JP2933737B2 - Consumable electrode arc 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 consumable electrode-type arc welding method capable of reliably detecting a groove width variation and controlling a constant bead height in groove profiling control by arc sensing. .

[0002]

2. Description of the Related Art Since welding grooves have insufficient groove processing and assembling accuracy, and deformation due to distortion during welding, the groove must be measured during welding to control scanning and welding conditions. Must. As a method of sensing the groove during welding, an arc sensing method has been developed (Japanese Patent Application Laid-Open No. Sho 61-230476). However, this method is based on the fluctuation of the welding current according to the swing of the welding torch in the direction of the root gap. It is considered that the method of detecting the above change does not require a special sensor near the welding torch, is easy to handle and maintain, and is most suitable for application to a welding site. Practical use of such a scanning control method using arc sensing control has been attempted for a long time, but at present, stable control is difficult and not practically used.

The groove scanning control by arc sensing mainly includes line scanning, height scanning and width scanning. The most basic method is to detect and compare current values near both ends of the swing width. As another example, as shown in FIG. 2, the welding line tracing is an integrated value ILG of a welding current value in a process from the center of oscillation of the welding torch to the left end (corresponding to the area under the line shown as ILG in FIG. 2, ILC Etc.) and the difference SL from the integrated value ILC of the welding current value in the process from the left end to the swing center.
= ILG-ILC, welding in the process from swing center to right end
The difference between the integrated value IRC welding current value of the integrated values IRG and process from the right end to the center of swinging of the current SR = IRG-IRC
, The center of the swing in the direction of the smaller current value is corrected, and control is performed so that SL and SR become equal. That is, when SL> SR, the swing center is controlled to the right, and SL <S
At the time of R, the swing center is controlled to the left.

When the current value obtained by adding ILG, ILC, IRG and IRC is smaller (or larger) than a predetermined current value SAK corresponding to a target distance between chip base materials, the welding torch is lowered. (Or raise) to control the welding torch height. That is, ILG + ILC + IR
When G + IRC> SAK, raise the torch, ILG + IL
When C + IRG + IRC <SAK, lower the torch.

In the width scanning, SL and SR are compared with a width control threshold value SBK corresponding to a target swing width corresponding to the root gap, and when both SL and SR are large (or small), the swing width is large. And make welding speed faster (or slower)
This is a method of controlling the bead height to be constant. That is, when SL> SBK and SR> SBK, the swing width is small, the welding speed is high, and SL <SBK and SR <SBK.
In this case, the swing width is increased and the welding speed is reduced.

[0006]

However, FIG. 3 shows the welding current when rocking welding is performed at a groove angle of 40 degrees and a root gap of 5 mm, but the fluctuation is large, so that fluctuations in control by arc sensing can be avoided. Absent. In particular, width scanning controls welding conditions such as welding speed and swing width,
This has an effect on the bead shape, the melting, and the height of the extra pile, and there is a problem that the fluctuations of each layer are accumulated when forming layers are welded, so that it has been extremely difficult to put them into practical use. An object of the present invention is to solve the problem of groove width tracking control in arc sensing, and to provide a consumable electrode type arc welding method capable of forming layers by stable arc sensing.

[0007]

SUMMARY OF THE INVENTION The present invention focuses on such problems and solves the problem. The gist of the present invention is that the swing width of the welding torch and the welding speed or the wire speed are adjusted in accordance with the variation of the root gap G. By controlling the feed speed, the bead height H
In the consumable electrode type arc welding method of performing one-layer one-pass welding by arc sensing control in which the H is sequentially controlled so that H is constant, the H (mm) is 2 or more and 12 or less, and in relation to the G (mm), G ≧ 0.6H + 0.8
The consumable electrode type arc welding method is characterized in that control is performed in a region where the following equation is satisfied. Hereinafter, the present invention will be described in more detail.

[0008]

The present inventors have investigated why arc controlling cannot perform stable control, and as a result, the following causes have been found. As shown in FIG. 4, the position of the swing of the welding torch controlled by arc-securing during welding is not on the groove but on the molten pool. FIGS. 5 and 6 show only the swinging width by arc sensing, and the welding speed is the swinging position when welding is intentionally fast and slow. The welding speed is shown even when the same root gap G is arc sensed. As the welding speed increases, the swinging position moves forward of the molten pool and the swing width decreases, and if the welding speed decreases, the swinging position moves backward and the swing width increases. Become. For this reason, in arc sensing in which a change in the root gap is detected based on a change in the swing width, the root gap is apparently detected as fluctuating.

