A steel backing casting process for train brake pads

Abstract

This invention relates to the field of casting technology and discloses a casting process for the steel backing of train brake pads, which includes steps such as mold design, sand mold making, melting, spheroidizing, pouring, and cooling. This invention solves the problems of substandard metallographic structure and insufficient cold-stamping strength at -20 to -40 degrees Celsius in existing casting processes. It also addresses the quality issues of porosity, tensile strength, bending strength, and cold-stamping strength in the core area of ​​the middle section of the steel backing, ensuring high-strength performance of the steel backing. By optimizing the mold structure, utilizing precise matching of the counter-pressure plate and positive pressure plate, positioning and venting structure design, and sand mold / sand core technology, it effectively reduces defects such as sand holes, porosity, shrinkage cavities, sand adhesion, cracking, and dimensional deviations in the castings, ensuring dimensional accuracy, surface quality, and internal density, and improving the product qualification rate.

Description

Technical Field

[0001] This invention relates to the field of casting technology, specifically to a steel backing casting process for train brake pads. Background Technology

[0002] As a key load-bearing component of the braking system, the steel backing of train brake pads is subjected to high-frequency braking impacts, alternating loads, and high and low temperature environments over long periods. Therefore, extremely high requirements are placed on its metallographic structure, internal density, tensile strength, bending strength, and low-temperature impact performance. Currently, traditional casting processes for producing this type of steel backing casting generally suffer from several technical shortcomings: On the one hand, conventional sand mold and core formulations and molding processes are not stable enough, and the strength and permeability of sand molds are not well controlled, which can easily lead to appearance defects such as sand adhesion, porosity and sand holes in castings. At the same time, the positioning accuracy of the mold cavity is poor, making it difficult to ensure the consistency of the steel back dimensions.

[0003] On the other hand, the large fluctuations in the chemical composition of molten iron and the insufficient uniformity and thoroughness of spheroidization and inoculation treatments easily lead to substandard metallographic structures and a pronounced tendency towards white iron structures. Furthermore, improper control of pouring temperature and cooling rhythm makes the steel backing, especially in the central section, highly susceptible to casting porosity, directly resulting in insufficient tensile and bending strength of the casting. More significantly, steel backings prepared using existing processes generally suffer from poor low-temperature performance; their cold-stamping strength is insufficient to meet usage requirements under conditions of -20℃ to -40℃, posing a safety hazard.

[0004] In addition, traditional mold structures are mostly single-cavity or poorly arranged, with uneven distribution of flow channels, poor venting, and insufficient feeding capacity, which further aggravates shrinkage defects, resulting in low casting qualification rate and inability to meet the needs of efficient mass production.

[0005] In summary, existing casting processes can no longer simultaneously meet the comprehensive requirements of high strength, high density, low-temperature toughness, and large-scale production of steel backing for train brake pads. There is an urgent need for a steel backing casting process that offers stable molding quality, excellent mechanical properties, and higher production efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a steel backing casting process for train brake pads, which solves the problems of substandard metallographic structure of steel backing and insufficient strength in the core area of ​​the middle section cast by existing processing techniques.

[0007] This invention is achieved through the following technical solution: a steel backing casting process for train brake pads, comprising the following steps in sequence: Step S1, Mold Design: Adopting a vertical sand line molding structure, a matching mold for coated sand core molding is designed to ensure that the mold is compatible with subsequent molding and core-making processes; Step S2, Sand mold making: The molding process adopts the vertical sand line tide mold sand method, and the core making process adopts the film-coated sand hot core box heating method. After the sand core is placed, a qualified sand mold is obtained for use. Step S3, Smelting: The smelting operation is carried out using a medium-frequency induction furnace. First, the scrap steel and the main body recycled material are put into the furnace. After heating to 1600-1620℃, the carbon raiser, ferrosilicon and ferromanganese are added in sequence. The temperature is held for 10-15 minutes to obtain qualified molten iron. Step S4, Spheroidizing: Spheroidizing is carried out using a wire feeding spheroidizing machine. The molten iron that has reached the tapping temperature in step S3 is poured into the spheroidizing ladle. After weighing, the molten iron in the spheroidizing ladle is transported to the spheroidizing chamber to complete the spheroidizing operation. Step S5, Casting: The molten iron that has undergone spheroidization treatment in step S4 is precisely cast into the sand mold prepared in step S2; Step S6, Cooling: After pouring, remove the casting from the mold and cool it to room temperature. Then, perform sand removal cleaning and shot blasting to finally obtain a qualified steel back casting.

