Lost foam casting method for hot blast stove pillar

Abstract

The invention provides an evanescent mode casting method for a hot-blast stove pillar, which is used for casting the hot-blast stove pillar with a hollow structure, and belongs to the technical field of casting, and comprises the following steps: manufacturing a hot melting evanescent mode according to the structure of the hot-blast stove pillar in a one-to-one manner; a core shaft is arranged in a hollow cavity of the hot melting evanescent mode in a penetrating mode, a sand cavity is formed between the peripheral wall of the core shaft and the cavity wall of the hollow cavity, and the two ends of the core shaft penetrate out of the hollow cavity and are fixed to a support; the sand cavity is filled with sand; and the hot melting evanescent mode and the support are placed in a negative pressure sand box together, and casting is carried out after sand filling and jolt ramming. According to the lost foam casting method for the hot-blast stove supporting column, the hollow cavity is filled with the sand before sand burying of the hot-melting lost foam, the pressure relief problem caused by sand core loosening can be avoided, meanwhile, the core shaft can be used for positioning the sand core, and therefore the core floating problem of the sand core under the action of molten iron buoyancy in the casting process is solved, and the casting quality of the hot-blast stove supporting column is improved. And the casting molding quality of the hot-blast stove strut is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of casting, and particularly relates to a lost foam casting method for the stanchions of a hot blast stove. Background Art

[0002] The hot blast stove is the core of the air supply system of a steelmaking blast furnace. The performance of the stanchions that support the refractory materials and grates in the hot blast stove is very important, which is directly related to the service life of the hot blast stove. The stanchions of the hot blast stove are hollow castings with a relatively large length-to-diameter ratio. The traditional manufacturing process uses wooden models and core boxes, and shapes with resin sand, which has a long production cycle, high cost, and general surface quality. With the development of lost foam technology, some manufacturers have begun to try to use the lost foam casting process to process the stanchions of the hot blast stove. However, in actual production, since the inside of the stanchions of the hot blast stove is a slender hole, when the lost foam is placed in the sand box and filled with sand by the conventional vibration method, the sand in the inner hole cannot be filled tightly, resulting in easy pressure relief during the casting process and affecting the forming quality. In addition, since the lost foam has vaporized and disappeared in the sand mold to form a cavity during the casting process, the center of the cavity is a sand core filled in the hole of the lost foam. At this time, the molten iron poured into the cavity will generate a large buoyancy force on the sand core, and the sand core will float upward under the action of the buoyancy force of the molten iron, resulting in the phenomenon of sand core floating. This will cause the thickness deviation between the upper and lower parts of the cavity, resulting in the quality problem of uneven circumferential wall thickness of the cast hot blast stove stanchions, and a solution needs to be urgently sought. Summary of the Invention

[0003] An embodiment of the present invention provides a lost foam casting method for the stanchions of a hot blast stove, aiming to solve the problem of sand core floating during the lost foam casting process and improve the forming quality of the hot blast stove stanchions.

[0004] To achieve the above object, the technical solution adopted by the present invention is: to provide a lost foam casting method for the stanchions of a hot blast stove, used for casting the stanchions of a hot blast stove with a hollow structure, including the following steps: Manufacture a hot melt lost foam according to a one-to-one ratio of the structure of the hot blast stove stanchion; Insert a core shaft into the hollow cavity of the hot melt lost foam. A sand cavity is formed between the peripheral wall of the core shaft and the cavity wall of the hollow cavity. Both ends of the core shaft penetrate out of the hollow cavity and are fixed to a bracket; Fill the sand cavity with sand; Place the hot melt lost foam together with the bracket in a negative pressure sand box and perform casting after filling and vibrating the sand.

[0005] In a possible implementation manner, the core shaft is coaxially inserted into the hollow cavity, and both ends of the core shaft are connected to the bracket through adjustable clamping parts.

