Preparation method of high-strength long-life red copper bottom pad

Abstract

The application discloses a preparation method of high-strength long-life red copper bottom pad, which comprises the following steps: upsetting forging of red copper ingot to obtain a pie-shaped blank; machining the pie-shaped blank into a stepped cylindrical blank; cold forging of the stepped cylindrical blank by using a 3000-ton oil press, the large-diameter surface of the blank forging is in contact with a lower anvil, and a die steel force receiving piece is arranged on the small-diameter surface of the blank forging, during the forging, the upper anvil of the oil press is fully loaded on the die steel force receiving piece, the die steel force receiving piece is moved clockwise or counterclockwise once under the clamping of the operating machine clamp lever every time the loading is performed, and the upper surface is forged once until the upper surface is forged once; semi-finishing and finishing of the bottom pad blank after the cold forging, and scribing, drilling and tapping of the threaded hole after the machining, so that the machining of the bottom pad is completed. The hardness of the red copper bottom pad processed by the method is inconsistent on the upper surface and the lower surface, the hardness of the upper working surface is higher than that of the lower working surface, and the red copper bottom pad has high yield point strength and tensile strength.

Description

Technical Field

[0001] This invention belongs to the field of vacuum metallurgical methods, specifically relating to a method for preparing a high-strength, long-life copper base pad. Background Technology

[0002] A vacuum arc furnace utilizes the heat generated by an electric arc to melt metal. A copper crucible and a copper base are assembled to form a crystallizer. The molten metal melted by the electric arc crystallizes into an ingot within the crystallizer, which is externally cooled by water. The heat released during the solidification of the ingot is transferred to the cooling water through the copper crucible and base. After the ingot has cooled sufficiently, the copper crucible and base separate, and the ingot is removed from the crystallizer. The upper working surface of the copper base comes into contact successively with molten titanium (melting point 1668℃) and the hot titanium ingot, while its lower working surface and outer circumferential surface come into contact with rapidly flowing cooling water at a temperature not exceeding 40℃. Through heat exchange, the molten metal in contact with these surfaces solidifies, and the temperature of the solidified metal continues to decrease.

[0003] Copper is an elastic material with typical metallic characteristics. During operation, the upper working surface and the core of the copper base pad experience reduced strength due to high temperatures, while the lower working surface and outer circumferential surface have higher strength than the core and upper working surface. Due to the symmetry of the base pad structure, it bears both horizontal and vertical thermal stresses relative to the entire structure. The resultant direction of these two stresses determines the deformation direction of the base pad. Frequent and prolonged use at high temperatures causes creep deformation. This deformation leads to a failure in the fit between the base pad and the crucible body, rendering the base pad unusable.

[0004] The current conventional process for manufacturing base pads involves heating T2 copper ingots to 780℃~875℃, then forging them freely on a high-speed forging hydraulic press or oil press from a cylindrical shape to a disc shape. The disc-shaped blank is then cooled in air and machined on a lathe. The resulting base pad has a hardness of HB35~45, is in the annealed state, with a yield strength of 50MPa~70MPa and a tensile strength of 220MPa~240MPa. While this process produces base pads with uniform hardness across all parts, the temperature and thermal stress experienced by different parts of the base pad vary when operating in a consumable arc furnace. Furthermore, the aforementioned yield strength and tensile strength are clearly insufficient for the high-strength operating conditions of the base pad. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-strength, long-life copper base pad. The copper base pad processed by this method has inconsistent hardness on the upper and lower surfaces, with the upper working surface having a higher hardness than the lower working surface, and it also has higher yield strength and tensile strength.

[0006] The technical solution adopted in this invention is a method for preparing a high-strength, long-life copper base pad, which is implemented according to the following steps:

[0007] Step 1: Upsetting the copper ingot to obtain a disc-shaped blank;

[0008] Step 2: Machine the disc-shaped blank obtained in Step 1 into a stepped cylindrical blank, smooth the top and bottom surfaces, and remove defects from the outer cylindrical surface of the forging.

