KR20180043358A - High current pulse arc welding method and flux cored welding wire - Google Patents

Abstract

A flux cored welding wire containing a specific amount of at least one element selected from the group consisting of C, Si, Mn, P, S, Al, Ti, Zr and Mg is used, To 950 A, pulse base current less than 550 A, and difference between pulse peak current and pulse base current from 200 to 600 A.

Description

High current pulse arc welding method and flux cored welding wire

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-current pulse arc welding method, and more particularly, to a high-current pulse arc welding method in which a fillet or an improvement is applied in a single layer or multi- To a new high current pulsed arc welding method which can be welded and can also prevent pore defects. The present invention also relates to a novel flux cored welding wire used in the high current pulse arc welding method.

In the welding of the heavy plate which is applied in the field of transportation machine, construction machine, etc., welding of the fillet or improvement is often carried out by one layer or multiple layers of overlap welding using consumable electrode type gas shield arc welding. At that time, high quality and high efficiency Is a task that is always required.

With respect to high efficiency, a method of increasing the melting rate of the welding wire by using a high current is generally used. However, as the current increases, a large amount of spatters are generated. As a result, the labor of the sputter removing process is increased, and the production efficiency is lowered.

As a consumable electrode (hereinafter also referred to as " welding wire "), a solid wire is generally used conventionally. However, when a method of increasing the melting speed of the welding wire with a high current and employing a method of achieving high efficiency is shown, the solid wire shows a volumetric transfer form called rotating transition at a high current welding of 400 A or more.

In this mode of implementation, in the protruding portion of the solid wire extending from the power supply tip to the arc generation point, excessive heating of the wire causes the softened and melted solid wire to be melted by the influence of the electromagnetic force generated in the arc, It is to rotate and move along the arc. At this time, most of the displaced volume is scattered around, and the amount of spatter generated becomes remarkable.

In addition, in the case of welding carried out at a high current, in addition to the generation of spatter, there arises problems concerning pore defects and wear of the contact tip. In the case of high current welding, the temperature of the melting paper rises and the time until solidification is increased. Therefore, solidification is not completed within the gas shielded range, nitrogen in the atmosphere is incorporated into the melting zone, and it is likely to be solidified. The dissolved nitrogen becomes a gas as a nitrogen molecule upon cooling and is generated as bubbles in the molten metal.

When the bubbles in the molten metal solidify as they are, they become pore defects called blow holes. Also, pore defects that solidify while escaping into the atmosphere and remain as pores in the bead surface are called pits. As described above, in a high current welding, a porosity defect tends to occur as the current value increases.

In addition, there is a problem in that high-current welding becomes high at the periphery of the contact tip, and wear of the contact surface of the contact tip (hereinafter sometimes referred to as " tip wear ") which energizes the welding wire becomes large. When the tip wear becomes large, the positional deviation and the tip change frequently, and the work efficiency is lowered.

With respect to the high efficiency of the consumable electrode type gas shielded arc welding having these problems, the following techniques are available.

Patent Document 1 discloses a method in which a solid wire is used as an electrode wire and a mixture of four kinds of gases containing 40 to 70 vol% of argon, 25 to 60 vol% of helium, 3 to 10 vol% of carbon dioxide, and 0.1 to 1 vol% There has been proposed a welding method for obtaining a solid solution weight by using a gas as a shielding gas.

In Patent Document 2, by employing a slag flux cored wire as an electrode wire and further using a carbon dioxide gas as a shield gas and welding at a current density of 300 A / mm 2 or more, A welding method in which an effect can be obtained is proposed.

Patent Documents 3 and 4 propose a welding method using a multi-electrode having two or more electrodes, thereby achieving high efficiency and low spatter.

Patent Document 5 proposes a welding method in which the flux cored wire is used as a consumable electrode to suppress the rotational transition even at a high current density and to achieve high efficiency and low spatter.

Japanese Patent Application Laid-Open No. 59-45084 Japanese Patent Application Laid-Open No. 03-169485 Japanese Patent Laid-Open No. 2008-55509 Japanese Patent Application Laid-Open No. 2010-264487 Japanese Patent Application Laid-Open No. 2011-218437

In the welding method of Patent Document 1, although aiming at stabilizing the spray transfer, it is not reached to improve the rotational transfer when the current is further increased, and a large amount of spatter is generated. Further, in the welding method of Patent Document 2, since the carbon dioxide gas is used as the shielding gas and the welding is performed by the direct current, the mode of transfer of the volume becomes globule transition, and the large- .

In Patent Documents 3 and 4, high efficiency is achieved by using a multi-electrode, but since it is an excessively large apparatus including a multi-electrode, operability is not excellent and spatter may increase due to arc interference. In Patent Document 5, the flux cored wire electrode is used to avoid the rotational transition in the single-torch and the high current density at the high current density. However, since the pulse arc has a high current density, the arc length fluctuation is large and the arc tends to become unstable Therefore, there is a fear that the quality may deteriorate due to a fine spatter or bad appearance of the beads.

Further, none of Patent Documents 1 to 5 discloses the prevention of pore defects and the tip wear which can be a problem of high current welding.

In view of the above, it is an object of the present invention to provide a high-current pulse arc welding method and apparatus capable of realizing suppression of pore defects and tip abrasion while achieving solid- Arc welding method and a flux cored welding wire used for the welding method.

As a result of intensive studies, the present inventors have found that the above problems can be solved by appropriately setting high-current welding conditions in the composition of a specific flux cored welding wire, and have completed the present invention .

That is, the present invention is in accordance with the following [1] to [12].

[1] A pulse arc welding method for supplying a consumable electrode by the above-described supply device through a welding torch, using a welding system including a welding power source, a welding torch and a feeder, and performing welding while flowing a shielding gas ,

Wherein the consumable electrode is a flux cored welding wire filled with flux within the envelope,

Wherein the flux cored welding wire is made of a material selected from the group consisting of 0.30 mass% or less of C, 0.30 to 1.60 mass% of Si, 1.00 to 2.80 mass% of Mn, 0.050 mass% or less of P, 0.050 mass% or less of S, Zr and Mg in a total amount of 0.05 to 1.50% by mass,

Wherein the pulse peak current during welding is 550 to 950 A, the pulse base current is 550 A or less, and the difference between the pulse peak current and the pulse base current is 200 to 600 A.

