Crucible preparation method and crucible

Abstract

This invention provides a crucible preparation method and a crucible, relating to the field of crystal pulling crucible preparation technology. During the preparation of the current crucible: before starting arc melting, the graphite electrode is preheated so that during arc melting, the temperature of the tip of the graphite electrode near the arc starting point is T1, where 200℃ ≤ T1. The preheating heat comes from: the heat of the graphite electrode itself after the preparation of the previous crucible, and / or the heat from preheating the graphite electrode using a heating source; the previous crucible is the one with the shortest time difference between the current crucible and all crucibles obtained from graphite electrode melting. Therefore, during arc melting, the temperature difference at the tip of the graphite electrode near the arc starting point is relatively small, resulting in relatively low thermal stress at the tip, thus reducing spattering or chipping at the tip.

Description

Technical Field

[0001] This invention relates to the field of crystal pulling crucible preparation technology, and in particular to a crucible preparation method and a crucible. Background Technology

[0002] Crucibles for pulling single-crystal silicon are typically manufactured using an electric arc method. Specifically, a high-temperature electric arc is generated between graphite electrodes used in crucible production to melt the slag. The core temperature of this arc often exceeds 5000℃. Due to the high temperature, the graphite electrodes are prone to splashing during the melting process. This splashing of graphite electrodes causes defects such as black spots, pits, and bubbles on the inner wall of the crucible, leading to a decrease in crucible quality or even its rejection.

[0003] Currently, the crucible preparation method to reduce sputtering of graphite electrodes used in production crucibles is to directly remove the easily sputtered parts from the cylindrical graphite electrode.

[0004] However, simply removing the easily splashed parts of the graphite electrode does not completely eliminate the possibility of the graphite electrode splashing during the molten sand process. Summary of the Invention

[0005] This invention provides a crucible preparation method and a crucible, aiming to solve the problem of sputtering of graphite electrodes during the molten sand process in the crucible preparation method.

[0006] A first aspect of the present invention provides a method for preparing a crucible, comprising:

[0007] During the preparation of the current crucible: before starting the arc melting, the graphite electrode is preheated so that the temperature of the tip of the graphite electrode near the arc starting point is T1, where 200℃≤T1; the preheating heat comes from: the heat of the graphite electrode itself after the previous crucible was prepared, and / or the heat from preheating the graphite electrode using a heating source; the previous crucible is: the crucible with the shortest time difference with the current crucible among all the crucibles obtained from melting the graphite electrode.

[0008] In this embodiment of the invention, before starting the arc-initiating melting process, the temperature of the tip of the graphite electrode near the arc-initiating point is preheated to T1, where 200℃ ≤ T1. Therefore, during arc-initiating melting, the temperature difference at the tip of the graphite electrode near the arc-initiating point is relatively small, resulting in relatively low thermal stress at this tip. This reduces spattering or chipping at the tip. Furthermore, if the preheating heat comes entirely from the heat already generated by the graphite electrode after the previous crucible preparation, no additional heating is required, reducing costs and steps, and improving crucible preparation efficiency. If the preheating heat comes partly from the heat already generated by the graphite electrode after the previous crucible preparation, less additional heating is needed, again reducing costs and potentially shortening the additional heating time, thus improving crucible preparation efficiency.

[0009] Optionally, after preheating the graphite electrode before starting arc melting, the process further includes:

[0010] In the early stage of arc initiation and melting, the power applied to the preheated graphite electrode is set to w1; w1≤80%×w2, the duration of the early stage of arc initiation and melting is t1, 10s≤t1≤300s; w2 is the maximum power applied to the graphite electrode during the melting of the sand; the starting time of the early stage of arc initiation and melting is: the moment when the graphite electrode just begins to initiate arc melting during the preparation of the current crucible.

[0011] Optionally, the resistivity of the graphite electrode is r, where r ≤ 10 μΩ·m.

[0012] Optionally, during the preparation of the current crucible:

[0013] If the graphite electrode is not a newly replaced graphite electrode, and the time since the end of the previous crucible melting is less than or equal to 1 hour, the preheating of the graphite electrode before starting the arc ignition melting further includes:

[0014] The temperature of the tip of the graphite electrode near the arc initiation point is detected;

[0015] The step of preheating the graphite electrode before starting the arc melting process includes: when the temperature of the tip of the graphite electrode near the arc starting point is less than 200°C, using a heating source to preheat the graphite electrode so that the temperature of the tip of the graphite electrode near the arc starting point is T1 during the arc melting process.

