Gas shield arc-welding method, gas shield arc-welding system, and welding wire

Abstract

To provide excellent tip wear resistance.SOLUTION: In a gas shield arc-welding method applying a feeding control method that feeds a welding wire at a predetermined average wire feeding speed while alternately repeating normal feeding and reverse feeding, the welding wire has plating by Fe or an Fe-based alloy and Cu or a Cu-based alloy, and at least a solid lubricant of a lamellar crystal structure and sulfide on a plating surface. In the feeding control method, at a step of controlling at least a welding current according to a tip position of the welding wire, an average welding current ITPAVE during the normal feeding and the reverse feeding periods becomes current higher than the predetermined current value, and when a wire position phase based on the tip position of the welding wire during switching from the reverse feeding period to the normal feeding period is so made as to be 0deg, the wire position phase switching from a low current period to a high current period is set in a range of 280° to 350°.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gas-shielded arc welding method, a gas-shielded arc welding system, and a welding wire. [Background technology]

[0002] In consumable electrode gas-shielded arc welding, a current is sent to a constantly fed consumable electrode (hereinafter also referred to as welding wire) via a contact tip, melting the welding wire and performing arc welding. During this process, the welding wire slides against the contact tip while current is being applied, resulting in significant wear phenomena, primarily adhesive wear and abrasive wear. Abrasive wear is also known as scratch wear.

[0003] Such wear generally occurs on the contact tip side, which is made of a softer material with a lower melting point than the welding wire. Hereinafter, this wear on the contact tip side will also be referred to as tip wear. Tip wear tends to increase as the welding wire feed speed increases or the welding current fluctuates. Therefore, feed control methods that have been increasingly adopted in recent years have the problem of increasing the likelihood of tip wear, since the welding wire is alternately fed forward and backward at high speeds and the welding current fluctuates.

[0004] Patent Document 1 discloses a technology for providing a solid wire for arc welding having a copper plating layer formed on the surface of a steel material, wherein the Cu content in the steel material and the copper plating layer is 0.05 to 0.30 mass% based on the total mass of the wire, 0.05 to 0.20 g of oil is applied to the wire surface per 1 kg of wire, and the copper plating layer surface has an arithmetic mean roughness Rac of 0.25 to 1.00 μm in the circumferential direction and an arithmetic mean roughness Ral of 0.07 to 0.50 μm in the longitudinal direction, the solid wire for arc welding having excellent arc stability even when used for continuous welding over long periods of time.

[0005] Patent Document 2 discloses a welding power source that includes a feed control means for controlling wire feed while periodically switching between forward and reverse wire feed periods, and a current control means for changing the welding current according to the position of the wire tip, the distance from which to the surface of the base metal periodically changes. The feed control means controls the time it takes for the wire tip to move from the nearest point, which is the position closest to the base metal, to the farthest point, which is the position farthest from the base metal, so that it is shorter than the time it takes for the wire tip to move from the farthest point to the nearest point. The current control means controls the welding current to be lowered below a predetermined current value during the period in which the wire tip is reverse fed, and discloses a technology that makes it less likely for spatter to scatter and makes the contact tip less likely to wear. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-159957 [Patent Document 2] Japanese Patent Application Publication No. 2022-33399 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 describes a technology based on a feed control method for a low current of approximately 200 A. There are two types of feed control welding methods: one type performs welding in a low current range based on a short-circuit transition mode in which the welding wire feed speed is alternately switched between forward and reverse periods, generating short-circuit periods and arc periods (hereinafter also referred to as a "short-circuit feed control method"), and another type performs welding in a medium current range or higher based on a globule transition mode in which the welding wire feed speed is alternately switched between forward and reverse periods, suppressing the occurrence of short-circuit periods (hereinafter also referred to as a "short-circuit suppression feed control method"). Patent Document 1 describes a short-circuit feed control method, which performs welding in a low current range of approximately 250 A or less, and therefore does not take into consideration the effects of adhesive wear.

[0008] On the other hand, Patent Document 2 discloses a short-circuit suppression type feed control method suitable for medium current ranges and above, which discloses that reducing the wire feed speed, lengthening the non-current suppression period, and maintaining a low welding current are effective in reducing tip wear. However, the application conditions are limited because the wire feed speed must be reduced and the current during the non-current suppression period must be kept low. Specifically, because there are restrictions on increasing the wire feed speed and welding current, no effect on tip wear can be expected for welding in the high current range. Furthermore, the extent of the effect on tip wear is not clearly stated, and the impact of adhesive wear caused by current fluctuations resulting from providing non-current suppression periods and current suppression periods is not taken into consideration.

[0009] Therefore, the present invention is devised to solve the above-mentioned problems, and has an object to provide a gas-shielded arc welding method that can obtain excellent tip wear resistance regardless of the current range in a feed control method in which a welding wire is fed at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, and a welding system and welding wire used in this method. [Means for solving the problem]

[0010] The present invention comprises the following configurations.

[0011] (1) A gas-shielded arc welding method employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, The welding wire is Fe or an Fe-based alloy, Plating with Cu or Cu-based alloy, and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface, The feed control method includes a step of controlling at least a welding current in accordance with a tip position of the welding wire, In the step of controlling at least the welding current, The welding current has at least a high current period in which the welding current is higher than the predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and an average welding current ITP during the forward feed period AVE is a current higher than a predetermined current value, When a wire position phase based on the tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, the wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°. Gas shielded arc welding method.

[0012] (2) A gas-shielded arc welding system employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, a welding wire feed control device; The welding wire is Fe or an Fe-based alloy, Plating with Cu or Cu-based alloy, and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface, the feed control device controls at least the welding current in accordance with the tip position of the welding wire; The welding current has at least a high current period in which the welding current is higher than the predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and the feed control device controls the welding current to be equal to an average welding current ITP during the forward feed period. AVE is a current higher than a predetermined current value, When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°. Gas shielded arc welding system.

[0013] (3) A welding wire for use in a feed control method that alternately repeats forward feed and reverse feed, controls an average welding current at least during a period of forward feed to be higher than a predetermined current value depending on a tip position of the welding wire, and feeds the welding wire at a predetermined average wire feed speed, Fe or an Fe-based alloy, Plating with Cu or Cu-based alloy, and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface. Welding wire. [Effects of the Invention]

[0014] According to the present invention, in a feed control method in which welding wire is fed at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, excellent tip wear resistance can be obtained regardless of the current range. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a conceptual diagram illustrating tip wear. [Figure 2] FIG. 2 is a conceptual diagram illustrating the configuration of the welding wire according to this embodiment. [Figure 3] FIG. 3 is an explanatory diagram of the timing at which the low current period is provided. [Figure 4] FIG. 4 shows the wear state of the contact tip when a test was conducted with the current phase changed. [Figure 5] FIG. 5 is a schematic diagram showing an example of the configuration of a welding system according to this embodiment. [Figure 6] FIG. 6 is a block diagram showing a schematic configuration relating to the control of the welding power source, welding control device, and servo amplifier in this embodiment. [Figure 7] FIG. 7 is a graph illustrating the relationship between the wire feed speed, the wire tip position, and the current detection signal in this embodiment. [Figure 8] FIG. 8 is a diagram showing the composition of the welding wire in this embodiment. [Figure 9] FIG. 9 is a diagram showing conditions for feed control in this embodiment. [Figure 10] FIG. 10 is a diagram showing the results of an evaluation test in this embodiment. [Figure 11] FIG. 11 is a diagram showing the relationship between the amount of solid lubricant, the square of the current during the normal feeding period, and the amount of wear. DETAILED DESCRIPTION OF THE INVENTION

[0016] FIG. 1 is a conceptual diagram illustrating tip wear.

[0017] A contact tip used in gas-shielded arc welding is a hollow contact tip with a welding wire passing through it. Welding is performed while the welding wire is being fed, but as shown in the figure, the welding wire comes into contact with one side of the contact tip, causing current to flow, which causes wear on the contact tip.

[0018] The main wear modes that affect tip wear are adhesive wear and abrasive wear. Adhesive wear is a wear phenomenon in which adhesion occurs between sliding contact surfaces, causing the material with the weaker interface bond to be torn off and adhere to one surface. Abrasive wear occurs when the surface protrusions of the harder material on the sliding contact surfaces mechanically scrape away the opposing material, and when there are hard particles sandwiched between the contact surfaces, the hard particles scrape away both surfaces, causing wear.

