Gas shielded arc welding method, gas shielded arc welding system and welding wire

Abstract

Excellent nozzle wear resistance is achieved regardless of the current range. In the gas-shielded arc welding method, the welding wire has a coating composed of Fe or Fe-based alloys, Cu or Cu-based alloys, and a solid lubricant of at least a layered crystalline structure and sulfides on the coating surface. In the feed control method, there is a step of controlling the welding current based on the tip position of the welding wire. In the step of controlling the welding current, the welding current has at least a high current range above a predetermined current value and a low current range below a predetermined current value, and the average welding current ITP during the positive wire feed is kept constant. AVE When the current is higher than the predetermined current value, and the welding wire position phase is set to 0° with reference to the position of the welding wire tip when switching from the reverse feeding period to the forward feeding period, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

Description

Technical Field

[0001] This invention relates to a gas-shielded arc welding method, a gas-shielded arc welding system, and welding wire. Background Technology

[0002] In gas shielded arc welding using a consumable electrode, current is supplied to a continuously fed consumable electrode (hereinafter referred to as welding wire) via a contact tip, melting the welding wire and performing arc welding. Because the welding wire slides within the contact tip while being energized, adhesive wear and abrasive wear are particularly pronounced. Abrasive wear is also known as scraping wear.

[0003] Such wear generally occurs on the contact tip side, where the melting point is lower than that of the welding wire and a softer raw material is used. Hereinafter, wear on this contact tip side will also be referred to as welding tip wear. Welding tip wear tends to increase with the faster the welding wire feed speed or the more drastic the fluctuations in welding current. Therefore, in recent years, a commonly used feed control method involves rapidly switching the welding wire between forward and reverse feeds. Simultaneously, the welding current also fluctuates, making welding tip wear particularly prone to occur.

[0004] Patent Document 1 discloses a technology that provides a solid arc welding wire with a copper plating layer formed on the surface of steel. The Cu content in the steel and the copper plating layer is 0.05 to 0.30% by mass in the total mass of the welding wire. 0.05 to 0.20 g of oil is applied to the surface of the welding wire per 1 kg of wire. The circumferential arithmetic mean roughness Rac of the copper plating layer is 0.25 to 1.00 μm, and the longitudinal arithmetic mean roughness Ral is 0.07 to 0.50 μm. The arc stability is excellent even under long-term continuous welding conditions.

[0005] Patent document 2 discloses a technology that prevents spatter from scattering and reduces wear on the contact tip. This technology is a welding power source comprising: a feed control mechanism that controls the feeding of the welding wire during the periodic switching between forward and reverse wire feeding; and a current control mechanism that changes the welding current based on the periodic variation in the position of the welding wire tip relative to the base material surface, thereby controlling the current so that the time from the closest point to the base material (the nearest point) to the farthest point (the farthest point) is shorter than the time from the farthest point to the closest point. The current control mechanism is a welding power source that controls the welding current during the reverse wire feeding period, setting it in a low current range lower than a predetermined current value.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-159957

[0009] Patent Document 2: Japanese Patent Application Publication No. 2022-33399 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] Patent Document 1 relates to a method for controlling the feed current of a low current of approximately 200A. Among these feed control welding methods, several types can be listed as follows: A type in which the feed speed of the welding wire is alternately switched between forward and reverse feed periods to produce a short-circuit transition during the short-circuit period and arc period, thus performing welding in a low-current region (hereinafter also referred to as the "short-circuit type feed control method"); and a type in which the feed speed of the welding wire is alternately switched between forward and reverse feed periods to suppress a coarse droplet transition that occurs during the short-circuit period, thus performing welding in a medium-current region or higher (hereinafter also referred to as the "short-circuit suppression type feed control method"). Patent Document 1 is the short-circuit type feed control method, because it involves welding in a low-current region of approximately 250A or less, and therefore does not consider the effects of adhesive wear.

[0012] On the other hand, Patent Document 2 is a short-circuit suppression type feed control method suitable for medium-current regions and above. It discloses reducing the wire feed speed, extending the current non-suppression period, and lowering the holding welding current, which is effective against nozzle wear. However, reducing the wire feed speed and ensuring the current during the current non-suppression period is kept low limits its applicability. Specifically, because increasing the wire feed speed and welding current is restricted, it cannot be expected to be effective against nozzle wear in high-current regions. Furthermore, it does not clearly state the extent of its effect on nozzle wear, nor does it consider the influence of adhesive wear caused by current fluctuations due to the setting of the current non-suppression and current suppression periods.

[0013] Therefore, the present invention addresses the aforementioned problems and aims to provide a gas-shielded arc welding method that, in a feeding control method that feeds the welding wire at a predetermined average wire feeding speed while alternately and repeatedly feeding the wire in the forward and reverse directions, achieves excellent nozzle wear resistance regardless of the current range, and provides a welding system and welding wire for this method.

[0014] Problem-solving methods

[0015] The present invention is composed of the following structure.

[0016] (1) A gas-shielded arc welding method, characterized in that it employs an alternating forward and reverse wire feeding method, and feeds the welding wire at a predetermined average wire feeding speed, wherein,

[0017] The welding wire has the following characteristics:

[0018] Fe or Fe-based alloys;

[0019] A coating formed from Cu or a Cu-based alloy;

[0020] A solid lubricant having at least a layered crystalline structure and containing sulfides on the surface of the coating.

[0021] The feeding control method includes a step of controlling at least the welding current based on the tip position of the welding wire.

[0022] In the step of at least controlling the welding current

[0023] The welding current has at least a high current range above the predetermined current value and a low current range below the predetermined current value, and the average welding current ITP during the wire feed period is... AVE For a current higher than the predetermined current value,

[0024] When the welding wire position phase is set to 0° based on the position of the welding wire tip when switching from the reverse feeding period to the forward feeding period, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

[0025] (2) A gas-shielded arc welding system, characterized in that it employs an alternating forward and reverse wire feeding method, and feeds the welding wire at a predetermined average wire feeding speed, wherein,

[0026] Equipped with the aforementioned welding wire and feeding control device,

[0027] The welding wire has the following characteristics:

[0028] Fe or Fe-based alloys;

[0029] A coating formed from Cu or a Cu-based alloy;

[0030] A solid lubricant having at least a layered crystalline structure and containing sulfides on the surface of the coating.

[0031] The control device controls at least the welding current based on the position of the welding wire's tip.

[0032] The welding current has at least a high current range above the predetermined current value and a low current range below the predetermined current value. The feeding control device controls the welding current to ensure that the average welding current ITP during the wire feeding period is... AVEFor a current higher than the predetermined current value,

[0033] When the welding wire position phase is set to 0° based on the position of the welding wire tip when switching from the reverse feeding period to the forward feeding period, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

[0034] (3) A welding wire used for alternating forward and reverse wire feeding, wherein, based on the tip position of the welding wire, the average welding current during the forward wire feeding period is controlled to be higher than a predetermined current value, and the welding wire is fed at a predetermined average wire feeding speed, wherein the method comprises:

[0035] Fe or Fe-based alloys;

[0036] A coating formed from Cu or a Cu-based alloy;

[0037] A solid lubricant having at least a layered crystal structure and containing sulfides on the surface of the coating.

[0038] The effects of the invention

[0039] According to the present invention, in the feeding control method of feeding welding wire at a predetermined average wire feeding speed while alternately and repeatedly feeding forward and reverse wire, excellent welding nozzle wear resistance can be obtained regardless of the current range. Attached Figure Description

[0040] Figure 1 This is a conceptual diagram illustrating welding nozzle wear.

[0041] Figure 2 This is a conceptual diagram illustrating the structure of the welding wire in this embodiment.

[0042] Figure 3 This is an explanatory diagram regarding the timing of setting the low current range.

[0043] Figure 4 This is a diagram showing the wear condition of the contact tip when testing by changing the phase of the current.

[0044] Figure 5 This is a schematic diagram showing a structural example of the welding system of this embodiment.

[0045] Figure 6 This is a block diagram illustrating the schematic structure related to the control of the welding power source, welding control device, and servo amplifier in this embodiment.

[0046] Figure 7 This is a graph illustrating the relationship between the wire feeding speed, the wire tip position, and the current detection signal in this embodiment.

[0047] Figure 8 This is a diagram showing the composition of the welding wire in this embodiment.

[0048] Figure 9 This is a diagram illustrating the conditions for sending to control in this embodiment.

[0049] Figure 10 This is a graph showing the results of the evaluation test in this embodiment.

[0050] Figure 11 This is a graph showing the relationship between the amount of solid lubricant, the square of the current during wire feeding, and the amount of wear. Detailed Implementation

[0051] Figure 1 This is a conceptual diagram illustrating welding nozzle wear.

[0052] The contact tip used in gas-shielded arc welding is used with the welding wire passing through the hollow contact tip. Welding is performed while the welding wire is being fed, but as shown in the figure, the contact tip wears down because the welding wire is in contact with and energized on the side of the contact tip.

[0053] The main wear patterns affecting welding nozzle wear are adhesive wear and abrasive wear. Adhesive wear occurs when material adheres to the sliding contact surface, causing the weaker bond to peel off and adhere to the other surface. Abrasive wear occurs when the harder material on the sliding contact surface mechanically scrapes away the mating material. If hard particles are trapped between the contact surfaces, these particles will scrape against both surfaces, resulting in wear.