[2] The steel sheet according to any one of [1] to [5], wherein the ratio of the total mass% of Al, Ti, Zr and Mg contained in the flux cored welding wire to the total mass% of Si and Mn satisfies 0.03? (Al + Ti + Zr + Mg) / (Si + Mn) The high-current pulse arc welding method according to the above-mentioned [1]

[3] The flux cored welding wire according to any one of [1] to [3], wherein the flux cored welding wire is selected from the group consisting of Al powder, Ti powder, Zr powder, Mg powder and alloy powder containing at least one element selected from the group consisting of Al, Ti, Zr and Mg , And at least 30 mass% of the powder is a powder having a particle size of not more than 100 탆. The high-current pulse arc welding method according to [1] or [2] above,

[4] The flux-cored welding wire of Al oxide, Ti oxide, Zr oxide and at least one oxide selected from the group consisting of Mg oxide, in terms of the Al oxide Al ₂ O _3, in terms of the Ti oxide TiO ₂ , a Zr oxide ZrO ₂ (Al ₂ O ₃ + TiO ₂ + ZrO ₂ + MgO)? 1.50% by mass based on the total mass of the flux cored welding wire in terms of MgO converted to MgO, The high-current pulse arc welding method according to any one of [1] to [3] above,

[5] The high-current pulse arc welding method according to any one of [1] to [4], wherein the pulse frequency at the time of welding is 50 to 200 Hz.

[6] The method as set forth in any one of [1] to [6], wherein the ratio of the pulse frequency during welding to the feed rate for feeding the consumable electrode is 1.50 (mm / (1) to (5), wherein the relationship (mm / 1 pulse) is satisfied.

[7] The high-current pulse arc welding method according to any one of [1] to [6], wherein the slope of the external characteristic of the welding power source is -14.0 to -4.0 (V / 100A).

[8] The shielding gas is an Ar-containing mixed gas comprising Ar and impurities, or an Ar-containing gas containing 0 to 40% by volume of CO ₂ and 0 to 10% by volume of O ₂ and the balance of Ar and impurities The high-current pulse arc welding method according to any one of [1] to [7]

[9] A flux cored welding wire for high current pulse arc welding having a shell and containing flux in the shell,

The average current during welding is over 400A,

Wherein the steel is selected from the group consisting of Al, Ti, Zr, and Mg; 0.30 to 1.60 mass% of C, 0.30 to 1.60 mass% of Si, 1.00 to 2.80 mass% of Mn, 0.050 mass% or less of P, 0.050 mass% By mass of at least one element selected from the group consisting of iron, copper, and alloys.

It is preferable that the ratio of the total mass% of Al, Ti, Zr and Mg contained in the flux cored welding wire to the total mass% of Si and Mn satisfies the relation of 0.03? (Al + Ti + Zr + Mg) / (Si + Mn)? 0.60 The flux cored welding wire according to the above [9], characterized in that

[11] An alloy powder containing at least one powder selected from the group consisting of an Al powder, a Ti powder, a Zr powder, a Mg powder, and an alloy powder containing at least one element selected from the group consisting of Al, Ti, Zr and Mg The flux cored welding wire according to the above [9] or [10], wherein 30% by mass or more of the powder is a powder having a particle size of 100 탆 or less.

[12] A catalyst comprising at least one oxide selected from the group consisting of Al oxide, Ti oxide, Zr oxide and Mg oxide, wherein the Al oxide is converted into Al ₂ O ₃ , the Ti oxide is converted to TiO ₂ , the Zr oxide is converted to ZrO ₂ , And the total amount of the oxides when the Mg oxide is converted into MgO satisfies the relation of 0.05 mass% ≦ (Al ₂ O ₃ + TiO ₂ + ZrO ₂ + MgO) ≦ 1.50 mass% with respect to the total mass of the flux cored welding wire The flux cored welding wire according to any one of the above-mentioned 9 to 11,

According to the present invention, the pulse peak current, the pulse base current, and the flux cored welding wire composition in the pulse arc welding are combined in a specific combination, so that compared with the conventional high current welding method, So that effects such as the effect of pore defects, low spatter, and tip wear can be obtained.

In other words, it is possible to realize high-efficiency welding more than conventional in high-current welding of a single electrode having excellent operability and at the same time, it is possible to reduce the labor of the quenching process by improving low spatter and pore defects, . In addition, since pore defects and tip wear can be suppressed, it is possible to improve work efficiency and realize low cost.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an overall structural view showing an example of an apparatus used in a welding method according to the present invention; Fig.
2 is a graph showing an example of a pulse waveform used in the welding method according to the present invention,
Fig. 3 is an explanatory diagram showing a self-controlling action of an arc length in the welding method according to the present invention; Fig.

Hereinafter, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the embodiments described below.

A high current pulse arc welding method according to the present invention is a method of welding a consumable electrode by a feeder through a welding torch including a welding power source, a welding torch and a feeder, Lt; / RTI >

Wherein the consumable electrode is a flux cored welding wire filled with flux within the envelope,

Wherein the flux cored welding wire is made of a material selected from the group consisting of 0.30 mass% or less of C, 0.30 to 1.60 mass% of Si, 1.00 to 2.80 mass% of Mn, 0.050 mass% or less of P, 0.050 mass% or less of S, Zr and Mg in a total amount of 0.05 to 1.50% by mass,

The pulse peak current during welding is 550 to 950 A, the pulse base current is 550 A or less, and the difference between the pulse peak current and the pulse base current is 200 to 600 A.

Also, a flux cored welding wire according to the present invention is a flux cored welding wire for high current pulse arc welding having a sheath and containing flux in the sheath,

The average current during welding is over 400A,

Wherein the steel is selected from the group consisting of Al, Ti, Zr, and Mg; 0.30 to 1.60 mass% of C, 0.30 to 1.60 mass% of Si, 1.00 to 2.80 mass% of Mn, 0.050 mass% or less of P, 0.050 mass% By mass in total of at least one element.

[Welding apparatus]

First, a welding apparatus usable in the high current pulse arc welding method according to the present invention will be described. The welding apparatus is not particularly limited as long as it is a welding apparatus that performs high-current pulse arc welding, and a conventionally used welding apparatus can be used.

