CN1994623A - Semi-continuous casting device and method for 7xxx aluminium - Google Patents

Semi-continuous casting device and method for 7xxx aluminium Download PDF

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Publication number
CN1994623A
CN1994623A CN 200610157657 CN200610157657A CN1994623A CN 1994623 A CN1994623 A CN 1994623A CN 200610157657 CN200610157657 CN 200610157657 CN 200610157657 A CN200610157657 A CN 200610157657A CN 1994623 A CN1994623 A CN 1994623A
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casting
crystallizer
aluminium alloy
cooling
water
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CN1994623B (en
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李丘林
刘伟
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Shenzhen Graduate School Tsinghua University
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Shenzhen Graduate School Tsinghua University
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Abstract

The invention relates to a semi-continuous-casting device of 7xxx aluminum alloy and relative casting method, wherein said device comprises crystallizer 1, with cooling channel 2 which has water inlet 5 and water outlet 7; the channel 2 has sensitive coil 3; the lower part of crystallizer 1 has bottom mould 10.And the casting method comprises that: filling cooling water into water inlet 5; connecting middle-frequency alternative current into sensitive coil 3, to generate alternative magnetic field; pouring 7xxx aluminum alloy at 680-740Deg. C into crystallizer 1; drawing bottom mould 10 at 40-160mm/min. The invention can improve the quality of 7xxx aluminum alloy.

