A high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles and its manufacturing process

Abstract

This invention relates to the field of balance shaft bracket manufacturing technology, specifically to a high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles and its manufacturing process. The mass percentages of each element in this balance shaft bracket are as follows: C: 3.65–3.75%, Si: 2.65–2.75%, Mn: ≤0.3%, Cu: 0.65–0.75%, Mo: 0.25–0.3%, Mg: 0.035–0.055%, P: ≤0.035%, S: ≤0.035%, RE: 0.015–0.03%, Al: ≤0.001%, Ca: ≤0.0025%, Ba: ≤0.005%, and Cr: ≤0.03%, with the remainder being Fe and unavoidable impurities. This invention adjusts the chemical composition of existing balance shaft supports and improves their smelting and heat treatment processes. The resulting balance shaft support has an overall weight of less than 46 kg, a tensile strength of more than 1050 MPa, an elongation of more than 6%, and a hardness of more than 310 Hbw. Compared with the original, the weight is reduced by about 5 kg, and the tensile strength is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of balance shaft bracket manufacturing technology, specifically to a high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles and its manufacturing process. Background Technology

[0002] Experiments have shown that if the overall weight of a car is reduced by 10%, fuel efficiency can be improved by 6-8%, and for every 100kg reduction in weight, fuel consumption per 100km can be reduced by 0.3-0.6L. Reducing the weight of a car can lower fuel consumption, reduce harmful emissions, save on weigh-in-charge expenses, improve load capacity utilization, and increase transportation profits. Furthermore, reducing the weight of a car lowers its center of gravity, making the car more stable and comfortable to drive, and also reduces rolling resistance, acceleration resistance, and climbing resistance, creating conditions for achieving higher power output.

[0003] The balance shaft bracket is a key component of the balance shaft suspension, and achieving its lightweight design is of great significance for reducing the overall vehicle weight. Summary of the Invention

[0004] Based on this, the present invention improves the elemental composition and heat treatment process by modifying the elemental composition and heat treatment process. The resulting balance shaft support has an overall weight of less than 46 kg, a tensile strength of more than 1050 MPa, an elongation of more than 6%, and a hardness of more than 310 Hbw. Compared with the previous version, the weight is reduced by about 5 kg and the tensile strength is significantly improved.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical solution: The present invention provides a high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles. The mass percentage of each element in the balance shaft bracket is as follows: C: 3.5-3.75%, Si: 2.5-2.75%, Mn: ≤0.3%, Cu: 0.65-0.75%, Mo: 0.25-0.33%, Mg: 0.035-0.055%, P: ≤0.035%, S: ≤0.035%, RE: 0.015-0.03%, Al: ≤0.001%, Ca: ≤0.0025%, Ba: ≤0.005%, and Cr: ≤0.03%, with the remainder being Fe and unavoidable impurities. The preparation of the balance shaft bracket includes the following steps:

[0006] Step S1: Raw material smelting, selecting pig iron, scrap steel and recycled materials, adding pretreatment agents and carbonizers to melt into the first molten iron;

[0007] Step S2: Add the first inoculant, copper, and molybdenum to the first molten iron to perform the first inoculation, and obtain the second molten iron. The first inoculant is an inoculant containing silicon, barium, and calcium.

[0008] Step S3: Add low-magnesium spheroidizing wire to the second molten iron for spheroidization treatment, and add a second inoculant for a second inoculation to obtain the third molten iron. The low-magnesium spheroidizing wire contains magnesium, silicon, calcium, aluminum and rare earth elements. The second inoculant is an inoculant containing silicon, barium and calcium.

[0009] Step S4: Pour the third molten iron into the mold and add the third inoculant at the same time for in-flow inoculation. After all the element ratios are adjusted, the third inoculant is an inoculant containing silicon, barium, calcium and aluminum.

