Full mold casting process for large machine tool cross beam

Abstract

The invention relates to the technical field of full-mold casting, and provides a full-mold casting process of a large machine tool cross beam, a cross beam model is divided into several parts during earlier-stage model manufacturing, so that sand burying during box type casting molding is facilitated, molten iron is uniformly fed into a casting through a paper tube step pouring system in the pouring process, and the casting quality is improved. The temperature field distribution of the casting in the length direction is close, the defects of air holes and cold shut caused by too low local temperature are avoided, and meanwhile the defects of stress deformation, cracking and the like in the casting cooling process caused by too large temperature gradient are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of full-mold casting, and in particular to a full-mold casting process for a large machine tool crossbeam. Background Art

[0002] Machine tool parts are generally box-type structures with small wall thickness and thin structure, which are easy to deform and crack. Customers have strict requirements on the deformation control of castings, and there must be no defects such as sand holes and pores on the guide rail surface. CN107737873A discloses a full-mold casting method for a large grinding machine bed. By adopting a multi-runner open pouring system, it is ensured that the casting guide rail does not produce slag pores; a reasonable anti-deformation deflection and molding support method are designed to ensure that the over-long casting does not deform. However, the machine tool crossbeam is a long box-type structure. Conventionally, foam runners are used to produce large-sized machine tool castings, which are prone to cold shuts and pore defects in the middle area. The temperature difference of the casting is large in the length direction. The stress of the casting during solidification is too large, resulting in deformation and even cracking of the casting, which reduces the success rate of full-mold production of large machine tool parts. Summary of the invention

[0003] In view of this, the purpose of the present invention is to propose a full-mold casting process for large machine tool beams to solve the problem that in the conventional production of large-sized machine tool castings using foam runners, cold shut and air hole defects in the middle area are very likely to occur, the temperature difference of the castings in the length direction is large, and the stress during the solidification process of the castings is too large, resulting in deformation or even cracking of the castings, which reduces the success rate of the full-mold process for producing large machine tool parts.

[0004] Based on the above purpose, the present invention provides a full-mold casting process for a large machine tool beam. The machine tool beam is a large box-type structure, including the following steps: Step 1, model making: dividing the model into two sections along the center line of the length direction, dividing the model into two sections along the center line of the height direction, and making two upper cover plates separately; Step 2, casting process design: confirmed by casting CAE simulation, setting a paper tube step pouring system, each inner gate directly enters the molten iron from the straight runner position, according to the casting process simulated by CAE, affixed the inner gate patch at the inner gate position, and pasted the cloth-based tape on the model splicing position before pouring; Step 3, pouring paint, pouring paint on the model separately and drying it, and the splicing surface of the separately made cover plate is not poured. Apply paint to ensure that the coating thickness is not less than 1.5mm. After drying, reinforce the inside of the model to prevent the model from being deformed by the molding sand when burying the sand; Step 4, modeling: first splice the two lower sections of the model on the modeling platform, and stick the joints with cloth-based tape. On the modeling platform, surround the model with a 100mm wide and 100mm high foam strip, and fix the foam strip and the model with bamboo sticks; connect the pouring system according to the preset casting process, connect the stepped pouring system with a paper tube, the inner gate is 50mm in diameter, and each 70mm diameter straight runner connects two sets of stepped inner gates; place the sand box frame, start to bury the molding sand layer by layer, fill and scrape the top surface, and wait for the molding sand to solidify. During the waiting process, clamp the box cards between the sand boxes of each layer to ensure that each layer The sand boxes are locked; box turning: the sand box is turned over and buried inside the cavity. The sand is compacted with a tamping rod during the burying process. After the inside of the cavity is compacted and scraped flat, wait for the molding sand to solidify. After the molding sand is completely solidified, paint is applied on the surface of the molding sand to ensure that the coating thickness after drying is not less than 1.5mm. After the coating is dry, the tape pasted on the splicing position is torn off, and the 100*100mm foam strip that surrounds the model during molding is taken out from the molding sand, and one of the cover plates and the upper two sections of the model are spliced ​​and fixed on the sand box; connect the sprue with a heightened diameter of 70, superimpose the sand box frame, start to bury the sand layer by layer and compact it. When it is buried to the top surface of the model, scrape it flat and wait for the molding sand to solidify. After the molding sand is solidified, brush alcohol-based paint on the surface of the molding sand within the range where another cover plate is needed to be covered to ensure Ensure that the coating thickness is not less than 1.5mm after the coating is dry. After the coating is dry, tear off the cloth-based tape on the top surface of the model to expose the foam, fit another cover plate on the surface of the sand box, and fix it with iron nails, continue to connect the heightened sprue, stack the sand box frame, fill sand layer by layer and tamp it, ensure that the minimum sand consumption of the top layer of the model is not less than 400mm, connect the paper tube sprue to the two ends of the sand box to set the pouring cup area; step five, the sand box is transported to the area to be poured, the top surface of the sand box is pressed with iron, and the negative pressure pipeline is connected; step six, smelting molten iron, controlling the pouring temperature at 1400-1410℃, and pouring from both ends with two ladles; step seven, unpacking and dropping sand, and hanging out the casting; step eight, shot blasting, removing the pouring system, grinding, painting, and inspecting the hardness of the casting.

