JP2001347361A - Surface treatment method of metal member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unfilled defect. SOLUTION: In a surface treatment method of a metal member in which a projecting part is provided on the tip of a rotor which is pressed on the surface of a metal member and the surface of the metal member to improve it friction-stirring the surface in a non-molten state while rotating the rotor. A recess having a volume substantially equal to the volume of the projecting part is formed at a treatment starting point of the rotor on the surface of the metal member, the projecting part is disposed in the recess while rotating the rotor, and the tip of the rotor and the projecting part are advanced while pressing them on the surface of the metal member, and the volume V1 of a starting end hole formed in the surface to be treated and the volume V2 of the projecting part are set to satisfy the inequalities 0<V1/V2<1.1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a surface of, for example, an aluminum alloy casting.

[0002]

2. Description of the Related Art In recent years, the maximum compression pressure in a combustion chamber has been increased to 120 kgf with an increase in the output of a diesel engine of an automobile.
/ Cm ^{2 to} about 150 kgf / cm ^2, increasing the heat load on aluminum alloy castings such as cylinder heads that constitute the combustion chamber, and locally increasing the heat resistance to thermal fatigue and thermal stress. A remelt process is performed (for example, between adjacent ports (intervals)).
Also, the required remelt depth is larger than in the past.

FIG. 46 is a flow chart for explaining a manufacturing process of a conventional cylinder head for a diesel engine. FIG. 47 is a view for explaining the outline of the remelting process in the manufacturing process of FIG.

As shown in FIG. 46, in step T1, a cylinder head as an intermediate is cast. Step T2
Then remove it from the mold and remove the gate. Step T3
Then, the casting is subjected to a T6 heat treatment mainly for sand removal.
In step T4, pre-remelting processing is performed. In Step T5, the casting is preheated. In Step T6, a remelt process is performed on the inter-valve portion of the casting. In Step T7, the casting is subjected to T6 heat treatment again. In step T8, a finishing process is performed.

In the remelt treatment, as shown in FIG. 47, a sand casting is preheated, an electrode is brought close to a surface treatment area, and a TIG or a plasma arc is generated between the electrode and the surface treatment member. By moving and melting the structure to be processed at a predetermined depth and solidifying it again, the metal structure is refined, and casting defects are reduced and elongation is increased. Furthermore, the residual stress due to the remelting process is released by performing the T6 heat treatment again after the remelting process. In the remelt treatment, the metal structure is refined by increasing the cooling rate during resolidification, and the eutectic silicon is uniformly dispersed.

[0006] Further, although this is a technical field different from the surface treatment technique, Japanese Patent No. 2712838 discloses that a probe is inserted and translated while rotating a joint surface of two members to frictionally dispose a metal structure near the joint surface. A welding technique of plasticizing and bonding by heat is disclosed.

[0007]

However, in the above remelting process, since the heat capacity of the inter-valve portion is small, the amount of heat input is increased in order to increase the processing depth in order to cope with an increase in the thermal load on the cylinder head. Even so, shoulder melting occurs due to over-melting, and there is a limit to the processable depth.
In addition, when the heat input is increased, the solidification time of the treated part is prolonged, and the effect of the refinement of the structure is reduced, and the number of pinhole defects is also increased. It is difficult to obtain improvement effects.

[0008] In terms of quality, large variations in processing depth due to variations in the amount of heat input and misalignment due to magnetic blowing, and pinhole defects in the processing portion affect the gas content of the base material and the area ratio of the voids. Ensuring quality stability has become an issue due to the quality of the product.

In terms of productivity, since the processing section is melted, a shielding gas for preventing oxidation of the melted portion is required. In addition, in order to prevent defects due to gas generated from surface oxides and impurities, A step of removing the casting surface before the treatment is added. Furthermore, cost reduction is an issue because post-heat treatment is required to release high tensile residual stress generated in the processing section.

Therefore, Japanese Patent Application No. Hei.
In No. 1-371097, a protruding portion is provided at the tip of the rotor, and the tip of the rotor is pressed against the surface of the metal member while rotating the rotor, so that the surface of the metal member is not melted. There has been proposed a surface treatment technique for improving the properties by stirring with friction.

In the above-mentioned prior application, in order to improve the processing efficiency, a recess in which the tip of the rotor can be arranged is formed in advance at a position corresponding to the starting point of the processing region.

However, even if a recess is simply formed with reference to the above-mentioned surface treatment technique, there is a problem that voids are generated in the internal structure of the surface modified region of the metal member, and unfilled defects are generated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface treatment method for a metal member which can be modified into a metal structure having high heat resistance without causing unfilled defects in the surface treatment region of the metal member. It is to provide.

[0014]

In order to solve the above-mentioned problems and achieve the object, a method for surface treating a metal member according to the present invention comprises providing a protruding portion at the tip of a rotor and rotating the rotor. A method for treating a surface of a metal member in which the tip of the rotor is pressed against the surface of a metal member while the surface of the metal member is agitated by friction in a non-molten state by friction. A recess having a volume substantially equal to the volume of the protrusion is formed at a processing start point of the rotor on the surface of the member, and the protrusion is arranged in the recess while rotating the rotor. Of the metal member while pressing against the surface of the metal member.

