A method for preparing a shrinkage-free electroslag ingot

Abstract

This invention belongs to the field of high-temperature alloy smelting technology and relates to a method for preparing a shrinkage-cavity-free electroslag ingot. By adding a heating agent after the power is cut off during electroslag melting, the slag pool temperature is maintained after the power is cut off to compensate for heat loss, thereby improving the slag-metal separation and feeding effect at the ingot head and completing the preparation of a shrinkage-cavity-free electroslag ingot. By adding a certain amount of heating agent after the power is cut off during feeding, the slag pool can continue to maintain a high temperature under the action of the heating agent after the power is cut off, ensuring the slag-metal separation effect at the ingot head, achieving slow cooling of the molten metal at the ingot head, eliminating macroscopic shrinkage cavities at the ingot head, and improving the ingot yield.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy smelting technology and relates to a method for preparing a shrinkage-cavity-free electroslag ingot. Background Technology

[0002] Nickel-based superalloys combine high strength at high temperatures, excellent oxidation and corrosion resistance, as well as good fatigue resistance, fracture toughness, and plasticity. They exhibit good structural stability and service reliability at various temperatures. Therefore, they are widely used in critical components operating under extreme conditions, such as rocket turbine disks and high-temperature rotating parts of aircraft engines.

[0003] Currently, wrought superalloys face significant cost pressures in their preparation and use. Due to lengthy processes and high losses, the net weight ultimately used for parts manufacturing accounts for only about 5% of the raw material input, resulting in extremely low material utilization. Among these processes, protective atmosphere electroslag remelting is a key step affecting the overall yield. In this step, poor slag-metal separation and improper feeding process control lead to deep shrinkage cavities or deep slag inclusions in the center of the ingot head. To ensure final product quality, significant material removal from the ingot head is necessary, further reducing material utilization. Therefore, improving the metallurgical quality of the electroslag ingot head is the core approach to increasing the yield of wrought superalloy ingots.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a shrinkage-free electroslag ingot.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a shrinkage-cavity-free electroslag ingot involves adding a heating agent after the electroslag melting process is interrupted. This agent compensates for the heat loss after the power is cut off, thereby maintaining the temperature of the slag pool and improving the slag-metal separation and feeding effect at the ingot head, thus completing the preparation of a shrinkage-cavity-free electroslag ingot.

[0007] Specifically, in combination Figure 1 The above preparation method includes the following steps: Step 1, Material Preparation: Weld the electroslag electrodes to be melted and prepare a specific weight of pre-melted slag material to be added; Step 2: The welded electroslag electrode is placed into a protective atmosphere electroslag furnace, and the pre-melted slag material is added according to the preset process parameters and ingot smelting is carried out. Step 3: Select a heating agent based on the weight of the pre-melted slag and add the heating agent to the feeding hopper; the weight of the heating agent is 1% to 5% of the weight of the pre-melted slag. Step 4: Within a specified time T1 after power failure, raise the electrode rod and add the heating agent to the slag pool; Step 5: After the heating agent has fully reacted and cooled for a specified time T2, the ingot is removed from the furnace, completing the preparation of the shrinkage-cavity-free electroslag casting.

[0008] Specifically, in step 1, the weight of the pre-melted slag material is 20~200kg.

[0009] Specifically, in step 1, the diameter of the electroslag electrode is 200~700mm.

[0010] Furthermore, step 2 specifically includes: Step 2.1, Slag Refining Stage: Before powering on, add 20% to 50% of the pre-melted slag to the crystallizer, then power on for melting. After powering on, add the remaining pre-melted slag to the slag pool within 20 minutes. It should be noted that the remaining slag can be added to the slag pool within 20 minutes, and there are no specific restrictions on the number of times or the amount added. Step 2.2, Smelting Stage: After the slag formation stage is completed, the slag resistance oscillation range is set to 0.10~2.50 mohm, and the melting rate is set to 2kg / min~7kg / min for ingot smelting; Step 2.3, Feeding Stage: The power of the feeding stage is based on the power of the melting stage and is gradually reduced by a decreasing percentage to achieve a gradual reduction in the depth of the molten pool; wherein, the feeding power before power failure / the melting stage power is ≤40%.

