CN112553493B - Method and device for continuously preparing long-size foam metal in atmospheric environment - Google Patents

Method and device for continuously preparing long-size foam metal in atmospheric environment Download PDF

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CN112553493B
CN112553493B CN202011175109.0A CN202011175109A CN112553493B CN 112553493 B CN112553493 B CN 112553493B CN 202011175109 A CN202011175109 A CN 202011175109A CN 112553493 B CN112553493 B CN 112553493B
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graphite crucible
continuous casting
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metal melt
water
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CN112553493A (en
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钟云波
沈喆
朱家乐
林中泽
任朗
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University of Shanghai for Science and Technology
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C1/00Making non-ferrous alloys
    • C22C1/08Alloys with open or closed pores
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/006Continuous casting of metals, i.e. casting in indefinite lengths of tubes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/055Cooling the moulds
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/059Mould materials or platings
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10Supplying or treating molten metal
    • B22D11/11Treating the molten metal
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C1/00Making non-ferrous alloys
    • C22C1/08Alloys with open or closed pores
    • C22C1/083Foaming process in molten metal other than by powder metallurgy
    • C22C1/086Gas foaming process

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Abstract

The invention discloses a method and a device for continuously preparing long-size foam metal in atmospheric environment, wherein the method comprises the following steps: in the metal continuous casting process under the atmospheric environment, an induction heating coil is applied to the front edge of a solidification interface of a graphite crystallizer, and medium/high frequency alternating current is introduced into the coil, so that a metal melt at the front edge of the graphite crystallizer and a solid-liquid interface is heated to form a high-temperature over-heat melt, the reaction of water vapor formed by heating of secondary cooling water with the wall of the graphite crystallizer is accelerated, hydrogen is generated, the dissolution of the hydrogen in the metal melt is promoted, then the metal melt immediately enters a cooling zone with high temperature gradient, bubbles are separated from the melt and are immediately solidified, and finally the foamed metal material is formed. The above process is continuously performed, so that a long-sized foamed metal material can be prepared. The continuous casting device does not need to be arranged in a high-pressure cavity, does not need to prepare foam materials in forms of external templates, air blowing and the like, has simple equipment and easy operation, and can be suitable for preparing various metal materials.

Description

Method and device for continuously preparing long-size foam metal in atmospheric environment
Technical Field
The invention belongs to the field of foam metal material preparation, and particularly provides a method and a device for preparing a long-size foam metal material in an atmospheric environment.
Background
The foam metal material has excellent physical properties and good mechanical properties, and is widely considered to be one of novel engineering materials with the most application prospect in the 21 st century. According to the characteristics of the preparation process, the preparation of the foam material can be divided into three main categories, namely a metal deposition method, a solid treatment method, a liquid treatment method and the like. The metal deposition method is a method for obtaining a metal deposition layer by performing chemical ion deposition or vapor deposition on a pretreated surface, and the method has strict requirements on operating conditions, complicated procedures and higher production cost. The solid-state treatment method is a method for preparing a foamed metal material by sintering using solid-state metal powder, and has disadvantages of high energy consumption and easy contamination of impurities. The liquid treatment method is the most commonly used method in the process of preparing foam metal, and the principle of the method is mainly to add a foaming agent into liquid phase metal or directly inject inert gas into liquid so that the gas can be remained in the liquid phase metal in the solidification process, thereby obtaining a foam structure. The foam metal obtained by different preparation methods has larger differences in appearance, performance and application. To solve the problem of mass production in industrial applications, professor Nakajima in japan applies a continuous casting technique to a method for producing a foamed metal, which comprises: and in a high-pressure container, heating and melting the metal in the crucible by an induction coil in a hydrogen atmosphere, preserving heat for a long time, and after the hydrogen is fully dissolved in the liquid metal, starting a down-leading mechanism to carry out continuous production. The continuous casting method is successfully applied to the preparation of the foam copper strip at present, but a high-pressure container is required, and a large amount of hydrogen is required to be introduced, so that the production cost and the process difficulty are greatly increased. How to overcome the problems, realize industrial continuous production and continuously prepare the porous foam material in the atmospheric environment becomes a technical problem to be solved urgently.
