Semi-true centrifugal casting mold for large barrel-shaped casting product

Abstract

The utility model discloses a semi-true centrifugal casting mould for a large barrel-shaped casting product, which comprises an outer mould and a sand core, the lower end of the sand core is suspended in the outer mould, the upper end of the sand core is fixedly connected with the upper end of the outer mould, a blind riser is processed at the bottom of the sand core, a casting channel is arranged at the center of the sand core, and the blind riser is communicated with the casting channel. The casting channel is communicated with the top of the blind riser, a net-shaped steel framework playing a supporting role is arranged in the sand core, an exhaust rope for casting is arranged in the sand core, and the exhaust rope extends to the upper surface of the sand core. Compared with the prior art, the suspension type sand core has the advantages that the suspension type design of the sand core is realized, the overall structural strength of the sand core is high, the air permeability is good, the bottom of a product is prevented from shrinkage porosity or shrinkage cavity in the centrifugal process by utilizing the blind riser, and the integrated centrifugal casting molding of a bottom plate and a barrel body of a casting product is realized.

Description

Technical Field

[0001] The utility model relates to the stainless steel casting industry, in particular to a semi-true centrifugal casting mold for large barrel-shaped casting products. Background Art

[0002] The current centrifugal casting process can only be used to cast tubular casting products. Some barrel-shaped casting products with bottoms cannot be centrifugally cast because during the centrifugal rotation of the mold, the molten steel at the bottom will spread out due to centrifugal force, causing shrinkage or shrinkage holes at the bottom of the product, which will directly lead to product scrapping.

[0003] Currently, barrel-shaped castings are manufactured by casting the barrel wall and base plate separately, then welding the base plate to the bottom of the barrel wall. Due to the thickness of the casting, welding alone would be difficult to achieve the designed strength. Therefore, a new casting mold was urgently needed to integrally cast the barrel wall and base plate to meet product design requirements. Utility Model Content

[0004] The purpose of the utility model is to provide a semi-true centrifugal casting mold for large barrel-shaped casting products which solves the above-mentioned problems.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is: a semi-true centrifugal casting mold for large barrel-shaped casting products, including an outer mold and a sand core, the lower end of the sand core is suspended in the outer mold, the upper end of the sand core is fixedly connected to the upper end of the outer mold, the bottom of the sand core is processed with a blind riser, a casting channel is opened at the center of the sand core, the casting channel is connected to the top of the blind riser, a mesh steel skeleton for supporting is provided in the sand core, and an exhaust rope for casting is provided inside the sand core, and the exhaust rope extends all the way to the upper surface of the sand core.

[0006] Preferably, the upper end of the sand core is provided with a flange structure, the upper end of the outer mold is provided with a positioning step matching the diameter of the flange structure, and the upper end of the sand core is positioned at the center of the outer mold through the positioning step.

[0007] Preferably, a cover plate is further included, which is arranged above the sand core. Pin holes are provided around the outer mold, and the cover plate is fixed in the outer mold by pins matching the pin holes.

[0008] Preferably, the cover plate is provided with a plurality of small holes for facilitating the pulling out of the exhaust rope.

[0009] Preferably, a central hole is opened at the center of the cover plate to facilitate the installation of cast bricks.

[0010] Preferably, the mesh steel skeleton has a shape similar to that of the sand core and is located inside the sand core. The mesh spacing of the mesh steel skeleton is 250-300 mm and the skeleton is made of steel bars with a diameter of φ8-16 mm.

[0011] Compared with the prior art, the advantages of the present invention are:

[0012] 1. The utility model realizes the hanging design of the sand core by designing the installation structure of the sand core and the outer mold, and ensures that the sand core is always located at the center of the mold during the centrifugal rotation process.

[0013] 2. Through the structural design of the sand core, the overall structural strength of the sand core is improved, and it has good air permeability, so that it will not deform or crack during the centrifugal casting process.

