Molding structure of low-modulus nodular cast iron box hub casting

Abstract

A modeling structure of a low-modulus nodular cast iron box hub casting belongs to the field of casting, when the box hub casting is modeled, the box hub casting is in vertical pouring modeling with the outer side face of a box hub facing upwards, a plurality of bosses are arranged on the outer side face of the box hub, a chilling block is arranged on the bosses every other boss in the circumferential direction, and the chilling block is arranged on the box hub. Exhaust pieces are evenly arranged on the interval inner bosses in the circumferential direction at the same time, a plurality of inner circumferential exhaust pieces are evenly arranged on the surface of the convex edge of the center hole in the circumferential direction, a sprue is arranged in the center hole of the box hub, molten iron is injected upwards in the reverse direction from the bottom of the sprue, and a filter is arranged at the bottom of the sprue. According to the utility model, the riser can be omitted, the shrinkage defect can be reduced or eliminated, the quality and the yield of castings can be improved, the production cost can be reduced, and the requirements of customers can be met.

Description

Technical Field

[0001] The invention relates to a molding structure of a casting, in particular to a molding structure of a low-modulus ductile iron box hub casting, and belongs to the field of casting. Background Art

[0002] In the foundry industry, currently, when producing ductile iron castings, thick-walled castings with a modulus greater than 2.5cm can be produced without feeding risers to meet quality standards. However, castings with a modulus less than 2.5cm generally require feeding risers to achieve acceptable quality. For complex-shaped ductile iron parts for critical equipment, producing high-quality castings completely free of internal shrinkage defects requires larger and more feeding risers, which undoubtedly increases production costs. Our company's ductile iron box hub is one such example. Its features are a modulus less than 2.5cm, dispersed multiple heat nodes, and medium wall thickness. During trial production, we used traditional processes, installing multiple feeding risers. As a result, internal shrinkage defects were present in the castings, resulting in a high scrap rate that exceeded the normal scrap rate. Many of the qualified products were marginally defective, resulting in virtually no profit.

[0003] In order to improve the quality of hub castings and meet the needs of the high-end equipment industry, research on low-cost hub castings has become a major issue for the company. Summary of the Invention

[0004] In view of the current situation that the scrap rate of ductile iron box hub castings is high and the product quality is low during the trial production process, the present invention provides a molding structure of a low-modulus ductile iron box hub casting, the purpose of which is to reduce or cancel the riser setting, reduce or eliminate shrinkage defects, improve the manufacturing quality of low-modulus ductile iron box hub castings, reduce production costs, and meet customer needs.

[0005] The technical solution of the present invention is: a molding of a low-modulus ductile iron box hub casting, the box hub comprising a center hole and a rim, a spoke connected between the center hole on the outer side of the box hub and the rim, and an outer rim on the outer side of the rim; when molding the box hub casting, the box hub casting is a vertical pouring molding with the outer side of the box hub facing upward; a plurality of bosses facing upward are provided on the outer side of the box hub near the outer rim; a plurality of bosses are provided with a chill on the surface of every other boss in the circumferential direction; a plurality of peripheral exhaust fins are uniformly provided on the surfaces of the plurality of bosses in the intervals provided with the chill; a plurality of inner peripheral exhaust fins, which are less in number than the outer peripheral exhaust fins, are uniformly provided on the circumferential surface of the convex edge of the center hole in the same direction as the surface of the boss; a straight runner is provided in the center hole of the box hub, The pouring cup at the top of the sprue is set above the casting. The sprue adopts a ceramic sprue tube. The bottom of the sprue is provided with a molten iron ceramic filter. Below the filter, there are radially arranged ingates consisting of multiple ceramic sprue tubes connected to the rim. The ingates are a form of molten iron pouring form that injects the molten iron upward from the bottom of the ingates into the mold cavity. The box hub casting is not provided with a feeding riser.

[0006] Furthermore, the chill provided on the boss on the outer side of the hub is cylindrical and made of iron, steel, copper or graphite, and a magnet is provided in the mold below the chill;

[0007] Furthermore, the length of the connection portion between the bottom of the outer peripheral exhaust plate and the inner peripheral exhaust plate and the table top of the boss is 30 to 70 mm, and the width is 3 to 12 mm. The height of the outer peripheral exhaust plate and the inner peripheral exhaust plate exceeds the height of the upper sand box. The inner peripheral exhaust plate and the peripheral exhaust plate are in a wedge-shaped structure with a larger upper portion and a smaller lower portion in the height direction.

