Method for gas-mixture-shielded welding using solid welding wire

Abstract

A method for gas-mixture-shielded welding using a solid welding wire, the method involving a gas mixture being used as a welding shielding gas, and a solid welding wire being used for welding. Oxygen is added to the gas mixture. The gas mixture comprises carbon dioxide and oxygen, wherein in percentage by volume, the oxygen accounts for 1-5%, and the carbon dioxide accounts for 95-99%. Compared with simply using carbon dioxide as a shielding gas, the present invention has the advantages that the stability of an electric arc and the phenomenon of splashing are improved immediately; when the method of the present invention is used for replacing flux-cored welding, the welding cost is greatly reduced, pollution caused to the surroundings and the atmospheric environment during welding is greatly reduced, and dust and harmful gases are reduced by about 70%; moreover, compared with performing welding by using a flux-cored welding wire, the electric energy of the welding method of the present invention is reduced by 20%.

Description

A solid wire mixed gas shielded welding method Technical Field

[0001] The invention relates to the technical field of gas shielded welding, in particular to a solid wire mixed gas shielded welding method. Background Art

[0002] Conventional gas shielded welding uses a fusible wire as an electrode. The arc burning between the wire and the workpiece acts as a heat source to melt the wire and the base metal. The wire continues to melt as molten droplets transfer into the weld pool, where they fuse with the molten base metal and condense to form the weld metal. During the welding process, a shielding gas mixture is used to protect the arc, the weld pool, and the surrounding base metal from the harmful effects of the surrounding air.

[0003] Welding wire is generally classified into two types based on its structural form: flux-cored wire and solid-core wire. The advantages of using flux-cored wire include arc stability, a wide range of applications, minimal spatter, excellent workability, and the ability to weld in both vertical and overhead positions. However, its disadvantages are its high price and the generation of significant amounts of toxic and hazardous gases and smoke, which pollute the surrounding environment. Flux-cored wire uses high welding currents and has a high melting rate, but its weld filler deposition rate is low, resulting in relatively low welding efficiency. The advantages of using solid-core wire include its low price, economical cost, and low pollution levels. However, its disadvantages include poor arc stability, extremely poor weld pool stability, high spatter levels during welding, which can easily burn the welder. Metal spatter around the weld seam seriously affects the surface quality of the base metal, requiring post-weld grinding and cleaning. Solid-core wire welding is not suitable for vertical and overhead positions. Therefore, the industry needs a welding method that combines the advantages of both flux-cored and solid-core wires while addressing their disadvantages.

[0004] After searching the literature in the relevant technical field, an invention patent with application number "CN201310033048.8" in the field of gas shielded welding and titled "A ternary mixed shielding gas and welding method for MIG welding of aluminum alloys" was obtained. The technical solution disclosed in the above invention patent is: the ternary mixed shielding gas includes helium, argon and a small amount of nitrogen, which are distributed by volume as follows: helium: 20%~40%, argon: 59.974%~79.995%, and nitrogen: 0.005%~0.026%. The technical problem solved by the above technical solution is to improve the fracture resistance and fatigue performance of aluminum alloy welded structures. The technical solution cannot solve welding problems other than aluminum alloys, such as carbon steel. Compared with the present invention, the technical solution disclosed in the above invention patent and the technical problem solved are different. Summary of the Invention

[0005] The purpose of the present invention is to provide a solid wire mixed gas shielded welding method, which, when used for welding operations, combines the advantages of flux-cored wire and solid wire welding while overcoming the disadvantages of both.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A solid wire mixed gas shielded welding method is disclosed. The solid wire mixed gas shielded welding method uses a mixed gas as welding shielding gas, and oxygen is added to the mixed gas.

[0008] In the above-mentioned solid wire mixed gas shielded welding method, the mixed gas includes carbon dioxide gas and oxygen, and the composition is distributed according to the gas volume percentage, with oxygen accounting for 1% to 5% and carbon dioxide accounting for 95% to 99%.

[0009] The above-mentioned solid wire mixed gas shielded welding method uses solid wire for welding.

[0010] In the above-mentioned solid wire mixed gas shielded welding method, the carbon dioxide gas in the carbon dioxide gas source enters the mixing tee through a pipeline after the flow rate is controlled by the carbon dioxide flow control valve; the oxygen in the oxygen gas source enters the mixing tee through a pipeline after the flow rate is controlled by the oxygen flow control valve; the carbon dioxide gas and oxygen are mixed at the mixing tee; the mixed gas is output as a mixed gas through the machine head and the welding gun during welding; the welding machine is turned on, and the solid welding wire is continuously fed into the welding area as an electrode, and the arc burning between the welding wire and the workpiece to be welded is used as a heat source to melt the welding wire and the base metal, and the mixed gas is continuously delivered to the welding area through the nozzle of the welding gun.

