Casting method of shell

Abstract

The invention discloses a casting method of a shell, which comprises the following steps: a sand mold manufacturing step: placing a shell mold comprising a pouring system and an auxiliary feeding system on a jolt ramming table of resin sand mixing equipment, buckling a matched welding sand box, and filling sand grains mixed with resin and a curing agent into the welding sand box; after full filling, molding, curing and closing the box; molten iron smelting is conducted, specifically, all the components are molten and then continue to be heated for smelting, tapping is conducted after molten iron is killed, melted down and cooled, and the molten iron comprises, by mass, 3.4%-3.8% of C, 2.5%-3.2% of Si, 0.2%-0.4% of Mn, 0.06%-0.11% of S, 0.2%-0.5% of Cu and the balance iron and inevitable impurities; a spheroidizing and pouring step, specifically, molten iron is poured into a spheroidizing ladle, a spheroidizing reaction is performed in a wire feeding spheroidizing mode, after the spheroidizing reaction is completed, the molten iron is poured into a pouring ladle filled with a covering agent and a nucleating agent, pouring is performed, and stream inoculation is performed in the pouring process; and a post-treatment step: cooling and unpacking after pouring is completed, removing a casting head, polishing, and carrying out stress relief annealing.

Description

Technical Field

[0001] The invention relates to a casting method, in particular to a casting method for a shell. Background Art

[0002] The standard urban rail EMU braking system adopts a four-point clamp structure. In order to further optimize the spatial structure, reduce the weight of the braking system, and meet the needs of lightweight trains, the original four-point structure of the lifting shell and the brake cylinder are combined to form a new shell structure. The inner cavity of the combined shell is a fully machined surface. In order to prevent the urban rail EMU train from forming thermal fatigue cracks under the action of a large impact force during emergency braking, high requirements are placed on the density of the machined surface of the inner cavity. At the same time, the shell structure itself is a special-shaped structure design with many cross-heat nodes, and the cross-heat node position is often the key stress area. The inherent defect level of the cross-heat node position affects the operational safety of the entire braking system. Due to the special structure and the harsh service operation environment, the casting process design of the shell casting is difficult, the product qualification rate is low, and it is difficult to meet the quality requirements of mass production and supply.

[0003] Prior art CN115608920A discloses a brake shoe support casting method, comprising the following steps:

[0004] Step 1: Making the coated sand shell mold; Step 2: Melting molten iron; Step 3: Spheroidizing treatment; Step 4: Pouring; Step 5: Post-processing. Step 1: When making the coated sand shell mold, a shrinkage compensation process channel is made between the first thick hot node and the second thick hot node. The two ends of the shrinkage compensation process channel are respectively connected to the first thick hot node and the second thick hot node, and are connected to the casting cavity and the heating riser, which solves the technical problem that the heating riser cannot be placed in the thick hot node in the local space to compensate for liquid shrinkage during solidification.

[0005] Prior art CN106734896A discloses a casting method for a forklift drive axle housing, comprising the following steps: (1) using two-box split molds for molding, (2) using the resin sand to make a sand mold, (3) making a casting liquid, (4) heating the above raw materials in an electric furnace to a melting temperature to form a casting liquid; (5) pouring the casting liquid into the resin sand mold to form a casting after solidification.

[0006] No relevant content related to solving the shell casting problem of this application has been found in the prior art.

[0007] In view of the above technical problems, the present invention is specially introduced. Summary of the invention

[0008] The main purpose of the present invention is to provide a casting method for a shell, which is used to solve the problems of a high proportion of defects on the inner cavity machining surface of a shell for a standard urban vehicle brake system and excessive intrinsic defects at the cross-heat node position, so as to obtain a shell casting with dense structure and stable quality.

[0009] In order to achieve the above-mentioned object, the present invention proposes a casting method for a shell, comprising the following steps: a sand mold making step, placing a shell mold including a pouring system and an auxiliary shrinkage feeding system on a resin sand mixing equipment vibration compaction table, buckling a matching welding sand box, and filling sand particles mixed with resin and curing agent into the welding sand box; after filling, forming and curing, pressing the matching sand core to the core position, placing it in the lower sand model cavity, and fastening the upper and lower sand molds together;

[0010] The molten iron smelting step is to continue heating up the smelting after all the components are melted, and the molten iron is calmed and melted, and the iron is tapped after the temperature is lowered. The mass percentages of the components are C: 3.4-3.8%, Si: 2.5-3.2%, Mn: 0.2-0.4%, S: 0.06-0.11%, Cu: 0.2-0.5%, and the balance is iron and inevitable impurities;

[0011] Spheroidizing and pouring step, pouring the smelted molten iron into the spheroidizing bag, using the wire feeding spheroidizing method to carry out spheroidizing reaction, after the spheroidizing reaction is complete, pouring it into the casting bag filled with covering agent and inoculant, and casting, and carrying out flow inoculation during the casting process;

[0012] Post-processing steps include cooling and unpacking after pouring, removing the pouring head, grinding and stress relief annealing.

