A method for casting a front axle main reducer housing

Abstract

A method for casting a front-axle main reducer housing includes the following steps: A. closing the upper mold and the lower mold; B. after the upper mold is closed on the lower mold, pressing the reset rod down, the front end face of the reset rod is flush with the parting surface, and the front section of the ejector rod fixed on the ejector plate is flush with the height of the mold cavity; C. casting and molding the casting; D. opening the upper and lower molds, and when the casting is ejected from the mold, the ejector rod and the reset rod are lifted up; E. after the casting is ejected from the mold, repeating steps A-D to cast the next casting. The present invention avoids welding suspension arms through reasonable mold design, so that the front-axle main reducer housing casting is a molded one-piece structure. The present invention uses core adhesive to bond cold iron to the surface of the sand core corresponding to the three openings of the main reducer housing casting. The cold iron cools faster than the sand core. The cold iron accelerates the local cooling rate of the main reducer housing casting, improves the density of the main reducer housing casting, and thus reduces the shrinkage defects of the product.

Description

Technical Field

[0001] The invention belongs to the field of casting, and in particular relates to a method for casting a front axle main reducer housing. Background Art

[0002] The main reducer housing is one of the important components of the drive axle. The main reducer housing is assembled on the front axle of the car.

[0003] The front axle final reducer housing is a large thin-walled casting (such as Figure 3 、 4 ), with a front nozzle A at the front end and two symmetrical bearing holes B at the rear. Near one of the bearing holes, the front axle final drive housing has an outwardly protruding suspension arm C, with a suspension hole at the end of the suspension arm. The front and rear sides of the suspension arm have concave structures C1, resulting in a complex structure. During the casting process, the front axle final drive housing (i.e., a large, thin-walled casting) is prone to shrinkage defects near the front nozzle and the inner end of the bearing holes, resulting in poor product density and low strength. Using such a low-strength front axle final drive housing can be dangerous during use.

[0004] Due to the special structure and position of the suspension arm, the front axle main reducer housing currently adopts a split casting. The suspension arm is cast separately and then welded to the main structure of the front axle main reducer housing.

[0005] There are many processing steps, and the quality of welding at the welding point will also affect the quality of the product. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for casting a front axle final reducer housing, which does not use welding processing and uses a mold to form an integrated structure of the front axle final reducer housing to ensure stable product quality.

[0007] The technical solution of the present invention is:

[0008] A method for casting a front axle main reducer housing, mold A

[0009] The mold includes a mold body consisting of an upper mold and a lower mold, a sand core placed in the mold body for forming the inner wall of the front axle final reducer housing, a ejector mechanism, a pouring system, and an exhaust rod;

[0010] The lower die is provided with a movable die for forming the suspension arm, the movable die comprising a side draw block, a second movable block matched with the side draw block, and a first movable block placed on the lower die for demoulding the suspension arm;

[0011] Chill 1 is installed on the sand core surface at the boss sidewall D on the inner end face of one bearing hole, while Chill 4 is installed on the sand core surface at the boss sidewall on the inner end face of the other bearing hole. Chills 2 and 3 are installed on the sand core surface at the inner wall E of the front end tube mouth. Chills 2 and 3 are interlocked to form a semicircle and bonded to the sand core. Due to the chilling effect of the chills, the thick and large parts of the casting's inner wall cool more quickly during solidification, thereby ensuring the internal structure density of these areas. The other two chills are placed on the sand core surfaces of the bearing holes on both sides. Similarly, they accelerate the solidification of the molten aluminum in these areas, ensuring that these areas do not suffer from quality issues such as looseness and shrinkage.

[0012] The ejection mechanism includes an ejection plate, an ejection fixing plate connected to the ejection plate, and an ejection rod. The reset rod and the ejection rod are installed and fixed between the ejection plate and the ejection fixing plate. The ejection plate and the ejection fixing plate press the reset rod and the end of the ejection rod to prevent them from moving back and forth. The length of the ejection rod is flush with the surfaces of different shapes in the mold cavity. The lengths of the ejection rods are different. The front end faces of the reset rods are flush with the parting surface of the mold and the lengths of the reset rods are the same. The reset rods function to push the ejection plate back. The reset rod pushes the ejection plate and the ejection fixing plate of the mold back, and the front section of the ejection rod fixed on the ejection plate is flush with the height of the mold cavity.

[0013] The mold also includes two cylindrical side core pullers for forming two bearing holes;

[0014] B. After the upper mold is closed on the lower mold, press the reset rod down so that the front end of the reset rod is flush with the parting surface, and the front section of the ejector rod fixed on the ejector plate is flush with the height of the mold cavity;

[0015] C casting molding;

[0016] D. When the upper and lower molds are opened and the casting is ejected from the mold, the ejector rod and the reset rod are lifted up;

[0017] After casting E is ejected from the mold, steps A to D are repeated to cast the next casting.

[0018] There is a withdrawal hole on the side of the lower mold that matches the side withdrawal block, and the outer end of the side withdrawal block is connected to the shock hammer through the support rod; the front end of the side withdrawal block has a molding surface for forming the concave structure on the rear side of the suspension arm, and the movable block 2 has a molding surface for forming the concave structure on the front side of the suspension arm. The design of the side withdrawal block, movable block 2 and movable block 1 enables the casting to smoothly escape from the mold cavity from the side.

