Vacuum constant-temperature semi-continuous casting system and method for beryllium-copper alloy ingot blank

Abstract

The invention provides a vacuum constant-temperature semi-continuous casting system and method for a beryllium-copper alloy ingot blank, and relates to the technical field of copper alloy casting. The casting system comprises a vacuum furnace, a launder, a crystallizer, a vertical continuous casting dummy ingot mechanism and a heat preservation bag capable of achieving on-line heating and heat preservation functions. The beryllium-copper alloy molten metal is obtained through smelting of a vacuum induction furnace, part of the obtained beryllium-copper alloy molten metal is poured into a launder and drained into a heat preservation bag through the launder, a preset number of beryllium-copper alloy molten metal is stored in the heat preservation bag, and a crystallizer is placed below the heat preservation bag; and a plug rod flow control device is adopted to control the flow of the beryllium copper alloy molten metal flowing into the crystallizer. Constant-temperature casting is achieved, the appearance quality of a cast ingot is good, and the consistency of the internal structure of an ingot blank is better; the chemical component uniformity of the ingot blank is improved, and after the ingot blank is processed, the performance stability of a finished product is also greatly improved; the metal burning loss is reduced, the material transfer temperature is reduced, and the production cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of copper alloy casting, and particularly relates to a vacuum constant temperature semi-continuous casting system and method for beryllium copper alloy ingots. Background Art

[0002] Beryllium copper alloy, also known as beryllium bronze, is the only non-ferrous alloy with good combination of mechanical properties, physical properties, chemical properties and corrosion resistance. It has the characteristics of high strength, high hardness, high electrical conductivity, high elasticity, wear resistance, fatigue resistance, corrosion resistance and small elastic hysteresis. It also has good casting performance, non-magnetic property and no spark discharge performance during impact. Therefore, it is known as the "king of elasticity" in copper alloys. Due to its good comprehensive properties, it is widely used in the fields of electronics, telecommunications, computers, mobile phones and precision instruments, as well as military industries such as aviation, aerospace and weapons. It is a strategic material for the development of science and technology and the construction of national defense modernization.

[0003] At present, the commonly used production method for beryllium copper alloy ingots is vacuum / non-vacuum melting + semi-continuous casting. During the casting process, the casting temperature is a very critical parameter, and the stability of the casting temperature directly determines the consistency of the internal structure of the ingot; and the Be element in the beryllium copper alloy is extremely easy to oxidize and burn out, and the stability of the casting temperature also determines the uniformity of the Be element in the ingot. Whether it is non-vacuum semi-continuous casting or vacuum semi-continuous casting, generally the methods of tundish drainage casting or furnace head box flow transfer casting are adopted. However, in this casting mode, there is a large and uncontrollable temperature drop problem of the molten metal in the tundish or furnace head box during the casting process. Therefore, the casting temperature is unstable, which easily causes defects in the ingot and affects the internal structure of the ingot. At the same time, it will also cause a large deviation in the Be content at the head and tail of the ingot blank and poor compositional consistency.

[0004] Figure 1 、 Figure 2 respectively show the commonly used production systems and method flows of the existing beryllium copper alloy ingots. After the beryllium copper alloy is melted in the furnace and the composition is adjusted to be qualified, part of the molten metal is poured into the tundish or furnace head box. A certain amount of molten metal is stored in the tundish or furnace head box. The mold is placed below the tundish or furnace head box, and a flow control device is used to control the flow rate of the molten metal flowing into the mold. After the molten metal flows into the mold, the vertical continuous casting dummy bar mechanism starts to work and enters the casting state. As the casting progresses, it is necessary to intermittently supplement the molten metal from the furnace into the tundish or furnace head box to avoid casting failure caused by interruption of the flow and excessive temperature drop.

[0005] The above-mentioned existing technologies have the following disadvantages:

[0006] 1. During the casting process, the molten metal in the tundish is inevitably affected by the external environment and causes a temperature drop problem, and it is necessary to rely on raising the temperature of the molten metal in the furnace for compensation;

[0007] 2. The compensation temperature is uncontrollable, resulting in the casting temperature fluctuating, poor matching with parameters such as drawing speed and cooling intensity, leading to unstable ingot quality and easy generation of defects.

