CN103639217A - Process method for secondary cold extrusion forming of large-diameter outer spline - Google Patents

Abstract

The invention relates to a process method for the secondary cold extrusion forming of a large-diameter outer spline. An inclined wedge device is designed, so that a spline forming tool (rack-shaped) can move along the radial direction of a workpiece; since the workpiece does not separate from the tool, the normal involute generating attribute is kept, so that the process system has the capability of secondary extrusion processing, the processing range of equipment is expanded and the suitability for processing large-diameter workpieces is achieved. A spherical annealing temperature area is optimized, so that the rigidity of the workpiece is remained, simultaneously the cold-extrusion plasticity of a material is improved and the processing characteristic of cold deformation is improved. As principle tests, test bar processing and batch production are carried out, the spline processing of a phi70mm workpiece is finished on cold-extrusion equipment with the maximum allowable processing diameter phi 40mm. The wedge-shaped device of the tool is designed by adopting the method, a carbon-alloy-steel spherical temperature area in the workpiece is optimized, and the fatigue resistance of a torsion shaft of the spline is enhanced by 28%-32%.

Description

Major diameter external splines secondary cold extrusion technology method

Technical field

The invention belongs to field of machining, relate in particular to a kind of major diameter external splines secondary cold extrusion technology method.

Background technology

Splined shaft is the part of moment of torsion between transmitter shaft and axle in machine driven system, has that linking intensity is high, a compact conformation, the feature such as easy to loading and unloading.Spline processing normally adopts cutting process, as milling, gear hobbing, broaching etc.

Splined intensity is high, compact conformation, the feature such as easy to loading and unloading are used and are also applied at some special dimension: torsion shaft is widely used in the undercarriage of military armored vehicle, two ends is larger, the design of employing external splines, middle bar portion diameter is less than two ends splined section, and with circular arc and splined end transition and linkage.

When torsion shaft is used, one end spline is fixedly connected with car body, the other end connects balance arm and bogie wheel, shock loading under the static weight of panzer and fluctuating road conditions all passes to torsion shaft and cushions, and to keep the stability of vehicle horizontal direction, is convenient to fire control system precision fire.So torsion shaft working environment is very severe: moment of torsion is large, windup-degree is large and torsional frequency changes greatly etc.Torsion shaft failure mode shows as unexpected fracture, fracture location mainly occurs in the transitional region of spline root and bar portion, reason is very clear and definite---and the stress that in spline process, small tool marks produce is concentrated, and under the effect of change pulsating stress, expansion extension causes fatigue damage.

Torsion shaft splined section diameter approaches φ 70mm, length 2000mm.With conventional hobbing method processing, any damage of cutting edge roundness all will be inscribed in spline tooth surface, after processing, still have not obvious indentation residual by polishing, become stress concentration point.So torsion shaft rolling cut processing method directly causes the defect that its life-span is shorter, working (machining) efficiency is lower.

Spline cold extrusion processing is a kind of without cutting working method, in order to adapt to automobile industry large-scale production, invent, workpiece clamp is between spline-simulating cutter at two, cutter relatively moves one on the other, drive workpiece to rotate around Pivot Point Center line, and the spline that completes workpiece in the total travel moving at tooth bar is shaped, because extruding force is large, cutter translational speed is fast, process is without cutting, the integrality that has retained to greatest extent metallic fiber, has the outstanding features such as spline intensity is high, working (machining) efficiency is high, compact conformation.

If with cold extrusion method processing torsion shaft two ends spline, can obtain high-quality spline and improve torsion shaft fatigue life.But the spline machining of state's internal spline cold extrusion equipment Shi Wei family's passenger car and large truck designs, maximum machining diameter is φ 40, modulus 1.75, and maximum length 1000mm, conventionally processes diameter and is less than φ 35, can not directly apply to torsion shaft processing.

Major diameter external splines secondary cold extrusion technology method arises thus.

Summary of the invention

This method is designed the wedge device of cutter, and workpiece 1 medium carbon alloy steel nodularization warm area is optimized, and makes spline torsion shaft anti-fatigue ability increase by 28% ~ 32%.