[0014] 3. Through the design of the structure and size of the blind riser, the blind riser is used to continuously feed the shrinkage of the molten steel during the centrifugal process, thereby avoiding shrinkage or shrinkage holes at the bottom of the product during the centrifugal process, and realizing the integrated centrifugal casting of the bottom plate and the barrel of the casting product. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of the mold of the utility model;

[0016] Figure 2 This is a process flow chart of the utility model.

[0017] In the figure: 1. Outer mold; 11. Pin hole; 2. Sand core; 21. Mesh steel skeleton; 22. Exhaust rope; 3. Casting channel; 4. Blind riser; 5. Cover plate; 51. Small hole; 6. Product. DETAILED DESCRIPTION

[0018] The utility model will be further described below. The casting product to be processed has an upper end diameter of about 1100mm, a lower end diameter of about 1000mm, a height of 960mm, and a thickness of 60mm. It is large in size, heavy in weight, and thick in thickness. It requires high connectivity between the barrel body and the bottom plate. If a split type is used for separate processing, the connectivity between the bottom plate and the barrel body is poor. Even if welding is performed, the weld strength is difficult to meet the requirements. If it can be cast as one piece, the product performance requirements can be met. The conventional centrifugal casting method will inevitably lead to shrinkage or shrinkage holes in the bottom plate during the centrifugal process. Therefore, there is no precedent in this field for large-volume, high-thickness barrel-shaped casting products formed by centrifugal casting.

[0019] Example: A semi-true centrifugal casting mold for a large barrel-shaped casting product, see Figure 1, including an outer mold 1 and a sand core 2, the lower end of the sand core 2 is suspended in the outer mold 1, the upper end of the sand core 2 is fixedly connected to the upper end of the outer mold 1, the bottom of the sand core 2 is processed with a blind riser 4, and a casting channel 3 is opened at the center of the sand core 2. The casting channel 3 is connected to the top of the blind riser 4, and the molten steel is fed during the centrifugal process through the blind riser 4 to avoid shrinkage or shrinkage holes at the bottom of the product 6 during the centrifugal process. A mesh steel skeleton 21 is provided in the sand core 2 for support. The strength of the sand core is improved by the mesh steel skeleton 21 to meet the needs of centrifugal casting. A casting exhaust rope 22 is provided inside the sand core 2, and the exhaust rope 22 extends all the way to the upper surface of the sand core 2. The design of the exhaust rope 22 is to facilitate the rapid discharge of gas from the sand core 2 during centrifugal casting to avoid the sand core 2 from bursting.

[0020] The upper end of the sand core 2 is provided with a flange structure, and the upper end of the outer mold 1 is provided with a positioning step that matches the diameter of the flange structure. The upper end of the sand core 2 is positioned at the center of the outer mold 1 through the positioning step, and the positioning step and the flange are used to ensure that the core head of the sand core 2 can be accurately positioned.

[0021] A cover plate 5, perforated with small holes 51, is located above the sand core 2. This cover plate 5 is secured to the outer mold 1 via pins. The flange of the sand core 2 is pressed against the positioning steps of the outer mold 1, ensuring safe and stable centrifugal rotation of the sand core 2 under centrifugal force. A central hole matching or slightly larger than the outer diameter of the lower end of the pouring brick is defined within the cover plate 5 to facilitate placement of the pouring brick. Pin holes 2 are located around the outer mold 1, and the cover plate 5 is secured within the outer mold 1 via pins that match these holes.

[0022] The cover plate 5 is provided with a plurality of small holes 51 for facilitating the pulling out of the exhaust rope 22. The small holes 51 on the cover plate 5 are used for ventilation of the sand core 2 and for facilitating the passing out of the exhaust rope 22 so as to exhaust the inside of the sand core 2. A central hole is provided at the center of the cover plate 5 for facilitating the installation of casting bricks.

[0023] The mesh steel skeleton 21 is similar in shape to the sand core 2 and is located inside the sand core 2. The steel skeleton imitates the structural design of the sand core 2 and has a mesh structure for enhancing the strength of the sand core 2. The grid distance of the steel skeleton is 250-300mm, and the steel bar diameter is φ8-16mm to ensure that the sand core 2 has good strength during centrifugal use. The minimum distance between the skeleton and the outer wall of the sand core 2 is not less than 40mm, so that it still has a certain degree of yield after cooling.