[0019] The pouring system includes a pouring cup, a runner, and a riser. The pouring cup is arranged on the side of the position mold and installed on the lower mold. The gate subsidy is used to prevent the instantaneous flow of molten aluminum from being too large during pouring and overflowing from the top surface of the upper mold. The gate subsidy is installed on the top surface of the gate part of the upper mold, and its front side surface is tightly fitted with the inclined part of the pouring cup. The riser corresponds to the front end nozzle part of the main reducer housing and the bearing hole parts on both sides, providing sufficient molten aluminum shrinkage source for the thick and large hot nodes in this part.

[0020] The upper die is connected to the upper die connecting plate via an upper die connecting rod.

[0021] The ejection mechanism also includes a guide assembly, which includes a guide rod and a guide sleeve. The guide rod is inserted into the guide sleeve, and the guide sleeve is fixed in the mounting hole. There is an upper mounting hole on the ejection plate, and a lower mounting hole on the ejection fixing plate. The upper and lower mounting holes form a neat mounting hole, and the lower end surface of the upper mounting hole of the upper mounting hole has a recessed portion that matches the flange portion in the middle of the guide sleeve.

[0022] The lower end of the exhaust rod matches the exhaust rod hole on the upper mold, the exhaust rod head placed on the upper end of the ejector plate has a pulling hole, and the ejector plate and the ejector fixing plate have a clearance hole matching the exhaust rod.

[0023] Core making:

[0024] Core box heating: Connect the power cables of each electric heating tube, turn on the power, and heat the mold. The mold temperature is: 200°C-240°C for the static mold and 210°C-250°C for the dynamic mold. The dynamic mold temperature should be at least 10°C higher than the static mold temperature. Manually make the core two to three times. After the operation is correct and the sand core is qualified, use the KW957 shell core machine to use semi-automatic or fully automatic core making. Spray mold release agent on the cavity surface and adjust the sand shooting pressure, sand shooting time, and heating time. The sand shooting pressure is 0.4-0.6MPa, the sand shooting time is 4-7s, the shelling time is 1.5-2min, and the heating time is 5-6min. Use a saw blade to file the sand core parting seams, smooth the ejector pin marks and concave parts, and use core adhesive to bond the chiller to the sand core.

[0025] pouring:

[0026] Preheat the mold to 150-250°C; spray the coating, first spray the base material, then the outer layer. The thickness of the base material should be controlled at 0.1mm, and the thickness of the outer layer should be about 0.05-0.1mm. The pouring and riser should be sprayed with thermal insulation coating with a thickness of about 1.5-2mm. Continue to preheat the mold to 250-450°C to meet the pouring requirements.

[0027] Pouring: scrape off the paint on the parting surface, blow the mold clean, start the mold opener, and level the mold; accurately place the sand core into the lower mold cavity; scoop an appropriate amount of molten aluminum, pour it continuously and steadily, with a pouring time of 8-12 seconds and a temperature of 700-720℃. Self-inspect and mark castings with serious surface defects.

[0028] The processing steps after the casting is demoulded are:

[0029] a. Use a punch to flush out the sprue and runner;

[0030] b. Remove the riser: Place the casting on the band saw, position the casting, start the saw, and saw off the riser. The remaining height should not exceed 3-5mm.

[0031] c. Sand cleaning: Use a hammer to remove the seams, use a hammer to hit the thick parts of the casting and the processed surface, and use a vibrating sand cleaning machine to shake off the core sand and loose blocks;

[0032] d. Deburring: Use a chisel to remove the flash, burrs, and nodules on the inner and outer surfaces of the casting, and use an air shovel or grinder to remove the batch seams and nodules and grind them flat. The height of the parting burr on the non-machined surface must be within 1mm, and the height of the parting burr on the machined surface must not exceed 3mm;

[0033] eHeat treatment: castings are treated with T6 heat treatment, which is divided into two stages: aging treatment and solution treatment;

[0034] f Shot blasting: Place the castings into the drum shot blasting machine, with no more than 5 pieces placed each time, and the shot blasting time is 5-10 minutes; the appearance of the inner and outer surfaces is consistent; check whether there are holes on the inner and outer surfaces of the product, mark the holes if there are, scrape them open, weld them and then shot blast; the role and function of shot blasting are many: it not only removes rust and surface oxide scale, but also improves surface roughness, removes machining burrs on parts, eliminates internal stress of parts, reduces deformation of parts after heat treatment, and improves surface wear resistance and pressure bearing capacity of parts.

[0035] g Mechanical properties test: hardness ≥80HBS, tensile strength ≥270Mpa, elongation ≥7%;

[0036] h. Inspection of castings: Check whether there are defects such as pores, cold shuts and penetrating cracks on the surface of the castings. For pores with a diameter of less than 2mm on the non-machined surface, repair them. Defects that can be machined away on the machined surface are allowed to remain. The depth of the parting marks on the non-machined surface of the castings shall not exceed 1mm.