[0019] Generally, tip wear occurs when current flows between a welding wire made of an iron-based material and a contact tip made of a copper-based material. This occurs mainly due to electrical resistance heat and frictional heat generated by the sliding of the welding wire, which softens or melts the copper-based material of the contact tip, which has a low melting point. The softened or molten copper adheres to the surface of the welding wire and is expelled from the contact tip. In particular, when the current periodically increases and decreases, as in pulse welding, the copper-based material of the contact tip repeatedly melts and solidifies. Upon solidification, it bonds strongly to the welding wire, and the copper on the contact tip solidifies and is then torn off by the welding wire, resulting in significant tip wear. Therefore, the challenge is how to suppress adhesive wear during forward welding of the welding wire.

[0020] The present invention focuses on the following points: first, to keep the interface state on the contact tip side unchanged during the forward feed period of the welding wire, and second, to prevent Cu from adhering to the contact surface on the welding wire side even if the contact tip softens or melts, and has thereby solved the problem from the perspective of the timing of feeding and current control in the welding wire and feed control method. Below, the technical features of the welding wire and the timing of feeding and current control in the feed control method will be described.

[0021] [Features of welding wire] 2 is a conceptual diagram illustrating the configuration of a welding wire according to this embodiment. The welding wire is made of Fe or an Fe-based alloy (hereinafter, Fe or an Fe-based alloy will be collectively referred to as an Fe-based metal). The surface of the welding wire is plated with Cu or a Cu-based alloy, and at least a solid lubricant having a layered crystal structure and a sulfide is applied to the plated surface. Examples of solid lubricants having a layered crystal structure and a sulfide include molybdenum disulfide (MoS2) and tungsten disulfide (WS2). Here, examples of Fe-based alloys include mild steel and stainless steel, and examples of Cu-based alloys include those commonly used for electrodes, such as chromium copper, chromium zirconium copper, and beryllium copper.

[0022] [Characteristics of feed and current control in feed control method] In the feed control method, the welding current is controlled to have at least a high current period in which the welding current is higher than the predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and the welding current is controlled so as to be switched to at least the high current period or the low current period according to the tip position of the welding wire, and an average welding current ITP during the period in which the welding wire is fed in the forward direction is controlled. AVE The current is set or controlled so that the average welding current I is higher than a predetermined current value. AVE In addition, when the wire position phase is set to 0° with respect to the tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period, the wire position phase at which the low current period is switched to the high current period is set in the range of 280° to 350°.

[0023] Due to the characteristics of the welding wire and the feed control method conditions described above, it is estimated that the following phenomena (a) to (c) occur on the contact surface between the welding wire and the contact tip (hereinafter simply referred to as the "contact surface") during the forward feed period.

[0024] (a) Average welding current I during the forward feeding period of the welding wire AVE The above current is applied. At this time, the Fe-based metal side of the welding wire, which has a high electrical resistance, becomes hot due to resistance heat, and the Fe-based metal of the wire and the Cu-based metal of the plating melt.

[0025] (b) The molten Fe in the wire and Cu in the plating react with the S in the sulfide to produce FeS or Cu2S. FeS has a melting point of 1190°C, and Cu2S has a melting point of 1130°C, making them good electrical conductors. During the forward feed period, the average welding current I AVE As a result of the application of the above current, the FeS and Cu2S melt and come into contact with the solid portion (unmelted Fe-based metal) of the sliding welding wire.

[0026] (c) The interface between the solid portion of the wire and the molten portion of the FeS and Cu2S has poor wettability, making it difficult for the molten FeS and Cu2S to adhere to the solid portion of the sliding wire. In other words, the molten FeS and Cu2S are not expelled from the tip during the forward feed period. Here, FeS and Cu2S act as a liquid lubricant film during the forward feed period, suppressing adhesive wear. In addition, the liquid lubricant film stabilizes the current-carrying surface, which is also effective for arc stability. Note that if sulfides are not present on the plating surface, an excellent liquid lubricant film is not formed, and the molten Fe of the welding wire and Cu of the contact tip adhere to the sliding solid portion of the welding wire during the forward feed period, causing adhesive wear in which the molten Fe and Cu adhere to the solid portion of the welding wire and are expelled from the contact tip.

[0027] [Timing for low current periods] FIG. 3 is an explanatory diagram of the timing for providing a low current period. In the short circuit suppression type feed control method, it is necessary to provide a low current period due to the nature of the control. In the present invention, in the short circuit suppression type feed control method, it is preferable to provide a low current period in the reverse feed period, and the average welding current during the reverse feed period is the average welding current I AVE It is more preferable that:

[0028] By including a low-current period during the reverse feed period, the molten Fe and Cu, as well as the FeS and Cu2S that react with them, solidify and transfer to the contact tip. As mentioned above, FeS and Cu2S do not easily adhere to the welding wire due to their wettability. Therefore, these solidified materials bond more strongly with the Cu-based metal of the contact tip and are transferred to the contact tip. This is also evident from the observation of the contact surface on the contact tip side after welding, as described later with reference to Figure 4. Therefore, during the low-current period, abrasive wear (mechanical wear) between the solid portion of the wire and the solidified adhesion portion on the contact tip side becomes dominant. The transferred layer on the contact tip side, which has a lower melting point and is softer than the solid portion of the wire, is pushed toward the back of the contact tip by the sliding of the welding wire. If the timing of switching from the low-current period to the high-current period is appropriate, it will be remelted during the next forward feed period, and this will not affect contact tip wear. Specifically, when the wire position phase is 0° with respect to the tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period, the wire position phase at the time of switching from the low current period to the high current period must be set to a timing in the range of 280° to 350°. If this timing is not met, abrasive wear will occur on the contact tip.

[0029] Figure 4 shows the state of wear of the contact tip observed when a test was conducted with the current phase changed.

[0030] 4(a) shows the contact surface of the contact tip after welding under phase conditions in which a peak current was set in the forward feed period and a low current period was set in the reverse feed period, i.e., standard conditions. Under the standard conditions, almost no trace of contact with the welding wire was observed on the contact surface of the contact tip.

[0031] Figure 4(b) shows the contact surface of the contact tip after welding under phase conditions in which the current phase was advanced by 200 degrees from the standard conditions, so that the low current period was set in the forward feed period and the peak current was set in the reverse feed period. Under the phase condition in which the current phase was advanced by 200 degrees, abrasive wear was observed on the contact surface of the contact tip.

[0032] [Ratio of forward feeding period to reverse feeding period] The ratio of the forward feed period to the reverse feed period in one cycle is preferably 1:1, as in this embodiment, or a smaller ratio for the forward feed period. This shortens the period during which wear accelerates and allows for a high current to be applied to stably generate a liquid lubricant film. In other words, tip wear resistance tends to improve when the ratio is 1:1 or when the forward feed period is smaller.

[0033] The following describes specific embodiments of wires and feed control that can provide more favorable effects on tip wear resistance. Note that these are merely examples, and the present invention is not limited to these as long as the above technical features are met.

[0034] [Surface properties of welding wire] (plating of welding wire) In order to generate a stable liquid lubricant film during the forward feed period, the welding wire must be plated with Cu or a Cu-based alloy. As mentioned above, the resistance heat is greatest when the welding wire is Fe or an Fe-based alloy, so the molten Cu required to generate the liquid lubricant film must be secured by plating. As will be described later, wires without plating cannot achieve wear resistance, which can be inferred to be due to an insufficient amount of molten Cu required to generate the liquid lubricant film. In the present invention, the composition, plating thickness, and amount of plated Cu are not particularly important, and are sufficient as long as they fall within the commonly used range. However, in order to generate a stable liquid lubricant film, the amount of plated Cu is preferably 0.05 to 0.30 mass% of the total mass of the wire.