[0008] 3. At the same time, in order to reduce the temperature drop, the temperature in the furnace needs to be raised, generally controlled at the charge transfer temperature in the furnace of 1300 - 1380 °C, resulting in large Be loss and a deviation of up to 0.1% in the Be content at the head and tail of the ingot blank. SUMMARY OF THE INVENTION

[0009] In view of this, the present invention provides a vacuum constant-temperature semi-continuous casting system for beryllium copper alloy ingot blanks, including: a vacuum furnace, a launder, a mold, and a vertical continuous casting dummy bar mechanism; characterized in that the system further includes a thermal insulation ladle capable of realizing the function of on-line heating and heat preservation; the beryllium copper alloy metal liquid is obtained by melting in a vacuum induction furnace, and part of the obtained beryllium copper alloy metal liquid is poured into the launder and drained through the launder into the thermal insulation ladle, and a preset amount of beryllium copper alloy molten metal is stored in the thermal insulation ladle. The mold is placed below the thermal insulation ladle, and a stopper rod flow control device is used to control the flow rate of the beryllium copper alloy metal liquid flowing into the mold.

[0010] Further, the thermal insulation ladle includes: an iron shell, an induction coil, a graphite crucible, a temperature control unit for beryllium copper alloy metal liquid, and a lining filler; wherein, the iron shell is the shell of the thermal insulation ladle; the graphite crucible serves as the furnace lining; the lining filler is filled between the iron shell and the graphite crucible for heat preservation and heat insulation; the induction coil is used to on-line heat and keep warm the beryllium copper alloy metal liquid in the ladle; the temperature control unit includes: a temperature measuring component and a temperature control component; wherein,

[0011] The temperature measuring component is used to measure the temperature of the beryllium copper alloy metal liquid in the thermal insulation ladle;

[0012] The temperature control component is used to compare the temperature of the beryllium copper alloy metal liquid measured by the temperature measuring component with a preset temperature. When the temperature of the beryllium copper alloy metal liquid is less than the preset temperature, the heating power of the induction coil is controlled according to the difference between the temperature of the beryllium copper alloy metal liquid and the preset temperature.

[0013] Further, an inert gas is introduced into the thermal insulation ladle to keep the pressure in the thermal insulation ladle at a preset first positive value.

[0014] Further, the inert gas is argon or nitrogen.

[0015] Further, a water-cooled cable is connected to the induction coil to provide an electrical connection between the induction coil and the power supply.

[0016] Further, after the beryllium copper alloy metal liquid flows into the mold, the vertical continuous casting dummy bar mechanism starts to work. As the casting progresses, the beryllium copper alloy metal liquid is intermittently replenished from the vacuum furnace into the thermal insulation ladle through the launder.

[0017] The present invention also provides a vacuum isothermal semi - continuous casting method for beryllium copper alloy ingot blanks using the casting system as described above, including:

[0018] Step 1, after the refining of the beryllium copper alloy molten metal in the vacuum furnace is completed, the vacuum degree in the furnace is 5 - 10 Pa, and the temperature of the beryllium copper alloy molten metal is 1150 - 1200 °C;

[0019] Step 2, the convection chute is heated and baked using a baking device, and the temperature after baking is 1000 - 1200 °C. The baked chute is placed in the chute chamber;

[0020] Step 3, the vacuum furnace and the chute chamber are simultaneously filled with inert gas to a preset first positive pressure; the set temperature of the heat - preservation ladle is set to the preset temperature of 1160 °C, and inert gas is introduced into the heat - preservation ladle to the preset first positive pressure;

[0021] Step 4, open the gate valve, tilt the vacuum furnace body, and the beryllium copper alloy molten metal is transferred from the vacuum furnace into the heat - preservation ladle through the chute;

[0022] Step 5, the temperature control component in the heat - preservation ladle compares the temperature of the beryllium copper alloy molten metal measured by the temperature - measuring component with the preset temperature. When the temperature of the beryllium copper alloy molten metal in the heat - preservation ladle is lower than the preset temperature, the heating power of the induction coil is controlled according to the difference between the temperature of the beryllium copper alloy molten metal and the preset temperature, and the temperature of the beryllium copper alloy molten metal in the heat - preservation ladle is raised to the preset temperature;

[0023] Step 6, start the stopper rod flow - control device to start casting. As the casting progresses, the ingot blank is continuously pulled out from the mold.

