JPS6316869A - Mag pulse welding method - Google Patents

Abstract

PURPOSE:To realize the soundness for forming a bead, etc. by deriving a reference frequency characteristic from a correct frequency characteristic corresponding to a chemical component and a use condition, respectively, of a steel wire, and setting a pulse power source frequency, within a specific % range of this reference. CONSTITUTION:A natural frequency (correct frequency) in which the limiting arc length for generating not short circuit becomes the shortest exists by depending on a chemical component and a welding condition of a steel wire. Based on an expression I, a reference correct frequency F is derived from the sum of a correct frequency characteristic Fw depending on the chemical component of the wire and a correct frequency characteristic Fc depending on the welding condition, and a pulse power source frequency is set within a range of 90-110% of a reference characteristic F, by which welding is executed. According to this method, the pulse power source frequency for conforming with both the frequency characteristics of the chemical component and the welding condition of the wire can be set. Accordingly, a bead is formed soundly, and also, welding which has reduced the spatter quantity can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a high-speed welding method with good bead formation and less spatter generation in MAG welding using a pulsed power source.

(Conventional technology) Gas metal arc welding uses a relatively small diameter wire.
Due to its high current density and good arc concentration,
As a welding method suitable for high-speed welding, it is especially used in combination with welding robots.

With the spread of welding robots, there is a growing trend toward higher efficiency and faster welding, and there is a demand for stable, high-speed welding.

However, conventionally, high-speed welding has had two major problems: spatter generation and bead formation.

Spatter not only adheres to the base metal and welding torch, impairing efficiency and shielding properties, but also invades robots, peripheral equipment, and jigs, and impairs their smooth operation.

There are various factors that can be considered to cause this spatter, but
The biggest influence is the arc force during the process of contact short circuit and arc regeneration when the droplet grows and moves to the molten pool.
It scatters due to pinch force.

Therefore, it is considered effective to reduce spatter by keeping the arc long enough to prevent short circuits.

On the other hand, if the welding speed is increased while maintaining a long arc length, undercuts are likely to occur, and furthermore, bead formation such as humping beads and arc breaks may occur at high speeds.

In order to suppress the occurrence of spatter while ensuring bead forming properties as described above, it is necessary to make the arc length as short as possible to the extent that short circuits do not occur.

Since the arc length without short circuit depends on the diameter of the transferred droplet, measures are taken to increase the number of droplet transfers, and Ar - CO□ (generally about 20% CO□) is used as a shielding gas. Ratio) MA using pulsed power supply with mixed gas
Considerable effects have been achieved by G-pulse welding.

However, even in MAG pulse welding, the welding speed at which a good bead can be obtained in a non-short circuit region is about 50 to 80 cm/min.

On the other hand, as a measure against the amount of spatter generated in the event of a short circuit, a means of adjusting the secondary inductance of the welding power source was proposed in the Japanese Patent Publication No. 4'14.
Although this has been done in the technology described in Publication No. 1659, etc., in pulse power supplies, the rise and fall times of the pulse waveform become long, which limits the increase in inductance. At times, a large amount of spatter is generated.

As detailed above, although individual measures have been taken to address the two major problems in high-speed welding, bead formation and spatter, none of them are sufficient, and even more so, no means have been taken to solve both at the same time. .

(Problems to be Solved by the Invention) In view of the current situation, the present invention aims to improve the composition of the steel wire used, the wire feeding speed, and the wire diameter in order to simultaneously achieve bead formation properties and reduction of spatter in high-speed welding. As a result of a detailed study on the relationship between the usage conditions such as , etc. and the pulse waveform characteristics, by matching the frequency characteristics of the pulse power source with the control parameters that depend on the wire component and the control parameters that depend on the usage conditions, By reducing the diameter of the transition droplet, we were able to keep the arc length to the shortest possible length. Furthermore, by performing the peak rise during a short circuit under the above conditions after the short circuit ends, MA can suppress the amount of spatter during a short circuit and satisfy high-speed weldability at the same time.
A G-pulse welding method is provided.

(Means for Solving the Problems) The gist of the present invention is that in the MAG pulse welding method, an appropriate frequency characteristic (Fw) dependent on the mesh wire component and an appropriate frequency characteristic (Fc dependent on the usage conditions) shown in the following equation are obtained. 90 to 110% of F, based on the appropriate frequency (F) consisting of the sum of
The MAG pulse welding method is characterized in that the frequency of the pulse power source is set to match the range of .

Fw (Hz) −952×C-59×Si-67XMn
+3820XS+2970xN-190xΩ However, each element symbol indicates weight%.