[0005] Preferably, in the molding process of step 4, after the splicing is completed, the deformation is detected by pulling the wire to control the deformation in the length direction to not exceed 2 mm.

[0006] Preferably, the resin addition amount in the molding sand in the molding process of step 4 is 1%, the 2H strength of the resin sand sample is not less than 1MPa, the sand intake around is not less than 150mm, and the sand intake of the upper layer of the model is not less than 350mm.

[0007] Preferably, the curing time of the molding process in step 4 is not less than 6 hours to avoid cracking of the sand mold due to insufficient strength of the sand mold caused by premature turning over.

[0008] Preferably, in the box turning process of step 4, after one of the cover plates and the upper part of the model are spliced ​​and fixed on the sand box, it is necessary to check whether the outer ring splicing is smooth. If there is deformation, take out the groove formed by the 100*100mm foam strip and grind the deformed position to avoid dislocation and seam crack defects on the final casting.

[0009] Preferably, before the sand mold is transferred to the pouring area in step five, the ground of the pouring area should be raked and leveled, and the ground of the sand box placement area should be free of large sand blocks and iron slag to avoid the top crack of the sand mold leading to fire leakage, deformation and crack defects of the casting; preferably, in step five, an iron pressure of not less than 7 times the pouring weight is pressed on the top surface of the sand box to avoid arching and deformation of the casting during the pouring and solidification processes.

[0010] Preferably, the negative pressure of the vacuum pump of the negative pressure pipeline in step five is controlled at 0.04-0.07Mpa to ensure that there is no back-spray of molten iron during the pouring process, and the smoke from foam gasification and combustion can be promptly pumped away by the vacuum pump.

[0011] Preferably, in step 7, the sand is removed about 200 hours after pouring, and the temperature of the casting in the sand mold is ensured not to exceed 300°C before the sand is removed. The beneficial effects of the present invention are as follows: the present invention divides the crossbeam model into several parts during the early model making to facilitate the embedding of sand during the box-type casting molding, and uses the paper tube step pouring system to allow the casting to evenly feed molten iron during the pouring process, thereby ensuring that the temperature field distribution of the casting in the length direction is similar, avoiding the formation of pores and cold shut defects due to local low temperature, and at the same time avoiding defects such as stress deformation and cracking during the cooling process of the casting due to excessive temperature gradient. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1It is an overall schematic diagram of the pouring system and the model of the present invention; Figure 2 It is a schematic diagram of the splitting of the model of the present invention; Figure 3 It is a schematic diagram of the machine tool crossbeam casting of the present invention. DETAILED DESCRIPTION