For example, as shown in Fig. 1, the welding apparatus 1 is configured such that the welding torch 11 is attached to the front end and the welding torch 11 is welded to the welding material (hereinafter, (Not shown) for supplying a welding wire to the welding torch 11, and a current supplying unit for supplying current to the consuming electrode through the wire supplying unit And a welding power source 30 for generating an arc between the consumable electrode and the welded material. The welding apparatus also includes a robot control unit 20 for controlling the robot operation for moving the welding torch 11.

<Flux cored welding wire>

The consumable electrode in the present invention is a flux cored welding wire filled with flux in the shell. That is, the flux cored welding wire is composed of a tubular sheath and a flux filled inside the sheath.

The flux cored welding wire may be of any of the seamless type having no joint on the sheath and the seam type having a joint on the sheath. Further, the surface of the wire (the outer side of the outer shell) may or may not be plated with copper.

The flux cored welding wire contains a predetermined amount of at least one element selected from the group consisting of Al, Ti, Zr and Mg in a predetermined amount, and contains C, Si, Mn, P and S in predetermined amounts. The corresponding Al, Ti, Zr and Mg are known as strong acid elements, but at the same time, they have strong denitrification effect and are an element which reacts with N and tends to become a nitride.

Hereinafter, the numerical range of the amount of the component of the flux cored welding wire will be described together with the reason for the limitation. Unless otherwise specified, the amount of components is represented by the sum of the amounts of the components in the shell and flux, and the mass of each component contained in the flux cored welding wire (sheath + flux) .

(C: 0.30 mass% or less)

The C in the welding wire or in the welding metal is effective in increasing the strength of the welding metal. The lower limit is not set because there is no problem even if the content of the spatter is small, and if it is contained in a large amount exceeding 0.30 mass%, it is combined with oxygen during welding, and CO gas is generated to generate bubbles on the volume surface. The generated bubbles are scattered to generate a spatter. Therefore, the content of C is specified to be 0.30 mass% or less.

On the other hand, C may not be contained, but is preferably 0.01% by mass or more for securing strength.

(Si: 0.30 to 1.60 mass%)

Si in the welding wire is a deoxidizing element and is an element necessary for securing the strength and toughness of the weld metal. If the addition amount is small, blowholes are generated due to insufficient deoxidation. Therefore, it is contained in an amount of 0.30 mass% or more, preferably 0.50 mass% or more.

On the other hand, if it is contained in a large amount exceeding 1.60 mass%, a large amount of slag which is difficult to be peeled off during welding is generated and welding defects such as slag inclusion occur, so 1.6 mass% is the upper limit and 1.30 mass% or less is preferable.

(Mn: 1.00 to 2.80 mass%)

Mn in the welding wire exhibits an effect as a deoxidizing agent or a sulfur capturing agent in the same manner as Si and is necessary for securing the strength and toughness of the weld metal. 1.00% by mass or more is contained in order to prevent the occurrence of welding defects due to deoxidization shortage. It is preferably 1.10 mass% or more.

On the other hand, if it is contained in a large amount exceeding 2.80 mass%, a large amount of slag which is difficult to be peeled off during welding is generated, resulting in weld defect such as inclusion of slag. Further, the strength is excessively increased, and the toughness of the weld metal is remarkably lowered. For this reason, the content of Mn is limited to 2.80% by mass, preferably 2.30% by mass or less.

(P: 0.050 mass% or less (including 0 mass%))

(S: 0.050 mass% or less (including 0 mass%))

S (sulfur) and P (phosphorus) are both impurity elements, and it is desirable to set the content to a very small amount, and therefore the lower limit is not set. If they are present in a large amount exceeding 0.050 mass% each, welding defects such as cracks of the weld metal occur. Therefore, the upper limit of both is 0.050 mass%.

(Hot rolled element: 0.05 to 1.50 mass% in total)

Al, Ti, Zr, and Mg are elements (strong releasing elements) having a strong denitrification effect. The lower limit of the content of the at least one indulgent element selected from the group consisting of Al, Ti, Zr and Mg is 0.05% by mass in total. If the amount is 0.05% by mass or more, N dissolved in the weld and the corresponding indolent nitrogen element react with each other to form a nitride, so that pore defects occurring when N ₂ (gas) is released into the atmosphere can be prevented. The lower limit of the content of the total of the offensive elements is preferably 0.10% by mass or more, and more preferably 0.25% by mass or more.

On the other hand, in the case where the total of the raindrop elements exceeds 1.50 mass%, a nitride or an oxide generated by the raindrop element is generated on the surface of the fused paper and the arc is deflected, so that a large amount of spatter is generated . Therefore, the upper limit of 1.50% by mass in total of the raindrop elements is preferably 1.00% by mass or less, more preferably 0.80% by mass or less.

(Other elements)

(Mo, Ni, Cr, B)

Mo, Ni, Cr, and B may be added to improve the strength or toughness of the weld metal. If these elements are added in excess, cracks tend to occur. Therefore, the content of Mo is preferably 1.00 mass% or less, Ni is preferably 1.00 mass% or less, Cr is preferably 5.00 mass% or less, and B is preferably 0.0050 mass% or less.

(Li, K, Na)

Li, K, and Na may be added to stabilize the arc, reduce the amount of spatter generated, and improve the penetration performance. Each of the elements is preferably contained in an amount of 0.010 to 1.000 mass%.

Examples of the compounds of Li, K, and Na included in the flux cored welding wire include oxides and carbonates such as LiO ₂ , Li ₂ CO ₃ , K ₂ O and Na ₂ O, and fluorides such as K ₂ SiF ₆ For example.

(The remainder)

Other elements constituting the flux cored welding wire include Fe and impurities. Examples of the impurities include Co, W and the like. In the case of having plating, Cu is also included as other elements.

(The content ratio of the entangled element)

Al, Ti, Zr and Mg are denitrifying elements and also act as deoxidizing elements. Therefore, by adding Si and Mn as deoxidizing elements, pores caused by oxygen can be prevented by Si and Mn, and Al, Ti, Zr and Mg are more effective as denitrifying elements than deoxidizing elements, And the like. Therefore, the ratio (Al + Ti + Zr + Mg) / (Si + Mn) of the total mass% of Al, Ti, Zr and Mg contained in the flux cored welding wire to the total mass% of Si and Mn is preferably 0.03 or more, more preferably 0.08 or more desirable.

