METHOD FOR SURFACE-TREATING FORGING MEMBER

TECHNICAL FIELD

The present invention relates to a method for surface-treating a forging member.

BACKGROUND ART

Cold-forging, adopted as a method for manufacturing machine components, is limited to a greater extent than manufacturing by cutting in terms of the forms that can be manufactured. Nevertheless, cold-forging has numerous merits, making it possible to mass-produce the same forms, obtain higher strength, shorten machining time, and economize on materials, among other benefits.

It has traditionally been desirable to lubricate the surface of a columnar forging member serving as a workpiece to be cold-forged (such lubrication commonly being referred to as bonderizing, which is a lubricating-film-attaching treatment) and firmly anchor a lubrication film on the surface of the forging member in order to improve the die-releasing properties, to prevent damage to the mold due to heat or contact pressure arising during processing, as well as to prevent damage to the forging member itself.

The inventor(s) proposed workpiece surface treatment devices disclosed in JP-A 2007-38309 and U.S. Pat. No. 5,523,507. Prior to attaching a lubricating film to the surface of a forging member serving as a workpiece, these devices spray a slurry comprising a mixture of a liquid and an abrasive to perform a wet-blasting treatment on the surface of the forging member.

By performing this wet-blasting treatment, removal of oxidized films, oil, and other pollutants attached to the surface of the forging member is reliably and satisfactorily performed, and minute irregularities are formed on the surface of the forging member, whereby a lubricating film is satisfactorily established so as to not readily peel off.

PRIOR ART DOCUMENTS
Patent Documents

[Patent Document 1] JP-A 2007-38309

[Patent Document 2] Patent No. 5523507

DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention

As a result of further research and development regarding surface treatment of forging members such as is described above, the inventor(s) developed an innovative method for surface-treating a forging member, the method exhibiting unprecedented operations and effects.

Means for Solving the Problem

The main points of the present invention are described below with reference to the attached drawings.

The present invention relates to a method for surface-treating a forging member 1, the method being characterized in that a slurry 4 comprising a mixture of a liquid 2 and an abrasive 3 is mixed with pressurized air and sprayed on a surface 1a of the forging member 1, and innumerable recesses 5 measuring 0.5-2.00 μm in depth and 75-150 μm in opening width are provided on the surface 1a of the forging member 1.

The present invention also relates to a method for surface-treating a forging member according to the first aspect, characterized in that the forging member 1 is made from chromium-molybdenum steel.

The present invention also relates to a method for surface-treating a forging member according to either of the first and second aspects, characterized in that a stainless-steel abrasive having an average particle diameter of approximately 150 μm is adopted as the abrasive 3.

Effect of the Invention

Because the present invention is configured as described above, this innovative method for surface-treating a forging member exhibits the satisfactory establishment of a lubricating film so that the lubricating film formed on the surface of the forging member does not readily peel off, among other unprecedented operations and effects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a device for implementing the method for surface-treating a forging member as pertains to the present example;

FIG. 2 is a schematic view showing the state of a surface-treated forging member in the present example;

FIG. 3 is a partial enlarged view of the surface of the surface-treated forging member in the present example;

FIG. 4 is a schematic view illustrating conditions of testing that indicates the effectiveness of the present example;

FIG. 5 is a schematic view showing a test of the performance of a forging member using a forward rod/backward can extrusion tester;

FIG. 6 is a schematic view showing a test of the performance of a forging member using a forward rod/backward can extrusion tester;

FIG. 7 is a schematic view illustrating test results that indicate the effectiveness of the present example;

FIG. 8 is a schematic view illustrating test results that indicate the effectiveness of the present example;

FIG. 9 is a schematic view illustrating test results that indicate the effectiveness of the present example;

FIG. 10 is a schematic view illustrating test results that indicate the effectiveness of the present example;

FIG. 11 is a schematic view illustrating test results that indicate the effectiveness of the present example;

FIG. 12 is a schematic view illustrating test results that indicate the effectiveness of the present example; and

FIG. 13 is a schematic view illustrating test results that indicate the effectiveness of the present example.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are briefly described below with reference to the diagrams while indicating the action of the present invention.

In the present invention, a slurry 4 comprising a mixture of a liquid 2 and an abrasive 3 is mixed with pressurized air and sprayed on a surface of a forging member 1, and innumerable recesses 5 measuring 0.5-2.00 μm in depth and 75-150 μm in opening width are provided on the surface of the forging member 1.

The forging member 1 comprising the innumerable recesses 5 does not readily lose lubricity once the lubricating treatment has been performed, and is highly exceptional as a raw material for forging.

Examples

A specific example of the present invention is described below with reference to the diagrams.

