Noble metal crucible and method for producing the same

Abstract

The application discloses a noble metal crucible and a preparation method thereof. The noble metal crucible comprises a crucible body and a crucible bottom connected to the bottom of the crucible body, the crucible body and the crucible bottom are integrally formed, and the inner surface of the crucible bottom is covered with a protective layer. The preparation method comprises the steps of plate preparation, mold preparation and spinning forming in sequence. The application avoids the welding seam caused by the welding of the crucible body and the crucible bottom, fundamentally eliminates the cracking problem of the welding seam caused by the performance difference between the welding seam and the crucible body, solves the defect problem caused by the existence of the welding seam, effectively improves the service life of the noble metal crucible, realizes the rapid preparation of the noble metal crucible through a simple process, realizes the integrally forming of the crucible body and the crucible bottom, and effectively improves the production efficiency and the product quality of the noble metal crucible.

Description

Technical Field

[0001] This invention relates to the field of glass melting equipment technology, and in particular to a precious metal crucible and a method for preparing a precious metal crucible. Background Technology

[0002] Precious metal crucibles are commonly used tools in glass melting and production. They are typically used to melt various glass raw materials. After the glass raw materials are fully melted in the precious metal crucible, the molten glass is poured out and cooled to room temperature for glass-related performance analysis. Common precious metal crucibles include platinum crucibles, platinum-rhodium crucibles, and platinum-yellow crucibles.

[0003] In the glass melting process, a precious metal crucible needs to be heated to 1200–1680°C, and then powdered or lumpy glass raw materials are continuously poured into it. Because precious metals have good ductility, the bottom of the crucible is prone to deformation after repeated impacts from the glass raw materials at high temperatures. This deformation creates wrinkles, preventing the molten glass flowing into the wrinkles from being completely poured out. It is necessary to repeatedly melt and pour out glass raw materials of other formulations in the crucible before melting other formulations to rinse the crucible and prevent the original molten glass residue from affecting the composition of the subsequent molten glass. However, rinsing is time-consuming, and if there are many wrinkles on the bottom of the crucible, rinsing becomes extremely difficult. The precious metal crucible will be repeatedly subjected to thermal shocks due to continuous rinsing, which can easily cause cracks at the wrinkles, rendering the crucible unusable. Furthermore, precious metal crucibles are exposed to high temperatures for extended periods, and the bottom of the crucible is constantly subjected to the weight of the molten glass, making it prone to cracking. Corrosion defects may also occur at the bottom of the crucible due to the precipitation of certain elements in elemental form from the molten glass. All of these defects severely impact the service life of precious metal crucibles.

[0004] Currently, commercially available precious metal crucibles typically use spinning or stamping methods to produce the crucible bottom, while the crucible body is made by rolling and welding rolled sheet metal, ultimately welding the bottom and body together. In precious metal crucibles prepared using these methods, a weld seam exists at the connection between the bottom and body. Although this weld seam can be eliminated through processing, its properties are far inferior to those of the crucible body, making it prone to defects such as cracking.

[0005] Chinese utility model patent CN220745678U discloses a platinum or platinum-rhodium alloy crucible, comprising a crucible body and a crucible bottom made of platinum or platinum-rhodium alloy. The inner side of the crucible bottom has an annular corrugated groove protruding outwards and concentric with the crucible bottom. The depth of the annular corrugated groove is 5-7 mm, and the width is 15-20 mm. This utility model, by setting an annular corrugated groove on the bottom of the crucible, can increase the structural strength of the crucible bottom and its resistance to thermal shock, making it less prone to deformation. Furthermore, when the crucible is subjected to thermal shock, the annular corrugated groove can compensate for the thermal expansion and contraction of the crucible bottom, thereby preventing wrinkles caused by deformation and ensuring long-term stable use of the crucible.

[0006] Although the technical solution disclosed in the above-mentioned utility model patent can improve the strength of the crucible bottom, the crucible body and the crucible bottom are still welded together. Therefore, it cannot avoid the problems of wrinkles easily appearing on the crucible bottom and cracks occurring at the weld due to differences in weld performance. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a precious metal crucible with high overall structural strength and long service life.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a precious metal crucible, including a crucible body and a crucible bottom connected to the bottom of the crucible body, wherein the crucible body and the crucible bottom are integrally formed, and a protective layer is covered on the inner surface of the crucible bottom.

