Transversely coupled integral tramcar axle bridge and method of manufacturing same

Abstract

The application discloses a transversely coupled integrated tram box axle bridge and a manufacturing method thereof. The axle bridge comprises a bridge body, a first box and a second box which are symmetrically arranged at two ends of the bridge body and are suitable for mounting a gear transmission mechanism. The bridge body is a hollow structure and is communicated with the first box and the second box at two ends respectively. First mounting holes suitable for mounting wheel assemblies are formed in the outer sides of the first box and the second box. An installation platform suitable for mounting a vehicle frame is arranged at the top. Second mounting holes suitable for mounting motor assemblies are formed in the front sides of the first box and the second box. The application can position independent wheels, so that a transversely coupled bogie becomes possible. The independent wheels of the tram are automatically centered, and the tram has the advantages of good self-guiding, small eccentric wear and the like. The manufacturing method is comprehensively controlled from raw material design to casting forming, so that the finally manufactured castings meet design requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of axle bridge manufacturing, and in particular to a transversely coupled integrated tram box-type axle bridge and a manufacturing method thereof. Background Art

[0002] With the rapid development of urban rail transit in my country, low-floor light rail transit is gaining increasing popularity in cities due to its environmentally friendly, convenient, and cost-effective advantages. However, the domestic low-floor tram market is still in its infancy. Currently operating low-floor trams generally lack coupling between their elastic wheels. The elastic wheels on these low-floor vehicles, connected on both sides of the axle bridge, suffer from a lack of automatic centering and self-steering, rapid wheel wear, and a short lifespan. Furthermore, the elastic wheels are consumable parts, resulting in significant replacement costs.

[0003] In order to solve the problem that independent wheels cannot automatically align and self-guide, and to reduce the amount of wheel wear, foreign low-floor bogies mainly use two methods: lateral coupling and longitudinal coupling.

[0004] Longitudinal coupling is generally achieved through motors arranged longitudinally on the left and right sides. The motors drive the front and rear independent wheels on the same side. Representative products at home and abroad are Siemens' Combino bogies. Although longitudinal coupling can also achieve self-steering functions, it is prone to longitudinal creep force, resulting in greater eccentric wear of the wheels on a straight line.

[0005] The lateral coupling method mainly uses the axle bridge to position the independent wheels, and the drive shaft connects the left and right wheels horizontally to achieve the purpose of synchronous rotation. Due to the complex structure of the lateral coupling, it has high requirements for design and manufacturing level, especially for the axle bridge. Since the axle bridge not only positions the independent wheels, but also needs to bear the weight of the entire vehicle body, its quality directly determines the safety performance of the entire bogie. The casting process is difficult. It is the most critical part of the vehicle bogie. Its mechanical performance requirements, surface defect magnetic particle inspection requirements and radiographic inspection defects must meet the requirements of Table 1, Table 2 and Table 3 respectively.

[0006] Table 1 Mechanical properties requirements

[0007]

[0008] Table 2 Acceptable levels of defects in magnetic particle inspection

[0009] Defect Description Key areas Other external surface areas Nonlinear defects SM2 SM3 Linear defects LM2 LM3 Point and line defects AM2 AM3

[0010] Table 3 Acceptable levels of radiographic defects

[0011] Defect Type Defect Category Key areas Other areas pores A Level 2 Level 3 Sand and slag inclusions B Level 2 Level 3 loose CA, CB, CC, CD Level 2 Level 3 Cracks, thermal cracks, internal chill, streaks D, E, F, G Not accepted Not accepted

[0012] In view of this, there are currently no independently developed products in China. Summary of the Invention

[0013] The purpose of the present invention is to address the shortcomings of the existing technology and propose a transversely coupled integrated tram box-type axle bridge and a manufacturing method thereof, which can position the independent wheels, make the transverse coupling of the bogie possible, realize the automatic centering of the independent wheels of the tram, and have the advantages of good self-guiding and small eccentric wear. At the same time, the prepared castings meet the requirements of mechanical properties, surface defects magnetic particle inspection and radiographic inspection defects.

[0014] The technical solution for achieving the purpose of the present invention is:

[0015] A transversely coupled, integrated tram box-type axle bridge comprises an integrally formed bridge body and a first box body and a second box body symmetrically located at both ends of the bridge body and suitable for installing a gear speed change mechanism. The bridge body is a hollow structure and the first and second boxes are connected at both ends respectively. The outer sides of the first and second boxes are each provided with a first mounting hole suitable for installing a wheel assembly, and the top is provided with a mounting platform suitable for installing a frame. The front side of the first or second box body is provided with a second mounting hole suitable for installing a motor assembly.

[0016] Furthermore, the bridge body, the first box and the second box are all made of QT450-18 material.

[0017] Furthermore, the composition ratio of the QT450-18 material is as follows by mass percentage: C: 3.6% to 3.8%, Si: 2.5% to 2.8%, Mn: ≦1.5%, P: ≦0.025%, S: 0.005% to 0.015%, Ni: 0.3% to 0.5%, Mg: 0.035% to 0.055%, and the rest is Fe.