Description

A kind of 7xxx line aluminium alloy semi-continuous casting device and method
Technical field
The present invention relates to the aluminum alloy processing technology field, particularly a kind of 7xxx line aluminium alloy semi-continuous casting device and use the casting method of its device.
Background technology
The 7xxx line aluminium alloy is important aeronautic structure material, have high strength, low-density and higher fracture toughness, the expansion of antifatigue crackle and stress corrosion performance, be widely used in primary structure member important in the aircaft configuration, as fuselage frame beam, horizontal tail integral panel, upper limb covering, keel bar, ejector seat and guide rail thereof etc.Also has great application potential at aspects such as small-sized air-to-air missile, antitank missile, large span military floating bridges.The technology of preparing of 7xxx line aluminium alloy is the research and the focus of attention of domestic and international aluminium alloy manufacture field always.
Semicontinuous casting technique is one of conventional method of producing at present the aluminium alloy strand, although have that strand mills that the face amount is big, solidified structure is thick, a problem such as inside and outside structure property lack of homogeneity and segregation are serious, increased the following process difficulty, can't reach desirable production requirement, but the semi-continuous casting method remains the casting method that present domestic aluminium processing enterprise generally adopts.This method is very big for 7xxx aluminium alloy plate ingot casting difficulty, except that surface quality difference and inside and outside defective are many, because this is that alloy two-phase section temperature range is wide, hot cracking tendency is big, in the high-temperature brittleness district, easily form fire check, the duralumin, hard alumin ium alloy elastic modelling quantity is big simultaneously, plasticity is poor, the thermal stress that produces in the cooling procedure is big, when formation of crack occurring, its intensity reduces rapidly makes crackle be able to rapid expansion, therefore the explosion phenomenon often occurs in the put procedure of strand after casting and casting, yield rate is extremely low.How to obtain that surface quality is good, interior tissue crystal grain is tiny, segregation is little, especially low stress, indehiscent 7xxx line aluminium alloy strand technology of preparing are the focuses that people pay close attention to always.
Adopt rapid solidification/powder metallurgic method can prepare the 7xxx line aluminium alloy, the alloy grain of acquisition is tiny, composition is even, intensity height, unstressed concentration phenomenon, but this method is difficult to prepare the large scale material, production cost height, and zinc content sintering difficulty when high.
Reaction-injection moulding is the alloy blank-making method that develops on the powder metallurgy process basis, and the cooling velocity of this method is higher, can reach 10 2~4℃/s, kept that crystal grain is tiny, even tissue, stress is little and can suppress advantages such as segregation, but this method lumber recovery is low, production cost is high, strand air content height is not suitable for the preparation of large-scale industry alloy.
In traditional semi-continuous casting process, reduce casting speed, reduce the secondary intensity of cooling, adopt short crystallizer and hot direct casting fabrication technique, obtain less liquid point depth, reduce D.C.casting strand internal-external temperature difference, can reduce the tendentiousness that crackle forms.But selection of process parameters such as casting speed, crystallizer height are subjected to the restriction of alloy species, a plurality of selection of process parameters need be considered as a whole simultaneously, therefore under certain process conditions, effectively solve relatively difficulty of strand crack problem by adjusting the common process condition.
Electromagnetic casting (EMC, ElectroMagnetic Casting) technology is to be the Lorentz force that the intermediate frequency alternating magnetic field of 2000~3000Hz produces in aluminium melt surface zone by applying frequency, inwardly oppress liquid metal, make melt break away from crystallizer, avoid once cooling off, directly the secondary cooled and solidified is shaped, and obtains the strand of segregation-free, any surface finish.But this method is high to the stability requirement of casting machine, and casting machine is a shake slightly, and casting billet surface then forms ripple, and the foundation of casting beginning process is very difficult, has therefore limited the application of this technology in industry.
Cui Jianzhong etc. apply the low frequency electromagnetic field that frequency is 15~50Hz in the D.C.casting process, prepared 7075,7A60 duralumin, hard alumin ium alloy strand.The electromagnetic confinement power that low frequency magnetic field produces reduces the pressure that contacts with crystallizer, has reduced intensity of cooling one time, eliminates the surface segregation knurl, improves surface quality (seeing Chinese patent CN1425520A).The function composite by electromagnetic stirring that low frequency magnetic field produces is crystal grain thinning, elimination element segregation on the one hand, reduces liquid point depth on the other hand, reduces the temperature difference on the crystal region cross section, and the strand internal stress reduces, and the trend of crackle reduces.Adopt this method can effectively improve 7xxx aluminium alloy slab quality, alleviate the cracking phenomena in the strand casting process, but the explosion phenomenon happens occasionally still in put procedure.
