CN112496269A

CN112496269A - Casting process for improving performance of high-temperature alloy and utilization rate of old materials

Info

Publication number: CN112496269A
Application number: CN202011276467.0A
Authority: CN
Inventors: 刘锋; 谭黎明; 刘咏; 郝新; 喻石亚
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2020-11-16
Filing date: 2020-11-16
Publication date: 2021-03-16

Abstract

The invention discloses a casting process for improving the performance of superalloy and the utilization rate of old materials, comprising the following steps: first, using nickel-based precipitation hardening type isocrystalline casting superalloy K403 new and old material mixture as raw materials, vacuum induction melting is carried out, The refining period is controlled at 1560-1580°C, and the vacuum degree is kept within 0.6 Pa; second, the mold shell is prepared, baked at a certain temperature, and the mold shell is preheated to a certain temperature before pouring; third, the steps The smelting liquid in No. 1 is cast in the baked and preheated mold shell at a certain temperature. After cooling, it is vibrated and shelled. After cutting and sand blowing, K403 castings are obtained, and the durable performance at 975℃/195MPa is tested. The technical scheme of the invention can increase the recovery rate of old materials to 30-100%. The optimization of product performance by changing the parameters in the alloy production process can greatly shorten the cycle from experiment to production and reduce production costs.

Description

Casting process for improving performance of high-temperature alloy and utilization rate of old materials

Technical Field

The invention relates to the technical field of high-temperature alloy preparation, in particular to a casting process for improving the performance of a high-temperature alloy and the utilization rate of old materials.

Background

High-temperature alloy castings represented by an aircraft engine casing, a turbine guide, a blade and the like are core components of an advanced aircraft engine, and a precision casting technology is a key technology for manufacturing a high-performance aircraft engine. In addition, a large amount of waste materials (return materials and old materials) such as risers and stub bars are generated in the production process of precision castings, the utilization rate of most castings is lower than 30%, and the utilization rate of thin-wall regulating sheets and blade precision castings with complex shapes is even lower than 10%, so that how to improve the structure and performance of high-temperature alloy through improving the casting process and improve the utilization rate of return materials is urgent work to be carried out in the field of casting high-temperature alloy. The high-temperature alloy casting prepared by the prior art takes nickel-based precipitation strengthening type equal-crystal casting high-temperature alloy K403 as an example, the creep endurance life of the alloy prepared from the whole old material is obviously reduced compared with that of the alloy prepared from the whole new material or 50% old material under the condition of 975 ℃/195MPa, the endurance life of the alloy prepared from the whole old material is only 18-35 hours, the endurance life of the alloy prepared from the whole new material can reach 50-70 hours, and the endurance life of the alloy prepared from 50% old material is 32-70 hours. .

There are two main ways to improve the properties of cast superalloys. Firstly, through a component design mode, the alloy structure can be optimized and the mechanical property of the alloy can be greatly improved by adjusting the composition elements in the alloy. On the other hand, the casting process also has a large influence on the alloy structure properties. But changing the alloy components can greatly increase the difficulty in the production and material recovery processes, so that the qualification rate of the old material casting material can be quickly improved by adjusting the process.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the casting process for improving the performance of the high-temperature alloy and the utilization rate of the old material is provided, and the problems that the recovery rate of the old material is low and the performance of the high-temperature alloy is reduced by improving the utilization rate of the old material in the prior art are solved.

The technical scheme of the invention is as follows: a casting process for improving the performance of high-temperature alloy and the utilization rate of old materials comprises the following steps:

firstly, taking a nickel-based precipitation hardening type iso-crystal casting high-temperature alloy K403 new and old material mixture as a raw material, and carrying out vacuum induction smelting, wherein the refining period is controlled to be 1560-1580 ℃, and the vacuum degree is kept within 0.6 Pa;

secondly, preparing a formwork, baking at a certain temperature, and preheating the formwork to a certain temperature before casting;

and thirdly, casting the smelting liquid in the step one in a mold shell after baking and preheating at a certain temperature, cooling, vibrating and unshelling, cutting and blowing sand to obtain a K403 casting, and detecting the durability of 975 ℃/195 MPa.