The relationship between the bead height and the appropriate swing width is as follows.
Determined experimentally by the method. Groove angle 40 ° constant, root root
With cap 5mm constant V groove, the Akusen Thing
Weld only by controlling the swing width with the width control threshold value SBK
Was done. First, the welding speed will be 6mm bead height
(The welding speed is not controlled and the bead height is
Fixed). The appropriate swing width for starting welding is determined by controlling the swing width.
5. The swing width converges to the swing width corresponding to SBK, and the swing width at this time
6 mm and a bead width of 9.2 mm were obtained.
I filled it out.

Next, the welding speed is reduced to a bead height of 7 mm.
(Weld speed is not controlled and bead height is
Fixed). The appropriate swing width for starting welding is determined by controlling the swing width.
6. The swing width converges to the swing width according to SBK.
9 mm and a bead width of 10.1 mm were obtained, and the graph of FIG. 7 was obtained.
Filled in. Carry out a bead height of 8 mm in the same way,
The swing width and the bead width were determined and entered in the graph of FIG. Groove
V groove with constant angle of 40 ° and root gap of 10mm
And the width control threshold value SBK of arc sensing
Only the swing width was controlled and welding was performed. Root gap
Conduct bead heights 4, 5, and 6 mm in the same way as 5 mm
Then, the swing width and the bead width were determined and entered in the graph of FIG.

From FIG. 7 obtained by such an experiment , the change of the swing width is about 1.3 mm with respect to the change of the bead height of 1 mm.
The change in the bead width is larger than the change in the bead width shown in FIG. 7 of about 0.7 mm, and the change in the swing width is apparently caused not only by the change in the bead width, but also shown in FIGS. 4, 5 and 6. It is considered that the amount of change in the swing width was added due to the change in the swing position on the molten pool. Therefore, the fluctuation of the bead height has a large effect on the swing width during arc sensing, and this greatly hinders stable detection of a change in the root gap.

[0012] The width of the groove by arc sensing is before
As described above, SL and SR are compared with the width scanning threshold SBK.
The swing width is controlled according to the comparison result, and the swing width is controlled.
Unified to keep the bead height constant
Control welding speed. According to FIG. 7, the bead height is 6 mm.
Welding torch swing of the kicking root gap 5mm and 10mm
The width is about 6.5mm and about 11.5mm, the difference is about 5mm
It matches the difference in the root gap. Therefore, bee
If the height is constant, the swing width by arc sensing
Changes in the route gap can be accurately detected.
Can be However, it should be kept constant due to some fluctuation.
When the bead height fluctuates, the swing width has a large effect.
Given, unable to accurately detect the root gap
It is shown that.

Further , as shown in FIG. 3, the welding current fluctuates greatly during welding, and therefore, in arc sensing using the welding current, control fluctuations cannot be avoided. For this reason, even when welding a groove with a fixed root gap, the root gap is controlled so as to fluctuate, so that the swing width is widened and the welding speed is controlled to be slow. Fast control is repeated randomly.

Groove width imitation by general arc sensing
Control method is the SL obtained by arc sensing.
And SR values only correspond to changes in groove width
And SL> SBK and SR> SBK (or SL <SB
K and SR <SBK), the swing width is set to a certain amount DOW.
Narrow (or wide) and the groove width is DRG (=
DOW) It is assumed that changes have been made narrowly (or widely), and
From the cross-sectional area due to the change of the tip width, the welding speed is set to the specified speed.
(Or slower) to keep the bead height constant.
I will.

[0015] SL obtained by arc sensing and
The SR value changes due to three causes: a ) change in groove width b) change in bead height c) fluctuation in welding current . But Arc Sensin
The SL and SR values are different depending on the cause of a), b) and c).
It cannot be determined whether the result has changed. For this reason
Changes in SL and SR values correspond only to changes in groove width
Assuming that the groove width is copied. I), b), c)
Control fluctuations due to the cause c) frequently occur
You. The groove width does not change, and the SL and SR values due to the cause c)
Is changed, the bead break shown in FIGS. 9A and 9B is cut.
The following phenomena occur depending on the surface shape (groove shape).

