阅读说明：本技术 一种高纯稀土金属的电子束熔炼连续铸锭方法 (Electron beam melting continuous ingot casting method for high-purity rare earth metal ) 是由 邓月华 刘华 黄美松 马小波 黄培 樊玉川 于 2018-06-07 设计创作，主要内容包括：本发明公开了一种高纯稀土金属的电子束熔炼连续铸锭方法,其具体工艺过程为:(1)将稀土金属原料进行备料、装炉、抽真空；(2)电子束对金属原料进行加热融化,得到金属熔体；(3)进料,经步骤(2)融化后得到的金属熔体进入冷床,在冷床的后部进行精炼；(4)经步骤(3)得到的熔体进入水冷坩埚,电子束枪对其扫描加热,保持熔体的温度均匀性,熔体通过水冷坩埚结晶,成型得到高纯稀土金属铸锭；(5)通过拉锭系统连续下拉出锭,出锭系统设有偏振器,使拉锭杆振动,达到振动促进晶核形成及在成长中枝晶破碎,改善铸锭晶粒结构,细化晶粒的目的。本发明可连续铸锭,所制备的稀土金属铸锭部分金属杂质及气体杂质大幅度降低,能够提高铸锭纯度。(The invention discloses an electron beam melting and continuous ingot casting method of high-purity rare earth metal, which comprises the following specific process steps of (1) preparing rare earth metal raw materials, charging and vacuumizing; (2) heating and melting the metal raw material by using an electron beam to obtain a metal melt; (3) feeding, wherein the molten metal obtained after melting in the step (2) enters a cooling bed, and refining at the rear part of the cooling bed; (4) enabling the melt obtained in the step (3) to enter a water-cooled crucible, scanning and heating the melt by an electron beam gun, keeping the temperature uniformity of the melt, crystallizing the melt through the water-cooled crucible, and forming to obtain a high-purity rare earth metal ingot; (5) the ingot is continuously pulled out through the ingot pulling system, the ingot pulling system is provided with a polarizer, and the ingot pulling rod is made to vibrate, so that the aims of promoting crystal nucleus formation through vibration, breaking dendritic crystals during growth, improving the crystal grain structure of the ingot and refining the crystal grains are fulfilled. The invention can continuously cast ingots, greatly reduces partial metal impurities and gas impurities of the prepared rare earth metal cast ingots, and can improve the purity of the cast ingots.)

1. An electron beam melting continuous ingot casting method of high-purity rare earth metal comprises the following specific process steps:

Preparing a rare earth metal raw material (purity: 3N ~ 3N5), charging, and vacuumizing;

heating and melting the metal raw material by using an electron beam to obtain a metal melt;

Feeding, wherein the metal melt obtained after melting in the step (2) enters a cooling bed, refining the metal melt at the rear part of the cooling bed, and removing impurities and gas; the high-density and low-density inclusions can be separated by gravity;

enabling the melt obtained in the step (3) to enter a water-cooled crucible, wherein the size phi of the water-cooled crucible is 60-500mm, scanning and heating the melt by an electron beam gun, keeping the temperature uniformity of the melt, keeping proper refining time, fully removing impurities and gas, crystallizing the melt through the water-cooled crucible, and forming to obtain a high-purity rare earth metal ingot;

The ingot is continuously pulled out through the ingot pulling system, the ingot pulling system is provided with a polarizer, and the ingot pulling rod is made to vibrate, so that the aims of promoting crystal nucleus formation through vibration, breaking dendritic crystals during growth, improving the crystal grain structure of the ingot and refining the crystal grains are fulfilled.

2. The method for continuously casting the ingot by the electron beam melting of the high-purity rare earth metal as claimed in claim 1, wherein the rare earth metal raw material is at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), gadolinium (Gd), terbium (Tb), holmium (Ho), erbium (Er), lutetium (Lu), yttrium (Y) or scandium (Sc).

Technical Field

the invention relates to the technical field of metallurgy, in particular to an electron beam melting continuous ingot casting method for high-purity rare earth metals.

Background

The high-purity rare earth metal generally refers to rare earth metal with the purity higher than 99.99 percent, and is a key raw material for preparing the rare earth functional material, a small amount of even trace impurities can also cause remarkable influence on the physical and chemical properties of the metal, and certain special properties of the rare earth material can be generally shown under the condition of higher purity. The high-purity rare earth metal can be used for preparing high-purity reagents and base materials configured by standard samples, and can also be used for preparing high-technology fields such as magnetic sensing materials, light sensing materials, magnetic recording sputtering targets, ion plating, aerospace high-grade alloys and the like. High-purity rare earth metals are mostly prepared into pure rare earth metal targets or alloy targets in the high-tech field, and functional films meeting the requirements are obtained in a film coating mode. In large-scale integrated circuits and flat panel displays, as the process size of integrated circuits is continuously reduced and the requirements on inclusions and defects in films are higher and higher, extremely high requirements are provided for the chemical purity, the density and the like of a raw material, namely a high-purity rare earth metal cast ingot, prepared from a target material.

