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With the development of China's automobile industry, motorcycle industry and other processing industries, the demand for involute toothed spline shafts is increasing, and all manufacturers of involute toothed spline shafts urgently need one. An efficient, economical, and practical manufacturing process for processing involute splined portions. Practice has shown that it is suitable to process the splines of the involute spline shaft by cold extrusion.
1 Cold extrusion principle of involute tooth spline The gear shaft is the shifting shaft of a miniature car transmission. The tooth profile parameters are: number of teeth Z = 12, modulus M = 1.25, pressure angle α = 20 °, change The bit coefficient X=0.60, the tip circle diameter da=16.75mm, the root circle diameter df=14.0mm, the involute spline effective length is 44mm; the involute spline part is connected with the shift fork, and the shifting is changed. The role of the file. Since the involute tooth spline and the shifting fork are only the transmission torque, the spline has low requirements on the motion accuracy of the tooth profile. Involute gear parts that do not require high motion accuracy are suitable for mass production using cold extrusion.
The cold extrusion of the involute spline is mainly processed by the reduced diameter extrusion method. The forming process of the extrusion die is installed on the work surface of the extrusion equipment, and the workpiece blank is installed in the upper and lower mold cavities; When the upper die is moved downward, the workpiece blank is forced into the toothed cavity of the extrusion die; as the upper die of the die is moved downward, the toothed cavity of the die is deformed by contact with the blank to deform it. That is, the same tooth shape as the extrusion die is pressed out on the outer surface of the workpiece blank.
2 Preparation of Cold Extrusion Blank of Involute Toothed Spline Shaft 2.1 Formulation of Cold Extrusion Drawing The toothed part of the gear shaft is processed by cold extrusion, and the tooth shape after cold extrusion processing The design requirements of the part can be achieved without subsequent processing; the outer hexagonal and groove parts of the part must be processed by subsequent machining methods; for the shaft part of the part, due to its high precision requirements and high surface quality requirements, Leave the machining allowance.
2.2 Determination of the diameter of the extruded blank of the toothed part In the cold extrusion process, the correct determination of the diameter of the extruded part of the toothed part is one of the key factors determining the success or failure of the extrusion process.
The correct extruded blank diameter is generally near the indexing circle (or the median diameter of the tooth) and is expressed by the formula: dm=d±Δd where: dm is the diameter of the extruded blank; d is the gear indexing circle of the part ( Or medium diameter) diameter; Δd is the amount of change in diameter, which is determined by the structure and material properties of the extrusion.
The diameter of the extruded blank determined by the above formula is only a theoretical value, and the final diameter needs to be determined in the test.
2.3 Preparation of extruded blank 2.3.1 The shearing and blanking of the original blank is cut and cut by J23-35 punching machine. It is required that the cut blank of the blank is flat, the roundness difference is less than 0.50mm, and the unevenness is not more than 0.60mm. The mass error is 1.0%. According to the above requirements, in order to ensure the roundness error after cutting, the gap between the inner hole of the fixed scissors and the raw material is 0.2~0.4mm; in order to ensure the flatness of the fracture, the punching gap should be as small as possible, actually take 0.2 ~0.4mm.
2.3.2 Local hot rolling blank The small-sized medium frequency induction heating furnace (the power of which is 20 kW) is used to locally heat the head of the original blank, and the heating temperature is 1000-1100 °C. Partial upsetting was then carried out on a J23-100 type 100t punch.
2.3.3 Softening Annealing of Hot Billet Blanks Since the material of the spline guide shaft is medium and high strength structural steel 45 steel, the bar material in the supply state has high strength and hardness, and the internal structure is uneven. Therefore, the material of the extruded blank must be softened and annealed before cold extrusion, and the hardness after annealing is 140-170HBS to improve the cutting performance and plastic deformation property of the material and reduce the deformation resistance.
2.3.4 Processing of extruded blanks The annealed blanks are processed on a lathe. When processing extruded blanks, it is required that each step should have better coaxiality requirements, and the surface quality should not be too bad.
2.3.5 Surface lubrication treatment of extruded blanks During the cold extrusion forming process of involute splines, the deformation area is concentrated near the tooth shape, and the metal flow at this place is very intense, and the degree of deformation is extremely large; A toothed extrusion with good surface quality must be surface lubricated for the extruded blank after machining. In the process, the extruded blank is surface-treated with a phosphating solution containing zinc phosphate as a main raw material, and then surface-lubricated by using molten stearic acid soap as a saponification liquid.