[0010] Step S5: After pouring and cooling, remove from the mold to obtain as-cast cast iron;

[0011] Step S6: Heat the empty furnace of the heat treatment furnace to 620-670℃, then place the cast iron into the heat treatment furnace and heat it to 900-920℃, hold it for 50-70 minutes. After holding, quickly lift the product out and transfer it to a constant temperature salt bath at 330-350℃ to cool it down rapidly. After cooling, lift the product into the heat treatment furnace for tempering heat treatment, heat it to 570-590℃ and hold it for 1-2 hours. After tempering, lift the product out and let it cool naturally in the air to room temperature to obtain the final product.

[0012] In a preferred embodiment, the temperature of the first molten iron during the first inoculation treatment is 1510-1520℃, and the temperature of the second molten iron during the spheroidizing treatment and the second inoculation treatment is 1470-1480℃.

[0013] In a preferred embodiment, in step S1, the mass percentage of pig iron is 15-25%, the mass percentage of scrap steel is 40-55%, the mass percentage of recycled material is 20-45%, the mass percentage of pretreatment agent is 0.5%, and the mass percentage of carburizing agent is 3.3-3.8% of the mass of scrap steel.

[0014] In a preferred embodiment, the first inoculant is a silicon-barium-calcium inoculant with a particle size of 3-8 mm, the second inoculant is an inoculum line, and the third inoculant is a silicon-barium-calcium inoculant with a particle size of 0.2-0.8 mm.

[0015] In a preferred embodiment, the amount of the first inoculant added is 0.6 to 0.7% of the mass of the first molten iron, the amount of the second inoculant added is 13 to 18m per 980kg of the first molten iron, the wire feed speed is 25 to 30m / min, and the amount of the third inoculant added is 0.1 to 0.15% of the mass of the first molten iron.

[0016] In a preferred embodiment, the amount of low-magnesium spheroidizing wire added in step S3 is 22-24m of spheroidizing wire per 980kg, and the wire feeding speed is 32-36m / min.

[0017] In a preferred embodiment, the temperature during pouring in step S4 is 1420–1430°C, and the pouring time is ≤8 min.

[0018] As a preferred embodiment, a two-part mold structure is used during casting, with two balance shaft supports symmetrically arranged and the pouring gate located in the middle of the two molds.

[0019] In a preferred embodiment, the mass percentages of each element in the first molten iron are: C: 3.7–3.9%, Si: 1.2–1.5%, Mn: ≤0.3%, P: ≤0.035%, S: ≤0.035%, Cr: ≤0.03%.

[0020] As a preferred embodiment, a heat treatment deformation control step is also included.

[0021] In a preferred embodiment, the heat treatment deformation control step includes original heat treatment deformation prevention control and improved deformation prevention control. The original heat treatment deformation prevention control involves tilting the easily deformable parts upwards during heat treatment and securing the parts with wire. The improved deformation prevention control involves placing the heat-treated workpiece on a fixture with the push rod mounting assembly facing upwards, the balance shaft mounting assembly placed in the U-shaped groove of the fixture, the frame connecting part corresponding to the balance shaft mounting part placed horizontally on the fixture, and the downwardly extending frame connecting part clamped in the clamping groove of the fixture.

[0022] This invention reduces the content of manganese (Mn) and adds copper (Cu) and molybdenum (Mo) to replace manganese (Mn), adaptively adjusts the content of other elements, and improves the smelting and heat treatment processes. By employing unbalanced isothermal heat treatment, the resulting balance shaft support has an overall weight of less than 46 kg, a tensile strength of more than 1050 MPa, an elongation of more than 6%, and a hardness of more than 310 Hbw. Compared with the previous version, not only is the weight reduced by about 5 kg, but the tensile strength is also significantly improved, meeting the QT1050-6 standard. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the balance shaft support prepared according to the present invention;

[0024] Figure 2 This is a schematic diagram of the iron mold used in casting;

[0025] Figure 3 This is a schematic diagram of the fixture structure for placing workpieces after heat treatment.

[0026] Figure 4The images shown are spheroidized and pearlitic images from the examples, where a, b, and c are spheroidized images of cast iron in Examples 1-3, and d, e, and f are pearlitic images of cast iron in Examples 1-3, respectively.

