CN100586636C - A precision composite plastic forming method for a special-shaped curved surface stator - Google Patents

Abstract

The invention discloses a precision composite plastic forming method for a stator with a special-shaped curved surface of a power steering pump. The following steps are carried out: blanking, heating the billet to the complete recrystallization temperature ±10°C, and keeping it warm; preheating the thermoplastic back-extrusion mold at a temperature of 200°C to 400°C, coating the mold with lubricant, and placing the billet in the thermoplastic back-extrusion Extrude in a press die to obtain a blank with a unilateral machining allowance of ≤0.4mm on the curved surface of the inner cavity; then heat treatment to eliminate residual stress, process the upper and lower end faces of the blank to make the parallelism ≤0.02mm, and put the blank into a cold finishing mold for cooling Finishing, unilateral machining allowance 0.15mm ~ 0.25mm; machining position tolerance ≤ φ0.02mm positioning hole, heat treatment again to make the surface and core hardness meet the requirements, grinding, that is, the special-shaped surface of the power steering pump stator. The method of the invention has the characteristics of small forming force, good forming quality, high production efficiency and low cost; and the formed parts have good wear resistance and high fatigue resistance.

Description

A precision composite plastic forming method for a special-shaped curved surface stator

technical field

The invention belongs to the technical field of forging, and relates to a plastic forming method, in particular to a precision composite plastic forming method for a stator with a special-shaped curved surface, and also relates to a mold used for forming the stator in the method.

Background technique

The machining of the surface of the cavity in the stator of the automobile power steering pump usually adopts direct machining of raw materials, machining of raw materials after free upsetting, or powder metallurgy.

The strength and performance of the stator parts made by direct mechanical processing of raw materials cannot meet the requirements of the automotive power steering pump for stator parts during high-speed movement; Performance requirements, but this method processes the inner cavity surface of the stator parts, long working hours, many procedures, low efficiency, and high production costs; powder metallurgy manufacturing stator parts has the characteristics of energy saving, material saving, high efficiency, and time saving, etc., but the manufacturing The internal structure of the finished stator parts is loose, and the wear resistance is poor. The stator parts move at high speed in the automobile power steering pump and are easy to wear.

Contents of the invention

The purpose of the present invention is to provide a precision composite plastic forming method for a stator with a special-shaped curved surface, which saves the processing time of the parts, improves the production efficiency, and at the same time improves the strength and wear resistance of the parts.

Another object of the present invention is to provide a mold for forming the stator in the above method.

The technical solution adopted in the present invention is a precision composite plastic forming method for a stator with a special-shaped curved surface, which includes the following steps:

Step 1: Cutting the material to obtain the original billet, heating the original billet to the complete recrystallization temperature ±10°C, and keeping it warm for a corresponding period of time;

Adopting a thermoplastic reverse extrusion die, preheating the thermoplastic reverse extrusion die in an environment with a temperature of 200°C to 400°C, and then applying a lubricant to the working part of the die;

Step 2: Extrude the heated billet in step 1 in a preheated thermoplastic reverse extrusion die to form a stator blank, and control the unilateral machining allowance of the inner cavity surface of the stator blank to be ≤0.4mm;

Step 3: Using the residual heat of extrusion, the stator blank obtained in step 2 is subjected to corresponding heat treatment to eliminate the residual stress formed during the hot extrusion deformation of the blank and reduce the hardness;

Step 4: Machining the blank after the heat treatment in step 3 to ensure that the parallelism between the upper and lower end surfaces of the blank is ≤0.02mm, and obtain a semi-finished stator;

Step 5: Place the stator semi-finished product obtained in step 4 in the cold finishing mold, and perform cold plastic finishing of the inner surface, and control the unilateral machining allowance of the inner cavity surface size of the blank after finishing to 0.15mm to 0.25mm ;

Step 6: Process positioning holes on the stator semi-finished product after cold finishing in the previous step, and control the position tolerance of the positioning holes to ≤0.02mm;

Step 7: heat-treat the semi-finished product after the positioning hole has been processed in the previous step to make the surface and core hardness reach the required hardness value, and obtain the heat-treated part;

Step 8: Grinding the heat-treated parts obtained in Step 7 to obtain a stator with a special-shaped curved surface for the power steering pump.