In addition, oxides of Al, Ti, Zr, and Mg have excellent thermoluminescence ability, and therefore, when an appropriate amount is present on the fused paper, it contributes to arc stability. (Al + Ti + Zr + Mg) / (Si + Mn) is preferably 0.60 or less, and more preferably 0.40 or less, from the viewpoint that the arc stability is increased by the optimum cathode point forming effect and the slag detachability becomes better.

(Metal powder)

In the case where Al, Ti, Zr and Mg contained in the flux cored welding wire are powder or alloy powder, that is, from the group consisting of Al powder, Ti powder, Zr powder, Mg powder and Al, Ti, Zr and Mg And at least one element selected from the group consisting of alloy powder containing at least one element selected from the group consisting of iron and iron, and more preferably at least 30 mass% of the total of the powders is a powder having a grain size of 100 탆 or less.

This is because the smaller the particle diameter, the more easily it is dissolved in the melting paper uniformly, so that the reaction with N is promoted and the pore defect becomes more excellent. The smaller the particle diameter of the powder is, the better the content of the powder having a particle size of 100 탆 or less is more preferably 50% by mass or more, and the upper limit may be 100% by mass.

Examples of the alloy powder include Fe-Al (ferroaluminum), Fe-Ti (ferrotitan) and the like.

The content of the powder having a particle size of 100 mu m or less is measured by dividing the Al powder, the Ti powder, the Zr powder, the Mg powder and the alloy powder by a sieve having a sieve interval of 100 mu m based on JIS Z 8801-1: 2006 .

(High melting point oxide)

The flux cored welding wire may include at least one oxide selected from the group consisting of Al oxide, Ti oxide, Zr oxide, and Mg oxide, and the Al oxide may be Al ₂ O ₃ Conversion of Ti oxide to TiO _2, conversion of Zr oxide to ZrO ₂ (Al ₂ O ₃ + TiO ₂ + ZrO ₂ + MgO)? 1.50% by mass based on the total mass of the flux cored welding wire in terms of MgO converted to MgO, Is satisfied.

Al oxides, Ti oxides, Zr oxides, and Mg oxides are both high-melting oxides at 1800 ° C or higher. By including the oxide having a high melting point, the flux column can remain in the arc at a high temperature, and stable volume transfer can be realized, which is preferable.

If the content of the high melting point oxide in the flux cored welding wire is less than 0.05 mass%, the flux column may be dissolved. Therefore, the content of the high melting point oxide is preferably 0.05% by mass or more, more preferably 0.25% by mass or more.

On the other hand, when it exceeds 1.50% by mass, a large amount of slag is generated, and welding defects such as slag inclusion may occur. Therefore, it is preferably 1.50% by mass or less, more preferably 1.00% by mass or less.

If the average particle diameter of the high melting point oxide composed of the Al oxide, Ti oxide, Zr oxide and Mg oxide is too large, there is a possibility that the oxide penetrates into the flux during wire forming and is broken. Therefore, the average particle diameter of the Al oxide, Ti oxide, Zr oxide and Mg oxide is preferably 350 탆 or less, more preferably 300 탆 or less. The smaller the average particle diameter, the more difficult it is to break, and the more the components in the flux are evenly distributed, the lower limit is not particularly set.

The particle diameters of the oxides can be measured by sieving the sieves at a body interval of 75, 100, 150, 200, 250, 300, 355 and 425 μm according to JIS Z 8801-1: 2006.

(Flux filling rate)

The flux filling rate in the flux cored welding wire is preferably 10 to 25 mass%. If the flux filling rate is less than 10% by mass, there is a risk of losing the arc stabilizing effect due to the flux column. On the other hand, when the content exceeds 25% by mass, there is a fear that the breakage in feeding and the arc pressure directly beneath the wire become small and the penetration may not be caused. The flux filling rate is more preferably 12 mass% or more, and more preferably 22 mass% or less.

The flux filling rate is defined as the ratio of the mass of the flux filled in the shell to the total mass of the wire (sheath + flux).

Although the final product diameter of the flux cored welding wire is not a problem, it is preferably 1.2 to 1.6 mm as a general use range.

<Manufacturing Method of Flux Cored Welding Wire>

The method of producing the flux cored welding wire is not particularly limited and may be manufactured by a general manufacturing process. For example, by forming the U-shaped hoop of mild steel or stainless steel into a U-shape, filling the U-shaped forming hoop with a flux, molding the flux into a tubular shape filled in the inside, It is good to manufacture.

The material of the sheath can be used without particular limitation, such as mild steel or stainless steel. The composition of the element in the total weight of the flux cored welding wire may be within the above range.

The particle size of the flux can be judged by sieving. According to JIS Z 8801-1: 2006, the spacing of the sieves may be 75, 100, 150, 200, 250, 300, 355, or 425 탆.

<Shielding gas>

The shield gas used in the high-current pulse arc welding method according to the present invention is not particularly limited, and Ar gas, carbon dioxide gas (carbon dioxide, CO ₂ ), oxygen gas (O ₂ ) and mixed gas thereof can be used. These may include oxygen, nitrogen, hydrogen, and the like as inevitable impurities.

Even in the case of welding using 100% CO ₂ as the shielding gas, the gas shielded arc welding method according to the present invention can suppress the mixing of the atmosphere and prevent the oxidation reaction. However, by using an Ar gas or an Ar-containing mixed gas as the shielding gas, it is possible to further reduce the oxidation reaction of the molten metal. Therefore, it is preferable to use Ar gas (100% Ar) or Ar-containing mixed gas composed of Ar and inevitable impurities as the shielding gas.

In the case of the Ar-containing mixed gas, it is preferable that the gas mixture contains at least any one of Ar, CO ₂ and O ₂ and inevitable impurities, and that the CO ₂ content is 0 to 40% by volume and the O ₂ content is 0 to 10% by volume desirable. Further, it is more preferable that Ar contains at least 80% by volume, and the remainder is at least one of carbon dioxide and oxygen and inevitable impurities.