Fc(llz) = (φ/1.2)x (453Xl
og (revised/3) ) +33 However, φ is the wire diameter (1■
”), Wf indicates the wire feeding speed (m/llin), F (Ilz) = Fiv + Pc The operation and configuration of the welding method of the present invention will be described below.

(Function) Figure 1 shows the two types of steel wires shown in Table 1 (diameter = 1.2
Using Tsuru φ) and a conventional pulse power source, shielding gas ^r
-20% CO, welding current: 21OA.

Distance between tip and base metals: Under each condition of 18 dragons, the welding voltage was set to the shortest arc length (hereinafter referred to as the limit arc length) without causing a short circuit for both wires, and horizontal fillet welding (plate thickness 4.5 mat) is a diagram showing the relationship between the welding speed and the amount of spatter collected. The pulse frequency was approximately constant at about 21011z as read from an oscilloscope that recorded changes in current and voltage.

The figure shows that both wires agree that the amount of spatter increases slightly as the welding speed increases, but there are large differences in the amount of spatter and the critical speed at which a good bead can be obtained. Wire a is superior.

In order to resolve these differences between wires from the point of view of wire components, we used various component wires, determined the minimum voltage that would not cause a short circuit in each wire, and then conducted the same study as in Figure 1. However, not only was it not possible to obtain a performance superior to that of wire a, but there was also no clear correlation between the wire components, the amount of sputtering, and the critical speed for good bead shape.

The inventors attributed these results to the incompatibility of the wire and pulse waveform conditions.

That is, the pulse frequency in a conventional pulse power source is unified with the welding current (or wire feeding speed), and is almost fixed if this condition is kept constant. Therefore, in normal welding performed at low speeds where the arc length is kept relatively long, even if there are differences in arc length depending on the type of wire, the welding result will not be affected that much, and the welding result will be Welding is possible.

However, in high-speed welding where a slight difference in arc length directly affects the welding result, it is essential to make the arc length as short as possible, that is, to select pulse waveform conditions suitable for the wire components.

Therefore, at the same wire feeding speed, we used an inverter-controlled pulse power source that can adjust the frequency over a wider range than conventional power sources with a fixed frequency, and in combination with the same wire and shielding gas as shown in Figure 1, Figure 2 qualitatively shows the results of the study on the arc length and the limit arc length that does not cause a short circuit.

In this case, the wire feeding speed is 7 m/n+in,
Welding speed is 80cm/min, Ext (chip base metal open circuit M) is 18m5, downward direction (Bead on pla
te), the current is 210-220A.

For any wire, there is a point at the frequency where the critical arc length is the shortest, and the critical arc length becomes longer around this frequency. The frequency of this point differs depending on the wire; wire a has a 215H2% wire b has a frequency of 250H.
It was about Hz.

It is thought that the critical arc length is determined by the diameter of the migrating droplet. Therefore, at the appropriate frequency, the minimum droplet diameter, that is, the maximum number of droplets, shifts to 1 droplet/1 pulse, and in the frequency range lower than the appropriate frequency, n droplets/1 pulse, It is considered that a transition of 1 m drop/n pulse occurs in the high frequency region.

The results shown in Figure 1 were obtained using a conventional power source with a fixed frequency, and the amount of sputtering for wire a was smaller than that for wire b.
What was superior in terms of high speed was the frequency (
210Hz) happened to be close to the optimum frequency of wire a, and wire b was compared at the low frequency side where the critical arc length is long, and when comparing the optimum frequency of wire b, wire b was better than wire a. showed excellent results.

In most cases, the appropriate frequency is much higher than the fixed frequency of conventional power supplies, approximately 40Hz for wire b.
it was high.

In this way, each wire has its own unique frequency (hereinafter referred to as appropriate frequency) at which the critical arc length at which no short circuit occurs is the shortest.

Figure 3 shows the appropriate frequency F when welding conditions are changed for wire b in Table 1, where (1) is the same condition as in Figure 2, and (2) is when the wire feed speed is 5 m/min. %(3)
(4) has a wire diameter of 1.0 mmφ, (4) has an Ext of 30 cranes, (
5) is a case where the welding speed is 50 cm/min, other conditions are the same as +11, and [ ] indicates the amount of spatter.

From the results shown in Figures 2 and 3, the appropriate frequency not only depends on the wire components but also on the welding conditions, and the frequency of the pulse power source should be set to match both of these frequency characteristics. This makes it possible to perform high-speed welding with a small amount of spatter and a good bead shape.

Pulse welding is performed by wire melting, droplet detachment, transition characteristics, and the electrical and thermal balance provided by the pulse, so it is necessary to synchronize with the pulse frequency at the appropriate frequency (point 2 in Figure 2). If stable droplet transfer is achieved, the appropriate frequency is considered to be related to the physical properties of the droplet and to have a certain relationship with the wire components.

