CN104493122A - Semi-continuous casting method and device for gas pressure mould filling - Google Patents

Abstract

The invention discloses a semi-continuous casting method and device for air pressure filling. The method is to set a sprue between the tundish and the crystallizer, and control the flow rate of the metal melt at the outlet of the sprue to strengthen the metal melt. Convective effect and agitation in the liquid pockets to refine the crystals in the ingot. The device includes a tundish, a diversion groove, a plunger rod, a sprue and a crystallizer. A diversion groove is arranged on one side of the tundish, and a plunger rod is arranged at the interface between the diversion groove and the tundish. The two are connected by a sprue, and a liquid cavity is formed at the outlet of the sprue; the tundish is of a sealed structure, and the top of the tundish is connected with an air pressure control system. The invention can achieve the purpose of making the structure and composition of the ingot uniform, eliminating coarse columnar crystals, forming equiaxed crystals with fine crystal grains, and suppressing the segregation of macroscopic components in the ingot.

Description

A semi-continuous casting method and device for air pressure filling

technical field

The invention relates to the technical field of metal material forming, in particular to a semi-continuous casting method and device for air pressure filling.

Background technique

Semi-continuous casting is an important means of preparing ingots of metal materials, and has been widely used in the field of non-ferrous alloys. However, for some copper alloys with a wide crystallization temperature range (such as copper-nickel-tin alloys, etc.), it is easy to produce coarse columnar crystals and severe macroscopic component segregation during the semi-continuous casting process of large-scale ingots. A large number of production practices have shown that strengthening the melt agitation in the liquid cavity in the mold area during the semi-continuous casting process is an effective way to suppress the segregation of coarse columnar crystals and macroscopic components.

In order to strengthen the melt stirring in the liquid cavity area, some new casting methods and devices have been developed successively on the basis of traditional semi-continuous casting methods at home and abroad. For example, the application with the publication number US 4612970 discloses a continuous casting equipment, including a vibrating mold, a mold lifting platform, a fixed frame and a guiding device, and the vibrating mold is used to strengthen the agitation of the melt, but the leaf springs in the equipment must have appropriate The mechanical parameters to withstand the inertia of the mold components, the technical difficulty is large, difficult to control, and the stirring effect is limited; the application number is 201210143369.9 A casting device and casting method disclosed, using an ultrasonic device for melt stirring, can refine the ingot crystal grains, but the ultrasonic range is limited, and cannot solve the problems of large-scale ingot grain coarseness and component segregation; Japanese Patent Application Publication No. 63-188461 and Japanese Patent Application Publication No. 60-44157 respectively disclose the use of electromagnetic stirring. The casting device has a certain grain refining effect; the continuous casting method and device for manufacturing highly oriented uniform fine grains disclosed in the application number 201310443606. Electromagnetic braking and electromagnetic stirring technologies are applied, but because these methods need to be equipped with electromagnetic coils near the high-temperature melt, not only the coils need to be cooled, but also the power consumption is large, especially the device is complicated and the maintenance is difficult; the application number is JP 0213765 The application disclosed a method and device for adjusting the metal liquid level in the metal continuous casting process. The main principle is to adjust the position of the stop rod according to the result of comparing the required liquid level with the actual measured liquid level. The liquid level is measured with a single Inductive sensor or optical sensor, but this method and device can not guarantee the constant flow rate of molten metal at the outlet, and the flow rate adjustment range is limited; publication number is US 4315538 and US 5279353 The disclosed casting method and device of the application, respectively It uses the weight of the molten metal to stir the molten metal in the liquid cavity. The structure is simple, but the stirring effect is very limited because the pressure generated by gravity is neither constant nor controllable.

It can be seen from the study of strengthening the stirring of the melt in the crystallization zone during the semi-continuous casting process that the above-mentioned prior art has the following deficiencies:

(1) When the method of vibration is adopted, the vibration device is relatively complicated, and the effect of vibration leading to grain refinement is very limited.

(2) When electromagnetic stirring or ultrasonic stirring is used, the structure of the device is complex, the cost of equipment maintenance is high, and the effect of grain refinement is limited, especially for large-scale ingots or alloys with relatively large specific gravity, to achieve ideal stirring As a result, it is necessary to greatly increase the strength of the electromagnetic field or the power of the ultrasonic wave, resulting in a substantial increase in equipment investment costs and a significant increase in technical difficulty.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a semi-continuous casting method of air pressure filling. Equiaxed crystals, the purpose of inhibiting the segregation of macroscopic components in the ingot.

