CN106925732B - A uniform cooler and method for preparing large-scale aluminum alloy ingots - Google Patents

Abstract

The invention relates to a uniform cooler and a method for preparing large-scale aluminum alloy ingots, belonging to the field of metal material processing. The uniform cooler is composed of an inner tube and an outer tube; the upper part of the outer tube is a heat-insulating end, and the lower part is a cooling end; The tube is arranged in a helical fashion within the cooling end of the outer tube. The uniform cooler is set on the semi-continuous casting platform, and goes deep into the crystallizer during the casting process to apply uniform cooling to the melt from the inside of the melt. The invention has the advantages of simple structure and convenient use, can remarkably improve casting speed and production efficiency, and the prepared large-scale aluminum alloy ingot has uniform and fine structure, and has wide industrial application prospect.

Description

A uniform cooler and method for preparing large-scale aluminum alloy ingots

technical field

The invention belongs to the field of metal material processing, and in particular relates to a uniform cooler and a method for preparing large-scale aluminum alloy ingots.

Background technique

Semi-continuous casting is the first process for preparing deformed aluminum alloy, and the quality of the ingot directly affects the subsequent deformation process. In the production of ingots by traditional semi-continuous casting methods, there will always be irreversible defects such as coarse and uneven structures, macro-segregation and even cracking. The emergence of these problems has a lot to do with the solidification forming method of semi-continuous casting. Semi-continuous casting is to continuously cast high-temperature metal melt into a forced water-cooled mold to form an initial solidification shell. After the initial solidification shell comes out of the crystallizer, it is cooled by the secondary cooling water to make the metal melt in the initial solidification Solidified and formed, and finally formed ingot. The solidification of the melt in the whole semi-continuous casting process only depends on the external cooling of the melt such as the crystallizer and the secondary cooling water. During the solidification process, the heat dissipation direction of the melt is single, and the temperature gradient is large. When casting large-scale ingots, deep liquid pockets will be formed, which will eventually cause problems such as coarse and uneven ingot structure, composition segregation, and cracking.

At present, researchers at home and abroad have carried out a lot of research work on improving the cooling conditions of ingots, including improving the water spraying method of the mold and applying external fields to improve the convective heat transfer of the melt and improve the uniformity of the temperature field. However, these methods have not fundamentally solved the problem of uneven cooling inside and outside the melt in the semi-continuous casting process, especially for large-scale ingots, it is even more difficult to effectively control the temperature field and composition field uniformity in the melt, so casting The ingot structure is still coarse and unevenly distributed.

Patent CN102581238 B discloses a crystallizer with variable cooling intensity for aluminum alloy semi-continuous casting. The crystallizer is provided with two upper and lower water tanks, the upper water tank is provided with a set of cooling water holes, and the lower water tank is provided with two sets of cooling water holes. In the initial stage, the third group of cooling water is used for cooling alone, and in the stable stage, three groups of cooling water are used to impact the surface of the ingot at the same time, which can improve the cooling effect of the ingot and help improve the metallurgical quality of the ingot. The invention hopes to improve the cooling effect of the ingot during the continuous casting process by changing the cooling mode of the external cooling water, thereby solving the problems of cracking and warping of the ingot. However, the root cause of the cracking and warping of the ingot is the very large temperature gradient and deep liquid pockets on the cross-section of the ingot, and the single water spray cooling method around the semi-continuous casting process will make the ingot Larger temperature gradients and deeper liquid pockets are generated. Therefore, only improving this single cooling method cannot fundamentally solve the problem of uneven cooling inside and outside the ingot, and the solidification of the melt is still from the outside to the inside. Sequential solidification, ingot cracking and warping problems caused by large temperature gradients cannot be effectively solved.

