CN112399895A - Method and apparatus for double acting liquid forging - Google Patents
Method and apparatus for double acting liquid forging Download PDFInfo
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- CN112399895A CN112399895A CN201980046552.7A CN201980046552A CN112399895A CN 112399895 A CN112399895 A CN 112399895A CN 201980046552 A CN201980046552 A CN 201980046552A CN 112399895 A CN112399895 A CN 112399895A
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Abstract
The liquid forging method of the present invention includes producing a metal melt by melting an ingot using an electromagnetic field of an inductor, restraining a side surface of the melt on a punch, and then moving the melt into a die at a high speed, wherein the melt is crystallized in the volume of a part under an excessive punch pressure. The body of the part is exposed to additional pressure pulses generated by shock waves generated during solid collisions which embed additional needle punches into the metal, said needles moving at high speed and generating higher pressure on said metal, transitioning the casting process under pressure to a stage where the metal crystallizes under pressure.
Description
The present invention relates to the field of casting and metal working. The method can be used to produce complex shaped parts from any metal, including refractory metals or chemically active metals. The method enables the production of high strength parts as well as composite products.
[1] A method for liquid metal forging and pulse machining, the so-called "pulse closed die forging" (RU 2194595, C27B22D 18/02, 03.2000), is considered to be prior art to the proposed invention. The molten pool is formed in the heated blank and moves towards the mould, which in turn moves towards the blank. After full contact, the melt pool is exposed to gas pressure and forging forces exerted by the punch. This prior art method is capable of processing any metal including refractory metals and reactive metals.
[2] The closest prior art to the present invention is a liquid forging method and apparatus (RU 2353470C 2, B22D 18/02, 07.2004) for casting reactive metals using a method of induction melting and retaining a melt in a vessel.
The object of the present invention is to increase the efficiency of use and to expand the technical possibilities by producing high-strength monolithic or composite parts of the most complex shape with a fine-grained or amorphous microstructure.
This object is achieved by the fact that: although the known liquid forging method forms a molten metal bath by heating a billet by the electromagnetic field of an inductor while holding the side surface of the bath on a punch and then moving the bath at high speed into a die, wherein the melt crystallizes in the closed die under excessive punch pressure, the invention provides, in addition to the action of the punch, the action of an additional pressure pulse on the body of the part, the pressure pulse being generated by a shock wave generated by the impact of a solid which embeds an additional needle punch in the metal, the needle (punch) moving at high speed and exerting a higher pressure on the metal, thereby allowing the casting process under pressure to transition to a stage in which the metal crystallizes under pressure; the explosion of the explosive substance coming into direct contact with the needle to be inserted in the body of the component causes a shock wave which generates a further additional pressure pulse which acts on the body of the component in the die, so that the crystallization process of the metal under pressure passes to the metal working stage, the shock wave being generated by the explosive substance accelerating the die, the punch and the needle, so that components with a modified phase composition can be produced. The proposed method allows to perform a pulse closed die forging process (ICDF process) by supercooling the melt to a predetermined degree in a first stage of moving the bath and filling the die, and compressing the metal in the die to a predetermined value in a second stage, forming a component with a fine-grained microstructure and phase composition that are not typical for conventional metal machining. The liquid forging apparatus includes a clutch, a rod, a die, a punch, a pipe, a slide frame, a tracking sensor, a vacuum melting chamber, a needle, a striker, a sensor, and a billet to be remelted mounted on the punch, which moves a melt to a die pressing chamber after forming a molten pool while the die moves toward the punch, both accelerated by air pressure, wherein additional pressure is generated on a part body in the die by the accelerated striker striking the needle embedded in the metal. After the clutch is disengaged from the rod, the mold may be accelerated by its own weight. The frame is fixed to the rod by a clutch at the moment of collision of the die with the punch, the fixing being determined by a tracking sensor, the vertically moving die and punch being sealed with bellows attached to the vacuum chamber, so that the parts can be moved while maintaining the vacuum in the melting chamber. There may be multiple needles embedded in the component body, all of which are activated by the impact of a firing pin or an explosive substance applied to the needle. The ingot to be remelted may be heated simultaneously by the inductor and the electron beam generated by the electron gun (or guns) mounted on the vacuum chamber (instead of just the inductor). Prior to forging, a metal or non-metal reinforcement can be installed in the mold cavity, which is then combined with the metal into a composite part after filling the mold cavity with melt under the action of the needle.