[0009] As an improvement to the above solution: the bottom of the crucible is provided with a central arc portion, a first connecting arc segment, a flat bottom segment, and a second connecting arc segment in sequence from the center outward; the central arc portion protrudes upward, and the first connecting arc segment, the flat bottom segment, and the second connecting arc segment are connected in sequence to form a downwardly recessed annular groove; the central arc portion, the first connecting arc segment, the flat bottom segment, and the second connecting arc segment are arranged tangent to each other in sequence, and the second connecting arc segment is connected to the crucible body.

[0010] As an improvement to the above scheme: the thickness of the precious metal crucible decreases sequentially from the central arc portion of the bottom of the crucible outwards to the body of the crucible, and the thickness tolerance is ±0.05mm; the thickness difference between the first connecting arc segment and the central arc portion is 0.1~0.2mm, the thickness difference between the flat bottom segment and the central arc portion is 0.2~0.3mm, the thickness difference between the second connecting arc segment and the central arc portion is 0.3~0.4mm, and the thickness difference between the crucible body and the central arc portion is 0.4~0.6mm; the roundness dimension of the central arc portion ranges from 20 to 50mm, the roundness dimension of the first connecting arc segment ranges from 20 to 50mm, and the roundness dimension of the second connecting arc segment ranges from 30 to 60mm; the overall height dimension of the precious metal crucible ranges from 150 to 200mm; and the angle dimension of the inclined wall of the crucible body ranges from 20 to 30°.

[0011] The present invention also discloses a method for preparing the precious metal crucible described above, which includes the steps of preparing a plate, preparing a mold, and spinning.

[0012] In the plate preparation step, a circular precious metal plate is prepared as the base material, and a circular dispersion-strengthened platinum or dispersion-strengthened platinum-rhodium alloy is prepared as the reinforcing material. The reinforcing material is forged onto the base material, and after leveling, it is prepared into a conical crucible blank with a cone tip and a rounded surface by multi-die stamping or spinning.

[0013] In the mold preparation step, a frustum-shaped mold is prepared according to the outer dimensions of the precious metal crucible. The small end of the mold is provided with a concave arc groove, and the large end of the mold is provided with a rotating shaft.

[0014] In the spinning forming step, the mold is installed on a spinning machine and the cone tip of the crucible blank is inserted into the arc groove of the mold. Then, the crucible blank is repeatedly heated, spun and annealed until a noble metal crucible that meets the requirements is obtained.

[0015] As an improvement to the above scheme: In the plate preparation step, the diameter of the precious metal plate is φ1, φ1=π×r1+π×r2+2L+π×r3+2h-(50~100)mm, and the thickness of the precious metal plate is 1.2~2.5mm; the diameter of the reinforcing material is φ2, φ2=π×r1+π×r2+2L+π×r3+(5~10)mm, and the thickness of the reinforcing material is 0.3~0.5mm; where r1 is the roundness of the central arc, r2 is the roundness of the first connecting arc segment, L is the length of the flat bottom segment, r3 is the roundness of the second connecting arc segment, and h is the overall height of the precious metal crucible.

[0016] As an improvement to the above solution: In the mold preparation step, the mold is provided with multiple weight reduction holes. The weight reduction holes are blind holes that extend axially from the end of the mold with the rotating shaft to the inside of the mold. The multiple weight reduction holes are evenly distributed in a ring around the rotating shaft.

[0017] As an improvement to the above solution: the distance between the bottom of the weight reduction hole and the end face of the mold with the arc groove is 10-20mm, the outer diameter of the mold end is smaller than the outer diameter of the precious metal crucible end, and the height of the inclined wall of the mold is greater than the height of the inclined wall of the crucible body; the mold material is H13 and the quenching hardness is greater than HRC55.

[0018] As an improvement to the above scheme: in the spinning forming step, a spinning tool is used to spin from the outside to the inside of the crucible blank in sequence during spinning, and the outer edge of the crucible blank is turned out during the first spinning process; the material of the spinning tool is H13, and the heating temperature of the crucible blank during spinning is 1200~1350℃.

[0019] As an improvement to the above scheme: In the spinning forming step, after the first spinning, the first annealing is performed. First, the crucible blank is wiped with alcohol and soaked in hydrochloric acid with a concentration of 36-38% for 30 minutes. Then, it is cleaned with pure water and placed in an annealing furnace for annealing for 30 minutes at an annealing temperature of 1350-1450℃.

