WO2019218377A1

WO2019218377A1 - Casting apparatus and method for suppressing component segregation of aluminium alloy ingots

Info

Publication number: WO2019218377A1
Application number: PCT/CN2018/087691
Authority: WO
Inventors: 王向杰; 崔建忠
Original assignee: 东北大学
Priority date: 2018-05-18
Filing date: 2018-05-21
Publication date: 2019-11-21
Also published as: CN108568500A

Abstract

A casting apparatus and method for suppressing the component segregation of aluminium alloy ingots, the apparatus comprising a crystalliser (1), a dummy bar head (2), a thermal insulation cap (3), a cooling aluminium bar/strip (4), a clamping delivery mechanism, a pre-heating mechanism, and a speed adjustment mechanism, the components of the cooling aluminium bar/strip (4) and the aluminium alloy ingots being the same. The method comprises: raising the dummy bar head (2) into the crystalliser (1), and introducing cooling water into the crystalliser (1) until water outlet holes of the crystalliser (1) spray out secondary water (6); controlling aluminium alloy melt (7) to first enter the thermal insulation cap (3) via a channel and then enter the crystalliser (1) and, after the melt (7) forms blank shells in the crystalliser (1), controlling the dummy bar head (2) to move downward, and starting casting; after implementing casting for 30s, first pre-heating the cooling aluminium bar/strip (4) by means of the pre-heating mechanism, and then activating the clamping delivery mechanism to insert the cooling aluminium bar/strip (4) into the core of the melt (7) to reduce the temperature of same, and controlling the descent speed of the cooling aluminium bar/strip (4) by means of the speed adjustment mechanism until casting is finished.

Description

Casting device and method for inhibiting segregation of aluminum alloy ingot composition

Technical field

The invention belongs to the technical field of aluminum alloy casting, and particularly relates to a casting device and a method for suppressing segregation of aluminum alloy ingot components.

Background technique

In the aluminum alloy casting process, the aluminum alloy melt enters the thermal insulation cap through the flow passage and then enters the crystallizer. Under the cooling action of the crystallizer, the aluminum alloy melt gradually forms an ingot, and the edge of the ingot is subjected to the crystallizer. The cooling water spray of the second cold water has a fast cooling speed, but the core of the ingot can only rely on conduction heat transfer, so the cooling rate is slow, resulting in a significant temperature difference between the edge and the core.

For aluminum alloys, the melt temperature is high and the density is small, and the melt temperature is low, the density is high. Therefore, when the melt temperature is higher than the liquidus temperature, the temperature gradient causes the melt to convect, when the melt temperature drops to Below the liquidus, due to the formation and growth of nucleation sites, solute redistribution occurs, resulting in differences in solute distribution gradients and densities, and convection caused by solute concentration gradients, convection caused by temperature gradients and solute concentration gradients. The melt with a higher solute concentration is gradually pushed to the bottom of the molten pool, so that the crystal grains are transported between the two-phase region and the liquid phase region with a lower solid-phase ratio, thereby accentuating the positive segregation at the center of the ingot and simultaneously casting The solute is poor in the edge of the ingot, and the negative segregation of the alloying elements occurs, which eventually leads to uneven composition of the entire ingot in a large scale range, that is, component segregation occurs. For alloying elements having a solute partition coefficient k < 1, the composition segregation of the alloying elements of the aluminum alloy ingot is as shown in FIG.

At present, in order to suppress the segregation of the composition of the aluminum alloy ingot, the method of lowering the casting speed and increasing the cooling rate is usually adopted, but the specific alloy composition and the size of the ingot are limited, and the range of process parameters that can be adjusted is very narrow. The actual effect is not ideal. Further, a method of adding a refiner may be employed, but it is also limited by a specific alloy composition, and the range of addition of the refiner is also very limited, and the actual effect is not satisfactory. Furthermore, it is also possible to apply a method of applying an external electromagnetic field to generate strong convection in the melt by the electromagnetic field, thereby making the temperature difference field uniform, although this method can reduce the depth of the cavity to a certain extent, and suppress the composition of the aluminum alloy ingot. The effect of segregation, however, requires a substantial modification of the conventional aluminum alloy casting device, which inevitably leads to a substantial increase in the production cost of the enterprise.