[0054] The main cause of welding tip wear is that, when current flows between an Fe-based welding wire and a Cu-based contact tip, the resistance heat and frictional heat generated by the sliding of the welding wire cause the Cu-based material of the contact tip, which has a lower melting point, to soften or melt. The softened or molten Cu adheres to the surface of the welding wire side and is expelled from the contact tip. Especially in pulse welding, where the current fluctuates periodically, the Cu-based material of the contact tip repeatedly melts and solidifies. During solidification, it firmly bonds to the welding wire side, while the Cu on the contact tip side solidifies and is pulled off by the welding wire side, resulting in significant tip wear. Therefore, suppressing adhesive wear during wire feeding becomes a key challenge.

[0055] In this invention, the following two points are addressed: First, to prevent the interface state on the contact tip side from changing during the forward feeding of the welding wire; second, to suppress the adhesion of Cu from the contact tip to the contact surface on the welding wire side even if the contact tip softens or melts. The solution to the problem is derived from the viewpoint of timing of feeding and current control in the welding wire and feeding control method. The technical features regarding the timing of feeding and current control in the welding wire and feeding control method will be explained below.

[0056] [Characteristics of welding wire]

[0057] Figure 2 This is a conceptual diagram illustrating the structure of the welding wire according to this embodiment. The welding wire is made of Fe or an Fe-based alloy (hereafter referred to as Fe-based metals). A Cu or Cu-based alloy is plated onto the surface of the welding wire, and a layered crystalline solid lubricant of sulfide is applied to the surface of this plating. Examples of layered crystalline solid lubricants of sulfide include molybdenum disulfide (MoS2) and tungsten disulfide (WS2). Fe-based alloys include, for example, mild steel and stainless steel, while Cu-based alloys include materials commonly used in electrodes, such as chromium copper, chromium zirconium copper, or beryllium copper.

[0058] [Characteristics of current control in the control method]

[0059] Furthermore, in the feeding control method, the welding current is set to at least a high current range higher than the predetermined current value and a low current range lower than the predetermined current value. The welding current is controlled by switching between at least the high current range and the low current range based on the tip position of the welding wire, and the average welding current ITP of the welding wire during the forward wire feeding period is kept constant. AVE This is done by setting or controlling a current higher than a predetermined current value. Furthermore, the predetermined current value is, for example, the average welding current I. AVE That's it. In addition, when the welding wire position phase is set to 0° based on the tip position of the welding wire when switching from the reverse feeding period to the forward feeding period, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

[0060] Based on the characteristics of the welding wire and the feeding control method described above, it is presumed that the following phenomena (a) to (c) will occur at the contact surface (hereinafter referred to as "contact surface") between the welding wire and the contact tip during the wire feeding period.

[0061] (a) During the positive wire feed of the welding wire, an average welding current I is applied. AVEThe current is above that. At this point, the Fe-based metal side of the high-resistance welding wire reaches a high temperature due to resistance heat, and the Fe-based metal of the welding wire and the Cu-based metal of the coating melt.

[0062] (b) The Fe in the molten welding wire, the Cu in the coating, and the S in the sulfide react to form FeS or Cu2S. FeS has a melting point of 1190℃, and Cu2S has a melting point of 1130℃; both are highly conductive materials. During the wire feeding period, due to the applied average welding current I... AVE The current is so high that FeS and Cu2S melt and come into contact with the solid part (non-molten Fe-based metal) of the sliding welding wire.

[0063] (c) The interface between the solid portion of the welding wire and the molten portions of FeS and Cu2S has poor wettability, making it difficult for the molten portions of FeS and Cu2S to adhere to the solid portion side of the sliding welding wire. That is, the molten portions of FeS and Cu2S are not discharged from the nozzle during forward wire feeding. Here, FeS and Cu2S act as a liquid lubricating film during forward wire feeding, suppressing adhesive wear. Furthermore, the liquid lubricating film stabilizes the conductive surface, thus also contributing to arc stability. However, when sulfides are absent on the coating surface, an excellent liquid lubricating film is not formed; therefore, during forward wire feeding, the Fe of the molten welding wire and the Cu of the contact tip adhere to the solid portion of the sliding welding wire, resulting in adhesive wear that causes it to be discharged from the contact tip.

[0064] [When to set the low current range]

[0065] Figure 3 This diagram illustrates the timing of setting a low-current range. In short-circuit suppression type feed control methods, a low-current range is required due to the nature of the control. In the present invention, in the case of short-circuit suppression type feed control methods, it is preferable to set the low-current range during the reverse wire feeding period, and more preferably, the average welding current during the reverse wire feeding period is the average welding current I. AVE the following.

[0066] By setting a low current range during wire feeding, molten Fe, Cu, and their reaction-generated FeS and Cu₂S solidify and transfer to the contact tip side. As mentioned earlier, due to wettability, FeS and Cu₂S are difficult to adhere to the welding wire side; therefore, these solidified substances have a strong bond with the Cu-based metal of the contact tip and transfer to the contact tip side. This is based on reference... Figure 4The observation of the contact surface on the contact tip side after welding, as described later, is also clear. Therefore, in the low current range, abrasive wear (mechanical wear) between the solid portion of the welding wire and the solidified adhesion portion on the contact tip side is dominant. The soft adhesion layer on the contact tip side, with a melting point lower than that of the solid portion of the welding wire, is pushed deep into the contact tip by the sliding of the welding wire. At this time, if the timing of switching from the low current range to the high current range is appropriate, it will remelt during the next forward wire feed, thus not affecting the wear of the contact tip. Specifically, the following timing is required: when the phase of the welding wire position, based on the tip position of the welding wire during the switch from the reverse feed period to the forward feed period, is set to 0°, and the phase of the welding wire position during the switch from the low current range to the high current range is in the range of 280° to 350°. If this timing is missed, abrasive wear will cause wear on the contact tip.

[0067] Figure 4 This is a diagram showing the wear condition of the contact tip when testing by changing the phase of the current.

[0068] Figure 4 (a) shows the contact surface of the contact tip after welding under standard conditions, with the phase condition of setting a peak current during the forward wire feed and a low current range during the reverse wire feed. Under standard conditions, almost no trace of contact between the contact tip and the welding wire is visible on the contact surface of the contact tip.

[0069] Figure 4 (b) shows the contact surface of the contact tip after welding, with the current phase led by 200 degrees from the standard condition, thereby setting a low current range during forward wire feed and a peak current during reverse wire feed. Abrasive wear is visible on the contact surface of the contact tip under the phase condition of leading the current phase by 200 degrees.

[0070] [Ratio of forward feed period to reverse feed period]

[0071] In this embodiment, the ratio of the forward feed period to the reverse feed period within one cycle is preferably 1:1 or a reduced ratio during the forward feed period. This is to shorten the period that promotes wear and to ensure the stable formation of the liquid lubricating film, hence the use of a high current. That is, the smaller the ratio of 1:1 or the forward feed period, the greater the tendency for improved wear resistance of the welding nozzle.

[0072] The following describes a specific implementation of a welding wire and a feeding control system that can achieve better results in terms of welding nozzle wear resistance. This is just one example; it is not limited to this one as long as the above-described technical features are met.

[0073] [Surface properties of welding wire]

[0074] (Coating of welding wire)

[0075] During wire feeding, in order to generate a stable liquid lubricating film, the welding wire needs to have a coating of Cu or a Cu-based alloy. As mentioned above, the welding wire has the greatest resistance heat, which is generated by Fe or Fe-based alloys. Therefore, the molten Cu required to generate the liquid lubricating film needs to be ensured by the coating. Furthermore, as will be discussed later, wear resistance cannot be achieved with welding wires that do not use a coating, suggesting that the amount of molten Cu used to generate the liquid lubricating film is insufficient. In this invention, the composition, thickness, and amount of Cu in the coating are not particularly limited, as long as they are within the commonly used range. However, in order to generate a stable liquid lubricating film, it is preferable that the amount of Cu in the coating is 0.05 to 0.30% of the total mass of the welding wire.

[0076] (sulfides)

[0077] The sulfide can be applied by adhering it to the coating surface, preferably by uniformly adhering it to the coating surface without deviation. Furthermore, as a solid lubricant with a layered crystalline structure, the sulfide acts as a solid lubricant to stabilize the delivery before reaching the contact tip. At the contact surface inside the contact tip, it functions to generate a liquid lubricating film, suppressing adhesive wear. Examples of solid lubricants that perform this function include molybdenum disulfide (MoS2) and tungsten disulfide (WS2). While molybdenum disulfide and tungsten disulfide are stable at room temperature, FeS and Cu2S are stable at temperatures above 1000°C. Therefore, in this invention, it is preferable to include either molybdenum disulfide or tungsten disulfide.

[0078] Furthermore, in order to generate a liquid lubricating film, the amount of sulfide applied is preferably 0.05g or more and 0.40g or less per 10kg of welding wire, more preferably 0.10g or more and 0.30g or less. Additionally, the sulfide is applied to the coating surface of the welding wire in a state of being mixed with lubricating oil; by adjusting the mixing ratio, the amount of adhesion can be controlled.

