Method for eliminating excessive welding space and welding protrusion of non-product ingot butt welding

Abstract

The application discloses a method for eliminating excessive welding space and welding protrusion of non-product ingot butt welding, and particularly relates to machining of the head of the non-product ingot which is located at the butt welding position after assembly, wherein the distance between the center of the end face of the head of the non-product ingot and the center of the bottom end face is less than or equal to 5 mm during assembly, the arc light and the molten drop falling position are located inward during butt welding, a large stable arc current value is provided during butt welding, and the arc is restrained to prevent irregular wandering; meanwhile, the current is gradually increased, the butt welding time is controlled within a certain range, the molten liquid flowing down along the ingot body is greatly reduced, the risk of forming a large welding protrusion is avoided, sufficient molten liquid is ensured during butt welding of the non-product, the casting ingot welding space is prevented, the smelting safety risk is reduced, and the production efficiency is ensured.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and specifically to a method for eliminating weld voids and excessive weld beads in butt welding of non-finished ingots. Background Technology

[0002] Vacuum arc remelting furnaces (VARs) are commonly used equipment in titanium alloy production. To improve production efficiency, two or more non-finished ingots are often butt-welded together to form a single electrode (also known as an assembled electrode) for melting. During butt welding of non-finished ingots, due to the presence of flash at the ingot head and the concave surface of the head end, the arc light concentrates near the edge for a long time. Molten droplets fall onto the bottom edge of the lower non-finished ingot, which can easily cause the bottom edge of the ingot to melt and the molten droplets to flow along the ingot body, forming large weld beads or even weld voids.

[0003] For VAR ingot smelting, excessively large weld beads or voids in the butt welding of unfinished ingots can affect smelting safety (excessively large weld beads are prone to arcing against the crucible wall, and voids pose a risk of ingot breakage during smelting). Generally, it requires repair welding using a vacuum plasma welding box or re-sawing and butt welding in the VAR furnace. This repeated rework severely reduces production efficiency, and voided electrodes also pose safety risks during hoisting. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for eliminating weld voids and excessive weld beads in the butt welding of non-finished ingots. This method can solve the problems of excessive weld beads and even weld voids that occur during the butt welding of non-finished ingots in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for eliminating weld voids and excessively large weld beads in butt welding of non-finished ingots, characterized by comprising the following steps: Step 1), Preprocessing: For ingots whose head end face is not located at the weld joint after assembly, the head edge is flattened to obtain a flat-headed ingot; for ingots whose head end face is located at the weld joint after assembly, machining is performed. Specifically, the side of the ingot within 60mm-100mm of its head end face is peeled off using a lathe, requiring 10mm-55mm to be machined on one side. Then, the head end face is machined to make it flat (machined width ≥3mm) to obtain a machined ingot. The flash height is ≤20mm and the flatness is ≤2mm. The advantage of flattening the head is that it can make the head of the non-finished ingot so that it can stand well on the bottom of the crucible. Step 2), Assembly: The assembly is carried out in sequence, with the flat-headed non-finished ingot turned upside down so that its head end face is down and its bottom end face is up, and then the head of the flat-headed non-finished ingot is placed on the bottom pad of the crucible; the machined non-finished ingot is turned upside down so that its head end face is down and its bottom end face is up, and then it is placed on the bottom end face of the flat-headed non-finished ingot. Taking the assembly of two non-finished ingots as an example, the assembly refers to the following: both pre-treated non-finished ingots (cylinders) are erected with their head end face down and their bottom end face up, with one non-finished ingot standing on the bottom end face of the other non-finished ingot (the contact point between the end faces of the two non-finished ingots is the butt weld). Step 3), Welding: The assembled non-finished ingots are loaded into the furnace, sealed, and evacuated. The auxiliary electrode (the head of the auxiliary electrode is connected to the electrode rod of the vacuum self-consuming arc furnace and is located on top of the assembled electrode (non-finished ingot)) is welded to the non-finished ingot. The welding current is 3kA-20kA and the welding voltage is 18V-33V. After cooling for ≥40 minutes, the welding is inspected, and the non-finished ingots to be butted are re-aligned. (During the furnace loading process, a crane is used to hoist the crucible to the designated position, which may cause horizontal displacement of the non-finished ingots during the crucible hoisting process. When the auxiliary electrode and the non-finished ingot are welded, the horizontal position of "electrode rod of the vacuum self-consuming arc furnace - auxiliary electrode - uppermost welded non-finished ingot" can be adjusted by the XY adjustment device of the vacuum self-consuming arc furnace. By adjusting the horizontal position of the non-finished ingot welded with the auxiliary electrode, the center distance between the head end face and the bottom end face of the non-finished ingot at the butt weld point is ensured to be ≤5mm.) The furnace is then sealed and evacuated. Step 4) Butt welding is performed between the non-finished ingots processed in Step 3), and the welding current is gradually increased during the butt welding process.