[0020] As an improvement to the above scheme: In the spinning forming step, a second spinning is performed after the first annealing. During the second spinning process, an angle of 15 to 25° is formed between the inclined wall of the crucible blank and the inclined wall of the mold, and the thickness of the inclined wall of the crucible blank is spun to be 0.1 mm greater than the thickness of the inclined wall of the crucible body. Then, after repeated cleaning and annealing, the crucible blank is spun to fit the mold and the thickness of the inclined wall of the crucible blank is spun to be 0.05 mm greater than the thickness of the inclined wall of the crucible body. Finally, the crucible blank is removed from the mold, cleaned, and trimmed to the qualified size.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention sets the body and bottom of the precious metal crucible as an integral molding structure, thereby avoiding the weld seam caused by welding to connect the body and bottom of the crucible. This fundamentally eliminates the problem of weld seam cracking caused by the performance difference between the weld seam and the crucible body, solves the defect problem caused by the existence of weld seam, and thus effectively improves the service life of the precious metal crucible.

[0023] 2. In this invention, since there is no weld seam between the crucible body and the crucible bottom as an intermediate connecting component, there will be no significant strength difference at various positions on the crucible body and the crucible bottom, which ensures the consistency of the overall strength of the precious metal crucible, making it less prone to local damage, and thus further improving the service life of the precious metal crucible.

[0024] 3. The precious metal crucible of the present invention has high structural strength and is not easily deformed under long-term thermal shock of glass raw materials. This reduces wrinkle defects caused by deformation, reduces the risk of cracking of the precious metal crucible, and because the risk of wrinkle defects is reduced, it is not necessary to rinse the bottom of the crucible to remove the glass liquid residue in the wrinkles. This avoids cracking problems caused by repeated rinsing of the bottom of the crucible.

[0025] 4. This invention strengthens the bottom of the precious metal crucible by adding a protective layer to the bottom surface. On the one hand, it can enhance the bottom strength of the precious metal crucible, and on the other hand, it can effectively prevent the elemental substances precipitated from the molten glass from corroding the bottom of the precious metal crucible.

[0026] 5. This invention improves the preparation method of precious metal crucibles by first forging reinforcing materials onto the precious metal sheet used as the raw material to form a protective layer, and then processing it into a crucible blank of a simple shape. In the spinning process, the crucible blank is plasticized using a mold. This allows for the rapid preparation of precious metal crucibles through a simple process, achieving the integral molding of the crucible body and bottom. At the same time, due to the supporting and shaping effect of the mold on the crucible blank during spinning plasticization, there are no defects in the overall shape, which enables the finished product to have a good yield, thereby effectively improving the production efficiency and finished product quality of precious metal crucibles. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the precious metal crucible in this invention;

[0028] Figure 2 This is a side sectional view of the precious metal crucible in this invention;

[0029] Figure 3 This is a schematic diagram of the crucible blank prepared in this invention;

[0030] Figure 4 This is a schematic diagram of the mold used in this invention;

[0031] Figure 5 This is a side sectional view of the mold used in this invention;

[0032] Figure 6 This is a schematic diagram illustrating the fit between the mold and the crucible blank in the preparation method of the present invention;

[0033] Figure 7 This is a schematic diagram showing the state of the crucible blank after its first spinning in the preparation method of the present invention;

[0034] Figure 8 This is a schematic diagram showing the state of the crucible blank after secondary spinning in the preparation method of the present invention;

[0035] Figure 9 This is a schematic diagram showing the state of the crucible blank after spinning in the preparation method of the present invention;

[0036] Figure 10 This is a schematic diagram showing the state of the crucible blank after it has been demolded from the mold in the preparation method of the present invention.

[0037] The markings in the diagram are as follows: 100-cruise body, 200-cruise bottom, 210-central arc section, 220-first connecting arc section, 230-flat bottom section, 240-second connecting arc section, 300-protective layer, 400-crucible blank, 500-mold, 510-arc groove, 520-rotating shaft, 530-weight reduction hole. Detailed Implementation

[0038] To facilitate understanding of the present invention, the invention will be further described below with reference to the accompanying drawings.