The present example is a method for surface-treating a transported columnar forging member 1, a surface treatment being performed on a surface 1a of the forging member 1. The forging member 1 is columnar and is made from metal (chromium-molybdenum steel). In the present document, “columnar” refers to a long shape of circular cross-section; in the broadest sense, “columnar” includes cylindrical shapes having hollow interiors.

Specifically, the method for surface-treating a forging member 1 as pertains to the present example is performed using the surface treatment device 10 disclosed in U.S. Pat. No. 5,523,507.

The surface treatment device 10 is equipped with a transportation part 12 for transporting the columnar forging member 1 on a base 11, as illustrated in FIG. 1, and a surface treatment part for performing wet-blasting treatment and other treatments on the forging member 1 transported by the transportation part 12.

Specifically, the surface treatment part is configured from a wet-blasting treatment part 13, and other treatment parts (a cleaning treatment part, a hot-water washing part, a lubrication treatment part, and a drying treatment part) (not shown).

The wet-blasting treatment part 13 is provided to the base 11, over which the columnar forging member 1 is caused to pass, as shown in FIG. 1. The wet-blasting treatment part 13 is equipped with a slurry-spraying part 14, a slurry reservoir part 15 arranged at a position below the slurry-spraying part 14, and a slurry-transporting part 17 for transporting a slurry 4 from the slurry reservoir part 15 to the slurry-spraying part 14 via a pump device 16, and is configured such that the slurry 4 sprayed from the slurry-spraying part 14 is delivered to the slurry reservoir part 15 and reused.

The slurry-spraying part 14 is configured from a wide spray nozzle arranged above the transportation part 12 for transporting the columnar forging member 1, as shown in FIG. 1.

The slurry-transporting part 17 described above is connected to the spray nozzle, and a compressed-air-transporting part 19 provided in a separate circuit and extending from a compressed-air-supplying part 18 is connected to the spray nozzle, the spray nozzle being configured such that the slurry 4 supplied from the slurry-transporting part 17 is accelerated by compressed air supplied from the compressed-air-transporting part 19 and is sprayed from the spray nozzle at a prescribed spraying speed.

The slurry 4 used in the present example is a mixture of a liquid 2 and a fine-particle abrasive 3.

The surface treatment used on the forging member 1 using the surface treatment device 10 comprising the configuration described above will now be described.

The surface 1a of the columnar forging member 1 transported by the transporting part 12 is appropriately treated by the surface treatment part.

Specifically, once the columnar forging member 1 transported by the transporting part 12 passes the wet-blasting treatment part 13, the slurry 4 is sprayed to blast the entire surface 1a (peripheral and lengthwise-end surfaces) of the columnar forging member 1, and innumerable minute recesses 5 are formed on the entire surface 1a (peripheral and lengthwise-end surfaces).

Next, once the columnar forging member 1 that has been blasted by the wet-blasting treatment part 13 passes the cleaning treatment part, the columnar forging member 1 is sprayed with cleaning fluid, whereby the forging member 1 is washed with water (to remove the slurry, chips, and the like).

Next, once the columnar forging member 1 that has been washed by the cleaning treatment part passes the hot-water washing part, the columnar forging member 1 is sprayed with hot water, whereby the forging member 1 is washed with water and heat-treated.

Next, once the columnar forging member 1 that has been washed and heat-treated by the hot-water washing part passes the lubrication treatment part, the columnar forging member 1 is coated with lubricant (e.g., metallic soap), whereby the forging member 1 is lubricated.

Next, once the columnar forging member 1 that has been lubricated by the lubrication treatment part passes the drying treatment part, the columnar forging member 1 is blown with hot air, whereby the forging member 1 is dried (solidifying the lubricant), and a lubricating film is formed on the entire surface 1a (peripheral and lengthwise-end surfaces) of the columnar forging member 1.

The columnar forging member 1 that has been dried by the drying treatment part is then guided out of the surface treatment device 10 by a guiding part. The lubricating film is satisfactorily established on the entire surface 1a (peripheral and lengthwise-end surfaces) of the guided columnar forging member 1.

In the present example, innumerable (approximately 74,000) recesses 5 (pyramid-shaped recesses) are formed on the surface 1a of the forging member 1 having the raw materials and size described below, the recesses 5 measuring 0.5-2.00 μm in depth, 75-150 μm in opening width, and 0.006-0.023 mm²in area, the forging member 1 being highly exceptional.

This is confirmed by the testing described below.

