JPS59159275A - Mig arc welding method - Google Patents

Abstract

PURPOSE:To perform stably and satisfactorily MIG arc welding in any case of a DC reversed polarity, DC positive polarity and AC by incorporating a rare earth element in a specific amt. into a base plate to be welded. CONSTITUTION:A steel material for structural purpose added with 0.02-0.30wt% a rare earth element is used as a base plate to be welded. The stable reiteration of instantaneous contact short-circuiting between the surface of the molten metal in a molten pool formed on the base plate side and the molten metal at the tip of a welding wire is induced continuously so that the molten metal at the tip of the wire is transferred to the base plate side by said contact short-circuiting. Not only the arc stabilization in both positive and reverse halfwaves but also the stabilization of the refiring characteristic in the stage of polarity inversion are made possible and the weld bead having extremely good quality is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, 0.02 to 0.30 wt.

By containing L-class elements, the stable arc generation mode and the transfer mode of wire ☆ 116 droplets to the base plate in MIG arc welding are achieved, and MIG arc welding in pure Alcon atmosphere is achieved. It can be applied stably and well in any case of DC reverse polarity, direct +I polarity, or AC.
Regarding the welding technology that can be used.

As is well known, MIG arc welding has traditionally been carried out using reverse polarity, where the welding torch is the positive pole and the base plate to be welded is the negative pole. The most common method was to use inert sludge to which some active sludge was added.

Mixing the above active gas components into the shielding gas 1~
The reason why it was necessary is as follows.

That is, in an atmosphere of gas, dirt, or pure inert gas without the addition of active residue components, (1) the extreme point is fixed at the foot position of the 6t plate to be melted; 1' runs around the surface of the I plate under the behavior of eating away the oxide film of mill scale that exists at Difficult to obtain results (2) Weld metal obtained under arc instability as described above may cause significant fin-like penetration at the bottom of the penetration, resulting in poor fusion, slag inclusion, and There was a problem in that blowholes and other welding defects/defects frequently occurred.

From the point of view of ensuring the safety of welded joints, the above-mentioned defects cannot be tolerated, so as a means to ensure a sound welded joint, an appropriate amount of active scum is added to the inert gas to stabilize the arc. Conventionally, it has been indispensable to prevent defects as a means of preventing defects.

By the way, depending on the purpose of welding, the type of wire, the material to be welded, etc., the mixing ratio of active gas may not necessarily be constant. -de and argon (Lynch Co., USA) are famous,
It is known to be particularly effective for spray transfer of wire end droplets.

Regarding stabilization of welding arc or prevention of welding defects 1
-As mentioned above, is it effective to mix active gas into the inert gas? On the other hand, it inevitably increases the amount of oxygen contained in the weld metal, for example, -196℃
9%N requires high toughness even at extremely low temperatures.
It is not possible to meet this requirement by welding 1 steel with the same metal. Therefore, it is clear that the active 4R type is not suitable for welding purposes where toughness is particularly important.

On the other hand, as already mentioned, conventional MIG-arc welding is conventionally used exclusively with DC reverse polarity. The reason for this is that only when the DC polarity is reversed, the wire droplets can be smoothly transferred to the +T) plate to be welded, and a good weld bead can be formed.

On the other hand, the DC positive polarity, that is, the welding I.
In this case, a particularly strong arc force acts on the wire droplets, causing the droplets to be torn off and transferred to the base plate, and often to be scattered as large chunks of spatter. Therefore, it was completely impossible to form a heat that could be used for Amakawa unless active gas was added to the shielding gas.

Therefore, in AC MIG arc welding where the polarity periodically changes (+), unstable droplet transfer during half-waves when the polarity becomes positive prevents the formation of a good bead. When the polarity changes [jl, the current value becomes zero and the arc is -1-extinguished, which has the disadvantage of requiring a high voltage of approximately 300 V as the restriking iE pressure to re-ignite this. The above-mentioned high-voltage power source is not acceptable in practice because it requires an increase in the capacity of the welding power source, and as a result, there is an increased risk of electric shock to the welding operator.

For the reasons mentioned above, MIG arc welding using direct current positive polarity and alternating current has not been considered in the past.

The present invention aims to overcome the current state of MIG arc welding as described above, to establish a MIG arc welding technology with a low oxygen content, and to further expand the scope of application of MIG arc welding. This is an attempt to further the inventors' objectives.

The present invention has already been disclosed in Japanese Patent Application Laid-Open No. 114469/1983, which allows a droplet at the tip of a welding wire to instantly repeat a stable contact short circuit on the surface of a molten pool formed on a mother plate to be welded. We found that transferring the welding wire to the base plate side is extremely advantageous for the DC reverse polarity arc phenomenon in pure argon atmosphere, and as a condition for this, welding wire with 0.02
~0.30 weight 1% rare 1-. It was disclosed that it is effective to add similar elements.