[0016] If the graphite electrode is a newly replaced graphite electrode, or if the graphite electrode is not a newly replaced graphite electrode and more than 1 hour has elapsed since the end of the previous crucible melting, the preheating of the graphite electrode before starting the arc melting includes: preheating the graphite electrode with a heating source so that the temperature of the tip of the graphite electrode near the arc starting point is T1 during the arc melting.

[0017] Optionally, before preheating the graphite electrode with a heating source, the method further includes:

[0018] Heated sand is laid in the mold used to prepare the current crucible to avoid damaging the mold during the preheating process of the graphite electrode.

[0019] Optionally, the mass of the heated sand is 40-50 kg.

[0020] Optionally, preheating the graphite electrode using a heating source includes:

[0021] When the purity of silicon dioxide in the heated sand is greater than or equal to 99.5%, the graphite electrode is preheated at low temperature using a heating source; during the low-temperature preheating process, the heated sand does not melt; during the preparation of the current crucible, the heated sand melts as part of the current crucible, and / or the heated sand exists in the mold as floating sand;

[0022] When the purity of silicon dioxide in the heated sand is less than 99.5%, the graphite electrode is preheated at low temperature using a heating source; during the low-temperature preheating process, the heated sand does not melt; after the low-temperature preheating, the method further includes: cleaning out a portion of the heated sand in the mold, so that the mass of the remaining heated sand in the mold is m1, and the remaining heated sand in the mold exists only as floating sand in the mold; m1≤5kg;

[0023] When the purity of silicon dioxide in the heated sand is less than 99.5%, the graphite electrode is preheated by arc initiation using a three-phase voltage; during the arc initiation preheating process, the heated sand melts; after the arc initiation preheating, the method further includes: cleaning the melted heated sand from the mold.

[0024] Optionally, during the arc ignition preheating process, the power applied to the graphite electrode is set to w3; 50% × w2 ≤ w3 ≤ w2; where w2 is the maximum power applied to the graphite electrode during the melting of the sand.

[0025] The duration of arc initiation and preheating is t2, where 30s ≤ t2 ≤ 300s.

[0026] Optional, 50% × w2 ≤ w1 ≤ 80% × w2.

[0027] In a second aspect, the present invention provides a crucible prepared by any of the aforementioned crucible preparation methods. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart illustrating the steps of a crucible preparation method according to an embodiment of the present invention is shown;

[0030] Figure 2 A flowchart illustrating the steps of another crucible preparation method in an embodiment of the present invention is shown. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Figure 1 A flowchart illustrating the steps of a crucible preparation method according to an embodiment of the present invention is shown. (Refer to...) Figure 1 As shown, the method for preparing the crucible includes:

[0033] Step S1, during the preparation of the current crucible: before starting the arc melting, the graphite electrode is preheated so that the temperature of the tip of the graphite electrode near the arc starting point is T1, 200℃≤T1 during the arc melting; the preheating heat comes from: the heat of the graphite electrode itself after the previous crucible was prepared, and / or the heat from preheating the graphite electrode using a heating source; the previous crucible is: the crucible with the shortest time difference with the current crucible among all the crucibles obtained by melting the graphite electrode.

[0034] The current crucible is used for preparing sand by arc melting of graphite electrodes. The inventors discovered that the splashing point of the graphite electrode during the sand melting process is usually at the tip near the arc initiation point. Simply removing the easily splashing portion of the graphite electrode does not completely eliminate the problem. The reason for the splashing during the sand melting process is that the tip of the graphite electrode near the arc initiation point experiences greater thermal stress, making it prone to splashing. In this embodiment of the invention, during the preparation of the current crucible: before arc melting of the sand with the graphite electrode, the graphite electrode is preheated so that the temperature of the tip near the arc initiation point is preheated to T1, where 200℃ ≤ T1. Therefore, during arc melting, the temperature difference at the tip of the graphite electrode near the arc initiation point is relatively small, resulting in relatively less thermal stress at the tip, thus reducing splashing or chipping at the tip of the graphite electrode near the arc initiation point.