[0008] Furthermore, in the vertical pouring molding, the cross-sectional area ratio of the sprue to the gate is: A 直 :A 内 =1:1.25, which is an open pouring system;

[0009] Furthermore, the number of the outer peripheral exhaust fins is between 3 and 6, the number of the inner peripheral exhaust fins is between 2 and 4, the inner diameter of the sprue ceramic tube is between Ø35 and 60 mm, and the inner diameter of the ingrown ceramic tube is between Ø15 and 25 mm;

[0010] Furthermore, the hub casting has a medium wall thickness and a modulus of less than 2.5 cm;

[0011] Furthermore, the size of the cylindrical chiller is between Ø30 and 60 mm and the height is between 50 and 150 mm.

[0012] The positive effects of the present invention are as follows: by arranging a cold iron on the surface of every other boss in the circumferential direction of the outer side surface of the box hub, it is intended to artificially create a difference in the solidification speed of adjacent boss positions after pouring molten iron, so as to utilize the graphite precipitated during the solidification of the molten iron and the expansion to compensate for the shrinkage caused by the cooling of the molten iron, thereby creating conditions for eliminating shrinkage defects and breaking the traditional structure of setting risers during casting; by designing the box hub casting into a vertical molding and pouring structure with the outer side of the box hub facing upward, and arranging the sprue in the center hole of the box hub casting, and arranging a filter at the bottom of the sprue, the outer dimensions of the sand box can be reduced, thereby reducing the amount of sand used for molding and saving production costs; by designing the pouring system into a pouring form in which the molten iron enters the bottom of the center hole from the sprue and then enters the mold cavity from the bottom in the opposite direction upward, and the cross-sectional area ratio of the sprue to the ingrowth is designed to be A 直 :A 内 =1:1.25 opening form, when molten iron falls from the sprue to the bottom of the filter, the impact force brought by the molten iron is greatly reduced by bending 180 degrees, so that the molten iron can flow smoothly into the cavity without being involved in gas and slag, and there will be no molten iron sand washing defects. At the same time, the molten iron is gradually filled from the bottom of the casting upward, and the molten iron filling direction is consistent with the exhaust direction in the cavity, which is conducive to exhaust and slag removal, and avoids slag holes and air holes in the casting; by evenly arranging radial dispersed ingrows under the filter, the molten iron and heat are evenly distributed everywhere after the molten iron enters the cavity, avoiding local overheating, thereby ensuring the consistency of the metallographic structure everywhere inside the casting. A plurality of outer circumferential exhaust fins are evenly arranged on the table surface of the multiple spaced bosses of the box hub casting with the outer side of the box hub facing upward, and a plurality of inner circumferential exhaust fins are evenly arranged on the circumferential surface of the convex edge of the center hole, so that the pouring direction and the exhaust direction are in the same direction, which is conducive to the smooth discharge of gas in the mold cavity when the molten iron is filled, ensuring that the casting does not produce air hole defects, can reduce defects caused by poor exhaust, and can improve the product quality of the casting. The length of the connection between the bottom of the inner circumferential exhaust fins and the casting boss surface is 30 to 70 mm, the width is 3 to 12 mm, and the height exceeds the height of the upper sand box, which is conducive to smooth exhaust and demoulding in the height direction; the use of the present invention to cast low modulus ductile iron box hub realizes riser-free casting, which changes the traditional theory and process method that low modulus ductile iron parts cannot be cast without risers. The use of the process of the present invention to produce box hub castings not only improves the quality of castings, reduces the scrap rate, but also reduces production costs. The present invention creates a more scientific process method for the production of similar ductile iron parts, and its effect is that the castings are of better quality and the production cost is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the box hub casting structure of the present invention Figure 1 .

[0014] Figure 2 This is a schematic diagram of the box hub casting structure of the present invention Figure 2 .

[0015] Figure 3 It is a structural diagram of the box hub casting.

[0016] Explanation of reference numbers: 001—hub casting, 002—inner exhaust fin, 003—outer exhaust fin, 004—chill, 005—pouring cup, 006—sprue, 007—filter, 008—introducing channel, 009—magnet, 010—boss, 011—center hole, 012—outer rim, 013—spoke, 014—rim, 015—convex edge. DETAILED DESCRIPTION

[0017] The following is a detailed description of the specific embodiments of the invention with reference to the accompanying drawings. In the following description, the outer side of the hub refers to the side of the hub facing the outside of the equipment, that is, the side close to the end of the equipment shaft, and the inner side of the rim refers to the side of the hub facing the outside of the equipment.