[0027] The components corresponding to each mark in the diagram are as follows:

[0028] 01 Thrust rod mounting and integration unit, 02 Chassis connection unit, 03 Balance shaft mounting unit;

[0029] 1 clamping groove, 2 support platform, 3 U-shaped groove. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0031] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the specific embodiments of the invention without inventive effort are within the protection scope of the invention.

[0032] The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket produced by this invention has the same structure as the balance suspension bracket disclosed in publication number CN112210708A, and can also be found in [other sources]. Figure 1 .

[0033] The following embodiments all use the following iron molds for casting: such as Figure 2 As shown, the iron mold dimensions are 1650*1000mm. Based on the casting dimensions, it is distributed in sets of two per mold. Each casting has two sprues, and each ingate has an area of ​​8*90mm. This means that a two-mold structure is used during casting. Two balance shaft supports are symmetrically arranged, and the pouring gate is located between the two molds to quickly increase the filling speed. Straight-through vents with a diameter of 5-7mm are provided at the top of the casting and on the bosses to facilitate rapid gas discharge from the mold cavity during pouring. Vent holes are also added at the high points of the mold cavity and on the bosses to facilitate rapid gas discharge. Vent plugs are installed at the sand-covered areas, and vent grooves are provided on the parting surface for auxiliary venting.

[0034] First, a core shooter is used for core making. During core making, the mold temperature is 190-210℃, the sand shooting time is 3s, the curing time is 230s, and the top hole time is 2500ms. Then, a core shooter is used for molding. During molding, the sand box temperature is 180-230℃, the mold temperature is 180-230℃, the sand shooting time is 10s, the holding pressure time is 12s, and the curing time is 120s. After molding, melting and casting are carried out.

[0035] The material composition used in the melting and casting process is as follows:

[0036] Pig iron: High-quality foundry pig iron from Longfengshan or low-phosphorus (P≤0.03) and low-sulfur (S≤0.02) rust-free pig iron;

[0037] Scrap steel: low carbon and low alloy (carbon: 0.03%~0.06%, silicon: 0.16%, manganese: 0.38%, sulfur: ≤0.02%, phosphorus ≤0.03%);

[0038] Recycled material: refers to raw materials that are reused from the residues produced by this invention;

[0039] Pretreatment agent: SiC≧98%, FC≦0.5%, Fe2O3≦0.5%, moisture≦0.5%, particle size 1mm~5mm;

[0040] Carbon raiser: carbon ≥ 98.5%, sulfur ≤ 0.1%, nitrogen ≤ 300 ppm, moisture ≤ 0.5%, volatile matter ≤ 0.5%, ash ≤ 0.5%, particle size 0-5 mm;

[0041] First inoculant (silicon-barium-calcium inoculant): silicon (Si) 70-72%, barium (Ba) 4-5%, calcium (Ca) 1-25%, the remainder is iron (Fe), particle size 3-8mm;

[0042] Low-magnesium spherical wire: 435-450g per meter of wire, 255-265g per meter of flour, 15-16% magnesium (Mg), 45-47% silicon (Si), 2-3% calcium (Ca), 0.5-1.0% aluminum (Al), 1-2% rare earth elements (lanthanum La, cerium Ce), and the remainder is iron (Fe);

[0043] Second inoculant (inoculant thread): Each meter of thread weighs 400-430g, each meter of rice flour weighs 230-250g, silicon (Si) 72-75%, calcium (Ca) 1-2%, barium (Ba) 1-2%, and the remainder is iron (Fe);

[0044] The third inoculant consists of 65-70% silicon (Si), 1-2% calcium (Ca), 2-3% barium (Ba), 1-2% aluminum (Al), and the remainder iron (Fe), with a particle size of 0.2-0.7 mm.

[0045] The heating medium in the salt bath is industrial salt.