The flow rate of the shield gas is generally 35 L / min or less. As a result, it is possible to prevent an excessive increase in the flow rate of the shielding gas, thereby suppressing the entry of the atmosphere into the shielding atmosphere by the high-speed gas flow.

<Welding power source>

The welding power source is not particularly limited, and a power source conventionally used for pulse arc welding can be used.

<Welding Torch>

The welding torch is not particularly limited, and the same torch as the conventional one can be used.

An example of a welding torch is shown below. The welding torch is equipped with a torch clamp. The current-carrying metal is used to flow a weak current to the nozzle, which is used to detect contact between the nozzle and the workpiece. The torch clamp fixes the welding torch to the robot.

The torch barrel (gun body) is supported by the torch clamp and has a mechanism for supporting the nozzle and the tip body. The torch barrel can supply the supplied welding wire to the tip end (the rear end of the contact tip) of the tip body via the inner tube, with the tip body mounted. Further, the torch barrel supplies a welding current to the tip body and also supplies shield gas to the space formed between the inner tube and the tip body. The tip body includes an orifice, an orifice support nut, and a mechanism for supporting the contact tip. Further, the tip body is formed of a material having conductivity such as metal.

The orifice is provided with a mechanism for performing the rectification of the shield gas. That is, the orifice is generally cylindrical and is mounted by being inserted from the tip side of the outer periphery of the tip body. The contact tip is provided with a mechanism for feeding the welding current to the welding wire and for guiding the welding wire to the work to be welded. In addition, like the tip body, the contact tip is also made of a material having conductivity such as metal.

The attitude of the welding torch may be vertical or inclined with respect to the base material.

In the case where the welding torch is inclined toward the opposite side of the welding direction, the angle between the waterline and the corresponding torch is referred to as a forward angle, and when the welding torch is inclined toward the welding direction, The angle formed is called the retraction angle.

By giving a forward angle to the welding torch, the shielding property during arc welding can be improved more effectively. Further, by providing a retraction angle to the electrode, it is possible to shield the rear of the bead, so that the oxidation reaction of the bead immediately after welding can be suppressed.

In order to obtain a proper penetration on the weld line and a good bead shape, it is preferable to tilt the electrode within the range of the forward angle range of -15 to 40 degrees, that is, the upper limit of the forward angle of 40 degrees and the upper limit of the backward angle of 15 degrees More preferable.

(Nozzle)

The nozzle is provided with a mechanism for spraying a shield gas supplied from a gas supply device (not shown) to the base material to be welded. The nozzle is formed in a tubular shape having an integrally assembled tip body, an orifice, and an inner space capable of accommodating the contact tip therein. In addition, the nozzle has a female screw portion on the inner surface of the rear end, to which a male screw portion formed at the tip of the torch barrel is screwed. With this configuration, the nozzle can shield the welded portion from the atmosphere by using the shielding gas rectified by the orifice.

In the welding method according to the present invention, from the viewpoint of the tip abrasion, it is preferable to use a torch which is water-cooled to the vicinity of the nozzle.

<Feeder>

The feeder is not particularly limited, and a conventionally used feeder can be used.

<Pulse arc welding condition>

The pulse defined in the present invention is a current waveform that repeats the shape of a rectangle or a trapezoid. FIG. 2 shows an example of the current waveform. The time of the upper bottom portion of the rectangular or trapezoid is expressed as a pulse peak current period (pulse peak period) Tp and a time period of the lower bottom portion as a pulse base The current in the pulse peak period Tp is referred to as the pulse peak current Ip and the current in the pulse base period Tb is defined as the pulse base current Ib. The average current Ia is obtained by temporally averaging the time integral of the welding current. That is, in the case of a rectangular wave, Ia = (Ip Tp + Ib Tb) / (Tp + Tb). The number of pulses for one second (the number of times one wavelength is repeated) is set as a pulse frequency.

The pulse arc welding method is a method in which the volume generated in the pulse base period Tb having a low current and the pulse peak period Tp having a high current is separated by the electromagnetic force of the pulse peak current Ip. However, If the displacement timing of the volume is shifted, the spatter may increase, the arc may be deflected, and the appearance of the bead may become coarse.

For example, if the pulse peak current Ip is too low, the stiffness of the arc can not be obtained, and the arc may be deflected. Also, when the pulse base current Ib is too high, the volume is released at the start of the peak current, and the volume thereof is scattered by the arc pressure of the peak current, so that the spatter may increase. Particularly, in the case of high-current pulse arc welding, it is difficult to obtain an appropriate pulse condition because rotation is easily transferred.

In the high current pulse arc welding method according to the present invention, the conditions of the pulse arc welding optimal for limiting the flux cored welding wire to be used to a specific composition and exhibiting a synergistic effect when the welding wire is used are defined below.

(Pulse peak current (Ip): 550 to 950 A)

The pulse peak current at the time of welding shall be 550A or more and 950A or less. 550 A, arc stiffness becomes insufficient, so that the arc tends to be attracted to a cathode point based on an oxide produced from Al, Ti, Zr and Mg in the high-current welding wire, resulting in arc deflection , The spatter becomes easy to increase. On the other hand, if it exceeds 950 A, the current becomes excessively high and therefore the flux column of the flux cored welding wire does not remain, and the arc stability is deteriorated, and the amount of spatter is likely to be increased.

(Pulse base current Ib: 550 A or less)

The pulse base current at welding shall be 550 A or less. When the pulse base current exceeds 550 A, the arc pressure to the volume in the pulse base period (Tb) becomes excessive, thereby promoting the instability of the arc, and the spatter generation amount is easily increased.

(Difference between pulse peak current (Ip) and pulse base current (Ib): 200 to 600 A)

The difference between the pulse peak current (Ip) and the pulse base current (Ib) at the time of welding is 200 A or more and 600 A or less. When the difference of the current is less than 200A, the balance of the volume transition is broken, and the possibility of volumetric deviation occurs at the peak current becomes high, and the spatter becomes easy to increase. On the other hand, when the difference of the current exceeds 600 A, the fluctuation of the arc length becomes large at the time of peak current, and nitrogen is easily mixed, and pore defects are likely to occur.

That is, by using the flux cored welding wire of the present invention, by setting the pulse peak current, the pulse base current, and the difference of the currents in the above-mentioned range, the volume transfer and the arc So that excellent effects such as effect of pore defects, low spatter, and wear resistance can be obtained.