[0018] A low modulus ductile iron box hub casting shape, Figure 1 This is a schematic diagram of the box hub casting structure of the present invention Figure 1 、 Figure 2 This is a schematic diagram of the box hub casting structure of the present invention Figure 2 、 Figure 3 014, an outer rim 012 on the outside of the rim 014, and an inner rim on the inside of the rim 014. When the hub casting 001 is molded, the hub casting 001 is vertically poured with the outer side facing upward. A plurality of bosses with upward table surfaces are provided on the outer side of the hub near the outer rim. A chill 004 is provided on the table surface of each of the plurality of bosses 010 in the circumferential direction. A plurality of outer peripheral exhaust fins 003 are uniformly provided on the table surfaces of the plurality of bosses 010 in the intervals provided with the chill 004. A plurality of inner peripheral exhaust fins 002, which are less in number than the outer peripheral exhaust fins 003, are uniformly provided on the surface of the convex edge 015 of the center hole 011 in the same direction as the table surface of the boss 010. A sprue 006 is provided in the center hole 011 of the hub. The pouring cup 005 of the sprue 006 is arranged above the casting. The sprue 006 adopts a ceramic sprue tube. A molten iron ceramic filter 007 is arranged at the bottom of the sprue 006. An inner runner 008 composed of multiple ceramic runner tubes connected to the bottom surface of the rim 014 is radially arranged below the filter 007. The inner runner 008 is a form of molten iron pouring that is injected upward from the bottom of the rim. The box hub casting 001 is not provided with a shrinkage feed riser.

[0019] Reference Figure 1 、 Figure 2 The chiller 004 provided on the boss 010 on the outer side of the box hub is in the shape of a cylindrical chiller 004. The chiller 004 is made of iron, steel, copper metal or graphite material, etc. A magnet 009 is provided in the mold below the chiller. In this embodiment, in order to reduce costs, gray cast iron material is used to make the chiller.

[0020] Reference Figure 1 、 Figure 2 The length of the connection part between the bottom of the inner peripheral exhaust plate 002 and the outer peripheral exhaust plate 003 and the table top of the boss 010 is 30 to 70 mm, and the width is 3 to 12 mm. The height of the inner peripheral exhaust plate 002 and the outer peripheral exhaust plate 003 exceeds the height of the upper sand box. The inner peripheral exhaust plate 002 and the outer peripheral exhaust plate 003 are wedge-shaped structures with the upper part larger and the lower part smaller in the height direction.

[0021] In the vertical pouring molding, the cross-sectional area ratio of the sprue 006 to the ingrown 008 is: 直 :A 内 =1:1.25, which is an open pouring system.

[0022] The number of the outer peripheral exhaust fins 003 is between 3 and 6, the number of the inner peripheral exhaust fins 002 is between 2 and 4, the inner diameter of the sprue 006 ceramic tube is between Ø35 and 60 mm, and the inner diameter of the endocastor 006 ceramic tube is between Ø15 and 25 mm.

[0023] The hub casting 001 has a medium wall thickness, and the module of the hub casting 001 is less than 2.5 cm.

[0024] The cylindrical chiller 004 has a diameter of Ø30 to 60 mm and a height of 50 to 150 mm.

[0025] Specific implementation steps:

[0026] ① First, conduct process analysis and evaluation based on the structural characteristics of the ductile iron castings to be produced, and determine the preliminary process plan;

[0027] ② Design and draw casting production process diagrams; including designing sand box and drawing sand box diagrams; designing chillers and drawing chiller diagrams; designing pouring risers and exhaust fins;

[0028] ③Design and draw mold drawings for modeling;

[0029] ④ Purchase the sand box, chiller, mold and various materials required for production;

[0030] ⑤ Make molds for modeling, make sand boxes, make chills, and inspect whether the molds, sand boxes, and chills are qualified;

[0031] ⑥ Molding and core making, painting, drying, core unloading and box assembly;

[0032] ⑦ Melting molten iron while carrying out step ⑥;

[0033] ⑧ Molten iron is discharged from the furnace and spheroidized;