As a result of further studies based on one or more findings, the present inventors discovered that it is very effective to add surface elements not only to the welding wire but also to the base material to be welded, thereby completing the present invention. This is what led to this.

That is, various types of steels with different addition amounts of tJ earth elements were prepared, and these steels were used as base plates to be welded.
Arc welding is performed, and the welding of the wire tip to the molten pool surface is carried out as a lower step to produce a stable contact short-circuit with 1111 repetitions. We have come to find out that this method has an extremely effective effect.

Using such a fi7 plate to be welded, and direct current reverse polarity,
Under an appropriate range of welding conditions in a pure argon atmosphere, the tip of the wire becomes sharp in the arc, and the sharpened tip of the wire continuously repeats an instantaneous contact short circuit with the molten pool metal surface. However, when the rare earth element is added to 0.02 weight + j14%, neither sharpening nor stable maintenance of contact short circuit transition as shown in L will occur, and critical behavior will occur here. be.

Under such stabilization of the DC reverse polarity arc, tests were conducted in the customary setting range of the existing welding power source to examine the relationship between welding current and arc pressure in order to maintain stable contact transfer of droplets. As a result, we were able to obtain the stable region shown in Figure 1. For this test, a 9% N1 steel plate with a thickness of 1.2 mm containing o, io% of rare earth elements and a commonly used wire with a diameter of 1.2 mm were used. FIG. 1 shows the results, and a fully satisfactory weld bead was obtained within the area bordered by the solid line in FIG. Although the compliance conditions shown in Figure 1 may vary slightly depending on the wire diameter and current value, in the area below the solid line at the bottom of the figure, the wire thrust may not occur in the same direction. There is an unstable arc in one region from the solid line at the top of the figure, and in the middle, it is divided by both the upper and lower solid lines.
There is a region where contact short-circuit transition should be stably achieved. The width of this stable region can be expanded by adding rare earth elements to the base plate to be welded.

In conventional pure argon direct current reverse polarity MIG arc welding, when the arc voltage drops due to the spray transfer condition accompanied by irregular movement of the cathode spot, wire thrusting suddenly occurs, but with the present invention, contact short circuit can be stably prevented. It can be continued stably, which is a feature that is significantly different from conventional methods.

When the amount of rare earth elements added is 0.02% by weight or more, it is recognized that they make a significant contribution to the above-mentioned arc stabilization, but excessive addition of more than 0.30% by weight may cause non-metallic inclusions in the base rust plate and weld metal. 0.02 to 0.30% by weight is the limit for an appropriate amount, since it tends to increase the amount of carbon dioxide and deteriorate the toughness.

Here, 6' class 2 elements are generally Mitsushi metals that are easy to handle, for example, about half of them are Ce', and half of Ce' is La.
It is easy to handle a general commercially available product such as the following by setting the Cei at 1" and determining the yield of the rare earth element in the mother plate to be welded, and then determining the addition 1.

Although the present invention can be applied to various structural steel materials,
No. 1 of the applicable base plate to be welded (this component can exhibit the effect of this invention method on any structural steel material used for various purposes. What is steel material?
SS material and 3M material are 1;me! -L, N1-containing low temperature steel,
It is a general term for Cr-Mott4, ferritic stainless steel, austenitic stainless steel, etc.

Next, when the mother plate to be welded with an appropriate amount of earth elements added like a two-legged pair is applied to DC positive polarity pure argon MIG arc welding, the droplets at the wire end melted by the arc heat The biggest problem with the conventional method, which is that it is pushed up by a strong arc force and does not transfer smoothly to the HI root side, becomes a large lump, and finally scatters, causing spatter, has been advantageously overcome, and it can be used in pure argon atmosphere, direct current positive polarity. It was found that a single droplet () caused smooth contact short-circuit transfer even under The necessary range of welding conditions at this time is shown in the area between the broken lines below ``2'' in FIG.

In this case, the critical value of the amount of rare earth element added that should bring about smooth transition of the wire end droplets to small particles was also the same as that already described for the case of the DC reverse positive electrode.

