Dual smelting process for nickel-based superalloy GH4648 large-specification cast ingot

Abstract

The invention provides a duplex smelting process of a nickel-based superalloy GH4648 large-specification cast ingot. The duplex smelting process specifically comprises the steps of vacuum induction melting (VIM), stress relief annealing and vacuum consumable melting (VAR). VIM smelting is adopted, and the VIM electrode with uniform components and low gas content is obtained through strong electromagnetic stirring and vacuum atmosphere. And through the rapid cooling and stress relief annealing method, the precipitation number of brittle phases in the electrode is reduced, the structural stress and thermal stress of the cast ingot are reduced, the cast ingot is prevented from cracking in the VAR smelting process, and the stability of the subsequent vacuum consumable finished product smelting process is improved. By the adoption of the method, the GH4648 alloy large-specification cast ingot which is compact in structure, uniform in component and low in impurity element and gas element content can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloy smelting, and in particular to a two-in-one smelting process for a large-size ingot of a nickel-based high-temperature alloy GH4648. Background Art

[0002] GH4648 alloy is a Ni-Cr based precipitation hardening deformation high temperature alloy, which is characterized by a high Cr content of about 32%, which makes the high temperature alloy have excellent oxidation resistance and corrosion resistance in a high temperature environment of 900°C. GH4648 alloy is widely used in petrochemical, aerospace, shipbuilding and other fields. With the increasing market demand for large-sized discs and pipes, higher requirements are placed on the composition uniformity and specifications of GH4648 ingots produced by metallurgical plants.

[0003] At present, the GH4648 ingots produced at home and abroad generally adopt the double process (vacuum induction melting + vacuum consumable melting). Since the α-Cr phase in the GH4648 alloy will precipitate in the form of needle phase during the solidification process, the internal structural stress of the ingot is large. Therefore, large-scale GH4648 alloy VIM electrodes often have microscopic grain boundary cracking, which will induce a large fluctuation in the melting rate during the vacuum consumable melting process. More importantly, due to the poor stability of the melting rate during the vacuum consumable melting process, the composition of the final finished ingot is seriously segregated. Summary of the invention

[0004] The object of the present invention is to provide a two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648 to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648, comprising the following steps:

[0006] Step 1: Obtain GH4648 alloy VIM electrode by vacuum induction melting (VIM);

[0007] Step 2: air-cooling the VIM electrode obtained in step 1;

[0008] Step 3: annealing the VIM electrode obtained in step 2;

[0009] Step 4: The VIM electrode obtained after step 3 is subjected to vacuum autoclave melting (VAR) to obtain a GH4648 alloy ingot.

[0010] Preferably, the specifications corresponding to the process evolve into Φ430mm-Φ508mm.

[0011] Preferably, the GH4648 alloy VIM electrode in step 1 has the following chemical compositions by mass percentage: C: 0.040%-0.060%, W: 4.80%-5.10%, Mo: 2.90%-3.10%, Cr: 33.0%-33.5%, Nb: 0.80%-1.00%, Ti: 0.80%-1.00%, Al: 0.80%-1.00%, B: 0.0030%-0.0065%, Ce: 0.020%-0.025%, Fe: 0.35%-1.00%, and the rest is Ni, and the sum of the mass percentages of the above components is 100%.

[0012] Preferably, in step 2, a blower is used to air-cool the demoulded GH4648 alloy VIM electrode until the surface temperature is ≤50°C.

[0013] Preferably, in step 3, the GH4648 alloy VIM electrode is placed in a natural gas furnace for heating treatment, the heating temperature is 950°C to 1050°C, the insulation time is 6h to 10h, and after the insulation is completed, the natural gas furnace is cooled to 200°C to 400°C, and then air-cooled.

