CN111331077A - Size control method for casting high-silicon light hypereutectic aluminum-silicon alloy product - Google Patents

Abstract

The invention belongs to the technical field of metal material application, and particularly discloses a size control method for casting a high-silicon light hypereutectic aluminum-silicon alloy product, which comprises the following steps of 1, and determining the cast product. And 2, after the model is established. And 3, after the setting of the pretreatment parameters is finished, selecting a view module to observe the simulation result, and determining the material of the wax mould. And 4, printing the crystal grain selector through a 3D printer. And 5, connecting the crystal grain selectors manufactured in the step 4 together on a tree. And 6, preheating the shell mold wax component or cluster, measuring the size of the crystal grain selector by using a vernier caliper, and calculating the size tolerance of the material. The invention has the beneficial effects that: 1. based on the rapid manufacturing capability of an investment casting technology and a 3D printing technology, a fused deposition modeling technology and a photocuring modeling technology are selected through comparative analysis; 2. the method for producing the wax pattern by traditional investment casting and single crystal casting is researched and improved.

Description

Size control method for casting high-silicon light hypereutectic aluminum-silicon alloy product

Technical Field

The invention belongs to the technical field of metal material application, and particularly relates to a size control method for casting a hypereutectic aluminum-silicon alloy product based on high-silicon light weight.

Background

The A390 hypereutectic aluminum-silicon alloy blank has the advantages of light weight, high strength, high wear resistance, high heat resistance, low thermal expansion and the like, and is usually used for manufacturing key parts such as pistons, rotors, swash plates and the like of automobile transmitters. Compared with the conventional casting, the casting is lighter than the common iron casting, the structural segregation is eliminated through the nodular treatment of silicon, the uniform structure and fine crystal grains are obtained through the solid solution treatment, the mechanical property and the thermal process property of the alloy can be obviously improved, and the casting is widely applied to the automobile industry, particularly the application of light-weight automobiles and new energy automobiles.

Because China has a huge gap in the research and development of the high-purity A390 supersaturated aluminum alloy compared with the automobile industry strong countries such as America, Japan and the like, particularly under the large background that new energy automobiles are applied to new generation aluminum alloys with light weight, high strength and high wear resistance, the research on the aspect is still in the starting stage, so the research work of the A390 supersaturated aluminum alloy is carried out, and the research work is very significant.

Investment casting has the advantages of high dimensional accuracy and high surface smoothness, but has the limitations of too many manufacturing processes, long processing period and the like, and particularly, in the process of developing a new product, the design drawing of a sample needs to be repeatedly modified before production, so that the manufacturing period is long. In order to shorten the manufacturing period, considering that it is difficult to shorten the time of the case-making process, research groups consider the 3D printing technique to be an effective method to replace the conventional wax pattern manufacturing process. The research in this aspect in foreign countries accumulates experience for many years and gradually popularizes the research to commercial application, the research in this aspect in domestic countries is relatively late, but is actively producing and popularizing, however, the research lacks theoretical foundation, and limits the application of the technology in enterprises, so that more experience and innovation are necessary to be obtained from the level of basic research, and further the application of the technology in enterprise production is promoted.

Therefore, in view of the above problems, the present invention provides a method for controlling the dimensions of a cast high silicon light hypereutectic aluminum-silicon alloy product.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a dimension control method for casting high-silicon light hypereutectic aluminum-silicon alloy products, which researches and improves the traditional wax pattern production methods of investment casting (non-directional solidification) and single crystal casting (directional solidification) by selecting a Fused Deposition Modeling (FDM) technology and a photocuring modeling (SLA) technology through comparative analysis, and simultaneously, the application of the 3D printing technology in the traditional casting is applied due to the short period and low cost, and the optimal 3D printing material meeting the requirements of the traditional casting (thermal cracking performance and dimensional tolerance) is found.

