Submerged arc welder and submerged arc welding method

Abstract

To provide a submerged arc welding method that even when changing various kinds of control parameters for controlling waveforms of AC currents, can quickly calculate other various kinds of parameters for setting the waveforms of the AC currents in accordance with the change of the control parameters to obtain effective currents corresponding to target predetermined currents, in AC submerged arc welding.SOLUTION: In a submerged arc welding method, a plurality of tables in which two or three control parameters are made to correspond to function values is prepared in order to associate a plurality of control parameters for controlling AC waveforms of currents outputted from a welding power source with parameters for setting the AC waveforms together with the plurality of control parameters, under a constraint condition that effective values of the outputted currents match predetermined currents, and the plurality of control parameters is received, and the parameters are calculated while referring to the plurality of tables, using the received plurality of control parameters.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] In AC submerged arc welding, the polarity of the welding wire is alternately switched between positive and negative, and it is known that the penetration shape or wire deposition rate can be controlled by manipulating the length or peak current of the EP (Electrode Positive) period and EN (Electrode Negative) period (for example, Patent Document 1). 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 electrode polarity of the welding wire is negative.

[0003] The longer the EP period or the higher the peak current during the EP period, the narrower and deeper the weld penetration shape becomes, and the wire deposition speed tends to be slower.The longer the EN period or the higher the peak current during the EN period, the wider and shallower the weld penetration shape becomes, and the wire deposition speed tends to be faster. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP2018-153866A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the length of the EP period and 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 used in which multiple related parameters are linked to reduce the change in effective current. Linking the parameters can reduce the change in effective current to a certain extent, but a simple operation (linking) alone cannot completely eliminate the change in effective current, and in some cases a large change in effective current of more than 100 A can occur.

[0006] An object of the present disclosure is to provide a submerged arc welding machine and a submerged arc welding method that can quickly calculate various other parameters of an AC current waveform, which makes it possible to obtain a target effective current that is the specified current, even when various operating parameters for manipulating the AC current waveform are changed in AC submerged arc welding. [Means for solving the problem]

[0007] A submerged arc welding machine according to one aspect of the present disclosure is a submerged arc welding machine comprising: a memory unit that stores a plurality of tables that associate two or three operating parameters with function values, in order to associate a plurality of operating parameters for manipulating the 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, with the constraint that the effective value of the output current matches a predetermined current; a setting reception unit that receives the plurality of operating parameters; and an arithmetic processing unit that calculates the parameters by referring to the plurality of tables stored in the memory unit using the plurality of operating parameters received by the setting reception unit.

[0008] A submerged arc welding method according to one aspect of the present disclosure is a submerged arc welding method which prepares a plurality of tables in which two or three of the operating parameters correspond to function values, in order to associate a plurality of operating parameters for manipulating the AC waveform of a current output from a welding power source with a parameter for determining the AC waveform together with the plurality of operating parameters, with the constraint that the effective value of the output current matches a predetermined current, receives the plurality of operating parameters, and calculates the parameters by referring to the plurality of tables using the received plurality of operating parameters. Effect of the Invention

[0009] According to one aspect of the present disclosure, in AC submerged arc welding, even when various operating parameters for manipulating the AC waveform are changed, various other parameters of the AC waveform that enable an effective current that is the target predetermined current to be obtained can be quickly calculated. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing one configuration of a submerged arc welder according to an embodiment of the present invention; [Diagram 2] 1 is a block diagram showing one configuration of a submerged arc welder according to an embodiment of the present invention; [Diagram 3] FIG. 2 is a schematic diagram showing an example of an AC waveform of a current output from a welding power source. [Figure 4] 4 is a flowchart showing a control method according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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 below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0012] Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof. <Submerged arc welding machine configuration> Fig. 1 is a schematic diagram showing one configuration of a submerged arc welder according to this embodiment, and Fig. 2 is a block diagram showing one configuration of the submerged arc welder according to this embodiment. The submerged arc welder according to this embodiment includes a welding power source 1, a control device 2, a torch 3, a wire reel 4, a wire feeder 5, a flux supply device 6, a carriage 7, a voltage sensor 8, and a current sensor 9.

[0013] The torch 3 is made of a conductive material such as a copper alloy, and has a cylindrical contact tip that guides the welding wire W to the part to be welded of the base metal A and supplies a welding current necessary to generate an arc. The contact tip comes into contact with the welding wire W that passes through its interior and supplies the welding current to the welding wire W.