The thermoplastic reverse extrusion die includes an upper mold and a lower mold, wherein the upper mold is composed of a thermoplastic reverse extrusion punch backing plate and a thermoplastic reverse extrusion punch punch arranged in sequence from top to bottom, and the thermoplastic reverse extrusion punch The outer surface of the punch is fixed with an annular thermoplastic back-extrusion punch punch hoop, and the upper end surface of the thermoplastic back-extrusion punch punch hoop is in contact with the lower end surface of the thermoplastic back-extrusion punch backing plate,

The lower die is composed of a thermoplastic back-extrusion spacer, a ring-shaped thermoplastic back-extrusion die block and a ring-shaped thermoplastic back-extrusion die, which are sequentially connected from the inside to the outside. The lower surface of the extrusion die and the soil block of the thermoplastic back-extrusion die is at the same level, and the thickness of the thermoplastic back-extrusion spacer is smaller than that of the thermoplastic back-extrusion die block.

Cold finishing die, including the cold finishing punch of the upper die and the ring-shaped cold finishing lower die, the profile of the side surface of the cold finishing punch is an approximate ellipse with circular arcs at both ends, cold finishing The upper surface of the lower mold has a groove.

The present invention is also characterized in that,

The cross-sectional profile of the thermoplastic back-extrusion punch head is an approximate ellipse with arcs at both ends.

The working end of the thermoplastic reverse extrusion punch is provided with a radial split angle γ of 5°-25°.

A working fillet R1 with a radius of 3 mm to 6 mm is set between the radial diversion angle γ and the working end surface, and an anti-extrusion angle R2 with a radius of 8 mm to 15 mm is set between the radial diversion angle γ and the side wall.

The thermoplastic back-extrusion punch is coaxial with the thermoplastic back-extrusion die block.

The cold finishing punch punch is composed of a cold finishing shrinking part, a cold finishing punch working belt and a cold finishing self-adaptive guiding part arranged in sequence.

There is a radial deviation of 0.1mm to 0.5mm on one side between the cold finishing punch working belt and the cross section of the cold finishing adaptive guide part and the cold finishing shrinking part, and the width of the cold finishing working belt is 20mm ~25mm, the length of the cold-finishing adaptive guiding part is 25mm-30mm, and the pouring angle of the end face of the cold-finishing adaptive guiding part is 3°-5°.

The cold finishing punch is coaxial with the cold finishing die.

Compared with the existing three methods of raw material mechanical processing, raw material free forging + mechanical processing and powder metallurgy process, the present invention has the following beneficial effects:

1. Compared with bar machining, its raw material utilization rate is high and processing cost is low; it not only shortens the production cycle, refines the grain, but also reduces the production cost.

2. Compared with bar free forging + mechanical processing technology, it reduces the man-hours of CNC processing, improves productivity and reduces production costs.

3. Compared with powder metallurgy, the internal structure of the stator is denser, which improves the wear resistance of the stator and prolongs its service life.

4. The present invention is applicable to the production of special-shaped curved surfaces in the inner cavity of various types of automobile power steering pump stators.

5. Through the thermoplastic deformation process, the axial pressure of the blank is reduced, and the forming problem of the inner cavity surface of the blank is solved; through the cold plastic forming process, the inner cavity surface is finished to ensure the dimensional accuracy of the inner cavity surface and Surface roughness requirements. The invention solves the problems of long working hours for parts processing, low production efficiency, and low strength and wear resistance existing in the prior art.

6. The present invention has the advantages of small forming force, good forming quality, high production efficiency, and low cost; the formed parts have the characteristics of good mechanical properties, high wear resistance, and high forming precision of curved surfaces.

Description of drawings

Fig. 1 is the thermoplastic extrusion die structure schematic diagram that is used for hot extrusion in the inventive method;

Fig. 2 is the schematic diagram of the structure of the thermoplastic reverse extrusion punch of the thermoplastic extrusion die in the method of the present invention; wherein, a is a front view, and b is a left view;

Fig. 3 is the cold finishing die structure schematic diagram that is used for fine shaping in the inventive method;

Fig. 4 is a schematic structural view of the cold finishing punch of the cold finishing mold in the method of the present invention; wherein, a is a front view, and b is a left side view.