Another object of the present invention is to provide a semi-continuous casting device for air pressure filling for realizing the above method.

The technical solution of the present invention is: a semi-continuous casting method of air pressure filling, by setting a sprue between the tundish and the crystallizer, and controlling the flow rate of the molten metal at the outlet of the sprue, strengthening the flow of the molten metal The convective effect and agitation in the liquid pockets refine the crystals in the ingot.

The flow rate control of the molten metal at the outlet of the sprue is realized by adjusting the gas pressure in the tundish, and the flow rate of the molten metal at the outlet of the sprue and the gas pressure in the tundish satisfy the following relationship:

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; nd</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; Hg</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; P</span>}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}}<span\; class="notranslate">\; ,</span>$

In the formula: v is the flow rate of the molten metal at the outlet of the sprue, P is the gas pressure in the tundish, ρ is the density of the molten metal, g is the acceleration of gravity, H is the liquid level of the tundish and the outlet of the sprue The height difference, D is the diameter of the sprue entrance, d is the opening diameter of the sprue exit, n is the number of openings at the sprue exit.

The gas pressure in the tundish is adjusted in real time through an external air pressure control system.

A pneumatically filled semi-continuous casting device for realizing the above method, including a tundish, a diversion groove, a plunger rod, a sprue and a crystallizer, a diversion groove is arranged on one side of the tundish, and the diversion groove and the A plunger rod is set at the interface of the tundish, the tundish and the crystallizer are connected through a sprue, and a liquid cavity is formed at the outlet of the sprue; the tundish is of a sealed structure, and the top of the tundish is connected with an air pressure control system.

The sprue is a circular tubular flow path, the top of the sprue communicates with the tundish, the bottom of the sprue is located in the crystallizer, the bottom end of the sprue is sealed, and the side wall of the sprue close to the bottom end is opened There are a plurality of openings as sprue outlets, and each opening is arranged obliquely. Through the setting of each opening structure, the metal melt flowing out from the sprue has a multi-directional convection effect on the metal melt in the liquid cavity, thereby intensifying the convection and stirring effect of the metal melt, which is conducive to reducing the temperature gradient in the liquid cavity. At the same time, it intensifies the erosion of the crystallized structure, promotes its shedding and swimming, which is conducive to the formation of equiaxed crystals.

In order to achieve the best convection effect and stirring effect for the metal melt in the liquid cavity, at the outlet of the runner, a plurality of openings are evenly distributed along the circumferential direction of the runner, and the distribution of each opening is inclined downward. There is an included angle of 15-60° with the axis of the sprue.

A weighing sensor is provided at the bottom of the tundish, and the weighing sensor is connected with the air pressure control system. The function of the load cell is to transmit the instantaneous weight change in the tundish to the air pressure control system, which is converted into an instantaneous mass difference by the air pressure control system, and then calculate the instantaneous liquid level difference in the tundish from the instantaneous mass difference.

A supporting frame is arranged on the outer periphery of the sprue, and the tundish and the load cell are both arranged on the supporting frame.

A cooling water channel is provided on the crystallizer, and a traction chuck is provided at the bottom of the crystallizer.

When the above air pressure filling semi-continuous casting method and device are used, by controlling the flow velocity of the molten metal at the outlet of the sprue, the convection effect and stirring effect of the molten metal in the liquid cavity are strengthened, thereby refining the crystals in the ingot. During use, with the progress of the semi-continuous casting process, the liquid level in the tundish is constantly decreasing, that is, H is constantly changing. In order to ensure that the flow rate v of the molten metal at the sprue exit is a constant value, it is necessary to continuously Adjust the gas pressure P in the tundish, the specific method is as follows: when the liquid level in the tundish drops, the gravity sensor transmits the instantaneous change in the weight of the tundish to the air pressure control system, which is converted into an instantaneous mass difference Δm through the air pressure control system, Then calculate the instantaneous liquid level difference ΔH in the tundish from the instantaneous mass difference. Through the relationship between the liquid level difference and the pressure difference ΔP=ρgΔH, the instantaneous pressure change ΔP can be obtained, and then adjust the intermediate level in time through the air pressure controller. The gas pressure P in the bag can ensure the flow rate v of the molten metal at the outlet of the sprue to be a constant value.

In order to strengthen the convection effect of the molten metal in the liquid cavity, the flow velocity v of the molten metal at the outlet of the sprue can also be adjusted by changing the direction and diameter of each opening.