Korean Patent KR2002091532-A proposition applies the aluminium alloy strand of the aluminium alloy soft-contact electromagnetic D.C.casting method acquisition free of surface defects of electromagnetic field of high frequency outside the crystallizer that cracks, the restraining force of utilizing high frequency magnetic field to produce realizes soft contact, alleviate intensity of cooling one time, the induction heat of high frequency magnetic field generation simultaneously reduces initial solidification position and liquid point depth, reduce the temperature difference on the strand cross section, help alleviating the stress concentration phenomenon that produces in the casting process, but strong induction heat effect makes its interior tissue thick, and the element segregation problem does not effectively solve yet; Korean Patent KR2005064741-A adds a rotation stirring magnetic field and is used for the refinement interior tissue on the basis of Korean Patent KR2002091532-A, but because the element density variation is big, rotating excitation field still can't be eliminated element segregation phenomenon and subsidiary and come that grain-boundary strength is low, stress is concentrated the casting blank cleavage phenomenon that produces.
Summary of the invention
The purpose of this invention is to provide the device of a kind of 7xxx series alloys semi-continuous casting and the casting method of using this device, to improve the metallurgical quality of 7xxx series alloys D.C.casting strand.
For achieving the above object, a kind of 7xxx series alloys semi-continuous casting device provided by the invention comprises crystallizer, cooling-water duct, induction coil and bed die; Cooling-water duct is arranged in the crystallizer, comprises water inlet and delivery port; Be provided with induction coil in the cooling-water duct; Bed die is at crystallizer bottom sealing crystallizer, and wherein induction coil is the Medium frequency induction coil.Owing to be provided with the Medium frequency induction coil, produce the intermediate frequency alternating magnetic field behind the logical medium frequency alternating current of Medium frequency induction coil, make 7xxx series alloys melt crystallization and freezing in the intermediate frequency alternating magnetic field, can improve the quality of 7xxx series alloys strand greatly.
The technical scheme of optimizing is that the Medium frequency induction coil is made by copper coin or copper pipe.
Further also comprise graphite annulus and Re Ding in the technical scheme of optimizing; Graphite annulus is positioned at the top of crystallizer, the periphery of melt; Ring-type heat top is positioned at the upper end of graphite annulus.
The graphite annulus heat transfer rate is fast, can guarantee good cooling effect; Hot top good heat insulating can reduce melt top and cross cold and flake.
Further also comprise branch water plate in the technical scheme of optimizing, divide the water plate to be positioned at the porch of cooling water channel.Divide the water plate that cooling water is shunted, cooling effect can better be provided.
A kind of 7xxx line aluminium alloy semi-continuous casting provided by the invention comprises the steps:
A, cooling water inserted the water inlet of 7xxx line aluminium alloy D.C.casting casting device;
B, medium frequency alternating current is fed the induction coil of 7xxx line aluminium alloy D.C.casting casting device, produce alternating magnetic field;
C, be the crystallizer that 680-740 ℃ 7xxx line aluminium alloy melt cast is gone into 7xxx line aluminium alloy D.C.casting casting device with temperature;
D, with the bed die 10 of the hauling speed of 40~160mm/min traction 7xxx line aluminium alloy D.C.casting casting device.
In the optimized technical scheme of the present invention, the frequency of medium frequency alternating current is the 60-2500 hertz, and it is 0.05~0.35T in the inner magnetic field intensity that produces of crystallizer.Experiment showed, low, the flawless of strand stress that adopts the technical program to obtain, thin brilliant, homogeneous, any surface finish, segregation-free knurl.
Further in the optimized technical scheme, the hydraulic pressure of logical cooling water be 0.06~0.12MPa.Can guarantee favorable cooling effect, help to obtain the better strand of quality.
Description of drawings
Fig. 1 is an embodiment of the invention electromagnetism semi-continuous casting device structure of mould schematic diagram.
Fig. 2 is the schematic diagram of embodiment of the invention electromagnetism semi-continuous casting system.
Among the figure: 1, crystallizer; 2, cooling-water duct; 3, induction coil; 4, graphite annulus; 5, water inlet; 6, divide the water plate; 7, delivery port; 8, melt; 9, strand; 10, bed die; 11, Re Ding.
The specific embodiment
The 7xxx series alloys electromagnetism D.C.casting device that the embodiment of the invention provides comprises crystallizer 1, and 7xxx series alloys melt 8 is cast in crystallizer 1 intercrystalline and solidifies.Be provided with cooling-water duct 2 in the crystallizer 1, comprise water inlet 5, divide water plate 6 and delivery port 7.Cooling water flows into cooling-water duct 2 through water inlet 5, and through 6 shuntings of minute water plate, is flowed out by delivery port 7 at last, thereby take away a large amount of heat.Also be provided with one group of induction coil 3 in the cooling-water duct 2, induction coil 3 is made by copper coin in the present embodiment, is connected with the intermediate frequency alternating current in it, thereby produces the intermediate frequency alternating magnetic field in crystallizer 1.Be provided with graphite annulus 4 between aluminium alloy melt 8 and cooling-water duct, graphite annulus 4 upper ends also are provided with heat top 11.Aluminium alloy melt 8 is come in by crystallizer 1 upper pouring, forms strand 9 after cooled and solidified, and crystallizer 1 bottom is provided with bed die 10, and bed die 10 is connected with outside haulage gear, and the strand 9 that forms is slowly pulled out crystallizer 1.