[0046] Example 1

[0047] This embodiment provides a manufacturing process for a high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles. The smelting and casting method is as follows:

[0048] Step S1: Raw material smelting ratio: 15%-25% pig iron, 40%-50% scrap steel, 20%-45% recycled material, 3.3%-3.8% of the total scrap steel, 0.5% of the carbon raiser, and 0.5% of the pretreatment agent; the carbon raiser is added in batches after the scrap steel, which helps to lower the melting point of the furnace charge and improve the absorption rate. Adding it too early will corrode the furnace lining.

[0049] In this step, the chemical composition of the material is determined using an OBLF photoelectric direct-reading spectrometer, and the batching ratio is controlled within the range of C: 3.7–3.9%, Si: 1.2–1.5%, Mn: ≤0.3%, P: ≤0.035%, S: ≤0.035%, Cr: ≤0.03%. The temperature of the first molten iron is 1525℃.

[0050] Step S2: Transfer the first molten iron to a ladle at a standard of 980 kg / bundle for further smelting, controlling the temperature at around 1514℃. First, add 0.64% of the first inoculant (silicon barium calcium inoculant), copper (Cu), and molybdenum (Mo) to obtain the second molten iron.

[0051] Step S3: Control the temperature of the second molten iron at about 1475℃, add low-magnesium spheroidizing wire for spheroidization treatment, and add the second inoculant (inoculation wire) for the second inoculation to obtain the third molten iron; in this step, the amount of low-magnesium spheroidizing wire added is 22m, the wire feed speed is 34m / min, the amount of inoculation wire added is 14m, and the wire feed speed is 28m / min;

[0052] In step S4, the temperature of the third molten iron is controlled at 1424℃, and the third molten iron is poured into the mold. At the same time, the third inoculant is added for in-flow inoculation. The addition flow rate of the third inoculant is 0.1-0.15%. At this time, the proportion of all elements is adjusted. In this step, the pouring time is 7.2 minutes.

[0053] Step S5: After pouring and cooling, the mold is opened after 35 minutes to obtain as-cast cast iron. The chemical composition of the as-cast iron is determined, and the results are shown in Table 1 below. Its properties are tested, and the results are shown in Table 2.

[0054] Step S6: Heat the empty heat treatment furnace to 650℃, then place the cast iron into the furnace and heat to 900-910℃, holding for 1 hour. After holding, quickly remove the product and transfer it to a 340℃ constant temperature salt bath to rapidly cool the cast iron to below 340℃. After cooling, remove the product into the heat treatment furnace for tempering heat treatment, heating to 580℃ and holding for 1.5 hours. After tempering, remove the product and allow it to cool naturally to room temperature in the air. In this step, to prevent deformation of the workpiece during heat treatment, the easily deformable parts of the cast iron are placed diagonally upwards and secured with wire to prevent slippage during transport and heating, thus reducing stress during heating.

[0055] Step S7: After heat treatment, place the workpiece on the optimized fixture with the thrust rod mounting integration part 01 facing upwards, the balance shaft mounting part 03 placed in the U-shaped groove 3 of the fixture, the frame connecting part corresponding to the balance shaft mounting part 03 placed horizontally on the support platform 2 of the fixture, and the downward-extending frame connecting part 02 clamped in the clamping groove 1 of the fixture.

[0056] Example 2

[0057] This embodiment provides a manufacturing process for a high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles. The smelting and casting method is as follows:

[0058] Step S1: Raw material smelting ratio: 15%-25% pig iron, 40%-50% scrap steel, 20%-45% recycled material, 3.3%-3.8% of the total scrap steel, 0.5% of the carbon raiser, and 0.5% of the pretreatment agent; the carbon raiser is added in batches after the scrap steel, which helps to lower the melting point of the furnace charge and improve the absorption rate. Adding it too early will corrode the furnace lining.

[0059] In this step, the chemical composition of the material is determined using an OBLF photoelectric direct-reading spectrometer, and the batching ratio is controlled within the range of C: 3.7–3.9%, Si: 1.2–1.5%, Mn: ≤0.3%, P: ≤0.035%, S: ≤0.035%, Cr: ≤0.03%. The temperature of the first molten iron is 1528℃.