[0014] The wire feeder 5 has a feed roller 51 that pulls out the welding wire W wound around the wire reel 4 and feeds it to the torch 3, and a motor 52 that rotates the feed roller 51. The wire feeder 5 supplies the welding wire W to the torch 3 by rotating the feed roller 51. The feed speed of the welding wire W is adjusted in accordance with the welding voltage so that the arc length does not fluctuate. The feed speed of the welding wire W by the wire feeder 5 is controlled by the control device 2.

[0015] The flux supply device 6 includes a flux hopper 61, a nozzle 62, a valve 63, a flux recovery machine (not shown), and the like. The flux hopper 61 stores flux B input from above, and the flux B is supplied to the part to be welded of the base material A through a 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 flux B. The opening and closing and the opening and closing amount of the valve 63 are controlled by the control device 2. The opening and closing and the opening and closing amount of the valve 63 may be configured to be manually operated.

[0016] The cart 7 is a transport device that carries the welding power source 1, control device 2, torch 3, wire reel 4, wire feeder 5, flux supply device 6, etc., and moves along the welding line. The cart 7 is equipped with a travel motor that rotates the wheels. The traveling cart 7 moves the torch 3 and flux supply device 6 along the welding line of the base material A, granular flux B stored in a flux hopper 61 is scattered along the welding line, and the wire feeder 5 feeds the welding wire W into the flux B. The travel speed of the cart 7 is controlled by the control device 2.

[0017] The voltage sensor 8 is a sensor that detects the voltage between an arc voltage detection lead wire attached to the torch 3 and an arc voltage detection lead wire attached to the base material A as a welding voltage (arc voltage) and outputs a voltage value signal indicating the detected voltage value to the control device 2.

[0018] The current sensor 9 is a sensor that detects the welding current that is supplied from the welding power source 1 via the torch 3 to the welding wire W and flows through the arc to the base material A, and outputs a current value signal indicating the detected current value to the control device 2.

[0019] The welding power source 1 is an inverter-controlled AC welding power source having constant current characteristics, and includes a rectifier 11, a primary inverter 12, a transformer 13, a rectifier 14, a DC reactor 15, and a secondary inverter 16, which are connected in series in this order from the input side of the commercial power source. The welding power source 1 is connected to the contact tip of the torch 3 and the base material A via a power supply cable. The welding power source 1 receives the commercial power source as input, and supplies welding power between the welding wire W and the base material A to generate an arc.

[0020] The rectifier 11 rectifies the AC current from the commercial power supply and outputs it to the primary inverter 12. The primary inverter 12 is driven at a high frequency of several tens of kHz to several tens of kHz, and provides the high-frequency AC current to the primary coil of the transformer 13. The transformer 13 transforms the AC current, and the transformed AC current is rectified by the rectifier 14 and output to the secondary inverter 16 via the DC reactor 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 current. The AC current output applies an AC welding voltage between the torch 3 and the base material A, and the welding current supplied from the welding power source 1 flows from the torch 3 to the welding wire W via the power cable. The base material A is welded by the heat of the arc generated between the base material A and the welding wire W by the welding current. The arc is covered with the flux B supplied by the flux supply device 6.

[0021] The control device 2 is a circuit that outputs control signals to each of the primary inverter 12 and the secondary inverter 16 of the welding power source 1, and digitally controls each inverter independently. The control device 2 also controls the feeding speed of the welding wire W by the wire feeding device 5, the supply amount of the flux B by the flux supply device 6, the traveling speed of the carriage 7, etc.

[0022] The control device 2 is a processor and includes an arithmetic processing unit 21 such as a CPU or a multi-core CPU, a memory unit 22, a setting reception unit 23, a wire feed speed control unit 24, a flux supply control unit 25, and a carriage travel speed control unit .

[0023] The storage unit 22 is a storage device including a non-volatile memory such as a Read Only Memory (ROM) and an EEPROM, and a volatile memory such as a Random Access Memory (RAM). The storage unit 22 stores a first table 22a and a second table 22b used to match the effective value of the AC current with a set current. The first table 22a and the second table 22b will be described in detail later.

[0024] Setting reception unit 23 is an input device such as a button, key, dial, etc., and receives setting information including the set current of the submerged arc welding machine and other welding conditions. Setting reception unit 23 also receives settings or changes of operation parameters for controlling the AC waveform of the current output from welding power source 1.

