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外文資料翻譯
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2010年4月
Compression casting craft and compression casting mold design main point
Abstract: The die-casting machine, the mold and the alloy three, take press the casting as this, among the compression casting craft penetration, their conformity is organically a effective system, causes the die-casting machine and the mold obtains the good match, plays the optimization to press the casting structure, the optimal die-casting machine, the optimization presses the mold design, enhances the craft operating point the flexible role, thus provides the reliable guarantee for the compression casting production.Therefore, the compression casting craft lies within in the mold saying, depth of the connotation is self-evident.
Key word: Die-casting machine; Mold; Compression casting craft; The mold designs
1.Die-casting machine - mold - alloy system
Die-casting machine, the mold and alloy these three factors, in presses in the casting production process, they constituted a system, namely the die-casting machine - mold - alloy system, it is take presses the casting as this, among the craft penetration, entrusts with the system vigor and the efficiency, but the mold is the craft enters the system the platform.The die-casting machine, the mold and the alloy three relations expressed vividly as shown in Figure 1.
The die-casting machine - mold - alloy system main performance is:
(1)Ingate position influence backfill metal melt flow direction and the condition, with the backfill die space quality, have the decisive influence to the mold structure and the craft, this is the key is at.
(2)Designation best sufficient time, this is extremely important one step, affects to sufficient time metal melt rate of volume flow (Q), also is the sufficient power, according to the above and computation ingate size.
(3)Choice exhaust, overflow position and size, except outside normal exhaust, pollution discharge and temperature balance, but also may reduce the impact pressure, avoids the metal splashing and producing the burr.
(4) Heating and cooling, balanced mold temperature, maintenance operating temperature.
2.Compression casting crafts and the mold design key technologies
When compression casting the ingate position influence presses the casting the structural design, the quality and the compression casting mold design, may obtain the correct establishment ingate position prompt through the inquiry material.As a result of the casting structure multiplicity, must choose the ingate the correct position is very difficult, but also has some basic requests, like thought generally the establishment ingate must cause sufficient when the metallic jet has as far as possible compared the long distance by the open jet in the die space average, also is the correct ingate position, the shape, the size (flows to angle) to coordinate the compression casting parameter to be possible to obtain the metallic jet to expand along the wall unceasing order, to change, and continuously expands to the terminus.The die space majority (i.e. branch die space) completes by the jet flow backfill, only then a small part of die space (i.e. non-branch die space) by the metal melt branch supplemented completes or collides by the metal melt stock class completes the backfill, and overflows the system elimination vestiges through the platoon.Figure 2 is in the pouring position and branch die space schematic drawing [1]”.
The identical pressure casting choice different ingate position and flows to the angle, when may obtain the area percentage which the different branch die space, the non-branch die space and hold respectively, Figure 2 the shell compression casting, because the ingate position is different, obtains the different branch die space and the non-branch die space.The chart 2a ingate is vertical to one side wall, because the components crown long square edged orifice separates two sidewalls, the result is only then one side for the branch die space; Must fill another one side wall, must pass through the running channel both sides attachment point, the final two liquid flow gathering completes the packing, this part is the non-branch die space.Because the branch die space accounts for the area percentage not to be high, therefore can produce the massive waste products, like chart 2a1.In chart 2b, the ingate position does not make the change, only is wall thickness and so on crown rectangle Kong Yong craft muscles connects, like this fills when the metal melt changes, fills another one side wall along the muscle board, caused two sidewalls both to become the branch die space, increased the branch die space to account for the percentage, the casting quality also large scale enhances, like chart 2b1.In chart 2c, the components and chart 2a are same, the crown square edged orifice does not add the craft muscle, but establishes the ingate in a components end, such metal melt simultaneously carries on the backfill from two sidewalls, thus expanded the branch die space percentage, had guaranteed the quality, enhanced the qualified rate.This is the identical components three kind of ingate establishment plan, the proof ingate position crucial nature.
