KR102344891B1 - Manufacturing method for spline hub - Google Patents

Abstract

The present invention is a spline hub manufacturing method capable of manufacturing a spline hub having a precise shape while minimizing the amount of input and wasted raw materials by eliminating hot forging, primary turning, and secondary turning processes when manufacturing the spline hub. is about
The spline hub manufacturing method according to the present invention includes a preparation step of preparing a raw material, a first heat treatment step of annealing the raw material, and shot blasting the raw material on which the first heat treatment step is completed. A surface treatment step, a lubrication step of bonding the raw material on which the surface treatment step has been completed, and a primary forming step of cold forging the raw material on which the lubrication step has been completed to produce a preform having the outline of a spline hub; A secondary forming step of cold forging the preform to manufacture a work-in-progress with improved dimensional accuracy, a second heat treatment step of normalizing the work-in-progress, and a boss hole passing through the center of the work-in-progress on which the second heat treatment step is completed and a piercing step of forming a plurality of flow path holes formed at predetermined intervals along the outer diameter of the work-in-progress, a broaching step of forming splines in the boss hole, and finishing the work-in-progress on which the broaching step is completed to finish the finished product It includes a processing step to manufacture.

Description

Spline hub manufacturing method

The present invention relates to a method for manufacturing a spline hub, and more particularly, to a method for manufacturing a spline hub capable of minimizing the amount of raw materials initially input when manufacturing the spline hub.

A spline hub, one of the components of an automatic transmission, is a core part mounted at the center of the turbine of the torque converter, and serves to transmit the power of the turbine to the input shaft of the transmission.

Such a spline hub is a part where complex shape and dimensional control are very important, and the quality and precision are greatly affected depending on the processing technology, and a complicated processing process is performed to manufacture a product with high precision.

The general process for manufacturing a spline hub consists of raw material input → hot forging → 1st turning → 2nd turning → Hole and spline machining (Piercing & Broaching) → Finishing machining → Washing → Finished product packaging → Shipping.

However, in order to perform hot forging on raw materials, there is a problem in that the process and equipment are complicated, so that the production cost is rapidly increased, and defects such as decarburization, surface defects, scale, and scratches are generated due to high temperature.

In addition, primary and secondary turning are performed on the heat-treated raw material to be processed into the shape of a spline hub, and there is a problem in that the amount of raw material lost at this time reaches about 55% of the amount of raw material initially input.

That is, if about 760 g of raw material is input and the finished product is manufactured after 1st/2nd turning and 1st/2nd finishing machining, the weight of the final finished spline hub will be about 350g, and the remaining 410g of raw material is It is discarded through the processing step.

An embodiment of the present invention is capable of manufacturing a spline hub having a precise shape while minimizing the amount of input and wasted raw materials by eliminating hot forging, primary turning, and secondary turning processes when manufacturing the spline hub. An object of the present invention is to provide a method for manufacturing a spline hub.

A spline hub manufacturing method according to the present invention for achieving this object includes a preparation step of preparing a raw material, a first heat treatment step of annealing the raw material, and shot blasting the raw material on which the first heat treatment step is completed. Shot blast) surface treatment step, lubrication step of bonding the raw material on which the surface treatment step has been completed, and cold forging the raw material on which the lubrication step has been completed 1 to manufacture a preform having the outline of a spline hub The secondary forming step, the secondary forming step of cold forging the preform to manufacture a work-in-progress with improved dimensional accuracy, a second heat treatment step of normalizing the work-in-progress, and the center of the work-in-progress on which the second heat treatment step is completed A piercing step of forming a boss hole passing through and a plurality of flow path holes formed at predetermined intervals along the outer diameter of the work-in-process, a broaching step of forming splines in the boss hole, and a work-in-progress on which the broaching step is completed It includes a processing step of manufacturing a finished product by finishing processing.

The work-in-process manufactured through the secondary molding step is characterized in that it has a thickness processing allowance of 0.5 mm to 1.0 mm compared to the finished product.

The primary molding step and the secondary molding step are performed using different molds, and the mold used in the secondary molding step has a more precise overall outline of the spline hub than the mold used in the primary molding step. characterized in that

The raw material is characterized in that the SCM415 alloy.

Between the broaching step and the processing step, a third heat treatment step of performing carburizing heat treatment on the work-in-progress on which the broaching step is completed is included.

The weight of the raw material input in the surface treatment step is characterized in that 1.5 times or less of the weight of the finished product.

The present invention has various effects as follows.

First, the present invention can minimize the amount of raw materials consumed by manufacturing a spline hub having a precise shape by inputting raw materials having a weight of 1.5 times or less compared to the weight of the final target finished product.

Second, the present invention can secure high strength, hardness, and toughness by performing the second heat treatment step using the SCM415 alloy.

Third, the present invention has the effect of maximizing the miniaturization and cost reduction of equipment by not performing the conventional hot forging.

Fourth, the present invention can shorten the manufacturing process and time by not performing the conventional primary and secondary turning, and has an effect of solving the problem of wasting a lot of raw materials through turning.