[0035] Specifically, if the temperature of the tip of the graphite electrode near the arc-starting point is T2 during arc-starting melting, and the graphite electrode is preheated to a preheated temperature of T1 during arc-starting melting, then the temperature difference of the tip of the graphite electrode near the arc-starting point during arc-starting melting is: T2 - T1, where 200℃ ≤ T1. If the graphite electrode is preheated directly without preheating, the temperature difference of the tip of the graphite electrode near the arc-starting point during arc-starting melting is: T2 - room temperature. Room temperature is typically around 25℃. Compared to T2 - room temperature, the temperature difference T2 - T1 in this embodiment of the invention is significantly smaller. Consequently, the thermal stress borne by the tip of the graphite electrode near the arc-starting point is significantly smaller, thus reducing spattering or chipping at the tip of the graphite electrode near the arc-starting point.

[0036] The previous crucible is the one with the shortest time difference between the current crucible and all crucibles obtained from melting this graphite electrode. For example, if the time for preheating the graphite electrode used in the current crucible preparation process is 11:20:20 on November 20, 2021, and if before 11:20:20 on November 20, 2021, three crucibles have been melted from the graphite electrode used in the current crucible preparation process, these three crucibles are: Crucible No. 1, completed at 10:50:20 on November 20, 2021; Crucible No. 2, completed at 10:00:03 on November 20, 2021; and Crucible No. 3, completed at 8:55:20 on November 20, 2021. Therefore, the time difference between crucible No. 1 and 11:20:20 on November 20, 2021 is the smallest. The previous crucible is crucible No. 1, which was prepared at 10:50:20 on November 20, 2021.

[0037] During the preparation of the current crucible, the heat used to preheat the graphite electrode before arc initiation comes from: the heat of the graphite electrode itself after the previous crucible preparation, and / or, the heat used to preheat the graphite electrode using a heating source. The preheating heat can come entirely from the heat of the graphite electrode itself after the previous crucible preparation. Alternatively, the preheating heat can come entirely from the heat used to preheat the graphite electrode using a heating source. Alternatively, the preheating heat can come partly from the heat of the graphite electrode itself after the previous crucible preparation, and partly from the heat used to preheat the graphite electrode using a heating source. When the preheating heat comes from both the heat of the graphite electrode itself after the previous crucible preparation and the heat used to preheat the graphite electrode using a heating source, the specific ratio of the two parts is not limited.

[0038] If the preheating heat comes entirely from the heat of the graphite electrode itself after the previous crucible preparation, then no additional heating or additional heat is required, which can reduce costs and decrease the number of steps, thereby improving crucible preparation efficiency. If part of the preheating heat comes from the heat of the graphite electrode itself after the previous crucible preparation, then less additional heating is needed, which can also reduce costs, and the additional heating time may be shorter, thus also improving crucible preparation efficiency.

[0039] Figure 2 A flowchart illustrating another crucible preparation method according to an embodiment of the present invention is shown. (Refer to...) Figure 2 As shown, the method for preparing the crucible includes:

[0040] Step S1, during the preparation of the current crucible: before starting the arc melting, the graphite electrode is preheated so that the temperature of the tip of the graphite electrode near the arc starting point is T1, 200℃≤T1 during the arc melting; the preheating heat comes from: the heat of the graphite electrode itself after the previous crucible was prepared, and / or the heat from preheating the graphite electrode using a heating source; the previous crucible is: the crucible with the shortest time difference with the current crucible among all the crucibles obtained by melting the graphite electrode.

[0041] Step S1 can be referred to the aforementioned records; to avoid repetition, it will not be repeated here.

[0042] Step S2: In the early stage of arc initiation and melting, the power applied to the preheated graphite electrode is set to w1; w1≤80%×w2, the duration of the early stage of arc initiation and melting is t1, 10s≤t1≤300s; w2 is the maximum power applied to the graphite electrode during the melting of the sand; the starting time of the early stage of arc initiation and melting is: the moment when the graphite electrode just begins to initiate arc melting during the preparation of the current crucible.

[0043] w2 represents the maximum power applied to the graphite electrode during the melting of the sand. The initial moment of arc initiation for melting the sand is the moment when the graphite electrode just begins to initiate arc melting during the preparation of the current crucible.