[0079] (lubricating oil)

[0080] In this invention, the type and amount of lubricating oil are not particularly limited. For example, animal oils and vegetable oils, or mixtures thereof (hereinafter collectively referred to as animal and vegetable oils), or mineral oils and synthetic oils (hereinafter collectively referred to as non-mineral oils) may be used as lubricating oils. Specifically, examples of animal and vegetable oils include palm oil, rapeseed oil, castor oil, lard, and tallow; examples of mineral oils include petroleum refineries containing paraffinic hydrocarbons and cycloalkane hydrocarbons, which are commonly used as lubricating oils. Regarding the amount of lubricating oil, it is acceptable as long as a stable supply is maintained without forming an oil pool in the feed nozzle; for example, 0.4g to 2.0g per 10kg of welding wire is acceptable.

[0081] (Surface solid material)

[0082] The solid substances present on the surface of the copper plating are copper powder that has peeled off or re-adhered during the manufacturing process. Additionally, they include lubricants used during wire drawing. Specifically, for example, they are copper powder, calcium or sodium-based metal soaps, etc. While this invention does not impose particular limitations, excessive adhesion can lead to buildup inside the wire guide tube or feed nozzle, potentially causing feed interruption. Therefore, the total amount of solid substances present on the surface of the welding wire is preferably controlled to be below 500 mg per 10 kg of welding wire.

[0083] [Composition of welding wire]

[0084] In this invention, as described above, the welding wire can be composed of Fe or an Fe alloy. For example, it conforms to JIS Z3312:2009 (MAG and MIG welding solid wires for mild steel, high-tensile steel, and low-temperature steel), JIS Z 3313:2009 (Arc welding flux-cored wires for mild steel, high-tensile steel, and low-temperature steel), JIS Z 3315:2012 (MAG and MIG welding solid wires for weathering steel), JIS Z 3317:2011 (Gas-shielded arc welding deposit rods and solid wires for molybdenum steel and chromium-molybdenum steel), JIS Z 3320:2012 (Arc welding flux-cored wires for weathering steel), JIS Z 3321:2013 (Welding stainless steel deposit rods, solid wires, and steel strips), JIS Z The composition is as specified in JIS standard 3323:2007 (Fluid-cored welding wires and welding rods for stainless steel arc welding). Specifically, mild steel, high-tensile steel, low-temperature steel, molybdenum steel, chromium-molybdenum steel, or stainless steel are preferred as the steel type. In particular, regarding the feed control method, a composition based on or approximate to JIS standard Z 3312:2009 with a higher Fe content is more preferred for nozzle wear resistance. Specifically, the wire composition described below is acceptable.

[0085] The reasons for adding and limiting the alloy composition of the welding wire according to this embodiment will be explained in detail below. In the following description, the content of each element in the welding wire is defined as the content of the element contained as an alloy component relative to the total mass of the welding wire. Furthermore, the welding wire can be a solid wire composed of alloying elements, or a flux-cored wire whose flux is formed only of metal powder (hereinafter also referred to as a metal-based flux-cored wire). It can also be a flux-cored wire whose flux contains a small amount of compounds (mainly oxides, fluorides, etc.) (hereinafter also referred to as a slag-based flux-cored wire). However, from a manufacturing viewpoint that it is easier to apply a Cu-based coating to the surface of the welding wire, a solid wire is more preferred.

[0086] Furthermore, in metal-cored or slag-cored welding wires, the alloying elements described below, unless otherwise specified, are contained in the welding wire in either metallic or compound form. Alternatively, they may be contained in both metallic and compound forms. Therefore, the form in which each element is contained in the welding wire is specified by its conversion value to its elemental form. For example, taking Si as an example, the Si content represents the sum of the conversion values ​​of metallic Si and Si compounds. Metallic Si includes elemental Si and Si alloys.

[0087] (Fe: 90% by mass or more)

[0088] In this invention, Fe in the welding wire is required to generate a liquid lubricating film during wire feeding. To obtain more stable nozzle wear resistance, an Fe content of 90% by mass or more is preferred, and more preferably 95% by mass or more. On the other hand, while the welding wire can be made of pure iron to achieve the nozzle wear resistance effect of this invention, from the viewpoint of welding workability and the mechanical properties of the weld metal, an Fe content of 99% by mass or less is preferred, and the presence of the elements described below is even more desirable.

[0089] (C: less than 0.15% by mass (including 0% by mass))

[0090] Carbon (C) has a deoxidizing effect, and the presence of C in the welding wire can improve the mechanical properties of the weld metal. The C content can be adjusted appropriately according to the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire may not contain C, and can be 0% by mass.

[0091] However, if the welding wire contains excessive carbon, the deoxidation effect becomes greater, and CO may be generated near the arc, potentially causing spatter due to explosion or increasing the amount of smoke and dust. Therefore, from the viewpoint of weldability, the carbon content in the welding wire, relative to the total mass of the welding wire, is preferably 0.15% by mass or less, more preferably 0.10% by mass or less, and even more preferably 0.08% by mass or less.

[0092] (Si: less than 1.10% by mass (including 0% by mass))

[0093] Si is a deoxidizer. If the welding wire contains Si, the mechanical properties of the weld metal can be improved. The Si content can be adjusted appropriately according to the required strength. However, in this embodiment, if the strength can be ensured by other elements, the welding wire may not contain Si and may contain 0% by mass. Furthermore, in order to achieve the above-mentioned effect, it is preferable to make the Si content 0.20% by mass or more.

[0094] On the other hand, if the Si content in the welding wire is excessive, deoxidation will occur, reducing the oxygen content in the molten pool. Consequently, the surface tension of the molten droplets will increase, and the weld bead shape will be damaged. Therefore, the Si content in the welding wire, relative to the total mass of the welding wire, can be 1.10% by mass or less, preferably 1.00% by mass or less.

[0095] (Mn: less than 2.30% by mass (including 0% by mass))

[0096] Like Si, manganese (Mn) is a deoxidizer. The presence of Mn in the welding wire improves the mechanical properties of the weld metal. The Mn content can be adjusted appropriately according to the required strength. However, in this embodiment, if strength can be ensured by other elements, the welding wire may be free of Mn, even at 0% by mass. Nevertheless, Mn is suitable for improving mechanical properties, and its presence is preferred. To achieve the above effects, it is preferable that the Mn content be 0.90% by mass or more.

[0097] On the other hand, if the Mn content in the welding wire is excessive, deoxidation will occur, reducing the oxygen content in the molten pool, increasing the surface tension of the molten droplets, and damaging the weld bead shape. Therefore, the Mn content in the welding wire, relative to the total mass of the welding wire, can be 2.30% by mass or less, preferably 2.20% by mass or less.

[0098] (Ti: less than 0.30% by mass (including 0% by mass))

[0099] Ti is a strong deoxidizing, denitrifying, and desulfurizing element, and it preferentially forms compounds under these effects. These compounds precipitate within the weld metal structure, thereby improving the mechanical properties of the weld metal. The Ti content can be adjusted appropriately according to the required strength. However, in this embodiment, if strength can be ensured by other elements, the welding wire may be Ti-free, and can be 0% by mass. Furthermore, to achieve the above effects, it is preferable to have a Ti content of 0.02% by mass or more.

[0100] On the other hand, if Ti is excessively contained in the welding wire, the inclusions in the weld metal become coarser, and there is a particular risk of reduced toughness. Therefore, the Ti content in the welding wire is preferably suppressed to 0.30% by mass or less, and more preferably 0.25% by mass or less, relative to the total mass of the welding wire.

[0101] (Al: less than 0.30% by mass (including 0% by mass))

[0102] Like Ti, Al is a strong deoxidizing, denitrifying, and desulfurizing element, preferentially forming compounds under these effects. These compounds precipitate within the weld metal structure, thereby improving the mechanical properties of the weld metal. The Al content can be adjusted appropriately according to the required strength; however, in this embodiment, if strength can be ensured by other elements, the welding wire may be free of Al, and can be 0% by mass. Furthermore, to achieve the above effects, it is preferable to have an Al content of 0.02% by mass or more.

[0103] On the other hand, if Al is excessively present in the welding wire, the inclusions in the weld metal become coarser, which in particular poses a risk of reduced toughness. Therefore, the Al content in the welding wire is preferably suppressed to 0.30% by mass or less, and more preferably 0.25% by mass or less, relative to the total mass of the welding wire.

[0104] (Zr: less than 0.30% by mass (including 0% by mass))

[0105] Like Al and Ti, Zr is a strong deoxidizing, denitrifying, and desulfurizing element. It preferentially forms compounds under these effects, which precipitate within the weld metal microstructure, thereby improving the mechanical properties of the weld metal. The Zr content can be adjusted appropriately according to the required strength. However, in this embodiment, if strength can be ensured by other elements, the welding wire may be Zr-free, and can be 0% by mass. Furthermore, to achieve the aforementioned effects, it is preferable to have a Zr content of 0.02% by mass or more.

