JPH10272572A - Welding method by arc welding - Google Patents

Abstract

(57) [Summary] [Problem] To obtain a good welding result even if the gap of a welded joint fluctuates. SOLUTION: The height of a welding torch and a target position of the welding torch are always controlled to predetermined positions with respect to a welding joint,
Next, welding is performed at a predetermined wire feeding speed, a predetermined welding power supply output terminal voltage, and a predetermined welding speed, which are preset welding conditions.
a, and then a difference ΔIa = Io between the welding current Ia and the welding current Io at a preset standard gap.
-Ia is calculated, and if ΔIa> 0 or equal to or greater than e which is the dead zone width, the welding speed is set to ΔIa = 0 or ΔIa.
increases until the absolute value of a is less than or equal to e, then ΔIa
If <0 or −e or less, the welding speed is reduced until ΔIa = 0 or the absolute value of ΔIa becomes equal to or less than e.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method using arc welding which enables welding under appropriate welding conditions.

[0002]

2. Description of the Related Art When the gap of a weld joint fluctuates, the following problems (a) and (b) occur unless the welding conditions are properly controlled in accordance with the gap. (A) Excessive gap: Fillet welding; insufficient leg length, butt welding; insufficient filling height, insufficient penetration. (B) When the gap is too small: fillet welding; excessive leg length, unequal leg length (drooping bead), butt welding; excessive filling height, poor fusion.

In the prior art, the above-mentioned problem has been dealt with by the following method. (1) Operator teaching method: A method in which an operator of a welding device actually measures a gap at a welding start point, inputs the value to a welding condition control device of the welding device, and teaches it (hereinafter referred to as “prior art 1”). (2) Automatic detection by wire touch sensor: This method is widely used in portable butt welding robots (hereinafter referred to as “prior art 2”). 3) Automatically detected by an optical sensor. How to: CCD
There are many methods such as a method using a camera and a light cutting method using laser slit light (hereinafter, referred to as “prior art 3”).

[0004]

The problems of the prior arts 1 to 3 are as follows. Prior art 1 requires a gap measurement and a teaching operation, and requires enormous man-hours to measure gaps at a large number of welding positions over the entire length of the welding line. In addition, even when the gap is measured before welding, the gap may fluctuate due to thermal deformation of the workpiece during welding.

In prior art 2, since a wire touch sensing step is required, the number of steps is increased, and welding efficiency is reduced. Further, the same problem as in the prior art 1 remains. Prior Art 3 solves the above problem, but requires a sensor system for measuring the gap. Since the cost of the control device is high and the sensor is placed around the welding torch,
In a narrow portion, welding may not be possible due to interference between the workpiece and the sensor. In addition, the applicable range of the work to be welded is restricted.

Accordingly, it is an object of the present invention to solve the above-mentioned problems and to provide a welding method by arc welding capable of performing welding under appropriate welding conditions.

[0007]

According to the first aspect of the present invention,
In the welding method by the consumable electrode type arc welding, the height of the welding torch and the target position of the welding torch are always controlled to predetermined positions with respect to the welding joint, and then a predetermined wire feeding which is a preset welding condition is performed. The welding is performed at a predetermined speed, a predetermined welding power source output terminal voltage, and a predetermined welding speed, and then, during welding, the welding current Ia is always detected, and then the welding current Ia is compared with the welding current Io at a preset standard gap. The difference ΔIa = Io−Ia is calculated. Then, when ΔIa> 0 or equal to or more than e which is the dead zone width,
The welding speed is increased until ΔIa = 0 or the absolute value of ΔIa becomes less than or equal to e, and then, when ΔIa <0 or −e or less, the welding speed is increased until ΔIa = 0 or the absolute value of ΔIa becomes less than or equal to e. The characteristic feature is that a good welding result is obtained even if the gap of the welded joint fluctuates due to the decrease.

According to a second aspect of the present invention, in the welding method using consumable electrode arc welding, the height of the welding torch and the target position of the welding torch are always controlled to predetermined positions with respect to the welding joint, and then set in advance. The welding is started at a predetermined wire feeding speed, a predetermined welding power source output terminal voltage and a predetermined welding speed, which are the initial welding conditions thus set, and then, during welding, a welding current Ia is always detected. Ia and welding current Io at a preset standard gap
ΔIa = Io−Ia, and then ΔIa>
In the case of 0 or more than e which is the dead zone width, the welding conditions are modified from the initial conditions to the wire feeding speed, welding power supply output terminal voltage and welding speed which are the welding conditions on the larger gap side, and then ΔIa <0 or −Ia. In the case of e or less, the welding speed is corrected from the initial condition to the wire feeding speed, welding power output terminal voltage and welding speed, which are the welding conditions on the small gap side,
At the same time, the reference welding current Io is corrected each time, and by continuing the control, a good welding result is obtained even if the gap of the weld joint changes.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings. Although the present embodiment is described taking a fillet joint as an example, the claims of the present invention also cover weld joints other than fillet such as butt joints. The welding method is described as a consumable electrode type gas shielded arc welding using a welding power source having a constant voltage characteristic.
It is also applicable to W (submerged arc) and TIG welding. (1) In the present invention, it is assumed that the torch height and the torch target position at the start of welding are appropriate. Therefore,
For example, it is necessary to detect a position of a welding joint with respect to a welding torch by an electromagnetic distance sensor or the like as shown in FIG. 2, and to control a height and a target position of the welding torch to a predetermined position during welding. Become. Specifically, as shown in FIG. 1, it is assumed that the following values are set to predetermined values. 1 and 2, 1 is an upright plate, 2 is a welding wire, 3 is an electrode, 4 is an energizing tip, 5 is a lower plate, 6 is a welding torch, 7 is a sensor for detecting an upright plate, 8 is a mounting plate, 9 Is a horizontal slide block, and 10 is a vertical slide block.

