Submerged arc welding machine and submerged arc welding method

Abstract

The invention provides a submerged arc welding machine and a submerged arc welding method. Provided is a submerged arc welding method with which, in AC submerged arc welding, even when various operating parameters for operating the waveform of an AC current change, it is possible to quickly calculate various other parameters for specifying the waveform of the AC current in accordance with the change in the operating parameters, and to obtain an effective current such as a target given current. In a submerged arc welding method, a plurality of operating parameters for operating an AC waveform of a current output from a welding power source and a parameter for determining the AC waveform together with the plurality of operating parameters are associated with a constraint condition that an effective value of the output current coincides with a given current, a plurality of tables in which two or three operating parameters and function values are associated are prepared, the plurality of operating parameters are accepted, and the parameters are calculated by referring to the plurality of tables using the accepted plurality of operating parameters.

Description

Technical Field

[0001] The invention relates to a submerged arc welding machine and a submerged arc welding method. Background Art

[0002] In AC submerged arc welding, it is known that the polarity of the welding wire is alternately switched between positive and negative, and therefore, the penetration shape or the welding wire deposition speed can be controlled by manipulating the length or peak current of the EP (Electrode Positive) period and the EN (Electrode Negative) period (e.g., Patent Document 1). The EP period is a period when the voltage polarity of the welding wire is positive, and the EN period is a period when the voltage polarity of the welding wire is negative.

[0003] The longer the EP period is extended, or the higher the peak current during the EP period is, the narrower and deeper the penetration shape becomes, and the wire deposition rate tends to decrease. In addition, the longer the EN period is extended, or the higher the peak current during the EN period is, the wider and shallower the penetration shape becomes, and the wire deposition rate tends to increase.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: JP Patent Publication No. 2018-153866

[0007] If the length of the EP period and the EN period or the peak current changes, the effective current (effective value of the output current) changes accordingly. For this reason, a method is generally adopted to make the associated multiple parameters work together to reduce the change in effective current. Although the change in effective current can be suppressed to a certain extent if the parameters are linked, the change in effective current cannot be completely eliminated by simple operation (linkage), and depending on the situation, a large effective current change of more than 100A may occur. Summary of the invention

[0008] The purpose of the present disclosure is to provide a submerged arc welding machine and a submerged arc welding method, which can obtain an effective current like a given current set as a target even when various operating parameters used to operate the waveform of the AC current are changed in AC submerged arc welding, and can quickly calculate various other parameters of the AC current waveform.

[0009] The submerged arc welding machine involved in one aspect of the present disclosure is a submerged arc welding machine, comprising: a storage unit, which associates multiple operating parameters for operating the AC waveform of the current output from the welding power supply and parameters for determining the AC waveform together with the multiple operating parameters in order to establish a constraint condition that the effective value of the output current is consistent with a given current, and stores multiple tables that establish correspondence between 2 or 3 of the operating parameters and function values; a setting acceptance unit, which accepts the multiple operating parameters; and an operation processing unit, which uses the multiple operating parameters received by the setting acceptance unit to calculate the parameters with reference to the multiple tables stored in the storage unit.

[0010] The submerged arc welding method involved in one aspect of the present disclosure is a submerged arc welding method, which establishes an association between multiple operating parameters for operating the AC waveform of the current output from the welding power supply and parameters for determining the AC waveform together with the multiple operating parameters in order to constrain the effective value of the output current to be consistent with a given current. A plurality of tables corresponding to 2 or 3 of the operating parameters and function values ​​are prepared, the plurality of operating parameters are accepted, the plurality of operating parameters are used, and the parameters are calculated with reference to the plurality of tables.

[0011] Effects of the Invention

[0012] According to one aspect of the present disclosure, in AC submerged arc welding, even when various operating parameters used to operate the AC current waveform are changed, an effective current as the target given current can be obtained, and various other parameters of the AC current waveform can be quickly calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram showing a structure of a submerged arc welding machine according to the present embodiment.

[0014] Figure 2 This is a block diagram showing a configuration of a submerged arc welding machine according to the present embodiment.