[0006] Furthermore, in step 4), when butt welding between non-finished ingots, the specific operation of gradually increasing the butt welding current is as follows: when the diameter of the non-finished ingot is Φ580mm-Φ800mm, the magnitude of the butt welding current (kA) / corresponding duration (min) changes gradually as follows: 3 / (2~3)→3.5 / (2~3)→4 / (2~3)→4.5 / (2~3)→5 / (2~3)→5.5 / (3~4)→6 / (3~4)→6.5 / (3~4)→Subsequently, when the current... When the current is below 9kA, increase it by 0.5kA each time and maintain for 3-4 minutes. When the current is 9kA or above, increase it by 1kA each time and maintain for 3-4 minutes until unsolidified molten metal is observed throughout the welding area in the video through the camera of the vacuum arc furnace. Maintain the current at this point ("at this point" is between 7kA and 13kA in this specification range) and hold for 1 minute after the molten pool is full. Then, press down the electrode rod to end the welding (total welding time controlled). The welding current (kA) and the corresponding duration (min) change progressively as follows: 3 / (2~3)→3.5 / (2~3)→4 / (2~3)→4.5 / (2~3)→5 / (2~3)→5.5 / (3~4)→6 / (3~4)→6.5 / (3~4)→7 / (3~4)→7.5 / (3~4)→8 / (3~3)→6.5 ... ~4)→8.5 / (3~4)→9 / (3~4)→Increase by 1kA each time and maintain for 3min~4min until the camera of the vacuum arc furnace shows that there is unsolidified molten metal in the entire welding position in the video. Maintain the current at this time (the current at this time is between 13kA and 20kA in this specification range) unchanged. After the molten pool is full, maintain for 1min, and then press down the electrode rod to end the welding (the total welding time is controlled between 20min and 60min).

[0007] Furthermore, in step 5), when butt welding between non-finished ingots, the welding voltage is 20V~30V and the arc stabilizing current is set to 14A~20A.

[0008] The working principle of this invention is as follows: When butt welding non-finished ingots, the normal cooling of the molten metal causes the ingot head to be concave. Additionally, during furnace loading, the flash at the head contacts the bottom of the ingot. When the arc is initiated, the arc is located at the edge, causing molten droplets to accumulate there. This easily leads to the molten droplets flowing down the ingot body after the bottom edge melts due to heat, resulting in large weld beads and weld voids. This invention reduces the size of the ingot head, causing the molten droplets to fall further inwards during butt welding (compared to non-finished ingots where the head is only flattened, the arc is located at the edge of the end face, and the molten droplets fall further outwards). Simultaneously, a large, stable arc current is used to concentrate the arc, preventing discharge at the bottom edge and preventing molten metal from flowing down the non-finished ingot body. The welding current is gradually increased, and the welding time is controlled to ensure a full molten metal flow during butt welding. Statistically, the probability of weld voids is 0%. This invention reduces the difficulty of butt welding operations and lowers safety risks.

[0009] Compared with the prior art, the present invention has the following beneficial effects: This invention machined the head of the non-finished ingot, which will be located at the butt welding point after assembly, to obtain an ingot with a machined diameter smaller than the normal diameter within a certain range from the head. Then, the head end face is machined to ensure a good fit between the head end face and the bottom end face during assembly. During assembly, the center distance between the head end face and the bottom end face of the non-finished ingot is ≤5mm. During butt welding, the arc and molten droplet positions are further inward (compared to the ingot head which only undergoes flattening, with the arc located at the edge of the end face and the molten droplet area further outward). A large, stable arc current value is applied during butt welding to generate a large Lorentz centripetal force, binding the arc and preventing it from wandering erratically. Simultaneously, the current is gradually increased to control the butt welding time within a certain range (too long a time can easily lead to weld beads, while too short a time can result in insufficient molten material and voids), greatly reducing the risk of molten material flowing down the ingot body and forming large weld beads. This ensures sufficient molten material during butt welding of the non-finished ingot, prevents voids in the ingot, reduces smelting safety risks, and guarantees production efficiency. Attached Figure Description