[0044] The inventors discovered that if the power applied to the graphite electrode is set to greater than 80% × w2 in the early stage of arc melting of the sand, it will result in: a large amount of heat generation and an extremely rapid heating rate at the tip of the graphite electrode near the arc starting point; and very high thermal stress at the tip of the graphite electrode near the arc starting point, which will lead to spattering and chipping due to excessive thermal stress. If the power applied to the preheated graphite electrode is set to w1, where w1 ≤ 80% × w2, in the early stage of arc melting of the sand, but if the duration of the early stage of arc melting of the sand is less than 10 seconds, this short power duration will still result in a large amount of heat generation and an extremely rapid heating rate at the tip of the graphite electrode near the arc starting point; and very high thermal stress at the tip of the graphite electrode near the arc starting point, which will also lead to spattering and chipping due to excessive thermal stress.

[0045] In this embodiment of the invention, in the early stage of arc-initiating and melting the sand, the power applied to the preheated graphite electrode is set to w1, where w1 ≤ 80% × w2, and the duration of the early stage of arc-initiating and melting the sand is t1, where 10s ≤ t1 ≤ 300s. In this embodiment of the invention, the power applied to the preheated graphite electrode is set to be less than or equal to 80% of w2 in the early stage of arc-initiating and melting the sand. Consequently, the heat generated at the tip of the graphite electrode near the arc-initiating point is small, and the heating rate is relatively slow. Therefore, the thermal stress borne by the tip of the graphite electrode near the arc-initiating point is significantly smaller, thereby reducing splashing or chipping at the tip of the graphite electrode near the arc-initiating point. The duration of the low-power arc initiation phase is t1, with 10s ≤ t1. This relatively long low-power duration results in less heat generation at the tip of the graphite electrode near the arc initiation point, leading to a slower heating rate. Consequently, the thermal stress experienced by this tip is significantly reduced, thus decreasing the likelihood of sputtering or chipping. Furthermore, the duration of the low-power arc initiation phase is t1, with t1 ≤ 300s. This not only reduces the probability of sputtering or chipping at the tip of the graphite electrode near the arc initiation point but also does not affect the quality of the prepared crucible, does not prolong the crucible production time, and does not reduce production efficiency.

[0046] Optionally, in the early stage of arc initiation and sand melting, the power applied to the preheated graphite electrode is set to w1, where 50% × w2 ≤ w1 ≤ 80% × w2. In this early stage, the heat generation at the tip of the graphite electrode near the arc initiation point is small, and the heating rate is relatively slow. Consequently, the thermal stress borne by this tip is significantly lower, reducing spattering or chipping. Simultaneously, within this range, the current density on the graphite electrode is suitable, facilitating successful arc initiation and ensuring a stable arc without the need for repeated initiation. Furthermore, with w1 = 70% × w2, there is even less spattering or chipping, a higher arc initiation success rate, and a more stable arc.

[0047] Optionally, t1 = 30s. When the duration of the low-power arc initiation is 30s, the probability of the tip of the graphite electrode near the arc initiation point splashing or falling off is small, the quality of the crucible is good, the production time of the crucible is relatively short, and the production efficiency is high.

[0048] Optionally, the resistivity of the graphite electrode is r, r≤10μΩ·m (microohm·meter). When the resistivity r of the graphite electrode is within the above range, the heat generated by the electrode itself is relatively small under the same power, the temperature rise rate is relatively slow, and the thermal stress is small, which can reduce the sputtering or chipping of the graphite electrode tip near the arc initiation point.

[0049] Optionally, the voltage applied to the graphite electrode is greater than or equal to 300V, for example, 380V or 410V. Within this voltage range, the graphite electrode can easily break down the air to generate a stable electric arc.

[0050] Optionally, if the graphite electrode is not a newly replaced graphite electrode and the time since the end of the previous crucible melting is less than or equal to 1 hour, before step S1, the method may further include: detecting the temperature of the tip of the graphite electrode near the arc initiation point. Step S1 includes: if the temperature of the tip of the graphite electrode near the arc initiation point is less than 200°C, preheating the graphite electrode with a heating source so that during arc initiation melting, the temperature of the tip of the graphite electrode near the arc initiation point is the aforementioned T1.