[0014] Preferably, in the consumable smelting stage in step 4, melting rate + droplet control is adopted, with the melting rate being 3.5-5.0 kg / min and the droplet being 3-121 / s.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) The GH4648 alloy VIM electrode produced by the two-in-one smelting process of the present invention does not crack, and the melting rate curve of the vacuum consumable smelting process is stable;

[0017] 2) The GH4648 alloy ingot produced by the two-way smelting process of the present invention has good composition uniformity, and the radial range of elements such as Cr, Mo, W, Nb, Ti, and Al is small;

[0018] 3) The GH4648 alloy ingot produced by the double smelting process of the present invention has good surface quality and high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the actual picture of Φ508mm GH4648 high temperature alloy ingot;

[0020] Figure 2 The melting rate curve of vacuum consumable melting in the embodiment;

[0021] Figure 3 It is the melting rate curve of vacuum consumable smelting in the comparative example. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] See also Figure 1-3 The present invention provides a technical solution: a two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648, comprising the following steps:

[0024] Step 1, obtaining a GH4648 alloy VIM electrode with a diameter of 450 (± 20) mm by vacuum induction melting (VIM), wherein the chemical composition thereof is as follows by mass percentage: C: 0.040% to 0.060%, W: 4.80% to 5.10%, Mo: 2.90% to 3.10%, Cr: 33.0% to 33.5%, Nb: 0.80% to 1.00%, Ti: 0.80% to 1.00%, Al: 0.80% to 1.00%, B: 0.0030% to 0.0065%, Ce: 0.020% to 0.025%, Fe: 0.35% to 1.00%, and the rest is Ni, and the sum of the mass percentages of the above components is 100%;

[0025] Step 2, air-cooling the VIM electrode obtained in step 1, specifically, using a blower to air-cool the demolded GH4648 alloy VIM electrode until the surface temperature is ≤50°C;

[0026] Step 3, annealing the VIM electrode obtained after step 2, specifically: placing the GH4648 alloy VIM electrode in a natural gas furnace for heating treatment, the heating temperature is 950° C. to 1050° C., the insulation time is 6 h to 10 h, after the insulation is completed, the natural gas furnace is cooled to 200° C. to 400° C., and then air-cooled;

[0027] Step 4: The VIM electrode obtained after step 3 is subjected to vacuum consumable melting. The consumable stable melting stage adopts melting rate + droplet control, the melting rate is 3.5-5.0 kg / min, and the droplet is 3-121 / s. A GH4648 alloy ingot with a diameter of 500 (±20) mm is obtained.

[0028] Example

[0029] The present invention discloses a two-in-one smelting process for a large-size ingot of a nickel-based high-temperature alloy GH4648, which is specifically implemented according to the following steps:

[0030] Step 1, a GH4648 alloy VIM electrode with a diameter of 430 mm is obtained by vacuum induction melting (VIM), and its chemical composition is as follows by mass percentage: C: 0.055%, W: 5.00%, Mo: 3.00%, Cr: 33.2%, Nb: 0.85%, Ti: 0.85%, Al: 0.85%, B: 0.0060%, Ce: 0.022%, Fe: 0.5%, and the rest is Ni, and the sum of the mass percentages of the above components is 100%;

[0031] Step 2, air-cooling the VIM electrode obtained in step 1, specifically, using a blower to air-cool the demolded GH4648 alloy VIM electrode until the surface temperature reaches 40° C.;

[0032] Step 3, annealing the VIM electrode obtained after step 2, specifically: placing the GH4648 alloy VIM electrode in a natural gas furnace for heating treatment, the heating temperature is 950° C., the heat preservation time is 6 hours, after the heat preservation is completed, the natural gas furnace is cooled to 250° C., and then air-cooled;

[0033] Step 4: The VIM electrode obtained after step 3 is subjected to vacuum consumable melting. The consumable stable melting stage adopts melting rate + droplet control, the melting rate is 4.0 kg / min, and the droplet is 81 / s. A GH4648 alloy ingot with a diameter of 508 mm is obtained.

[0034] The ingot head was sliced, and samples were taken from the edge and core in the radial direction for composition testing. The results are shown in Table 1.

[0035] Table 1 GH4648 alloy ingot composition

[0036]

[0037] After air cooling and low-temperature stress relief annealing, the melting rate curve of GH4648 alloy VIM electrode vacuum consumable melting is stable, the radial range of main elements and trace elements in the ingot is small, and the composition uniformity is good.

