JP2015134370A - Manufacturing method of forging product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a crack in a flange-like swollen part even in a cold forging method, in a manufacturing method of a forging product for providing the forging product by plastically processing a cutting material of leaving a fracture surface on a cutting surface.SOLUTION: The fracture surface of remaining on the cutting surface of the cutting material is ground and removed by a wet type shot blast. In a wet type shot blast process, fluid 32 including a shot grain 31 is projected to a spherical head part 28 by a projection gun 38. Thus, the fracture surface 17 remaining on the cutting surface 16 is ground and removed. Since a grinding-finished material of removing the fracture surface 17 of becoming a crack occurrence factor is sent to a cold forging process, even if the flange-like swollen part is overhung and molded in cold forging, there is no fear of causing a crack in the swollen part.

Description

  The present invention relates to a method for manufacturing a forged product that obtains a forged product by plastic working a cut material having a fracture surface remaining on a cut surface.

  A manufacturing method for obtaining a tie rod end housing by subjecting a rod-shaped material to a forging process is known (see, for example, Patent Document 1 (FIG. 1)).

FIG. 11 is a diagram for explaining a conventional manufacturing method. As shown in FIG. 11A, a cutting material 101 is prepared. The cutting material 101 is obtained by cutting a steel round bar with an appropriate length.
By subjecting the cutting material 101 to upset processing (upsetting processing), as shown in FIG. 11B, a preform 102 having a spherical head 102a at one end is obtained.

A lubricant is applied to the preform 102 and cold forging is performed to obtain a forged product 103 as shown in FIG. The forged product 103 is a tie rod end housing, and includes a cup portion 105 having a concave portion called a socket portion 104 at one end.
The tie rod end housing has a complicated shape, and in the manufacturing method machined by machining, the material yield is low and the machining time is long. In this regard, the cold forging method has the advantage that the material yield is extremely good and the processing time is shortened.

  By the way, in the case of a tie rod end housing, a boot (not shown) is attached to the outer periphery of the cup portion 105 so that dust and dirt do not enter the socket portion 104. Along with this, it is necessary to attach a flange-like flange for positioning the boot to the cup portion 105.

  FIG. 12A shows a cross section of a tie rod end housing formed by extending a flange 106 on a cup portion 105. The flange 106 can be cut out by machining, but the material yield is poor and the machining time is long. Therefore, cold forging is preferred.

However, when the inventors made a prototype by cold forging, it was found that a crack 107 was formed in the flange 106 as shown in FIG. Furthermore, it was discovered that the fracture surface remaining on the cut surface of the cutting material appeared around the crack 107. From this, it is considered that a crack occurred from the valley of the fracture surface.
For example, in a pressure vessel, it is known that a hoop stress is generated along the circumferential surface of a cylinder that receives an internal pressure, and this stress is proportional to the outer diameter.

When the socket part 104 is formed by forging, the cup part 105 is strongly expanded in diameter. Assuming that this diameter expansion approximates the above internal pressure, the stress generated along the circumferential surface of the outer periphery 106a of the flange 106 is larger than that of the outer periphery 105a of the cup portion 105.
It can be understood that the outer periphery 105a of the cup portion 105 does not crack, but the outer periphery 106a of the flange 106 cracks.

Cracks can be eliminated by hot forging. However, in the case of hot forging, since the dimensional accuracy of the forged product is not good, it is necessary to cut sufficiently by machining, and the manufacturing cost including the material cost increases.
In this regard, if the cold forging method is used, the dimensional accuracy of the forged product is improved, and the manufacturing cost including the material cost can be reduced.

  Therefore, while a reduction in manufacturing cost is required, a manufacturing method that does not cause cracks in the ridge-like bulged portion is required even in the cold forging method.

Japanese Patent Publication No. 2-52577

  The present invention is a method for producing a forged product in which a forged product is obtained by plastic working a cut material having a fracture surface remaining on the cut surface. The problem is not to let them.

  The inventors removed the fracture surface remaining on the cut surface of the cut material before cold forging. As a result, no cracks occurred. The invention completed based on this knowledge is as follows.