Five methods for purifying rare earth metals have been developed [ Zhang Weiping, Yangqingshan, Chenjianjun, high purity rare earth metal preparation method and development trend, metallic material and metallurgical engineering, 2007,3(35):61-64 ]: vacuum Remelting (VR), distillation/sublimation (DIS/SUB), zone melting (ZR), Solid State Electromigration (SSE), and Electrorefining (ER).

Vacuum remelting is effective for most rare earth metals to remove high vapor pressure impurities such as C and F. The distillation/sublimation method is to purify rare earth metals under high vacuum by utilizing the difference of vapor pressure of each element. The zone melting process is a redistribution process of impurities, the impurities are enriched at two ends of the metal rod, the zone melting is effective for moving metal impurities such as Fe, Al and Cu, the effect for redistributing gap impurities C, N, O and H is poor, and solid-state electromigration can effectively purify elements embedded between crystal lattices, such as main impurity gap elements C, H, O, N in rare earth metals. The electrolytic refining is effective for removing metal impurities having weaker electrical activity than rare earth metals and some interstitial impurities, but the molten salt electrolytic refining has high requirements on the purity of electrolytes and crucibles.

In the aspect of preparing high-purity rare earth metal ingots, vacuum induction melting ingots, suspension melting ingots and the like are commonly used, documents of electron beam melting rare earth metals are rarely reported, and electron beam melting is commonly used for refractory metal purification and ingot casting, for example:

Patent document [ Yangxianqiang, Ailin, etc., a method for producing a high-purity metal ingot, application No.: 201410732839.4 discloses a method for manufacturing high-purity metal cast ingot, which comprises melting 99.99% raw material with electron beam, removing impurities and gas from the melt in a water-cooled crucible by electromagnetic induction heating, feeding into a water-cooled crystallizer, and molding to obtain high-purity metal cast ingot with higher purity, better physical properties and higher yield than the cast ingot obtained by conventional electron beam casting method, but the size of the cast ingot is not described specifically;

Patent literature [ stapi, guo zhang, etc., method and apparatus for preparing polysilicon by coupling electron beam melting and directional solidification technology, application No.: 201310382641.3 discloses a method and a device for preparing polysilicon by coupling electron beam melting and directional solidification technology, which breaks the traditional electron beam melting mode, only carries out melting and preliminary electron beam melting in a melting tank, carries out concentrated electron beam melting in a diversion area, and silicon liquid after melting and purification flows into a solidification crucible to carry out directional solidification through a water-cooling ingot pulling rotating mechanism. The method reduces energy consumption, and the obtained specified phosphorus content and total metal content are extremely low, but the method has the problem of uneven melt temperature in the solidification crucible;

Patent document [ gorgeous and precious, and english-substituted, etc., a high purity copper vacuum electron beam melting directional solidification continuous casting device, application No.: 201320559609.3 discloses a high-purity copper vacuum electron beam melting directional solidification continuous casting device, which can produce high-purity uninterrupted copper foil, and the product produced by the method has single shape and is not suitable for continuously producing high-purity rare earth cast ingots;

Patent document [ zingiberagawa, wangdanceke, etc., a method for manufacturing a niobium-based ultra-high temperature alloy using an electron beam melting apparatus, application No.: 201410315788.5 discloses an electron beam melting device and a method for preparing niobium-based super high temperature alloy by using the device, the device comprises a melting chamber, a directional solidification ingot pulling device is arranged in the melting chamber, the content of impurities S and P in the niobium-based super high temperature alloy prepared by using the device can be reduced to be less than 0.1ppmw, the oxygen content can be reduced to be less than 0.1ppmw, the carbon content can be reduced to be less than 10ppmw, and the yield of alloy elements is more than 95%;

Patent document [ allin, bai yanli, etc., an apparatus for continuously producing high-purity metal ingots, application No.: 201420757269.X ] discloses a device for continuously preparing high-purity metal ingots, which comprises a crucible, a water cooling jacket arranged outside the crucible, and an induction heating device arranged at the upper part of the crucible; a continuous feeding device arranged above the crucible. The device melts metal in a water-cooled crucible induction melting mode, and realizes the continuity of melting and forming processes through the continuous feeding device; however, this method has a limitation on the ingot size;

Patent literature [ Liu Qingsheng, Tangweidong, Jiangxuanghua, electrolytic refining and in-situ directional solidification method and device for preparing high-purity rare earth metal, application number: 201510239832.3 discloses a method and a device for preparing high-purity rare earth metal by electrolytic refining and in-situ directional solidification, the device comprises an electrolytic furnace and an ingot furnace which are arranged on a frame, the high-purity rare earth metal can be continuously and automatically prepared, and the average per hour can produce 2.8kg of rare earth metal La with the purity of 99.96 percent; the purity of the rare earth metal prepared by the method can not meet the requirement of a target material and continuous ingot casting can not be realized.

