JPH07214469A - Efficient shot peening method of steel wire - Google Patents

Abstract

PURPOSE:To improve processing effciency by way of decreasing shot-balls not directly hitting a steel wire by supplying a gassy material in a container surrounded by a flat or curved inwall, forming a scattering atmosphere by way of giving an agitating and scattering motion to the shot-balls in this container and making the steel wire travel in the splashing atmosphere. CONSTITUTION:A splashing atmosphere is formed by agitating and scattering shot-balls 4 by way of supplying compressed air from a compressed air suplly pipe 3 to a cylindrical container 2 which is about 300mm in length and about 100mm in radius so as to carry out shot-peening of about 300mm of the steel wire 1 in length. The surface of a material to process is uniformly shot-peened by making the shot-balls repeated and reflectively moving on the inwall of this container 2 collide against the steel wire 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shot peening method for improving the fatigue characteristics of steel wire, especially for adjusting the residual stress on the surface of ultra-fine drawn wire, removing surface deposits and adjusting the surface roughness.

[0002]

2. Description of the Related Art Extra-fine steel wire used for reinforcing automobile tires, various industrial belts, etc., has better wire drawing workability and adhesiveness with rubber than hot-rolled wire after final patenting. It is manufactured by performing a brass plating treatment for applying and finish drawing. Recently, as a method for improving the fatigue characteristics of the brass-plated steel wire, attention has been paid to converting the residual tensile stress on the surface of the steel wire into a residual compressive stress by shot peening. However, when performing shot peening on this ultrafine steel wire, adjustment of the surface roughness and peeling of the brass plating layer have become problems.

As one of the measures against this problem, the present inventors have disclosed in Japanese Patent Application No. 3-518217 the basic method of air injection, which is a new shot peening method for extra-fine steel wire, and surface roughening as its treatment material. We proposed an ultrafine steel wire with improved fatigue strength and excellent fatigue resistance. In most conventional shot peening methods, a shot sphere is directly projected onto a material to be processed. For example, Japanese Unexamined Patent Publication (Kokai) No. 4-57672 discloses a method of directly projecting a shot ball with a high pressure gas or a rotary blade. In addition, JP-A-60-2
In 21263, the specific shot method is unknown, but by adjusting the arrangement position and projection angle of the projector,
A method of directly projecting a shot ball onto a material to be processed is also disclosed.

In such a method of directly projecting a shot ball, it is of course the strongest against the material to be processed and can be shot at an accurate position. However, when the material to be treated is a steel wire of about 1 mm or less, the surface area is so small that the number of shot spheres that do not directly contribute to shot peening is overwhelmingly large. . Further, in the case of direct projection, if shot peening is performed uniformly in the circumferential direction of the steel wire, nozzles must be provided at a plurality of locations.

Therefore, it has been desired to solve the above problems and develop a more efficient shot peening method.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to make shot spheres indirect projection so as to reduce the shot spheres that do not directly hit the steel wire and improve the processing efficiency. Provide a way. Another object is to improve the fatigue characteristics of the treated material by uniformly projecting shot balls onto the surface of the steel wire. Further, another object is to achieve a simplification of equipment and save space by reducing the projection density.

[0007]

The present invention is intended to solve the above-mentioned problems, and the gist thereof is as follows: (1) A container surrounded by a flat and / or curved inner wall in shot peening of a steel wire. By supplying a gaseous substance therein, a shot sphere in the container is agitated, a scattering motion is imparted to form a flying atmosphere, and a steel wire is run in the flying atmosphere to move the shot ball. An efficient shot peening method for a steel wire, characterized by uniformly colliding with the surface of the steel wire.

(2) The efficient shot peening method for steel wire according to (1), wherein the container has a tubular or box-like shape. (3) Efficient shot peening method for steel wire according to (1) or (2), wherein the first shot ball is supplied to the bottom of the container, the gaseous substance is supplied from the top of the container, and the steel wire is run in the central part of the container. .

(4) The efficient shot peening method for steel wire according to any one of (1) to (3), wherein the amount of shot balls in the previous period is 5 to 40% in volume ratio with the container. (5) The effective shot peening method for a steel wire as set forth in any one of (1) to (4), wherein the supply angle of the gaseous substance is set so that the gas does not directly hit the steel wire.

[0010]

The present invention is a so-called indirect projection method in which a shot ball is stirred and scattered in a container, and a steel wire is run in a scattering atmosphere due to its movement to perform shot peening. Therefore, the shot balls that have collided can be used immediately and repeatedly, and the usage amount is small and the cost can be reduced.
In addition, since there are very few useless shot spheres that do not collide, the projection density can be reduced, and it is possible to effectively collide the shot spheres that are repeatedly reciprocating on the inner wall of the container with the steel wire. Peening is possible.