Preferably, the concave portion is set to be less than 1.1 times the volume of the projecting portion.

[0016] Preferably, the rotor is inclined and advanced with respect to the surface of the metal member, and the recess is formed so as to match the inclination of the rotor.

Preferably, the shape of the concave portion is substantially equal to the shape of the protruding portion of the rotor.

[0018]

As described above, according to the first aspect of the present invention, at the processing start point of the rotor on the surface of the metal member, a recess having a volume substantially equal to the volume of the protruding portion is formed. By causing the protrusions to be disposed in the recesses while rotating the rotor, and by moving the tip of the rotor and the protrusions while pressing them against the surface of the metal member, unfilled defects are generated in the surface treatment area of the metal member. And can be modified into a metal structure with high heat resistance.

According to the second aspect of the present invention, the recess is set to be less than 1.1 times the volume of the protrusion, thereby processing the gap between the protrusion and the recess which causes an unfilled defect. It can be reduced at the start.

According to the third aspect of the present invention, the rotor is inclined and advanced with respect to the surface of the metal member, and the recess is formed so as to match the inclination of the rotor. At the start of processing.

According to the invention of claim 4, the shape of the concave portion is
Since the protrusions of the rotor are formed to have substantially the same shape, the metal structure can be modified into a metal structure having high heat resistance without generating unfilled defects in the surface treatment region of the metal member.

[0022]

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

FIG. 1 is a schematic view of a friction stirrer for performing a surface treatment method of a metal member according to an embodiment of the present invention. FIG. 2 is an enlarged view of the vicinity of the rotary tool in FIG.
FIG. 3 is a diagram showing an example of a spherical shape as the shape of the protruding portion of the rotary tool. FIG. 4 is a diagram illustrating an example of a cylindrical shape as the protruding portion shape of the rotary tool. FIG. 5 is a diagram illustrating a screw-shaped example of the protruding portion shape of the rotary tool. FIG. 6 is a diagram illustrating an example of a tapered shape of the protruding portion of the rotary tool. FIG.
It is a figure which shows the example of the concentric shape as a protrusion part shape of a rotary tool.

The surface treatment method of a metal member by friction stirring of the present embodiment is intended for an aluminum alloy casting as an example of the metal member, and particularly between adjacent ports (intervals) formed in a cylinder head of an automobile. Used for surface modification treatment of pistons, brake discs, etc., by agitating the surface modified area of aluminum alloy casting without melting it by frictional heat, it can refine the metallographic structure and uniformize the eutectic silicon (Si) particles. Dispersion and reduction of casting defects can be achieved, and material properties such as thermal fatigue (low cycle fatigue) life, elongation, impact resistance, and the like can be obtained that are higher than those of conventional remelt processing.

Here, the state of stirring without melting is as follows.
It means that the metal structure is softened by frictional heat at a temperature lower than the lowest melting point among the components or eutectic compounds contained in the base material, and the mixture is stirred.

As shown in FIGS. 1 and 2, the friction stirrer 1 includes a cylindrical rotary tool 4 having a spherical (see FIG. 3) projection 2 fixed or mounted on a flat tip 3. A tool driving mechanism 5 for rotating the rotary tool 4 together with the protruding portion 2 and relatively moving the rotary tool 4 while pressing the rotary tool 4 against the surface reforming region of the metal member W.

The tool driving mechanism 5 is a device that can rotate the rotary tool 4 by a motor or the like and can move in all directions of up, down, left and right by a feed screw mechanism or a robot arm. An NC processing device, an articulated robot, or the like that can numerically control the rotation direction, the feed speed, and the pressing force is used. As another form, the rotary tool 4 may be rotatably supported, and the metal member W may be relatively moved in all directions, up, down, left, and right.

The rotary tool 4 including the protruding portion 2
The metal member W is not limited to an aluminum alloy as long as the metal member W is softer than the rotary tool 4, though it is formed of a non-wear type material formed of a steel material (hard metal or the like) having a higher hardness.

The rotary tool 4 is designed to have a diameter φ1 of about 10 to 15 mm, and the protrusion 2 is designed to have a diameter φ2 of about 5 to 7.5 mm.

The shape of the protruding portion 2 may be cylindrical (FIG. 4), screw (FIG. 5), tapered (FIG. 6), concentric (FIG. 7), etc., in addition to the spherical shape shown in FIG. However, for reasons to be described later, a spherical shape, a screw shape (however, the rotating tool is rotated in a direction opposite to the winding direction of the screw), or a tapered stirring ability is preferable.

In the following description, for convenience of explanation, the screw-shaped projecting portion 2 for rotating the rotary tool 4 in the reverse direction of the screw winding direction is referred to as a reverse screw shape, and the screw-shaped projection portion 2 for rotating the rotating tool 4 in the same direction as the screw winding direction is referred to as a forward screw. We call it shape.