[0006] In some embodiments, the support includes a frame and a plurality of legs arrayed at the bottom of the frame; wherein, both ends of the mandrel are lapped on the frame and fixed respectively by adjustable fasteners, and each leg supports together on the bottom of the negative pressure sand box to separate the hot-melt expendable pattern from the bottom wall of the negative pressure sand box.

[0007] Exemplarily, the adjustable fastener includes a U-shaped clip and a ejector rod. One end of the U-shaped clip is buckled upward on the bottom surface of the frame, the other end vertically penetrates the ejector rod and is in threaded cooperation with the ejector rod, and the ejector rod presses downward on the mandrel.

[0008] For example, before the mandrel is inserted into the hollow cavity, the inner and outer surfaces of the hot-melt expendable pattern are evenly coated with expendable pattern coating.

[0009] In a possible implementation, a runner expendable pattern is arranged on the side of the hot-melt expendable pattern before the hot-melt expendable pattern is placed in the negative pressure sand box. The runner expendable pattern is fixed in the sand mold compacted in the negative pressure sand box and a runner is formed at its top end.

[0010] In some embodiments, the runner expendable pattern includes a vertical mold, a horizontal mold and a plurality of branch molds; wherein, each branch mold is spaced along the axial direction of the hot-melt expendable pattern on the side wall of the hot-melt expendable pattern, each branch mold extends horizontally along the radial direction of the hot-melt expendable pattern and is connected to the horizontal mold together; one end of the vertical mold is connected to the middle of the horizontal mold, and the other end extends upward to the top surface of the sand mold.

[0011] For example, risers are provided at both positions of the sand mold compacted in the negative pressure sand box corresponding to the two ends of the hot-melt expendable pattern.

[0012] Exemplarily, the support has a plurality of support units, and each support unit is provided with a hot-melt expendable pattern respectively.

[0013] The beneficial effects of the lost foam casting method for the hot blast stove support columns provided by the present invention are as follows: Compared with the prior art, in the lost foam casting method for the hot blast stove support columns of the present invention, after the hot melt lost foam is manufactured, a core shaft is inserted into the hollow cavity of the hot melt lost foam, and then the sand cavity formed between the outer periphery of the core shaft and the cavity wall of the hollow cavity is filled with sand material. By pre-filling the sand, the compactness of the sand material in the hollow cavity is improved, avoiding pressure relief during the casting process and affecting the forming quality. At the same time, the filled sand material can also connect the hot melt lost foam and the core shaft into one body and connect them to the support through both ends of the core shaft. The support can be used to suspend the hot melt lost foam, thus avoiding the hot melt lost foam from bumping and rubbing against surrounding objects during surface treatment and transfer, which may damage the surface quality. In addition, after the hot melt lost foam is placed in the negative pressure sand box, the support can be used to ensure that there is sufficient sand filling gap between the hot melt lost foam and the box wall of the negative pressure sand box. This can not only avoid the problem of the negative pressure sand box scratching the surface of the hot melt lost foam, but also ensure the sand filling amount around the hot melt lost foam, thus avoiding sand mold pressure relief. After the hot melt lost foam is vaporized by heat, the filled sand material and sand core in the sand cavity can resist the buoyancy of the molten iron under the connection and protection of the core shaft, thereby avoiding the phenomenon of core floating during the casting process, and improving the circumferential wall thickness uniformity and forming quality of the hot blast stove support column after casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a process block diagram of the lost foam casting method for the hot blast stove support columns provided by the embodiment of the present invention; Figure 2 is a schematic connection structure diagram of the hot melt lost foam on the support in the lost foam casting method for the hot blast stove support columns provided by the embodiment of the present invention; Figure 3 is a schematic cross-sectional structure diagram of the hot melt lost foam adopted by the embodiment of the present invention; Figure 4 is a schematic diagram of the fixed state of the hot melt lost foam in the negative pressure sand box in the lost foam casting method for the hot blast stove support columns provided by the embodiment of the present invention.