Disclosure of Invention
In order to solve the problems of the prior art, the invention aims to overcome the defects of technologies of needing a high-pressure container and introducing a large amount of hydrogen in the process of producing the foam metal, overcome the great limitation of the high-pressure container on the preparation of the long-size foam metal, and provide a method and a device for continuously preparing the foam metal in the atmospheric environment.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a long-size foam metal material in an atmospheric environment is characterized by comprising the following steps:
step 1: placing metal to be cast into an upper graphite crucible, arranging an upper induction coil outside the upper graphite crucible, introducing alternating current into the upper induction coil, and heating and melting the metal raw material in the upper graphite crucible by an induction heating method to form a metal melt; a lower graphite crucible is connected and arranged below the upper graphite crucible and used as a graphite crystallizer, a lower induction coil is arranged outside the lower graphite crucible, a water-cooled crystallizer is connected and arranged below the lower graphite crucible, secondary cold water is arranged at the drawing-out position of a continuous casting billet of the water-cooled crystallizer, and cooling water is introduced into the water-cooled crystallizer;
step 2: when the melted metal melt flows into the lower graphite crystallizer from the upper graphite crucible, alternating current is introduced into the lower induction coil, and the metal melt further enters the lower graphite crucible to be heated; meanwhile, the secondary cooling water is started;
and step 3: starting drawing continuous casting equipment, drawing the continuous casting billet out of the water-cooled crystallizer by using the drawing continuous casting equipment, and forcibly cooling the continuous casting billet through the water-cooled crystallizer and secondary cooling water, wherein the secondary cooling water is heated to become water vapor in the process of cooling the continuous casting billet;
and 4, step 4: the water vapor generated in the step 3 passes through the gap between the continuous casting billet and the inner surface of the wall of the lower graphite crucible to rise, finally reaches the solid-liquid interface where the metal melt in the lower graphite crucible is solidified, and under the heating effect of the heating of the lower induction coil, the water vapor and the graphite material on the wall surface of the lower graphite crucible with high temperature at the solid-liquid interface can perform the following chemical reaction:
Figure BDA0002748486730000021
and 5: carbon monoxide generated by the chemical reaction in the step 4 has extremely low solubility in the metal melt and can float upwards immediately; however, the hydrogen generated by the reaction has higher solubility in the metal melt, and as the continuous casting equipment is started, the continuous casting blank is continuously formed, part of the hydrogen dissolved in the metal melt enters the continuous casting blank, air holes are formed in the blank of the continuous casting blank, and finally the long-size foam metal material is obtained through the continuous casting process.
Preferably, the method is carried out in an atmospheric environment without a closed container and gas introduction, and without an additional auxiliary porous forming device such as a porous template or a solid core.
Preferably, the foamed metal material can be prepared by applying one more lower induction heating coil in the conventional continuous casting process without using a porous template or a solid core material or the like and an additional auxiliary porous forming device.
Preferably, the metal foam is continuously produced in a continuous casting mode and ultimately formed into a long length of metal foam of a desired length.
Preferably, the lower graphite crucible is made of graphite, and an induction heating coil is additionally arranged outside the lower graphite crucible, so that the high-temperature condition formed on the wall surface of the lower graphite crucible is regulated and controlled, the reaction of carbon on the lower graphite crucible and water vapor is promoted, and carbon monoxide and hydrogen are generated. In the step 2, an induction heating coil is added outside the lower graphite crucible and is used for heating the graphite crystallizer, so that the formation of high-temperature conditions on the wall surface of the crystallizer is facilitated, and the reaction of carbon on the wall surface of the water-cooled crystallizer and water vapor in the step 4 is facilitated.
Preferably, an induction heating coil is additionally arranged outside the lower graphite crucible to heat the metal melt, and the solubility of water vapor in the metal melt is related to the melt temperature, and the higher the temperature of the metal melt is, the higher the solubility of water vapor is; the solubility of the water vapor is improved by further heating the metal melt, and more raw materials are provided for the chemical reaction between the wall surface of the lower graphite crucible and the water vapor. In the step 2, the solubility of the water vapor generated in the step 3 in the metal melt is further improved, so that more raw materials are provided for the chemical reaction in the step 4, and more reaction products, namely hydrogen, are generated.
Preferably, an induction heating coil is additionally arranged outside the lower graphite crucible to heat the metal melt, and the solubility of hydrogen in the metal melt is related to the melt temperature, and the higher the melt temperature is, the higher the solubility of hydrogen is; the added lower induction coil is used for further heating the metal melt, and the content of hydrogen generated by the reaction in the metal melt is regulated, controlled and improved.