In the figure, 1. Thermoplastic reverse extrusion punch, 2. Thermoplastic reverse extrusion punch clamp, 3. Thermoplastic reverse extrusion punch pad, 4. Thermoplastic reverse extrusion die, 5. Thermoplastic reverse extrusion die block, 6. Thermoplastic reverse extrusion pad, 7. Cold finishing punch punch, 8. Work piece, 9. Cold finishing lower die.

Among them, I. cold finishing shrinking part, II. cold finishing punch working belt, III. cold finishing self-adaptive guiding part.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The inventive method, carries out according to the following steps:

Step 1: Cutting the material to obtain the original billet, heating the original billet to the complete recrystallization temperature of the material ±10°C, and keeping it warm for a corresponding period of time;

The stator thermoplastic back-extrusion die is used to preheat the thermoplastic back-extrusion die at a temperature of 200°C to 400°C. Then, a lubricant composed of graphite and cannon oil is applied to the working part of the die. Die lubrication;

Step 2: Put the billet obtained in Step 1 into the processed thermoplastic reverse extrusion die for thermoplastic extrusion to obtain a blank, and control the unilateral machining allowance of the inner cavity surface size of the blank to be ≤0.4mm;

Step 4: According to the material of the selected blank, use the forging waste heat of the blank obtained in step 3, put the blank into a box-type resistance furnace for corresponding heat treatment process, so as to eliminate the residual stress in the process of hot extrusion deformation and reduce the material hardness;

Step 5: Cut the blank after the heat treatment in the previous step to remove the continuous skin of the blank produced by thermoplastic reverse extrusion, and process the upper and lower end faces and the outer circle of the stator blank at the same time to ensure that the parallelism of the upper and lower ends is ≤0.02mm, and obtain a semi-finished stator ;

Step 6: Using a cold finishing mold, place the stator semi-finished product obtained in step 5 in the cold finishing mold, perform cold plastic finishing forming of the inner curved surface, and use the self-adaptive guiding function of the cold finishing punch 7, Make the unilateral machining allowance of the inner cavity surface size of the stator semi-finished product after cold finishing be 0.15mm to 0.25mm;

Step 7: Process positioning holes on the stator semi-finished product after cold finishing in the previous step, and control the position tolerance of the positioning holes to ≤φ0.02mm;

Step 8: Carry out heat treatment on the stator semi-finished product with positioning holes processed in the previous step corresponding to its material, so that the surface hardness of the inner curved surface and the hardness of the core part reach the specified hardness range, and the heat treated part is obtained;

Step 9: Place the heat-treated parts obtained in Step 8 on a QCK005B inner curved surface special grinding machine, and perform grinding processing to obtain a special-shaped curved surface stator.

The structure of the thermoplastic extrusion die used for hot extrusion in the method of the present invention is as shown in Figure 1. An upper die consisting of a thermoplastic reverse extrusion punch block 3 and a thermoplastic reverse extrusion punch 1 arranged sequentially from top to bottom, one end of the thermoplastic reverse extrusion punch 1 is provided with an annular thermoplastic reverse extrusion Compression punch ring 2, the outer diameter of thermoplastic reverse extrusion punch 1 is closely matched with the inner hole of thermoplastic reverse extrusion punch ring 2, and the thermoplastic reverse extrusion punch is tight. The upper surface of the hoop 2 is in contact with the lower surface of the thermoplastic reverse extrusion punch block 3 .

The thermoplastic extrusion die also includes a lower die consisting of an annular thermoplastic back-extrusion die 4, an annular thermoplastic back-extrusion die block 5 and a thermoplastic back-extrusion spacer 6, and the thermoplastic back-extrusion die block 5 It is fixed in the inner hole of the thermoplastic back-extrusion die 4, and the thermoplastic back-extrusion pad 6 is fixed in the inner hole of the thermoplastic back-extrusion die soil block 5, and the thickness of the thermoplastic back-extrusion pad 6 is smaller than that of the thermoplastic back-extrusion The thickness of the pressing die soil block 5, the lower surface of the thermoplastic reverse extrusion pad 6, the thermoplastic reverse extrusion die soil block 5 and the thermoplastic reverse extrusion die 4 are at the same level.

