Method for preparing copper-embedded cathode steel rod by explosive cladding welding

Abstract

The application discloses a method for preparing a copper-embedded cathode steel rod by explosion composite welding, and comprises the following steps: processing grooves on a steel rod blank with a square cross section to obtain a slotted steel rod; taking a copper rod with a diameter larger than that of the grooves; polishing one side of the slotted steel rod with the processed grooves to remove iron powder and obtain a cleaned slotted steel rod; polishing the surface of the copper rod to remove copper powder and obtain a cleaned copper rod; sequentially placing one cleaned slotted steel rod, the cleaned copper rod and another cleaned slotted steel rod from bottom to top; oppositely arranging the grooves on the two cleaned slotted steel rods; laying explosive on the upper surface of the upper cleaned slotted steel rod and installing a detonating detonator; performing explosion composite welding according to an explosion composite process to obtain a copper-embedded cathode steel rod blank; and performing heat treatment, straightening, polishing and repairing to obtain the explosion composite welding copper-embedded cathode steel rod. The preparation method has high efficiency and low cost, and can prepare the copper-embedded cathode steel rod with a copper-steel interface without gaps, high bonding strength and enhanced electric conductivity.

Description

Technical Field

[0001] This invention belongs to the field of cathode steel rod manufacturing technology, and relates to a method for preparing copper-embedded cathode steel rods for electrolytic aluminum. Specifically, it relates to a method for preparing copper-embedded cathode steel rods by explosive composite welding, which is a new method for increasing the bonding strength of metal interfaces and improving the conductivity of cathode steel rods. Background Technology

[0002] The cathode steel rod is a crucial component for conductivity in electrolytic aluminum production, and its conductivity and service life directly impact the cost of aluminum electrolysis. Currently, the cathode steel rods used in domestic electrolytic aluminum production are primarily made of Q195 carbon steel, with a small portion using industrial pure iron. During operation, a graphite cathode is wrapped around the cathode steel rod, with refractory material, molten aluminum cathode, and electrolyte placed on top of the graphite. Over long-term use, the surrounding carbon reacts with the cathode steel rod through a carburizing reaction, affecting its conductivity, increasing the cathode voltage drop in the electrolytic cell, and raising power consumption. Furthermore, sodium in the electrolyte corrodes the refractory material and graphite cathode from top to bottom, causing aluminum liquid leakage, severely corroding the cathode steel rod, and reducing the lifespan of the electrolytic cell. To address these problems, copper-embedded cathode steel rods have emerged, which can reduce the cathode voltage drop in the electrolytic cell and significantly decrease power consumption; for example, the patent "Novel Copper-Embedded Cathode Steel Rod" (Patent No. 201920810240.6, Publication Date 2020.04.03).