[0013] Furthermore, in the sand mold making step, the casting system adopts a filtered center pouring method, the molten iron filling position of the casting system is set at the horizontal center position of the oil surface agent boss of the shell, and side risers are used for filling, and the side risers are used to compensate for the shrinkage of the local processing position of the inner cavity.

[0014] Furthermore, the pouring system includes a sprue, a runner and an inner runner which are vertically connected in sequence and have a cross-sectional area ratio of 1.3 to 1.4:1.6 to 1.7:1, and a filter is provided between the sprue and the runner.

[0015] Furthermore, the filter screen is a foam ceramic filter screen with a porosity of 10 to 20 ppi.

[0016] Furthermore, the ingates are filled into the sand mold cavity through risers on the ingates side, and the auxiliary shrinkage compensation system includes an elliptical boss thickening structure arranged at the risers on the ingates side.

[0017] Furthermore, the parting surface of the shell mold is located at the horizontal center position of the oil surface agent boss, the shell model is placed horizontally, and a one-mold two-piece production process is adopted.

[0018] Furthermore, the auxiliary shrinkage compensation system includes filling the processing hole at the lifting through hole of the shell mold above the parting surface to form a shrinkage compensation channel, and arranging a heating riser above it for liquid shrinkage compensation, adding a process processing subsidy in the processing hole, and adding an auxiliary inner cavity chiller in the inner cavity of the shell mold.

[0019] Furthermore, the process processing subsidy occupies more than 1 / 4 of the circumference of the processing hole, and the circumference of the auxiliary inner cavity cold iron occupies 1 / 3 to 1 / 2 of the circumference.

[0020] Furthermore, the auxiliary shrinkage compensation system includes lifting boss hole filling parts respectively arranged at the left first lifting boss and the left second lifting boss of the shell mold, and a left side riser and a left second side riser with embedded heating riser sleeves to perform liquid shrinkage compensation during the solidification process.

[0021] Furthermore, the auxiliary shrinkage compensation system includes setting a right side riser inlaid with a heating riser sleeve in the area between the right first lifting boss and the right second lifting boss of the shell mold, and adding local process subsidies in the inner cavity of the shell mold.

[0022] Furthermore, the auxiliary shrinkage compensation system also includes a lifting boss hole filling portion arranged at the right first lifting boss and the right second lifting boss of the shell mold, and a first cylindrical steel refrigeration iron and a second cylindrical steel refrigeration iron respectively arranged in a cylindrical shape.

[0023] Furthermore, the auxiliary shrinkage-feeding system includes a conformal steel refrigeration iron arranged at the ventilation boss of the shell mold.

[0024] Furthermore, in the sand mold making step, after filling the sand mold, it is kept for at least 15 minutes, the sand box is hoisted, and the sand mold is flow coated to evenly cover the sand mold with a layer of coating, and then cured.

[0025] Furthermore, in the sand mold making step, the sand particles are silica sand with an angular coefficient of ≤1.2 and a particle size of 40 / 70 mesh.

[0026] Furthermore, in the sand mold making step, the resin is furan resin, and the addition amount is 0.9wt.% to 1.1wt.% of the weight of the sand particles; the curing agent is benzenesulfonic acid curing agent, and the addition amount is 30wt.% to 60wt.% of the weight of the resin.

[0027] Furthermore, in the molten iron smelting step, after all components are melted, the temperature is continued to be raised to 1540-1580° C. for smelting, and after the molten iron is calmed and melted, the temperature is lowered to 1460-1480° C. for tapping.

[0028] Furthermore, in the spheroidizing pouring step, the temperature of the molten iron is controlled at 1360-1380° C. during the pouring process.

[0029] Furthermore, in the spheroidizing pouring step, a rare earth silicon bismuth inoculant with a particle size of 0.2 to 0.7 mm is used for inoculation during the pouring process, and the added amount of the rare earth silicon bismuth inoculant accounts for 0.1 to 0.4% by mass of the total amount of molten iron.

[0030] By applying the technical solution of the present invention, at least the following beneficial effects are achieved:

[0031] 1. The shell casting method of the present invention provides a casting method for a shell for a standard urban EMU braking system, which solves the process bottleneck in the shell casting production process, improves the yield rate of castings, and is simple and convenient to operate, and can meet the requirements of large-scale production.