It below is the specific embodiment of 7xxx series alloys electromagnetism semi-continuous casting provided by the invention.
7075 aluminum alloy round ingot of embodiment 1 preparation Φ 200mm, concrete steps are as follows:
At first 7075 aluminium alloys are melted the processing of after being warming up to 700 ℃~740 ℃, degassing, remove the gred in intermediate frequency furnace; Check cooling system before the casting, guarantee that the water route is unobstructed, cooling water pressure is 0.08MPa; In the time of 690 ℃~720 ℃, metal bath is cast in the die cavity that is formed by heat top 11, graphite annulus 4, crystallizer 1 and bed die 10.During casting, start intermediate frequency power supply earlier, make electric current of intermediate frequency pass through Medium frequency induction coil 3, the middle frequency electromagnetic field frequency is 500Hz, and intensity is 15000AZ, and draws bed die 10 downwards with the speed of 100mm/min; After strand 9 reaches requirement length, stop casting of molten metal, the intermediate frequency power supply of cutting off the electricity supply treats that strand 9 leaves crystallizer 1 and stops chilled(cooling) water supply (CWS).
Prepare 7075 aluminium alloys with traditional D.C.casting and compare, adopt 7075 aluminium alloy grain sizes of the present invention's preparation to have only about 1/6 when not adding magnetic field, grain shape is changed into by thick column and waits spool or rosiness; Intracrystalline element solid solution degree improves 20%, and the element gross segregation is eliminated; Internal stress significantly reduces, and the hoop maximum stress reduces by 83%, and radially maximum stress reduces by 76%; Any surface finish has been eliminated defectives such as surface segregation knurl.
The 7050 aluminium alloy plate ingots of embodiment 2 preparation 600mm * 200mm, concrete steps are as follows:
At first 7050 aluminium alloys are melted the processing of after being warming up to 700 ℃~740 ℃, degassing, remove the gred in intermediate frequency furnace; Check cooling system before the casting, guarantee that the water route is unobstructed, cooling water pressure is 0.08MPa; In the time of 690 ℃~720 ℃, metal bath is cast in the die cavity that is formed by heat top 11, graphite annulus 4, crystallizer 1 and bed die 10.During casting, start intermediate frequency power supply earlier, make electric current of intermediate frequency pass through coil 3, the middle frequency electromagnetic field frequency is 200Hz, and intensity is 20000AZ, and draws bed die 10 downwards with the speed of 120mm/min; After strand 9 reaches requirement length, stop casting of molten metal, the intermediate frequency power supply of cutting off the electricity supply is treated to stop chilled(cooling) water supply (CWS) after strand 9 leaves crystallizer 1.
Prepare 7050 aluminium alloys with traditional D.C.casting and compare, adopt 7050 aluminium alloy grain sizes of the present invention's preparation to have only about 1/8 when not adding magnetic field, grain shape is changed into by thick column and waits spool or rosiness; Intracrystalline element solid solution degree improves 24%, and the element gross segregation is eliminated; Internal stress significantly reduces, and the hoop maximum stress reduces by 80%, and radially maximum stress reduces by 72%; Any surface finish has been eliminated defectives such as surface segregation knurl.
The inventive method is that one group of Medium frequency induction coil is installed in the crystallizer of particular design, and is interior by the intermediate frequency alternating current, produces the intermediate frequency alternating magnetic field in crystallizer.The intermediate frequency alternating magnetic field is subjected to two aspect effects to alloy, the one, heat effect, cause by kelvin effect, be the power effect on the other hand, cause by Lorentz force, comprise gesture component (showing as the electromagnetic pressure of castering action) and axial rotational component (showing as the electromagnetic stirring force of agitaion) being arranged perpendicular to the casting billet surface ecto-entad.Stronger on the one hand kelvin effect is to the heat effect of initial solidification base shell; On the other hand because the effect of electromagnetic pressure, weaken the pressure that contacts between metal and crystallizer, reduce heat transfer intensity, two aspect comprehensive functions can reduce the initial solidification position of strand, improve the intensity of initial solidification base shell, reduce liquid point depth, reduce the big and stress that produces of thermograde on the strand cross section, help improving the cracking resistance ability of strand.In addition, temperature field and solute field are more even in the electromagnetic stirring force promotion molten bath, and induction heat promotes the temperature of solidified shell, solidification front forms less thermograde, acquisition helps the condition that the equiax crystal forming core is grown up, and solidified structure also obtains refinement, and segregation is controlled.A kind of 7xxx line aluminium alloy electromagnetism D.C.casting casting device that the embodiment of the invention provides and the casting method of using its device, economical, efficient, it is bad effectively to control 7xxx line aluminium alloy strand stress cracking and as-cast structure.
Above content be in conjunction with concrete preferred implementation to further describing that the present invention did, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.