[0008] To better realize the present invention, the coated sand used in steps S1 and S2 is based on quartz sand, and the components are as follows by mass fraction: resin 2.4-2.6%, hardener 15-16%, calcium stearate 0.14-0.15%; the total amount of the above additives is 0.315% per 500 kg of quartz sand.

[0009] To better realize the present invention, in step S2, the vertical sand line tidal sand is based on silica sand, and the components are as follows by mass fraction: bentonite 3-6%, coal powder 2-5%, and water 3-4%.

[0010] To better realize the present invention, the molten iron obtained in step S3 has the following chemical composition by mass fraction: C 3.4-3.8%, Si 2.2-2.5%, Mn 0.3-0.6%, P < 0.04%, S < 0.02%, Cu 0.3-0.5%, Ni < 0.2%, Cr < 0.12%, Mo < 0.2%, and the remainder is Fe.

[0011] To better realize the present invention, the temperature of the spheroidizing treatment in step S4 is controlled at 1500-1550℃ and the spheroidizing time is 25-45 seconds; the spheroidizing line adopts the inoculation method, and the amount of inoculant added is 2 meters / 100kg of molten iron.

[0012] To better realize the present invention, in step S5, the pouring temperature of the molten iron is controlled at 1330-1430°C, the single-mold pouring time is 9 seconds, and the casting removal time is not less than 1.5 hours.

[0013] To better realize the present invention, the mold in step S1 further includes a counter-pressure plate and a positive pressure plate; The back pressure plate includes a back pressure base plate. One side of the back pressure base plate is integrally provided with a back pressure pouring cup, a back pressure filter, a back pressure straight sprue, a back pressure horizontal sprue, a back pressure product mold, and a partition sand core feeding riser. The other side is provided with a back pressure venting groove. A back pressure positioning hole and a back pressure venting hole are provided through the back pressure base plate, and the back pressure venting hole is located in the back pressure venting groove. The positive pressure plate includes a positive pressure base plate. One side of the positive pressure base plate is integrally provided with a positive pressure pouring cup, a positive pressure filter, a positive pressure straight sprue, a positive pressure horizontal sprue, a positive pressure product mold, and a positioning rod. The other side is provided with a positive pressure venting groove. A positive pressure positioning hole and a positive pressure venting hole are provided through the positive pressure base plate, and the positive pressure venting hole is located in the positive pressure venting groove.

[0014] To better realize the present invention, the number of the reverse pressure product mold and the positive pressure product mold is four, and the four reverse pressure product molds and the four positive pressure product molds are respectively grouped in pairs and distributed on both sides of the reverse pressure sprue and the positive pressure sprue.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention effectively solves the problems of substandard metallographic structure and insufficient cold stamping strength at -20-40℃ in the existing process of casting steel backing. At the same time, it overcomes the casting porosity defect in the core of the middle section of the steel backing, significantly improves the tensile strength, bending strength and cold stamping strength of the steel backing, and ensures that the steel backing has high strength performance and meets the stringent requirements of train brake pads. (2) By optimizing the mold structure, utilizing the precise matching of the counter-pressure plate and the positive pressure plate, the positioning and venting structure design, and the sand mold / sand core process, this invention effectively reduces defects such as sand holes, porosity, shrinkage cavities, sand adhesion, cracking, and dimensional deviations in castings, ensuring the dimensional accuracy, surface quality, and internal density of castings, and improving the product qualification rate. (3) By precisely controlling the chemical composition of molten iron, spheroidization and inoculation parameters, the present invention avoids the formation of white iron structure, significantly enhances the toughness, strength and wear resistance of steel backing castings, ensures long-term stable service of castings, and adapts to the high temperature, high pressure and wear conditions during train braking process. Attached Figure Description

[0016] Figure 1 This is a flowchart of the overall process of the present invention.

[0017] Figure 2 This is a schematic diagram of the mold structure.

[0018] Figure 3 Schematic diagram of positive pressure plate structure Figure 1 .

[0019] Figure 4 Schematic diagram of positive pressure plate structure Figure 2 .

[0020] Figure 5 Schematic diagram of the anti-pressure plate structure Figure 1 .