The proposed method is implemented by the apparatus shown in fig. 1. The apparatus comprises a melting chamber 1 in which a cooling inductor 2 is installed. The billet 3 to be remelted is mounted on a cooled punch 4 inside the inductor. The inductor may be one or more turns. Further, the inductor may have a number of turns with independent power supplies. The inductor melts the billet from the side until the entire volume of the billet is melted. The inductor envelopes the molten metal in such a way that the lateral surface of the molten bath is maintained by the electromagnetic field of the inductor.
[3]The electromagnetic pressure (Pa) on the metal at the apparent surface effect of penetration of the magnetic field into the metal is represented by the formula: mu n2And/4, wherein the NEs are the intensity amplitude, A/m, of the magnetic component of the electromagnetic field on the metal surface. A piece of metal that is non-conductive to the magnetic field is subjected to a pressure generated by the electromagnetic field that is proportional to the square of the magnetic field strength at the surface of the metal and independent of the frequency of the magnetic field. Thus, the same current in the inductor produces the same force on the metal. The higher the frequency of the current, the higher the voltage that must be applied to the inductor to provide the same field strength.
A die 5 is mounted in the body of the upper slide frame 6 at a distance above the blank along the axis of the punch, the die being held on a tool post 8 fixed to a base plate 9 by an upper clutch 7. A pneumatic cylinder 10 having a piston rod 11 is mounted on the base plate to push a lower slide frame 12 equipped with a lower clutch 13. The punch 4 is mounted on the lower frame and houses a water cooling circuit through the inside of the punch. The melting chamber 1 is firmly fixed to the tool post 8 and evacuated, maintaining a vacuum by means of the lower bellows 14 and the upper bellows 15.
When the upper clutch is pushed away from the rod, the upper slip frame is released and begins to move downward under the force of gravity. The upper frame carries a power cylinder 16 rigidly attached thereto, the power cylinder 16 containing an acceleration piston 17, which acceleration piston 17 is designed to accelerate the movement of the upper frame when high-pressure gas is supplied to the cylinder by opening an acceleration valve 18. When the poppet valve 19 is opened, the piston rod 11 moves upward under air pressure. After the majority of the billet has been melted by the electromagnetic field of the inductor, the crucible sleeve 20, which can slide along the punch under the action of the lever 21, rises and closes the space between the inductor and the melt. The melt is enclosed in the crucible sleeve and then the punch together with the melt and sleeve starts moving upwards while the die moves downwards. The collision of the crucible sleeve and the mold occurs above the upper plane of the inductor. After the collision, the sleeve moves downward while the punch continues to push the molten metal into the pressing chamber 22 of the die. In the pressing chamber, the melt is compressed and begins to fill the inner cavity of the part 23 at high speed. When the interior space of the die is completely filled with melt, the needle 24, which acts as an upper punch, begins to move downward, compressing the melt and crystallized metal, deforming the microstructure of the crystallized metal, and providing additional pressure to the base plane of the part to the die plane. The needle starts moving in a pulsed mode under the action of a striker 25 accelerated by air pressure due to the opening of the upper valve 26. The striker accelerates in a cylinder 27 rigidly mounted on the upper frame and transmits a force pulse to the component by striking the needle.
After the part body is formed and the metal cools, the punch 4 can be lowered by the gas pressure on the piston rod by opening the side valve 28, opening the poppet valve 19 to release gas from below the piston.
To remove the die and remove the part from the apparatus, the top cover 30 over the melting chamber must be opened. The compression mold with the parts is removed together with the upper frame by lifting the compression mold and the upper frame and removing them from the apparatus using the rope 29. The reassembly of the parts is performed in the reverse order.
FIGS. 2a, 2b, and 2c respectively illustrate the apparatus at various times of melting the billet; filling the mould with a melt, which is recorded by a tracking sensor and read by a selected control program running on the ACS and initiating an additional metal treatment; and the needle is pulsed through the metal of the component.
This method is known as liquid forging, considering the need to influence the metal melt at very high speed to fill the thin-walled cavities of complex-shaped parts and at the same time to carry out a double metalworking of the metal directly in the die, in order to ensure the high strength characteristics of the parts that cannot be obtained by conventional casting and deformation methods.
To estimate the forces acting on the metal of the part during the two forging processes, an example of the calculation of a titanium billet 120mm in diameter, 60mm in height and 3 kg in total mass is given below, and the following values are used. Total weight m of the punch assembly1The punch assembly moves from bottom to top and consists of a cooling punch, a lower frame, a piston rod and a blank, the total weight of which is equal to 600 kg.