[0032] 2. The shell casting method of the present invention overcomes the shrinkage problem of each cross-heat node of the shell by reasonably designing the pouring system and the shrinkage feeding riser, thereby meeting the index requirements of intrinsic quality radiographic flaw detection level 2 and above.

[0033] 3. The shell casting method of the present invention forms a good solidification sequence by providing side risers at multiple positions on the outside of the shell inner cavity to compensate for shrinkage, assisted by the local use of process chillers, thereby overcoming the difficulty of compensating for shrinkage in the shell inner cavity and meeting the inherent quality requirement of defect-free inner cavity processing after magnetic particle inspection.

[0034] 4. The shell casting method of the present invention reduces the shrinkage tendency of the molten iron by controlling the temperature of the molten iron in the spheroidizing pouring step, and enhances the inoculation effect by selecting rare earth silicon bismuth inoculant for inoculation, thereby increasing the number of graphite nodules in the shell casting and eliminating local micro-shrinkage. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 A front view of the housing of the present application is shown;

[0037] Figure 2 Shows Figure 1 AA cross-section diagram of ;

[0038] Figure 3 A top view of the housing of the present application is shown;

[0039] Figure 4 Shows Figure 3 BB cross-section diagram;

[0040] Figure 5 A right side view of the housing of the present application is shown;

[0041] Figure 6 A top view of the resin sand mold process of the present application is shown;

[0042] Figure 7 Shows Figure 6 AA cross-section diagram of ;

[0043] Figure 8 Shows Figure 6 BB cross-section diagram;

[0044] Fig. 9 The right side view of the resin sand mold process of the present application is shown;

[0045] Fig.10 Shows Fig. 9 Schematic diagram of CC cross section;

[0046] Fig.11 The rear view of the resin sand mold process of the present application is shown;

[0047] Fig.12 Shows Fig.11 Schematic diagram of DD cross section.

[0048] The above drawings include the following reference numerals:

[0049] 1. Lifting through hole; 2. First lifting boss on the left; 3. Second lifting boss on the left; 4. First lifting boss on the right; 5. Second lifting boss on the right; 6. Ventilation boss; 7. Oiling agent boss; 8. Sealing mating surface; 9. Top of the inner cavity; 1-1. First cross heat node; 1-2. Second cross heat node; 1-3. Third cross heat node; 1-4. Fourth cross heat node; 1-5. Fifth cross heat node; 1-6. Sixth cross heat node;

[0050] 10. Sand mold; 11. Straight runner; 12. Filter; 13. Cross runner; 14. Ingate; 15. Ingate side riser; 16. Right side riser; 17. Heat-generating riser; 18. Left side riser; 19. Left second side riser; 20. First cylindrical steel cooling iron; 21. Second cylindrical steel cooling iron; 22. Conformal steel cooling iron; 23. Auxiliary inner cavity cooling iron; 2-1. Process processing subsidy; 2-2. Boss thickening structure; 2-3. Local process subsidy; 2-4. Heat-generating riser sleeve; 2-5. Lifting boss hole filling part. DETAILED DESCRIPTION

[0051] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] The present invention is further described in detail below in conjunction with specific embodiments, and these embodiments cannot be understood as limiting the scope of protection claimed by the present invention. The term "including" when used indicates the existence of a feature, but does not exclude the existence or addition of one or more other features; the orientation or position relationship indicated by the terms "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; in addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

[0053] In the description, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0054] The present invention requires a shell structure diagram of the casting Figure 1-5 As shown, the housing is suspended on the standard urban vehicle bogie through the lifting through hole 1, and bears the supporting role of the entire braking system. It is the area with the greatest force during the braking process. The first cross heat joint 1-1 and the second cross heat joint 1-2 here have high tissue density requirements to prevent micro-shrinkage inside the tissue from causing cracks in the service process of the braking system.

[0055] The first left lifting boss 2 and the second left lifting boss 3 are mounting bosses located on one side of the housing for interconnecting with the brake lever, and the first right lifting boss 4 and the second right lifting boss 5 are mounting bosses located on the other side of the housing for connecting with the brake lever to achieve the fixation and rotation of the lever. In addition, the ventilation boss 6 is connected to the compressed air transmission pipe to achieve the inflation and pressure of the compressed air into the inner cavity of the housing. The oil level agent boss 7 of the housing is used to measure the volume of lubricating oil inside the housing.