The thermoplastic reverse extrusion loam block 5 and the thermoplastic reverse extrusion punch 1 are coaxial.

The roughness of the upper surface of the thermoplastic back-extrusion pad 6 and the surface of the inner hole of the thermoplastic back-extrusion die block 5 is not greater than Ra1.6.

The structure of the thermoplastic reverse extrusion punch of the thermoplastic extrusion die in the method of the present invention is as shown in FIG. 2 . It consists of a thermoplastic back-extrusion punch 1 and an annular thermoplastic back-extrusion punch hoop 2 . The working end face of the thermoplastic back-extrusion punch 1 is provided with a radial split angle γ, with a value of 5°-25°, and the working part is provided with a rounded corner R1 with a radius of 3mm-6mm and a back-extrusion angle with a radius of 8mm-15mm. The pressure angle R2, the profile of its side surface is an approximate ellipse with two ends being circular arcs, and the surface roughness of the thermoplastic reverse extrusion punch 1 is not greater than Ra1.6.

The structure of the cold finishing mold used in the method of the present invention is as shown in Figure 3. Comprising the cold finishing punch punch 7 of the upper die and the annular cold finishing lower die 9, the upper surface of the cold finishing lower die 9 is processed with a groove, which is the same as the inner hole of the cold finishing lower die 9 Shaft, the cold finishing punch 7 is coaxial with the cold finishing lower die 9, and the surface roughness of the side wall and bottom surface of the groove is not greater than Ra1.6.

The structure of the cold finishing punch is shown in Figure 4. The cold finishing punch punch 7 is composed of a cold finishing punch diameter reducing part I, a cold finishing punch working belt II and a cold finishing self-adaptive guide part III arranged in sequence, and the cold finishing punch working belt II and the cold finishing punch working belt II There is a unilateral radial deviation h between the cross-sections of the finishing adaptive guide part III and the cold finishing reducing part I, and the value is 0.1mm~0.5mm, and the width of the cold finishing punch working belt II is 20mm~ 25mm, cold finishing self-adaptive guiding part III, length 25mm~30mm, pouring angle 3°~5°, surface roughness of cold finishing punch 7 not greater than Ra1.6, cold finishing punch The profile of the side surface of the punch 7 is an approximate ellipse with both ends being circular arcs.

The plastic forming die of the present invention is made of die steel 5CrMnMo, wherein the thermoplastic reverse extrusion punch 1 uses hot work die steel H13 or 3Cr2W8V, and the cold finishing punch 7 uses cold work die steel Cr12MoV.

The projection of the stator surface of the power steering pump of an automobile is an approximate ellipse with arcs at both ends. In the process of thermoplastic reverse extrusion, the distribution of metal flow is uneven, the flow is fast at the thick wall, and the flow is slow at the thin wall. The blank produces rebound, cold shrinkage deformation and flow phenomenon, which causes the mold to wear. In the direction of the long axis of the thermoplastic reverse extrusion punch 1, the size of the reverse extrusion workpiece 8 is less consistent with the mold, the consistency is poor, and the mold wears faster; in the direction of the short axis of the thermoplastic reverse extrusion punch 1, The size of the back-extruded workpiece 8 has a greater degree of coincidence with the mold, better consistency, and slower wear of the mold.

During hot extrusion, the mold is in contact with the high-temperature billet, and the metal flow at the rounded corner of the working part of the thermoplastic reverse extrusion punch 1 is the most intense, and the temperature of the working part of the thermoplastic reverse extrusion punch 1 rises, causing high temperature tempering in the working part , the working part of the mold becomes soft, resulting in slight collapse and deformation at the rounded corner of the working part, resulting in uneven pressure at the collapsed part, which causes slight pull marks on the stator reverse extrusion workpiece 8. If the thermoplastic reverse extrusion punch 1 working part If the fillet radius R is too small and not smooth, the working part is prone to cracks, and the cracks will continue to expand. The fillet R1 of the working part of the thermoplastic reverse extrusion punch 1 of the mold of the present invention has a value of 3 mm to 6 mm.