[0015] In the figure: 10, hot melt lost foam; 20, core shaft; 30, sand cavity; 40, support; 41, frame; 42, leg; 50, adjustable clamping part; 51, U-shaped clamp; 52, ejector rod; 60, runner lost foam; 61, vertical mold; 62, horizontal mold; 63, support mold; 70, sand mold; 71, riser. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] It should be noted that when an element is referred to as being "disposed on" or "connected to" another element, it can be directly on the other element or indirectly on the other element. It should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present application. The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or several of such features. In the description of the present application, the meaning of "a plurality of" or "several" is two or more, unless otherwise specifically defined.

[0018] Please refer to Figures 1 to 4 simultaneously, and a lost foam casting method for the hot blast stove pillar provided by the present invention will be described hereinafter. The lost foam casting method for the hot blast stove pillar is used for casting a hot blast stove pillar with a hollow structure, and comprises the following steps: S100. Manufacture a hot-melt lost foam 10 according to a one-to-one ratio of the structure of the hot blast stove pillar.

[0019] Specifically, the hot-melt lost foam 10 can be formed by bonding foam models to be completely consistent with the size and shape of the hot blast stove pillar. During casting, the hot-melt lost foam 10 is vaporized by heat so that the molten iron occupies its position, and finally the molten iron solidifies into a shape.

[0020] S200. Insert a core shaft 20 into the hollow cavity of the hot-melt lost foam 10. A sand cavity 30 is formed between the peripheral wall of the core shaft 20 and the cavity wall of the hollow cavity. Both ends of the core shaft 20 penetrate out of the hollow cavity and are fixed to a support 40.

[0021] The core shaft 20 is made of high-temperature resistant steel with sufficient bending and torsion resistance. The diameter of the core shaft 20 is smaller than the inner diameter of the hollow cavity to ensure that there is enough sand filling space between the two, ensuring that the sand material (i.e., the sand core) filled in the sand cavity 30 has sufficient thickness in the radial direction of the sand cavity 30. On the one hand, it can improve the airtightness of the cavity after the hot-melt lost foam 10 is vaporized, thus avoiding the problem of air pressure leakage during the casting process. On the other hand, it can also improve the bonding force between the sand core and the core shaft 20, thereby improving the stability of the hot-melt lost foam 10 fixed on the support 40 through the core shaft 20.

[0022] The function of the support 40 is to suspend the hot-melt expendable pattern 10 before it is placed in the negative-pressure sand box. This not only facilitates surface treatment of the hot-melt expendable pattern 10, such as coating dipping, but also avoids damage to the surface quality caused by the hot-melt expendable pattern 10 bumping and rubbing against surrounding parts. After the hot-melt expendable pattern 10 is placed in the negative-pressure sand box, it can also be supported by the support 40, so that the hot-melt expendable pattern 10 is separated from the bottom of the negative-pressure sand box, ensuring the thickness of the sand filling around the hot-melt expendable pattern 10, and then improving the airtightness of the cavity after the hot-melt expendable pattern 10 is vaporized by heat.

[0023] S300. Fill the sand cavity 30 with sand material.

[0024] Here, the sand material can be quartz sand or resin sand, and the sand material can be added from one end of the sand cavity 30 or added simultaneously from both ends of the sand cavity 30. After filling, it is compacted along the axial direction of the sand cavity 30. Compared with the vibration filling method in the negative-pressure sand box, it can improve the sand filling compactness of the sand cavity 30, thus ensuring the airtightness of the cavity during the subsequent casting process.

[0025] S400. Place the hot-melt expendable pattern 10 together with the support 40 in the negative-pressure sand box and perform casting after the sand filling is vibrated and compacted.

