Casting method of large gray cast iron workbench base

Abstract

The invention discloses a casting method for a large gray cast iron workbench base, and belongs to the technical field of sand mold casting, the method comprises the following steps: modeling: dividing a base casting mold into an upper casting mold, a middle casting mold and a lower casting mold, forming a cavity in the casting mold, and arranging a sprue and a riser in the upper casting mold; core manufacturing: manufacturing a sand core of the base; the sand core is made of a core box, the simple core box is made of an evanescent mode, and the complex core box is made of wood and the evanescent mode in a combined mode; a lower casting mold is placed, and sand cores are sequentially placed in cavities of the middle casting mold and the upper casting mold according to the corresponding sequence; pouring: pouring molten iron into a cavity of the base casting mold through a pouring system; and shakeout is conducted, specifically, the base casting is subjected to heat preservation in a casting mold to be below 150 DEG C, box opening and shakeout are conducted, and sand on the surface of the base casting is cleaned.

Description

Technical Field

[0001] The present invention belongs to the technical field of sand casting, and particularly relates to a casting method for a large gray cast iron workbench base. Background Art

[0002] As the main component of a large workbench, the base has a contour diameter greater than 8000 mm, a main wall thickness of 60 mm, a maximum wall thickness of 280 mm, a complex internal cavity structure, and precise dimensional requirements for the keyways on the working surface without allowing quality defects. It weighs more than a hundred tons, and has strict internal quality and dimensional requirements. The base provides support for the workbench to ensure its stability during use and prevent unstable influences on part processing accuracy caused by movement or vibration. The base needs to have sufficient strength and stiffness to bear the weight of the workbench and the objects on it, and the quality of its castings plays an extremely important role in the normal operation of the hobbing machine.

[0003] As a basic component of heavy equipment, large gray cast iron usually has large contour dimensions and wall thicknesses, a more complex structure, numerous production processes, high labor intensity, extremely high manufacturing costs, and it is not easy to ensure the quality of castings.

[0004] The traditional casting method for large gray cast iron parts combines a full-size model and assembled cores. Due to the large outer contour, complex structure, and significant differences in the structure of the same type of position, usually a large amount of wood is consumed in making the full-size model and core boxes, and the mold manufacturing cost is high. As a basic component of heavy equipment, large gray cast iron parts have few openings in the part structure and limited core support due to service requirements. To avoid core floating and ensure the wall thickness of the casting, a large amount of steel core supports are used in the traditional casting method, and quality problems such as poor fusion of core supports are likely to occur in the castings, which bring many quality hidden dangers to subsequent processing and service, and may lead to casting cracking and even ultimate scrapping, with relatively high production risks. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a casting method for a large gray cast iron workbench base, which can overcome the shortcomings of the traditional process for producing large gray cast iron parts, reduce the labor intensity of workers, reduce production costs, weaken quality hidden dangers, comply with the national environmental protection policy, reasonably reduce production costs, ensure the quality of castings, and is an environmentally friendly casting method.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] The embodiments of the present invention provide a casting method for a large gray cast iron workbench base, and the method includes the following steps:

[0008] Molding: Divide the base mold into an upper mold, a middle mold, and a lower mold, and form a cavity in the mold. Among them, a sprue and a riser are provided in the upper mold;

[0009] Core making: Making the sand core for the base; the sand core is made by a core box, where a simple core box is made using expendable patterns, and a complex core box is made by combining wood and expendable patterns;

[0010] Mold assembling: Placing the lower mold, and sequentially putting the sand core into the cavities of the middle mold and the upper mold in the corresponding order;

[0011] Pouring: Pouring molten iron into the cavity of the base mold through the gating system;

[0012] Shakeout: Keeping the base casting in the mold for heat preservation until the temperature is below 150 °C, opening the mold, shakeout, and cleaning the sand on the surface of the base casting.

[0013] In some embodiments, in the core making step, the following steps are included:

[0014] In the base, sand cores at the same type of positions and sand cores with similar sizes share the same core box. Wood or expendable patterns are filled in the areas of the core box where the sand cores have different sizes. According to the parts with different sizes and structures of the sand cores, the wood or expendable pattern inserts in the corresponding areas in the core box are replaced.

