JPH0631444A - One-side automatic penetration welding method - Google Patents

Abstract

PURPOSE:To optimize the reinforcement of weld shape of reverse side beads by controlling the supply speed of a welding wire and the torch voltage between a welding tip and materials to be welded in one-side automatic penetration welding. CONSTITUTION:The one-side automatic penetration welding is executed by placing a backing strip 2 to the rear surface of a groove formed between the two materials 1 and 1 to be welded, passing a welding wire 4 through a welding torch 3, blowing a shielding gas toward the groove, moving the welding torch 3 at a specified speed to the groove under the control of the height of the welding torch 3 in such a manner that a specified welding current is supplied via the tip to the welding wire 4 and executing the welding while supplying the specified welding current to the welding wire 4. The above-mentioned welding is executed by controlling the supply speed of the welding wire 4 and the torch voltage. The specified bead height is maintained regardless of the shape change of the groove and the optimum reinforcement of weld shape of the reverse side beads is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-sided automatic back bead welding method, and in particular, it maintains a constant bead height regardless of changes in the groove shape such as the root gap distance and optimizes the pre-bead shape of the back bead The present invention relates to a single-sided automatic backside welding method that can be maintained.

[0002]

2. Description of the Related Art For example, two objects to be welded such as steel plates are joined to each other along a longitudinal direction of a groove formed therebetween by a single-sided backside arc welding method using a welding wire as a consumable welding electrode. In order to secure the desired initial layer bead shape, conventionally, the groove shape data before welding, that is,
It was common to measure the root gap distance, groove angle, root surface height, etc. in advance along the longitudinal direction of the groove and perform welding under the optimum welding conditions suitable for the groove shape. .

However, according to the above-mentioned method, since it is necessary to measure the groove shape data in advance, recently, the variation value of the groove shape data such as the root gap distance is automatically measured during welding by the television camera or the like. A method is proposed in which automatic welding is performed by using the measured data and the experimental data previously input for each different welding condition and input to the controller.

[0004]

However, according to the above-mentioned prior application technique, it is necessary to obtain an empirical formula by an experiment for each different welding condition, which requires a great deal of labor,
There is a problem that the empirical formula created in this way is not versatile.

Therefore, the object of the present invention is to eliminate the need to previously obtain an empirical formula for each different welding condition, to maintain a constant bead height regardless of the change in the groove shape such as the root gap distance, and to predict the back bead. It is an object of the present invention to provide a single-sided automatic backside welding method capable of maintaining the heap shape optimally.

[0006]

According to the present invention, a backing plate is applied to the back surface of a groove formed between two objects to be welded,
A welding wire as a consumable electrode is continuously supplied to the groove through a welding torch, a shield gas is blown toward the groove through the welding torch, and a constant welding current is applied to the welding wire through a tip. The height of the welding torch is controlled so as to be supplied, the welding torch is moved along the groove at a constant welding speed, the constant welding current is supplied to the welding wire, and the welding wire is supplied. An arc is generated between the groove and the groove, and thus the object to be welded by arc heat along the groove, in a single-sided automatic backside welding method consisting of welding each other at the constant welding speed, The welding wire supply speed and the torch voltage between the tip and the object to be welded are controlled, thus forming the groove regardless of the shape change of the groove. Those having features to maintain optimal 予盛 Ri shape of the back bead formed the over de height on the back of and the groove is kept constant.

An embodiment of the one-sided automatic backside welding method of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the single-sided automatic backside welding method of the present invention. In FIG.
1 is a steel plate as an object to be welded, 1A is two objects to be welded 1
The groove 2 formed between them is a backing plate applied to the back surface of the groove 1A, and 3 is a welding torch for supplying a shield gas toward the groove 1A. The welding torch 3 has an energizing tip (not shown) for supplying a welding current to a welding wire, which will be described later, inside the tip thereof. Welding torch 3
Is continuously rotated at a high speed in one direction about its central axis by a rotating means (not shown). 4 is a welding wire as a consumable electrode that is continuously supplied toward the groove 1A through the welding torch 3. Welding wire 4
Is deviated from the central axis of the welding torch 3 and the welding torch 3
It is continuously supplied vertically from the tip of the to the groove 1A by the welding wire supply device 5. Reference numeral 6 is an XY moving device for moving the welding torch 3 in the width direction (X) of the groove 1A and in the height direction (Y) of the groove 1A.

Numeral 7 is a gap sensor consisting of a TV camera and an image processing device for photographing the groove 1A on the downstream side in the traveling direction of the welding torch 3, and measures the distance of the root gap (G) of the groove 1A. To do. 8 is a welding carriage for moving the XY moving device 6 along with the welding torch 3 along the longitudinal direction of the groove 1A, and 9 is for supplying a welding current between the steel plate 1 and the current-carrying tip in the welding torch 3. It is a welding power source for.