[0026] Lifting lugs can be provided on the support 40, and the support 40 is lifted by a lifting device such as a crane, so that the hot-melt expendable pattern 10 can be transferred to the negative-pressure sand box together with the support 40. Here, another function of the support 40 is reflected, that is, during the transfer of the hot-melt expendable pattern 10 to the negative-pressure sand box, the lifting equipment does not need to contact the hot-melt expendable pattern 10, thus avoiding damage to the hot-melt expendable pattern 10 during the transfer process. After the hot-melt expendable pattern 10 enters the negative-pressure sand box, it is supported on the bottom of the negative-pressure sand box by the support 40. On the one hand, it can improve the placement stability of the hot-melt expendable pattern 10 in the sand box, and on the other hand, it can make the hot-melt expendable pattern 10 in a suspended state in the negative-pressure sand box, so that there is sufficient sand filling space below it. Compared with the conventional method of directly placing the hot-melt expendable pattern 10 above the sand layer in the negative-pressure sand box, it can avoid the problem of the hot-melt expendable pattern 10 sinking during the process of vibrating and compacting the sand material. After filling the negative-pressure sand box with sand material such as quartz sand or resin sand, the sand material is vibrated to closely wrap around the hot-melt expendable pattern 10, and then casting can be carried out according to the conventional expendable pattern casting process.

[0027] Compared with the prior art, the lost foam casting method for the hot blast stove pillar provided in this embodiment includes inserting a core shaft 20 into the hollow cavity of the hot melt lost foam 10 after the hot melt lost foam 10 is fabricated. Then, the sand cavity 30 formed between the outer periphery of the core shaft 20 and the cavity wall of the hollow cavity is filled with sand material. By pre-filling the sand, the compactness of the sand material in the hollow cavity is improved, avoiding pressure relief during the casting process and affecting the forming quality. At the same time, the filled sand material can also integrate the hot melt lost foam 10 and the core shaft 20 and connect them to the bracket 40 through both ends of the core shaft 20. With the support of the bracket 40, the hot melt lost foam 10 can be suspended, thus avoiding damage to the surface quality due to the collision and friction of the hot melt lost foam 10 with surrounding objects during surface treatment and transfer. In addition, after the hot melt lost foam 10 is placed in the negative pressure sand box, with the support of the bracket 40, there is sufficient sand filling gap between the hot melt lost foam 10 and the box wall of the negative pressure sand box, which can not only avoid the problem of the negative pressure sand box scratching the surface of the hot melt lost foam 10, but also ensure the sand filling amount around the hot melt lost foam 10, thus avoiding pressure relief of the sand mold 70. After the hot melt lost foam 10 is gasified by heat, the filled sand material and the sand core in the sand cavity 30 can resist the buoyancy of the molten iron under the connection and protection of the core shaft 20, thereby avoiding the phenomenon of core floating during the casting process and improving the circumferential wall thickness uniformity and forming quality of the hot blast stove pillar after casting.

[0028] In some embodiments, referring to Figure 3 , the core shaft 20 is coaxially inserted into the hollow cavity, and both ends of the core shaft 20 are connected to the bracket 40 through adjustable fasteners 50. The coaxial arrangement of the core shaft 20 and the hollow cavity can improve the uniformity of the circumferential sand filling thickness of the sand cavity 30, avoid local positions with insufficient wall thickness in the cavity after the hot melt lost foam 10 is gasified and cause pressure relief, and is beneficial to improving the casting forming quality. The two ends of the core shaft 20 are connected to the bracket 40 through adjustable fasteners 50, so that the position of the hot melt lost foam 10 on the bracket 40 can be adjusted by adjusting the fixed position of the core shaft 20 and the bracket 40. Thus, when two or more hot melt lost foams 10 are placed on the bracket 40 for simultaneous casting of multiple parts, the interval between adjacent hot melt lost foams 10 can be adjusted through the adjustable fasteners 50, so as to meet the simultaneous casting of multiple hot blast stove pillars while ensuring the wall thickness of the cavity, which is beneficial to improving the manufacturing efficiency.

