Processing method for reducing melting speed fluctuation of GH2150 high-temperature alloy ingot electroslag smelting

Abstract

The invention discloses a processing method for reducing melting speed fluctuation of GH2150 high-temperature alloy ingot electroslag smelting. According to the GH2150 alloy component requirements, raw materials are selected and classified, a matrix alloy material, an alloying material and a micro-alloying material are put into a vacuum induction furnace to be smelted, and pouring is conducted after a launder and an ingot mold are preheated. And after pouring is finished, an induction cast ingot is subjected to vacuum cooling in an ingot mold, demolding is conducted 40-60 min after pouring is finished, the induction cast ingot is immediately fed into an annealing furnace within the time window, heat preservation is conducted for 15-20 h at the temperature of 930-1030 DEG C, and the induction cast ingot is cooled to 300 DEG C along with the furnace and taken out of the furnace for air cooling. By shortening the time interval from pouring to entering the annealing furnace of the induction cast ingot, and combining with the narrow-interval annealing temperature of 930-1030 DEG C and long-time annealing, the internal thermal stress of the cast ingot can be eliminated in time, the transformation of unfavorable structures can be inhibited, and the vacuum induction cast ingot with good surface quality and stable melting speed in the electroslag smelting process can be obtained. The method disclosed by the invention is particularly suitable for preparing the Ni-Fe-Cr-based GH2150 high-temperature alloy cast ingot.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature alloy smelting, in particular to a processing method for reducing the smelting speed fluctuation of GH2150 high-temperature alloy ingot electric slag. BACKGROUND

[0002] The GH2150 alloy belongs to an iron-based deformation and aging strengthening type high-temperature alloy, the matrix of which is a Fe-Ni-Cr ternary system, and Mo and W are used for solid solution strengthening, and Ti, Al and Nb are used for precipitation strengthening, and the alloy is widely used in hot end components of aero-engine and gas turbine under the service condition of 650-750 DEG C. Due to the thermal physical properties and the organization evolution characteristics of the GH2150 alloy, the ingot after vacuum induction smelting under the traditional process:

[0003] Cracks are prone to occur on the surface of the ingot;

[0004] Large smelting speed fluctuation is prone to occur in the subsequent electric slag smelting process, which affects the ingot quality and the safety of subsequent forging processing.

[0005] The prior art mainly adjusts the pouring temperature, ingot mold preheating temperature, and increases the annealing temperature and holding time to improve the surface quality of the ingot. However, in actual production, there is often a long residence time between the induction ingot after pouring and entering the annealing furnace, which is prone to produce or retain large residual thermal stress and adverse organization during slow cooling and long time storage, so that even if a higher annealing temperature is used, the smelting speed fluctuation may still occur in the electric slag smelting process.

[0006] Therefore, it is necessary to propose a new process control idea to overcome the above problems. SUMMARY

[0007] The purpose of the present application is to provide a processing method for reducing the smelting speed fluctuation of GH2150 high-temperature alloy ingot electric slag, which accelerates the speed of induction ingot into the annealing furnace, and strictly controls the time from pouring to entering the annealing furnace within 40-60 min; the annealing temperature of the induction ingot is limited within a narrow range of 930-1030 DEG C, and the annealing time is limited within 15-20 h; so that under the premise that the alloy composition and the smelting and pouring system are basically unchanged, the surface quality of the ingot and the stability of the smelting speed in the subsequent electric slag smelting process are significantly improved, so as to solve the problems proposed in the background art.

[0008] To achieve the above purpose, the present application provides the following technical scheme: a processing method for reducing the smelting speed fluctuation of GH2150 high-temperature alloy ingot electric slag, comprising the following steps:

[0009] Step 1, selection and classification of raw materials:

[0010] According to the component requirement of GH2150 alloy, the base alloy material, alloying material and micro-alloying material with certain element weight are weighed;

[0011] Step 2, vacuum induction melting:

[0012] The base alloy material, alloying material and micro-alloying material are added into the vacuum induction furnace in a specific order, and vacuum induction melting is carried out.

[0013] Step 3, mold preheating and pouring:

[0014] 3.1 Before vacuum induction melting, the runner is placed in the preheating station for preheating.

[0015] 3.2 During vacuum induction melting, the ingot mold is placed in the preheating station for preheating.

[0016] 3.3 At the end of vacuum induction melting, the preheated runner and ingot mold are respectively loaded into the runner chamber and ingot mold chamber for pouring.

[0017] Step 4, induction ingot cooling and annealing:

[0018] 4.1 After pouring is completed, the induction ingot is vacuum cooled in the ingot mold chamber, and is demolded after a period of time after pouring is completed.