[0035] (sulfide) The sulfide is preferably applied so that it adheres to the plated surface, and preferably so that it adheres uniformly to the plated surface without any bias. The sulfide acts as a solid lubricant with a layered crystal structure, stabilizing feedability as a solid lubricant up to the contact tip, and acts to generate a liquid lubricant film on the contact surface within the contact tip, suppressing adhesive wear. Examples of solid lubricants that function in this way include molybdenum disulfide (MoS2) and tungsten disulfide (WS2). While molybdenum disulfide and tungsten disulfide are stable at room temperature, FeS and Cu2S are more stable at temperatures above 1000°C. Therefore, in the present invention, it is preferable to include either molybdenum disulfide or tungsten disulfide.

[0036] Furthermore, the amount of sulfide to be applied to generate a liquid lubricating film is preferably 0.05 g to 0.40 g, more preferably 0.10 g to 0.30 g, per 10 kg of welding wire. The sulfide is mixed with lubricating oil and applied to the plated surface of the welding wire, and the amount of sulfide attached can be controlled by adjusting the mixture ratio.

[0037] (lubricating oil) In the present invention, the type and amount of lubricant are not particularly limited. Examples of lubricant include animal oil, vegetable oil, or a mixture of these (hereinafter collectively referred to as animal and vegetable oils), as well as mineral oil and synthetic oil (hereinafter collectively referred to as mineral oils). Specific examples of animal and vegetable oils include palm oil, rapeseed oil, castor oil, lard, and beef tallow. Examples of mineral oils include refined petroleum products containing paraffinic hydrocarbons and naphthenic hydrocarbons, which are commonly used as lubricants. The amount of lubricant may be within a range that ensures stable feeding and prevents the lubricant from forming a pool in the power feed tip; for example, 0.4 g to 2.0 g per 10 kg of welding wire may be used.

[0038] (Surface solids) The solid matter present on the surface of the copper plating layer is copper powder that has fallen off the copper plating or re-adhered during the manufacturing process. It may also be a lubricant used during wire drawing. Specific examples include copper powder, calcium- or sodium-based soaps, etc. Although this is not a particular issue in the present invention, if there is an excessive amount of solid matter, it may adhere and accumulate inside the conduit liner or power feed tip, potentially causing wire feed to stop. Therefore, it is preferable to limit the total amount of solid matter present on the wire surface to 500 mg or less per 10 kg of wire.

[0039] [Wire composition of welding wire] In the present invention, as described above, the composition of the wire may be Fe or an Fe alloy, and examples of such compositions include those specified in JIS standards such as JIS Z 3312:2009 (MAG and MIG welding solid wires for mild steel, high-tensile steel, and low-temperature steel), JIS Z 3313:2009 (flux-cored arc welding 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 filler rods and solid wires for molybdenum steel and chromium-molybdenum steel), JIS Z 3320:2012 (flux-cored arc welding wires for weathering steel), JIS Z 3321:2013 (stainless steel filler rods, solid wires, and steel strips for welding), and JIS Z 3323:2007 (stainless steel arc welding flux-cored wires and filler rods). That is, the steel type is preferably mild steel, high-tensile steel, low-temperature steel, molybdenum steel, chromium-molybdenum steel, or stainless steel. In particular, with regard to the feed control method, a composition based on or similar to the JIS Z 3312:2009 standard, which has a high Fe content, is more preferable for tip wear resistance. Specifically, the wire composition described below is preferred.

[0040] The alloying elements contained in the welding wire according to this embodiment will be described in detail below, along with the reasons for their addition and the reasons for limiting the numerical values. In the following description, the content of each element in the welding wire is defined as the content of the element contained as an alloying element relative to the total mass of the welding wire. The welding wire may be a solid wire composed of alloying elements, or a flux-cored wire in which the flux is formed only of metal powder (hereinafter also referred to as a metal-based flux-cored wire). Furthermore, the welding wire may be a flux-cored wire in which the flux contains even a small amount of compounds (mainly oxides, fluorides, etc.) (hereinafter also referred to as a slag-based flux-cored wire). However, from the viewpoint of manufacturing, which makes it easier to apply Cu-based plating to the wire surface, it is more preferable that the welding wire be a solid wire.

[0041] In a metal-based flux-cored wire or a slag-based flux-cored wire, the alloying elements described below may be contained in the flux-cored wire in the form of metal, in the form of compound, or in the form of both metal and compound, unless otherwise specified. Therefore, regardless of the form in which each element is contained in the flux-cored wire, the element is defined as a value converted into a single element. For example, in the case of Si, the Si content refers to the sum of the Si-converted values ​​of metal Si and Si compounds, and metal Si includes both simple Si and Si alloys.

[0042] (Fe:90% by mass or more) In the present invention, Fe in the welding wire is required to generate a liquid lubricant film during the forward feed period. To obtain more stable tip wear resistance, the Fe content is preferably 90 mass% or more, and more preferably 95 mass% or more. On the other hand, to obtain the tip wear resistance effect of the present invention, the welding wire may be made of pure iron, but from the viewpoint of welding workability and the mechanical properties of the weld metal, it is more preferable to set the Fe content to 99 mass% or less and to contain the elements described below.

[0043] (C: 0.15% by mass or less (including 0% by mass)) C has a deoxidizing effect, and when C is contained in the welding wire, it is possible to obtain the effect of improving the mechanical performance of the weld metal. The C content can be adjusted appropriately depending on the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire does not need to contain C, and the C content may be 0 mass %.

[0044] However, if the welding wire contains an excessive amount of C, the deoxidizing effect becomes strong, and CO is generated near the arc, which may cause an explosion, resulting in the generation of spatter and an increase in the amount of fumes. Therefore, from the viewpoint of welding workability, the C content in the welding wire is preferably 0.15 mass% or less, more preferably 0.10 mass% or less, and even more preferably 0.08 mass% or less, relative to the total mass of the welding wire.

[0045] (Si: 1.10 mass% or less (including 0 mass%)) Si is a deoxidizing agent, and when Si is contained in the welding wire, the effect of improving the mechanical properties of the weld metal can be obtained. The Si content can be adjusted appropriately depending on the required strength, but in this embodiment, as long as the strength can be ensured by other elements, the welding wire does not need to contain Si, and the Si content may be 0 mass%. Note that, in order to obtain the above effect, the Si content is preferably 0.20 mass% or more.

[0046] On the other hand, if the Si content in the wire is excessive, deoxidation proceeds, the amount of oxygen in the molten pool decreases, and the surface tension of the droplets increases, damaging the bead shape. Therefore, the Si content in the welding wire should be 1.10 mass% or less, and preferably 1.00 mass% or less, relative to the total mass of the wire.

[0047] (Mn: 2.30 mass% or less (including 0 mass%)) Like Si, Mn is a deoxidizer, and when Mn is contained in a welding wire, the effect of improving the mechanical properties of the weld metal can be obtained. The Mn content can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, the welding wire does not need to contain Mn, and may even contain 0 mass% Mn. However, Mn is suitable for improving mechanical properties, and it is preferable to preferentially include Mn. To obtain the above effect, the Mn content is preferably 0.90 mass% or more.

[0048] On the other hand, if the Mn content in the wire is excessive, deoxidation proceeds and the amount of oxygen in the molten pool decreases, which increases the surface tension of the droplets and impairs the bead shape. Therefore, the Mn content in the welding wire should be 2.30 mass% or less, and preferably 2.20 mass% or less, relative to the total mass of the wire.

[0049] (Ti: 0.30 mass% or less (including 0 mass%)) Ti is an element that has strong deoxidizing, denitrifying, and desulfurizing properties, and is an element that preferentially forms compounds through these actions. Precipitation of these elements in the weld metal structure can enhance the mechanical performance of the weld metal. The Ti content can be adjusted appropriately depending on the required strength. In this embodiment, however, as long as the strength can be ensured by other elements, the welding wire does not need to contain Ti, and the Ti content may be 0 mass %. To obtain the above effects, the Ti content is preferably 0.02 mass % or more.

[0050] On the other hand, if the welding wire contains an excessive amount of Ti, inclusions in the weld metal may become coarse, and the toughness may be particularly reduced. Therefore, the Ti content in the welding wire is preferably limited to 0.30 mass% or less, and more preferably 0.25 mass% or less, relative to the total mass of the wire.

[0051] (Al: 0.30 mass% or less (including 0 mass%)) Like Ti, Al is an element that strongly deoxidizes, denitrifies, and desulfurizes, and these elements preferentially form compounds due to these actions. Precipitation of these elements in the weld metal structure can enhance the mechanical performance of the weld metal. The Al content can be adjusted appropriately depending on the required strength. In this embodiment, however, as long as the strength can be ensured by other elements, the welding wire does not need to contain Al, and the content may be 0 mass %. To obtain the above effects, the Al content is preferably 0.02 mass % or more.