[0029] As a specific structural form of the above bracket 40, please refer to Figure 4, the support 40 includes a frame 41 and a number of legs 42 arrayed at the bottom of the frame 41; wherein, both ends of the mandrel 20 are lapped on the frame 41 and fixed respectively by adjustable fasteners 50, and each of the legs 42 supports together on the bottom of the negative pressure sand box to separate the hot-melt expendable pattern 10 from the bottom wall of the negative pressure sand box. The frame 41 can specifically be a rectangular frame welded by high-temperature resistant steel. A leg 42 is welded at each position near the four corners of the frame 41. The two ends of the mandrel 20 can be directly lapped on the opposite two side frames of the frame 41 and fixed by the adjustable fasteners 50, with a simple and stable structure.

[0030] As an optional structure of the above adjustable fastener 50, please refer to Figure 3 , the adjustable fastener 50 includes a U-shaped clamp 51 and a push rod 52. One end of the U-shaped clamp 51 is buckled upward on the bottom surface of the frame 41, and the other end vertically penetrates the push rod 52 and is in threaded cooperation with the push rod 52. The push rod 52 presses downward on the mandrel 20. The mouth size of the U-shaped clamp 51 is larger than the sum of the vertical dimensions of the mandrel 20 and the frame 41. Thus, the U-shaped clamp 51 can be straddled on the edge of the frame 41 and on the end of its mandrel 20, and then by screwing the push rod 52, the push rod 52 presses on the mandrel 20, thereby realizing the clamping and fixing of the mandrel 20 and the frame 41. When the position of the mandrel 20 needs to be adjusted, just loosen the push rod 52, which is simple and convenient to operate.

[0031] It should be noted that, in this embodiment, before the mandrel 20 is inserted into the hollow cavity, the inner and outer surfaces of the hot-melt expendable pattern 10 are evenly coated with expendable pattern coating. The expendable pattern coating generally consists of refractory materials, binders, carriers (solvents), surfactants, suspending agents, thixotropic agents, and other additives. Various components are evenly mixed together and play a comprehensive role during the coating hanging of the coating and the pouring process of the molten metal, which can avoid the penetration of molten iron into the gaps between the sand grains and form sand adhering defects. At the same time, it can also improve the stiffness of the hot-melt expendable pattern 10 and avoid the deformation of the hot-melt expendable pattern 10 during the filling and vibration of the sand in the negative pressure sand box, which affects the forming quality of the hot blast stove support.

[0032] In some embodiments, in combination with Figure 2 understanding, before the hot-melt expendable pattern 10 is placed in the negative pressure sand box, a runner expendable pattern 60 is provided on the side of the hot-melt expendable pattern 10. The runner expendable pattern 60 is fixed in the sand mold 70 compacted in the negative pressure sand box and forms a pouring gate at its top. The function of the runner expendable pattern 60 is not only to pour molten iron into the cavity, but also to be buried in the sand in the negative pressure sand box to improve the stability of the hot-melt expendable pattern 10, avoid the sag deformation due to the lack of force in the middle of the hot-melt expendable pattern 10, and is beneficial to further improving the forming quality of the hot blast stove support.

[0033] Specifically, as shown in Figure 2As shown in the figure, in this embodiment, the runner lost foam pattern 60 includes a vertical pattern 61, a horizontal pattern 62, and several support patterns 63. Among them, each support pattern 63 is distributed at intervals along the axial direction of the hot-melt lost foam pattern 10 on the side wall of the hot-melt lost foam pattern 10. Each support pattern 63 extends horizontally along the radial direction of the hot-melt lost foam pattern 10 and is jointly connected to the horizontal pattern 62. One end of the vertical pattern 61 is connected to the middle of the horizontal pattern 62, and the other end extends upward to the top surface of the sand mold 70. The method of arranging multiple support patterns 63 at intervals can enable the molten iron to enter from different axial positions of the cavity, improve the pouring efficiency of the molten iron and the pouring fullness of the molten iron in the cavity, thereby improving the forming quality. In addition, each support pattern 63 can evenly disperse the force on the hot-melt lost foam pattern 10 into the sand mold 70, thereby avoiding the problem of the middle part sagging and deforming due to insufficient bending resistance before the molten iron solidifies.