Chinese patent (CN1485452A) discloses a method of applying electromagnetic stirring to prepare alloy slurry and billet. This method generates an induced current in molten metal by using an electromagnetic field, and the molten metal forms a violent force on the molten metal under the action of Lorentz force Stirring, the dendrites precipitated by metal solidification are fully fragmented or spheroidized, so as to achieve the purpose of refining grains and improving the quality of casting slabs. However, due to the existence of the skin effect of the alternating electromagnetic field, when the electromagnetic field acts on the metal melt, its force decays exponentially with the increase of the distance, that is, the force on the outside of the melt is large, while the force on the inside of the melt is small. The force is not uniform, and the stirring effect of the metal melt is not uniform, which will eventually lead to uneven grain structure. Especially for large-scale ingots, the stirring effect of the melt is more limited, the solidification of the melt is still sequentially solidified from the outside to the inside, the cooling method of the melt is single, the casting efficiency is not high, and the aluminum alloy solidification process is not fundamentally solved. Inhomogeneity of the medium temperature field.

Contents of the invention

In view of the shortcomings of the existing semi-continuous casting method that the melt can only be cooled from the outside to the inside during the solidification process, and the large-scale aluminum alloy ingots prepared by the traditional semi-continuous casting method have relatively high temperatures during the solidification process Gradients and deep liquid pockets lead to problems such as coarse and uneven structure, composition segregation, thermal cracking, slow casting speed, and low production efficiency. A uniform cooler and method for preparing large-scale aluminum alloy ingots is proposed.

In view of the cooling characteristics of the melt from the inside to the outside during the semi-continuous casting solidification process, the present invention installs a uniform cooler on the ordinary semi-continuous casting equipment, and uses the heat exchange effect of the cooler to change the single cooling direction of the melt and increase the cooling dimension. Combining the functions of primary cooling and secondary cooling of ordinary semi-continuous casting crystallizers, the melt is cooled simultaneously inside and outside during the solidification process, and the cooling of the uniform cooler is adjusted according to actual production needs to make the temperature field of the melt more uniform during the solidification process. The finally obtained ingot structure is fine and uniform.

For realizing the purpose of above invention, adopt following technical scheme:

A uniform cooler for preparing large-scale aluminum alloy ingots, consisting of an inner tube and an outer tube; the upper part of the outer tube is an adiabatic end, and the lower part is a cooling end; the inner tube includes a spiral inner tube and a At the inlet and outlet ends of the inlet and outlet of the spiral inner pipe, said spiral inner pipe is arranged in the cooling end of the outer pipe in a spiral manner.

The insulating end of the outer tube of the uniform cooler is cylindrical, and the cooling end is hemispherical; the outer diameter of the insulating end is not larger than the outer diameter of the cooling end, and the outer diameter of both is 100-800mm, and the thickness is 3-20mm. same end.

The cooling end of the outer tube of the uniform cooler is made of high temperature resistant heat conducting material, such as graphite, copper, molybdenum, titanium, etc.; to make.

The bottom of the heat insulating end is provided with a blade structure, the number of blades is 0-8, preferably 3-5, the width of the blade is 10-100 mm, and the thickness of the blade is 2-8 mm. When the blade rotates, it has the ability to drive the melt flow downward. As a result, the blades are made of high temperature resistant materials, such as molybdenum, titanium, ceramics, graphite and other materials.

The inner pipe of the uniform cooler is made of heat-conducting materials, such as copper, steel, titanium, etc. and their composite materials; the inner diameter of the inner pipe is 2-30mm, and the thickness is 0.5-5mm; the helical number of the spiral inner pipe is 3-50, and the helical pitch is 0 to 10 mm, preferably 3 to 5 mm.

The inlet of the spiral inner tube is set at the bottom center of the cooling end of the outer tube, and the outlet of the spiral inner tube is set at the bottom of the insulating end of the outer tube. At the insulated end of the outer tube, it then exits from the outlet of the inner tube through the outlet end.

The cooling medium used in the inner tube is various fluids such as air, nitrogen, argon, water, oil, etc. The flow rate of the cooling medium is 0-2000L/min, the flow rate of the liquid cooling medium is preferably 10-50L/min, and the flow rate of the gas cooling medium is preferably It is 500～1000L/min.

Based on the above-mentioned uniform cooler, the present invention provides a method for preparing large-scale aluminum alloy ingots using the uniform cooler of the present invention.

