CN115519102A - Casting method of low segregation fine crystal ingot of high melting point metal - Google Patents
Casting method of low segregation fine crystal ingot of high melting point metal Download PDFInfo
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- CN115519102A CN115519102A CN202211152357.2A CN202211152357A CN115519102A CN 115519102 A CN115519102 A CN 115519102A CN 202211152357 A CN202211152357 A CN 202211152357A CN 115519102 A CN115519102 A CN 115519102A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/20—Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D15/00—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/02—Use of electric or magnetic effects
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D37/00—Controlling or regulating the pouring of molten metal from a casting melt-holding vessel
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Abstract
The application relates to the technical field of ingot casting, in particular to a casting method of a low segregation fine crystal ingot of high-melting-point metal, which comprises the following steps of S1: melting and preserving heat; s2: adjusting the height and starting rotation; s3: conducting drainage and performing temperature equalization by spinning; s4: lifting a rod and continuously casting: after the casting is started, the lifting rod keeps rotating while slowly rising, and the rotating moment M of the metal rod is continuously measured; if M is larger than or equal to F, the metal rod is lifted, the PLC controls the crucible to continuously tilt, the tilting degree is matched with the height of the lifting rod, and the metal melt in the crucible flows into the mold along the metal rod, so that the amount of the metal melt in the mold is kept consistent until the ingot casting is finished; s5: arc starting and temperature supplementing; the designed casting method of the low segregation fine crystal ingot of the high melting point metal improves the temperature and the uniformity of components in the ingot casting process through the drainage, the heat conduction and the stirring of the metal rod, and can obtain the low segregation ingot mainly comprising fine isometric crystals.
Description
Technical Field
The application relates to the technical field of ingot casting, in particular to a casting method of a low segregation fine crystal ingot of high-melting-point metal.
Background
At present, aiming at materials such as special alloy, rare and noble metals and the like, a casting method is still adopted to produce a plurality of cast ingots; ingots are made by pouring molten metal into permanent or reusable molds; the ingot can be further machined into a variety of new shapes; the cast ingot is an as-cast structure, and metal grows up in a dendritic crystal mode in a stable state in the traditional casting, and composition segregation and coarse columnar crystals are easy to appear in the solidification process.
Segregation is mainly caused by redistribution of solute in the solidification process of the alloy, columnar crystal solidification segregation is obvious, and fine equiaxed crystal solidification can improve segregation. Keeping the unsolidified melt low and rapidly solidifying in a controlled state, and with the assistance of mechanical stirring, the segregation in the solidification structure can be made extremely low.
The patent document with the application number of 201711302710.X discloses a melt electromagnetic stirring type low-pressure casting device and a casting method, wherein the device comprises a melting furnace, a crucible, a sealing ring, an air inlet, exhaust and pressure signal interface, a cover plate, a vacuum air source and an electric control pneumatic stop valve; the device also comprises a side strong magnet, a bottom strong magnet and a variable frequency power supply; the side strong magnets are positioned around the melting furnace, the bottom strong magnet is the bottom of the melting furnace, and the two strong magnets are electrically connected with the variable frequency power supply; the side strong magnet and the bottom strong magnet adopt coil structures.
In view of the above related technologies, the inventor thinks that the designed melt electromagnetic stirring type low-pressure casting device and casting method drive the metal liquid in the melting furnace to move by adopting an electromagnetic stirring manner, but are limited by the skin effect of induced current, the penetration depth of the electromagnetic stirring is limited, the action on the metal liquid in the middle area of the melting furnace is very small, the temperature equalizing effect of the metal liquid in the middle area of the melting furnace is poor, and the forming quality of an ingot is affected.