[0039] In the description of this invention, it should be noted that the terms "front", "rear", "left", "right", "up", "down", "inner", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0040] like Figure 1 and Figure 2 As shown, the precious metal crucible disclosed in this invention consists of a crucible body 100, a crucible bottom 200, and a protective layer 300. The upper part of the crucible body 100 is larger than the lower part, and the inclined wall of the crucible body 100 is connected to the crucible bottom 200. The crucible body 100 and the crucible bottom 200 are integrally formed, so there is no connecting part between the crucible body 100 and the crucible bottom 200. The center of the crucible bottom 200 bulges upward toward the opening of the precious metal crucible to form a central arc portion 210. The central arc portion 210 arcs downward to the bottom of the crucible bottom 200. The transition section between the central arc portion 210 and the bottom of the crucible bottom 200 is the first connecting arc segment 220. The bottom of the crucible bottom 200 extends horizontally to form a flat bottom segment 230. The flat bottom segment 230 arcs upward to connect with the inclined wall of the crucible body 100. The transition section between the flat bottom segment 230 and the crucible body 100 is the second connecting arc segment 240. Furthermore, the central arc portion 210 is tangent to the first connecting arc segment 220, the first connecting arc segment 220 is tangent to the flat bottom segment 230, and the flat bottom segment 230 is tangent to the second connecting arc segment 240. Figure 2 As shown, the first connecting arc segment 220, the flat bottom segment 230, and the second connecting arc segment 240 are sequentially connected to the bottom of the crucible 200 to form a downwardly recessed annular groove.

[0041] like Figure 1 and Figure 2 As shown, the protective layer 300 covers the inner surface of the crucible bottom 200. The height of the protective layer 300 in the vertical direction is slightly higher than the height of the crucible bottom 200 so that the protective layer 300 can completely cover the crucible bottom 200. In this invention, the material of the protective layer 300 is dispersion-strengthened platinum or dispersion-strengthened platinum-rhodium alloy. By setting the protective layer 300 on the crucible bottom 200, it plays a reinforcing role. While improving the strength of the crucible bottom 200, the protective layer 300 can also isolate the elemental substances precipitated from the molten glass from the crucible bottom 200 during the glass melting process, thereby avoiding corrosion of the crucible bottom 200.

[0042] Furthermore, the present invention specifies the dimensional parameters of various parts of the precious metal crucible. Specifically, this includes specifying that the thickness of the crucible bottom 200 gradually decreases from the center outwards; setting the thickness of the central arc portion 210 as t1, the roundness as r1, and the height as h2; the thickness of the first connecting arc segment 220 as t2 and the roundness as r2; the thickness of the flat bottom segment 230 as t3 and the length as L; the thickness of the second connecting arc segment 240 as t4 and the roundness as r3; the thickness of the inclined wall of the crucible body 100 as t5; the overall height of the precious metal crucible as h; and the angle of the inclined wall of the crucible body 100 as k. The present invention specifies that the above dimensional parameters satisfy the relationship: t1 > t2 > t3 > t4 > t5, and the thicknesses of t1, t2, t3, t4, and t5 are... The thickness tolerance is ±0.05mm, and the thickness difference between the first connecting arc segment 220 and the central arc portion 210 is 0.1~0.2mm, i.e. t1-t2=0.1~0.2mm, the thickness difference between the flat bottom segment 230 and the central arc portion 210 is 0.2~0.3mm, i.e. t1-t3=0.2~0.3mm, the thickness difference between the second connecting arc segment 240 and the central arc portion 210 is 0.3~0.4mm, i.e. t1-t4=0.3~0.4mm, and the thickness difference between the crucible body 100 and the central arc portion 210 is 0.4~0.6mm, i.e. t1-t5=0.4~0.6mm. The present invention further defines the roundness dimension of the central arc portion 210 as 20-50 mm, i.e., r1 = 20-50 mm; the roundness dimension of the first connecting arc segment 220 as 30-60 mm, i.e., r3 = 30-60 mm; the roundness dimension of the second connecting arc segment 240 as 20-50 mm, i.e., r2 = 20-50 mm; the overall height dimension of the precious metal crucible as 150-200 mm, i.e., h = 150-200 mm; and the inclined wall angle dimension of the crucible body 100 as 20-30°, i.e., k = 20-30°. By limiting the dimensions described above, this invention can provide a precious metal crucible with superior performance for melting glass. When the glass raw material is melted in the precious metal crucible with the above-mentioned dimensional parameters, it can be heated from the bottom 200 of the crucible to provide a better heating effect for the glass raw material. Furthermore, the resulting molten glass has better fluidity at the bottom 200 of the crucible, making it easier to completely pour out the molten glass in the precious metal crucible and preventing the presence of molten glass residue at the bottom 200 of the crucible.