[0018] A method for manufacturing a transversely coupled integrated tram box-type axle bridge comprises the following steps:

[0019] Step S1: molding, using a two-box molding process of handmade resin sand to respectively make an upper box sand mold and a lower box sand mold;

[0020] Step S2: core making, respectively making the bridge body clay core, the first box body clay core and the second box body clay core by a mold; the bridge body clay core is pre-embedded with a core bone, the core bone is a hollow steel tube, and is sealed with steel plugs at both ends, and the center of the steel plug is provided with an internal thread; the first box body clay core and the second box body clay core are provided with a special-shaped positioning hole on the side close to the bridge body clay core for positioning the bridge body clay core, the center of the special-shaped positioning hole is preset with a screw rod reserved installation hole suitable for passing the screw rod, and the other side is provided with a hoisting hole suitable for core lowering tooling to transport the clay core and a sleeve reserved hole concentric with the screw rod reserved installation hole and suitable for placing the screw rod sleeve;

[0021] Step S3: Assemble the core, place the bridge body clay core on the core assembly tooling, lock the screw and the internal thread on the steel plug of the bridge body clay core, then place the first box clay core and the second box clay core on the two ends of the core assembly tooling respectively, and at the same time pass the screw connected to the steel plug of the bridge body clay core through the reserved installation hole of the screw. The bridge body clay core and the first box clay core and the second box clay core at both ends are first positioned through the special-shaped positioning holes. On the other side, pass the screw sleeve through the screw and install it into the screw sleeve reserved hole, and clamp the fixing plate between the inner sides of the first box clay core and the second box clay core. Tighten the nuts and screws on both sides of the first box clay core and the second box clay core, lock the bridge body clay core with the first box clay core and the second box clay core respectively, and complete the assembly;

[0022] Step S4: core setting: using the core setting tool to clamp the two lifting holes on the outside of the first box body clay core and the second box body clay core respectively and lock them, lifting them into the lower box sand mold, and then removing the clamping fixing plate between the inner sides of the first box body clay core and the second box body clay core;

[0023] Step S5: Assembling the boxes, by testing the distances between the bridge body core, the first box core, and the second box core and the upper surface of the lower box sand mold, whether the lower core is qualified is determined. If qualified, the upper box sand mold is assembled and fixed with screws to form a casting cavity;

[0024] Step S6: Melting and pouring: After selecting raw materials and sequentially melting, spheroidizing, and inoculating, the molten iron is poured into the casting cavity through a pouring system to form the axle bridge casting as described above.

[0025] Furthermore, the resin sand used in the molding process is 40 / 70 mesh raw sand added with wood-modified furan resin and curing agent, the resin addition amount is 1.0% to 1.2%, and the curing agent addition amount is 30% to 50% of the resin addition amount.

[0026] Furthermore, the raw sand for the core making process is Dalin sand with a SiO2 content of ≥92%, and 0.2% of red iron oxide and 1.3% to 1.5% of resin binder are added based on the weight of the sand.

[0027] Furthermore, the lower core tooling includes an L-shaped hanger and a pressure rod and a locking handle rotatably installed at the end of the L-shaped hanger. The top of the pressure rod is provided with an arc-shaped recess and is suitable for being fixed by clamping the locking handle into the arc-shaped recess. The bottom end of the pressure rod is flush with the bottom end of the L-shaped hanger and is respectively fixedly connected with relatively arranged plug plates, and the plug plates are inserted into the lifting holes.

[0028] Furthermore, the pouring system includes a lower horizontal runner and a straight runner vertically arranged in the middle of the lower horizontal runner, the bottom of the straight runner extends to the bottom of the lower horizontal runner and forms a nest, and upper horizontal runners are symmetrically provided at both ends of the upper side of the lower horizontal runner, and the upper horizontal runner is provided with a longitudinal runner connected to the bottom of the casting cavity.

[0029] Furthermore, a foam ceramic filter is provided between the outlet of the lower horizontal runner and the outlet of the straight runner, a slag collecting bag is provided at the end of the upper horizontal runner, and a flat gate is connected between the slag collecting bag and the upper horizontal runner, so that the slag included in the molten iron in the pouring system can be easily discharged into the slag collecting bag at the end of the upper horizontal runner and is not easy to flow back to the upper horizontal runner. The longitudinal runner includes a flat inged runner arranged at the bottom of the side of the upper horizontal runner and a side riser vertically arranged on the flat inged runner.

[0030] Furthermore, the pouring system also includes a plurality of first heating risers arranged at the top of the casting cavity and facing the first box body clay core and the second box body clay core, a second heating riser facing the bridge body clay core, and a plurality of chills arranged on the surface of the casting cavity. By cooperating with the side risers, the first heating risers and the second heating risers and the chills, the solidification process of the molten iron is controlled to obtain a casting with a dense interior.

[0031] Furthermore, a riser exhaust rod is provided at the top of the first heating riser; a flat vent plate located on the side of the second heating riser is provided at the top of the casting cavity, and the thickness of the flat vent plate is 3 to 5 mm and the length is 50 to 70 mm. Since the molten iron enters the cavity from both sides of the first and second boxes, the molten iron forms a collection area at the top of the bridge body, and the cavity gas forms a suffocation phenomenon in the longitudinal direction of the bridge body. The flat vent plate method is adopted. On the one hand, the exhaust channel in the longitudinal direction of the bridge body is maximized. At the same time, the flat vent plate can realize that after the exhaust is completed, the molten iron in the flat vent plate is quickly cooled, and the hot node area formed by the flat vent plate and the casting is minimized, reducing the risk of shrinkage defects. The heating riser is designed next to the flat vent plate, which first collects the top gas, and at the same time, the slag brought by the flat vent plate can be discharged into the heating riser, playing the triple role of slag removal, exhaust and shrinkage compensation.

[0032] Furthermore, the distance between the flat vent plate and the second heating riser is 20 to 50 mm, and the design distance between the riser and the flat vent plate is maintained at a smaller spacing, so as to facilitate the riser and the flat vent plate to cooperate in exhaust and slag removal. At the same time, the heating riser compensates for the local hot node formed by the flat vent plate and the casting, thereby reducing casting defects of the casting.

