阅读说明：本技术 一种减弱合金偏析的多维剪切流铸造装置和方法 (multidimensional shear flow casting device and method for weakening alloy segregation ) 是由 王自东 陈凯旋 曹裕栋 陈晓华 于 2019-09-17 设计创作，主要内容包括：一种减弱合金偏析的铸造装置和方法。装置由熔炼系统、浇注系统、铸型、底部转动盘,联接轴,离心桶组成,方法采用感应加热法熔炼合金,铸型嵌在多维剪切流施加装置中的离心桶中,离心桶在联接轴驱动下随着底部转动盘共同旋转,使铸型进行复合运动,合金熔体凝固,即实现合金中偏析的减弱甚至消除。本发明采用感应熔炼和多维剪切流技术实现合金铸锭中偏析的显著减少甚至消除。多维剪切流在熔体凝固过程中,一方面促进宏观尺度上熔体浓度的均匀化,另一方面配合各向异性表面张力的作用,引起晶体生长过程中的分裂,促进铸锭晶粒尺寸的细化。本发明消除了M50钢铸锭的宏观偏析,显著减弱Al-7wt％Si合金铸锭的微观偏析,铸造工期短,成本低廉,对产品复杂程度限制少。(A casting apparatus and method for reducing alloy segregation. The device consists of a smelting system, a pouring system, a casting mold, a bottom rotating disc, a connecting shaft and a centrifugal barrel, wherein the method adopts an induction heating method to smelt the alloy, the casting mold is embedded in the centrifugal barrel in the multi-dimensional shear flow applying device, the centrifugal barrel rotates together with the bottom rotating disc under the driving of the connecting shaft, the casting mold carries out compound motion, and the alloy melt is solidified, namely the weakening and even elimination of segregation in the alloy are realized. The invention adopts the induction melting and multidimensional shear flow technology to realize the obvious reduction and even elimination of segregation in the alloy ingot. In the process of melt solidification, the multi-dimensional shear flow promotes the homogenization of melt concentration on a macroscopic scale on one hand, and on the other hand, under the action of anisotropic surface tension, the multi-dimensional shear flow causes the splitting in the process of crystal growth and promotes the refinement of the grain size of cast ingots. The invention eliminates the macrosegregation of M50 steel ingots, obviously weakens the microsegregation of Al-7 wt% Si alloy ingots, and has short casting period, low cost and little limit to the complexity of products.)

1. a casting device for weakening alloy segregation is characterized by comprising a smelting system, a pouring system, a casting mold, a bottom rotating disc, a connecting shaft and a centrifugal barrel; the casting mold is embedded in a centrifugal barrel, and the centrifugal barrel is connected with a bottom rotating disc through a connecting shaft; the bottom rotating disc rotates under the control of the motor, the centrifugal barrel rotates under the drive of the connecting shaft, and the rotating speed ratio of the bottom rotating disc and the centrifugal barrel is realized by changing the gear of the connecting shaft so as to adjust the transmission ratio.

2. A casting method for reducing alloy segregation using the apparatus of claim 1, comprising the steps of:

(1) Preparing raw materials required for smelting;

(2) putting raw materials into a crucible of a smelting system, embedding a casting mold into a centrifugal barrel, filling a refractory heat-insulating material between the casting mold and the centrifugal barrel, and preheating the casting mold according to the requirements of different alloys;

(3) Heating and melting the raw materials in the crucible by adopting an induction melting process, preserving heat, and pouring the alloy melt into a casting mold after the heat preservation is finished;

(4) And starting a motor to drive a bottom rotating disc to drive a centrifugal barrel, and moving the centrifugal barrel according to a set rotation speed ratio until the alloy is completely solidified and then taking out.