[0003] In existing technologies, copper-embedded cathode steel rods are mainly manufactured using machining methods. This involves machining a circular hole in the center of the cathode steel rod, inserting a copper rod (either a cast copper rod or a ferrule of metal), and then sealing it to form the copper-embedded cathode steel rod. The main drawbacks of this method are: 1) Machining the circular hole in the steel rod, especially when using pure iron, results in severe "tool sticking," making machining difficult and inefficient, requiring several hours to process a single rod; 2) Because a tighter bond between the steel and copper rods is crucial, extremely high machining precision is required, making assembly extremely difficult. However, regardless of the method, a gap is inevitable between the copper and steel rods; otherwise, the rod cannot be inserted. This affects the conductivity of the copper-embedded cathode steel rod. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing copper-embedded cathode steel rods by explosive composite welding, which has low manufacturing cost and high manufacturing efficiency.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing copper-embedded cathode steel rods by explosive composite welding, comprising the following steps: 1) Take a steel bar blank made of square steel or flat steel, and a copper bar made of industrial brass round copper bar; The steel billet 1 is placed flat on a milling machine and fixed. Then, a semi-circular groove 2 is machined on the steel billet 1 according to the dimensional requirements. The axial direction of the groove 2 is consistent with the length direction of the steel billet 1, thus producing a slotted steel billet. Figure 1 As shown; The weight ratio of copper rod to steel rod blank 1 is generally 1:6 to 20; The steel billet 1 is made of Q195 steel or industrial pure iron, and the cross-section is square or rectangular. The size and position of groove 2 are controlled according to different design requirements. The diameter of groove 2 is generally 3-5mm smaller than the diameter of the copper rod. The milling cutter speed is determined according to the material of the steel rod blank 1 to ensure the surface quality of groove 2, generally between 10 and 60 mm / min. 2) Grind and clean the side of the slotted steel bar with groove 2 using a grinding wheel or sandpaper. Then, wipe the cleaned surface with a soft gauze soaked in alcohol to remove iron filings and obtain the cleaned slotted steel bar 3. Use a grinding wheel or sandpaper to polish and clean the surface of the copper rod. Then, wipe the polished surface with a soft gauze soaked in alcohol to remove copper dust, and you will get a cleaned copper rod 4. 3) Place a cleaned and slotted steel bar 3 on a flat surface, with the groove 2 on the bar facing upwards. Then, place a cleaned copper bar 4 into the groove 2 on the steel bar 3. Next, place another cleaned and slotted steel bar 3 with its groove 2 facing downwards, and then place it onto the copper bar 4, aligning the ends of the two steel bars 3 and the copper bar 4 to obtain the billet assembly. Figure 2 As shown; 4) Place the billet assembly on the prepared blasting site. The two slotted steel bars 3 in the billet assembly are set one above the other. Explosives are laid on the upper slotted steel bar 3. Then, the detonator is installed in the middle of the upper surface of the upper slotted steel bar 3. Explosive composite welding is carried out according to the explosive composite process to obtain the copper-embedded cathode steel bar billet. The total amount of explosives used for laying is Wg = K(δρ). 1 / 2 ; Where: Wg—total amount of explosive used for laying (g / cm³) 2 ); K—a coefficient, the value of which depends on the properties of the composite material, and is taken as 1.3 to 1.5 in this invention; δ—Thickness of the slotted steel bar (cm); ρ—Density of the slotted steel bar (g / cm³) 3 ); 5) Place the copper-embedded cathode steel rod blank into a heating furnace and heat it to 500-700℃ at a heating rate of less than or equal to 200℃ / h. Hold it at that temperature for 3-4 hours and then slowly cool it to room temperature in the furnace to obtain the heat-treated copper-embedded cathode steel rod. The purpose of annealing is to eliminate residual stress at and near the weld interface after an explosion. 6) Straighten and level the heat-treated steel rod with a straightening machine and then embed copper cathodes; 7) Use a grinding wheel to grind and repair the explosively welded parts at both ends of the straightened annealed copper-embedded cathode steel rod to make an explosively composite welded copper-embedded cathode steel rod.

[0006] The preparation method of this invention can produce explosively welded copper-embedded cathode steel rods of various specifications and sizes (unit: mm): 195×170×2200, 220×1260×3000, 160×230×1970, 170×195×1900, 170×210×2255, 100×230×2040, etc.

[0007] Explosive welding (EW) is a pressure welding method that uses explosives as an energy source. The impact force generated during an explosion causes the workpieces to collide violently, undergo plastic deformation, melt, and diffuse between atoms, thus achieving a connection. Explosive welding can form a high-strength metallurgical bond between similar or dissimilar metals, and it can minimize or even eliminate the formation of a brittle compound layer.

[0008] This invention utilizes the advantages of explosive welding to tightly embed a copper rod within a steel rod. The resulting copper-embedded cathode steel rod exhibits a seamless copper-steel interface, strong bonding, and high connection strength, effectively improving the conductivity of the cathode steel rod and reducing power consumption. Testing shows that the copper-embedded cathode steel rod prepared using this method, when applied to a 500KA aluminum electrolysis cell, reduces power consumption by 85 kWh / ton of aluminum compared to machined copper-embedded cathode steel rods, significantly lowering production costs. Furthermore, existing machined copper-embedded cathode steel rod manufacturing methods are difficult to process and assemble; machining a hole in one steel rod takes approximately 3-4 hours on a milling machine, and with the time for assembling the copper rod and sealing, the total time is 4-5 hours, resulting in very low efficiency. However, when preparing a copper-embedded cathode steel rod using this invention, the total slotting time for the two steel rod blanks is only about 2-2.5 hours, and explosive composite assembly allows for batch welding of dozens of rods at once, greatly improving efficiency.

