A method for directly connecting anodized aluminum guide rods and steel claws

Abstract

The present invention discloses a method for directly connecting an anodized aluminum guide rod and a steel claw, belonging to the field of electrolytic aluminum technology. The method comprises: (1) sandblasting the surface of the steel claw to be welded; (2) spraying a mixed powder on the surface of the steel claw to be welded to form a transition layer of a certain thickness; (3) depositing an aluminum alloy layer by selecting an aluminum-zinc welding wire, melting the welding wire, and then depositing it on the surface of the steel claw modified in step (2) to form an aluminum alloy layer; and (4) welding the aluminum guide rod and the steel claw coated with an aluminum-steel composite layer using an argon arc welding method. This method solves the problems of the complex welding process of anodized aluminum guide rods and steel claws in the electrolytic aluminum industry, the need for explosive welding blocks for transition, and poor electrical conductivity.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytic aluminum, and in particular to a method for directly connecting an anode aluminum guide rod and a steel claw. Background Art

[0002] my country's electrolytic aluminum production capacity is approximately 37 million tons, accounting for 56% of the global total. Electrolytic aluminum production is also a significant energy consumer, using 501.535 billion kilowatt-hours of electricity annually, representing approximately 6% of the nation's total energy consumption, with an average electricity consumption of 13,555 kilowatt-hours per ton of aluminum. Currently, energy conservation, consumption reduction, and emission reduction are pressing needs for electrolytic aluminum companies.

[0003] Currently, aluminum guide rods and anode steel claws are all connected via explosive block transitions. This connection method has poor electrical conductivity due to numerous welds and a small effective weld area. It also suffers from low production efficiency, high welding costs, high joint resistance, and prone to cracking at the weld joints. Aluminum-aluminum and steel-steel welds are welded using a groove method. Conductive conduction occurs through the welds around the perimeter, where the conductive cross-section is much smaller than that of the guide rod, resulting in a significant voltage drop.

[0004] In addition, the use of explosive block transition connection between aluminum guide rod and anode steel claw has the following major disadvantages:

[0005] Since the aluminum-steel explosive welding block does not achieve arc metallurgical bonding during welding, the temperature of its joint surface is sometimes too high due to uneven current distribution in the electrolytic cell and heat transfer of the bath liquid during use. At the same time, its joint surface is exposed to the dust environment of the electrolytic cell, which is prone to cracking, resulting in anode drop accidents, which can easily cause production accidents. The conductive cross-sections of aluminum-aluminum welds and steel-steel welds are all conductive around the weld position, and their conductive cross-sections are smaller than the conductive cross-section of the guide rod. The voltage drop here is relatively large, about 20-25mv. The current connection method of the anode guide rod and the steel claw is cumbersome and costly. According to the current connection method, explosive blocks need to be used, and aluminum-aluminum welding and steel-steel welding need to be performed at the same time. The process is cumbersome, and therefore the welding cost is high.

[0006] Energy conservation and consumption reduction are crucial today. Therefore, reducing electrical energy loss during the aluminum electrolysis process is crucial. Chinese patent CN203696261U discloses a seamless connection method for connecting steel claws and aluminum guide rods in electrolytic aluminum production. The method involves creating a steel sleeve with a threaded inner wall, fitting it over the aluminum guide rod, and applying a pressure of 30 MPa to the rod from the other end. A heating agent is placed at the bottom of the sleeve, and a high current of 3.5-4.0 kA is passed through both ends. This heats the heating agent, generating temperatures of 1200-1300°C and a high pressure of 250-350 MPa inside the sleeve. This causes intense infiltration of the aluminum and steel, forming atomically strong bonds and achieving a high-strength bond. This method is extremely complex to implement. For an aluminum guide rod with a cross-section of 170×200 in a 400 kA electrolytic cell, achieving a pressure of 30 MPa and a current of 3.5-4.0 kA is difficult to implement with the necessary tooling and equipment. Even if it were feasible, it would be costly and difficult to implement.