[0019] 4.2 The induction ingot demolded from the ingot mold is sent into the annealing furnace within 40-60 minutes after pouring is completed, is cooled with the furnace after being kept for a period of time, is discharged from the furnace and is air cooled to obtain a vacuum induction ingot with good surface quality.

[0020] Preferably, the component range (wt%) of the GH2150 alloy is: Ni: 40.0-50.0, C≤0.08, Mo: 5.0-7.0, W: 2.0-3.5, Cr: 10.0-15.0, Nb: 1.0-3.0, Ti: 1.3-2.2, Al: 0.5-1.2, B: 0.003-0.007, Zr: 0.03-0.07, Mn≤0.4, Si≤0.4, Cu≤0.07, P≤0.015, S≤0.015, O≤0.0020, N≤0.0020, Fe: balance.

[0021] Preferably, the weight of the base alloy material (Ni plate, C block, Fe ingot, metallic Cr) is 50-75 wt%, the weight of the alloying material (Mo strip, W strip, NiNb alloy, Ti block, Al ingot) is 15-40 wt%, and the weight of the micro-alloying material (NiB alloy, sponge Zr) is 0.001-10 wt%.

[0022] Preferably, the vacuum induction melting time in step 2 is preferably 9-11 h.

[0023] Preferably, the preheating temperature of the flow channel in step 3.1 is 1100-1150℃, and the preheating time is 10-12h.

[0024] Preferably, the preheating temperature of the ingot mold in step 3.2 is 300-350°C, and the preheating time is 2.5-3.5 hours.

[0025] Preferably, the pouring temperature in step 3.3 is 1450–1480°C.

[0026] Preferably, in step 4.1, the 40-60 minute time period after the pouring is also defined as the time window from the end of the induction casting to the start of annealing in the annealing furnace, that is, demolding is completed and the induction casting is sent into the annealing furnace for heat preservation within 40-60 minutes after the pouring is completed.

[0027] Preferably, in step 4.2, the annealing temperature is preferably 950-1030℃ and held for 18-20 hours, then cooled in the furnace to 300℃ and air-cooled.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] The time from the end of casting to entering the annealing furnace is shortened: by using 40 to 60 minutes after casting as a unified time window for demolding and entering the furnace, the ingot is prevented from staying at room temperature or semi-high temperature for a long time, reducing the chance of thermal stress redistribution and unfavorable microstructure evolution.

[0030] The annealing temperature is narrowed to 930-1030℃: Compared with the wide range of 700-1200℃, the present invention narrows the annealing temperature to 930-1030℃, which not only ensures sufficient thermal stress relief, but also reduces the risk of abnormal grain growth and further diffusion of compositional segregation at excessively high temperatures, which is conducive to obtaining a uniform and refined microstructure.

[0031] Synergistic improvement of electroslag remelting melting rate stability: Due to the more uniform internal thermal stress and microstructure of induction ingots, the electroslag layer is more stable and the fluctuations in the shape of the molten pool and melting rate are significantly reduced during subsequent electroslag remelting, which is conducive to obtaining electroslag remelting ingots with good comprehensive performance.

[0032] The process is simple to implement and has good compatibility with existing equipment: This invention does not change the alloy composition and the main equipment structure, but only controls the cooling time after casting, the furnace feeding rhythm and the annealing temperature range, which is easy to promote and apply on existing vacuum induction melting production lines. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the appearance of the GH2150 alloy vacuum induction casting in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the melting rate curve of GH2150 alloy prepared by the method of the present invention during the electroslag melting process;

[0035] Figure 3 A schematic diagram showing the surface cracking of GH2150 alloy vacuum induction casting ingots obtained by comparison process;

[0036] Figure 4 This diagram illustrates the melting rate fluctuations during the electroslag remelting process of GH2150 alloy under different comparative processes. Detailed Implementation

[0037] 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 embodiments of the present invention, and not all embodiments. 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.

[0038] Please see Figures 1-4 The present invention provides a technical solution:

[0039] Example 1 includes the following steps:

[0040] Step 1: Selection and classification of raw materials

[0041] Raw materials were selected according to the composition requirements of GH2150 alloy.

[0042] 65wt% Ni plates, C blocks, Fe ingots, and metallic Cr were selected as the base alloy material;

[0043] 34 wt% of Mo strips, W strips, NiNb alloy, Ti blocks, Al ingots, etc. were selected as alloying materials;

[0044] 1 wt% NiB alloy and sponge Zr were selected as microalloying materials.