Compared with the prior art, the present invention has the following beneficial effects:

In the air pressure filling semi-continuous casting method and device, a sprue with a special structure is set between the tundish and the mold, so that the metal melt can enter the mold under the joint action of the air pressure control system and the sprue In the liquid cavity, by controlling the flow rate, the copper alloy melt is promoted to form strong convection in the liquid cavity, so as to achieve uniform structure and composition of the ingot, eliminate coarse columnar crystals, form equiaxed crystals with fine grains, and suppress macroscopic The purpose of component segregation. The specific performance is:

1) The flow rate of the metal melt at the outlet of the sprue is controllable, which is easy to achieve uniform temperature distribution in the melt, and promotes the free crystal nuclei, thereby greatly refining the grains of the ingot and suppressing the composition segregation of the ingot.

2) The device and method have a simple principle and a simple device structure, and are easy to transform on a traditional copper alloy semi-continuous casting device, and are also easy to realize automation by setting an air pressure control system and a weighing sensor.

3) The method is particularly suitable for producing copper alloy ingots that are prone to macroscopic component segregation, such as large-scale tin cupronickel.

Description of drawings

Fig. 1 is a schematic structural view of the air-filled semi-continuous casting device.

FIG. 2 is a schematic structural view of the sprue in FIG. 1 .

Fig. 3a is a diagram of the grain morphology of the ingot produced according to the traditional semi-continuous casting process in Example 2.

Fig. 3b is a diagram of the grain morphology of the ingot produced according to the semi-continuous casting method in Example 2.

Fig. 4a is a diagram of the grain morphology of the ingot produced according to the traditional semi-continuous casting process in Example 3.

Fig. 4b is a diagram of the grain morphology of the ingot produced according to the semi-continuous casting method in Example 3.

detailed description

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

This embodiment is a semi-continuous casting method for air pressure filling. By setting a sprue between the tundish and the crystallizer, and controlling the flow rate of the molten metal at the outlet of the sprue, the convection of the molten metal in the liquid cavity is strengthened. effect and agitation to refine the crystals in the ingot.

The flow rate control of the molten metal at the outlet of the sprue is realized by adjusting the gas pressure in the tundish. The flow rate of the molten metal at the outlet of the sprue and the gas pressure in the tundish satisfy the following relationship:

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; nd</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; Hg</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; P</span>}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}}<span\; class="notranslate">\; ,</span>$

In the formula: v is the flow rate of the molten metal at the outlet of the sprue, P is the gas pressure in the tundish, ρ is the density of the molten metal, g is the acceleration of gravity, H is the liquid level of the tundish and the outlet of the sprue The height difference, D is the diameter of the sprue entrance, d is the opening diameter of the sprue exit, n is the number of openings at the sprue exit.

The gas pressure in the tundish is adjusted in real time through an external air pressure control system.

The semi-continuous casting device for air pressure filling used to realize the above method, as shown in Figure 1, includes a tundish 1, a diversion groove 2, a plunger rod 3, a sprue 4 and a crystallizer 5, and one side of the tundish is set A diversion groove, a plunger rod is arranged at the interface between the diversion groove and the tundish, the tundish and the crystallizer are connected through a sprue, and a liquid cavity 6 is formed at the outlet of the sprue; the tundish is a sealed structure, and The air pressure control system 7 is externally connected to the top of the tundish. Wherein, by opening the plunger rod, the molten metal in the diversion groove can flow into the tundish, and by closing the plunger rod, the molten metal in the diversion groove can be prevented from flowing into the tundish.

As shown in Figure 2, the sprue is a circular tubular runner, the top of the sprue communicates with the tundish, the bottom of the sprue is located in the crystallizer, the bottom end of the sprue is sealed, and the sprue close to the bottom end The side wall is provided with a plurality of openings 4-1 as sprue outlets, and each opening is arranged obliquely. Through the setting of each opening structure, the metal melt flowing out from the sprue has a multi-directional convection effect on the metal melt in the liquid cavity, thereby intensifying the convection and stirring effect of the metal melt, which is conducive to reducing the temperature gradient in the liquid cavity. At the same time, it intensifies the erosion of the crystallized structure, promotes its shedding and swimming, which is conducive to the formation of equiaxed crystals.