[0007] Chinese patent CN106270890B discloses a method for brazing aluminum and steel. The aluminum surface is first cleaned and then chromized. Then, using an aluminum-based solder as a filler material, the chromized aluminum and steel are joined by brazing. The chromized steel and aluminum alloy are brazed in a furnace, resulting in a high-quality joint with a tensile strength of 182-205 MPa. This method requires furnace brazing, and for aluminum-steel welding in the electrolytic aluminum industry, aluminum guide rods typically come in sizes of 130×130×2538mm, 145×145×2538mm, and 220×180×2328mm. Together with the steel claws, the total height can reach approximately 3 meters. This requires a high furnace requirement, making equipment manufacturing difficult and costly.

[0008] Chinese patent CN108406027A discloses a method for fusion brazing of electrolytic aluminum anode steel to aluminum. This invention involves uniformly coating a 100-150 μm thick layer of flux on the workpieces after removing the surface oxide layer. The aluminum workpiece is fusion welded, and the steel workpiece is brazed. The aluminum and steel workpieces are preheated separately, and aluminum-based solid wire or aluminum-based flux-cored wire is used to weld the dissimilar steel-aluminum metals. This welding method requires preheating the anode aluminum guide rod and steel claws. However, the anode aluminum guide rods and steel claws used for electrolytic aluminum are relatively large, with sizes ranging from 130 × 130 × 2538 mm, 145 × 145 × 2538 mm, and 220 × 180 × 2328 mm. Furthermore, the aluminum guide rods dissipate heat quickly, making preheating the aluminum guide rods extremely complex, time-consuming, and inefficient. Even if this method is feasible, the welding stability is poor. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for directly connecting an anodized aluminum guide rod and a steel claw. The method solves the problems of complex welding process of anodized aluminum guide rods and steel claws in the electrolytic aluminum industry, the need for explosive welding block transition, and poor conductivity, and especially solves the current problems of difficulty in obtaining explosive blocks and increased procurement costs.

[0010] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0011] A method for directly connecting an anodized aluminum guide rod and a steel claw, the method comprising the following steps:

[0012] (1) Sandblast the surface of the steel claw to be welded;

[0013] (2) performing surface modification on the steel claw after sandblasting, that is, using powder spraying equipment to spray the mixed powder on the surface of the steel claw to be welded, forming a transition layer of a certain thickness on the surface of the steel claw to be welded;

[0014] (3) depositing an aluminum alloy layer: selecting an aluminum-zinc welding wire, melting the welding wire and depositing it on the surface of the steel claw after the modification treatment in step (2) to form an aluminum alloy layer;

[0015] (4) The aluminum guide rod is welded to the steel claw coated with an aluminum alloy layer by argon arc welding.

[0016] In the above step (1), sandblasting is used to remove rust on the surface to be welded and reveal the metallic luster, while making the surface roughness of the steel to be welded reach Sa3 level or above; the purpose of this process is: first, to remove oxides and oil stains on the steel surface; second, to increase the surface area of ​​the aluminum-steel joint surface to improve the overall connection strength.

[0017] In the above step (2), the mixed powder is composed of 30-40% copper, 10-30% silicon, 30-40% cesium fluoroaluminate, and 30-40% aluminum-based brazing flux in terms of weight percentage; wherein the aluminum-based brazing flux is composed of 147-51wt.% KC, 31-35wt.% LiCl, 6-10wt.% ZnCl3, and 9-11wt.% NaF.

[0018] In the above step (2), the thickness of the transition layer is 0.2-0.6 mm.

[0019] Step (2) Surface modification mechanism: The physical and chemical properties of aluminum and steel are quite different, and it is difficult to achieve welding by fusion welding. AlFe brittle metal compounds are easily formed between aluminum and steel. Therefore, according to the brazing principle, the present invention first sprays an appropriate amount of copper, silicon, brazing flux, etc. on the steel surface to change the surface properties of the steel. Cu and Si elements can inhibit the formation of AlFe intermetallic compounds. Cu element can replace FeAl intermetallic compounds to form Al2Cu, and Si element can generate AlFe intermetallic compounds at the bonding surface during the diffusion process. 0.5 Fe3Si 0.5， However, excessive amounts of Cu and Si elements will also deteriorate the performance of the welded joint, so the amount of Cu and Si elements added must be controlled.