[0009] The preparation method of this invention is highly operable, simple and easy to master, and has more reliable quality and higher manufacturing efficiency than the machining method used in the prior art for preparing copper-embedded steel rods. Attached Figure Description

[0010] Figure 1This is a schematic diagram of the slotted steel bar prepared by the method of the present invention.

[0011] Figure 2 This is a schematic diagram of the blank assembly obtained by the preparation method of the present invention.

[0012] Figure 3 This is a schematic diagram of the copper-embedded cathode steel rod prepared by the method of the present invention.

[0013] In the picture: 1. Steel bar blank, 2. Groove, 3. Slotted steel bar, 4. Cleaned copper bar. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0015] Example 1 A rectangular steel bar blank with a thickness × width × length of 85.5 mm × 210 mm × 2255 mm and made of Q195 material is placed flat on a milling machine and fixed. A semi-circular groove with a diameter of 80 mm is machined in the middle of the upper surface of the steel bar blank. The axis of the groove is aligned with the length of the steel bar blank to obtain a slotted steel bar. Then, a second slotted steel bar is obtained by the same process. Take a copper rod with a diameter of 83mm and a length of 2255mm; Grind and clean the grooved side of the two slotted steel bars and the surface of the copper bar with a grinding wheel. Then wipe the iron filings off the surface of the slotted steel bars with a soft gauze soaked in alcohol. Wipe the copper filings off the surface of the copper bar with a soft gauze soaked in alcohol. Place a cleaned slotted steel bar on a flat surface with the groove on the bar facing upwards. Place a copper bar into the groove on the bar. Then, place another slotted steel bar with the groove facing downwards onto the copper bar. Make sure the ends of the slotted steel bar and the copper bar are aligned to obtain the billet assembly. The blank assembly is placed on the prepared blasting site, 50kg of explosives are laid on the slotted steel bar located above, and then the detonator is installed in the middle of the upper surface of the slotted steel bar located above; explosive composite welding is carried out according to the explosive composite process to obtain the copper-embedded cathode steel bar blank. The copper-embedded cathode steel rod blank is placed in a heating furnace and heated to 600°C for 4.5 hours. It is then held at that temperature for 3.5 hours and cooled to room temperature in the furnace to obtain the annealed copper-embedded cathode steel rod. The steel rod with embedded copper cathode is straightened and leveled by a straightening machine and then heat-treated. The explosive welded areas at both ends of the straightened heat-treated copper-embedded cathode steel rod were ground and smoothed with a grinding wheel to obtain a copper-embedded cathode steel rod with dimensions of 170 mm × 210 mm × 2255 mm.