[0037] A casting mold for a front axle main reducer housing, characterized in that it comprises a mold body consisting of an upper mold and a lower mold, two cylindrical side core pullers for forming two bearing holes; a sand core placed in the mold body for forming the inner wall of the front axle main reducer housing; a movable mold for forming a suspension arm is provided on the lower mold, the movable mold comprising a side withdrawal block, a second movable block matched with the side withdrawal block, and a first movable block placed on the lower mold for allowing the suspension arm to be demoulded; a withdrawal hole matched with the side withdrawal block is provided on the side surface of the lower mold, the outer end of the side withdrawal block is connected to a shock hammer via a support rod; the front end of the side withdrawal block has a molding surface for molding an inward concave structure on the rear side surface of the suspension arm, and the second movable block has a molding surface for molding an inward concave structure on the front side surface of the suspension arm;

[0038] A first chill is provided on the sand core surface corresponding to the boss side wall D on the inner end face of one bearing hole, a fourth chill is provided on the sand core surface corresponding to the boss side wall on the inner end face of the other bearing hole, and two and three chills are provided on the sand core surface corresponding to the inner wall E of the front end pipe mouth.

[0039] The mold also includes a ejection mechanism; the ejection mechanism includes a ejection plate, a ejection fixing plate connected to the ejection plate, and an ejection rod. The reset rod and the ejection rod are both installed and fixed between the ejection plate and the ejection fixing plate. The ejection plate and the ejection fixing plate press the reset rod and the end of the ejection rod to prevent them from moving back and forth; the length of the ejection rod is flush with the surfaces of different shapes in the mold cavity, the lengths of the various ejection rods are inconsistent, the front end surface of each reset rod is flush with the parting surface of the mold, and the lengths of the reset rods are the same.

[0040] The mold also includes a pouring system and an exhaust rod; the pouring system includes a pouring cup, a runner, and a riser. The pouring cup is arranged on the side of the position mold and installed on the lower mold. The pouring gate is installed on the top surface of the upper mold gate. Its front side is tightly fitted with the inclined part of the pouring cup. The riser corresponds to the front end pipe mouth part of the main reducer housing and the bearing hole parts on both sides.

[0041] A casting mold for a front axle main reducer housing includes a mold body consisting of an upper mold and a lower mold, two cylindrical side core pullers mounted on the mold body for forming two bearing holes, and a sand core placed in the mold body for forming the inner wall of the front axle main reducer housing; the lower mold is provided with a movable module for forming a suspension arm, the movable module includes a side puller block and a movable block 1, the movable block 1 is arranged opposite to the side puller block, and the lower mold is also provided with a movable block 2 for allowing the suspension arm to be demolded.

[0042] There is a block hole on the side of the lower mold that matches the side pull-out block. The second movable block is placed above the suspension arm C, and there is a mounting recess on the lower mold that matches the second movable block.

[0043] The outer end of the side drawer block is connected to the jar hammer via a support rod.

[0044] The front end of the side drawer block has a forming surface for forming the concave structure of the rear side of the suspension arm, and the movable block 2 has a forming surface for forming the concave structure of the front side of the suspension arm.

[0045] A first chill is provided on the sand core surface corresponding to the inner wall of one bearing hole, a second chill is provided on the sand core surface corresponding to the inner end face of the other bearing hole, and three chills and three chills are provided on the sand core surface corresponding to the inner wall of the front end pipe mouth.

[0046] The mold also includes a ejection mechanism; the ejection mechanism includes a ejection plate, a ejection fixing plate connected to the ejection plate, and an ejection rod. The reset rod and the ejection rod are both installed and fixed between the ejection plate and the ejection fixing plate. The ejection plate and the ejection fixing plate press the reset rod and the end of the ejection rod to prevent them from moving back and forth; the length of the ejection rod is flush with the surfaces of different shapes in the mold cavity, the lengths of the various ejection rods are inconsistent, the front end surface of each reset rod is flush with the parting surface of the mold, and the lengths of the reset rods are the same.

[0047] The mold also includes a pouring system and an exhaust rod; the pouring system includes a pouring cup, a runner, and a riser. The pouring cup is arranged on the side of the position mold and installed on the lower mold. The pouring gate is installed on the top surface of the upper mold gate. Its front side is tightly fitted with the inclined part of the pouring cup. The riser corresponds to the front end pipe mouth part of the main reducer housing and the bearing hole parts on both sides.

[0048] The present invention avoids welding suspension arms through reasonable mold design, so that the front axle main reducer housing casting is a molded integrated structure.

[0049] After research, the inventors discovered that because the walls at the three openings of the main reducer housing are thicker than those in other parts of the housing, the main reducer housing casting suffers from insufficient structural density during solidification in these thick-walled areas, which is prone to shrinkage defects and low yields. The present invention employs core bonding adhesive to attach chills to the surfaces of the sand cores at the three openings of the main reducer housing casting. The chills cool faster than the sand cores, accelerating the local cooling rate of the main reducer housing casting and improving the density of the main reducer housing casting, thereby reducing shrinkage defects in the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a structural schematic diagram of the casting mold of the present invention;

[0051] Figure 2 yes Figure 1 A top view of

[0052] Figure 3 This is one of the structural diagrams of the main reducer housing;

[0053] Figure 4 This is the second structural diagram of the main reducer housing;

[0054] Figure 5 It is the main view of the lower die;

[0055] Figure 6 This is the bottom view of the lower die;

[0056] Figure 7 It is a side view of the lower die;

[0057] Figure 8 It is a structural diagram of the side draw block;

[0058] Figure 9 yes Figure 8 Side view of;

[0059] Figure 10 This is a schematic diagram of the structure of the movable block 2;

[0060] Figure 11 This is a top view of Activity 2;