Claims (7)

1, a kind of 7xxx line aluminium alloy D.C.casting device comprises crystallizer 1, cooling-water duct 2, induction coil 3 and bed die 10; Cooling-water duct 2 is arranged in the crystallizer 1, comprises water inlet 5 and delivery port 7; Be provided with induction coil 3 in the cooling-water duct 2; Bed die 10 is characterized in that at crystallizer 1 bottom sealing crystallizer 1 described induction coil 3 is the Medium frequency induction coil.
2,7xxx line aluminium alloy D.C.casting device according to claim 1 is characterized in that described induction coil is that copper coin or copper pipe are made.
3,7xxx line aluminium alloy D.C.casting device according to claim 2 is characterized in that also comprising graphite annulus 4 and heat top 11; Described graphite annulus 4 is positioned at the top of crystallizer 1, the periphery of melt 8; Ring-type heat top 11 is positioned at the upper end of graphite annulus 4.
4,7xxx line aluminium alloy D.C.casting device according to claim 3 is characterized in that also comprising branch water plate 6, and described minute water plate 6 is positioned at the porch of cooling water channel 2.
5, a kind of 7xxx line aluminium alloy D.C.casting method comprises the steps:
A, cooling water is inserted the described water inlet 5 of one of claim 1 to 4;
B, medium frequency alternating current is fed the described induction coil 3 of one of claim 1 to 4, produce alternating magnetic field;
C, be that 680-740 ℃ 7xxx line aluminium alloy melt cast is gone into the described crystallizer 1 of one of claim 1 to 4 with temperature;
D, with one of the hauling speed of 40~160mm/min traction claim 1 to 4 described bed die 10.
6,7xxx line aluminium alloy D.C.casting method according to claim 3, the frequency that it is characterized in that described medium frequency alternating current is the 60-2500 hertz, it is 0.05~0.35T in the inner magnetic field intensity that produces of crystallizer.
7,7xxx line aluminium alloy D.C.casting method according to claim 3, the hydraulic pressure that it is characterized in that described logical cooling water is 0.06~0.12MPa.
CN2006101576574A 2006-12-15 2006-12-15 Semi-continuous casting device and method for 7xxx aluminium Expired - Fee Related CN1994623B (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102328065A (en) * 2011-07-20 2012-01-25 辽宁忠旺集团有限公司 Hot-top casting process of 7075 aluminium alloy round rod with diameter of phi582 mm
CN102788499A (en) * 2012-09-07 2012-11-21 无锡豪特维思热能科技有限公司 Hearth structure of induction heating smelting furnace
CN103658579A (en) * 2012-09-06 2014-03-26 北京有色金属研究总院 Device and method for continuously manufacturing high-quality alloy cast ingots
CN103894566A (en) * 2014-04-22 2014-07-02 江苏亚太轻合金科技股份有限公司 Crystallizer for aluminum and aluminum alloy hot top casting

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102328065A (en) * 2011-07-20 2012-01-25 辽宁忠旺集团有限公司 Hot-top casting process of 7075 aluminium alloy round rod with diameter of phi582 mm
CN102328065B (en) * 2011-07-20 2013-03-13 辽宁忠旺集团有限公司 Hot-top casting process of 7075 aluminium alloy round rod with diameter of phi582 mm
CN103658579A (en) * 2012-09-06 2014-03-26 北京有色金属研究总院 Device and method for continuously manufacturing high-quality alloy cast ingots
CN102788499A (en) * 2012-09-07 2012-11-21 无锡豪特维思热能科技有限公司 Hearth structure of induction heating smelting furnace
CN103894566A (en) * 2014-04-22 2014-07-02 江苏亚太轻合金科技股份有限公司 Crystallizer for aluminum and aluminum alloy hot top casting
CN103894566B (en) * 2014-04-22 2016-02-17 江苏亚太轻合金科技股份有限公司 Al and Alalloy heat top crystallizer for casting

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