Preferably, the content of hydrogen in the metal melt is increased by further heating the metal melt by using a lower induction coil; in the continuous casting process, the front edge of a solid-liquid interface generates a phase change process from liquid to solid, hydrogen which is not discharged in time from a liquid metal melt is fixed in a solid-phase continuous casting blank along with the phase change process, and holes in the continuous casting blank are formed finally; the content of hydrogen in the metal melt is controlled to form the long-size porous foam metal material. In the step 5, as the temperature of the metal melt is increased, the solubility of the reaction product hydrogen in the metal melt is also increased, which promotes the increase of the hydrogen content in the metal melt at the front edge of the solid-liquid interface and is beneficial to forming the porous foam metal material in the solidification process.
Preferably, a gap exists between the lower graphite crucible and the continuous cast slab, the gap is mainly due to the fact that the lower graphite crucible has a certain draft, and the draft is set to be 0.01-10 degrees.
Preferably, the above method is suitable for preparing foamed metal materials of various metals and alloys thereof, including any one of aluminum, aluminum alloys, magnesium alloys, copper alloys, iron alloys, nickel, and nickel alloys.
Preferably, the method is suitable for any one of horizontal, vertical and vertical bending type continuous casting processes of the foam metal.
Preferably, the method is suitable for preparing any continuous casting billet of a round billet, a square billet, a plate billet, a tube billet and a special-shaped billet.
Preferably, the alternating current passed through the upper and lower induction heating coils is a medium/high frequency alternating current having a frequency ranging from 1kHz to 100kHz and a current ranging from 0 to 500000A, preferably a current ranging from 0 to 500A.
A preparation device of a long-size foam metal material in an atmospheric environment comprises an upper graphite crucible, an upper induction coil, a lower graphite crucible, a lower induction coil, a water-cooled crystallizer, secondary cooling water and a continuous casting equipment traction device; the upper graphite crucible and the lower graphite crucible are used for containing metal melt, and the upper graphite crucible and the lower graphite crucible are connected through threads to realize sealing connection; placing metal to be cast into an upper graphite crucible, arranging an upper induction coil outside the upper graphite crucible, introducing alternating current into the upper induction coil, and heating and melting the metal raw material in the upper graphite crucible by an induction heating method to form a metal melt; a lower graphite crucible is connected and arranged below the upper graphite crucible and serves as a graphite crystallizer, a lower induction coil is arranged outside the lower graphite crucible, and the lower induction coil heats metal melt in the lower graphite crucible after alternating current is introduced; a water-cooled crystallizer is connected and arranged at the outer side or the lower part of the lower graphite crucible and is used for cooling the metal melt which flows out of the lower graphite crucible and enters the water-cooled crystallizer; setting secondary cooling water at the outer side of the continuous casting billet at the drawing-out position of the continuous casting billet of the water-cooled crystallizer to further cool the continuous casting billet, and introducing the cooling water into the water-cooled crystallizer, wherein the secondary cooling water forms vapor in the cooling process; the water vapor rises to pass through the gap between the lower graphite crucible and the continuous casting billet and reaches and enters a solid-liquid interface; the continuous casting equipment traction devices are arranged on two sides of the continuous casting billet and used for drawing the continuous casting billet; the water vapor reacts with carbon on the surface of the high-temperature lower graphite crucible to generate hydrogen; the hydrogen is not discharged in time during the continuous casting process and is fixed in the continuous casting billet, thereby forming the long-size porous foam metal material.
Preferably, the upper graphite crucible is replaced with a tundish to facilitate continuous production.
Preferably, the lower graphite crucible is made of graphite or other carbon materials, and has a draft angle of 0.01-10 degrees.
Preferably, the continuous casting apparatus is of any one of a drop-down type, an arc type and a horizontal type.
Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:
1. the method and the device can be carried out in the atmospheric environment without being carried out in a high-pressure cavity, which is not only beneficial to reducing the operation difficulty and reducing the production cost, but also beneficial to breaking through the limit of the cavity space on the length of the prepared material and beneficial to large-scale industrial continuous casting production;
2. according to the method and the device, gases such as hydrogen and the like do not need to be introduced into the melt, so that the production cost can be reduced, the production risk is reduced, and the method and the device are also beneficial to large-scale industrial continuous casting production;
3. the method and the device do not need to adopt an auxiliary porous forming device such as a porous template or a solid core material, so that the complexity of the equipment is greatly reduced, and the pollution of the template, the core material and other external equipment to the melt is reduced;
4. the invention provides a graphite crystallizer with a lower graphite crucible, wherein an induction heating coil is applied to the front edge of an external solid-liquid interface of the graphite crystallizer and is used for heating the graphite crystallizer and a metal melt in the graphite crystallizer, so that more water vapor can be dissolved in the metal melt, and the reaction of the water vapor and the wall surface of the graphite crystallizer is promoted; meanwhile, the method is also favorable for improving the content of a reaction product, namely hydrogen, in the metal melt and promoting the preparation of the porous foam material. The method can generate hydrogen in situ, and does not need to introduce hydrogen in the process of preparing the foam metal, thereby being beneficial to reducing the production cost and carrying out large-scale industrial production.
