Method for recycling scrapped auxiliary electrode

Abstract

The invention discloses a method for recycling a scrapped auxiliary electrode, and relates to the technical field of titanium alloy materials, and the method comprises the following steps: carrying out machining, sand blasting or acid pickling on the auxiliary electrode to remove black skin and weld beading on the surface; the head and bottom end faces are machined and flattened; the treated auxiliary electrodes with the diameter error not exceeding 5% are connected end to end in series to form a 1 * N consumable electrode, the alloy adding procedure is transferred to the vacuum consumable smelting procedure from electrode preparation, the risk that high-density inclusion is introduced due to punch cracking when an oil press is used in the electrode preparation process is avoided, and technical innovation is achieved; before wrapping, the sponge titanium and the alloy additive are mixed in a stainless steel or titanium container, it is ensured that TiO2, C powder, aluminum molybdenum and other alloy additives are fully dispersed, a blocky low-density inclusion source formed after the powdery alloy additive is stacked and subjected to high-pressure compression molding is avoided, and the technical principle is obviously superior to that of a traditional compression process.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy materials, and in particular to a method for recycling scrapped auxiliary electrodes. Background Art

[0002] Titanium alloys are widely used in aviation, aerospace, weapons, ships, nuclear industry, medical equipment and other fields due to their excellent properties such as high strength, good corrosion resistance and high heat resistance. Due to the high cost of titanium raw materials, the complex processing technology, low yield rate and the strong demand for titanium materials, the combined factors lead to high costs of titanium alloy products. How to reasonably and low-costly utilize the waste generated in the titanium alloy production process to achieve remelting and recycling is one of the necessary ways to reduce the production cost of titanium alloy products. At present, the main production method of titanium alloy ingots is vacuum consumable arc furnace smelting (VAR).

[0003] In vacuum consumable arc melting, the auxiliary electrode is a transition material connecting the electrode rod and the consumable electrode, which protects the electrode rod from arc damage. Considering the cost of materials and the versatility of grades, the auxiliary electrode or parent material is mostly pure titanium rods machined from the machine. The auxiliary electrode will experience varying degrees of loss during each melting process until it is scrapped because its length is less than the safe melting distance (about 300mm) or it is deformed due to frequent use. For an enterprise that produces 10,000 tons of titanium ingots annually, about 15 to 20 tons of scrapped pure titanium auxiliary electrodes are generated each year, resulting in huge cost losses.

[0004] The existing pure titanium auxiliary electrode recycling technology is mainly to melt it into pure titanium ingots through an electron beam melting furnace (EB furnace). The EB furnace equipment used in this method is expensive. Compared with the imported VAR furnace of the same capacity, its cost is 3.5 to 4 times that of the latter, and there are only a handful of manufacturers with EB furnaces. In addition, when this method produces alloy-type titanium alloys, it is difficult to control the composition, and only scrapped auxiliary electrodes can be prepared into pure titanium with low economic value.

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for recycling and reusing pure titanium auxiliary electrodes and a new titanium alloy manufacturing process, which can directly prepare titanium alloy ingots of different grades after casting and melting alloy ladles of pure titanium auxiliary electrodes in units. It saves resources, improves the utilization rate of raw materials, has strong economic value, and can be promoted and applied in large quantities. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for recycling scrapped auxiliary electrodes, which can directly prepare titanium alloy ingots of different grades by casting and smelting the pure titanium auxiliary electrodes in units, thereby saving resources, improving the utilization rate of raw materials, and having strong economic value.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for recycling scrapped auxiliary electrodes, wherein the auxiliary electrodes are subjected to mechanical processing, sandblasting or pickling to remove black skin and weld nodules on the surface; the head and bottom end faces are machined flat; the processed auxiliary electrodes with a diameter error of no more than 5% are end-to-end connected in series to form 1×N consumable electrodes, and the number of auxiliary electrodes assembled for a single consumable electrode is required to be no more than 15, that is, N≤15, and N represents a single electrode unit.

[0008] Preferably, the assembled consumable electrode is placed horizontally in a vacuum argon arc welding box for argon filling welding, or is vertically erected on the center of the crucible of a vacuum consumable arc furnace for furnace butt welding; vacuum argon arc welding process parameter requirements: furnace pre-vacuum ≤ 5Pa, leakage rate ≤ 1.0Pa / min, welding current 150-500A, argon gas flow rate 10-40L / min, and annular weld width 20mm~35mm.