The technical scheme is as follows: the invention provides a size control method for casting a high-silicon light hypereutectic aluminum-silicon alloy product, which comprises the following steps of 1, determining the cast product, and then performing 3D modeling by utilizing UG 100. And 2, after the model is established, outputting the model to a file in an XYT format, operating the PROSTAST software, selecting a MasHCAST module, importing the MasHCAST module into the XYT file for gridding, and generating and importing the grid model into the PROSTAST module for parameter setting. And 3, after the setting of the preprocessing parameters is finished, carrying out finite element solving operation, and after the calculation is finished, selecting a view module to observe the simulation result to determine the material of the wax mould. And 4, printing the crystal grain selector by using a 3D printer, wherein the wax mould of the crystal grain selector in the step 3 is matched for use. And 5, connecting the crystal grain selectors manufactured in the step 4 together on a tree, and forming the wax components or clusters through a hot spatula by using a wax flow device and a required pouring device. And 6, preheating a shell mold wax component or cluster in a Bridgman furnace, pouring a high-temperature alloy melt on a high-temperature plate, then drawing the high-temperature alloy melt out of a heating area through a baffle plate and entering a cooling area, wherein the used heater and the pouring temperature are 1460-1500 ℃ and 1520-1550 ℃ respectively, the V is 3-3.5 mm/min of extraction speed, and finally, the size of a crystal grain selector is measured by using a vernier caliper to calculate the size tolerance of the material.

In the technical scheme, the heater and the pouring temperature used in the step 6 are 1460 ℃ and 1520 ℃, respectively, and the extraction speed is 3 mm/min in V.

Compared with the prior art, the size control method for casting the high-silicon light hypereutectic aluminum-silicon alloy product has the advantages that: 1. selecting Fused Deposition Modeling (FDM) technology and light-cured modeling technology (SLA) through comparative analysis based on the rapid manufacturing capabilities of investment casting technology and 3D printing technology; 2. the method for producing the wax pattern by traditional investment casting (non-directional solidification) and single crystal casting (directional solidification) is researched and improved; 3. the application of 3D printing technology in conventional casting has been applied due to its short cycle time, low cost, and finding the best 3D printed material that meets the requirements of conventional casting (hot crack performance, dimensional tolerance). With the final best material applied to DS (single crystal casting) and compared to several other 3D printed samples, 3D printed materials suitable for traditional casting and directional solidification were finally found.

Drawings

FIG. 1 (a) is a three-dimensional model of an EGR joint with a door;

FIG. 1 (b) is a 3D model of an EGR joint module;

FIG. 2 is an EGR connector module and housing model thereof;

FIGS. 3 (a), (b), (c), and (d) are simulation results of the EGR joint filling process;

FIG. 4 is a simulation of the solidification process of an EGR joint;

FIG. 5 is a simulation of EGR joint shrinkage cavity position;

FIG. 6 is a SLA printed EGR connection sample of a photopolymer;

FIG. 7 is a SLA printed EGR of a photoresist connecting the gate of the sample connecting portion;

FIG. 8 (a) shows a second layer form of the transition layer;

fig. 8 (b) shows the case when the fourth layer is completed;

in fig. 9 (a), (b) the cracks on the mold shell are clearly seen from different angles;

FIGS. 10 (a), (b), (c), (d) are four prints;

FIGS. 11 (a), (b), (c), (d) are four-piece castings;

FIG. 12 (a) is a Bridgman process during superalloy casting;

FIG. 12 (b) is a Bridgman process;

FIG. 13 is a mold cast in a Bridgman furnace;

fig. 14 is a grain selector cast from MM247 LC.

Detailed Description

The invention is further elucidated with reference to the drawings and the embodiments.