Drawings
Fig. 1 is a schematic structural diagram of an apparatus for manufacturing a long foamed metal bar by a down-casting method in an atmospheric environment according to an embodiment of the present invention.
Fig. 2 is a macroscopic metallographic image of a longitudinal section of a continuous casting billet obtained by introducing alternating currents with different parameters into a lower induction coil in a first embodiment of the invention.
Fig. 3 is a schematic structural diagram of an apparatus for producing a long-size foamed metal pipe blank by a horizontal continuous casting method in an atmospheric environment according to an embodiment of the present invention.
FIG. 4 is a macroscopic gold phase diagram of the cross section of a continuous casting pipe billet obtained by introducing alternating currents with different parameters into a lower induction coil in the second embodiment of the invention.
FIG. 5 is a macroscopic metallographic image of a longitudinal section of a continuous casting tube billet obtained by passing alternating currents with different parameters through a lower induction coil in the second embodiment of the invention.
Detailed Description
The preferred embodiments of the present invention are detailed below:
the first embodiment is as follows:
in this embodiment, referring to fig. 1, a device for preparing a long foamed metal material in an atmospheric environment comprises an upper graphite crucible 2, an upper induction coil 3, a lower graphite crucible 4, a lower induction coil 5, a water-cooled crystallizer 6, secondary cooling water 7, and a continuous casting equipment traction device 8; the upper graphite crucible 2 and the lower graphite crucible 4 are used for containing the metal melt 1, and the upper graphite crucible 2 and the lower graphite crucible 4 are connected through threads to realize sealing connection; putting metal to be cast into an upper graphite crucible 2, arranging an upper induction coil 3 outside the upper graphite crucible 2, introducing alternating current into the upper induction coil 3, and heating and melting metal raw materials in the upper graphite crucible 2 by an induction heating method to form a metal melt 1; a lower graphite crucible 4 is connected and arranged below the upper graphite crucible 2, the lower graphite crucible 4 is used as a graphite crystallizer, a lower induction coil 5 is arranged outside the lower graphite crucible 4, and the lower induction coil 5 heats the metal melt 1 in the lower graphite crucible 4 after alternating current is introduced; a water-cooled crystallizer 6 is connected and arranged at the outer side or the lower part of the lower graphite crucible 4 and is used for cooling the metal melt 1 which flows out of the lower graphite crucible 4 and enters the water-cooled crystallizer 6; setting secondary cooling water 7 outside the continuous casting billet 9 at the drawing-out position of the continuous casting billet 9 of the water-cooled crystallizer 6 to further cool the continuous casting billet 9, introducing cooling water into the water-cooled crystallizer 6, and forming vapor 12 in the cooling process of the secondary cooling water 7; the water vapor 12 rises through the gap between the lower graphite crucible 4 and the continuous casting slab 9, reaches and enters the solid-liquid interface 11; the traction devices 8 of the continuous casting equipment are arranged on two sides of the continuous casting billet 9 and are used for drawing the continuous casting billet 9; the water vapor 12 reacts with carbon on the surface of the lower graphite crucible 4 with high temperature to generate hydrogen 10; the hydrogen gas 10 is not discharged in time during the continuous casting process and is fixed in the continuous casting slab 9, thereby forming a long-size porous foamed metal material.