The invention according to claim 1 is a method of manufacturing a forged product,
A cutting process with a cutting machine to cut a material to obtain a cutting material of a predetermined dimension;
In a wet shot blasting machine, a wet shot blasting process for obtaining a ground material by grinding a surface of an area including a cut surface in the cutting material,
In a lubricant applicator, a lubricant application step of applying a lubricant to a surface including a ground surface of the ground material,
And a cold forging step of obtaining a forged product obtained by performing cold forging on a region including the ground surface to which the lubricant is applied by a cold forging machine.

  The invention according to claim 2 is characterized in that, in the cold forging step, a bulging portion protruding from the ground surface is formed.

  The invention according to claim 3 is characterized in that a polygonal abrasive is used as the shot grain in the wet shot blasting process.

  In the invention according to claim 4, a preforming step of preforming a region including the cut surface of the cutting material by a preforming machine to obtain a preformed product is added between the cutting step and the wet shot blasting step. In the shot blasting process, the surface of the region including the preformed portion in the preform is ground.

  In the invention which concerns on Claim 1, the torn surface which remains in the cut surface of a cutting material is ground and removed by wet shot blasting. Since the fracture surface is removed before cold forging, it is possible to prevent the occurrence of cracks and obtain a good forged product.

If the fracture surface is mechanically removed with a cutting tool or a grinding wheel, the processing cost increases and the productivity decreases.
In this respect, since shot blasting only projects shot grains, productivity is increased and processing costs can be easily reduced.

  Shot blasting includes a dry blast method and a wet blast method. The dry blast method projects dry shot grains. In the wet blast method, a fluid (for example, water) containing shot grains is projected.

In the cutting process, cutting oil is used in combination to extend the life of the cutting blade.
In the dry blasting method, since only the shot grains are applied, the cutting oil adhering to the cut surface of the cutting material cannot be completely degreased. For this reason, the lubricant applied in the lubricant application process is not fixed, and a degreasing process is required separately.
In this regard, the wet blasting method eliminates the need for a separate degreasing step because the fluid washes away the cutting oil.

Further, in the dry blast method, when shot grains are applied, the surface becomes hard due to work hardening phenomenon, and the forging load in the cold forging process increases. In addition, the temperature of the surface rises due to the collision of shot grains.
In this respect, the wet blast method does not increase the temperature because the fluid becomes a coolant, and the fluid becomes a cushion and the work hardening phenomenon hardly occurs.

  As described above, by removing the fracture surface remaining on the cut surface of the cutting material with wet shot blasting, it is possible to omit the degreasing process and prevent work hardening of the surface, while also achieving high productivity and processing cost. Can be reduced.

In the invention which concerns on Claim 2, the bulging part which protrudes from a grinding surface is formed in a cold forging process. Although the bulging portion where a large stress is generated during forging is likely to crack, according to the present invention, the occurrence of a crack can be suppressed even in the bulging portion.
Therefore, according to the present invention, a manufacturing method is provided that does not cause cracks in the bowl-shaped bulged portion even by the cold forging method.

  In the invention which concerns on Claim 3, a polygonal abrasive is used as a shot grain in a wet shot blasting process. Compared with spherical shot grains, polygonal shot grains can be ground without crushing the fracture surface, and therefore can be reliably removed without leaving a fracture surface.

  In the invention according to claim 4, a preforming step of preforming a region including the cut surface of the cutting material by a preforming machine to obtain a preformed product is added between the cutting step and the wet shot blasting step. In the shot blasting process, the surface of the region including the preformed portion in the preform is ground. By adding the preforming step, a spherical head or the like can be formed in advance at one end of the rod-shaped cutting material, and a forged product having a more complicated shape can be manufactured. If a spherical head or the like is formed in advance, it becomes difficult to grind the fractured surface by machining, but according to the present invention, the fractured surface can be easily ground by using wet shot blasting.

It is a figure explaining the cutting process concerning the present invention. It is a perspective view of a cutting material. It is a figure explaining a preforming process. It is a side view of a preforming product. It is an enlarged view of polygonal shot grains. It is a principle diagram of a wet shot blasting machine. It is a figure explaining a wet shot blasting process. It is a figure explaining a lubricant application process. It is a figure explaining a cold forging process. It is sectional drawing and a top view of a forged product. It is a figure explaining the conventional manufacturing method. It is a figure explaining the problem in the prior art.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the cutting machine 10 includes a bed 12 on which a rod-shaped material (for example, a round steel bar) 11 is placed, a clamper 13 that holds the material 11 placed on the bed 12, and a cutting blade 14. .
The rod-shaped material 11 is a long steel rod, protrudes from the bed 12 by a predetermined dimension L, and lowers the cutting blade 14 (cutting process). At this time, cutting oil is applied or sprayed in advance on the cutting portion of the material 11.