[0015] Figure 3 This is a schematic diagram showing an example of an AC waveform of a current output from a welding power source.

[0016] Figure 4 It is a flowchart which shows the control method concerning this embodiment.

[0017] Explanation of symbols

[0018] 1: welding power source, 2: control device, 3: welding torch, 4: wire reel, 5: wire feeding device, 6: flux supply device, 7: trolley, 8: voltage sensor, 9: current sensor, 21: calculation processing unit, 22: storage unit, 22a: first table, 22b: second table, 23: setting receiving unit, 24: wire feeding speed control unit, 25: flux supply control unit, 26: trolley travel speed control unit, A: base material, B: flux, W: welding wire. DETAILED DESCRIPTION

[0019] Hereinafter, specific examples of the submerged arc welding machine and the submerged arc welding method according to the embodiments of the present disclosure will be described with reference to the accompanying drawings. In addition, the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0020] Hereinafter, the present invention will be described in detail based on the drawings showing the embodiments.

[0021] <Structure of submerged arc welding machine>

[0022] Figure 1 1 is a schematic diagram showing a structure of a submerged arc welding machine according to the present embodiment. Figure 2 The block diagram shows a structure of a submerged arc welding machine according to the present embodiment. The submerged arc welding machine according to the present embodiment includes a welding power source 1, a control device 2, a welding torch 3, a welding wire reel 4, a welding wire feeding device 5, a flux supply device 6, a carriage 7, a voltage sensor 8, and a current sensor 9.

[0023] The welding torch 3 is made of a conductive material such as copper alloy, guides the welding wire W to the welded portion of the base material A, and has a cylindrical contact tip for supplying welding current required for arc generation. The contact tip contacts the welding wire W inserted therein and supplies welding current to the welding wire W.

[0024] The welding wire feeding device 5 includes a feeding roller 51 for pulling out the welding wire W wound on the welding wire reel 4 and feeding it to the welding torch 3, and a motor 52 for rotating the feeding roller 51. The welding wire feeding device 5 supplies the welding wire W to the welding torch 3 by rotating the feeding roller 51. The feeding speed of the welding wire W is adjusted according to the welding voltage so that the arc length does not change. The feeding speed of the welding wire W of the welding wire feeding device 5 is controlled by the control device 2.

[0025] The flux supply device 6 includes a flux hopper 61, a nozzle 62, a valve 63, a flux recovery machine (not shown), etc. The flux hopper 61 accumulates the flux B introduced from the top, and supplies the flux B to the welded portion of the base material A through the nozzle 62 connected to the bottom of the flux hopper 61. The valve 63 opens and closes the path from the flux hopper 61 to the nozzle 62 to adjust the supply amount of the flux B. The opening and closing of the valve 63 and the opening and closing amount are controlled by the control device 2. In addition, the opening and closing of the valve 63 and the opening and closing amount can also be configured to be manually operated.

[0026] The trolley 7 is a transport device that carries the welding power source 1, the control device 2, the welding torch 3, the welding wire reel 4, the welding wire feeding device 5, the flux supply device 6, etc. and moves along the welding line. The trolley 7 has a travel motor that rotates the wheels. The trolley 7 moves along the welding line of the base material A, and the granular flux B stored in the flux hopper 61 is spread along the welding line, and the welding wire W is fed into the flux B by the welding wire feeding device 5. The travel speed of the trolley 7 is controlled by the control device 2.

[0027] The voltage sensor 8 is a sensor that detects the voltage between the arc voltage detection lead wire attached to the welding torch 3 and the arc voltage detection lead wire attached to the base material A, and outputs a voltage value signal indicating the detected voltage value to the control device 2 as a welding voltage (arc voltage).

[0028] The current sensor 9 detects the welding current supplied from the welding power source 1 to the welding wire W via the welding torch 3 and flowing to the base material A via the arc, and outputs a current value signal indicating the detected current value to the control device 2 .

