JPH05507882A - Apparatus and method for direct chill casting of metal ingots - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Equipment and methods for direct chill casting of metal ingots Technical details field The present invention improves the internal macro- and microstructure and homogeneity of metal ingots aluminum alloys produced by direct chill casting, especially for Reduce macrosegregation in the central region of the web. The present invention relates to an apparatus and method for reducing the amount of water used.

Background technology The main technology used today for the production of aluminum ingots is die-cutting. Cuttyl (D, C,) casting. This direct chill casting The platen is initially closed at its lower end by a downwardly movable platen. It is done in a vertical mold. Molten aluminum is introduced into the upper end of the mold. the mold by continuously supplying coolant fluid to its outer surface. Once cooled and the molten metal solidifies in the area adjacent to the periphery of the mold, the plastic Move the marten downward. Effective continuous downward movement of this platen and corresponding Ingots of desired length are produced by continuously feeding molten metal into the mold. be done. On an economic scale, the thickness of these ingots was 1 8" ingots were thought to be large, but today's ingots are 26 to 3 0" thickness has continued to increase to the point where it has become normal.

Macro separation measures the properties of the finished ingot as it determines its usefulness This is one of the parameters used for In commercial scale casting Changes in macroseparation, especially alcohols produced by direct chill casting Variations in minium alloy ingots occur throughout the entire cross-section or thickness of the casting. making it difficult to maintain specific concentrations of alloying elements within a certain range. Macro in casting The degree of separation depends on the casting thickness, casting speed, alloying elements and their concentrations, and the quality of the ingot. Determined to a large extent by the method used for casting. However, macro separation The most influential parameter is the thickness or diameter of the ingot being cast; When this thickness or diameter exceeds 18”, macroseparation becomes a very serious problem. It's coming. For these large size ingots, macro separation is by changing the heat extraction rate from local to local within the ingot, and by changing the rate of heat extraction from local to local. and of the inevitable changes in solidification brought about by convective forces in the muddy zone. This is a direct result.

Normal liquid is used in the direct chill casting method of aluminum alloy ingots. A muddy zone or sump is followed by a muddy zone and then a solid region, all of which are arranged vertically. This mold is water-cooled, so its outer surface is It tends to solidify before the central portion adjacent to the manual centerline. In this way , the upper end of the ingot formed contains molten metal surrounded by solidified metal. A liquid zone or reservoir is formed. Dendrites poor in eutectic elements are It tends to grow around the periphery of liquid zones or reservoirs. Strong against this liquid zone In the presence of strong convection, the tips of the dendrites move apart and move toward the center of the liquid zone due to convection. It is believed that it will be carried to the department. Particle refiners achieve the formation of discrete crystals. It is also known that The above dendrites move towards the center (and they are thermally bounded) It grows isothermally within the interfacial layer and finally solidifies adjacent to the longitudinal center. this den Due to the lack of dorite in the alloying elements, these make the final product Low concentration of alloying elements. This low concentration makes it favorable for the reasons mentioned above. This will result in a large change in the macro separation of the ingot.

To reduce macro-segregation adjacent to the longitudinal centerline of commercial size ingots. Various attempts have been made to this end. In U.S. Pat. No. 4,709,747 to Ni et al. is located within this liquid zone to control the magnitude of the flow within said liquid zone. Mechanical dampers are used. Macro separation in the solidified casting It was expected that this would reduce the Bridge U.S. Patent No. 3°672.431 describes the use of a baffle structure located below the metal supply pipe to the mold. This baffle directs the main flow of molten aluminum to the side and directs the remaining It is suitable for guiding molten metal downward.

Another attempt to solve this problem is U.S. Pat. No. 3,506,059 to Burkhart et al. where the core member or displacer is placed inside the mold cavity. After starting casting, it is lowered to a certain position in the liquid zone. Also, in this case, the The placer guides the heated liquid metal around the mold cavity. is also used.

All of the above techniques have only a limited effect on the macro separation problem.