The target position of the torch: ΔX (mm). That is, the root portion of the fillet joint is set to ΔX = 0, and the direction of the lower plate side is set to positive. Torch height (tip-base metal distance): Ex (mm) Torch angle: α (deg) (2) Welding is started under preset initial welding conditions. Specifically, the welding conditions are a wire feeding speed, an output terminal voltage of a welding power source, and a welding speed.

Wire feeding speed: Vf (m / min) Output terminal voltage of welding power supply: Et (V) Welding speed: Vz (cm / min) (3) After welding is started, a predetermined time (the welding bead is in a steady state) Time until: The welding current after the elapse of about 3 seconds is detected, and this detected welding current is defined as Ia (A) (4) Here, the welding current in the reference gap Go of the initial welding conditions is defined as Io, and ΔIa = Io−Ia, ΔG = G−
If Go, a relationship as shown in FIG. 3 is established between the two. That is, when the gap increases (ΔG> 0), ΔIa
Increases and the gap decreases (ΔG <0), ΔIa
Decreases. (5) The reason will be described. 4 and 5 are side views schematically showing a welding situation when a predetermined time has elapsed after the start of welding. FIG. 4 shows gap: standard, welding speed: standard,
FIG. 5 shows a case where the gap is excessive and the welding speed is standard. In FIGS. 4 and 5, a black-painted portion S of the welding bead indicates a welded welding wire.

The torch height is constant at Ex as described in the premise of the above (1). Since the wire feeding speed is constant as described in the premise of (2), FIGS.
The cross-sectional area S of the weld wire 2 welded in black is almost the same. Therefore, as shown in FIG. 5, when the gap is too large, the welding welding wire 2 penetrates into the gap, so that the surface height of the weld bead (molten pool), that is, "throat thickness".
T decreases. T “throat thickness” is the distance from the groove route. That is, the To <T _1.

The welding arc length is almost constant due to the constant voltage characteristics of the welding power source. That is, lo ≒ l ₁ . Therefore, as shown in FIG. 5, the wire projection length increases. In other words, the Lo <L _1.

If the wire projection length increases at a constant wire feeding speed, the welding current decreases due to the characteristics of the consumable electrode type arc welding method. In other words, the Io> I _1. 4 and FIG. 5, (To−T ₁ ) ≒ (L ₁ −Lo) ΔT ₁ ≒ ΔL ₁ .

The amount of decrease in throat thickness ΔT ₁ monotonically increases with respect to the amount of increase (deviation from the standard gap) ΔGs, and ΔL ₁ and ΔI ₁ monotonically increase with respect to ΔT ₁ . _{With 1} , a monotonically increasing relationship as shown in FIG. 3 is established.

[0016] To summarize the state of FIG. _{5, L 1> Lo l 1} ≒ lo T 1 <To S 1 = So. (6) Therefore, when ΔIa> 0 or more than e, the welding speed is decreased by a predetermined amount, and when ΔIa <0 or less than −e, the welding speed is increased by a predetermined amount (e is a dead zone of this control). (7) The above reason (when ΔG> 0) will be described with reference to FIG.

When the welding speed is reduced, the welding cross-sectional area S (black portion in the figure) of the weld bead increases (even if the wire feeding speed-wire welding speed is constant). Therefore, since the throat thickness Ts increases and Ls decreases, ΔIa decreases.

To summarize the state of FIG. 6, L ₂ = Lol ₂ ≒ lo T ₂ = To S ₂ > So. (8) Therefore, the absolute value of ΔIa decreases by the condition control of (6). The above control is continued until ΔIa = 0 or its absolute value becomes equal to or less than the dead zone e. (9) In the above (6), the method of controlling only the welding speed has been described. However, in order to expand the applicable range of the present invention (the range of the groove gap where a good welding result is obtained), the welding speed is controlled. It is apparent that a method of controlling the wire feeding speed and the output terminal voltage of the welding power source is also preferable.