[0060] Step S2: Transfer the first batch of molten iron to a ladle at a standard rate of 980 kg / bundle and continue smelting, controlling the temperature at around 1516℃. First, add 0.62% of the first inoculant (silicon barium calcium inoculant) to obtain the second batch of molten iron.

[0061] Step S3: Control the temperature of the second molten iron to about 1477℃, add low-magnesium spheroidizing wire for spheroidization treatment, and add the second inoculant (inoculation wire) for the second inoculation to obtain the third molten iron; in this step, the amount of low-magnesium spheroidizing wire added is 23m, the wire feed speed is 34m / min, the amount of inoculation wire added is 16m, and the wire feed speed is 26m / min.

[0062] Step S4: Control the temperature of the third molten iron at 1427℃, pour the third molten iron into the mold, and simultaneously add the third inoculant for in-flow inoculation. The addition flow rate of the third inoculant is 0.1-0.15%. At this time, the proportion of all elements is adjusted. In this step, the pouring time is 7.5 minutes.

[0063] Step S5: After pouring and cooling, the mold is opened after 35 minutes to obtain as-cast cast iron. The chemical composition of the as-cast iron is determined, and the results are shown in Table 1 below. Its properties are tested, and the results are shown in Table 2.

[0064] Step S6: Heat the empty heat treatment furnace to 630℃, then place the cast iron into the furnace and heat to 910-920℃, holding for 50 minutes. After holding, quickly remove the product and transfer it to a 330℃ constant temperature salt bath to rapidly cool the cast iron to below 330℃. After cooling, remove the product into the heat treatment furnace for tempering heat treatment, heating to 590℃ and holding for 1.5 hours. After tempering, remove the product and allow it to cool naturally to room temperature in the air. In this step, to prevent deformation of the workpiece during heat treatment, the easily deformable parts of the cast iron are placed diagonally upwards and secured with wire to prevent slippage during transport and heating, thus reducing stress during heating.

[0065] Step S7: After heat treatment, place the workpiece on the optimized fixture with the thrust rod mounting assembly facing upwards, the balance shaft mounting assembly placed in the U-shaped groove of the fixture, the frame connecting part corresponding to the balance shaft mounting part placed horizontally on the fixture, and the downward-extending frame connecting part clamped in the clamping groove of the fixture.

[0066] Example 3

[0067] This embodiment provides a manufacturing process for a high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles. The smelting and casting method is as follows:

[0068] Step S1: Raw material smelting ratio: 15%-25% pig iron, 40%-50% scrap steel, 20%-45% recycled material, 3.3%-3.8% of the total scrap steel, 0.5% of the carbon raiser, and 0.5% of the pretreatment agent; the carbon raiser is added in batches after the scrap steel, which helps to lower the melting point of the furnace charge and improve the absorption rate. Adding it too early will corrode the furnace lining.

[0069] In this step, the chemical composition of the material is determined using an OBLF photoelectric direct-reading spectrometer, and the batching ratio is controlled within the range of C: 3.7–3.9%, Si: 1.2–1.5%, Mn: ≤0.3%, P: ≤0.035%, S: ≤0.035%, Cr: ≤0.03%. The temperature of the first molten iron is 1528℃.

[0070] Step S2: Transfer the first batch of molten iron to a ladle at a standard rate of 980 kg / bundle and continue smelting, controlling the temperature at around 1513℃. First, add 0.65% of the first inoculant (silicon barium calcium inoculant) to obtain the second batch of molten iron.

[0071] Step S3: Control the temperature of the second molten iron at about 1472℃, add low-magnesium spheroidizing wire for spheroidization treatment, and add the second inoculant (inoculation wire) for a second inoculation to obtain the third molten iron; in this step, the amount of low-magnesium spheroidizing wire added is 24m, the wire feed speed is 35m / min, the amount of inoculation wire added is 18m, and the wire feed speed is 30m / min;

[0072] In step S4, the temperature of the third molten iron is controlled at 1423℃, and the third molten iron is poured into the mold. At the same time, the third inoculant is added for in-flow inoculation. The addition flow rate of the third inoculant is 0.1-0.15%. At this time, the proportion of all elements is adjusted. In this step, the pouring time is 6.8 minutes.