In this embodiment, as shown in FIG. 8, AC4D which is an aluminum alloy conforming to JIS is used as an example of a metal member to be subjected to the surface treatment method. The composition ratio can be changed in the range of 0.2 to 1.5% by weight, and the silicon (Si) content in the range of 1 to 24% by weight, preferably 4 to 13% by weight. AC4B, AC2
B, AC8A used for the piston and the like can also be used. The reason why the upper limit of the silicon content is set to 24% is that even if silicon is further increased, material properties and castability are saturated and agitation is deteriorated.

An aluminum alloy casting containing magnesium precipitates Mg ₂ Si by heat treatment to increase the strength. However, when the metal structure is refined by melting as in a remelt treatment, magnesium having a low melting point (650 ° C.) may evaporate to reduce the content. When the magnesium content is reduced, the hardness and strength are reduced even if heat treatment is performed, so that desired material properties cannot be obtained.

On the other hand, the surface treatment by friction stir, since magnesium does not melt the metal structure nor evaporates, Mg ₂ of the aluminum alloy casting heat treatment
The strength is increased by precipitating Si.

By adding silicon to the aluminum alloy, the castability (fluidity of the molten metal, shrinkage properties, hot cracking resistance) is improved, but the eutectic silicon acts as a kind of defect and mechanical properties (elongation). ) Decreases.

Eutectic silicon is hard and brittle, and serves as a starting point and a propagation path for crack generation, so that elongation is reduced. In addition, the fatigue life of a portion that is repeatedly subjected to thermal stress, such as an inter-valve portion, is reduced. In the metal structure, eutectic silicon is connected along the dendrite.However, cracking due to stress concentration and propagation of the generated cracks are suppressed by miniaturizing and uniformly dispersing the eutectic silicon. It is possible to do.

FIG. 9A is a diagram showing the processing depth according to the length of the protrusion, FIG. 9B is a diagram showing the length X1 of the protrusion, and FIG. 9C is the maximum processing depth. It is a figure showing Dmax. FIG. 10 is a diagram illustrating the processing depth Wd according to the rotation speed and the feed speed of the rotary tool.

In this embodiment, the projection length X1 is set to 80 to 90% of the required depth. The required depth is 1.1 to 1.2 times the length of the protruding portion, and the processing depth can be up to about 9 mm, which is about 2 to 3 times the processing depth in the remelt processing. Also, as shown in FIG. 9A, the maximum processing depth Dmax is proportional to the protrusion length X1 (1.1 to 1.2 times the protrusion length).
And the processing width Wd also increases in proportion to the diameter φ2 of the protruding portion, and becomes 1.3 to 1.5 times. FIG.
As shown in (1), the maximum processing depth Dmax is determined by the protruding portion length X1, and it can be said that the influence of the rotation speed and the feed speed is small. Further, the variation is smaller than the maximum processing depth Dmax by the remelt processing illustrated in FIG. 10, and the reliability can be improved.

When the tip diameter φ1 and the protrusion diameter φ2 are increased in order to increase the processing width Wd, unfilled defects are more likely to occur in the surface modified region. Therefore, FIG.
As shown in (1), by moving the rotary tool 4 forward with respect to the processing surface and moving the rotary tool 4 in a lateral direction intersecting with the forward direction (for example, moving the rotary tool 4 in a saw-tooth shape), the size of the rotary tool 4 can be suppressed, The processing area can be increased with small equipment.

In the case where the inter-valve portion of the cylinder head having the maximum compression pressure of about 150 kgf / cm ² as in this embodiment is subjected to surface reforming treatment, the rotation of the rotary tool 4 is considered in consideration of productivity. The number is 1200-2400 rpm, the feed speed is 30-150 mm / min, and the maximum processing depth Dmax
4mm or more after finishing (processing allowance 1mm or less)
It is preferable to set

Further, as shown in FIG. 12, the rotary tool 4 is inclined with respect to the processing surface in the direction opposite to the feed direction by an angle of 0 °.
By moving in an inclined state in the range of <θ ≦ 5 °, unfilled defects, the amount of dents and burrs on the surface can be suppressed, the processing depth and the feed rate can be further increased, and the productivity can be improved. The reason for this is that, by tilting the rotary tool 4 with respect to the processing surface, the metal structure in the surface-modified region is also agitated in the thickness direction of the metal member W by the shoulder 3a of the tip 3, and This is because stirring is performed in the width direction. However, in the case of a reverse screw, since the metal structure that has been stirred acts to be pushed into the inside of the surface modification region, the same effect as when the rotary tool 4 is tilted can be obtained without tilting.

When the rotary tool 4 is perpendicular to the processing surface (the tilt angle θ of the rotary tool 4 is 0 °), it is difficult to prevent an unfilled defect occurring near the shoulder 3a of the tip 3, and the tilt angle θ is small. 5
When the angle is larger than 0 °, a deep groove is formed on the processing surface at the shoulder 3a of the tip 3 of the rotary tool 4, and a large amount of burrs are generated, which deteriorates the appearance and increases the allowance during finishing, which is not preferable. . [Processing Cross Section Due to Difference in Shape of Projection] FIG. 13 is a view showing a processing cross section of the metal member when the shape of the projection of the rotary tool is spherical. FIG. 14 is a diagram illustrating a processing cross section of the metal member when the shape of the protruding portion of the rotary tool is a reverse screw shape. FIG. 15 is a diagram illustrating a processing cross section of the metal member when the shape of the protruding portion of the rotary tool is a forward screw. FIG. 16 is a diagram illustrating a processing cross section of the metal member when the shape of the protrusion of the rotary tool is tapered. FIG. 17 is a diagram illustrating a processing cross section of the metal member when the shape of the protruding portion of the rotary tool is concentric.