1 is a flowchart of a spline hub manufacturing method according to the present invention.
Figure 2 is a state diagram of the Fe-C-based alloy.
3 is a view showing the shape and cross section of the preform and the finished product according to the present invention.
4 is a view showing a state in which raw materials are molded during the primary forming step and the secondary forming step according to the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, and reference numerals of the background art and the previously described configurations are the same unless otherwise noted.

The description of the spline hub manufacturing method of the present invention described below is a preferred embodiment of the present invention, and is not limited to the embodiment, but may be implemented in various forms.

In addition, the shape and size of each configuration described below are merely representative of the exemplary embodiment, and are not fixed, and can be variously changed if the same effect can be realized.

1 and 4, the spline 270 hub manufacturing method according to an embodiment of the present invention includes a preparation step (S10), a first heat treatment step (S20), a surface treatment step (S30), and lubrication. Treatment step (S40), primary forming step (S50), secondary forming step (S60), second heat treatment step (S70), piercing step (S80), broaching step (S81), third heat treatment step (S90) and a processing step (S100).

The preparation step (S10) is a step of preparing the solid raw material 100 in the form of a cylinder, and a process of cutting or washing to an appropriate size for input to a surface treatment step (S30) to be described later may be added.

In an embodiment of the present invention, SCM415 alloy was applied as a material of the solid raw material 100 . SCM415 alloy is an alloy steel in which small amounts of chromium (Cr) and molybdenum (Mo) are added and 0.15% carbon is added, and it is preferable to perform the third heat treatment step (S90), which will be described later, in order to improve the mechanical properties of the SCM415 alloy, By applying SCM415 alloy, it is possible to manufacture a spline hub having high surface strength and ductility at the same time.

The first heat treatment step (S20) is a step for improving ductility by refining grains while removing internal residual stress by performing annealing heat treatment of the prepared raw material 100, and as shown in FIG. 2, recrystallize the SCM415 alloy It is annealed at a temperature below the A1 transformation point (726°C) to prevent this from occurring, and more preferably, it is preferable to slowly cool after heating to a temperature below 680°C to prevent recrystallization from occurring finely.

The raw material 100 on which the first heat treatment step (S20) has been completed is subjected to a surface treatment step (S30) of removing scale present on the surface and performing a shot blast process so that more lubricant can be attached at the same time.

The process of cutting the raw material 100 to an appropriate size may be performed in the above-described preparation step (S10), but it is also possible to perform the surface treatment step (S30) after the first heat treatment step (S20) is completed.

In order to manufacture the spline 270 hub using the conventional hot forging, raw material 100 having a weight of about twice or more compared to the weight of the final target finished product 130 must be input, but the primary forming step according to the present invention When applying (S50) and the secondary molding step (S60), the final finished product 130 having the same weight can be manufactured just by adding the raw material 100 having a weight of 1.5 times or less compared to the weight of the finished product 130. have.

In order to minimize the loss of the raw material 100, which is the most important object of the present invention, in the embodiment of the present invention, raw materials 100 (508 g) having a weight of 1.5 times or less of the weight (346 g) of the finished product 130 were added, and the finished product Until 130 was produced, a loss of 162 g of raw material (100) occurred.

The raw material 100 on which the surface treatment step (S30) is completed is subjected to a lubrication treatment step (S40) to improve corrosion resistance by forming a phosphate film through bonderite treatment.

The raw material 100 that has been lubricated is molded into the shape of the spline 270 hub through cold forging. If the shape of the spline 270 hub is precisely formed with only one cold forging, a very large amount of It is not preferable because a load is generated and a problem of damage occurs.

Therefore, as in one embodiment of the present invention, it is preferable to carry out the primary forming step (S50) and the secondary forming step (S60) separately, and rather than performing cold forging by dividing it twice in one mold (spline ( 270) It is preferable to form a more precise spline 270 hub twice by using a mold in which the shape precision of the hub is different from each other.

Prior to a detailed description with reference to FIGS. 3 and 4, (a) of FIG. 4 is a view showing a cross section of the work-in-work 120 in the form of a spline 270 hub in which the secondary forming step (S60) is completed, (b) ) is a view of putting the raw material between the first upper mold 210 and the first lower mold 220 before the primary forming step (S50), (c) is a view of performing the primary forming step (S50), (d) is a view in which the secondary forming step (S60) is being performed, (d) is a view in which the secondary forming step (S60) is completed.

As shown in FIG. 2, after putting the cut raw material between the first upper mold 210 and the first lower mold 220 on which the outline of the spline 270 hub is formed, the first cold forming is performed. Thus, the preform 110 having the outline of the spline 270 hub having low dimensional accuracy is manufactured.

Thereafter, using the second upper mold 230 and the second lower mold 240 having improved dimensional accuracy than the first upper mold 210 and the first lower mold 220, the preform 110 is secondary cold. By performing molding, the workpiece 120 with improved dimensional accuracy is manufactured.

Since the manufactured work-in-process 120 is manufactured as a finished product 130 through a processing step S100 to be described later, the overall volume should be larger than that of the final target finished product 130 . Therefore, it is preferable that the work-in-process 120 manufactured through the secondary forming step S60 has a thickness processing allowance 140 of 0.5 mm to 1.0 mm compared to the final target finished product 130 .