[0009] Preferably, the welding process parameters in the vacuum consumable arc furnace are as follows: pre-vacuum in the furnace ≤5Pa, leakage rate ≤1.0Pa / min, welding current 3kA~10kA, and weld area not less than 2 / 3 of the electrode diameter; the type and quantity of alloy additives vary according to the brand of the prepared ingot, including but not limited to: one or more of Al beans, aluminum vanadium, TiO2, titanium iron, C powder, HZr, copper titanium, aluminum silicon, aluminum molybdenum, aluminum niobium, titanium tin, aluminum tantalum and other alloy additives.

[0010] Preferably, the alloy additives are evenly distributed according to a preset number of portions, and the alloy is packaged with aluminum foil, copy paper, or a plastic box. 50g to 150g of small-particle titanium sponge with a particle size of 0.83 to 12.7μm is added to each portion of the alloy. Before packaging, the small-particle titanium sponge with a particle size of 0.83 to 12.7μm and the alloy additives are mixed in a stainless steel or titanium container to ensure that the alloy additives such as TiO2, C powder, aluminum molybdenum, etc. are fully dispersed, thereby avoiding the formation of blocky low-density inclusions after the powdered alloy additives are piled up and pressed under high pressure, which is significantly superior to the traditional pressing process in terms of technical principles.

[0011] Preferably, the size of the alloy package is determined by the diameter of the water-cooled copper crucible and the type of alloy additive. The maximum size of the alloy package is generally not greater than 0.3 times the diameter of the crucible, the size range is about 30 to 130 mm, the number is 2 to 10, and the alloy additive is required to be spilled during weighing. The shape of the packaged alloy package is spherical or lumpy, and it is required to be free of damage; the number of smelting times is selected according to the grade of the ingot alloy, and generally, it should be smelted no less than 2 times; the prepared consumable electrode is smelted in a vacuum consumable arc furnace, and the pre-vacuum in the furnace is required to be ≤5Pa and the leakage rate is ≤1.0Pa / min.

[0012] Preferably, the primary smelting requirements are: use of a large crucible ratio, low voltage short arc smelting and lifting process to prevent the ingot flash from flowing during the alloy solution, increase the molten pool depth and activity through a strong DC arc stabilization and high current casting and smelting process to improve the distribution uniformity of the primary ingot alloy, and the primary smelting process parameters are: crucible φ300mm~φ480mm (crucible diameter: electrode diameter = 1.5~2.5), normal smelting stage current 10~16kA, voltage 28~32V, arc stabilization (DC) 8~12A; during the primary smelting, after melting 1 / 2 of the electrode unit weight, the circuit breaker trips and breaks the arc, and the electrode rod is quickly lifted to an appropriate position. After the metal molten pool is cooled in the furnace for 3~7 minutes, the alloy package is cast, and then the melting of the remaining 1 / 2 of the electrode unit weight is completed to achieve the molten liquid wrapping the alloy package, and the remaining consumable electrode melting is completed according to this smelting method.

[0013] Preferably, the secondary and tertiary smelting adopt a weak stirring AC stable arc smelting process to ensure that an ingot with uniform chemical composition is smelted. The secondary smelting crucible is φ400mm~φ580mm, the current is 15~20kA, the stable arc (AC) is 5~8A, and the voltage is 30~36V; the tertiary smelting crucible is φ480mm~φ650mm, the current is 18~24kA, the voltage is 31~36V, and the stable arc (AC) is 4~8A; the ingot after the tertiary smelting is machined, sampled and sawed at the riser.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention transfers the alloy adding process from electrode preparation to the vacuum consumable melting process, thus avoiding the risk of high-density inclusions introduced by punch cracking when using an oil press during electrode preparation, thus achieving technical innovation; before packaging, the titanium sponge and alloy additives are mixed in a stainless steel or titanium container to ensure that alloy additives such as TiO2, C powder, aluminum and molybdenum are fully dispersed, thus avoiding the formation of blocky low-density inclusions after the powdered alloy additives are piled up and pressed under high pressure, which is significantly superior to the traditional pressing process in terms of technical principle; the present technology proposes a large crucible ratio, Low voltage is used to increase the flash of the casting ingot to prevent the alloy from flowing. The strong stable arc and high current casting and melting process is used to increase the depth and activity of the molten pool and improve the uniformity of the distribution of the primary casting alloy. Then, by selecting a reasonable crucible size, the height of the primary casting ingot, i.e. the electrode unit, and the secondary and tertiary melting processes with low current and weak stirring, it is ensured that the chemical composition of the ingot is uniformly melted, and the technical problem of the recycling of auxiliary electrodes is solved. The backlog of scrapped auxiliary electrodes in the production process can be digested, and a higher yield is achieved. There is basically no residual waste generated during the processing process, which is conducive to improving the utilization rate of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of the auxiliary electrode recovery process of the present invention. DETAILED DESCRIPTION

