JPS60255276A - Consumable electrode type arc welding method - Google Patents

Abstract

PURPOSE:To suppress the generation of defective shape beads such as welding defects lacking in fusion, etc., and drooping of beads in attitude welding by repreating alternately by an optional number of times each a short-circuit shift and a spray shift for controlling a heat input and controlling the bead shape. CONSTITUTION:Electric conduction is executed between a wire 31 and a material to be welded 35 from a welding power source 37 while supplying a shielding gas (g) from a feed port 32b, the wire 31 is melted by generating an arc (a) and dropped down onto a base metal 35, and a welding torch 32 is moved and the base metal is deposited by heating it and making molten pool (m). Its welding condition and a wire 31 feed speed are set by setting devices 40, 41, and an output of the power source 37 and rotation of a motor 46 are controlled by a controller 42 so as to reach said set condition. The welding condition is controlled by monitoring a welding current level, but a welding current and a current waveform being the origin of this control are obtained from an output of a welding current detector 38, for instance, short-circuit and pulse shifting periods Ta, Tb are as shown by waveforms in the figure. This waveform is processed by a device 39, and each shifting time T1, T2 is detected.

Description

[Detailed description of the invention] The present invention relates to a consumable electrode arc welding method.

The consumable electrode arc welding method is an automatic or semi-automatic welding method that performs visible arc welding while flowing shielding gas around the wire (solid or flux-cored) that is fed to the welding location. This consumable electrode type arc welding method is divided into MIG, MAG, and carbon dioxide arc welding methods depending on the type of shielding gas used, and these are in practical use.

Among these, the MIG welding method uses an inert gas such as argon (Ar) or helium (He) or a small amount of oxygen (
02), a mixed gas containing carbon dioxide (CO2) is used as a shielding gas, and is applied to welding aluminum alloys, stainless steel, heat-resistant alloy steel, etc.

In addition, carbon dioxide welding is a welding method that uses carbon dioxide gas as a shielding gas, and MAG welding is a welding method that uses a mixed gas of carbon dioxide and argon gas (and oxygen) as a shielding gas. Widely used for low alloy steels.

By the way, in the MAG welding method, a solid wire is used as the wire. With solid wire, high current density can be applied, droplet transfer is smooth in shielding gas mainly composed of inert gas, and the welding speed is high, so work efficiency is good. On the other hand, in the low current range, short-circuit arc welding or pulsed arc welding can be employed, and these are extremely advantageous for welding thin plates, all-position welding, and the like.

Figure 1 shows the droplet transfer state when welding is performed in a shielded atmosphere with a mixed gas of Ar and CO2, with the welding current set low and the arc length kept short. . That is, Fig. 1(a) is a diagram showing changes in current value during welding, and Fig. 1(b) shows the state of arc welding droplets at each current value in Fig. 1(a). ing.

A is the average current value, and this average current value A is the drop
The critical current from rate transition to spray transition is usually selected to be smaller than the critical current, and the transition form shown in Figure 1 (a) is called short circuit transition. Figure 1 (b) shows the welding material 11 and wire 1.
2 shows how the molten pool 13 and the droplets 14 of the wire 12 change, and in the state (2), the welded material 1
The first wire 12 melts and a molten pool 13 is formed on the material 11 to be welded.
This shows how it is made. Then, from this state, the state shifts to ■. In this state, the droplet 14 of the wire 12 causes
The molten metal in the molten pool 13 gradually swells up, and eventually the globule 14 fills up between the wire 12 and the material to be welded 11 as shown in (3), resulting in a short-circuit condition.

Since no arc 15 is generated in this state, the melting surface gradually lowers, passing through the state (2) and then moving to the state (2). and,
Welding is performed by repeating the above-mentioned cycle again. According to this welding method using short-circuit transfer, the heat input is low during short-circuit, so the molten pool becomes small and dripping of globule is suppressed, so it is suitable for all-position welding and welding of thin plates. There is.

In addition, welding in which a current larger than the above-mentioned critical current is applied in a pulsed manner to cause pulse transfer (or spray transfer) is called pulse arc welding. Shown in Figure 2.

That is, FIG. 2(a) is a diagram showing changes in current value during welding, and as shown in the figure, the welding current has a period T where B is the base current, P is the peak current, and the average current is A. change in a pulse-like manner. Moreover, FIG. 2(b) shows the state of arc welding droplets at each current value in FIG. 2(a).