The surface parameters of the thermoplastic back-extrusion punch 1 are corrected and compensated by the piecewise arithmetic sequence method to overcome the cold shrinkage and deformation of the blank, and the stator The problem of uneven metal flow during plastic forming of inner curved surfaces.

Segment the inner surface of the stator according to the parameter change, and determine the difference between the maximum value and the minimum value of each segment. The surface of the inner cavity of the stator is a variable curved surface, and the maximum point size and the minimum point size are not easy to measure. After multiple measurements, the maximum value and minimum value are obtained to reduce the size measurement error. Divide the difference into 9-15 equal parts, then calculate the angle difference, and divide the angle difference into 9-15 equal parts.

Take the Y0307-01-01W stator as an example: the 360°circle is divided into 6 parts, two arc parts, two curved surface increasing parts and two curved surface reducing parts. Wherein, each of the two arc parts contains a value of 30°, each of the two gradually increasing parts of the curved surface contains a value of 96°, and each of the two gradually decreasing parts of the curved surface contains a value of 54°. The radius value of the arc part remains unchanged, the difference is zero, and it is not equally divided; the increased part of the arc of the curved surface is 96°, which is divided into 12 equal parts, each equal part is 8°, the minimum value of the curved surface is 20.715mm, and the curved surface The maximum value ρ is 24.274mm, the maximum size parameter in the long axis direction is reduced by 0.1mm, the surface value ρ increases from 20.715mm to 24.174mm, the value increased by each equal part is about 0.288mm, and the value increased by each degree is about 0.036mm , because the size of the surface does not increase uniformly, some parameter values need to be compensated and corrected, so that the change of the corrected parameter value is basically consistent with the change of the part parameter; the reduced part of the surface arc is 54°, which is divided into 9 equal parts, each equal part is 6°, the maximum value ρ of the surface is 24.274mm, the maximum size parameter in the direction of the long axis is reduced by 0.1mm, the surface value ρ is reduced from 24.174mm to 20.715mm, and the value reduced by each equal part is about 0.384 mm, the reduction value per degree is about 0.064mm. Since the surface size value is not uniformly reduced, some parameter values need to be compensated and corrected, so that the change of the corrected parameter value is basically consistent with the change of the part parameter.

Using the arithmetic sequence method to modify the above surface parameters, the parameters in individual equal parts may be the same or very close after modification. According to the principle of gradual increase or decrease of parameters, compensate the parameters of several points with the same or very close values in the equal portion, so that the increase or decrease value is less than the increase or decrease value of each equal portion, ensuring that the In this curve segment and every equal part, the parameters gradually increase or decrease, and the curve transitions smoothly, so as to obtain the surface parameters of the thermoplastic reverse extrusion punch 1 .

A large amount of data was recorded during the production process of the mold, and the measured data was analyzed and compared with the theoretical data of the stator to obtain the value of the unilateral margin; The machining allowance and heat release are 0.3mm to 0.5mm.

In order to reduce the frictional resistance of the plastic flow of the metal, the working end of the thermoplastic reverse extrusion punch 1 is provided with a radial split angle γ, which takes a value of 5°-25°.

According to the parameters and machining allowance determined above, the shape of the thermoplastic back-extrusion punch 1 is processed by electric machining, and the surface of the punch is ground and polished after processing.

Mix 20% of graphite and 80% of cannon oil as a lubricant for the mold to improve the lubricating effect.

Based on the surface parameters of the above-mentioned thermoplastic reverse extrusion punch 1, the parameters are rebounded and increased, and the surface parameters are corrected and compensated by the piecewise arithmetic sequence method to determine the curved surface of the cold plastic finishing punch 3 parameter. The amount of unilateral rebound is increased by 0.3mm to 0.4mm on the basis of the surface parameters of the thermoplastic reverse extrusion punch 1, and then the cold finishing punch working zone II of the cold finishing punch 7 is processed by EDM. The shape of the machine is machined, followed by grinding of the cold-finished adaptive guide part III.