The processing conditions are as follows: the rotational speed of the rotary tool is 1200
rpm, the feed rate is 63 mm / min, the inclination angle is 1 °, the length of the protrusion is 6 mm, and the diameter φ1 of the protrusion is 8 mm.

When the protrusion 2 of the rotary tool 4 has a spherical shape (FIG. 13), a reverse screw shape (FIG. 14) and a taper shape (FIG. 16), the processing depth and the processing width are as follows. In the case of the reverse screw shape, the largest value was obtained, and then, in the case of the spherical shape and the tapered shape, the smallest value was obtained. In each case, no unfilled defect was generated in the surface modified region, and good results were obtained. In the case of the reverse screw shape shown in FIG. 14, the rotating tool 4 is turned in the direction opposite to the winding direction of the screw.
In order to rotate the material, the material in the surface modification region is pressed toward the material.

When the protruding portion 2 of the rotary tool 4 has a forward screw shape (FIG. 15), the rotary tool 4 is rotated in the same direction as the direction of winding of the screw to push up the material in the surface modified area to the front side. In order to rotate the rotary tool 4 in the direction, the processing depth and the processing width are substantially the same as in the case of the spherical shape, but the material is pushed up to the surface and the material to be stirred is insufficient.
An unfilled defect S1 has occurred in the surface modified region.

Further, when the protruding portion 2 of the rotary tool 4 is concentric (FIG. 17), unfilled defects S1 occur in the surface reforming region due to insufficient stirring in the thickness direction of the material. I have.

As can be seen from FIGS. 13 to 17,
In the surface treatment of the present embodiment, it is preferable that the projecting portion 2 of the rotary tool 4 has a spherical shape, a reverse screw shape, and a tapered shape. In particular, in the case of the reverse screw shape, as shown in FIGS. In comparison, the processing depth Dmax can be formed substantially uniformly between the end portion and the center portion of the inter-valve portion, so that it is optimal as a tool.

Since the material may adhere to the projection 2 depending on the processing conditions, the surface of the projection 2 may be coated with titanium cyanide (TiCN) or the like. [Effects of Projection Diameter φ2 and Tip Diameter φ1] Using a rotary tool 4 whose projection 2 has a reverse screw shape, the rotation speed is 1200 rpm.
m, the feed rate is 63 mm / min, and the inclination angle is 1 °, when φ1 / φ2 is 2 as shown in FIG.
Unfilled defects occurred in the vicinity, processing was not possible in the vicinity of 4, and the result that the vicinity was appropriate in 3 was obtained. [Relationship between feed speed and rotation speed of rotary tool] FIG. 21 is a diagram showing a relationship between feed speed and rotation speed of the rotary tool.

When the protruding portion 2 has an inclination angle of 1 ° using the reverse screw-shaped rotary tool 4, the feed speed and the number of rotations of the rotary tool 4 are determined according to the appropriate region shown in FIG.
The processing speed can be increased. [Method of Manufacturing Cylinder Head] Next, the process of manufacturing the cylinder head for a diesel engine according to the present embodiment will be described.

FIG. 22 is a flowchart illustrating the steps of manufacturing the cylinder head for a diesel engine according to the present embodiment.

As shown in FIG. 22, in step S1, a cylinder head as an intermediate is cast from an aluminum alloy. In step S2, the casting is removed from the casting mold and the gate is deleted. In step S3, the casting removed from the casting mold is subjected to a T6 heat treatment mainly for sand removal.
In step S4, a surface treatment is applied to the inter-valve portion of the casting by friction stirring. In step S5, the casting is subjected to T6 heat treatment again to increase hardness and strength. In step S6, finishing is performed.

As described above, by performing the surface treatment by friction stirring, the pre-remelting processing in step T4 of FIG. 46, the preheating of the casting in step T5, and the heat treatment in re-T6 are not required. Can be simplified and the manufacturing cost can be reduced. [Cylinder Head Valve Processing] Next, the valve processing of the cylinder head for a diesel engine according to the present embodiment will be described.

FIG. 23 is a view for explaining the traversing process of the inter-valve portion of the cylinder head.

As shown in FIG. 23, in the traversing process, the processing path E1
It is moved while stirring by friction so as to traverse the inter-valve portion at the shortest distance along E3, so that the processing depth can be kept uniform and the processing time is short, but the protruding portion is inserted into the processing surface. In order to form the starting end hole, it is necessary to form a surplus portion and a cast hole in an extension of each port in the inter-valve portion, as described later.