[0056] like Figure 4As shown, the sealing mating surface 8 is the sealing mating surface between the inner cavity of the shell and the piston. To ensure the sealing performance, the structural density of the sealing mating surface here is extremely high, and magnetic traces are not allowed to appear during magnetic particle inspection. The top of the inner cavity 9 is the area where the compressed air in the inner cavity of the shell exerts pressure. To ensure the necessary compression pressure, there are also high requirements for structural density here. Structures 8 and 9 are both thin-walled areas with a wall thickness of 10mm. The process shrinkage compensation is difficult. Relying on a single riser for shrinkage compensation, due to the limitation of the effective shrinkage compensation distance, it is impossible to ensure the structural density of the entire inner cavity at the sealing mating surface 8.

[0057] like Figure 4 and Figure 5 As shown, the first left lifting boss 2 and the second left lifting boss 3 respectively form the fifth cross heat node 1-5 and the sixth cross heat node 1-6 with the inner cavity top 9 area, and the first right lifting boss 4 and the second right lifting boss 5 respectively form the third cross heat node 1-3 and the fourth cross heat node 1-4 with the inner cavity structure area of ​​the sealing mating surface 8. These four cross heat nodes are narrow in structure, and it is difficult to set the shrinkage feed riser or place the formed chill, which is easy to produce micro shrinkage at the cross heat node position, affecting the operation safety during the lifting lever braking process.

[0058] The present invention further proposes a casting method for a shell, which specifically comprises the following steps:

[0059] (1) Sand mold making step S1, placing the shell mold including the pouring system and the auxiliary shrinkage feeding system on the vibrating table of the resin sand mixing equipment, buckling the matching welding sand box, filling the sand mixed with resin and curing agent into the welding sand box; after filling, forming and curing are carried out, the matching sand core is pressed to the core position, placed in the lower sand model cavity, and the upper and lower sand molds are fastened together.

[0060] Combination Figure 6-12 The figure shows a schematic diagram of the mold process including the pouring system and the auxiliary shrinkage compensation system. The pouring system adopts a filtered center pouring method. The iron liquid filling position of the pouring system is set at the horizontal center position of the oil surface agent boss 7 of the shell, and the side riser is used for filling. The side riser is used for shrinkage compensation of the local processing position of the inner cavity. The parting surface of the shell mold is located at the horizontal center position of the oil surface agent boss 7, the shell model is placed horizontally, and a one-mold two-piece production process is adopted.

[0061] Specifically, if Figure 6 As shown, the pouring system includes a sprue 11, a runner 13 and an inner gate 14 which are vertically connected in sequence and have a cross-sectional area ratio of 1.3-1.4:1.6-1.7:1, and a filter 2 is arranged between the sprue 11 and the runner 13. Preferably, the filter 2 is a foam ceramic filter with a porosity of 10-20 ppi.

[0062] Furthermore, combined with Figure 8As shown, the ingates 14 are filled into the sand mold cavity through the ingates side risers 15, and the auxiliary shrinkage compensation system includes an elliptical boss thickening structure 2-2 arranged at the ingates side risers 15. To form a good solidification sequence, and to perform corresponding liquid shrinkage compensation on the corresponding half structure of the inner cavity sealing mating surface 8 of the shell.

[0063] Combination Figure 7 As shown, the auxiliary shrinkage feeding system also includes filling the processing hole located above the parting surface at the hoisting through hole 1 of the shell mold to form a shrinkage feeding channel for the second cross heat node 1-2, and setting a heating riser 17 above it for liquid shrinkage feeding. In order to further meet the shrinkage feeding requirements of the first cross heat node 1-1, a process processing subsidy 2-1 is added to the processing hole, and an auxiliary inner cavity chiller 23 is added to the inner cavity of the shell mold to accelerate local cooling and form a shrinkage feeding gradient from top to bottom.

[0064] Preferably, the process processing subsidy 2-1 occupies more than 1 / 4 of the circumference of the processing hole, and the circumference of the auxiliary inner cavity cold iron 23 occupies 1 / 3 to 1 / 2 of the circumference.

[0065] In order to meet the shrinkage requirements of the fifth cross heat section 1-5 and the sixth cross heat section 1-6, combined with Fig.12 As shown, the auxiliary shrinkage compensation system includes a lifting boss hole filling part 2-5 respectively arranged at the left first lifting boss 2 and the left second lifting boss 3 of the shell mold to fill the lifting boss hole. At the same time, the left side riser 18 and the left second side riser 19 embedded with the heat-generating riser sleeve are used to perform liquid shrinkage compensation during the solidification process. Preferably, the inner diameter size of the heat-generating riser sleeve is 50mm to 80mm.