If the direction of the cold finishing punch 7 is reversed, the gap between the cold finishing punch 7 and the cavity of the workpiece 8 is uneven, which is easy to find and ensures that the cold finishing punch 7 can be placed conveniently. Into the cavity of the workpiece 8, it plays the role of self-adaptive guidance in the finishing process to achieve the finishing effect.

A large number of actual measurement results show that the error in the long axis direction between the forging obtained by extrusion of the thermoplastic reverse extrusion punch 1 and the punch 7 of the cold finishing punch is 0.08 mm to 0.14 mm, and the unilateral error is 0.04 mm to 0.07 mm. mm, the error in the minor axis direction is 0.01mm~0.02mm, and the unilateral error is 0.005mm~0.01mm. According to this result, the actual size of the thermoplastic reverse extrusion punch 1 in the long axis direction is reduced by 0.08 mm to 0.14 mm compared with the theoretical size, and the maximum size parameter in the long axis direction is actually reduced by 0.1 mm for error compensation. The short axis ( That is, the error of the arc part) is small, and no error compensation is given to ensure that the finishing size of the stator of the automobile power steering pump meets the requirements.

Example 1

Select a bar material with a material of 20CrMnTi and a diameter of Φ65mm, and cut it to obtain an original billet with a length of 26mm. The original billet is heated in a box-type resistance furnace at a heating temperature of 950±10°C and kept for 1 hour; The thermoplastic reverse extrusion mold is preheated, the mold preheating temperature is 200°C, and then the lubricant formed by mixing graphite and gun oil is applied to the working part of the mold to lubricate the mold; the heated billet is placed in the thermoplastic The stator blank is formed by extruding in the reverse extrusion die, and the unilateral machining allowance of the inner cavity surface size of the blank is ≤0.4mm; using the forging waste heat of the blank in a 30KW box-type resistance furnace, the temperature of the stator blank after forging is Under the condition of 730℃～660℃, cooling at a cooling rate of ≤20℃/h can eliminate residual stress during hot extrusion deformation and reduce material hardness;

Cut the normalized blank to ensure that the parallelism between the upper and lower ends of the blank is ≤0.02mm to obtain a semi-finished product; place the semi-finished product in a cold finishing mold for cold plastic finishing of the inner surface, and use cold finishing convex The self-adaptive guiding function of the die punch makes the unilateral machining allowance of the inner cavity surface size of the blank after finishing be 0.15mm. For the positioning hole of the stator semi-finished product after cold finishing, the position tolerance of the positioning hole is controlled to be ≤φ0.02mm ;Then carburize and quench the stator semi-finished product, the carburized layer depth is 1.1mm~1.3mm, the surface hardness of the inner curved surface of the stator is ≥HRC62, and the hardness of the core is HRC37~45, and the heat treatment part is obtained; the heat treatment part is placed in the QCK005B inner mold Grinding on the special grinding machine for cavity curved surface, that is, the stator of the power steering pump of the automobile is made.

Example 2

According to the calculation results, select a bar material with a material of GCr15 and a diameter of Φ65mm for blanking to obtain an original billet with a length of 26mm, and place the original billet in a 45KW box-type resistance furnace for heating at a heating temperature of 990±10°C , the holding time is 1 hour; the thermoplastic reverse extrusion mold is preheated, and the mold preheating temperature is 300 ° C, and then the lubricant formed by mixing graphite and gun oil is applied to the working part of the mold to lubricate the mold. The heated billet is extruded in a thermoplastic back-extrusion die to form a stator blank. The unilateral machining allowance of the inner cavity surface size of the blank is ≤0.4mm; the blank is processed in a 30KW box-type resistance furnace by using the forging waste heat Spheroidizing annealing, the annealing temperature is 860±10°C, and the holding time is 3 hours. When the temperature drops to 500°C, it is air-cooled to eliminate the residual stress in the hot extrusion deformation process and reduce the hardness of the material; Cutting process, to ensure that the parallelism between the upper and lower ends of the blank is ≤0.02mm, to obtain a semi-finished product; place the semi-finished product in a cold finishing mold, and perform cold plastic finishing of the inner curved surface, using the self-adaptive guiding function of the finishing punch, Make the unilateral machining allowance of the inner cavity surface size of the blank after finishing be 0.15mm; process the positioning hole for the stator semi-finished product after cold finishing, and control the position tolerance of the positioning hole ≤ φ0.02mm; after processing the positioning hole The semi-finished stator of the stator is quenched, the surface hardness of the inner curved surface of the stator is ≥HRC63, and the hardness of the core is HRC40-48, and the heat-treated part is obtained; the heat-treated part is placed on a QCK005B internal cavity curved surface special grinding machine for grinding, that is The stator of the power steering pump of the automobile is manufactured.