3. a casting method for reducing or even eliminating alloy segregation during solidification as claimed in claim 2, wherein: aiming at different alloys, different casting process parameters are adopted, including induction heating power, smelting temperature control, superheat degree, pouring temperature, casting mold preheating temperature, supercooling degree and rotation speed ratio in the solidification process, multidimensional shear flow strength control, superheat degree control in the pouring process, supercooling degree control in the casting cooling process and strong multidimensional shear flow generation in an alloy melt are ensured; the smelting and casting processes can be carried out in vacuum or non-vacuum according to the smelting requirements of different alloys.

4. a casting method for reducing or even eliminating alloy segregation during solidification as claimed in claim 2, wherein said mold is preheated and filled with refractory insulation in step 2 to ensure that the melt remains in a liquid state after being poured into the mold, thereby ensuring that the multi-dimensional shear flow acts on the solidification of the alloy melt.

5. A casting method for reducing or even eliminating alloy segregation during solidification as claimed in claim 2, wherein said induction heating process in step 3 ensures uniform distribution of alloying elements in the melt during melting, providing favorable conditions for uniform nucleation and growth of crystals in the melt during later solidification.

6. A casting method for reducing or even eliminating alloy segregation during solidification as claimed in claim 2, wherein said bottom centrifugal disc and said centrifugal barrel rotate simultaneously in step 4, creating multi-dimensional shear flow inside the alloy melt during solidification; on one hand, the multi-dimensional shear flow promotes the homogenization of a temperature field and a concentration field in the solidification process, and on the other hand, the multi-dimensional shear flow and the anisotropic surface tension act synergistically to split and refine crystals in the growth process, and finally the refinement of the grain size of the cast ingot is realized; the homogenization of the macroscopic concentration field and the refinement of the grain size reduce the segregation in the alloy and inhibit the generation of a coarse segregation phase.

Technical Field

The invention relates to a casting device and a method for weakening alloy segregation. In particular, it is a casting technique that promotes uniform distribution of elements and refinement of grains during solidification of an alloy melt using multi-dimensional shear flow, thereby reducing alloy segregation.

background

Compositional segregation is caused by redistribution of solute during Solidification of the metal, with the liquid-solid interface leading to a progressive enrichment of solute atoms, producing a segregation phase where Solidification ends [ literature one m.c. metals, solid Processing, McGraw-Hill, New York,1974 ]. Macrosegregation is that a liquid phase concentrated by solute elements and impurity elements flows under the action of a certain mechanism to form segregation with the same size as a casting blank. Center segregation in a large continuous casting slab, V-shaped segregation in a small parison, inverse V-shaped segregation in an ingot and the like are typical macro-segregation [ the second highest in the literature is a macro-fitness, the isometric crystal scale and the morphology are controlled to reduce the macro-segregation [ J ]. the world metal report, 2019, B08:1-7 ]. Generally, the brittle segregation phase generated by segregation will deteriorate the mechanical properties of the alloy [ Sanlian warm, Lili, Korean, Yangtze, Liuzongjie. 1420 aluminum lithium alloy forging quality control measure [ J ] aerospace material technology, 2017,6:87-90 ]. The ingot is subjected to cogging-rolling-diffusion heat treatment, segregation is difficult to be harmless, so that a technology for not generating macrosegregation and weakening microcosmic component segregation during casting is required to be developed [ document II is high and suitable for reducing macrosegregation [ J ] by controlling equiaxed crystal size and form, and world metal report, 2019, B08:1-7 ].

The rapid solidification is an extreme method for completely eliminating segregation, and is generally realized under the conditions of extremely high cooling speed (104-109 ℃) or deep supercooling (supercooling degree reaches dozens to hundreds of ℃), the alloy is transformed from a liquid state to a solid state at extremely high speed, solute atoms are captured into a solid phase by a liquid-solid interface, and the homogenization of the solute atoms is realized [ document four P.V.Evans, A.L.Green.modeling of crystalline growth and solute redistribution vertical solid [ J ] of mater.Sci.Eng.,1988,98: 357-. However, under ordinary casting conditions, the cooling rate is generally not more than 100 ℃/s, and it is difficult to eliminate or reduce segregation to achieve homogenization of the ingot.