[0017] See also Figure 1 , the present invention provides a technical solution:

[0018] Embodiment 1:

[0019] A method for recycling scrapped auxiliary electrodes, which includes mechanical processing, sandblasting or pickling of the auxiliary electrodes to remove black skin and weld nodules on the surface; machining the head and bottom end faces flat; assembling the processed auxiliary electrodes with a diameter error of no more than 5% end to end in series to form 1×N consumable electrodes, requiring that the number of auxiliary electrodes assembled for a single consumable electrode does not exceed 15, that is, N≤15, N represents a single electrode unit; placing the assembled consumable electrodes horizontally in a vacuum argon arc welding box for argon filling welding, or vertically erecting them on the center of the crucible of a vacuum consumable arc furnace for in-furnace butt welding; vacuum argon arc welding process parameter requirements: pre-vacuum in the furnace ≤5P a, leakage rate ≤1.0Pa / min, welding current 150-500A, argon flow rate 10-40L / min, girth weld width 20mm~35mm; butt welding process parameter requirements in vacuum consumable arc furnace: pre-vacuum in the furnace ≤5Pa, leakage rate ≤1.0Pa / min, welding current 3kA~10kA, weld area not less than 2 / 3 electrode diameter; the type and quantity of alloy additives vary according to the grade of the prepared ingot, including but not limited to: one or more of Al beans, aluminum vanadium, TiO2, titanium iron, C powder, HZr, copper titanium, aluminum silicon, aluminum molybdenum, aluminum niobium, titanium tin, aluminum tantalum and other alloy additives;

[0020] The alloy additives are evenly distributed according to the preset number of portions, and the alloy is packaged with aluminum foil, copy paper, or plastic boxes. 50g to 150g of small-particle titanium sponge with a particle size of 0.83 to 12.7μm is added to each portion of the alloy. Before packaging, the 0.83 to 12.7μm small-particle titanium sponge and alloy additives are mixed in a stainless steel or titanium container to ensure that the TiO2, C powder, aluminum molybdenum and other alloy additives are fully dispersed, avoiding the formation of blocky low-density inclusions due to the accumulation of powdered alloy additives and high-pressure pressing. The technical principle is significantly superior to the traditional Pressing process; the size of the alloy package is determined by the diameter of the water-cooled copper crucible and the type of alloy additives. The maximum size of the alloy package is generally not greater than 0.3 times the diameter of the crucible, the size range is about 30-130mm, and the number is 2-10. The alloy additives must not be spilled during weighing. The shape of the packaged alloy package is spherical or lumpy, and it must not be damaged; the number of smelting times is selected according to the ingot alloy grade. Generally, it should be smelted for no less than 2 times; the prepared consumable electrode is melted in a vacuum consumable arc furnace, and the pre-vacuum in the furnace is required to be ≤5Pa and the leakage rate is ≤1.0Pa / min;

[0021] Primary smelting requirements: Use large crucible ratio, low voltage short arc melting and ingot flash during lifting to prevent alloy solution from flowing, increase molten pool depth and activity through strong DC arc stabilization and high current casting and smelting process to improve the uniformity of primary ingot alloy distribution, primary smelting process parameters: crucible φ300mm~φ480mm (crucible diameter: electrode diameter = 1.5~2.5), current 10~16kA, voltage 28~32V, arc stabilization (DC) 8~12A in normal smelting stage; during primary smelting, trip the circuit breaker after melting 1 / 2 of the electrode unit weight, quickly lift the electrode rod to the appropriate position, and wait for the metal molten pool to cool in the furnace for 3~7min, Cast the alloy package, and then complete the melting of the remaining 1 / 2 electrode unit weight to achieve the molten metal wrapping the alloy package. According to this melting method, complete the melting of the remaining consumable electrode; the secondary and tertiary melting adopt the weak stirring AC stable arc melting process to ensure the melting of ingots with uniform chemical composition. The secondary melting crucible is φ400mm~φ580mm, the current is 15~20kA, the stable arc (AC) is 5~8A, and the voltage is 30~36V; the tertiary melting crucible is φ480mm~φ650mm, the current is 18~24kA, the voltage is 31~36V, and the stable arc (AC) is 4~8A; the ingots after the third melting are machined, sampled and sawed at the riser.