[0034] ⑨Pouring: Pour the molten iron that has passed the spheroidization treatment into the mold;

[0035] ⑩ After keeping warm and cooling naturally to below 300℃, unpack and remove sand;

[0036] ⑪ Polishing and inspection: Finally, qualified box hub castings are obtained. Specific embodiments

[0037] Our company actually produces a box hub made of QT450-10, weighing 293kg, with a casting modulus of Mc=1.98cm and a main wall thickness of 35mm. In the past, according to traditional theoretical design technology, during the molding process, whether the outer side of the box hub faces up or down during pouring, a larger shrinkage feed riser is required. The process yield is 75%, and the internal shrinkage defect scrap rate is as high as 10%. Even the qualified castings have slight shrinkage inside. According to the process method of the present invention, the casting is vertically molded and poured vertically, the outer side of the box hub faces upward, and there is no need to set a shrinkage feeder. On the boss 010 on the outer side of the box hub, 12 Ø50×100 cylindrical chillers 004 are set on every other boss 010, and the chillers 004 are evenly distributed in the circumferential direction. In this embodiment, 6 5×60 outer peripheral exhaust fins 003 are evenly set on the upper side of the boss 010; 4 4×40 inner peripheral exhaust fins 002 are evenly set on the circumferential surface of the convex edge 015 of the center hole 011, and the casting system is designed in the form of a pouring cup 005 higher than the upper side. After passing through the upper runner, the flask enters the sprue 006, located within the center hole of the hub cast iron 001. Sprue 006 is formed from a Ø40mm ceramic runner tube. A molten iron ceramic filter 007 is located at its base. Below filter 007 are six Ø18mm ceramic runner tubes forming ingates 008. Ingates 008 are radially connected to the rim 014 (specifically, the bottom outer edge of the mold). After passing through ingates 008, the molten iron is redirected 180 degrees and injected upward from the bottom of the casting rim into the sand mold cavity. Due to the reduced size of the flask, each hub production unit uses 480kg less molding sand, saving 60 yuan. Furthermore, the lack of a feeder riser reduces molten iron consumption by 33kg per unit, saving 10 yuan. A total of 43 yuan can be saved per piece, and 146 yuan per ton. The production process yield rate has increased from 75% to 86%, and the qualified rate is over 98%. The defective products are other casting defects, there are no internal shrinkage defects, and the quality has always been good.

[0038] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. The present invention can be applied to similar casting production.

[0039] The positive effects of the present invention are as follows: by arranging a chill 004 on the surface of every other boss 010 on the outer surface of the hub, it is intended to artificially create a difference in solidification speed between adjacent bosses 010 after pouring molten iron, so as to utilize the expansion of graphite precipitated during solidification of the molten iron to compensate for the shrinkage caused by the cooling of the molten iron, thereby creating conditions for avoiding shrinkage defects and breaking the traditional structure of setting risers during casting; by designing the hub casting 001 as a vertical molding casting with the outer surface of the hub facing upward, and arranging the sprue 006 in the center hole 011 of the hub cast iron 001, and arranging a filter 007 at the bottom of the sprue 006, this molding structure can reduce the external dimensions of the sand box, thereby reducing the amount of molding sand and saving production costs; the cross-sectional area ratio of the sprue 006 to the ingrowth 008 is designed to be A 直 :A 内 =1:1.25 open form, the pouring system is designed so that the molten iron enters the bottom of the casting from the sprue 006, and then pours upward from the bottom of the sprue 006 through the ingrown gate into the mold cavity. When the molten iron falls from the sprue 006 to the bottom of the filter 007, it bends 180 degrees to greatly reduce the impact of the molten iron, allowing the molten iron to flow smoothly into the sand mold cavity without being involved in gas and slag, and without causing molten iron sand washing defects. At the same time, the molten iron gradually fills up from the bottom of the casting, and the molten iron filling method is convenient. The exhaust direction is consistent with that in the cavity, which is beneficial to exhaust and slag removal, avoiding slag holes and air hole defects in the casting; by evenly arranging radial dispersed ingrowns 008 on the filter 007, the molten iron and heat are evenly distributed everywhere after the molten iron enters the cavity, avoiding local overheating, thereby ensuring the consistency of the metallographic structure everywhere inside the casting; by evenly arranging multiple peripheral exhaust fins 003 on the surface of the upward boss 010 on the outer side of the box hub, the circumferential direction is evenly distributed on the upward surface of the convex edge 015 of the center hole 011. A plurality of inner circumference exhaust fins 002 are provided so that the pouring direction and the exhaust direction are in the same direction, which is beneficial to the smooth exhaust of gas in the mold cavity when the molten iron is filled, ensuring that the casting does not produce air hole defects, reducing defects caused by poor exhaust, and improving the product quality of the casting; by controlling the connection length between the bottom of the inner circumference exhaust fins 002 and the outer circumference exhaust fins 003 and the table top of the casting boss 010 to be 30-70 mm, 3-12 mm in width, and a height exceeding the height of the upper sand box, it is beneficial to smooth exhaust and to demoulding in the height direction; the use of the present invention to cast low modulus ductile iron box hubs can achieve riser-free casting, which changes the traditional theory and process method that low modulus ductile iron parts cannot be cast without risers. The use of the process of the present invention to produce box hub castings not only improves the quality of the castings, but also reduces the defective rate from 10% in the past to 2%, and also reduces the production cost. The present invention creates a more scientific process method for the production of similar ductile iron parts, with the effect of better casting quality and lower production cost.