[0066] To ensure the tissue density at the third cross heat node 1-3 and the fourth cross heat node 1-4, as Fig.10 As shown, the auxiliary shrinkage compensation system includes setting a right riser 16 inlaid with a heat-generating riser sleeve 2-4 in the area between the right first lifting boss 4 and the right second lifting boss 5 of the shell mold to perform liquid shrinkage compensation around the cross heat node. A local process subsidy 2-3 is added to the inner cavity of the shell mold. Preferably, the thickness of the local process subsidy 2-3 is 20 to 30 mm.

[0067] Further, combined with Fig. 9 As shown, the auxiliary shrinkage feeding system also includes a lifting boss hole filling portion provided at the right first lifting boss 4 and the right second lifting boss 5 of the shell mold, and a cylindrical first cylindrical steel refrigeration iron 20 and a second cylindrical steel refrigeration iron 21 are provided respectively. To achieve a good solidification sequence from the cross heat node position to the right side riser 16. Preferably, the diameter of the two cylindrical steel refrigeration irons is 50mm to 65mm, and the thickness is 55mm to 70mm. To extend the right side riser shrinkage feeding distance, meet the shrinkage feeding requirements of the cross heat node, and eliminate micro shrinkage.

[0068] In addition, combined Figure 8 , 9 As shown, the auxiliary shrinkage feeding system also includes a conformable steel refrigeration iron 22 arranged at the vent boss 6 of the shell mold to achieve local rapid cooling. To ensure a good chilling effect, the thickness of the conformable steel refrigeration iron 22 is preferably 25mm to 40mm.

[0069] The shell casting method of the present invention overcomes the problem of shrinkage feeding of each cross-heat joint of the shell by reasonably designing the pouring system and the shrinkage feeding riser, thereby meeting the index requirements of the internal quality radiographic flaw detection level 2 and above. Assisted by the local use of process chillers, a good solidification sequence is formed, which overcomes the problem of shrinkage feeding of the inner cavity of the shell and meets the internal quality requirements of no defects after magnetic particle flaw detection of the inner cavity processing.

[0070] Preferably, after filling the sand mold, keep it for at least 15 minutes, lift the sand box, and perform sand mold flow coating to evenly cover the sand mold with a layer of coating, and then cure it.

[0071] Preferably, the sand particles are silica sand with an angular coefficient of ≤1.2 and a particle size of 40 / 70 mesh.

[0072] Preferably, the resin is furan resin, and the addition amount is 0.9wt.% to 1.1wt.% based on the weight of the sand particles; the curing agent is benzenesulfonic acid curing agent, and the addition amount is 30wt.% to 60wt.% based on the weight of the resin.

[0073] (2) In the molten iron smelting step S2, after all the components are melted, the temperature is continued to be raised for smelting, and the molten iron is calmed and melted, and the iron is tapped after the temperature is lowered. The mass percentages of the components are C: 3.4-3.8%, Si: 2.5-3.2%, Mn: 0.2-0.4%, S: 0.06-0.11%, Cu: 0.2-0.5%, and the remainder is iron and unavoidable impurities.

[0074] Preferably, in the molten iron smelting step, after all components are melted, the temperature is continued to be raised to 1540-1580° C. for smelting, and after the molten iron is calmed and melted, the temperature is lowered to 1460-1480° C. for tapping.

[0075] (3) Spheroidization and pouring step S3, pouring the smelted molten iron into a spheroidizing bag, and performing a spheroidization reaction by a wire feeding spheroidizing method. After the spheroidization reaction is complete, pouring the molten iron into a casting bag filled with a covering agent and an inoculant for casting, and performing in-flow inoculation during the casting process.

[0076] Preferably, in order to reduce the shrinkage tendency of the molten iron, the temperature of the molten iron is controlled at 1360-1380° C. during the pouring process.

[0077] Preferably, during the pouring process, rare earth silicon bismuth inoculant with a particle size of 0.2-0.7 mm is used for inoculation, and the amount of rare earth silicon bismuth inoculant added is 0.1-0.4% by mass of the total amount of molten iron, so as to enhance the inoculation effect, increase the number of graphite nodules in the shell casting, and eliminate local micro-shrinkage.

[0078] (4) Post-processing step S4: After pouring, cooling and unpacking, removing the pouring head, grinding and stress relief annealing.

[0079] Several specific embodiments of the shell casting method of the present invention are as follows:

[0080] Embodiment 1:

[0081] (1) Sand mold making step S1, place the shell mold including the pouring system and the auxiliary shrinkage compensation system on the vibrating table of the resin sand mixing equipment, and buckle the matching welding sand box. Adjust the amount of resin added to 0.9wt.% of the weight of the sand particles, and the amount of benzenesulfonic acid curing agent added to 35wt.% of the weight of the resin. Turn on the sand mixer and fill the sand particles mixed with resin and curing agent into the welding sand box. After filling, keep it for 15 minutes, lift the sand box, and perform sand mold flow coating to evenly cover the sand mold with a layer of coating, and perform molding and curing. After coating, press the matching sand core to the core position, place it in the lower sand model cavity, and fasten the upper and lower sand molds together with bolts.