[0061] Figure 12 It is a structural diagram of movable block 1;

[0062] Figure 13 It is a side view of movable block 2. DETAILED DESCRIPTION

[0063] The method for casting a front axle final reducer housing of the present invention comprises the following steps:

[0064] A mold closing

[0065] like Figure 1 、 2 The mold includes a mold body composed of an upper mold 3 and a lower mold 2, a sand core placed in the mold body for forming the inner wall of the front axle final reducer housing, a material ejection mechanism, a pouring system, and an exhaust rod 7;

[0066] The lower mold 2 is provided with a movable mold for molding the suspension arm, the movable mold comprising a side withdrawal block 18, a second movable block 26 cooperating with the side withdrawal block 18, and a first movable block 25 placed on the lower mold 2 for allowing the suspension arm to be demoulded;

[0067] Chill 1 (27) is installed on the sand core surface at the boss sidewall D on the inner end face of one bearing hole. Chill 4 (30) is installed on the sand core surface at the boss sidewall on the inner end face of the other bearing hole. Chills 3 (29) and 2 (28) are installed on the sand core surface at the inner wall E of the front end tube mouth. Chills 3 (29) and 2 (28) are interlocked to form a semicircle and bonded to the sand core. Due to the chilling effect of the chills, the thicker areas of the casting's inner wall cool more quickly during solidification, thereby ensuring the internal structure density of these areas. Two other chills are placed on the sand core surfaces of the bearing holes on either side. Similarly, they accelerate the solidification of the molten aluminum in these areas, ensuring that these areas do not suffer from quality issues such as porosity and shrinkage.

[0068] The ejection mechanism includes an ejection plate 9, an ejection fixing plate 10 connected to the ejection plate 9, and an ejection rod 15. The reset rod 14 and the ejection rod 15 are all installed and fixed between the ejection plate and the ejection fixing plate. The ejection plate 9 and the ejection fixing plate 10 press the reset rod 14 and the end of the ejection rod 15 to prevent them from moving back and forth; the length of the ejection rod 15 is flush with the surfaces of different shapes in the mold cavity, the lengths of the various ejection rods 15 are inconsistent, the front end faces of the reset rods 14 are flush with the parting surface of the mold, and the lengths of the reset rods 14 are the same; the function of the reset rod 14 is to push the ejection plate back; the reset rod 14 pushes the ejection plate and the ejection fixing plate of the mold back, and the front section of the ejection rod fixed on the ejection plate is flush with the height of the mold cavity.

[0069] The mold also includes two cylindrical side pulls 17 for forming the two bearing holes. The side of the lower mold 2 has pull-out holes that mate with side pull-out blocks 18. The outer ends of the side pull-out blocks 18 are connected to a jarring hammer 19 via support rods 20. The front end of the side pull-out blocks 18 has a molding surface for forming the concave structure on the rear side of the cantilever arm, while the second movable block 26 has a molding surface for forming the concave structure on the front side of the cantilever arm. The design of the side pulls 18, the second movable block 26, and the first movable block 25 allows the casting to be smoothly ejected from the mold cavity from the side. The curved surface 261 of the second movable block 26 mates with the cylindrical side pulls 17.

[0070] The pouring system includes a pouring cup 1, a runner, and a riser. The pouring cup 1 is set on the side of the position mold and installed on the lower mold. The gate pad 4 is used to prevent the instantaneous flow of molten aluminum from being too large during pouring and overflowing from the top surface of the upper mold. The gate pad 4 is installed on the top surface of the upper mold gate area, and its front side is tightly fitted with the inclined surface of the pouring cup. The riser corresponds to the front nozzle area of ​​the main reducer housing and the bearing holes on both sides, providing a sufficient source of molten aluminum shrinkage for the thick and large hot sections in this area. The upper mold 3 is connected to the upper mold connecting plate 6 via the upper mold connecting rod 5. The ejection mechanism also includes a guide assembly, which includes a guide rod 12 and a guide sleeve 13. The guide rod 12 is inserted into the guide sleeve, and the guide sleeve is fixed in the mounting hole. The ejection plate 9 has an upper mounting hole, and the ejection fixing plate 10 has a lower mounting hole. The upper and lower mounting holes form a smooth mounting hole. The lower end surface of the upper mounting hole has a recess that matches the flange portion in the middle of the guide sleeve. The lower end of the exhaust rod 7 cooperates with the exhaust rod hole on the upper mold 3, and the head of the exhaust rod 7 placed on the upper end of the ejector plate 9 has a pulling hole, and the ejector plate 9 and the ejector fixing plate 10 have a clearance hole that cooperates with the exhaust rod 7.

[0071] B After the upper mold is closed on the lower mold, the reset rod 14 is pressed down, and the front end surface of the reset rod 14 is flush with the parting surface. The front section of the ejector rod fixed on the ejector plate is flush with the height of the mold cavity;

[0072] C casting molding;

[0073] D. When the upper and lower molds are opened and the casting is ejected from the mold, the ejector rod 15 and the reset rod 14 are lifted up;

[0074] After casting E is ejected from the mold, steps A to D are repeated to cast the next casting.