[0015] In some embodiments, in the mold assembling step, the following steps are included:

[0016] Before sequentially placing the sand cores in the corresponding order, chaplets for supporting the sand cores are placed.

[0017] In some embodiments, the raw material of the chaplets is the ingates used when casting other castings before, and a filter screen is arranged at the front end of the ingate during pouring.

[0018] In some embodiments, in the molding step, the following steps are included:

[0019] The lower mold is placed on the ground, and the reference surface of the lower mold is supported and calibrated using a level.

[0020] In some embodiments, in the molding step, the following steps are further included:

[0021] The cavities of the upper mold, the middle mold, and the lower mold are trimmed.

[0022] In some embodiments, in the molding step, the following steps are further included: [

[0023] The cavities of the upper mold, the middle mold, and the lower mold are brushed with coating.

[0024] In some embodiments, in the pouring step, the following steps are included:

[0025] Inoculation treatment: Inoculation materials are pre-added into the ladle and the sprue box respectively.

[0026] In some embodiments, a silicon-barium inoculant is added into the ladle.

[0027] In some embodiments, a ferrosilicon inoculation block is added into the sprue box. A casting method for a large gray cast iron workbench base provided by the present invention. On the core box, a lost foam pattern is used for a simple core box, and a combination of wood and a lost foam pattern is used for a complex core box, which can reduce the amount of wood used, lower the mold manufacturing cost, effectively reduce the production cost. The method is reasonably designed, can overcome the disadvantages of high mold manufacturing cost and poor fusion of chaplets in traditional casting, reduce the labor intensity of workers, reduce the production cost, reduce the probability of quality hidden dangers, comply with the national environmental protection policy, and greatly improve the quality of castings. It is an environmentally friendly casting method. Specific embodiments

[0028] The technical solutions in some embodiments of the present disclosure are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present disclosure.

[0029] Unless otherwise required by the context, throughout the specification and claims, the term "comprising" is interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "an embodiment", "some embodiments", "exemplary embodiments", "examples" or "some examples", etc. are intended to indicate that specific features, structures, materials or characteristics related to the embodiment or example are included in at least one embodiment or example of the present disclosure. The above schematic representations do not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0030] An embodiment of the present invention provides a casting method for a large gray cast iron workbench base, and the method includes steps: S100-S500.

[0031] S100, molding: The base mold is divided into an upper mold, a middle mold, and a lower mold, and a cavity is formed in the mold. Among them, a sprue and a riser are provided in the upper mold.

[0032] Since the contour size of the base casting is relatively large, the base mold is divided into three sections, namely, an upper mold, a middle mold, and a lower mold, according to the contour size of the casting, the position of the gating system, the pattern draw direction, and the height of the sand box.

[0033] Exemplarily, the function of the sprue is the inlet for pouring molten metal, and the function of the riser is to compensate for the shrinkage during the solidification of the casting, avoid defects such as porosity, and also has the function of exhausting gas.

[0034] S200, core making: Making the sand core for the base. Since the base has large contour dimensions and complex internal cavity structures, in order to facilitate operation and control costs, multiple different sand cores are set according to the part structure zoning.

[0035] S200, the sand core is made by a core box. Among them, the simple core box is made using a lost foam pattern, and the complex core box is made by combining wood and a lost foam pattern. In this way, the amount of wood used can be reduced, the number of core boxes can be greatly reduced, and the cost of mold making can be reduced.

[0036] The simple core box is made using a lost foam pattern. After making the core mold, the lost foam pattern can be directly removed.

[0037] The complex core box is made by combining wood and a lost foam pattern. The core box frame is made of wood, and the internal rib plates of the core box use a lost foam pattern that meets the strength requirements. The part using the lost foam pattern can be directly removed, and the rest can be removed by removing the wood. In this way, the amount of wood used can be reduced, and the cost of mold making can be reduced.

[0038] S300, mold assembly: Place the lower casting mold, and sequentially place the sand cores into the cavities of the middle casting mold and the upper casting mold in the corresponding order.