[0024] Further, in Step 5, the heating power of the induction coil is 0 - 600 Kw.

[0025] Further, in Step 6, the entire casting process takes 1.5 h, and through real - time monitoring, the temperature of the molten metal in the heat - preservation ladle remains stable at 1160 ± 2 °C throughout the entire casting process 。

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] 1. It realizes isothermal casting, ensures better matching of the casting process, has good appearance quality of the ingot, significantly reduces the probability of defects, and has better internal tissue consistency of the ingot blank;

[0028] 2. It improves the chemical composition uniformity of the ingot blank. The Be content deviation between the head and the tail of the ingot blank is reduced to less than 0.02%, and after the ingot blank is processed, the performance stability of the finished product is also greatly improved;

[0029] 3. It reduces metal burning loss, reduces the transfer temperature, and saves more than 2.5 million yuan in production costs such as power consumption and raw materials every year. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the specific embodiments of the present invention, the following will briefly introduce the drawings required for use in the description of the specific embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 is a schematic diagram of a commonly used production system for beryllium copper alloy ingot blanks in the prior art;

[0032] Figure 2 is a flowchart of a commonly used production method for beryllium copper alloy ingot blanks in the prior art;

[0033] Figure 3 is a schematic diagram of a commonly used production system for beryllium copper alloy ingot blanks of the present invention;

[0034] Figure 4 is a flowchart of a commonly used production method for beryllium copper alloy ingot blanks of the present invention;

[0035] Figure 5 is a macro metallographic photograph of an ingot in isothermal casting in Example 1 of the present invention;

[0036] Figure 6 is a macro metallographic photograph of an ingot in Comparative Example 2 of the present invention. SPECIFIC EMBODIMENTS

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, rather than all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0038] The present invention has improved the Figure 1 , Figure 2 shown production system and production method: an inert gas protected heat preservation ladle is added below the launder, and the molten metal originally stored in the launder is changed to be stored in the heat preservation ladle. There is a certain temperature drop when the molten metal enters the heat preservation ladle from the furnace through the launder, but semi-continuous casting is carried out simultaneously. Therefore, the temperature must be rapidly increased to ensure isothermal casting.

[0039] The heat preservation ladle consists of an iron shell, an induction coil, a water-cooled cable, a graphite crucible, a temperature measuring thermocouple, a lining filler, etc.

[0040] The heat preservation ladle can realize the function of online heating and heat preservation. The heat preservation ladle uses an induction coil for online heating, with a heating power of 0 - 600KW. The furnace lining uses a graphite crucible with fast heat conduction. The induction heating speed is fast and the efficiency is high, which can quickly heat and keep warm the molten metal entering the heat preservation ladle. At the same time, the graphite crucible has a good heat preservation effect, thus realizing constant-temperature casting.

[0041] The heating method of the heat preservation ladle can also adopt methods such as silicon carbide rods or resistance wires, but this heating method is slow and requires a long time, and it cannot achieve rapid temperature rise and cannot meet the ability of constant-temperature casting.

[0042] During the heating process of the heat preservation ladle, inert gases such as argon or nitrogen can be introduced, and the flow rate is controlled at 15 - 35l / min, with a slightly positive pressure (2 - 4Kpa).

[0043] Such as Figure 3 、 Figure 4 As shown in

[0044] The heat preservation ladle can realize the function of online heating and heat preservation, which can heat and keep warm the molten metal entering the heat preservation ladle, thus realizing constant-temperature casting.

[0045] The heat preservation ladle is composed of an iron shell, an induction coil, a water-cooled cable, a graphite crucible, a temperature-measuring thermocouple, a lining filler, etc.

[0046] The heat preservation ladle can realize the function of online heating and heat preservation. The heat preservation ladle uses an induction coil for online heating, with a heating power of 0 - 600KW. The furnace lining uses a graphite crucible with fast heat conduction. The induction heating speed is fast and the efficiency is high, which can quickly heat and keep warm the molten metal entering the heat preservation ladle, thus realizing constant-temperature casting.