Disclosure of Invention
In order to improve the forming quality of the cast ingot, the application provides a casting method of a low segregation fine crystal ingot of high-melting point metal, which adopts the following technical scheme:
a method for casting low segregation fine crystal ingot of high melting point metal includes
S1: melting and heat preservation: heating the solid metal to be completely melted to form a metal melt, and keeping the temperature of the metal melt above the melting point all the time;
s2: height adjustment and starting rotation: a metal rod is coaxially arranged above the bottom wall of a forming cavity of the die by 5-20mm and is driven to rotate; wherein the material of the metal rod is the same as that of the metal melt, and the metal rod is coaxial with the die;
s3: drainage and cloth rotating temperature equalization: enabling the metal melt prepared in the step S1 to flow into a forming cavity of a die along a metal rod until the lower end of the metal rod is immersed into the metal melt in the die by 5-15mm, and driving the metal melt in the die to flow in a rotating mode;
s4: lifting a rod and continuously casting: setting a lifting lever moment F and continuously measuring the rotation moment M of the metal rod, if M is less than F, enabling the metal rod to continuously rotate while ascending at a basic speed of 1-3 mm/s; and if M is larger than or equal to F, lifting the metal rod by 5-10mm, controlling the metal melt prepared in the step S1 to continuously flow into the mold along the metal rod at a matching speed in the process so as to keep the quantity of the metal melt in the mold consistent all the time, and enabling the metal rod to extend into the metal melt all the time until the ingot casting is finished.
By adopting the technical scheme, the solid metal is heated until the fixed metal is completely melted to form a metal melt, and then the temperature of the metal melt is kept above the melting point all the time so that the metal melt is kept in a liquid state; a metal rod is coaxially arranged above the bottom wall of the mold by 5-20mm and is driven to rotate; enabling the metal melt prepared in the step S1 to flow into a forming cavity of a mold along a metal rod; part of heat in the process that the metal melt flows into the die along the metal rod is transferred to the outside through the metal rod, the rotating metal rod breaks primary dendrites in the metal melt in the die in a strong stirring mode, a large amount of nucleation is provided through stirring to generate fine isometric crystals, and alloy components in the metal melt can be homogenized through strong stirring to reduce segregation; meanwhile, when the metal rod rotates, the metal melt with higher temperature is thrown to a position close to the wall of the inner cavity of the mold due to lower viscosity, the cooling capacity of the position close to the wall of the inner cavity of the mold is strong, the metal melt with lower temperature falls to a position close to the center of the mold due to higher viscosity, the cooling capacity of the position close to the center of the mold is weak, and the difference of the cooling capacities of the central area and the edge area in the horizontal direction is reduced under the rotary distribution of the metal rod; meanwhile, the metal rod plays a role in heat dissipation of the metal melt in the middle area of a part of the die, so that the cooling speed difference of the metal melt in the middle area and the metal melt in the edge area is further reduced; setting a lifting rod moment F, continuously measuring the rotation moment M of the metal rod in the rotation process of the metal rod, when the solidification structure in the central area of the mold is close to the end part of the metal rod, obviously increasing the rotation moment M of the metal rod, if the rotation moment M of the metal rod is smaller than the lifting set lifting rod moment F, enabling the metal rod to be lifted at a lower basic speed and maintain rotation, if the rotation moment M of the metal rod is larger than or equal to the lifting set lifting rod moment F, controlling the metal rod to lift the mold by 5-10mm, meanwhile, controlling the metal melt prepared in the step S1 to continuously flow into the mold along the metal rod at a matched speed, and enabling the quantity of the metal melt in the mold to be consistent all the time until the whole cast ingot is molded; the metal rod is raised at a low rate during the entire casting process and the casting is uninterrupted to avoid possible delamination during the casting solidification and to obtain a continuous and complete ingot.
The first point of the designed casting method of low segregation fine crystal ingot of high melting point metal is as follows: the metal melt in the die is uniformly and spatially controllable in solidification time and space through the rotation of the metal rod; and a second point: the solidification condition of the metal melt in the die can be directly sensed by measuring the rotating torque of the metal rod, and the casting speed is controlled accordingly; and a third point: the primary dendrite is broken through the powerful stirring of the metal rod, the crystal grains are refined, and the segregation is improved; a fourth point: the splashing phenomenon of the metal melt can be reduced during casting through the drainage effect of the metal rod; and fifth, the method comprises the following steps: the method is beneficial to quickly solidifying the metal melt to obtain a fine crystalline structure by controlling the flow rate and continuously casting; and a sixth point: through the heat conduction and the rotation of the metal rod, the cooling speed difference of the metal melt in the middle area and the edge area is further reduced, and the ingot casting quality is improved; the seventh point is that: simple structure and low cost.
Optionally, also includes
S5: arc starting and temperature supplementing: and after the metal melt is completely poured into the die, controlling the metal rod to be lifted to be 5-10mm above the liquid level of the metal melt and stop rotating, and supplying power to the metal rod to enable an electric arc to be formed between the lower end of the metal rod and the liquid level of the metal melt so as to delay liquid level skull formation.