FIG. 24 is a view for explaining the longitudinal processing of the inter-valve portion of the cylinder head.

As shown in FIG. 24, in the longitudinal sectioning process, the rotary tool is moved along the processing trajectories F1 to
It is moved while stirring by friction so as to traverse the inter-valve portion along F3, so that a surplus portion and a casting hole are not required.

Also, as shown in FIG. 25, the end point of the tension bolt hole 21 of the cylinder head close to the port,
By using the injector hole 22 (or plug hole) as shown in FIG. 26, the terminal hole is not formed at the end point of the processing locus.

Further, as shown in FIG. 27, the rotary tool 4 is swingably supported so that the direction of the inclination angle θ can be changed, so that the rotary tool 4 can be connected to one starting hole (injector hole 22) in FIG. ), The processing trajectories G1 to G3 can be set by inverting the inclination angle θ so that the terminal hole is not required.

Further, by gradually moving the protruding portion 2 (preferably a reverse screw shape) near the terminal end so as to be pulled up from the surface, the terminal hole can be reduced.

Further, as shown in FIG. 28, a built-up portion W1 having a length equal to or longer than the length of the projecting portion may be formed on the surface of the metal member W in advance, and the terminal hole may be deleted after the surface treatment.

FIG. 29 is a diagram showing the thermal shock life of the transverse processing and the longitudinal processing.

As shown in FIG. 29, for example, in the case where the hardness and strength are increased by subjecting the casting to T6 heat treatment after subjecting the inter-valve portion of the cylinder head to surface treatment by friction stirring,
Longitudinal processing can be made stronger than transverse processing, but sufficient strength can be obtained even in transverse processing. [Surface Treatment by Crossing Process] Next, the surface treatment by traversing process shown in FIG. 23 will be described.

FIGS. 30 to 34 are diagrams for explaining the procedure of the friction stir processing of the inter-valve portion.

As a pre-process of the friction stir processing, as shown in FIG. 30, when the cylinder head is cast, the inter-valve portion 10 along the line L1 connecting the centers of the adjacent ports 14 and 15 is formed.
An intermediate having a surplus portion 11 and a cast-out hole 12 is formed in an extension of each port. The cast hole 12 may be machined with a drill or the like after casting, and is formed to have dimensions substantially the same as the diameter and length of the protrusion 2.

Next, as shown in FIG. 31, while the rotary tool 4 is being driven to rotate, the protrusion 2 is inserted into the cast hole 12 for positioning, and the tip 3 of the rotary tool 4 is connected to the inter-valve portion 1.
Pressing on the surface of 0 determines the processing depth.

Subsequently, as shown in FIG. 32, the line L1 connecting the centers of the adjacent ports is set as the movement trajectory of the rotary tool 4, and the tool drive mechanism 5 starts the casting hole 12 of one of the excess portions 11 as the starting point. The other excess portion 11 is moved along the movement path while being stirred by friction. At this time, an arc-shaped groove 16 is formed on the surface of the inter-valve portion along the line L1 by pressing the tip 3 of the rotary tool 4.

Further, as shown in FIG. 33, after moving the rotary tool 4 to the other excess portion 11, the rotary tool 4 is separated from the inter-valve portion 11. At this time, an end hole 13 is formed in the other excess portion 11 as an end point of the protruding portion 2 of the rotary tool 4.

Finally, as shown in FIG.
Is deleted and the ports 14 and 15 are finished. [Heat Treatment After Surface Treatment] FIG. 35 is a diagram showing a comparison between the hardness when the T6 heat treatment is performed after the surface treatment by stirring and the hardness when the T6 heat treatment is not performed. FIG. 36 is a diagram comparing the mechanical properties of the case where only the T6 heat treatment is performed after the surface treatment by stirring and the case where the T6 heat treatment is performed after the remelt treatment. FIG. 37 is a diagram showing a comparison of thermal shock life when only T6 heat treatment, only surface treatment by stirring, and when T6 heat treatment is performed after surface treatment by stirring. FIG.
FIG. 4 is a diagram showing a comparison between the relationship between the thermal shock life and the treatment depth when a T6 heat treatment is performed after the surface treatment by stirring and only the surface treatment by stirring;

When heat treatment is performed before finishing in addition to the above-described surface treatment by friction stirring, the metal structure in the surface-modified region and the base material under the metal structure as shown in FIG. In both cases, the hardness (Hv) can be increased. Further, as shown in FIG. 36, those obtained by performing only the T6 treatment, those subjected to the T6 heat treatment after the remelting treatment, and those subjected to only the friction stir treatment can obtain excellent tensile strength and elongation characteristics as compared with each mechanical property. it can.

As can be seen from FIG. 37, the surface treatment by stirring in this embodiment can greatly improve the thermal fatigue life and increase the strength against thermal shock. Therefore, it is effective to use a portion requiring high thermal fatigue strength in a state where only the friction stir processing is performed and the elongation property is high.

Further, as can be seen from FIG. 38, by increasing the processing depth, the thermal fatigue life can be greatly improved and the strength against thermal shock increases as the processing depth exceeds the remelting processing.