[0052] On the other hand, if the welding wire contains an excessive amount of Al, the inclusions in the weld metal may become coarse, and the toughness in particular may be reduced. Therefore, the Al content in the welding wire is preferably limited to 0.30 mass % or less, and more preferably 0.25 mass % or less, with respect to the total mass of the wire.

[0053] (Zr: 0.30 mass% or less (including 0 mass%)) Like Al and Ti, Zr is an element that has strong deoxidation, denitrification, and desulfurization properties, and these properties are used to form compounds preferentially. Precipitation of these compounds in the weld metal structure enhances the mechanical properties of the weld metal. The Zr content can be adjusted appropriately depending on the required strength. In this embodiment, however, the welding wire does not need to contain Zr, and Zr may be 0% by mass, provided that the strength can be ensured by other elements. To achieve the above effects, the Zr content is preferably 0.02% by mass or more.

[0054] On the other hand, if Zr is contained in the welding wire in excess, inclusions in the weld metal may become coarse, and the toughness in particular may be reduced. Therefore, the Zr content in the welding wire is preferably limited to 0.30 mass% or less, and more preferably 0.25 mass% or less, with respect to the total mass of the wire.

[0055] (Mg: 0.30% by mass or less (including 0% by mass)) Like Zr, Al, and Ti, Mg is an element that strongly deoxidizes, denitrifies, and desulfurizes, and is an element that preferentially forms compounds through these actions. Precipitation of these elements in the weld metal structure can enhance the mechanical performance of the weld metal. The Mg content can be adjusted appropriately depending on the required strength. In this embodiment, however, as long as strength can be ensured by other elements, the welding wire does not need to contain Mg, and the content may be 0 mass%. To obtain the above effects, the Mg content is preferably 0.02 mass% or more.

[0056] On the other hand, if the welding wire contains an excessive amount of Mg, inclusions in the weld metal may become coarse, and the toughness may be particularly reduced. Therefore, the Mg content in the welding wire is preferably limited to 0.30 mass% or less, and more preferably 0.25 mass% or less, relative to the total mass of the wire.

[0057] (Ni: 4.75 mass% or less (including 0 mass%)) When the welding wire contains Ni, it is possible to obtain the effect of improving the mechanical properties of the weld metal. The Ni content can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, the welding wire does not need to contain Ni, and the Ni content may be 0 mass%. When using the welding wire according to this embodiment, the Ni content is preferably 4.75 mass% or less with respect to the total mass of the welding wire. By suppressing the Ni content as described above, a balance is achieved with other elements that improve mechanical properties, and it is possible to prevent the weld metal from becoming excessively strong.

[0058] (Cr: 0.60% by mass or less (including 0% by mass)) When Cr is contained in the welding wire, the effect of improving the mechanical properties of the weld metal can be obtained. The Cr content can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, the welding wire does not need to contain Cr, and the Cr content may be 0 mass%. Note that the Cr content is preferably 0.60 mass% or less with respect to the total mass of the welding wire. By suppressing the Cr content as described above, a balance is achieved with other elements that improve mechanical properties, and it is possible to prevent the weld metal from becoming excessively strong.

[0059] (Mo: 0.90 mass% or less (including 0 mass%)) When Mo is contained in the welding wire, it is possible to obtain the effect of improving the mechanical properties of the weld metal. The Mo content can be adjusted appropriately depending on the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire does not need to contain Mo, and the Mo content may be 0 mass%. The Mo content is preferably 0.90 mass% or less with respect to the total mass of the welding wire. By suppressing the Mo content as described above, a balance is achieved with other elements that improve the mechanical properties, and it is possible to prevent the weld metal from becoming excessively strong.

[0060] (Cu (excluding plated Cu): 0.50 mass% or less (including 0 mass%)) When Cu is contained in the welding wire, the effect of improving the mechanical properties of the weld metal can be obtained. The Cu content can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, the welding wire does not need to contain Cu, and it may even be 0 mass %. The Cu content in the welding wire is preferably 0.50 mass % or less with respect to the total mass of the welding wire. By suppressing the Cu content as described above, a balance is achieved with other elements that improve mechanical properties, and it is possible to prevent the weld metal from becoming excessively strong.

[0061] (Nb: 0.50 mass% or less (including 0 mass%)) (V: 0.50% by mass or less (including 0% by mass)) When Nb and V are contained in the welding wire, the effect of improving the mechanical properties of the weld metal can be obtained. The contents of Nb and V can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, the welding wire does not need to contain Nb or V, and may contain 0 mass%. The Nb content and V content in the welding wire are preferably 0.50 mass% or less, respectively, with respect to the total mass of the welding wire. By suppressing the Nb content and V content as described above, a balance with other elements that improve mechanical properties can be achieved, and excessive strength of the weld metal can be suppressed.

[0062] (B: 0.0050% by mass or less (including 0% by mass)) When the welding wire contains B, it is possible to obtain the effect of improving the mechanical properties of the weld metal. The B content can be adjusted appropriately depending on the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire does not need to contain B, and the B content may be 0 mass%. The B content is preferably 0.0050 mass% or less with respect to the total mass of the welding wire. By suppressing the B content as described above, a balance is achieved with other elements that improve mechanical properties, and it is possible to prevent the weld metal from becoming excessively strong.

[0063] (P: 0.050% by mass or less (including 0% by mass)) (S: 0.050% by mass or less (including 0% by mass)) P and S are elements that affect the cracking resistance of the weld metal, and the lower the P and S contents in the welding wire, the better the cracking resistance of the weld metal, so the welding wire according to this embodiment does not need to contain P and S, and may contain 0 mass %. Note that when the welding wire contains P and S, from the viewpoint of cracking resistance, the P and S contents in the welding wire are preferably 0.050 mass % or less with respect to the total mass of the welding wire.

[0064] (Remainder: unavoidable impurities) In this embodiment, the balance of the alloy elements of the wire preferably used is 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, and more preferably 0.0050% by mass or less, based on the total mass of the wire. Furthermore, the total content of these unavoidable impurities is preferably 0.0200% by mass or less, based on the total mass of the wire.

[0065] (wire diameter) In the welding wire according to this embodiment, the wire diameter (diameter) is not particularly limited, but a wire having a diameter specified in welding material standards such as AWS or JIS can be used.

[0066] (Wire manufacturing) The welding wire according to this embodiment is not particularly limited in its manufacturing method, and no special manufacturing conditions are required, and it can be manufactured by a conventional method. For example, in the case of a solid wire, a steel containing the above alloy elements in a specified content is melted to obtain an ingot. Next, the ingot is subjected to hot forging or the like as needed, followed by hot rolling and cold wire drawing to form a wire. Thereafter, the obtained wire is annealed at a temperature of about 500 to 900°C as needed, pickled, copper plated as needed, and further subjected to finish wire drawing as needed to obtain a target wire diameter. Thereafter, a lubricant is applied as needed, and the welding wire can be manufactured.

[0067] (Feeding control method) Next, the conditions for the feed control method according to this embodiment will be described in detail below.

[0068] [Welding System] Next, an embodiment of a system for implementing the feed control method used in the present invention will be described in detail with reference to the drawings. Note that this embodiment is an example of a system using a welding robot, and the welding control method according to the present invention is not limited to the configuration of this embodiment. For example, an automatic welding device using a cart instead of a welding robot body may be applied, or a portable, small welding robot may be applied. Furthermore, in this embodiment, the tip wear suppression effect will be described using as an example the system configuration of a short-circuit suppression type feed control method, in which tip wear is particularly noticeable.

[0069] In this embodiment, additive manufacturing technology utilizing the gas-shielded arc welding method of the present invention is also useful, specifically, in wire and arc additive manufacturing (WAAM). The term additive manufacturing is sometimes broadly used to refer to additive manufacturing or rapid prototyping, but in the present invention, the term additive manufacturing is used consistently. When the method of the present invention is utilized in additive manufacturing technology, "welding" can be rephrased as "deposition," "additive manufacturing," or "additive manufacturing." For example, when treated as welding, it is referred to as "welding conditions," but when the present invention is utilized as additive manufacturing, it can be rephrased as "deposition conditions," or when the present invention is utilized as additive manufacturing, it can be rephrased as "welding system," but when the present invention is utilized as additive manufacturing, it can be rephrased as "additive manufacturing system."