[0029] The welding power source 1 is an inverter-controlled AC welding power source having a constant current characteristic, and includes a rectifier 11, a primary inverter 12, a transformer 13, a rectifier 14, a DC inductor 15, and a secondary inverter 16 connected in series in order from the input side of the commercial power source. The welding power source 1 is connected to the contact tip of the welding torch 3 and the base material A via a power supply cable. The welding power source 1 supplies welding power between the welding wire W and the base material A using the commercial power source as input, thereby generating an arc.

[0030] The rectifier 11 rectifies the AC of the commercial power supply and outputs it to the primary inverter 12. The primary inverter 12 is driven at a high frequency of more than ten kHz to several tens of kHz, and supplies the high-frequency AC to the primary coil of the transformer 13. The transformer 13 transforms the AC, rectifies the transformed AC in the rectifier 14, and outputs it to the secondary inverter 16 via the DC inductor 15. The secondary inverter 16 is driven at a low frequency of several tens to several hundreds of Hz, and outputs the low-frequency AC. By the output of the AC, an AC welding voltage is applied between the welding torch 3 and the base material A, and the welding current supplied from the welding power source 1 flows from the welding torch 3 to the welding wire W via the power cable. The welding current is used to weld the base material A using the heat of the arc generated between the base material A and the welding wire W. The arc is covered with the flux B supplied by the flux supply device 6.

[0031] The control device 2 is a circuit that outputs control signals to the primary inverter 12 and the secondary inverter 16 of the welding power source 1 to independently digitally control each inverter. In addition, the control device 2 controls the feeding speed of the welding wire W of the wire feeding device 5, the supply amount of the flux B of the flux supply device 6, the travel speed of the carriage 7, and the like.

[0032] Control device 2 is a processor and includes a calculation processing unit 21 such as a CPU or a multi-core CPU, a storage unit 22 , a setting receiving unit 23 , a wire feeding speed control unit 24 , a flux supply control unit 25 , and a carriage travel speed control unit 26 .

[0033] The storage unit 22 is a storage device including a nonvolatile memory such as a ROM (Read Only Memory) or an EEPROM, and a volatile memory such as a RAM (Random Access Memory). The storage unit 22 stores a first table 22a and a second table 22b used to make the effective value of the alternating current consistent with the set current. The first table 22a and the second table 22b will be described in detail later.

[0034] The setting receiving unit 23 is an input device such as a button, a dial, etc., and receives setting information including the set current of the submerged arc welding machine and other welding conditions. In addition, the setting receiving unit 23 receives setting or changing of operating parameters for operating the AC waveform of the current output from the welding power source 1.

[0035] The wire feeding speed control unit 24 is connected to the driving circuit of the motor 52, and controls the feeding of the welding wire W of the wire feeding device 5 by outputting a rotation control signal corresponding to the welding wire feeding speed to the driving circuit. The feeding roller 51 rotates at a speed corresponding to the rotation control signal, and supplies the welding wire W to the welded portion of the base material A via the welding torch 3.

[0036] The arc length is proportional to the welding voltage (arc voltage). The welding voltage is the voltage between the conductive tip of the welding torch 3 and the base material A, and is detected by the voltage sensor 8. The wire feed speed control unit 24 sets the feed speed setting value as the target value. The wire feed speed control unit 24 controls the feed speed of the welding wire W using the difference between the feed speed setting value and the welding voltage detected by the voltage sensor 8 as the operation amount so that the arc length becomes constant.

[0037] The flux supply control unit 25 is connected to a drive circuit that opens and closes the valve 63 of the flux supply device 6, and controls the supply of the flux B of the flux supply device 6 by outputting an opening and closing signal corresponding to the flux supply amount to the drive circuit. In the case of a structure in which the opening and closing of the valve 63 is manually operated, the flux supply control unit 25 is not required.

[0038] The carriage travel speed control unit 26 is connected to a drive circuit of a travel motor that drives the carriage 7 , and controls the travel of the carriage 7 by outputting a travel control signal according to the travel speed of the carriage 7 to the drive circuit.

[0039] In addition, the voltage sensor 8, the current sensor 9, the primary inverter 12, and the secondary inverter 16 are connected to the signal input and output terminals (not shown) of the control device 2, and the control device 2 performs PWM control on the primary inverter 12 based on the set welding conditions, the detected welding current, and the welding voltage so as to operate with constant current characteristics. In addition, the control device 2 operates or controls the AC current waveform based on the set current and the operating parameters received by the setting receiving unit 23. The welding voltage used is applied between the base material A and the welding wire W, and the welding current is energized.