The invention provides a size control method for casting a high-silicon light hypereutectic aluminum-silicon alloy product, which comprises the following steps of 1, determining the cast product, and then performing 3D modeling by utilizing UG 100. And 2, after the model is established, outputting the model to a file in an XYT format, operating the PROSTAST software, selecting a MasHCAST module, importing the MasHCAST module into the XYT file for gridding, and generating and importing the grid model into the PROSTAST module for parameter setting. And 3, after the setting of the preprocessing parameters is finished, carrying out finite element solving operation, and after the calculation is finished, selecting a view module to observe the simulation result to determine the material of the wax mould. And 4, printing the grain selector by using the wax mould material obtained in the step 3 through a 3D printer. And 5, connecting the crystal grain selectors manufactured in the step 4 together on a tree, and forming the wax components or clusters through a hot spatula by using a wax flow device and a required pouring device. And 6, preheating a shell mold wax component or cluster in a Bridgman furnace, pouring a high-temperature alloy melt on a high-temperature plate, then drawing the high-temperature alloy melt out of a heating area through a baffle plate and entering a cooling area, wherein the used heater and the pouring temperature are 1460-1500 ℃ and 1520-1550 ℃ respectively, the V is 3-3.5 mm/min of extraction speed, and finally, the size of a crystal grain selector is measured by using a vernier caliper to calculate the size tolerance of the material.

Further preferably, the heater and the casting temperature used in step 6 are 1460 degrees celsius and 1520 degrees celsius, respectively, and V is 3 mm/min extraction rate.

Examples

Simulation of 3D printing mode of automobile mechanical parts: the experiment adopts four parts (1) EGR connecting pieces, (2) automobile parts blocks, (3) middle plates for electric tools and (4) sewing machine parts, and researches the application of the wax mold of the FDM forming machine in the traditional investment casting experiment. FIG. 1 (a) is a three-dimensional model of an EGR joint with a door, FIG. 1 (b) is a 3D model of an EGR joint module, as shown, UG100 is firstly used for 3D modeling, a runner joint design is shown in FIG. 1 (a), EGR is then assembled into the design shown in FIG. 1 (b), and in order to verify the feasibility of the casting process, the casting process of a part is pre-tested by PROCAST software before actual production, and the cold end air inlet of the EGR valve is simulated. After the model is built, the model is output to a file in an XYT format, PROSTAST software is run, a MasHCAST module is selected to guide the XYT file to carry out gridding treatment, the mesh size of a part is set to be 1mm, and the mesh size of a pouring system is set to be 4 mm. A 7mm thick housing was created using the shelling function in MelHCAST and fig. 2 shows a grid model of the EGR connector module and its housing, with a total number of nodes of 168743 and grid cells of 786499. And generating and importing the grid model into a PROSTAST module for parameter setting. The material used to cast the EGR fitting was 1.4511 stainless steel, while the housing material was zircon sand, the type of contact between the casting and the form was CONC, and the interfacial heat transfer coefficient was 750W/(M2K). Boundary conditions and initial conditions were determined, boundary temperature was 1620 ℃, heat was selected as air cooling, pressure was 0.1MPa, fill time was 3s, and calculated fill rate was 0.974 kg/s. Under initial conditions, the casting temperature T is 1620 ℃, the mold shell temperature T is 1150 ℃, and finally the operating parameters are set. Gravity filling is preferred, with the maximum step size (NSTEP) set to 300000 and the simulated end temperature (TSTEP) 600 ℃. A porosity reduction analysis (POROS) is set in the thermal block and the effect of the gas (gas) is set to ON in the flow block.

After the setting of the preprocessing parameters is completed, a finite element solution operation is performed. And after the calculation is finished, selecting a view module to observe the simulation result. As shown in FIG. 3, the result of the filling simulation showed that the high-temperature molten metal rapidly flowed through the main runner at the initial stage of the pouring. After the main runner is filled, the lower member is filled before the upper member, the filling rate is slow and steady, no significant gas turbulence is observed, and the entire filling process is completed when the filling machine is filled with molten metal.

Fig. 4 and 5 show the simulation results of the solidification process, and it can be seen that the temperature gradient distribution of the casting gradually increases from bottom to top. Therefore, the solidification process of the joint pouring process is a sequential solidification process from bottom to top, the solidification process is reasonable, the pouring of a pouring system to parts is facilitated, and casting defects such as shrinkage and cold separation can be effectively prevented. The merle position of the EGR connector, as shown in fig. 5, is where the constriction is only present in the riser and main channel, and part is not loose.