Summary of the invention

In view of the problems existing in the prior art, the present invention provides a casting apparatus and method for suppressing segregation of an aluminum alloy ingot composition, which can actively reduce the temperature of the melt core in the crystallizer to reduce the temperature between the core and the side portion. Poor, and can increase the number of core nucleation sites, effectively reduce the depth of the liquid cavity, effectively refine the solidification structure of the core, and finally achieve the purpose of inhibiting segregation of aluminum alloy ingot composition.

In order to achieve the above object, the present invention adopts the following technical scheme: a casting device for suppressing segregation of an aluminum alloy ingot composition, comprising a crystallizer, a spindle head and a heat insulating cap, the spindle head being located directly below the crystallizer, and the heat insulating cap being installed in the crystallizing Just above the device, the cooling water jacket of the crystallizer adopts the structure of inlaid graphite ring or not embedded with graphite ring; it is characterized by: further comprising a cooling aluminum alloy rod/belt, a clamping conveying mechanism, a preheating mechanism and a speed regulating mechanism, and The composition of the cooling aluminum alloy rod/belt is the same as that of the aluminum alloy ingot; the cooling aluminum alloy rod/belt is vertically clamped on the clamping conveying mechanism, and the cooling aluminum alloy rod/belt is vertically passed by the clamping conveying mechanism Lifting in the direction; preheating the cooled aluminum alloy rod/belt by a preheating mechanism before the cooling aluminum alloy rod/belt is inserted into the melt core in the crystallizer, and the preheating temperature is lower than the melt core Temperature; the lifting speed of the cooling aluminum alloy rod/belt is regulated by a speed governing mechanism.

The reduced temperature aluminum alloy rod/belt has a cross-sectional area of 10 to 10000 mm ² .

A casting method for suppressing segregation of an aluminum alloy ingot composition, which employs the casting device for suppressing segregation of an aluminum alloy ingot composition, comprising the following steps:

Step 1: Raise the spindle head into the crystallizer, and pass cooling water into the crystallizer until the water outlet in the lower part of the crystallizer ejects secondary water;

Step 2: Control the aluminum alloy melt into the thermal insulation cap through the flow passage, and then enter the crystallizer. When the melt forms a blank shell in the crystallizer, control the starter head to move down and start casting;

Step 3: After the casting is carried out for 30 s, the cooling aluminum alloy rod/belt is first preheated by a preheating mechanism, and then the clamping and transport mechanism is started to cool the cooled aluminum alloy rod/belt into the melt core to cool and pass The speed governing mechanism controls the descending speed of the cooling aluminum alloy rod/belt until the end of casting.

In the second step, the time taken for the melt to form the shell in the crystallizer is 5 to 60 s.

In the second step, after the start of casting, the initial downward movement speed of the spindle head is 5 to 50 mm/min, and is increased to 10 to 150 mm/min in 2 minutes.

In step three, the descending speed of the cooled aluminum alloy rod/belt is 1 to 50 mm/min.

The beneficial effects of the invention:

The casting device and method for suppressing segregation of aluminum alloy ingot components of the invention can actively reduce the temperature of the melt core in the crystallizer to reduce the temperature difference between the core and the side, and can improve the core nucleation point The quantity effectively reduces the depth of the liquid cavity, effectively refines the solidification structure of the core, and finally achieves the purpose of suppressing the segregation of the composition of the aluminum alloy ingot.