[0024] The outer mold 1 and sand core 2 of the cover plate 5 are designed according to the shape of the product 6. The inner cavity formed between the outer mold 1 and the sand core 2 is the molten steel casting channel 3 of the product 6. After centrifugal forming, rough processing and fine processing are performed to obtain the product 6. The barrel body and the bottom plate of the product 6 are formed in one piece, which is convenient and fast. The sealing, safety and structural stability between the bottom plate and the whole body are much higher than the welding process. Moreover, the product 6 obtained by this process method has no shrinkage or shrinkage holes, and its thickness after fine processing can fully meet the thickness requirements of the product 6.

[0025] The method flow of semi-true centrifugal casting of the utility model is as follows: Figure 2 ,

[0026] Step 1: Design an outer mold 1 according to the product part drawing. The design of the outer mold 1 must ensure that the part's outer dimensions can be shrunk into shape after casting and meet the outer dimensions requirements of the part drawing after fine machining. Design a sand core 2 according to the inner cavity dimensions of the product part drawing. The design of the inner core must ensure that the part's inner dimensions and bottom can be integrally formed with the cylindrical surface of the part, and that the part's bottom and inner cavity dimensions can be shrunk into shape after casting and meet the bottom and inner cavity dimensions requirements of the part drawing after fine machining.

[0027] Step 2: Design a flange on the top of the sand core 2 and a positioning step on the top of the outer mold 1. When designing the sand core 2, it is necessary to ensure that the sand core 2 has sufficient strength to withstand the centrifugal force after being positioned and closed. Therefore, the flange of the sand core 2 should have sufficient thickness.

[0028] Step 3: When manufacturing the sand core 2, the casting of molten steel must be considered. A through hole is made in the middle of the sand core 2 as a casting channel to meet the needs of casting molten steel. At the same time, considering that the molten steel still needs to be fed at the end, the feeding requirements of the bottom plate thickness of the product 6 are calculated, and an expanded blind riser 4 is made at the bottom of the casting channel with a height range of 200-350mm;

[0029] The size design of the blind riser 4 is one of the technical difficulties of the present invention. Through many experiments and combined with empirical formulas, the size calculation method of the blind riser 4 is as follows: taking the base plate with a thickness of 60 mm as the benchmark, the diameter of the blind riser 4 is 3.5 times the thickness of the base plate, and the height of the blind riser 4 is 1.5-2 times the diameter of the blind riser 4, which is specifically determined according to the diameter of the base plate. If the diameter of the base plate is greater than 1000 mm, the diameter of the blind riser 4 is increased. If the diameter of the base plate is less than 1000 mm, the diameter of the blind riser 4 is reduced.

[0030] In step four, the sand core 2 needs to rotate with the outer membrane, and the sand core 2 is suspended. In order to prevent the sand core 2 from loosening during the centrifugal process, the strength requirement of the sand core 2 is particularly important. Regarding the design of the strength of the sand core 2, the sand core 2 described in the utility model is made using a water glass + carbon dioxide blowing hardening process. In the existing blowing hardening process, when the blowing steel bar is inserted to a depth of 100mm, the sand core 2 can be stopped after it has a certain strength to complete the curing. However, due to the high strength requirements of the utility model, the blowing steel bar needs to be inserted about 200mm until it is difficult to press down, proving that the strength of the sand core 2 meets the requirements. At this time, the blowing is stopped to complete the curing, and a mesh steel skeleton 21 is made in the shape of the sand core 2. By comparing the test blocks, a strength comparison is performed. The strength of the sand core 2 of the utility model needs to be ≥1.5Mp to meet the requirements of this process.

[0031] Step 5: During the working process, the sand core 2 is heated by the high-temperature molten steel and will emit a large amount of gas. Therefore, the exhaust problem of the sand core 2 needs to be considered. In the design, a casting exhaust rope 22 is designed in the steel support and some empty spaces inside the sand core 2. The exhaust rope 22 extends all the way to the surface of the sand core 2 and passes through the cover plate 5.