The changes in the molten pool 13 and the droplets 14 of the wire 12 between the welded material 11 and the wire 12 are shown in FIG. 2(b). The figure shows how the material 11 to be welded and the wire 12 are melted by the heat of the arc 15 generated during this process, creating a molten pool 13 on the material 1 and the material 11 to be welded. Then, from this state, the state shifts to ■. In this state, the molten pool 1 is caused by the droplets 14 of the wire 12.
The molten metal 3 gradually rises, but since the current is pulsed with the base current B being the lowest level, the current value eventually drops to B, the arc 14 weakens, and the droplets 14 stop dripping. As shown in (2), the liquid level of the molten pool 13 is at the same level as the surface of the welded material 11. Then, due to the heat generated by the arc 15, the molten pool 13 portion of the welded material 11 spreads inside the welded material 11 as shown in (2). After that, the current value rises again, so the state shifts to ■'. Then, welding is performed by repeating the above-mentioned cycle again. According to this pulsed arc welding, stable droplet transfer can be achieved.

By the way, the short-circuit transition welding method and pulsed arc welding method described above have the following drawbacks.

=5- That is, (1) As explained in Fig. 1, the short-circuit transition welding method has a short arc length and the heat input by the arc is small during the short-circuit period, so welding defects such as poor fusion may occur. easy.

In addition, spatter is often generated due to similar arc lengths and short circuits.

(2) Pulsed arc welding requires less heat input than spray transfer using a constant current that exceeds the critical current, but a somewhat long arc length is required to maintain stable pulse transfer; It is not possible to suppress the heat. Therefore, in so-called positional welding such as vertical or upward welding, defects in the shape of the bead, such as sagging of the bead, are likely to occur.

The present invention has been made in view of the above circumstances, and in the consumable electrode type arc welding method, short-circuit transition and spray transition are alternately repeated an arbitrary number of times for heat input control and bead shape control. By controlling transfer and spray transfer by the number of droplet transfers, heat input and bead shape control can be performed. The object of the present invention is to provide a consumable electrode type arc welding method that can suppress bead formation.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 is a block diagram showing the configuration of an apparatus used in the method of the present invention. In the figure, 31 is a welding wire, which is wound around a reel and supplied to a welding torch 32. Welding 1 to 32 includes a tubular main body 32a in the middle thereof.
Gas supply port 32 for supplying shielding gas q to 2a
b is provided. The distal end side of the main body 32a is a shield nozzle, and a tubular electrode tip 32c is disposed at the center of the shield nozzle. It is sent to the tip side. The wire 31 is fed by rotating a pair of feed rollers 33 which are provided on the base end side of the main body 32a and sandwich the wire 31 from both sides. Further, the main body 32a forms a gas supply path so that the shielding gas Q is blown out toward the tip side. 34 is a metal fitting for attaching the main body 32 to a cart (not shown) for holding the main body 32 and moving the main body 32 in the welding progress direction. The shield nozzle is used to shield the arc a and the welding part of the welded material from the atmosphere by the blown-out shield gas q.

35 is a material to be welded, and 36 is a backing metal provided on the back surface of the welded portion of the material to be welded 35. 37 is a welding power source, one pole of this welding power source 37 is connected to the power supply part 32d of the welding torch 32, and the other pole is connected to the workpiece 35 via a welding current detector 38 such as a shunt. It is connected to the.

The power supply section 32d is connected to the electrode tip 32c, and the wire 31 receives current supply via the electrode tip 32c.

39 is a waveform processing device that processes the output (welding current value) from the welding current detector 38 and determines, from that level, when the droplets move from the tip of the wire 31 to the molten pool, which is liquid weld metal. To detect. 4O is a welding condition setting device,
The power supply voltage during short-circuit transition welding, the number of short-circuit transitions, the pulse conditions (pulse period, voltage at peak current, voltage at base current) during pulsed arc welding, and the number of pulse transitions are set in advance.

Reference numeral 41 denotes a wire speed setting device, which presets the wire feeding speed during short-circuit transition welding and the wire feeding speed during pulsed arc welding. 42 is a controller which adjusts the feeding amount of the wire 31 and the welding current control amount based on the detection signal of the waveform processing device 39 so as to match the conditions set by the welding condition setting device 40 and wire speed setting device 41. The welding current is controlled so that the welding current is alternately set to short circuit transition welding and spray (pulse) transition welding mode by a set number of times. 43 is a welding power source controller that receives a signal from this controller 42 and controls the output of the welding power source 37;
A motor controller 44 receives the output of the controller 42 and controls a motor drive device 45 for generating motor drive output. 46 is a motor for rotationally driving the feeding roller 33, and is rotationally driven by the output of the motor driving device 45.

Next, the operation of this device having the above configuration will be explained.

In this device, the shielding gas is zero from the gas supply port 32b.
While supplying current to shield the arc a and the welding part from the outside air, a current is supplied between the wire 31 and the welded material 35 from the welding power source 37, thereby generating an arc a between the wire 31 and the welded material 35. and melt the wire 31 with that heat,
The welding torch 34 moves the welding torch 34 while heating the welding material 35 to create a molten pool m, moving the molten pool m and performing welding.