On the other hand, in a part where thermal fatigue and mechanical high cycle fatigue are superimposed, not only elongation but also strength is required. Therefore, in order to achieve both high strength and elongation, friction stirring is performed. It is effective to perform the treatment and the T6 heat treatment.
Further, even in the case where the vicinity of the treated structure is softened due to the influence of heat and the strength is reduced, the T6 heat treatment is effective for recovering the strength.

As an example of the heat treatment, JIS standard T6 heat treatment (solution treatment and aging treatment) is effective. In the solution treatment, the solution is kept at a solution solution temperature of 535 ° C. (± 5 ° C.) for 4 hours and then quenched with boiling water. The aging treatment is performed at an aging temperature of 18
After holding at 0 ° C. (± 5 ° C.) for 6 hours, air-cool. [Effect of Volume of Starting Hole for Inserting Projecting Portion] FIG. 39 is a diagram showing unfilled defects generated in the surface modified region when the volume of the starting hole is larger than the volume of the projecting portion. FIG.
FIG. 4 is a diagram showing whether or not an unfilled defect occurs in the surface modified region when the size of the starting end hole is changed.

When the volume V1 of the starting hole shown as the cast hole 12 in FIG. 30 is formed to be equal to or less than the volume V2 of the projecting portion 2 (V1 ≦ V2), the periphery of the starting hole is softened by the rotation of the projecting portion 2. Because of the insertion, the resistance to the tool drive mechanism 5 increases, but no unfilled defect occurs on the processing surface. However, the volume V1 of the starting end hole is changed to the volume V2 of the protrusion 2.
When formed as described above (V1 ≧ V2), as shown in FIG. 39, since a gap is formed between the protruding portion and the starting end hole from the initial stage of the surface treatment, there is not enough material to fill the gap. Unfilled defects P are generated in the surface modified region. However, the processing condition in FIG. 39 is that the rotational speed of the rotary tool 4 is 12
00 rpm, feed rate 63 mm / min, tilt angle 1 °
It is.

More specifically, as shown in FIG. 40, the diameter and the depth of the starting end hole are made larger than those of the protruding portions so that the volume ratio V1 / V2
Was set to 1.1 or more, an unfilled defect occurred in the surface-modified region in each case.

Therefore, in the present embodiment, the volume V1 of the starting end hole formed in the processing surface is set to 0 <
It is set to be less than V1 / V2 <1.1, and preferably, the shape of the starting end hole is formed substantially equal to the shape of the protruding portion to prevent the occurrence of unfilled defects.

When the rotary tool 4 is moved forward at an inclination angle θ with respect to the processing surface, the starting hole is formed so as to match the inclination angle θ of the rotor, and when the projecting portion is inserted into the starting hole. The projection is inserted in parallel with the starting end hole in accordance with the inclination angle θ. [Effect of Projection Length on Surface Modification Area] FIG.
It is a figure explaining a defect which arises in a surface modification field when the thickness of a metal member becomes thin with respect to the direction of advance of a rotary tool. FIG. 42 is a diagram illustrating a method of changing the embedding amount of the rotary tool according to the thickness of the metal member when the thickness of the metal member is reduced.

As shown in FIG. 41, when the thickness of the metal member W is reduced with respect to the traveling direction of the rotary tool 4,
For example, if there is a portion thinner than the length of the protrusion 2, the rotating tool 4 may penetrate the back surface of the metal member W,
If the thickness of the metal member W is insufficient with respect to the length of the metal member W, the material in the surface-modified region flows to the rear surface, and a defect such as swelling occurs on the rear surface.

Therefore, in the present embodiment, as shown in FIG. 42, the processing depth is determined according to the thickness of the metal member W, and the metal member of the projecting portion 2 of the rotary tool 4 is determined according to the processing depth. W
The occurrence of the above-mentioned defects is prevented by making the depth of embedding in the surface modified region variable.

Specifically, when the rotary tool 4 is advanced by the tool driving mechanism 5 and reaches the thin portion of the surface reforming region, the burial depth of the protrusion 2 is determined according to the thickness. Decrease the

The contact of the tip 3 of the rotary tool 4 with the surface of the metal member W is controlled according to the processing area of the surface of the metal member W.

That is, with respect to the traveling direction of the rotary tool 4,
When the height of the surface of the metal member W is the same and the thickness of the metal member W is reduced, the shoulder portion of the tip end portion 3 of the rotating tool 4 is raised by raising the rotating tool 4 according to the thickness of the metal member W. Member W
Stir without contacting the surface of.

When the height of the surface of the metal member W is reduced with respect to the traveling direction of the rotating tool 4 to reduce the thickness, the rotating tool 4 is moved in accordance with the thickness of the metal member W. By lowering or maintaining, the shoulder of the tip 3 of the rotary tool 4 is stirred without contacting the surface of the metal member W.