By adopting the technical scheme, after the metal melt prepared in the step S1 is completely cast into a forming cavity of a die, the cast ingot enters a final stage, the heat dissipation speed of the top of the liquid level of the metal melt in the die is high, in order to avoid premature solidification of the top area of the cast ingot to form a skull, the metal rod is lifted to be 5-10mm above the liquid level of the metal melt, power is supplied to the metal rod to form electric arcs between the lower end of the metal rod and the metal melt, and electric arc discharge is used for supplementing the temperature of the top of the liquid level of the metal melt to delay the skull condensation of the liquid level; and the designed step S5 can avoid the internal shrinkage cavity caused by the excessively fast solidified shell at the top of the metal melt in the casting ending stage.
Optionally, the metal rod is provided as a hollow tube.
Through adopting above-mentioned technical scheme, the design is the metal pole of hollow tube, can control the radiating effect of metal pole self and the ability of cloth metal melt soon, avoids leading to the too strong metal melt too early solidification of mould central zone because of metal pole heat dissipation cooling capacity.
Optionally, the mould includes water-cooling metal mold section and ceramic mold section, the water-cooling metal mold section with the coaxial setting of ceramic mold section, just the water-cooling metal mold section is located ceramic mold section below.
By adopting the technical scheme, the designed mould is arranged in a segmented manner to reduce the heat dissipation speed of the top in the later stage of pouring and flatten the liquidus in the last stage of solidification of the metal melt.
Optionally, the steps S1 to S4 are all performed under an air pressure of 40 to 60 Pa.
By adopting the technical scheme, the designed S1-S4 steps carried out under the air pressure condition of 40-60Pa can reduce the splashing of the metal melt during casting and reduce the convection.
Optionally, the rotation speed of the metal rod is 2-5 revolutions/second.
By adopting the technical scheme, the designed metal rod with the rotating speed of 2-5 revolutions per second can play a role in stirring the metal melt in the die and reduce the phenomenon of splashing of the metal melt caused by the excessively high rotating speed of the metal rod.
Optionally, the duration of the arc in S5 is 5 to 8 seconds.
By adopting the technical scheme, the designed electric arc with the duration of 5-8 seconds can reduce the interference of temperature compensation on the metallurgical structure of the cast ingot under the condition of delaying the skull on the top of the liquid level of the metal melt in the die.
Optionally, the relationship between the outer diameter D of the metal rod, the tube thickness H of the metal rod, and the diameter R of the mold cavity is: d =0.25r =10h.
By adopting the technical scheme, a balance can be formed between the drainage capacity, the heat conduction capacity and the stirring capacity of the metal rod and the outer diameter of the metal ingot.
In summary, the present application includes at least one of the following beneficial technical effects:
1. the casting method of the low segregation fine crystal ingot of the designed high melting point metal comprises the following steps: the metal melt in the die is uniformly and spatially controllable in solidification time and space through the rotation of the metal rod; and a second point: the solidification condition of the metal melt in the mold can be directly sensed by observing the rotation torque of the metal rod, and the casting speed is controlled accordingly; and a third point: the primary dendrite is broken through the strong stirring of a metal rod, and crystal grains are refined; a fourth point: the splashing phenomenon of the metal melt can be reduced during casting through the drainage effect of the metal rod; and fifth, the method comprises the following steps: the formation of columnar crystals is avoided to the greatest extent by controlling the flow rate and continuous casting, and the rapid solidification of the metal melt is facilitated to obtain a fine crystalline structure; and a sixth point: through the heat conduction and the rotation of the metal rod, the cooling speed difference of the metal melt in the middle area and the edge area is further reduced, and the ingot casting quality is improved; the seventh point is that: simple structure and low cost.
2. According to the designed casting method of the low segregation fine crystal ingot of the high-melting-point metal, arc discharge is used for supplementing temperature to the top of the liquid level of the metal melt so as to delay liquid level skull solidification, and internal shrinkage cavity caused by the fact that the top of the liquid level of the metal melt is solidified too fast in the casting ending stage can be avoided.
3. The designed casting method of the low segregation fine crystal ingot of the high melting point metal can control the self heat dissipation effect of the metal rod and the capability of spirally distributing the metal melt, and avoid the premature solidification of the central area of the die caused by the over-strong heat dissipation and cooling capability of the metal rod.
