CN101274361A - Low speed vacuum squeeze casting technology - Google Patents

Abstract

A low-speed vacuum extrusion casting process, the steps are: (1) mold, vacuum system and hot runner design; (2) hot runner and mold installation preheating, spraying paint; (3) molten metal poured into hot runner (4) Low speed, vacuum filling; (5) Squeeze and solidify; (6) Open the mold and take the parts. The technical effects of the invention are: the temperature field of the die-casting process is improved, and the casting method of low-speed injection, high-pressure solidification and no vacuum shrinkage cavity is realized. The low-speed vacuum extrusion casting process can effectively reduce the probability of pores and shrinkage defects in die castings. Die castings can be heat treated. After heat treatment, the tensile strength and elongation of die castings are increased by 25%, so that die castings The quality has been greatly improved.

Description

Low Speed Vacuum Squeeze Casting Process

technical field

The invention relates to a casting process, in particular to a full vertical die-casting process.

Background technique

Die casting - the most important and advanced technology in the modern foundry industry. However, in the die-casting process, due to the high-speed filling, it is difficult to discharge the gas in the cavity; in addition, the liquid metal cools quickly in the cavity, and it is actually difficult to feed the shrinkage, so that the die-casting often has pores and shrinkage defects. The larger the thickness value, the more serious this defect is; because the gas expansion in the pores at high temperature will cause the surface of the die-casting to bubble, so the die-casting cannot be heat-treated; these will seriously affect the quality of the die-casting, and the expansion and use of die-casting production Range is limited. Vacuum die-casting once flourished for a while, but it is not widely used now. The main reason is that although this technology reduces the pores of die-casting parts, shrinkage cavities often become more serious. The precision, speed and precision die-casting method can play a greater role in eliminating pores and shrinkage defects, but this method has strict requirements on the heat balance and temperature field of the mold, and there are no effective measures. Casting, coupled with the difficulty in maintenance of double punches, the scope of its promotion and application is not large.

Contents of the invention

The purpose of the present invention is to provide a low-speed vacuum extrusion casting process, which comprehensively applies low-speed and vacuum filling, extrusion and solidification methods, and carries out technical innovation on the full vertical die-casting process.

The present invention is achieved in this way, and its process steps are (1) mold, vacuum system and hot runner design: the requirements of mold design are: the thickness of the inner gate is 6-12mm thicker than that of ordinary die-casting molds, when the inner gate When it is set at the thick wall (18-25mm) of the casting, it can be 15-18mm; the location of the installation of the hot runner should consider the safety of electricity and be more than 200mm away from the injection cylinder; the requirements for the design of the hot runner are: the heater is divided into Multiple groups, respectively controlled by different temperature controllers; the requirements for vacuum system design are: the displacement of the vacuum pump and the volume of the vacuum tank should be determined according to the volume of the cavity, to ensure that the vacuum of the cavity reaches -0.09MPa or higher within 3 seconds, and the vacuum The performance of the plug should ensure the fast communication between the cavity and the vacuum system, and prevent the molten metal from entering the vacuum system with the air flow; the flow rate and action time of the vacuum valve and each component of the vacuum system should match the entire vacuum system; (2) hot pouring Road and mold installation preheating: The principle of hot runner temperature field control is: the temperature on the mouth of the pressure chamber (connected with the mold) is about 50°C higher than the temperature in the center of the pressure chamber. The average temperature in the pressure chamber is taken according to different die-casting alloys (the aluminum alloy should reach above 500°C). The mold should also be preheated at the same time. The preheating temperature varies with the die-casting alloy. The aluminum alloy should reach about 350°C, and the zinc alloy should reach about 250°C; the pressure chamber and the cavity should be sprayed with paint immediately after preheating; (3) metal Liquid pouring into the hot runner, mold clamping, and vacuuming: After the molten metal is poured into the hot-press chamber of the lower mold, the mold is quickly closed to seal the parting surface and the vacuum valve is activated to vacuumize the cavity. Carry out vacuuming and reach the control vacuum value (-0.09MPa) within 3 seconds. (4) Low-speed, vacuum filling: select the filling speed according to different castings (pre-set, the speed of the injection punch is controlled at 10-100 mm/s). When the vacuum value reaches -0.09MPa, press the injection switch immediately to start injection; during the whole injection process, the vacuum system is always connected with the cavity and maintains the control value; (5) Squeeze solidification: In the post-injection stage (at this time, the cavity is full and the center of the casting has not yet solidified), the injection hydraulic cylinder is rapidly pressurized, and the injection punch presses the metal in the sprue with a high specific pressure of hundreds of MPa and maintains it for several minutes , fully feed the castings to make the castings more compact; (6) open the mold and take the parts:

The technical effect of the present invention is: the application of the hot runner, good thermal insulation performance, improves the temperature field in the die-casting process; realizes: 1. Low-speed injection, so that the molten metal for filling the mold moves forward smoothly along the full wall thickness Propelling, no eddy current, enough time for cavity gas to be discharged, reducing porosity and porosity of die castings; 2. Solidification under high pressure. The metal in the sprue exerts pressure, because the metal in the sprue is still liquid at this time, and the casting can be fully fed under high pressure to make the casting more compact; 3. There is no vacuum shrinkage cavity, because the casting can be fully fed, so Vacuum shrinkage defects can be avoided, while maintaining the favorable aspect of eliminating air in the cavity in a vacuum environment; therefore, the low-speed vacuum extrusion casting process can effectively reduce the probability of air holes and shrinkage defects in die castings. It can be heat treated, and the tensile strength and elongation of the die casting after heat treatment are increased by 25%, especially for thick-walled castings, so that the quality of the die casting is greatly improved.

