Lost foam casting method for machine tool part body
By optimizing the foam model, chill design, and gating system, and combining CAE simulation and reinforcement processes, the problems of slag inclusions, sand inclusions, and shrinkage cavities in the castings of the machine tool parts were solved, and high-quality casting production was achieved.
Patent Information
- Application Number
- CN202510911083.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-02
- Publication Date
- 2025-11-07
AI Technical Summary
In the process of casting machine tool parts using existing technology, problems such as slag inclusions, sand inclusions, shrinkage cavities, and porosity are prone to occur, especially on the bottom surface and in thick areas, which can lead to irreparable castings that must be scrapped.
By employing techniques such as low-density foam model fabrication, direct chill and conformal chill design, stepped single-head gating system, multi-point dispersed ingate, casting CAE simulation, heat-insulating risers, and direct chill quenching, combined with optimized pouring temperature and reinforced model process, we ensure that the casting is filled completely and internally fed.
It effectively avoids defects such as slag inclusions, sand inclusions, shrinkage cavities, and shrinkage porosity in castings, ensuring that the quality of castings meets acceptance standards, solving the problem of shrinkage cavities on the bottom surface and thick areas of castings, and improving the integrity and repairability of castings.
Smart Images
Figure CN120901243A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lost foam casting, and more particularly to a lost foam casting method for machine tool parts. Background Technology
[0002] This machine tool component has extremely high requirements for casting quality. The part measures 3500mm*1622mm*1685mm and has a theoretical weight of 1160KG. Its use is subject to strict requirements; the end has multiple deep holes, and the machining quality within these holes must be high. Slag inclusions, sand inclusions, and shrinkage cavities are not permitted during machining, and their positions must be guaranteed according to the dimensions in the drawings. Currently, during the lost-wax casting production of this component, a stepped side-pouring method is used. However, due to the large thickness of the machined hole area and the significant shrinkage of the poured molten iron, large-area shrinkage cavities and depressions easily appear on the bottom surface of the component. Because the defect area is too large to repair, this part must be scrapped. While the stepped pouring method facilitates rapid filling of the mold with molten iron and is beneficial to the temperature field of the casting, the model itself is over 1622mm high. The area with the round hole is particularly striking, resembling a solid cuboid of 525mm x 345mm x 1333mm. Conventional molding and pouring processes, the gating system, and the casting itself cannot meet the demand for substantial molten iron feeding during the solidification process of this thick core area after pouring. This results in shrinkage cavities and collapse at the bottom end face of the casting. Furthermore, the overall thickness of this component makes it highly susceptible to sand embrittlement in areas such as the grooves. Therefore, addressing these issues is crucial. Summary of the Invention
[0003] In view of this, the purpose of this invention is to provide a lost foam casting method for machine tool parts, which solves the problems in the background art.
[0004] To achieve the above objectives, the present invention provides a method for lost foam casting of machine tool parts, characterized by comprising the following steps:
[0005] Step 1, make a foam model: make a foam model of the lost foam casting of the machine tool part by CNC machining. The slag discharge surface of the end of the foam model is 15mm larger. Then, perform acetone steam polishing at a temperature of 50-60℃ for 3-5 minutes to eliminate CNC machining tool marks and improve surface roughness.
[0006] Step 2, Design and fabrication of direct chills and conformal chills: Based on the model's surface and bottom surface, cast the direct chills and conformal chills to obtain the surface and bottom surfaces. Match and polish the chills to the model, mark them, and seal the chill areas with tape.
[0007] Step 3, setting up the casting system: Select a stepped single-head casting system, with the thicker end serving as the molding surface and the thinner end serving as the slag discharge surface;
[0008] Step four, casting CAE simulation design: after setting the gating system, simulate on the casting CAE software, adjust the position of the sprue during the process until all the defects are eliminated;
[0009] Step five, coating, drying: first, match the profile direct chill iron and the profile conformal chill iron with the foam model, and mark them, and paste the cloth adhesive tape on the position of the foam model laying the chill iron, then, coat the foam model, coat three times and dry;
[0010] Step six, reinforcing the model, molding: before molding, pre-set the gating system and ingates, and brush the alcohol coating again on the thick and large position and the key position which is easy to wrap sand, adopt the turning molding process, adopt the way of layer by layer sanding and layer by layer box netting, after sanding, wait for the sand to solidify and strengthen, turn the box after 5-6 hours, remove the reinforcing foam after turning the box, clean the sand edge and broken coating around the model contour, repair the position of the bottom surface damage, place the coating and drying well at the position of pre-setting the deslag seat, and connect them together, place the conformal chill iron at the thick position in the middle of the bottom surface, place four risers at the four corners of the model to provide feeding, after molding, fix the sand box with the clamp, after completely solidifying, hoist to the waiting pouring area;
[0011] Step seven, pouring: place the chill iron on the surface of the sand box, then pour the molten iron, control the pouring temperature to be 1380℃;
[0012] Step eight, cooling: after pouring, measure and record the temperature of the casting in the sand mold through the thermocouple pasted during molding, when the temperature drops to about 350℃, drop the sand and hoist out the casting, after cooling to room temperature, remove the gating system, riser and other parts, polish, machine, and remove the excess 10mm of the end of the casting.
