed after the second layer was decided. The relationship between the groove width and the optimum welding speed is obtained in advance. The average welding speed at the time of the first layer welding may be calculated by storing the welding speed in the memory of the control device for each welding section of a certain length or for each welding time and smoothing the welding speed. If the groove width is constant over the entire weld length, the average value of the welding speeds of three or more points may be used, but if the groove width changes, for example, in a taper shape, welding of a certain length of welding section or welding time The average speed is applied for each weld zone. Then, the groove width of the welding section is estimated from the average welding speed at the time of the first layer welding obtained as described above, and the optimum welding speed for the second and subsequent layers is determined by the relationship between the groove width and the optimum welding speed obtained in advance. Therefore, the welding width is set according to the groove width estimated for each welding section.

Although the method disclosed in Japanese Patent Laid-Open No. 64-15278 can be adopted as the method for controlling the back bead at the time of welding the first layer, the present invention is a simpler method with better controllability. As a known high-speed rotating arc welding method for rotating the arc at a high speed, the integrated value difference Sd (Sd = Scf-Scr) of the arc voltage or welding current at the arc rotation positions Cf point and Cr point before and after the welding proceeding direction is used. The back bead control method that controls the welding speed during the first layer welding is adopted so that the value of s matches the reference value.

[0010]

[Function] When welding the first layer, the back bead is controlled by controlling the welding speed.
If you calculate the average welding speed from the controlled welding speed,
The groove width of the welding section corresponding to the average welding speed can be estimated. Therefore, it is possible to automatically determine the optimum welding speed for the second and subsequent layers from the estimated groove width without measuring the groove width in advance. Since the second and subsequent layers are welded at the optimum welding speed determined in this way, a narrower groove width will result in a faster welding speed, and a wider groove width will result in a slower welding speed in the welding section. Since each of the layers is welded, the multi-layer welding can be satisfactorily performed without causing welding defects such as insufficient penetration and undercut with the bead thicknesses of the respective layers being substantially the same. Since the groove width changes in the third and subsequent layers are almost the same as in the first layer, the first layer may be used as a reference.

Further, since the high-speed rotating arc welding is performed by rotating the arc, a difference in the arc lengths between the Cf point and the Cr point is caused as the arc rotates and the welding speed changes. The arc voltage or welding current at the points Cf and Cr changes. So Cf
If the welding speed is controlled so that the arc voltage or welding current at the points Cr and Cr is integrated and the difference Sd between the integrated values Scf and Scr matches the reference value S0, the first layer can be used with a general backing material. You can control the back bead of. The welding speed controlled by this back bead control method can be used when determining the optimum welding speed for the second and subsequent layers.

[0012]

【Example】

(1) Welding of the first layer First, the welding method of the first layer in the multilayer arc welding of the present invention will be described. Welding of the first layer is performed using the back bead control method as described above. This back bead control method may be the method disclosed in Japanese Patent Laid-Open No. 64-15278, but here, as a simpler method with better controllability,
A back bead control method by high-speed rotating arc welding will be described.

FIG. 1 is an explanatory view showing a back bead control method at the time of first layer welding, FIG. 2 is a front sectional view of a first layer welded portion, and FIG. 3 is a plan view thereof. 1 to 3, 1 is a base material, 3 is a narrow groove, 4 is a backing material, 5 is a groove for forming a back bead formed in the backing material 10, 10 is an electrode wire, and 11 is a rotating member. Ark,
12 is a weld bead forming the first layer bead W1, 13 is a weld pool, 14 is a back bead, 20 is an electrode nozzle, 21 is an eccentric electrode tip for obtaining the rotating arc 11, 22 is a motor for rotating the electrode nozzle 20. , 23 is a gear mechanism, 24 is a feed roller for the electrode wire 10, 25 is an encoder for detecting the arc rotation position (Cf, R, Cr, L),
26 is a welding power source, 27 is a voltmeter for detecting an arc voltage, and 28 is an ammeter for detecting a welding current.

In the above structure, the electrode nozzle 20 is rotated by the motor 22 via the gear mechanism 23 to rotate the arc 11 with a predetermined radius. As a method of rotating the arc, a method using an eccentric electrode tip 21 as shown in FIG. 1 (Japanese Patent Publication No. 63-39346) is used.
Alternatively, there is a method of precessing the electrode nozzle 20 with the upper part as a fulcrum (Japanese Patent Laid-Open No. 62-106484), but any method may be used. The rotation speed of the arc 11 is 10 Hz
That is all. Usually, it is about 50 Hz to 100 Hz. The rotating diameter of the arc 11 can be changed according to the groove width even during welding by using a double eccentric ring and changing the amount of eccentricity (Japanese Patent Application No. 2-284478).
issue). As the backing material 4, for example, an insulating material such as ceramics, a combination of a backing tape and a backing metal such as glass tape, a combination of a flux and a backing metal, a solid flux, or the like is used. It may be one used in the backing method. Such an ordinary backing material 4 is adhered so as to cover the lower part of the narrow groove 3, for example. Furthermore, the arc voltage is detected by the voltmeter 27 or the welding current is detected by the ammeter 28 for each revolution of the arc. These detected waveforms are used in the back bead control method described later.