A method for preparing large-scale aluminum alloy ingots, comprising the following steps: in the process of preparing large-scale aluminum alloy ingots by semi-continuous casting, a uniform cooler is installed in the crystallizer, and a cooling medium is introduced and turned on at the same time, and cooled The medium enters from the inlet of the inner tube and reaches the center of the bottom of the homogeneous cooler, then spirals up to exchange heat with the melt through the heat-conducting material at the bottom, and at the same time, the rotation and agitation of the homogeneous cooler can accelerate the heat exchange of the melt in the core; combined with the crystallizer The external cooling effect applied to the melt increases the cooling dimension and realizes the simultaneous forced continuous dynamic uniform cooling inside and outside the melt. At the same time, the blades at the cooling end of the uniform cooler drive the melt to gather at the bottom of the uniform cooler. After being cooled by the bottom of the uniform cooler, the melt continues to flow down into the mushy area of the liquid cavity, so that the melt can be continuously and dynamically cooled and melted. Forced feeding to finally prepare fine-grained homogeneous large-scale ingots.

The uniform cooler is set on the semi-continuous casting platform. During the semi-continuous casting process, the uniform cooler penetrates deep into the crystallizer to the height of the crystallizer. The bottom of the uniform cooler is flush with the crystallizer. Uniform cooling is applied to the melt. The number of uniform coolers can be one or more; the rotation speed of the whole set of uniform coolers is 0-300r/min, preferably 50-150r/min.

The inner tube of the uniform cooler of the present invention is made of heat-conducting material, the cooling medium enters from the inlet of the inner tube, reaches the cooling end of the outer tube for uniform cooling, passes through the spiral inner tube at the bottom, the cooling medium exchanges heat with the melt at the cooling end, and cools the melt. body, and then flow out from the outlet of the inner tube. The cooling end of the outer tube has blades, which force the melt to flow downward, so that the melt is continuously replenished downward into the liquid cavity, achieving the effect of dynamic, continuous and uniform cooling.

The device and method of the present invention can be used to prepare aluminum alloy round ingots with a diameter greater than 300 mm and aluminum alloy flat ingots with a thickness greater than 300 mm in semi-continuous casting equipment.

The advantages of the present invention are as follows:

1. A uniform cooler is placed inside the crystallizer. The cooling medium enters from the inner tube and reaches the center of the cooling end of the outer tube, then spirals up along the bottom of the tube, and exchanges heat with the metal melt through the cooling end. The heat transfer effect is from the edge to the outer tube. The core is gradually strengthened, which can effectively take away the heat of the core of the metal melt in the mold. Combined with the cooling effect of the mold, it creatively changes the traditional continuous casting process, which only transfers heat in one direction from the outside to the inside, and increases the solidification. The cooling dimension in the process realizes the multi-dimensional forced uniform solidification mode.

2. For the first time, the rotating motion of the uniform cooler is ingeniously combined with the special structure of the cooling end. The stirring effect can effectively drive the melt to flow, so that the entire melt has forced convection. On the basis of increasing the cooling intensity, the melt temperature can be significantly improved. Uniformity of field and component fields. At the same time, the combined effect of cooling and stirring at the cooling end enables rapid heat and mass transfer exchange between the superheated melt and the alloy melt at the solidification front, which can realize the forced dynamic continuous homogenization cooling treatment of the melt.

3. The present invention is simple in structure, easy to use, can significantly improve casting speed and production efficiency, and can produce large-size aluminum alloy ingots with uniform and fine structure, which fundamentally solves the problem of traditional semi-continuous casting methods for preparing large-size aluminum alloy ingots. Coarse and uneven structure, macro segregation, cracking and other problems have a wide range of industrial application prospects.

Description of drawings

Fig. 1 is that the present invention prepares the homogeneous cooler sectional view of large-scale aluminum alloy ingot;

Fig. 2 is a schematic diagram of setting of the present invention in Embodiment 1;

FIG. 3 is a schematic diagram of the setting of Embodiment 2 of the present invention.