[0013] Preferably, the foam model in step one adopts the expandable polystyrene and polymethyl methacrylate composite foam board, and the density is 18-20kg / m 3 .
[0014] Preferably, the ingate in step three adopts the ceramic pipe, and is dispersedly injected in multiple points, and a 500mm pot table is placed at the position of the direct ingate.
[0015] Preferably, the step four is simulated by CAE casting, accurately positioning the position where the shrinkage cavity and shrinkage porosity of the casting may occur, supplementing the shrinkage by placing four heat preservation risers at the bottom, and using direct chill iron to chill the position which cannot be directly supplemented by the riser at the lower and middle area.
[0016] Preferably, the step five, the water-based coating of the coating has a Baume degree of 55-75, and the drying is performed by stepwise drying, first drying at 40 DEG C for 2h, then drying at 60 DEG C for 3h, and finally drying at 80 DEG C for 1h.
[0017] Preferably, the step five, after three times of spraying, the minimum thickness of the dried model coating is 1.0-2.0mm, preventing the coating from being too thin to cause sand sticking.
[0018] Preferably, the step six, when the sand mold is made, the resin addition ratio of the molding sand is 1.0%, ensuring that the strength of the molding sand is greater than 1.5MPa.
[0019] Preferably, the step seven, the weight of the pressing iron is 7 times the weight of the pouring.
[0020] The present application has the following advantages: the present application first uses a low-density foam board to make a foam model, thereby reducing the probability of slag defects in the pouring process of the processing surface; then directly cold iron and cold iron with the shape of the model surface are made; then a stepwise single-head pouring system is selected, and a ceramic tube is used for the inner gate to be injected in multiple points, thereby ensuring that the molten iron fills the mold layer by layer and quickly, fully considering the flow of the molten iron, avoiding other defects such as cold shut, insufficient pouring, etc., and placing a 500mm pot table at the position of the direct gate to improve the filling speed of the molten iron during pouring, so that the foam quickly gasifies and decomposes, ensuring that the casting is filled perfectly; then the casting CAE simulation design is performed to accurately position the position where the shrinkage hole and shrinkage are likely to occur, and four heat preservation risers are placed at the bottom for feeding, and it can be seen from the defect + liquid phase CAE analysis that the shrinkage and shrinkage defects are moved to the upper part of the heat preservation riser, and the lower part is well fed by the molten iron during the solidification process, and at the same time, direct cold iron is used to activate the lower part and the middle area which cannot be directly fed by the riser. In order to further reduce the risk of shrinkage, the pouring temperature is designed to be 1380 DEG C, which reduces the probability of shrinkage and shrinkage in the thick core area. Then the coating is sprayed and dried, and the drying is performed by stepwise drying to avoid the rapid solidification of the surface coating, thereby reducing the gas defects during pouring. Then the reinforcing model and molding are performed, and the turning molding process is used to avoid the shrinkage and shrinkage defects. Then pouring is performed, and the weight of the pressing iron on the surface of the sand box during pouring is about 7 times the weight of the pouring, so as to resist the pressure of the molten iron during pouring, the pressure formed after the foam gasifies, and the expansion force of the nodular iron during the graphitization expansion process, maintain the strength of the sand mold to make the internal expansion of the casting, and achieve the purpose of internal feeding. Finally, cooling, polishing and leveling are performed to remove the excess 10mm of the casting end, thereby ensuring the quality of the present application.
[0021] The present application optimizes the lost foam casting process, solves the problems of slag and sand inclusion and shrinkage in the processing hole, and the problems of shrinkage and shrinkage in the bottom end, avoids the shrinkage and shrinkage defects by using the pouring system, pouring process, cold iron process and riser in cooperation, and provides a casting meeting the acceptance standard. BRIEF DESCRIPTION OF DRAWINGS
[0022] In order to more clearly illustrate the technical solutions of the present application or the prior art, the drawings required to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only illustrate the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.
[0023] Fig. 1 is a schematic diagram of the whole application;
[0024] Fig. 2 is a schematic diagram of the lower part of the application;
[0025] Fig. 3 is a schematic diagram of the upper part of the application.
[0026] The marks in the figure are:
[0027] 1 - riser, 2 - shaped chill, 3 - machine tool base casting, 4 - gating system, 5 - direct chill. DETAILED DESCRIPTION
[0028] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below in combination with specific embodiments.
