CN103056179B - Warm extrusion forming method for straight toothed spur gear - Google Patents

Abstract

The invention discloses a warm extrusion forming process for spur gears, aiming to use warm forming combined with differential temperature forming to heat the blank, reasonable mold design and lubrication selection. The main points of the technical solution are: Method 1: Extrusion + upsetting + reverse second extrusion (same set of extrusion dies); method 2: extrusion + reverse second extrusion (die with different sizes). This forming process can effectively reduce the forming force, and at the same time the tooth shape is well filled. Its advantages are: it not only overcomes the disadvantages of low material utilization rate, low production efficiency and high product cost in cutting processing methods, but also reduces the strength and service life of gears due to the cutting of metal fibers. At the same time, it overcomes the problems encountered by other plastic forming methods such as large forming force, difficulty in corner filling, and low service life of the mold. It is expected to realize the industrial production of spur gears in the field of plastic forming.

Description

A Warm Extrusion Forming Method for Spur Gears

technical field

The invention relates to a mechanical processing method, in particular to a warm extrusion forming method of spur gears.

Background technique

As one of the most basic parts for transmitting motion and power, gears are widely used in the engineering field, especially in the manufacturing industry. Among them, spur gears are not only complex in shape, but also require high dimensional accuracy, surface quality and comprehensive mechanical properties, and have the characteristics of large production batches. At present, most spur gears are produced by traditional cutting methods, which have low material utilization rate, low production efficiency, high product cost, and at the same time, the strength and service life of gears are reduced due to the cutting of metal fibers. In short, the current processing technology of spur gears has the following disadvantages: 1. Low material utilization rate; 2. Low production efficiency; 3. High product cost; 4. Low product strength and service life.

Contents of the invention

The invention overcomes the deficiencies in the prior art, and provides a processing technology for a spur gear refined billet.

In order to solve the above-mentioned technical problems, the present invention is achieved through the following technical solutions:

Option One:

A kind of warm extrusion forming method of spur gear, its specific steps are as follows:

The first step of blanking: determine the size of the blank according to the target gear, and carry out blanking. The lower part of the blank is cylindrical, and the upper part is conical. The diameter of the bottom cylinder is 6%~10% larger than the diameter of the target gear pitch circle. 12°~15°;

The second step of mold preheating: use acetylene flame to preheat the mold to 200°C~250°C to reduce the heat loss when the billet is in contact with the mold;

Step 3 Billet heating: After applying lubricant on the surface of the billet, the billet is heated by differential temperature through medium and high frequency induction heating, so that the external temperature of the billet reaches the temperature range of warm extrusion, while the interior maintains a relatively low temperature;

The fourth step is the first extrusion: the billet is extruded for the first time, and the lubricant is applied on the surface of the mold before extrusion to make the friction coefficient reach 0.4~0.6;

At this time, the obtained workpiece head has a certain size of slump angle, and if the subsequent processing is directly carried out, more material waste will be caused.

Step 5 Upsetting: Upsetting with a certain upsetting ratio after reheating the billet;

The sixth step is to reverse the second extrusion: put the slump section of the upsetting billet upwards, that is, turn the placement state of the billet for the first extrusion by 180°, and then perform the second extrusion.

In this way, a refined gear blank that meets the size requirements can be obtained, and has a high material utilization rate.

The mold described in the fourth step of method one includes a punch and a die, and the punch is designed with a gear-like design with an incomplete tooth shape, which is equivalent to the shape of the target gear to be produced after the tooth top part is cut off ;

The punch designed in this way avoids the reverse flow of the metal caused by the unconstrained tooth-shaped part during the extrusion process of the cylindrical punch, resulting in large burrs. The reason why the full tooth profile design is not used is to allow a certain amount of reverse flow of metal, thereby reducing the forming force and protecting the die.

The concave mold includes a concave mold entry section and a concave mold forming section;

The inner contour of the forming section of the die is consistent with the planar projection shape of the target gear, but the size is too large, which is obtained by offsetting the tooth profile of the target gear outward by a certain value;

The purpose of designing the forming section of the die in this way is to ensure that the tooth profile after extrusion reaches or is slightly larger than the target gear, even if it is difficult to fill the corners of the teeth during the extrusion process and cannot be completely filled, so as to meet the requirements of the refined gear blank. requirements.

The mold-entry part is an inclined section with a corresponding mold-entry angle, and the height of the mold-entry section and the mold-entry angle are determined according to the parameters of the target gear. If the gear modulus is 2, the mold entry angle is generally selected as 35°~55°. If the mold entry angle is too large or too small, it will cause a large collapse angle at the end of the workpiece or insufficient filling. The profile of the entry section is the three transitional surfaces that transition from a point on the tooth root circle in the middle of the die to the forming section. This design is to make sufficient metal flow to the forming section to meet the needs of filling.