[0106] On the other hand, if Zr is excessively present in the welding wire, the inclusions in the weld metal will become coarser, and in particular, there is a risk of reduced toughness. Therefore, the Zr content in the welding wire, relative to the total mass of the welding wire, is preferably suppressed to 0.30% by mass or less, more preferably 0.25% by mass or less.

[0107] (Mg: less than 0.30% by mass (including 0% by mass))

[0108] Like Zr, Al, and Ti, Mg is a strong deoxidizing, denitrifying, and desulfurizing element. It preferentially forms compounds under these effects, which precipitate within the weld metal structure, thereby improving the mechanical properties of the weld metal. The Mg content can be adjusted appropriately according to the required strength; however, in this embodiment, if strength can be ensured by other elements, the welding wire may be Mg-free, and can be 0% by mass. Furthermore, to achieve the aforementioned effects, it is preferable to have a Mg content of 0.02% by mass or more.

[0109] On the other hand, if Mg is excessively present in the welding wire, the inclusions in the weld metal will become coarser, and there is a particular risk of reduced toughness. Therefore, the Mg content in the welding wire is preferably suppressed to 0.30% by mass or less, and more preferably 0.25% by mass or less, relative to the total mass of the welding wire.

[0110] (Ni: less than 4.75% by mass (including 0% by mass))

[0111] If the welding wire contains Ni, the mechanical properties of the weld metal can be improved. The Ni content can be adjusted appropriately according to the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire may not contain Ni, and can be 0% by mass. Furthermore, when using the welding wire of this embodiment, the Ni content relative to the total mass of the welding wire is preferably 4.75% by mass or less. By suppressing the Ni content in the above manner, a balance can be maintained with other mechanical property-improving elements, and excessive strength of the weld metal can be prevented.

[0112] (Cr: less than 0.60% by mass (including 0% by mass))

[0113] If the welding wire contains Cr, the mechanical properties of the weld metal can be improved. The Cr content can be adjusted appropriately according to the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire may be Cr-free, and can be 0% by mass. Furthermore, the Cr content relative to the total mass of the welding wire is preferably 0.60% by mass or less. By suppressing the Cr content in the above manner, a balance can be maintained with other mechanical property-enhancing elements, and excessive strength of the weld metal can be prevented.

[0114] (Mo: less than 0.90% by mass (including 0% by mass))

[0115] If the welding wire contains Mo, the mechanical properties of the weld metal can be improved. The Mo content can be adjusted appropriately according to the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire may not contain Mo, and can be 0% by mass. The Mo content relative to the total mass of the welding wire is preferably 0.90% by mass or less. By suppressing the Mo content in the above manner, a balance can be maintained with other mechanical property-improving elements, and excessive strength of the weld metal can be prevented.

[0116] (Cu (excluding the coating Cu): less than 0.50% by mass (including 0% by mass))

[0117] If the welding wire contains Cu, the mechanical properties of the weld metal can be improved. The Cu content can be adjusted appropriately according to the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire may not contain Cu, and can be 0% by mass. The Cu content in the welding wire relative to the total mass of the welding wire is preferably 0.50% by mass or less. By suppressing the Cu content in the above manner, a balance can be maintained with other mechanical property-improving elements, and excessive strength of the weld metal can be prevented.

[0118] (Nb: less than 0.50% by mass (including 0% by mass))

[0119] (V: less than 0.50% by mass (including 0% by mass))

[0120] If the welding wire contains Nb and V, the mechanical properties of the weld metal can be improved. The content of Nb and V can be adjusted appropriately according to the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire may also be free of Nb and V, and can be 0% by mass. The Nb content and V content in the welding wire are preferably 0.50% by mass or less, respectively, relative to the total mass of the welding wire. By suppressing the Nb and V content in the above manner, a balance can be maintained with other mechanical property-improving elements, and excessive strength of the weld metal can be prevented.

[0121] (B: less than 0.0050% by mass (including 0% by mass))

[0122] If the welding wire contains boron (B), the mechanical properties of the weld metal can be improved. The content of boron can be adjusted appropriately according to the required strength. However, in this embodiment, if the strength can be ensured by other elements, the welding wire may not contain boron and can be 0% by mass. The content of boron relative to the total mass of the welding wire is preferably 0.0050% by mass or less. By suppressing the boron content in the above manner, a balance can be maintained with other mechanical property-enhancing elements, and excessive strength of the weld metal can be prevented.

[0123] (P: less than 0.050% by mass (including 0% by mass))

[0124] (S: less than 0.050% by mass (including 0% by mass))

[0125] P and S are elements that affect the crackability of weld metal. The lower the P and S content in the welding wire, the better the crack resistance of the weld metal. Therefore, the welding wire in this embodiment may also be free of P and S, and can be 0% by mass. Furthermore, when the welding wire contains P and S, from the viewpoint of crack resistance, the P and S content in the welding wire relative to the total mass of the welding wire is preferably 0.050% by mass or less.

[0126] (Balance: unavoidable impurities)

[0127] In this embodiment, the balance of alloying elements in the welding wire preferably consists of unavoidable impurities. Examples of unavoidable impurities include O, N, Li, Bi, and As. The content of each of these unavoidable impurities is preferably 0.0100% by mass or less, more preferably 0.0050% by mass or less, relative to the total mass of the welding wire. Furthermore, the total content of these unavoidable impurities is preferably 0.0200% by mass or less, relative to the total mass of the welding wire.

[0128] (Welding wire diameter)

[0129] In the welding wire of this embodiment, there is no particular limitation on the diameter of the welding wire, but welding wires with diameters specified by welding material standards such as AWS or JIS can be used.

[0130] (Manufacturing of welding wire)

[0131] In this embodiment of the welding wire, the manufacturing method is not particularly limited and does not require special manufacturing conditions; it can be manufactured using conventional methods. For example, in the case of a solid welding wire, steel containing the aforementioned alloying elements at a specified content is melted to obtain an ingot. Next, the ingot is subjected to hot forging, hot rolling, and then cold drawing to form a wire blank. Subsequently, the obtained wire blank is annealed at a temperature of approximately 500–900°C, pickled, copper-plated, and then finely drawn to the desired wire diameter. Afterward, a lubricant is applied as needed to manufacture the welding wire.

[0132] (Sent to the control method)

[0133] Next, the conditions for sending the data to the control method in this embodiment will be described in detail below.

[0134] [Welding System]

[0135] Next, based on the accompanying drawings, a specific embodiment of the system used to implement the feed control method of this application will be described. Furthermore, this embodiment is an example using a welding robot, and the welding control method of the present invention is not limited to the configuration of this embodiment. For example, an automatic welding device using a trolley may be used instead of the welding robot body, or a small, mobile welding robot may be applied. In this embodiment, the effect of suppressing nozzle wear will be explained using a system configuration of a short-circuit suppression type feed control method where nozzle wear is particularly significant as an example.

[0136] Furthermore, in this embodiment, it is also useful for additive manufacturing technologies that utilize the gas-shielded arc welding method of this application, specifically in wire and arc additive manufacturing (WAAM). Also, while the term "additive manufacturing" is sometimes used broadly in the context of slab modeling or rapid prototyping, it is used uniformly throughout this invention. When applying the method of this invention to additive manufacturing technology, "welding" is referred to as "deposition," "additive manufacturing," or "slab modeling," etc. For example, "welding conditions" may be used as a welding process, but when using this invention for additive manufacturing, it can be referred to as "deposition conditions," or "welding system" may be used as a welding process, but when using this invention for additive manufacturing, it can be referred to as "additive manufacturing system."

[0137] Figure 5 This is a schematic diagram showing a structural example of the welding system 50 according to this embodiment. The welding system 50 includes a welding robot 110, a welding control device 120, a welding power source 140, a controller 150, a servo amplifier 160, a servo motor 170, a wire pusher motor 180, and a welding wire buffer 190. The wire pusher motor 180 feeds the welding wire 100.

[0138] Welding power source 140 is connected to welding robot 110 via a positive power cable (not shown) to energize welding wire 100, and to workpiece (hereinafter referred to as "base material") 200 via a negative power cable (not shown). This connection is for welding with reverse polarity (DC reverse polarity). For welding with positive polarity (DC positive polarity), the polarity of welding power source 140 is simply reversed.

[0139] Furthermore, the welding power supply 140 and the wire feed motor 180 are connected by a signal line, enabling control of the wire feeding speed. In the feeding control of this embodiment, the wire feed motor 180 only performs forward rotation, while the servo motor 170, described later, can switch between forward and reverse rotation.

[0140] The welding robot 110, as an end effector, includes a welding torch 111. The welding torch 111 has an energizing mechanism, i.e., a contact tip, for energizing the welding wire 100. The gas-shielded arc welding method, gas-shielded arc welding system, and welding wire involved in this application provide excellent wear resistance for this contact tip. The welding wire 100 generates an arc from its tip by energizing the contact tip, and uses the heat to weld the workpiece 200, which is the object of welding.