The diameter of the piston rod is 400 mm.
Total weight m of the die assembly2The mold assembly moves from top to bottom and consists of a mold, an upper frame and other parts, the total weight of which is equal to 500 kg.
The accelerating piston has a diameter of 60mm, a striker has a diameter of 200mm, a mass of 10kg, and travels a distance of 300mm until it collides with a needle having a mass of 5 kg.
The needle had a diameter of 12mm and was pressed into the metal by 5 mm.
After leaving the inductor, the molten billet moved upwards 150mm and the die moved downwards 500 mm. The part to be produced had the shape of a rod with a diameter of 12mm, a length of 4m and a mass of 2 kg.
[4]The momentum of the closed body system remains constant according to the law of conservation of momentum. In the example considered, if at the moment of collision m1And V1The mass and speed of the punch, the punch impulse is m1*V1By analogy, the impulse of the die is m2*V2And the total impulse of the punch and the die before the collision is equal to m1*V1+m2*V2. After a collision, the total impulse must be equal to m, regardless of the speed and mass of the collision and the frontal or angular nature of the collision1*V'+m2V'. From the above, it follows that, for example, if the momentum of the mold is reduced by a certain amount, the impulse of the piston must be increased by the same amount. If the impact is fully elastic and the mass of the piston and die are equal, the punch and piston must fly in opposite directions at the same speed after impact. In the case of metal forging, a pattern must be selected such that the die and punch begin to deflect after the part is formed. In other words, a mode must be selected such that the main impact energy is dissipated to force the melt into the mold cavity and apply pressure to the crystallized metal.
For conventional die casting, the die filling time can be shortened to 0.1sec since the inlet flow rate is increased to 100 m/sec. This fact helps to reproduce the high quality relief of complex castings. In addition, the accuracy of part formation by conventional die casting depends largely on the pressing pressure and the duration after filling the die. In this case, the pressing is performed by small diameter punches which are pressed into the component body by hydraulic pistons at a relatively low speed of 0.1 ÷ 0.5 mm/sec.
In order to implement the proposed method, higher mold fill and metal working rates in the mold must be provided by the pulsed pressure. It is possible to provide an additional pressure pulse immediately after termination of the first pressure pulse in order to form a fine-grained or amorphous microstructure of the body of the component. For this purpose, the moment of mold filling must be tracked using special sensors that can record the mechanical movements and the hydraulic impacts of the bath. According to the invention, the second pulse is transmitted to the metal at the end of the first pressure pulse by means of a needle which exerts a strong pressure on the metal. In particular, the pressure generated by the needle may exceed the pressure generated by the piston by several orders of magnitude. To prevent the mold and piston from wandering, it is necessary to secure them to the tool post by clutches that can be released at the appropriate time to apply additional impulse pressure to the melt.
The method comprises the following steps: producing a metal melt by induction melting of the ingot; the melt in the container is retained at the tail end of the punch through an electromagnetic field of the inductor; lifting the crucible sleeve to limit the melt from spreading when the punch is lifted from the inductor; driving the die and punch to meet each other until the collision forces the melt into the die and fills all of the cavities due to hydraulic impact inside the melt; and immediately after the hydraulic impact, an additional pressure pulse is provided in the form of a punch pin acting on the melt in the mould.
The following is an estimate of the momentum transferred by a mold with a mass of 500kg from a height of 0.5m falling onto the metal melt under its own weight.
[4] Momentum (or impulse) is expressed as: p-m-v, and P-m-v,
wherein m is mass, kg; v is the velocity, m/sec.
During the collision, the center of mass moves 40 mm. The free fall velocity at the moment of contact of the mould with the melt was:
V1＝√2g*0.5m＝3.13m/sec。
the momentum acting on the die and the metal melt is equal to the impulse change:
J＝Δp＝p1–p2＝0–(500kg)*(3.13m/sec)＝-1565N*sec。
before stopping, the centre of mass decelerates from a speed of 3.13m/sec to zero and over a distance h of 40mm, which corresponds to the average melt compression speed V21.57m/sec and an impact time Δ t h/V20.025 seconds. Thus, the force acting on the melt is approximately equal to:
F＝J/Δt＝1565N*sec/0.025sec＝62.6kN。
the diameter of the pressing chamber filled with the liquid melt is 120mm, so that its area is S ═ π R2＝π*(6*10-2)2m2＝1.13*10-2m2. The pressure generated when the mould is placed on the melt thus reaches:
P＝62.6kN/1.13*10-2m2＝55.4*105Pa，
which corresponds to 55.4 atmospheres.