3 tooth-shaped mold structure design and manufacturing process 3.1 cold extrusion forming die structure characteristics The cold extrusion die structure is characterized by: 1 the upper and lower mold guiding is guided by the guiding sleeve, the guiding precision is higher; 2 mold The structure is relatively simple, the mold processing, replacement and adjustment are very convenient; 3 the upper mold is fastened by the fastening nut, and the lower mold is fastened by the lower mold pressing plate, which is beneficial to the "centering" of the upper and lower molds.
3.2 Structural design of the toothed core The involute spline extrusion toothed core is designed to select the appropriate tooth profile and tooth diameter, determine the extrusion transition, the extrusion section and the ejection return. The angle of the segment 3.2.1 The tooth profile of the toothed core design The tooth profile design of the core is required to be able to coldly extrude the desired workpiece tooth profile according to the specified tooth thickness and tooth height, so the modulus of the core tooth profile and The number of teeth is the same as the workpiece; considering the thermal expansion and contraction of the extruded workpiece and the elastic recovery of the die and the extruded workpiece, the pressure angle or displacement coefficient of the core tooth shape cannot be the tooth pressure angle of the spline shaft part or The displacement coefficient is the same.
Normally, the core tooth-shaped displacement coefficient is corrected while keeping the pressure angle constant. The displacement coefficient X of the core tooth profile is mainly related to the modulus M of the gear part, the pressure angle α and the degree of extrusion deformation ε, which can be expressed by the following empirical formula: X=Xo-λM-ηα/180-ξε Where: X is the displacement coefficient of the core tooth shape; Xo is the displacement coefficient of the gear part; λ is the correction coefficient of the modulus M, which is related to the modulus M of the gear; η is the correction coefficient of the pressure angle α, and The pressure angle α of the gear is related; the correction coefficient of the degree of deformation ε is determined by the geometry of the gear part, the shape and size of the extruded blank, and the properties of the extruded material.
The tooth-shaped deformation coefficient determined by the above formula is only a theoretical value, and the final value of the displacement coefficient needs to be determined in the test.
In addition, in consideration of the problem that the cold extrusion forming force and the extrusion tooth shape can be assembled without subsequent processing, the height of the tooth tip of the core is smaller than the root height of the tooth profile of the workpiece, and the root height of the extrusion core is high. The crest is larger than the tooth profile of the workpiece.
3.2.2 Extrusion transition section of the toothed core The design of the extrusion transition section of the toothed core is mainly to select the appropriate slope. When the inclination is too large, although the flow of metal is short and the friction is low, the radial pressure component during extrusion is large, so that the axial pressure component required for extrusion is reduced, which increases The forming force of the extrusion makes the axial flow of the metal difficult, thereby causing the "upset" of the extruded blank, making extrusion difficult to continue. When the inclination is too small, the metal has a long flow path and a large frictional force, which also causes difficulty in metal flow during extrusion.
In the present process, the inclination angle α of the extrusion transition section of the core is preferably 22.5 to 30°.
3.2.3 Length of the extrusion section of the toothed core The length of the extrusion section of the toothed core has a certain influence on the quality of the toothed part after extrusion. The length C of the extrusion section is most suitable from 2.5 to 8.0 mm; if the length of the extrusion section is C>8.0 mm, the frictional force of the metal flow is greatly increased, the metal flow is difficult, and the rod portion of the extrusion member is easily bent and unstable. Therefore, the normal production of the extrusion is affected; and when the length of the extrusion section is c < 2.5 mm, although the metal flow is easy and the forming force is small, the extruded tooth portion is easily distorted.
3.2.4 Top-out return section of the toothed core design The design method of the top-out return section of the toothed core is similar to that of the extrusion transition section, mainly selecting the appropriate slope. When the inclination is too large, although the metal flow is short in flow and low in friction, it is easy to be extruded. However, in the process of ejecting and returning, since the guide section is small, it is easy to cause the "upset" of the extrusion, so that the extrusion It is difficult to eject. When the inclination is too small, the ejector guide section is long, and the extrusion member is easy to eject, but since the metal flow path is long and the friction is large during the backlog, it is difficult to perform normally during the extrusion process. In the present process, it is preferable that the inclination angle β of the ejection return section of the core is 45 to 60°.