Furthermore, the proportion of the old material in the step one is more than or equal to 30 percent,

further, the process for preparing the formwork in the second step is as follows: uniformly stirring silica sol and zircon powder according to a certain proportion to form slurry with certain fluidity, immersing the combined wax model group tree into the slurry, uniformly coating, draining the slurry to ensure that the slurry is uniformly coated on the surface of a wax model, then uniformly coating zircon sand in a floating sand barrel, drying for 12 hours to harden, coating silica sol and mullite slurry on the surface, coating mullite sand, repeating the coating process to coat 6 layers to finally form a mould shell with the thickness of about 6mm and the strength, then removing wax in a dewaxing kettle, pre-roasting in a roasting furnace at 600 ℃, completely burning the wax which is not completely removed from the surface of the mould shell, and obtaining the mould shell with a cavity.

Further, in the second step, the baking temperature of the die shell is 300-400 ℃, and the preheating temperature is 950 ℃ or 1050 ℃.

Further, the casting temperature in the third step is 1420-1460 ℃.

Further, the cooling mode in the third step is air cooling with a shell or air cooling.

Furthermore, the used material ratio in the step one is 100%, the preheating temperature of the mold shell in the step two is 1050 ℃, and the casting temperature in the step three is 1420 ℃.

The invention has the beneficial effects that:

1. the technical scheme of the invention is adopted, the optimization of the product performance is realized by changing the parameters in the alloy production process, the period from experiment to production can be greatly shortened, and the production cost is reduced.

2. A large amount of old materials such as risers, stub bars and the like can be generated in the production process of precision castings, the utilization rate of most castings is lower than 30%, and the utilization rate of thin-wall regulating sheets and blade precision castings with complex shapes is even lower than 10%. The technical scheme of the invention can improve the recovery rate of the old material to 30-100%.

Drawings

FIG. 1 is a microstructure diagram of grain boundaries in an all-used material permanent sample according to a comparative example of the present invention;

FIG. 2 is a microstructure diagram at grain boundaries in a permanent sample according to example 1 of the present invention;

FIG. 3 is a microstructure diagram at grain boundaries in a permanent sample according to example 2 of the present invention;

FIG. 4 is a microstructure diagram at grain boundaries of a permanent sample according to example 3 of the present invention.

Detailed Description

The comparative examples and examples 1 to 3 both use K403 as a starting material and have the standard composition ranges shown in Table 1:

TABLE 1 chemical composition Range of K403 alloy

Comparative example:

the morphology of the fully-used K403 durable sample prepared by adopting the process parameters of the traditional casting temperature of 1450-1500 ℃ and the preheating temperature of the mold shell of about 1000 ℃ is shown in figure 1, and further analysis shows that the alloy crystal boundary consists of gamma + gamma', carbide, gamma and gammaWherein gamma is a matrix phase, and gamma' is a reinforcing phase with a face-centered cubic structure. In the endurance test process, cracks are initiated at the crystal boundary and are cracked along the crystal boundary, and the cracks belong to intergranular fracture. The grain boundary of the samples with the full-new material and the semi-new and semi-old material has small and evenly distributed M₂₃C₆Type carbide, and only M exists at grain boundary in all-old material durable sample₆Type C carbide. The average endurance life of the whole new material, the semi-new and semi-old material and the whole old material at 975 ℃/195MPa is 59h, 51h and 25h respectively, which shows that the M is finely and uniformly distributed₂₃C₆The model carbide can improve the endurance quality of the K403 alloy, and the reasons of the failure and the low percent of pass of the casting are explored based on the coupling relation of the process, the structure and the performance of the casting superalloy. For example, lowering the casting temperature may reduce the grain size, refine the dendrite trunk, and reduce the size of carbides and eutectic phases, but may also increase the tendency for micro-porosity and defect formation, deteriorating alloy properties. At slower cooling rates, the dendrites in the cast superalloy are coarse and the dendrite gaps are larger, with the cooling rate increasing, the eutectic size and quantity significantly decrease, and the size of carbides and gamma prime phases also decrease. While the generally finer carbides and gamma prime phases help to improve the properties of the alloy. Therefore, the optimization of the casting process is carried out in a targeted manner through the relationship among the established process, the structure and the performance. Analysis suggests that reducing the size of carbides and gamma prime phases at grain boundaries is critical to improving alloy properties, which can be achieved by lowering the casting temperature, increasing the cooling rate, and the like.

Examples 1 to 3

A casting process for improving the performance of high-temperature alloy and the utilization rate of old materials is characterized by comprising the following steps:

secondly, preparing a formwork, baking at the temperature of 300-400 ℃, and preheating the formwork to a certain temperature before casting;

and thirdly, casting the smelting liquid in the step one in a mold shell after baking and preheating at a certain temperature, carrying out air cooling or air cooling with a shell, carrying out vibration shelling, cutting and sand blowing to obtain a K403 casting, and detecting the lasting property of 975 ℃/195 MPa.