[0010] Figure 1 This describes the processing morphology of flattening the head of a non-finished ingot in the existing technology; Figure 2 This refers to the machining morphology of the non-finished ingot head that will be located at the welding point after assembly in this invention. Figure 3 This is a diagram illustrating the welding area of ​​the titanium alloy ingot obtained after processing in Embodiment 1 of the present invention. Figure 4 This is a diagram illustrating the welding area of ​​the titanium alloy ingot obtained after processing in Embodiment 2 of the present invention; Figure 5 This is a diagram of the welding part of the titanium alloy ingot obtained after the treatment in Comparative Example 1 of the present invention. Figure 6 This is a diagram of the welding area of ​​the titanium alloy ingot obtained after treatment in Comparative Example 2 of the present invention. Detailed Implementation

[0011] The present invention will now be further described in conjunction with specific embodiments and comparative examples. Example 1

[0012] Step 1) Take two non-finished ingots (numbered A and B, with B on top and A on the bottom during assembly, and the head end face of B standing upright on the bottom end face of A) with a specification of Φ980mm, and flatten the head edge of the A ingot (flash height ≤ 20mm, unevenness ≤ 2mm) to make its head flat so that it can stand well on the bottom pad of the crucible, thus obtaining a flat-headed non-finished ingot. See the processing effect. Figure 1 ; Step 2) Machining the Φ980mm non-finished ingot B requires using a lathe to peel off the outer surface of the side within 100mm of the head end face, turning 50mm on each side, resulting in a non-finished ingot with a reduced radius of 50mm after peeling. Then, the head end face of B is machined to flatten it (machining width ≥ 3mm), resulting in a machined non-finished ingot. See the processing result below. Figure 2 .

[0013] Step 3) Assemble the ingots obtained in Step 1) and Step 2) with B on top and A on the bottom, and with the head end face of B standing on the bottom end face of A. Make B (the side of the non-finished ingot within 100mm of the head end face of the non-finished ingot is machined (50mm on one side) with a diameter smaller than the normal diameter) with the head end face down above the butt welding position (i.e., above the bottom end face of A). Step 4) Load the assembled non-finished ingots from Step 3) into the furnace, seal the furnace, evacuate the furnace, and weld the auxiliary electrode to the non-finished ingots. The welding current is 3kA~20kA and the welding voltage is 18V~33V. After cooling for ≥40min, check the welding. Re-align the non-finished ingots to be welded and seal the furnace and evacuate the furnace. The center distance is ≤5mm. Step 5) Perform butt welding between the electrodes completed in Step 4), using a progressively increasing current (kA / min): 3 / 2 → 3.5 / 2 → 4 / 2 → 4.5 / 2 → 5 / 2 → 5.5 / 3 → 6 / 3 → 6.5 / 3 → 7 / 3 → 7.5 / 3 → 8 / 3 → 8.5 / 3 → 9 / 3 → 10 / 3 → 11 / 3 → 12 / 3 → 13 / (6 min + 1 min for holding the molten pool after it is full). Then, press down the electrode rod to end the butt welding. The butt welding time is 50 min. The butt welding uses a large stable arc current of 14A~20A and a welding voltage of 20V~30V. After the butt welding is completed, cool and inspect the welding.

[0014] After testing, the probability of large weld beads and weld voids in the titanium alloy ingot obtained in this embodiment was 0%. Figure 3 As shown. Example 2

[0015] Step 1) Take two non-finished ingots (numbered C and D, with D on top and C on the bottom during assembly, and the head end face of D standing upright on the bottom end face of C) with a specification of Φ780mm, and flatten the burr at the head of C (burr height ≤ 20mm, unevenness ≤ 2mm) to make its head flat so that it can stand well on the bottom pad of the crucible, thus obtaining a flat-headed non-finished ingot. See the processing effect. Figure 1 ; Step 2) Machining the Φ780mm non-finished ingot D requires using a lathe to peel off the outer surface of the side within 60mm of the head end face, turning 10mm on each side, resulting in a non-finished ingot with a reduced radius of 10mm after peeling. Then, the head end face of D is machined to make it flat (machining width ≥ 3mm), resulting in a machined non-finished ingot. The machining effect is shown in the figure. Figure 2 .