Drawings
FIG. 1 is a schematic view of the state of the initial casting stage of the present application;
FIG. 2 is a state diagram of the arc discharge temperature compensation stage of the present application;
FIG. 3 is a sectional view of an ingot produced in production example 1 of the present application;
FIG. 4 is a sectional view of an ingot produced in comparative example 1 of the present application.
Reference numerals: 1. melting the crucible; 2. a vacuum furnace; 3. a lifting rod; 4. a metal rod; 5. a mold; 51. water-cooling the metal mold section; 52. a ceramic mold section; 6. an electrical contactor; 7. an arc power supply.
Detailed Description
The present application is described in further detail below with reference to figures 1-2.
The embodiment of the application discloses a casting method of a low segregation fine crystal ingot of high-melting-point metal.
Referring to fig. 1 and 2, a low segregation fine grain ingot molding apparatus for a high melting point metal at least includes a vacuum furnace, a vacuum induction furnace, a PLC controller, a tilting motor, a rotating motor, a crucible, a mold, an arc power source, an electric contactor, a lifting rod, and a metal rod; the crucible, the die and the metal rod are all positioned in an inner cavity of the vacuum furnace, and the vacuum induction furnace heats solid metal in the crucible in an electromagnetic induction mode; the lifting rod and the metal rod are coaxially welded, the lifting rod penetrates through the vacuum furnace and is rotatably connected with the vacuum furnace, and the rotating motor is located outside the vacuum furnace and is connected with the lifting rod and used for driving the lifting rod to rotate.
Referring to fig. 1 and 2, in order to form a balance between the current-carrying capacity, the heat-conducting capacity and the stirring capacity of the metal rod 4 and the size of the ingot, the metal rod 4 is provided as a hollow tube; and the relation among the outer diameter D of the metal rod 4, the tube thickness H of the metal rod 4 and the inner cavity diameter R of the die 5 is as follows: d =0.25r =10h.
Referring to fig. 1 and 2, in the later stage of ingot casting, in order to avoid the temperature loss of the metal melt in the forming cavity of the mold 5 too fast, the mold 5 comprises a water-cooling metal mold section 51 and a ceramic mold section 52, the water-cooling metal mold section 51 and the ceramic mold section 52 are coaxially arranged, and the water-cooling metal mold section 51 is positioned below the ceramic mold section 52; in this embodiment, the water-cooled metal mold section 51 is made of copper, and the ceramic mold section 52 is made of magnesium oxide.
Referring to fig. 1 and 2, an arc power supply 7 has one end electrically connected to the water-cooled metal mold section 51 and the other end electrically connected to the lifter bar 3 through an electric contactor 6, and when the metal bar 4 is lifted 5mm above the top of the molten metal level and stops rotating, the electric contactor 6 and the lifter bar 3 automatically close to form a closed loop with the water-cooled metal mold section 51.
A casting method of low segregation fine crystal ingot of high melting point metal comprises
S1: melting, pressure regulating and heat preservation;
s11: melting and heat preservation: solid metal is accommodated through the crucible 1, the solid metal in the crucible 1 is heated through the vacuum induction furnace until the solid metal in the crucible 1 is completely melted to form metal melt, and the power of the vacuum induction furnace is maintained so that the temperature of the metal melt in the crucible 1 is always higher than the melting point of the metal melt by 100-150 ℃; the temperature of the metal melt in this example is 120 degrees celsius above its own melting point.