[0073] Step S5: After pouring and cooling, the mold is opened after 35 minutes to obtain as-cast cast iron. The chemical composition of the as-cast iron is determined, and the results are shown in Table 1 below. Its properties are tested, and the results are shown in Table 2.

[0074] Step S6: Heat the empty furnace of the heat treatment furnace to 670℃, then place the cast iron into the furnace and heat it to 900-910℃, holding it at that temperature for 1 hour. After holding, quickly remove the product and transfer it to a 350℃ constant temperature salt bath to rapidly cool the cast iron to below 350℃. After cooling, remove the product and place it in the heat treatment furnace for tempering heat treatment, heating it to 570℃ and holding it for 2 hours. After tempering, remove the product and allow it to cool naturally to room temperature in the air. In this step, to prevent deformation of the workpiece during heat treatment, the easily deformable parts of the cast iron are placed diagonally upwards and secured with wire to prevent slippage during transport and heating, thus reducing stress during heating.

[0075] Step S7: After heat treatment, place the workpiece on the optimized fixture with the thrust rod mounting assembly facing upwards, the balance shaft mounting assembly placed in the U-shaped groove of the fixture, the frame connecting part corresponding to the balance shaft mounting part placed horizontally on the fixture, and the downward-extending frame connecting part clamped in the clamping groove of the fixture.

[0076] Table 1 shows the chemical composition of the as-cast state in the embodiments.

[0077]

[0078]

[0079] The metallographic structure, tensile strength, yield strength, elongation, hardness, spheroidization grade, graphite size, number of graphite spheroids, and pearlite content of the as-cast parts were tested according to GB / T9441-2009 standard. The results are shown in Table 2 below.

[0080] Table 2 shows the performance test results of the as-cast parts in the embodiments.

[0081] Inspection items Technical Standards Example 1 Example 2 Example 3 Tensile strength / MPa ≥700 731 729 733 Yield strength / MPa ≥420 464 459 468 Elongation / % ≥8 10.5 10.0 10.0 Hardness / Hbw 225-305 256.3 252.4 261.3 sphericity level 1-3 3(89.3％) 3(90.2％) 3(90.5％) Graphite size 5-8 6 6 6 Quantity of graphite spheres / piece ≥250 294 286 302 Pearlite content / % ≥50 55 52 58

[0082] The prepared workpiece was inspected for metallographic properties, tensile strength, elongation, hardness, etc., according to GB / T24733-2009 standard. The results are shown in Table 3 below.

[0083] Table 3 shows the performance test results of the castings obtained in each embodiment.

[0084]

[0085]

[0086] Images of spheroidization and pearlite in Examples 1-3 are as follows: Figure 4 As shown, a, b, and c are spheroidized images of cast iron in Examples 1 to 3, respectively, and d, e, and f are pearlitic images of cast iron in Examples 1 to 3, respectively.