[0011] The present invention has the following advantages:

[0012] First, using the mixed gas of the present invention as the shielding gas for welding with solid wire immediately improves arc stability and spatter compared to using only carbon dioxide as the shielding gas. The fluidity of the liquid metal, the volume of the molten pool, and the welder's operating experience during welding are similar to those of flux-cored wire welding. The inspection report numbered "(2023) YKJC-013" issued by Qinhuangdao Yanke Metal Materials Testing Co., Ltd. after welding tests shows that the test data for tensile strength, impact strength, bending strength, joint hardness, and macroscopic cross-section acid etching fully meet or significantly exceed the corresponding national standards for weld quality. Second, using the present invention instead of flux-cored welding significantly reduces welding costs. Because flux-cored wire contains approximately 20% flux, the effective rate of molten metal recovery during welding is approximately 80%. Using solid wire, the effective rate is 100%. After deducting losses such as spatter, the actual purchase amount of solid wire is approximately 15% lower than that of flux-cored wire for the same welding volume. The price difference between flux-cored welding wire and solid welding wire in the welding wire market is more than 30%. Therefore, under the same welding conditions, the present invention can reduce welding costs by more than 30%. Third, the welding power used during welding is saved by about 20% compared with flux-cored welding wire. Since flux-cored welding wire requires a larger heat input, its current is usually between 200~220A. However, since solid welding wire requires a smaller heat input, the current is only about 150~160A. Therefore, under the condition of a certain voltage, the power saving of the present invention is 20% lower than that of flux-cored welding wire. Fourth, the pollution of the surrounding and atmospheric environment by the welding process is greatly improved. There is no powder in solid welding wire, so the harmful gases and dust generated by the powder under high temperature will be greatly reduced and disappear. Compared with flux-cored welding wire, the dust and harmful gases of the present invention are reduced by about 70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of the present invention;

[0014] The numbers in the figure represent: 1. carbon dioxide gas source, 2. oxygen gas source, 3. carbon dioxide flow control valve, 4. oxygen flow control valve, 5. oxygen gas check valve, 6. carbon dioxide gas check valve, 7. mixing tee, 8. electric welding machine, 9. machine head, 10. welding gun. DETAILED DESCRIPTION

[0015] The present invention provides a solid wire mixed gas shielded welding method, which uses a mixed gas as the welding shielding gas and a solid wire for welding. Oxygen is added to the mixed gas. The mixed gas includes carbon dioxide gas and oxygen, with the gas volume percentage being 1% to 5% oxygen and 95% to 99% carbon dioxide.

[0016] The present invention provides a solid wire mixed gas shielded welding method, the welding process is as follows: carbon dioxide gas in a carbon dioxide gas source 1 passes through a pipeline, is flow-controlled by a carbon dioxide flow control valve 3, and then enters a mixing tee 7; oxygen in an oxygen gas source 2 passes through a pipeline, is flow-controlled by an oxygen flow control valve 4, and then enters the mixing tee 7; carbon dioxide gas and oxygen are mixed at the mixing tee 7; the mixed gas is output through a machine head 9 and a welding gun 10 for mixed gas protection during welding; the welding machine 8 is turned on, a solid welding wire is continuously fed into the welding area as an electrode, the arc burning between the welding wire and the workpiece to be welded serves as a heat source to melt the welding wire and the base metal, and the mixed gas is continuously fed into the welding area through the nozzle of the welding gun 10.

[0017] In a solid wire mixed gas shielded welding method of the present invention, an oxygen gas check valve 5 and a carbon dioxide gas check valve 6 are provided in the gas transmission pipeline to prevent backflow of gas in the pipeline.

[0018] The technical principle of the solid wire mixed gas shielded welding method of the present invention is as follows:

[0019] 1. After adding a very small amount of oxygen to the shielding gas, since its ionization potential (i.e. electromotive force) is the lowest, the ionization and conductivity in the arc depend on the gas component with low ionization potential (the appropriate amount must be controlled), which improves the reliability of arc initiation and the stability of the arc.

[0020] 2. Oxygen is a diatomic gas that decomposes in a high-temperature arc, absorbing heat and compressing the arc. Therefore, it can increase the electric field strength in the arc and further enhance the stability of the arc.

[0021] 3. Since oxygen is a paramagnetic material, its increase will increase the magnetic induction intensity in the arc, resulting in an increase in the electromagnetic force on the charged particle flow in the arc, further compressing the arc and stabilizing the molten pool.

[0022] 4. In gas shielded welding (regardless of whether using solid or flux-cored wire), the droplet transfers through a short circuit. Spatter generally occurs in two ways. The first is instantaneous short-circuit spatter, which occurs at the initial stage of a short circuit. This occurs immediately after the droplet contacts the molten pool, before it has time to spread and transfer across the surface. The surface tension of the molten pool exerts an effort to pull the droplet into the pool. This short circuit causes a sudden increase in the short-circuit current, rapidly increasing the electromagnetic force that repels the droplet. The interaction between the electromagnetic force and surface tension determines the amount of spatter.