In order to achieve the best convection effect and stirring effect for the metal melt in the liquid cavity, at the outlet of the sprue, multiple openings are evenly distributed along the circumferential direction of the sprue, and the distribution of each opening is inclined downward. The axes of the runners form an included angle θ of 15-60°.

A weighing sensor 8 is also arranged at the bottom of the tundish, and the weighing sensor is connected with the air pressure control system. The function of the load cell is to transmit the instantaneous weight change in the tundish to the air pressure control system, which is converted into an instantaneous mass difference by the air pressure control system, and then calculate the instantaneous liquid level difference in the tundish from the instantaneous mass difference.

A supporting frame 9 is arranged on the periphery of the sprue, and the tundish and the load cell are all arranged on the supporting frame.

A cooling water channel 10 is provided on the crystallizer, and a traction chuck 11 is provided at the bottom of the crystallizer.

When the above air pressure filling semi-continuous casting method and device are used, by controlling the flow velocity of the molten metal at the outlet of the sprue, the convection effect and stirring effect of the molten metal in the liquid cavity are strengthened, thereby refining the crystals in the ingot. During use, with the progress of the semi-continuous casting process, the liquid level in the tundish is constantly decreasing, that is, H is constantly changing. In order to ensure that the flow rate v of the molten metal at the sprue exit is a constant value, it is necessary to continuously Adjust the gas pressure P in the tundish, the specific method is as follows: when the liquid level in the tundish drops, the gravity sensor transmits the instantaneous change in the weight of the tundish to the air pressure control system, which is converted into an instantaneous mass difference Δm through the air pressure control system, Then calculate the instantaneous liquid level difference ΔH in the tundish from the instantaneous mass difference. Through the relationship between the liquid level difference and the pressure difference ΔP=ρgΔH, the instantaneous pressure change ΔP can be obtained, and then adjust the intermediate level in time through the air pressure controller. The gas pressure P in the bag can ensure the flow rate v of the molten metal at the outlet of the sprue to be a constant value.

In order to strengthen the convection effect of the molten metal in the liquid cavity, the flow velocity v of the molten metal at the outlet of the sprue can also be adjusted by changing the direction and diameter of each opening.

Example 2

In this embodiment, the copper-nickel-tin alloy is a solid solution alloy with a wide crystallization temperature. During slow cooling, thick dendrites tend to appear in the ingot structure, and the Sn solute tends to move outward along the dendrites. A reverse segregation of tin is formed.

The first: utilize the semi-continuous casting method and device of embodiment 1, take following process:

(1) The alloy composition is Cu-15Ni-8Sn. The ingot specification is φ180mm.

(2) The technological parameters in the casting process are as follows: the pouring temperature is 1250-1260°C, the ingot pulling speed is 1.6mms/s, the cooling water pressure is 0.06MPa, and the pressurized gas is argon.

(3) The diameter D of the inlet of the sprue is 3.7mm, and the diameter d of each opening at the outlet of the sprue is 1.5mm. There are 6 openings in total. The angle θ between the center line of the sprue and the center line of each opening is 60°. According to this scheme, the velocity v at the outlet of the draft tube is about 2400 times the pulling velocity of the ingot. Therefore, it has a strong stirring effect on the molten metal in the liquid cavity.

Second: use the traditional semi-continuous casting process to produce the same alloy composition and size.

The ingots obtained by two different processes were analyzed, and the results are as follows:

The appearance of the ingot obtained by the first casting process is good, the grains are small and all equiaxed, as shown in Figure 3b (Figure 3a shows the grain morphology of the ingot obtained by the second casting process) Compared with the two, the grain size of the ingot obtained by the first casting process is reduced from 1.54-6.23mm in the traditional semi-continuous casting to 0.48-1.15mm, and the reverse segregation of tin in the ingot is also basically eliminated (see the comparison results for details). Table 1).

Table 1 Energy spectrum analysis of Cu-15Ni-8Sn alloy as-cast macroscopic composition (Sn)

Example 3

In this embodiment, the copper-nickel-tin alloy is a solid solution alloy with a wide crystallization temperature. During slow cooling, thick dendrites tend to appear in the ingot structure, and the Sn solute tends to move outward along the dendrites. A reverse segregation of tin is formed.

The first: utilize the semi-continuous casting method and device of embodiment 1, take following process:

(1) The alloy composition is Cu-15Ni-8Sn-0.35Ti. The ingot specification is φ350mm.

