CO2 gas shielded aluminum welding rod and preparation process thereof

Abstract

The invention discloses a CO2 gas shielded aluminum welding rod and a preparation process thereof, and relates to the technical field of advanced steel and iron materials. A CO2 gas protection aluminum welding rod is composed of an aluminum alloy core wire and a coating on the outer surface of the aluminum alloy core wire, and the coating is prepared from, by mass, 0.5-3 parts of rare earth oxide, 18-30 parts of potassium fluoroaluminate, 5-12 parts of lithium fluoride, 8-18 parts of calcium fluoride, 4-10 parts of ferrotitanium, 3-9 parts of ferrosilicon and 2.5-6 parts of binder. Welding defects are remarkably reduced, an aluminum oxide film can be efficiently broken, oxidation of a molten pool is inhibited, and the occurrence probability of slag inclusion, air holes and other problems is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of advanced steel materials, and particularly relates to a CO2 gas shielded aluminum electrode and a preparation process thereof. BACKGROUND

[0002] CO2 gas shielded welding is widely used in the fields of mechanical manufacturing, construction engineering, automobile industry and the like due to the advantages of high welding efficiency, low cost and beautiful weld forming. Aluminum and aluminum alloy become the core material of lightweight structure due to the excellent performances of small density, high strength and strong corrosion resistance, and the welding demand thereof increases in high-end equipment manufacturing such as aerospace and rail transit. However, the application of CO2 gas shielded welding technology to aluminum and aluminum alloy welding still faces many technical bottlenecks.

[0003] Aluminum has a lively chemical property, and an aluminum oxide film with a high melting point of 2050 DEG C can be easily formed at room temperature. The film is difficult to remove in the welding process, and can easily lead to defects such as slag inclusion and pores in the weld, which seriously affect the mechanical properties of the welded joint. At the same time, CO2 gas is easy to decompose to produce CO and O2 at high temperature, which aggravates the oxidation reaction of the molten pool and further deteriorates the weld quality. Traditional aluminum electrodes are mostly protected by argon, and the preparation process is complex, which limits the application of the electrodes in large-scale production.

[0004] The existing CO2 gas shielded aluminum electrode has problems such as unreasonable coating formula, poor arc stability and poor weld forming. The content of fluoride in the coating of some electrodes is too high, which leads to serious spatter in the welding process and cracks in the weld. When the content of fluoride is insufficient, the aluminum oxide film cannot be effectively removed, and the density of the welded joint cannot be guaranteed. In addition, the matching of the coating and the welding core is not good, the coating process is not mature, and other factors can also cause problems such as coating falling off and electrode moisture deterioration, which reduces the welding stability and reliability.

[0005] Therefore, it is necessary to develop a CO2 gas shielded aluminum electrode with a scientific formula and a reasonable preparation process to solve the technical problems such as difficulty in removing the aluminum oxide film, serious oxidation of the molten pool and many defects in the weld, improve the welding efficiency and joint quality, reduce the welding cost, and meet the actual needs of industrial production. SUMMARY

[0006] The present application relates to the technical field of advanced steel materials, and particularly relates to a CO2 gas shielded aluminum electrode and a preparation process thereof.

[0007] To achieve the above object, the technical scheme adopted by the present application is: A CO2 gas shielded aluminum electrode is composed of an aluminum alloy core and a coating on the surface of the core, wherein the coating is prepared from the following components by mass: 0.5-3 parts of rare earth oxide, 18-30 parts of potassium fluoroaluminate, 5-12 parts of lithium fluoride, 8-18 parts of calcium fluoride, 4-10 parts of ferro-titanium alloy, 3-9 parts of ferro-silicon alloy, and 2.5-6 parts of binder.

[0008] Preferably, the rare earth oxide is at least one of cerium oxide or lanthanum oxide.

[0009] Preferably, the potassium fluoroaluminate is potassium hexafluoroaluminate or potassium tetrafluoroaluminate.

[0010] Preferably, the ferro-titanium alloy contains titanium with a mass fraction of ≥70%, and the ferro-silicon alloy contains silicon with a mass fraction of ≥75%.