[0021] Figure 6 Schematic diagram of the anti-pressure plate structure Figure 2 .

[0022] Wherein: 10-Reverse pressure plate; 20-Positive pressure plate; 101-Reverse pressure base plate; 102-Reverse pressure gating cup; 103-Reverse pressure filter sheet; 104-Reverse pressure sprue; 105-Reverse pressure runner; 106-Reverse pressure product mold; 107-Reverse pressure positioning hole; 108-Reverse pressure venting groove; 109-Reverse pressure venting hole; 110-Partition sand core shrinkage riser; 201-Positive pressure base plate; 202-Positive pressure gating cup; 203-Positive pressure filter sheet; 204-Positive pressure sprue; 205-Positive pressure runner; 206-Positive pressure product mold; 207-Positive pressure positioning hole; 208-Positive pressure venting groove; 209-Positive pressure venting hole; 210-Positioning rod. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1:

[0025] This embodiment provides a steel backing casting process for train brake pads, such as... Figure 1 As shown, the steps are as follows: Step S1, Mold Design: A vertical sand line molding structure is adopted, and a matching mold with a coated sand core is designed to ensure that the mold is compatible with subsequent molding and core making processes; this improves molding efficiency, reduces operational errors, ensures accurate sand core positioning, provides a guarantee for casting forming accuracy, and achieves smooth process connection; Step S2, Sand mold making: The molding process adopts the vertical sand line wet mold sand method, and the core making process adopts the coated sand hot core box heating method. After the sand core is placed, a qualified sand mold is obtained for use. This process improves the efficiency and accuracy of sand mold and sand core forming, reduces production costs, reduces defects such as sand holes and air holes in castings, and ensures the stability of the forming space. Step S3, Smelting: The smelting operation is carried out using a medium-frequency induction furnace. First, the scrap steel and the main body recycled material are put into the furnace and heated to 1600-1620℃. Then, the carbon raiser, ferrosilicon and ferromanganese are added in sequence to improve the purity and composition stability of the molten iron, reduce the cost of raw materials, and provide a guarantee for subsequent spheroidization and casting performance. After that, the temperature is held for 10-15 minutes to obtain qualified molten iron. Step S4, Spheroidizing: Spheroidizing is carried out using a wire-feeding spheroidizing machine to ensure uniform and stable spheroidizing, improve spheroidizing quality, and enhance the toughness, strength and wear resistance of the casting. The molten iron that has reached the tapping temperature in step S3 is poured into the spheroidizing ladle. After weighing, the molten iron in the spheroidizing ladle is transported to the spheroidizing chamber to complete the spheroidizing operation. Step S5, Casting: The molten iron that has undergone spheroidization treatment in step S4 is precisely cast into the sand mold prepared in step S2; Step S6, Cooling: After pouring, remove the casting from the mold and cool it to room temperature. Then, perform sand removal cleaning and shot blasting to finally obtain a qualified steel back casting.

[0026] This invention solves the problems of substandard metallographic structure and insufficient cold stamping strength at -20 to -40 degrees Celsius in steel backing cast by existing processes. It also solves the quality problems of casting porosity, tensile strength, bending strength, and cold stamping strength in the core area of ​​the middle section of the steel backing, thus ensuring the high strength performance of the steel backing. Example 2:

[0027] This embodiment further expands upon the above embodiment. The coated sand used in steps S1 and S2 uses quartz sand as the base material, and the components, by mass fraction, are: resin 2.4–2.6%, hardener 15–16%, and calcium stearate 0.14–0.15%. The total addition amount of the above additives is 0.315% per 500 kg of quartz sand. This ensures the strength, permeability, and dimensional accuracy of the sand core, prevents sand core damage and collapse, and guarantees the quality of the casting.

[0028] Furthermore, in step S2, the vertical sand mold line uses silica sand as the base material, and the components, by mass fraction, are: bentonite 3-6%, coal powder 2-5%, and water 3-4%. This improves the strength, permeability, and reusability of the sand mold, reduces defects such as sand adhesion and porosity in the casting, and ensures the sand mold forming effect. Furthermore, the molten iron obtained in step S3 has the following chemical composition by mass fraction: C 3.4–3.8%, Si 2.2–2.5%, Mn 0.3–0.6%, P < 0.04%, S < 0.02%, Cu 0.3–0.5%, Ni < 0.2%, Cr < 0.12%, Mo < 0.2%, with the remainder being Fe. This configuration ensures the fluidity of the molten iron, improves the strength, toughness, and wear resistance of the castings, avoids casting defects caused by harmful impurities, and meets the requirements for long-term use.