[0033] Furthermore, the smelting and pouring comprises the following steps:

[0034] Step S61: selecting raw materials, using Q10 pig iron, scrap steel, 75 ferrosilicon, and nickel plate as furnace charge, and performing shot blasting on the charge with rust or oil stains on the surface;

[0035] Step S62: Melting: Weigh the charge and add it to the medium frequency induction furnace, start the furnace for melting, add 75% ferrosilicon and nickel plate after melting, take a sample before the furnace, test the content of C, Si, Mn, P, S, and Ni, and adjust the content of each element in the molten iron in the furnace according to the results; when the temperature in the furnace rises to 1510℃±10℃, prepare to take the charge out of the furnace and put it into the spheroidizing bag;

[0036] Step S63: Spheroidizing. Clean the spheroidizing ladle and add 1.0% to 1.2% of the mass of the molten iron into the ladle pit at the bottom of the spheroidizing ladle. The particle size of the spheroidizing agent is 5 to 25 mm. Add 0.4% to 0.6% of the mass of the molten iron into the spheroidizing agent. The particle size of the spheroidizing agent is 3 to 8 mm. Then add 0.4% to 0.6% of the mass of the molten iron into the spheroidizing agent. The composition of the spheroidizing agent is: Si: 40% to 50%, Mg: 5.5% to 7.5%, RE: 1.5% to 2.5%, Ca: 2.5% to 3.0%, and the rest is Fe. The composition of the inoculant is: Si :70% to 75%, Ca:1% to 1.5%, Al≤1%, and the rest is Fe; the covering agent composition is: C:0.009% to 0.013%, Si:0.4% to 1.01%, Mn:0.22% to 0.56%, P:0.011% to 0.09%, S:0.002%, Cr:0.03% to 0.09%, Ni:0.01% to 0.02%, Cu:0.01% to 0.04%, Al:0.12% to 0.35%, and the rest is Fe; measuring the temperature, transferring the molten iron into a spheroidizing bag at a furnace temperature of 1500 to 1520°C, and performing spheroidizing inoculation treatment;

[0037] Step S64: After the spheroidization reaction is completed, 0.3% to 0.4% of the mass of the molten iron inoculant-1 and 0.2% to 0.3% of the mass of the molten iron inoculant-2 are added to the casting ladle. The particle size of the molten iron inoculant-2 is 3 to 8 mm, and the composition is as follows: Si: 69%; Ca: 1.72%, Al: 0.78%, Bi: 1.0%. The molten iron is poured from the spheroidizing ladle into the casting ladle, and the molten iron is allowed to stand for about 10 seconds. Finally, the slag is scraped off.

[0038] Step S65: Pouring: Control the pouring temperature to 1400-1420°C to ensure a steady pouring speed, and perform in-stream inoculation during the pouring process. The content of the inoculant-3 in the in-stream inoculation is 0.005%-0.1% of the mass of the molten iron, and the particle size is 0.2-0.7 mm. The composition of the inoculant-3 in the in-stream inoculation is: Si: 72%, Al: 1.63%, and Ca: 0.66%.

[0039] By adopting the above technical solution, the present invention has the following beneficial effects:

[0040] (1) The present invention provides an installation space for the gear speed change mechanism by setting a box body, and provides a first installation hole to provide an installation position for the wheel assembly, a second installation hole to provide an installation position for the motor assembly, and an installation platform to provide an installation position for the frame. The boxes at both ends are connected by a bridge body with a hollow structure, which not only realizes the positioning of the wheel assembly installed on the outside of the box body, but also provides an installation space for the axle. The gear speed change mechanism in the box body is connected by the axle, and the gear speed change mechanisms at both ends are respectively connected to the wheels, and one of the gear speed change mechanisms is connected to the motor, thereby realizing power transmission, making the lateral coupling mode of the bogie possible, and realizing automatic centering of the independent wheels of the tram, and at the same time having the advantages of good self-guiding and small eccentric wear.

[0041] (2) The bridge body, the first box body and the second box body of the present invention are all made of QT450-18 material, which has the advantages of high strength and high toughness. When the wall thickness of the main body is 12 mm, it can still bear the weight of the entire vehicle and ensure driving safety.

[0042] (3) The present invention controls the C content in the QT450-18 formula to between 3.6% and 3.8%, the Si content to between 2.5% and 2.8%, and the pouring temperature to 1400-1420°C. The combination of these three factors not only improves the fluidity of the molten iron, but also enhances its graphitization expansion during solidification, while preventing graphite from floating. By controlling the Mn content to below 1.5% and the Si content to 2.5% to 2.8%, a matrix structure of ferrite and pearlite is formed, wherein the pearlite content is controlled to between 5% and 15%. Meanwhile, by controlling the Ni content to between 0.3% and 0.5%, the strength of the ferrite is enhanced by dissolving Ni atoms between iron atoms without promoting the formation of pearlite. The Mg content is controlled between 0.035% and 0.055%, and the S content is controlled between 0.005% and 0.015%, ensuring that the graphite form in the material is VI or V, with VI graphite ≥80%. At the same time, through the three-step inoculation process of bottom inoculation, secondary inoculation, and flow inoculation, the graphite size is controlled to be above level 5, and the grain size is small, which can simultaneously ensure that the strength, elongation and impact toughness of the material meet the product requirements.

[0043] (4) The present invention manufactures the bridge body mud core, the first box body mud core and the second box body mud core respectively, and puts them into a sand mold to form a casting cavity after assembly. By pre-embedding the core bone in the bridge body mud core, on the one hand, it avoids the deformation and bending of the bridge body mud core due to the slender structure, which causes the casting to be unqualified. On the other hand, it lays a foundation for the assembly of the first box body mud core, the second box body mud core and the bridge body mud core, avoids the bolts being directly tightened on the bridge body mud core to cause stress fracture, realizes threaded connection and fixation, improves assembly accuracy, and effectively solves the technical difficulties existing in the assembly of the special structure casting after segmented molding.

[0044] (5) The present invention prevents deformation and damage of the core during the core lowering and lifting process by using a fixed plate and a core lowering tool.

[0045] (6) The present invention uses Dalin sand added with red iron oxide to prepare the core, which effectively solves the vein defects on the surface of the casting.