S12: pressure regulation: in order to reduce the influence of splashing caused by too low air pressure and obvious convection caused by too high air pressure on the heat dissipation speed of the cast ingot during casting, a low-pressure environment of 40-60Pa is provided for the whole casting process of the low segregation fine crystal ingot by the vacuum furnace 2, and the air pressure is preferably 50Pa;
s2: adjusting the height and starting rotation;
s21: height adjustment: the metal rod 4 is coaxially arranged above the bottom wall of a forming cavity of the die 5 by 5-20mm, preferably 10mm, wherein the material of the metal rod 4 is the same as that of the metal melt;
s22: starting rotation: driving the metal rod 4 to rotate, wherein the rotating speed of the metal rod 4 is 2-5 revolutions per second, and preferably 3 revolutions per second;
s3: drainage and cloth rotating: a PLC controller and a tilting motor are matched to control the tilting of the crucible 1, so that the metal melt in the crucible 1 flows into a forming cavity of a mold 5 along a metal rod 4; until the lower end of the metal rod 4 is immersed into the metal melt in the forming cavity of the mould 5 by 5-15mm, and the metal melt in the forming cavity of the mould 5 is driven to flow in a rotating mode;
s4: lifting a rod and continuously casting;
s41: lifting a rod: after the start of casting, the lifting bar is raised at a basic speed of 1-2mm/s and maintained in rotation. Setting a lifting rod torque F, driving a metal rod 4 by matching a rotating motor and a lifting rod 3, coaxially welding the lifting rod 3 and the metal rod 4, enabling the lifting rod 3 to be conductive, when the rotating motor is close to a locked-rotor current, enabling the rotating torque of the lifting rod 3 to reach F, indirectly measuring the rotating torque M of the metal rod 4 in a mode of continuously measuring the current of the rotating motor, comparing the rotating torque M of the metal rod 4 with the lifting rod torque F, and if M is larger than or equal to F, enabling the metal rod 4 to ascend at a speed of 3-4mm/s by 5-8mm, and enabling the metal rod 4 to always stretch into a metal melt in a mold in the lifting rod process;
s42: continuous casting: according to the position of the lifting rod, the crucible 1 is controlled by a furnace tilting motor to slowly and continuously tilt, so that the metal melt in the crucible 1 continuously flows into a forming cavity of the mold 5 along the metal rod 4, and the quantity of the metal melt in the forming cavity of the mold 5 is always kept consistent;
s5: arc starting and temperature supplementing: after all the metal melt in the crucible 1 is poured into a forming cavity of the mold 5, controlling the metal rod 4 to lift until the lower end of the metal rod 4 is 5-10mm higher than the top of the liquid level of the metal melt in the mold 5 and stopping rotating, preferably 5mm; an electric contactor 6 is adopted to be in contact with a lifting rod 3, a closed loop is formed among the lifting rod 3, a metal rod 4, an electric arc power supply 7 and a mould 5, so that electric arc is formed between the lower end of the metal rod 4 and the liquid level of the metal melt and lasts for 5-8 seconds, and liquid level skull solidification is delayed; the arc duration in this embodiment is preferably 6 seconds.
The casting method of the low segregation fine crystal ingot of the high melting point metal in the embodiment of the application has the following implementation principle: the method comprises the steps of heating solid metal in a melting crucible 1 in a vacuum induction furnace air-isolation induction heating mode until fixed metal is heated to be molten, keeping the induction power of the vacuum induction furnace unchanged to enable metal melt in the melting crucible 1 to be kept in a liquid state, and adjusting the air pressure in a vacuum furnace 2 to 50Pa to reduce splashing caused by too low air pressure and the heat dissipation speed of an ingot caused by too high air pressure during casting.
Then the metal rod 4 is controlled to descend by the lifting rod 3 until the distance between the lower end of the metal rod 4 and the bottom wall of the forming cavity of the die 5 is between 5 and 20mm, and the metal rod 4 is driven to start rotating; then control crucible 1 verts, pour the metal melt in crucible 1 and flow into mould 5 molding cavity along metal pole 4, the metal melt passes through metal pole 4 transmission to the external world along the in-process partial heat of metal pole 4 inflow mould 5 molding cavity, rotatory metal pole 4 smashes the primary dendrite in the metal melt in the 5 molding cavity of mould through the mode of powerful stirring, and provide a large amount of nucleation in order to generate tiny isometric crystal through the stirring, and can make the homogenization of the alloy composition in the metal melt through powerful stirring, avoid composition segregation.
Meanwhile, when the metal rod 4 rotates, the metal melt with higher temperature is thrown to a position close to the periphery of the molding cavity of the mold 5 due to lower viscosity, and the cooling capacity of the position close to the periphery of the molding cavity of the mold 5 is strong; the metal melt close to the melting point falls at a position close to the center of the mold 5 due to high viscosity, and the cooling capacity of the position close to the center of the mold 5 is weak, so that the difference of the cooling capacity of the central area and the cooling capacity of the edge area in the horizontal direction are reduced under the rotary distribution of the metal rod 4, and meanwhile, the metal rod 4 bears the heat dissipation effect of the metal melt in the middle area of a part of the mold 5, and the difference of the cooling speed of the metal melt in the middle area and the cooling speed of the metal melt in the edge area are further reduced.
