JPS63260676A - Multi-electrode submerged arc welding method - Google Patents

Abstract

PURPOSE:To improve the weld quality by calculating the depth of penetration of each electrode from a function of a parameter on a welding condition of each electrode and a gouging cross-sectional area of an electrode just before to control a welding source of each electrode based on it. CONSTITUTION:A groove shape detector 7 is set up in front of plural welding electrodes 4a and 4b and an arithmetic and control unit 1 and a welding speed controller 6 are arranged. First, the number (n) of electrodes, the prescribed depth Pm of penetration and its torelance Jp and groove dimensions and the torelance Jk are inputted to the arithmetic and control unit 1 and a setting condition is extracted from a data base stored in advance. Information of the groove shape detector 7 is read and compared with the tolerance Jk and welding sources 2a and 2b are controlled. Further, a welding current value is corrected with respect to the excess and deficiency of a welding current and the welding sources 2a and 2b are again controlled automatically. Since the depth of penetration is maintained constant, the weld quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to bead shape control in double-sided, single-layer submerged arc welding used in the manufacture of UOE steel pipes, and particularly to automatic control of penetration depth.

[Conventional technology]

Submerged arc welding is still widely used as a highly efficient welding method, but compared to other production processing techniques,
Automation and unmanned operation are still insufficient, and in order to strengthen competitiveness, the manufacturing industry in particular is promoting the rationalization of welding work with the aim of further increasing efficiency and reducing costs.

An example of labor saving and automation in submerged arc welding is the submerged arc welding method, published in Japanese Patent Application Laid-Open No. 61-18067.
As seen in Publication No. 7, back bead formation is achieved by applying a specific electrical signal between the base material and the backing metal plate, comparing the voltage applied to both with a reference voltage during welding, and controlling the output of the welding power source. In addition to the method of controlling the bead shape by detecting groove fluctuations and automatically setting the optimal conditions stored in the computer ("Welding Technology J vol.
33. No. 1° p39.1985), etc. have been proposed. However, this single-sided submerged arc welding method requires a large welding heat input, resulting in poor weld toughness and productivity.
The field of application is limited due to low speed welding), and in the field of manufacturing high-grade line pipes where low-temperature toughness is required, single-sided, single-layer submerged arc welding is mainly adopted.

When attempting to automatically control double-sided, single-layer submerged arc welding used in the manufacture of UOEtl pipes, penetration depth in each layer becomes particularly important, unlike single-sided submerged arc welding.

That is, when welding is carried out first on the inner surface, if penetration becomes excessive due to groove variation, fatal burn-through will occur. On the other hand, when welding the outside surface, burn-through is less likely to occur, but on the other hand, if there is insufficient penetration, an unwelded part will remain in the center of the plate thickness. The present inventors have already proposed a penetration depth control method that can be applied to double-sided single-layer submerged arc welding in Japanese Patent Application Laid-open No. 60-92083, but the content is that the electrode arrangement is not in a straight line and that This is applied to deep penetration control of relatively thick materials, such as the penetration when the arc is ignited within the welding tip. It is impossible to apply.

[Problem that the invention seeks to solve]

In order to prevent welding defects such as double-sided submerged arc welding, when welding conditions are automatically controlled, welding current,
It is necessary to control not only the welding voltage but also the welding speed, but it is essential that penetration be maintained at a predetermined value no matter which control is performed. Particularly when the welding speed is controlled, it is important that the welding current value is also automatically controlled in order to ensure penetration at a predetermined value.

However, regarding penetration in multi-electrode submerged arc welding, as mentioned above, although there is knowledge about a specific range, there is still no technology that can be applied over a wide range regardless of the presence or absence of a groove or differences in penetration levels. Currently, a huge amount of effort is required to carry out welding using a trial and error method under various welding conditions and to accumulate the results in a database.

Therefore, in submerged arc welding using 2 or more and 7 or less ff1tI, the present invention clarifies the correlation between welding conditions and the penetration depth of each electrode, and calculates the welding current of each electrode based on a penetration control algorithm. The purpose is to provide a method that calculates the value by calculation, automatically controls the penetration, and obtains stable penetration.