Referring to fig. 1, a method for preparing a long-size foamed metal material in an atmospheric environment is characterized by comprising the following steps:
step 1: putting a metal to be cast into an upper graphite crucible 2, arranging an upper induction coil 3 outside the upper graphite crucible 2, introducing alternating current into the upper induction coil 3, and heating and melting a metal raw material in the upper graphite crucible 2 by an induction heating method to form a metal melt 1; a lower graphite crucible 4 is connected and arranged below the upper graphite crucible 2, the lower graphite crucible 4 is used as a graphite crystallizer, a lower induction coil 5 is arranged outside the lower graphite crucible 4, a water-cooled crystallizer 6 is connected and arranged at the lower part of the lower graphite crucible 4, secondary cooling water 7 is arranged at the pulling-out position of a continuous casting billet 9 of the water-cooled crystallizer 6, and cooling water is introduced into the water-cooled crystallizer 6;
and 2, step: when the melted metal melt 1 flows into the lower graphite crystallizer 4 from the upper graphite crucible 2, alternating current is introduced into the lower induction coil 5, and the metal melt further enters the lower graphite crucible 4 to be heated; at the same time, the secondary cooling water 7 is started;
and 3, step 3: starting a drawing continuous casting device 8, drawing out a continuous casting billet 9 from a water-cooled crystallizer 6 by using the drawing continuous casting device 8, forcibly cooling the continuous casting billet 9 through the water-cooled crystallizer 6 and secondary cooling water 7, and changing the secondary cooling water 7 into steam 12 when the secondary cooling water is heated in the process of cooling the continuous casting billet 9;
and 4, step 4: the water vapor 12 generated in the step 3 passes through the gap between the continuous cast slab 9 and the inner surface of the wall of the lower graphite crucible 4, rises up, and finally reaches the solid-liquid interface 11 where the molten metal in the lower graphite crucible 4 is solidified, and the water vapor 12 and the graphite material on the wall of the lower graphite crucible 4 having a high temperature at the solid-liquid interface 11 are chemically reacted as follows under the action of the temperature rise by the heating of the lower induction coil 5:
Figure BDA0002748486730000061
and 5: carbon monoxide generated by the chemical reaction in the step 4 has extremely low solubility in the metal melt and can float upwards immediately; however, the hydrogen 10 generated by the reaction has high solubility in the metal melt, and as the continuous casting equipment 8 is started, the continuous casting blank 9 is continuously formed, a part of the hydrogen 10 dissolved in the metal melt 1 enters the continuous casting blank 9, air holes are formed in a blank body of the continuous casting blank 9, and finally the long-size foam metal material is obtained through a continuous casting process.
Preparing a long-size porous foam metal bar by adopting a down-drawing continuous casting method in an atmospheric environment, wherein the preparation device adopts an upper graphite crucible 2 for containing a metal melt 1; introducing medium/high frequency alternating current into an induction heating coil 3 arranged outside the upper graphite crucible 2 to heat the metal melt 1; the lower graphite crucible 4 is used as a lower graphite crystallizer; the water-cooled crystallizer 6 is arranged outside the graphite crystallizer at the lower part and is used for cooling the metal melt 1 and inducing solid-liquid phase change; in order to further reduce the temperature of the continuous casting billet 9, the continuous casting billet 9 is cooled by adopting a direct spraying mode of secondary cooling water 7, and the continuous casting process is completed through a continuous casting drawing traction device 8. During the cooling process, the secondary cooling water 7 is changed into water vapor 12 when heated, floats upwards along the gap between the continuous casting billet 9 and the lower graphite crystallizer 4 and finally reaches the position of a solid-liquid interface 11 of the metal melt. Since the solubility of water vapor in a metal melt is related to the melt temperature, the higher the melt temperature, the greater the gas solubility. The metal melt 1 in the lower graphite crystallizer is heated by the induction heating coil 5, and the concentration of the water vapor 12 in the metal melt 1 is greatly increased by increasing the temperature of the metal melt, so that the reaction of the water vapor 12 with the wall surface of the graphite crystallizer is promoted. In addition, due to the increase of the temperature of the metal melt 1 in the lower graphite crystallizer, the solubility of the hydrogen 10 generated by the reaction in the metal melt 1 is also improved, and the content of the hydrogen 10 in the metal melt at the front edge 11 position of the solid-liquid interface is increased. During the solid-liquid phase change, hydrogen 10 which is not discharged in time is retained in the continuous casting billet 9, and finally, the long-size foam metal material is formed. Referring to fig. 2, a macroscopic metallographic graph of a longitudinal section of a continuous casting bar of a copper bar is obtained by passing alternating currents with different parameters into the lower induction coil of the present embodiment. As can be seen from FIG. 2, when the alternating current is applied at a low intensity, the longitudinal section of the continuous cast red copper bar has a dense and non-porous structure under the current parameter # 7. Along with the improvement of the intensity of the introduced current, the air holes in the longitudinal section of the continuous casting bar billet are gradually increased. Under the current parameter of #1, the longitudinal section structure of the continuous casting billet is porous and the pore size is uniform. This shows that the porosity of the continuous casting billet can be regulated by changing the current intensity in the lower induction coil 5, thereby realizing the preparation of the long-size porous foam billet material.