In this back bead control method, the back bead 14 is controlled by controlling the welding speed v according to the groove width G while rotating the arc 11 at high speed during the first layer welding.
That is, if the groove width G is narrowed, the welding speed v is increased,
If the groove width G becomes narrower, the welding speed v is slowed down, and the first layer is welded with a bead thickness that is almost the same for the overall welding length. The welding speed v is determined from the waveform of the arc voltage or the welding current detected for each rotation of the arc as described above, as shown in FIG. The areas Scf and Scr of θ are integrated, the difference Sd (Sd = Scf−Scr) between these integrated values is compared with the reference value S0, and control is performed so that they match. That is, Sd
If> S0, reduce the welding speed. If Sd <S0, increase welding speed. The back bead control method based on this integrated value difference Sd is
This is because the arc voltage difference or the welding current difference is generated due to the difference between the arc length at the point Cf and the arc length at the point Cr, that is, the height difference from the surface of the molten pool 13. During the initial layer welding, the welding speed when the back bead is controlled as described above is stored in a memory of a controller (not shown) for each welding section or welding time.

(2) Welding of Second Layer and Later Next, before welding the second layer, the average welding speed at the time of first layer welding is calculated, and the groove width is estimated from this average welding speed.
FIG. 5A is a graph showing the relationship between the groove width and the average welding speed at the time of first layer welding in the case of a rail. Now, the average welding speed of a certain welding section when calculated by the procedure is 7.5 cm /
If it is min, the groove width of the section is about 14.2m according to the procedure.
It is estimated to be m. Therefore, when welding the second layer, as shown in FIG. 5 (b), as shown in FIG. 5 (b), the above 14.
If the intersection between the groove width estimated to be 2 mm and the speed curve is obtained and the optimum welding speed corresponding to the intersection is obtained by the procedure, the optimum welding speed in that section is determined to be 20 cm / min. Therefore, the second layer in the section is welded at a speed of 20 cm / min. If the average welding speed during initial layer welding changes depending on the welding section, the estimated groove width also changes.
The optimum welding speed of the layer is naturally changed in that section. The optimum welding speed for the third and subsequent layers may be the same as that for the second layer. This is because the change in groove width can be considered to be almost the same as that in the first layer. Therefore, the groove width can be based on the first layer. In this manner, the optimum welding speed for the second and subsequent layers can be automatically determined and multilayer welding can be performed up to the final layer without measuring the groove width at all.

FIG. 6 shows waveforms of Sd when the integrated value difference Sd of the arc voltage is set to 1 V and the controlled welding speed during the first layer welding. In this case, there is a disturbance in the welding speed immediately after the start of welding and immediately before the end of welding.This is due to the influence of the tab plates at both ends of the welding length, and the welding length is controlled at almost the same welding speed. .. Therefore, in this example, the average welding speed is about 6 cm / min, and the groove width is estimated to be about 18 mm which is almost constant from FIG. 5 (a). Therefore, the optimum welding speed for the second and subsequent layers is shown in FIG.
From (b), the welding speed should be determined to be 15 cm / min.

FIG. 7 is a schematic view of a cross section of a rail joint welded by this method. It was confirmed that the beads W1, W2, W3, ... Of each layer have almost the same thickness and are well formed without welding defects. ing.

[0019]

As described above, according to the present invention, in multi-layer arc welding, the optimum welding speed for the second and subsequent layers is automatically determined without measuring the groove width at all. Can be efficiently dealt with, and a good welded joint having no welding defects can be obtained. Further, since the back bead control during the first layer welding is simplified and the controllability is improved, the groove width estimation accuracy is improved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a back bead control method at the time of first layer welding in the present invention.

FIG. 2 is a front cross-sectional view of a first layer welded portion.

FIG. 3 is a plan view of a first layer welded portion.

FIG. 4 is an explanatory diagram showing integration regions at Cf points and Cr points before and after the arc rotation position.

FIG. 5 is a graph showing the relationship between the groove width and the average welding speed during the first layer welding, and the optimum welding speed and groove width for the second and subsequent layers.

FIG. 6 is a waveform diagram of the arc voltage difference Sd during the first layer welding and the controlled welding speed.

FIG. 7 is a schematic diagram of a cross section of a rail joint welded according to the present invention.

FIG. 8 is an explanatory diagram showing a conventional back bead control method at the time of conventional first layer welding.

FIG. 9 is a front sectional view of a conventional first layer welded portion.

FIG. 10 is a plan view of a conventional first layer welded portion.

FIG. 11 is a schematic cross-sectional view showing how welding defects are generated depending on whether the welding speed is suitable or not for the groove width.

[Explanation of symbols]

 1, 2 base material 3 narrow groove 4 backing material 10 electrode wire 11 arc 12 welding bead 13 molten pool 14 back bead 20 electrode nozzle 21 electrode tip 22 motor 23 gear mechanism 24 feeding roller 25 encoder 26 welding power source 27 voltmeter 28 ammeter

Claims (2)

[Claims] 1. In multi-layer arc welding in which a back bead is formed while controlling the welding speed during the first layer welding, and then the second and subsequent layers are welded, the average welding speed during the first layer welding is determined, and the average welding is performed. The groove width is estimated from the speed, and the optimum welding speed for the second and subsequent layers corresponding to the estimated groove width is determined from the relationship between the groove width and the optimum welding speed that has been obtained in advance. Method for determining welding speed in multi-layer arc welding. 2. An integrated value difference Sd (Sd = Scf-Sc) of arc voltage or welding current at arc rotation positions (Cf, Cr) before and after the welding advancing direction using a high-speed rotation arc welding method.
2. The method for determining the welding speed in multi-layer arc welding according to claim 1, wherein the welding speed during the first layer welding is controlled so that r) matches the reference value.