According to Wang's mathematical physical model about the interface evolution during the Crystal grain growth process from Crystal nucleus [ five Mingwen Chen, Zidong Wang, Jian-Jun Xu, Journal of Crystal growth.385(2014) 115-120 ], during the solidification process, the crystals are melted inwards at some interfaces under the combined action of anisotropic surface tension and shear flow, and the depressed crystals are fused and broken under the action of strong shear flow to form fine sub-crystals, finally, the grain size of the alloy is refined. The grain refinement can significantly shorten the segregation path and hinder the generation of segregation phase [ document six K.X.Chen, X.H.Chen, Z.D.Wang, H.H.Mao, R.optimization of transformation properties in as-cast copper by microstructural engineering part I.microstructural [ J ]. J.alloy.Comp., 2018,763:592 ℃ 605 ]. Meanwhile, by applying shear flow in multiple directions, the uniform distribution of elements in the alloy melt can be promoted, and further the macrosegregation in the solidification process is improved.

Disclosure of Invention

the invention aims to provide a casting device and a casting method for weakening or even eliminating segregation in alloy by utilizing a multi-dimensional shear flow technology.

To achieve the above object, the principle of the apparatus used in the present invention is schematically shown in FIG. 1

a device for applying multidimensional shear flow is characterized by comprising a smelting system, a pouring system, a casting mold, a bottom rotating disc, a connecting shaft and a centrifugal barrel; the casting mould is arranged in the centrifugal barrel, and the centrifugal barrel is connected with the bottom rotating disc through a connecting shaft; the bottom rotating disc rotates under the control of the motor, the centrifugal barrel is driven to rotate through the connecting shaft, and the rotating speed ratio of the bottom rotating disc and the centrifugal barrel is realized by changing the gear of the connecting shaft so as to adjust the transmission ratio.

A casting method for reducing alloy segregation using the apparatus described above, comprising the steps of:

(1) preparing raw materials required for smelting;

(2) Putting raw materials into a crucible of a smelting system, embedding a casting mold into a centrifugal barrel, filling a refractory heat-insulating material between the casting mold and the centrifugal barrel, and preheating the casting mold according to the requirements of different alloys;

(3) heating and melting the raw materials in the crucible by adopting an induction melting process, preserving heat, and pouring the alloy melt into a casting mold after the heat preservation is finished;

(4) and starting a motor to drive a bottom rotating disc to drive a centrifugal barrel, and moving the centrifugal barrel according to a set rotation speed ratio until the alloy is completely solidified and then taking out.

furthermore, aiming at different alloys, different casting process parameters are adopted, wherein the casting process parameters comprise induction heating power, smelting temperature control, superheat degree, pouring temperature, casting mold preheating temperature, supercooling degree and rotation speed ratio control in the solidification process, multidimensional shear flow strength control, superheat degree control in the pouring process, supercooling degree control in the casting cooling process and strong multidimensional shear flow generation in an alloy melt; the smelting and casting processes can be carried out in vacuum or non-vacuum according to the smelting requirements of different alloys.

Furthermore, the preheating of the casting mold and the filling of the refractory heat-insulating material in the step 2 are to maintain a certain supercooling degree after the melt is poured into the casting mold, avoid the melt from being rapidly solidified, and ensure that multidimensional shear flow is applied to the alloy melt through the rotation of the bottom rotating disc and the centrifugal barrel. The liquid state of the melt is kept after the melt is poured into the casting mold, so that the multidimensional shear flow is ensured to play a role in the solidification process of the alloy melt.

Furthermore, the induction heating process is adopted in the step 3, so that the uniform distribution of alloy elements in the melt in the smelting process is ensured, and favorable conditions are provided for uniform nucleation and growth of crystals in the melt in the later solidification process.