The present invention therefore provides a new apparatus and method that substantially reduces macro-separation. The purpose is to

Disclosure of invention The present invention reduces macro-segregation and direct-chip metals such as aluminum alloys. A method and method for improving the homogeneity of ingots produced by casting and equipment. According to the present invention, the main part of the molten metal supply is into the ingot to substantially the bottom of the reservoir formed within the ingot, and then preferably outwardly and along the interface between the reservoir and the surrounding solidified metal; Substantial improvements can be made by providing upward flow guide means. Wear. This system delivers the highest temperature feed metal to the central core of the ingot. It operates by ensuring that the highest temperature metal as a whole is This is the opposite of the existing operation of feeding the surface area of the cut and distributing it laterally. Book The invented system is commonly used in direct chill casting of large ingots. It counteracts the naturally occurring buoyancy-driven flow that would normally occur, and This prohibits the movement of dendrites that deplete the alloy relative to the central core of the . Additionally, the heated fluid is supplied to these areas of the ingot, where the There is a muddy zone with a large thickness, thus deepening the local temperature gradient, It is believed that this reduces the thickness of the muddy zone.

In a broad sense, the device according to the present invention has the following features: (a) having walls defining an axially perpendicular casting zone with an open lower end; mold, (b) means for providing a downward flow of molten metal into the upper region of said casting zone; c) means for closing the lower end of said mold, said means being connected to said casting zone. The mold is positioned to support the lower end of the ingot during casting. The part of the ingot that exits the central reservoir or zone surrounded by solidified metal. The above motor is used to carry out continuous downward movement of the ingot during casting to include It can be moved downward from the table. The feature of the present invention is that the main part of the molten metal supply mentioned above is A flow guide means is provided below the center and substantially at the bottom of the liquid reservoir. It's there.

This can be achieved in a number of different ways, and substantially Baffle or vertically movable dip tube to guide molten metal supply at the bottom or direct the main part of the molten metal supply through the above-mentioned sump. Means may be provided to increase the molten metal feed rate sufficient to force the bottom of the target.

The molten metal supply also flows from the bottom of the sump to the sump and surrounding solidified metal. Preferably, the material is guided outwardly and upwardly along the interface.

When using the baffle, in the upper region of the casting zone and within the reservoir. The baffle means is arranged to protrude and has a substantially closable sidewall and a small ( Both have one bottom opening through which the main portion of the molten metal supply is directed upward. the liquid reservoir and the solidified gold surrounding it. Guided outward and upward along the interface between the genera.

The interface between the liquid reservoir and the solidified metal is generally formed in the lower part of the ingot. and the baffle generally conforms to the shape of the reservoir. Preferably, it is formed. Therefore, the baffle is tapered downward and inwardly. It is preferable to be kicked. Can be a fixed baffle or baffle row , their position is independent during casting to give a favorable interfacial profile dynamically. It is good to be able to adjust it. This baffle is of solid metal construction, e.g. alloy steel. may be used as a disposable unit with walls formed by grass cloth. It is preferable that the This glass cloth is typically woven from glass fibers. The present invention can be used without any actuating pressure across the screen. impermeable to liquid metal. Homogeneous fabrics are fitted with a metal screen to remove coarse inclusions. Liquid metal due to the pressure drop that exists in the flow of metal in a mobile machine used for lean pass.

According to a preferred embodiment, the baffle is foldable in an accordion shape. When the liquid reservoir is formed with the start of the direct chill casting process, the stage It is expanded downward. In the casting of commercially large ingots, the above-mentioned liquid reservoir is The baffle may be at the bottom of the reservoir, which may be 2 to 3 feet deep. Preferably, it extends into the inner region.

The top of the baffle typically has a width of about 75% of the ingot width, and its walls are The side surface of the reservoir section is generally parallel to and inclined inward. Usual shape of casting mold Any shape can be used, including rectangular, square, rectangular, circular, etc.

The baffle device of the present invention may be pushed deep into the ingot head during casting. However, in some cases it may be pushed below the original solid phase position. This baffle The liquid and solid phase isotherms are dynamic by pushing into the solidifying metal during casting. is adjusted to match the given Brofino σ.