(Phenomenon 1) In the case of FIG. 9B, SL <SBK and SR <SBK
When it becomes, the swing width is increased by a certain amount DOW,
Considering that the groove width was wide and changed DRG (= DOW),
Change the groove width so that the groove height is constant.
Calculate the change DSB of the cross-sectional area, and set the welding speed to the specified speed.
Slow down. At this time, the groove width has not actually changed.
The bead height BH, which should be kept constant,
(= BH1-BH).

FIG . 9B shows the height / bottom of the cross-sectional shape of the bead.
Since the side was small, it was considered as a change in the groove width DRG and modified
Oscillation width OW + DOW is increase in bead height DBH1 is small
Therefore, it is clearly larger than the appropriate swing width, and the next
The SL and SR values of sensing increase. SL> SB
In accordance with K and SR> SBK, the swing width is set to a fixed amount DOW.
Along with narrowing, the groove width changes to narrow DRG (= DOW)
From the cross-sectional area due to the change in groove width,
The welding speed is controlled to be higher by a predetermined speed. This phenomenon
And control, the groove width does not change, and the fluctuation of welding current causes
Erroneous control is corrected.

(Phenomenon 2) In the cross-sectional shape of the bead in FIG.
When L> SBK and SR> SBK, the swing width is
Narrow, controlled welding speed fast. But the next arc
Since the SL and SR values of sensing become smaller,
The welding speed is controlled to be slower as well as wider. This
Phenomena and control, the groove width does not change, the welding current fluctuates
Erroneous control due to is corrected.

(Phenomenon 3) In the case of FIG. 9A, SL <SBK and SR <SBK
When it becomes, the swing width is increased by a certain amount DOW,
Considering that the groove width was wide and changed DRG (= DOW),
Change the groove width so that the groove height is constant.
Calculate the change DSA of the cross-sectional area, and set the welding speed to the specified speed.
Slow down. At this time, the groove width has not actually changed.
The bead height BH, which should be kept constant,
(= BH1-BH).

FIG . 9A shows the height / bottom of the cross section of the bead.
The DSA is large because the side is large, and the beads by DSA
The height increase DBH1 (= BH1-BH) is large. FIG.
6 and FIG. 7 show the increase in bead height DBH1.
Therefore, the appropriate swing width of the SBK threshold greatly increases.

Change in groove width DRG considered as DRG
Appropriate swing width of SBK threshold is larger than width OW + DOW
The next arc sensing SL and SR values are small.
It becomes. Swing according to SL <SBK and SR <SBK
The moving width is increased by a certain amount DOW and the groove width is DRG
(= DOW) Change in groove width, assuming that it has changed widely
The welding speed is controlled to a predetermined speed
You. Thus, in the cross-sectional shape of the bead in FIG.
Correction of erroneous control caused by fluctuation of welding current without changing groove width
Not controlled, the welding speed is slower and the swing width is wider.
Repeated and runaway.

(Phenomenon 4) In the cross-sectional shape of the bead shown in FIG.
When L> SBK and SR> SBK, the swing width is
Narrow, controlled welding speed fast. But the next arc
The SL and SR values of sensing are still large and therefore fluctuate
The welding speed is controlled to be high while the width is reduced. This
As shown in the cross-sectional shape of the bead in FIG.
Does not change, and erroneous control due to fluctuations in welding current is corrected.
Not further welding speed is fast, the swing width is narrowed control is repeated
Returned and runaway.

Thus, the groove by arc sensing
The width scanning control method depends on the cross-sectional shape (groove shape) of the bead.
Therefore, even if erroneous control occurs as in Phenomena 1 and 2,
When control is performed to return to the normal groove width copying state,
If erroneous control occurs as in Elephant 3 and Phenomenon 4, the normal gap
Control diverges in the opposite direction to the
May run.