[0009] Step 3: Use a 3000-ton hydraulic press to cold forge the stepped cylindrical blank obtained in Step 2. The large diameter surface of the blank forging is in contact with the lower flat anvil, and a die steel bearing component is placed on its small diameter surface. During forging, the upper flat anvil of the hydraulic press is fully loaded on the die steel bearing component. Each time it is loaded, the die steel bearing component moves clockwise or counterclockwise once under the clamping of the operating machine clamp bar until the entire upper surface is forged once.

[0010] Step 4: Perform semi-finishing and finishing on the bottom pad blank after cold forging in Step 3. After finishing, scribing and drilling to make threaded holes, thus completing the processing of the bottom pad.

[0011] The invention is further characterized by:

[0012] The upsetting forging process in step 1 is as follows:

[0013] Cylindrical copper ingots with a height-to-diameter ratio of 0.8-1.1 are heated to 780℃-875℃ and then upsetting and forging are performed on a 3000-ton hydraulic press. Both the upper and lower anvils are flat, and the forging ratio is 3-5. The shape of the copper ingot changes from cylindrical to disc-shaped. The forging is then cooled to room temperature in air.

[0014] The surface hardness range of the copper blank obtained in step 1 is HB35-45, its diameter is 1.08-1.1 times the size of the finished base pad, and its height is 1.3-1.35 times the size of the finished base pad.

[0015] The stepped cylindrical blank obtained in step 2 has a diameter ratio of 0.8-0.9 between the upper and lower steps. The blank diameter is 1.03-1.05 times the finished size of the base pad, and the height is 1.2-1.25 times the finished size of the base pad.

[0016] In step 3, the diameter of the die steel load-bearing component is 1 / 4 to 1 / 3 of the diameter of the forged blank, and the thickness is 3 to 6 times the thickness of the forged blank.

[0017] In step 3, the pressure applied to the forging is not less than 210 MPa, and the height deformation of the stepped cylinder of the forging is controlled at 1%-1.5% of its original height.

[0018] The beneficial effects of this invention are:

[0019] The method of this invention first involves hot forging and machining a copper ingot to obtain a stepped cylindrical base blank. This blank is then placed on a hydraulic press for forging. During forging, the lower working surface of the base (the working surface in contact with the low-temperature cooling water) contacts the lower anvil of the hydraulic press, while a die steel load-bearing component is placed on its upper working surface (the working surface in contact with molten titanium). The upper anvil of the hydraulic press is then fully loaded onto the die steel load-bearing component for forging. This forging method allows for different strengths and hardnesses in different parts of the finished base, resulting in a high-strength, high-performance base. The hardness region is distributed on the upper working surface of the base pad, while the low strength and low hardness region is distributed on the lower working surface. This distribution pattern is adapted to the stress conditions of the copper base pad during use, thereby reducing the deformation rate of the base pad, significantly improving its service life, and reducing production costs. In addition, the yield strength of the high strength region of the copper base pad prepared by the method of the present invention reaches 300MPa to 310MPa, and the tensile strength reaches 350MPa to 360MPa, indicating that the copper base pad prepared by the method of the present invention has high strength. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the finished copper base pad processed according to Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the disc-shaped forging in the method of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of the stepped cylindrical forging in the method of the present invention;

[0023] Figure 4 This is a schematic diagram of forging a stepped cylindrical forging in the method of the present invention.

[0024] In the figure, 1. Copper base blank, 2. Mold steel load-bearing component, 3. Working surface under the base, 4. Surface of the mold steel load-bearing component. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0026] The preparation method of the high-strength, long-life copper base pad of the present invention is carried out according to the following steps:

[0027] Step 1: After heating a cylindrical copper ingot of material grade T2 with a height-to-diameter ratio of 0.8-1.1 to 780℃-875℃ in a heating furnace, the cylindrical copper ingot is clamped and upset and forged on a 3000-ton hydraulic press. Both the upper and lower anvils are flat anvils, and the forging ratio is 3-5. The shape of the copper ingot changes from cylindrical to disc-shaped. The forging is cooled to room temperature in air. The surface hardness of the obtained copper blank is HB35-45. Its diameter is 1.08-1.1 times the size of the finished product, and its height is 1.3-1.35 times the size of the finished product.