Example 3

According to the calculation results, a bar material with a material of 38CrMoAl and a diameter of Φ65mm was selected for blanking to obtain an original billet with a length of 26mm. The original billet was heated in a 45KW box-type resistance furnace at a heating temperature of 990±10°C , the holding time is 1 hour; the thermoplastic reverse extrusion mold is preheated, and the mold preheating temperature is 400 ° C, and then the mixture of graphite (20%) and gun oil (80%) is painted on the mold; the heated The blank is extruded in a thermoplastic reverse extrusion die to form a stator blank. The machining allowance on one side of the inner cavity surface size of the blank is ≤0.4mm; the blank is quenched and tempered in a 30KW box-type resistance furnace using forging waste heat Treatment, the quenching temperature of this process is 930 ° C ~ 970 ° C, the actual heating temperature is 940 ± 10 ° C, the holding time is 2 hours, after the furnace is air-oil cooled, and then tempered at 640 ± 10 ° C with a box-type resistance furnace to eliminate The residual stress in the hot extrusion deformation process reduces the hardness of the material; the processed blank is cut to ensure that the parallelism of the upper and lower ends of the blank is ≤0.02mm, and a semi-finished product is obtained; the semi-finished product is placed in a cold finishing mold, Carry out the cold plastic finishing forming of the inner curved surface, and use the self-adaptive guiding function of the finishing punch to make the unilateral machining allowance of the inner cavity surface size of the blank after finishing be 0.15mm; For the processing of the positioning hole, the position tolerance of the positioning hole is controlled to be ≤φ0.02mm; the semi-finished product of the stator after processing the positioning hole is subjected to nitriding and quenching treatment, the thickness of the carburized layer is 0.4mm～0.7mm, and the surface hardness of the inner curved surface of the stator is ≥HRC65 , the hardness of the core is HRC39-47, and a heat-treated part is obtained; the heat-treated part is placed on a QCK005B internal cavity surface special grinding machine for grinding, and the automobile power steering pump stator is obtained.

The invention adopts the method of combining thermoplastic reverse extrusion forming and cold finishing forming, heats the billet to above the complete recrystallization temperature for thermoplastic forming, and uses the waste heat of thermoplastic reverse extrusion forming to slowly cool and anneal and soften the billet, reducing the Hardness and toughness are improved. After the blank is machined, it is cold finished at room temperature.

Thermoplastic and cold plastic composite forming is a composite forming technology that combines hot forging and cold forging, making full use of the respective advantages of thermoplastic forming and cold plastic forming: metal plastic forming is good in hot state, deformation resistance is low, and the required deformation force Small, forgings with complex shapes can be formed; cold plastic forming has high precision, and parts with no margin and high precision can be obtained. Combining the advantages of the two, complex curved surfaces are formed through thermoplastic forming, and then cold plastic forming is used to achieve high precision.

Claims (8)

1. special-shaped curved surface stator precise compound plasticity shaping process may further comprise the steps:

Step 1: blanking, obtain original blank, this original blank is heated to perfect recrystallization temperature ± 10 ℃, and is incubated the corresponding time,

Adopting the thermoplasticity indirect-extrusion mould, is preheating in 200 ℃～400 ℃ the environment with this thermoplasticity indirect-extrusion mould in temperature, then at the working position of mould brushing lubricant,

Described thermoplasticity indirect-extrusion mould, comprise upper die and lower die, patrix is made up of the thermoplasticity Back Extrusion Punches backing plate (3) and the thermoplasticity Back Extrusion Punches drift (1) that are provided with from top to bottom, the outer surface of thermoplasticity Back Extrusion Punches drift (1) is fixed with the thermoplasticity Back Extrusion Punches drift tighten ring (2) of annular, the upper surface of thermoplasticity Back Extrusion Punches drift tighten ring (2) contacts with the lower surface of thermoplasticity Back Extrusion Punches backing plate (3)