[0039] When placing the sand cores, it is necessary to pay attention to checking the shape, position, surface quality and size of the sand cores.

[0040] When combining the upper casting mold, the middle casting mold and the lower casting mold, the joint can be stuffed with sealing clay strips to prevent molten iron from leaking during pouring.

[0041] S400, pouring: Pour the molten iron into the cavity of the base casting mold through the gating system.

[0042] S500, shakeout: Keep the base casting in the mold at a temperature below 150 °C, open the mold, shake out the sand, and clean the sand on the surface of the base casting.

[0043] A casting method for a large gray cast iron workbench base provided by the present invention. On the core box, the simple core box is made using a lost foam pattern, and the complex core box is made by combining wood and a lost foam pattern, which can reduce the amount of wood used, reduce the cost of mold making, effectively reduce the production cost, the method is reasonably designed, can overcome the disadvantages of high mold making cost and poor fusion of chaplets in traditional casting, reduce the labor intensity of workers, reduce the production cost, reduce the probability of quality hazards, comply with the national environmental protection policy, and greatly improve the quality of the casting. It is an environmentally friendly casting method.

[0044] In the molding step, i.e., step S100, it includes the step: S110.

[0045] S110, the lower mold is placed on the ground, and the reference surface of the lower mold is calibrated by using a spirit level and shims. In this way, the flatness and dimensional accuracy of the mold reference surface can be ensured.

[0046] In the molding step, i.e., step S100, it also includes the step: S120.

[0047] S120, the cavities of the upper mold, the middle mold, and the lower mold are trimmed.

[0048] The trimming can be carried out by means of manual sanding to ensure the smoothness and flatness of the surface of the mold cavity.

[0049] In the molding step, i.e., step S100, it also includes the step: S130.

[0050] S130, the cavities of the upper mold, the middle mold, and the lower mold are coated with a coating. In this way, the surface of the cast base can be made smoother, and at the same time, the thermal shock of extremely high temperature on the molding sand in the mold cavity can be weakened, and the premature cracking of the molding sand can be avoided.

[0051] In the core-making step, i.e., step S200, it includes the step: S210.

[0052] S210, in the base, the cores in the same type of positions and the cores with similar sizes share the same core box. The areas with different core sizes are filled with wood or expendable patterns in the core box, and the wood or expendable pattern inserts are replaced in the corresponding areas in the core box according to the parts with different core sizes and structures. In this way, the number of core boxes can be greatly reduced, and the manufacturing cost of the core boxes can be lowered.

[0053] For the parts in the core box where it is not easy to make rounded corners, after the cores are formed, they are made by manual sanding according to the technical requirements, and means such as templates and tape measures can also be used to check whether the core sizes and rounded corner shapes meet the requirements.

[0054] In the mold assembling step, i.e., step S300, it includes the step: S310.

[0055] S310, before placing the cores in sequence, chaplets for supporting the cores are put in.

[0056] The chaplets are manufactured based on the wall thickness of the casting area where the chaplets are placed, and the sizes and materials of the chaplets in different areas are all different. Special chaplets of corresponding specifications are used in different casting areas.

[0057] Exemplarily, the raw material of the chaplets is the ingate of ductile iron.

[0058] The ingate of the ductile iron is the same ingate used for casting other castings before, and a filter screen is provided at the front end of the ingate during pouring, which can ensure good quality inside the ingate.

[0059] Using the ingate of ductile iron to make chaplets can effectively utilize the return materials. At the same time, since the ductile iron is similar to the gray iron material of the base, the fusion quality between the two after casting is better, thus ensuring the fusion quality of the base casting.

[0060] In the box-matching step, that is, in step S300, it further includes step: S320.

[0061] S320, the base uses the overall core-assembly method, and the sand cores are placed in sequence according to the corresponding order.

[0062] In the pouring step, that is, in step S400, it includes step: S410: inoculation treatment.

[0063] S410, inoculation treatment: pre-add inoculation materials in the ladle and the gating box respectively.

