Vacuum consumable electric arc furnace smelting method for titanium and titanium alloy

Abstract

The invention discloses a titanium and titanium alloy vacuum consumable electric arc furnace smelting method in the technical field of metallurgy. The titanium and titanium alloy vacuum consumable electric arc furnace smelting method comprises the following steps that an electrode block with the preset size and density is machined; an electrode bar formed by splicing the electrode blocks is put into a vacuum arc welding box to be vacuumized; argon is filled, argon filling is stopped when the preset pressure is reached, and standing is maintained for the preset duration; argon is continuously filled, the pressure in the welding box reaches a preset range, electrode bar welding is conducted, and cooling is conducted for a preset duration after electrode bar welding is completed; the welded electrode bar and the prepared auxiliary electrode are placed in a VAR furnace for butt welding, and the self-consuming machine after butt welding is cooled for a preset time length; primary smelting; carrying out secondary smelting; after the electrode blocks are spliced and placed in a vacuum arc welding box, argon with preset pressure is filled, and standing is carried out for preset time, so that it is guaranteed that the argon can penetrate into the electrodes, oxidation in the welding process is reduced, ingot inclusion is reduced, and the surface quality is improved.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for smelting titanium and titanium alloys in a vacuum consumable electric arc furnace. Background Technology

[0002] The VAR furnace, short for Vacuum Consumable Arc Furnace, is one of the main equipment used in China for smelting titanium and titanium alloys. Compared with traditional smelting processes, it has advantages such as high uniformity of ingot composition, less environmental pollution, and a better working environment, and therefore has been widely used in the production of titanium and titanium alloys.

[0003] Before smelting pure titanium in a VAR furnace, the raw material sponge titanium and alloying elements need to be pressed into electrode blocks, and then multiple electrode blocks are welded into electrode rods. During the electrode welding process, oxidation often occurs on the weld seam and electrode surface. Usually, the degree of oxidation is judged by the color of the weld seam and then polished; however, this only treats the surface oxidation of the weld seam and cannot remove the oxidation inside the weld seam. Internal oxidation can also lead to the introduction of inclusions during the smelting process, and the final result is peeling and cracking on the product surface. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is: how to reduce the oxidation state in the weld and improve the quality problems of peeling and wrinkles on the product surface.

[0005] The technical solution adopted by this invention to solve its technical problem is: A method for smelting titanium and titanium alloys in a vacuum consumable arc furnace includes the following steps: S1: Process electrode blocks of preset size and density; S2: Place the electrode rod assembled from the electrode blocks into a vacuum arc welding box and evacuate it; fill it with argon gas, stop filling with argon gas when the preset pressure is reached, and maintain it in place for a preset time; S3: Continuously purge with argon and bring the pressure inside the welding box to the preset range, then perform electrode rod welding, and cool for the preset time after the electrode rod welding is completed; S4: Place the welded electrode rod and the prepared auxiliary electrode in a VAR furnace for butt welding, and set a preset cooling time for the consumable electrode after butt welding. S5: One-time smelting; S6: Secondary smelting.

[0006] Furthermore, in step S1, the electrode diameter ranges from φ470mm to 1050mm, and the electrode density ranges from 3.2g / cm³ to 3.5g / cm³.

[0007] Furthermore, in step S2, argon gas is introduced, and the argon introduction is stopped when the pressure reaches 2000Pa-8000Pa, and the gas is kept stationary for a preset time.

[0008] Furthermore, the settling time ranges from 1 hour to 5 hours.

[0009] Furthermore, in step S3, the pressure range inside the welding box of the welding electric rod is 2000Pa-35000Pa.

[0010] Furthermore, the arc current of the welding electrode rod is in the range of 2000A-8000A, the welding speed is in the range of 0.5mm / min-2mm / min, the welding depth is in the range of 5mm-10mm, the number of welds is 6-10, and the cooling time after welding is ≥60min.

[0011] Furthermore, in step S4, before welding, the gas pressure inside the VAR furnace is reduced to ≤10Pa and the leakage rate is ≤5Pa.

[0012] Furthermore, during butt welding, the arc current range is 3kA-12kA, the voltage range is 28V-36V, and the cooling time after butt welding is ≥45min.

[0013] Furthermore, in step S5, during a single melting process, the current range is 15kA-26kA, the voltage range is 33V-36V, the arc stabilization current range is 9A-30A, and the arc stabilization stirring time is 5-25s.