[0045] The proportions of the above-mentioned base alloy, alloying material, and micro-alloying material meet the composition range requirements of GH2150 alloy.

[0046] Step 2, Vacuum induction melting

[0047] Raw materials such as Ni plates, C blocks, Fe ingots, metallic Cr, Mo strips, W strips, NiNb alloy, Ti blocks, Al ingots, NiB alloy, and sponge Zr are added to a vacuum induction furnace in a predetermined order. Induction melting is carried out under vacuum conditions for 10 hours to ensure that all alloying elements are fully melted and uniformly mixed to obtain a melt with uniform composition.

[0048] Step 3, Module preheating and casting

[0049] 3.1 Place the flow channel in a preheating furnace and preheat it at 1100℃ for 10 hours to allow the flow channel to reach a stable high temperature state;

[0050] 3.2 Place the ingot mold in a preheating furnace and preheat it at 350℃ for 3 hours to ensure uniform temperature of the ingot mold;

[0051] 3.3 When the vacuum induction melting is nearing its end, adjust the melt pouring temperature to 1450℃, and then load the preheated trough and ingot mold into the trough chamber and ingot mold chamber respectively, and pour under vacuum conditions to complete the process of injecting the melt into the ingot mold.

[0052] Step 4, Cooling and Annealing

[0053] 4.1 After pouring, the induction casting ingot is vacuum cooled in the mold. The ingot is kept in the mold under vacuum until 50 minutes have elapsed since pouring, at which point it is removed from the mold.

[0054] 4.2 After completing the above demolding operation 50 minutes after the pouring is completed, the removed ingot is immediately sent into the annealing furnace and held at 1030℃ for 18 hours. After the holding period, it is cooled to 300℃ with the furnace and then air-cooled to complete the cooling and annealing process of the vacuum induction casting.

[0055] The vacuum induction castings prepared under the above process conditions have good surface quality and no obvious cracks. When the vacuum induction castings are used as electrodes for electroslag melting, the melting rate curve of the electroslag melting process is stable and there is no obvious melting rate fluctuation problem. This shows that the process parameter combination of "complete demolding 50 minutes after casting and immediately put into the furnace, and anneal at 1030℃ for 18 hours" in this embodiment is conducive to obtaining vacuum induction castings with good surface quality and stable melting rate.

[0056] Example 2 includes the following steps:

[0057] Step 1: Selection and classification of raw materials

[0058] Raw materials were selected according to the composition requirements of GH2150 alloy.

[0059] 60wt% Ni plates, C blocks, Fe ingots, and metallic Cr were selected as the base alloy material;

[0060] 39 wt% of Mo strips, W strips, NiNb alloy, Ti blocks, Al ingots, etc. were selected as alloying materials; 1 wt% of NiB alloy and sponge Zr, etc. were selected as microalloying materials.

[0061] The proportions of the aforementioned base alloy, alloying material, and microalloying material also meet the composition range requirements of GH2150 alloy.

[0062] Step 2, Vacuum induction melting

[0063] Raw materials such as Ni plates, C blocks, Fe ingots, metallic Cr, Mo strips, W strips, NiNb alloy, Ti blocks, Al ingots, NiB alloy, and sponge Zr are added to a vacuum induction furnace in a predetermined order. Induction melting is carried out under vacuum conditions, and the melting time is also controlled to be 10 hours, so that the alloying elements are fully melted and uniformly mixed to obtain a melt with uniform composition.

[0064] Step 3, Module preheating and casting

[0065] 3.1 Place the flow channel in a preheating furnace and preheat it at 1100℃ for 10 hours to allow the flow channel to reach a stable high temperature state;

[0066] 3.2 Place the ingot mold in a preheating furnace and preheat it at 340°C for 4 hours to make the ingot mold temperature uniform and slightly lower than the preheating temperature and time in Example 1;

[0067] 3.3 When the vacuum induction melting is nearing its end, adjust the melt pouring temperature to 1460℃, and then load the preheated trough and ingot mold into the trough chamber and ingot mold chamber respectively, and pour under vacuum conditions to complete the process of injecting the melt into the ingot mold.

[0068] Step 4, Cooling and Annealing

[0069] 4.1 After pouring, the induction casting ingot is also vacuum cooled in the ingot mold. The ingot is kept in the mold under vacuum until 60 minutes have elapsed since pouring, at which point it is removed from the mold.

[0070] 4.2 After the demolding operation is completed 60 minutes after the casting is finished, the removed ingot is immediately sent into the annealing furnace and held at 1000℃ for 20 hours. After the holding period, it is cooled to 300℃ in the furnace and then air-cooled to complete the cooling and annealing process of the vacuum induction casting.

