A high-efficiency casting chilled sand device and preparation process

Abstract

The application discloses a high-efficiency casting chilling sand device, which comprises a sand hopper formed with a plurality of sand loading areas by metal partitions, a sand amount control device connected below the sand hopper, and a stirring cage connected with the sand amount control device, and a heating device is additionally arranged on the stirring cage; and a preparation process of the casting chilling sand, wherein a sand amount regulator with three different diameter leakage holes is selected, so that the mixed steel shots account for 60-70% of the total volume of the sand mold, the resin sand accounts for 20-40%, and the proportion of the chromite sand is not less than 5%; then the sand is dropped into the stirring cage according to the mixing ratio, and the sand in the stirring cage is preheated by the heating device; the preheated sand is conveyed to a resin spraying area by a conveying screw rod, then enters a curing agent spraying area, and finally is sent to a sand outlet by the conveying screw rod and discharged from a discharge hopper. The chilling effect can replace part of the cold iron, effectively solves the problem that the cold iron is difficult to be placed for the castings with special-shaped structures, simultaneously can reduce the cold iron consumption of the castings, and improves the forming quality of the castings and the production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of casting technology, specifically relating to an apparatus and preparation process for efficient casting chilled sand. Background Technology

[0002] In sand casting production, resin sand, clay sand, and chromite sand are commonly used for making casting cores, outer molds, and other molds. Among them, resin sand has a wide range of applications in the aluminum and magnesium alloy sand casting industry due to its advantages such as strong production adaptability, clear outline and high dimensional accuracy of the formed castings, and good recyclability of old sand. Chromite sand has better thermal conductivity than ordinary silica sand, which can significantly increase the cooling rate during the solidification process of castings. At the same time, due to its high hardness, chromite sand can be used to replace part of the chills in the sand mold making process, solving the problem of difficult chill placement and improving the quality of casting formation.

[0003] In the sand casting industry, the demand for resin sand is substantial. Therefore, automatic sand mixers are often used to prepare the resin sand, reducing the workload for operators. However, these mixers typically only heat the resin and hardener during the mixing process. This is done to improve the spraying effect of the resin and hardener, ensuring uniform mixing, and to accelerate the curing speed of the sand mold in low-temperature environments. Since the heat generated by heating the resin and hardener is limited, a longer curing time is often required after the sand mold is formed in low-temperature environments to ensure that the curing effect meets process requirements.

[0004] Although chromite sand can be used to replace some chills, its chilling effect is limited, and it is not effective in thick parts of castings, leading to casting defects such as porosity. Furthermore, the secondary recycling of chromite sand is difficult, and its use on a large scale in mass production would significantly increase manufacturing costs. Chinese invention patent CN103056300A discloses a manufacturing process for high-strength sand molds and cores with the addition of a novel chill. The process involves selecting foundry sand, adding steel shot equivalent to 30%-100% of the total weight of the sand, and then adding water glass at 2.5-7% of the total weight of the sand and steel shot as a binder. The mixture is then thoroughly mixed in a sand mixer to obtain a final product. Alternatively, foundry sand can be selected, and water glass at 6%-8% of the total weight of the sand can be added as a binder. This invention fully utilizes the excellent heat dissipation properties of the steel shot and sand mixture, combined with the overall casting process, to effectively control the cooling rate of thicker parts of the casting. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to provide an apparatus and preparation process for highly efficient casting chilled sand.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an apparatus for high-efficiency casting chilling sand, comprising a sand hopper with several sand filling zones formed by metal partitions, a sand quantity control device connected below the sand hopper, the sand quantity control device being connected to a stirring cage, and a heating device being provided on the stirring cage.

[0007] The sand quantity control device includes an upper sand inlet, a sand quantity adjuster with a leakage hole, and a lower sand outlet equipped with a fixed retaining ring.

[0008] The stirring cage is equipped with heating devices on three sides to form a preheating zone. The heating devices have a temperature range of 40℃ to 80℃. A transmission screw is provided in the stirring cage, and resin nozzles and curing agent nozzles are arranged in sequence.

