JP2991854B2 - Single side welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-side welding method in which a backing material is applied to the back surface of a groove and welding is performed from the front surface.

[0002]

2. Description of the Related Art Single-sided welding, in which a backing material is applied to the back surface of a groove and welding is performed from the front surface to form a back seam, is widely used for on-site welding in which the base material cannot be reversed and plate-joining welding of large steel plates. I have.

[0003] In this single-sided welding, when the width of the groove bottom is uniform over the entire length of the welding line, a good backwash can be formed relatively easily. However, in practice, it is very difficult to keep the groove bottom width constant over the entire length of the welding line due to factors such as processing accuracy and assembly accuracy. When performing single-sided welding of a groove with such a change in the groove bottom width, the operator must constantly monitor the situation and adjust the welding speed, welding current, etc., which requires enormous labor and labor. In addition, there is a problem that the finish of the Uranami bead varies greatly depending on the skill and experience of the worker. Various single-sided welding methods and apparatuses have been proposed as techniques for solving these problems. For example, JP
In Japanese Patent Application Laid-Open No. 1-333769, a change in welding current during welding is converted into a digital signal and measured, and this is compared with a preset threshold value to automatically control the welding speed so that the welding current becomes appropriate. A method has been proposed.

Japanese Patent Application Laid-Open No. 63-80970 discloses that a detected welding current is compared with a preset threshold value, and one of two preset welding speeds is selected according to the comparison result. A welding method has been proposed.

[0005] The basic relationship between the welding current and welding speed used in these techniques and the formation of a backside bead will be described. First, the relationship between the formation of a backside bead and the welding speed is schematically shown in FIG. Become like FIG. 5A shows a case where the welding speed is appropriate, and the arc 24 does not precede the molten pool 25 and a good backwash is formed without delay. FIG. 5B shows a case where the welding speed is higher than the appropriate value, in which the arc 24 precedes the molten pool 25, and not only an excessive backwash is formed, but in the worst case, the backing material is used. And the welding wire 15 and the base material 1 cannot be electrically connected, making welding impossible. FIG. 5C shows a case in which the welding speed is lower than the appropriate value. In this case, the molten pool 25 precedes the arc 24, and a sufficient backwash is not formed.

Here, focusing on the distance (hereinafter referred to as EXT) from the tip of the tip to the arc occurrence point of the tip of the wire in each of FIGS. 5 (a), 5 (b) and 5 (c),
The EXT of FIG. 5B is longer than the EXT of FIG. 5A, and the EXT of FIG. 5C is shorter.

[0007] When welding is performed by feeding a wire at a constant speed using a power source having a DC constant voltage characteristic as a welding power source, the welding current becomes lower when the EXT becomes longer, and the welding current becomes higher when the EXT becomes shorter. The change can be measured as a change in welding current. In the conventional method described in Japanese Patent Application Laid-Open No. 63-80970, a change in EXT is detected by a change in welding current I, and a welding current Is (hereinafter referred to as threshold I) in EXT shown in FIG.
s), and the welding speed is selected by judging the state of formation of the backwash. However, at this time, the distance H between the tip and the base material must be constant. In the conventional method, the threshold value Is is constant even if the groove bottom width G changes. Here, the tip / base metal distance H refers to the distance from the tip of the tip to the bottom surface of the base material.

[0008]

When a groove having a changing groove bottom width G is welded on one side by the conventional method, when the groove bottom width G becomes narrower, no Uranami bead is formed, and the groove bottom width G becomes smaller. When the width became wide, the arc 24 was cut off and welding was often interrupted. When the groove bottom width G is reduced, the welding pool 25 precedes the arc 24 (FIG. 5 (c)), so that the groove bottom is not sufficiently melted and the back bead shape is deteriorated. When the groove bottom width G is increased, the arc 24 precedes the molten pool 25 [(b) of FIG. 5], so that conduction between the welding wire 15 and the base material 1 is not established, and the arc 24 is cut off. Therefore, it was found that the conventional method does not control the welding speed to an appropriate value according to the change in the groove bottom width G.

It is an object of the present invention to provide a single-side welding method for stably forming a good Uranami bead even if the groove bottom width G changes during welding.