The concrete technical scheme of this method is as follows:

1) designed a kind of expansion spline cold extrusion equipment range of work: in maximum, allow on the cold extrusion equipment of the long 1000mm of processing diameter phi 40mm, complete the shaping processing that diameter phi 70mm length reaches 2040mm workpiece;

On lathe, increase supplemental support frock, workpiece processing length expanded to 2040mm,

2) cutter improves:changed system into spline pitch circle by parallel with spline pitch circle in the back side of conventional cutter, be used in conjunction with the steel bar of another equal gradient, form wedge structure, by adjusting cutter (tooth bar) with respect to the position of steel bar, cutter can be moved in workpiece radial parallel;

3) spline secondary forming: workpiece 1 is between left tooth bar mould 2 and right tooth bar mould 3.Routine is once completed to extrusion process and be decomposed into two discontinuous processes, the first process is roughing, completes 80% tooth depth extruding, and the second process is fine finishining, completes fully teeth height extruding and finishing profile of tooth;

4) the expansion of rapidoprint:the mild steel that is suitable for cold-extrusion shaping is extended to medium high carbon superior alloy steel.The material of auto parts is used mild steel conventionally, take 35# steel as many, and hardness is no more than 180HB, and the torsion shaft of workpiece adopts special-purpose high-quality medium carbon alloy steel 45CrNiMoVA, and requiring the hardness before heat treatment is 190HB ~ 215HB;

5) the heat treatment method that is applicable to high-quality medium carbon steel steel alloy: by practice and optimization, find out suitable heat treatment method---(760-780) ℃ insulation 7.5 hours, than recommending holding time 1.5 hours ~ 2 hours.To reduce Residual Carbides, obtain inhomogeneous austenite and a large amount of tiny Residual Carbides, and using this non-spontaneous core as nodularization to promote carbide spheroidization.Control cooling velocity simultaneously, cool to 500 ℃ ± 15 ℃ with the furnace and transfer again air cooling to;

The heat treated validity of this nodularization has obtained checking in actual cold-extrusion shaping process, and with respect to comparative group coupon (35# steel, 180HB) processing, torsion shaft is under hardness 200HB condition, and steady, the soft invasive of extrusion process is good, and vibration obviously reduces.

6) the asymmetric setting of cutter: the installation method of its cutter of multiple spline one-time cold extruding processing method is that reverse symmetry is installed, and cutter is made move toward one another---workpiece enters introduction segment, plastic section and the section of exiting simultaneously.The initial installation site of left and right cutter need guarantee plastic section mid point and rotating center contour.Spline secondary forming method must guarantee the secondary movement locus of workpiece and cutter and overlap completely for the first time---keep being each other generate state.So, cutter initial position is installed and is changed into asymmetric installation by symmetry---cutter plastic section mid point departs from 10mm left and right (high or low) than rotating center on one side, when another side cutter falls back on latter end, workpiece tooth is also engaged in plastic section, moving up and down cutter (20mm) preparation, to carry out wedge centripetal when mobile, the workpiece movement of both having had living space, also remains in the profile of tooth being shaped.

7) the design of wedge angle:according to test, grope, when secondary extrusion amount is 0.35mm, profile accuracy, roughness combination the best, process system vibration is little, and cutter is good in the movable length controllability of upper and lower 20mm, and wedge angle is now 0.5 °, also in self-locking angle of friction, process system is in optimum state.

The present invention is by the operating characteristic of research spline cold-extrusion shaping equipment, design a kind of oblique contract device, spline forming tool (spline-simulating) can be moved in workpiece radial direction, because workpiece does not depart from cutter restriction, kept normal involute generate attribute, make process system possess the ability of carrying out secondary extrusion processing, expanded the equipment range of work, be suitable for large-diameter workpiece processing.

Research high-quality medium carbon alloy steel (45CrNiMoVA) material behavior, optimizes spheroidizing warm area, in holding workpiece rigidity, improves material cold extrusion plasticity, improves cold deformation processing characteristics.Through principle tests, coupon processing and batch production, in maximum, allow, on processing diameter phi 40mm cold extrusion equipment, to complete the spline processing of φ 70mm workpiece.Stable by facts have proved process system, workpiece size high conformity, roughness is much better than designing requirement.

Accompanying drawing explanation

Fig. 1 tooth bar extruding spline schematic diagram,

Fig. 2 workpiece schematic diagram.

The specific embodiment

The detailed process of this method is:

1, preparation:

Cutter: increase wedge design, cutter is designed to wedge structure together, and 0.5 °, wedge angle adopts cutter and wedge method for grinding on the same group during manufacture, guarantees that angle is unified, and carves sign on the same group.

Workpiece: torsion shaft two ends spline is by size finish turning before cold extrusion, and roughness 1.6, has not allowed the blemish such as oxide skin, rust staining;

Workpiece is processed through spheroidizing, and hardness is 190HB ~ 215HB;

Wedge mechanism installs: by design drawing requirement, by wedge mechanism and the connection of lathe left and right support, with the bevel protractor groove that aligns, the left side (or the right) cutter plastic section mid point and rotating center is contour, and another side is than the low 10mm of rotating center.Trial run cutter moves, and requires guide finger without clamping stagnation;

Workpiece is installed: with servo-actuated chuck holding workpiece one end, adjust other end dead head position, spline processing sections is placed in cutter width, and fills suds on surface;

Numerical control program: comprise that initial point position, a secondary operations terminating point, cutter are to the setting of rotating center line position and cutter translational speed etc.;

2, processing:

Follow procedure completes time processing, and stops at precalculated position;

Unclamp wedge device connecting bolt, adjust cutter mobile 20mm along its length, after alignment groove, tighten again wedge device connecting bolt;

Starting device completes secondary operations, a more reciprocal stroke, to repair, to proofread and correct profile of tooth and the polishing flank of tooth, reaches roughness requirement.