Explanation of main reference signs:

1 inlet port 2 outlet port

3 Insulated end 4 Blades

5 Spiral inner tube 6 Cooling end

Detailed ways

The present invention can be implemented according to the following examples, but is not limited thereto. These examples are only to illustrate the implementation process of the present invention, but not to limit the scope of the present invention in any way. In the following examples, various processes that are not described in detail and methods are conventional methods well known in the art.

As shown in Figure 1, the uniform cooler for preparing large-scale aluminum alloy ingots in the present invention is composed of an inner tube and an outer tube; the upper part of the outer tube is an insulating end 3, the lower part is a cooling end 6, and the inner tube includes a spiral inner tube 5 and an outer tube. The inlet end 1 and the outlet end 2 of the inlet and outlet of the spiral inner tube 5 are arranged respectively, and the spiral inner tube 5 is arranged in the cooling end 6 of the outer tube in a spiral manner.

The outer tube of the uniform cooler is composed of an upper insulating end 3 and a lower cooling end 6. The insulating end 3 is cylindrical, and the cooling end 6 is hemispherical. The outer diameter of the insulating end 3 is not greater than the outer diameter of the cooling end 6. The size is 100-800mm, the thickness is 3-20mm, and the thickness is the same as that of the cooling end 6; the cooling end 6 is made of high-temperature-resistant and heat-conducting materials, such as graphite, copper, molybdenum, titanium, etc.; The pipe wall is covered with high-temperature-resistant heat-insulating materials, such as asbestos, or the heat-insulating end 3 of the outer pipe is made of high-temperature-resistant heat-insulating ceramics; the bottom of the heat-insulating end 3 is provided with blades 4, the number of blades is 0-8, and the width of blades 4 is 10-100mm. The blade 4 has a thickness of 2-8mm. When the blade 4 rotates, it has the effect of driving the melt flow downward. The blade 4 is made of high temperature resistant materials, such as molybdenum, titanium, ceramics, graphite and other materials.

The inner pipe of the uniform cooler is made of materials with good thermal conductivity, such as copper, steel, titanium, etc. and their composite materials; the inner diameter of the inner pipe is 2-30mm, the thickness is 0.5-5mm, and the spiral number of the spiral inner pipe 5 is 3-50 , The helical pitch is 0-10mm. The inner pipe of the uniform cooler is arranged in a spiral manner at the bottom of the uniform cooler, and the inner pipe is provided with an inlet and an outlet. The inlet of the spiral inner pipe 5 is arranged at the bottom center of the cooling end 6 of the outer pipe, and the outlet of the spiral inner pipe 5 is arranged at the insulating end of the outer pipe. At the bottom of 3, the cooling medium enters from the inlet of the inner tube to the center of the cooling end 6 of the outer tube, spirals up through the inner tube at the bottom to the adiabatic end 3 of the outer tube, and then exits from the outlet of the inner tube.

The cooling medium used in the inner tube is air, nitrogen, argon, water, oil and other fluids, and the flow rate of the cooling medium is 0-2000L/min.

In the process of using semi-continuous casting to prepare large-scale aluminum alloy ingots, the uniform cooler is installed in the crystallizer, and the cooling medium is introduced and turned on at the same time. The cooling medium enters from the inlet of the inner tube and reaches the cooling end at the bottom of the uniform cooler 6 The center passes through the spiral inner tube at the bottom, and then spirals up. The cooling medium exchanges heat with the melt through the heat-conducting material at the bottom, thereby cooling the melt, and then flows out from the outlet of the inner tube. The cooling effect of the uniform cooler gradually increases from the bottom edge to the center. , the stirring effect of the uniform cooler makes the melt cool through the bottom of the uniform cooler, combined with the cooling effect of the crystallizer on the melt, realizes three-dimensional, all-round cooling and heat dissipation, and achieves the purpose of simultaneous cooling inside and outside the melt, realizing Forced continuous dynamic uniform cooling of the melt.