The melt will fill the mold cavity in the form of a rod of 12mm diameter and 4m length at an average speed of 157m/sec for a period of 0.025 seconds.
If the mould is also at 5atm (-5 x 10)5Pa) instead of falling only under gravity, the air pressure will act on two 60mm diameter pieces with a total area of 2.26 x 10-2m2On the accelerating piston, a force F is added2Will be equal to:
F2＝P*S＝5*105Pa*2.26*10-2m2＝11.3*103N。
thus, the gas pressure increased the force on the melt by about 18%.
By increasing the gas pressure in the accelerating piston to 50atm, the force F acting on the piston can be increased3Increasing to 113kN so that the effect of gravity can be neglected. The acceleration time for a mass of 500kg will become:
t3＝√m*h/F3
t3＝√500kg*0.5m/113*103N＝0.047sec。
the speed of the mould in contact with the metal melt will increase to:
V3＝0.5m/0.047sec＝10.6m/sec
the momentum now acting on the mould and the metal melt becomes:
J3＝500kg*10.6m/sec＝5300N*sec。
average impact velocity of V4＝5.3m/sec。
Shortening the impact time to delta t4＝4*10-2m/5.3m/sec＝0.0075sec。
The average total force will be equal to:
F4＝5300N*sec/0.0075sec＝707kN。
the pressure will then reach:
Р4＝707*103N/1.13*10-2m2＝799*105Pa。
in the above example, the pressure reaches 800 atmospheres. Thus, the high pressure forces the metal melt to flow with a very high acceleration, which helps to fill the mould well. This collision ensures a flow rate of the metal melt of up to about 530m/sec and a reduction of the mold filling time to about 7.5 x 10-3sec。
In addition to the forces generated by the die assembly, the proposed method also affects the melt additionally due to the accelerated upward movement of the punch assembly. For example, if the die imparts a momentum on the metal melt equal to 5300N sec, the punch must impart about the same momentum. For example, assume that the mass of the mold assembly is 600kg, the diameter of the piston rod is 400mm, the air pressure on the piston is 50atm, and the distance of collision with the mold is 150 mm.
Then, the force F acting on the piston5Comprises the following steps:
F5＝P5*S5＝50*105Pa*0.126m2＝628kN。
punch travel time: t is t5＝√m5*h5/F5
t5＝√600kg*0.15m/628kN＝0.014sec。
The punch speed is as follows:
V5＝0.15m/0.014sec＝10.7m/sec。
the momentum acting on the melt is equal to:
J5＝600kg*10.7m/sec＝6420N*sec。
the momentum of the die and punch is approximately equal in view of gravity, so that the pressure applied to the melt during the collision of the die and punch reaches 1600atm while the melt flow velocity inside the die exceeds 1000 m/sec.
The above calculations illustrate the potential capabilities of the proposed pulse pressure based approach. The method allows the required pressure to be built up on the metal melt over a wide range to produce parts of extremely high quality.
[5]The clutch (mechanical or magnetic) that secures the frame to the tool post is designed to prevent the punch and die from bouncing back in the opposite direction and to apply additional impact pressure to the crystallized metal. After the first pulse to push the melt into the mold cavity is terminated, a second pulse (hydraulic shock) is generated. Both of these pulses acting on the melt pool can be recorded by special seismic sensors or position sensors responsive to the position of the melt in the mold. From the readings of these sensors, the moment of final forging of the metal in the die is determined. At this point, the melt stops in the mold and an additional pressure pulse is applied to the metal through the needle. The time period from the time of filling the mould with melt to the time of the start of the needle is in the range from 0,1sec to 1 x 10-9sec, in other words, the time period is very short. [6]The additional final pressure pulse is designed to eventually shape the part against the die and provide deformation of the crystallized metal.
[7] Such high mold fill rates allow the most complex part shapes to be filled with melt. However, if the mold filling time falls within the range of 0.1sec to 0.001sec, the time for the needle to be embedded into the part body must be much less, and should fall within the range of 0.01sec to 0.0001 sec. Immediately after the die is filled with melt and hydraulic impact occurs, the metal must be treated by an additional final pressure pulse through the needle.