[0082] (2) In the molten iron smelting step S2, components having a mass percentage of C: 3.6%, Si: 2.9%, Mn: 0.30%, S: 0.11%, Cu: 0.25%, and the remainder being iron and inevitable impurities are melted and then heated to 1540-1580° C. for smelting. After the molten iron is calmed and melted, the temperature is lowered to 1480° C. for tapping.

[0083] (3) Spheroidization and pouring step S3, pour the smelted molten iron into the spheroidization bag, use the wire feeding spheroidization method to carry out spheroidization reaction, after the spheroidization reaction is complete, control the temperature of the molten iron at 1380°C and pour it into the casting bag filled with covering agent and inoculant for casting. During the casting process, a rare earth silicon bismuth inoculant with a particle size of 0.2-0.7 mm is used for inoculation, and the mass percentage of the inoculant added in the total amount of molten iron is 0.2%. In the casting process, inoculation is carried out.

[0084] (4) Post-processing step S4: After pouring is completed, the box is opened after cooling for 4 to 6 hours, the pouring head is removed, and the surface is polished and stress-relief annealed.

[0085] Embodiment 2:

[0086] (1) Sand mold making step S1, place the shell mold including the pouring system and the auxiliary shrinkage compensation system on the vibrating table of the resin sand mixing equipment, and buckle the matching welding sand box. Adjust the amount of resin added to 1.0wt.% of the weight of the sand particles, and the amount of benzenesulfonic acid curing agent added to 40wt.% of the weight of the resin. Turn on the sand mixer and fill the sand particles mixed with resin and curing agent into the welding sand box. After filling, keep it for 15 minutes, lift the sand box, and perform sand mold flow coating to evenly cover the sand mold with a layer of coating, and perform molding and curing. After coating, press the matching sand core to the core position, place it in the lower sand model cavity, and fasten the upper and lower sand molds together with bolts.

[0087] (2) In the molten iron smelting step S2, components having a mass percentage of C: 3.7%, Si: 2.9%, Mn: 0.35%, S: 0.11%, Cu: 0.30%, and the remainder being iron and inevitable impurities are melted and then heated to 1540-1580° C. for smelting. After the molten iron is calmed and melted, the temperature is lowered to 1470° C. for tapping.

[0088] (3) Spheroidization and pouring step S3, pour the smelted molten iron into the spheroidization bag, use the wire feeding spheroidization method to carry out spheroidization reaction, after the spheroidization reaction is complete, control the temperature of the molten iron at 1370°C and pour it into the casting bag filled with covering agent and inoculant for casting. During the casting process, a rare earth silicon bismuth inoculant with a particle size of 0.2-0.7 mm is used for inoculation, and the mass percentage of the inoculant added in the total amount of molten iron is 0.2%. In the casting process, inoculation is carried out.

[0089] (4) Post-processing step S4: After pouring is completed, the box is opened after cooling for 4 to 6 hours, the pouring head is removed, and the surface is polished and stress-relief annealed.

[0090] Embodiment 3:

[0091] (1) Sand mold making step S1, place the shell mold including the pouring system and the auxiliary shrinkage compensation system on the vibrating table of the resin sand mixing equipment, and buckle the matching welding sand box. Adjust the amount of resin added to 1.1wt.% of the weight of the sand particles, and the amount of benzenesulfonic acid curing agent added to 50wt.% of the weight of the resin. Turn on the sand mixer and fill the sand particles mixed with resin and curing agent into the welding sand box. After filling, keep it for 20 minutes, lift the sand box, and perform sand mold flow coating to evenly cover the sand mold with a layer of coating, and perform molding and curing. After coating, press the matching sand core to the core position, place it in the lower sand model cavity, and fasten the upper and lower sand molds together with bolts.

[0092] (2) In the molten iron smelting step S2, components having a mass percentage of C: 3.7%, Si: 2.9%, Mn: 0.40%, S: 0.11%, Cu: 0.35%, and the remainder being iron and inevitable impurities are melted and then heated to 1540-1580° C. for smelting. After the molten iron is calmed and melted, the temperature is lowered to 1460° C. for tapping.