[0032] Step 6: Apply alcohol-based paint on the surface of the prepared sand core 2 with a thickness of 1.5-2mm to ensure smooth demoulding. After the paint is dry, place the sand core 2 in an oven and bake it at 180°C for 4 hours, then take it out of the oven and cool it down. After the sand core 2 cools to below 60°C, bake the metal outer mold 1 until the inner cavity temperature reaches 220°C. Then, apply a water-based paint specially used for centrifugal casting and ensure that it is completely dry.

[0033] Step 7: Use a crane to hoist the sand core 2 onto the sand core 2 positioning step of the outer mold 1, position it, and close the box. Then, fix the cover plate 5 to the outer mold 1 with pins, and place a pouring brick at the center hole of the cover plate 5 and fix it with water glass sand.

[0034] Step 8: Hoist the assembled and checked mold onto the centrifuge and install it. After running the machine without load and confirming that it is correct, adjust the speed to 50-300RPM according to the process and run it at full speed.

[0035] Step 9: After the quenched molten steel reaches the casting temperature, it is quickly cast. When the calculated process weight is observed, the flow is slowly reduced and poured until the molten steel reaches the pouring cup;

[0036] In order to ensure good shrinkage compensation for the blind riser 4 during the casting process, the casting process is very important. This method requires calculating the process weight, which is calculated based on the total amount of molten steel. When the weight of the molten steel poured to the bottom of the blind riser 4 is observed, slow pouring must be performed to ensure good shrinkage compensation for the blind riser 4.

[0037] Step 10: The cooling capacity of the sand core 2 is weak. Depending on the structure of the product 6, the centrifuge is continuously operated for 1-3 hours and then stopped. The mold is unlocked and hoisted into the sand pit. After natural cooling for 24 hours, it is unpacked and the workpiece with the sand core 2 is taken out. The sand is shaken out by a sand shaker and the sand core 2 is cleaned to obtain a complete casting.

[0038] The above is a detailed introduction to a semi-true centrifugal casting mold for a large barrel-shaped casting product provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, based on the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. Changes and improvements to the present invention will be possible without exceeding the concept and scope specified in the appended claims. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A semi-true centrifugal casting mold for large barrel-shaped casting products, characterized by: It includes an outer mold and a sand core. The lower end of the sand core is suspended in the outer mold, and the upper end of the sand core is fixedly connected to the upper end of the outer mold. A blind riser is processed at the bottom of the sand core, and a casting channel is opened at the center of the sand core. The casting channel is connected to the top of the blind riser. A mesh steel skeleton is provided in the sand core for support. An exhaust rope for casting is provided inside the sand core, and the exhaust rope extends all the way to the upper surface of the sand core.

2. The semi-centrifugal casting mold for a large barrel-shaped casting product according to claim 1, characterized in that: The upper end of the sand core is provided with a flange structure, the upper end of the outer mold is provided with a positioning step matching the diameter of the flange structure, and the upper end of the sand core is positioned at the center of the outer mold through the positioning step.

3. The semi-centrifugal casting mold for a large barrel-shaped casting product according to claim 1, characterized in that: It also includes a cover plate, which is arranged above the sand core. Pin holes are arranged around the outer mold, and the cover plate is fixed in the outer mold through pins that match the pin holes.

4. The semi-centrifugal casting mold for a large barrel-shaped casting product according to claim 3, characterized in that: The cover plate is provided with a plurality of small holes for facilitating the pulling out of the exhaust rope.

5. The semi-centrifugal casting mold for a large barrel-shaped casting product according to claim 3, characterized in that: A central hole is provided at the center of the cover plate for easy installation of cast bricks.

6. The semi-centrifugal casting mold for a large barrel-shaped casting product according to claim 1, characterized in that: The mesh steel frame is similar in shape to the sand core and is located inside the sand core. The mesh distance of the mesh steel frame is 250-300 mm and the frame is made of steel bars with a diameter of φ8-16 mm.

Images