3.3 Manufacturing process of toothed core 3.3.1 Core material and heat treatment requirements The tooth core material is made of high speed steel or high chromium steel. The material must be fully forged to make the metal matrix dense, and the carbide non-uniformity is fully improved, thereby improving the processability and performance, and prolonging the service life of the toothed core. The hardness of the core after heat treatment is 60-62HRC.
3.3.2 Process of the core blank The core of the core refers to the former core of the wire-cut internal tooth.
3.3.3 Internal Tooth Forming Generally, the toothed core is a non-standard special internal toothed part, so the machining of the internal tooth shape must be completed in a dedicated wire cutting machine tool. After the internal tooth line is cut, the metallographic sandpaper should be used to polish the tooth shape, and then subjected to stress relief annealing in an oil furnace of about 200 °C to eliminate internal stress and prevent early failure of the core.
4 Conclusions (1) Production practice shows that the production of involute toothed spline shaft by cold extrusion forming process is a high-quality, high-efficiency, economical and practical near-net forming production process.
(2) Since the degree of deformation at the time of spline extrusion is small, the life of the mold for cold extrusion is greatly improved.
(3) The machining process of the toothed core is simple and the manufacturing cost is low.
(4) The involute toothed spline of cold extrusion is full, the contour is clear, the surface finish is high, and the tooth shape accuracy is also high. The toothed spline is no longer processed to meet the design requirements of the product.
(5) The production of such a toothed shaft can generally achieve a production efficiency of 1500 to 1800 pieces per shift, and the production efficiency is high.
Some process measures can also be taken to control the composite forming of the main hole. On the one hand, reducing the radius of the die radius, increasing the blanking force of the flange portion, adding no lubricant to the die, etc., improving the resistance of the flange portion material into the die, increasing the drawing deformation force, and the above measures The invention can reduce the drawing deformation during the deformation process, thereby reducing the outer diameter of the blank and improving the utilization rate of the material. In actual production, according to the theoretical analysis of the forming process combined with the test mode, when the outer diameter of the blank is 62mm, it can ensure the smooth running of the turning hole, and it is convenient for the flange trimming, and the material utilization rate is within a reasonable range. Inside.
4 Conclusion For the forming process of straight cylindrical workpiece, the process of forming and deforming the deep drawing and turning hole is analyzed and discussed. In the production practice, the composite forming can be effectively controlled by adopting certain technological measures. The required shape and size of the workpiece can increase material utilization and reduce production costs.
1 Cold extrusion principle of involute tooth spline The gear shaft is the shifting shaft of a miniature car transmission. The tooth profile parameters are: number of teeth Z = 12, modulus M = 1.25, pressure angle α = 20 °, change The bit coefficient X=0.60, the tip circle diameter da=16.75mm, the root circle diameter df=14.0mm, the involute spline effective length is 44mm; the involute spline part is connected with the shift fork, and the shifting is changed. The role of the file. Since the involute tooth spline and the shifting fork are only the transmission torque, the spline has low requirements on the motion accuracy of the tooth profile. Involute gear parts that do not require high motion accuracy are suitable for mass production using cold extrusion.
The cold extrusion of the involute spline is mainly processed by the reduced diameter extrusion method. The forming process of the extrusion die is installed on the work surface of the extrusion equipment, and the workpiece blank is installed in the upper and lower mold cavities; When the upper die is moved downward, the workpiece blank is forced into the toothed cavity of the extrusion die; as the upper die of the die is moved downward, the toothed cavity of the die is deformed by contact with the blank to deform it. That is, the same tooth shape as the extrusion die is pressed out on the outer surface of the workpiece blank.
2 Preparation of Cold Extrusion Blank of Involute Toothed Spline Shaft 2.1 Formulation of Cold Extrusion Drawing The toothed part of the gear shaft is processed by cold extrusion, and the tooth shape after cold extrusion processing The design requirements of the part can be achieved without subsequent processing; the outer hexagonal and groove parts of the part must be processed by subsequent machining methods; for the shaft part of the part, due to its high precision requirements and high surface quality requirements, Leave the machining allowance.
2.2 Determination of the diameter of the extruded blank of the toothed part In the cold extrusion process, the correct determination of the diameter of the extruded part of the toothed part is one of the key factors determining the success or failure of the extrusion process.
The correct extruded blank diameter is generally near the indexing circle (or the median diameter of the tooth) and is expressed by the formula: dm=d±Δd where: dm is the diameter of the extruded blank; d is the gear indexing circle of the part ( Or medium diameter) diameter; Δd is the amount of change in diameter, which is determined by the structure and material properties of the extrusion.