In the embodiment, the lower graphite crucible is used as a graphite crystallizer, and an induction heating coil is applied to the front edge of the solid-liquid interface outside the graphite crystallizer for heating the graphite crystallizer and the metal melt therein, so that more water vapor can be dissolved in the metal melt, and the reaction of the water vapor and the wall surface of the graphite crystallizer is promoted; meanwhile, the method is also favorable for improving the content of a reaction product, namely hydrogen, in the metal melt and promoting the preparation of the porous foam material. The device and the method can generate hydrogen in situ, do not need to introduce hydrogen in the process of preparing the foam metal, are favorable for reducing the production cost and carrying out large-scale industrial production, realize industrial continuous production and continuously prepare the porous foam material in the atmospheric environment.
The second embodiment:
the present embodiment is substantially the same as the first embodiment, and the special points are that:
in this embodiment, referring to fig. 3, an apparatus for producing a long-size porous foamed metal tubular blank by a horizontal continuous casting method in an atmospheric environment comprises a main graphite crucible 2 for containing a molten metal 1; introducing medium/high frequency alternating current into an induction heating coil 3 arranged outside the graphite crucible 2 to heat the metal melt 1; the lower graphite crucible 4 is a horizontal graphite crucible and is used as a lower graphite crystallizer; the water-cooled crystallizer 6 is arranged outside the horizontal graphite crucible and used for cooling the metal melt 1 and inducing solid-liquid phase change; in order to further reduce the temperature of the continuous casting billet 9, secondary cooling water 7 is adopted to directly spray the continuous casting billet 9, and the continuous casting process is completed through a continuous casting traction device 8. The secondary cooling water is heated to be changed into water vapor 12, moves along the gap between the horizontal graphite crucible and the continuous casting billet 9 and finally reaches the solid-liquid interface 11 of the metal melt 1. The water vapor 12 reacts with the high temperature graphite wall to produce hydrogen 10. During the continuous casting process, hydrogen gas 10 which has not been discharged in time will remain in the continuous cast slab 9 and eventually form a long-sized foamed metal material. The horizontal induction heating coil 5 is used for increasing the temperature of the metal melt 1 and the horizontal graphite crucible 4, promoting the reaction of the water vapor 12 and the wall surface of the horizontal graphite crucible, and increasing the content of the water vapor 12 and the hydrogen 10 in the metal melt 1. Fig. 4 is a macroscopic metallographic image of the cross section of the continuous casting shell obtained by passing alternating currents of different parameters through the lower induction coil of the present example. As can be seen from FIG. 4, when the intensity of the applied current is low, the cross-sectional structure of the continuous cast pipe billet is dense and no holes appear under the conditions of #4 and # 5. But with the increase of the intensity of the alternating current, holes gradually appear in the cross section structure of the continuous casting tube blank. Under the condition of the highest current intensity of #1, larger holes appear in the cross section structure of the continuous casting tube blank, and the holes are uniformly distributed on the tube blank. Fig. 5 is a macroscopic metallographic image of a longitudinal section of a continuous casting tube billet obtained by applying alternating currents of two different parameters #1 and #5 to the lower induction coil of the present example. As can be seen from the combination of FIG. 4 and FIG. 5, no holes are formed on the transverse/longitudinal sections of the continuous casting pipe blank structure under the condition of low current intensity #5, and uniform holes are formed on the transverse/longitudinal sections of the continuous casting pipe blank structure when the current intensity is increased to the condition of # 1. Therefore, the generation of holes in the continuous casting pipe blank can be promoted by adjusting the current intensity in the lower induction coil, and the preparation of the long-size porous foam pipe blank material is realized.
Example three:
this embodiment is substantially the same as the above embodiment, and is characterized in that:
in this embodiment, there is a gap between the lower graphite crucible 4 and the continuous cast slab 9, which is mainly due to the fact that the lower graphite crucible 4 has a certain draft, and the draft is set to any draft in the range of 0.01 to 10 degrees, so as to create a gas passage for the water vapor 12 to go upward and create a space condition for the reaction of the water vapor and the carbon material.
Example four:
this embodiment is substantially the same as the above embodiment, and is characterized in that:
in the embodiment, the method and the device are not only suitable for any one of horizontal, vertical and vertical bending type continuous casting processes of the foam metal; but also suitable for the preparation of any continuous casting billet of round billet, square billet, plate blank and special-shaped billet, and has wide application.