[0029] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present application should be understood as the usual meanings understood by those skilled in the art to which the present application belongs. The terms "first", "second" and similar terms used in the present application do not represent any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the elements or objects before the terms cover the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.
[0030] As shown in Figs. 1 to 3 A machine tool base lost foam casting method, characterized in that it comprises the following steps:
[0031] S1, making a foam model: a foam model with a density of 18-20 kg / m 3DE expandable polystyrene and polymethyl methacrylate composite foam board, the foam model of the lost foam casting of the machine tool part is made by numerical control machining, the end of the foam model is arranged with a 15mm deslagging surface, then the end is polished by acetone vapor, the temperature is 50-60℃, the time is 3-5 minutes, the numerical control machining tool marks are eliminated, and the surface roughness is improved;
[0032] S2, direct chill iron, conformal chill iron design and production: when adopting the molding process without chill iron and without riser, a large amount of molten iron is needed for feeding in the thick area during solidification and cooling, so that the upper part of the casting is drawn away, and shrinkage collapse occurs, which cannot be repaired and is scrapped, according to the structure characteristics of the part, under the condition that the gating system is unchanged, the surface direct chill iron and the bottom conformal chill iron are obtained by model surface and bottom surface spraying molding, the chill iron is matched with the model and polished, and is marked, and the chill iron area is sealed with adhesive tape;
[0033] S3, gating system setting: the size of the part is 3500mm*1622mm*1685mm, the theoretical weight is 1160KG, the main body wall thickness is 55mm, and it belongs to a relatively thick casting, therefore, a stepped single-head gating system is selected, one end is thick and the other end is thin, the end with thick part is the surface, and the end with thin part is the deslagging surface, the sprue is made of ceramic pipe and is injected in multiple points, a 500mm pot table is placed at the position of the direct sprue to improve the filling speed of the molten iron during pouring, so that the foam is quickly gasified and decomposed, and the filling of the casting is ensured to be complete;
[0034] S4, CAE simulation design: after setting the gating system, the simulation is carried out on the CAE software, the position of the gate is adjusted until all the defects are eliminated; through the simulation of the CAE casting, the positions where the shrinkage holes and shrinkage porosities are likely to occur are accurately positioned, four heat preservation risers are placed at the bottom for feeding, and the direct chill iron is used for exciting cooling at the positions which cannot be directly fed by the riser in the lower and middle regions;
[0035] S5, spraying coating and drying: first, the surface direct chill iron and the surface conformal chill iron are matched with the foam model, and the marks are made, and the cloth adhesive tape is pasted on the position of the foam model where the chill iron is laid, then the foam model is sprayed with coating, and is dried after being sprayed for three times, the minimum thickness of the coating of the dried model after being sprayed for three times is 1.0-2.0mm, so as to prevent the sand sticking caused by the thin coating; the Baumé degree of the water-based coating is 55-75, the drying adopts a stepped drying, first, drying at 40℃ for 2h, then drying at 60℃ for 3h, and finally drying at 80℃ for 1h;
[0036] S6, reinforcing model, modeling: before modeling, the preset pouring system and ingates are advanced, and the alcohol paint is brushed again at the thick and large position where the sand is easy to wrap and at the key position, the turning modeling process is adopted, the resin addition rate of the sand mold is 1.0% during the sand embedding, the strength of the sand mold is ensured to be greater than 1.5MPa, the sand embedding is performed in the way of layer-by-layer embedding and layer-by-layer box netting, the sand mold is waited for curing and strength after the sand embedding, the box is turned after 5-6 hours, the reinforcing foam is removed after the turning, the sand edge around the model contour and the broken paint are cleaned, the position of the bottom surface damage is repaired in place, the slag discharging seat dried by spraying is placed at the position where the slag discharging seat is pre-set, and the slag discharging seats are connected in series, the shaped chill is placed at a thick position in the middle of the bottom surface, the alcohol paint is brushed, four risers are placed at four corners of the model to provide feeding, after the modeling is completed, the sand molds are fixed by the clamps, and after the complete curing, the sand molds are lifted to the waiting pouring area;
[0037] S7, pouring: the press iron is placed on the surface of the sand mold, the weight of the press iron is 7 times of the pouring weight, then the molten iron is poured, so as to resist the pressure of the molten iron pouring, the pressure formed after the foam gasification and the expansion force of the nodular iron in the graphitization expansion process, maintain the strength of the sand mold to make the internal expansion of the casting, and achieve the purpose of internal feeding; in order to further reduce the risk of shrinkage, the method of lowering the pouring temperature is adopted, the pouring temperature is designed to be 1380℃, and the shrinkage and porosity probability of the thick core area is reduced;
[0038] S8, cooling: after the pouring is completed, the temperature of the casting in the sand mold is measured and recorded by the thermocouple pasted during the modeling, the casting is lifted out after the temperature drops to about 350℃, the pouring system, riser and the like are removed and polished, the machining is performed, the excess 10mm of the casting end is removed, and the quality of the machine is ensured.