[0047] Example 1 (Heat preservation ladle casting)

[0048] ① After the molten metal in the vacuum furnace is refined, the vacuum degree in the furnace is 5 - 10Pa, the temperature of the molten metal is 1150 - 1200℃, the convection chute is heated and baked by a baking device, and the temperature after baking is 1000 - 1200℃. The chute is placed in the chute chamber, and inert gas is filled into the melting chamber and the chute chamber to a slightly positive pressure. The gate valve is opened, and after the chute is in place, the furnace body can be tilted and the molten metal can be discharged.

[0049] ② The heat preservation ladle is set to a process temperature of 1160℃, and argon or nitrogen is passed through, such as Figure 3The molten metal shown is transferred from the vacuum furnace into the holding ladle through a launder. The heating power of the holding ladle is 0 - 600 Kw. Start the stopper rod flow control device to start casting. As casting progresses, the ingot billet is continuously drawn out from the mold. The entire casting process takes 1.5 h. Through real-time monitoring of the temperature of the molten metal in the holding ladle, the entire casting process is always stable at 1160 ± 2 °C.

[0050] ③ The surface of the ingot is smooth, without defects such as inclusions and porosity. The average grain size is about 3 mm, and the morphology is mostly equiaxed grains, accounting for more than 50%. See the macro metallographic photo of the ingot Figure 5 。

[0051] ④ By drilling chip samples from the head and tail of the ingot billet to detect the chemical composition, the chemical composition consistency of the ingot is significantly improved. The deviation of Be content between the head and tail of the ingot is 0.01%, as shown in Table 1.

[0052] Table 1 Chemical composition of the ingot Wt%

[0053] Sampling site Be Ni Fe Al Si Pb Head of ingot 1.98 0.32 0.038 0.012 0.041 0.001 Tail of ingot 1.97 0.32 0.034 0.012 0.041 0.001

[0054] Comparative Example 2 (Original launder / furnace head box casting)

[0055] ① After the molten metal in the vacuum furnace is refined, the vacuum degree in the furnace is 5 - 10 Pa, and the temperature of the molten metal is 1300 - 1380 °C. The launder is heated and baked using a baking device. After baking, the temperature is 1000 - 1200 °C. Place the launder in the launder chamber, and both the melting chamber and the launder chamber are filled with inert gas to a slightly positive pressure. Open the gate valve. After the launder is in place, the furnace body can be tilted and the molten metal can be discharged.

[0056] ② As Figure 2 shown, the molten metal flows from the vacuum furnace into the launder. When the molten metal in the launder reaches 200 - 500 kg, start the stopper rod flow control device to start casting. As casting progresses, the ingot billet is continuously drawn out from the mold. The entire casting process takes 1.5 h.

[0057] ③ The surface of the ingot has inclusion defects. The average grain size is about 7 mm, and the morphology is mostly columnar grains, accounting for more than 50%. See the macro metallographic photo of the ingot produced in the comparative example Figure 6 。

[0058] ④ By drilling chip samples from the head and tail of the ingot billet to detect the chemical composition, the chemical composition consistency of the ingot is significantly improved. The deviation of Be content between the head and tail of the ingot is 0.09%, as shown in Table 2.

[0059] Table 2 Chemical composition of the ingot Wt%

[0060] Sampling site Be Ni Fe Al Si Pb Head of ingot 1.96 0.31 0.041 0.022 0.054 0.001 Tail of ingot 1.87 0.31 0.041 0.022 0.054 0.001

[0061] As can be seen from the above introduction, the present invention realizes isothermal casting by adding an inert gas protected intermediate tundish to heat up and compensate the molten metal flowing into the tundish from the launder and keep it at a constant temperature, thus solving the problem of temperature drop. Further, the process parameters of the entire casting process are more matched, and the consistency of the ingot structure is better. Among them, the proportions of dendrites, columnar crystals, and mixed crystals are all reduced, the equiaxed crystals are significantly increased, and the internal defects such as porosity are also greatly reduced, significantly improving the quality of beryllium copper ingots. Since isothermal casting can be realized and there is no need to raise the temperature of the molten metal in the furnace for temperature compensation, and with the protection of inert gas in the tundish, the burning loss of Be during the entire casting process is significantly reduced, the chemical composition uniformity of the entire ingot is good, the Be content deviation between the head and tail of the ingot is ≤0.02%, and after the ingot is processed, the performance stability of the finished product is also significantly improved.