The side walls of the baffle are provided with holes or slots (bottom openings and side wall openings). The flow through them is maintained at the top of the baffle in a relatively high temperature liquid. The system is fast enough to significantly reduce the diffusive cooling of the sub-baffle to the Preferably, it is configured to ensure that the

As a result, the baffle prevents the metal being fed near the solidification front, as normally occurs. The temperature can also be as high as, for example, 20°. This is a slurry (solid and liquid) ) has the effect of increasing or deepening the local temperature gradient within or in front of the region; to reduce local clotting time. Microstructure scale (secondary phase particles dendrite arm spacing and size) depends on the local solidification time and is The baffle configuration has sufficient effect on its structure.

The baffles described above are fully functional whether made of thermally conductive or insulating materials. function. In either configuration, the reservoir is thermally isolated from external cooling. There is usually a temperature difference of 50-70°C within the liquid reservoir on each side of the baffle. It will be done. The molten metal thus descends through the baffle to the bottom of the sump. Only then will it be exposed to the full effect of external cooling.

Alternative to the above baffles, melting vertically movable gutters, downward spouts or manifolds Used to guide the main part of the metal supply down the center into the bottom of the liquid reservoir. and preferably have a varying cross section. vertically movable downwards With the spout, the ingot is formed in the upper part of the DC mold with the Formed with the bottom edge of the spout. The casting condition is such that the liquid reservoir is sufficiently formed. When a steady state is reached, the lower end of the lower spout falls into the liquid reservoir and is immersed therein. This directs the molten metal supply to substantially the bottom of the sump. metal The flow rate and positioning of the lower spout above dynamically adjusts the liquid and solid phase isotherms and to fit the given profile. Similar to using baffles as described above, A vertically movable downward spout directs the feed metal near the solidification front in the normal Temperatures can be much higher than normal.

Another method for guiding molten metal to the substantial bottom of the liquid reservoir is supplying molten metal. sufficient supply to supply the main portion of the liquid through the sump down the center and substantially at the bottom. There are ways to increase the feeding rate. One convenient way to accomplish this is in the note below above. The provision of an electromagnetic device surrounding the part of the opening. With this configuration, The outlet of the lower spout is located in the upper region of the DC casting mold. Become. This electromagnetic device is used until the liquid reservoir is sufficiently formed and the casting reaches a steady state. Do not activate. At this point, activate this electromagnetic device so that the liquid metal supply reaches the sump. Adjusted to move to substantially the bottom of.

If the metal has a temperature higher than the average reservoir temperature, the temperature between the reservoir and the surrounding solidified metal supplied to the interface. The velocity of liquid metal varies between liquid and solid phases within a given profile. Adjustments can be made to maintain the isotherm. Electromagnetic speed increasing means are particularly desirable. However, the speed may be increased by other means such as water pressure or hydraulic systems. Can be done.

The present invention also provides novel products, namely aluminum mags with improved homogeneity. This invention relates to a nesium alloy ingot. In this way, direct chill cap Aluminum-magnesium alloy ingot by Sting is the average mag of the alloy Magnesium across the cross-section of the cast ingot between +5% and -5% of the nesium content. It has the largest change in um content.

Brief description of the drawing Certain preferred embodiments of the invention are illustrated by the accompanying drawings below.

Figure 1 is a simplified cross-sectional elevation view of the direct chill casting device of the present invention. Born.

FIG. 2 is a top plan view of the baffle shown in FIG. 1.

FIG. 3 shows a direct chill caster having a tilting baffle unit according to the present invention. FIG.

FIG. 4 is a perspective view of half of the baffle shown in FIG. 3.

Figure 5 shows a direct chill casting with foldable baffles according to the present invention. Simplified cross-sectional elevation view of the equipment, with the baffles fully folded.

Figure 6 is a simplified cross-section of the configuration shown in Figure 5 with the baffle partially unfolded. It is a front view.

FIG. 7 is a cross-sectional elevation view showing the baffle not fully folded.

Figure 8 shows a simplified casting device with a vertically movable downward spout. FIG.