[0010]

The gist of the present invention is that a backing material is applied to the back surface of a groove, a welding current detected during welding is compared with a threshold value, and a welding speed is determined when the welding current is higher than the threshold value. The high
In a single-sided welding method in which welding is performed while lowering the welding speed when the threshold value is lower than the threshold value , if the width is wide in accordance with the groove bottom width detected or pre-input during welding,
High or long threshold or tip / base material distance
If it is narrow, the threshold value or the tip / base material distance is low.
This is a single-sided welding method characterized in that welding is performed with a shorter or shorter length .

[0011]

The present invention will be described below in detail with reference to the drawings, including the operation thereof. When welding is performed by the above-described conventional method, as described above, when the groove bottom width G becomes narrow, the welding pool 25 precedes the arc 24 and no backwash occurs, as described above. Occurs when the value is significantly lower than the value. Also, when the groove bottom width G is increased, the arc 24 precedes the welding pool 25 and the welding wire 15 and the base metal 1 cannot be conducted, and the arc 24 is cut off. This is because the welding speed is significantly higher than an appropriate value. Happens. FIG. 2 shows the relationship between the groove bottom width G and the welding speed v when welding is performed by the conventional method in which the threshold value Is is constant with respect to the groove bottom width G.

On the other hand, the inventors of the present invention have determined by experiment the relationship between the groove bottom width G and the welding speed at which a good Uranami bead is formed. As shown in FIG. The welding result for the welding speed v was confirmed. The welding current with respect to the groove bottom width G when the approximate center curve (appropriate reference line 1) shown in FIG. 3 was obtained was as shown in FIG.

By comparing the relationship between the groove bottom width G and the welding speed v by the conventional welding method (FIG. 2) and the relationship between the groove bottom width G and the welding speed v in the proper range shown in FIG. In the method (FIG. 3), it can be seen that when the groove bottom width G is reduced, the welding speed is shifted to a lower side than the appropriate range, and when the groove bottom width G is increased, the welding speed is shifted to a higher side than the appropriate range. The conditions other than the groove bottom width, welding current and welding speed at the time of performing the welding shown in FIG. 2, FIG. 3 and FIG. 4A were as follows.

Wire feeding speed: 5.6 m / min Welding voltage: 29 V Shielding gas: CO ₂ shielding scum flow rate: 25 liter / min Oscillating width: As shown in Table 1 Oscillating frequency: 60 times / min Distance between chip / base metal : 35 mm Welding wire: Solid wire Outer diameter 1.6
mm (JIS Z3312 YGW11) Base material: Mild steel (JIS G3106)
SM400B plate thickness 25mm) Groove shape: 40 ° V-shaped groove.

FIG. 3 shows the proper welding speed at each groove bottom width, and FIG. 4A shows the welding current when welding is performed at the proper welding speed at each groove bottom width.

From the relationship between the welding speed v in an appropriate range and the groove bottom width G shown in FIG. 3 and the relationship between the welding current and the groove bottom width G shown in FIG. 4A, the welding at each groove bottom width is performed. If the current [(a) in FIG. 4] is a threshold value Is assigned to the groove bottom width G, the welding speed v is controlled so that the welding current matches the threshold value Is. v
Is automatically determined to be appropriate for the groove bottom width G.
That is, when the relationship between the welding current to obtain an appropriate welding result and the welding speed v is obtained from the curve (appropriate reference line 1) substantially at the center of the appropriate range shown in FIG. 3 and the curve shown in FIG. 4
The appropriate reference line 2 shown in FIG. Therefore, the groove bottom width G is always grasped by an arc sensor or the like, and when the groove bottom width G changes, the current value corresponding to the groove bottom width G in the relationship of FIG. Is, and FIG.
Assuming that the welding speed v corresponds to this value Is in the relationship shown in FIG. 3, even if the groove bottom width G changes, the welding speed v always falls within the appropriate range shown in FIG.