DRAWINGS

1 is a schematic view showing the structure of a casting device (inlaid graphite ring) for suppressing segregation of an aluminum alloy ingot composition according to the present invention;

2 is a schematic view showing the structure of a casting device (not embedded with a graphite ring) for suppressing segregation of an aluminum alloy ingot composition according to the present invention;

Fig. 3 is a graph showing the content change of magnesium element from the edge of the ingot to the core in the first embodiment.

Fig. 4 is a graph showing the content change of zinc element from the edge of the ingot to the core in the second embodiment.

Figure 5 is a schematic view showing the segregation of components of an alloying element of an aluminum alloy ingot;

In the figure, 1 - crystallizer, 2 - spindle head, 3 - thermal insulation cap, 4 - cooling aluminum alloy rod / belt, 5 - graphite ring, 6 - secondary water, 7 - melt, 8 - solidified body.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in Fig. 1 and 2, a casting device for suppressing segregation of aluminum alloy ingot components, including crystallizer 1, spindle head 2, heat insulating cap 3, cooling aluminum alloy rod/belt 4, holding conveying mechanism, preheating The mechanism and the speed governing mechanism, and the composition of the cooled aluminum alloy rod/belt 4 is the same as that of the aluminum alloy ingot, and the cross-sectional area of the cooled aluminum alloy rod/belt 4 is 10 to 10000 mm ² ; the starting head 2 is located in the crystallization Directly below the device 1, the heat insulating cap 3 is installed directly above the crystallizer 1, and the cooling water jacket of the crystallizer 1 is in the form of a mosaic graphite ring 5 or a graphite ring 5; the cooling aluminum alloy rod/belt 4 vertical mounting Sandwiched on the clamp transport mechanism, the temperature-lowering aluminum alloy rod/belt 4 is lifted and lowered in the vertical direction by the clamp transport mechanism; before the temperature-lowering aluminum alloy rod/belt 4 is inserted into the melt core in the crystallizer 1, The cooling aluminum alloy rod/belt 4 is preheated by a preheating mechanism, and the preheating temperature is lower than the melt core temperature; the lifting speed of the cooling aluminum alloy rod/belt 4 is regulated by a speed governing mechanism.

Example 1: The ingot was an aluminum alloy containing 4.5 wt% of magnesium.

Step 1: Raise the spindle head 2 into the crystallizer 1, and pass cooling water to the crystallizer 1 until the water outlet hole in the lower part of the crystallizer 1 ejects the secondary water 6;

Step 2: control the aluminum alloy melt to enter the thermal insulation cap 3 through the flow passage, and then enter the crystallizer 1. When the melt 7 forms a green shell in the crystallizer 1, the distillate head 2 is controlled to move down and the casting is started; The time taken for the melt 7 to form the shell in the crystallizer 1 is set to 10 s. After the start of the casting process, the initial downward moving speed of the spindle head 2 is set to 50 mm/min, and is increased to 80 mm/min in 2 minutes;

Step 3: After the casting is carried out for 30 s, the cooling aluminum alloy rod/belt 4 is preheated by a preheating mechanism, and then the clamping transport mechanism is started to cool the cooled aluminum alloy rod/belt 4 into the melt 7 core portion to cool it. And the speed of the cooling aluminum alloy rod/belt 4 is controlled by the speed governing mechanism, and the descending speed is set to 40 mm/min until the end of casting. As shown in Fig. 3, as a graph showing the content variation of magnesium from the edge of the ingot to the core, it can be seen that the degree of segregation of the composition of the aluminum alloy ingot containing 4.5 wt% of magnesium is remarkably lowered.

Example 2: The ingot is an aluminum alloy containing 6.2 wt% of zinc.