Figure 9 is a drawing similar to Figure 8, showing the state in which the lower spout is lowered. .

FIG. 10 is a simplified cross-sectional view of a casting device with an electromagnetic accelerator.

Figure 11 is a graph showing the variation of magnesium content across the thickness of the ingot. be.

Optimal form for carrying out the invention According to FIG. 1, the direct chill ingot casting mold 10 is elongated. It is shown for forming a large rectangular ingot 17. all practical For this purpose, this casting equipment can be Continuous or anti-continuous casting mold for producing long ingots can be used. This mold has a water cooling chamber 11, a mold surface 12 and a cooling Includes a water discharge outlet 18. Molten aluminum feed 13 is from Launzo-14 The stopper rod 3 is supplied into the mold 10 via the dip tube 15. 3.

At the beginning of the casting operation, the lower end of the casting zone between the mold faces 12 is supported by a hydraulic ram. It is closed by a held platen 19. The molten aluminum in the casting zone is As it solidifies adjacent to the casting surface 12, the platen 19 is removed by the actuation of the hydraulic ram. The solidifying base of the ingot being cast is slowly pulled vertically downward. The base is located in the form of a platform and begins to emerge from below the casting zone. From exit 18 water spray is applied to the emerging solidified ingot surface directly below the mold surface 12. . This water spray causes the ingot surface to contract, causing downward pressure from the mold. It serves to increase the cooling and solidification of the ingot 17 as it moves.

As can be seen in Figure 1, the ingot area formed within the casting zone and the casting zone Immediately below the area is a reservoir of molten metal surrounded by solidified metal 2o or A pool exists. Interface 21 between solidified metal 2o and molten metal reservoir 16 are tilted downward and inward for cooling of the mold surface 12 and water spray 18. It's slanted. Below the area of this liquid reservoir 16 is a well-formed ingot 17. exists.

A feature of the invention is the baffle arrangement 25, which allows molten metal to reach the lower end of the sump 16. and the bottom outlet 2 moves upward adjacent to the baffle outer interface 21. 7 to guide the molten metal flowing out of the dip tube 15 axially downward. It is designed to. The baffle has inwardly sloping sidewalls 26 and are generally parallel to the interface 21 and the end wall 28. preferred Especially, this baffle has side walls 26 and ends made of grass cloth! 28 Preferably, it is assembled as a disposable unit with a roll frame. each At the end of the casting process, this baffle is pulled up from the sump, e.g. by a winch. Remove the glass cloth part and replace it with a new one.

Figures 3 and 4 show other forms of baffle arrangement, in which the baffle 3o has two hands. It includes portions 30a and 30b. Each of these hand portions 30a and 30b is It is pivotably mounted by an arm 34 that is pivotably suspended from a bracket 35. It is worn. The hand portion of each baffle is a pair of side walls 31 and an end! Contains 32. the Preferably, the bottom is open and its wall portions are tapered.

At the start of casting work, move to the position indicated by the dotted line in Figure 3 and pour the molten liquid into the reservoir. When the depth of Therefore, it will come to the indicated position. In this position the baffle is placed over the rest of the ingot. It will be fully functional for the purpose of construction. This baffle also has a steel frame and made disposable by assembling the hand part with grasscloth walls. can be built.

Other forms of baffle configurations are shown in FIGS. 5-7. This configuration 5, the baffle 40 is completely disposed within the container 43 as shown in FIG. connected by support rods 42 for cordon-folding. It has a flexible graph cloth fabric wall 41.

This baffle section allows the reservoir to reach its maximum depth as shown in Figure 7. And it can be expanded. Deployment of such baffles uses a solenoid. can be fully automated by lowering the baffle section and using a computer. to control the solenoid.

Other flow guiding means of the invention are shown in FIGS. 8 and 9. In this specific example A considerable length of downward spout or manifold 15 is used to facilitate this distribution. The arrangement and lander 14 are vertically movable as shown.