[0040] <Method for keeping the effective current value constant>

[0041] The control device 2 according to the present embodiment is a welding system that can calculate the peak current during EN according to the set values ​​of various parameters of the waveform of the specified AC current so that an effective current like the set current can be obtained. As a result, the submerged arc welding machine can keep the effective current constant from the beginning of the AC output, and can stabilize the penetration depth.

[0042] (A) Determination of parameter operation method

[0043] Figure 3 This is a schematic diagram showing an example of an AC waveform of a current output from welding power source 1 . Figure 3 The AC waveform shown is a waveform based on a sine wave.

[0044] First, it is determined how to operate the AC waveform or the multiple parameters involved in its adjustment. That is, the multiple parameters are the number of patterns that define the shape of the AC waveform. Although it also depends on the shape of the AC waveform and the control method, for example, in a sine wave waveform, the length of the EP (Electrode Positive) period and the EN (Electrode Negative) period, the peak current of each of the EP period and the EN period, and the polarity switching current are the parameters that determine the AC waveform.

[0045] The EP period is a period during which the voltage polarity of the welding wire is positive, and the EN period is a period during which the voltage polarity of the welding wire is negative.

[0046] The polarity switching current is the threshold current for switching the positive and negative of the alternating current. If the current decreases, the arc rigidity will weaken, and magnetic blow may occur, which may cause unstable penetration. Therefore, in order to shorten the period when the current decreases to suppress magnetic blow, sometimes Figure 3 As shown, it is used in conjunction with control to change the current at a high speed during the polarity switching current.

[0047] If all these parameters are set directly, the AC waveform will be uniquely determined, so the effective current may not necessarily match the set current. In addition, if the length of the EP period and the EN period is set separately, the AC frequency changes, making it difficult to adjust the welding conditions.

[0048] For this purpose, a plurality of operating parameters for operating the AC waveform of the current output from the welding power source 1 are determined. For example, the AC frequency of the current, the EN ratio, the EP / EN peak current ratio, the polarity switching current, and the set current are set as the operating parameters. The EN ratio is the ratio of the EN period to the length of the AC 1 cycle, and the EP / EN peak current ratio is the ratio of the peak current during the EP period to the peak current during the EN period. The set current is a current value set as a target value of the effective value of the current output from the welding power source 1.

[0049] When the operating parameters are determined as described above, the lengths of the EP period and the EN period are determined according to the set AC frequency and the EN ratio. In addition, the polarity switching current and the set current are directly set, and the value is determined to be one. On the other hand, regarding the peak currents during the EP period and the EN period, these ratios are set but the values ​​are not determined, and there is operational freedom. For this reason, the effective current is given to be consistent with the set current as a constraint condition to determine the peak current during the EP period and the EN period. That is, the peak currents during the EP period and the EN period can be calculated in accordance with various operating parameters so that the effective current is consistent with the set current.

[0050] (B) Analysis and derivation of peak current (preliminary derivation)

[0051] The peak currents mentioned above are derived analytically. The peak currents in each period can be characterized as functions of various other operating parameters. Of course, depending on the waveform pattern and control method, not all operating parameters may affect the peak current.

[0052] In addition, the derived formula of the peak current obtained here is often a complicated calculation formula including square roots, etc., and if it is directly calculated algebraically, the calculation burden is large and time-consuming. However, the various operating parameters mentioned above may be changed during welding. Therefore, when the settings are changed, for example, the peak current needs to be recalculated and updated quickly within a short time of less than 10ms. For this reason, the peak current calculation in a short time is realized by the following method.

[0053] (C) Variable separation of peak current derivation formula

[0054] The peak current derivation formula is transformed into a composite function of multiple element functions with as few variables as possible. The element functions constituting the composite function are preferably functions with 2 to 3 operating parameters as variables. More preferably, the element functions are preferably functions with 2 operating parameters as variables. For example, in the above-mentioned sine wave-based waveform, the peak current is characterized as a composite function of element functions with both the EN ratio and the EP / EN peak current ratio as variables, and element functions with both the polarity switching current and the set current as variables. The composite function can be characterized by addition, subtraction, multiplication and division of multiple element functions.