Although the computer technology is helpful to the designation ingate position, but the computer technology is only one method, but the ingate position design did not lose was still a key technologies.
Between 3 compression casting craftmain point
3.1 metal pressures, the speed and the current capacity relations
In the principle the die-casting machine are a liquid metal pump, it transports under the pressure the metal melt to the compression casting model cavity in.The pump characteristic is transports the power (rate of volume flow), is the pressure function, this aspect as early as in the 70's, first makes the valuable development work by Australian Asia CSIRO, has established a useful tool with the pQ2 chart, according to the casting i.e. mold request, decided the machine the adjustment value, is originally uses in the hot cell die-casting machine the zinc base alloy pressing in the casting, but very quick expands to Leng Shiji on.In principle, now the pressure and the rate of volume flow relations which knew very well from the hydromechanics principle, shifts to the die-casting machine practical application.
The metal pressure is higher, is also quicker in the spray nozzle and the ingate place metal melt flow rate, but also must consider victory flow resistance which as a result of the flowing section change, the direction change and the wall roughness existence produces, xi expresses sum of the these resistance with the friction coefficient.
If the known immeasurable steel coefficient xi, may calculate the metal pressure which certain ingate speed needs, according to the compression casting alloy and the casting request, the ingate speed has an empirical value, should observe, see Table 1, therefore needs the die-casting machine to provide the corresponding speed.
Table 1 ingate speed selection
Table 1 Choice of velocity at ingate
Project
A1
Mg
Cu
Zn
υa(m.s-1)
25-60
40-90
30-45
30-50
The low value uses in the relatively thick casting, the high value uses in the relatively thin casting, common magnesium alloy casting ingate speed compared to aluminum high25%. Time the vacuum die casting ingate speed is 15-30m/s.
3.2 Take the casting as this, optimizes the die-casting machine - mold - alloy system, enhances the craft flexibility
In the die-casting machine - mold - alloy system, through the adjustment craft parameter, may improve presses the casting the quality and the performance.These craft parameter defined with work window (OW).This indicated OW is these craft parameter limit chart.In the compression casting craft, the sufficient time, the ingate speed and the final metal static pressure use to define OW, these parameters and sufficient phenomenon related, relies on in the mold design and the die-casting machine performance.Designs when the mold, in OW all spots were considered all is equal, and does not have the priority, may think the best operating point exists in OW unknown lights, in presses the mold installs on the die-casting machine in front of the experimental mold is unable to find it.In the mold design stage guaranteed easy to find the good operating point is based on the flexible consideration, the flexibility is obtains in OW through the adjustment.
Therefore, divides into the craft parameter the soft parameter and the hard parameter two kinds, the soft parameter is refers through the operation or a control device carries on the adjustment the parameter, like parameters and so on power level, metal pressure, melt temperature, mold temperature and cycle time.The die-casting machine which the hard parameter is refers to which one kind to have to revise the mold or simultaneously must revise, like drift diameter, ingate area, air discharge duct and so on.Soft parameter when experimental mold easy to change and to obtain successfully, the hard parameter changes then both the difficulty and costs a great deal of money, time-consuming, needs to disassemble the mold frequently in order to revise.Therefore, the optimized method is and expands the OW internal assignment integral point based on the soft parameter the flexibility, thus provides the great scope for the mold experiment, avoids the time-consuming expensive mold change.
3.3 shoots the curve from the pressure to mention
Now die-casting machine Chang Peiyi three level of compression casting systems: The level advances gradually for the drift idling speed, pushes the metal melt to the ingate, namely the so-called slow pressure shoots the stage; The second level is the drift by high speed the metal melt through the ingate, fills the die space in the stipulation time, namely sufficient stage; The third level for the casting which not yet completely coagulates under the high pressure (starts pressure intensifier) to carry on the coagulation and by the compaction, namely compaction stage.Shown in Figure 17 for the model three levels of pressures shoots the curve schematic drawing, attempts the curvature to divide into the level slow pressure to shoot, two levels sufficient and three level of turbo-charged compaction three stages.Some pressures shoot the system to shoot the level pressure divide into two small parts, the first part is the drift seals up the pouring material mouth (shown in Figure 18 the X1 line) first, the second part shoots the stage for the slow pressure, then carries on the light again and the compaction, this became four levels of pressures to shoot the system, like this except might avoid the melt splashing the pouring material mouth, might raise the compression chamber initial fullness.