[0023] Flux-cored wire (pure gas shielded) welding is a jet transfer in short-circuit transfer. The molten droplets are small and numerous, the welding current used is large (the horizontal welding current is generally 200-220A), the current density is high, and the electromagnetic force is large and dispersed. When pure gas is used as the shielding body, the surface tension is close to a constant value.

[0024] Solid wire (pure gas + a small amount of oxygen protection) welding is a large drop transfer in short-circuit transfer. The welding current used is small (the horizontal welding current is generally 150-160A), the current density is small, and the electromagnetic force is small and concentrated. When a small amount of oxygen is added to the carbon dioxide gas as a shielding gas, the temperature of the arc column area is slightly increased, the viscosity of the molten pool is reduced, and the surface tension of the molten pool is slightly reduced.

[0025] That is, the electromagnetic force of flux-cored wire is large and dispersed, the droplet volume is small, and the surface tension of the molten pool is constant, which easily forms a large number of small particles and splashes.

[0026] Solid wire has a small and concentrated electromagnetic force, resulting in a large droplet volume and slightly lower surface tension in the molten pool. This tends to cause a small number of larger particles to spatter, meaning that the smaller electromagnetic force makes it difficult to expel the larger droplets.

[0027] Ultimately, the spatter of flux-cored wire (pure single gas protection) is close to that of solid wire (pure single gas + a small amount of oxygen protection).

[0028] In addition, there is no spatter caused by slag droplets in solid wire.

[0029] 5. The explosive spatter of the molten droplet is the spatter caused by the violent release of carbon monoxide gas produced by the intense metallurgical process of carbon and oxygen inside the molten droplet during welding. This spatter phenomenon is generally caused by large current.

[0030] The welding current used in flux-cored wire welding is large (200-220A), and the short-circuit current is also large. Under the action of the large electromagnetic force generated during high-current welding, the molten droplet immediately explodes, causing part of the molten droplet to detach from the end of the welding wire (some may also be pulled into the molten pool under the action of surface tension), and the separated small metal particles form spatter.

[0031] Solid wire welding uses a small welding current (150-160A), a small short-circuit current, a small electromagnetic force, and the surface tension of the molten pool is almost the same as that of the flux core. Therefore, the explosion and splash of the molten droplet are naturally much smaller.

[0032] For the spattering of gas escaping from the molten pool, the spattering of gas escaping from the molten droplets, and the spattering of the molten droplets, whether it is welding with solid wire + shielding gas + a small amount of oxygen or welding with flux-cored wire + pure shielding gas, the two are similar.

[0033] 6. Because oxygen is the most paramagnetic of commonly used gases, adding a small amount of oxygen to the arc during discharge enhances the magnetic field generated by the current magnetic effect. This creates a circular, normal-space current magnetic field perpendicular to the arc. This field further enhances the magnetic compression of the welding plasma, concentrating the welding energy and preventing spatter from escaping. This provides a strong constraint on the high-temperature molten metal in the weld pool, stabilizing it and preventing it from spreading. This effectively addresses the difficulty in controlling the weld pool during horizontal, vertical, and overhead welding of solid wires. Numerous welding tests have demonstrated that paramagnetic shielding gases exhibit this effect.

[0034] 7. In summary, the total spatter volume of welding with solid wire + shielding gas + a small amount of oxygen and flux-cored wire + pure shielding gas is similar. However, the arc stability of welding with solid wire + shielding gas + a small amount of oxygen is slightly better.

[0035] 8. For pure gas shielded welding, carbon dioxide shielding gas has certain oxidizing properties at high temperature. After adding a very small amount of oxygen, the oxygen molecules neutralize its oxidizing effect, making the oxidizing properties, molten pool temperature, liquid metal fluidity, and molten pool volume similar to those of pure carbon dioxide gas protection. Example 1:

[0036] The composition of the mixed gas of the present invention is distributed according to the volume percentage of the gas, with oxygen accounting for 1% and carbon dioxide accounting for 99%.

[0037] Using the above-mentioned mixed gas and a solid welding wire, the carbon dioxide gas in the carbon dioxide gas source 1 passes through a pipeline, is flow-controlled by a carbon dioxide flow control valve 3, and then enters the mixing tee 7; the oxygen in the oxygen gas source 2 passes through a pipeline, is flow-controlled by an oxygen flow control valve 4, and then enters the mixing tee 7; the carbon dioxide gas and oxygen are mixed at the mixing tee 7; the mixed gas is output as a mixed gas through the machine head 9 and the welding gun 10 during welding; the welding machine 8 is turned on, and the solid welding wire is continuously fed into the welding area as an electrode. The arc burning between the welding wire and the workpiece to be welded serves as a heat source to melt the welding wire and the base metal, and the mixed gas is continuously delivered to the welding area through the nozzle of the welding gun 10.