To illustrate the above, it is assumed that before striking the needle at a distance of 300mm, a firing pin having a diameter of 200mm and a mass of 10kg is accelerated by an air pressure of 100 atm. A needle having a mass of 5kg was embedded in the body of the part to a depth of 5 mm. The momentum acting on the metal can then be estimated as follows. Force F acting on the striker6Comprises the following steps:
F6＝P6*S6＝100*105Pa*0.03m2＝314kN。
striker travel time:
t6＝√10kg*0.3m/314kN＝0.03sec。
the firing pin speed is:
V6＝0.3m/0.03sec＝10m/sec。
if the impact is elastic, the needle speed will be equal to 20m/sec, since its mass is two times smaller than that of the striker according to the law of conservation of momentum. The momentum acting on the part metal is equal to:
J6＝5kg*20m/sec＝100N*sec。
during the depth of 5mm, the needle speed drops to zero, so the average needle speed within the metal is 10 m/sec. Thus, the impact time (the time for the needle to penetrate the body of the part) is about 0.0005sec, and the force on the metal reaches 100 nsec/0.0005 sec-200 kN
When the diameter of the needle head is equal to 12mm, the pressure acting on the metal reaches:
200kN/113*10-6m2＝1.8*109Pa。
this value is close to the ultimate strength of many high strength alloys.
[8] Fig. 2a, 2b, 2c schematically illustrate the sequence of the apparatus operating steps in the case when the liquid forging assembly is driven by gas pressure on the piston. [9] Fig. 3a, 3b, 3c show the increase in velocity and pressure due to the explosive pressure applied to the piston, especially on the needle.
To apply more pressure to the metal through the needle, explosives placed directly on the needle may be used. Explosives can transmit pressures of up to tens of GPa to metal through needles. [10] Under such pressure, phase changes and chemical reactions may occur in the metal. In fact, after the passage of the shock wave, the formation of, for example, zinc ferrite, titanium carbide, tungsten carbide and barium titanate is observed. Thus, it is possible to produce components from superconducting materials, and also to synthesize materials comprising diamond, boron carbide or boron nitride.
[9] When a solid collides or when an explosive explodes, a shock wave is generated.
Assuming that the speed of motion of the material is equal to V0. At a time interval Δ t ═ l/c2In the above, the travel path of the striker will be Δ l ═ V0*Δt＝(V0*l)/c0. Under the action of the striker, the sample will shorten this travel path (Δ l), so its compression can be estimated as ∈ - Δ l/l ═ -V0/c0. The sample will now respond like a compression spring, so its free right end will be released and at 2V0Will move to the right and the carrier discharge will be at c0Reaches the left side of the sample. The duration of the acceleration phase is t 2l/c0The magnitude of the impact compression is epsilon ═ V0/c0。
In order to understand the sequence of the elastic stress generated in the steel bar due to the collision, the above equation is evaluated below so that the body is V0The striker rod was flown at a speed of 20 m/sec. By using a steel with an E-modulus of 210000N/mm2The impact compression strain epsilon-0.4% and the elastic stress sigma-epsilon-840N/mm can be easily obtained2. It can be concluded that the elastic wave generated even at a moderate impact can reach a strength exceeding the elastic limit.
[9] The shock wave can induce a number of phenomena in the solid including the transformation of the crystal lattice, dislocation nucleation or point defects and the subsequent twinning at higher pressures, and phase changes at very high dynamic pressures.
According to Holtzman and Kauan, the elastic strain of the impact wavefront becomes:
ε＝(2/3)ln(V1/V0) (1)
for example, if a shock wave having a strength of 10GPa is propagated in iron, the volume strain at this pressure is about 5%, i.e. V1＝0.95*V0. According to equation (1), the volume strain corresponds to a plastic deformation ∈ -3.4%, and the plastic strain rate is as high as
The size of the crystals formed after shock wave loading is significantly smaller than after conventional deformation, so that the hardness and strength of the resulting material are higher.
Some solids undergo one or several phase changes under the action of the shock wave. In particular, at a pressure of 13GPa, the alpha → beta transition in iron occurs. In titanium, a sudden increase in strength is found at pressures in excess of 20GPa due to the α → β transition. During explosive extrusion of metals, compression thereof can be achieved with a smaller amount of explosive due to heating of the metal. At the same time, the maximum density becomes higher, which helps to reduce the negative effects of carrier unloading.
[9] The Hugoniot curve shows that the heated powder approaches the solid phase curve even at lower pressures. Furthermore, hot pressing provides less internal energy gain than cold pressing. The proposed method will thus achieve high efficiency due to the fact that the heated metal or melt is processed in a mould, deformed by the shock wave, so as to obtain a particular structure with particular strength.