The diameter of the extruded blank determined by the above formula is only a theoretical value, and the final diameter needs to be determined in the test.
2.3 Preparation of extruded blank 2.3.1 The shearing and blanking of the original blank is cut and cut by J23-35 punching machine. It is required that the cut blank of the blank is flat, the roundness difference is less than 0.50mm, and the unevenness is not more than 0.60mm. The mass error is 1.0%. According to the above requirements, in order to ensure the roundness error after cutting, the gap between the inner hole of the fixed scissors and the raw material is 0.2~0.4mm; in order to ensure the flatness of the fracture, the punching gap should be as small as possible, actually take 0.2 ~0.4mm.
2.3.2 Local hot rolling blank The small-sized medium frequency induction heating furnace (the power of which is 20 kW) is used to locally heat the head of the original blank, and the heating temperature is 1000-1100 °C. Partial upsetting was then carried out on a J23-100 type 100t punch.
2.3.3 Softening Annealing of Hot Billet Blanks Since the material of the spline guide shaft is medium and high strength structural steel 45 steel, the bar material in the supply state has high strength and hardness, and the internal structure is uneven. Therefore, the material of the extruded blank must be softened and annealed before cold extrusion, and the hardness after annealing is 140-170HBS to improve the cutting performance and plastic deformation property of the material and reduce the deformation resistance.
2.3.4 Processing of extruded blanks The annealed blanks are processed on a lathe. When processing extruded blanks, it is required that each step should have better coaxiality requirements, and the surface quality should not be too bad.
2.3.5 Surface lubrication treatment of extruded blanks During the cold extrusion forming process of involute splines, the deformation area is concentrated near the tooth shape, and the metal flow at this place is very intense, and the degree of deformation is extremely large; A toothed extrusion with good surface quality must be surface lubricated for the extruded blank after machining. In the process, the extruded blank is surface-treated with a phosphating solution containing zinc phosphate as a main raw material, and then surface-lubricated by using molten stearic acid soap as a saponification liquid.
3 tooth-shaped mold structure design and manufacturing process 3.1 cold extrusion forming die structure characteristics The cold extrusion die structure is characterized by: 1 the upper and lower mold guiding is guided by the guiding sleeve, the guiding precision is higher; 2 mold The structure is relatively simple, the mold processing, replacement and adjustment are very convenient; 3 the upper mold is fastened by the fastening nut, and the lower mold is fastened by the lower mold pressing plate, which is beneficial to the "centering" of the upper and lower molds.
3.2 Structural design of the toothed core The involute spline extrusion toothed core is designed to select the appropriate tooth profile and tooth diameter, determine the extrusion transition, the extrusion section and the ejection return. The angle of the segment 3.2.1 The tooth profile of the toothed core design The tooth profile design of the core is required to be able to coldly extrude the desired workpiece tooth profile according to the specified tooth thickness and tooth height, so the modulus of the core tooth profile and The number of teeth is the same as the workpiece; considering the thermal expansion and contraction of the extruded workpiece and the elastic recovery of the die and the extruded workpiece, the pressure angle or displacement coefficient of the core tooth shape cannot be the tooth pressure angle of the spline shaft part or The displacement coefficient is the same.
Normally, the core tooth-shaped displacement coefficient is corrected while keeping the pressure angle constant. The displacement coefficient X of the core tooth profile is mainly related to the modulus M of the gear part, the pressure angle α and the degree of extrusion deformation ε, which can be expressed by the following empirical formula: X=Xo-λM-ηα/180-ξε Where: X is the displacement coefficient of the core tooth shape; Xo is the displacement coefficient of the gear part; λ is the correction coefficient of the modulus M, which is related to the modulus M of the gear; η is the correction coefficient of the pressure angle α, and The pressure angle α of the gear is related; the correction coefficient of the degree of deformation ε is determined by the geometry of the gear part, the shape and size of the extruded blank, and the properties of the extruded material.
The tooth-shaped deformation coefficient determined by the above formula is only a theoretical value, and the final value of the displacement coefficient needs to be determined in the test.
In addition, in consideration of the problem that the cold extrusion forming force and the extrusion tooth shape can be assembled without subsequent processing, the height of the tooth tip of the core is smaller than the root height of the tooth profile of the workpiece, and the root height of the extrusion core is high. The crest is larger than the tooth profile of the workpiece.