[0043] The method for preparing the above-mentioned precious metal crucible disclosed in this invention comprises the steps of preparing the plate, preparing the mold, and spinning.

[0044] In the above-mentioned plate preparation steps, a circular precious metal plate is used as the base material to prepare the crucible body 100 and the crucible bottom 200, and a circular dispersion-strengthened platinum or dispersion-strengthened platinum-rhodium alloy is used as the reinforcing material to prepare the protective layer 300. The material dimensions are determined based on the dimensional parameters of the precious metal crucible. The thickness of the precious metal plate is set as t, and its diameter as φ1. The thickness of the reinforcing material is set as t6, and its diameter as φ2. The thickness of the precious metal plate must be greater than the thickness of the thickest part of the precious metal crucible, i.e., the central arc portion 210, i.e., t > t1. Therefore, the range of t is 1.2–2.5 mm. The diameter of the precious metal plate satisfies the condition: φ1 = π×r1 + π×r2 + 2L + π×r3 + 2h - (50–100) mm. The thickness t6 of the reinforcing material ranges from 0.3 to 0.5 mm, and the diameter of the reinforcing material meets the condition: φ2=π×r1+π×r2+2L+π×r3+(5~10)mm; In addition, in order to match the thickness distribution of the bottom 200 of the precious metal crucible after it is formed, the thickness of the reinforcing material needs to be processed. The thickness of the circumferential edge of the reinforcing material is thinned to 0.2~0.3 mm using a stainless steel hammer, and the width of the thinning area ranges from 5~10 mm.

[0045] After the base material and reinforcing material are sourced, the reinforcing material is forged onto the base material. After leveling, the raw material is processed into the desired shape using multi-die stamping or spinning. Figure 3 The crucible blank 400 shown is a conical shell structure with a rounded tip. The crucible blank 400 of the above shape is adapted to the mold 500 in the subsequent steps, so that the crucible blank 400 can be fitted onto the surface of the mold 500 after processing. The mold 500 supports the crucible blank 400 inside and plays a shaping role to shape the crucible blank 400.

[0046] In the above mold preparation steps, the required mold 500 is as follows: Figure 4 and Figure 5As shown, the main structure of mold 500 is a frustum shape with a large end and a small end. The external dimensions of mold 500 gradually increase from the small end to the large end. Since mold 500 needs to be supported inside crucible blank 400 during processing, the shape of mold 500 should be compatible with the shape of the precious metal crucible, and the external dimensions of mold 500 should be slightly smaller than the dimensions of the precious metal crucible, with a difference of 0.1 to 0.3 mm. The outer diameter of the end of mold 500 is smaller than the outer diameter of the end of the precious metal crucible, and the height of the inclined wall of mold 500 is greater than the height of the inclined wall of crucible body 100, with a difference of 30 to 50 mm. To ensure the strength of mold 500, the material of mold 500 is initially H13, with a quenching hardness greater than HRC55. An arc groove 510 is provided at the small end of the mold 500. The arc groove 510 is axially recessed towards the large end and is used to insert the arc surface cone tip of the crucible blank 400. A rotating shaft 520 is fixedly provided at the large end of the mold 500 and is used to connect with the lathe used in the spinning process.

[0047] Furthermore, to ensure the driving effect of the mold 500 and prevent it from becoming too heavy, this invention provides multiple weight-reducing holes 530 on the mold 500. Each weight-reducing hole 530 is a blind hole extending axially from the end face of the mold 500 with the rotating shaft 520 into the interior of the mold 500. These holes reduce the overall weight of the mold 500. To ensure force balance and structural strength balance, the weight-reducing holes 530 are evenly distributed in a ring around the rotating shaft 520. In addition, to prevent the mold 500 from being punctured due to excessive depth of the weight-reducing holes 530, this invention limits the distance between the bottom of the weight-reducing hole 530 and the end face of the mold 500 with the arc groove 510 to 10-20 mm.