To sum up, in the method and the apparatus for continuously preparing a long-size foamed metal in an atmospheric environment according to the above embodiments, in the process of continuously casting a metal in an atmospheric environment, an induction heating coil is applied to the front edge of a solidification interface of a graphite crystallizer, and a medium/high frequency alternating current is introduced into the coil, so as to heat a metal melt at the front edge of the graphite crystallizer and a solid-liquid interface, to form a high-superheat melt, so that the reaction of water vapor formed by heating secondary cooling water with the wall of the graphite crystallizer is accelerated, hydrogen is generated, the dissolution of hydrogen in the metal melt is promoted, then the metal melt immediately enters a cooling zone with a high temperature gradient, bubbles are separated from the melt and the melt is immediately solidified, and finally a foamed metal material is formed. The above process is continuously performed, so that a long-sized foamed metal material can be prepared. The continuous casting device of the embodiment does not need to be arranged in a high-pressure cavity, does not need to prepare the foam material through an external template or air blowing and other forms, has simple equipment and easy operation, and can be suitable for preparing various metal materials.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes may be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention shall be equivalent substitutions, so long as the purpose of the present invention is met, and the technical principle and inventive concept of the method and apparatus for continuously preparing long-sized foamed metal material in atmospheric environment of the present invention shall fall within the protection scope of the present invention.

Claims (13)

1. A preparation method of a long-size foam metal material in an atmospheric environment is characterized by comprising the following steps:
step 1: putting a metal to be cast into an upper graphite crucible (2), arranging an upper induction coil (3) outside the upper graphite crucible (2), introducing alternating current into the upper induction coil (3), and heating and melting a metal raw material in the upper graphite crucible (2) by an induction heating method to form a metal melt (1); a lower graphite crucible (4) is connected and arranged below the upper graphite crucible (2), the lower graphite crucible (4) is used as a graphite crystallizer, a lower induction coil (5) is arranged outside the lower graphite crucible (4), a water-cooled crystallizer (6) is connected and arranged at the lower part of the lower graphite crucible (4), secondary cold water (7) is arranged at the pulling-out position of a continuous casting billet (9) of the water-cooled crystallizer (6), and cooling water is introduced into the water-cooled crystallizer (6);
step 2: when the molten metal (1) flows into the lower graphite crucible (4) from the upper graphite crucible (2), alternating current is introduced into the lower induction coil (5), and the molten metal further enters the lower graphite crucible (4) to be heated; at the same time, the secondary cooling water (7) is started;
and step 3: starting a drawing continuous casting device (8), drawing the continuous casting blank (9) out of a water-cooled crystallizer (6) by using the drawing continuous casting device (8), forcibly cooling the continuous casting blank (9) through the water-cooled crystallizer (6) and secondary cooling water (7), and changing the secondary cooling water (7) into steam (12) when the secondary cooling water is heated in the process of cooling the continuous casting blank (9);
and 4, step 4: the water vapor (12) generated in the step 3 passes through the gap between the continuous casting billet (9) and the inner surface of the wall of the lower graphite crucible (4) to rise and finally reaches the solid-liquid interface (11) where the metal melt in the lower graphite crucible (4) is solidified, and the water vapor (12) and the high-temperature graphite material on the wall of the lower graphite crucible (4) at the solid-liquid interface (11) are subjected to the following chemical reaction under the heating effect of the heating of the lower induction coil (5):
Figure FDA0003460531890000011
and 5: carbon monoxide generated by the chemical reaction in the step 4 has extremely low solubility in the metal melt and can float upwards immediately; however, the hydrogen (10) generated by the reaction has higher solubility in the metal melt, the continuous casting billet (9) is continuously formed due to the opening of the drawing continuous casting equipment (8), a part of the hydrogen (10) dissolved in the metal melt (1) enters the continuous casting billet (9), the billet of the continuous casting billet (9) forms air holes, and finally the long-size foamed metal material is obtained through the continuous casting process.
2. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: the method is carried out in an atmospheric environment, a closed container is not needed, and various gases are not needed to be introduced into the equipment.
3. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: the lower graphite crucible (4) is made of graphite, an induction heating coil is additionally arranged outside the lower graphite crucible (4), and the high-temperature condition formed on the wall surface of the lower graphite crucible (4) is regulated and controlled to promote the reaction of carbon on the lower graphite crucible (4) and water vapor (12) and generate carbon monoxide and hydrogen.
4. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: an induction heating coil is additionally arranged outside the lower graphite crucible (4) to heat the metal melt (1), and the solubility of the water vapor (12) in the metal melt (1) is related to the melt temperature, and the higher the temperature of the metal melt (1), the higher the solubility of the water vapor (12); the solubility of the water vapor (12) is improved by further heating the metal melt (1), and more raw materials are provided for the chemical reaction between the wall surface of the lower graphite crucible (4) and the water vapor (12).
5. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: an induction heating coil is additionally arranged outside the lower graphite crucible (4) to heat the metal melt (1), and as the solubility of hydrogen (10) in the metal melt (1) is related to the melt temperature, the higher the temperature of the metal melt (1), the higher the solubility of the hydrogen (10); the metal melt (1) is further heated by the additionally arranged lower induction coil (5), and the content of hydrogen (10) generated by the reaction in the metal melt (1) is regulated, controlled and improved.
6. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: a method for further heating the metal melt (1) by utilizing the lower induction coil (5) is used for increasing the content of hydrogen (10) in the metal melt (1); in the continuous casting process, the front edge of a solid-liquid interface (11) generates a liquid-solid phase change process, hydrogen (10) which is not discharged in time in the liquid metal melt (1) is fixed in a solid-phase continuous casting billet along with the phase change process, and holes in the continuous casting billet are finally formed; the content of hydrogen (10) in the metal melt (1) is controlled to form a long-size porous foam metal material.
7. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: a gap exists between the lower graphite crucible (4) and the continuous casting billet (9), and the gap is mainly caused by the fact that the lower graphite crucible (4) has a certain draft angle which is set to be 0.01-10 degrees.
8. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: the method is suitable for any one of horizontal, vertical and vertical bending type continuous casting process of foam metal; or the method is suitable for preparing any continuous casting billet of a round billet, a square billet, a plate billet, a tube billet and a special-shaped billet.
9. The method for preparing the long-size foamed metal material in the atmospheric environment according to claim 1, wherein the method comprises the following steps: the alternating current introduced into the upper induction coil (3) and the lower induction coil (5) is medium/high frequency alternating current, the frequency range is 1kHz-100kHz, and the current range is 0-500A.
10. A device for preparing a long-size foamed metal material in an atmospheric environment is characterized by comprising an upper graphite crucible (2), an upper induction coil (3), a lower graphite crucible (4), a lower induction coil (5), a water-cooled crystallizer (6), secondary cooling water (7) and drawing continuous casting equipment (8); the upper graphite crucible (2) and the lower graphite crucible (4) are used for containing the metal melt (1), and the upper graphite crucible (2) and the lower graphite crucible (4) are connected through threads to realize sealing connection; putting metal to be cast into an upper graphite crucible (2), arranging an upper induction coil (3) outside the upper graphite crucible (2), introducing alternating current into the upper induction coil (3), and heating and melting metal raw materials in the upper graphite crucible (2) by an induction heating method to form a metal melt (1); a lower graphite crucible (4) is connected and arranged below the upper graphite crucible (2), the lower graphite crucible (4) is used as a graphite crystallizer, a lower induction coil (5) is arranged outside the lower graphite crucible (4), and the lower induction coil (5) heats the metal melt (1) in the lower graphite crucible (4) after alternating current is introduced; a water-cooled crystallizer (6) is connected and arranged at the outer side or the lower part of the lower graphite crucible (4) and is used for cooling the metal melt (1) which flows out of the lower graphite crucible (4) and enters the water-cooled crystallizer (6); arranging secondary cold water (7) at the outer side of the continuous casting blank (9) at the pulling-out position of the continuous casting blank (9) of the water-cooled crystallizer (6) to further cool the continuous casting blank (9), introducing cooling water into the water-cooled crystallizer (6), and forming water vapor (12) in the cooling process of the secondary cold water (7); the water vapor (12) rises to pass through the gap between the lower graphite crucible (4) and the continuous casting billet (9) and reaches and enters the solid-liquid interface (11); the drawing continuous casting equipment (8) is arranged at two sides of the continuous casting billet (9) and is used for drawing the continuous casting billet (9); the water vapor (12) reacts with carbon on the surface of the lower graphite crucible (4) with high temperature to generate hydrogen (10); the hydrogen (10) is not discharged in time during the continuous casting process and is fixed in the continuous casting billet (9), thereby forming the long-size porous foam metal material.
11. The apparatus for the preparation of expanded metal material of long size in atmospheric air according to claim 10, wherein said upper graphite crucible (2) is replaced with a tundish for continuous production.
12. The apparatus for preparing a long-size foamed metal material under atmospheric conditions as defined in claim 10, wherein the lower graphite crucible (4) is made of graphite or other carbon material and has a draft angle of 0.01-10 degrees.
13. The apparatus for preparing a long-size foamed metal material according to claim 10, wherein the continuous casting equipment is any one of a down-draw type, an arc type and a horizontal type.
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