[0022] Embodiment 2:

[0023] Step 1: Select 10 pure titanium auxiliary electrodes with a size of φ260×(312~345)mm that have been scrapped due to size, and use turning and sawing to machine them into φ250×

[0024] (300~320)mm, and the end surfaces of both ends are flat and reveal the metallic luster of pure titanium rod blank;

[0025] Step 2: Precisely batch the 10 pure titanium rods in step 1. Each electrode unit requires 3 alloy packages. Take TC4 ingot as an example. The target composition of TC4 titanium ingot is Ti-6.0Al-4.0V-0.15Fe-0.08O, i.e., Al content (5.5-6.75)%, V content (3.5-4.5)%, Fe content (0.10-0.20)%, O content (0.06-0.12)%, and the rest is Ti element.

[0026] Step 3: Al is added in the form of aluminum foil and aluminum beans, V, Fe, and O elements are added in the form of AlV65 particles, Ti-32Fe particles, and TiO2 powder, respectively. 50g of titanium sponge with a particle size of 0.83-12.7μm is added to each alloy package; each alloy package is made of aluminum foil, and the alloy content is: 100g aluminum foil, 768g aluminum beans, 1389g AlV65 particles, 106g Ti-32Fe particles, 45.2g TiO2 powder, and the size of the alloy package is 100mm;

[0027] Step 4: Before each alloy bag is packaged, the alloy additives need to be fully mixed in a stainless steel material basin. During the packaging process, there is no alloy additive spillage and alloy bag leakage;

[0028] Step 5: Assemble 10 pure titanium rods into a 1×10 pattern and weld them end to end in a vacuum plasma welding box. The vacuum argon arc welding process parameters are: pre-vacuum in the furnace ≤5Pa, leakage rate ≤1.0Pa / min, welding current 150-400A, argon gas flow rate 20L / min, and girth weld width of about 30mm;

[0029] Step 6: Melt the consumable electrode in a vacuum consumable arc furnace. Use a φ400mm crucible ((crucible diameter: electrode diameter = 1.6)) for one melting. Set the current to 14KA, the voltage to 28V, the arc stabilization DC12A, and ensure short arc operation during the melting process. When the electrode length is consumed by 150mm (1 / 2 of the length of a single electrode unit), trip the circuit breaker to break the arc, add 3 alloy packages, and start the arc to continue melting the remaining 1 / 2 of the single electrode unit. Repeat this process to complete the remaining 9 single electrode units.

[0030] Step 7: Flatten the primary ingot smelted in step 6 and then turn it over for secondary smelting;

[0031] Step 8: Use a φ480mm crucible for secondary smelting, set the current to 20KA, the voltage to 32V, and the arc stabilization DC7A;

[0032] Step 9: After flattening the secondary ingot melted out of the furnace in step 8, perform tertiary smelting. The process parameters for the tertiary smelting are: use a φ550mm crucible, set the current to 22KA, the voltage to 34V, and the arc stabilization DC6A;

[0033] Step 10: Take samples from the head, middle and tail of the ingot three times to analyze all elements, and the test results are qualified.

[0034] Under this process, the composition test results of the TC4 titanium alloy ingot prepared are as follows:

[0035]

[0036]

Claims

1. A method for recycling scrapped auxiliary electrodes, characterized in that: The auxiliary electrode is subjected to mechanical processing, sandblasting or pickling to remove black skin and weld nodules on the surface; the head and bottom end faces are machined flat; the processed auxiliary electrodes with a diameter error of no more than 5% are end-to-end connected in series to form 1×N consumable electrodes, and the number of auxiliary electrodes of a single consumable electrode is required to be no more than 15, that is, N≤15, and N represents a single electrode unit.