[0141] In addition, the welding torch 111 is equipped with a protective gas nozzle, which is a mechanism for ejecting the protective gas. The protective gas is not particularly limited, but for the control characteristics used in this embodiment, a gas composition that achieves a coarse droplet transition state is more preferred. Specifically, it is preferable to include at least one of carbon dioxide, nitrogen, hydrogen, and oxygen, which have a high potential gradient. Furthermore, from a general viewpoint, if it is a mixture with argon (hereinafter also referred to as "Ar"), a system containing at least 10% by volume of carbon dioxide is more preferred, a system containing at least 90% by volume of carbon dioxide is even more preferred, and elemental carbon dioxide is even more preferred. The protective gas is supplied by a protective gas supply device (not shown).

[0142] A servo motor 170 is located near the welding torch 111. A servo amplifier 160 connected to the servo motor 170 controls the servo motor 170. In this embodiment, the welding torch 111 is structured independently of the servo motor 170, but it could also be a welding torch with a structure in which the servo motor 170 is integrated within the welding torch 111. The servo motor 170 switches between forward and reverse directions based on forward and reverse wire feed commands for wire feeding control. Furthermore, the servo amplifier 160 can perform high-speed computation processing and, as described later, includes a forward and reverse wire feed command generation unit 161.

[0143] A wire feeder 190 is disposed between the wire feeder motor 180 and the servo motor 170. The wire feeder motor 180 feeds the wire only in the forward direction, while the servo motor 170 feeds the wire in both the forward and reverse directions. Therefore, the feeding directions of the wire feeder motor 180 and the servo motor 170 may sometimes differ. This results in the wire being easily subjected to a large load within its feeding path. To ensure proper feeding control even under such conditions, the wire feeder 190 is provided to suppress wire buckling, etc.

[0144] Furthermore, in this embodiment, the specific structure of the workpiece 200 is not particularly limited, nor are the welding conditions such as joint shape, welding posture, and bevel shape. The welding control device 120 primarily controls the movements of the welding robot 110. Therefore, the welding control device 120 can also be referred to as a robot controller. The welding control device 120 pre-stores teaching data that determines the welding robot 110's movement mode, welding start position, welding end position, welding conditions, and electrode manipulation, and uses this data as instructions to control the movements of the welding robot 110. Additionally, following the teaching data, the welding control device 120 provides welding conditions such as welding current, welding voltage, and feed rate to the welding power source 140 during the welding operation.

[0145] Also, such as Figure 5As shown, the welding system 50 of the embodiment has a structure in which the welding control device 120 is independent of the welding power source 140, but it can also have a structure in which the welding control device 120 is included in the welding power source 140.

[0146] The controller 150 is connected to the welding control device 120 and is used for writing and displaying programs for operating the welding robot 110, as well as inputting teach data. Information input by the user into the controller 150 is provided to the welding control device 120. Additionally, the controller 150 has the function of manually operating the welding robot 110. The connection between the controller 150 and the welding control device 120 is not particularly limited to wired or wireless methods.

[0147] The welding power source 140 supplies power to the welding wire 100 and the workpiece 200 according to instructions from the welding control device 120, thereby generating an electric arc between the welding wire 100 and the workpiece 200. In addition, the welding power source 140 outputs control signals to the wire pusher motor 180 according to instructions from the welding control device 120.

[0148] Next, refer to Figure 6 and Figure 7 The functional configuration of the welding system 50 in this embodiment is described in detail below. Figure 6 This is a block diagram illustrating the schematic structure related to the control of the welding power source 140, welding control device 120, and servo amplifier 160 in this embodiment. In this invention, a device or group of devices having power supply control-related functions is referred to as a power supply control device. In this embodiment, the structure of the welding power source 140, welding control device 120, and servo amplifier 160 related to power supply control is used as the power supply control device. Figure 7 This is a graph illustrating the relationship between the wire feed speed, the wire tip position, and the current detection signal in this embodiment.

[0149] The welding power source 140 and the welding control device 120 are connected via digital communication, and the welding control device 120 and the servo amplifier 160 are also connected via digital communication. That is, they are connected in a linear fashion in the order of servo amplifier 160, welding control device 120, and welding power source 140, which can be understood as the servo amplifier 160 and welding power source 140 being indirectly connected via digital communication. Alternatively, they can be connected in a linear fashion in the order of servo amplifier 160, welding power source 140, and welding control device 120. This can be understood as the servo amplifier 160 and welding power source 140 being directly connected via digital communication.

[0150] Furthermore, in this embodiment, the welding power source 140 and the welding control device 120 communicate via CAN (Controller Area Network), an industrial field network, and the welding control device 120 and the servo amplifier 160 communicate via EtherCAT (Ethernet for Control Automation Technology), an industrial field network, but are not limited thereto.

[0151] (Functional configuration of welding power source)

[0152] The control system unit 141 of the welding power source 140 is operated, for example, by executing a program via the welding control device 120 or a computer (not shown). The control system unit 141 of the welding power source 140 includes a current setting unit 36. In this embodiment, the current setting unit 36 ​​has the function of setting various current values ​​for the welding current flowing on the welding wire 100. The current setting unit 36 ​​has the function of setting the start and end times of each period of current control. The current setting unit 36 ​​includes a target current setting unit 36A, a wire tip position conversion unit 36B, and a voltage setting unit 36C. The target current setting unit 36A has the function of setting the start and end times of each period for the peak period Dap, the falling period Ddwn, the base period Db, and the rising period Dup of the current control. The wire tip position conversion unit 36B has the function of obtaining information about the tip position of the welding wire 100.

[0153] Furthermore, various conditions can be set, for example, based on pre-entered settings by the operator, pre-prepared waveform control tables, and welding condition databases. These settings, tables, and databases can be stored in any component of the welding system 50. For example, they can be stored in the welding control device 120 or the welding power source 140.

[0154] Furthermore, the various condition settings for each period of the peak period Dap, falling period Ddwn, base period Db, and rising period Dup involved in the high current range TIP (the sum of Dup and Dap periods in this embodiment) and the low current range TIB (the sum of Ddwn and Db periods in this embodiment) can be determined by the waveform control table linear operation unit 37 based on a pre-prepared waveform control table. Also, the various condition settings mentioned here in this embodiment refer to the settings of current value, time, or phase, etc.

[0155] The welding current is represented by a pulse waveform of welding current alternating between the high current range TIP and the low current range TIB, based on the phase of the welding wire tip position (hereinafter referred to as "welding wire position phase" or "position phase"). Furthermore, in this embodiment, the timing of the peak period Dap, the falling period Ddwn, the base period Db, and the rising period Dup are controlled based on the welding wire position phase of 0 to 360° (0 to 2π), where 0° is taken as the position of the welding wire tip closest to the nozzle and 180° is taken as the position closest to the base material. Additionally, the aforementioned welding wire position phase can also be represented as 0°, based on the welding wire tip position when switching from the reverse feed period to the forward feed period.

[0156] Based on the average feed rate Favg setpoint stored in the welding condition information in the control system unit 141, the set current value Iap (hereinafter also referred to as "peak current Iap") for the peak period Dap of the high current range TIP and the set current value Ib (hereinafter also referred to as "base current Ib") for the base period Db of the low current range TIB, calculated by the waveform control table linear calculation unit 37, are set in the current setting unit 36. In this invention, by pre-setting at least the set current value Iap and the wire position phases at the beginning and end of the high current range (described later) to optimal values, welding current control with good nozzle wear resistance can be achieved, thereby achieving an average welding current ITP during the positive wire feed period. AVE The value is higher than the predetermined current value (in this embodiment, the average welding current I). AVE The current of 。

[0157] In this embodiment, the welding current is basically controlled by two values: the peak current Iap and the base current Ib. Therefore, the start time of the low current range TIB can also be represented as the time of transition to the base current Ib, i.e., the start time of the falling period Ddwn, as the low current start time. Similarly, the end time of the low current range TIB can also be represented as the end time of the base current Ib, i.e., the low current end time. The periods of the falling period Ddwn and the base period Db involved in the start and end times of the low current range TIB are calculated in the waveform control table linear operation unit 37. The start time of the high current range TIP, i.e., the start time of the rising period Dup, can also be represented as the high current start time, and the end time of the high current range TIP can also be represented as the high current end time.

[0158] Also, such as Figure 7As shown, the timing of the high current end time is determined by the set period d1 when the welding wire position phase is 0°, and the timing of the high current start time is determined by the set period d2 when the high current end time is used as the start time. This set period can be set by phase. For example, if d1 is set to 190° and d2 is set to 120°, the high current interval ends at the welding wire position phase of 190° (d1), and begins at the welding wire position phase of 310° (d1 + d2). Alternatively, the setting method is as described above, using d1 and d2, but it can also be set by the value of d1 and the value of d1 + d2. In this embodiment, it is preferable to set d1 within the range of 100° to 200°, and preferably to set d2 such that d1 + d2 (the welding wire position phase at the start of the high current interval) is within the range of 280° to 350°. For example, if d1 is set to 180°, and d1 + d2 is desired to be 340°, then d2 can be set to 160°. As mentioned above, by setting d1 and d2, good wear resistance of the welding nozzle can be obtained.

[0159] Furthermore, the peak current Iap is preferably set within the range of 300–650 A. Alternatively, the peak current Iap can be set in stages to increase the current in the latter half of the high-current TIP range. By selecting at least one value from the range of 300–650 A and setting the peak current Iap accordingly, a stable liquid lubricating film can be generated, resulting in good nozzle wear resistance.