For example, when the gap is too large, reducing the wire feeding speed and reducing the welding current lowers the pressure of the welding arc and makes it more difficult for the weld metal to enter the cutting gap. (10) Table 1 below shows the specific method of the above (9).
This will be described with reference to FIG.

[0020]

[Table 1]

At the torch position set above, Table 1
Appropriate welding conditions for each gap as shown in (1) are determined.
Actually, the control accuracy is improved by linearly interpolating the numerical values in Table 1 and obtaining, for example, every 0.1 mm gap.

First, it is assumed that welding is started under the welding condition of the standard gap (G = 0). ΔIa (Io−Ia) is detected, for example, ΔIa>
In the case of 0 or more than e, G = 0 mm
Changed to Io of 0.1mm, and at the same time, the reference welding current
Change to Io of 0.1 mm.

The next detection of ΔIa is G = 0.1
mm is calculated as a reference current. Thereafter, similarly, the difference ΔIa between the reference welding current Io corresponding to the current output welding condition and the welding current Ia at that time.
Controls welding conditions during welding.

[0024]

Next, the present invention will be described with reference to embodiments. An embodiment of the control circuit is shown in FIGS. FIG. 7 shows an embodiment 1 in which only the welding speed of claim 1 is controlled, and FIG. 8 shows an embodiment 2 in which all welding conditions (wire feed speed, welding power output terminal voltage and welding speed) of claim 2 are controlled. is there. In addition,
The dead zone e of the control is set to about 5A in the embodiment. Also,
In particular, the control pitch for changing the welding conditions is about 0.1 to 1.0.

[0025]

As described above, according to the present invention, the following industrially useful effects are provided. (1) The above method is a method called an arc sensor, and solves all the problems of the prior arts 1 to 3. The problems related to the excessively large and small gaps described in (a) and (b) of the related art are solved. (2) Prior arts 1 and 2 detect a groove gap in front of a welding torch before welding, and prior art 3 detects a groove gap in front of a welding torch, but this method detects a groove gap immediately below a welding arc. Therefore, there is also an advantage that the gap is not affected by the thermal deformation during welding.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a side view showing an electromagnetic distance sensor.

FIG. 3 is a graph showing a relationship between ΔIs and Gs.

FIG. 4 is a side view schematically showing a welding state (gap: standard, welding speed: standard) when a predetermined time has elapsed after the start of welding.

FIG. 5 is a side view schematically showing a welding situation when a predetermined time has elapsed after the start of welding (gap: excessive, welding speed: standard).

FIG. 6 is a side view schematically showing a welding situation when a predetermined time has elapsed after the start of welding (gap: excessive, welding speed: decreasing).

FIG. 7 is a flowchart showing Embodiment 1 of the present invention.

FIG. 8 is a flowchart showing Embodiment 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Standing plate 2 Welding wire 3 Electrode 4 Current-carrying tip 5 Lower plate 6 Welding torch 7 Standing plate detection sensor 8 Mounting plate 9 Left-right sliding block 10 Up-down sliding block

Claims (2)

[Claims] In a welding method using consumable electrode type arc welding, a height of a welding torch and a target position of the welding torch are always controlled to predetermined positions with respect to a welding joint.
A predetermined wire feed speed, which is a preset welding condition,
Welding is performed at a predetermined welding power source output terminal voltage and a predetermined welding speed. Then, during welding, a welding current Ia is constantly detected. Then, a difference ΔIa between the welding current Ia and the welding current Io at a preset standard gap is determined. = Io-Ia, then if ΔIa> 0 or greater than or equal to e, which is the dead zone width, increase the welding speed until ΔIa = 0 or the absolute value of ΔIa becomes less than or equal to e, then ΔIa <0 or -E or less, the welding speed is set to ΔIa = 0 or ΔIa.
A welding method by arc welding characterized in that a good welding result is obtained even if the gap of a welded joint fluctuates by decreasing the absolute value of a until it becomes equal to or less than e. 2. In a welding method using consumable electrode arc welding, a height of a welding torch and a target position of the welding torch are always controlled to predetermined positions with respect to a welding joint.
Welding is started at a predetermined wire feeding speed, a predetermined welding power supply output terminal voltage and a predetermined welding speed, which are preset initial welding conditions, and then, during welding, the welding current Ia is always detected, Difference ΔIa = Io−I between welding current Ia and welding current Io at a preset standard gap
Calculate a, and if ΔIa> 0 or equal to or greater than e, which is the dead zone width, correct the welding conditions from the initial conditions to the wire feed speed, welding power output terminal voltage, and welding speed, which are the welding conditions on the larger gap side. Then, if ΔIa <0 or −e or less, the welding speed is corrected from the initial condition to the wire feeding speed, welding power output terminal voltage, and welding speed, which are the welding conditions on the smaller gap side, and at the same time, the reference welding current is adjusted. Io
A welding method by arc welding characterized in that a good welding result is obtained even if the gap of the welded joint changes by continuing the control by correcting each time.