[0016] Example 2 A rectangular steel bar blank, measuring 50.5 mm in thickness, 230 mm in width, and 2040 mm in length, and made of industrial pure iron, is placed flat on a milling machine and fixed. A semi-circular groove with a diameter of 45 mm is machined in the middle of the upper surface of the steel bar blank. The axis of the groove is aligned with the length of the steel bar blank, thus producing a slotted steel bar. A second slotted steel bar is then produced using the same process. Take a copper rod with a diameter of 48mm and a length of 2040mm; Grind and clean the grooved side of the two slotted steel bars and the surface of the copper bar with a grinding wheel. Then wipe the iron filings off the surface of the slotted steel bars with a soft gauze soaked in alcohol. Wipe the copper filings off the surface of the copper bar with a soft gauze soaked in alcohol. Place a cleaned slotted steel bar on a flat surface with the groove on the bar facing upwards. Place a copper bar into the groove on the bar. Then, place another slotted steel bar with the groove facing downwards onto the copper bar. Make sure the ends of the slotted steel bar and the copper bar are aligned to obtain the billet assembly. The blank assembly is placed on the prepared blasting site, 38 kg of explosives are laid on the slotted steel bar located above, and then the detonator is installed in the middle of the upper surface of the slotted steel bar located above; explosive composite welding is carried out according to the explosive composite process to obtain the copper-embedded cathode steel bar blank. The copper-embedded cathode steel rod blank is placed in a heating furnace, heated to 600°C for 2.5 hours, held at that temperature for 3 hours, and then cooled to room temperature with the furnace to obtain the annealed copper-embedded cathode steel rod. The steel rod with embedded copper cathode is straightened and leveled by a straightening machine and then heat-treated. After straightening and heat treatment, the explosive welded parts at both ends of the copper-embedded cathode steel rod are ground and smoothed with a grinding wheel to obtain a copper-embedded cathode steel rod with dimensions of 100 mm × 230 mm × 2040 mm.

Claims

1. A method for preparing copper-embedded cathode steel rods by explosive composite welding, characterized in that, The preparation method is carried out according to the following steps: 1) Take a square-shaped steel bar blank (1) and machine a semi-circular groove (2) on one surface of the steel bar blank (1). The axial direction of the groove (2) is consistent with the length direction of the steel bar blank (1) to obtain a slotted steel bar. Take a copper rod with a diameter 3~5mm larger than the diameter of the groove (2); the steel rod blank (1) is made of Q195 steel or industrial pure iron; 2) Grind and clean the side of the slotted steel bar with groove (2) to remove iron dust and obtain the cleaned slotted steel bar (3); grind and clean the surface of the copper bar to remove copper dust and obtain the cleaned copper bar (4). 3) Place a cleaned and slotted steel bar (3) on a flat ground with the groove (2) on the cleaned and slotted steel bar (3) facing upwards. Place a cleaned copper bar (4) into the groove (2) on the cleaned and slotted steel bar (3). Then place another cleaned and slotted steel bar (3) with the groove (2) facing downwards on the cleaned copper bar (4) so ​​that the two cleaned and slotted steel bars (3) and the cleaned copper bar (4) are aligned at both ends to obtain a blank assembly. 4) Place the billet assembly on the prepared blasting site. Set the two cleaned and slotted steel bars (3) in the billet assembly one above the other. Lay explosives on the slotted steel bar (3) located above. Then install the detonator in the middle position on the upper surface of the slotted steel bar (3) located above. Perform explosive composite welding according to the explosive composite process to obtain copper-embedded cathode steel bar billet. The total amount of explosives used for laying is Wg = K(δρ). 1 / 2 In the formula: Wg is the total amount of explosive used for laying (g / cm³) 2 K is a coefficient, ranging from 1.3 to 1.5, δ is the thickness of the slotted steel bar (cm), and ρ is the density of the slotted steel bar (g / cm³). 3 ); 5) Place the copper-embedded cathode steel rod blank into a heating furnace and heat it to 500-700°C at a heating rate of less than or equal to 200°C / h. Hold it at that temperature for 3-4 hours and then slowly cool it to room temperature in the furnace to obtain the heat-treated copper-embedded cathode steel rod. 6) Straighten and level the heat-treated steel rod with a straightening machine and then embed copper cathodes; 7) Use a grinding wheel to grind and repair the explosively welded parts at both ends of the straightened annealed copper-embedded cathode steel rod to make an explosively composite welded copper-embedded cathode steel rod.

2. An explosively welded copper-embedded cathode steel rod prepared by the method described in claim 1.

3. The explosively composite welded copper-embedded cathode steel rod as described in claim 2, characterized in that, The copper-embedded cathode steel rod has the following dimensions: 195mm×170mm×2200mm, 220mm×1260mm×3000mm, 160mm×230mm×1970mm, 170mm×195mm×1900mm, 170mm×210mm×2255mm, or 100mm×230mm×2040mm.

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