[0075] The core making method is:

[0076] Core box heating: Connect the power cables of each electric heating tube, turn on the power, and heat the mold. The mold temperature is: 200°C-240°C for the static mold and 210°C-250°C for the dynamic mold. The dynamic mold temperature should be at least 10°C higher than the static mold temperature. Manually make the core two to three times. After the operation is correct and the sand core is qualified, use the KW957 shell core machine to use semi-automatic or fully automatic core making. Spray mold release agent on the cavity surface and adjust the sand shooting pressure, sand shooting time, and heating time. The sand shooting pressure is 0.4-0.6MPa, the sand shooting time is 4-7s, the shelling time is 1.5-2min, and the heating time is 5-6min. Use a saw blade to file the sand core parting seams, smooth the ejector pin marks and concave parts, and use core adhesive to bond the chiller to the sand core.

[0077] The pouring method is:

[0078] Preheat the mold to 150-250°C; spray the coating, first spray the base material, then the outer layer. The thickness of the base material should be controlled at 0.1mm, and the thickness of the outer layer should be about 0.05-0.1mm. The pouring and riser should be sprayed with thermal insulation coating with a thickness of about 1.5-2mm. Continue to preheat the mold to 250-450°C to meet the pouring requirements.

[0079] Pouring: scrape off the paint on the parting surface, blow the mold clean, start the mold opener, and level the mold; accurately place the sand core into the lower mold cavity; scoop an appropriate amount of molten aluminum, pour it continuously and steadily, with a pouring time of 8-12 seconds and a temperature of 700-720℃. Self-inspect and mark castings with serious surface defects.

[0080] The processing steps after the casting is demoulded are:

[0081] a. Use a punch to flush out the sprue and runner;

[0082] b. Remove the riser: Place the casting on the band saw, position the casting, start the saw, and saw off the riser. The remaining height should not exceed 3-5mm.

[0083] c. Sand cleaning: Use a hammer to remove the seams, use a hammer to hit the thick parts of the casting and the processed surface, and use a vibrating sand cleaning machine to shake off the core sand and loose blocks;

[0084] d. Deburring: Use a chisel to remove the flash, burrs, and nodules on the inner and outer surfaces of the casting, and use an air shovel or grinder to remove the batch seams and nodules and grind them flat. The height of the parting burr on the non-machined surface must be within 1mm, and the height of the parting burr on the machined surface must not exceed 3mm;

[0085] eHeat treatment: castings are treated with T6 heat treatment, which is divided into two stages: aging treatment and solution treatment;

[0086] f Shot blasting: Place the castings into the drum shot blasting machine, with no more than 5 pieces placed each time, and the shot blasting time is 5-10 minutes; the appearance of the inner and outer surfaces is consistent; check whether there are holes on the inner and outer surfaces of the product, mark the holes if there are, scrape them open, weld them and then shot blast; the role and function of shot blasting are many: it not only removes rust and surface oxide scale, but also improves surface roughness, removes machining burrs on parts, eliminates internal stress of parts, reduces deformation of parts after heat treatment, and improves surface wear resistance and pressure bearing capacity of parts.

[0087] g Mechanical properties test: hardness ≥80HBS, tensile strength ≥270Mpa, elongation ≥7%;

[0088] h. Inspection of castings: Check whether there are defects such as pores, cold shuts and penetrating cracks on the surface of the castings. For pores with a diameter of less than 2mm on the non-machined surface, repair them. Defects that can be machined away on the machined surface are allowed to remain. The depth of the parting marks on the non-machined surface of the castings shall not exceed 1mm.

[0089] The main steps of aluminum alloy smelting are as follows:

[0090] ①Charging: Put the prefabricated alloy ingot, high-quality recycled materials into the preheated crucible, then add the mid-fol alloy, and finally add the alloying elements.

[0091] ② Temperature control. Strictly control the temperature of aluminum alloy melting. Only the appropriate temperature can produce high-quality alloy liquid, and avoid overheating. If the temperature is too high, the oxidation and burning of various elements in the alloy will increase, causing changes in the chemical composition of the alloy. If the temperature is too low, the chemical composition of the alloy will be uneven, and the oxidation inclusions and gases in the alloy will be difficult to discharge. The physical and chemical properties of the alloy will decline, affecting the casting performance.

[0092] ③ Time control. Strictly control the melting time and operate quickly to reduce alloy absorption and oxidation inclusions, increase the burnout of alloy elements, and affect the chemical composition of the alloy.

[0093] ④ Refining operation. The main purpose of aluminum alloy refining is to remove gas and non-metallic inclusions in the melt and to make the alloy composition uniform. Refining is an extremely important process in smelting. The refining agent should be selected correctly, the addition amount should be controlled, generally 0.5%-0.7% of the alloy mass, and the refining temperature should be controlled. The refining temperature is generally controlled at 700-720°C. During the refining process, the refining agent is pressed into the melt in batches about 2 / 3 below the surface using a bell jar, and rotated evenly and slowly in a clockwise direction. The speed should be slow and the movement should be steady to avoid large-scale stirring of the molten metal to prevent an increase in hydrogen content and the inclusion of inclusions.

[0094] ⑤Deterioration treatment.

[0095] The purpose of alloy modification is to refine the grain size and improve casting performance. The modifier should be preheated. Key control points are: ① The modification temperature should generally not exceed 740°C; ② The modification time should generally be 10 minutes; ③ The amount of modifier added (for two-color modifiers, the dosage is generally 1.0%-1.2% of the alloy mass); and ④ Proper operation methods. After alloy refining, pouring should be completed as quickly as possible. Sand casting should generally be completed within 40 minutes, and metal mold casting within 2 hours. Otherwise, refining and modification are required, with the refining agent added during the second refining process being approximately 0.2% of the alloy mass.