[0016] Step 3) Assemble the ingots obtained in Step 1) and Step 2) with D on top and C on the bottom, and with the head end face of D standing on the bottom end face of C. Make the head end face of D (the side of the non-finished ingot within 60mm of the head end face of the non-finished ingot is machined (10mm on one side) with a diameter smaller than the normal diameter) face down and stand on the upper part of the butt welding position (i.e., on the top of the bottom end face of A). Step 4: Load the assembled non-finished ingots from Step 3) into the furnace, seal the furnace, evacuate the furnace, and weld the auxiliary electrode to the non-finished ingots. The welding current is 3kA~20kA and the welding voltage is 18V~33V. After cooling for ≥40min, check the welding. Re-align the non-finished ingots to be welded and seal the furnace and evacuate the furnace. The center distance is ≤5mm. Step 5: Perform butt welding between the electrodes completed in Step 4). The welding current is increased stepwise in kA / min: 3 / 2→3.5 / 2→4 / 2→4.5 / 2→5 / 2→5.5 / 3→6 / 3→6.5 / 3→7 / 3→7.5 / 3→8 / 3→8.5 / 3→9 / 3→10 / (7 min + 1 min holding time after the molten pool is full). Then press down the electrode rod to end the butt welding. The butt welding time is 42 min. The butt welding uses a large stable arc current of 14A~20A and a welding voltage of 20V~30V. After the butt welding is completed, cool and inspect the welding.

[0017] After testing, the probability of large weld beads and weld voids in the titanium alloy ingot obtained in this embodiment was 0%. Figure 4 As shown. Comparative Example 1

[0018] Step 1) Flatten the flash on the heads of the two non-finished ingots (Φ580mm, numbered E and F, with F on top and E on the bottom during assembly, and the head end face of F standing on the bottom end face of E) for welding (flash height ≤ 20mm, unevenness ≤ 2mm) to make the heads flat. See the processing effect. Figure 1 ; Step 2) Assemble the non-finished ingots obtained in Step 1) with F on top and E on the bottom, and with the head end face of F standing on the bottom end face of E. Step 3) Load the assembled non-finished ingots from Step 2) into the furnace, seal the furnace, evacuate the furnace, and weld the auxiliary electrode to the non-finished ingots. The welding current is 3kA-20kA and the welding voltage is 18V-33V. After cooling for ≥40min, check the welding. Re-align the non-finished ingots to be welded and seal the furnace and evacuate the furnace. The center distance is ≤5mm. Step 4) Perform butt welding between the electrodes completed in Step 3) using non-finished ingots. The welding current is 3kA~20kA, the welding voltage is 18V~33V, the arc current is 5A~12A, and the welding time is 50min. After the butt welding is completed, cool and inspect the welding.

[0019] After testing, the probability of large weld beads and weld voids in the titanium alloy ingot obtained in this embodiment was 15%. Figure 5 As shown. Comparative Example 2

[0020] Step 1) Flatten the flash on the heads of the two non-finished ingots (Φ680mm, numbered G and H, with H on top and G on the bottom during assembly, and the head end face of H standing on the bottom end face of G) for welding (flash height ≤ 20mm, unevenness ≤ 2mm) to make the heads flat. See the processing effect. Figure 1 ; Step 2) Assemble the non-finished ingots obtained in Step 1) with H on top and G on the bottom, and with the head end face of H standing on the bottom end face of G. Step 3) Load the assembled non-finished ingots from Step 2) into the furnace, seal the furnace, evacuate the furnace, and weld the auxiliary electrode to the non-finished ingots. The welding current is 3kA-20kA and the welding voltage is 18V-33V. After cooling for ≥40min, check the welding. Re-align the non-finished ingots to be welded and seal the furnace and evacuate the furnace. The center distance is ≤5mm. Step 4) Perform butt welding between the electrodes completed in Step 3). The welding current is increased stepwise in kA / min: 3 / 2→3.5 / 2→4 / 2→4.5 / 2→5 / 2→5.5 / 3→6 / 3→6.5 / 3→7 / 3→7.5 / 3→8 / 3→8.5 / 3→9 / 3→10 / (5min + 1min holding time after the molten pool is full). Then press down the electrode rod to end the butt welding. The butt welding time is 40min. The butt welding uses a large stable arc current of 14A~20A and a welding voltage of 20V~30V. After the butt welding is completed, cool and inspect the welding.