[0034] On the basis of the above, combined with Figure 4 Understand that in this embodiment, risers 71 are provided at both ends of the sand mold 70 vibrated and compacted in the negative pressure sand box corresponding to the hot-melt lost foam pattern 10. The molten iron enters from the middle of the cavity and gradually fills from the middle to both ends in the cavity. During this process, the slag and dirt gather at the position of the riser 71, and the riser 71 material can be cut off after the final forming. In this way, it can avoid the slag and dirt remaining in the cavity and affecting the quality of the hot blast stove support.

[0035] It should be understood that, as Figure 2 shown, in this embodiment, the bracket 40 has several support units, and each support unit is provided with a hot-melt lost foam pattern 10. Multiple hot blast stove supports can be formed in a single casting, and only the distance between adjacent hot-melt lost foam patterns 10 needs to be ensured, which is beneficial to improving the manufacturing efficiency.

[0036] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lost foam casting method for a hot blast furnace pillar, which is used for casting a hot blast furnace pillar with a hollow structure, characterized in that: The following steps are involved: According to the structure of the hot air furnace support, a hot melt lost foam is made in a one-to-one ratio; A mandrel is inserted into the hollow cavity of the hot melt lost foam, a sand cavity is formed between the peripheral wall of the mandrel and the cavity wall of the hollow cavity, and two ends of the mandrel pass through the hollow cavity and are fixed to a bracket; Filling the sand cavity with sand material; The hot melt lost foam and the bracket are placed in a negative pressure sand box and cast after filling sand and vibrating it.

2. The lost foam casting method of hot blast furnace pillar according to claim 1, characterized in that: The core shaft is coaxially arranged in the hollow cavity, and both ends of the core shaft are connected to the bracket through adjustable clamps.

3. The lost foam casting method of hot blast furnace pillar according to claim 2, characterized in that: The bracket includes a frame and a plurality of legs distributed in an array at the bottom of the frame; wherein both ends of the core shaft are overlapped on the frame and fixed by the adjustable clamps respectively, and each of the legs is supported on the bottom of the negative pressure sand box to separate the hot melt lost foam from the bottom wall of the negative pressure sand box.

4. The lost foam casting method of hot blast furnace pillar according to claim 3, characterized in that: The adjustable clamp includes a U-shaped clamp and a push rod, one end of the U-shaped clamp is buckled upward on the bottom surface of the frame, and the other end vertically penetrates the push rod and cooperates with the push rod thread, and the push rod is pressed downward on the core shaft.

5. The lost foam casting method of hot blast furnace pillar according to claim 1, characterized in that: Before the core shaft is passed through the hollow cavity, the inner and outer surfaces of the hot melt lost foam are evenly coated with lost foam coating.

6. The lost foam casting method of hot blast furnace pillar according to claim 1, characterized in that: Before the hot melt lost mold is placed in the negative pressure sand box, a runner lost mold is arranged on the side of the hot melt lost mold. The runner lost mold is fixed in the sand mold compacted in the negative pressure sand box and a gate is formed at the top thereof.

7. The lost foam casting method of hot blast furnace pillar according to claim 6, characterized in that: The runner lost mold includes a vertical mold, a horizontal mold and a plurality of supporting molds; wherein each of the supporting molds is distributed on the side wall of the hot melt lost mold at intervals along the axial direction of the hot melt lost mold, and each of the supporting molds extends horizontally along the radial direction of the hot melt lost mold and is commonly connected to the horizontal mold; one end of the vertical mold is connected to the middle of the horizontal mold, and the other end extends upward to the top surface of the sand mold.

8. The lost foam casting method of hot blast furnace pillar according to claim 1, characterized in that: Riser openings are arranged at both ends of the sand mold compacted by vibration in the negative pressure sand box corresponding to the hot melt lost foam.

9. The lost foam casting method of a hot blast furnace pillar according to any one of claims 1 to 8, characterized in that: The bracket has a plurality of supporting units, and each supporting unit is respectively provided with a hot melt lost foam.

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