[0025] Wire feed speed control unit 24 is connected to a drive circuit of motor 52, and outputs a rotation control signal corresponding to the wire feed speed to the drive circuit, thereby controlling the feeding of welding wire W by wire feeder 5. Feeding roller 51 rotates at a speed corresponding to the rotation control signal, and welding wire W is fed to the portion to be welded of base material A via torch 3.

[0026] The arc length is proportional to the welding voltage (arc voltage). The welding voltage is the voltage between the contact tip of the torch 3 and the base material A, and is detected by the voltage sensor 8. A feed speed set value, which is a target value, is set in the wire feed speed control unit 24. The wire feed speed control unit 24 uses the difference between the feed speed set value and the welding voltage detected by the voltage sensor 8 as an operation amount, and controls the feed speed of the welding wire W so that the arc length is constant.

[0027] 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 flux B by the flux supply device 6 by outputting an opening / closing signal to the drive circuit according to the amount of flux supply. Note that, in the case where the valve 63 is manually opened and closed, the flux supply control unit 25 is not necessary.

[0028] The bogie traveling speed control unit 26 is connected to a drive circuit that drives the traveling motor of the bogie 7, and controls the traveling of the bogie 7 by outputting a traveling control signal corresponding to the traveling speed of the bogie 7 to the drive circuit.

[0029] In addition, a voltage sensor 8, a current sensor 9, a primary inverter 12, and a secondary inverter 16 are connected to signal input / output terminals (not shown) of the control device 2, and the control device 2 PWM controls the primary inverter 12 so that it operates with constant current characteristics based on the set welding conditions and the detected welding current and welding voltage. The control device 2 also operates or controls the AC current waveform based on the set current and operation parameters received by a setting reception unit 23. A required welding voltage is applied between the base material A and the welding wire W, and a welding current flows.

[0030] <How to keep the effective current constant> The control device 2 according to this embodiment is a welding system that can quickly calculate the peak current during the EN period so that the effective current is equal to the set current, according to the set values ​​of various parameters that define the AC current waveform. This allows the submerged arc welder to keep the effective current constant immediately after the start of AC output, and stabilize the penetration depth.

[0031] (A) Deciding how to operate parameters Fig. 3 is a schematic diagram showing an example of an AC waveform of a current output from welding power supply 1. The AC waveform shown in Fig. 3 is a sine wave-based waveform.

[0032] First, a number of parameters related to the adjustment of the AC waveform are determined. In other words, the number of parameters is a quantity that defines the shape pattern of the AC waveform. For example, in the case of a sine wave waveform, the parameters that determine the AC waveform are the length of an EP (Electrode Positive) period and an EN (Electrode Negative) period, the peak currents of the EP period and the EN period, and the polarity switching current, although this depends on the shape of the AC waveform and the control method. 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 electrode polarity of the welding wire is negative. The polarity switching current is a threshold current for switching the positive and negative sides of the AC current. When the current becomes small, the rigidity of the arc weakens, which may cause magnetic blow and destabilize the penetration. Therefore, in order to shorten the period when the current is small and suppress magnetic blow, a control that changes the current at high speed between the polarity switching currents as shown in Figure 3 is sometimes used in combination.

[0033] If all of these parameters are set directly, the AC waveform is determined to be unique, and the effective current cannot necessarily be made to match the set current. Also, if the lengths of the EP period and EN period are set separately, the AC frequency changes, making it difficult to adjust the welding conditions.

[0034] Therefore, a number of operation parameters are defined for manipulating the AC waveform of the current output from the welding power source 1. For example, the operation parameters are the AC frequency of the current, the EN ratio, the EP / EN peak current ratio, the polarity switching current, and the set current. The EN ratio is the ratio of the EN period to the length of one AC cycle, and the EP / EN peak current ratio is the ratio of the peak current in the EP period to the peak current in the EN period. The set current is a current value that is set as a target value for the effective value of the current output from the welding power source 1.

[0035] When the operation parameters are determined as above, the lengths of the EP and EN periods are determined by the set AC frequency and EN ratio. Furthermore, the polarity switching current and set current are set directly and have a single value. On the other hand, the peak currents in the EP and EN periods have their ratios set, but their values ​​are not determined, allowing freedom of operation. Therefore, the peak currents in the EP and EN periods are determined by imposing a constraint that the effective current matches the set current. In other words, the peak currents in the EP and EN periods are calculated so that the effective current matches the set current according to the various operation parameters.