Patent application No. [ gazuku gaku gazu gahui, nhui et al, method for producing high-purity lanthanum, sputtering target containing high-purity lanthanum, and metal gate film containing high-purity lanthanum as a main component: 201280021193.8 describes a sputtering target material that uses high purity lanthanum, preferably reduced in Al, Fe, Cu content and alkali and alkaline earth metals, transition metal elements, refractory metal elements, radioactive elements. Rare earth elements contained in lanthanum include Sc, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu in addition to lanthanum (La), and their characteristics are similar, so that it is difficult to separate and purify them from La. In particular, Ce is close to La, and therefore, it is not easy to reduce Ce, but since these rare earth elements have similar properties, if the total amount of the rare earth elements is less than 100 ppm by weight, it does not become a problem particularly when used as a material for electronic components.

At present, a vacuum induction furnace and suspension smelting are the most common devices for preparing high-purity rare earth metal ingots, the vacuum induction furnace is adopted to prepare the high-purity rare earth metal ingots, the cost is low, the efficiency is high, but in the process, the vacuum induction furnace must be in contact with materials of a crucible and a casting mold, the pollution of the high-purity rare earth metal is easily caused, and in addition, the casting mold must be broken after the high-purity rare earth metal is formed, so the casting cost is increased; a water-cooled copper crucible magnetic suspension smelting furnace is a device for smelting high-melting point and high-purity metal which is developed rapidly in recent years, and forms electromagnetic force which is counteracted with gravity in metal smelting through a high-frequency or medium-frequency alternating magnetic field to suspend a melt, so that the melt is separated from contact with the inner wall of a crucible, and the metal obtains high purity; however, this method has certain drawbacks, such as small equipment capacity, generally used only for experimental and purification studies, not involving molding, or continuous casting of ingots even if molding. The method adopts the common vacuum electron beam to prepare the high-purity metal ingot, because the electron beam scanning melting stock is adopted, the method is more suitable for melting high-melting-point and difficult-to-accommodate metal, the forming adopts a water-cooled crystallizer, so no medium is introduced to pollute the ingot, but in the melting process, the melting of materials and the formation of a melting pool are obtained by the electron beam heating, great impact and volatilization are provided for a crucible and a metal belt, meanwhile, the height of the formed melt in the crystallizer is very small, the temperature is not uniform, the impurity and gas content in the melt can not be sufficiently removed due to short refining time, and the prepared ingot can not meet the performance requirements of the preparation of the high-end thin film of the integrated circuit on the purity, particularly the physical properties including internal defects and surface quality.

Disclosure of Invention

The invention aims to provide an electron beam melting continuous ingot casting method for high-purity rare earth metal, which can continuously cast ingots, fully control the impurity, gas content and internal defect conditions in the ingots, and the prepared ingots have the characteristics of high purity, uniform macroscopic solidification structure, high yield, diversified product specifications and the like, and can meet the performance requirements of high-purity rare earth metal target preparation.

In order to solve the problems in the background technology, an electron beam melting continuous ingot casting method of high-purity rare earth metal comprises the following specific process steps:

(1) Preparing a rare earth metal raw material (purity: 3N ~ 3N5), charging, and vacuumizing;

(2) Heating and melting the metal raw material by using an electron beam to obtain a metal melt;

(3) feeding, wherein the metal melt obtained after melting in the step (2) enters a cooling bed, refining the metal melt at the rear part of the cooling bed, and removing impurities and gas; the high-density and low-density inclusions can be separated by gravity;

(4) Enabling the melt obtained in the step (3) to enter a water-cooled crucible, wherein the size phi of the water-cooled crucible is 60-500mm, scanning and heating the melt by an electron beam gun, keeping the temperature uniformity of the melt, keeping proper refining time, fully removing impurities and gas, crystallizing the melt through the water-cooled crucible, and forming to obtain a high-purity rare earth metal ingot;

(5) The ingot is continuously pulled out through the ingot pulling system, the ingot pulling system is provided with a polarizer, so that the ingot pulling rod vibrates, the vibration is realized to promote the formation of crystal nuclei and the crushing of dendritic crystals during growth, the crystal grain structure of the ingot is improved, and the crystal grains are refined.

The feeding in the step (3) is vertical feeding and transverse feeding, and the rare earth metal raw material is a block or ingot cast by primary or secondary smelting in other furnace bodies.

The rare earth metal raw material is at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), gadolinium (Gd), terbium (Tb), holmium (Ho), erbium (Er), lutetium (Lu), yttrium (Y) or scandium (Sc).

The high-purity rare earth metal purity is the purity except rare earth elements and gas components.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

1. According to the method, the ingot can be continuously cast, the metal impurities and the gas impurities of the prepared rare earth metal ingot are greatly reduced, and the ingot purity can be improved;

2. According to the method, the high-purity rare earth metal cast ingot has few internal defects, uniform macroscopic solidification structure and average grain size less than 100 mu m;

3. The size of the high-purity rare earth metal cast ingot is adjustable within 60-500mm, the yield is high, and the specification is various; the performance requirements of integrated circuits and the like for high-end thin film preparation are met.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the technical scheme in the embodiment of the invention will be clearly and completely described below by combining the table in the embodiment of the invention.