[0011] Preferably, the heating agent is a mixture of aluminum powder and iron oxide powder, aluminum granules, or calcium silicon.

[0012] Specifically, in step 4, the specified time T1 is 5 minutes.

[0013] Specifically, in step 5, the specified time T2 > 60 min.

[0014] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: Within 5 minutes of power failure, the electrode rod is raised and the heating agent is added to the slag pool. The heating agent reacts with the high-temperature slag pool in an aluminothermic reaction, compensating for the heat loss at the top caused by the water-cooled crystallizer, extending the time that the top molten metal remains liquid, and promoting sufficient molten metal feeding. Sufficient feeding can reduce the length of risers that have to be cut off due to excessive shrinkage cavities, thus reducing the amount of subsequent riser sawing. Raising the electrode in time also prevents the heating agent from being blocked by the pre-reserved plate during the addition of the heating agent, which would affect the heating effect. In summary, by adding a specific amount of heating agent after the power is cut off during feeding, the slag pool can continue to maintain a high temperature under the action of the heating agent after the power is cut off in electroslag casting. This ensures the slag-metal separation effect at the ingot head, achieves slow cooling of the molten metal at the head of the electroslag ingot, eliminates macroscopic shrinkage cavities at the head of the electroslag ingot, and improves the ingot yield. Attached Figure Description

[0015] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating a method for preparing a shrinkage-cavity-free electroslag ingot provided by the present invention; Figure 2 This is a photograph of the electroslag ingot without shrinkage cavities obtained in Example 1 of the present invention. Figure 3 This is a photograph of the electroslag ingot prepared in Comparative Example 1. Detailed Implementation

[0018] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] Example 1 This embodiment provides a method for preparing a shrinkage-cavity-free electroslag ingot, including the following steps: Step 1, Material Preparation: Weld the GH4738 electroslag electrode to be melted and prepare a specific weight of pre-melted slag to be added; wherein, the electrode diameter is 230mm, the pre-melted slag to be added is weighed and the weight is recorded as W=25kg; Step 2: Place the welded electroslag electrodes into a protective atmosphere electroslag furnace and perform ingot casting and melting according to the preset process parameters; Step 2.1, Slag-forming stage: Before powering on, add 20% of the pre-melted slag to the crystallizer, then power on for melting, and after powering on, gradually add the remaining pre-melted slag to the slag pool. Power control is used in the slag-forming stage. Step 2.2, Smelting Stage: After the slag formation stage is completed, set the slag swing (slag resistance oscillation) to 0.15 mohm and the melting rate to 2.3 kg / min for ingot smelting; Step 2.3, Feeding Stage: The power during the feeding stage is based on the power during the melting stage, and is reduced step by step by a decreasing percentage (90%→82%→68%→53%→38%) to achieve a gradual reduction in the depth of the molten pool; wherein, the feeding power / melting stage power before power failure is 38%; Step 3: Select the heating agent according to the weight of the pre-melted slag material. Here, aluminum briquettes are selected and added to the feeding hopper. The weight of the aluminum briquettes is 5% of the weight of the pre-melted slag material, i.e., 1.25 kg. Step 4: As the smelting proceeds, 2 minutes after the power is cut off, raise the electrode rod to the upper limit position, and then add the heating agent into the slag pool through the slag addition pipe. Step 5: After the heating agent has fully reacted and cooled for 70 minutes, remove the ingot from the furnace to achieve the preparation of a shrinkage-cavity-free GH4738 electroslag ingot. See [link to relevant documentation]. Figure 2 .