[Means for solving problems]

The present invention has been made as a result of various studies to solve the above problems and achieve the objectives.The penetration depth of each electrode after the second electrode in multi-electrode submerged arc welding is a parameter determined by the welding conditions of the electrode. It was discovered that it can be found as a function of the cross-sectional area gouged with the previous electrode.
In multi-electrode submerged arc welding using 2 to 7 electrodes arranged in a straight line, the amount of base metal melted for each electrode, the welding speed, the width gouged by the arc, and the groove cut for the first electrode. Calculate the penetration depth for each electrode from a function that uses as variables the area and the gouging cross-sectional area of the previous electrode after the second electrode, and compare the maximum value of the penetration depth with a predetermined value, The multi-electrode submerged arc welding method is characterized in that each electrode welding current value that should be a predetermined value is determined by calculation, and each electrode welding power source is automatically controlled so that the welding current value is achieved.

[Function/Example]

FIG. 1 is a block diagram schematically showing an embodiment of two-electrode submerged arc welding according to the present invention. The arithmetic/control unit 1 is a computer system including a microprocessor, an A/D converter 8, and a D/A converter 9 as luxurious components.
In the block of the controller 1, a control flow executed by the arithmetic/controller 1 is shown.

In Figure 1, first, the number of electrodes n (in the figure, n=-
2), predetermined penetration depth Pn+ and its allowable range JP,
And groove shape (width) as required.

When inputting the depth d, etc.) and its allowable range Jk to the calculation/controller 1, the calculation/controller 1 reads these (step S
1: Hereinafter, the word step is omitted in parentheses), setting conditions are extracted from a database that has been created and stored based on appropriate welding conditions that have been obtained empirically (S3).

At this time, there is no problem even if there is no database, and in that case, the welding conditions required for calculation may be appropriately input. Then, each extracted or input electrode welding current value 1 (1 to n)
The relaxation Isum of each electrode current is determined from the equation, and the welding current distribution Ih (1=n) of each electrode is determined (S3). Here, Ih (1 to n) based on the first electrode welding current value is I h (1 to n) = 1 (1 to n) / I (1)
is required. This welding current distribution ratio is necessary to obtain a sound bead shape, and each electrode welded with the corrected r5
．． Even if the flow value increases or decreases, it is desirable that the welding current distribution ratio for each electrode be the same.

Next, the groove information of the welding start portion detected by the groove shape detector 7 installed at the welding electrode hydraulic station is read (S4).

This information is digitally converted and read via the A/D converter 8 built into the arithmetic/controller 1.

The groove shape detector 7 used here may be of any type, such as a roller type using a differential transformer or a laser beam type, as long as it can measure the groove shape. And a total of 3
111 Check whether the prepared groove is outside the allowable range Jk (S5), and if it is outside the allowable range Jk, calculate a correction value for the set welding current to obtain a predetermined penetration depth using the procedure described below ( S6), the obtained welding current value I (
1), I (2) is calculated using D built into the controller 1.
/A converter 9 to welding power sources 2a and 2b, welding voltage value E(1).

E(2) outputs the wire feed control bag [1ff3a, 3b, and the welding speed V to the welding speed control JA position 6 (
S7).

Next, start welding (S8), measure the groove shape again using the method described above (S9), judge whether it is within the allowable range Jk (5IO), and adjust the correction value of the set welding current as necessary. Calculate it (Sll) and apply the corrected value to the welding power source 2.
a and 2b, and the welding speed is increased or decreased depending on the welding situation (S12). For example, in order to maintain high efficiency, the welding speed is generally used near the limit speed for the occurrence of welding defects (such as adder cuts), and in some cases, adder cuts may occur.