In the shot ball container of the present invention, the shape of the inner wall may be such that the shot ball reflects and collides intensively with the steel wire in the central portion, and preferably the inner wall is spherical. In addition, shot peening can be performed even if the shape is polygonal or flat. If the amount of shot spheres used for the scattered shot spheres to sufficiently collide with the steel wire is less than 5% in terms of the volume ratio with the container, the shot sphere scattering density will be low and the shot peening efficiency will be low, exceeding 40%. In the present invention, it is limited to 5 to 40% because the consumption amount of the supply gas for scattering the shot balls is large because it is excessive. Furthermore, preferably 10
In the range of up to 20%, the scattering of shot balls effectively affects shot peening.

In addition, cheap compressed air is usually sufficient as the supply gaseous substance for scattering the shot balls, but it is preferable to use a compressed gas having a higher density, such as nitrogen or carbon dioxide. It is possible. But,
In the present invention, the gaseous substance is always supplied during the shot peening process, so it is necessary to provide the container with an exhaust port to discharge it. Therefore, it is important from the viewpoint of processing cost to select a gaseous substance that is cost-effective.

In the present invention, the gaseous substance supplied is
Since it is not a direct projection to the steel wire in the container but an indirect projection, it is sprayed from the top or side of the container onto the shot ball at the bottom of the container to stir and scatter to form a scattering atmosphere. For this reason, when shot directly onto the steel wire, the shot balls around the steel wire which collide with the steel wire are eliminated, and the original shot peening becomes difficult. In the present invention, the nozzle angle is not particularly restricted, but the gas supply direction is preferably displaced (5 to 10 °) from the line connecting the steel wire and the vertical line of the container in FIG. Supply from the upper surface is good.

Hereinafter, further explanation will be given based on embodiments of the present invention and comparative examples.

[0015]

EXAMPLE In this example, a brass plating (2 μm thickness, Cu / Zn = 65/35) was used after the lead patenting treatment, and 0.5 mm of a 1.3 mm steel wire equivalent to SWRS82A was used.
m, 0.25 mm, and 0.1 mm wire diameters were drawn, and shot peening was performed while continuously running.

A direct nozzle projection system of a comparative example is shown in FIG. In this case, in order to uniformly shot-peen the steel wire 1 in a length direction of 300 mm, the positions of the compressed air and shot ball supply nozzles 9 were adjusted so that the shot peening could be performed from two facing directions. If the number of nozzles is increased, the uniformity in the circumferential direction is improved, but there is a problem in the space of the shot ball supply pipe 8 and the compressed air supply pipe 3, and in this comparative example, two directions are used.

A direct rotary blade projection system is shown in FIG. 4 as another comparative example. Also in this case, the shot ball supply pipe 8 was adjusted in the positional relationship with the rotary vane 10 so as to shot peen the length of the steel wire 300 mm from two directions as in the case of FIG. An indirect projection system as an embodiment of the present invention is shown in FIG. In the same manner as above, in order to perform shot peening on a length of 300 mm of the steel wire 1, a length of 300 mm and a radius of 100 mm
Compressed air was supplied to the cylindrical container 2 from the compressed gas supply pipe 3 to stir and scatter the shot balls 4 to form a scattering atmosphere. Further, only the compressed air is discharged from the exhaust port 5, and the shot ball 4 is shielded by the filter so as not to be discharged. FIG. 2 shows how the shot sphere 4 creates a scattered atmosphere in this case. FIG. 2A shows a state in which the shot spheres 4 before processing stand still and gather at the bottom of the container.
FIG. 2B shows a state in which the air 7 is supplied as gas from the three nozzles 6 which are displaced with respect to the steel wire 1 to cause stirring, scattering, and start shot peening. further,
As a comparative example of the shape of the container, another rectangular parallelepiped type container having a volume of 170 × 170 × 300 mm, which is almost the same as the cylindrical type, was used. The shot ball of this embodiment has a ball diameter of 10
~ 80μm steel, compressed air 4kgf
/ Cm ² shot peening treatment was performed for 3 seconds.

The characteristics of the treated steel wire were evaluated by the fatigue limit of a Hunter type rotary bending fatigue test. FIG. 5 shows a hunter fatigue test method. The steel wire sample 11 is rotated by the rotating jig 14 with one end having bending stress applied by the rotating end 12 and the fixed end 13, and the bending and compressive tensile stress is applied to the steel wire by the rotation. Then, the fatigue property is evaluated from the relationship between the number of revolutions and stress until the fracture. The results are summarized in Table 1.