Figure 3a shows an embodiment of the device in which the needle is embedded in the body of the component under the influence of a shock wave generated by an explosive substance. An explosive 31 is placed on the upper end of the needle and a detonator 32 emits a shock wave upon receiving an electrical signal 33 from a computer program which determines the moment of detonation from the tracking sensor readings. [10] The amplitude of the pressure pulse depends on the size d of the explosive, which determines the length of the detonation head and is determined by the time interval over which each point is subjected to the same pressure. The thicker the layer of explosive, the longer the constant pressure will be maintained at each point of the surface and the larger the pressure pulse will be, although the value of the pressure itself is not dependent on the thickness of the layer of explosive. Elastic theory shows that the stress σ in the wave propagation direction is determined by the following expression:
wherein
Is the initial density of the material;
Vlis the particle velocity; and
Clis the wave velocity.
[11] The proposed method has industrial applicability because it allows to practice the impulse closed die forging method theoretically developed in 1994.
This prior art method is based on the ability of the melt to remain liquid below the theoretical melting temperature, which has been demonstrated and confirmed by amorphous metal theory, which allows the prediction of the required melt subcooling value in this case; another part of the process is based on the ability of the supercooled melt to transform into the solid state at a high rate under pressure.
[11]In order to make the above transformation irreversible, i.e. to prevent the reverse transformation of the solid metal into a melt upon release of the pressure, it is necessary to have the heat Q lost by the molten metal when it is transported into the mould and stays in the mould during compression and finally fills the mould cavitypExceeding the heat Q released during the crystallization of the metalкр。
From this condition, the melt supercooling degree δ tt can be calculated, where the crystallization time is close to zero:
Q＝с*m*δT；
Q＝m*qк；
δT＝qк/c,
wherein c is the specific heat capacity of the metal;
m is the mass of the crystallized metal;
qкis the specific heat capacity of the metal for crystallization.
For example, for Ti, the supercooling temperature δ T at the crystallization time δ T → 0 is equal to:
δT＝qк/c＝(392kJ/kg)/(0.53·kJ/(kg°С))＝739°С。
heat dissipation Q of metal lost in liquid phaseрThe following formula can be used for calculation:
Qp＝Aq·r·δt，
wherein A is the surface area of the cooled substrate in contact with the metal melt, m2；
qrIs the specific heat flux, W/m2；
δ t is the contact time between the liquid phase and the substrate, sec.
δt＝α·ΔТ，
Wherein α is the contact heat transfer coefficient;
Δ T is the temperature difference between the melt and the substrate.
Another important parameter that determines the possibility of implementing the ICDF process and affects the phase transition of the metal is pressure.
For those metals that occupy a smaller volume in the solid state than in the liquid state, the increase in pressure causes an increase in the solidification temperature. In order to convert a liquid metal into a solid state, a sufficiently high pressure is required to be applied to the melt to compress the melt to a density ξ corresponding to the solid state near the melting temperature Ts.
For example, to convert molten Ti to a solid phase near its melting point, a compressed melt must be used with ξ ═ 1%. The degree of melt compression required can be determined from the compression theory of shock waves as:
ξ＝(νв/С0)·100％,
wherein vвMaterial compressibility;
С0is the propagation velocity of a longitudinal wave in a substance.
From this, the speed required for the collision of the melt with the walls of the mould cavity can be calculated:
νв＝ξ·С0/100％。
for example, to bring the melting temperature to TsOf Ti melt intoIn the solid state, must pass through the melt at about vвThe metal is compressed by the collision with the die at a speed of 27 m/sec.
The compression time of the body under the impact pressure is equal to:
δtc＝2l/C0，
where l is the length of the body.
Assuming that l is 0.5m, it can be concluded that δ t is the sum of Ti and tc＝7.4·10-4sec。
From the above examples it can be seen that the time for applying the pressure to the melt is so short that only time is available for forming a very small crystal. In addition, the intercrystalline spaces formed by the metal shrinkage during its transformation are continuously filled due to its forced compression.
Fig. 3a shows the apparatus as the metal melts, fig. 3b shows the forging of the metal resulting in the filling of the mould and subsequent shock wave treatment due to the explosion of an explosive mounted on the needle, and fig. 3c demonstrates the last moment of forging by embedding the needle in the body of the part.
Fig. 3 shows an apparatus which makes it possible in practice to carry out the impulse closed die forging process (ICDF process) with the aim of producing very strong components. The apparatus allows a pressure pulse of over 30GPa to be applied to a melt-filled mould through a needle using an explosive. Such pressure directly causes the metal to deform in the closed mold with a compressive strain of 5% or more. [3] Additional effects can be achieved by heating the blank by an electron beam from an electron beam gun (EBH) mounted on a vacuum enclosure and shown in fig. 3 a.