[0071] The vacuum induction castings prepared under the above process conditions can also achieve good surface quality, with no obvious cracks or defects on the surface. When the vacuum induction castings are used as electrodes for electroslag melting, the melting rate is stable and there are no obvious melting rate fluctuations. This indicates that under the process conditions of "demolding 60 minutes after casting and immediately placing it into the furnace, and annealing at 1000℃ for 20 hours", ingots with stable melting rate and good surface quality can also be obtained.

[0072] Comparative Example 1 includes the following steps:

[0073] Step 1: Selection and classification of raw materials

[0074] The raw materials selected in the comparative example also meet the composition requirements of GH2150 alloy. The same combination of raw materials as in Example 1 above, including Ni plate, C block, Fe ingot, metallic Cr, Mo strip, W strip, NiNb alloy, Ti block, Al ingot, NiB alloy and sponge Zr, are used to compare the effects of different cooling and annealing process conditions on ingot quality and electroslag melting rate stability.

[0075] Step 2, Vacuum induction melting

[0076] The selected Ni plates, C blocks, Fe ingots, metallic Cr, Mo strips, W strips, NiNb alloy, Ti blocks, Al ingots, NiB alloy, and sponge Zr are added to the vacuum induction furnace in the conventional production process order for vacuum induction melting. The melting regime is set with reference to the conventional parameters of the existing production line, and the melting process is completed under the premise of ensuring that the alloy composition meets the requirements of GH2150 alloy.

[0077] Step 3, Module preheating and casting

[0078] In the comparative example, the preheating and casting conditions of the runner and ingot mold adopt the process parameters commonly used in existing production processes. Under the premise of ensuring smooth casting of the melt, the steps of runner preheating, ingot mold preheating and melt casting are completed to obtain the comparative example vacuum induction casting ingot.

[0079] Step 4, Cooling and Annealing

[0080] 4.1 After the casting is completed, the induction casting ingot is cooled in the ingot mold. After staying in the ingot mold for 75 to 90 minutes, the ingot is removed from the ingot mold.

[0081] 4.2 After demolding, the ingot is not immediately sent to the annealing furnace, but is placed at room temperature for several hours before annealing. It is then held at 700℃ for 10 hours. After the holding period, it is cooled to 300℃ with the furnace and then air-cooled to obtain a comparative vacuum induction casting.

[0082] The comparison revealed that the vacuum induction castings obtained under the above comparative process conditions had significantly more surface cracks and serious surface defects. When the vacuum induction castings were used as electrodes for electroslag melting, the melting rate fluctuated significantly and the melting rate curve was unstable.

[0083] Comparative Example 2 includes the following steps:

[0084] Step 1: Selection and classification of raw materials

[0085] The raw materials selected in the comparative example also meet the composition requirements of GH2150 alloy. The same combination of raw materials as in Example 1 above, including Ni plate, C block, Fe ingot, metallic Cr, Mo strip, W strip, NiNb alloy, Ti block, Al ingot, NiB alloy and sponge Zr, are used to compare the effects of different cooling and annealing process conditions on ingot quality and electroslag melting rate stability.

[0086] Step 2, Vacuum induction melting

[0087] The selected Ni plates, C blocks, Fe ingots, metallic Cr, Mo strips, W strips, NiNb alloy, Ti blocks, Al ingots, NiB alloy, and sponge Zr are added to the vacuum induction furnace in the conventional production process order for vacuum induction melting. The melting regime is set with reference to the conventional parameters of the existing production line, and the melting process is completed under the premise of ensuring that the alloy composition meets the requirements of GH2150 alloy.

[0088] Step 3, Module preheating and casting

[0089] In the comparative example, the preheating and casting conditions of the runner and ingot mold adopt the process parameters commonly used in existing production processes. Under the premise of ensuring smooth casting of the melt, the steps of runner preheating, ingot mold preheating and melt casting are completed to obtain the comparative example vacuum induction casting ingot.

[0090] Step 4, Cooling and Annealing

[0091] 4.1 After pouring, the induction casting ingot is also vacuum cooled in the ingot mold. The ingot is kept in the mold under vacuum until 60 minutes have elapsed since pouring, at which point it is removed from the mold.

[0092] 4.2 After the demolding operation is completed 60 minutes after the pouring is finished, the removed ingot is immediately sent into the annealing furnace and held at 900℃ for 5 hours. After the holding is completed, it is cooled to 300℃ in the furnace and then air-cooled to obtain a comparative vacuum induction casting ingot.