3.3.1. Slow pressures shoot the stage
Slow pressure to shoot the stage mainly are elect in the craft to control the slow pressure to shoot the speed, the goal are wells up when the metal melt to the ingate, presses in the room the gas to be able completely from the runner to enter the die space, but by the metal melt package, does not avoid in the casting forming the blowhole; Therefore, needs to choose a critical drift speed, may be the constant acceleration, also may be the constant speed, said generally, the constant acceleration effect is good.The overseas die-casting machine matches by “Parashot'' or “SIMUI” the constant acceleration slow pressure shoots the speed elects to control the system, Figure 19, chart 20[2] may take elects to control the slow pressure to shoot reference the speed.
3.3.2. Sufficient stages
This stage most should pay attention in the craft: The sufficient time, the pressure shoot the speed, the ingate speed and the air pressure shoot the speed the reciprocity, and mainly wants the parameter the choice.
3.3.2.1.Best sufficient time
The sufficient time is the metal melt has flowed the ingate, by the high ingate speed, fills the die space before the metal melt stop flowing the time.This time is very short, is an extremely essential parameter, selects the die-casting machine, carries on foundation which the technological design and the mold design.
The sufficient time must be short, the goal is sufficient when does not have the early time in the casting smallest spot or the liquid flow far-end to coagulate, avoids the casting appearing lacks flaws and so on meat, cold shot.The sufficient time is shorter, the sufficient speed is higher, can enlarge the die space to wear, but but also possible to splash because of zhang the metal and to produce the edge; The sufficient speed is high, can enable in the die space the gas not to have the enough time to transgress from the die space.The sufficient time correct choice only then the overall evaluation can obtain, Table 3 gave has chosen the sufficient time and ingate speed correlation factor [4].
The metal melt had decided from the operating temperature to the temperature of solidification release quantity of heat it maintains the castability under the same thermal conductivity time, therefore this kind of thermal then achievement determines its may imitate the time criterion most greatly.The release quantity of heat and the sufficient time are proportional, compared to may obtain several kind of alloy sufficient time relations according to the quantity of heat.The Mg alloy, the Zn alloy, the A1 alloy and the Cu alloy under the same coagulation condition, from the operating temperature to the temperature of solidification release quantity of heat respectively are 261, 329, 509, 918kCal/dm3, then they the time ratio is τMg: τZn: τAI: τCu ≈0.51: 0.65:1:1.8.In other words, τMg=: 0.51τAI, τZn=0.65τAI, τCu=1.8τAI.
When compression casting obvious molten metal in die space not superheat, the people observe the melt to flow have certain quantity solid phase, when the solid phase rate achieved30%-80%, In the die space the bath movement only can through the high rate of inflow, when best sufficient time according to type (17) computation, quite Yu Fzhi is70%-80%.
The best sufficient time speaking of each kind of magnesium alloy shoots when the pressure must the aluminum alloy be quicker than at least 2 times, the copper alloy best sufficient time and the alloy composition element related, the leaded brass (CuZn37Pb) and the magnesium alloy is close, the silicon brass (CuZnl5Si4) and the aluminum alloy is close.
The casting surface quality quantity increases along with the sufficient time changes, the sufficient time is short, the pressure shoots the power to be big, sufficient is quick, but because of the ingate thickness limit, the excessively short sufficient time causes the casting the factor of porosity increase.Figure 22 is the sufficient time presses the casting quality to the aluminum influence [7].Chart 23[3,8] is one kind which the recent years proposed to the aluminum, the magnesium presses the casting wall thickness and the sufficient time relations relational graph.The superficial quality requests to choose the short sufficient time high.