[0014] Furthermore, in step S6, during the secondary melting process, the current range is 20kA-36kA, the voltage range is 32V-37V, the arc stabilization current range is 9A-30A, and the arc stabilization stirring time is 5-25s.

[0015] The beneficial effects of this invention are: Before welding the electrode rods, the electrode blocks are assembled and placed in the vacuum arc welding box, then filled with argon gas at a preset pressure and left to stand for a preset time. The purpose is to ensure that the argon gas can penetrate deep into the electrode, thereby reducing oxidation during the welding process, improving the quality of the electrode rod weld, reducing ingot inclusions, and improving the surface quality of the subsequent titanium plate coil. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the present invention; Detailed Implementation

[0017] The invention will be further described below with reference to the accompanying drawings.

[0018] Vacuum arc remelting (VAR) of titanium alloys is a technology that uses electric arc heating to melt metals in a vacuum environment. In this process, sponge titanium and alloy materials are first mixed uniformly according to a specific chemical composition ratio and then pressed into blocks. These blocks are then welded into electrode rods using a vacuum plasma welding box. The preparation of the electrode rods is the first step in the VAR process, involving multiple steps such as mixing, pressing, and welding.

[0019] Vacuum welding of the electrode rods is performed in a vacuum environment to ensure weld quality and reduce oxidation. The consumable electrode and auxiliary electrode are loaded into the VAR furnace and centered in the crucible. After pre-vacuuming, arc welding is performed under vacuum, completing the welding instantaneously. The welded electrode rods will be used in subsequent melting processes.

[0020] In a single melting process, an electrode rod is heated and melted by an electric arc in a vacuum environment. The molten metal drips into a copper crucible to form a titanium ingot. This process requires strict control of process parameters such as voltage, vacuum level, and melting rate to ensure the quality of the titanium ingot. During melting, the length of the electric arc has a significant impact on the melting effect. An arc that is too long or too short will result in an undesirable state of the molten metal pool, affecting the purity and structural uniformity of the titanium ingot.

[0021] After the first melting, a second melting process is required, especially for titanium alloys for special applications, to further improve their quality and performance. Multiple melting processes help reduce shrinkage cavities and porosity at the ingot head, decrease the amount of cut-off, and increase the yield of the billet.

[0022] like Figure 1 As shown in the embodiments of this application, a method for melting titanium and titanium alloys in a vacuum consumable arc furnace is proposed, including the following steps: S1: Process electrode blocks of preset size and density; the electrode diameter ranges from 470mm to 1050mm, and the electrode density ranges from 3.2g / cm³ to 3.5g / cm³. By setting electrode blocks of reasonable size and density, the welding time and welding quality of a single weld are relatively better in the actual welding process.

[0023] S2: Place the electrode rod, assembled from the electrode blocks, into a vacuum arc welding box and evacuate it. Introduce argon gas, stopping when the preset pressure is reached and maintaining this position for a preset time. This ensures the argon gas penetrates deeply into the electrode, effectively reducing oxidation during welding compared to traditional welding processes, improving the weld quality of the electrode rod, reducing ingot inclusions, and improving the surface quality of the subsequent titanium plate / coil. Furthermore, argon gas is introduced, stopping when the pressure reaches 2000Pa-8000Pa and maintaining this position for a preset time (1-5 hours). By appropriately setting the argon gas pressure and position time, the argon gas is ensured to fully penetrate the joint between adjacent electrode blocks.

[0024] S3: Continuously purge with argon to bring the pressure inside the welding box to the preset range, and perform electrode rod welding; the pressure range inside the welding box for welding electric rods is 2000Pa-35000Pa, the arc current range for welding electrode rods is 2000A-8000A, the welding speed range is 0.5mm / min-2mm / min, the welding depth range is 5mm-10mm, the number of welds is 6-10, and the cooling time after welding is ≥60min. By limiting the parameters, it is ensured that the formed welds are sufficiently stable and of high quality.

[0025] S4: Place the welded electrode rod and the prepared auxiliary electrode in a VAR furnace for butt welding; before butt welding, reduce the gas pressure in the VAR furnace to ≤10Pa and the leakage rate to ≤5Pa, that is, almost completely evacuate the VAR furnace. During the welding process, control the arc current range to 3kA-12kA and the voltage range to 28V-36V. The cooling time after butt welding is ≥45min. Cooling ensures the forming quality after welding.