[0046] (7) The present invention adopts a special pouring system, which flows into the lower runner through the middle straight runner, then flows into the upper runners on both sides through the lower runner, and finally enters the bottom of the mold cavity through the longitudinal runner, and then slowly converges to the center of the mold cavity to form a unique molten iron gathering area. Compared with other top pouring processes or methods such as water entry from the middle, the molten iron gathering area is minimized, the turbulent oxidation of the molten iron at the front of the molten iron is reduced, and the dimple at the bottom of the straight runner and the overlap of the upper runner and the lower runner play a role in slowing down the flow, thereby improving the quality of the casting.

[0047] (8) The pouring system of the present invention is provided with multi-stage filtration. The foam ceramic filter screen is used to filter and purify the molten iron for the first time. The impure molten iron with slag initially entering the pouring system is filtered out through the slag collecting bag, which is used to filter and purify the molten iron for the second time. Then the molten iron passes through the flat inner runner. Since the flat inner runner is used, its height is lower than the upper horizontal runner, which acts as a slag barrier, which is used to filter and purify the molten iron for the third time. Finally, the molten iron enters the casting through the side riser designed between the upper horizontal runner and the casting. The tiny slag inclusions in the molten iron will float up in the side riser and cannot enter the casting cavity, which is used to filter and purify the molten iron for the fourth time, thereby obtaining high-purity molten iron to the greatest extent possible to ensure the quality of the casting.

[0048] (9) The inoculation process of the present invention adopts a three-step inoculation process of bottom ladle inoculation, inverted ladle inoculation and flow inoculation. The inverted ladle inoculation process is used to pour the molten iron from the spheroidizing ladle into the casting ladle for inverted ladle inoculation. This process can make the inoculant evenly distributed in the molten iron during the inverted ladle process, and the inoculation is uniform. In the secondary inoculation, by using inoculant-1 and inoculant-2 in combination, adding a trace amount of Bi to inoculant-2, a large amount of stable complex compounds containing Bi elements are generated in the molten iron. These compounds become heterogeneous crystallization cores of graphite. The presence of these stable cores can effectively eliminate distorted graphite in thick-section ductile iron. At the same time, the amount of graphite is increased, the eutectic group structure is refined, the formation of cementite is hindered, the brittle inclusions at the grain boundary are reduced, and the mechanical properties are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments and in conjunction with the accompanying drawings, wherein:

[0050] Figure 1 Schematic diagram of the structure of the casting of the present invention;

[0051] Figure 2 This is a structural diagram of the present invention wherein the clay core is placed in the lower sand mold;

[0052] Figure 3 This is a schematic structural diagram of the bridge body mud core of the present invention;

[0053] Figure 4 This is a three-dimensional diagram of the assembly structure of the clay core of the present invention;

[0054] Figure 5 This is a schematic diagram of the internal structure of the clay core assembly of the present invention;

[0055] Figure 6 It is a structural schematic diagram of the pouring system of the present invention.

[0056] The reference numerals in the accompanying drawings are:

[0057] Bridge body 1, first box body 2, second box body 3, first mounting hole 4, mounting platform 5, second mounting hole 6, bridge body clay core 7, first box body clay core 8, second box body clay core 9, core bone 10, plug 11, screw hole 12, lifting hole 13, core assembly tooling 14, screw 15, fixing plate 16, lower core tooling 17, hanging rod 17-1, pressure rod 17-2, locking handle 17-3, arc-shaped recess 17-4, plug plate 17-5, first accompanying inspection fixture 18, second accompanying inspection fixture 19, lower horizontal runner 20, upper horizontal runner 21, straight runner 22, flat ingredient 23, side riser 24, foam ceramic filter 25, slag collecting bag 26, first heating riser 27, second heating riser 28, chiller 29, riser exhaust rod 30, flat air outlet plate 31. DETAILED DESCRIPTION

[0058] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0059] (Example 1)

[0060] like Figure 1The illustrated transversely coupled integrated tram box-type axle bridge comprises an integrally formed bridge body 1, a first box body 2, and a second box body 3. The first box body 2 and the second box body 3 are symmetrically located at the two ends of the bridge body 1. The internal cavity is used to install the gear speed change mechanism. The outer sides are provided with first mounting holes 4 for installing the wheel assembly. The top is provided with a mounting platform 5 for installing the frame. The front side of the second box body 3 is also provided with a second mounting hole 6 for installing the motor assembly. The bridge body 1 is a hollow structure, and the internal cavity is used to pass the axle. The integrated design not only positions the wheel assembly installed on the outer side of the box body, but also connects the gear speed change mechanism in the box body through the axle. The gear speed change mechanisms at both ends are respectively connected to the wheels, and one of the gear speed change mechanisms is connected to the motor, thereby realizing power transmission, making the transverse coupling of the bogie possible, and realizing automatic centering of the independent wheels of the tram. At the same time, it has the advantages of good self-guiding and small eccentric wear.

[0061] The length of this embodiment is 1272 mm, and the main body wall thickness is only 12 mm. Existing castings made of existing materials could not meet the design requirements. Therefore, a new casting material, QT450-18, was developed to cast the bridge body, first and second tanks, with a total weight of approximately 220 kg. The composition of QT450-18 material, by mass percentage, is as follows: C: 3.6% to 3.8%, Si: 2.5% to 2.8%, Mn: ≤1.5%, P: ≤0.025%, S: 0.005% to 0.015%, Ni: 0.3% to 0.5%, Mg: 0.035% to 0.055%, and the remainder is Fe. In this embodiment, C: 3.6%, Si: 2.8%, Mn: ≤1.5%, P: ≤0.025%, S: 0.01%, Ni: 0.3%, Mg: 0.035% to 0.055%, and the remainder is Fe.

[0062] Due to the particularity of the structure, the overall molding is poor in processability and needs to be formed in sections. The manufacturing method of the transversely coupled integrated tram box-type axle bridge of this embodiment includes the following steps:

[0063] Step S1: Molding, using a manual resin sand two-box molding process, respectively making an upper box sand mold and a lower box sand mold according to the above-mentioned casting structure; the resin sand in the molding process is 40 / 70 mesh raw sand added with wood-modified furan resin and a curing agent, wherein the resin addition amount is 1.0% to 1.2%, the curing agent addition amount is 30% to 50% of the resin addition amount, and the curing agent ratio is 65wt.% type A curing agent and 35wt.% type B curing agent.