[0020] In the above step (3), the cladding process controls the welding heat input to 200-300 J / mm; preferably, the cold metal transition welding process is used for wire cladding, and the cladding parameters are: wire diameter is 1.2mm / 1.0mm; welding current is 90-95A, voltage is 9-12.5V, travel speed is 4-5mm / s, and argon flow rate is 15-20L / min.

[0021] In the above step (3), the aluminum-zinc welding wire has high strength, and zinc can also increase the wettability of aluminum on the steel surface.

[0022] In the above step (3), the thickness of the deposited aluminum alloy layer is 8-12 mm.

[0023] The design principles and beneficial effects of the present invention are as follows:

[0024] 1. Energy saving and consumption reduction: This invention changes the surface properties of steel by spraying a transition layer containing elements such as Cu and Si, inhibiting the generation of brittle intermetallic compounds and achieving direct bonding between aluminum and steel. It can replace the traditional method of connecting the anode guide rod and the steel claw with the explosive block transition, reducing the two welds during the explosive block transition welding process and significantly reducing the voltage drop by more than 10mV, with obvious power saving advantages. Taking a 400KA electrolytic cell as an example, it can save about 30KWh for every ton of aluminum produced.

[0025] 2. Reduced production costs: This invention utilizes a structural design that directly connects aluminum and steel, eliminating the need for explosive blocks as a transition, saving on welding wire, welding materials, and labor, thereby reducing production costs. Compared to traditional welding processes, this method simplifies the welding process, is easy to operate, and has high welding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural schematic diagram of an embodiment of the direct connection between the aluminum guide rod and the steel claw of the present invention.

[0027] Figure 2 It is a process flow chart of the present invention.

[0028] Figure 3 This is the finished product of welding the aluminum guide rod and the steel claw in Example 1. DETAILED DESCRIPTION

[0029] In order to further understand the present invention, the present invention is described below with reference to examples. However, the examples are only for further elaboration of the features and advantages of the present invention, rather than for limitation of the claims of the present invention.

[0030] Example 1:

[0031] This embodiment is a method for directly connecting anodized aluminum guide rods and steel claws. For the process, refer to Figure 1-2 , a total of 20 groups of samples were directly connected, the specific process is as follows:

[0032] Step 1: Sandblast the surface of the steel claw to be welded: Use YT-420 sandblasting machine to sandblast the surface to be welded, clean up dust, rust and other impurities, and make the steel surface roughness reach Sa3 level to increase the bonding area of ​​the alloy layer on the steel surface, and at the same time increase the area of ​​the subsequent aluminum-steel bonding surface, that is, increase the overall bonding strength.

[0033] Step 2: The sandblasted steel claw surface is then sprayed with a transition layer: Using a powder spraying machine, alloy powder is sprayed onto the surface of the steel claw to be welded. (Spraying process: Mix the prepared powder with anhydrous ethanol in a 2:1 ratio, pour it into a fluidized cup, and spray with a handheld MS-K19 spray gun.) The alloy powder composition (wt.%) is: 30% Cu, 10% Si, 40% cesium fluoroaluminate, 20% aluminum-based brazing flux; the aluminum-based brazing flux composition (wt.%) is: 47-51% KCl, 31-35% LiCl, 36-10% ZnCl2, 9-11% NaF, with a spray thickness of 0.2mm. The main function of the alloy layer is to increase the wettability of the aluminum on the steel surface and inhibit the formation of brittle metal compounds in the aluminum-steel bond layer.