[0038] Comparative Example

[0039] The present invention discloses a two-in-one smelting process for a large-size ingot of a nickel-based high-temperature alloy GH4648, which is specifically implemented according to the following steps:

[0040] Step 1, a GH4648 alloy VIM electrode with a diameter of 430 mm is obtained by vacuum induction melting (VIM), and its chemical composition is as follows by mass percentage: C: 0.055%, W: 5.00%, Mo: 3.00%, Cr: 33.2%, Nb: 0.85%, Ti: 0.85%, Al: 0.85%, B: 0.0060%, Ce: 0.022%, Fe: 0.5%, and the rest is Ni, and the sum of the mass percentages of the above components is 100%;

[0041] Step 2, air-cooling the VIM electrode obtained in step 1, specifically, using a blower to air-cool the demolded GH4648 alloy VIM electrode until the surface temperature reaches 40° C.;

[0042] Step 3, annealing the VIM electrode obtained after step 2, specifically: placing the GH4648 alloy VIM electrode in a natural gas furnace for heating treatment, the heating temperature is 750° C., the heat preservation time is 6 hours, after the heat preservation is completed, the natural gas furnace is cooled to 250° C., and then air-cooled;

[0043] Step 4: The VIM electrode obtained after step 3 is subjected to vacuum consumable melting. The consumable stable melting stage adopts melting rate + droplet control, the melting rate is 4.0 kg / min, and the droplet is 81 / s. A GH4648 alloy ingot with a diameter of 508 mm is obtained.

[0044] The ingot head was sliced ​​and samples were taken from the edge and core in the radial direction for composition testing. The results are shown in Table 2.

[0045] Table 2 GH4648 alloy ingot composition

[0046]

[0047] Without air cooling treatment, the melting rate curve of GH4648 alloy VIM electrode vacuum consumable melting shows violent fluctuations, the Mo, Nb and Ti elements in the ingot show serious segregation in the radial direction, and the composition uniformity is poor.

[0048] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648, characterized in that: The following steps are involved: Step 1: Obtain GH4648 alloy VIM electrode by vacuum induction melting (VIM); Step 2: air-cooling the VIM electrode obtained in step 1; Step 3: annealing the VIM electrode obtained in step 2; Step 4: The VIM electrode obtained after step 3 is subjected to vacuum autoclave melting (VAR) to obtain a GH4648 alloy ingot.

2. The two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648 according to claim 1 is characterized in that: The specifications corresponding to the process have evolved into Φ430mm-Φ508mm.

3. The two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648 according to claim 1 is characterized in that: The GH4648 alloy VIM electrode in step 1 has the following chemical compositions by mass percentage: C: 0.040%-0.060%, W: 4.80%-5.10%, Mo: 2.90%-3.10%, Cr: 33.0%-33.5%, Nb: 0.80%-1.00%, Ti: 0.80%-1.00%, Al: 0.80%-1.00%, B: 0.0030%-0.0065%, Ce: 0.020%-0.025%, Fe: 0.35%-1.00%, and the rest is Ni, and the sum of the mass percentages of the above components is 100%.

4. The two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648 according to claim 1 is characterized in that: In the step 2, a blower is used to air-cool the demoulded GH4648 alloy VIM electrode until the surface temperature is ≤50°C.

5. The two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648 according to claim 1 is characterized in that: In step 3, the GH4648 alloy VIM electrode is placed in a natural gas furnace for heating treatment, the heating temperature is 950° C. to 1050° C., the insulation time is 6 h to 10 h, and after the insulation is completed, the natural gas furnace is cooled to 200° C. to 400° C., and then air-cooled.

6. The two-in-one smelting process for large-size ingots of nickel-based high-temperature alloy GH4648 according to claim 1 is characterized in that: In the consumable smelting stage in step 4, the melting rate + droplet control is adopted, the melting rate is 3.5-5.0 kg / min, and the droplet is 3-121 / s.

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