Next, the phenomena 1 to 4 will be described quantitatively. FIG.
Torch swing width against bead height change DBH
Is DOW = 1.3 × DBH (1) . Therefore, the width scanning system of a certain arc sensing
And the corrected swing width increase DOW1 and the swing width
Bead height increase according to welding speed corrected centrally
If the added DBH1 is DOW1> 1.3 × DBH1 (2) , the swing width change is too large,
The probability that the SL and SR of the tag will increase increases, and the next width
In copying control, the swing width is corrected to be small and stable control is achieved.
You. However, if DOW1 <1.3 × DBH1 (3) , the swing width is still small, so that arc sensing is not possible.
The probability that SL and SR become small increases, and
In the control, the swing width is corrected even more and unstable control and
Become. Therefore, DOW1 is compared with 1.3 × DBH1,
When DOW1> 1.3 × DBH1, stable width scanning control and
Become. FIG. 13 shows a comparison result at a groove angle of 40 °.
You.

The coefficients of the equations (1), (2) and (3)
1.3 shows the relationship between the bead height and the torch swing width in FIG.
By the slope of the graph, both root gap 5mm and 10mm
Has a slope of 1.3. The experiment in FIG.
For a given root gap and bead height
Find the appropriate swing width according to the width scanning control threshold value SBK
In this experiment, the welding speed was controlled in accordance with the swing width.
Absent. The actual width tracing control is the swing width
The welding speed is adjusted according to the amount of adjustment.

[0026] Thus, the scope of the bead height to the root gap capable stable control can be determined by geometrical calculation of the experimental results and the bead cross-sectional area shown in FIG. 7 Turkey
And are shown below. The calculation method will be described with reference to FIG.
You. Root gap RG = constant, groove angle θ = constant opening
During welding ahead, a certain control result shows the fluctuation of welding current shown in FIG.
When SL <SBK and SR <SBK,
Increase the correction amount DOW of the swing width and increase the welding speed
Assuming that the gap has increased by DRG (= DOW1),
The increase in the cross-sectional area of the DSA (the shaded area on the right side in Fig. 9 (a))
Reduces the applicable welding speed. But actually the root
Since the gap does not change, the bead cross section increases DSA
Indicates an increase in the bead height (the upper hatched portion in FIG. 9A).
And the bead height increases from BH to BH1 by DBH1.
You.

Cross-sectional area change DSA by DRG (FIG. 9
(A) A hatched portion on the right side is DSA = BH × DRG (4) . On the other hand, the cross-sectional area change DS increased by DBH1
A (upper shaded area in to FIG. 9 (a)) is, DSA = DBH1 × (RG + 2 × BH × tan (θ / 2)) + DBH1 × DBH1 × tan (θ / 2) ······ (5) thus From formulas (4) and (5), BH × DRG = DBH1 × (RG + 2 × BH × tan (θ / 2)) + DBH1 × DBH1 × tan (θ / 2) (6)

By transforming this, tan (θ / 2) × (DBH1) ² + (RG + 2 × BH × tan (θ / 2)) × DBH1− BH × DRG = 0 (7) . Here, if α = tan (θ / 2) β = RG + 2 × BH × tan (θ / 2) γ = −BH × DRG , then α × (DBH1) ² + β × DBH1 + γ = 0 , and the positive of DBH1 From the mathematical formula, the root is: DBH1 = {− β + (β ² −4 × α × γ) ^1/2 α / (2 × α) (8)

The [0029]. Here, as an example, when the groove angle θ = 40 ° tan (θ / 2) = 0.36397702 When one width scanning control DOW = 0.1 mm (DRG) , the root gap RG = 4 mm and the bead height
If DBH1 is calculated for BH = 7 mm, DBH1 = 0.0767247 . Here, DOW = 0.11.3 × DBH1 = 0.0997421 , which satisfies the expression (2) and achieves stable control. Ma
In addition, root gap RG = 4 mm, bead height BH = 8
If DBH1 is calculated for mm, DBH1 becomes 0.081934 , and 1.3 × DBH1 becomes 0.105551 . Therefore, the equation (3) is satisfied and unstable control is achieved.
You.

FIG . 8 shows a groove angle θ = 40 ° and one width imitation.
Control DOW = 0.1 mm, root gap RG = 2
Formula for 10mm, bead height BH = 2-12mm
DBH1 is calculated in (8), and from equations (2) and (3),
The stable control is indicated by 、, and the unstable control is indicated by ×. Cheap
The determined control area is determined from now on, and G ≧ 0.6H +
0.8 (G: root gap, H: bead height)
be able to. Therefore, the good controllability range is shown in FIG.
Above the straight line AB. That is, G ≧ G in the relationship between the root gap G (mm) and the bead height H (mm).
This is a range in which 0.6H + 0.8 is satisfied.