As described above, by reducing the amount of embedding of the protruding portion 2 of the rotary tool 4 in the surface reforming region in accordance with the thickness thereof, the protruding portion penetrates the back surface of the metal member,
It is possible to prevent the material in the surface-modified region from flowing to the rear surface, thereby preventing the material in the surface-modified region from being insufficient and causing defects such as dents on the surface. [Alternative Configuration of Rotary Tool] FIG. 43 shows an example of another configuration of the rotary tool according to the present embodiment, in which a mechanism for varying the amount of protrusion of the projecting portion of the rotary tool is provided.

As shown in FIG. 43, the rotary tool 40 has a hollow cylindrical outer cylindrical member 41 and a protruding portion 43 provided inside the outer cylindrical member 41 and capable of protruding and retracting from the distal end portion 42 of the outer cylindrical member 41. And

The protruding portion 43 is provided at the distal end portion 42 of the outer cylinder member 41.
The amount of protrusion from the outside cylindrical member 41 is variable.
The projection 43 is integrally rotated by spline fitting or the like.

With this configuration, even if the thickness of the surface-treated portion changes without changing the height of the tip 3 of the rotary tool 4 according to the thickness of the metal member W as shown in FIG.
It can respond well. [Relationship between Length of Projection and Thickness of Surface Modification Area of Metal Member] FIG. 44 is a diagram showing a test piece for measuring the relationship between the length of the projection and the thickness of the surface modification area of the metal member. . FIG.
FIG. 5 is a diagram showing a defect generated on the back surface of the test piece when surface treatment is performed using the test piece of FIG. 44 with a rotating tool having a spherical and a reverse screw-shaped protrusion.

In the test piece shown in FIG. 44, a portion S2 where the thickness of the surface modified region changes linearly in the range of 5 to 20 mm is formed, and a spherical surface and a reverse screw are formed on the back surface of the portion S2 of the test piece. The surface treatment is performed by the rotary tool 4 having a protruding portion having a shape, and the thickness of the surface modified region at the position where the defect occurs in the portion S2 of the test piece is measured.

The test conditions were as follows: using a rotary tool having spherical and reverse screw-shaped protrusions (diameter 8 mm, length 6 mm), the number of rotations was 1200 rpm, and the feed speed was 47 mm / m.
In, the processing is performed with an inclination angle of 1 °.

According to the test results, when a spherical protrusion is used, the thickness of the surface-modified region is required to be 2.1 times the length of the protrusion. When used, the thickness of the surface modified region was required to be 2.5 times the length of the protruding portion because the stirring ability was higher than that of the spherical one.

Therefore, by setting the thickness of the surface-treated portion of the metal member W to be at least twice the depth of embedding the protrusion 2 of the rotary tool 4 in the surface of the metal member W, Defects on the back surface can be prevented, and for example, it can be effectively applied to the surface treatment of the inter-valve portion of the cylinder head.

In order to suppress defects on the back surface of the surface modified region, the surface treatment may be performed while cooling the surface modified region.

Further, in order to set the thickness of the surface treatment portion of the metal member W to be at least twice the depth of embedding the protrusion 2 of the rotary tool 4 in the surface of the metal member W, as described with reference to FIG. In addition, the embedding depth of the projecting portion 2 of the rotary tool 4 in the surface of the metal member W is made variable, and when the embedding depth of the projecting portion 2 of the rotating tool 4 in the surface of the metal member W is shallow, the projecting portion 2 is removed. You may make it raise with respect to the surface of the metal member W.

The present invention can be applied to a modification or a modification of the above embodiment without departing from the gist of the invention.

[Brief description of the drawings]

FIG. 1 is a schematic view of a friction stirrer for performing a surface treatment method according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the vicinity of the rotary tool in FIG.

FIG. 3 is a diagram showing a spherical protrusion.

FIG. 4 is a view showing a cylindrical protrusion.

FIG. 5 is a view showing a screw-shaped protrusion.

FIG. 6 is a view showing a tapered protrusion.

FIG. 7 is a diagram showing concentric protrusions.

FIG. 8 is a diagram showing a component ratio of the aluminum alloy of the present embodiment.

9A is a diagram illustrating a processing depth according to a protrusion length, FIG. 9B is a diagram illustrating a protrusion length X1, and FIG. 9C is a diagram illustrating a maximum processing depth Dmax.

FIG. 10 is a diagram showing a processing depth according to a rotation speed and a feed speed of a rotary tool.

FIG. 11 is a diagram showing a movement locus of a rotary tool when a processing width is enlarged.

FIG. 12 is a diagram showing a tilt angle of a rotary tool.

FIG. 13 is a diagram showing a processing cross section of a metal member when the shape of the protruding portion of the rotary tool is spherical.

FIG. 14 is a diagram showing a processing cross section of a metal member when the shape of the protruding portion of the rotary tool is a reverse screw shape.

FIG. 15 is a diagram showing a processing cross section of a metal member when the shape of the protruding portion of the rotary tool is a forward screw.

FIG. 16 is a diagram showing a processing cross section of the metal member when the shape of the protrusion of the rotary tool is tapered.

FIG. 17 is a diagram showing a processing cross section of the metal member when the shape of the protruding portion of the rotary tool is concentric.

FIG. 18 is a cross-sectional view of a surface modified region when a spherical protrusion is used.