  For example, if cardboard is cut with a scissors that are not cut well, fuzz called “swell” occurs on the cut surface, or a rough surface remains. When the steel material is broken by a shearing action, a peeling or rough surface remains in the same manner. This “peel” or rough surface is hereinafter referred to as a fracture surface.

  As shown in FIG. 2, the cutting material 15 obtained by cutting the material 11 has a cutting surface 16 on the end surface, but the fracture surface 17 remains on the cutting surface 16.

Next, as shown in FIG. 3, the cutting material 15 is set in the preforming machine 20. The preforming machine 20 includes, for example, an upset lower mold 23 having a cutting material insertion hole 21 and a hemispherical recess 22, and an upset upper mold 25 having a hemispherical recess 24.
The cutting material 15 is inserted into the cutting material insertion hole 21 so that the cutting surface 16 is positioned higher. Next, the upper die 25 for upset is lowered and the diameter is increased while compressing the upper end portion of the cutting material 15 (preliminary molding step). At this time, cutting oil is applied or sprayed to the deformed portion in advance.

As a result, a preform 27 as shown in FIG. 4 can be obtained. The preform 27 has a spherical head 28 at one end, and the contact surface 16 and the fracture surface 17 remain on the spherical head 28.
Polygonal shot grains 31 as shown in FIG. 5 are prepared for wet shot blasting to be performed next. The shot grain 31 is a stainless steel abrasive having a representative dimension A of 100 μm.

The principle of the wet shot blasting machine 30 that projects such shot grains 31 will be described with reference to FIG.
As shown in FIG. 6, the wet shot blasting machine 30 includes a tank 33 that stores a mixture of a liquid 32 typified by water and a shot grain 31, and a pump 34 that pumps the liquid 32 containing the shot grain 31 from the tank 33. A liquid hose 35 extending from the pump 34, a high-pressure air source 36 provided separately from the tank 33, an air hose 37 extending from the high-pressure air source 36, and a projection gun connected to the liquid hose 35 and the tip of the air hose 37. 38.

The position of the projection gun 38 is accurately controlled in the range B along the spherical head 28 where the fracture surface 17 remains by a robot hand or the like.
At this time, the preform 27 is rotated around the longitudinal axis.
The liquid 32 atomized with high-pressure air is projected from the projection gun 38 onto the spherical head 28. The liquid 32 to be atomized contains a predetermined proportion of shot particles 31.

  FIG. 7A is a cross-sectional view of the main part of the spherical head 28 before the wet shot blasting process, the fracture surface 17 remains, and the maximum depth of the valley is d. This maximum depth d can be determined in advance by preparing a plurality of preforms (FIG. 4, reference numeral 27) and measuring them with a surface roughness meter.

When the liquid 32 is projected onto the spherical head 28 by the projection gun 38 shown in FIG. 6, the surface of the spherical head 28 is ground by the included shot grains 31. At this time, the cutting oil is washed away with the liquid 32 and degreased. Since the grinding depth is proportional to the projection time, the projection is continued until the grinding depth reaches d.
After the projection, as shown in FIG. 7B, a ground material 39 having a smooth surface is obtained.

  That is, by grinding the surface of the region including the cut surface 16 (fracture surface 17) in the preform 27 shown in FIG. 7A using the wet shot blasting machine 30 shown in FIG. The ground material 39 shown in FIG.

Next, as shown in FIG. 8, the lubricant application material 40 is applied to the surface including the ground surface of the ground material 39 by the lubricant application machine 40 to obtain the lubricant applied material 42 (lubricant application process). .
The lubricant 41 is preferably a one-step type lubricant. The one-step lubricant is obtained by dispersing a lubricating component and an inorganic base component in an aqueous medium. By drying after application, moisture can be evaporated, a lubricating component film can be formed on the surface, and an inorganic base component film can be formed thereon. In order to reduce the drying time, it is recommended to preheat the material before applying the lubricant.

For comparison, a description will be given of a bonder treatment that has been widely used.
According to the bond treatment, a phosphate film is formed on the surface of the material, a metal soap film is formed thereon, and an unreacted soap film is formed thereon.
A general bond treatment is carried out in multiple steps of degreasing, washing with water, pickling, washing with water, phosphate treatment, washing with water, neutralization, soap treatment and drying.