[0011] Preferably, the binder is a potassium-sodium mixed water glass with a modulus of 2.8-3.2.

[0012] Preferably, the aluminum alloy core has a grade of ER4043 or ER4047.

[0013] A preparation process of a CO2 gas shielded aluminum electrode includes the following steps: S1. Raw material pretreatment: dry and crush all the components by mass, i.e. potassium fluoroaluminate, lithium fluoride, calcium fluoride, ferro-titanium alloy, ferro-silicon alloy, and rare earth oxide, to 100-200 mesh, to obtain a powder; S2. Dry mixing: put the powder into a mixer according to the ratio, and mix for 20-40 minutes to obtain a uniform powder mixture; S3. Paste preparation: add the binder to the powder mixture, and stir in a stirrer to obtain a uniform paste; S4. Coating: straighten the aluminum alloy core, and uniformly coat the paste on the surface of the core through a coating die, and control the outer diameter of the coating to obtain an electrode; S5. Drying: preliminarily dry the coated electrode at 80-120℃ for 30-60 minutes, and finally dry at 250-350℃ for 60-120 minutes; S6. Cooling and packaging: place the dried electrode in a heat preservation oven, and cool to below 60℃, and immediately perform vacuum moisture-proof packaging after taking out, to obtain a CO2 gas shielded aluminum electrode.

[0014] A CO2 gas shielded aluminum electrode is a welding material product for special steel, new alloy, and special repair.

[0015] The present application overcomes the technical difficulties of the prior art by the synergistic effect of the specific proportion of the coating components and the aluminum alloy welding core. Potassium fluoroaluminate, lithium fluoride and calcium fluoride are matched in a specific proportion to generate slag at high welding temperature, which can quickly break the dense aluminum oxide film on the surface of aluminum, absorb gas impurities in the molten pool, and avoid slag inclusion and porosity defects. The addition of rare earth oxides not only refines the weld grain and improves the mechanical properties of the joint, but also enhances the stability of the electric arc and improves the welding spatter problem. The synergistic effect of ferro-titanium alloy and ferro-silicon alloy improves the deoxidizing ability of the weld and inhibits the oxidation of the molten pool by O2 generated by the decomposition of CO2, and optimizes the chemical composition of the weld to reduce the crack sensitivity. The binder and other powders form a good combination with the aluminum alloy welding core, which not only ensures the strong adhesion of the coating and the welding core to avoid the coating falling off during welding, but also reduces the risk of moisture absorption and deterioration of the coating through subsequent drying process, finally realizes the technical effects of beautiful weld forming, high welding stability and controllable cost, and meets the industrial demand of CO2 gas protection aluminum welding.

[0016] Compared with the prior art, the present application has the following advantages: 1. Welding defects are significantly reduced, which can efficiently break the aluminum oxide film, inhibit the oxidation of the molten pool, and reduce the probability of problems such as slag inclusion and porosity.

[0017] 2. Welding stability and weld quality are improved, arc stability is better, weld forming effect is better, and mechanical properties are more stable.

[0018] 3. It meets the industrial scale production demand, the coating and the welding core are more firmly combined and less likely to absorb moisture and fall off, and the welding cost is reduced. DETAILED DESCRIPTION

[0019] The technical solutions of the present application will be described below. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0020] EMBODIMENT Preparation of a CO2 gas protection aluminum electrode: 1. Raw material components Rare earth oxide: 1.5 parts (lanthanum oxide); Potassium fluoroaluminate: 24 parts (hexafluoroaluminate potassium); Lithium fluoride: 8 parts; Calcium fluoride: 13 parts; Ferro-titanium alloy: 7 parts (72% of titanium by mass); Ferro-silicon alloy: 6 parts (78% of silicon by mass); Binder: 4 parts (potassium-sodium mixed water glass, modulus 3.0); Aluminum alloy welding core: grade ER4043.