By the way, when a welding power source having a DC constant voltage characteristic is used, if the wire feeding speed is constant, if the distance H between the tip and the base material is increased, the EXT becomes longer and the welding current I becomes lower.
When the distance H between the tip and the base material is shortened, EXT becomes shorter and the welding current I becomes higher. From this relationship, instead of increasing or decreasing the threshold value Is in accordance with the groove bottom width G, the tip / base metal distance H is changed according to the groove bottom width G while keeping the threshold value Is constant.
The same effect can be obtained even if is increased or decreased.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment welded by the method of the present invention will be described below. FIG. 1 shows an apparatus used in the single-sided welding method according to the present invention. Base material 1 which is formed by forming a V-shaped groove
A solid backing material 3 having fire resistance is applied to the back surface of the base material 2 and a guide rail 4 is fixed to the surface of the base material 2 by magnets 5 and 6. Reference numeral 7 denotes a welding carriage driven and driven by a motor (not shown) along the guide rail 4. The bogie 7 is equipped with a weaving device 8 and a vertical drive device 9. The weaving device 8 weaves the weaving shaft 10 in the direction of the arrow 11, that is, in the width direction of the groove bottom, and the welding torch 13 held by the welding torch holder 12 provided at the tip of the weaving shaft 10.
Is similarly weaved in the width direction of the groove bottom. The welding wire 15 is supplied through the welding torch 13 into the groove,
A voltage is applied from the welding power source 16 through the tip 17,
Welding is performed. 18 is a gas shield nozzle.

The welding current I is sampled by the shunt 19, and the isolation amplifier 20 and the low-pass filter 2
1 and the CPU 23
It is taken in. The CPU 23 compares the received welding current I with the threshold value Is and calculates a welding speed of 3 when I > Is.
0 cm / min, and when I ≦ Is, the welding speed is 5 cm / min to form a good backside bead. A pulse encoder 14 is attached to the weaving device 8, and C
The PU 23 detects the weaving width W by counting generated pulses. Weaving width W and groove bottom width G
Is set as shown in Table 1, the groove bottom width G can be known from the weaving width W detected and controlled during welding by an arc sensor or the like. Of course, if the groove bottom width G is input in advance, the weaving width W can be dealt with by simpler arithmetic control and the like, without being controlled by an arc sensor or the like. The CPU 23 increases or decreases the threshold value Is or the tip / base metal distance H according to the value of the groove bottom width G.

[0020]

[Table 1]

Using the apparatus as described above, a groove having a changing groove bottom width G as shown in FIG. 6 was welded by the method of the present invention. FIG. 6A is a plan view of the base materials 1 and 2 and FIG.
(B) is a left side view. The welding method is a carbon dioxide gas shielded arc welding method. The wire is a solid wire having an outer diameter of 1.6 mm (JIS Z3312 YGW11), and the base material is mild steel having a plate thickness t = 25 mm (JIS G3106 SM400).
B), welding length L = 500 mm, groove angle θ = 40
°, starting end groove bottom width Gs = 4 mm, ending groove bottom width G
A V-shaped groove of e = 8 mm was formed, and a refractory solid backing material was applied to the back surface of the groove and welded. Other welding conditions were as shown below.

Wire feeding speed: 5.6 m / min Welding voltage: 29 V Shielding gas: CO ₂ Shielding gas flow rate: 25 L / min Oscillating width: As shown in Table 1 Oscillating frequency: 60 times / min Chip / base metal Distance H: 35 mm In this example, the relationship between the groove bottom width G and the threshold value Is was set as shown in Table 2. Further, a method of increasing and decreasing the tip / base metal distance H according to the groove bottom width G was also implemented. Table 3 shows the relationship between the groove bottom width G and the tip / base metal distance H.

[0023]

[Table 2]

[0024]

[Table 3]

For comparison with the method of the present invention, see
In the conventional method in which the threshold value Is is constant with respect to the groove bottom width G described in JP-A-80970, the same material was used and welding was performed under the same welding conditions. Further, contrary to the above embodiment, the starting end groove bottom width Gs = 8 mm and the ending groove bottom width Ge.
Welding was carried out with a groove of 4 mm in both the method of the present invention and the conventional method.