Step 1: Raise the spindle head 2 into the crystallizer 1, and pass cooling water into the crystallizer 1 until the water outlet hole in the lower part of the crystallizer 1 ejects the secondary water 6;

Step 2: control the aluminum alloy melt to enter the thermal insulation cap 3 through the flow passage, and then enter the crystallizer 1. When the melt 7 forms a green shell in the crystallizer 1, the distillate head 2 is controlled to move down and the casting is started; The time taken for the melt 7 to form the shell in the crystallizer 1 is set to 10 s. After the start of the casting process, the initial downward moving speed of the spindle head 2 is set to 10 mm/min, and is increased to 25 mm/min in 2 minutes;

Step 3: After the casting is carried out for 30 s, the cooling aluminum alloy rod/belt 4 is preheated by a preheating mechanism, and then the clamping transport mechanism is started to cool the cooled aluminum alloy rod/belt 4 into the melt 7 core portion to cool it. And the speed of the cooling aluminum alloy rod/belt 4 is controlled by the speed governing mechanism, and the descending speed is set to 10 mm/min until the end of casting. As shown in Fig. 4, as a graph showing the content change of zinc element from the edge of the ingot to the core, it can be seen that the degree of segregation of the composition of the aluminum alloy ingot containing 6.2 wt% of zinc is remarkably lowered.

The embodiments of the present invention are not intended to limit the scope of the invention, and the equivalents and modifications of the invention are not included in the scope of the invention.

Claims

A casting device for suppressing segregation of aluminum alloy ingot composition, comprising a crystallizer, a spindle head and a heat preservation cap, the spindle head being located directly below the crystallizer, the heat preservation cap being mounted directly above the crystallizer, and the cooling water jacket of the crystallizer being inlaid Graphite ring or structure without graphite ring; characterized by: further comprising a cooling aluminum alloy rod/belt, a clamping and transporting mechanism, a preheating mechanism and a speed regulating mechanism, and the composition of the cooled aluminum alloy rod/belt and the aluminum alloy casting The components of the ingot are the same; the cooling aluminum alloy rod/belt is vertically clamped on the clamping and transporting mechanism, and the cooling aluminum alloy rod/belt is lifted and lowered in the vertical direction by the clamping and transporting mechanism; /Before inserting the melt core in the crystallizer, preheating the cooled aluminum alloy rod/belt by a preheating mechanism, and the preheating temperature is lower than the temperature of the melt core; the lifting and lowering of the aluminum alloy rod/belt The speed is regulated by a speed governing mechanism.
A casting apparatus for suppressing segregation of an aluminum alloy ingot composition according to claim 1, wherein said temperature-lowering aluminum alloy rod/belt has a cross-sectional area of 10 to 10,000 mm 2 .
A casting method for suppressing segregation of an aluminum alloy ingot composition, comprising the casting apparatus for suppressing segregation of an aluminum alloy ingot composition according to claim 1, comprising the steps of:

Step 1: Raise the spindle head into the crystallizer, and pass cooling water into the crystallizer until the water outlet in the lower part of the crystallizer ejects secondary water;

Step 2: Control the aluminum alloy melt into the thermal insulation cap through the flow passage, and then enter the crystallizer. When the melt forms a blank shell in the crystallizer, control the starter head to move down and start casting;

Step 3: After the casting is carried out for 30 s, the cooling aluminum alloy rod/belt is first preheated by a preheating mechanism, and then the clamping and transport mechanism is started to cool the cooled aluminum alloy rod/belt into the melt core to cool and pass The speed governing mechanism controls the descending speed of the cooling aluminum alloy rod/belt until the end of casting.
A casting method for suppressing segregation of an aluminum alloy ingot composition according to claim 3, wherein in the second step, the time taken for the melt to form the shell in the crystallizer is 5 to 60 s.
A casting method for suppressing segregation of an aluminum alloy ingot composition according to claim 3, wherein in the second step, after the start of casting, the initial downward moving speed of the spindle head is 5 to 50 mm/min, and Increase to 10 ~ 150mm / min within 2 minutes.
A casting method for suppressing segregation of an aluminum alloy ingot composition according to claim 3, wherein in the third step, the descending speed of the lowered aluminum alloy rod/belt is 1 to 50 mm/min.