[0160] Furthermore, the various start and end times mentioned above are explained based on time. However, the value of the welding wire position phase can also be used as a reference, and the value can be converted from the welding wire position phase into time or period cyc for processing. That is, the values ​​of welding wire position phase, time, and period cyc can be converted to each other, so any value can be used as a reference for control.

[0161] Furthermore, the wire tip position conversion unit 36B determines the wire tip position based on the phase synchronization signal and the phase delay compensation signal from the servo amplifier 160. Also, in this embodiment, the wire tip position, as described above, can be represented as the wire position phase using an angle (0 to 2π).

[0162] A phase delay compensation signal is output from the phase delay compensation unit 38. The phase delay compensation unit 38 has a database (not shown). This database stores data on the difference between pre-calculated periodic setting information and the actual forward and reverse wire feeding operation signals of the servo motor 170 for each welding condition. For example, when the welding condition is the forward and reverse frequency of the welding wire, the phase delay compensation amount is determined based on the aforementioned database according to the values ​​of the forward and reverse frequencies of the welding wire used, and is output by the phase delay compensation unit 38 as a phase delay compensation signal.

[0163] The main power supply circuit of welding power supply 140 consists of the following: three-phase AC power supply (hereinafter also referred to as "AC power supply") 1; primary side rectifier 2; smoothing capacitor 3; switching element 4; transformer 5; secondary side rectifier 6; reactor 7.

[0164] The AC power input from AC power source 1 is fully rectified by primary-side rectifier 2 and then smoothed by smoothing capacitor 3 to become DC power. Next, the DC power is converted into high-frequency AC power by inverter control via switching element 4, and then converted into secondary-side power via transformer 5. The AC output of transformer 5 is fully rectified by secondary-side rectifier 6 and then smoothed by reactor 7. The output current of reactor 7 is supplied as output from the main power circuit to the contact tip, energizing the welding wire 100, which serves as a consumable electrode.

[0165] The welding wire 100 is fed by a wire feed motor 180 and a servo motor 170, generating an arc between it and the base material 200. The forward feed period, during which the tip of the welding wire 100 moves toward the base material 200, is denoted as the forward feed period TP. The reverse feed period, during which the tip of the welding wire 100 moves in the opposite direction to the setting direction of the base material 200, is denoted as the reverse feed period TN. In this embodiment, the feed motor combines the forward feed period TP and the reverse feed period TN into one cycle, periodically feeding the welding wire 100. Furthermore, the term "tip of the welding wire" generally refers to the tip of the wire when the presence of molten droplets hanging from it is ignored. That is, the welding wire molten by the arc is considered to immediately transition to the base material 200.

[0166] The feeding of the welding wire 100 by the wire feeder motor 180 is controlled by a control signal based on the wire feeder control unit 39. Furthermore, the average feeding speed is approximately the same as the melting speed. In this embodiment, the feeding of the welding wire 100 by the wire feeder motor 180 is also controlled by the welding power source 140.

[0167] Additionally, the wire feeder control unit 39 controls the wire feeder based on the state of the wire feeder 190. In this embodiment, the wire feeder 190 has a wire clearance portion (a gap portion that may slip off due to wire slack caused by the feeding influence between motors) to prevent the wire from bearing a large load on the feeding path between the wire feeder motor 180 and the servo motor 170. An absolute encoder, which is built into the wire feeder 190 as a sensor, detects the wire clearance amount as the rotation angle. The detected value is converted into an analog signal by the serial analog converter 191, and the electrical angle is calculated by the electrical angle calculation unit. The calculated electrical angle is input to the A / D input unit 40 of the welding power supply.

[0168] A differential signal, which is the difference between the electrical angle obtained from the A / D input unit 40 and the reference value of the electrical angle preset in the electrical angle adjustment unit 41, is input to the wire feeder control unit 39. Based on this differential signal, the wire feeder control unit 39 controls the wire feeder motor 180 with an appropriate wire buffer amount, thereby performing interference control that does not impose a large load on the feeding system. Furthermore, while this interference control is performed in this embodiment, it is not limited to this. Additionally, in this embodiment, an absolute encoder built into the wire buffer 190 is used, but it is not limited to this. For example, a rotation angle sensor can also be used, in which case the serial-to-analog converter 191 may not be required.

[0169] In the current setting unit 36, a voltage setting signal Vap, which is the target voltage value, is provided from the voltage setting unit 36C and applied between the welding nozzle and the base material 200.

[0170] On the other hand, the voltage detection signal Vo is a measured value. In this embodiment, the voltage detection signal Vo passes through a low-pass filter LPF, then through the separation detection unit 33 (described later), and is input to the current setting unit 36 ​​together with the separation detection signal DTR (described later). Alternatively, a voltage comparison unit may be provided to amplify the difference between the voltage setting signal Vap and the voltage detection signal Vo, and output it to the current setting unit 36 ​​as a voltage error amplification signal.

[0171] The current setting unit 36 ​​controls the welding current during the peak period Dap in a manner that maintains a constant arc length (hereinafter also referred to as "arc length"). Based on the voltage setting signal Vap and the voltage detection signal Vo, the current setting unit 36 ​​determines and sets at least the peak period, rise period, base period, and fall period. Furthermore, the values ​​of the peak current Ip and the base current Ib can also be set again. The current setting signal CCset corresponding to the set period or value is output to the current error amplifier (PWM) 34.

[0172] The current error amplification unit 34 amplifies the difference between the current setting signal CCset, which is provided as the target value, and the current detection signal Io detected by the current detection unit 31, and outputs it as a current error amplification signal Ed to the inverter drive unit 30. The inverter drive unit 30 corrects the drive signal Ec of the switching element 4 based on the current error amplification signal Ed.

[0173] In the current setting unit 36, a detachment detection signal DTR, which senses the detachment of molten droplets from the tip of the welding wire 100, is also input. The detachment detection signal DTR is output from the detachment detection unit 33. The detachment detection unit 33 monitors the change in the voltage detection signal Vo output by the voltage detection unit 32, and senses the detachment of the molten droplet from the welding wire 100 based on the change. Furthermore, the detachment detection unit 33 is an example of a detection mechanism.

[0174] The droplet detachment detection unit 33 compares, for example, the differential or second-order derivative of the voltage detection signal Vo that has passed through the LPF with a predetermined threshold for detection, thereby detecting the detachment of the molten droplet. The detection threshold is stored in advance in a storage unit (not shown in the diagram). Furthermore, the droplet detachment detection unit 33 can also generate a droplet detachment detection signal DTR based on the change in resistance calculated from the measured voltage detection signal Vo and the current detection signal Io.

[0175] In the waveform control table linear calculation unit 37, the average feed speed Favg of the fed welding wire 100 is obtained. The average feed speed Favg is stored in advance in the feed setting data unit 35. In this embodiment, the feed setting data unit 35 is located in the welding power source 140, but it can also store various feed setting related information in advance in the welding control device 120, and output various information from the welding control device 120 to the welding power source 140.

[0176] The waveform control table linear calculation unit 37 determines the values ​​of peak current Ip, base current Ib, the start time of base current Ib, and the end time of base current Ib based on the given average feed rate Favg, and outputs them to the current setting unit 36. Furthermore, as mentioned above, the values ​​of the welding wire position phase, time, and period cyc can be converted to each other; therefore, the set value of the phase starting at the base current can also be converted into the value of time or period cyc, and the converted value can be output to the current setting unit 36.

[0177] In this embodiment, the average feed rate Favg is input to the waveform control table linear calculation unit 37. However, the value associated with the average feed rate Favg can also be input to the waveform control table linear calculation unit 37 as a setting value, and the waveform control table linear calculation unit 37 replaces the setting value with the average feed rate Favg and uses it. For example, when the storage unit (not shown) stores a database of the average feed rate Favg and the average current value at which optimal welding can be performed under this average feed rate Favg, the average current value can be used as the setting value, and the setting value can be replaced with the average feed rate Favg.

[0178] The data sent to the setting data unit 35 can store setting values ​​for wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf, in addition to the average feed speed Favg. Furthermore, the wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf can be determined based on the input average feed speed Favg. Additionally, the data sent to the setting data unit 35 can also store other setting values ​​as feed setting data. Furthermore, in this embodiment, the value of wire amplitude Wf ​​refers to... Figure 7The wave height Wh is shown. That is, the wire amplitude Wf, which is a set value, is the same as the wave height Wh.

[0179] In this embodiment, the period during which the feed speed is greater than the average feed speed Favg is the forward feed period, and the period during which the feed speed is less than the average feed speed Favg is the reverse feed period, thus configuring the feed to alternate between the forward and reverse feed periods (hereinafter referred to as "amplitude feed"). Furthermore, the period during which the feed speed is less than the average feed speed Favg refers to a feed speed lower than the average feed speed Favg, including negative feed speeds, i.e., the speed at which the tip of the welding wire moves in the opposite direction to the location of the base material 200. The welding wire amplitude Wf ​​provides the variation range corresponding to the average feed speed Favg, and the welding wire forward / reverse period Tf provides the time of the welding wire amplitude variation as a repeating unit. The welding wire forward / reverse frequency Hf is the reciprocal of the welding wire forward / reverse period Tf. In this embodiment, the setting values ​​of the welding wire amplitude Wf ​​and the welding wire forward and reverse frequency Hf are not particularly limited. For example, if the welding wire forward and reverse frequency is selected and set from the range of 50Hz or more and 150Hz or less, and the welding wire amplitude represented by the wave height Wh is 3.3mm or more and 6.3mm or less, it is preferred from the viewpoint of welding workability.