[0034] Step 3: Use The 7050 aluminum-zinc welding wire is deposited on the surface of the modified steel claw to be welded using the cold metal transfer welding process, forming an aluminum alloy layer on the upper surface of the steel claw; wherein: the welding current is 90A, the welding voltage is 9.5V, the welding speed is 4mm / s, and the argon gas flow rate is 15L / min; the thickness of the cladding aluminum alloy layer is 8mm.

[0035] Step 4: Place the aluminum guide rod in the center of the steel claw surface to be welded, and use a conventional argon arc welding machine to weld the aluminum guide rod and the steel claw with the cladding aluminum alloy layer together. The welding process parameters are: the first 6 welding currents are 260A, the welding voltage is 25.4V, and the welding speed is 45cm / min; the last 6 welding currents are 240A, the welding voltage is 23.9V, and the welding speed is 40cm / min. After welding, an aluminum-aluminum weld is formed, and the finished product of the aluminum guide rod and the steel claw is obtained. Figure 3 .

[0036] The aluminum-aluminum welds were tested, and their average tensile strength was 102 MPa. The comparison of the pressure drop effect of the welding parts of 20 samples in this embodiment and the pressure drop effect of the conventional explosive block transition connection joint (20 samples) is shown in Table 1.

[0037] Table 1 Comparison of pressure drop effects between the direct welding connection weld of the present invention and the conventional explosive block transition connection weld

[0038]

[0039]

[0040] The present invention addresses the problem of brittle intermetallic compounds being easily generated between aluminum and steel. By adding an aluminum alloy layer transition between aluminum and steel, the generation of brittle metal compounds is reduced. At the same time, by controlling process parameters, the nucleation energy is reduced, which can inhibit the generation of brittle intermetallic compounds between aluminum and steel, thereby improving the connection strength of the joint.

Claims

1. A method for directly connecting an anodized aluminum guide rod and a steel claw, characterized in that: The method comprises the following steps: (1) Sandblast the surface of the steel claw to be welded; (2) performing surface modification on the steel claw after sandblasting, that is, using powder spraying equipment to spray the mixed powder on the surface of the steel claw to be welded, forming a transition layer of a certain thickness on the surface of the steel claw to be welded; The mixed powder is composed of 30% copper, 10% silicon, 40% cesium fluoroaluminate, and 20% aluminum-based brazing flux by weight; wherein the aluminum-based brazing flux is composed of 47-51% by weight of KCl, 31-35% by weight of LiCl, 6-10% by weight of ZnCl2, and 9-11% by weight of NaF; (3) depositing an aluminum alloy layer: selecting an aluminum-zinc welding wire, melting the welding wire and depositing it on the surface of the steel claw after the modification treatment in step (2) to form an aluminum alloy layer; (4) The aluminum guide rod and the steel claw with the aluminum alloy layer deposited thereon are welded together using an argon arc welding method.

2. The method for directly connecting anodized aluminum guide rods and steel claws according to claim 1, characterized in that: In step (1), sandblasting is used to remove rust on the surface to be welded and reveal the metallic luster, while at the same time making the surface roughness of the steel to be welded reach Sa3 level or above.

3. The method for directly connecting anodized aluminum guide rods and steel claws according to claim 1, characterized in that: In step (2), the thickness of the transition layer is 0.2-0.6 mm.

4. The method for directly connecting anodized aluminum guide rods and steel claws according to claim 1, characterized in that: In step (3), the welding heat input is controlled within a range of 200-300 J / mm during the deposition process.

5. The method for directly connecting anodized aluminum guide rods and steel claws according to claim 1 or 4, characterized in that: In step (3), the cold metal transition welding process is used for wire deposition, and the deposition parameters are: wire diameter is 1.2mm / 1.0mm; welding current is 90-95A, voltage is 9-12.5V, travel speed is 4-5mm / s, and argon flow rate is 15-20L / min.

6. The method for directly connecting anodized aluminum guide rods and steel claws according to claim 1, characterized in that: In step (3), the thickness of the deposited aluminum alloy layer is 8-12 mm.

Images