Option II:

A kind of warm extrusion forming method of spur gear, its specific steps are as follows:

The first step of blanking: blanking according to the designed blank size, the lower part of the blank is cylindrical, the upper part is conical, the diameter of the bottom cylinder is 6%~10% larger than the diameter of the target gear index circle, and the top chamfer is 12°~15° °;

The second step of mold preheating: use acetylene flame to preheat the mold to 200°C~250°C to reduce the heat loss when the billet is in contact with the mold;

Step 3 Billet heating: After applying lubricant on the surface of the billet, the billet is heated by differential temperature through medium and high frequency induction heating, so that the external temperature of the billet reaches the temperature range of warm extrusion, while the interior maintains a relatively low temperature;

The fourth step is the first extrusion: the billet is extruded for the first time, and the lubricant is applied on the surface of the mold before extrusion to make the friction coefficient reach 0.4~0.6;

The fifth step reverses the second extrusion: after the first extrusion billet is placed and turned 180°, the second extrusion is performed.

The difference between the method two process and the above method one process is that two sets of dies are used, and the die used for the first extrusion is larger than the tooth profile of the die used for the second extrusion. It can be considered that the above method one process The first extrusion and upsetting process in the combined process.

It should be noted that, in order to avoid damage to the mold caused by the tilt of the blank when placing the billet, the ejector rod should be pushed out to a suitable position when the billet is placed, and the billet should be placed on the upper end of the ejector rod stably. The rod is pressed back together with the blank.

The warm extrusion forming method of spur gears provided by the present invention retains the characteristics of high material utilization rate, high production efficiency, good mechanical properties of products and the like of the plastic forming method. At the same time, it overcomes the problems of high forming force, difficulty in filling corners and low service life of molds encountered by other plastic forming methods. Coupled with subsequent finishing, it is expected to realize the industrial production of spur gears in the field of plastic forming. The invention mainly includes: the design of the forming die of the spur gear warm extrusion process; the design of the shape and size of the blank; the process flow of the gear processing; the realization of the lubricating conditions in the forming process;

Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the traditional spur gear processing technology:

1. Adopting the process method of the present invention has greatly improved material utilization and production efficiency;

2. The present invention adopts the extrusion forming process, and the blank is subjected to a three-dimensional compressive stress state, which makes the grain of the material finer, improves the density, and the plastic forming retains the integrity of the metal fiber, so that the product performance is greatly improved;

3. The present invention adopts warm forming combined with differential temperature method, which reduces the influence of scale on machining precision and ensures the precision of refined billets;

4. The mold design required by the process method of the present invention is unique, which can effectively improve the service life of the mold and reduce production costs.

Description of drawings

Fig. 1 is a schematic diagram of the refined blank of the spur gear of Embodiment 1 of the present invention;

Fig. 2 is a schematic diagram of the shape of a blank in Example 1 of the present invention;

Fig. 3 is the assembly drawing of mold of embodiment 1 of the present invention;

Fig. 4 is a schematic diagram of the profile of the punch in Embodiment 1 of the present invention;

Fig. 5 is a schematic diagram of the profile of the die in Embodiment 1 of the present invention;

Fig. 6 is a schematic diagram of extrusion in Embodiment 1 of the present invention;

Fig. 7 is a comparison diagram of the contours of two extrusion dies in Example 2 of the present invention;

In the figure: 1. Base, 2. Sleeve, 3. Nut, 4. Blank, 5. Guide post, 6. Guide sleeve, 7. Upper die holder, 8. Punch fixing sleeve, 9. Screw, 10. Convex Die, 11. Compression ring, 12. Screw, 13. Upper backing ring, 14. Die, 15. Collar, 16. Lower backing ring, 17. Screw, 18. Ejector

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

Take the warm extrusion forming of a standard spur gear with a modulus of 2, a number of teeth of 31, and a pressure angle of 20° as an example. The material is 20Cr2Ni4, and the shape and size of the refined blank are shown in Figure 1. The tooth width B=17.5mm; the pitch circle diameter D=62mm; the addendum circle diameter D ₁ =66.9mm; mm.

method one:

The first step is to cut the material

The Ф70 bar is cut and turned to obtain the shape and size of the designed blank, as shown in Figure 2. The bottom cylinder diameter is D=67.5mm; the top diameter d=57.5mm; H=35mm; h=15mm. This blank can be used to produce gear blanks with two tooth thicknesses at one time.