[0087] It should be noted that the above embodiments are only for further elaboration and explanation of the technical solution of the present invention, and are not intended to further limit the technical solution of the present invention. The method of the present invention is only a preferred embodiment and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-grade balance shaft bracket for heavy-duty lightweight commercial vehicles, characterized in that, The mass percentages of each element in the balance shaft support are as follows: C: 3.65–3.75%, Si: 2.65–2.75%, Mn: ≤0.3%, Cu: 0.65–0.75%, Mo: 0.25–0.3%, Mg: 0.035~0.055%, P: ≤0.035%, S: ≤0.035%, RE: 0.015-0.03%, Al: ≤0.001%, Ca: ≤0.0025%, Ba: ≤0.005%, and Cr: ≤0.03%, with the remainder being Fe and unavoidable impurities; the preparation of the balance shaft support includes the following steps: Step S1: Raw material smelting, selecting pig iron, scrap steel, recycled materials, carbonizer, and pretreatment agent to melt into the first molten iron; Step S2: Add the first inoculant, copper, and molybdenum to the first molten iron to perform the first inoculation, and obtain the second molten iron. The first inoculant is an inoculant containing silicon, barium, and calcium. Step S3: Add low-magnesium spheroidizing wire to the second molten iron for spheroidization treatment, and add a second inoculant for a second inoculation to obtain the third molten iron. The low-magnesium spheroidizing wire contains magnesium, silicon, calcium, aluminum and rare earth elements. The second inoculant is an inoculant containing silicon, barium and calcium. Step S4: Pour the third molten iron into the mold and add the third inoculant at the same time for in-flow inoculation. After all the element ratios are adjusted, the third inoculant is an inoculant containing silicon, barium, calcium and aluminum. Step S5: After pouring and cooling, remove from the mold to obtain as-cast cast iron; Step S6: Heat the empty furnace of the heat treatment furnace to 620-670℃, then place the cast iron into the heat treatment furnace and heat it to 900-920℃, hold it for 50-70 minutes. After holding, quickly lift the product out and transfer it to a constant temperature salt bath at 330-350℃ to cool it down rapidly. After cooling, lift the product into the heat treatment furnace for tempering heat treatment, heat it to 570-590℃ and hold it for 1-2 hours. After tempering, lift the product out and let it cool naturally in the air to room temperature to obtain the final product.

2. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, The temperature of the first molten iron during the first inoculation treatment is 1510–1520℃, and the temperature of the second molten iron during the spheroidizing treatment and the second inoculation treatment is 1470–1480℃.

3. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, In step S1, the mass percentage of pig iron is 15-25%, the mass percentage of scrap steel is 40-55%, the mass percentage of recycled material is 20-45%, the mass percentage of pretreatment agent is 0.5%, and the mass percentage of carburizing agent is 3.3-3.8% of the mass of scrap steel.

4. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, The first inoculant is a silicon-barium-calcium inoculant with a particle size of 3-8 mm, the second inoculant is an inoculum line, and the third inoculant is a silicon-barium-calcium inoculant with a particle size of 0.2-0.8 mm. The amount of the first inoculant added is 0.6 to 0.7% of the mass of the first molten iron. The amount of the second inoculant added is 13 to 18m per 980kg of the first molten iron. The feed speed is 25 to 30m / min. The amount of the third inoculant added is 0.1 to 0.15% of the mass of the first molten iron.

5. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, In step S3, the amount of low-magnesium spheroidizing wire added is 22-24m per 980kg, and the wire feeding speed is 32-36m / min.

6. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, In step S4, the pouring temperature is 1420–1430℃, and the pouring time is ≤8 min.

7. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, The casting process employs a two-part mold structure, with two symmetrically arranged balance shaft supports and the casting port positioned between the two molds.

8. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, The mass percentages of each element in the first batch of molten iron are as follows: C: 3.7–3.9%, Si: 1.2–1.5%, Mn: ≤0.3%, P: ≤0.035%, S: ≤0.035%, Cr: ≤0.03%.

9. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 1, characterized in that, It also includes heat treatment deformation control steps.

10. The heavy-duty lightweight commercial vehicle high-grade balance shaft bracket according to claim 9, characterized in that, The heat treatment deformation control steps include original heat treatment deformation prevention control and improved deformation prevention control. The original heat treatment deformation prevention control involves tilting the easily deformable parts upwards during the heat treatment process and securing the parts with wire. The improved deformation prevention control involves placing the heat-treated workpiece on a fixture with the push rod mounting assembly facing upwards, the balance shaft mounting assembly placed in the U-shaped groove of the fixture, and the frame connecting part corresponding to the balance shaft mounting part placed horizontally on the support platform of the fixture. The downwardly extending frame connecting part is clamped in the clamping groove of the fixture.

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