Specifically, first, an abrasive A (50-μm stainless-steel abrasive), an abrasive B (150-μm stainless-steel abrasive), an abrasive C (210-μm stainless-steel abrasive), an abrasive D (320-μm stainless-steel abrasive), an abrasive E (250-μm alumina abrasive), and an abrasive F (300-μm steel abrasive) are prepared. The abrasives A-E are used to treat the forging member 1 (chromium-molybdenum steel, SCM420, 19.9 mm in diameter, 20 mm long, approximately 1,030 mm²in surface area) using the surface treatment device 10 described above (the abrasive F is used to perform shot-blasting), and the amounts of the resulting forging member 1 extruded forward and backward are measured using a forward rod/backward can extrusion tester(see FIGS. 4 and 5).

FIG. 7 shows the relationship between the abrasives A-F and the forward extrusion amount, and FIG. 8 shows the relationship between the abrasives A-F and the backward extrusion amount.

When the punch stroke in forward rod/backward can extrusion is fixed, the frictional resistance of the surface decreases in correspondence with an increase in the forward extrusion amount and a decrease in the backward extrusion amount; ordering the abrasive B, the abrasive C, the abrasive D, the abrasive E, the abrasive F, and the abrasive A in the stated order results in the best forward extrusion amount and backward extrusion amount as well as low frictional resistance of the surface.

Specifically, a forging member 1 treated using the abrasive B has more forward elongation and less backward elongation than does a forging member 1 treated using another abrasive; accordingly, it was evident that the frictional resistance in the surface 1a of the forging member 1 treated using the abrasive B is low. It is apparent from these results that the molding load is strongly affected by the abrasive used.

FIG. 9 shows the relationship between the maximum load during cold-forging molding and the forward extrusion amount.

The forging member 1 treated using abrasive B described above has a lower maximum load during cold-forging molding than does a forging member 1 treated using another abrasive.

Specifically, the forging member 1 comprising a surface 1a in which a high forward extrusion amount is produced results in a lower maximum load during cold-forging molding, the maximum load during cold-forging molding and the extrusion amounts being approximately inversely proportional, as predicted.

FIG. 10 shows the relationship between the forward extrusion amount and the depth (H) of the recesses 5 produced in the end surfaces of the forging member 1 when surface treatment is performed on the forging member 1 using the abrasives A-F, and FIG. 11 shows the relationship between the forward extrusion amount and the opening width (W) of the recesses 5 produced in the end surfaces of the forging member 1 when surface treatment is performed on the forging member 1 using the abrasives A-F.

As is apparent from FIG. 10, the depth of the recesses 5 produced by treatment using the abrasive B is 0.5 μm when the air pressure is 0.2 MPa, and is 1.5 μm when the air pressure is 0.4 MPa. As is apparent from FIG. 11, the opening width of the recesses 5 produced by treatment using the abrasive B is 150 μm when the air pressure is 0.2 MPa, and is 140 μm when the air pressure is 0.4 MPa.

FIG. 12 shows the relationship between the forward extrusion amount and the depth (H) of the recesses 5 produced in the side surface of the forging member 1 when surface treatment is performed on the forging member 1 using the abrasives A-F, and FIG. 13 shows the relationship between the forward extrusion amount and the opening width (W) of the recesses 5 produced in the side surface of the forging member 1 when surface treatment is performed on the forging member 1 using the abrasives A-F.

As is apparent from FIG. 12, the depth of the recesses 5 produced by treatment using the abrasive B is 0.5 μm when the air pressure is 0.2 MPa, and is 2.00 μm when the air pressure is 0.4 MPa. As is apparent from FIG. 13, the opening width of the recesses 5 produced by treatment using the abrasive B is 75 μm when the air pressure is 0.2 MPa, and is 125 μm when the air pressure is 0.4 MPa.

The testing described above makes it possible to confirm that a forging member 1 treated using an abrasive B determined to be optimal and comprising innumerable recesses 5 produced in a surface 1a of the forging member 1, the recesses 5 measuring 0.5-2.00 μm in depth and 75-150 μm in opening width, does not readily lose lubricity once a lubricating treatment has been performed, and is highly exceptional as a raw material for cold-forging.

Because the present example is configured as described above, a slurry 4 comprising a mixture of a liquid 2 and an abrasive 3 is mixed with pressurized air and sprayed on a surface of a forging member 1, and innumerable recesses 5 measuring 0.5-2.00 μm in depth and 75-150 μm in opening width are provided on the surface of the forging member 1.

The forging member 1 comprising the innumerable recesses 5 does not readily lose lubricity once the lubricating treatment has been performed, and is highly exceptional as a raw material for forging.

Because the forging member 1 is made from chromium-molybdenum steel, the present example can reliably exhibit the operations and effects described above.

Because a stainless-steel abrasive having an average particle diameter of approximately 150 μm is adopted as the abrasive 3, the present example can reliably exhibit the operations and effects described above.

The present invention is not limited to the present example; the specific configuration of the configuration requirements can be optimized.

METHOD FOR SURFACE-TREATING FORGING MEMBER

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