2. A method for recycling scrapped auxiliary electrodes according to claim 1, characterized in that: The assembled consumable electrode is placed horizontally in a vacuum argon arc welding box for argon filling welding, or is vertically erected on the center of the crucible of a vacuum consumable arc furnace for furnace butt welding; the vacuum argon arc welding process parameter requirements are: furnace pre-vacuum ≤5Pa, leakage rate ≤1.0Pa / min, welding current 150-500A, argon gas flow rate 10-40L / min, and annular weld width 20mm~35mm.

3. A method for recycling scrapped auxiliary electrodes according to claim 1, characterized in that: The welding process parameter requirements in the vacuum consumable arc furnace are: pre-vacuum in the furnace ≤5Pa, leakage rate ≤1.0Pa / min, welding current 3kA~10kA, and the weld area is not less than 2 / 3 of the electrode diameter; the type and quantity of alloy additives vary according to the brand of the prepared ingot, including but not limited to: one or more of Al beans, aluminum vanadium, TiO2, titanium iron, C powder, HZr, copper titanium, aluminum silicon, aluminum molybdenum, aluminum niobium, titanium tin, aluminum tantalum and other alloy additives.

4. A method for recycling scrapped auxiliary electrodes according to claim 1, characterized in that: The alloy additives are evenly distributed according to a preset number of portions, and the alloy is packaged with aluminum foil, copy paper, or a plastic box. 50g to 150g of small-particle sponge titanium with a particle size of 0.83 to 12.7μm is added to each portion of the alloy. Before packaging, the small-particle sponge titanium with a particle size of 0.83 to 12.7μm and the alloy additives are mixed in a stainless steel or titanium container to ensure that the TiO2, C powder, aluminum molybdenum and other alloy additives are fully dispersed, thereby avoiding the formation of blocky low-density inclusions after the powdered alloy additives are piled up and pressed at high pressure. The technical principle is significantly superior to the traditional pressing process.

5. A method for recycling scrapped auxiliary electrodes according to claim 1, characterized in that: The size of the alloy package is determined by the diameter of the water-cooled copper crucible and the type of alloy additives. The maximum size of the alloy package is generally not greater than 0.3 times the diameter of the crucible, the size range is about 30 to 130 mm, and the number is 2 to 10. The alloy additives must not be spilled during the weighing process. The shape of the alloy package is spherical or lumpy, and it is required to be free of damage. The number of smelting times is selected according to the ingot alloy grade. Generally, it should be smelted for no less than 2 times. The prepared consumable electrode is melted in a vacuum consumable arc furnace, and the pre-vacuum in the furnace is required to be ≤5Pa and the leakage rate is ≤1.0Pa / min.

6. A method for recycling scrapped auxiliary electrodes according to claim 1, characterized in that: The primary smelting requirements include: selecting a large crucible ratio, low voltage short arc smelting and lifting process to prevent the ingot flash from flowing during the alloy solution, increasing the depth and activity of the molten pool through a strong DC arc stabilization and high current casting and smelting process to improve the uniformity of the distribution of the primary ingot alloy, and the primary smelting process parameters: crucible φ300mm~φ480mm (crucible diameter: electrode diameter=1.5~2.5), current 10~16kA in the normal smelting stage, voltage 28~32V, arc stabilization (DC) 8~12A; during the primary smelting, after smelting 1 / 2 of the electrode unit weight, the circuit breaker trips and breaks the arc, and the electrode rod is quickly lifted to an appropriate position. After the metal molten pool is cooled in the furnace for 3~7 minutes, the alloy package is cast, and then the smelting of the remaining 1 / 2 of the electrode unit weight is completed to achieve the wrapping of the alloy package by the molten liquid. According to this smelting method, the remaining consumable electrode is smelted.

7. A method for recycling scrapped auxiliary electrodes according to claim 1, characterized in that: The secondary and tertiary smelting adopt a weak stirring AC stable arc smelting process to ensure that an ingot with uniform chemical composition is smelted. The secondary smelting crucible is φ400mm~φ580mm, the current is 15~20kA, the stable arc (AC) is 5~8A, and the voltage is 30~36V; the tertiary smelting crucible is φ480mm~φ650mm, the current is 18~24kA, the voltage is 31~36V, and the stable arc (AC) is 4~8A; the ingot after the tertiary smelting is machined, sampled and sawed at the riser.

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