By the way, in AC MIG arc welding, the positive and reverse polarities periodically alternate, so the welding phenomenon can basically be understood as a combination of phenomena in both the positive and reverse polarities. In the case of a logic arc, the arc is once extinguished at the change of pole 11, so an extremely high voltage is required to re-ignite the arc - generally causing a disturbance. However, in order to achieve the stabilization of the arc at the opposite polarity PI and the stable transfer of the wire end droplet, the ratio is set to 0.02 to 0 as described above.
．． The molten pool of the mother plate to be welded with 30% of rare-1-class elements added can significantly reduce the ITf ignition voltage of 1 F-, and the wire end droplet comes into contact with the molten pool metal surface. It was discovered that it was possible to stabilize the AC MIG arc by simply selecting the voltage and current so that the transition would occur from a short circuit I7. In the middle region of the dashed line, a large number of V was obtained.

If the rare earth element content is less than 0.02% or less than 1%, it will be impossible to stabilize the arc and the droplet transfer in IF reverse polarity, and the change in polarity will occur. The re-ignition voltage cannot be lowered, and if the content of L-class elements exceeds 0.30 tons F4%, an increase in II metal inclusions in the weld metal will occur if the +1 steel plate is used. The tendency of toughness deterioration based on

Hereinafter, the present invention will be explained in more detail based on examples.

Using six types of 9% Ni steel samples containing rare earth elements in the range of 0 to 0.36% by weight, shown in Table 1,
MIG arc welding was carried out according to the method of the invention. Minsche metal was used as the rare earth element, and the amount added was expressed as twice the amount of analyzed Ce.

The welding wire used was a matching wire for 9% Nl steel having the composition shown in Table 2, and 1. , 2 m
It is of mφ.

Table 3 shows welding examples in which the above-mentioned steel samples were used with a pure argon shield and reverse polarity was used.

The welding speed was kept constant at 60 cm/min, and the shielding gas flow was kept constant at 4.0 M/min.

When welding a base plate to be welded (steel plate number 1) that does not contain ``box'' elements, the wire plunges into the molten pool and significant spatter occurs. As a result of observing the arc voltage waveform in this case, it was found that many arc interruptions, that is, the occurrence of no-load voltage, occurred due to the wire thrust phenomenon, and as a result, as shown in Table 3, the arc voltage was lower than the set value. was also measured to be high. In order to avoid such a wire thrust phenomenon, welding was attempted by increasing the set arc voltage by 11", or although the wire thrust phenomenon was resolved at a certain critical voltage, instead of this, the defective wire tip Spray migration accompanied by stable fluctuations appeared, and a stable region of instantaneous contact short circuit could not be found.

When welding fil plates (steel plates No. 2 to 5) containing 0.02 to 0.30% by weight of Class 6 elements, instantaneous contact short-circuit transition occurs stably, and the beat shape also changes. An extremely good product was obtained. As shown in Table 3, the actually measured welding conditions at this time are stable at a constant value commensurate with the set value.

In addition, the addition of class elements ψ is increased to 0.36% by weight (
With steel plate No. 6), the welding arc itself was stable and the weld bead had a good appearance, but the cleanliness of the base steel plate and weld metal tended to decrease significantly, or the toughness of the weld metal This resulted in the deterioration of the .

Next, the mother plate to be welded (
Looking at an example in which the arc voltage was varied in welding steel plate No. 3), it was found that at 17.5 V, a practical beat could not be obtained due to wire thrusting and the resulting spatter. However, an unstable phenomenon did not occur to the extent that the setting conditions could not be reproduced, as was observed in the case of the material to be welded without addition of Class 10 elements (steel plate number 1). When the arc voltage is set to 22.5V, sharpening 1. The tip of the wire made contact with the molten pool surface in an extremely stable manner and short-circuited, resulting in a good weld beat. When the arc voltage was further reduced to 32.degree. 5V, it became impossible to stably maintain the contact short circuit at the wire tip, and stable welding became impossible to continue due to unstable oscillation of the wire tip and cathode spot. The data shown in Table 3 is based on the DC+! in Figure 1. ! This corresponds to the phenomenon of polarity.

Next, Table 4 shows welding examples when direct current positive polarity is used with a pure argon shield.

a When welding the base material to be welded (steel plate number 1) with no earth element additives, the strong arc force prevents the droplets from smoothly transferring to the LJ plate side, and they grow into a large lump at the wire tip. It scattered irregularly, and as a result, the arc itself became extremely unstable, making it difficult to reproduce the set conditions. 0 rare earth elements
．． When welding the base metal to be welded (steel plates No. 2 to 5) containing 0.02 to 0.30% by weight, the arc force weakens due to the molten pool surface effect of the rare earth element, causing the droplets at the wire end to momentarily shorten. I was able to transition smoothly with the rhythm, and an extremely stable beat was obtained. In the 1uJ material to be welded (#4 plate number 6) in which the amount of rare earth elements added was increased to 0.36% by weight, the stability of the arc itself and the appearance of the beat were good, but there were many inclusions in the weld metal. As a result, the toughness of the weld metal deteriorated.