[0021] 2. Preparation process S1. Raw material pretreatment: 1.5 parts of rare earth oxide (lanthanum oxide), 24 parts of potassium fluoroaluminate (potassium hexafluoroaluminate), 8 parts of lithium fluoride, 13 parts of calcium fluoride, 7 parts of titanium-iron alloy and 6 parts of silicon-iron alloy were placed in a drying oven and dried at 120°C for 4 hours; then the dried raw materials were put into a pulverizer and pulverized, and then screened through a 150-mesh standard sieve to obtain powder. S2. Dry mixing: Put the above powder into a twin-shaft mixer, set the mixer speed to 30 r / min and the mixing time to 30 minutes, so that the powders are fully mixed to obtain a uniform powder mixture; S3. Preparation of paste: Slowly add 4 parts of binder (potassium sodium mixed water glass) to the above powder mixture, and start the mixer at the same time. Set the mixing speed to 60 r / min and the mixing time to 20 minutes until the powder mixture and binder are completely blended to form a paste with uniform texture, no lumps and suitable fluidity. S4. Coating: First, the ER4043 aluminum alloy welding core is straightened using a straightening machine. Then, the straightened welding core is fed into a coating mold. The above-mentioned paste is evenly applied to the surface of the welding core using a pressure pump. By adjusting the aperture of the coating mold, the ratio of the outer diameter of the coating to the diameter of the welding core is controlled to be 1.6, resulting in a welding rod with uniform coating thickness and tight bonding with the welding core. S5. Drying: The above welding rods are sent into a drying oven for preliminary drying. The drying temperature is set to 100℃ and the holding time is 45 minutes. After the preliminary drying is completed, the temperature is raised to 300℃ for final drying and the holding time is 90 minutes. S6. Cooling and Packaging: The dried welding rod is placed in an insulated oven and cooled to below 60°C. After cooling, it is immediately removed and sealed with vacuum moisture-proof packaging material to obtain a CO2 gas-protected aluminum welding rod.

[0022] Example 2 A CO2 gas shielded aluminum welding electrode is prepared by referring to the preparation method of Example 1, except that the mass fraction of rare earth oxides is replaced with 0.5 parts, and the rest remains the same as in Example 1.

[0023] Example 3 A method for preparing CO2 gas-shielded aluminum welding electrodes is described, referring to the preparation method of Example 1, except that the mass fraction of rare earth oxides is replaced with 3 parts, while the rest remains the same as in Example 1.

[0024] Comparative Example 1 A CO2 gas-shielded aluminum welding electrode, prepared according to the method of the embodiment, without the addition of rare earth oxides, is otherwise the same as in Example 1.

[0025] Comparative Example 2 A CO2 gas-shielded aluminum welding electrode, prepared according to the method of the embodiment, with the mass ratio of ferro-titanium alloy and ferrosilicon alloy reduced (30% and 20% respectively in the embodiment), while the rest remains the same as in embodiment 1.

[0026] Comparative Example 3 A CO2 gas shielded aluminum welding electrode, prepared according to the method of the embodiment, with the mass ratio of potassium fluoroaluminate, lithium fluoride and calcium fluoride adjusted so that the total fluoride content is reduced by 40% compared with the embodiment, while the rest remains the same as in embodiment 1.

[0027] Performance testing: 1. Arc stability test: Flat plate butt welding was adopted, and the welding parameters were fixed as follows: current 130±10A, voltage 22±2V, welding speed 4±0.5mm / s, CO2 gas flow rate 18±2L / min; the entire welding process was recorded with a high-speed camera (frame rate 500fps), and 100mm weld seams were welded continuously. Each group of samples was tested 3 times.

[0028] Judgment indicators: Count the number of arc breaks (a single arc break time ≥0.1s is considered a valid arc break), and rate them as "no arc break (excellent), 1-2 times (good), 3-5 times (medium), >5 times (poor)", and the data is shown in Table 1.

[0029] 2. Mechanical property testing of weld: Standard tensile specimens (with the weld as the central area, specimen size Φ10mm×50mm) were prepared according to GB / T2651-2008. Three specimens were prepared for each group. Tensile testing machine was used to load the specimens at a rate of 2mm / min. The tensile strength, yield strength and elongation were recorded. The data are shown in Table 1.