3.3.2.2 Pressure shoots the speed, the sufficient speed and the air pressure shoots the speed.
(1) Pressure shoots the speed (drift speed)
The pressure to shoot the speed (drift speed) is in the sufficient stage unit time drift displacement.In traveling schedule curve sufficient stage no matter what chooses two spots, the survey traveling schedule distance and the sufficient time, then obtain the pressure to shoot the speed = survey the distance (mm)/pressure to shoot time (ms).
(2)Sufficient speed (ingate speed)
The sufficient speed is the ingate speed, concerns with the drift speed and the drift area.In presses in the room - - mold this loop system, take the sufficient time metal passes the ingate rate of volume flow Q as the foundation.Only then after designated generally the die-casting machine, can determine the drift area, the ingate speed may according to Table 1 selection.
The ingate speed is the important parameter, has the important influence to the casting quality and the mold life.The ingate speed excessively is high can increase the die space surface because corrodes, sticks the probability which the mold receives damages; Although the low ingate speed is advantageous in the gas discharges from in vivo, but also can cause the casting mechanics performance and the surface quality goes bad.The casting volume flaw often appears by the uniform distribution micro hole or by the big hole in the casting, high ingate speed compression casting strength ratio low ingate speed low, is helpful in forms the micro hole in the casting, causes the casting surface to be brighter and cleaner, the organization is more compact.
Ingate speed and casting wall thickness related, but decided by the ingate thickness, the actual same wall thickness casting, possibly has the different thickness ingate, from this also can use the different ingate speed to come the compression casting.
But has to ingate structure experience graph [2], confirmed the ingate structure and the ingate speed, when to casting quality influence, recommendation fine casting operating point region thin-walled casting, in choice neighbor chart grid area.Obviously, when very thin ingate, because the ingate parameter is the low value, the need higher ingate speed.
Sufficient time drift speed υo excessively high, besides to mold life and casting quality influential, but also can because the sufficient end time drift impact function, has caused to move, to decide the mold to push, when is pushed the slit to surpass 0.05-0.15 mm, but also can produce the molten metal the phenomenon which splashes from the mold comes out.
Sufficient time ingate speed υa with casting wall thickness and metal melt in die space flow length related, as shown in Figure 27.
(3) Biggest air pressure shoots the speed
Biggest air pressure to shoot speed υot max is presses in the room not to have in the situation which the metal also the governor valve all start, in unit time drift displacement.It is the cold room die-casting machine important technical parameter, to has the metal sufficient time drift speed υ0, in the running channel speed υa and presses the casting quality to have the important influence.
(a) Compression casting machine-pressed shoots the power which the system can provide
For in the short sufficient time introverted die space to fill the large capacity metal melt, needs the high drift speed and in the running channel speed, this must entrust with the die-casting machine high biggest air pressure to shoot the speed.The modern Europe die-casting machine biggest air pressure shoots the speed to achieve 11m/s, Japan recent years also appeared 10m/s the supervelocity die-casting machine.
(b) Air pressure shoots the speed
Air pressure to shoot the speed is the die-casting machine adjustable parameter.Because presses the room - die space system resistance the existence, the sufficient time drift speed always shoots the speed the air pressure to be much smaller than.May know by chart 30[4], when certain in running channel area υot max increases from 4m/s to 8m/s, but the sufficient time drift speed υo enhances from 2.4m/s (I) to 3.1 m/s(II), does not look like υot max such to enhance 1 time.
Theoretically, when the pressure shoots the output is biggest υ02/υ ot max2=Q2/Q at max2=1/3, then υ0/υot max2=Q/Qot max=0.577, as shown in Figure 31.Thenυ0=0.577 upsilon ot max.
The cold-press room die-casting machine must have the high level most greatly spatial
Pressure to shoot the speed, like this may improve the craft operating point spiriactiveness.The graphic solution may help us to choose the die-casting