[0096] The specific method of charging the furnace to melt the aluminum liquid for pouring is:

[0097] The returned materials are smashed into small pieces and loaded into the bottom of the furnace. Then, some of the aluminum ingots and crystalline silicon in the new materials are mixed and placed in the furnace. The materials should be mixed with large and small pieces to improve the density until the industrial frequency furnace is full.

[0098] Power on for melting, and add new charge as it melts until all charge (except titanium additive, magnesium, and antimony) is added. After all charge is melted, heat up to 730℃ and turn off the power. Add titanium additive and antimony first, then magnesium. Press the bell jar into the center of the furnace and move it gently to allow the magnesium to diffuse around.

[0099] Power on to increase the temperature, use magnetic stirring to homogenize the Ti and Sb elements, and turn off the power when the smelting temperature reaches 730-760℃;

[0100] Take the spectrum analysis test block for spectrum analysis, and adjust the chemical composition to meet the requirements according to the analysis results;

[0101] After the composition is qualified, the power is turned on and the temperature is raised to 760-770℃. After the power is turned off, the molten aluminum is transferred to the holding furnace. The transfer should be completed within 30 minutes. Before transfer, the subcontract temperature is preheated to 400-450℃, and the holding crucible furnace is preheated to 730-750℃.

[0102] Refining and modification

[0103] Sprinkle an appropriate amount of aluminum deslagging agent onto the surface of the molten aluminum in the holding furnace. Use a slag skimmer to rub the slag in a "frying" manner. When the slag and aluminum are clearly separated, remove the slag from the liquid surface. Adjust the temperature of the molten aluminum to 720-740℃ and sprinkle strontium salt modifier (0.8-1% of the weight of the new aluminum liquid) onto the liquid surface.

[0104] Turn on the argon cylinder switch of the refiner, adjust the flow meter so that the reading is 5-10L, use the crane to place the refining rotor head into the holding furnace, the depth of which should not be less than half of the furnace body, and set the refining time of the refiner according to the air humidity (when the humidity is less than 50%, the refining time is set to 5 minutes; when the humidity is 50%≤humidity≤75%, it is set to 6 minutes; when the humidity is greater than 75%, it is set to 8 minutes).

[0105] Start the refining machine and after refining, use a slag skimmer to rub the strontium salt modifier in a "frying" manner and remove the slag, and use a slag skimmer to clean the slag on the liquid surface.

[0106] After refining and modification, the molten aluminum should be sampled immediately to check the refining effect (measure hydrogen content). The hydrogen test requires a density of 2.59 g / cm³ or higher to qualify. Otherwise, re-refining and degassing are required until the requirements are met. A fracture inspection should also be performed. One set of test bars and test blocks should be poured per furnace. The pouring temperature should be 720-740°C. Three test blocks should be collected from each furnace, with one sample taken after melting, after modification, and mid-pouring. Three test bars should be sampled 15 minutes after modification. The test bars and test blocks should be clearly labeled (date, furnace number, and code) as required.

[0107] The time from deterioration to completion of pouring shall not exceed 3 hours to prevent deterioration from failing. Otherwise, it is necessary to re-refine and deteriorate, and add a certain amount of magnesium. The amount of magnesium added should account for 0.04~0.05% of the weight of the remaining molten aluminum.

[0108] T6 heat treatment and aging treatment: (Equipment: aluminum alloy aging furnace)

[0109] Aging treatment involves heating solution-treated aluminum alloy castings to a certain temperature, holding them at that temperature for a certain period of time, then removing them from the furnace and slowly cooling them to room temperature in air. Aging hardening performed at room temperature is called natural aging, while aging hardening performed above room temperature and after a period of holding is called artificial aging. Aging treatment involves the spontaneous decomposition of the supersaturated solid solution, restoring the alloy matrix lattice to a relatively stable state.

[0110] The choice of aging temperature and time depends on the required alloy properties, the alloy's characteristics, the degree of supersaturation of the solid solution, and the casting method. Artificial aging can be divided into three categories: incomplete artificial aging, complete artificial aging, and overaging. Incomplete artificial aging uses relatively low aging temperatures or short holding times to achieve excellent overall mechanical properties, namely, relatively high strength, good ductility, and toughness, but may result in lower corrosion resistance. Complete artificial aging uses higher aging temperatures and longer holding times to achieve maximum hardness and tensile strength, but lower elongation. Overaging is carried out at higher temperatures, where the alloy maintains high strength while improving ductility, primarily to achieve good stress corrosion resistance. To achieve stable microstructure and geometric dimensions, aging should be carried out at higher temperatures. Overaging is generally divided into stabilization and softening treatments depending on the intended use.

[0111] Solution treatment: (Equipment: Aluminum alloy solution quenching furnace)

[0112] Solution treatment involves heating the casting to the highest possible temperature, close to the melting point of the eutectic. The higher the temperature, the faster the dissolution of the strengthening elements, and the greater the strengthening effect. The upper limit of the heating temperature is generally below the temperature at which the alloy begins to overheat, while the lower limit is set to allow as much of the strengthening component as possible to dissolve into the solid solution. This temperature is maintained long enough to maximize the dissolution of the strengthening component. This high temperature state is then stabilized and stored at room temperature. The holding time is determined by the dissolution rate of the strengthening elements, which depends on the alloy type, composition, structure, casting method, and the shape and wall thickness of the casting.