The present invention guarantees the torsion shaft high reliability that certain special dimension is used and improves fatigue life, has researched and developed major diameter external splines secondary cold extrusion technology method, and has completed know-why checking, test specimen processing and batch steady production.

Claims (2)

1. major diameter external splines secondary cold extrusion technology method, is characterized in that: the method specifically comprises:

1) designed a kind of expansion spline cold extrusion equipment range of work: in maximum, allow on the cold extrusion equipment of the long 1000mm of processing diameter phi 40mm, complete the shaping processing that diameter phi 70mm length reaches 2040mm workpiece;

On lathe, increase supplemental support frock, workpiece processing length is expanded to 2040mm, on left tooth bar mould, be provided with wedge, expand the maximum processing diameter that allows of workpiece to φ 70mm;

2) cutter improves:the back side of conventional cutter is tilted with spline pitch circle by make into parallel with spline pitch circle, be used in conjunction with the wedge of equal gradient on left tooth bar mould, form wedge structure, by adjusting cutter with respect to the position of wedge, cutter can be moved in workpiece radial parallel;

3) spline secondary forming:workpiece (1) is positioned between left tooth bar mould (2) and right tooth bar mould (3), routine is once completed to extrusion process and be decomposed into two discontinuous processes, the first process is roughing, completes 80% tooth depth extruding, the second process is fine finishining, completes fully teeth height extruding and finishing profile of tooth;

4) the expansion of rapidoprint:the material of workpiece is extended to medium high carbon superior alloy steel by mild steel;

5) the heat treatment method that is applicable to high-quality medium carbon steel steel alloy: 760-780 ℃ of insulation 7.5 ~ 11 hours, to reduce Residual Carbides, obtain inhomogeneous austenite and a large amount of tiny Residual Carbides, and using this non-spontaneous core as nodularization to promote carbide spheroidization; Control afterwards cooling velocity, cool to 500 ℃ ± 15 ℃ with the furnace and transfer again air cooling to;

6) the asymmetric setting of cutter: the installation method of cutter is that reverse symmetry is installed, cutter initial position is installed and is changed into asymmetric installation by symmetry, limit cutter plastic section mid point departs from 10mm left and right than rotating center, when another side cutter falls back on latter end, workpiece tooth is also engaged in plastic section, moving up and down cutter preparation, to carry out wedge centripetal when mobile, and the workpiece movement of both having had living space, also remains in the profile of tooth being shaped;

7) the design of wedge angle:when secondary extrusion amount is 0.35mm, profile accuracy, roughness combination the best, process system vibration is little, and cutter is good in the movable length controllability of upper and lower 20mm, and wedge angle is now 0.5 °, and also, in self-locking angle of friction, process system is in optimum state.

2. major diameter external splines secondary cold extrusion technology method according to claim 1, is characterized in that, detailed process is:

(1), preparation:

Cutter: increase wedge design, cutter is designed to wedge structure together, and 0.5 °, wedge angle adopts cutter and wedge method for grinding on the same group during manufacture, guarantees that angle is unified, and carves sign on the same group;

Workpiece: torsion shaft two ends spline is by size finish turning before cold extrusion, and roughness 1.6, has not allowed the blemish such as oxide skin, rust staining;

Workpiece is processed through spheroidizing, and hardness is 190HB ~ 215HB;

Wedge mechanism installs: by design drawing requirement, wedge mechanism and lathe left and right support are connect, with the bevel protractor groove that aligns, the left side or the right cutter plastic section mid point and rotating center is contour, and another side is than the low 10mm of rotating center, trial run cutter moves, and requires guide finger without clamping stagnation;

Workpiece is installed: with servo-actuated chuck holding workpiece one end, adjust other end dead head position, spline processing sections is placed in cutter width, and fills suds on surface;

Numerical control program: comprise that initial point position, a secondary operations terminating point, cutter are to the setting of rotating center line position and cutter translational speed etc.;

(2), processing:

Follow procedure completes time processing, and stops at precalculated position;

Unclamp wedge device connecting bolt, adjust cutter mobile 20mm along its length, after alignment groove, tighten again wedge device connecting bolt;

Starting device completes secondary operations, a more reciprocal stroke, to repair, to proofread and correct profile of tooth and the polishing flank of tooth, reaches roughness requirement.

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