[0026] S5: Single melting; In single melting, the current range is 15kA-26kA, the voltage range is 33V-36V, the arc stabilization current range is 9A-30A, and the arc stabilization stirring time is 5-25s. Through the experimental process, reasonable current values, voltage values, arc stabilization current values, and arc stabilization stirring time are selected to ensure high ingot quality in single melting.

[0027] S6: Secondary melting. In secondary melting, the current range is 20kA-36kA, the voltage range is 32V-37V, the arc stabilization current range is 9A-30A, and the arc stabilization stirring time is 5-25s. Through the experimental process, reasonable current, voltage, arc stabilization current and arc stabilization stirring time are selected to ensure that the quality of the ingots from the primary melting is further improved, and the inclusions in the ingots are reduced, thereby improving the surface quality of the subsequent titanium plate coils.

[0028] First, it should be stated that the above process can effectively reduce the probability of core inclusions during the smelting and casting of pure titanium, thereby reducing surface peeling and core stripe defects in titanium plates and coils, and providing assistance for the subsequent resolution and treatment of quality issues.

[0029] Example 1 Pure titanium TA1 was selected for smelting, and the electrode welding method described above was used. The steps are as follows: Select an electrode with a diameter of 850mm; place the electrode rod assembled from the electrode blocks into a vacuum arc welding box and evacuate; fill with argon gas, stop filling when the pressure reaches 2000Pa-8000Pa, and maintain stillness for 1h-5h; continue filling with argon gas until the pressure inside the welding box reaches 20000Pa-35000Pa, then perform electrode rod welding, selecting 10 longitudinal weld seams, argon protection at 15000-30000Pa, welding speed range of 0.5mm / min-2mm / min, welding depth range of 5mm-10mm, welding cooling time ≥80min; place the welded electrode rod and the prepared auxiliary electrode in a VAR furnace for butt welding, with a vacuum degree ≤10Pa, leakage rate ≤5Pa, welding current of 450-500A, and welding voltage of 45-55V before welding.

[0030] Using the above process, 9 tons of TA1 were smelted in actual production, with the same raw materials and smelting process, and no abnormalities occurred during the smelting process. Compared with the traditional process, the surface peeling defect of the final titanium plate coil was reduced to 12.11%, and the crack defect was reduced to 15.16%.

[0031] Example 2 Pure titanium TA1 was selected for smelting, and the electrode welding method described above was used. The steps are as follows: Select an electrode with a diameter of 650mm; place the electrode rod assembled from the electrode blocks into a vacuum arc welding box and evacuate; fill with argon gas, stop filling with argon gas when it reaches 2000Pa-8000Pa, and keep it stationary for 1h-5h; continue filling with argon gas until the pressure inside the welding box reaches 20000Pa-35000Pa, and perform electrode rod welding, selecting 8 longitudinal weld seams, with an argon gas pressure of 10000-20000Pa, a welding speed range of 0.5mm / min-2mm / min, a welding depth range of 5mm-10mm, and a welding cooling time ≥60min; place the welded electrode rod and the prepared auxiliary electrode in a VAR furnace for butt welding, with a vacuum degree ≤10Pa, a leakage rate ≤5Pa, a welding current of 420-460A, and a welding voltage of 40-54V before welding.

[0032] Using the above process, 6 tons of TA1 were smelted in actual production, with the same raw materials and smelting process, and no abnormalities occurred during the smelting process. Compared with the traditional process, the surface peeling defect of the final titanium plate coil was reduced to 6.39%, and the crack defect was reduced to 13.85%.

[0033] Example 3 Pure titanium alloy TC4 was selected for smelting, and the electrode welding method described above was used. The steps are as follows: Select an electrode with a diameter of 480mm; place the electrode rod assembled from the electrode blocks into a vacuum arc welding box and evacuate; fill with argon gas, stop filling with argon gas when it reaches 2000Pa-8000Pa, and keep it stationary for 1h-5h; continue filling with argon gas until the pressure inside the welding box reaches 20000Pa-35000Pa, and perform electrode rod welding, selecting 6 longitudinal weld seams, with an argon gas pressure of 20000-35000Pa, a welding speed range of 0.5mm / min-2mm / min, a welding depth range of 5mm-10mm, and a welding cooling time ≥90min; place the welded electrode rod and the prepared auxiliary electrode in a VAR furnace for butt welding, with a vacuum degree ≤5Pa, a leakage rate ≤2Pa, a welding current of 400-440A, and a welding voltage of 40-60V before welding.