An effective means for preventing such welding defects is to reduce the welding speed. Furthermore, if no welding defects occur and the welding speed is less than the upper limit speed, the welding speed may be increased to the upper limit speed in order to increase efficiency. However, when the welding speed is changed (Sl
3) If welding is performed with the welding current values T (1) and I (2) unchanged, excess or deficiency in penetration will inevitably occur. Therefore, using the new welding speed setting value input (S14), the corrected value of the set welding current is calculated again (S14).
15), the correction values I (1) and I (2) are sent to the welding power sources 2a and 2b, and the welding speed setting value V is sent to the welding speed control device 6.
(S16). Finally, it is determined whether welding has been completed (517), and if it is continuing, the groove shape is detected again (S9), the calculation of the corrected welding current value is repeated (SIO, 5ll), and the welding current value is controlled ( S12)
This maintains the penetration depth at a predetermined value.

Figure 2 shows the extracted or input data shown in Figure 1 (St, S
2); Setting conditions: each electrode welding current I (1 to n), welding voltage E (1 to nL), wire diameter Y
(1-n), fd pole spacing D d (1-n-1),
A flowchart for determining the welding current value for each electrode to obtain a predetermined temperature penetration depth based on the welding speed V, that is, step S6 in FIG. Sl 1. This is a subroutine that executes S15.

As shown in Figure 2, the penetration depth P (1~
n), the maximum penetration depth P+aax is determined by the procedure described below (518), and Pmax is determined as the predetermined penetration depth Pm.
Check whether it is within the allowable range (S19), and if it is outside the range, increase or decrease the total of each electrode welding current value by 150 + 11 (
In the example in the same figure, 100A) and (S20, 21) P again
(1 to n) and P wax are calculated (318), and if the values are within the allowable range, the welding current value 1 (1 to nL) used in the calculation is outputted, as is the welding voltage value E (1 to nL) and the welding speed V (S2
2=S7.512) Now, the means for determining the penetration depth P(1 to n) and the maximum penetration depth Pmax for each electrode in the V-groove groove in step S18 are obtained by the procedure shown in FIG. It will be done. In other words, in the same figure, first,
Counter J is 1, maximum weight penetration depth P max is 0, groove cross-sectional area Sa is 0. The temporary groove width Lx is set as L (S23
), the sum of each electrode welding '-E flow I sum and the welding current distribution dead eye + (1-n) to J? llt pole welding current value 1 (
, J) is determined (S24). Next, use the constants and formulas determined in advance to determine the width W (J) gouged by the arc of the J electrode, and the cross-sectional area for determining the arc form to determine the penetration formula to be used based on the arc form shown in Figure 4. Sm (J) and the cross-sectional area 5 (J) of the base metal that is melted by the welding power (product of welding voltage E (J) and welding current I (J)) applied to the electrode are determined (S25). and,
To determine the presence or absence of a groove (32G), if there is no groove, the groove cross-sectional area Sa and groove internal arc identification value K are set to O. Vertical distance d1 from the surface of the welded material to the arc toe on the side surface of the groove
is set to 0 (S27), the arc form is determined (S37
) Use different formulas to calculate penetration depth (538, 53
9). On the other hand, if there is a groove, check whether it is the first electrode (828), and if it is the first electrode, the arc gouging width W
(J) and the groove width529), and in the case of penetration type (A), the groove cross-sectional area Sa that affects penetration.
Then, the vertical distance d + from the surface of the welded material to the arc toe on the side surface of the groove is determined (S32), and this d is expressed as 2'fJ,
Melting type (c) and (d) S after piA
dy for use in the calculation t7 (S34 and 535) of "a' and Sa", and the groove internal arc identification value K is set to 1.
(S32).

In the case of type (B), the groove cross-sectional area Sa is determined, dl and K are set to 0 (S33), the arc form is determined (S37), and a formula for determining the penetration depth is used (S38, 539). In other words, compare the sum of S (J) and Sa with Sm (J)537), and if the sum of S (, J) and Sa is equal to or larger than Sm (J), then B as shown in Figure 5
The penetration depth P (J) of the J electrode is determined from the following equation (1) as the arc form (338).

ρ・■・W(J) 2 4 W(J
) Here, m is the weight of the base material melted per unit time and unit welding input, and ρ is the base material density.