[0051] Specifically, if the graphite electrode mentioned above is not a newly replaced graphite electrode, meaning that other crucibles were prepared using this graphite electrode before the current crucible was prepared, and the time since the previous crucible's melting ended is less than or equal to one hour, the graphite electrode's temperature may not have decreased significantly. In this case, first measure the temperature of the tip of the graphite electrode near the arc-starting point using an infrared thermometer. The method for measuring the temperature of this tip is not specifically limited. After measurement, three phenomena may occur: First, after measurement, the temperature of the graphite electrode after the previous crucible preparation is greater than or equal to 200℃. Second, after measurement, the temperature of the graphite electrode after the previous crucible preparation is less than 200℃ but greater than room temperature. Third, after measurement, the temperature of the graphite electrode after the previous crucible preparation is equal to room temperature. For the first scenario, during the preparation of the current crucible, the heat used to preheat the graphite electrode before starting arc melting comes entirely from the heat of the graphite electrode itself after the preparation of the previous crucible. For the second scenario, after the preparation of the previous crucible, during the preparation of the current crucible, the heat used to preheat the graphite electrode before starting arc melting comes partly from the heat of the graphite electrode itself after the preparation of the previous crucible, and partly from the heat generated by using a heating source to preheat the graphite electrode. For the third scenario, during the preparation of the current crucible, the heat used to preheat the graphite electrode before starting arc melting comes entirely from the heat generated by using a heating source to preheat the graphite electrode. In both the second and third scenarios, after preheating, the temperature of the tip of the graphite electrode near the arc ignition point can be checked again. If the temperature of the tip of the graphite electrode near the arc ignition point is greater than or equal to 200°C, then the arc melting step can proceed. If, after testing, the temperature of the tip of the graphite electrode near the arc initiation point is still less than 200°C, the graphite electrode needs to be preheated using a heating source, and the testing procedure repeated, until the temperature of the tip of the graphite electrode near the arc initiation point is greater than or equal to 200°C after preheating. There are no specific limits on the number of tests or preheating cycles.

[0052] Optionally, if the graphite electrode is a newly replaced graphite electrode, or if the graphite electrode is not a newly replaced graphite electrode and the time since the end of the previous crucible melting is less than or equal to 1 hour, step S1 includes: preheating the graphite electrode with a heating source so that the temperature of the tip of the graphite electrode near the arc initiation point is the aforementioned T1 during arc initiation melting.

[0053] Specifically, if the graphite electrode is a newly replaced graphite electrode (meaning no other crucible was prepared before the current crucible was made), then the temperature of the tip of the graphite electrode near the arc initiation point is typically room temperature. Alternatively, if the graphite electrode is not a newly replaced one, and more than one hour has passed since the previous crucible's melting ended, the graphite electrode's temperature will have decreased significantly. In both cases, the temperature of the tip of the graphite electrode near the arc initiation point is typically below 200°C. If room temperature is acceptable, the temperature of the tip of the graphite electrode near the arc initiation point is not measured; instead, the graphite electrode is preheated directly using a heating source. After preheating, the temperature of the tip of the graphite electrode near the arc initiation point is measured. If the measured temperature is greater than or equal to 200°C, then the arc initiation melting step can proceed. If, after testing, the temperature of the tip of the graphite electrode near the arc initiation point is less than 200°C, the graphite electrode needs to be preheated using a heating source, and the testing process repeated until the temperature of the tip of the graphite electrode near the arc initiation point is greater than or equal to 200°C after preheating. No specific limits are made on the number of tests or preheating cycles.

[0054] The graphite electrode mentioned above is a newly replaced graphite electrode, meaning that no other crucible was prepared using this graphite electrode before the current crucible was prepared. Alternatively, if the graphite electrode is not a newly replaced graphite electrode, and more than one hour has passed since the previous crucible's melting ended, the graphite electrode's temperature will drop significantly. In both of these cases, the temperature of the tip of the graphite electrode near the arc initiation point is usually below 200°C. By not measuring the temperature of this tip and directly preheating the graphite electrode with a heating source, the temperature measurement steps are reduced, production efficiency is improved, and there is virtually no waste of heat or resources.

[0055] Optionally, in step S1 above, before preheating the graphite electrode with a heating source, the method may further include: laying heated sand in the mold for preparing the current crucible to avoid damaging the mold during the preheating process of the graphite electrode.

[0056] Optionally, the mass of the heated sand material laid in the mold is 40-50 kg. Laying heated sand material within the above-mentioned mass range in the mold can better avoid damage to the mold during the preheating process of the graphite electrode, and the economic cost is low.