[0036] (B) Analytical derivation of peak current (pre-derivation) The above peak currents are analytically derived. The peak currents in each period can be expressed as a function of various other operation parameters. However, it goes without saying that, depending on the waveform pattern and control method, not all operation parameters necessarily affect the peak current.

[0037] In addition, the equation for deriving the peak current obtained here is often a complicated equation including roots, etc., so directly calculating it algebraically imposes a large calculation load and takes a lot of time. However, since all of the above-mentioned various operation parameters may be changed during welding, when the settings are changed, the peak current must be quickly recalculated and updated within a short period of time, for example, within 10 ms or less. Therefore, the following method is used to realize the calculation of the peak current in a short period of time.

[0038] (C) Separation of variables in the peak current derivation equation The above peak current derivation formula is modified 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 two to three operation parameters as variables. More preferably, the element function is a function with two operation parameters as variables. For example, in the above sine wave-based waveform, the peak current can be expressed as a composite function of an element function with two variables, the EN ratio and the EP / EN peak current ratio, and an element function with two variables, the polarity switching current and the set current. The composite function can be expressed by addition, subtraction, multiplication and division of multiple element functions.

[0039] (D) Algebraic calculation of element functions For each of the element functions, the calculation results when each variable, i.e., each operation parameter, is changed at a fixed interval are tabulated. The calculation processing unit 21 calculates the calculation results of each element function from the values ​​of each variable that are actually set based on these multiple tables by linear interpolation. The reason why the element functions are subjected to variable separation is that the fewer the types of variables, the more simplified the table can be. Details will be described later.

[0040] (E) Calculation of peak current From each element function thus obtained, the peak currents in the EP and EN periods are calculated. Specifically, function values ​​are obtained by referencing multiple tables using the operation parameters as keys, and the peak currents in the EP and EN periods are calculated by addition, subtraction, multiplication, and division of the function values.

[0041] According to the above procedure, even if the operation parameters are changed during welding, the peak currents in the EP and EN periods are quickly calculated so that the effective current is equal to the set current according to the set values ​​of the various parameters. By controlling the output of the welding power source 1 based on the calculated peak currents in the EP and EN periods and the values ​​of other parameters, the control device 2 can keep the effective current constant immediately after the start of AC output or immediately after the welding conditions are changed, and can stabilize the penetration depth.

[0042] <Example of a sine wave waveform> (A) Deciding how to operate parameters The AC frequency, EN ratio, EP / EN peak current ratio, polarity switching current and set current are the operation parameters for controlling the AC waveform of the current.

[0043] (B) Analytical derivation of peak current (pre-derivation) The peak current in the EN period and the peak current in the EP period are analytically derived by the following equations (1) and (2).

[0044]

number

[0045] (C) Separation of variables in the peak current derivation equation If the peak current during the EN period is expressed by the following equations (3) and (4), then the variables can be separated as shown in the following equation (5).

[0046]

number

[0047] (D) Algebraic calculation of element functions The calculation results (function values) of the function F when the EN ratio r and the EP / EN peak current ratio R are changed at regular intervals, and the calculation results (function values) of the function G when the polarity switching current Ichg and the set current Iset are changed at regular 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 values ​​of the function F correspond to each other. The storage unit 22 also stores a second table 22b in which the polarity switching current Ichg, the set current Iset, and the function values ​​of the function G correspond to each other. The control device 2 uses the first table 22a and the second table 22b to calculate the calculation results (function values) of the functions F and G by linear interpolation according to each operation parameter that is actually set.

[0048] (E) Calculation of peak current The control device 2 calculates the peak currents in the EP period and the EN period using the above equations (5) and (2).

[0049] 4 is a flowchart showing a control method according to this embodiment. In the following explanation, the AC waveform control output from welding power source 1 will be mainly explained, and other details of arc welding control will be omitted or will be explained in a simplified manner.

[0050] The control device 2 receives various settings of the submerged arc welding machine and starts submerged arc welding control (step S11).

[0051] Next, the control device 2 accepts the change of the operation parameters at the setting acceptance unit 23 (step S12). Then, the control device 2 refers to the first table 22a and the second table 22b using the changed operation parameters as a key, and calculates the peak currents for the EN period and the EP period (step S13). The control device 2 controls the output current of the welding power source 1 based on the peak currents for the EN period and the EP period and various parameters based on the set operation parameters (step S14).