It was also believed that increasing the appropriate frequency would make the droplets finer and the length shorter, which would lead to an increase in welding speed without defects.

Therefore, as a result of using wires of various component systems and determining the appropriate frequency under the same welding conditions as in the case of Fig. 2, we obtained Equation 11, which shows the relationship between the wire components and the appropriate frequency. ) is 7 m/min, the appropriate frequency f7 is as follows.

f, (Hz) =952×C-59×Si-67XMn
+3820XS 12970×N-190XO+200
(Formula 11 Each element symbol indicates weight %. (The same applies hereinafter) This +1) formula makes it possible to always obtain an appropriate frequency even if the type of wire is different. But+
Type 11 has a wire feeding speed (Wf) of 7111/ll1
This is for the case of in.

In order to enable welding at an appropriate frequency under any current conditions, the relationship between wire feeding speed and appropriate frequency must be clarified.

The relationship between the appropriate frequency and wire feeding speed shows quite complex changes depending on the wire component system, but after examining many wires, it was found that the degree of change can be expressed using the following equation (2). Do you get it.

Δf =453Xlog (edited) (tlz) =-・
+21 formula Therefore, the appropriate frequency when changing the wire feeding speed (current) under the condition that the wire diameter is 1.2fiφ is the practical limit wire feeding speed 3 using +11 formula and (2) formula.
Based on m 2 /min, it is given by the following equation (3).

f(fiz) =952×C-59×Si-67XMn
+3820×S+2970×N-190XΩ+453
X log(revised/3}+33... Formula (3) and in the same way, we investigated the relationship with the appropriate frequency when the wire diameter is different, and found that under the same wire feeding speed, the wire It was found that the appropriate frequency changes almost in proportion to the diameter (φ), and it became possible to give the appropriate frequency using equation (4).

F(llz)=952×C-59XS1 67XMn+
3B20XS+2970x N-190xQ+(φ/1
．． 2) X (453Xlog(Wf/3)) +33 ・-
・・Type 141 In addition, as a factor of welding construction conditions, Ext.
(distance between chip base metal), welding speed, welding voltage, etc. The appropriate frequency changes in inverse proportion to the change in Ext, and the degree of this change is affected in a complex manner that varies depending on the wire feeding speed.

However, the appropriate frequency change range is 10 to 30mX for Ext.
±1011z in the range of Wf 7±411I/ll1in
Since the frequency is small, in practice it can be adjusted sufficiently using a frequency fine adjustment dial or the like.

The appropriate frequency is also inversely proportional to changes in welding speed, but the degree of this is 50 to 100 an/min and 10H.
It is about z.

As the voltage is lowered to shorten the arc length from the non-short circuit region, short circuits eventually begin to occur, and the number of short circuits increases as the voltage decreases.

In the short circuit region, since the arc length is short, the limit welding speed at which a good single weld shape can be obtained becomes large, and although bead formation is improved, spars occur frequently.

FIG. 4 shows this relationship. This drawing shows a board with a thickness of 2m.
mt horizontal corner joint with wire b (1,2mW
φ), the shielding gas was Ar-20% CO, the wire feeding speed was 7 m/win -, the Ext was 18 dragons, the torch angle was 45° horizontally, and the welding voltage was under the conditions that the advance angle was 0°. The limit welding speed (a
It shows the relationship between l and sputtering amount (bl), where (a) is a frequency of 215Hz, (n) is a frequency of 250Hz.
(appropriate frequency). Although the welding speed at which a good bead can be obtained is generally on the high speed side in case (U), the high speed performance is also good in both cases below 25 V, where short circuits begin to occur.

However, in the case of (a), the amount of spatter increases rapidly on the low voltage side, but under the condition of (0) conducted at an appropriate frequency, although there is a slight tendency to increase due to the decrease in voltage, it remains at a constant low level. .

In this way, when welding is performed using the appropriate frequency "formula (4)", high-speed welding with excellent bead formation properties and spatter amount is possible over a wide voltage range.

By the way, the appropriate frequency obtained from equation (4) is given as a point. In actual welding, it is unlikely that welding will be performed under exactly the same conditions, and even if welding current, voltage, Ext, speed, etc. are selected depending on the combination of each condition such as plate thickness, welding posture, groove shape, etc. Conditions change constantly depending on shape, groove gap, etc.

Regarding the wire, even in the specifications under the highest control technology of today's commercial thermal materials, the wire composition between the ronds,
Variations in properties are unavoidable.

It is nearly impossible from a control and practical standpoint to perfectly match each frequency condition to these various changes.

Therefore, it is an extremely important factor to determine the tolerance of the appropriate frequency that can be tolerated in practice.