[0009] The sand hopper is formed by four base plates enclosing each other with sloping walls. The middle part of the sand hopper is a rectangular through groove. Two triangular metal plates are set at the diagonal of the inner wall of the rectangular through groove to form three areas. Two of the areas have the same volume and the sum of their volumes is equal to that of the other area. A pneumatic shut-off valve is also provided at the discharge port of the sand hopper.

[0010] The orifice diameter of the sand quantity adjuster in the sand quantity control device is changed according to the sand usage ratio.

[0011] The stirring cage is a long rectangular trough. A transmission screw is set along the long side of the rectangular trough on the center line inside the trough. A heating device is set at one end near the sand hopper outlet, and a discharge hopper is set below the other end. A resin nozzle and a curing agent nozzle are set in the middle area between the discharge hopper and the heating device.

[0012] The sand hopper is mounted on a load-bearing support, which consists of four vertical support frames. The sand hopper is vertically installed inside the load-bearing support, and the stirring cage is vertically connected to the sand hopper through a sand quantity control device. The stirring cage is fixed between two support frames.

[0013] A process for preparing casting chilled sand includes the following steps:

[0014] Step 1: Add steel shot, resin sand, and chromite sand to the three packing zones of the sand hopper, respectively;

[0015] Step 2: Select three sand quantity adjusters with different diameter orifices so that the mixed steel shot accounts for 60-70% of the total volume of the sand mold, resin sand accounts for 20-40%, and chromite sand accounts for no less than 5%. Then, drop the sand into the stirring cage according to this mixing ratio.

[0016] Step 3: Turn on the mixing cage. The three types of sand are mixed evenly by the rotation of the screw in the mixing cage. During the sand mixing and feeding process, the heating device preheats the sand in the mixing cage. The preheated sand is conveyed to the resin spraying area by the conveying screw, then enters the curing agent spraying area, and finally is sent to the sand outlet by the conveying screw and comes out from the discharge hopper.

[0017] The total amount of resin and hardener sprayed from the resin nozzle and hardener nozzle is 0.5% to 1.5% of the total weight of the sand mold.

[0018] The steel shot recycling after mixing is completed using a magnetic separator, and then excess resin and curing agent are removed from the surface. The removal methods include, but are not limited to, baking and sintering.

[0019] The added steel shot is steel shot that has undergone shot blasting or is scrap steel shot produced by shot blasting.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention proposes a high-efficiency chilling sand preparation process, whose chilling effect can replace part of the chills, effectively solving the problem of difficult placement of chills in irregularly shaped castings, while reducing the amount of chills used in castings, improving the casting quality and accelerating production efficiency.

[0022] 2. The sand mixer proposed in this invention can automatically mix sand using a sand quantity adjuster. The heating device equipped with it can not only effectively accelerate the solidification speed of high-efficiency chilled sand, but also be applicable to the mixing of ordinary resin sand, which helps to improve the production efficiency of sand casting. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the apparatus for high-efficiency casting chilled sand in this invention;

[0025] Figure 2 This is a top view of the sand bucket in this invention;

[0026] Figure 3 This is a schematic diagram of the structure of the upper part of the sandfall point;

[0027] Figure 4 A schematic diagram of the structure for adjusting the amount of sand;

[0028] Figure 5 This is a schematic diagram of the structure of the sandfall outlet;

[0029] Figure 6 This is a schematic diagram of the agitator structure;