FIG. 8 shows the beginning of casting when the liquid reservoir 16 begins to form. Casting zone melting As the molten metal solidifies adjacent the mold surface 12, the platform 19 is placed over it. The solidifying base of the ingot during casting is located vertically below the move it towards the

After all, a relatively deep sump or boule of molten metal surrounded by solidified metal 16, a steady state is reached as shown in FIG. solidified metal 20 and melted The interface 21 with the saliva reservoir 16 is cooled by the cooling action of the mold surface 12 and water spray. Tapered downward and inward. It is well molded below the area of the liquid reservoir 16. Therefore, there will be ingots.

When the casting operation reaches the steady state shown in FIG. is lowered so that the lower end of the lower spout 15 is deeply immersed in the liquid reservoir 16. child At the position, the heated feed liquid is guided downward through the lower spout 15 into the liquid reservoir. It is discharged into the lower region of the receptacle 16.

A specific example of a casting apparatus equipped with a flow rate accelerator is shown in FIG. This is shown in Figures 8 and 9. Using a casting system with a lower spout 15 and a lander 14 as shown in the figure Can be done. However, in the specific example shown in FIG. by an electromagnetic device 50 to increase the flow rate of molten metal supplied downwardly through the surrounded by people. Casting work using electromagnetic equipment is performed in the direct chill mold 10. 8 with the lower spout 15 located in the upper region of the . As shown in Figure 10, the casting operation is in a steady state with a well-formed liquid reservoir. When reaching the point, the electromagnetic device is activated and the liquid reservoir 16 is passed through the metal coming out of the lower spout. This provides sufficient velocity to feed molten metal to the bottom of the pipe shown in Figure 10. . Preferred embodiments of the invention are illustrated by the following non-limiting examples.

! Twisting Direct chill casting, as shown in Figures 1 and 2, was attempted in an actual plant. It was carried out using a device and baffles. The mold is rectangular and 635m1lX It is configured to cast 1350+m ingots. The cast metal is publicly available. Aluminum alloy AA3004 containing 1.1% Mg, usually used in beverage can bodies. It is used. The casting method is applicable both with and without baffles. It was carried out. The results were compared as shown in FIG. Where there is no baffle Combined magnesium changes exceed Aluminum Association limits for 3004 alloy You can see that there are many °. The measured change is about +4 to the nominal 1.15% Mg. % to -11%.

Approximately +1% to -5% for ingot casting with buckles shown in Figures 1 and 2 Magnesium changes up to well within the Aluminum Association limits, and the ingot It is close to the nominal 1.15% Mg over the entire cross section.

In the description of a specific specific example of the present invention, there are many alternatives, modifications, and variations to this technology. It is clear that it is clear to those skilled in the art.

For example, Figures 1 through 10 all represent rectangular models with corresponding rectangular baffles. It is based on the field. The present invention applies to molds with cross-sectional views such as triangular and circular shapes. works equally well. For example, if the mold is circular, the baffle should be placed on top of the cone. It is shaped like a section. In various C-form ingots, complex machining (b) be limited by any single theory that explains the result that separation occurs; (, the inventor has discovered the main macro-separation patterns that occur in DC type ingots. The system of the present invention controls fluid flow and heat flow in a unique way. A combination is likely to occur.

Thus, the present invention is subject to modification and substitution without departing from the spirit and scope of the claims. It will be understood that alterations and variations are acceptable.

abstract Direct chilling in ingot casting of aluminum alloys, especially large cross sections In casting, macro-separation was significantly reduced and compositional homogeneity was formed. Crossing the ingot greatly improves it. such as baffle 25 or flow rate accelerator 50. The main part of the molten metal supply is moved down the center using a similar flow guiding means and the casting substantially the bottom of the liquid zone or reservoir 16 formed in the reservoir 1 6 and the surrounding solidified metal 20, moving outward and upward along the interface 21. By casting in such a way that the hottest metal supply reaches the bottom of the sump, ensure that the central core of the ingot is fed downwards at the bottom of the ingot.