That is, it is preferable to process the finished product 130 while improving the dimensional accuracy through a processing step ( S100 ) to be described later after molding to have a larger volume by a thickness of 0.5 mm to 1.0 mm from the surface of the finished product 130 .

The second heat treatment step (S70) of normalizing the work-in-work 120 after the secondary forming step (S60) is completed is changed to a standard structure of the material to improve machinability.

Since the raw material 100 according to the present invention is an SCM415 alloy, it is preferable to be carried out in a temperature range of 30°C to 50°C lower than the A3 transformation point (about 910°C).

A piercing step of forming a boss hole 250 penetrating through the center of the work-in-progress 120 after the secondary forming step (S60) and a plurality of passage holes 260 formed at predetermined intervals along the outer diameter of the work-in-work 120 (S80) is performed.

The boss hole 250 and the flow hole 260 are a configuration that must be basically provided in the spline 270 hub, and it is difficult to precisely form the above-described primary forming step (S50) and secondary forming step (S60). It would be desirable to form using the piercing step (S80).

When the piercing step (S80) is completed, the spline 270 is formed along the inner surface of the boss hole 250 through cutting so that it can be tooth-engaged with the shaft to be inserted through the boss hole 250. Broaching Steps are performed, and in some cases, it is also possible to form the splines 270 along the outer diameter of the workpiece 120 .

The work piece 120 of the SCM415 alloy after the broaching step (S81) is completed has carbon infiltrated into the surface through carburizing heat treatment to change the surface to high carbon steel, and at the same time maintain ductility in the core to secure high strength, high hardness and toughness at the same time A third heat treatment step (S90) is performed.

In this third heat treatment step (S90), the SCM415 work piece 120 is heated at 900 ° C. to 950 ° C. for 3 to 4 hours, then carbon is penetrated to a depth of about 1 mm, quenching is performed twice, and then tempering is performed.

When the SCM415 work piece 120 is heated to a temperature range of 900°C to 950°C, it has an austenite phase, and in this region, the carburizing layer deepens and more carbon is dissolved to increase the carbon concentration.

For carburizing, it is heated at high temperature for a long time, so to refine the grown tissue, it is heated to 940℃ higher than the A3 transformation point and first quenched in oil. Then, in order to change the carburized part on the surface to martensite and harden it, it is heated to a temperature above the A3 transformation point, and then secondary quenching is performed in water.

When the secondary quenching is completed, it is heated at a temperature of 150°C to 200°C for about 10 minutes to remove stress and perform tempering to improve toughness.

When this second heat treatment step (S70) is completed, the target spline (270) shape of the hub is obtained while precisely removing the thickness machining allowance 140 part given during the above-described secondary forming step (S60) through finishing machining. A processing step (S100) of manufacturing the finished product 130 by processing is performed.

The finished product 130 manufactured through the processing step (S100) is moved through separate washing and packaging, and when the weight of the finished product 130 manufactured according to the present invention is compared with the weight of the raw material 100 initially input, about A weight difference of 1.5 times or less occurs.

S10: preparation step S20: first heat treatment step
S30: surface treatment step S40: lubrication treatment step
S50: first forming step S60: second forming step
S70: Piercing step S80: Broaching step
S90: second heat treatment step S100: processing step

Claims (6)

A preparatory step to prepare SCM 415 alloy as a raw material;
a first heat treatment step of annealing the raw material at a temperature of 680° C. or less;
a surface treatment step of shot blasting the raw material on which the first heat treatment step has been completed;
a lubrication treatment step of bonding the raw material on which the surface treatment step has been completed;
a primary forming step of cold forging the raw material on which the lubrication step has been completed to manufacture a preform having the outline of a spline hub;
a secondary forming step of cold forging the preform to manufacture a work-in-process with improved dimensional accuracy;
a second heat treatment step of normalizing the work-in-process to a temperature below the A3 transformation point;
a piercing step of forming a boss hole passing through the center of the work-in-progress on which the second heat treatment step has been completed and a plurality of passage holes formed at predetermined intervals along the outer diameter of the work-in-work;
Broaching step of forming a spline (Spline) in the boss hole;
a third heat treatment step of performing carburizing heat treatment at a temperature of 900° C. to 950° C. on the work-in-process on which the broaching step is completed; and
and a machining step of manufacturing a finished product by finishing the work-in-progress on which the third heat treatment step has been completed.
The method of claim 1,
The method for manufacturing a spline hub, characterized in that the work-in-process manufactured through the secondary forming step has a thickness processing allowance of 0.5 mm to 1.0 mm compared to the finished product.
The method of claim 1,
The primary molding step and the secondary molding step are performed using different molds, and the mold used in the secondary molding step has a more precise overall outline of the spline hub than the mold used in the primary molding step. A spline hub manufacturing method, characterized in that.
delete delete The method of claim 1,
The method of manufacturing a spline hub, characterized in that the weight of the raw material input in the surface treatment step is 1.5 times or less of the weight of the finished product.

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