[0057] Optionally, in step S1 above, preheating the graphite electrode with a heating source includes: if the purity of silicon dioxide in the heated sand is greater than or equal to 99.5%, preheating the graphite electrode at a low temperature using a heating source. During the low-temperature preheating process, the heated sand does not melt. In the current crucible preparation process, the heated sand melts and becomes part of the current crucible, and / or, the heated sand exists in the mold as floating sand. That is to say, the purity of the heated sand meets the requirements for crucible preparation sand. Since the heated sand does not melt during low-temperature preheating, all of the heated sand can be used directly as the sand for preparing the current crucible, or a portion of the heated sand can be used as the sand for preparing the current crucible, and a portion can be used as floating sand, or all of the heated sand can be used as floating sand. In this embodiment of the invention, no specific limitation is made in this regard. The relative magnitudes of the mass of the heated sand used as the sand for preparing the current crucible and the mass of the heated sand used as floating sand are not specifically limited. In this method, when the current crucible is being melted by arc initiation, the heated sand material does not need to be cleaned, which can reduce steps, reduce process time, improve production efficiency, and reduce waste.

[0058] Optionally, in step S1 above, preheating the graphite electrode with a heating source includes: if the silica purity in the heated sand is less than 99.5%, preheating the graphite electrode at a low temperature using a heating source. After low-temperature preheating, the heated sand does not melt. The method may further include: removing a portion of the heated sand from the mold, leaving a mass of m1 in the mold, which exists only as floating sand; m1 ≤ 5 kg. That is, the purity of the heated sand is relatively poor and does not meet the requirements for crucible preparation. Due to low-temperature preheating, the heated sand does not melt. A portion of the heated sand is removed from the mold, leaving only a suitable amount as floating sand, with a mass of less than or equal to 5 kg. This method eliminates the need for dedicated floating sand, reducing steps, processing time, production efficiency, and waste.

[0059] Optionally, in step S1 above, preheating the graphite electrode with a heating source includes: if the silica purity in the heated sand is less than 99.5%, using a three-phase voltage to perform arc-initiating preheating on the graphite electrode. During the arc-initiating preheating process, the heated sand melts. After the arc-initiating preheating, the method may further include: cleaning the melted heated sand from the mold. That is to say, during arc-initiating preheating, the heated sand melts. The melted heated sand cannot be used as floating sand or as sand for preparing the crucible and needs to be cleaned away. Therefore, using heated sand with lower purity can reduce costs, and at the same time, no external heating source is required, simplifying the process.

[0060] Optionally, during the above-mentioned arc ignition preheating process, the power applied to the graphite electrode is set to w3, where 50% × w2 ≤ w3 ≤ w2, and the arc ignition preheating duration is t2, where 30s ≤ t2 ≤ 300s. Within this power and duration range, before arc melting, the temperature of the tip of the graphite electrode near the arc ignition point will not drop below 200℃, preventing repeated heating. Furthermore, the appropriate arc ignition preheating duration will not cause excessive oxidation and ablation of the graphite electrode, thus not affecting its service life.

[0061] Optionally, t2 = 120s. Within this arc-starting preheating time range, the preheating effect is good and there is little oxidation and ablation of the graphite electrode.

[0062] Optionally, the graphite electrode contains 98% or more graphite, which provides better thermal stress resistance.

[0063] During the arc-initiating melting process of the current crucible, the purity of silicon dioxide in the sand to be melted is greater than or equal to 99.5%. This sand can be quartz sand. In this embodiment of the invention, no specific limitation is made.

[0064] This invention also provides a crucible prepared using any of the aforementioned crucible preparation methods. The aforementioned crucible and the aforementioned crucible preparation methods can achieve the same or similar beneficial effects, and their related contents can be referred to each other. To avoid repetition, they will not be repeated here.

[0065] Table 1 below shows the experimental results of the temperature at the tip of the graphite electrode near the arc initiation point and the corresponding sputtering rate at the start of arc initiation melting. Table 2 shows the experimental results of the power applied to the graphite electrode and the corresponding sputtering rate during the early stage of arc initiation melting.

[0066] The following explanation, based on specific experimental data such as Tables 1 and 2, further illustrates this application:

[0067] Table 1 shows the experimental results of the temperature at the tip of the graphite electrode near the arc initiation point and the corresponding sputtering rate at the start of arc ignition and melting.

[0068]

[0069] Table 1 lists the preparation process for 100 crucibles for each number. In the preparation processes of crucibles numbered 1-7 in Table 1, all production parameters are identical except for those listed in the table. According to Table 1, when the power applied to the graphite electrode is equal at the start of arc melting, the sputtering rate of the graphite electrode decreases as the temperature of the tip near the arc starting point increases. When the temperature of the tip near the arc starting point is less than 200℃ at the start of arc melting, the sputtering rate is relatively high. When the temperature of the tip near the arc starting point is greater than or equal to 200℃ at the start of arc melting, the sputtering rate decreases significantly.