Wherein the process for preparing the formwork in the second step is as follows: uniformly stirring silica sol and zircon powder according to a certain proportion to form slurry with certain fluidity, immersing the combined wax model group tree into the slurry, uniformly coating, draining the slurry to ensure that the slurry is uniformly coated on the surface of a wax model, then uniformly coating zircon sand in a floating sand bucket, drying for 12 hours to harden, coating silica sol and mullite slurry on the surface, coating mullite sand, repeatedly coating in such a way to coat 6 layers in total to finally form a mould shell with the thickness of about 6mm and the strength, then removing wax in a dewaxing kettle, pre-roasting in a roasting furnace at 600 ℃, completely burning the wax which is not completely removed on the surface of the mould shell, and obtaining the mould shell with a cavity.

In the embodiment 1, the used material accounts for 50% in the first step, the preheating temperature of the formwork in the second step is 1050 ℃, the casting temperature in the third step is 1460 ℃, the hollow shell molding is adopted, and the durable life of 975 ℃/195MPa reaches 60 h. The structure morphology of the casting durable sample is shown in figure 2, fine and evenly distributed carbides exist in the grain boundary, and no coarse gamma/gamma' phase eutectic structure exists.

In the embodiment 2, the used material in the first step accounts for 50 percent, the baking temperature in the second step is 1050 ℃, the casting temperature in the third step is 1420 ℃, a shell is adopted for molding, and the durable life of 975 ℃/195MPa reaches 58 h. The texture of the permanent sample of the casting is shown in FIG. 3.

In the example 3, the used material ratio in the first step is 100%, the baking temperature in the second step is 1050 ℃, the casting temperature in the third step is 1420 ℃, and the hollow shell molding is adopted. The durability of 975 ℃/195MPa is 51.0-97.5h, the average durability time is 59h, and the durability of 26 batches of samples is all qualified.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims

1. a casting technique that improves superalloy performance and old material utilization rate, is characterized in that, comprises the steps:

First, using nickel-based precipitation hardening type isocrystalline casting superalloy K403 new and old material mixture as raw material, vacuum induction melting is carried out, the refining period is controlled at 1560-1580 °C, and the vacuum degree is kept within 0.6 Pa;

Second, prepare the mold shell, bake it at a certain temperature, and preheat the mold shell to a certain temperature before pouring;

Third, cast the smelting liquid in step 1 into the baked and preheated mold shell at a certain temperature, after cooling, vibrate the shell, cut and blow sand to obtain K403 castings, and test the durability at 975℃/195MPa performance.

2 . The casting process for improving the performance of superalloy and the utilization rate of old materials according to claim 1 , wherein the proportion of old materials in step 1 is ≥30%. 3 .

3. a kind of casting technique that improves superalloy performance and the utilization rate of old material according to claim 1, is characterized in that, in step 2, the process of preparing mould shell is as follows: silica sol and zircon powder are stirred according to a certain proportion After uniform, a slurry with a certain fluidity is formed, and the combined wax module tree is immersed in the slurry. After evenly coating and hanging, the slurry is drained so that the slurry is evenly coated and hung on the surface of the wax mold. The zircon sand is evenly hung in the bucket, and after drying and hardening for 12 hours, the silica sol and mullite slurry are coated on the surface, and the mullite sand is hung on the surface. About 6mm, with a strong mold shell, then remove the wax from the mold shell in a dewaxing kettle, pre-bake it in a calciner at 600 ° C, and burn off the wax that has not been removed from the surface of the mold shell to obtain Formwork with cavities.

4. a kind of casting process that improves superalloy performance and old material utilization rate according to claim 1, is characterized in that, in step 2, mould shell baking temperature is 300～400 ℃ temperature, and preheating temperature is 950 ℃ or 1050°C.

5. a kind of casting process that improves superalloy performance and used material utilization rate according to claim 1, is characterized in that, the casting temperature in step 3 is 1420～1460 ℃.

6 . The casting process for improving the performance of superalloys and the utilization rate of old materials according to claim 1 , wherein the cooling method in step 3 is air cooling with shell or air cooling. 7 .

7. a kind of casting technology that improves superalloy performance and the utilization rate of old material according to claim 1, is characterized in that, the proportion of old material in step 1 is 100%, and the preheating temperature of mould shell in step 2 is 1050°C, and the casting temperature in step 3 is 1420°C.