At the same time, the cooling end 6 of the uniform cooler has blades 4. During use, the uniform cooler rotates, forcing the melt to converge to the cooling end 6 at the bottom of the uniform cooler, so as to realize continuous dynamic and uniform supercooling of the melt, and the melt passes through The bottom of the uniform cooler is cooled, and continues to flow downward into the mushy zone of the liquid cavity, realizing continuous dynamic uniform cooling and forced feeding of the melt, and finally preparing a fine-grained homogeneous large-scale ingot.

The uniform cooler is set on the semi-continuous casting platform, and goes deep into the crystallizer during the casting process to apply uniform cooling to the melt from the inside of the melt. In the semi-continuous casting process, one or more uniform coolers can be installed deep into the height of the crystallizer; the rotation speed of the whole set of devices is 0-300r/min.

Example 1

Adopt the device and method of the present invention to prepare Φ582mm specification 7055 aluminum alloy casting ingot, the uniform cooler has no blade structure, the inner pipe is made of pure copper, the inner diameter of the inner pipe is 10mm, the thickness is 1mm, the number of spirals is 20, and the pitch of the spirals is 3mm; The tube insulation end 3 is made of high temperature resistant heat insulation ceramics with an outer diameter of 300 mm and a thickness of 10 mm. The lower cooling end 6 is made of graphite with a diameter of 350 mm.

Set a uniform cooler on the casting platform, as shown in Figure 2, the uniform cooler is concentric with the crystallizer, and the bottom of the uniform cooler is flush with the crystallizer. During the continuous casting process, when the melt enters the crystallizer, start the continuous casting traction equipment and open the uniform cooler at the same time, the cooling medium is water, the flow rate is 10L/min, and the casting speed is 50mm/min, until the continuous casting ends.

The 7055 aluminum alloy cast ingot with a specification of Φ582mm prepared by the device and method of the present invention has a fine and uniform structure, an average grain size of 219 μm, and a grain size deviation of 8.72%.

Example 2

The device and method of the present invention are used to prepare 7055 aluminum alloy ingots of Φ582 mm in size, the uniform cooler is provided with a blade structure, the inner pipe is made of pure copper, the inner diameter of the inner pipe is 10 mm, the thickness is 1 mm, the number of spirals is 20, and the pitch of the spirals is 3 mm; The tube insulation end 3 is made of high temperature resistant heat insulation ceramics with an outer diameter of 300 mm and a thickness of 10 mm. The lower cooling end 6 has a diameter of 350 mm and is made of graphite. The blades 4 are made of ceramics. The number of blades is 3 and the width of the blades 4 is 50mm.

A uniform cooler is set on the casting platform, as shown in Figure 3, the uniform cooler is concentric with the crystallizer, and the bottom of the uniform cooler is flush with the crystallizer. In the continuous casting process, when the melt enters the crystallizer, start the continuous casting traction equipment and open the uniform cooler at the same time, the cooling medium is water, the flow rate is 13L/min, the rotational speed is 60r/min, and the casting speed is 90mm/min. until the end of continuous casting.

The 7055 aluminum alloy casting ingot with a specification of Φ582mm prepared by the device and method of the present invention has a fine and uniform structure, an average grain size of 164 μm, and a grain size deviation of 5.37%.

Comparing Examples 1 and 2, the Φ582mm specification 7055 aluminum alloy ingot prepared by a uniform cooler with a blade structure in a rotating manner, the casting speed increased by 80%, the average grain size decreased by 53%, and the grain size deviation decreased by 38%.

The uniform cooler of the present invention is arranged on the semi-continuous casting platform, penetrates into the crystallizer during the casting process, and applies uniform cooling to the melt from the inside of the melt. The uniform cooler is composed of an inner tube and an outer tube. The inner tube is spiral and is installed at the bottom of the uniform cooler. The cooling medium passes through the inlet of the inner tube to the cooling end of the outer tube of the uniform cooler for heat exchange. At the same time, the rotation of the uniform cooler, Can accelerate the heat exchange of the melt. The cooling end has a blade structure. When the cooler rotates, the blade has a stirring effect, which forces the surrounding high-temperature melt to continuously gather to the bottom of the uniform cooler, and continuously replenishes downwards into the liquid cavity, achieving the effect of dynamic, continuous and uniform cooling. The cooling dimension is increased, and the forced continuous dynamic uniform cooling inside and outside the melt is realized. The invention has the advantages of simple structure and convenient use, can remarkably improve casting speed and production efficiency, and the prepared large-scale aluminum alloy ingot has uniform and fine structure, and has wide industrial application prospect.