[0113] During quenching, rapid cooling is applied to the casting. The faster the cooling rate, the higher the supersaturation temperature at which the solid solution remains from its high temperature state, resulting in higher mechanical properties. However, this also increases the internal stresses formed, increasing the likelihood of deformation, making the cooling medium temperature highly sensitive. This process is called solution treatment. Solution treatment can improve the strength and plasticity of the casting and enhance the corrosion resistance of the alloy. The quenching transition time during solution heat treatment should be as short as possible, generally no longer than 15 seconds, to prevent diffusion and precipitation of alloying elements, which could degrade the alloy's properties.

Claims

1. A method for casting a front axle final reducer housing, characterized in that: The following steps are involved: A mold closing The mold includes a mold body consisting of an upper mold (3) and a lower mold (2), a sand core placed in the mold body for forming the inner wall of the front axle main reducer housing, a material ejection mechanism, a pouring system, and an exhaust rod (7); The lower mold (2) is provided with a movable mold for forming the suspension arm, the movable mold comprising a side withdrawal block (18) and a movable block (25), the movable block (25) being arranged opposite to the side withdrawal block (18), and the lower mold (2) is further provided with a movable block (26) for demoulding the suspension arm; A sand core surface corresponding to the boss side wall D of the inner end face of one bearing hole is provided with a chill 1 (27), a sand core surface corresponding to the boss side wall of the inner end face of the other bearing hole is provided with a chill 4 (30), and a sand core surface corresponding to the inner wall E of the front end pipe mouth is provided with a chill 3 (29) and a chill 2 (28); The ejection mechanism comprises an ejection plate (9), an ejection fixing plate (10) connected to the ejection plate (9), and an ejection rod (15). The reset rod (14) and the ejection rod (15) are both installed and fixed between the ejection plate and the ejection fixing plate. The ejection plate (9) and the ejection fixing plate (10) press the reset rod (14) and the end of the ejection rod (15) to prevent them from moving back and forth. The length of the ejection rod (15) is flush with the surfaces of different shapes in the mold cavity. The lengths of the ejection rods (15) are different. The front end faces of the reset rods (14) are flush with the parting surface of the mold. The reset rods (14) are the same length. The mold also includes two cylindrical side core pullers (17) for forming two bearing holes; After the upper mold B is closed on the lower mold, the reset rod (14) is pressed down, the front end surface of the reset rod (14) is flush with the parting surface, and the front section of the ejector rod fixed on the ejector plate is flush with the height of the mold cavity; C casting molding; D. The upper and lower molds are opened, and when the casting is ejected from the mold, the ejector rod (15) and the reset rod (14) are lifted up; After casting E is ejected from the mold, steps A to D are repeated to cast the next casting.

2. The method for casting a front axle final reducer housing according to claim 1, characterized in that: The side of the lower mold (2) has a block hole that matches the side pull-out block (18), and the outer end of the side pull-out block (18) is connected to the shock hammer (19) through the support rod (20); the front end of the side pull-out block (18) has a molding surface for molding the concave structure of the rear side of the suspension arm, and the movable block (25) has a molding surface for molding the concave structure of the front side of the suspension arm.

3. The method for casting a front axle final reducer housing according to claim 1, characterized in that: The pouring system includes a pouring cup (1), a runner, and a riser. The pouring cup (1) is arranged on the side of the position mold and installed on the lower mold. The pouring gate supplement (4) is installed on the top surface of the pouring part of the upper mold. Its front side is tightly fitted with the inclined part of the pouring cup. The riser corresponds to the front end nozzle part of the main reducer housing and the bearing hole parts on both sides, providing a sufficient source of aluminum liquid shrinkage for the thick and large hot section of this part.

4. The method for casting a front axle final reducer housing according to claim 1, characterized in that: The upper die (3) is connected to the upper die connecting plate (6) via an upper die connecting rod (5).

5. The method for casting a front axle final reducer housing according to claim 1, characterized in that: The ejection mechanism also includes a guide assembly, which includes a guide rod (12) and a guide sleeve (13). The guide rod (12) is inserted into the guide sleeve, and the guide sleeve is fixed in the mounting hole. An upper mounting hole is provided on the ejection plate (9), and a lower mounting hole is provided on the ejection fixing plate (10). The upper and lower mounting holes form a neat mounting hole, and the lower end surface of the upper mounting hole has a recessed portion that matches the flange portion in the middle of the guide sleeve.

6. The method for casting a front axle final reducer housing according to claim 1, characterized in that: The lower end of the exhaust rod (7) cooperates with the exhaust rod hole on the upper mold (3), and the head of the exhaust rod (7) placed on the upper end of the ejector plate (9) has a pulling hole, and the ejector plate (9) and the ejector fixing plate (10) have a clearance hole that cooperates with the exhaust rod (7).