[0021] Comparative Example 1 This comparative example provides a method for preparing electroslag ingots, which adopts the traditional electroslag remelting process, namely, three stages: preliminary preparation, smelting operation, and post-processing. First, the consumable electrode is prepared and cleaned, the slag is baked, and the crystallizer is inspected. Then, an initial slag pool is established by injecting pre-melted slag. During the remelting period, Joule heating generated by current passing through the high-resistance molten slag is used to heat and melt the electrode tip, allowing the molten metal droplets to pass through the slag pool for deep refining (removing inclusions and harmful elements) before falling into the water-cooled crystallizer and solidifying sequentially from bottom to top. Towards the end of the melting process, power is gradually reduced to compensate for shrinkage defects. Finally, after cooling, demolding, heat treatment, and surface cleaning, the target ingot is obtained. (See [link to relevant documentation]). Figure 3 This shows the shrinkage cavity situation of GH4738 ingot.

[0022] By comparison Figure 2 and Figure 3 It can be seen that the preparation method provided by the present invention eliminates the shrinkage cavity caused by slag inclusions in the ingot, and the shrinkage cavity effect is significantly better than that of Comparative Example 1.

[0023] Example 2 This embodiment provides a method for preparing a shrinkage-cavity-free electroslag ingot, including the following steps: Step 1, Material Preparation: Weld the GH4169 electroslag electrode to be melted and prepare a specific weight of pre-melted slag to be added; wherein, the electrode diameter is 400mm, the pre-melted slag to be added is weighed and the weight is recorded as W=80kg; Step 2: Place the welded electroslag electrodes into a protective atmosphere electroslag furnace and perform ingot casting and melting according to the preset process parameters; Step 2.1, Slag-forming stage: Before powering on, add 35% of the pre-melted slag to the crystallizer, then power on for melting, and after powering on, gradually add the remaining pre-melted slag to the slag pool. Power control is used in the slag-forming stage. Step 2.2, Smelting Stage: After the slag formation stage is completed, set the slag swing (slag resistance oscillation) to 1.15 mohm and the melting rate to 5 kg / min for ingot smelting; Step 2.3, Feeding Stage: The power during the feeding stage is based on the power during the melting stage, and is reduced step by step (90%→75%→60%→45%→30%) to achieve a gradual reduction in the depth of the molten pool; wherein, the feeding power before power failure / melting stage power is 30%; Step 3: Select the heating agent according to the weight of the pre-melted slag material. Here, calcium silicon is selected and added to the feeding hopper. The weight of the calcium silicon is 3.5% of the weight of the pre-melted slag material, i.e., 2.8 kg. Step 4: As the smelting proceeds, 30 seconds after the power is cut off, raise the electrode rod to the upper limit position, and then add the heating agent into the slag pool through the slag addition pipe. Step 5: After the heating agent has fully reacted and cooled for 120 minutes, the product is removed from the furnace to achieve the preparation of GH4169 electroslag ingot A without shrinkage cavities.

[0024] Example 3 This embodiment provides a method for preparing a shrinkage-cavity-free electroslag ingot, including the following steps: Step 1, Material Preparation: Weld the GH4169 electroslag electrode to be melted and prepare a specific weight of pre-melted slag to be added; wherein, the electrode diameter is 650mm, the pre-melted slag to be added is weighed and the weight is recorded as W=180kg. Step 2: The welded electroslag electrode is placed into a protective atmosphere electroslag furnace, and the pre-melted slag material is added according to the preset process parameters and ingot smelting is carried out. Step 2.1, Slag-forming stage: Before powering on, 47% of the pre-melted slag is added to the crystallizer, and then power is supplied for melting. After powering on, the remaining pre-melted slag is gradually added to the slag pool. Power control is used in the slag-forming stage. Step 2.2, Smelting Stage: After the slag formation stage is completed, set the slag swing (slag resistance oscillation) to 2.30 mohm and the melting rate to 6.8 kg / min for ingot smelting; Step 2.3, Feeding Stage: The power during the feeding stage is based on the power during the melting stage, and is reduced step by step by a decreasing percentage (85%→60%→45%→30%→17%) to achieve a gradual reduction in the depth of the molten pool; wherein, the feeding power / melting stage power before power failure is 17%; Step 3: Select the heating agent according to the weight of the pre-melted slag. Here, a mixture of aluminum powder and iron oxide powder is selected, and the mixture is added to the feeding hopper. The weight of the mixture is 1.5% of the weight of the pre-melted slag, i.e., 2.775 kg. Step 4: As the smelting proceeds, 5 minutes after the power is cut off, raise the electrode rod to the upper limit position, and then add the heating agent into the slag pool through the slag addition pipe. Step 5: After the heating agent has fully reacted and cooled for 180 minutes, the product is removed from the furnace to achieve the preparation of GH4169 electroslag ingot B without shrinkage cavities.