[0055] (D) Algebraic calculation of element functions

[0056] For each of the above-mentioned element functions, the calculation results of the case where each variable, i.e., each operating parameter changes at a fixed interval are tabulated. Based on the multiple tables, the calculation processing unit 21 calculates the calculation results of each element function by linear interpolation according to the values ​​of each variable actually set. In addition, the reason for separating the variables of the element function is that the fewer the types of variables, the simpler the table can be. Details will be described later.

[0057] (E) Calculation of peak current

[0058] The peak currents during the EP and EN periods are calculated based on the obtained element functions. Specifically, the operation parameters are used as the key, and multiple tables are referred to to obtain function values, and the peak currents during the EP and EN periods are calculated by adding, subtracting, multiplying and dividing the function values.

[0059] According to the above steps, even when the operation parameters are changed during welding, the peak currents during the EP period and the EN period are quickly calculated according to the set values ​​of various parameters so that the effective current as the set current can be obtained. The control device 2 controls the output of the power supply 1 based on the calculated peak currents during the EP period and the EN period and the values ​​of other parameters, and can keep the effective current constant immediately after the start of the AC output or the change of the welding conditions, and can stabilize the penetration depth.

[0060] <Example of the case of a sinusoidal waveform>

[0061] (A) Determination of parameter operation method

[0062] The AC frequency, the EN ratio, the EP / EN peak current ratio, the polarity switching current, and the set current are set as operating parameters of the AC waveform for the operating current.

[0063] (B) Analysis and derivation of peak current (preliminary derivation)

[0064] The peak current during the EN period and the peak current during the EP period are analytically derived from the following equations (1) and (2).

[0065]

[0066] I p =RI n ...(2)

[0067] in,

[0068] I n : Peak current during EN period

[0069] I p : Peak current during EP period

[0070] r: EN ratio

[0071] R: EP / EN peak current ratio

[0072] I chg : Polarity switching current

[0073] I set : Set current

[0074] (C) Variable separation of peak current derivation formula

[0075] If the peak current during the EN period is arranged as shown in the following equations (3) and (4), variable separation can be performed as shown in the following equation (5).

[0076]

[0077]

[0078] I n =F(r, R)×G(I chg , I set )…(5)

[0079] (D) Algebraic calculation of element functions

[0080] The calculation results (function values) of the function F in the case where the EN ratio r and the EP / EN peak current ratio R are changed at fixed intervals, and the calculation results (function values) of the function G in the case where the polarity switching current Ichg and the set current Iset are changed at fixed intervals are calculated in advance and tabulated. That is, the storage unit 22 of the control device 2 stores a first table 22a in which the EN ratio r, the EP / EN peak current ratio R, and the function value of the function F are established in correspondence. In addition, the storage unit 22 stores a second table 22b in which the polarity switching current Ichg, the set current Iset, and the function value of the function G are established in correspondence. The control device 2 uses the first table 22a and the second table 22b to calculate the calculation results (function values) of the function F and the function G by linear interpolation corresponding to each operating parameter actually set.

[0081] (E) Calculation of peak current

[0082] The control device 2 calculates the peak currents during the EP period and the EN period using the above equations (5) and (2).

[0083] Figure 4 1 is a flowchart showing a control method according to the present embodiment. In the following description, the AC waveform control output from the welding power source 1 is mainly described, and the details of other arc welding controls are omitted or simplified.

[0084] The control device 2 receives various settings of the submerged arc welding machine and starts submerged arc welding control (step S11).

[0085] Next, the control device 2 receives the change of the operating parameter through the setting receiving unit 23 (step S12). Then, the control device 2 calculates the peak current of each of the EN period and the EP period by referring to the first table 22a and the second table 22b with reference to the changed operating parameter (step S13). The control device 2 controls the output current of the welding power source 1 based on the peak current of each of the EN period and the EP period and various parameters based on the set operating parameter (step S14).

