JPH0358829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In order to transfer droplets by spraying with relatively low heat input, the present invention applies a welding voltage, which is a base voltage periodically superimposed with a pulse voltage, at a nearly constant speed using a wire feed motor. The present invention relates to an improvement of an arc welding machine used for arc welding (hereinafter referred to as pulsed arc welding) in which an electric current is applied between a fed welding wire and a base metal.

The main factors that determine the welding conditions for pulsed arc welding are pulse voltage, base voltage, and wire feeding speed. Conventionally, this type of welding machine has been equipped with a pulse voltage setting device, a base voltage setting device, and a wire feed speed setting device independently, but these three types of factors can be independently changed to obtain the appropriate welding conditions. A considerable amount of experience is required to determine the pulse voltage, and in particular, the pulse voltage requires a voltage waveform with a narrow pulse width and a high pulse peak value from the viewpoint of weldability, so the setting is extremely delicate. .

In order to reduce the trouble of setting such conditions,
Some welding machines set the base voltage to a constant value in stages, and then change two factors, pulse voltage and wire feed speed, within this range to determine the welding conditions; however, this will be discussed later. The three factors of pulse voltage, base voltage, and wire feed speed each have appropriate values depending on the welding current (average value), so the base
If the voltage is set to a constant value in stages, appropriate welding conditions can only be obtained in stages.

In view of the above points, the present invention aims to provide an arc welding machine that unifies the setting of conditions for pulsed arc welding and allows suitable welding conditions to be easily and continuously selected.

The droplet transfer phenomenon in pulsed arc welding is
The average welding current takes on a somewhat different appearance when it reaches a certain critical value (hereinafter referred to as the critical welding current value).
Below the critical welding current value, as shown in FIG.
preheating, growth of the droplet, pulse voltage section 5
The pinch force of the pulsed current flowing through the wire 1
The droplets 2 are separated from the wire, and spray transfer is performed without causing a short circuit between the wire and the base material.

In a large current range exceeding the critical welding current value, spray transfer occurs without applying a pulse voltage, but by applying a pulse voltage, droplet growth can be suppressed and droplet transfer in fine particles can be promoted. In this case, since the pulse voltage acts in an auxiliary manner, a large output is not required when the welding current is below the critical welding current value.

From the above, the proper welding conditions for pulsed arc welding are the welding current (average value), the peak value of the pulse voltage, and the base value.
The following relationship holds true with the average value of the current voltage. In other words, the peak value of the pulse voltage is expressed as a function of the welding current with a peak near the critical welding current value _Ic (see Figure 2), and the average value of the base voltage is approximately proportional to the welding current value. have a relationship (third
(see figure).

Furthermore, in pulsed arc welding in which the welding wire is fed at a substantially constant speed, the welding current and the wire feeding speed have a substantially proportional relationship as shown in FIG.

In this way, the three factors that determine the welding conditions of pulsed arc welding, pulse voltage, base voltage, and wire feed speed, can all be expressed as a function with welding current as a parameter, and the relationship between them is Varies depending on wire diameter, type of shielding gas, etc. This can be expressed as an experimental formula as follows.

The peak value of the pulse voltage is V _P [V], the average value of the base voltage is V _B [V], and the wire feeding speed is f _W [m/min].
When the melt current (average value) is I [A], when using iron wire (1.2 mmφ) (shielding gas
Ar + 20% CO ₂ ) V _P = -0.00062I ² +0.251I + 12.5 V _B = 0.0001I ² +0.0024I + 13.6 f _W = 1.79e ^0.006I When using Al-Mg wire (1.2mmφ) (shielding gas Ar ) V _P = -0.00058I ² +0.244I + 10.3 V _B = 0.039I + 14.3 f _W = 0.052I - 0.078 The present invention was made based on the above considerations and experimental results. The configuration of the present invention will be explained with reference to the drawings.