[0180] The average feed speed Favg, wire amplitude Wf, wire forward and reverse frequency Hf, and wire forward and reverse period Tf stored in the setting data unit 35 are input from the digital communication unit 42 to the digital communication unit 122 of the welding control device 120. In this embodiment, the communication of this setting data is performed by CAN communication.

[0181] The welding timing unit 43, based on the teaching data, processes each task in the order of Idle, Gas Flow, Arc Start, Welding, and Anti-stick. Furthermore, in... Figure 6 In the welding control device 120, the welding condition information is also indicated by a dashed circle in the welding power source 140 for convenience.

[0182] (Functional composition of welding control device)

[0183] In the digital communication unit 122 of the welding control device 120, as described above, transmission setting data such as average feed speed Favg, wire amplitude Wf, wire forward and reverse frequency Hf, and wire forward and reverse period Tf are input from the transmission setting data unit 35 of the welding power source 140 via CAN communication. The welding control device 120 has a digital communication unit 123, which outputs this transmission setting data to the digital communication unit 162 of the servo amplifier 160. In this embodiment, the digital communication unit 123 of the welding control device 120 and the digital communication unit 162 of the servo amplifier 160 are connected via EtherCAT (registered trademark).

[0184] (Functional composition of a servo amplifier)

[0185] In the digital communication unit 162 of the servo amplifier 160, feed setting data such as average feed speed Favg, wire amplitude Wf, wire forward and reverse frequency Hf, and wire forward and reverse period Tf are input via EtherCAT (registered trademark) communication. The forward / reverse wire feed command generation unit 161 of the servo amplifier 160 generates feed commands for forward or reverse wire feeding based on the setting information input via digital communication, i.e., the feed setting data. The forward / reverse wire feed command generation unit 161 calculates the amplitude feed speed Ff based on the wire amplitude Wf ​​and the wire forward and reverse period Tf, and outputs the feed speed command signal Fw to the servo motor 170 based on the amplitude feed speed Ff and the average feed speed Favg.

[0186] In this embodiment, the speed command signal Fw is represented by the following formula.

[0187] Fw = Ff + Favg … Equation (A)

[0188] Furthermore, the forward and reverse wire feed command generation unit 161 can also sense at which phase of the amplitude feed occurs during detachment by using the detachment detection signal DTR provided by the detachment detection unit 33. However, the feed speed command signal Fw, represented by equation (A), is only sensed during the assumed period when the molten droplet detaches from the tip of the welding wire 100. If no detachment of the molten droplet is detected during the assumed period, the forward and reverse wire feed command generation unit 161 can also switch the feed speed command signal Fw to feed control at a certain speed. For example, the forward and reverse wire feed command generation unit 161 can switch the feed speed command signal Fw to feed at an average feed speed Favg. The switch from feed at an average feed speed Favg to feed control represented by equation (A) is determined based on the timing of sensing the detachment of the molten droplet.

[0189] The servo amplifier 160 performs inverter control of the servo motor 170 based on the speed command signal Fw. Additionally, the synchronization signal generation unit 163 of the servo amplifier 160 outputs a phase synchronization signal to the welding power supply 140. This phase synchronization signal is generated based on the speed command signal Fw.

[0190] Example

[0191] The present invention will now be described in more detail, but it is not limited to these embodiments. Modifications may be made within the scope of the invention's spirit and are all included within its technical scope. Furthermore, the welding conditions described herein are illustrative, and the invention is not limited to these specific welding conditions.

[0192] [Gas-shielded arc welding]

[0193] Various welding wires with different compositions were used to perform gas-shielded arc welding using a controlled method, and the wear of the welding nozzle was evaluated. The composition of the welding wires used is shown in [the table / information]. Figure 8 In the middle, the conditions sent to the control are displayed Figure 9 In addition, other welding conditions are shown below. Figure 8 This is a diagram showing the composition of the welding wire in this embodiment. Figure 9 This is a diagram illustrating the conditions for sending to control in this embodiment.

[0194] [Other welding conditions]

[0195] Base material: SS400

[0196] Welding posture: Flat welding

[0197] Protective gas: 100% CO2 gas by volume

[0198] Average current: 280~320A

[0199] Average voltage: 34-40V

[0200] Distance between welding nozzle and base material: 25mm

[0201] Welding wire feed rate: 14-16 m / min

[0202] Welding speed: 30cm / min

[0203] Welding time: 1 hour

[0204] [Evaluation Experiment]

[0205] (Welding nozzle wear test)

[0206] Figure 10This is a graph showing the results of the evaluation test in this embodiment. The difference between the weight of the contact tip before welding and the weight of the contact tip after welding is measured as the wear amount. A wear amount of less than 2.0 mg is acceptable (Evaluation D), preferably less than 1.4 mg (Evaluation C), more preferably less than 1.0 mg (Evaluation B), and even more preferably less than 0.5 mg (Evaluation A). On the other hand, a wear amount greater than 2.0 mg is considered excessive and unacceptable (Evaluation E). Furthermore, a negative wear amount (increased weight after welding) is a phenomenon caused by the transfer of Fe or Cu from the welding wire side to the contact tip side, indicating that the wear of the contact tip is suppressed.

[0207] [(Amount of solid lubricant / Square of current during forward wire feed) × 10] 8 ]

[0208] Figure 11 It is a graph showing the relationship between the amount of solid lubricant, the square of the current during wire feeding, and the amount of wear.

[0209] The stable formation of the liquid lubricating film during the forward wire feed requires stable melting of the Fe in the welding wire and the Cu coating; therefore, a higher value is better, preferably 420A or more, more preferably 450A or more, and even more preferably 480A or more. Furthermore, the formation of the liquid lubricating film also depends on the amount of sulfide as a solid lubricant. In this embodiment, the value of Formula 1, derived from the amount of sulfide and the average current during the forward wire feed, is used as an indicator of nozzle wear. A value of Formula (B) is preferably 45 or more, more preferably 50 or more.

[0210] (Amount of solid lubricant / Square of current during wire feed) × 10 8 )≥45 …Formula (B)

[0211] Furthermore, when the average current during wire feeding is low, the Fe in the welding wire and the Cu coating cannot melt stably. Therefore, this parameter is preferably used at a current of 420A or higher. Figure 10 The tests T13 and T14 of this embodiment shown are within the range of the parameters in formula (B), but outside the scope of the invention of this application, so the wear of the welding nozzle increases.

[0212] This invention is not limited to the embodiments described above. Combining the various components of the embodiments with each other, or making changes and applications based on the description in the specification and well-known technologies by those skilled in the art, are also part of this invention and are included within the scope of protection.

[0213] As stated above, the following matters are disclosed in this specification.

[0214] (1) A gas-shielded arc welding method, characterized in that it employs an alternating forward and reverse wire feeding method, and feeds the welding wire at a predetermined average wire feeding speed, wherein,

[0215] The welding wire has the following characteristics:

[0216] Fe or Fe-based alloys;

[0217] A coating formed from Cu or a Cu-based alloy;

[0218] A solid lubricant having at least a layered crystalline structure and containing sulfides on the surface of the coating.

[0219] The feeding control method includes a step of controlling at least the welding current based on the tip position of the welding wire.

[0220] In the step of at least controlling the welding current

[0221] The welding current has at least a high current range above a predetermined current value and a low current range below the predetermined current value, and the average welding current ITP during the wire feed period is... AVE A current higher than the predetermined current value.

[0222] When the welding wire position phase is set to 0° based on the position of the welding wire tip when switching from the reverse feeding period to the forward feeding period, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

[0223] According to this gas-shielded arc welding method, excellent nozzle wear resistance can be obtained regardless of the current range.

[0224] (2) The gas shielded arc welding method according to (1) is characterized in that the feeding control method feeds the welding wire at the average feeding speed while periodically repeating the forward and reverse feeding while using the forward and reverse feeding frequency as one cycle.

[0225] According to this gas-shielded arc welding method, excellent nozzle wear resistance can be obtained in gas-shielded arc welding using a short-circuit suppression type feed control method, regardless of the current range.

[0226] (3) The gas shielded arc welding method according to (2) is characterized in that, in the step of controlling at least the welding current, the welding wire position phase d1 set in the range of 100° to 200° is switched from the high current range to the low current range.

[0227] According to this gas-shielded arc welding method, abrasive wear on the contact surface of the contact tip can be further suppressed.

[0228] (4) The gas-shielded arc welding method according to (1) is characterized in that the solid lubricant contains at least one of molybdenum disulfide and tungsten disulfide.

[0229] According to this gas-shielded arc welding method, before the sulfide reaches the contact tip, it acts as a solid lubricant to stabilize the feed properties. At the contact surface inside the contact tip, a liquid lubricating film is generated, which can suppress adhesive wear.