[0070] Table 2 shows the experimental results of the power applied to the graphite electrode and the corresponding sputtering rate during the early stage of arc initiation and melting.

[0071]

[0072] Table 2 lists the preparation process for 100 crucibles for each number. In Table 1, the preparation processes for crucibles numbered 1-7 are identical except for the production parameters listed in the table. Based on Table 2, it can be concluded that when the temperature of the graphite electrode tip near the arc initiation point is equal at the start of arc melting, as the power applied to the graphite electrode decreases in the early stage of arc melting, the spatter initially decreases and then increases. The inflection point is when the ratio of the power applied to the graphite electrode in the early stage of arc melting to the maximum power applied to the graphite electrode during the sand melting process is 50%. More specifically, when the ratio is greater than or equal to 50%, the spatter rate decreases as the ratio decreases; conversely, when the ratio is less than 50%, the spatter rate increases as the ratio decreases. When the ratio of the two components is less than 50%, the reason why the sputtering rate increases as the ratio decreases is mainly because: in the early stage of arc ignition and melting, the power applied to the graphite electrode is relatively small, which leads to a lower success rate of arc ignition and may require multiple arc ignitions. However, the graphite electrode is prone to sputtering when the arc is first ignited.

[0073] Table 3 shows the test results of a crucible preparation method according to an embodiment of the present invention, along with the corresponding splashing rate.

[0074] Current crucible dimensions (inches) 28 w2(kw) 1280 t2 120s w3(kw) 640 The average value of T1 1000℃ w1(kw) 896 t1 30s r(μΩ·m) 10.2 Average splash rate 0.8％

[0075] Table 3 shows the statistical results of the preparation process of 1000 crucibles. Specifically, the preparation method of the crucibles corresponding to Table 3 includes the following steps: First, during the preparation of the current crucible: before the start of arc ignition melting, the graphite electrode is preheated for arc ignition. During the arc ignition preheating process, the power w3 applied to the graphite electrode is 640 kW, and t2 is 120 s. The maximum power w2 applied to the graphite electrode during the melting of the sand is 1280 kW. Therefore, w3 / w2 = 50%, and after arc ignition preheating, the average temperature T1 of the tip of the graphite electrode near the arc ignition point is 1000℃. Second, in the early stage of arc ignition melting, the power w1 applied to the preheated graphite electrode is set to 896 kW; therefore, w1 / w2 = 70%, and the duration t1 of the early stage of arc ignition melting is 30 s. The resistivity r of the graphite electrode is 10.2 μΩ·m. Statistical analysis of the preparation process of 1000 crucibles revealed an average sputtering rate of only 0.8% for the graphite electrodes. In this embodiment of the invention, before the arc-initiating melting begins, the temperature of the tip of the graphite electrode near the arc-initiating point is preheated to 1000°C. This results in a relatively small temperature difference at the tip during arc-initiating melting, leading to lower thermal stress and thus reducing sputtering or chipping. Simultaneously, in the early stage of arc-initiating melting of the sand, the power applied to the preheated graphite electrode is set to 896 kW, and the duration of this initial stage is 30 seconds. During this early stage, the heat generation at the tip of the graphite electrode near the arc-initiating point is low, and the heating rate is relatively slow. Consequently, the thermal stress borne by this tip is significantly lower, further reducing sputtering or chipping. The low-power arc initiation process has a longer initial duration, resulting in less heat generation and a slower temperature rise at the tip of the graphite electrode near the arc initiation point. Consequently, the thermal stress experienced by this tip is significantly lower, reducing the likelihood of sputtering or chipping. The resistivity of the graphite electrode is 10.2 μΩ·m. At the same power, the electrode itself generates relatively little heat, resulting in a slower temperature rise and lower thermal stress, further reducing sputtering or chipping at the tip near the arc initiation point.

[0076] It should be noted that, in the process of preparing crucibles of various sizes, under the condition of stable arc initiation and minimal splashing and chipping, the formula for the optimal power w2 (in W) corresponding to the maximum power applied during the melting of sand material and the maximum outer diameter X (inches) of the crucible can be: 85000X-2100000≤P≤85000X.