[0064] Step S2: core making, such as Figure 2 As shown, the bridge body core 7, the first box body core 8 and the second box body core 9 are made by molds respectively. The specific process is as follows:

[0065] Step S21: Raw sand selection: Dalin sand with SiO2 content ≥ 92% is selected. The basic physical properties are shown in Table 4. The particle size is 50 / 100 mesh, the three-screen concentration rate is ≥ 85%, and the pH value is 6.5-7.2.

[0066] Table 4 Particle size distribution

[0067] granularity AFS Three-screen concentration Mud content Water content Loss on ignition Silicon content Acid consumption pH value 50 / 100 mesh 40～46 ≥85％ ≤0.25％ ≤0.2％ ≤0.2％ ≥92％ ≤5ml / 50g 6.5～7.2

[0068] Step S22: Selecting a resin binder, using a two-component resin, model XLI-318 and XLII-618, whose chemical performance indicators are shown in Table 5.

[0069] Table 5 Chemical properties of resin

[0070]

[0071] Step S23: Sand mixing: Add red iron oxide to the Dalin sand at a ratio of 0.2% by weight of the sand, which effectively solves the veining defects on the casting surface; add the resin binder at a ratio of 1.3-1.5% by weight of the sand, and the ratio of the two components is XLI-318:XLI-618=55%:45%. The stirring time is 90s-120s in summer and 150s-180s in winter.

[0072] Step S24: core making, using a Z8440 core shooting machine for core making, with the following parameters: sand shooting twice, sand shooting time 8-10s; sand shooting pressure 0.55-0.65MPa; amine (triethylamine) adding time 10-20s, thereby making a clay core.

[0073] Since the bridge body mud core 7 is a slender structure and is easily deformed and bent, a core bone 10 is pre-buried in the center when the bridge body mud core 7 is made. Figure 3 and Figure 4 The core 10 is a hollow steel tube with a diameter of 3.5 mm. Both ends are sealed with steel plugs 11 with internal threads in the center. The first and second box cores 8 and 9 are provided with special-shaped positioning holes on the side close to the bridge body core 7 for positioning with the bridge body core 7. A screw pre-installation hole 12 suitable for passing a screw is preset in the center of the special-shaped positioning hole. On the other side, a lifting hole 13 suitable for core lowering and transporting the core is provided, as well as a sleeve pre-installation hole concentric with the screw pre-installation hole and suitable for accommodating a screw sleeve.

[0074] Step S3: Assemble the core, such as Figure 4 and Figure 5As shown, the bridge body mud core 7 is placed on the core assembly tool 14, and the screw 15 is locked with the internal thread on the steel plug 11 of the bridge body mud core 7. Then, the first box mud core 8 and the second box mud core 9 are placed on the two ends of the core assembly tool 14 respectively, and the screws connected to the steel plug 11 of the bridge body mud core 7 are passed through the reserved mounting holes of the screws. The bridge body mud core 7 and the first box mud core 8 and the second box mud core 9 at both ends are locked. First, perform the first step of positioning through the special-shaped positioning hole, and on the other side, pass the screw sleeve through the screw 15 and install it into the reserved hole of the screw sleeve, and clamp the fixing plate 16 between the inner sides of the first box body clay core 8 and the second box body clay core 9, tighten the nuts and screws 15 on both sides of the first box body clay core 8 and the second box body clay core 9, lock the bridge body clay core 7 with the first box body clay core 8 and the second box body clay core 9 respectively, and complete the assembly.

[0075] Step S4: core down, such as Figure 2 As shown, the core is lifted by the core setting tool 17. Specifically, the core setting tool 17 includes an L-shaped suspension rod 17-1, a pressure rod 17-2 and a locking handle 17-3 rotatably mounted on the left end of the L-shaped suspension rod 17-1. The top of the pressure rod 17-2 is provided with an arc-shaped recess 17-4. The bottom end of the pressure rod 17-2 is flush with the bottom end of the L-shaped suspension rod 17-1 and is fixedly connected to a relatively arranged plug-in plate 17-5. The plug-in plate 17-5 is inserted into the lifting hole 13, and the locking handle 17-3 is pressed down to make it snap into the arc-shaped recess 17-4 for fixation, thereby clamping the core. The core is then lifted into the lower box sand mold to prevent the core from deformation and damage during the lifting process.

[0076] Step S5: closing the box, as shown in Figure 2 As shown, a dedicated first accompanying inspection fixture 18 adapted to the top of the bridge body clay core 7 and a second accompanying inspection fixture 19 adapted to the top of the first box body clay core 8 and the second box body clay core 9 are used to respectively detect the distance between the bridge body clay core 7, the first box body clay core 8 and the second box body clay core 9 and the upper surface of the lower box sand mold to determine whether the lower core is qualified. After passing the inspection, the upper box sand mold is assembled and fixed with screws to form a casting cavity.

[0077] Step S6: Melting and pouring: After selecting raw materials and sequentially melting, spheroidizing, and inoculating, the molten iron is poured into the casting cavity through a pouring system to form the axle bridge casting as described above.