[0048] In the above spinning forming step, such as Figure 6 As shown, the mold 500 is mounted on a lathe, and the rotating shaft 520 of the mold 500 is connected to the lathe drive. The lathe drives the rotating shaft 520 to rotate the mold 500, and inserts the conical tip of the crucible blank 400 into the arc groove 510 of the mold 500. The tail of the lathe is inserted into the crucible blank 400. A spinning gap should be left between the tail shaft of the lathe and the crucible blank 400 to facilitate the operation of the spinning tool. Then, the lathe is started to perform multiple spinning processes on the crucible blank 400. During the spinning process, the crucible blank 400 is heated using an oxyhydrogen flame. After each spinning process, the crucible blank 400 is removed and annealed until a noble metal crucible that meets the requirements is obtained.

[0049] Specifically, during this spinning step, a spinning tool made of H13 material is used to spin the crucible blank 400 sequentially from the outside to the inside, gradually bringing the crucible blank 400 closer to the mold 500, until the crucible blank 400 is completely adhered to the outer surface of the mold 500, forming a shape as shown. Figure 9 and Figure 10 The crucible blank shown is 400.

[0050] like Figure 7 As shown, during the spinning process, the crucible blank 400 is heated by an oxyhydrogen flame at a heating temperature of 1200-1350℃. The first spinning causes the outer edge of the crucible blank 400 to turn out. After the first spinning, the first annealing is performed. The crucible blank 400 is first wiped with alcohol and soaked in hydrochloric acid with a concentration of 36-38% for 30 minutes. Then it is cleaned with pure water and placed in an annealing furnace. It is annealed at an annealing temperature of 1350-1450℃ for 30 minutes. After annealing, it is naturally cooled to room temperature.

[0051] like Figure 8 As shown, after the initial annealing and cooling, a second spinning process is performed. During the second spinning process, the crucible blank 400 is turned outward until there is an angle of 15-25° between its inclined wall and the inclined wall of the mold 500. The thickness of the inclined wall of the crucible blank 400 is spun to be 0.1 mm greater than the thickness of the inclined wall of the crucible body 100. After the second spinning, a second annealing process is performed. First, the crucible blank 400 is wiped with alcohol and soaked in 36-38% hydrochloric acid for 30 minutes. Then, it is cleaned with pure water and placed in an annealing furnace. It is annealed at an annealing temperature of 1350-1450℃ for 30 minutes. After annealing, it is naturally cooled to room temperature.

[0052] After repeated cleaning and annealing, the crucible blank 400 is spun to fit completely with the mold 500, and the thickness of the inclined wall of the crucible blank 400 is spun to be 0.05mm greater than the thickness of the inclined wall of the crucible body 100; finally, the crucible blank 400 is removed from the mold 500, cleaned, and trimmed to the qualified size.

[0053] Example

[0054] The structure of the precious metal crucible to be prepared in this embodiment is as follows: Figure 1 and Figure 2 As shown, the overall height of the precious metal crucible is 200mm, and the upper diameter is 354mm; the thickness of the inclined wall of the crucible body 100 is 1.2mm, the included angle between the inclined walls of the crucible body 100 is 20°, and the height of the protective layer 300 covering the bottom 200 is 45mm; the thickness of the central arc portion 210 is 2.0mm, the height of the central arc portion 210 is 50mm, and the roundness of the central arc portion 210 is 50mm; the thickness of the first connecting arc segment 220 is 1.8mm, and the roundness of the first connecting arc segment 220 is 50mm; the thickness of the flat bottom segment 230 is 1.6mm; the thickness of the second connecting arc segment 240 is 1.4mm, and the roundness of the second connecting arc segment 240 is 50mm.

[0055] Based on the dimensional parameters of the required precious metal crucible, the raw materials are selected. The thickness of the precious metal plate used as the base material is 2.0 mm. Circular dispersion reinforced platinum is selected as the reinforcing material, and the thickness of the reinforcing material is 0.4 mm. The circumferential edge area of ​​the reinforcing material is thinned to 0.2 mm using a stainless steel hammer, and the width of the hammering area is 5 mm. The reinforcing material is forged onto the base material, and after leveling, it is prepared into a conical crucible blank with a rounded tip by multi-die stamping or spinning.