The welding conditions are set by the welding condition setting device 40, and also by the wire 3
The feeding speed of No. 1 is set in advance by the wire speed setting device 41,
The output of the welding power source 37 and the rotation of the motor 46 are controlled by the controller 42 so that these setting conditions are met.

Welding condition control is performed by monitoring the welding current level and controlling the welding part m37 to meet the set conditions.The welding current and current waveform that are the source of this control are determined by welding current detection. It is obtained from the output of the device 38.

An example of the waveform is shown in FIG. In the figure, Ta is a short circuit transition period and Tb is a pulse transition period.

Such a current waveform from the welding current detector 38 is processed by a waveform processing device 39 to determine the short circuit transition timing (Tlt
, Tt2, ~Tln) and pulse transition synchronization (T21, T22, ~T2m) are detected. The method for detecting each period is to detect when the instantaneous waveform 1(t) of the welding current changes from increasing to decreasing in the case of a short-circuit transition, and to set a certain threshold 1p when i(t) is larger in the case of a pulse transition. This is done at the time of crossing from the beginning to the smaller side. Therefore, I
By determining p and comparing it with that level, each pulse at the pulse transition period can be detected, and the current waveform can be
By detecting the peak in the period below p, it is possible to detect the timing and number of short-circuit transitions.

As described above, in the short-circuit transition welding mode, the welding condition setting device 40 sets in advance a power supply voltage that can stably perform short-circuit transition at the wire feeding speed set by the motor speed setting device 41. ing. Also,
The number of short circuits is also set in advance in the welding condition setting device 40. On the other hand, in the pulsed arc welding mode, the wire feeding speed is set by the wire feeding speed setting device 41 such that the wire feeding speed is combined with the pulse condition of the welding condition setting device 40 and the average current does not exceed the critical current. is set in advance. Further, the number of pulse transitions is also set in advance in the welding condition setting device 40.

Therefore, in this system, after receiving the output of the waveform processing device 39, the IIJ m device 42 performs the short-circuit transition for the number of times m (m≧1) set by the welding condition setting device 40, and then the welding condition The number of times n (n≧
1) Outputs a control output to perform pulse transition by the amount of time. Then, the welding power source control device 43 that receives the output of the 111all device 42 provides a control output to the welding power source device 37 so that a welding current waveform corresponding to the control output is obtained. As a result, the welding power source 37 outputs a current having a waveform as shown in FIG. 4, and applies it to the wire 31 and the material to be welded 35.

Further, since the regulator 42 provides a control output to the motor controller 44 so that the wire feeding speed corresponds to the current waveform, the motor drive device 45 operated by the control output of the motor controller 44 is operated by the power supply. The motor 46 is driven to rotate so that the wire feeding speed corresponds to the waveform. This allows the wire to be fed at an optimal speed.

As a result, welding is performed while short circuit transition and pulse transition are alternately repeated under the set conditions, and the wire 31 is fed at the optimum wire feeding speed for each mode at that time.

In this way, short-circuit transition welding with low heat input and pulsed arc welding with medium heat input are alternately repeated in a short period of time, so it is possible to realize a welding method that combines the advantages of both welding methods.

Further, by appropriately combining the number of short-circuit transitions and the number of pulse transitions, heat input can be easily controlled. Furthermore, this makes it possible to improve the bead shape and facilitate positional welding.

13- As detailed above, the present invention alternately repeats short-time transition and spray (pulse) transition an arbitrary number of times for heat input control and bead shape control, so short-time transition with low heat input can be achieved. By repeating welding and medium heat input pulse arc welding alternately in a short period of time, it is possible to realize a welding method that combines the advantages of both welding methods, and by appropriately combining the number of short-circuit transition welds and the number of pulse transition welds. It is an object of the present invention to provide a consumable electrode arc welding method that has the following characteristics: heat input can be easily controlled, the bead shape can be improved, and posture welding can be easily performed. can.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams for explaining short-circuit transition welding, Figures 2 (a) and (b) are pulse (spray)
FIG. 3 is a block diagram for explaining the configuration of a system used in the present invention, and FIG. 4 is a diagram showing an example of a welding current waveform used in the present invention. 31...Wire, 32...Welding torch, 32a...
- Book 14 - Body, 32b... Gas supply port, 32G... Electrode chip, 33... Feeding roller, 34... Metal fitting, 35...
Material to be welded, #+setting device, 41... Wire speed setting device, 42... Controller, 43... Welding power source controller, 44
... Motor controller, 45 ... Motor drive device, 46
···motor. Applicant Sub-Agent Patent Attorney Takehiko Suzue 15-

Claims (1)

[Claims] A consumable electrode arc welding method characterized by alternately repeating short circuit transfer and spray transfer an arbitrary number of times for heat input control and bead shape control.