3D printing crystal grain selector:

according to the requirements of precision casting, the wax mould material is judged according to melting point, thermal stability, fluidity, shrinkage rate, strength and plasticity, weldability, coating and ash content.

In experiments to print wax patterns in 3D printing technology, ABS plastic, PLA plastic and resin 8000 (resin 8000 is a printing material supplied by future factories) were selected, the parameters of these three materials are shown in Tab in table 1,

TABLE 1 RESI8000 Properties of ABS and PLA plastics

RESI8000 has proven to be the best wax pattern material because of its high accuracy as shown by Tab. 1.

The EGR joint sample made of photosensitive resin RS8000 is printed by SLA, which shows high printing precision and smooth surface (figure 6), then the template is made, the sand is made according to standard precision casting process, and the shell is 6 layers and half. In the experiment, the coating formula, the drying time, the relative humidity and the ambient wind speed are strictly controlled, and the forming and casting processes are shown in FIGS. 8 (a) and (b).

The wax in the corresponding position of the casting system was melted with a modified electric iron to form a pit filled with liquid wax, a sprue in the joint portion (as shown in fig. 7), the mold surface was cleaned, oil was removed, and after drying, coating was performed, the dipping process was repeated 5 times for producing a ceramic shell, and 4 parts of the drying process had a duration different from each layer, and the dewaxing process was performed in steam dewaxing, and the shell was heated at 170 ℃ for 12 min.

After steam kettle dewaxing, it was observed that the wax in the shell was removed, but the pattern of the resin material was not removed, and the shell cracked due to thermal expansion of the resin, and the experimental results showed that the coefficient of thermal expansion of the bright resin material selected was too high to be used directly for printing in the "wax mold" experimental protocol. In fig. 9 (a), (b), the cracks on the mold shell can be clearly seen from different angles.

The special requirements of the FDM technique for the printing material are (1) low shrinkage, (2) low melting temperature, (3) good adhesion, and (4) low viscosity. Finally, taking all these factors into account, ABS materials were selected for wax model experiments.

Casting equipment and procedure:

ABS model part adopts FDM printing, and the gating system adopts wax system, compares with the whole product of printing ABS, and this scheme is with low costs, and is fast. The 3D printing apparatus was a MaMBOT copier 2X, using FDM after selecting ABS consumables, the forming principle was a print, the maximum forming size was 246mm X152mm X155mm, the maximum printing accuracy was 0.1mm, introducing STL formatted file of the model derived from UG100 into aumword, selecting a support position, and printing ABS parts at parameters such as height and printing speed, the temperature of the pattern material and the support material was 230 ℃ at the time of printing. The layer thickness was 0.2mm and the wall thickness was 1.2mm, and then printed, as shown in fig. 10 (a), (b), (c), (d), (a) EGR connector printout (b) land printing, (c) pegboard printing, and (d) sewing machine attachment print.

The coating formulation was adjusted to avoid damage to the shell during dewaxing and ABS removal, the dipping process was repeated 5 times until a ceramic shell was produced, the duration of the drying process was different for 4 parts, and in the experiment, the coating formulation, drying time, humidity and blowing speed were controlled. The dewaxing process was carried out in a steam dewaxing process, first heating the shell at 170 ℃ for 12min, during which the ABS rapidly softened and flowed out of the ceramic shell. The left material is removed during firing, cleaning impurities. The ceramic shell was heated again before casting, and then the ceramic shell taken out of the furnace was filled with 200 kg of molten steel, and when the molten steel was cooled for 6 hours, the shell was broken, and the parts cut from the gating system were painted, as shown in fig. 11 (a), (b), (c), (d), four pieces, (a) EGR joint casting, (b) cushion block casting, (c) nail plate casting, and (d) sewing machine part casting.