[0086] Next, the control device 2 determines whether a given end condition is satisfied (step S15), and if the end condition is satisfied (step S15: yes), the welding process is terminated. If the end condition is not satisfied (step S15: no), the control device 2 repeatedly executes the process of steps S12 to S14 to perform the submerged arc welding method.

[0087] As described above, according to this embodiment, in AC submerged arc welding, even when various operating parameters for operating the waveform of the AC current are changed, the peak current that makes the effective current consistent with the set current can be quickly calculated. Therefore, no matter what values ​​the various operating parameters are set to, the effective current that is the set current can be obtained, thereby making it possible to keep the effective current constant from the beginning of the AC output and stabilize the penetration depth.

[0088] In addition, in this embodiment, the control for making the effective value of the output current consistent with the set current is described, but the peak current may be calculated so that the effective current meets an indicator other than the set current. For example, in the case of reproducing the constant voltage characteristic by moving the effective current along the desired external characteristic, the peak current may be recalculated and updated successively so that the output effective current meets the target effective current that changes moment by moment in accordance with the feedback value of the effective current and the effective voltage.

[0089] In addition, it can also be configured to directly set the peak current during the EP period and the EN period, calculate the length of the EP period or the length of the EN period based on the EN ratio, or other parameters such as the polarity switching current, and control the output of the AC current so that the effective current is consistent with the set current.

[0090] Furthermore, the polarity switching current may have different values ​​from the value for switching from the EN period to the EP period and the value for switching from the EP period to the EN period.

[0091] Furthermore, in the present embodiment, an example of operating a waveform based on a sine wave is described, but the present invention can also be applied to the case of operating a trapezoidal wave or any other current waveform. In addition, in the case of a trapezoidal wave, the AC frequency, EN ratio, EP / EN peak current ratio, upslope period ratio, downslope period ratio, polarity switching current, and set current can be set as operating parameters. The so-called upslope period ratio is a parameter that determines the time ratio at which the current is increased relative to the length of the EP period. The so-called downslope period ratio is a parameter that determines the time ratio at which the current is reduced relative to the length of the EN period.

Claims

1. A submerged arc welding machine, comprising: A storage unit for associating a plurality of operating parameters for operating the AC waveform of the current output from the welding power source with parameters for determining the AC waveform together with the plurality of operating parameters under the constraint that the effective value of the output current is consistent with the given current, and for storing a plurality of tables in which two or three of the operating parameters and the function values ​​are associated with each other; A setting accepting unit, which accepts the plurality of operation parameters; and The calculation processing unit calculates the parameters by referring to the plurality of tables stored in the storage unit, using the plurality of operation parameters received by the setting receiving unit.

2. The submerged arc welding machine according to claim 1, wherein: The operating parameters include the ratio of the length of the EP period, i.e., the electrode positive period, to the length of the EN period, i.e., the electrode negative period, the ratio of the peak currents during the EP period and the EN period, or the polarity switching current. The parameters include the length of the EP period, the length of the EN period, the peak current during the EP period, or the peak current during the EN period.

3. The submerged arc welding machine according to claim 1, wherein: The arithmetic processing unit calculates the peak current during the EN period or the peak current during the EP period based on the following equation: In=F(r,R)×G(Ichg,Iset) Ip=R×In in, In: Peak current during EN period Ip: Peak current during EP period F(r, R): Function involved in the table mentioned in 1 G (Ichg, Iset): Functions involved in the table described in Section 2 r: The ratio of the length of the EP period to the length of the EN period R: Ratio of peak current during EP and during EN Ichg: Polarity switching current Iset: given current.

4. A submerged arc welding method, In order to associate a plurality of operating parameters for operating the AC waveform of the current output from the welding power source with parameters for determining the AC waveform together with the plurality of operating parameters under the constraint that the effective value of the output current is consistent with the given current, a plurality of tables are prepared in which two or three of the operating parameters and the function values ​​are associated with each other. accepting the plurality of operation parameters, Using the received plurality of operating parameters, the parameters are calculated with reference to the plurality of tables.

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