FIG. 5 shows the relationship between the ratio of the amount of spatter when the set frequency is changed with respect to the appropriate frequency with respect to the amount of spatter when welding is performed under conditions where the appropriate frequency is 20011z and 300 Hz.

Under any appropriate frequency conditions, the spatter change is small when the frequency change rate is less than 10%, but when it exceeds this, it tends to increase rapidly.In the present invention, the frequency change width is set in the range of 90 to 110% of the appropriate frequency. Established.

The appropriate frequency in equation (4) is a frequency term F (wire) that depends on the wire component and a frequency term F (wire) that depends on the welding conditions.
cond, ) and a constant term C.

To match the frequency characteristics of the pulse power supply, change the wire feed speed (for example, the command voltage of the wire feed motor).
An arithmetic circuit is provided between the power supply pulse frequency oscillation circuit and a switch signal for selecting the wire diameter is input to the arithmetic circuit, and the wire feeding speed and frequency F (cond,
) + C, and set it so that the relationship is F w (
Added a function to shift the frequency by F wire),
This can be done by outputting a frequency of F=Fw+Fc. FIG. 6 shows this relationship as an example in a block diagram.

As described in detail above, the configuration of the welding method of the present invention is to match the pulse power characteristics to the relationship between steel wires of various compositions and the optimal frequency that changes depending on the usage conditions. This is a new MAG pulse welding method that enables high-speed welding with excellent bead formation and spatter amount in MAG pulse welding in the area.

The pulse waveform conditions other than the pulse frequency are pulse peak current (Ip> of 450A, base current (Ib) of 50A).
It is A. If these ip and Ib change, it is naturally possible that the appropriate frequency will shift.

For example, if Ip increases or decreases, the appropriate frequency increases or decreases in the opposite direction, but these should be included in the scope of the present invention as long as the frequency given from equation (4) is slightly modified according to the set conditions. .

The effects of the present invention will be specifically explained below using Examples.

(Example) Wire a shown in Table 1 was used to perform lateral lap fillet welding of plate thickness 'lx*t under the welding conditions shown in Table 2, and the results of measuring the bead shape and amount of spatter were reported in the second table. It is also shown in the table.

Conditions Nal to 1hlO are examples of the present invention, in which the pulse frequency was set near the optimum frequency under the conditions of each wire diameter and wire feeding speed, and in all cases, the amount of fluff was as small as 0.6 gr/min or less. The bead shape is also good, and high-speed welding with good bead formability and spatter amount is achieved. Conditions 11kLi1 to 20 are comparative examples, and 11 to l1h13 are wire diameters of 1°0.
In the case of φ, the wire feeding speed (rev.) of 11 is 5.8.
m/min, the pulse frequency is approximately 30% lower than the appropriate frequency.
This was done under conditions where the Hz was set low, and the amount of spatter increased significantly, and the bead shape was also slightly inferior.

For the following samples 11h12 to 1lh20, the frequency under each condition was set to be increased or decreased by 20 to 40% from the appropriate frequency, and in all cases, the amount of sputtering was significantly large and the bead formation properties were slightly inferior.

As described above, any of the welding methods outside the scope of the present invention cannot satisfy both the amount of spatter and the bead forming property at the same time.

(Effects of the Invention) As described above, the welding method of the present invention can accommodate a wide range of wire components and welding conditions, and has tolerance for variations in welding conditions and wire lofts.
Not only is it possible to form a single weld that is sound, but it is also possible to weld with an extremely small amount of spatter.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between welding speed and spatter amount, Figure 2 is a graph qualitatively showing the relationship between frequency and shortest arc length in the non-short circuit region, and Figure 3 is a graph showing the relationship between welding conditions and appropriate frequency. Figure 4 is a graph showing the relationship between welding voltage, welding speed, and amount of spatter. Figure 5 is a graph showing the relationship between rate of change in frequency and rate of change in amount of spatter. Figure 6 is a graph showing the relationship between welding voltage, welding speed, and amount of spatter. FIG. 2 is a block diagram showing an example. 150 200 250 3
0θ Same support CHx) Welding voltage (7) aOqo 100 /10 /20
Number of changes in use (%)

Claims (1)

[Claims] In the MAG pulse welding method, an appropriate frequency (F A MAG pulse welding method characterized in that the frequency of the pulse power source is set so as to match the range of 90 to 110% of F with F as a reference. Fw (Hz)=952×C-59×Si-67×Mn+
3820xS+2970xN-190xO However, each element symbol indicates weight%. Fc (Hz) = (φ/1.2) × {453 × log (W
f/3)}+33 where φ indicates the wire diameter (mm) and Wf indicates the wire feeding speed (m/min). F (Hz) = Fw + Fc