[0093] (3) Spheroidization and pouring step S3, pour the smelted molten iron into the spheroidization bag, use the wire feeding spheroidization method to carry out spheroidization reaction, after the spheroidization reaction is complete, control the temperature of the molten iron at 1360°C and pour it into the casting bag filled with covering agent and inoculant for casting. During the casting process, a rare earth silicon bismuth inoculant with a particle size of 0.2-0.7 mm is used for inoculation, and the mass percentage of the inoculant added in the total amount of molten iron is 0.2%. In the casting process, inoculation is carried out.

[0094] (4) Post-processing step S4: After pouring is completed, the box is opened after cooling for 4 to 6 hours, the pouring head is removed, and the surface is polished and stress-relief annealed.

[0095] The flaw detection results of the shells made in the above three embodiments are shown in the following table, and all meet the quality requirements.

[0096]

[0097] Comparative Example 1:

[0098] Compared with Example 1, the difference between Comparative Example 1 is that the process processing subsidy 2-1 added in the processing hole occupies 1 / 6 to 1 / 4 of the circumference of the processing hole, and the circumference of the auxiliary inner cavity cold iron 23 added to the inner cavity of the shell mold occupies 1 / 2 to 2 / 3 of the circumference, and the rest of the casting and auxiliary shrinkage compensation processes remain unchanged.

[0099] Comparative Example 2:

[0100] Compared with Example 2, the difference between Comparative Example 1 is that the lifting boss hole filling parts 2-5 respectively arranged at the left first lifting boss 2 and the left second lifting boss 3 of the shell mold do not use the left side riser 18 and the left second side riser 19 of the embedded heating riser sleeve to perform liquid shrinkage compensation during the solidification process, and the other casting and auxiliary shrinkage compensation processes remain unchanged.

[0101] Comparative Example 3:

[0102] Compared with Example 3, Comparative Example 3 differs in that, in the spheroidizing pouring step S3, ordinary 75 ferrosilicon inoculant is used for inoculation, the particle size and addition amount of the inoculant are the same as those of the rare earth silicon bismuth inoculant, and the rest of the casting and auxiliary shrinkage feeding processes remain unchanged.

[0103] The flaw detection results of the shells obtained in the above three comparative examples are shown in the following table. It can be seen that none of them meets the quality requirements.

[0104]

[0105] In summary, from the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0106] 1. The shell casting method of the present invention provides a casting method for a shell for a standard urban EMU braking system, which solves the process bottleneck in the shell casting production process, improves the yield rate of castings, and is simple and convenient to operate, and can meet the requirements of large-scale production.

[0107] 2. The shell casting method of the present invention overcomes the shrinkage problem of each cross-heat node of the shell by reasonably designing the pouring system and the shrinkage feeding riser, thereby meeting the index requirements of intrinsic quality radiographic flaw detection level 2 and above.

[0108] 3. The shell casting method of the present invention forms a good solidification sequence by providing side risers at multiple positions on the outside of the shell inner cavity to compensate for shrinkage, assisted by the local use of process chillers, thereby overcoming the difficulty of compensating for shrinkage in the shell inner cavity and meeting the inherent quality requirement of defect-free inner cavity processing after magnetic particle inspection.

[0109] 4. The shell casting method of the present invention reduces the shrinkage tendency of the molten iron by controlling the temperature of the molten iron in the spheroidizing pouring step, and enhances the inoculation effect by selecting rare earth silicon bismuth inoculant for inoculation, thereby increasing the number of graphite nodules in the shell casting and eliminating local micro-shrinkage.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for casting a shell, characterized in that: The steps include: Sand mold making step S1, placing the shell mold including the pouring system and the auxiliary shrinkage feeding system on the vibrating table of the resin sand mixing equipment, buckling the matching welding sand box, filling the sand mixed with resin and curing agent into the welding sand box; after filling, forming and curing, pressing the matching sand core to the core position, placing it in the lower sand model cavity, and fastening the upper and lower sand molds together; The molten iron smelting step S2 is to continue heating up the smelting after all the components are melted, and the molten iron is calmed and melted, and the iron is tapped after the temperature is lowered. The mass percentages of the components are C: 3.4-3.8%, Si: 2.5-3.2%, Mn: 0.2-0.4%, S: 0.06-0.11%, Cu: 0.2-0.5%, and the remainder is iron and unavoidable impurities; Spheroidizing and pouring step S3, pouring the smelted molten iron into a spheroidizing bag, using a wire feeding spheroidizing method to carry out a spheroidizing reaction, and after the spheroidizing reaction is complete, pouring it into a casting bag filled with a covering agent and an inoculant for casting, and performing flow inoculation during the casting process; Post-processing step S4, after pouring is completed, the box is cooled and opened, the pouring head is removed, and the stress relief annealing is performed by grinding.