In Fig. 5, 6 generates a welding voltage by superimposing a pulse voltage (approximately 25 to 500 Hz pulse frequency) on a base voltage, and is constructed so that the base voltage and pulse voltage can be adjusted independently. This is a welding power source. This welding power source itself is publicly known, and this figure schematically shows an example in which a pulse voltage output regulator 7 and a base voltage output regulator 8 (thyristor as an example) are provided separately, but the control element If a transistor is used as a transistor, it is possible to adjust the pulse voltage output and the base voltage output using the same element. The welding wire 1 is fed at a substantially constant speed by a feed roller 10 driven by a wire feed motor 9, and a welding arc is created between the welding wire 1 and the base metal 12, which are energized through a contact tip 11. 13
occurs.

Reference numeral 14 denotes a welding current setting device, which is composed of a potentiometer and the like that outputs a voltage signal _VI corresponding to a set current value. 15 is a pulse voltage output regulator which receives the voltage signal V _I and generates a control signal so that the peak value V _P of the pulse voltage has a predetermined relationship with respect to the set welding current I as shown in FIG. a pulse voltage control circuit for controlling the output of 7; 16;
receives the voltage signal V _I and generates a control signal so that the average value of the base voltage V _B has a predetermined relationship with respect to the set welding current I as shown in Fig. 3, and adjusts the base voltage. A base voltage control circuit 17 controls the output of the output regulator 8, and a wire feeding speed f _W is set to the fourth level with respect to the welding current I set by receiving the voltage signal V _I.
The wire feeding speed control circuit generates a control signal to control the wire feeding speed by the wire feeding motor 9 so as to have a predetermined relationship as shown in the figure.The functions of these control circuits 15, 16, and 17 are functions. This can be realized using an analog arithmetic circuit including a generator, a microcomputer, or the like. 18
is an analog or digital switch that sets the base material, wire diameter, shielding gas type, etc. This switch controls the control circuits 15, 16,
Select 17 input/output relationships.

According to the above configuration, the switch 18 sets the base material material, wire diameter, type of shielding gas, etc., and the welding current setting device 14 sets the appropriate current value determined by the base material plate thickness, groove shape, etc. By simply doing this, the pulse voltage, base voltage, and wire feeding speed are automatically controlled to appropriate values according to the set current value, allowing for good welding. Further, since these three factors change continuously while maintaining a predetermined correlation, continuity of appropriate welding conditions is ensured.

Therefore, even a beginner can easily set conditions for pulsed arc welding, which conventionally required considerable experience, and welding can always be performed under appropriate arc conditions.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the relationship between welding voltage waveform and droplet transfer, Figure 2 is a curve diagram showing the relationship between welding current and pulse voltage peak value under appropriate welding conditions, and Figure 3 is a diagram showing the relationship between welding current and pulse voltage peak value under appropriate welding conditions. Figure 4 is a curve diagram showing the relationship between the welding current and the average value of the base voltage; Figure 4 is a curve diagram showing the relationship between the welding current and wire feeding speed under appropriate welding conditions;
FIG. 5 is a block diagram showing an outline of an arc welding machine according to the present invention. 1: Welding wire, 6: Welding power source, 7: Pulse voltage output regulator, 8: Base voltage output regulator, 9:
Wire feeding motor, 12: base metal, 13: welding arc, 14: welding current setting device, 15: pulse voltage control circuit, 16: base voltage control circuit, 17: wire feeding speed control circuit.

Claims (1)

[Claims] 1. Using a welding power source configured to generate a welding voltage in which a pulse voltage is superimposed on a base voltage, and to be able to adjust the base voltage and the pulse voltage independently, approximately In an arc welding machine that generates a welding arc between a welding wire fed at a constant speed and the base metal, under appropriate welding conditions, the peak value is near the critical welding current I _C determined by experiment. Welding current I and pulse voltage peak value form a substantially quadratic curve convex to
The relationship between V _P and welding current I, which forms an almost proportional curve
The relationship between the average value of the base voltage V _B and the welding current I and the wire feed speed f _W , which also form a nearly proportional curve.
A voltage signal _{V I} corresponding to a welding current value I selected based on the appropriate welding conditions.
a welding current setting device that outputs a welding current setting device; a pulse voltage control circuit that controls the base voltage average value V B with the voltage signal V _I based on the memory; a pulse voltage control circuit that controls the base voltage average value V _B with the voltage signal V _I ; 1. An arc welding machine characterized by comprising a base voltage control circuit for controlling _P , and a wire feed speed control circuit for controlling the wire feed speed _fW using the voltage signal _VI .