And (3) casting process:

the above casting experiment was carried out in an industrial scale vacuum bridgeman furnace (ALD) installed at the aachen industry university foundry college, the solidification conditions of which are the same as those of furnaces generally used for commercial production of DS/SC parts, which is a double graphite heating zone vacuum furnace with a tiltable induction melting crucible, the degree of vacuum of which can reach 5 × 10-5 mbar, the melting capacity of which is 50 kg, and the material used in this experiment was 4.09kg.

The mold was placed on a cold plate and heated in two heating zones in a bridgman process. To achieve separation between the hot and cold zones, baffles are provided at the bottom of the heating system. For curing, the mold was withdrawn from the hot zone and heat was extracted by radiative heat exchange between the mold and a black furnace chamber. The driving factor for radiative heat exchange depends on the difference between TM4-TF 4. Tm is the temperature of the mold (about 1500 ℃) and TF is the temperature of the water-cooled furnace wall (about 40 ℃).

A central control computer is integrated in the furnace, by means of which all process parameters and other control commands can be given, and the control unit can also store all process information and measurement data, fig. 12 (a) the bridgman process in the superalloy casting process, fig. 12 (b) the bridgman process.

The study selected MM247LC superalloy, one of the directionally solidified materials, with MM247LC liquid temperature of about 1368 ± 2 ℃ and solidus temperature of about 1282 ± 6 ℃, in a bridgeman furnace, the shell die cluster was preheated, the superalloy melt was cast on a hot plate (fig. 12 (a)), then drawn from the heated zone through a baffle into the cooling zone (fig. 12 (b)), using heaters and casting temperatures of 1460 ℃ and 1520 ℃, respectively, using an extraction rate of V ═ 3 MM/min.

After the pouring test (fig. 13 mold after bridgman furnace casting), the mold was cooled to an in-furnace temperature of about 300 ℃, the vacuum was released, then the mold was taken out, then the cast piece was knocked out from the ceramic mold at room temperature and mark, this cast portion was sand blasted to remove the ceramic sticking to the surface, then we obtained a sample as shown in fig. 14 (grain selector cast from MM247 LC), and finally, the size of the grain selector was measured with a vernier caliper, and the dimensional tolerance of the material was calculated.

The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.

Claims (2)

1. The size control method based on the casting of the high-silicon light hypereutectic aluminum-silicon alloy product is characterized by comprising the following steps of: comprises the following steps of (a) carrying out,

step 1, determining a cast product, and then performing 3D modeling by utilizing UG 100;

step 2, after the model is established, outputting the model to a file in an XYT format, operating PROSTAST software, selecting a MasHCAST module, importing the MasHCAST module into the XYT file for gridding, generating a grid model, and importing the grid model into the PROSTAST module for parameter setting;

step 3, after the setting of the preprocessing parameters is finished, finite element solving operation is carried out, and after the calculation is finished, a view module is selected to observe a simulation result and determine the material of the wax pattern;

step 4, printing a crystal grain selector by using a 3D printer, wherein the wax pattern in the step 3 of the crystal grain selector is matched for use;

step 5, connecting the crystal grain selectors manufactured in the step 4 together on a tree, and forming a wax component or cluster by a wax flow device and a required pouring device through a hot spatula;

and 6, preheating a shell mold wax component or cluster in a Bridgman furnace, pouring a high-temperature alloy melt on a high-temperature plate, then drawing the high-temperature alloy melt out of a heating area through a baffle plate and entering a cooling area, wherein the used heater and the pouring temperature are 1460-1500 ℃ and 1520-1550 ℃ respectively, the V is 3-3.5 mm/min of extraction speed, and finally, the size of a crystal grain selector is measured by using a vernier caliper to calculate the size tolerance of the material.

2. The method of dimensional control of casting based on a high silicon lightweight hypereutectic aluminum-silicon alloy product according to claim 1, characterized in that: the heater and casting temperature used in step 6 were 1460 degrees celsius and 1520 degrees celsius, respectively, using a V-3 mm/min extraction rate.

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