2. The casting method according to claim 1, characterized in that: In the sand mold making step S1, the casting system adopts a filtered center pouring method, the molten iron filling position of the casting system is set at the horizontal center position of the oil surface agent boss (7) of the shell, and a side riser is used for filling the mold, and the side riser is used to compensate for the shrinkage of the local processing position of the inner cavity.

3. The casting method according to claim 2, characterized in that: The pouring system comprises a sprue (11), a runner (13) and an inner runner (14) which are vertically connected in sequence and have a cross-sectional area ratio of 1.3 to 1.4:1.6 to 1.7:

1. A filter screen (2) is arranged between the sprue (11) and the runner (13).

4. The casting method according to claim 3, characterized in that: The filter screen (2) is a foam ceramic filter screen with a porosity of 10 to 20 ppi.

5. The casting method according to claim 3, characterized in that: The ingrate (14) is filled into the sand model cavity through an ingrate side riser (15), and the auxiliary shrinkage compensation system comprises an elliptical boss thickening structure (2-2) arranged at the ingrate side riser (15).

6. The casting method according to any one of claims 2 to 5, characterized in that: The parting surface of the shell mold is located at the horizontal center position of the oil surface agent boss (7), the shell mold is placed horizontally, and adopts a one-mold two-piece production process.

7. The casting method according to claim 6, characterized in that: The auxiliary shrinkage compensation system includes filling a processing hole located above the parting surface at the hanging through hole (1) of the shell mold to form a shrinkage compensation channel, and arranging a heating riser (17) above it for liquid shrinkage compensation, adding a process processing subsidy (2-1) in the processing hole, and adding an auxiliary inner cavity cold iron (23) in the inner cavity of the shell mold.

8. The casting method according to claim 7, characterized in that: The process processing subsidy (2-1) occupies more than 1 / 4 of the circumference of the processing hole, and the circumference of the auxiliary inner cavity cold iron (23) occupies 1 / 3 to 1 / 2 of the circumference.

9. The casting method according to claim 1, characterized in that: The auxiliary shrinkage compensation system comprises a lifting boss hole filling portion (2-5) respectively arranged at the first left lifting boss (2) and the second left lifting boss (3) of the shell mold, and a left side riser (18) and a left second side riser (19) embedded with a heat-generating riser sleeve, so as to perform liquid shrinkage compensation during the solidification process.

10. The casting method according to claim 1, characterized in that: The auxiliary shrinkage compensation system comprises a right side riser (16) inlaid with a heat-generating riser sleeve (2-4) in the area between the first right lifting boss (4) and the second right lifting boss (5) of the shell mold, and a local process subsidy (2-3) is added to the inner cavity of the shell mold.

11. The casting method according to claim 10, characterized in that: The auxiliary shrinkage compensation system also includes a lifting boss hole filling portion arranged at the right first lifting boss (4) and the right second lifting boss (5) of the shell mold, and a first cylindrical steel cooling iron (20) and a second cylindrical steel cooling iron (21) respectively arranged in cylindrical shapes.

12. The casting method according to claim 1, characterized in that: The auxiliary shrinkage-feeding system comprises a conformable steel refrigeration iron (22) arranged at the vent boss (6) of the shell mold.

13. The casting method according to claim 1, characterized in that: In the sand mold making step S1, after filling the sand mold, keep it for at least 15 minutes, lift the sand box, and perform sand mold flow coating to evenly cover the sand mold with a layer of coating, and then solidify it.

14. The casting method according to claim 1, characterized in that: In the sand mold making step S1, the sand particles are silica sand, the angular coefficient is ≤1.2, and the particle size is 40 / 70 mesh.

15. The casting method according to claim 1, characterized in that: In the sand mold making step S1, the resin is furan resin, and the addition amount is 0.9wt.% to 1.1wt.% of the weight of the sand particles. The curing agent is benzenesulfonic acid curing agent, and the addition amount is 30wt.% to 60wt.% of the weight of the resin.

16. The casting method according to claim 1, characterized in that: In the molten iron smelting step S2, after all components are melted, the temperature is continued to be raised to 1540-1580° C. for smelting, and after the molten iron is calmed and melted, the temperature is lowered to 1460-1480° C. for tapping.

17. The casting method according to claim 1, characterized in that: In the spheroidizing pouring step S3, the temperature of the molten iron is controlled at 1360-1380° C. during the pouring process.

18. The casting method according to claim 1, characterized in that: In the spheroidizing and pouring step S3, a rare earth silicon bismuth inoculant with a particle size of 0.2-0.7 mm is used for inoculation during the pouring process, and the mass percentage of the rare earth silicon bismuth inoculant added to the total amount of molten iron is 0.1-0.4%.

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