In the rotating process of the metal rod 4, the rotating torque of the metal rod 4 is obtained indirectly through a mode of measuring the current of the numerical control motor all the time, when the solidification structure of the central area of the die 5 is close to the end part of the metal rod 4, the rotating torque of the metal rod 4 obviously rises, a lifting rod moment F is set, if the rotating torque M of the metal rod 4 is smaller than the lifting set lifting rod moment F, the metal rod 4 rises at a basic speed of 1-2mm/s and continuously rotates, if the rotating torque M of the metal rod 4 is larger than or equal to the lifting set lifting rod moment F, and the metal rod 4 is driven to lift through the lifting rod 3. The tilting of the crucible 1 is always associated with the lifting of the lifting rod. The metal melt in the crucible 1 flows into the forming cavity of the die 5 along the metal rod 4, and the quantity of the metal melt in the forming cavity of the die 5 is kept consistent until the whole ingot is formed.
After all the metal melt in the crucible 1 is poured into the forming cavity of the mold 5, the ingot casting and forming enter the ending stage, the heat dissipation speed of the top of the liquid level of the metal melt is high, the top area of the ingot is prevented from being solidified prematurely to form a skull, the metal rod 4 is lifted to be 5-10mm above the liquid level of the metal melt, the electric arc power supply 7 is turned on, the metal rod 4 and the metal melt in the forming cavity of the mold 5 are subjected to arcing and continue for 5-8 seconds, the electric arc discharge is used for supplementing the temperature to the top of the liquid level of the metal melt so as to delay the liquid level skull, and then the ingot is obtained through natural cooling and solidification.
Preparation example 1
S1: melting and heat preservation: heating 20 kg of platinum-rhodium alloy (PtRh 20) until the platinum-rhodium alloy is completely melted to form a platinum-rhodium alloy melt, and keeping the temperature of the platinum-rhodium alloy melt higher than the melting point of 120 ℃;
s2: heightening and starting rotation: a metal rod 4 is coaxially arranged 10mm above the bottom wall of a forming cavity of a die 5, and the metal rod 4 is driven to rotate; wherein the material of the metal rod 4 is the same as that of the metal melt, the metal rod 4 is coaxial with the die 5, the outer diameter of the metal rod 4 is 25mm, the thickness of the pipe is 2.5mm, the length, width and height of the inner cavity of the water-cooling copper die section are 75 x 100 x 130mm, and the length, width and height of the inner cavity of the magnesium oxide die section are 75 x 100 x 70mm;
s3: drainage and cloth rotating temperature equalization: enabling the platinum-rhodium alloy melt prepared in the step S1 to flow into a forming cavity of a mold 5 along a metal rod 4 until the lower end of the metal rod 4 is immersed into the platinum-rhodium alloy melt in the mold 5 by 10mm, and driving the platinum-rhodium alloy melt in the mold 5 to flow in a rotating mode;
s4: lifting a rod and casting: the lifting rod basically rises at a speed of 2 mm/s; setting a lifting lever moment F and continuously measuring a rotation moment M of the metal rod 4, if M is less than F, raising the metal rod 4 at a basic raising speed and maintaining rotation; if M is larger than or equal to F, lifting the metal rod 4 by 6mm; and (2) continuously flowing the platinum-rhodium alloy melt prepared in the step (S1) into the mold 5 along the metal rod 4, and controlling the casting speed of the platinum-rhodium alloy melt to be matched with the lifting speed of the metal rod 4 so that the quantity of the platinum-rhodium alloy melt in the mold 5 is always kept consistent until the ingot casting is finished.
S5: arc striking and temperature supplementing: after the platinum-rhodium alloy melt is completely poured into the mold 5, the metal rod 4 is controlled to be lifted to be 5mm above the liquid level of the platinum-rhodium alloy melt and stop rotating, power is supplied to the metal rod 4, so that an electric arc is formed between the lower end of the metal rod 4 and the liquid level of the platinum-rhodium alloy melt and lasts for 6 seconds, and the discharge current is 900A, so that liquid level skull solidification is delayed.
Comparative example 1
S1: heating 20 kg of platinum-rhodium alloy until the platinum-rhodium alloy is completely melted, enabling the temperature of the platinum-rhodium alloy melt to be higher than the melting point of the platinum-rhodium alloy melt by 75 ℃, gradually and slowly casting the platinum-rhodium alloy melt into a vertical water-cooling copper mold, wherein the total casting time is 50 seconds.