Submission of translation of written amendment (Article 184-8 of the Patent Law)

Claims (18)

[Claims] 1. A platform for continuous casting of metal ingots, comprising: (a) an open lower end; a mold having walls defining an axially perpendicular casting zone having (b) means for supplying a flow of molten metal downwardly into the upper region of said casting zone; (c) means for closing the lower end of said mold, said means being in said zone; The mold is placed so as to support the lower end of the ingot being cast. so that the part of the ingot that emerges contains a central reservoir surrounded by solidified metal. Can be moved downward from the mold to allow continuous downward advancement of the ingot during casting The main part of the molten metal supply is located centrally and downwardly and substantially at the bottom of the sump. flow guide means for guiding the hottest metal supply into the ingot. Continuous casting equipment whose improvement is to ensure that the central core is fed. 2. whether the flow guiding means is directed outwardly along the interface between the fluid reservoir and the surrounding solidified metal; 2. The molten metal according to claim 1, wherein the molten metal is guided upward from the bottom of the liquid reservoir. Device. 3. Flow guiding means substantially supply said molten metal through said sump to the bottom thereof. Increase the rate of descent of the molten metal supply enough so that the main portion of the molten metal is sent down the center. 2. The apparatus of claim 1, further comprising means for causing. 4. Flow guiding means are located in the upper region of said casting zone and extend downwardly into said sump. baffle means adapted to protrude into the substantially closed sidewall; and at least one bottom opening, the main portion of the supply of said molten metal being directed through said bottom opening. through the center downwardly and into substantially the bottom of the sump, connecting said sump and its 3. wherein the solidified metal is oriented outwardly and upwardly along the interface of the solidified metal surrounding the solidified metal. Device. 5. The baffle has a side wall that slopes downwardly and inwardly, and it has a reservoir and a 5. The apparatus of claim 4, wherein the surface is generally parallel to the interface with the surrounding solidified metal. 6. 5. The apparatus of claim 4, wherein said baffle wall is formed from grass cloth. 7. Once the fluid reservoir is formed, the flow guiding means directs the fluid flow downwards into the center of the fluid reservoir. Selectively vertically descendable downward spout with varying cross-sectional area suitable for guiding or a manifold. 8. 4. The device according to claim 3, wherein the flow rate increasing means is selected from hydraulic, hydraulic, and electromagnetic acceleration means. . 9. a downward pour in which the flow rate increasing means is at least partially surrounded by an electromagnetic accelerator; 4. The device of claim 3, comprising a mouth. 10. 10. The device of claim 9, wherein said device is a pump. 11. When continuously casting metal ingots, (a) perpendicular to the axial direction of the mold A continuous downward flow of molten metal is provided in the upper region of the casting zone where the molten metal collects. Initially, a central liquid reservoir surrounded by solidified metal is formed, and a sufficiently solid liquid is formed. gradually solidify to form an ingot, (b) The main part of the flow of molten metal supply moves downward to the center and reaches the liquid reservoir. Guide the ingot substantially to the bottom, thereby ensuring that the hottest metal feeds into the ingot. a central core of the invention. 12. The flow of molten metal from the bottom of the sump to the sump and solidification surrounding it. 12. The method of claim 11, further comprising guiding outwardly and upwardly along the interface with the metal. 13. The main part of the flow is moved downward to the center, and the flow is substantially Guide the hottest gold by increasing the molten metal velocity to a sufficient velocity to reach the bottom. 12. The method according to claim 11, which ensures that the metal supply is fed to the central core of the ingot. Law. 14. The main part of the above flow is separated by means of physical baffling of the molten metal supply. down the center to substantially the bottom of the reservoir and along the perimeter of the reservoir. 12. The method according to claim 11, wherein the method is guided to move upwardly. 15. 12. The method of claim 11, wherein the metal is aluminum or an alloy thereof. 16. 16. The method of claim 15, wherein said aluminum includes an alloying amount of magnesium. 17. Cuttings of cast ingots with +5% to -5% of the average magnesium content of the alloy Direct chill cast aluminum with maximum variation of magnesium across the plane Mu magnesium alloy ingot. 18. The ingot according to claim 17, wherein the average magnesium content is 1.15% by weight. t.