[0070] 5 is a schematic diagram showing an example configuration of a welding system 50 according to this embodiment. 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 push motor 180, and a wire buffer 190. Push motor 180 feeds welding wire 100.

[0071] Welding power source 140 is connected to welding robot 110 via a positive power cable (not shown) so that current can be applied to welding wire 100, and is connected to workpiece (hereinafter also referred to as "base material") 200 via a negative power cable (not shown). This connection is for welding with reverse polarity. When welding with positive polarity, the polarity of welding power source 140 can be reversed.

[0072] Furthermore, the welding power source 140 and the push motor 180 are connected by a signal line, and the feed speed of the welding wire can be controlled. In the feed control of this embodiment, the push motor 180 rotates only in the forward direction, and the servo motor 170, which will be described later, is switched between the forward and reverse directions.

[0073] The welding robot 110 is equipped with a welding torch 111 as an end effector. The welding torch 111 has a current-carrying mechanism, i.e., a contact tip, that applies current to the welding wire 100. The gas-shielded arc welding method, gas-shielded arc welding system, and welding wire according to the present invention provide this contact tip with excellent tip wear resistance. The welding wire 100 generates an arc from its tip when current is passed through the contact tip, and the generated heat welds the workpiece 200, which is the welding target.

[0074] The welding torch 111 also includes a shielding gas nozzle, which serves as a mechanism for ejecting the shielding gas. While the shielding gas is not particularly limited, a gas composition that exhibits globular transition is preferable due to the characteristics of the control used in this embodiment. Specifically, it is preferable for the gas to contain at least one gas with a high potential gradient: carbon dioxide, nitrogen, hydrogen, or oxygen. From the viewpoint of versatility, in the case of a mixed gas with argon gas (hereinafter also referred to as "Ar gas"), a system containing at least 10% by volume of carbon dioxide is more preferable, a system containing 90% by volume or more of carbon dioxide is even more preferable, and carbon dioxide alone is even more preferable. The shielding gas is supplied from a shielding gas supply device (not shown).

[0075] Servo motor 170 is provided near welding torch 111. Servo amplifier 160 connected to servo motor 170 controls servo motor 170. In this embodiment, welding torch 111 is configured independent of servo motor 170, but welding torch 111 may be configured to include servo motor 170 inside. Servo motor 170 switches between forward and reverse rotation based on a forward / reverse feed command to control feed. Servo amplifier 160 also enables high-speed calculation processing and includes a forward / reverse feed command generation unit 161, as described below.

[0076] A wire buffer 190 is disposed between the push motor 180 and the servo motor 170. Because the push motor 180 feeds the wire only in the forward direction and the servo motor 170 feeds the wire in both the forward and reverse directions, the feed directions of the push motor 180 and the servo motor 170 may differ. This can create a situation where a large load is likely to be placed on the wire within the feed path. To enable appropriate feed control even in such a feeding situation, the wire buffer 190 is provided to suppress buckling of the wire.

[0077] In this embodiment, the specific configuration of workpiece 200 is not particularly important, and welding conditions such as joint shape, welding posture, and groove shape are also not particularly important. Welding control device 120 mainly controls the operation of welding robot 110. Therefore, welding control device 120 can also be referred to as a robot controller. Welding control device 120 holds teaching data that predefines the operation pattern, welding start position, welding end position, welding conditions, weaving operation, etc. of welding robot 110, and instructs welding robot 110 on these data to control the operation of welding robot 110. Furthermore, welding control device 120 provides welding conditions such as welding current, welding voltage, and feed speed to welding power source 140 during welding work in accordance with the teaching data.

[0078] As shown in FIG. 5, welding system 50 of the present embodiment is configured such that welding control device 120 is independent from welding power source 140, but welding control device 120 may be provided within welding power source 140.

[0079] Controller 150 is connected to welding control device 120, and creates or displays a program for operating welding robot 110, inputs teaching data, etc. Information input by the user to controller 150 is provided to welding control device 120. Controller 150 may also have a function for manually operating welding robot 110. The connection between controller 150 and welding control device 120 may be wired or wireless.

[0080] In response to a command from welding control device 120, welding power source 140 supplies power to welding wire 100 and workpiece 200, thereby generating an arc between welding wire 100 and workpiece 200. In addition, in response to a command from welding control device 120, welding power source 140 outputs a control signal for push motor 180.

[0081] Next, the functional configuration of welding system 50 according to this embodiment will be described in detail with reference to FIGS. 6 and 7. FIG. 6 is a block diagram showing a schematic configuration relating to control of welding power source 140, welding control device 120, and servo amplifier 160 according to this embodiment. In the present invention, a device or group of devices having a function relating to feed control is referred to as a feed control device. In this embodiment, the configuration of welding power source 140, welding control device 120, and servo amplifier 160 relating to feed control is referred to as the feed control device. FIG. 7 is a graph illustrating an example of the relationship between the wire feed speed, wire tip position, and current detection signal according to this embodiment.

[0082] Welding power source 140 is connected to welding control device 120 via digital communication, and welding control device 120 is connected to servo amplifier 160 via digital communication. That is, servo amplifier 160, welding control device 120, and welding power source 140 are digitally connected in this order in a line configuration. This can be interpreted as a state in which servo amplifier 160 and welding power source 140 are indirectly connected via digital communication. Note that servo amplifier 160, welding power source 140, and welding control device 120 may also be connected in this order in a line configuration. This can be interpreted as a state in which servo amplifier 160 and welding power source 140 are directly connected via digital communication.

[0083] In this embodiment, communication between welding power source 140 and welding control device 120 is via CAN (Controller Area Network), which is one of the industrial field networks, and communication between welding control device 120 and servo amplifier 160 is via EtherCAT (Ethernet for Control Automation Technology) (registered trademark), which is also one of the industrial field networks, but this is not limited to these.

[0084] (Functional configuration of welding power source) The control system 141 of the welding power source 140 is executed, for example, by the welding control device 120 or a computer (not shown) executing a program. The control system 141 of the welding power source 140 includes a current setting unit 36. In this embodiment, the current setting unit 36 ​​has a function of setting various current values ​​that define the welding current flowing through the welding wire 100. The current setting unit 36 ​​has a function of setting the start and end times of each period of current control. The current setting unit 36 ​​has 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 a function of setting the start and end times of each period of the peak period Dap, the fall period Ddwn, the base period Db, and the rise period Dup related to the current control. The wire tip position conversion unit 36B has a function of obtaining information on the tip position of the welding wire 100.

[0085] The various condition settings may be determined based on, for example, setting values ​​input in advance by an operator, a waveform control table prepared in advance, a database of welding conditions, etc. The setting values, table, database, etc. may be stored in any of the components of welding system 50. The setting values, table, database, etc. may be stored in welding control device 120, welding power source 140, etc.

[0086] The various condition settings for the peak period Dap, fall period Ddwn, base period Db, and rise period Dup related to the high current period TIP (in this embodiment, the sum of the Dup and Dap periods) and the low current period TIB (in this embodiment, the sum of the Ddwn and Db periods) may be determined by the waveform control table linear calculation unit 37 based on a waveform control table prepared in advance. In this embodiment, the various condition settings refer to the setting of conditions such as current value, time, or phase.

[0087] The welding current exhibits a pulse waveform in which a high-current period TIP and a low-current period TIB are alternately repeated based on a phase related to the wire tip position (hereinafter referred to as the "wire position phase" or "position phase"). In this embodiment, the timing of the peak period Dap, the fall period Ddwn, the base period Db, and the rise period Dup are controlled based on the wire position phase of 0 to 360° (0 to 2π), where 0° is when the wire tip position is closest to the tip side and 180° is when the wire tip position is closest to the base metal side. The above wire position phase can also be expressed as a case in which the wire position phase based on the tip position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0°.