[0030] Bending test: Bending specimens (thickness 6mm, width 30mm, length 120mm) were prepared according to GB / T2653-2008. A 180° cold bending test was conducted (the diameter of the bending mandrel was 3 times the thickness of the specimen). After bending, the weld and heat-affected zone were observed to see if cracks appeared. The data are shown in Table 1.

[0031] Table 1 Adding appropriate amounts of rare earth oxides, ensuring a sufficient ratio of ferro-titanium alloy to ferrosilicon alloy, and controlling the appropriate total fluoride content can improve the arc stability of this CO2 gas-shielded aluminum welding electrode, resulting in increased tensile strength, yield strength, and elongation of the weld, and making it less prone to cracking or fracture during bending tests. However, when no rare earth oxides are added, the content of key alloy components is insufficient, or the total fluoride content is too low, the arc stability of the welding electrode will deteriorate, the mechanical properties of the weld will decline significantly, and it will be more prone to cracking or even fracture during bending.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A CO2 gas-shielded aluminum welding electrode, comprising an aluminum alloy core and a flux coating on its outer surface, characterized in that, The coating is prepared from the following components in parts by weight: 0.5-3 parts rare earth oxides, 18-30 parts potassium fluoroaluminate, 5-12 parts lithium fluoride, 8-18 parts calcium fluoride, 4-10 parts ferro-titanium alloy, 3-9 parts ferrosilicon alloy, and 2.5-6 parts binder.

2. The CO2 gas shielded aluminum welding electrode according to claim 1, characterized in that, The rare earth oxide is at least one of cerium oxide or lanthanum oxide.

3. The CO2 gas shielded aluminum welding electrode according to claim 1, characterized in that, The potassium fluoroaluminate is potassium hexafluoroaluminate or potassium tetrafluoroaluminate.

4. The CO2 gas shielded aluminum welding electrode according to claim 1, characterized in that, The titanium-iron alloy contains ≥70% titanium by mass. The silicon-iron alloy contains ≥75% silicon by mass.

5. The CO2 gas shielded aluminum welding electrode according to claim 1, characterized in that, The binder is a potassium-sodium mixed water glass with a modulus of 2.8-3.

2.

6. The CO2 gas shielded aluminum welding electrode according to claim 1, characterized in that, The aluminum alloy welding core is graded ER4043 or ER4047.

7. A method for preparing a CO2 gas-shielded aluminum welding electrode according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Raw material pretreatment: The potassium fluoroaluminate, lithium fluoride, calcium fluoride, ferro-titanium alloy, ferrosilicon alloy and rare earth oxides are dried, pulverized and sieved to 100-200 mesh to obtain powder. S2. Dry mixing: Add the powder to the mixer according to the ratio and mix for 20-40 minutes to obtain a uniform powder mixture; S3. Preparation of paste: The binder is added to the powder mixture and stirred in a mixer to form a uniform paste; S4. Coating: Straighten the aluminum alloy welding core, and apply the paste evenly to the surface of the welding core using a coating mold, controlling the outer diameter of the coating to obtain the welding rod; S5. Drying: The coated welding rod is first pre-dried at 80-120℃ for 30-60 minutes, and then finally dried at 250-350℃ for 60-120 minutes. S6. Cooling and Packaging: The dried welding rod is placed in an insulated oven and cooled to below 60°C with the furnace. After being taken out, it is immediately vacuum-sealed for moisture protection to obtain a CO2 gas-protected aluminum welding rod.

8. The method for preparing a CO2 gas-shielded aluminum welding electrode according to claim 7, characterized in that, The stirring time in step S3 is 15-30 minutes.

9. The method for preparing a CO2 gas-shielded aluminum welding electrode according to claim 7, characterized in that, In step S4, the ratio of the outer diameter of the coating to the diameter of the welding core is controlled between 1.4 and 1.8 by controlling the aperture of the coating mold.

10. The method for preparing a CO2 gas-shielded aluminum welding electrode according to claim 7, characterized in that, In step S5, the final drying temperature is 280-320℃, and the holding time is 90 minutes.

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