[0039] The lost foam casting process is optimized, the problems of slag and sand inclusion and shrinkage in the processing hole are solved, the problems of shrinkage and porosity in the bottom end are solved, the shrinkage and porosity defects are avoided through the cooperation of the pouring system setting, the pouring process, the chill process and the riser, and the casting meeting the acceptance standard is provided.
[0040] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to suggest that the scope of the present application is limited to these examples; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above. In order to be brief, they are not provided in details. Any omission, modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A method of LFT casting a machine tool component bed, characterized in that, The method comprises the following steps: Step one, making a foam model: making a foam model of the lost foam casting of the machine tool part through numerical control machining, the end of the foam model is provided with a 15mm deslagging surface, then performing acetone vapor polishing at a temperature of 50-60℃ for 3-5 minutes to eliminate the numerical control machining tool marks and improve the surface roughness; Step two, directly cold iron and shaped cold iron design and making: according to the model surface and bottom surface, the model surface directly cold iron and the bottom surface shaped cold iron are obtained by spraying molding and pouring, the cold iron is matched with the model and polished, and is marked, and the cold iron area is sealed and pasted with adhesive tape; Step three, setting a pouring system: a ladder type single head pouring system is selected, one side of the end is thick and large as the model surface, and the other side of the end is thin as the deslagging surface; Step four, casting CAE simulation design: after setting the pouring system, simulation is performed on the casting CAE software, and the position of the sprue is adjusted until all the defects are eliminated; Step five, spraying coating and drying: the model surface directly cold iron and the model surface shaped cold iron are matched with the foam model, and are well marked, and the positions of the foam model where the cold iron is laid are all pasted with cloth adhesive tape, then the foam model is sprayed with coating, and is dried after being sprayed for three times; Step six, reinforcing the model and molding: before molding, the preset pouring system and inner gate are set, the thick and large position and the key position where the sand is easy to be wrapped are brushed with alcohol coating again, the turning molding process is adopted, the sand is buried layer by layer in the way of layer-by-layer sand burying and layer-by-layer box net sleeving, after the sand is buried, the sand is waited to be solidified to have strength, the box is turned after 5-6 hours, the reinforcing foam is removed after the box is turned, the sand edge around the model contour and the broken coating are cleaned, the position of the bottom surface damage is repaired in place, the deslagging seat sprayed and dried is placed at the position of the pre-set deslagging seat, and is connected as a whole, the shaped cold iron is placed at a thick position in the middle of the bottom surface, four risers are placed at four corners of the model to provide feeding, after the molding is completed, the sand boxes are fixed with clamps, and are hoisted to the waiting pouring area after being completely solidified; Step seven, pouring: the press iron is placed on the surface of the sand box, then the molten iron is poured, and the pouring temperature is controlled to be 1380℃; Step eight, cooling: after the pouring is completed, the temperature of the casting in the sand mold is measured and recorded through the thermocouple pasted during molding, the sand is removed when the temperature is about 350℃, the casting is hoisted out, the pouring system, the riser and the like are removed and polished, the machine is processed, and the excess 10mm of the end of the casting is removed.
2. The method of claim 1, wherein the method is a lost foam molding method. The step one foam model uses a expandable polystyrene and polymethyl methacrylate composite foam board, with a density of 18-20 kg / m 3 .
3. The method of claim 1, wherein the method is a lost foam molding method. The inner gate in step three is made of a ceramic pipe and is injected in multiple points, and a 500mm pot table is placed at the straight gate position.
4. The method of claim 1, wherein the method is a lost foam molding method. In step four, the possible shrinkage cavity and shrinkage porosity positions of the casting are accurately positioned through the CAE casting simulation, the four heat preservation risers are used for feeding, and the direct cold iron is used for the positions which cannot be directly fed by the risers in the lower part and the middle area.
5. The method of claim 1, wherein the method is a lost foam molding method. In step five, the water-based coating has a Baumé degree of 55-75, the drying adopts a ladder type drying, the drying is first performed at 40℃ for 2h, then is performed at 60℃ for 3h, and finally is performed at 80℃ for 1h.
6. The method of claim 5, wherein the mold is a lost foam mold. The minimum thickness of the model coating after three times of coating and drying in the step five is 1.0-2.0 mm, which prevents the sand sticking caused by the thin coating.
7. The method of claim 1, wherein the method is a lost foam molding method. The resin addition ratio of the molding sand in the step six is 1.0%, which ensures that the strength of the molding sand is greater than 1.5 MPa.
8. The method of claim 1, wherein the method is a lost foam molding method. The weight of the pressed iron in the step seven is 7 times of the pouring weight.