Claims

1. A low-modulus ductile iron hub casting structure, the hub comprising a center hole (011) and a rim (014), spokes (013) connecting the center hole (011) and the rim (014), and an outer rim (012) outside the rim, characterized in that: During the molding of the hub casting, the hub casting is a vertical casting molding with the outer side of the hub facing upwards, a plurality of bosses with the table facing upwards are provided on the outer side of the hub near the outer rim, a chill (004) is provided on the table of each boss in the circumferential direction, a plurality of outer peripheral exhaust fins (003) are uniformly provided on the table (010) of the plurality of bosses in the intervals provided with the chill (004), a plurality of inner peripheral exhaust fins (002) whose number is less than the outer peripheral exhaust fins (003) are uniformly provided on the surface of the center hole convex edge (015) in the same direction as the table of the boss, and a straight runner (006) is provided in the center hole of the hub. The top pouring cup of the sprue (006) is arranged above the casting. The sprue (006) adopts a ceramic sprue tube. A molten iron ceramic filter (007) is arranged at the bottom of the sprue. An inner runner (008) composed of multiple ceramic sprue tubes connected to the rim is radially arranged below the filter. The inner runner (008) is a form of molten iron pouring that injects the molten iron into the mold cavity from the bottom of the rim in the reverse direction upward. The box hub casting is not provided with a shrinkage feed riser.

2. The molding structure of a low modulus ductile iron box hub casting according to claim 1, characterized in that: The cold iron arranged on the boss on the outer side of the box hub is in the shape of a cylindrical cold iron. The cold iron is made of iron, steel, copper or graphite. A magnet (009) is arranged in the mold below the cold iron.

3. The molding structure of a low modulus ductile iron box hub casting according to claim 1, characterized in that: The connection portion between the bottom of the outer peripheral exhaust piece (003) and the inner peripheral exhaust piece (002) and the table top of the boss is 30 to 70 mm long and 3 to 12 mm wide. The height of the outer peripheral exhaust piece (003) and the inner peripheral exhaust piece (002) exceeds the height of the upper sand box. The outer peripheral exhaust piece (003) and the inner peripheral exhaust piece (002) are in a wedge-shaped structure with a larger upper portion and a smaller lower portion in the height direction.

4. The low modulus ductile iron hub casting according to claim 1, characterized in that: In the vertical pouring molding, the cross-sectional area ratio of the sprue (006) to the ingrown (008) is: A 直 :A 内 =1:1.25, which is an open pouring system.

5. The molding structure of a low modulus ductile iron hub casting according to claim 1, characterized in that: The number of the outer peripheral exhaust fins (003) is between 3 and 6, the number of the inner peripheral exhaust fins (002) is between 2 and 4, the inner diameter of the sprue ceramic tube is between Ø35 and 60 mm, and the inner diameter of the ingrowth ceramic tube is between Ø15 and 25 mm.

6. The molding structure of a low modulus ductile iron box hub casting according to claim 1, characterized in that: The box hub casting has a medium wall thickness and a module of less than 2.5 cm.

7. The molding structure of a low modulus ductile iron hub casting according to claim 2, characterized in that: The cylindrical chiller has a diameter of 30 to 60 mm and a height of 50 to 150 mm.

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