Comparative example 2
S1: heating 20 kg of platinum-rhodium alloy until the platinum-rhodium alloy is completely melted, enabling the temperature of a platinum-rhodium alloy melt to be higher than the melting point of the platinum-rhodium alloy melt by 75 ℃, gradually and slowly casting the platinum-rhodium alloy melt into a vertical water-cooling copper die, and enabling the platinum-rhodium alloy melt in the vertical water-cooling copper die to flow in an electromagnetic stirring mode.
Performance test data
TABLE 1 table for comparison of measured data
| Standard test specimen | Macroscopic density (g/cm 3) | Relative density | Shrinkage and loosening |
| Preparation example 1 | 18.3 | 97.6％ | Is free of |
| Comparative example 1 | 16.2 | 86.2％ | Is provided with |
| Comparative example 2 | 17.4 | 92.7％ | Is provided with |
As can be seen by combining the preparation examples 1, comparative examples 1 and 2 and combining the table 1, the ingots processed by the examples of the present application have a macroscopic density and a relative density which are significantly higher than those of the ingots prepared by the comparative examples 1 and 2, which indicates that the ingots processed by the processing method of the present application have less shrinkage cavities and porosity.
The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: equivalent changes in structure, shape and principle of the present application shall be covered by the protection scope of the present application.
Claims (8)
1. A method of casting a low segregation fine grain ingot of a high melting point metal comprising
S1: melting and heat preservation: heating the solid metal to be completely melted to form a metal melt, and keeping the temperature of the metal melt above the melting point all the time;
s2: heightening and starting rotation: a metal rod is coaxially arranged above the bottom wall of a forming cavity of the die by 5-20mm and is driven to rotate; wherein the material of the metal rod is the same as that of the metal melt, and the metal rod is coaxial with the mold;
s3: drainage and cloth rotating temperature equalization: enabling the metal melt prepared in the step S1 to flow into a forming cavity of a mold along a metal rod until the lower end of the metal rod is immersed into the metal melt in the mold for 5-15mm, and driving the metal melt in the mold to flow in a rotating mode;
s4: lifting a rod and continuously casting: setting a lifting lever moment F and continuously measuring the rotation moment M of the metal lever, if M is less than F, enabling the metal lever to continuously rotate while ascending at a basic speed of 1-3 mm/s; and if M is larger than or equal to F, lifting the metal rod by 5-10mm, controlling the metal melt prepared in the step S1 to continuously flow into the mold along the metal rod at a matching speed in the process so as to keep the quantity of the metal melt in the mold consistent all the time, and enabling the metal rod to extend into the metal melt all the time until the ingot casting is finished.
2. The method of casting a low segregation fine crystal ingot of a high melting point metal as claimed in claim 1, further comprising
S5: arc starting and temperature supplementing: and after the metal melt is completely poured into the die, controlling the metal rod to be lifted to be 5-10mm above the liquid level of the metal melt and stop rotating, and supplying power to the metal rod to enable an electric arc to be formed between the lower end of the metal rod and the liquid level of the metal melt so as to delay liquid level skull formation.
3. The method of casting a low segregation fine grain ingot of high melting point metal of claim 1 wherein said metal rod is provided as a hollow tube.
4. The method of casting a low segregation fine grain ingot of a high melting point metal as claimed in claim 1 wherein said mold includes a water cooled metal mold section and a ceramic mold section, said water cooled metal mold section and said ceramic mold section being coaxially disposed with said water cooled metal mold section being located below said ceramic mold section.
5. The method of casting a low segregation fine crystal ingot of a high melting point metal as claimed in claim 1, wherein said steps S1 to S4 are all performed under a gas pressure condition of 40 to 60 Pa.
6. The method of casting a low segregation fine crystal ingot of high melting point metal as claimed in claim 1, wherein the rotation speed of said metal rod is 2-5 revolutions per second.
7. The method of casting a low segregation fine crystal ingot of high melting point metal as claimed in claim 2, wherein the duration of the electric arc in S5 is 5-8 seconds.
8. The method of casting a low segregation fine crystal ingot of high melting point metal as set forth in claim 3, wherein the relationship among the outer diameter D of said metal rod, the tube thickness H of said metal rod and the size R of said mold cavity is: d =0.25r =10h.
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| CN202211152357.2A CN115519102A (en) | 2022-09-21 | 2022-09-21 | Casting method of low segregation fine crystal ingot of high melting point metal |
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