Phosphate treatment forms a phosphate film. At this time, iron in the material reacts with phosphoric acid to produce iron phosphate as a reaction byproduct. Since this iron phosphate accumulates in the reaction tank in the form of sludge, its treatment is difficult.
In addition, oil is mixed in the degreasing waste liquid, and the waste liquid treatment is costly. Since the pickling waste liquid needs to be neutralized, the waste liquid treatment is costly.

In the present invention, a wet shot blasting process is performed before the lubricant application process. In the wet shot blasting process, oil and rust adhering to the surface of the material can be removed, so that degreasing and pickling are unnecessary. Therefore, the waste liquid processing cost can be significantly reduced.
In addition, since the phosphate treatment-washing-neutralization-soap treatment can be replaced with the application of a one-step lubricant, the number of steps can be greatly reduced.

Next, a cold forging process for cold forging the lubricant-coated material 42 described in FIG. 8 will be described.
As shown in FIG. 9, the cold forging machine 50 includes a lower die 51, a lower punch 52, a knockout 53, an upper die 54, and an upper punch 55.

The lubricant-coated material 42 is placed on the lower die 51, the upper die 54 is lowered, the lower punch 52 is raised, and the upper punch 55 is lowered. As a result, the bulging portion 61 is formed to protrude from the spherical head 28 (cold forging step).
Next, the lower punch 52 is lowered, and the upper die 54 and the upper punch 55 are raised. Next, the knockout 53 projects the molded product and discharges it from the lower mold 51.

  As shown in FIG. 10 (a), the obtained forged product 60 is a tie rod end housing, and has a cup part 63 having a concave part called a socket part 62 at one end. An exit 61 is provided.

Conventionally, such a bulging portion 61 has often been cracked. However, as shown in FIG. 10B, which is a view taken in the direction of arrow b in FIG. 10A, the bulging portion 61 of the forged product 60 is not cracked.
That is, as a result of removing the fracture surface 17 remaining on the cut surface 16 of the cutting material 15 before cold forging, generation of cracks can be prevented and a good forged product 60 can be obtained. Further, by removing the fracture surface 17 by wet shot blasting, it was possible to achieve high productivity and a reduction in processing cost.

In the examples, the forged product is a tie rod end housing, but it is suitable for products that show a fracture surface in the forging area, particularly those that show a fracture surface in the flange (bulging part) of the product. Does not matter.
Further, the shot grains are polygonal abrasives in the embodiment, but do not hinder the use of spherical abrasives.

  The present invention is suitable for forging a tie rod end housing.

  DESCRIPTION OF SYMBOLS 10 ... Cutting machine, 11 ... Raw material, 15 ... Cutting material, 16 ... Cutting surface, 17 ... Broken surface, 20 ... Preliminary molding machine, 27 ... Preliminary product, 30 ... Wet shot blasting machine, 31 ... Shot grain, 32 ... Liquid, 39 ... ground material, 40 ... lubricant coating machine, 41 ... lubricant, 42 ... lubricated material, 50 ... cold forging machine, 60 ... forged product, 61 ... bulging part.

Claims (4)

A method for manufacturing a forged product,
A cutting process with a cutting machine to cut a material to obtain a cutting material of a predetermined dimension;
In a wet shot blasting machine, a wet shot blasting process for obtaining a ground material by grinding a surface of an area including a cut surface in the cutting material,
In a lubricant applicator, a lubricant application step of applying a lubricant to a surface including a ground surface of the ground material,
A forging product manufacturing method comprising: a cold forging step for obtaining a forging product obtained by performing cold forging on a region including the ground surface to which the lubricant is applied, in a cold forging machine.   The method for producing a forged product according to claim 1, wherein, in the cold forging step, a bulging portion that protrudes from the ground surface is formed.   The method for producing a forged product according to claim 1, wherein a polygonal abrasive is used as the shot grain in the wet shot blasting step. Between the cutting step and the wet shot blasting step, a preforming step is performed by a preforming machine to preform a region including the cut surface of the cutting material to obtain a preformed product,
The method for producing a forged product according to any one of claims 1 to 3, wherein, in the wet shot blasting step, a surface of a region including the preformed portion in the preform is ground.

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