Described counterdie is made up of the thermoplasticity extrusion female mould earth piece (5) of thermoplasticity backward extrusion cushion block (6) affixed successively outside the lining, annular and the thermoplasticity extrusion female mould (4) of annular, thermoplasticity backward extrusion cushion block (6), thermoplasticity extrusion female mould (4) are in same horizontal plane with the lower surface of thermoplasticity extrusion female mould earth piece (5), and the thickness of thermoplasticity backward extrusion cushion block (6) is less than the thickness of thermoplasticity extrusion female mould earth piece (5);

Step 2: with the blank after step 1 heating, place the thermoplasticity indirect-extrusion mould after the preheating to push, form the stator blank, control the monolateral allowance≤0.4mm of profile surface in this stator blank;

Step 3: utilize the extruding preheating, the stator blank with step 2 obtains carries out corresponding heat treatment, eliminates the residual stress that blank forms in the hot extrusion deformation process, reduces hardness;

Step 4: with the blank machining after step 3 heat treatment, guarantee the depth of parallelism≤0.02mm of this blank upper/lower terminal face, make the stator semi-finished product;

Step 5: the stator semi-finished product that step 4 is obtained place the cold-finish mould, and the cold plasticity finishing of carrying out negative camber is shaped, and the monolateral allowance of the interior profile surface size of blank is 0.15mm～0.25mm after the control finishing,

Described cold-finish mould, comprise the cold-finish punch (7) of patrix and the cold-finish counterdie (9) of annular, the side surface appearance profile of described cold-finish punch (7) is that two ends are the sub-elliptical of circular arc, and the upper surface of described cold-finish counterdie (9) has a groove;

Step 6: to the processing of the stator semi-finished product after the cold-finish of last step locating hole, the position of related features≤0.02mm of control locating hole;

Step 7: will go up the semi-finished product after the step processes locating hole, and heat-treat once more, and make its surface and centre hardness, and meet the requirements of hardness number, and obtain the heat treatment part;

Step 8: with the heat treatment part that step 7 obtains, grinding promptly makes special-shaped curved surface stator.

2. precise compound plasticity shaping process according to claim 1 is characterized in that, the cross-sectional profile profile of thermoplasticity Back Extrusion Punches drift (1) is that two ends are the sub-elliptical of circular arc in the described step 1.

3. precise compound plasticity shaping process according to claim 2 is characterized in that, the working end of described thermoplasticity Back Extrusion Punches drift (1) is provided with 5 °～25 ° radially diversion angle γ.

4. precise compound plasticity shaping process according to claim 3, it is characterized in that, being provided with radius between described radially diversion angle γ and the operative end surface is the work fillet R1 of 3mm～6mm, and radially being provided with radius between diversion angle γ and the sidewall is the backward extrusion angle R2 of 8mm～15mm.

5. precise compound plasticity shaping process according to claim 4 is characterized in that, described thermoplasticity Back Extrusion Punches drift (1) is coaxial with thermoplasticity extrusion female mould earth piece (5).

6. precise compound plasticity shaping process according to claim 1, it is characterized in that the cold-finish punch (7) in the described step 5 is made up of the cold-finish diameter shrinkage part (I) that sets gradually, cold-finish punch work zone (II) and the adaptive directed part of cold-finish (III).

7. precise compound plasticity shaping process according to claim 6, it is characterized in that, be provided with the radial missing of monolateral 0.1mm～0.5mm between the cross section of described cold-finish punch work zone (II) and the adaptive directed part of cold-finish (III) and cold-finish diameter shrinkage part (I), the width of cold-finish punch work zone (II) is 20mm～25mm, the length of the adaptive directed part of cold-finish (III) is 25mm～30mm, and the angle of pouring into of the adaptive directed part of described cold-finish (III) end face is 3 °～5 °.

8. according to claim 6 or 7 described precise compound plasticity shaping process, it is characterized in that described cold-finish punch (7) is coaxial with cold-finish counterdie (9).

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