[0088] Based on the set value of the average feed rate Favg in the welding condition information stored by the control system unit 141, the set current value Iap (hereinafter also referred to as "peak current Iap") for the peak period Dap in the high current period TIP and the set current value Ib (hereinafter also referred to as "base current Ib") for the base period Db in the low current period TIB calculated by the waveform control table linear calculation unit 37 are set in the current setting unit 36. In the present invention, the average welding current ITP AVE The value of is set to a predetermined current value (in this embodiment, the average welding current I AVE By presetting at least the set current value Iap and the wire position phases at which the high current period, which will be described later, starts and ends to optimal values ​​so that the current is higher than Iap, it is possible to perform welding current control that provides good tip wear resistance.

[0089] 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 period TIB, i.e., the time when the current transitions to the base current Ib, may be expressed as the low current start time. The end time of the low current period TIB may be expressed as the time when the base current Ib ends, i.e., the low current end time. The duration (time) of the fall period Ddwn and the duration (time) of the base period Db, which relate to the start and end times of the low current period TIB, are calculated by the waveform control table linear calculation unit 37. The start time of the high current period TIP, i.e., the start time of the rise period Dup, may be expressed as the high current start time, and the end time of the high current period TIP may be expressed as the high current end time.

[0090] As shown in FIG. 7, the timing of the high current end time is preferably determined by a set period d1 when the wire position phase starts at 0°, and the timing of the high current start time is preferably determined by a set period d2 when the high current end time starts. This set period may be set by phase. For example, if d1 is set to 190° and d2 is set to 120°, the high current period ends when the wire position phase is 190° (d1) and starts when the wire position phase is 310° (d1+d2). While the setting method is described above using d1 and d2, it may also be set using the value of d1 and the value of d1+d2. In this embodiment, d1 is preferably set in the range of 100° to 200°, and d2 is preferably set so that d1+d2 (the wire position phase at which the high current period starts) is in the range of 280° to 350°. For example, if you want to set d1 to 180° and make d1 + d2 340°, you can set d2 to 160°. By setting d1 and d2 as above, good tip wear resistance can be achieved.

[0091] Furthermore, the set value of the peak current Iap is preferably set in the range of 300 to 650 A. The set value of the peak current Iap may be set in stages so that the current in the latter half of the high current period TIP becomes higher. In this way, by selecting and setting at least one value from the range of 300 to 650 A as the set value of the peak current Iap, a liquid lubricant film can be stably generated and good tip wear resistance can be obtained.

[0092] Note that the various start times, end times, etc. described above are explained based on time. However, processing may be performed by converting the value of the wire position phase into time or the cycle cyc, using the value of the wire position phase as the reference. In other words, since the values ​​of the wire position phase, time, and cycle cyc are mutually convertible, control may be performed based on any value.

[0093] Furthermore, the wire tip position converter 36B determines the wire tip position based on the phase synchronization signal and the phase delay correction amount signal from the servo amplifier 160. In this embodiment, the wire tip position may be expressed using an angle (0 to 2π) as the wire position phase, as described above.

[0094] The phase delay correction amount signal is output from phase delay correction unit 38. Phase delay correction unit 38 has a database (not shown). This database stores data that is calculated in advance for each welding condition, the difference between periodic setting information and the operation signal of the actual forward / reverse feed operation of servo motor 170. For example, when the welding condition is a wire forward / reverse frequency, the phase delay correction amount is determined based on the database in accordance with the value of the wire forward / reverse frequency to be used, and is output from phase delay correction unit 38 as a phase delay correction amount signal.

[0095] The main power supply circuit of the welding power supply 140 is composed of a three-phase AC power supply (hereinafter also referred to as "AC power supply") 1, a primary side rectifier 2, a smoothing capacitor 3, a switching element 4, a transformer 5, a secondary side rectifier 6, and a reactor 7.

[0096] AC power input from AC power supply 1 is full-wave rectified by primary-side rectifier 2, and further smoothed by smoothing capacitor 3 to be converted into DC power. Next, the DC power is converted into high-frequency AC power by inverter control using switching element 4, and then converted into secondary-side power via transformer 5. The AC output of transformer 5 is full-wave rectified by secondary-side rectifier 6, and further smoothed by reactor 7. The output current of reactor 7 is given to the contact tip as an output from the main power supply circuit, and is passed through welding wire 100, which serves as a consumable electrode.

[0097] The welding wire 100 is fed by a push motor 180 and a servo motor 170, generating an arc between the welding wire 100 and the base material 200. A forward feed period during which the tip of the welding wire 100 moves toward the base material 200 is referred to as a forward feed period TP. A reverse feed period during which the tip of the welding wire 100 moves in a direction opposite to the direction in which the base material 200 is located is referred to as a reverse feed period TN. In this embodiment, the feed motor periodically feeds the welding wire 100, with the forward feed period TP and the reverse feed period TN combined forming one cycle. Note that the tip of the welding wire usually refers to the tip of the wire when ignoring the presence of droplets hanging from the wire tip. In other words, the wire melted by the arc is considered to have immediately transferred to the base material 200.

[0098] The feeding of the welding wire 100 by the push motor 180 is controlled by a control signal from the push feeder control unit 39. The average value of the feeding speed is approximately the same as the melting speed. In this embodiment, the feeding of the welding wire 100 by the push motor 180 is also controlled by the welding power source 140.

[0099] Further, the push feeder control unit 39 performs control in accordance with the state of the wire buffer 190. In this embodiment, the wire buffer 190 is provided with a wire slack portion (a gap into which the wire can escape when it becomes loose due to the influence of feeding between the motors) so that a large load is not applied to the wire in the feeding path between the push motor 180 and the servo motor 170, and an absolute encoder, which is a sensor built into the wire buffer 190, detects the buffered amount of wire as a rotation angle. The detected value is converted into an analog signal by a serial-to-analog converter 191, and an electrical angle calculation unit calculates the electrical angle. The calculated electrical angle is input to an A / D input unit 40 of the welding power source.

[0100] A differential signal obtained by calculating the difference between the electrical angle from the A / D input unit 40 and a reference value of the electrical angle preset in the electrical angle adjustment unit 41 is input to the push feeder control unit 39. Based on this differential signal, the push feeder control unit 39 controls the push motor 180 to buffer an appropriate amount of wire, thereby performing interference control to prevent a large load from being placed on the feeding system. Note that, although the interference control described above is performed in this embodiment, it is not limited to this. Also, 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 may be used, in which case the serial-to-analog conversion unit 191 may not be provided.

[0101] A voltage setting signal Vap, which is a target value of the voltage to be applied between the welding tip and base metal 200, is provided to current setting unit 36 ​​from voltage setting unit 36C.

[0102] On the other hand, the voltage detection signal Vo is an actually measured value. In this embodiment, the voltage detection signal Vo passes through a low-pass filter LPF, passes through a separation detection unit 33 (described later), and is input to the current setting unit 36 ​​together with a separation detection signal DTR (described later). Note that 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 amplified signal.

[0103] The current setting unit 36 ​​controls the welding current during the peak period Dap so that the length of the arc (hereinafter also referred to as "arc length") remains constant. The current setting unit 36 ​​determines and sets at least the peak period, rise period, base period, and rising period based on the voltage setting signal Vap and the voltage detection signal Vo. The values ​​of the peak current Ip and the base current Ib may be reset. The current setting signal CCset corresponding to the set period or value is output to the current error amplifier (PWM) 34.

[0104] The current error amplifier 34 amplifies the difference between the current setting signal CCset given as a target value and the current detection signal Io detected by the current detector 31, and outputs the amplified current error signal Ed to the inverter driver 30. The inverter driver 30 corrects the drive signal Ec of the switching element 4 using the amplified current error signal Ed.

[0105] A detachment detection signal DTR, which is a signal for detecting the detachment of a droplet from the tip of the welding wire 100, is also input to the current setting unit 36. The detachment detection signal DTR is output from the detachment detection unit 33. The detachment detection unit 33 monitors a change in the voltage detection signal Vo output by the voltage detection unit 32, and detects the detachment of a droplet from the welding wire 100 from the change. Note that the detachment detection unit 33 is an example of a detection means.

[0106] The detachment detection unit 33 detects droplet detachment by, for example, comparing a value obtained by differentiating or second-order differentiating the voltage detection signal Vo after passing through an LPF with a predetermined detection threshold. The detection threshold is pre-stored in a memory unit (not shown). The detachment detection unit 33 may also generate the detachment detection signal DTR based on a change in resistance calculated from the voltage detection signal Vo and the current detection signal Io, which are actual measured values.