[0029] Furthermore, in step S4, the spheroidizing temperature is controlled at 1500-1550℃, and the spheroidizing time is 25-45 seconds; the spheroidizing line adopts a flow-inoculation method, and the inoculant addition amount is 2 m / 100kg of molten iron. This ensures the spheroidizing and inoculation effects, avoids white cast iron structure, and improves the toughness and plasticity of the casting.

[0030] Furthermore, in step S5, the pouring temperature of the molten iron is controlled at 1330-1430℃, the single-mold pouring time is 9 seconds, and the casting removal time is not less than 1.5 hours; this reduces pouring defects, avoids casting cracking and deformation, and ensures dimensional accuracy.

[0031] The other parts of this embodiment are the same as those in the above embodiments, and will not be described again. Example 3:

[0032] This embodiment further extends the above embodiment, specifically as follows: Figures 2-6 As shown, the mold in step S1 includes a counter-pressure plate 10 and a positive pressure plate 20 that cooperate with each other. The two are precisely connected to form a complete casting cavity, providing structural protection for the precise forming of steel back castings.

[0033] The counter-pressure plate 10 includes a counter-pressure base plate 101, which serves as the basic load-bearing structure of the counter-pressure plate. One side of the base plate is integrally formed with a counter-pressure gating cup 102, a counter-pressure filter 103, a counter-pressure sprue 104, a counter-pressure runner 105, a counter-pressure product mold 106, and a partition sand core feeding riser 110. The other side has a counter-pressure venting groove 108. A counter-pressure positioning hole 107 and a counter-pressure venting hole 109 are formed through the base plate 101, with the venting hole 109 corresponding to the venting groove 108, ensuring smooth connection of the venting channels. This ensures the overall rigidity and positioning accuracy of the mold. The counter-pressure filter can filter impurities in the molten iron and improve its purity. The sprue and runner work together to achieve uniform distribution of molten iron. The feeding riser reduces shrinkage cavities and porosity in the casting. The venting structure effectively discharges gas from the mold cavity, thereby reducing casting defects and ensuring the dimensional accuracy and density of the casting.

[0034] The positive pressure plate 20 includes a positive pressure base plate 201, which corresponds to and is adapted to the negative pressure base plate 101. One side of the positive pressure plate has an integrally formed positive pressure pouring cup 202, a positive pressure filter 203, a positive pressure sprue 204, a positive pressure runner 205, a positive pressure product mold 206, and a positioning rod 210. The positioning rod 210 precisely engages with the negative pressure positioning hole 107. The other side has a positive pressure venting groove 208. The positive pressure base plate 201 has a through-hole positive pressure positioning hole 207 and a positive pressure venting hole 209, with the positive pressure venting hole 209 correspondingly located within the positive pressure venting groove 208, working in conjunction with the venting structure of the negative pressure plate. This precise coordination with the negative pressure plate, along with the positioning rod further ensuring mold closing accuracy, and the symmetrical flow channel and filter structure combination, ensures stable molten iron transport. The venting structure also improves venting efficiency, effectively avoiding problems such as casting porosity and dimensional deviations, further improving the casting quality.

[0035] Furthermore, there are four counter-pressure product molds 106 and four positive pressure product molds 206, and the four counter-pressure product molds 106 and four positive pressure product molds 206 are arranged in pairs, symmetrically distributed on both sides of the counter-pressure sprue 104 and the positive pressure sprue 204, ensuring that the molten iron supply and supply speed of each product mold are consistent. This enables the casting of multiple parts in a single pour, significantly improving production efficiency. The symmetrically distributed product molds ensure uniform molten iron filling in each casting, thereby ensuring uniform dimensions and mechanical properties of each casting, effectively improving the product qualification rate and adapting to the needs of mass production.