[0034] Using the above process, 3 tons of TC4 were smelted in actual production with the same raw materials and smelting process, and no abnormalities occurred during the smelting process. Compared with the traditional process, the surface peeling defect of the final product was reduced to 9.11%, and the crack defect was reduced to 6.16%.

[0035] Comparative Example In this comparative example, pure titanium TA1 was selected for melting. The welding process was compared with that of Examples 1, 2, and 3. Step 2 (filling with argon gas, stopping the argon filling when the preset pressure is reached, and maintaining the position for a preset time) was missing. Welding was performed directly. The steps are as follows: Select an electrode with a diameter of 850mm; place the electrode rod assembled from the electrode blocks into a vacuum arc welding box and evacuate it; fill with argon gas to make the pressure inside the welding box reach 20000Pa-35000Pa, and perform electrode rod welding, selecting 10 longitudinal weld seams, argon protection at 15000-30000Pa, welding speed range of 0.5mm / min-2mm / min, welding depth range of 5mm-10mm, welding cooling time ≥80min; place the welded electrode rod and the prepared auxiliary electrode in a VAR furnace for butt welding, vacuum degree ≤10Pa, leakage rate ≤5Pa before welding, welding current 450-500A, welding voltage 45-55V.

[0036] Using the above process, 9 tons of TA1 were smelted in actual production, with the same raw materials and smelting process, and no abnormalities occurred during the smelting process. Compared with the traditional process, the surface peeling defect of the final titanium plate coil was reduced by 31.25%, and the crack defect was reduced by 21.74%.

[0037] In summary, through comparison of Examples 1, 2, 3 and the comparative example, before welding the electrode rod, assembling the electrode blocks and placing them in the vacuum arc welding box, filling them with argon gas at a preset pressure and letting them stand for a preset time, aims to ensure that the argon gas can penetrate deep into the electrode, thereby reducing oxidation during the welding process, improving the quality of the electrode rod weld, reducing ingot inclusions, and significantly improving the surface quality of the subsequent titanium plate coil.

Claims

1. A method for melting titanium and titanium alloys in a vacuum consumable arc furnace, characterized in that, Includes the following steps: S1: Process electrode blocks of preset size and density; S2: Place the electrode rod assembled from the electrode blocks into a vacuum arc welding box and evacuate it; fill the vacuum arc welding box with argon gas, stop filling with argon gas when the preset pressure is reached, and maintain it in place for a preset time. S3: Continuously purge with argon and bring the pressure inside the welding box to the preset range, then perform electrode rod welding, and cool for the preset time after the electrode rod welding is completed; S4: Place the welded electrode rod and the prepared auxiliary electrode in a VAR furnace for butt welding, and set a preset cooling time for the consumable electrode after butt welding. S5: One-time smelting; S6: Secondary smelting.

2. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 1, characterized in that, In step S1, the electrode diameter ranges from 470mm to 1050mm, and the electrode density ranges from 3.2g / cm³ to 3.5g / cm³.

3. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 1, characterized in that, In step S2, argon gas is introduced and stopped when the pressure reaches 2000Pa-8000Pa, and the gas is kept stationary for a preset time.

4. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 3, characterized in that, The settling time ranges from 1 hour to 5 hours.

5. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 1, characterized in that, In step S3, the pressure range inside the welding box of the welding electric rod is 2000Pa-35000Pa.

6. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 5, characterized in that, The arc current range of the welding electrode rod is 2000A-8000A, the welding speed range is 0.5mm / min-2mm / min, the welding depth range is 5mm-10mm, the number of welds is 6-10, and the cooling time after welding is greater than or equal to 60min.

7. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 1, characterized in that, In step S4, before welding, the gas pressure inside the VAR furnace is less than or equal to 10 Pa and the leakage rate is less than or equal to 5 Pa.

8. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 7, characterized in that, During butt welding, the arc current range is 3kA-12kA, the voltage range is 28V-36V, and the cooling time after butt welding is greater than or equal to 45 minutes.

9. The method for vacuum consumable arc furnace melting of titanium and titanium alloys according to claim 1, characterized in that, In step S5, during a single melting process, the current range is 15kA-26kA, the voltage range is 33V-36V, the arc stabilization current range is 9A-30A, and the arc stabilization stirring time is 5-25s.

10. The method for smelting titanium and titanium alloys in a vacuum consumable arc furnace according to claim 1, characterized in that, In step S6, during the secondary melting process, the current range is 20kA-36kA, the voltage range is 32V-37V, the arc stabilization current range is 9A-30A, and the arc stabilization stirring time range is 5-25s.

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