(Average current Ia)

The average of the time integral of the welding current during welding is the average current Ia. That is, in the case of a rectangular wave, the average current can be defined by Ia = (Ip · Tp + Ib · Tb) / (Tp + Tb).

(Pulse frequency Fp)

When the pulse frequency at the time of welding is in the range of low frequency of 50 to 200 Hz, it is preferable that the pulse base period can be secured for a long time, and sudden arc length fluctuation can be suppressed and arc deflection can be suppressed. Further, since the arc pressure according to the volume is small in the corresponding pulse base period, the movement of the volume increased during the pulse peak period can be suppressed, and as a result, the rotational transition can be suppressed, which is preferable. In addition, tip wear is also preferable because the tip frequency is low and the cooling effect of the tip is expected in the pulse base period.

(Feed speed / pulse frequency)

Pulse arc welding causes an increase in spatter if the displacement timing of the volume is deviated. Therefore, it is preferable that the volume is shifted by regulating the feeding speed of the consumable electrode (flux cored welding wire) in addition to the pulse frequency to obtain the stability of the low spatter and the arc. However, since the proper feed rate varies depending on the pulse frequency, the feed rate per millimeter (mm) is calculated as the feed rate (mm / sec) / pulse frequency (number of pulses / sec = Hz) / 1 pulse).

It is preferable that the feed rate per wavelength represented by the feed rate (mm / sec) / pulse frequency (number of pulses / sec = Hz) is 1.50 (mm / 1 pulse) or more and 9.00 (mm / 1 pulse) or less.

If it is less than 1.50 (mm / 1 pulse), the amount of deposition at the time of peak current becomes insufficient, and the arc tends to rise easily, so that arc instability such as arc length variation and arc deflection may occur. If it is more than 9.00 (mm / 1 pulse), there is a case where the spatter is increased by the wire being short-circuited with the wire digging into the melting paper at the time of the base current.

The pulse peak current, the pulse base current, the pulse peak period, the pulse base period, and the pulse frequency can all be adjusted by setting the welding power source.

The "high current" in the high current pulse arc welding method according to the present invention means that the value of the average current Ia is 400 A or more.

(External characteristic)

In the case of high-current pulse arc welding, the pulse peak current with a large current difference and the pulse base current change at high speed, so that the arc length fluctuation becomes large. In order to suppress such arc length fluctuation, fluctuation of the arc length can be suppressed by making the current change insensitive. On the other hand, if the variation of the current is too insensitive, the self-controlling action of the arc length is lost. For this reason, high current pulse arc welding has an appropriate range of external characteristic inclination.

As shown in FIG. 3, when the arc length is l _O To I _S , the current increases from I _O to I _S. Therefore, increasing the melting rate of the welding wire and acts to lengthen the arc length and the arc length returns to its original length l of _O. Conversely, if the arc length is l _O to l _L , the current decreases from I _O to I _L. Accordingly, the melting rate of the welding wire is reduced, and acts to shorten the arc length, arc length is too comes back to its original length l of _O. The phenomenon in which the arc length is automatically controlled so as to return to the original length is referred to as the arc control of the arc length. The effect of the self-controlled action appears as the slope of the current-voltage curve becomes milder. The slope in this current-voltage curve is the slope of the external characteristic of the welding power source.

In the present invention, the slope of the external characteristic is preferably -14.0 (V / 100A) or more and -4.0 (V / 100A) or less.

-4.0 (V / 100A) or less, it is possible to suppress a large current change at the time of high-current pulse arc welding and to suppress the arc length variation. Therefore, welding of a lower spatter can be realized, and tip abrasion is further suppressed. On the other hand, if it is less than -14.0 (V / 100A), the effect of suppressing arc length variation may not be exhibited because the self-control action of the arc is lost.

<Welded material (work, base material)>

Conventionally known welding materials can be used. Examples thereof include rolled steel materials for welded structures belonging to JIS G 3106: 2015, rolled steel sheets for general structure belonging to JIS G 3101: 2015, and the like.

<Welding materials>

Although the welding method according to the present invention is carried out with a high current, the welded material welded by the welding method is the welding of the heavy plate in the fields of the transport machine and the construction machine, and the fillet or the improvement is welded in one layer or multiple layers. And is particularly preferably used.

(Amount of spatters)

The amount of the spatters can be quantified by, for example, installing boxes on both sides of the weld, performing welding, collecting all of the generated spatters from the box (inside the box) and measuring the mass. The smaller the value of the spatter amount of the obtained weld metal is, the better, but the preferable value is changed depending on the wire composition used.

(Bead appearance)

It is preferable that there is no skew on the bead surface as the bead appearance. Further, the bead surface means a weld metal (a part of a welded portion, a metal that is melt-solidified during welding) made by one pass and conforms to the definition in JIS Z 3001-1: 2013.

(Welding defect)

It is preferable that the welded material does not have weld defects such as pore defects due to nitrogen such as pits and blow holes, slag inclusion, weld cracks. The weld defect can be evaluated by visual observation of the surface of the bead or by macro observation of the cross section of the bead.

(Arc stability)

The arc stability at the time of welding can be judged from the naked eye and the current waveform using the light shielding surface for the fluctuation of the arc length. In the current waveform, it is preferable that the ratio (rate of variation) at which a high current equal to or higher than the set peak current value or a current equal to or lower than the set base current value flows.

(Tip wear)

The smaller the value of the contact tip wear (tip wear) after welding, the better. For example, the tip abrasion amount per unit time can be evaluated by measuring the tip abrasion area after performing the welding.

Example

EXAMPLES The present invention will be described in more detail with reference to the following examples, but it should be understood that the present invention is not limited to these examples, but can be carried out with modifications within the scope of the present invention, And are included in the technical scope of the present invention. The welding conditions described here are only examples, and the present invention is not limited to the following welding conditions.

<Evaluation method>

(Particle size of the hot-rolled element powder)

The ratio of the powder having a grain size of not more than 100 占 퐉 in the total content of the single metal powder and the alloy powder of the stripping element made of Al, Ti, Zr and Mg contained in the flux cored welding wire is JIS Z 8801-1 : 2006, using a sieve having a sieve interval of 100 mu m.