[0107] An average feed speed Favg of the welding wire 100 being fed is provided to waveform control table linear calculation unit 37. Average feed speed Favg is stored in advance in feed setting data unit 35. Note that, although feed setting data unit 35 is provided in welding power source 140 in this embodiment, various pieces of information relating to feed settings may be stored in welding control device 120, and the various pieces of information may be output from welding control device 120 to welding power source 140.

[0108] Based on the given average feed speed Favg, the waveform control table linear calculation unit 37 determines values ​​such as the peak current Ip, the base current Ib, the time when the base current Ib starts, and the time when the base current Ib ends, and outputs these values ​​to the current setting unit 36. Note that, since the values ​​of the wire position phase, time, and cycle cyc can be converted into each other as described above, the setting value of the base start phase, etc. may be converted into a value of time or cycle cyc, and the converted value may be output to the current setting unit 36.

[0109] In this embodiment, the average feed speed Favg is input to waveform control table linear calculation unit 37, but a value related to the average feed speed Favg may be input as a set value to waveform control table linear calculation unit 37, and waveform control table linear calculation unit 37 may use the set value as the average feed speed Favg. For example, if a database of average feed speeds Favg and average current values ​​that enable optimal welding for that average feed speed Favg is stored in a storage unit (not shown), the average current value may be used as the set value, and the set value may be used as the average feed speed Favg.

[0110] The feed setting data unit 35 may store set values ​​such as the wire amplitude Wf, the wire forward / reverse frequency Hf, and the wire forward / reverse cycle Tf in addition to the average feed speed Favg. The wire amplitude Wf, the wire forward / reverse frequency Hf, and the wire forward / reverse cycle Tf may be determined based on the input average feed speed Favg. The feed setting data unit 35 may also store set values ​​other than these as feed setting data. In this embodiment, the value of the wire amplitude Wf ​​refers to the wave height Wh shown in FIG. 7. In other words, the set value of the wire amplitude Wf ​​is set to be the same as the wave height Wh.

[0111] In this embodiment, a period in which the feed rate is higher than the average feed rate Favg is defined as a forward feed period, and a period in which the feed rate is lower than the average feed rate Favg is defined as a reverse feed period, resulting in feed in which forward and reverse feed periods alternate (hereinafter abbreviated as "amplitude feed"). Note that a period in which the feed rate is lower than the average feed rate Favg refers to a rate lower than the average feed rate Favg, and includes a negative feed rate, i.e., a rate at which the wire tip moves in the opposite direction from the position of the base material 200. The wire amplitude Wf ​​determines the range of change relative to the average feed rate Favg, and the wire forward / reverse cycle Tf determines the time for change in the wire amplitude, which is the repetition unit. The wire forward / reverse frequency Hf is the reciprocal of the wire forward / reverse cycle Tf. In this embodiment, the set values ​​of the wire amplitude Wf ​​and the wire forward / reverse frequency Hf are not particularly limited, but from the viewpoint of welding workability, it is preferable to select and set, for example, the wire forward / reverse frequency from the range of 50 Hz to 150 Hz and the wire amplitude indicated by the wave height Wh from the range of 3.3 mm to 6.3 mm.

[0112] The average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse cycle Tf stored in feed setting data unit 35 are input from digital communication unit 42 to digital communication unit 122 of welding control device 120. In this embodiment, the communication of these feed setting data is performed via CAN communication.

[0113] Welding sequence unit 43 processes each task in the order of idle, gas flow, arc start, welding in progress, and anti-stick based on the teaching data. Note that in Fig. 6, welding condition information held by welding control device 120 is shown enclosed by a dashed line within welding power source 140 for convenience.

[0114] (Functional configuration of welding control device) As described above, feed setting data such as average feed rate Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse cycle Tf are input to digital communication unit 122 of welding control device 120 via CAN communication from feed setting data unit 35 of welding power source 140. Welding control device 120 has digital communication unit 123 for outputting this feed setting data to digital communication unit 162 of servo amplifier 160. In this embodiment, digital communication unit 123 of welding control device 120 and digital communication unit 162 of servo amplifier 160 are connected via EtherCAT (registered trademark) communication.

[0115] (Servo amplifier functional configuration) Feed setting data such as average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse cycle Tf are input to digital communication unit 162 of servo amplifier 160 via EtherCAT (registered trademark) communication. Forward / reverse feed command generation unit 161 of servo amplifier 160 generates a feed command for forward feed or reverse feed based on the setting information input via digital communication, i.e., the feed setting data. Forward / reverse feed command generation unit 161 calculates an amplitude feed speed Ff from the wire amplitude Wf ​​and the wire forward / reverse cycle Tf, and outputs a feed speed command signal Fw to servo motor 170 based on the amplitude feed speed Ff and average feed speed Favg.

[0116] In this embodiment, the feeding speed command signal Fw is expressed by the following equation. Fw=Ff+Favg...Formula (A)

[0117] Furthermore, the forward / reverse feed command generation unit 161 may detect at which wire position phase of the amplitude feed the detachment occurred, based on the detachment detection signal DTR provided by the detachment detection unit 33. However, the feed speed command signal Fw expressed by equation (A) is generated only when the detachment of a droplet from the tip of the welding wire 100 is detected within an expected period. If the detachment of a droplet is not detected within the expected period, the forward / reverse feed command generation unit 161 may switch the feed speed command signal Fw to feed control at a constant speed. For example, the forward / reverse feed command generation unit 161 switches the feed speed command signal Fw to feeding at an average feed speed Favg. The switch from feeding at the average feed speed Favg to the feed control expressed by equation (A) is determined depending on the timing at which the detachment of a droplet is detected.

[0118] Based on the feed speed command signal Fw, servo amplifier 160 performs inverter control of servo motor 170. Furthermore, a synchronization signal generating unit 163 of servo amplifier 160 outputs a phase synchronization signal to welding power source 140. This phase synchronization signal is generated based on the feed speed command signal Fw. [Example]

[0119] The present invention will be described in more detail below, but the present invention is not limited to these examples and can be implemented with modifications within the scope of the invention, all of which are included in the technical scope of the present invention. Furthermore, the welding conditions described here are merely examples, and the present embodiment is not limited to the following welding conditions.

[0120] [Gas-shielded arc welding] Gas-shielded arc welding was performed using welding wires with various compositions using a feed control method, and the amount of tip wear was evaluated. The compositions of the welding wires used are shown in Figure 8, and the feed control conditions are shown in Figure 9. Other welding conditions are also shown below. Figure 8 shows the compositions of the welding wires used in this embodiment. Figure 9 shows the feed control conditions in this embodiment.

[0121] [Other welding conditions] Base material: SS400 Welding position: Downward Shielding gas: 100% CO2 by volume Average current: 280~320A Average voltage: 34~40V Tip-to-workpiece distance: 25 mm Wire feed rate: 14~16m / min Welding speed: 30cm / min Welding time: 1 hour

[0122] [Evaluation test] (Tip wear test) 10 shows 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 was measured as the amount of wear. A wear amount of 2.0 mg or less was rated as pass (rating D), less than 1.4 mg was rated as preferable (rating C), less than 1.0 mg was rated as more preferable (rating B), and less than 0.5 mg was rated as even more preferable (rating A). On the other hand, a wear amount of more than 2.0 mg was rated as failing (rating E) because the amount of wear was too large. Note that a negative amount of wear (the weight after welding is greater) is a phenomenon that occurs when Fe or Cu from the welding wire side is transferred to the contact tip side, and indicates that wear of the contact tip is suppressed.

[0123] [(amount of solid lubricant / square of current during forward feeding period) x 10 8 ] FIG. 11 is a diagram showing the relationship between the amount of solid lubricant, the square of the current during the normal feeding period, and the amount of wear.

[0124] The average current during the forward feed period, which allows stable formation of a liquid lubricant film, is required to stably melt the wire's Fe and plated Cu, so the higher the value, the better. It is preferably 420 A or higher, more preferably 450 A or higher, and even more preferably 480 A or higher. Furthermore, the formation of a liquid lubricant film also depends on the amount of sulfide, which is a solid lubricant. In this embodiment, the value of Equation 1, derived from the amount of sulfide and the average current during the forward feed period, was used as an index of tip wear. The value of Equation (B) is preferably 45 or higher, and more preferably 50 or higher.