FIG. 19 is a cross-sectional view of a surface modified region when a reverse screw-shaped protrusion is used.

FIG. 20 is a diagram showing a surface treatment result based on a ratio between a protrusion diameter and a tip diameter.

FIG. 21 is a diagram illustrating a relationship between a feed speed and a rotation speed of a rotary tool.

FIG. 22 is a flowchart illustrating a manufacturing process of the cylinder head for a diesel engine of the present embodiment.

FIG. 23 is a diagram illustrating a crossing process of the inter-valve portion of the cylinder head.

FIG. 24 is a view for explaining longitudinal processing of an inter-valve portion of a cylinder head.

FIG. 25 is a diagram illustrating a method of not forming a terminal hole in the surface treatment of the embodiment.

FIG. 26 is a diagram illustrating a processing method in which a terminal hole is not formed in the surface processing according to the present embodiment.

FIG. 27 is a diagram illustrating a processing method for forming only a terminal hole in the surface treatment according to the present embodiment.

FIG. 28 is a diagram illustrating a method of not forming a terminal hole in the surface treatment according to the present embodiment.

FIG. 29 is a diagram showing the thermal shock life of the transverse treatment and the longitudinal treatment in the surface treatment of the present embodiment.

FIG. 30 is a view for explaining a surface treatment procedure of an inter-valve portion.

FIG. 31 is a view for explaining a surface treatment procedure of an inter-valve portion.

FIG. 32 is a view for explaining a surface treatment procedure of an inter-valve portion.

FIG. 33 is a diagram illustrating a procedure for surface treatment of an inter-valve portion.

FIG. 34 is a diagram illustrating a procedure for surface treatment of an inter-valve portion.

FIG. 35 is a graph showing a comparison of hardness between a case where a T6 heat treatment is performed after a surface treatment by stirring and a case where a T6 heat treatment is not performed.

FIG. 36: T6 heat treatment only, after surface treatment by stirring
FIG. 6 is a diagram showing a comparison between tensile strength and elongation characteristics when a T6 heat treatment is performed after a remelt treatment when a 6 heat treatment is performed.

FIG. 37: T6 heat treatment only, surface treatment by stirring only,
It is a figure which compares and shows the thermal shock life at the time of performing T6 heat processing after the surface treatment by stirring.

FIG. 38 is a diagram showing a comparison between the relationship between the thermal shock life and the treatment depth when a T6 heat treatment is performed after the surface treatment by stirring and only the surface treatment by stirring;

FIG. 39 is a diagram showing an unfilled defect generated in the surface modified region when the volume of the starting end hole is formed to be equal to or larger than the volume of the protrusion.

FIG. 40 is a diagram showing whether or not an unfilled defect occurs in the surface modified region when the size of the starting hole is changed.

FIG. 41 is a diagram illustrating a defect that occurs in the surface-modified region when the thickness of the metal member is reduced with respect to the traveling direction of the rotary tool.

FIG. 42 is a diagram illustrating a method of changing the embedding amount of the rotary tool according to the thickness of the metal member when the thickness of the metal member is reduced.

FIG. 43 is a view showing an example in which a mechanism for varying the amount of protrusion of a protruding portion of the rotating tool is provided as another configuration of the rotating tool according to the embodiment.

FIG. 44 is a diagram showing a test piece for measuring the relationship between the length of the protrusion and the thickness of the surface modified region of the metal member.

FIG. 45 is a diagram showing defects generated on the back surface of the test piece when surface treatment is performed using the test piece of FIG. 44 by a rotating tool having a spherical and a reverse screw-shaped protrusion.

FIG. 46 is a flowchart illustrating a manufacturing process of a conventional cylinder head for a diesel engine.

FIG. 47 is a diagram illustrating an outline of a remelt process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Friction stirrer 2 Projection part 3 Tip part 4 Rotary tool 5 Tool drive mechanism 10 Intervalve part 11 Excess part 12 Cast-out hole 13 Termination hole

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22F 1/00 611 C22F 1/00 611 630 630G 650 650A 651 651B 682 682 691 691 1/04 1/04 A

Claims (4)

[Claims] 1. A protruding portion is provided at the tip of a rotor, and the tip of the rotor is pressed against the surface of a metal member while rotating the rotor, so that the surface of the metal member is in a non-melted state. A method for surface treatment of a metal member that is modified by being stirred by friction in a processing start point of the rotor on the surface of the metal member,
Forming a concave portion having a volume substantially equal to the volume of the protruding portion; disposing the protruding portion in the concave portion while rotating the rotor; A surface treatment method for a metal member, wherein the metal member is advanced while being pressed against a surface. 2. The surface treatment method for a metal member according to claim 1, wherein the concave portion is set to be less than 1.1 times the volume of the projecting portion. 3. The rotor according to claim 1, wherein the rotor is inclined and advanced with respect to a surface of the metal member, and the recess is formed so as to match the inclination of the rotor.
Or the surface treatment method of a metal member according to 2. 4. The surface treatment of a metal member according to claim 1, wherein the shape of the recess is substantially equal to the shape of the protrusion of the rotor. Method.