Directional solidification method for local cooling of liquid metal of single crystal casting

Abstract

The invention belongs to the field of casting of single-crystal castings, and particularly relates to a directional solidification method for local cooling of liquid metal of a single-crystal casting. According to the method, a liquid metal cooling module capable of moving along with a casting set is designed, a water cooling ring is used for cooling liquid metal, the lower end of the casting set is combined through seed crystals, a fully-coated shell is prepared, and a shell system and the liquid metal cooling module synchronously descend to be away from a heating area, so that the directional solidification casting is obtained. By means of the method, pollution possibly occurring in the liquid metal cooling process is isolated, it is guaranteed that the shell is not infected by reducing contact, and the percent of pass of the liquid metal cooling method is effectively increased.

Description

Technical Field

[0001] The invention belongs to the field of crystal casting, and in particular relates to a directional solidification method for local cooling of liquid metal of single crystal casting. Background Art

[0002] As a material with a temperature bearing capacity of more than 1000℃, single crystal high temperature alloy castings have the ability to withstand high temperature loads, especially their strong ability to resist high temperature creep, and are widely used in aerospace, aviation and energy fields. Liquid metal cooling (LMC method) is currently the method that can provide the maximum temperature gradient, which can achieve the refinement of the primary dendrite orientation of single crystal castings. It is one of the mainstream methods for single crystal casting high-performance castings. Its biggest constraint is that the conventional LMC method requires the mold shell to be gradually and completely immersed in liquid metal, which will cause the mold shell to rupture and the casting to be contaminated, thus affecting the pass rate. In addition, the high requirements for the mold shell and process also affect its widespread use. Summary of the invention

[0003] In view of the problems in the prior art, the present invention provides a directional solidification method for local cooling of liquid metal for single crystal castings, which effectively solves the actual defects of the liquid metal cooling method that the shell is prone to rupture and cracks, resulting in casting contamination and even sparking, and can also ensure a better temperature gradient.

[0004] The technical solution of the present invention is: A directional solidification method for local cooling of liquid metal of a single crystal casting, the device used in the method includes a hot zone module and a liquid metal cooling module, the hot zone module includes a furnace body, a pouring port, a heating zone and a heat insulation baffle, the liquid metal cooling module includes liquid metal, a cooling water channel and a pulling system, and the method specifically includes the following steps: Step (1) using a seed crystal seeding combined casting pouring system and preparing a shell mold, wherein the seed crystal part shell mold is additionally prepared with 5 to 8 layers on the basis of the original shell mold to ensure the local shell mold strength, and the shell mold is a fully covered shell mold; Step (2) immersing the prepared shell covering the seed crystal below 1 / 2 in liquid metal to fix it; Step (3) performs directional solidification pouring in the order of vacuuming the equipment - preheating - alloy refining - melting and casting - pulling the shell downward, and the shell moves downward simultaneously with the liquid metal cooling module, away from the heating zone, to complete the directional solidification molding of the single crystal casting.

[0005] Furthermore, in the above-mentioned directional solidification method for local cooling of liquid metal for single crystal castings, the seed crystal used is prepared from the same alloy as the casting.

[0006] Furthermore, in the above-mentioned directional solidification method for local cooling of liquid metal for single crystal castings, the liquid metal used is a gallium-indium alloy or a tin alloy.

[0007] Furthermore, in the above-mentioned directional solidification method for local cooling of liquid metal for single crystal castings, the speed at which the mold shell moves downward simultaneously with the liquid metal cooling module is: 4~6mm / min.

[0008] Advantages and beneficial effects of the present invention: The present invention can reduce the erosion of the mold shell by the liquid metal cooling method, and isolate the contamination that may occur in the liquid metal cooling process under the premise of ensuring the temperature gradient. By reducing the contact, the mold shell is ensured not to be contaminated, and the qualified rate of the liquid metal cooling method is effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the liquid metal cooling module and the hot zone module of the present invention. DETAILED DESCRIPTION

[0010] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention. Example 1

[0011] The directional solidification method for local cooling of liquid metal for single crystal castings in this embodiment adopts a first generation nickel-based single crystal high temperature alloy and specifically includes the following steps: Step (1) using a seed crystal seeding combination of 8 test rods as a pouring system, and preparing a mold shell, the basic mold shell has 6 layers, and the seed crystal part mold shell has 6 layers additionally prepared on the basis of the original 6-layer mold shell; the seed crystal material is the same as a first-generation nickel-based single crystal high-temperature alloy; Step (2) is as follows Figure 1 As shown, the device used comprises a liquid metal cooling module and a hot zone module, the liquid metal cooling module comprises liquid metal, a cooling water circuit and a pulling system, and the device used further comprises a hot zone module, the hot zone module comprises a furnace body, a pouring port, a heating zone and a heat insulation baffle; the part below 1 / 2 of the prepared shell covering the seed crystal is immersed in the liquid metal and fixed; the liquid metal is a gallium-indium alloy; Step (3) performs directional solidification pouring in the order of vacuuming the equipment - preheating - alloy refining - melting and casting - pulling the mold shell downward. The mold shell moves downward at a speed of 4 mm / min along with the liquid metal cooling module, away from the heating zone, and finally completes the directional solidification molding of the single crystal casting.

[0012] In the pouring process of this embodiment, the mold shell did not crack, the test rod was well formed, and the single crystal had good integrity.

Claims

1. A method for directional solidification of liquid metal for local cooling of single crystal castings, characterized in that: The device used in the method includes a hot zone module and a liquid metal cooling module, the hot zone module includes a furnace body, a pouring port, a heating zone and a heat insulation baffle, and the liquid metal cooling module includes liquid metal, a cooling water channel and a pulling system. The method specifically includes the following steps: Step (1) using a seed crystal seeding combined casting pouring system and preparing a shell mold, wherein the seed crystal part shell mold is additionally prepared with 5 to 8 layers on the basis of the original shell mold to ensure the local shell mold strength, and the shell mold is a fully covered shell mold; Step (2) immersing the prepared shell covering the seed crystal below 1 / 2 in liquid metal to fix it; Step (3) performs directional solidification pouring in the order of vacuuming the equipment - preheating - alloy refining - melting and casting - pulling the shell downward, and the shell moves downward simultaneously with the liquid metal cooling module, away from the heating zone, to complete the directional solidification molding of the single crystal casting.

2. A directional solidification method for local cooling of liquid metal for single crystal casting according to claim 1, characterized in that: The seed crystals used are made of the same alloy as the castings.

3. A directional solidification method for local cooling of liquid metal for single crystal casting according to claim 1, characterized in that: The liquid metal used is gallium-indium alloy or tin alloy.

4. A directional solidification method for local cooling of liquid metal for single crystal casting according to claim 1, characterized in that: The speed at which the shell moves downward simultaneously with the liquid metal cooling module is: 4~6mm / min.

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