It is known that induction heating cannot melt metals having a melting point (melting temperature) exceeding 2000 ℃. Fig. 3a shows an electron beam gun 34 which, together with an inductor, melts the billet with an electron beam 35. The choice of electron beam melting is understandable from the fact that the process requires a deep vacuum. For example, if plasma heating in a gas atmosphere is used instead of EBH, the part forming process will be compromised because the gas will prevent filling the mold cavity. Meanwhile, if electron beam heating is used in combination with induction melting, it is possible to melt refractory metals such as niobium, molybdenum, tantalum, tungsten, or alloys and compounds thereof. In this embodiment, the apparatus can be used to produce, for example, rocket nozzles, turbine blades, or missile casings from refractory materials. The proposed method may be even more advantageous when implemented to produce composite parts. As shown in fig. 3a, carbon-carbon fibers, filamentous carbon crystals, silica fibers, boron nitride fibers, or simply metal reinforcements 36 may be installed in the mold cavity. The high pressure during forging causes the melt to completely fill all of the die cavities (fig. 3b) including the reinforcement and the explosive blast gases 37 are vented outward. Additional forging by a needle (fig. 3c) allows consolidation of the crystalline melt and reinforcement into a monolithic composite part 38.
In particular, the proposed method allows the production of components from metallic and non-metallic components (so-called cermets).
In view of the above, the method can be used to produce ultra-precise and expensive components for civilian and military use.
Reference to the literature
[1] Volkov a.e. -RF patent, RU 2194595-liquid metal forging and pulse processing Method, so-called ' pulse closed die forging ' Method for liquid metal forming and pulse processing, so called ' pulse closed die closed-die closing-die forming ', ' c27b22D 18/02, 10.03.2000.
[2] Volkov a.e. -RF patent, RU2353470 c2, induction melting Method and apparatus for melt retention in a vessel "Method and apparatus for insertion with in-vessel melt retention", b22D 18/02, 02.07.2004.
[3] Fogel-Induction method of maintaining liquid Metal in suspension "-Leningbad: Mashinotryyeniyye, 1989, p.6 ÷ 7, p.61 ÷ 64. - (russian).
[4] giancoli-Physics "-moscow: mir,1989, pp.302 ÷ 341. - (russian).
[5] Casting under m.b.becker-pressure "Casting under press" -moscow: mashinostroyenniye, 1990, page 14 ÷ 17. - (russian).
[6] glezer-Nanocrystals quenched from melt "Nanocrystals: fizmatit, 2012, p 192 ÷ 193. - (russian).
[7] Gilman-metallic glass "Metal glasses" -Moscow, Metallurgiya, 1984, p.22 ÷ 62. - (russian).
[8] Kudinov-fluid and gas dynamics "Hydro & gas dynamics" -Moscow: Infra-M, 2013, page 183 ÷ 193. - (russian).
[9].R.
-explosive processing of powdered materials "expansion processing of perforated materials" -Moscow: mir, 1990- (russian).
[10] Frank W.Wilson-High strain rate deformation of metals "-Moscow: mashinostroyenniye, 1966. - (russian).
[11] Development of a.e.volkov-pulse closed die forging process, tools and equipment "Development of pulse closed-die forming process, firing and equalisation": scientific candidate human academic thesis abstract-moscow, 1994.
Claims (10)
1. A method of liquid forging, comprising: heating the billet by the electromagnetic field of the inductor to form a molten metal bath while holding the side surface of the bath on the punch, and then moving the bath at high speed into the mould, wherein the melt crystallizes in the closed mould under excessive punch pressure, wherein, in addition to the action of the punch, the part body is subjected to additional pressure pulses generated by shock waves generated by solid collisions embedding additional needle punches in the metal, said needles moving at high speed and exerting a higher pressure on the metal, thereby allowing the casting process under pressure to transition to a stage in which the metal crystallizes under pressure.
2. A method according to claim 1, characterized in that the component body in the mould is subjected to a further additional pressure pulse generated by a shock wave generated by the explosion of an explosive substance directly in contact with the needle to be embedded in the component body, thereby transferring the metal crystallization process under pressure to a metal working stage.
3. A method according to claim 1, wherein the shock wave is generated by an explosive substance accelerating the die, the punch and the needle, whereby components with a modified phase composition can be produced.