[0038] Compared to using only carbon dioxide as a shielding gas, welding spatter is significantly reduced, approaching that produced by flux-cored wire. Fume is significantly reduced during welding. The weld seam is uniform, and post-weld testing shows that all mechanical properties meet relevant national standards. Example 2:

[0039] The composition of the mixed gas of the present invention is distributed according to the volume percentage of the gas, with oxygen accounting for 5% and carbon dioxide accounting for 95%.

[0040] Using the above-mentioned mixed gas and a solid welding wire, the carbon dioxide gas in the carbon dioxide gas source 1 passes through a pipeline, is flow-controlled by a carbon dioxide flow control valve 3, and then enters the mixing tee 7; the oxygen in the oxygen gas source 2 passes through a pipeline, is flow-controlled by an oxygen flow control valve 4, and then enters the mixing tee 7; the carbon dioxide gas and oxygen are mixed at the mixing tee 7; the mixed gas is output as a mixed gas through the machine head 9 and the welding gun 10 during welding; the welding machine 8 is turned on, and the solid welding wire is continuously fed into the welding area as an electrode. The arc burning between the welding wire and the workpiece to be welded serves as a heat source to melt the welding wire and the base metal, and the mixed gas is continuously delivered to the welding area through the nozzle of the welding gun 10.

[0041] Compared to using only carbon dioxide as a shielding gas, welding spatter is significantly reduced, approaching that produced by flux-cored wire. Fume is significantly reduced during welding. The weld seam is uniform, and post-weld testing shows that all mechanical properties meet relevant national standards. Example 3:

[0042] The composition of the mixed gas of the present invention is distributed according to the volume percentage of the gas, with oxygen accounting for 3% and carbon dioxide accounting for 97%.

[0043] Using the above-mentioned mixed gas and a solid welding wire, the carbon dioxide gas in the carbon dioxide gas source 1 passes through a pipeline, is flow-controlled by a carbon dioxide flow control valve 3, and then enters the mixing tee 7; the oxygen in the oxygen gas source 2 passes through a pipeline, is flow-controlled by an oxygen flow control valve 4, and then enters the mixing tee 7; the carbon dioxide gas and oxygen are mixed at the mixing tee 7; the mixed gas is output as a mixed gas through the machine head 9 and the welding gun 10 during welding; the welding machine 8 is turned on, and the solid welding wire is continuously fed into the welding area as an electrode. The arc burning between the welding wire and the workpiece to be welded serves as a heat source to melt the welding wire and the base metal, and the mixed gas is continuously delivered to the welding area through the nozzle of the welding gun 10.

[0044] Compared to using only carbon dioxide as a shielding gas, welding spatter is significantly reduced, approaching that produced by flux-cored wire. Fume is significantly reduced during welding. The weld seam is uniform, and post-weld testing shows that all mechanical properties meet relevant national standards.

[0045] In practical applications, for those skilled in the art, any mixed gas product and related processes produced according to the principles of the present invention are considered to be within the scope of protection of the present invention.

Claims

1. A solid wire mixed gas shielded welding method, characterized in that: The solid wire mixed gas shielded welding method uses a mixed gas as a welding shielding gas, and oxygen is added to the mixed gas.

2. A solid wire mixed gas shielded welding method according to claim 1, characterized in that: The mixed gas includes carbon dioxide gas and oxygen, and the composition is distributed according to the gas volume percentage, with oxygen accounting for 1% to 5% and carbon dioxide accounting for 95% to 99%.

3. A solid wire mixed gas shielded welding method according to claim 2, characterized in that: The solid welding wire mixed gas shielded welding method uses a solid welding wire for welding.

4. A solid wire mixed gas shielded welding method according to claim 3, characterized in that: The carbon dioxide gas in the carbon dioxide gas source (1) enters the mixing tee (7) through a pipeline after the flow rate is controlled by a carbon dioxide flow control valve (3); the oxygen in the oxygen gas source (2) enters the mixing tee (7) through a pipeline after the flow rate is controlled by an oxygen flow control valve (4); the carbon dioxide gas and the oxygen are mixed at the mixing tee (7); the mixed gas is output as a mixed gas through a machine head (9) and a welding gun (10) during welding; the welding machine (8) is turned on, and a solid welding wire is continuously fed into the welding area as an electrode, and the arc burning between the welding wire and the workpiece to be welded is used as a heat source to melt the welding wire and the base metal, and the mixed gas is continuously fed to the welding area through the nozzle of the welding gun (10).

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