[0062] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A vacuum constant temperature semi - continuous casting system for beryllium copper alloy ingots, the system comprising: Vacuum furnace, launder, mold, and vertical continuous casting dummy bar mechanism; characterized in that the system further includes a tundish capable of realizing the function of online heating and heat preservation; the beryllium copper alloy molten metal is obtained by melting in a vacuum induction furnace, and a part of the obtained beryllium copper alloy molten metal is poured into the launder and drained through the launder into the tundish, and a preset amount of beryllium copper alloy molten metal is stored in the tundish. The mold is placed below the tundish, and a stopper rod flow control device is used to control the flow rate of the beryllium copper alloy molten metal flowing into the mold.

2. The casting system according to claim 1, wherein, The tundish includes: an iron shell, an induction coil, a graphite crucible, a temperature control unit for beryllium copper alloy molten metal, and a lining filler; wherein, the iron shell is the tundish shell; the graphite crucible serves as the furnace lining; the lining filler is filled between the iron shell and the graphite crucible for heat preservation and heat insulation; the induction coil is used to heat and keep the beryllium copper alloy molten metal in the tundish at a constant temperature; the temperature control unit includes: a temperature measuring component and a temperature control component; wherein, The temperature measuring component is used to measure the temperature of the beryllium copper alloy molten metal in the tundish; The temperature control component is used to compare the temperature of the beryllium copper alloy molten metal measured by the temperature measuring component with a preset temperature. When the temperature of the beryllium copper alloy molten metal is lower than the preset temperature, the heating power of the induction coil is controlled according to the difference between the temperature of the beryllium copper alloy molten metal and the preset temperature.

3. The casting system according to claim 2, wherein An inert gas is introduced into the tundish to keep the pressure in the tundish at a preset first positive value.

4. The casting system according to claim 3, characterized in that, The inert gas is argon or nitrogen.

5. The casting system according to claim 2, wherein, A water-cooled cable is connected to the induction coil to provide an electrical connection between the induction coil and the power supply.

6. The casting system according to claim 1, wherein, After the beryllium copper alloy molten metal flows into the mold, the vertical continuous casting dummy bar mechanism starts to work. As the casting progresses, the beryllium copper alloy molten metal is intermittently replenished from the vacuum furnace into the tundish through the launder.

7. A vacuum isothermal semi - continuous casting method for beryllium - copper alloy ingots using the casting system according to any one of claims 1 - 6, characterized in that, The method includes: Step 1, the refining of the beryllium copper alloy molten metal in the vacuum furnace is completed, the vacuum degree in the furnace is 5 - 10 Pa, and the temperature of the beryllium copper alloy molten metal is 1150 - 1200 °C; Step 2, the launder is heated and baked by a baking device, and the temperature after baking is 1000 - 1200 °C. The baked launder is placed in the launder chamber; Step 3, the vacuum furnace and the launder chamber are simultaneously filled with an inert gas to a preset first positive value pressure; the set temperature of the tundish is set to a preset temperature of 1160 °C, and an inert gas is introduced into the tundish to a preset first positive value pressure; Step 4, the gate valve is opened, the vacuum furnace body is tilted, and the beryllium copper alloy molten metal is transferred from the vacuum furnace into the tundish through the launder; Step 5, the temperature control component in the tundish compares the temperature of the beryllium copper alloy molten metal measured by the temperature measuring component with the preset temperature. When the temperature of the beryllium copper alloy molten metal in the tundish is lower than the preset temperature, the heating power of the induction coil is controlled according to the difference between the temperature of the beryllium copper alloy molten metal and the preset temperature, and the temperature of the beryllium copper alloy molten metal in the tundish is raised to the preset temperature; Step 6, the stopper rod flow control device is started to start casting. As the casting progresses, the ingot billet is continuously pulled out from the mold.

8. The method according to claim 7, wherein In Step 5, the heating power of the induction coil is 0 - 600 Kw.

9. The method according to claim 7, wherein In Step 6, the entire casting process takes 1.5 h, and the temperature of the molten metal in the tundish is kept stable at 1160 ± 2 °C throughout the entire casting process by real-time monitoring.

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