Further, in the step 4, the bottom centrifugal disc and the centrifugal barrel rotate simultaneously, and multidimensional shear flow is generated inside the alloy melt in the solidification process; on one hand, the multi-dimensional shear flow promotes the homogenization of a temperature field and a concentration field in the solidification process, and on the other hand, the multi-dimensional shear flow and the anisotropic surface tension act synergistically to split and refine crystals in the growth process, and finally the refinement of the grain size of the cast ingot is realized; the homogenization of the macroscopic concentration field and the refinement of the grain size reduce the segregation in the alloy and inhibit the generation of a coarse segregation phase.

And 4, a rotation mode that the bottom centrifugal disc and the centrifugal barrel rotate simultaneously is designed based on a multi-dimensional shear flow theory, and the movement mode provides radial and tangential composite shear flow for the inside of the melt in the ingot casting solidification process, so that the melt moves in multiple dimensions. The principle of concentration field homogenization is shown in fig. 2, wherein the melt (low temperature zone) at the left edge of the casting mold continuously moves towards the center (high temperature zone) of the casting mold under the action of radial shear flow, so that the temperature of the melt at the center is reduced, and meanwhile, the melt at the center of the casting mold continuously moves towards the right edge, so that the temperature of the melt at the right edge is increased; under the action of the tangential shear flow, the melt at the right edge is brought to the left edge, and the movement is repeated, so that the homogenization of the temperature field and the concentration field of the melt is realized. The principle of the splitting mechanism in the crystal growth process is shown in figure 3, on one hand, the multi-dimensional shear flow realizes the homogenization of the temperature field and the concentration field in the solidification process, and simultaneously, the initially nucleated crystal continuously reciprocates along with the movement of the melt. Under the combined action of anisotropic surface tension and shear flow, the crystal with initial edge nucleation is split into several sub-crystals, which continue to grow and split as nucleation particles, and finally the size of cast ingot grains is refined. The refinement of the crystal grains shortens the discharge path of solute atoms from a liquid-solid interface and weakens segregation; the grain refinement produces a large number of grain boundaries that divide the segregation phase, further suppressing the generation of coarse segregation phases.

The invention has the beneficial effects that:

The segregation in the alloy ingot is obviously reduced and even eliminated by comprehensively adopting the induction melting and multi-dimensional shear flow technology. Firstly, in the smelting process, the induction heating promotes the violent flowing of the melt, further promotes the mutual mixing of different concentration areas, and realizes the homogenization of the melt concentration. Then, after the melt is injected into the casting mold, the multi-dimensional shear flow causes the mutual mixing of the melt on one hand, and promotes the uniform distribution of the concentration field on the macro scale; under the action of the multidimensional shear flow matched with the anisotropic surface tension, the crystal splitting can be caused, the refinement of the grain size of the cast ingot is promoted, the redistribution path of the solute is shortened, the segregation is weakened, and meanwhile, a large number of grain boundaries generated by the refinement of the grains divide the segregation phase, so that the generation of a coarse segregation phase is inhibited. The multi-dimensional shear flow casting method is simple and easy to implement, short in casting period, low in cost, capable of realizing mass production, less in limitation on product complexity, capable of directly preparing a structure with fine grains, weakened segregation and even no segregation in the smelting and solidification processes of metal materials such as nickel, aluminum, iron, copper, titanium and alloys thereof, and suitable for homogenization of large bulk metal materials.

Drawings

FIG. 1 is a schematic representation (elevation view) of a casting prepared by a multi-dimensional shear flow technique;

FIG. 2 is a top view of a metal bucket (i.e., a mold) reflecting the law of motion of a melt under the action of multi-dimensional shear flow;

FIG. 3 is a schematic diagram of the evolution of crystal morphology and cyclic splitting under the action of multi-dimensional shear flow and anisotropic surface tension;

FIG. 4 detection of segregation in M50 steel prepared by multi-dimensional shear flow technique;

FIG. 5(a) Al-7 wt% Si alloy structure for general casting and (b) multi-dimensional shear flow casting (magnification: 100X).

the specific implementation mode is as follows:

The invention is described in detail below by means of exemplary embodiments. It is pointed out that the person skilled in the art will readily understand that the following examples are given by way of illustration only and are not intended to limit the invention in any way.