[0019]

[Table 1]

From Table 1, the invention Nos. 1 to 3 are 0.1, 0.25, while shot spheres are scattered in the cylindrical container.
Shot peening is performed indirectly through a 0.5 mm steel wire. In the case of the example of the present invention, since the shot balls that have collided can be used immediately and repeatedly, the total required amount is small, and the useless shot balls that do not collide are extremely small, so that the projection density can be lowered. In this condition,
It can be seen that the hunter fatigue limit of the treated steel wire was significantly improved and shot peening was performed efficiently. Also,
It can be seen that the present invention enables uniform shot peening in the circumferential direction.

The invention No. 4 is one in which shot balls are scattered in a rectangular parallelepiped type container. In the case of the cylindrical type, the shot spheres rebound intensively in the direction of the central axis, but in the case of this rectangular parallelepiped, the rebounding of the steel wire position to the center portion becomes smaller as compared with the cylindrical type. Therefore, the effect of improving the fatigue limit is smaller than that of the present invention No. 2, but is improved as compared with the material without shot peening.

Comparative example No. 1 is a shot peening process by a method of directly projecting from a nozzle. In this case, about 2.3 kg / min is required as in this comparative example in order to uniformly project the nozzle without clogging, and this amount is considerably higher than that of the present invention. This direct projection method requires a supply tank that stores shot balls in advance,
Furthermore, in addition to the shot spheres being projected, a considerable amount of shot spheres that are not in direct shot peening, such as shot spheres that are in the path until they are collected in the supply tank after projection, and shot spheres that are stored in the supply tub are required as a result. Therefore, the total required amount is considerably larger than that of the present invention.

As a result, the hunter fatigue limit is improved,
The efficiency of shot peening is lower than that of the present invention. Further, in this comparative example, since the shot peening is not performed from multiple directions, the uniformity in the circumferential direction is inferior to the present invention,
For this reason, the hunter fatigue limit is slightly lower than in the present invention No. 2. On the other hand, the arrangement of the nozzles for shot peening the nozzles from multiple directions requires a considerable space, and the cost of the equipment is considerably high.

Comparative Example No. 2 is an example in which shot peening is performed directly using a rotary blade. Again, Comparative Example N
As in the case of o.1, both the shot density and the total required amount of shot spheres are higher than those of the present invention, and the efficiency and uniformity of shot peening are inferior to those of the present invention. Comparative Examples Nos. 3 to 5 are cases without shot peening, and the hunter fatigue limit is lower than that of the shot peened material.

[0025]

As described above, according to the present invention, shot balls are stirred and scattered in a cylindrical or box-like container to form a scattering atmosphere, and a steel wire is run therein to indirectly by the scattering shot balls. It is possible to provide a shot peening method that is extremely excellent in shot ball efficiency and shot peening uniformity.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a shot peening method according to the present invention.

FIG. 2 is a schematic view showing a situation of shot balls in a container according to the present invention, showing (a) a stationary state, (b) a stirring and scattering state.

FIG. 3 is a schematic diagram of a conventional direct nozzle projection method.

FIG. 4 is a schematic view of a conventional rotary blade type direct projection.

FIG. 5 is a diagram showing an outline of a Hunter type rotary bending fatigue test method according to the present embodiment.

[Explanation of symbols]

 1 ... Steel wire 2 ... Container 3 ... Compressed gas supply pipe 4 ... Shot sphere 5 ... Exhaust port (filter) 6 ... Gas supply nozzle 7 ... Air 8 ... Shot sphere supply pipe 9 ... Compressed air, shot sphere supply nozzle 10 ... Rotation Blade 11 ... Sample 12 ... Free end 13 ... Fixed end 14 ... Rotating jig

Claims (5)

[Claims] 1. In shot peening of a steel wire,
By supplying a gaseous substance into a container surrounded by a flat and / or curved inner wall, a shot sphere in the container is agitated and scattered to form a flying atmosphere, and a steel is placed in the flying atmosphere. An efficient shot peening method for a steel wire, which comprises causing the shot ball to collide uniformly with the surface of the steel wire by running the wire. 2. The efficient shot peening method for steel wire according to claim 1, wherein the container has a tubular shape or a box shape. 3. The efficient shot peening method for steel wire according to claim 1, wherein the shot ball is supplied to the bottom of the container, the gaseous substance is supplied from the top of the container, and the steel wire is run in the central part of the container. . 4. The shot sphere amount is 5 in volume ratio with the container.
It is -40%, The efficient shot peening method of the steel wire in any one of Claim 1 to 3. 5. The efficient shot peening method for a steel wire according to claim 1, wherein the angle of supplying the gaseous substance is such that the gas does not directly hit the steel wire.