[0030] In the diagram, 1-sand hopper; 2-transfer screw; 3-sand quantity control device; 4-discharge hopper; 5-stirring cage; 6-heating device; 7-load-bearing bracket; 8-resin nozzle; 9-curing agent nozzle; 31-mineral sand inlet; 32-sand quantity adjuster; 33-sand drop outlet. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0032] Reference Figures 1-6 The specialized sand mixer mainly consists of a sand hopper 1, a load-bearing support 7, a sand quantity control device 3, a discharge hopper 4, a stirring cage 5, and a heating device 6. The sand hopper 1 uses two metal partitions to form three sand filling zones, respectively filled with steel shot, resin sand, and chromite sand. A pneumatic shut-off valve is installed below the sand hopper, linked to the mixer's power supply. After the mixing program is started, the discharge valve automatically opens, and the steel shot, resin sand, and chromite sand in the sand hopper 1 begin to fall under gravity, entering the mixing preheating zone of the stirring cage 5 through the sand quantity control device 3. The sand quantity control device 3 mainly consists of a sand discharge upper inlet 31, a sand quantity adjuster 32, and a sand discharge lower inlet 33. The sand quantity control device can be replaced with sand quantity adjusters of different orifice sizes according to different sand ratios. A fixing ring is located on the end face of the sand discharge lower inlet 33 for positioning the sand quantity adjuster during assembly and connecting the sand discharge upper and lower inlets.

[0033] The connection between the stirring cage 5 and the sand hopper 1 is achieved through a sand quantity control device 3 and secured with bolts. The stirring cage 5, located below the sand inlet of the sand hopper 1, is preheated on three sides by electric heating devices 6. Before mixing, the heating devices 6 are heated to between 40 and 80°C according to process requirements, and automatically compensate for temperature changes. The sand in the sand hopper 1 falls into the preheating zone, where it begins to heat up and is uniformly mixed by the conveying screw 2 within the stirring cage. As the screw rotates, the sand in the stirring cage 5 is conveyed to the resin spraying zone and the curing agent spraying zone, and after being uniformly mixed by the conveying screw 2, it is discharged from the stirring cage discharge hopper 4. Because the sand undergoes heat treatment during the mixing process, the reaction efficiency of the resin and curing agent is much faster than at room temperature, especially in non-constant temperature environments during winter, where the effect is even more pronounced.

[0034] Example: High-efficiency casting chilling sand is prepared by mixing five raw materials: resin sand, steel shot, chromite sand, resin, and curing agent in a specific ratio. The proportions of raw materials are calculated based on the total volume of the sand mold, with resin sand accounting for 30%, steel shot for 65%, chromite sand for 5%, and resin and curing agent for 1% of the total weight of the sand mold. The steel shot used is scrap steel shot from shot blasting, which increases the surface roughness of the steel shot, improves adhesion, and prevents the sand mold from collapsing during baking. The resin sand fills the gaps between the steel shot, improving the surface finish of the formed casting. The chromite sand not only acts as a gap filler but also enhances the chilling effect at these gaps. The resin and curing agent work together chemically to solidify the sand mold.

[0035] During the sand mixing process, two metal plates are added to a sand hopper 1 to simultaneously fill the hopper with resin sand, steel shot, and chromite sand. A sand discharge rate adjustment device 32 is used at the sand outlet. This device has three through holes of different diameters made on the metal plates according to the required sand discharge rate, thereby controlling the discharge rate of different sands and ensuring that they are discharged in the correct mixing ratio.

[0036] Sand falling from sand hopper 1 enters the mixing cage 5 of the sand mixer. The rotating conveyor screw 2 within the mixing cage 5 mixes different types of sand evenly. A heating device 6 is installed in the mixing zone of the mixing cage 5. During mixing and feeding, the heating device 6 preheats the sand in the mixing cage 5 to 60°C. The preheated sand is then conveyed by the conveyor screw 2 to the resin spraying zone, and then to the curing agent spraying zone. The resin spraying zone and the curing agent spraying zone are formed by resin nozzles 8 and curing agent nozzles 9. Finally, the sand is conveyed by the conveyor screw 2 to the outlet and exits from the discharge hopper 4. This completes the sand mixing process for casting. Steel shot is recycled using a magnetic separator. After removing excess resin and curing agent from the surface through baking and sintering, it can be reused.

[0037] This equipment and process solves problems such as the difficulty of assembling chills for castings, the high cost of sand mold making, and the long production cycle of chills, thereby improving the forming quality and production efficiency of sand castings.