3.2.2 Extrusion transition section of the toothed core The design of the extrusion transition section of the toothed core is mainly to select the appropriate slope. When the inclination is too large, although the flow of metal is short and the friction is low, the radial pressure component during extrusion is large, so that the axial pressure component required for extrusion is reduced, which increases The forming force of the extrusion makes the axial flow of the metal difficult, thereby causing the "upset" of the extruded blank, making extrusion difficult to continue. When the inclination is too small, the metal has a long flow path and a large frictional force, which also causes difficulty in metal flow during extrusion.
In the present process, the inclination angle α of the extrusion transition section of the core is preferably 22.5 to 30°.
3.2.3 Length of the extrusion section of the toothed core The length of the extrusion section of the toothed core has a certain influence on the quality of the toothed part after extrusion. The length C of the extrusion section is most suitable from 2.5 to 8.0 mm; if the length of the extrusion section is C>8.0 mm, the frictional force of the metal flow is greatly increased, the metal flow is difficult, and the rod portion of the extrusion member is easily bent and unstable. Therefore, the normal production of the extrusion is affected; and when the length of the extrusion section is c < 2.5 mm, although the metal flow is easy and the forming force is small, the extruded tooth portion is easily distorted.
3.2.4 Top-out return section of the toothed core design The design method of the top-out return section of the toothed core is similar to that of the extrusion transition section, mainly selecting the appropriate slope. When the inclination is too large, although the metal flow is short in flow and low in friction, it is easy to be extruded. However, in the process of ejecting and returning, since the guide section is small, it is easy to cause the "upset" of the extrusion, so that the extrusion It is difficult to eject. When the inclination is too small, the ejector guide section is long, and the extrusion member is easy to eject, but since the metal flow path is long and the friction is large during the backlog, it is difficult to perform normally during the extrusion process. In the present process, it is preferable that the inclination angle β of the ejection return section of the core is 45 to 60°.
3.3 Manufacturing process of toothed core 3.3.1 Core material and heat treatment requirements The tooth core material is made of high speed steel or high chromium steel. The material must be fully forged to make the metal matrix dense, and the carbide non-uniformity is fully improved, thereby improving the processability and performance, and prolonging the service life of the toothed core. The hardness of the core after heat treatment is 60-62HRC.
3.3.2 Process of the core blank The core of the core refers to the former core of the wire-cut internal tooth.
3.3.3 Internal Tooth Forming Generally, the toothed core is a non-standard special internal toothed part, so the machining of the internal tooth shape must be completed in a dedicated wire cutting machine tool. After the internal tooth line is cut, the metallographic sandpaper should be used to polish the tooth shape, and then subjected to stress relief annealing in an oil furnace of about 200 °C to eliminate internal stress and prevent early failure of the core.
4 Conclusions (1) Production practice shows that the production of involute toothed spline shaft by cold extrusion forming process is a high-quality, high-efficiency, economical and practical near-net forming production process.
(2) Since the degree of deformation at the time of spline extrusion is small, the life of the mold for cold extrusion is greatly improved.
(3) The machining process of the toothed core is simple and the manufacturing cost is low.
(4) The involute toothed spline of cold extrusion is full, the contour is clear, the surface finish is high, and the tooth shape accuracy is also high. The toothed spline is no longer processed to meet the design requirements of the product.
(5) The production of such a toothed shaft can generally achieve a production efficiency of 1500 to 1800 pieces per shift, and the production efficiency is high.
Some process measures can also be taken to control the composite forming of the main hole. On the one hand, reducing the radius of the die radius, increasing the blanking force of the flange portion, adding no lubricant to the die, etc., improving the resistance of the flange portion material into the die, increasing the drawing deformation force, and the above measures The invention can reduce the drawing deformation during the deformation process, thereby reducing the outer diameter of the blank and improving the utilization rate of the material. In actual production, according to the theoretical analysis of the forming process combined with the test mode, when the outer diameter of the blank is 62mm, it can ensure the smooth running of the turning hole, and it is convenient for the flange trimming, and the material utilization rate is within a reasonable range. Inside.
4 Conclusion For the forming process of straight cylindrical workpiece, the process of forming and deforming the deep drawing and turning hole is analyzed and discussed. In the production practice, the composite forming can be effectively controlled by adopting certain technological measures. The required shape and size of the workpiece can increase material utilization and reduce production costs.
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