4. The method of claim 1, characterized in that it is capable of forming parts with a fine-grained microstructure and phase composition that are atypical for conventional metal machining by performing a pulse closed die forging process (ICDF process) by allowing the melt to be undercooled to a predetermined degree in a first stage of moving the melt pool and filling the die, and compressing the metal in the die to a predetermined value in a second stage.
5. A liquid forging apparatus, comprising: a clutch, a rod, a die, a punch, a pipe, a sliding frame, a tracking sensor, a vacuum melting chamber, a needle, a striker, a sensor and a billet to be remelted mounted on the punch, which moves the melt to a die pressing chamber after forming a molten bath while the die is moving towards the punch, both accelerated by air pressure, wherein additional pressure is generated on the part body in the die by the accelerated striker striking the needle embedded in the metal.
6. The apparatus of claim 5, wherein the die can be accelerated by its own weight after disengaging the clutch from the rod, a frame is fixed to the rod by the clutch at the time of collision of the die with the punch, and the fixation is determined by a tracking sensor.
7. The apparatus of claim 5, wherein the vertically moving die and punch are sealed using bellows attached to the vacuum chamber, thereby moving the parts while maintaining a vacuum in the melting chamber.
8. A device according to claim 5, characterised in that a plurality of needles may be embedded in the body of the component, all of which are activated by the impact of a firing pin or an explosive substance applied to the needle.
9. The apparatus according to claim 5, characterized in that the ingot to be remelted is heated simultaneously by the inductor and by the electron beam generated by the electron gun (or guns) mounted on the vacuum chamber.
10. The apparatus of claim 5, wherein the metal or non-metal reinforcement is installed in a mold cavity prior to forging and then combined with metal into a composite part after filling the mold cavity with the melt under the action of a needle.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| RU2018125356A RU2764620C2 (en) | 2018-07-10 | 2018-07-10 | Method and device for liquid forging of double action |
| RU2018125356 | 2018-07-10 | ||
| PCT/RU2019/050107 WO2020013734A1 (en) | 2018-07-10 | 2019-07-09 | Method and device for double-action liquid forging |
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| CN112399895A true CN112399895A (en) | 2021-02-23 |
| CN112399895B CN112399895B (en) | 2022-10-18 |
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| RU (1) | RU2764620C2 (en) |
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| CN104439158A (en) * | 2013-09-16 | 2015-03-25 | 慕贝尔碳纤维技术有限公司 | Method and device for producing a metallic component by means of a casting and mould |
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| US4254817A (en) * | 1979-05-30 | 1981-03-10 | Iwatani Sangyo Kabushiki Kaisha | Metal casting apparatus |
| US4580617A (en) * | 1982-05-07 | 1986-04-08 | Charles Blechner | Induction casting machine and method of casting |
| RU2353470C2 (en) * | 2004-07-02 | 2009-04-27 | Анатолий Евгеньевич Волков | Method and facility for liquid forging for casting of reactive metal with usage of method of induction keeping of melt |
-
2018
- 2018-07-10 RU RU2018125356A patent/RU2764620C2/en active
-
2019
- 2019-07-09 CN CN201980046552.7A patent/CN112399895B/en active Active
- 2019-07-09 WO PCT/RU2019/050107 patent/WO2020013734A1/en active Application Filing
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|---|---|---|---|---|
| AT271143B (en) * | 1967-10-09 | 1969-05-27 | Langestein & Schemann Ag | Machine for shaping a workpiece between two bears |
| DE2738674A1 (en) * | 1977-07-04 | 1979-01-18 | Cerac Inst Sa | METHOD FOR COMPRESSING POWDER |
| RU2033893C1 (en) * | 1992-06-03 | 1995-04-30 | Марширов Виктор Викторович | Method for pressure die casting |
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| CN102240763A (en) * | 2011-04-16 | 2011-11-16 | 湖北三环锻造有限公司 | Medium-heavy automobile flange die forging process and punching and calibrating composite die thereof |
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| CN104368790A (en) * | 2014-11-11 | 2015-02-25 | 创金美科技（深圳）有限公司 | Metal liquid-state fluctuation high pressure casting and forging once-molding method |
Also Published As
| Publication number | Publication date |
|---|---|
| RU2018125356A (en) | 2020-01-10 |
| WO2020013734A1 (en) | 2020-01-16 |
| CN112399895B (en) | 2022-10-18 |
| RU2764620C2 (en) | 2022-01-18 |
| RU2018125356A3 (en) | 2021-07-08 |
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