(2) The technological parameters in the casting process are as follows: the pouring temperature is 1250-1260°C, the ingot pulling speed is 1.1mms/s, the cooling water pressure is 0.1MPa, and the pressurized gas is argon.

(3) The diameter D of the inlet of the sprue is 9.8mm, the diameter d of each opening at the outlet of the sprue is 4mm, and there are 6 openings in total, and the included angle θ between the center line of the sprue and the center line of each opening is 15 °. According to this scheme, the velocity v at the outlet of the draft tube is about 1280 times the pulling velocity of the ingot. Therefore, it has a strong stirring effect on the molten metal in the liquid cavity.

Second: use the traditional semi-continuous casting process to produce the same alloy composition and size.

The ingots obtained by two different processes were analyzed, and the results are as follows:

The appearance of the ingot obtained by the first casting process is good, the grains are fine and all equiaxed, as shown in Figure 4b (Figure 4a shows the grain morphology of the ingot obtained by the second casting process) Compared with the two, the grain size of the ingot obtained by the first casting process is reduced from 1.60-6.35mm in the traditional semi-continuous casting to 0.51-1.27mm, and the reverse segregation of tin in the ingot is also basically eliminated (see the comparison results for details). Table 2).

Table 2 Energy spectrum analysis of Cu-15Ni-8Sn-0.35Ti alloy as-cast macroscopic composition (Sn)

As mentioned above, the present invention can be better realized. The above-mentioned embodiment is only a preferred embodiment of the present invention, and is not used to limit the scope of the present invention; Covered by the scope of protection required by the claims of the present invention.

Claims (9)

1. an air pressure fills the semi-continuous casting method of type, it is characterized in that, water runner by arranging between tundish and crystallizer, and control the flow velocity watering runner exit place metal bath, the convection effects of reinforced metal melt in liquid cave and stirring action, thus the crystal in refinement ingot casting.

2. a kind of air pressure fills the semi-continuous casting method of type according to claim 1, it is characterized in that, the described flow control watering runner exit place metal bath is by regulating the gas pressure in tundish to realize, and waters between the gas pressure in the flow velocity of runner exit place metal bath and tundish and meets following relational expression:

$v=\frac{D^2}{{\mathrm{nd}}^2}\sqrt{2\mathrm{Hg}+\frac{2P}{\mathrm{\&rho;}}},$

In formula: v is the flow velocity watering runner exit place metal bath, P is the gas pressure in tundish, ρ is the density of molten metal, g is acceleration of gravity, H is the liquid level of tundish and the difference in height of watering runner exit place, D is the diameter watering flow passage entry, and d is the opening diameter watering runner exit place, and n is the open amount of watering runner exit place.

3. a kind of air pressure fills the semi-continuous casting method of type according to claim 2, it is characterized in that, the gas pressure in described tundish is regulated in real time by external pneumatic control system.

4. an air pressure fills the semi-continuous casting device of type, it is characterized in that, comprise tundish, guiding gutter, plunger rod, water runner and crystallizer, tundish side arranges guiding gutter, the interface of guiding gutter and tundish arranges plunger rod, be connected by watering runner between tundish with crystallizer, the exit of watering runner forms liquid cave; Tundish is sealed construction, and tundish top external gas pressure control system.

5. a kind of air pressure fills the semi-continuous casting device of type according to claim 4, it is characterized in that, the described runner that waters is circular tube shaped runner, the top of watering runner communicates with tundish, the bottom of watering runner is positioned at crystallizer, watering the bottom end face sealing of runner, watering near bottom end face multiple openings runner sidewall had as watering runner exit, each opening is obliquely installed.

6. a kind of air pressure fills the semi-continuous casting device of type according to claim 5, it is characterized in that, described in water runner exit place, multiple opening is uniformly distributed along the circumferencial direction watering runner, each aperture distribution is downward-sloping, and the center line of each opening becomes the angle of 15 ~ 60 ° with between the axis watering runner.

7. a kind of air pressure fills the semi-continuous casting device of type according to claim 4, it is characterized in that, described tundish bottom is provided with LOAD CELLS, and LOAD CELLS is connected with pneumatic control system.

8. a kind of air pressure fills the semi-continuous casting device of type according to claim 4, it is characterized in that, described in water runner periphery and be provided with bracing frame, tundish and LOAD CELLS are all located on bracing frame.

9. a kind of air pressure fills the semi-continuous casting device of type according to claim 4, it is characterized in that, described crystallizer is provided with cooling water channel, and crystalliser feet is provided with traction chuck.