[0077] It should be noted that, for the sake of simplicity, the method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of this application are not limited to the described order of actions, because according to the embodiments of this application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also understand that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily essential to the embodiments of this application.

[0078] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0079] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0080] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a crucible, characterized in that, include: During the preparation of the current crucible: before the start of arc melting, the graphite electrode is preheated so that the temperature of the tip of the graphite electrode near the arc starting point is T1, where 200℃≤T1; the preheating heat comes from: the heat of the graphite electrode itself after the preparation of the previous crucible, and / or the heat from preheating the graphite electrode using a heating source; the previous crucible is: the crucible with the shortest time difference with the current crucible among all the crucibles obtained from melting the graphite electrode; The resistivity of the graphite electrode is r, where r ≤ 10 μΩ·m.

2. The crucible preparation method according to claim 1, characterized in that, After preheating the graphite electrode before starting the arc melting process, the process also includes: In the early stage of arc initiation and melting, the power applied to the preheated graphite electrode is set to w1; w1≤80%×w2, the duration of the early stage of arc initiation and melting is t1, 10s≤t1≤300s; w2 is the maximum power applied to the graphite electrode during the melting of the sand; the starting time of the early stage of arc initiation and melting is: the moment when the graphite electrode just begins to initiate arc melting during the preparation of the current crucible.

3. The crucible preparation method according to claim 1 or 2, characterized in that, During the preparation of the current crucible: If the graphite electrode is not a newly replaced graphite electrode, and the time since the end of the previous crucible melting is less than or equal to 1 hour, the preheating of the graphite electrode before starting the arc ignition melting further includes: The temperature of the tip of the graphite electrode near the arc initiation point is detected; The step of preheating the graphite electrode before starting the arc melting process includes: when the temperature of the tip of the graphite electrode near the arc starting point is less than 200°C, using a heating source to preheat the graphite electrode so that the temperature of the tip of the graphite electrode near the arc starting point is T1 during the arc melting process. If the graphite electrode is a newly replaced graphite electrode, or if the graphite electrode is not a newly replaced graphite electrode and more than 1 hour has elapsed since the end of the previous crucible melting, the preheating of the graphite electrode before starting the arc melting includes: preheating the graphite electrode with a heating source so that the temperature of the tip of the graphite electrode near the arc starting point is T1 during the arc melting.

4. The crucible preparation method according to claim 1 or 2, characterized in that, Before preheating the graphite electrode with a heating source, the method further includes: Heated sand is laid in the mold used to prepare the current crucible to avoid damaging the mold during the preheating process of the graphite electrode.

5. The crucible preparation method according to claim 4, characterized in that, The mass of heated sand is 40-50 kg.

6. The crucible preparation method according to claim 5, characterized in that, The step of preheating the graphite electrode using a heating source includes: When the purity of silicon dioxide in the heated sand is greater than or equal to 99.5%, the graphite electrode is preheated at low temperature using a heating source; during the low-temperature preheating process, the heated sand does not melt; during the preparation of the current crucible, the heated sand melts as part of the current crucible, and / or the heated sand exists in the mold as floating sand; When the purity of silicon dioxide in the heated sand is less than 99.5%, a heating source is used to preheat the graphite electrode at a low temperature; during the low-temperature preheating process, the heated sand does not melt; after the low-temperature preheating, the method further includes: cleaning out a portion of the heated sand in the mold, so that the mass of the remaining heated sand in the mold is m1, and the remaining heated sand in the mold exists only as floating sand in the mold; m1≤5kg; When the purity of silicon dioxide in the heated sand is less than 99.5%, the graphite electrode is preheated by arc initiation using a three-phase voltage; during the arc initiation preheating process, the heated sand melts; after the arc initiation preheating, the method further includes: cleaning the melted heated sand from the mold.

7. The crucible preparation method according to claim 6, characterized in that, During the arc initiation and preheating process, the power applied to the graphite electrode is set to w3; 50%×w2≤w3≤w2; where w2 is the maximum power applied to the graphite electrode during the melting of the sand. The duration of arc initiation and preheating is t2, where 30s ≤ t2 ≤ 300s.

8. The crucible preparation method according to claim 2, characterized in that, 50%×w2≤w1≤80%×w2.

9. A crucible, characterized in that, The crucible is prepared using the crucible preparation method as described in any one of claims 1-8.

Images