[0014] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0015] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0016] like Figures 1 to 3 As shown, a full-mold casting process for a large machine tool crossbeam, the machine tool crossbeam is a large box-type structure, including the following steps: S1, Model making: When making foam models, due to the large size of the product, in order to facilitate transportation and later coating and drying operations, the model is divided into two sections along the center line of the length direction. In order to facilitate the embedding of sand during modeling, the model is divided into two parts in the height direction, and the upper cover is made separately; S2, casting process design: The product height and length are relatively large. In the early stage, it was confirmed through casting CAE simulation. A paper tube step pouring system was set up. Each ingates directly enters the molten iron from the sprue position, ensuring that the temperature along the length of the casting is close to avoid defects such as stress deformation caused by excessive temperature difference and insufficient cold shut pouring in the low-temperature area. According to the casting process simulated by CAE, the ingates patch was pasted at the ingates position; before pouring, the model splicing position was pasted with cloth-based tape; S3, spray coating, spray coating the model separately and dry it, and do not spray coating the joint surface of the cover plate made separately, to ensure that the coating thickness is not less than 1.5mm. After drying, reinforce the inside of the model to prevent the model from being deformed by the molding sand when buried in the sand; S4, S41 modeling: first, splice the two lower parts of the model on the modeling platform. After the splicing is completed, pull the wire to detect the deformation, and control the deformation in the length direction not to exceed 2mm. The joint position is taped with cloth-based tape. On the modeling platform, a foam strip with a width of 100mm and a height of 100mm is placed around the model, and the foam strip and the model are fixed with bamboo sticks; connect the pouring system according to the preset casting process, and connect the step pouring system with paper tubes. The inner gate is 50mm in diameter and each has a diameter of 70mm. m straight runner connects two groups of stepped gates; place the sand box frame, start to bury sand layer by layer, add about 1% of the molding sand resin, ensure that the 2H strength of the resin sand is not less than 1MPa, the sand intake around is not less than 150mm, and the sand intake of the upper layer of the model is not less than 350mm. After filling and scraping the top surface, wait for the molding sand to solidify. The solidification time is not less than 6 hours to avoid premature turning over of the box and insufficient strength of the sand mold causing cracking of the sand mold. During the waiting process, the box clamps between the layers of sand boxes are clamped to ensure that the layers of sand boxes are locked; S42 Flipping the box: Flip the sand box and bury it inside the cavity. Use a tamping rod to tamp the sand during the burying process. After the inside of the cavity is buried and scraped flat, wait for the molding sand to solidify. After the molding sand is completely solidified, paint is applied to the surface of the molding sand to ensure that the coating thickness after drying is not less than 1.5mm. After the coating is dry, tear off the tape pasted on the splicing position, and take out the 100*100mm foam strip that surrounds the model during molding from the molding sand, and splice and fix one of the cover plates and the upper two sections of the model on the sand box; it is necessary to check whether the outer ring splicing is smooth. If there is deformation, take out the groove formed by the 100*100mm foam strip and grind the deformed position to avoid dislocation and Joint crack defects; connect the sprue with a heightened diameter of 70mm, stack the sand box frame, start to bury the sand layer by layer and tamp it. When it is buried to the top surface of the model, scrape it flat and wait for the molding sand to solidify. After the molding sand is solidified, brush the alcohol-based paint on the surface of the molding sand within the range where another cover plate is needed to cover it. Ensure that the coating thickness is not less than 1.5mm after the coating is dry. After the coating is dry, tear off the cloth-based tape on the top surface of the model to expose the foam, fit another cover plate on the surface of the sand box, and fix it with iron nails. Continue to connect the heightened sprue, stack the sand box frame, fill the sand layer by layer and tamp it, ensure that the minimum sand intake of the top layer of the model is not less than 400mm, and connect the paper tube sprue to the two ends of the sand box to set the gate cup area; S5, the sand box is transferred to the area to be poured. The ground of the pouring area should be raked and leveled. The ground of the sand box placement area should be free of large sand blocks and iron slag to avoid the top crack of the sand mold leading to fire leakage, deformation of the casting and crack defects; the top surface of the sand box is pressed with a pressure iron, which should be no less than 7 times the weight of the pouring to avoid the casting from arching and deformation during the pouring and solidification process; the negative pressure pipeline is connected, and the negative pressure of the vacuum pump of the negative pressure pipeline is controlled at 0.04-0.07Mpa to ensure that there is no back-spray of molten iron during the pouring process, and the smoke and dust from foam gasification and combustion can be sucked away in time by the vacuum pump; S6, smelting molten iron, controlling the pouring temperature at 1400-1410°C, and pouring from two ladles from both ends; S7, unpack and remove sand. Remove sand about 200 hours after pouring. Before removing sand, ensure that the temperature of the casting in the sand mold does not exceed 300℃, and then lift out the casting; S8, shot blasting, removal of pouring system, grinding, painting, inspection of casting hardness, to obtain the final casting, the final casting has a similar temperature field distribution in the length direction, will not crack, will not form pores, cold shut.