[0056] The mold is made of H13 material with a quenching hardness of HRC56. A frustum-shaped mold 500 is prepared according to the outer dimensions of the precious metal crucible. The bottom outer dimensions of the mold 500 are 0.2mm smaller than those of the precious metal crucible, and the length of the inclined wall of the mold 500 is 50mm longer than that of the precious metal crucible. A concave arc groove 510 is machined at the small end of the mold 500, and a rotating shaft 520 is fixedly installed at the large end of the mold 500. Four weight-reducing holes 530 are evenly machined around the rotating shaft 520, and the distance between the bottom of the weight-reducing hole 530 and the end face of the mold 500 is 15mm.

[0057] Spin forming is performed by mounting a mold 500 on a lathe. The rotation shaft 520 of the mold 500 is connected to the drive component of the lathe. The conical tip of the crucible blank 400 is inserted into the arc groove 510 of the mold 500, so that the crucible blank 400 fits into the mold 500. The rotating tail of the lathe pushes into the crucible blank 400, and the shape of the rotating tail is similar to that of the crucible blank 400. After starting the lathe, the crucible blank 400 is heated with an oxyhydrogen flame at a heating temperature of approximately 1250°C. At the same time, a spinning tool made of H13 material is used to spin the crucible blank 400.

[0058] After the first spinning, the outer edge of the crucible blank 400 is turned outward, initially forming a flat bottom section 230 with a thickness of 1.6 mm and a second connecting arc section 240 with a thickness of 1.4 mm. After the first spinning, the first annealing is performed. The crucible blank 400 is first wiped with alcohol and soaked in 38% hydrochloric acid for 30 minutes. Then it is cleaned with pure water and placed in an annealing furnace and annealed at an annealing temperature of 1350℃ for 30 minutes. After annealing, it is naturally cooled and the cooled crucible blank 400 is spun a second time.

[0059] The secondary spinning process creates a 20° angle between the inclined wall of the crucible blank 400 and the inclined wall of the mold 500, and the thickness of the inclined wall of the crucible blank 400 is processed to 1.4±0.1mm. After the secondary spinning, a secondary annealing is performed. First, the crucible blank 400 is wiped with alcohol and soaked in 38% hydrochloric acid for 30 minutes. Then, it is cleaned with pure water and placed in an annealing furnace and annealed at 1350℃ for 30 minutes. After annealing, it is allowed to cool naturally, and the cooled crucible blank 400 is spun again until the crucible blank 400 and the mold 500 are completely bonded together, and the thickness of the inclined wall of the crucible blank 400 reaches 1.4±0.05mm.

[0060] Finally, the formed crucible blank 400 is removed from the mold 500, cleaned, and then trimmed according to the required length of the precious metal crucible to obtain a qualified finished precious metal crucible.

Claims

1. A precious metal crucible, comprising a crucible body (100) and a crucible bottom (200) connected to the bottom of the crucible body (100), characterized in that: The crucible body (100) and the crucible bottom (200) are integrally formed, and the inner surface of the crucible bottom (200) is covered with a protective layer (300). The bottom of the crucible (200) is provided with a central arc portion (210), a first connecting arc segment (220), a flat bottom segment (230), and a second connecting arc segment (240) in sequence from the center outwards; the central arc portion (210) protrudes upwards, and the first connecting arc segment (220), the flat bottom segment (230), and the second connecting arc segment (240) are connected in sequence to form a downwardly recessed annular groove; the central arc portion (210), the first connecting arc segment (220), the flat bottom segment (230), and the second connecting arc segment (240) are arranged tangentially in sequence, and the second connecting arc segment (240) is connected to the crucible body (100); The thickness of the precious metal crucible decreases sequentially from the central arc portion (210) of the bottom (200) outwards to the body (100), with a thickness tolerance of ±0.05 mm; the thickness difference between the first connecting arc segment (220) and the central arc portion (210) is 0.1–0.2 mm, the thickness difference between the flat bottom segment (230) and the central arc portion (210) is 0.2–0.3 mm, and the thickness difference between the second connecting arc segment (240) and the central arc portion (210) is 0.3–0.4 mm. m, the thickness difference between the crucible body (100) and the central arc portion (210) is 0.4 to 0.6 mm; the roundness dimension of the central arc portion (210) is 20 to 50 mm, the roundness dimension of the first connecting arc segment (220) is 20 to 50 mm, the roundness dimension of the second connecting arc segment (240) is 30 to 60 mm; the overall height dimension of the precious metal crucible is 150 to 200 mm; the angle dimension of the inclined wall of the crucible body (100) is 20 to 30°.