[0093] The comparison revealed that the vacuum induction castings obtained under the above comparative process conditions had significantly more surface cracks and serious surface defects. When the vacuum induction castings were used as electrodes for electroslag melting, the melting rate fluctuated significantly and the melting rate curve was unstable.

[0094] Therefore, compared with the process conditions in the embodiment of the present invention, which are "demolding completed within 40 to 60 minutes after casting and annealing immediately in the furnace, with the annealing temperature controlled at 930 to 1030°C and the annealing time being 15 to 20 hours", the traditional process in the comparative example, which has "longer cooling time, longer standing time after demolding, lower annealing temperature and insufficient heat preservation", is not conducive to obtaining GH2150 high-temperature alloy ingots with good surface quality and stable melting rate.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A processing method for reducing melting rate fluctuations during electroslag remelting of GH2150 high-temperature alloy ingots, characterized in that: Includes the following steps: Step 1: Selection and classification of raw materials: According to the composition requirements of GH2150 alloy, weigh out the base alloy material, alloying material and micro-alloying material with a certain element weight; Step 2, Vacuum induction melting: The base alloy, alloying material and micro-alloying material are added to a vacuum induction furnace in a specific order for vacuum induction melting. Step 3, Module preheating and pouring: 3.1 Before vacuum induction melting, the ladle is placed in the preheating station for preheating; 3.2 During the vacuum induction melting process, the ingot mold is placed in the preheating station for preheating; 3.3 At the end of the vacuum induction melting process, the preheated flow channel and ingot mold are loaded into the flow channel chamber and ingot mold chamber respectively for casting; Step 4: Induction casting ingot cooling and annealing: 4.1 After the casting is completed, the induction casting ingot is vacuum cooled in the ingot mold chamber, and demolded some time after the casting is completed; 4.2 The induction casting ingot, after being removed from the mold, is sent into an annealing furnace within 40 to 60 minutes after casting. After being held at a certain temperature for a period of time, it is cooled with the furnace and then removed and air-cooled to obtain a vacuum induction casting ingot with good surface quality.

2. The processing method for reducing melting rate fluctuations in electroslag remelting of GH2150 high-temperature alloy ingots according to claim 1, characterized in that: The composition range (wt%) of the GH2150 alloy is as follows: Ni: 40.0~50.0, C≤0.08, Mo: 5.0~7.0, W: 2.0~3.5, Cr: 10.0~15.0, Nb: 1.0~3.0, Ti: 1.3~2.2, Al: 0.5~1.2, B: 0.003~0.007, Zr: 0.03~0.07, Mn≤0.4, Si≤0.4, Cu≤0.07, P≤0.015, S≤0.015, O≤0.0020, N≤0.0020, Fe: balance; The matrix alloy (Ni plate, C block, Fe ingot, metallic Cr) weighs 50–75 wt%, the alloying material (Mo strip, W strip, NiNb alloy, Ti block, Al ingot) weighs 15–40 wt%, and the micro-alloying material (NiB alloy, sponge Zr) weighs 0.001–10 wt%.

3. The processing method for reducing melting rate fluctuations in electroslag remelting of GH2150 high-temperature alloy ingots according to claim 1, characterized in that: The vacuum induction melting time in step 2 is 8 to 12 hours.

4. The processing method for reducing melting rate fluctuations in electroslag remelting of GH2150 high-temperature alloy ingots according to claim 1, characterized in that: In step 3.1, the temperature is preheated at 1100–1200℃ for 9–14 hours.

5. The processing method for reducing melting rate fluctuations in electroslag remelting of GH2150 high-temperature alloy ingots according to claim 1, characterized in that: In step 3.2, the ingot mold is preheated at 250-350℃ for 2-4 hours.

6. The processing method for reducing melting rate fluctuations in electroslag remelting of GH2150 high-temperature alloy ingots according to claim 1, characterized in that: The pouring temperature in section 3.3 is 1450–1500℃.

7. The processing method for reducing melting rate fluctuations in electroslag remelting of GH2150 high-temperature alloy ingots according to claim 1, characterized in that: In step 4.1, the 40-60 minute time period after the pouring is also defined as the time window from the end of the induction casting to the start of annealing in the annealing furnace, that is, demolding and sending into the annealing furnace to start heat preservation are completed within 40-60 minutes after the pouring is completed.

8. The processing method for reducing melting rate fluctuations in electroslag remelting of GH2150 high-temperature alloy ingots according to claim 1, characterized in that: In step 4.2, the annealing temperature is 930-1030℃, held for 15-20 hours, and then cooled in the furnace to 300℃ before being air-cooled.

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