[0230] (5) The gas-shielded arc welding method according to (1) is characterized in that the surface of the welding wire is coated with oil and the solid lubricant is contained in the oil.

[0231] According to this gas-shielded arc welding method, sulfides are coated on the surface of the welding wire in a state of being mixed with lubricating oil. By adjusting the mixing ratio, the amount of adhesion can be suppressed.

[0232] (6) The gas-shielded arc welding method according to (1) is characterized in that the solid lubricant is present in 0.05 to 0.40 g per 10 kg of welding wire.

[0233] According to this gas-shielded arc welding method, a liquid lubricating film can be appropriately generated.

[0234] (7) A gas-shielded arc welding system, characterized in that it employs an alternating forward and reverse wire feeding method, and feeds the welding wire at a predetermined average wire feeding speed, wherein,

[0235] Equipped with the aforementioned welding wire and feeding control device,

[0236] The welding wire has the following characteristics:

[0237] Fe or Fe-based alloys;

[0238] A coating formed from Cu or a Cu-based alloy;

[0239] A solid lubricant having at least a layered crystalline structure and containing sulfides on the surface of the coating.

[0240] The control device controls at least the welding current based on the position of the welding wire's tip.

[0241] The welding current has at least a high current range above a predetermined current value and a low current range below the predetermined current value. The welding current is controlled by the control device in such a way that the average welding current ITP during the wire feeding period is... AVEFor a current higher than the predetermined current value,

[0242] When the welding wire position phase is set to 0° based on the position of the welding wire tip when switching from the reverse feeding period to the forward feeding period, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

[0243] This gas-shielded arc welding system achieves excellent nozzle wear resistance regardless of the current range.

[0244] (8) A welding wire used for alternating forward and reverse wire feeding, wherein, based on the tip position of the welding wire, the average welding current during at least the forward wire feeding period is controlled to be higher than a predetermined current value, and the welding wire is fed at a predetermined average wire feeding speed, wherein the feeding control method comprises:

[0245] Fe or Fe-based alloys;

[0246] A coating formed from Cu or a Cu-based alloy;

[0247] A solid lubricant having at least a layered crystal structure and containing sulfides on the surface of the coating.

[0248] If these welding wires are used in gas-shielded arc welding with the aforementioned feed control method, excellent nozzle wear resistance can be obtained regardless of the current range.

[0249] (9) The welding wire according to (8), characterized in that, relative to the total mass of the welding wire, it contains

[0250] Fe: 90% or more by mass

[0251] C: Less than 0.15% by mass

[0252] Si: less than 1.10% by mass

[0253] Mn: less than 2.30% by mass

[0254] Ti: less than 0.30% by mass

[0255] Al: less than 0.30% by mass

[0256] Zr: less than 0.30% by mass

[0257] Mg: less than 0.30% by mass

[0258] Ni: less than 4.75% by mass

[0259] Cr: less than 0.60% by mass

[0260] Mo: less than 0.90% by mass

[0261] Cu: less than 0.50% by mass

[0262] Nb: less than 0.50% by mass

[0263] V: less than 0.50% by mass

[0264] B: Less than 0.0050% by mass

[0265] P: less than 0.050% by mass

[0266] S: less than 0.050% by mass.

[0267] If these welding wires are used in gas-shielded arc welding with the aforementioned feed control method, excellent nozzle wear resistance can be obtained regardless of the current range.

[0268] The various embodiments have been described above with reference to the accompanying drawings, but the present invention is certainly not limited to these examples. Those skilled in the art will obviously be able to conceive of various modifications or alterations within the scope of the claims, which are also understood to fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0269] Furthermore, this application is based on Japanese patent application (Japan Patent Application No. 2024-053556) filed on March 28, 2024, the contents of which are incorporated herein by reference.

[0270] Explanation of reference numerals in the attached figures

[0271] 1. AC power supply

[0272] 2. Primary side rectifier

[0273] 3. Smoothing capacitor

[0274] 4 Switching elements

[0275] 5 Transformers

[0276] 6 Secondary rectifier

[0277] 7. Reactor

[0278] 30 Inverter Drive Section

[0279] 31 Current Detection Section

[0280] 32 Voltage Detection Section

[0281] 33. Departure from the inspection department

[0282] 34 Current Error Amplification Section

[0283] 35 sent to the setting data department

[0284] 36 Current setting section

[0285] 37. Waveform Control Table Linear Operation Section

[0286] 38 Phase Delay Compensation Unit

[0287] 39. Wire pusher control unit

[0288] 40 A / D Input Section

[0289] 41 Electrical Angle Adjustment Section

[0290] 42. Digital Communications Department

[0291] 43 Welding sequence section

[0292] 50 Welding System

[0293] 100 welding wire

[0294] 110 Welding Robot

[0295] 111 Welding Torch

[0296] 120 Welding Control Device

[0297] 122, 123 Digital Communications Department

[0298] 140 welding power supply

[0299] 141 Control System Department

[0300] 150 controller

[0301] 160 Servo Amplifier

[0302] 161 Forward and Reverse Wire Feed Command Generation Unit

[0303] 162 Digital Communications Department

[0304] 163 Synchronous signal generation department

[0305] 170 servo motor

[0306] 180 wire pusher motor

[0307] 190 Welding Wire Buffer

[0308] 191 Serial-to-Analog Converter

[0309] 200 workpieces

Claims

1. A gas shielded arc welding method characterized by, A feeding control method was applied that alternates between forward and reverse wire feeding, and feeds the welding wire at a predetermined average wire feeding speed. The welding wire has the following characteristics: Fe or Fe-based alloys; A coating formed from Cu or a Cu-based alloy; and A solid lubricant having at least a layered crystalline structure and containing sulfides on the surface of the coating. The feeding control method includes a step of controlling at least the welding current based on the tip position of the welding wire. In the step of at least controlling the welding current The welding current has at least a high current range higher than a predetermined current value and a low current range lower than the predetermined current value, and the average welding current ITP during the positive wire feeding is made higher than the predetermined current value AVE is a current higher than the predetermined current value, When the welding wire position phase, which is based on the position of the welding wire tip when switching from the reverse feeding period to the forward feeding period, is set to 0°, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

2. The gas shielded arc welding method according to claim 1, characterized by, The feeding control method is a method of periodically repeating forward and reverse feeding based on the forward and reverse feeding frequencies of the welding wire, with the forward feeding period and reverse feeding period as one cycle, and feeding the welding wire at the average welding wire feeding speed.

3. The gas-shielded arc welding method according to claim 2, characterized in that, In the step of at least controlling the welding current The welding wire position phase d1, set within the range of 100° to 200°, switches from the high current range to the low current range.

4. The gas-shielded arc welding method according to claim 1, characterized in that, The solid lubricant contains at least one of molybdenum disulfide and tungsten disulfide.

5. The gas-shielded arc welding method according to claim 1, characterized in that, The surface of the welding wire is coated with oil, and the solid lubricant is contained in the oil.

6. The gas-shielded arc welding method according to claim 1, characterized in that, The solid lubricant is present in the form of 0.05–0.40 g per 10 kg of welding wire.

7. A gas-shielded arc welding system, characterized in that, A feeding control method was applied that alternates between forward and reverse wire feeding, and feeds the welding wire at a predetermined average wire feeding speed. Equipped with the aforementioned welding wire and feeding control device, The welding wire has the following characteristics: Fe or Fe-based alloys; A coating formed from Cu or a Cu-based alloy; and A solid lubricant having at least a layered crystalline structure and containing sulfides on the surface of the coating. The control device controls at least the welding current based on the position of the welding wire's tip. The welding current has at least a high current range above a predetermined current value and a low current range below the predetermined current value, and the feed control device controls the welding current such that the average welding current ITP AVE is a current higher than a predetermined current value, When the welding wire position phase, which is based on the position of the welding wire tip when switching from the reverse feeding period to the forward feeding period, is set to 0°, the welding wire position phase when switching from the low current range to the high current range is set in the range of 280° to 350°.

8. A welding wire used for alternating forward and reverse wire feeding, wherein the average welding current during the forward wire feeding period is controlled, based on the tip position of the welding wire, at least to a current higher than a predetermined current value, and the welding wire is fed at a predetermined average wire feeding speed, wherein... The welding wire has the following characteristics: Fe or Fe-based alloys; A coating formed from Cu or a Cu-based alloy; and A solid lubricant having at least a layered crystal structure and containing sulfides on the surface of the coating.

9. The welding wire according to claim 8, characterized in that, The welding wire, relative to its total mass, contains Fe: 90% or more by mass C: Less than 0.15% by mass Si: less than 1.10% by mass Mn: less than 2.30% by mass Ti: less than 0.30% by mass Al: less than 0.30% by mass Zr: less than 0.30% by mass Mg: less than 0.30% by mass Ni: less than 4.75% by mass Cr: less than 0.60% by mass Mo: less than 0.90% by mass Cu: less than 0.50% by mass Nb: less than 0.50% by mass V: less than 0.50% by mass B: Less than 0.0050% by mass P: less than 0.050% by mass S: less than 0.050% by mass.

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