Reference numeral 10 is a controller. The controller 10 controls the welding wire supply device 8 based on the gap distance data of the groove 1A from the gap sensor 7 in accordance with the arithmetic expressions (A) and (B) described later to control the supply speed of the welding wire 4. Maintaining a predetermined value and controlling the welding power source 9 to weld the work piece 1
The torch voltage between the conductive tip and the energizing tip is maintained at a predetermined value, thus maintaining the height of the first layer bead constant and the shape of the back bead constant even if the root gap distance changes. In addition to this, the controller 10 controls the rotation speed of the welding torch 3 and, based on the arc current detected by a sensor (not shown), according to a conventionally known method, XY
The moving device 6 is controlled to position the center axis of rotation of the welding torch 3 at the center of the groove 1A in the width direction, and to control the height of the torch 3 so that the welding current is constant. Needless to say, the present invention is not applied only to the above-mentioned so-called rotary arc welding method.

Next, the arithmetic expressions (A) and (B) previously set in the controller 10 will be described. In order to maintain a constant bead height regardless of the root gap distance, it is necessary to control the welding wire deposition amount. To that end, the welding wire feed rate is controlled. Formula (A) is
It calculates the welding wire supply speed and is calculated by the following formula.

V _f = V _W (S _DO + H · G) / S _φ --- (A) However, in the formula (A), V _f : welding wire supply speed (mm / sec), V _W : welding speed ( mm / sec) (constant), G: root gap distance (mm) (variable), S _DO : bead cross-sectional area when G = 0 (mm ² ) (constant), H: bead height (mm) (constant) ), Sφ: welding wire cross-sectional area (mm ² ) (constant).

On the other hand, the welding wire supply speed (V _f ) is expressed by the following equation (1) by the welding current (I _a ) and the welding wire protrusion length (L).

V _f = AI _a + BLI _a ² --- (1) However, in the equation (1), A and B: constants determined by the welding wire and the shielding gas.

In the present invention, the welding current (I _a )
Is constant. Therefore, the welding wire supply rate (V _f )
It is sufficient to change the welding wire protrusion length (L) in response to the above change, but the welding wire protrusion length (L) cannot be measured. Then, the above formula (1) is applied to the welding wire protrusion length (L).
When rewritten as the expression of, it becomes the following expression (2).

L = (V _f −AI _a ) / BI _a ² --- (2)

On the other hand, when the welding wire protrusion length (L) changes, the voltage drop ( _VL ) in the protrusion length portion also changes. The voltage drop ( _VL ) can be expressed by the following equation (3).

V _L = aLI _a −bV _f / I _a --- (3) However, in the equation (3), a and b are constants determined by the welding wire.

When the projection length (L) of the welding wire changes in this way, the torch voltage (V _t ) also changes. The torch voltage (V _t ) can be expressed by the following equation (4).

V _t = V _L + V _A --- (4) However, in the formula (4), V _L : voltage drop of the protruding portion of the welding wire, V _A : true arc voltage.

In the above equation (4), the true arc voltage (V
_A ) can be expressed by the following equation (5).

V _A = V ₀ + Xl _a --- (5) However, in the equation (5), V ₀ : arc voltage when the arc length (l _a ) is ₀ mm, X: voltage gradient of the arc column, l _a : arc length (constant).

V ₀ and X can be expressed by the following equations (6) and (7), respectively. V ₀ = k (1) I _a + k (2) --- (6) X = k (3) I _a + k (4) --- (7) However, in the formulas (6) and (7), k (1), k (2), k (3), k (4): constants determined by the wire and the shielding gas.

By substituting the above equations (6) and (7) into the above equation (5), the following equation (8) is obtained.

[0025] _{V A = k (1) I} a + k (2) + [k (3) l a + k (4)] l a --- (8)

By substituting the above equations (3) and (8) into the above equation (4), the following equation (9) is obtained.

[0027] _{V t = aLI a -bV f /} I a + [k (1) + k (3) l a] I a + k (2) + k (4) l a --- (9)

Substituting the equation (1) into the above equation (9), the following (1
It becomes like the expression (0).

[0029] _{V t = {(a-Bb} ) L + k (1) + k (3) l a} I a + k (4) l a + k (2) -Ab --- (10)

By substituting the equation (2) into the equation (10), the following equation (B) is obtained.

[0031] _{V t = [(a-B} · b) {(V f -AI a) / BI a 2} + k (1) + k (3) l a] I a + k (4) l a + k (2) −A ・ b --- (B)

[0032] FIG. _{2 (L), (l a} ), (V L), (V
_A ) and (V _t ) are illustrated.

According to the above equations (A) and (B), it is possible to maintain a constant bead height even if the root gap is changed and to optimally maintain the pre-bead shape of the back bead, without obtaining an experimental formula in advance. .

FIG. 3 shows the bead shape of the first layer when a steel sheet is welded by the method of the present invention. Table 1 shows the welding conditions at this time.