(Amount of spatters)

Welding was carried out for 1 minute in a state where a box made of a copper plate was provided on both sides of the welded portion, and the entire spatters generated during that time were taken out from the box (in the box) and the total mass of the collected spatters was measured. The mass at this time was defined as the amount of spatters (g / min).

(Bead appearance)

With respect to the obtained welded material, the presence or absence of winding on the surface of the bead was visually confirmed, and the judgment of the bead appearance was carried out.

(Welding defect)

The presence of pore defects, slag inclusion and welding cracks was evaluated as a weld defect by visual observation of the bead surface and macro observation of the cross section of the bead. In the macro observation of the section of the bead, macro observation was performed on any five of the sections of the bead to judge the presence or absence of a weld defect.

(Tip wear)

When a base plate having a size of 25 mm (t) x 650 mm (w) x 650 mm (l) was welded for 1 hour with a bead on plate and the tip after welding was viewed from the front with an optical microscope Was measured by the area of the tip abrasion area converted into the number of pixels of the electronic data.

(Arc stability)

The arc stability at the time of welding was judged by observing the arc length variation with naked eyes and current waveform using the light shielding surface. In the current waveform, the case where the current exceeding +50 A with respect to the set peak current value and the case where the current below -50 A with respect to the set base current value are obtained are counted for 60 seconds, And the sum of the counts at that time is defined as a variation value.

&Lt; Test Examples 1 to 55 &gt;

JIS G 3101: 2015 High current pulse arc welding using flux cored welding wire was carried out using the steel sheet of SS400 as the base material. The wire diameter of the welding material was 1.4 mm, and the shield gas was a mixed gas of Ar: CO ₂ at a volume ratio of 80:20.

In the case of evaluating the appearance of the bead, two plates (size 12 mm (t) x 50 mm (w) x 500 mm (l)) are made to be T-shaped to perform downward fillet welding, The angle was made perpendicular to the plane. On the other hand, when the evaluation is to be carried out, downward welding of the bead-on plate is carried out.

The composition of the flux cored welding wire used in each test example is shown in Table 1.

The pulse arc welding conditions are as shown below, and the specific welding conditions of the respective test examples are shown in Table 2.

· Pulse peak current: 550 ~ 1000A

· Pulse base current: 100 to 600A

· Pulse peak period: 1.5 to 7.5 msec

· Pulse frequency: 30 ~ 300㎐

Average current: 450 to 620A

· Feeding speed: 16.0 ~ 28.0m / min

· Arc voltage: Appropriate voltage (30 ~ 50V)

· External characteristics: -16.0 ~ -1.0 (V / 100A)

In Table 1, the chemical composition is &quot; - &quot; and it is an inevitable impurity, indicating that it is not positively added. The flux cored welding wire having wire numbers W1 to W23 satisfies the conditions of the flux cored welding wire of the present invention, and the flux cored welding wire of W24 to W34 is a wire that does not satisfy the condition to be. The flux cored welding wire of W34 is a conventional welding wire, and is a welding wire to which no Al, Ti, Zr and Mg are added.

In Table 2, &quot; f.rate &quot; indicates the feeding speed at which a consumable electrode (flux cored welding wire) is fed. No. 1 to No. 39 are examples satisfying the conditions of the welding method according to the present invention, and No. 40 to No. 44 are examples of the present invention No. 45 to No. 55 are comparative examples that do not satisfy the composition of the flux cored welding wire in the present invention.

[Table 1]

[Table 2]

The results of the spatters, bead appearance, weld defect, tip wear and arc stability of the welds obtained in Nos. 1 to 55 are shown in Table 3.

In Table 3, the evaluation of &quot; Spatter &quot; in Table 3 indicates that the value of? Is not more than 0.80 (g / min), and? Indicates that the value is more than 0.80 (g / min) and not more than 1.60 (g / min) g / min).

In the &quot; evaluation of bead appearance &quot;, &amp; cir &amp; indicates that the bead is normal, and X indicates that bead appearance defects exist.

In the &quot; weld defect evaluation &quot;, &amp; cir &amp; indicates a state in which none of pore defects, slag inclusion, and welding cracks exist, and X indicates a state in which at least one of them exists. Also, in the case of X, the defect shown by the parentheses was written.

Evaluation of &quot; tip wear &quot; means that the wear area is less than 0.65 mm &lt; 2 &gt;, and even when a pulse is applied, there is wear resistance effect equal to or more than that of the conventional constant current welding, and x indicates that the wear area is 0.65 mm &

Indicates that the fluctuation value is not less than 250 and not more than 500, and X indicates that the fluctuation value is not less than 500, and that when observing the arc with the naked eye using the light shielding surface, It indicates that the fluctuation of the arc length is large enough to confirm instability.

[Table 3]

Since the examples of Nos. 1 to 39 were welding wire of the optimum composition and the pulse peak current and pulse base current condition, no pore defects were generated and the arc was stable. In particular, Nos. 1 to 27 are welding wires of a more preferable composition, pulse frequency and external characteristics, and the arc stability and low spatteriness are further improved.

On the other hand, No. 40, which is a comparative example, is in the case where the pulse peak current is excessive, the tip of the wire becomes high temperature, and the flux column does not remain. As a result, arc deflection occurred and the arc became unstable, so that spatter was increased, and bead skewing also occurred. No. 41 is a case where the pulse peak current is too small, and the arc stiffness suitable for the pulse peak period is not obtained, and is affected by the cathode point formed by Al or Ti oxide. As a result, arc deflection occurred and the arc became unstable, so that spatter was increased, and bead skewing also occurred.

No.42 was the case where the difference between the pulse peak current and the pulse base current was excessive, and the arc became unstable and the occurrence of pore defects was confirmed. No.43 shows a case where the difference between the pulse peak current and the pulse base current is small, the advantage of the pulse is small, and the increase of the spatter is confirmed.

No.44 shows a case where the pulse base current is excessive, and the arc pressure increases in the pulse base period in which the volume deviates, so that the spatter is increased.

In No. 45, the amount of C in the welding wire was excessive, and the spatter was increased. In No. 46, the amount of Si was excessive, and slag inclusion occurred. No.47 and No.48 were found to have pore defects because the amount of Si or Mn was too small to obtain a deoxidation effect. In No. 49, the amount of Mn was excessive, and slag inclusion occurred. No.50 and No.51 had excessive amounts of P and S, respectively, and cracks occurred.