[0064] The base uses an intermediate frequency induction furnace to melt the molten iron to be poured, adjusts the molten iron to the required chemical composition, skims the slag, and cools it down to 1350 - 1400 °C. [

[0065] Before the molten iron is tapped, preheat the ladle in advance, add a silicon-barium inoculant in the ladle, pour the melted molten iron into the ladle, and add silicon-barium alloy into the ladle along with the flow during tapping to achieve in-furnace inoculation with the flow.

[0066] Add silicon-iron inoculation blocks with appropriate size in the gating box, and pour the molten iron in the ladle into the gating box to achieve in-gating-box inoculation with the flow.

[0067] The inoculation treatment adopts the multi-stage inoculation method of in-furnace inoculation with the flow and in-gating-box inoculation with the flow. The base adopts the multi-stage inoculation method for large gray iron castings, reasonably arranges the production process, shortens the inoculation time, achieves the effect of long-term and high-efficiency inoculation, and ensures the performance and internal quality requirements of the product. The inoculation amount in the inoculation treatment step is controlled at 0.4 - 0.6%.

[0068] Pour the molten iron into the gating box, and the molten iron is poured into the gating system through the gating box and enters the mold cavity. The time from the inoculation treatment step to the pouring end step is controlled within 25 minutes.

[0069] After pouring is completed, add a heat-insulating covering agent in the riser to ensure the temperature in the mold cavity. [[ID=q5]]

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Any other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A casting method for a large grey cast iron workbench base, characterized in that: The method includes the following steps: Modeling: Divide the base mold into an upper mold, a middle mold, and a lower mold, and form a cavity in the mold. Among them, a sprue and a riser are provided in the upper mold; Core making: Make the sand core of the base; the sand core is made by a core box. Among them, a simple core box is made using a lost foam pattern, and a complex core box is made by combining wood and a lost foam pattern; Mold assembly: Place the lower mold, and sequentially place the sand cores into the cavities of the middle mold and the upper mold in the corresponding order; Pouring: Pour molten iron into the cavity of the base mold through the gating system; Shakeout: Keep the base casting in the mold until the temperature is below 150°C, open the mold, perform shakeout, and clean the sand on the surface of the base casting.

2. The casting method of the large grey cast iron workbench base according to claim 1, characterized in that, In the core making step, it includes the following steps: In the base, sand cores at the same type of positions and sand cores with similar sizes share the same core box. Wood or a lost foam pattern is filled in the areas of the core box where the sizes of the sand cores are different or the same. According to the parts with different sizes and structures of the sand cores, replace the wood or lost foam pattern inserts in the corresponding areas in the core box.

3. The casting method of the large grey cast iron workbench base according to claim 1, characterized in that, In the mold assembly step, it includes the following steps: Before sequentially placing the sand cores in the corresponding order, place chaplets to support the sand cores.

4. The casting method of the large gray cast iron workbench base according to claim 3, characterized in that, The raw material of the chaplets is the ingates used when casting other castings before, and a filter screen is provided at the front end of the ingate during pouring.

5. The casting method of the large grey cast iron workbench base according to claim 1, characterized in that, In the modeling step, it includes the following steps: Place the lower mold on the ground and use a level to support and calibrate the reference surface of the lower mold.

6. The casting method of the large grey cast iron workbench base according to claim 1, characterized in that, In the modeling step, it also includes the following steps: Trim the cavities of the upper mold, the middle mold, and the lower mold.

7. The casting method of the large gray cast iron workbench base according to claim 1, characterized in that, In the modeling step, it also includes the following steps: Brush coatings on the cavities of the upper mold, the middle mold, and the lower mold.

8. The casting method of the large grey cast iron workbench base according to claim 1, characterized in that, In the pouring step, it includes the following steps: Inoculation treatment: Pre-add inoculation materials in the ladle and the sprue basin respectively.

9. The casting method of the large grey cast iron workbench base according to claim 8, characterized in that, Add a silicon-barium inoculant in the ladle.

10. The casting method of the large grey cast iron workbench base according to claim 8, characterized in that, Add silicon-iron inoculation blocks in the sprue basin.