Next, when welding a base material to be welded (Steel No. 43) containing 0.10% by weight of argon-class elements by varying the arc voltage, 2
0. In OV, the wire plunges into the molten pool, and 3
5. In OV, small droplets were scattered in all directions, so no beads of practical use could be obtained. However, at the intermediate voltage of 27.5 V, the instantaneous short circuit was stably maintained and an extremely good weld bead was obtained.

It should be noted that the data in Table 4 corresponds to the phenomenon I7 at the positive DC polarity of the first ffi.

Next, Table 5 shows examples of welding using alternating current with pure argon shield, and Table 6 shows examples of welding using alternating current with pure argon shield. This shows the case where the test was carried out.

It can be seen that there is no essential difference in welding phenomena due to the difference in shielding gas, and that the effect of stabilizing AC MIG arc by adding rare earth elements is equally exerted regardless of the shielding scum.

A subtle phenomenon in AC arcs is that when welding a parent phase to be welded with no rare earth elements added (steel plate number 1), the arc cannot be re-ignited stably, making it completely impossible to continue welding. It's something that happens. On the other hand, 0.02 to 0
．． When using the base material to be welded (steel plates No. 2 to 5) to which 30 wt.% of wasting earth elements were added, the arc stabilization in the forward and reverse polarity half-waves could not be improved, and when the polarity was reversed, It also became possible to stabilize the restriking property t1, and it was possible to form an extremely high quality weld bead I. When the rare earth content increases to 0.36%, it becomes a problem that the cleanliness of the weld metal decreases.
It lacked practicality.

Base material to be welded (m
When welding Plate No. 3) by changing the arc voltage, if the arc voltage is too low (20.OV), the wire will stick, and the arc voltage will be too high (35.OV).
With V), a good bead could not be formed because the instantaneous short circuit could not be maintained and the wire end oscillated, but with the Φ′ voltage (25, OV), the instantaneous contact short circuit could be stably maintained. , it was possible to obtain good welding heat.

Figure 2 illustrates droplet transfer and arc behavior during one cycle of AC MIG arc welding in pure argon atmosphere. Curve A shows the waveform of AC 1 cycle, and 1 to 15 are schematic representations of droplet transfer and arc behavior in corresponding portions of curve A, respectively.

As mentioned above, MIG arc welding can now be performed stably with direct current reverse polarity and positive polarity in a pure inert gas atmosphere. There is no need to add active gas to the inert residue,
This makes it possible to reduce the amount of alcohol in the weld metal and significantly improve its toughness, and when applied to AC arc welding, it is Ichihara's cheapest AC arc welding machine for manual welding. is sufficient, there is no need to invest in an expensive DC welding tool, and especially AC MIG arc,
Since the tF current pulsates, the external magnetic field (
For example, it is less susceptible to the negative effects of residual magnetism in the mother plate to be welded, and can solve the problem of magnetic blowing of the arc, which has traditionally been a problem with DC arcs. Even if the load voltage is low, the arc stability is good. Therefore, not only is there no need for a special device for stabilizing the 11-ignition characteristics, but it is also effective in that the risk level during a city strike is small.

[Brief explanation of the drawing]

Figure 1 is a graph showing an example of the relationship between current and arc voltage for MIG arc welding that should not result in arc stabilization in MIG arc welding using the method of the present invention, and Figure 2 is a graph showing an example of the relationship between current and arc voltage in MIG arc welding using the method of the present invention. FIG. 3 is an explanatory diagram showing droplet transfer and arc behavior in the case of Applicant Kawaichisaki Steel Co., Ltd. Agent Patent Attorney Yoshio Kosugi

Claims (1)

[Claims] ■ 1% of 0.02 to 0.30 modification in the structural steel phase. Using HX f' as a plate to which the above-mentioned elements have been added, instantaneous contact between the molten metal surface of the molten pool generated on the jtJ plate side and the molten metal at the tip of the welding wire l1iIJ! A MIG arc welding method V, characterized in that stable repetition of short circuits is caused continuously, and the molten gold 7iIX at the tip of the wire is transferred to the glue plate side by the contact short circuits. 2. When the polarity of the welding arc is DC reverse polarity, and the welding atmosphere is pure alcon without adding any active ingredients: 61 Claim 1-1 Welding method. 3. The welding method according to claim 1, wherein the polarity of the welding arc is DC positive polarity. 4 Claim 1-1-1 which is a welding main system or an alternating current system
One concubine, one nonon person.