[0028] Step 2: Machining the copper blank obtained in Step 1. On a lathe, the disc-shaped blank is machined into a stepped cylindrical blank, with both top and bottom surfaces smoothed. Defects such as cracks and folds on the outer surface of the forging are removed. The diameter ratio (smaller area to larger area) of the two steps is 0.8-0.9. The blank diameter is 1.03-1.05 times the finished size of the base pad, and the height is 1.2-1.25 times the finished size of the base pad.

[0029] Step 3: Place the stepped cylindrical blank machined in Step 2 onto the lower anvil of a 3000-ton hydraulic press. The large-diameter surface of the blank should contact the anvil. Place a die steel support component on the small-diameter surface of the blank. The diameter of the support component should be 1 / 4 to 1 / 3 of the diameter of the blank, and its thickness should be 3 to 6 times the thickness of the blank. Ensure sufficient rigidity and prevent deformation to transfer force to the blank. The upper anvil of the press should be fully loaded onto the die steel support component, ensuring a pressure of not less than 210 MPa on the forging. Each time the load is applied, the die steel support component should be moved clockwise or counterclockwise under the clamping of the manipulator clamp until the entire upper surface has been forged. The height deformation of the stepped cylindrical forging should be controlled at 1% to 1.5% of its original height; there are no requirements for the diameter dimension.

[0030] Step 4: The cold-forged copper base blank from Step 3 is semi-finished and finished on a lathe. After machining, the blank is scribing and drilling to create threaded holes, thus completing the machining of the base. The hardness of the upper working surface of the finished base is approximately HB80-100, and the hardness of the lower working surface is approximately HB50-55. This means that at room temperature, the strength and hardness of the upper working surface of the copper base are greater than those of the lower working surface.

[0031] Example 1

[0032] We are processing a crucible base pad with a diameter of Φ560 mm. Its maximum outer diameter is Φ638 mm, the stop dimension at the mating point with the crucible body is Φ576 mm, the pad thickness is 80 mm, and the net weight is 200 kg. The finished product structure is as follows: Figure 1 As shown.

[0033] Step 1: Cut T2 copper ingots with a diameter of Φ350mm and a height of 390±10mm. Heat the ingots to 800℃ in an electric furnace and place them on a 3000-ton hydraulic press for forging. Flat anvils are used on both the top and bottom. The ingot height is reduced from 143mm to 103mm. The final forging temperature is 600℃, and the diameter of the copper ingot is reduced from Φ350mm to Φ680mm. Cool the forging to room temperature in air. The resulting disc-shaped forging has the following structure: Figure 2 As shown.

[0034] Step 2: Machining the forging on a lathe. The upper and lower surfaces are finished with a light-drying process. The outer diameter of the disc-shaped forging is machined to remove all surface cracks, folds, and defects. Sharp angles are chamfered to create two cylinders with diameters of Φ670 and Φ590, corresponding to heights of 65mm and 35mm respectively. This completes the first machining of the base blank. The structure of the machined blank is as follows: Figure 3 As shown.

[0035] Step 3: Place the stepped T2 cylindrical blank on the anvil of the 3000-ton hydraulic press, as follows... Figure 4 As shown, the lower working surface 3 of the Φ670 copper base blank 1 contacts the lower flat anvil, and the Φ410×200mm mold steel support component 2 is placed on the Φ590 upper working surface. The upper flat anvil contacts the surface 4 of the mold steel support component, and the blank is forged. Each time it is forged, the mold steel support component moves clockwise or counterclockwise once under the clamp of the manipulator clamp bar until the entire upper surface is forged once. The height deformation of the forging is 0.8-1mm.

[0036] Step 4: Machin the cold-forged base pad on a lathe according to the finished size of the base pad. After machining, scribing and drilling holes to make threaded holes, and the machining of the base pad is completed.

[0037] The hardness and strength of the copper base pad prepared in this embodiment were tested. The results were as follows: the hardness of the upper working surface (the working surface in contact with molten titanium) of the base pad was HB80-100, the yield strength reached 300-310 MPa, and the tensile strength was 350-360 MPa. The hardness of the lower working surface (the working surface in contact with low-temperature cooling water) of the base pad was HB50-55, the yield strength was 80-100 MPa, and the tensile strength was 250-280 MPa. It can be seen that the base pad prepared using the method of this invention has higher hardness and strength on the upper working surface than on the lower working surface, and the overall strength of the upper working surface is significantly improved.