[0078] like Figure 6As shown, the pouring system includes a lower runner 20 and a sprue 22 vertically disposed in the middle of the lower runner 20. The bottom of the sprue 22 extends below the lower runner 20 and forms a dimple. Upper runners 21 are symmetrically disposed at both ends of the upper side of the lower runner 20. The dimple and the overlap of the upper and lower runners slow the flow of molten iron, thereby improving the quality of the casting. A flat ingrown runner 23 is connected to the rear bottom of the upper runner 20. A side riser 24 is vertically disposed on the flat ingrown runner 23. The outlet of the flat ingrown runner 23 is connected to the bottom of the casting cavity, forming a longitudinal runner. A foam ceramic filter 25 is provided between the outlet of the lower runner 20 and the outlet of the straight runner 22, and a slag collecting bag 26 is provided at the end of the upper runner 20. A flat gate is connected between the slag collecting bag 26 and the upper runner 21 to ensure that the slag included in the molten iron in the casting system can be easily discharged into the slag collecting bag at the end of the upper runner 21 and is not easy to flow back to the upper runner 21. A multi-stage filtration is formed, and the foam ceramic filter 25 is used to filter and purify the molten iron for the first time. The impure molten iron with slag initially entering the casting system is filtered out through the slag collecting bag 26, which plays a second filtering and purification role for the molten iron. The molten iron then passes through the flat ingrown 23. Since the flat ingrown 23 is used, its height is lower than the upper cross runner 20, which acts as a slag barrier, and plays a third filtering and purification role for the molten iron. Finally, the molten iron enters the casting through the side riser 24 designed between the upper cross runner 20 and the casting. The tiny slag inclusions in the molten iron will float up in the side riser 24 and cannot enter the casting cavity, which plays a fourth filtering and purification role for the molten iron, thereby obtaining high-purity molten iron to the greatest extent possible to ensure the quality of the casting.

[0079] The pouring system also includes a plurality of first heating risers 27 arranged at the top of the casting cavity and facing the first box body clay core 8 and the second box body clay core 9, a second heating riser 28 facing the bridge body clay core 7, and a plurality of chills 29 arranged on the surface of the casting cavity. By cooperating with the side risers 24, the first heating risers 27 and the second heating risers 28 and the chills 29, the solidification process of the molten iron is controlled to obtain a casting with a dense interior. A riser exhaust rod 30 is provided at the top of the first heating riser 27; a flat vent plate 31 located on the side of the second heating riser 28 is provided at the top of the casting cavity, and the thickness of the flat vent plate is 3 to 5 mm and the length is 50 to 70 mm. Since the molten iron enters the cavity from both sides of the first and second boxes, the molten iron forms a collection area at the top of the bridge body, and the cavity gas forms a suffocation phenomenon in the longitudinal direction of the bridge body. The flat vent plate method is adopted. On the one hand, the longitudinal exhaust channel of the bridge body is maximized. At the same time, the flat vent plate can realize that after the exhaust is completed, the molten iron in the flat vent plate is quickly cooled, and the hot node area formed by the flat vent plate and the casting is minimized, which increases the risk of shrinkage defects. The heating riser is designed next to the flat vent plate, which first collects the top gas. At the same time, the slag brought by the flat vent plate can be discharged into the heating riser, which plays the role of slag removal and exhaust. The distance between the flat vent plate 31 and the second heating riser 28 is 20 to 50 mm. The distance between the riser and the flat vent plate is designed to be kept at a small distance to facilitate the riser and the flat vent plate to cooperate in exhaust and slag removal. At the same time, the heating riser compensates for the thermal node formed by the vent plate and the casting, thereby reducing casting defects of the casting.

[0080] Specifically, the smelting and pouring process includes the following steps:

[0081] Step S61: selecting raw materials, using Q10 pig iron, scrap steel, 75 ferrosilicon, and nickel plate as furnace charge, and performing shot blasting on the charge with rust or oil stains on the surface;

[0082] Step S62: Melting: Weigh the charge and add it to the medium frequency induction furnace, start the furnace for melting, add 75% ferrosilicon and nickel plate after melting, take a sample before the furnace, test the content of C, Si, Mn, P, S, and Ni, and adjust the content of each element in the molten iron in the furnace according to the results; when the temperature in the furnace rises to 1510℃±10℃, prepare to take the charge out of the furnace and put it into the spheroidizing bag;

[0083] Step S63: Spheroidizing. Clean the spheroidizing ladle and add 1.0% to 1.2% of the mass of the molten iron into the ladle pit at the bottom of the spheroidizing ladle. The particle size of the spheroidizing agent is 5 to 25 mm. Add 0.4% to 0.6% of the mass of the molten iron into the spheroidizing agent. The particle size of the spheroidizing agent is 3 to 8 mm. Then add 0.4% to 0.6% of the mass of the molten iron into the spheroidizing agent. The composition of the spheroidizing agent is: Si: 40% to 50%, Mg: 5.5% to 7.5%, RE: 1.5% to 2.5%, Ca: 2.5% to 3.0%, and the rest is Fe. The composition of the inoculant is: Si: 70%. ~75%, Ca: 1%~1.5%, Al≤1%, and the rest is Fe; the covering agent composition is: C: 0.009%~0.013%, Si: 0.4%~1.01%, Mn: 0.22%~0.56%, P: 0.011%~0.09%, S: 0.002%, Cr: 0.03%~0.09%, Ni: 0.01%~0.02%, Cu: 0.01%~0.04%, Al: 0.12%~0.35%, and the rest is Fe; measuring the temperature, transferring the molten iron into a spheroidizing bag at a furnace temperature of 1500~1520℃, and performing spheroidizing inoculation treatment;

[0084] Step S64: After the spheroidization reaction is completed, add 0.3% to 0.4% of the mass of the molten iron inoculant-1 and 0.2% to 0.3% of the mass of the molten iron into the casting ladle. The particle size of the inoculant-2 is 3 to 8 mm, and the composition is: Si: 69%; Ca: 1.72%, Al: 0.78%, Bi: 1.0%. Pour the molten iron from the spheroidizing ladle into the casting ladle, let it stand for about 10 seconds, and finally scrape off the slag.

[0085] Step S65: Pouring: Control the pouring temperature at 1400-1420°C to ensure a steady pouring speed. In the pouring process, inoculation is performed using inoculant-3, which has a content of 0.005%-0.1% of the mass of the molten iron, a particle size of 0.2-0.7 mm, and a composition of Si: 72%, Al: 1.63%, and Ca: 0.66%.