[0125] (Amount of solid lubricant / square of current during positive feeding period) x 10 8 )≧45...Equation (B)

[0126] If the average current during the forward feed period is low, the Fe in the wire and the plated Cu do not melt stably, so this parameter is preferably adopted when the current is 420 A or more. Here, although Test Nos. T13 and T14 of this example shown in Figure 10 are within the range of the parameters of formula (B), they are outside the range of the present invention, and therefore the amount of tip wear is large.

[0127] The present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0128] As described above, the present specification discloses the following:

[0129] (1) A gas-shielded arc welding method employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, The welding wire is Fe or an Fe-based alloy, Plating with Cu or Cu-based alloy, and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface, The feed control method includes a step of controlling at least a welding current in accordance with a tip position of the welding wire, In the step of controlling at least the welding current, The welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and an average welding current ITP during the forward feed period AVE is a current higher than the predetermined current value, When a wire position phase based on the tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, the wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°. Gas shielded arc welding method.

[0130] According to this gas-shielded arc welding method, excellent tip wear resistance can be obtained regardless of the current range.

[0131] (2) The gas-shielded arc welding method according to (1), characterized in that the feed control method is a method of feeding the welding wire at the average wire feed speed while periodically repeating forward and reverse feed in accordance with a wire forward / reverse frequency, with a forward feed period and a reverse feed period being one cycle.

[0132] According to this gas-shielded arc welding method, excellent tip wear resistance can be obtained regardless of the current range in gas-shielded arc welding to which a short-circuit suppression type feed control method is applied.

[0133] (3) The gas-shielded arc welding method according to (2), characterized in that in the step of controlling at least the welding current, the high current period is switched to the low current period at a wire position phase d1 set in a range of 100° to 200°.

[0134] According to this gas-shielded arc welding method, abrasive wear on the contact surface of the contact tip can be further suppressed.

[0135] (4) The gas-shielded arc welding method according to (1), wherein the solid lubricant contains at least one of molybdenum disulfide and tungsten disulfide.

[0136] According to this gas-shielded arc welding method, the sulfide acts as a solid lubricant to stabilize the feedability until it reaches the contact tip, and acts to generate a liquid lubricant film on the contact surface within the contact tip, thereby suppressing adhesive wear.

[0137] (5) The gas-shielded arc welding method according to (1), characterized in that oil is applied to the surface of the welding wire, and the solid lubricant is contained in the oil.

[0138] According to this gas-shielded arc welding method, the sulfide is mixed with lubricating oil and applied to the plated surface of the welding wire, and the amount of adhesion can be controlled by adjusting the mixture ratio.

[0139] (6) The gas-shielded arc welding method according to (1), characterized in that the amount of the solid lubricant is 0.05 to 0.40 g per 10 kg of wire.

[0140] According to this gas-shielded arc welding method, a liquid lubricating film can be appropriately generated.

[0141] (7) A gas-shielded arc welding system employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, a welding wire feed control device; The welding wire is Fe or an Fe-based alloy, Plating with Cu or Cu-based alloy, and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface, the feed control device controls at least the welding current in accordance with the tip position of the welding wire; The welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and the feed control device controls the welding current to be equal to an average welding current ITP during the forward feed period. AVEis a current higher than a predetermined current value, When a wire position phase based on the tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, the wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°. Gas shielded arc welding system.

[0142] This gas-shielded arc welding system can provide excellent tip wear resistance regardless of the current range.

[0143] (8) A welding wire for use in a feed control method that alternately repeats forward feed and reverse feed, controls an average welding current at least during a period of forward feed according to a tip position of the welding wire so as to be higher than a predetermined current value, and feeds the welding wire at a predetermined average wire feed speed, Fe or an Fe-based alloy, Plating with Cu or Cu-based alloy, and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface. Welding wire.

[0144] When these welding wires are used in gas-shielded arc welding to which the above-described feed control method is applied, excellent tip wear resistance can be obtained regardless of the current range.

[0145] (9) The welding wire is With respect to the total mass of the welding wire, Fe: 90% by mass or more, C: 0.15% by mass or less, Si: 1.10% by mass or less, Mn: 2.30% by mass or less, Ti: 0.30% by mass or less, Al: 0.30% by mass or less, Zr: 0.30% by mass or less, Mg: 0.30% by mass or less, Ni: 4.75% by mass or less, Cr: 0.60% by mass or less, Mo: 0.90% by mass or less, Cu: 0.50% by mass or less, Nb: 0.50% by mass or less, V: 0.50% by mass or less, B: 0.0050% by mass or less, P: 0.050% by mass or less, S: 0.050% by mass or less, The welding wire according to (8), characterized in that it contains

[0146] When these welding wires are used in gas-shielded arc welding to which the above-described feed control method is applied, excellent tip wear resistance can be obtained regardless of the current range. [Explanation of symbols]

[0147] 1 AC power supply 2 Primary rectifier 3 smoothing capacitors 4 Switching elements 5. Transformer 6 Secondary rectifier 7 Reactor 30 Inverter drive unit 31 Current detection section 32 Voltage detection section 33 Separation detection unit 34 Current error amplifier 35 Feed setting data section 36 Current setting section 37 Waveform control table linear calculation section 38 Phase delay correction unit 39 Push feeder control section 40 A / D input section 41 Electrical angle adjustment unit 42 Digital Communications Department 43 Welding Sequence Division 50 Welding System 100 welding wire 110 Welding Robot 111 Welding Torch 120 Welding control device 122, 123 Digital Communications Department 140 Welding power source 141 Control System Department 150 Controller 160 Servo amplifier 161 Forward / reverse feed command generation unit 162 Digital Communications Department 163 Synchronization signal generator 170 Servo motor 180 Push Motor 190 Wire Buffer 191 Serial to Analog Converter 200 Work

Claims

1. A gas-shielded arc welding method employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, The welding wire is Fe or an Fe-based alloy; plating with Cu or a Cu-based alloy; and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface, The feed control method includes a step of controlling at least a welding current in accordance with a tip position of the welding wire, In the step of controlling at least the welding current, The welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and an average welding current ITP during the forward feed period ＡＶＥ is a current higher than the predetermined current value, When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°. Gas shielded arc welding method.

2. 2. The gas-shielded arc welding method according to claim 1, wherein the feed control method is a method of feeding the welding wire at the average wire feed speed while periodically repeating forward and reverse feed in accordance with a wire forward / reverse frequency, with a forward feed period and a reverse feed period forming one cycle.

3. In the step of controlling at least the welding current, 3. The gas-shielded arc welding method according to claim 2, wherein the high current period is switched to the low current period at a wire position phase d1 set in a range of 100° to 200°.

4. 2. The gas shielded arc welding method according to claim 1, wherein the solid lubricant contains at least one of molybdenum disulfide and tungsten disulfide.

5. 2. The gas-shielded arc welding method according to claim 1, wherein oil is applied to a surface of the welding wire, and the solid lubricant is contained in the oil.

6. 2. The gas shielded arc welding method according to claim 1, wherein the amount of the solid lubricant is 0.05 to 0.40 g per 10 kg of wire.

7. A gas-shielded arc welding system employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed, a welding wire feed control device; The welding wire is Fe or an Fe-based alloy; plating with Cu or a Cu-based alloy; and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface, the feed control device controls at least the welding current in accordance with the tip position of the welding wire; The welding current has at least a high current period in which the current is higher than a predetermined current value and a low current period in which the current is lower than the predetermined current value, and the feed control device controls the welding current to be equal to an average welding current ITP during the forward feed period. ＡＶＥ is a current higher than a predetermined current value, When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°. Gas shielded arc welding system.

8. 1. A welding wire for use in a feed control method that alternately repeats forward feed and reverse feed, and controls an average welding current at least during a period of forward feed to be higher than a predetermined current value according to a tip position of the welding wire, and feeds the welding wire at a predetermined average wire feed speed, Fe or an Fe-based alloy; plating with Cu or a Cu-based alloy; and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface. Welding wire.

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

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