On the other hand, if the sum of S (J) and Sa is smaller than Sm (J), the penetration depth P (J) is determined by trial and error using the method described below as the C arc shown in Figure 6.
S39), that is, the provisional gouging area 5b(J) obtained by successively decreasing the arc spread angle θ from 90° shown in the following equation (2) is compared with the sum of 5(J) and Sa,
Using 0 at the point where 5b (J) is equal to or smaller than the sum of S (J) and Sa, the penetration depth P (di) can be found from equation (3).

4 180・Sin”D
t, an θ2 Sinθ
Note that, if dl is the groove width and d is the groove depth, it is given by d 1 =d (L-W(J))/L. The calculation procedure for calculating the penetration depth is l
The present inventors have already disclosed ff 1-pole submerged arc welding (Summary of the National Conference of Welding Society, No. 39, 1986)
(September 1, p. 296-297), the key point of the present invention is to calculate the penetration depth of each electrode after the second electrode using the following method.

In other words, the penetration depth at the second and subsequent electrodes is determined by applying equations (1) to (3) above by regarding the gouging cross-sectional area Sa at the previous electrode as the groove cross-sectional area at the electrode. As a result of various experiments, it has become clear that the arc gouging width obtained with the electrode can be calculated using Set the sum of the cross-sectional area S (J) and the arc gouging cross-sectional area Sa at the previous electrode to a new Sa, and set J
is increased, and the penetration P(2 to n) is determined using equations (1) to (3) repeatedly until the final electrode n. The penetration types after the second electrode are shown in Figure 3 (c), (
(d) or (e), the arc gouging width W (J) at the electrode concerned.

If it is smaller than the groove width, the base metal melting still progresses within the groove, which is the penetration type (c). The sum of the groove cross-sectional areas Sa' acting on the electrode is defined as the groove cross-sectional area Sa of the electrode, and if dl is determined by the above-mentioned formula, then Sa' can be determined by the following formula (4).

W(J)+Ly Sa' = (dy dt) () ''・(4) Here, dy is the vertical distance from the base metal surface to the arc toe on the groove side surface at the previous electrode, and Lx is the gouging width at the previous electrode and is called the temporary groove width.On the other hand, if the arc gouging width W (J) is larger than the groove width, the in-groove arc identification value is determined by the penetration type ( Determine (d) and (e) (S3L). If K = 1, it is type (d), and like type (c), the arc gouging cross-sectional area Sa of the previous electrode and the opening that affects penetration are determined. Tip cross-sectional area S
The sum of al+ is set as the groove cross-sectional area Sa of the electrode, and dl and K are set to O (S35). Here, SaI+ is.

It is determined by the following equation (5).

L+Lx Sa" = (d-dy) ()... (5) Also, if it is determined to be type (e), the arc gouging cross-sectional area Sa of the previous electrode is changed to the groove of the current electrode. The cross-sectional area is Sa, and d1=0 (536).

The arc form is determined using this Sa, and the penetration formula for either B or C arc form is used.

Can you find the penetration depth P (J) of each electrode? Then, if the maximum value of the penetration P(J) for each electrode is P rrrax, the penetration depth under the welding conditions will be obtained.

In addition, as a result of experimentally finding, the base metal melting amount m per unit time and unit welding input in equation (1) is approximately proportional to the square root of the welding current 1(1-n)· for each electrode, and m =kJ
It can be expressed as below, and when using an AC droop characteristic power supply with no change in the constant for each electrode, it is approximately 8.5 × 1
6-#.

It is also necessary to experimentally determine the arc gouging width W (J) in advance. For example, when using a wire diameter of 0.48 cm in 3r single-pole submerged arc welding, each electrode W (J) is as follows (6) ~ The formula (8) is obtained.

W(1)=0.0088・I” '・E/ (v”
'・Dd(1)"" ) -(6)W(2)=0.
00578・I"・E"/Cv"・"'・Dd
(2)””@)-...(7)W(3)=0.0199
・I'・3' −E” ' /v” ' −
(8) Here, Dd(1) and Dd(2) are the first to second electrode spacing and the second to third electrode spacing, respectively.

Further, as can be seen from FIG. 4, the arc form determination cross-sectional area Sm(J) is expressed by the following equation (9).