[0052] Thereafter, the control device 2 determines whether or not a predetermined end condition is satisfied (step S15), and ends the welding process if the end condition is satisfied (step S15: YES). If the end condition is not satisfied (step S15: NO), the control device 2 repeatedly executes the processes of steps S12 to S14 to execute the submerged arc welding method.

[0053] As described above, according to this embodiment, even if various operation parameters for manipulating the waveform of the AC current are changed in AC submerged arc welding, the peak current for making the effective current coincide with the set current can be quickly calculated. Therefore, regardless of the values ​​set for the various operation parameters, the effective current can be obtained as the set current, and thus the effective current can be kept constant immediately after the start of AC output, and the penetration depth can be stabilized.

[0054] In this embodiment, the control for making the effective value of the output current coincide with the set current has been described, but the peak current may be calculated so that the effective current coincides with an index other than the set current. For example, in the case where the effective current is moved in accordance with a desired external characteristic to reproduce a constant voltage characteristic, the peak current may be successively recalculated and updated so that the output effective current coincides with a target effective current that changes from moment to moment according to feedback values ​​of the effective current and effective voltage.

[0055] In addition, the peak currents of the EP period and EN period may be directly set, and other parameters such as the length of the EP period or the length of the EN period based on the EN ratio, or the polarity switching current may be calculated so that the effective current matches the set current, and the output of AC current may be controlled.

[0056] Furthermore, the polarity switching current may have a different value for switching from an EN period to an EP period and a different value for switching from an EP period to an EN period.

[0057] Furthermore, although an example of manipulating a sine wave-based waveform has been described in this embodiment, the present invention may be applied to the case of manipulating a trapezoidal wave or any other arbitrary current waveform. In the case of a trapezoidal wave, the operation parameters may be the AC frequency, EN ratio, EP / EN peak current ratio, upslope period ratio, downslope period ratio, polarity switching current, and set current. The 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 downslope period ratio is a parameter that determines the time ratio at which the current is decreased relative to the length of the EN period. [Explanation of symbols]

[0058] 1: welding power source, 2: control device, 3: torch, 4: wire reel, 5: wire feeder, 6: flux supply device, 7: cart, 8: voltage sensor, 9: current sensor, 21: calculation processing unit, 22: memory unit, 22a: first table, 22b: second table, 23: setting reception unit, 24: wire feed speed control unit, 25: flux supply control unit, 26: cart travel speed control unit, A: base material, B: flux, W: welding wire

Claims

1. A submerged arc welding machine comprising: a storage unit that stores a plurality of tables in which two or three of the operation parameters for manipulating the AC waveform of the current output from the welding power source and a parameter for determining the AC waveform together with the plurality of operation parameters are associated with function values, in order to associate the operation parameters with a constraint that the effective value of the output current coincides with a predetermined current; a setting reception unit that receives the plurality of operation parameters; a calculation processing unit that calculates the plurality of operation parameters by referring to a plurality of tables stored in the storage unit, using the plurality of operation parameters received by the setting receiving unit; A submerged arc welding machine comprising:

2. The operating parameters are: The ratio of the length of an EP (Electrode Positive) period to an EN (Electrode Negative) period, the ratio of peak currents in the EP period to the EN period, or a polarity switching current, The parameters include a length of an EP period, a length of an EN period, a peak current in an EP period, or a peak current in an EN period.

2. The submerged arc welder according to claim 1.

3. The arithmetic processing unit is Calculate the peak current during the EN period or the peak current during the EP period based on the following formula:

2. The submerged arc welder according to claim 1. In=F(r,R)×G(Ichg,Iset) Ip = R x In however, In: Peak current during EN period Ip: Peak current during EP period F(r, R): function related to the first table G(Ichg, Iset): Function related to the second table r: Ratio of the length of the EP period and the EN period R: Ratio of peak current during EP period and EN period Ichg: polarity switching current Iset: Predetermined current

4. A submerged arc welding method comprising the steps of: a plurality of tables are prepared in which two or three of the operation parameters are associated with function values ​​in order to associate a plurality of operation parameters for manipulating an AC waveform of a current output from a welding power source with a parameter for determining the AC waveform together with the plurality of operation parameters, with the constraint that the effective value of the output current coincides with a predetermined current; accepting the plurality of operational parameters; Using the received operation parameters, the parameters are calculated by referring to the tables. Submerged arc welding method.

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