[0017] It should be understood by those skilled in the art that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A full-mold casting process for a large machine tool beam, the machine tool beam is a large box-type structure, characterized in that: The following steps are included: Step 1: Model making: Divide the model into two sections along the midline of the length direction, divide the model into two sections along the midline of the height direction, and make two upper cover plates separately; Step 2, casting process design: through casting CAE simulation confirmation, set up a paper tube step pouring system, each gate directly into the molten iron from the sprue position, according to the casting process simulated by CAE, paste the gate patch at the gate position, and paste the cloth-based tape on the model splicing position before coating; Step 3: coating the model with paint, coating the model with paint and drying it separately. The joint surface of the cover plate made separately is not coated with paint to ensure that the coating thickness is not less than 1.5 mm. After drying, the inside of the model is reinforced to prevent the model from being deformed by the molding sand when buried in the sand. Step 4, modeling: first, join the two lower sections of the model on the modeling platform, and tape the joints with cloth-based tape. On the modeling platform, surround the model with a foam strip with a width of 100mm and a height of 100mm, and fix the foam strip and the model with bamboo sticks; connect the pouring system according to the preset casting process, connect the step pouring system with a paper tube, the inner gate is 50mm in diameter, and each 70mm diameter straight runner connects two sets of step inner gates; place the sand box frame, start to bury the molding sand layer by layer, fill and scrape the top surface, and wait for the molding sand to solidify. During the waiting process, clamp the box clips between the layers of sand boxes to ensure that the layers of sand boxes are locked; Turn over the box: turn over the sand box and bury it inside the cavity. Use a tamping rod to tamp the sand during the burying process. After the inside of the cavity is buried and scraped flat, wait for the molding sand to solidify. After the molding sand is completely solidified, paint is applied to the surface of the molding sand to ensure that the coating thickness after drying is not less than 1.5mm. After the coating is dry, tear off the tape pasted on the splicing position, and take out the 100*100mm foam strip that surrounds the model during molding from the molding sand, splice and fix one of the cover plates and the upper two sections of the model on the sand box; connect the sprue with a heightened diameter of 70, superimpose the sand box frame, and start to bury the sand layer by layer. Tamp and bury to the top surface of the model, scrape and level, wait for the molding sand to solidify, and after the molding sand solidifies, brush alcohol-based paint on the surface of the molding sand within the range where another cover plate is needed to cover, and ensure that the coating thickness is not less than 1.5mm after the coating is dry. After the coating is dry, tear off the cloth-based tape on the top surface of the model to expose the foam, and attach another cover plate to the surface of the sand box and fix it with iron nails. Continue to connect the heightened sprue, stack the sand box frame, fill the sand layer by layer and tamp, ensure that the minimum sand intake of the top layer of the model is not less than 400mm, and connect the paper tube sprue to the two ends of the sand box to set the pouring cup area; Step 5: The sand box is transferred to the area to be poured, the top surface of the sand box is pressed with iron, and a negative pressure pipe is connected; Step 6: Melt molten iron, control the pouring temperature at 1400-1410°C, and pour from both ends of two ladles; Step 7: Unpack and remove sand, and then hoist out the castings; Step 8: Shot blasting, removing the pouring system, grinding, painting, and testing the hardness of the casting.

2. A full mold casting process for a large machine tool beam according to claim 1, characterized in that: In the molding process of step 4, after the splicing is completed, the deformation amount is detected by pulling the wire to control the deformation amount in the length direction to not exceed 2mm.

3. A full mold casting process for a large machine tool beam according to claim 2, characterized in that: The resin addition amount in the molding sand in the molding process of step 4 is 1%, the 2H strength of the resin sand sample is not less than 1MPa, the sand intake around is not less than 150mm, and the sand intake of the upper layer of the model is not less than 350mm.

4. A full mold casting process for a large machine tool beam according to claim 3, characterized in that: The curing time of the molding process in step 4 is not less than 6 hours to avoid premature turning over of the sand mold due to insufficient strength and resulting in cracking of the sand mold.

5. A full mold casting process for a large machine tool beam according to claim 4, characterized in that: During the box turning process in step 4, after one of the cover plates and the upper part of the model are spliced ​​and fixed on the sand box, it is necessary to check whether the outer ring splicing is smooth. If there is deformation, take out the groove formed by the 100*100mm foam strip and grind the deformed position to avoid dislocation and seam crack defects on the final casting.

6. The full mold casting process of a large machine tool beam according to claim 1, characterized in that: Before the sand mold is transferred to the pouring area in step 5, the ground of the pouring area must be raked and leveled, and the ground of the sand box placement area must be free of large sand blocks and iron slag to avoid cracking of the sand mold, leading to fire leakage, deformation of the casting, and crack defects.

7. A full mold casting process for a large machine tool beam according to claim 6, characterized in that: In the step 5, a weight of not less than 7 times the pouring weight is pressed on the top surface of the sand box to prevent the casting from arching and deforming during the pouring and solidification processes.

8. A full mold casting process for a large machine tool beam according to claim 7, characterized in that: The negative pressure of the vacuum pump of the negative pressure pipeline in step five is controlled at 0.04-0.07Mpa to ensure that there is no back-spray of molten iron during the pouring process, and the smoke and dust from foam gasification and combustion can be sucked away in time by the vacuum pump.

9. The full mold casting process of a large machine tool beam according to claim 1, characterized in that: In the step 7, the sand is removed about 200 hours after pouring, and before the sand is removed, the temperature of the casting in the sand mold is ensured not to exceed 300°C.

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