[0025] In summary, the preparation method provided by this invention, by adding a heating agent after the power is cut off during smelting, maintains the temperature of the slag pool after the power is cut off, improves the slag-gold separation effect and feeding effect at the ingot head, and increases the ingot yield.

[0026] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0027] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a shrinkage-cavity-free electroslag ingot, characterized in that, After the power is cut off in electroslag melting, an exothermic agent is added to compensate for the heat loss after the power is cut off and maintain the temperature of the slag pool after the power is cut off. This improves the slag-metal separation effect and the feeding effect at the ingot head, thus completing the preparation of a shrinkage-free electroslag ingot.

2. The method for preparing a shrinkage-cavity-free electroslag ingot according to claim 1, characterized in that, Includes the following steps: Step 1, Material Preparation: Weld the electroslag electrodes to be melted and prepare a specific weight of pre-melted slag material to be added; Step 2: The welded electroslag electrode is placed into a protective atmosphere electroslag furnace, and the pre-melted slag material is added according to the preset process parameters and ingot smelting is carried out. Step 3: Select a heating agent based on the weight of the pre-melted slag and add the heating agent to the feeding hopper; the weight of the heating agent is 1% to 5% of the weight of the pre-melted slag. Step 4: Within a specified time T1 after power failure, raise the electrode rod and add the heating agent to the slag pool; Step 5: After the heating agent has fully reacted and cooled for a specified time T2, the ingot is removed from the furnace, completing the preparation of the shrinkage-cavity-free electroslag casting.

3. The method for preparing a shrinkage-cavity-free electroslag ingot according to claim 2, characterized in that, In step 1, the weight of the pre-melted slag is 20~200kg.

4. The method for preparing a shrinkage-cavity-free electroslag ingot according to claim 2, characterized in that, In step 1, the diameter of the electroslag electrode is 200~700mm.

5. The method for preparing a shrinkage-cavity-free electroslag ingot according to claim 2, characterized in that, Step 2 specifically includes: Step 2.1, Slag-forming stage: Before powering on, add 20% to 50% of the pre-melted slag to the crystallizer, then power on for melting. After powering on, add the remaining pre-melted slag to the slag pool within 20 minutes. Step 2.2, Smelting Stage: After the slag formation stage is completed, the slag resistance oscillation range is set to 0.10~2.50 mohm, and the melting rate is set to 2kg / min~7kg / min for ingot smelting; Step 2.3, Feeding Stage: The power of the feeding stage is based on the power of the melting stage and is gradually reduced by a decreasing percentage to achieve a gradual reduction in the depth of the molten pool; wherein, the feeding power before power failure / the melting stage power is ≤40%.

6. The method for preparing a shrinkage-cavity-free electroslag ingot according to claim 2, characterized in that, The heating agent is selected from a mixture of aluminum powder and iron oxide powder, aluminum granules, or calcium silicon.

7. The method for preparing a shrinkage-cavity-free electroslag ingot according to claim 2, characterized in that, In step 4, the specified time T1 is 5 minutes.

8. The method for preparing a shrinkage-cavity-free electroslag ingot according to claim 2, characterized in that, In step 5, the specified time T2 is greater than 60 minutes.

Images