[0086] (Example 2)

[0087] This embodiment is similar to embodiment 1, except that heat treatment is performed after casting is completed. When heated to 900±20°C, it is kept warm for 2 to 3 hours to eliminate cementite, metastable ternary or composite phosphorus eutectic in the casting; then furnace cooling is performed at 80°C / h to 810±20°C, kept warm for 2 to 3 hours, and then air-cooled after being taken out of the furnace.

[0088] (Example 3)

[0089] This embodiment is similar to embodiment 2, except that the formula of QT450-18 material is C: 3.8%, Si: 2.5%, Mn: ≦1.5%, P: ≦0.025%, S: 0.01%, Ni: 0.4%, Mg: 0.035% to 0.055%, and the rest is Fe.

[0090] (Example 4)

[0091] This embodiment is similar to embodiment 2, except that the formula of QT450-18 material is C: 3.6%, Si: 2.5%, Mn: ≦1.5%, P: ≦0.025%, S: 0.01%, Ni: 0.5%, Mg: 0.035% to 0.055%, and the rest is Fe.

[0092] The QT450-18 materials of Examples 1, 2, 3, and 4 were tested, and the results are shown in Table 6. Several common materials were selected for the same test, and the results are shown in Table 7.

[0093] Table 6 QT450-18 performance test results

[0094]

[0095] Table 7 Performance indicators of QT400-18, QT450-10 and QT500-7 (GB / T 1348-2019)

[0096]

[0097] Strength refers to the ability of a material to resist permanent deformation and fracture under the action of external force. The magnitude of strength is characterized by the magnitude of strength; while toughness refers to the ability of a material to absorb energy during plastic deformation and fracture. The magnitude of toughness is characterized by the magnitude of impact energy absorbed. The better the toughness, the less likely it is to have brittle fracture. If the toughness of a material is to be high, it requires both high strength and large fracture strain. The fracture strain is characterized by the elongation after fracture. The material QT450-18 in this invention is a new ductile iron material. Its various mechanical properties are benchmarked against the three ductile iron materials QT400-18, QT450-10 and QT500-7 in GB / T1348-2019 "Ductile Iron Castings". Through a unique material formula combined with a unique process method, its mechanical properties have high tensile strength, high elongation after fracture and high impact absorption energy, so that its tensile strength is ≥450Mpa, the specified plastic extension strength Rp0.2 ≥310Mpa, the elongation after fracture ≥20%, and the room temperature impact absorption energy KV2 ≥14J, which is far superior to several common ductile iron materials.

[0098] In addition, the present invention provides installation space for the gear transmission mechanism by setting up a box, and provides a first installation hole to provide an installation position for the wheel assembly, a second installation hole to provide an installation position for the motor assembly, and an installation platform to provide an installation position for the frame. The boxes at both ends are connected by a hollow bridge body, which not only realizes the positioning of the wheel assembly installed on the outside of the box, but also provides installation space for the axle. The gear transmission mechanism in the box is connected by the axle, and the gear transmission mechanisms at both ends are respectively connected to the wheels, and one of the gear transmission mechanisms is connected to the motor, thereby realizing power transmission, making the transverse coupling mode of the bogie possible, and realizing automatic centering of the independent wheels of the tram, while having the advantages of good self-guiding and small eccentric wear. A new design is made in terms of material design and casting method to produce castings that meet the requirements of mechanical properties, surface defects, magnetic particle inspection and radiographic inspection defects, filling the gap of domestically developed transversely coupled integrated tram box-type axle bridges, and having broad application prospects.

[0099] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing a transversely coupled integrated tram box-type axle bridge, characterized in that: The axle bridge includes an integrally formed bridge body and a first box body and a second box body symmetrically located at both ends of the bridge body and suitable for installing a gear transmission mechanism. The bridge body is a hollow structure and the first box body and the second box body are respectively connected at both ends. The outer sides of the first box body and the second box body are each provided with a first mounting hole suitable for installing a wheel assembly, and a mounting platform suitable for installing a vehicle frame is provided on the top. The front side of the first box body or the second box body is provided with a second mounting hole suitable for installing a motor assembly. The manufacturing method includes the following steps: Step S1: molding, using a two-box molding process of handmade resin sand to respectively make an upper box sand mold and a lower box sand mold; Step S2: core making, respectively making the bridge body clay core, the first box body clay core and the second box body clay core by a mold; the bridge body clay core is pre-embedded with a core bone, the core bone is a hollow steel tube, and is sealed with steel plugs at both ends, and the center of the steel plug is provided with an internal thread; the first box body clay core and the second box body clay core are provided with a special-shaped positioning hole on the side close to the bridge body clay core for positioning the bridge body clay core, the center of the special-shaped positioning hole is preset with a screw rod reserved installation hole suitable for passing the screw rod, and the other side is provided with a hoisting hole suitable for core lowering tooling to transport the clay core and a sleeve reserved hole concentric with the screw rod reserved installation hole and suitable for placing the screw rod sleeve; Step S3: Assemble the core, place the bridge body clay core on the core assembly tooling, lock the screw and the internal thread on the steel plug of the bridge body clay core, then place the first box clay core and the second box clay core on the two ends of the core assembly tooling respectively, and at the same time pass the screw connected to the steel plug of the bridge body clay core through the reserved installation hole of the screw. The bridge body clay core and the first box clay core and the second box clay core at both ends are first positioned through the special-shaped positioning holes. On the other side, pass the screw sleeve through the screw and install it into the screw sleeve reserved hole, and clamp the fixing plate between the inner sides of the first box clay core and the second box clay core. Tighten the nuts and screws on both sides of the first box clay core and the second box clay core, lock the bridge body clay core with the first box clay core and the second box clay core respectively, and complete the assembly; Step S4: core setting: using the core setting tool to clamp the two lifting holes on the outside of the first box body clay core and the second box body clay core respectively and lock them, lifting them into the lower box sand mold, and then removing the clamping fixing plate between the inner sides of the first box body clay core and the second box body clay core; Step S5: Assembling the boxes, by testing the distances between the bridge body core, the first box core, and the second box core and the upper surface of the lower box sand mold, whether the lower core is qualified is determined. If qualified, the upper box sand mold is assembled and fixed with screws to form a casting cavity; Step S6: Melting and pouring: After selecting raw materials and sequentially melting, spheroidizing, and inoculating, the molten iron is poured into the casting cavity through a pouring system to form an axle bridge casting.

2. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 1, characterized in that: The resin sand used in the molding process is 40 / 70 mesh raw sand added with wood-modified furan resin and curing agent, the resin addition amount is 1.0% to 1.2%, and the curing agent addition amount is 30% to 50% of the resin addition amount.

3. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 1, characterized in that: The raw sand for the core making process is Dalin sand with a SiO2 content of ≥92%, and 0.2% of red iron oxide and 1.3% to 1.5% of resin binder are added based on the weight of the sand.

4. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 1, characterized in that: The lower core tooling includes an L-shaped hanger and a pressure rod and a locking handle rotatably installed at the end of the L-shaped hanger. The top of the pressure rod is provided with an arc-shaped recess and is suitable for being fixed by snapping the locking handle into the arc-shaped recess. The bottom end of the pressure rod is flush with the bottom end of the L-shaped hanger and is fixedly connected with relatively arranged plug plates, and the plug plates are inserted into the lifting holes.

5. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 1, characterized in that: The pouring system includes a lower horizontal runner and a straight runner vertically arranged in the middle of the lower horizontal runner. The bottom of the straight runner extends to the bottom of the lower horizontal runner and forms a nest. Upper horizontal runners are symmetrically arranged at both ends of the upper side of the lower horizontal runner. The upper horizontal runner is provided with a longitudinal runner connected to the bottom of the casting cavity.

6. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 5, characterized in that: A foam ceramic filter is provided between the outlet of the lower horizontal runner and the outlet of the straight runner, a slag collecting bag is provided at the end of the upper horizontal runner, a flat gate is connected between the slag collecting bag and the upper horizontal runner, and the longitudinal runner includes a flat inner runner provided at the bottom of the side of the upper horizontal runner and a side riser provided vertically on the flat inner runner.

7. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 1, characterized in that: The smelting and pouring process comprises the following steps: Step S61: selecting raw materials, using Q10 pig iron, scrap steel, 75 ferrosilicon, and nickel plate as furnace charge, and performing shot blasting on the charge with rust or oil stains on the surface; Step S62: Melting: Weigh the charge and add it to the medium frequency induction furnace, start the furnace for melting, add 75% ferrosilicon and nickel plate after melting, take a sample before the furnace, test the content of C, Si, Mn, P, S, and Ni, and adjust the content of each element in the molten iron in the furnace according to the results; when the temperature in the furnace rises to 1510℃±10℃, prepare to take the charge out of the furnace and put it into the spheroidizing bag; Step S63: Spheroidizing. Clean the spheroidizing ladle and add spheroidizing agent at a rate of 1.0% to 1.2% of the mass of the molten iron into the ladle pit at the bottom of the spheroidizing ladle. The particle size of the spheroidizing agent is 5 to 25 mm. Add inoculant-1 at a rate of 0.4% to 0.6% of the mass of the molten iron on the spheroidizing agent. The particle size of the inoculant-1 is 3 to 8 mm. Add a covering agent at a rate of 0.4% to 0.6% of the mass of the molten iron. The composition of the spheroidizing agent is as follows: Si: 40% to 50%, Mg: 5.5% to 7.5%, RE: 1.5% to 2.5%, Ca: 2.5% to 3.0%, and the remainder is Fe. The composition of the inoculant-1 is as follows: Si: 70% to 75%, Ca: 1% to 1.5%, Al ≤ 1%, and the rest is Fe; the covering agent composition is: C: 0.009% to 0.013%, Si: 0.4% to 1.01%, Mn: 0.22% to 0.56%, P: 0.011% to 0.09%, S: 0.002%, Cr: 0.03% to 0.09%, Ni: 0.01% to 0.02%, Cu: 0.01% to 0.04%, Al: 0.12% to 0.35%, and the rest is Fe; measuring the temperature, transferring the molten iron into a spheroidizing bag at a furnace temperature of 1500 to 1520°C for spheroidizing inoculation treatment; Step S64: After the spheroidization reaction is completed, add 0.3% to 0.4% of the mass of the molten iron inoculant-1 and 0.2% to 0.3% of the mass of the molten iron into the casting ladle. The particle size of the molten iron inoculant-2 is 3 to 8 mm, and the composition is: Si: 69%; Ca: 1.72%, Al: 0.78%, Bi: 1.0%. Pour the molten iron from the spheroidizing ladle into the casting ladle, let it stand for about 10 seconds, and finally scrape off the slag. Step S65: Pouring: Control the pouring temperature to 1400-1420°C to ensure a steady pouring speed. In the pouring process, inoculate the inoculant-3 in the inoculant stream. The content of the inoculant-3 in the inoculant stream is 0.005%-0.1% of the mass of the molten iron. The particle size is 0.2-0.7 mm. The composition of the inoculant-3 in the inoculant stream is: Si: 72%, Al: 1.63%, and Ca: 0.66%.

8. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 1, characterized in that: The bridge body, the first box body and the second box body are all made of QT450-18 material.

9. The method for manufacturing a transversely coupled integrated tram box-type axle bridge according to claim 8, characterized in that: The composition ratio of the QT450-18 material is as follows by mass percentage: C: 3.6%~3.8%, Si: 2.5%~2.8%, Mn: ≤1.5%, P: ≤0.025%, S: 0.005%~0.015%, Ni: 0.3%~0.5%, Mg: 0.035%~0.055%, the rest is Fe.

Images