By incorporating such constants and formulas into the calculation/controller l and calculating and outputting each electrode welding current value to obtain a predetermined penetration depth, it becomes possible to maintain a predetermined penetration depth. .

FIG. 7 shows that in order to verify the penetration depth calculation method of the present invention, the welding current of each electrode was 1200 A in order from the first electrode in three-electrode submerged arc welding.

1000A, 800A, welding voltage 30V, 3
FIG. 4 is a diagram showing the relationship between the calculated and measured penetration depth and the welding speed when only the welding speed is changed while keeping the voltage constant at 5V and 35V. The welding power source used was one with AC drooping characteristics, the wire was 2% Mn-based, the first and second electrodes were 0.48 cmφ, and the third electrode was 0.4 cmφ. A 5M50 steel plate with a thickness of 20+mm and a V-groove groove with an angle of 90'' and a depth of 0, 3c+* was used using melted flux.The electrode spacing was 2 between the first and second electrodes. .5CIIl, and the second-third electrode interval was 1.5 cm.

1 in the same figure. What is the actual measured penetration depth of the second electrode?

Welding was interrupted, and 81 cross-sectional macro specimens were taken from the places where the welding was interrupted and appeared to have been gouged by each electrode. For this reason, the first
．． 2nd f! ! Actual measurement of penetration depth at the pole (!) Although there is some variation from the calculated value shown by the dotted line and the dashed-dotted line, the measured value of the penetration depth at the steady-state macro shown by the black dot and the calculation of the third electrode shown by the solid line. It was verified that the values are in good agreement with each other.The calculation results in this case indicate that the maximum penetration depth is at the final electrode, but depending on the distribution of welding conditions for each electrode, the maximum penetration depth may be at the intermediate electrode. may be obtained.

Next, the present invention shown in Fig. 1 was configured for three-electrode submerged arc welding, and a groove angle of 90 m, a depth of 0.32 cm, and a groove angle of 90°, 0.30° was applied to a 5M50 material with a thickness of 12.7 mm.
m and a V-groove with different groove shapes are provided, the V-grooves are aligned in a straight line, welding is performed at a constant welding speed of 3.1cm/5ee, and the welding current is adjusted so that the penetration depth is 0.7cm. The value was automatically controlled. The power supply, wires, flux, and electrode spacing used were the same as described above. Note that a groove (■ with a groove angle of 90° and a depth of 0.32 cm) for external welding was provided on the back side of the test material.

As a result, as can be seen from the comparison of penetration depth under welding conditions corresponding to the groove shapes shown in Table 1, the groove angle was 90.
°, during V-groove welding at a depth of 0.32 cm, the welding current values of the first to third electrodes were 1040A and 7g0A, respectively.

620A ensures a penetration depth of approximately 0.7c+++,
In the part transitioned to the ■groove with a groove angle of 90a, a depth of 0, and 39cm, the first to third electrode welding current values are 97, respectively.
0A.

730A and 580A, and the amount of remaining rii decreases due to the enlargement of the groove cross-sectional area and the decrease in the total welding current value, but the penetration depth is approximately 0.7 cm, and no burn-through occurs. confirmed.

Table 1 Furthermore, as shown in Figures 8a, 8b, and 8C, even in 7-electrode submerged arc welding, the actual measured values and calculated values were compared, and the penetration depth was approximately 0.8 in both cases.
It was confirmed that there was good agreement with cm. In Fig. 8a, 4cm4g is a line diagram of the vertical penetration cross section drawn by calculation using the 1st to 7th electrodes, Fig. 8b is a line diagram of the penetration cross section similarly drawn by calculation, and Fig. 8C is a diagram using the conditions of the calculation result. , is a cross-sectional macro trace diagram of a bead subjected to 7-electrode submerging. In the welding power source used here, the first electrode has DC reverse polarity, the second to seventh electrodes all have AC drooping characteristics, the wire is the same as described above, and the wires from the 4th @ pole onwards are 0.
．． 4craφ is used. The back surface of the test material welded in Table 1 was used as the welding base material, and the groove angle was 90 @, depth was 0, and 34 cm. Note that the flux is the same as described above. The welding conditions (current/voltage) are 107OA/30V, 860A/35°81 in order from the 1st ffi pole.
OA/35V, 760A/35V, 720A/35
．． 66OA/35°600/35V, welding speed is 6
am/sec.