Description of drawings

Fig. 1 is the working principle diagram of the present invention.

Detailed ways

As shown in Figure 1, the process steps of the present invention are (1) mould, vacuum system and hot runner design: the requirement of mold design is: ingate thickness is 6-12mm thicker than common die-casting mould, when ingate is opened at When the casting has a thick wall (18-25mm), it can be 15-18mm; the position of installing the hot runner should consider the safety of electricity and be more than 200mm away from the injection cylinder 11; the requirements for the design of the hot runner are: the heater is divided into 7 parts Multiple groups, respectively controlled by different temperature controllers. The special requirements for the design of the vacuum system are: the displacement of the vacuum pump and the volume of the vacuum tank 1 should be determined according to the volume of the cavity 6, so as to ensure that the vacuum of the cavity reaches -0.09MPa or more within 3 seconds. High, the performance of the vacuum plug 2 must ensure that the cavity 6 is quickly connected to the vacuum system, and the molten metal will not enter the vacuum system with the air flow; the flow and action time of the vacuum valve 3 and each component of the vacuum system must match the entire vacuum system (2) Hot runner and mold installation preheating: The principle of hot runner temperature field control is: the temperature on the inner mouth of the pressure chamber 8 (connected with the mold) is about 50°C higher than the temperature in the center of the pressure chamber. The average temperature in the pressure chamber is taken according to different die-casting alloys (the aluminum alloy should reach above 500°C). The mold should also be preheated at the same time. The preheating temperature varies with the die-casting alloy. The aluminum alloy should reach about 350°C, and the zinc alloy should reach about 250°C; the pressure chamber and the cavity should be sprayed with paint immediately after preheating; (3) metal Liquid pouring into the hot runner, mold clamping, and vacuuming: After the metal liquid is poured into the hot-press chamber of the lower mold 9, the upper cylinder 4 quickly clamps the upper mold 5 and the lower mold 9, seals the parting surface and starts the vacuum Vacuum the valve, before the injection starts, vacuum the cavity 6, and reach the control vacuum value (-0.09MPa) within 3 seconds; (4) Low speed, vacuum filling: choose the filling speed according to different castings ( Pre-set, the movement speed of the injection punch is controlled at 10-100 mm/s). When the vacuum value reaches -0.09MPa, the injection cylinder 11 moves immediately to start injection; during the whole process of injection, the vacuum system is always connected with the cavity and maintains the control value.

(5) Squeeze solidification: In the post-injection stage (at this time, the cavity is full and the center of the casting has not yet solidified), the injection cylinder 11 is rapidly pressurized, and the injection punch 10 is aligned with the direct pressure at a high specific pressure of hundreds of MPa. The metal in the runner is pressed and kept for several minutes, and the casting is fully fed to make the casting more compact; (6) Open the mold and take the piece.

The invention is suitable for the full vertical die-casting machine with a booster system in the injection cylinder to carry out die-casting of aluminum alloy and zinc alloy.

Claims (1)

1, a kind of low speed vacuum squeeze casting technology is characterized in that processing step is as follows:

(1) mould, vacuum system and hot runner design: the specific (special) requirements of mould design is that ingate thickness is thicker than common compression mod, is 6-12mm, the position of hot runner is installed penetrates more than the cylinder body 200mm at tripping; The hot runner designing requirement is that heater is divided into many groups, respectively by different temperature controller controls; The requirement of Vacuum System Design is that vavuum pump discharge capacity and vacuum tank volume will be determined according to the die cavity volume size, guarantee that the die cavity vacuum reaches-0.09MPa or higher in 3 seconds, the performance of vacuum stopper will guarantee that die cavity is communicated with fast with vacuum system, make molten metal can not enter vacuum system with air-flow again, the flow of vacuum valve and each element of vacuum system and actuation time will be complementary with whole vacuum system;

(2) hot runner and mould are installed preheating: the principle of hot runner Temperature Field Control is: press the temperature at the indoor center of temperature specific pressure on indoor mouthful high about 50 ℃, press indoor mean temperature by different diecasting alloys values, mould preheating simultaneously, aluminium alloy should reach about 350 ℃, and kirsite should reach about 250 ℃; Should be after the preheating at once to pressing chamber and die cavity spray paint;

(3) molten metal pours into hot runner, matched moulds, vacuumizes: pour in the hot pressing chamber of counterdie when molten metal after, matched moulds seals die joint and starts vacuum valve and vacuumizes fast, before injection begins, die cavity is vacuumized, reach the control vacuum values in 3 seconds and be-0.09Mpa;

(4) low speed, vacuum are filled type: select filling velocity according to different foundry goods, when vacuum values reach-during 0.09MPa, press the injection switch immediately, the beginning injection, in the overall process of injection, vacuum system is communicated with die cavity always, and the retentive control value;

(5) extrusion is solidified: at the injection after-stage, and the rapid supercharging of injection hydraulic jack, injection punch head is exerted pressure to the metal in the sprue with the high specific pressure of hundreds of MPas and was kept several minutes, and fully the feeding foundry goods makes foundry goods finer and close;

(6) die sinking pickup.

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