In No. 52, the total content of the elements having the pulling-off effect was excessive, the spatter was increased, and the bead steaming occurred. No.53 had no additive element consisting of Al, Ti, Zr, and Mg and had an indulgence effect, so that a denitrification effect was not obtained, and pore defects occurred. In No. 54, the total content of the entangled elements was small, and the denitrification effect was not obtained, and pore defects occurred.

No. 55 is a conventional welding wire in which Al, Ti, Zr, and Mg are not added as conventional standards for the present invention, and welding is performed under a conventional welding condition (DC with a constant voltage) without using pulses. Since no Al, Ti, Zr, and Mg were added, a denitrification effect was not obtained, and pore defects were caused by welding under a high current of 550 A in average current. Further, since the welding was not performed by using a pulse, which is one of the welding methods according to the present invention, the arc was unstable because of the normal direct current welding, and the increase of the spatter and the bead shear occurred.

From the above, it can be seen that, in the case of Nos. 1 to 39 satisfying the welding method according to the present invention, it is possible to prevent pore defects in the high current welding and to have excellent arc stability, low spatter property, bead shape, Proved.

Although the present invention has been described in detail with reference to specific embodiments, it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

The present application is based on Japanese Patent Application (Japanese Patent Application No. 2015-191759) filed on September 29, 2015, the content of which is incorporated herein by reference.

Industrial availability

The present invention is useful for welding of a transport machine or a construction machine.

1: welding device
10: Robot
11: welding torch
20:
30: welding power source
W: Welded material (work, base material)

Claims (12)

A pulse arc welding method for supplying a consumable electrode by a feeder through a welding torch using a welding system including a welding power source, a welding torch and a feeder, and performing welding while flowing a shielding gas,
Wherein the consumable electrode is a flux cored welding wire filled with flux within the envelope,
Wherein the flux cored welding wire is made of a material selected from the group consisting of 0.30 mass% or less of C, 0.30 to 1.60 mass% of Si, 1.00 to 2.80 mass% of Mn, 0.050 mass% or less of P, 0.050 mass% or less of S, Zr and Mg in a total amount of 0.05 to 1.50% by mass,
The pulse peak current during welding is set to 550 to 950 A, the pulse base current is set to 550 A or less, and the difference between the pulse peak current and the pulse base current is set to 200 to 600 A
High current pulse arc welding method. The method according to claim 1,
Wherein the ratio of the total mass% of Al, Ti, Zr and Mg contained in the flux cored welding wire to the total mass% of Si and Mn satisfies a relation of 0.03? (Al + Ti + Zr + Mg) / (Si + Mn)? 0.60
High current pulse arc welding method. 3. The method according to claim 1 or 2,
Wherein the flux cored welding wire comprises at least one selected from the group consisting of Al powder, Ti powder, Zr powder, Mg powder, and alloy powder comprising at least one element selected from the group consisting of Al, Ti, Zr and Mg By mass of the powder, and 30% by mass or more of the powder is a powder having a particle size of 100 占 퐉 or less
High current pulse arc welding method. The method according to claim 1,
Wherein the flux cored welding wire comprises at least one oxide selected from the group consisting of Al oxide, Ti oxide, Zr oxide, and Mg oxide, wherein the Al oxide is reduced to Al ₂ O ₃ , the Ti oxide is reduced to TiO ₂ , (Al ₂ O ₃ + TiO ₂ + ZrO ₂ + MgO) ≦ 1.50 mass based on the total mass of the flux cored welding wire in terms of ZrO ₂ and Mg oxide converted to MgO %. &Lt; / RTI &gt;
High current pulse arc welding method. The method according to claim 1,
And the pulse frequency at the time of welding is 50 to 200 Hz.
High current pulse arc welding method. The method according to claim 1,
The ratio of the pulse frequency at the time of welding to the feeding speed for feeding the consumable electrode is 1.50 (mm / 1 pulse) ≤ [feeding speed (mm / sec) / pulse frequency (pulse frequency / sec)] 9.00 Pulse) is satisfied.
High current pulse arc welding method. The method according to claim 1,
Characterized in that the slope of the external characteristic of the welding power source is -14.0 to -4.0 (V / 100A)
High current pulse arc welding method. The method according to claim 1,
Characterized in that the shielding gas is an Ar-containing mixed gas containing Ar and impurities, or an Ar-containing gas containing 0 to 40% by volume of CO ₂ and 0 to 10% by volume of O ₂ and the balance of Ar and impurities
High current pulse arc welding method. A flux cored welding wire for high current pulse arc welding having a shell and comprising flux in said shell,
The average current during welding is over 400A,
Wherein the steel is selected from the group consisting of Al, Ti, Zr, and Mg; 0.30 to 1.60 mass% of C, 0.30 to 1.60 mass% of Si, 1.00 to 2.80 mass% of Mn, 0.050 mass% or less of P, 0.050 mass% By mass of at least one element selected from the group consisting of
Flux cored welding wire. 10. The method of claim 9,
Wherein the ratio of the total mass% of Al, Ti, Zr and Mg contained in the flux cored welding wire to the total mass% of Si and Mn satisfies a relation of 0.03? (Al + Ti + Zr + Mg) / (Si + Mn)? 0.60
Flux cored welding wire. 11. The method according to claim 9 or 10,
At least one powder selected from the group consisting of Al powder, Ti powder, Zr powder, Mg powder, and alloy powder containing at least one element selected from the group consisting of Al, Ti, Zr and Mg, Wherein at least 30% by mass of the powder is a powder having a particle size of 100 탆 or less
Flux cored welding wire. The method of claim 9, wherein
At least one oxide selected from the group consisting of Al oxide, Ti oxide, Zr oxide and Mg oxide, wherein the Al oxide is converted into Al ₂ O ₃ , the Ti oxide is converted to TiO ₂ , the Zr oxide is replaced with ZrO ₂ (Al ₂ O ₃ + TiO ₂ + ZrO ₂ + MgO)? 1.50% by mass with respect to the total mass of the flux cored welding wire, Characterized by satisfying
Flux cored welding wire.

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