The second step mold preheating

Use an acetylene flame to preheat the mold so that the temperature of the mold and the end of the ejector pin reaches about 200°C. The mold design is shown in Figure 3. The punch is shown in Figure 4 as D=62mm. Die as shown in Figure 5 D=65mm; D _a =100mm; D _b =67mm; D _c =55mm; H=45mm; h=11.5mm; mold entry angle α=36°.

The third step blank heating

First, the pre-prepared lubricant is coated on the surface of the billet, and then the billet is heated by medium and high frequency induction heating, so that the external temperature reaches the temperature range of warm forming, while the internal temperature is kept low.

Step 4 First Squeeze

Spread the lubricant evenly on the surface of the mold, then place the billet on the end of the ejector rod stably, and use the Y315 press for the first extrusion, as shown in Figure 6.

The fifth step upsetting

The billet after the first extrusion is reheated and subjected to upsetting with a certain upsetting ratio.

Step 6 Second Extrusion

Turn the slump section of the upsetting billet upwards, that is, turn the state of the billet for the first extrusion by 180°, and then perform the second extrusion.

Method Two:

The first step - the third step process is the same as method one;

Step 4 First Squeeze

Spread the lubricant evenly on the surface of the mold, then place the billet on the end of the ejector rod stably, and use the Y315 press for the first extrusion.

Step 5 Second Extrusion

The billet after the first extrusion is reheated, and then the slump section faces upwards, that is, after the billet placed for the first extrusion is turned 180°, the second extrusion is performed. The comparison of the dies used in the two extrusions is shown in Figure 7.

Claims (2)

1. a warm-extrusion forming method for straight spur gear, is characterized in that: the concrete steps of the method are as follows:

First step blanking: according to the size of target gear determination blank, carries out blanking, and blank bottom is cylindrical, and top is conical, bottom body diameter larger than target gear reference diameter 6% ~ 10%, and top chamfer is 12 ° ~ 15 °;

Second step mould and die preheating: use acetylene flame by mould and die preheating to 200 DEG C ~ 250 DEG C, to reduce thermal loss when blank and contacting dies;

3rd step blank heating: after blank surface smears lubricant, implements differential heating by medium-high frequency eddy-current heating to blank, makes blank external temperature reach the temperature range of Warm Extrusion, and the inner lower temperature that keeps;

4th step first time extruding: first time extruding is carried out to blank, smears lubricant at die surface before extruding, make coefficient of friction reach 0.4 ~ 0.6;

5th step jumping-up: the jumping-up carrying out certain upset ratio after blank is heated again;

6th step oppositely second time extruding: angle section of being collapsed by the blank after jumping-up, after the blank laying state being about to extrude for the first time turns 180 °, carries out second time extruding upward;

The mould adopted in the implementation step of said method comprises punch and die, and described punch adopts the type gear design with incomplete profile of tooth, and the target gear being equivalent to produce is cut the shape after tip portion; Described die includes mould section and shaped segment, and the Internal periphery of described die shaped segment is consistent with target gear plane projected shape, and size is bigger than normal, is by the outwards biased certain numerical value gained of target gear flank profil; Described die enter mould section be have corresponding enter the tilting section of modular angle degree, entering mould section height and entering modular angle degree is determine according to the parameter of target gear.

2. a warm-extrusion forming method for straight spur gear, is characterized in that: the concrete steps of the method are as follows:

First step blanking: according to the billet size blanking of design, blank bottom is cylindrical, top is conical, bottom body diameter larger than target gear reference diameter 6% ~ 10%, and top chamfer is 12 ° ~ 15 °;

Second step mould and die preheating: use acetylene flame by mould and die preheating to 200 DEG C ~ 250 DEG C, to reduce thermal loss when blank and contacting dies;

3rd step blank heating: after blank surface smears lubricant, implements differential heating by medium-high frequency eddy-current heating to blank, makes blank external temperature reach the temperature range of Warm Extrusion, and the inner lower temperature that keeps;

4th step first time extruding: first time extruding is carried out to blank, smears lubricant at die surface before extruding, make coefficient of friction reach 0.4 ~ 0.6;

5th step oppositely second time extruding: after the blank laying state of first time extruding is turned 180 °, carry out second time extruding;

The mould that the implementation step of said method adopts comprises punch and die, and described punch adopts the type gear design with incomplete profile of tooth, and the target gear being equivalent to produce is cut the shape after tip portion; Described die includes mould section and shaped segment, and the Internal periphery of described die shaped segment is consistent with target gear plane projected shape, and size is bigger than normal, is by the outwards biased certain numerical value gained of target gear flank profil; Described die enter mould section be have corresponding enter the tilting section of modular angle degree, entering mould section height and entering modular angle degree is determine according to the parameter of target gear; The second time extruded in the 5th comparatively described step of die used extruded die tooth profile used and wanted large first time in the 4th described step.