[0035]

[Table 1]

As is apparent from FIG. 3, the welding wire feed rate (V _f ) and the torch voltage (V _t ) were controlled by the method of the present invention, and per unit bead length was increased according to the increase of the root gap distance. It was found that increasing the amount of heat input in (1) can maintain a constant bead height even when the root gap changes, and can maintain the pre-filled shape of the back bead optimally.

On the other hand, as shown in Table 2, if the welding conditions are not changed even if the root gap is changed, a constant bead height cannot be maintained as shown in FIG. The heap shape cannot be optimally maintained.

[0038]

[Table 2]

In order to maintain a constant bead height even when the root gap changes and to maintain the optimum pre-bead shape of the back bead, it is necessary to secure an appropriate amount of welding corresponding to the distance of the root gap. There is. As the method, welding speed (V _W ) control, welding current (I _a ) and welding speed (V
_W ) simultaneous control. FIG. 5 shows the bead shape of the first layer when the welding speed control is carried out under the conditions shown in Table 3, and FIG. 6 shows the first layer bead when the welding current control and the welding speed control are carried out simultaneously under the conditions shown in Table 4. The bead shape is shown.
As is clear from FIGS. 5 and 6, it can be seen that the optimum pre-filled shape of the back bead cannot be obtained because the heat input amount per unit bead length fluctuates significantly in either method.

[0040]

[Table 3]

[0041]

[Table 4]

By controlling the welding current (I _a ), the welding wire supply speed (V _f ), the torch voltage (V _t ) and the welding speed (V _W ), the heat input amount per unit bead length is kept constant, and FIG. 7 shows the shape of the first layer bead when welding is performed by applying a predetermined amount of welding in order to keep the bead height constant.
Shown in. As is apparent from FIG. 7, the bead height is maintained substantially constant, but the pre-filled shape of the back bead projects downward downward as the distance of the root gap increases. As a result, it is possible to maintain a bead height that is almost constant and optimally maintain the pre-filling shape of the back bead at a root gap distance of up to about 1.5 mm.

[0043]

[Table 5]

[0044]

As described above, according to the present invention, it is possible to obtain an empirical formula in advance for each different welding condition.
Regardless of changes in the groove shape such as the root gap distance, it is possible to maintain a constant bead height and optimally maintain the pre-filled shape of the back bead, thereby providing various useful effects.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a single-sided automatic backside welding method of the present invention.

[2] (L), is an explanatory view of _{(l a), (V L} ), (V A) and (V _t).

FIG. 3 is a cross-sectional view showing the shape of an initial layer bead when welding is performed by the method of the present invention.

FIG. 4 is a cross-sectional view showing a shape of a first-layer bead when welding conditions are not changed even if a root gap is changed.

FIG. 5 is a cross-sectional view showing the shape of the first layer bead when the welding speed is controlled.

FIG. 6 is a cross-sectional view showing the shape of the first layer bead when the welding current control and the welding speed control are performed.

FIG. 7 is a cross-sectional view showing the shape of the first layer bead when the welding current, the welding wire supply speed, the torch voltage and the welding speed are controlled.

[Explanation of symbols]

 1: steel plate, 2: backing plate, 3: welding torch, 4: welding wire, 5: welding wire supply device, 6: XY moving device, 7: gap sensor, 8: welding carriage, 9: welding power source, 10: Controller.

Claims (2)

[Claims] 1. A backing plate is applied to the back surface of a groove formed between two objects to be welded, and a welding wire as a consumable electrode is continuously supplied toward the groove through a welding torch, A shield gas is blown toward the groove through a welding torch, the height of the welding torch is controlled so that a constant welding current is supplied to the welding wire through a tip, and the welding torch has a constant welding speed. By moving along the groove, to supply the constant welding current to the welding wire, to generate an arc between the welding wire and the groove, thus, the arc to heat the work piece. A single-sided automatic backside welding method comprising welding one another along the groove at the constant welding speed, the feed rate of the welding wire, and a torch between the tip and the workpiece. The pressure is controlled, thus maintaining the bead height formed on the groove constant regardless of the shape change of the groove and optimizing the pre-filled shape of the back bead formed on the back surface of the groove. A single-sided automatic Uranami welding method characterized by maintaining 2. The control of the supply speed (V _f ) of the welding wire is performed by the following formula (A), V _f = V _W (S _DO + H · G) / Sφ --- (A) where (A) In the formula, V _f : welding wire supply speed (mm / sec), V _W : welding speed (mm / sec), G: root gap distance (mm), S _DO : bead cross-sectional area when G = 0 (mm ² ), H: bead height (mm), Sφ: welding wire cross-sectional area (mm ² ). Done by the control of the torch voltage (V _t) is represented by the following formula _{(B), V t = [(a-} B · b) {(V f -AI a) / BI a 2} + k (1) + k ( _{3) l a] I a +} k (4) l a + k (2) -A · b --- (B) except that in (B) formula, I _a: welding current (A), l _a: arc length ( mm), A, B. a, b, k (1), k (2), k (3), k (4): constants. The single-sided automatic backside welding method according to claim 1, wherein