Claims (10)

1. a kind of uniform cooler for preparing large-size aluminum alloy ingot, it is characterised in that: be made of inner and outer tubes；Described The top of outer tube is insulation end, and lower part is colling end；The insulation end of the outer tube is cylindrical shape, and colling end is hemispherical；Institute The outer diameter at the insulation end for the outer tube stated is not more than the outer diameter of colling end, and blade is arranged in the insulation end bottom, and the number of blade is 3~8, Blade forces melt to flow downward, and adds to melt constantly downwards in liquid cave；The colling end of the outer tube is using resistance to High-temperature heat-conductive material is made, and is insulated the outer tube wall cladding heat-insulating material at end, or insulation end is made of high temperature resistant insulating ceramic；Institute The inner tube stated includes spiral inner tube and the arrival end for being separately positioned on spiral inner tube inlet and outlet and outlet end, the spiral Inner tube is arranged in a spiral manner in the colling end of outer tube.

2. the uniform cooler according to claim 1 for preparing large-size aluminum alloy ingot, it is characterised in that: described is outer The outer diameter at the insulation end of pipe is 100~800mm.

3. the uniform cooler according to claim 2 for preparing large-size aluminum alloy ingot, it is characterised in that: the leaf Piece width is 10~100mm, with a thickness of 2~8mm；The blade is made of heat-resisting material.

4. the uniform cooler according to claim 3 for preparing large-size aluminum alloy ingot, it is characterised in that: described is cold But end is made of graphite, copper, molybdenum or titanium, and the outer tube wall at the insulation end coats asbestos；The blade using molybdenum, titanium, Ceramics or graphite are made.

5. the uniform cooler according to claim 1 for preparing large-size aluminum alloy ingot, it is characterised in that: described is interior Bore is 2~30mm, 0.5~5mm of thickness；Spiral number is 20~50, and spiral spacing is 3~10mm；The inner tube is by leading Hot material is made.

6. the uniform cooler according to claim 5 for preparing large-size aluminum alloy ingot, it is characterised in that: described is interior Pipe is made of copper, steel or titanium.

7. a kind of method that large-size aluminum alloy ingot is prepared using uniform cooler of any of claims 1-6, Include the following steps: during preparing large-size aluminum alloy ingot using semi-continuous casting, by uniform cooler setting to crystallization It in device, while being passed through cooling medium and opening uniform cooler rotation, cooling medium enters from inner tube inlet and reaches uniformly cold Que Qi bottom centre, then spiral, is exchanged heat by bottom Heat Conduction Material and melt, while the uniformly Stirring of cooler Effect, can accelerate the heat exchange of center portion melt；In conjunction with the external cooling effect that crystallizer applies melt, increase cooling dimension, It is continuous dynamically uniformly cooling to realize synchronous pressure inside and outside melt, big size ingot-casting is finally prepared.

8. the method according to claim 7 for preparing large-size aluminum alloy ingot, it is characterised in that: the cooling medium For air, nitrogen, argon gas and water or oil, liquid cooling medium flow is 10~50L/min, gas cooling medium flow is 500~ 1000L/min。

9. the method according to claim 7 for preparing large-size aluminum alloy ingot, it is characterised in that: the uniform cooling Device is arranged on semi-continuous casting platform, and during semi-continuous casting, uniform cooler is deep into crystallizer height and position.

10. the method according to claim 7 for preparing large-size aluminum alloy ingot, it is characterised in that: described is uniform cold But the quantity of device is one or more；The rotation speed of the uniform cooler is 50~300r/min.