[0021] After testing, the probability of large weld beads and weld voids in the titanium alloy ingot obtained in this embodiment was 10%. Figure 6 As shown.

Claims

1. A method for eliminating weld voids and excessively large weld beads in butt welding of non-finished ingots, characterized in that, Includes the following steps: Step 1), Preprocessing: For ingots whose head end face is not located at the weld joint after assembly, the head edge is flattened to obtain a flat-headed ingot; for ingots whose head end face is located at the weld joint after assembly, machining is performed. Specifically, the side of the ingot within 60mm-100mm of its head end face is peeled off using a lathe, requiring 10mm-55mm to be machined on one side. Then, the head end face is machined to make it flat to obtain a machined ingot. Step 2), Assembly: The assembly is carried out in sequence, with the flat-headed non-finished ingot turned upside down so that its head end face is down and its bottom end face is up, and then the head of the flat-headed non-finished ingot is placed on the bottom pad of the crucible; the machined non-finished ingot is turned upside down so that its head end face is down and its bottom end face is up, and then it is placed on the bottom end face of the flat-headed non-finished ingot. Step 3), Welding: The assembled non-finished ingots are loaded into the furnace, sealed, and evacuated. The auxiliary electrodes are then welded to the non-finished ingots with a welding current of 3kA-20kA and a welding voltage of 18V-33V. After cooling for ≥40 minutes, the welding is inspected. The non-finished ingots to be welded are then re-aligned, and the furnace is sealed and evacuated to ensure that the center distance between the head end face and the bottom end face of the non-finished ingot is ≤5mm. Step 4) Butt welding is performed between the non-finished ingots processed in Step 3), and the welding current is gradually increased during the butt welding process.

2. The method for eliminating weld voids and excessive weld beads in non-finished ingot butt welding according to claim 1, characterized in that, Step 4) When butt welding between non-finished ingots, the specific operation of gradually increasing the butt welding current is as follows: When the diameter of the non-finished ingot is Φ580mm-Φ800mm, the magnitude of the butt welding current (kA) and the corresponding duration (min) are gradually changed as follows: 3 / (2-3)→3.5 / (2-3)→4 / (2-3)→4.5 / (2-3)→5 / (2-3)→5.5 / (3-4)→6 / (3-4)→6.5 / (3-4)→Subsequently, when the current is below 9kA, increase it by 0.5kA each time and maintain it for 3min-4min; when the current is 9kA or above, increase it by 1kA each time and maintain it for 3min-4min until the camera of the vacuum arc furnace observes that there is unsolidified molten liquid at the entire butt welding position in the video. Maintain the current unchanged at this time, and maintain it for 1min after the molten pool is full. Then press down the electrode rod. Butt welding; when the diameter of the non-finished ingot is Φ800mm-Φ980mm, the welding current kA / corresponding duration min changes step by step as follows: 3 / (2-3)→3.5 / (2-3)→4 / (2-3)→4.5 / (2-3)→5 / (2-3)→5.5 / (3-4)→6 / (3-4)→6.5 / (3-4)→7 / (3-4)→7.5 / (3-4)→8 / (3-4)→8.5 / (3-4)→9 / (3-4)→ Each subsequent increase of 1kA is maintained for 3min-4min until the entire welding position is observed to have unsolidified molten liquid in the video through the camera of the vacuum self-consuming electric arc furnace. The current is maintained at this time, and after the molten pool is full, it is maintained for 1min. Then the electrode rod is pressed down to end the welding; the total welding time is controlled between 20min-60min.

3. The method for eliminating weld voids and excessive weld beads in non-finished ingot butt welding according to claim 2, characterized in that, Step 5) When welding non-finished ingots together, the welding voltage is 20V-30V and the arc stabilization current is set to 14A-20A.

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