[0038] The above provides a detailed description of the apparatus and preparation process for a high-efficiency casting chiller sand provided by the present invention. Specific examples have been used to illustrate the structure and working principle of the invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A device for high-efficiency casting chilling sand, characterized in that: It includes a sand hopper (1) with several sand filling zones formed by metal partitions, a sand quantity control device (3) connected below the sand hopper (1), the sand quantity control device (3) being connected to the stirring cage (5), and a heating device (6) being provided on the stirring cage (5). The sand quantity control device (3) consists of an upper sand inlet (31), a sand quantity adjuster (32) with a leakage hole, and a lower sand outlet (33) equipped with a fixed baffle ring, forming an integral structure. The sand quantity control device (3) includes a sand outlet channel. After entering the sand outlet channel through the upper sand inlet (31), the sand exits through the lower sand outlet (33) and enters the stirring cage (5). The proportion of steel shot to the total volume of the sand mold is adjusted to 60-70%, resin sand to 20-40%, and chromite sand to be no less than 5% by adjusting the sand quantity adjuster (32). The leakage hole diameter of the sand quantity adjuster (32) in the sand quantity control device (3) is changed according to the sand usage ratio. The stirring cage (5) is a long rectangular trough. A transmission screw (2) is set along the long side of the rectangular trough on the center line inside the trough. A heating device (6) is set at one end near the discharge port of the sand hopper (1). The stirring cage (5) is also equipped with heating devices (6) on three sides to form a preheating zone. The heating device (6) has a heating range of 40℃ to 80℃. A discharge hopper (4) is set below the other end of the stirring cage (5). A resin nozzle (8) and a curing agent nozzle (9) are set in sequence in the middle area between the discharge hopper (4) and the heating device (6). The total amount of resin and curing agent sprayed from the resin nozzle (8) and the curing agent nozzle (9) is 0.5% to 1.5% of the total weight of the sand mold. The steel shot is shot blasted or scrap steel shot produced by shot blasting. The sand hopper (1) is formed by four base plates enclosing each other with inclined walls. The middle part of the sand hopper (1) is a rectangular through groove. Two triangular metal plates are set at the diagonal of the inner wall of the rectangular through groove to form three areas. Two of the areas have equal volumes and the sum of their volumes is equal to that of the other area. A pneumatic shut-off valve is also provided at the discharge port of the sand hopper (1).

2. The apparatus for high-efficiency casting chiller sand according to claim 1, characterized in that: The sand hopper (1) is mounted on a load-bearing bracket (7), which is composed of four vertical support frames. The sand hopper (1) is vertically installed inside the load-bearing bracket (7). The stirring cage (5) is vertically connected to the sand hopper (1) through a sand quantity control device (3). The stirring cage (5) is fixed between two support frames.

3. A process for preparing chilled sand for casting using the apparatus described in claim 1 or 2, characterized in that: Includes the following steps: Step 1: Add steel shot, resin sand and chromite sand to the three packing zones of the sand hopper (1) respectively; Step 2: Select three sand quantity adjusters (32) with different diameter holes so that the mixed steel shot accounts for 60-70% of the total volume of the sand mold, resin sand accounts for 20-40%, and chromite sand accounts for no less than 5%. Then, drop the sand into the stirring cage (5) according to the mixing ratio. Step 3: Turn on the stirring cage (5), and mix the three types of sand evenly by rotating the conveying screw (2) in the stirring cage (5). During the sand mixing and conveying process, the heating device (6) preheats the sand in the stirring cage (5). The preheated sand is conveyed to the resin spraying area by the conveying screw (2), then enters the curing agent spraying area, and finally is sent to the sand outlet by the conveying screw (2) and comes out from the discharge hopper (4). The total amount of resin and curing agent sprayed from the resin nozzle (8) and curing agent nozzle (9) is 0.5 to 1.5% of the total weight of the sand mold. The steel shot recycling after the mixing is completed is completed by magnetic separator, and then excess resin and curing agent on the surface are removed by baking and sintering.

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