2. The method for preparing the precious metal crucible as described in claim 1, characterized in that: The process includes, in sequence, sheet material preparation, mold preparation, and spin forming; In the plate preparation step, a circular precious metal plate is prepared as the base material, and a circular dispersion-strengthened platinum or dispersion-strengthened platinum-rhodium alloy is prepared as the reinforcing material. The reinforcing material is forged onto the base material, and after leveling, it is prepared into a conical crucible blank (400) with a cone tip and a rounded surface by multi-die stamping or spinning. In the mold preparation step, a frustum-shaped mold (500) is prepared according to the outer dimensions of the precious metal crucible. The small end of the mold (500) is provided with a concave arc groove (510), and the large end of the mold (500) is provided with a rotating shaft (520). In the spinning forming step, the mold (500) is installed on a spinning bed and the cone tip of the crucible blank (400) is inserted into the arc groove (510) of the mold (500). Then, the crucible blank (400) is repeatedly heated, spun and annealed until a noble metal crucible that meets the requirements is obtained.

3. The method for preparing the precious metal crucible as described in claim 2, characterized in that: In the plate preparation step, the diameter of the precious metal plate is φ1, φ1=π×r1+π×r2+2L+π×r3+2h-(50~100)mm, and the thickness of the precious metal plate is 1.2~2.5mm; the diameter of the reinforcing material is φ2, φ2=π×r1+π×r2+2L+π×r3+(5~10)mm, and the thickness of the reinforcing material is 0.3~0.5mm; where r1 is the roundness of the central arc part (210), r2 is the roundness of the first connecting arc segment (220), L is the length of the flat bottom segment (230), r3 is the roundness of the second connecting arc segment (240), and h is the overall height of the precious metal crucible.

4. The method for preparing the precious metal crucible as described in claim 2, characterized in that: In the mold preparation step, the mold (500) is provided with a plurality of weight reduction holes (530). The weight reduction holes (530) are blind holes that extend axially from the end face of the mold (500) with a rotating shaft (520) to the inside of the mold (500). The plurality of weight reduction holes (530) are arranged in a ring around the rotating shaft (520).

5. The method for preparing the precious metal crucible as described in claim 4, characterized in that: The bottom of the weight reduction hole (530) and the end face of the mold (500) with the arc groove (510) are 10-20mm apart. The outer diameter of the end of the mold (500) is smaller than the outer diameter of the end of the precious metal crucible. The height of the inclined wall of the mold (500) is greater than the height of the inclined wall of the crucible body (100). The material of the mold (500) is H13 and the quenching hardness is greater than HRC55.

6. The method for preparing the precious metal crucible as described in claim 2, characterized in that: In the spinning process, a spinning tool is used to spin the crucible blank (400) from the outside to the inside in sequence. The first spinning process causes the outer edge of the crucible blank (400) to turn out. The material of the spinning tool is H13, and the heating temperature of the crucible blank (400) during spinning is 1200-1350℃.

7. The method for preparing the precious metal crucible as described in claim 2, characterized in that: In the spinning process, after the first spinning, the first annealing is performed. The crucible blank (400) is first wiped with alcohol and soaked in hydrochloric acid with a concentration of 36-38% for 30 minutes. Then it is cleaned with pure water and placed in an annealing furnace for annealing for 30 minutes at a temperature of 1350-1450℃.

8. The method for preparing the precious metal crucible as described in claim 7, characterized in that: In the spinning forming step, a second spinning process is performed after the first annealing. During the second spinning process, there is an angle of 15 to 25° between the inclined wall of the crucible blank (400) and the inclined wall of the mold (500). The thickness of the inclined wall of the crucible blank (400) is spun to be 0.1 mm greater than the thickness of the inclined wall of the crucible body (100). Then, after repeated cleaning and annealing, the crucible blank (400) is spun to fit with the mold (500) and the thickness of the inclined wall of the crucible blank (400) is spun to be 0.05 mm greater than the thickness of the inclined wall of the crucible body (100). Finally, the crucible blank (400) is removed from the mold (500), cleaned, and trimmed to the qualified size.

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