[0036] The other parts of this embodiment are the same as those in the above embodiments, and will not be described again.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A steel backing casting process for train brake pads, characterized in that, The steps are as follows: Step S1, Mold Design: Adopting a vertical sand line molding structure, a matching mold for coated sand core molding is designed to ensure that the mold is compatible with subsequent molding and core-making processes; Step S2, Sand mold making: The molding process adopts the vertical sand line tide molding sand method, and the core making process adopts the coated sand hot core box heating method. After the sand core is placed, a qualified sand mold is obtained for use. Step S3, Smelting: The smelting operation is carried out using a medium-frequency induction furnace. First, the scrap steel and the main body recycled material are put into the furnace. After heating to 1600-1620℃, the carbon raiser, ferrosilicon and ferromanganese are added in sequence. The temperature is held for 10-15 minutes to obtain qualified molten iron. Step S4, Spheroidizing: Spheroidizing is carried out using a wire feeding spheroidizing machine. The molten iron that has reached the tapping temperature in step S3 is poured into the spheroidizing ladle. After weighing, the molten iron in the spheroidizing ladle is transported to the spheroidizing chamber to complete the spheroidizing operation. Step S5, Casting: The molten iron that has undergone spheroidization treatment in step S4 is precisely cast into the sand mold prepared in step S2; Step S6, Cooling: After pouring, remove the casting from the mold and cool it to room temperature. Then, perform sand removal cleaning and shot blasting to finally obtain a qualified steel back casting.

2. The steel backing casting process for train brake pads according to claim 1, characterized in that: The coated sand used in steps S1 and S2 is based on quartz sand, and the components by mass fraction are: resin 2.4-2.6%, hardener 15-16%, and calcium stearate 0.14-0.15%; the total amount of the above additives is 0.315% per 500 kg of quartz sand.

3. The steel backing casting process for train brake pads according to claim 1, characterized in that: In step S2, the vertical sand-line tidal molding sand uses silica sand as the base material, and the components are as follows by mass fraction: bentonite 3-6%, coal powder 2-5%, and water 3-4%.

4. The steel backing casting process for train brake pads according to claim 1, characterized in that: The molten iron obtained in step S3 has the following chemical composition by mass fraction: C 3.4-3.8%, Si 2.2-2.5%, Mn 0.3-0.6%, P < 0.04%, S < 0.02%, Cu 0.3-0.5%, Ni < 0.2%, Cr < 0.12%, Mo < 0.2%, and the remainder is Fe.

5. The steel backing casting process for train brake pads according to claim 1, characterized in that: In step S4, the spheroidizing temperature is controlled at 1500-1550℃, and the spheroidizing time is 25-45 seconds. The spheroidizing line adopts the inoculation method, and the amount of inoculant added is 2 meters / 100kg of molten iron.

6. The steel backing casting process for train brake pads according to claim 1, characterized in that: In step S5, the pouring temperature of the molten iron is controlled at 1330-1430℃, the single-mold pouring time is 9 seconds, and the casting removal time is not less than 1.5 hours.

7. A steel backing casting process for train brake pads according to any one of claims 1-6, characterized in that: The mold in step S1 includes a counter-pressure plate (10) and a positive pressure plate (20). The back pressure plate (10) includes a back pressure base plate (101). One side of the back pressure base plate (101) is integrally provided with a back pressure pouring cup (102), a back pressure filter (103), a back pressure sprue (104), a back pressure sprue (105), a back pressure product mold (106), and a partition sand core shrinkage riser (110). The other side is provided with a back pressure venting groove (108). A back pressure positioning hole (107) and a back pressure venting hole (109) are provided through the back pressure base plate (101), and the back pressure venting hole (109) is located in the back pressure venting groove (108). The positive pressure plate (20) includes a positive pressure base plate (201). One side of the positive pressure base plate (201) is integrally provided with a positive pressure pouring cup (202), a positive pressure filter (203), a positive pressure sprue (204), a positive pressure runner (205), a positive pressure product mold (206), and a positioning rod (210). The other side is provided with a positive pressure venting groove (208). A positive pressure positioning hole (207) and a positive pressure venting hole (209) are provided through the positive pressure base plate (201), and the positive pressure venting hole (209) is located in the positive pressure venting groove (208).

8. The steel backing casting process for train brake pads according to claim 7, characterized in that: The number of the reverse pressure product mold (106) and the positive pressure product mold (206) are both four, and the four reverse pressure product molds (106) and the four positive pressure product molds (206) are respectively paired up and distributed on both sides of the reverse pressure sprue (104) and the positive pressure sprue (204).

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