The appearance of the Uranami bead and the weld controllability were evaluated at the three locations of the starting end, the center and the end of each bead of the method of the present invention and the conventional method welded as described above. Figure 7 shows the appearance of Uranami Bead
As shown in the above, there is no Uranami bead, and
If the penetration between the Uranami bead and the base material was remarkably poor, it was regarded as defective. Regarding the controllability, those in which the arc was cut off or the backing material was melted in the middle were regarded as defective. Table 4 shows the evaluation results.

As shown in Table 4, the groove bottom width G of the present invention is
In any of the methods of increasing and decreasing the threshold value Is in accordance with the above-described method, and the method of increasing and decreasing the distance H between the tip and the base material in accordance with the groove bottom width G, the formation state of the backwash is stable from beginning to end. In the conventional method in which the threshold value Is and the tip / base material distance H were constant, the molten pool was smaller than the arc in the narrow portion of the groove bottom at the narrow portion of the groove bottom. In the portion where the groove bottom width is wide, the arc precedes the molten pool, an excessive backside wave is formed, and the arc is cut off.

[0028]

[Table 4]

In the above embodiment, a V-shaped groove was welded by a carbon dioxide shielded arc welding method using a refractory solid backing material as a backing material, but the method of the present invention is not limited to this. For example, the present invention can be applied to a groove of type I, type I, and the like. Even in the case of the submerged arc welding method, welding is performed by feeding a welding wire at a constant speed using a welding power source having a DC constant voltage characteristic. As long as the method of the present invention can be applied, the backing material may be a copper plate.

[0030]

As described above, according to the present invention, a single-sided welding of a member having a low groove accuracy can be easily performed, so that the operator does not have to adjust the conditions during welding, and the quality of the Uranami bead is good. Therefore, it greatly contributes to the promotion of automation of welding and quality improvement.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of a device configuration for implementing the present invention.

FIG. 2 is a graph showing a relationship between a groove bottom width and a welding speed by a conventional welding method.

FIG. 3 is a graph showing an appropriate welding speed range with respect to a groove bottom width obtained by the present inventors.

4 (a) is a graph showing the welding current of proper welding with respect to the groove bottom width obtained by the inventor of the present invention, and FIG. 4 (b) is the proper reference line 1 shown in FIG. 3 and FIG. 4 (a). 4 is a graph showing the relationship between welding current and welding speed of proper welding derived from the graph shown in FIG.

FIG. 5 is a schematic view showing a state in which a Uranami bead is formed, showing a cross section of a welded portion along a groove center line.

FIG. 6 shows a groove used in an embodiment of the present invention;
(A) is a plan view and (b) is a front view.

FIG. 7 is a sectional view showing a groove cross section of a welded groove.

[Explanation of symbols]

1, 2: Base material 3: Backing material 4: Guide rail 5, 6: Magnet 7: Welding trolley 8: Weaving device 9: Vertical drive device 10: Weaving shaft 11: Weaving direction 12: Torch holder 13: Welding torch 14: Pulse encoder 15: welding wire 16: welding power supply 17: chip 18: gas shield nozzle 19: shunt 20: isolation amplifier 21: low-pass filter 22: A / D converter 23: CPU 24: arc 24: arc pool

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Aoki 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd. (56) References JP-A-63-80970 (JP, A) JP-A-59-56156 (JP, A) JP-A-61-289969 (JP, A) JP-A-61-33769 (JP, A) JP-A-59-163081 (JP, A) -70474 (JP, A) JP-A-64-22467 (JP, A) JP-A-60-54276 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 9/095 B23K 9/035

Claims (2)

(57) [Claims] 1. A backing material is applied to the back surface of a groove, and a welding current detected during welding is compared with a threshold value.
Higher than the threshold, the welding speed is higher.
In the single-sided welding method of welding while lowering the height , according to the groove bottom width detected or pre-input during welding
A single-sided welding method characterized in that when the width is wide, the threshold value is raised, and when the width is narrow, the threshold value is lowered . 2. A backing material is applied to the back surface of a groove, and a welding current detected during welding is compared with a threshold value.
Higher than the threshold, the welding speed is higher.
In the single-sided welding method of welding while lowering the height , according to the groove bottom width detected or pre-input during welding
If it is wide, the distance between the tip and the base material will be long.
A single-sided welding method characterized by shortening and welding.