On the other hand, the bead becomes too fast welding speed in order to reduce the deposition rate per unit length in the height less than 2 mm, or, for that would the wire feed rate slow to excessively lower the welding current In addition, the shape of the beads is irregular and the melting becomes shallow, so that defects tend to occur and the weldability is poor. Further, in the region where the bead height exceeds 12 mm, the welding speed is too slow to increase the welding speed per unit length, or the welding current is too high by increasing the wire feeding speed. In addition, the bead shapes overlap and defects are likely to occur, which also results in poor weldability. Accordingly, the range in which both the controllability of the arc sensing width control and the weldability are good is a region where the bead height is 2 to 12 mm above the straight line AB in FIG.

In overlay welding, an appropriate bead height can be obtained by setting the bead width of the preceding layer to the root gap of the next layer, but the root gap is widened in the upper portion of the overlay welding of a thick plate. Since the upper limit of the root gap that can be welded by one layer and one pass depends on the required value of the mechanical performance of the weld metal, the welding material, the welded steel plate, and the welding conditions due to the influence of the heat input and the like, the upper limit of the root gap is not determined in the present invention. Was. Therefore, in the range of the root gap that can be welded by one layer and one pass from the weldability, it is above the straight line AB in FIG.
If 0.6H + 0.8 and the bead height is in the range of 2 to 12 mm, both controllability and weldability are good. In addition,
The method of measuring the bead height and the bead width is as shown in FIG. 10 by applying the hatched welding cross-sectional area to a trapezoid having the root gap as the upper base, and setting the height of the trapezoid having the same area as the bead height, The lower bottom was the bead width.

[0033]

EXAMPLES Example 1 The present invention will be described in more detail with reference to examples. FIG.
When the bead heights are equal according to the characteristics of the bead cross-sectional shape shown in Fig. 7, since the narrower the root gap, the larger the BH1, the one-layer one-pass welding while controlling the width of the groove where the root gap is continuously narrowed by arc sensing. Then, it was experimentally confirmed to what mm the root gap at which stable copying control can be performed. FIGS. 11 and 12 show a welding apparatus and a test plate used in the experiment. The test plate has a thickness T = 50 mm,
A groove with a start side root gap G1 = 10 mm, an end side root gap G2 = 1 mm, and a depth F = 30 mm was formed on a steel plate having a width W = 400 mm and a length L = 2000 mm. As for the welding device, the swinging device 11 to which the welding torch 5 is attached and the motor of the traveling trolley 10 on which the welding torch 5 is mounted are controlled by a swinging motor controller 21 and a microcomputer 23 via a traveling motor controller 22 to swing width. ,
And the traveling truck speed was controlled.

Further , the microcomputer detects at a time interval of 1/100 second by the shunt 18 attached to the output terminal of the welding power source through the low-pass filter 19 and the A / D converter 20 at an interval of 1/100 second.
The welding current value converted by the above is integrated, and I shown in FIG.
LG, ILC, IRG, and IRC are obtained, and SL and ISR are obtained by calculating the above-described equations of SL = ILS-ILC and SR = IRG-IRC. The SL and SR values are compared with a width control threshold value SBK experimentally obtained in advance. If SL> SBK and SR> SBK, the swing width is narrowed to increase the welding speed. Conversely, SL <SBK and SR <SB
If K, the swing width is wide and the welding speed is slow, and the swing width and the bogie speed are corrected as in the case of other than the above.

The amount of correction at one time is a swing width of 0.1 mm, and the speed of the bogie is the welding speed correction corresponding to the correction of the bead cross-sectional areas DSA and DSB shown in FIG. And the bead height constant control was performed. The initial value of the welding speed was set from the melting angle calculated from the wire feed speed determined from the bead angle calculated from the starting groove angle, the root gap and the target bead height, and the weldability. The initial value of the swing width was set according to the target bead height with reference to FIG. The swing speed was constant at a speed at which the swing pitch was 3 mm from the initial values of the swing width and the welding speed. The test plate was set so that the groove line was parallel to the rail, and repeated 5 times with the groove angle, wire diameter, and shield gas shown in Table 1 in consideration of the variation in the experiment for each condition code.
Repeat welding was performed.