[0038] Example 2

[0039] The preparation method of high-strength, long-life copper base pad is carried out according to the following steps:

[0040] Step 1: Upsetting the copper ingot to obtain a disc-shaped blank;

[0041] Step 2: Machine the disc-shaped blank obtained in Step 1 into a stepped cylindrical blank, smooth the top and bottom surfaces, and remove defects from the outer cylindrical surface of the forging.

[0042] Step 3: Use a 3000-ton hydraulic press to cold forge the stepped cylindrical blank obtained in Step 2. The large diameter surface of the blank forging is in contact with the lower flat anvil, and a die steel bearing component is placed on its small diameter surface. During forging, the upper flat anvil of the hydraulic press is fully loaded on the die steel bearing component. Each time it is loaded, the die steel bearing component moves clockwise or counterclockwise once under the clamping of the operating machine clamp bar until the entire upper surface is forged once.

[0043] Step 4: Perform semi-finishing and finishing on the bottom pad blank after cold forging in Step 3. After finishing, scribing and drilling to make threaded holes, thus completing the processing of the bottom pad.

[0044] Example 3

[0045] Based on Example 2, the upsetting forging process in step 1 is specifically as follows:

[0046] Cylindrical copper ingots with a height-to-diameter ratio of 0.8-1.1 are heated to 780℃-875℃ and then upsetting and forging are performed on a 3000-ton hydraulic press. Both the upper and lower anvils are flat, and the forging ratio is 3-5. The shape of the copper ingot changes from cylindrical to disc-shaped. The forging is then cooled to room temperature in air.

[0047] The surface hardness range of the copper blank obtained in step 1 is HB35-45, its diameter is 1.08-1.1 times the size of the finished base pad, and its height is 1.3-1.35 times the size of the finished base pad.

Claims

1. A method for preparing a high-strength, long-life copper base pad, characterized in that, The specific steps are as follows: Step 1: Upsetting the copper ingot to obtain a disc-shaped blank; Step 2: Machine the disc-shaped blank obtained in Step 1 into a stepped cylindrical blank, smooth the top and bottom surfaces, and remove defects from the outer cylindrical surface of the forging. Step 3: Use a 3000-ton hydraulic press to cold forge the stepped cylindrical blank obtained in Step 2. The large diameter surface of the blank forging is in contact with the lower flat anvil, and a die steel bearing component is placed on its small diameter surface. During forging, the upper flat anvil of the hydraulic press is fully loaded on the die steel bearing component. Each time it is loaded, the die steel bearing component moves clockwise or counterclockwise once under the clamping of the operating machine clamp bar until the entire upper surface is forged once. Step 4: Perform semi-finishing and finishing on the bottom pad blank after cold forging in Step 3. After finishing, scribing and drilling to make threaded holes, thus completing the processing of the bottom pad. The upsetting forging process in step 1 is as follows: Cylindrical copper ingots with a height-to-diameter ratio of 0.8-1.1 are heated to 780℃-875℃ and then upsetting and forging are performed on a 3000-ton hydraulic press. Both the upper and lower anvils are flat, and the forging ratio is 3-5. The shape of the copper ingot changes from cylindrical to disc-shaped. The forging is then cooled to room temperature in air. The surface hardness range of the copper blank obtained in step 1 is HB35-45, its diameter is 1.08-1.1 times the size of the finished base pad, and its height is 1.3-1.35 times the size of the finished base pad. The stepped cylindrical blank obtained in step 2 has a diameter ratio of 0.8-0.9 between the upper and lower steps. The blank diameter is 1.03-1.05 times the finished size of the base pad, and the height is 1.2-1.25 times the finished size of the base pad. In step 3, the diameter of the mold steel load-bearing component is 1 / 4 to 1 / 3 of the diameter of the forged blank, and the thickness is 3 to 6 times the thickness of the forged blank. In step 3, the pressure applied to the forging is not less than 210 MPa, and the height deformation of the stepped cylinder of the forging is controlled at 1%-1.5% of its original height.

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