As described above, the present invention can be applied to all multi-electrode submerged arc welding in which any number of electrodes, from 2 to 7, are arranged in a straight line to form one molten pool.

〔Effect of the invention〕

As described above, according to the present invention, the optimum welding current value for each electrode is automatically set in order to obtain a predetermined penetration depth regardless of the penetration depth level and the presence or absence of a groove. Even when unmanned, a proper weld bead with no melt-through and insufficient penetration can be obtained. In addition, since the present invention formulates the relationship between penetration depth and welding conditions, it does not require a huge database, the capacity of the calculation/controller 1 is simplified, and processing time is shortened, which is a great advantage for industrial use. Extremely effective.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing an embodiment in which the present invention is applied to two-electrode submerged arc welding. FIG. 2 shows the welding current value calculation S6°Sll shown in FIG.
It is a flowchart showing the contents of S15, and shows a procedure for obtaining each electrode welding current value that provides a predetermined penetration depth. FIG. 3 is a flowchart showing the contents of calculation 318 shown in FIG. 2, and shows a procedure for determining the maximum weight penetration depth of n-electrode submerged arc welding. FIG. 4 is a cross-sectional view of the base material 5, and shows a cross-sectional area for determining the arc form for determining the penetration formula to be used depending on the arc form. FIG. 5 is a cross-sectional view of the base material 5, showing the penetration shape according to the B arc form. FIG. 6 is a cross-sectional view of the base material 5, showing a welding shape according to the C-arc form. FIG. 7 is a graph showing the correlation between the calculated value and the measured value of penetration depth for each electrode in three-electrode submerged arc welding. Fig. 8a is a vertical cross-sectional view of a weld bead drawn by calculation of the penetration shape in 7-electrode submerged arc welding, Fig. 8b is a cross-sectional view, and Fig. 8c is a trace diagram of an actually measured macro cross-section. The figure shows a penetration vertical section drawn by calculation, Fig. 8b shows a penetration cross-section drawn by calculation as well, and Fig. 8c is a diagram tracing the cross-section of the actually measured macro. 1: Arithmetic/controller 2a, 2b: Welding power source 3a,
3b: Wire feeding control device 4a, 4b, 4c, 4d, 4e, 4f, 4g: Welding electrode 5: Base material 6: Welding speed control device 7: Groove shape detector 8: Δ/D converter 9: D /A conversion converter type number of poles PI! l: Complete penetration depth JP
: Penetration depth tolerance range Jk: Groove shape tolerance range I (1 to n): Each electrode welding current value T: (1 to mouth): Each electrode welding voltage value Y (1”n): Each electrode wire diameter L ) d (1-n-1) : Distance between each electrode V: Welding speed, : Groove width d: Groove depth T
h (1 to n): Welding current distribution for each electrode I sum: Total welding current P (J): Penetration depth of each electrode Prnax: Maximum weight penetration depth J: Counter Lx
: Temporary groove width W (J): Each electrode gouging width Sm (J): Cross-sectional area for determining arc form: Arc toe in groove Sθ: Groove cross-sectional area or gouging cross-sectional area that affects penetration depth dl: Vertical distance from the base metal surface to the arc toe of the groove surface 0: Arc spread angle

Claims (1)

[Claims] In multi-electrode submerged arc welding using 2 to 7 electrodes arranged in a straight line, the amount of base metal melted for each electrode, the welding speed, the width gouged by the arc, and the groove cut for the first electrode. Calculate the penetration depth for each electrode from a function that uses as variables the area and the gouging cross-sectional area of the previous electrode after the second electrode, and compare the maximum value of the penetration depth with a predetermined value, A multi-electrode submerged arc welding method, characterized in that each electrode welding current value that should be a predetermined value is determined by calculation, and each electrode welding power source is automatically controlled so as to achieve the welding current value.