[0036]

[Table 1]

As an evaluation method, the bead height after welding was measured at a position corresponding to the root gap shown in Table 1 as controllability evaluation. If the difference from the target bead height was 1 mm or less, it was good.
The position exceeding m was determined to be defective. In addition, as a weldability evaluation, a weld bead was subjected to an X-ray transmission test (JISZ3104),
IS class 1 or higher was evaluated as good, and less than class 1 was evaluated as poor. Table 1
It was found from the experimental results shown in the above that when the target bead height was 1 mm, the bead formation was unstable and the weldability was poor and poor. At the target bead height of 14 mm, the molten pool was too advanced, and a defect of poor penetration occurred from the start, and the width tracing control was not stable, and both the weldability and the controllability were poor.

In the target bead heights of 2, 4, 6, 8, 10 and 12 mm, when the root gap is wider than 2, 3, 5, 6, 7 and 8 mm, the width scanning control is stable and both controllability and weldability are good. However, in the range where the root gap is narrower than this, the bead height becomes too high or too low, and the control is unstable and the controllability is poor. Note that the conventional condition was that the bead height d was around 6 mm, but it was reproduced that stable welding was impossible in a narrow region where the root gap was 4 mm or less.

[0039]

[Table 2]

[0040] Example 2 Next, Table 2 steel sheet after welding g from condition b of Example 1
Under the welding conditions and the number of layers shown in FIG. Welding was performed on the beads having good weldability and controllability shown in Table 1. The root gap at the start position was measured by the method shown in FIG.

As an evaluation method, the bead height after the formation welding was measured as controllability evaluation, and the difference between the target bead height and the target bead height was 2 mm or less. Further, as a weldability evaluation, a weld bead was subjected to an X-ray transmission test (JISZ3
104) Then, JIS grade 1 or higher was evaluated as good, and less than JIS grade was evaluated as poor. The experimental results show that both the controllability and the weldability are good as shown in Table 2, and that even if the root gap is widened in the upper part of the formation welding, good arc sensing control is possible within the range of the present invention. I understand.

[0042]

As is apparent from the above-described results, the present invention controls the width of the arc sensing by selecting a bead height with respect to the root gap, thereby ensuring reliable control even in a narrow root gap, and achieving high efficiency in a wide root gap. Since stable automatic welding has become possible, the welding accuracy of thick plate welding, which requires multi-layer welding in particular, has been improved, greatly contributing to automation and robotization.

[Brief description of the drawings]

FIG. 1 is a graph showing a range of a bead height and a root gap in the present invention.

FIG. 2 is a graph showing fluctuation of a welding torch and a change in a welding current resulting therefrom.

FIG. 3 is a waveform chart showing a change in welding current.

FIG. 4 is a perspective view showing how an arc position on a molten pool moves during width control when a welding speed changes.

FIG. 5 is a perspective view showing how the arc position on the molten pool moves during width control when the welding speed changes.

FIG. 6 is a perspective view showing how the arc position on the molten pool moves during width control when the welding speed changes.

FIG. 7 is a graph showing changes in the torch swing width and the bead width depending on the bead height.

FIG. 8 shows the relationship between bead height and root gap.
Graph showing the area where stable welding is possible

FIG. 9 is an explanatory diagram showing a change in bead height when the welding speed is corrected to be low even though the root gap has not changed.

FIG. 10 is an explanatory diagram of a method for measuring a bead height and a bead width.

FIG. 11 is a schematic view of a welding device used in an example.

FIG. 12 is a plan view (a) and a side view (b) of a steel plate used in the examples.

Claims (1)

(57) [Claims] An arc sensing control for controlling a swing width of a welding torch and a welding speed or a wire feeding speed in accordance with a variation of a root gap G, and sequentially controlling the bead height H to be constant. In the consumable electrode type arc welding method for one-pass welding, the H (mm) is 2 or more and 12 or more.
And in relation to the G (mm), G
A consumable electrode type arc welding method, characterized in that control is performed in a region where an equation of ≧ 0.6H + 0.8 is satisfied.