7. The method for casting a front axle final reducer housing according to claim 1, characterized in that: Core making: Core box heating: Connect the power cables of each electric heating tube, turn on the power, and heat the mold. The mold temperature is: 200°C-240°C for the static mold and 210°C-250°C for the dynamic mold. The dynamic mold temperature should be at least 10°C higher than the static mold temperature. Manually make the core two to three times. After the operation is correct and the sand core is qualified, use the KW957 shell core machine to use semi-automatic or fully automatic core making. Spray mold release agent on the cavity surface and adjust the sand shooting pressure, sand shooting time, and heating time. The sand shooting pressure is 0.4-0.6MPa, the sand shooting time is 4-7s, the shelling time is 1.5-2min, and the heating time is 5-6min. Use a saw blade to file the sand core parting seams, smooth the ejector pin marks and concave parts, and use core adhesive to bond the chiller to the sand core. pouring: Preheat the mold so that the surface reaches 150-250°C; Spray the coating, first spray the base material, then spray the outer layer. The thickness of the base material should be controlled at 0.1mm, and the thickness of the outer layer should be 0.05-0.1mm. The pouring and riser should be sprayed with thermal insulation coating with a thickness of 1.5-2mm. Continue to preheat the mold to 250-450°C to meet the pouring requirements. Pouring: scrape off the paint on the parting surface, blow the mold clean, start the mold opener, and level the mold; accurately place the sand core into the lower mold cavity; scoop an appropriate amount of molten aluminum, pour it continuously and steadily, with a pouring time of 8-12 seconds and a temperature of 700-720℃. Self-inspect and mark castings with serious surface defects. The processing steps after the casting is demoulded are: a. Use a punch to flush out the sprue and runner; b. Remove the riser: Place the casting on the band saw, position the casting, start the saw, and saw off the riser. The remaining height should not exceed 3-5mm. c. Sand cleaning: Use a hammer to remove the seams, use a hammer to hit the thick parts of the casting and the processed surface, and use a vibrating sand cleaning machine to shake off the core sand and loose blocks; d. Deburring: Use a chisel to remove the flash, burrs, and nodules on the inner and outer surfaces of the casting, and use an air shovel or grinder to remove the batch seams and nodules and grind them flat. The height of the parting burr on the non-machined surface must be within 1mm, and the height of the parting burr on the machined surface must not exceed 3mm; eHeat treatment: castings are treated with T6 heat treatment, which is divided into two stages: aging treatment and solution treatment; f. Shot blasting: put the castings into the drum shot blasting machine, no more than 5 pieces at a time, and the shot blasting time is 5-10 minutes; The appearance of the inner and outer surfaces is consistent; Check whether there are holes on the inner and outer surfaces of the product. If there are holes, mark them, scrape them open, weld them and then shot blast them. g Mechanical properties test: hardness ≥80HBS, tensile strength ≥270Mpa, elongation ≥7%; h. Inspection of castings: Check whether there are defects such as pores, cold shuts and penetrating cracks on the surface of the castings. For pores with a diameter of less than 2mm on the non-machined surface, repair them. Defects that can be machined away on the machined surface are allowed to remain. The depth of the parting marks on the non-machined surface of the castings shall not exceed 1mm.

8. A casting mold for a front axle main reducer housing, characterized by: It comprises a mold body consisting of an upper mold (3), a lower mold (2), two cylindrical side core pullers (17) for forming two bearing holes; and a sand core placed in the mold body for forming the inner wall of the front axle main reducer housing; The lower die (2) is provided with a movable die for forming the suspension arm, the movable die including a side withdrawal block (18) and a movable block (25), the movable block (25) being arranged opposite to the side withdrawal block (18), and the lower die (2) being provided with a movable block (26) for demoulding the suspension arm, a block hole for matching with the side withdrawal block (18) being provided on the side surface of the lower die (2), the movable block (26) being placed above the suspension arm C, and a mounting recess for matching with the movable block (26) being provided on the lower die; the outer end of the side withdrawal block (18) is connected to the shock hammer (19) via the support rod (20); A sand core surface corresponding to the boss side wall D of the inner end face of one bearing hole is provided with a chill 1 (27), a sand core surface corresponding to the boss side wall of the inner end face of the other bearing hole is provided with a chill 4 (30), and a sand core surface corresponding to the inner wall E of the front end pipe mouth is provided with a chill 3 (29) and a chill 2 (28).

9. The front axle final reducer housing casting mold according to claim 8, characterized in that: The mold further includes a ejection mechanism; the ejection mechanism includes an ejection plate (9), an ejection fixing plate (10) connected to the ejection plate (9), and an ejection rod (15); the reset rod (14) and the ejection rod (15) are both installed and fixed between the ejection plate and the ejection fixing plate; the ejection plate (9) and the ejection fixing plate (10) press the reset rod (14) and the end of the ejection rod (15) to prevent them from moving back and forth; the length of the ejection rod (15) is flush with the surfaces of different shapes in the mold cavity, the lengths of the ejection rods (15) are different, the front end faces of the reset rods (14) are flush with the parting surface of the mold, and the lengths of the reset rods (14) are the same.

10. The front axle final reducer housing casting mold according to claim 8, characterized in that: The mold further comprises a pouring system and an exhaust rod (7); the pouring system comprises a pouring cup (1), a runner, and a riser, wherein the pouring cup (1) is arranged on the side of the mold and mounted on the lower mold, and the pouring patch (4) is mounted on the top surface of the pouring portion of the upper mold, and its front side surface is tightly fitted with the inclined portion of the pouring cup, and the riser corresponds to the front end nozzle portion of the main reducer housing and the bearing hole portions on both sides.

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