JP2000312980A - Cylinder inner face reforming method of metallic member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a reformed layer with a dense structure while softening and plastic-fluidizing a surface layer on a cylinder inner face with abrasion heating at a simple facility by relatively rotating a pressurizing rod while pressure-contacting along the cylinder inner face of a member composed of pure metal or alloy having the cylinder inner face. SOLUTION: For example, a pressurizing rod 16 composed of SKD61 is pushed in an axial direction from an opening 18 against a cylinder inner face 14 of a metallic member 10 with a bottom 12 made of an Al-Si alloy (AC8A) while the rod 16 is rotating at high speed, so as to reform the cylinder inner face 14. Diameter of the cylinder inner face 14 is 20 mmϕ, outside diameter of the pressurizing rod 16 is 23 mmϕ, rotational speed of the pressurizing rod 16 is 1,500 rpm, and pushing speed is 0.2 mm/see. Thereby, the surface layer of the cylinder inner face 14 is softened under pressure so as to cause plastic flow, and a reformed layer 20 with dense structure and high strength is formed along the surface layer of the cylinder inner face 14. The reformed layer 20 is fine in crystal grain and dense in structure compared with a base metal, and is solid-phase welded or fused integrally with the base metal in a good condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to metal parts suitable for application to machine parts, automobile and railway vehicle parts, especially engine cylinders, bearings, OA equipment parts, aircraft parts, marine equipment parts, medical equipment parts and the like. It relates to a method for modifying the inner surface of a cylinder.

[0002]

2. Description of the Related Art As a conventional method for producing a metal member having a cylindrical inner surface, a casting method has been widely used.
In particular, there is a problem that the solidification structure tends to be nonuniform due to the wall thickness, and casting defects such as cavities and pores are likely to occur.

[0003] On the other hand, there are semi-molten (thixo-molding) / semi-solidification (rheo-molding) methods and the like, but even in this method, unevenness and segregation of the product structure cannot be avoided. In addition, a so-called weld line is formed at the junction of the flows of the semi-molten metal, so
There is also a problem that the appearance and the function become uneven.

[0004] On the other hand, the powder metallurgy method has a problem that pores are generated although crystal grains can be made fine, and the ductility and strength of the sintered body are insufficient, and it is extremely difficult to predict and control the amount of shrinkage during various processing and heat treatment. , Coalescing into the inner surface of the cylinder,
Complexation is difficult. In addition, modification by welding, laser or the like is also performed, but it is extremely difficult to apply this method to the modification of the inner surface of a small-diameter column or a long-column.

[0005]

Means for Solving the Problems The method for modifying the inner surface of a cylindrical member of a metal member according to the present invention has been devised to solve such problems. According to the reforming method of the first aspect, a metal member made of a pure metal or an alloy having a cylindrical inner surface is rotated relative to the inner surface of the cylindrical member by pressing a pressing rod along the inner surface of the cylindrical member. The surface layer is softened and plastically flowed by frictional heat to form a modified layer having a dense structure.

According to a second aspect of the present invention, in the first aspect, the pressing rod has a softening temperature higher than a softening temperature of the metal member. It is characterized by.

According to a third aspect of the present invention, in the method for modifying the inner surface of a metal member according to any one of the first and second aspects, the pressure rod having an outer diameter larger than a diameter of the inner surface of the cylinder is used. By inserting the pressure rod into the inside of the cylindrical inner surface through the opening and moving it axially relative to the cylindrical inner surface while rotating the pressing rod relative to the cylindrical inner surface, the surface layer of the cylindrical inner surface is plastically flowed and the reforming is performed. Forming a porous layer.

[0008]

According to the present invention, a pure metal or alloy metal member having a cylindrical inner surface is cast and formed in advance.
It is created by a general processing method such as extrusion molding, press molding, and welding. Then, a relative rotational movement is performed while pressing the pressing rod along the inner surface of the cylinder of the metal member,
The inner surface layer is softened and plastically flowed by frictional heating. In the plastically flowed portion, the crystal grains are refined and surface defects are pressed to form a fine defect-free structure (modified layer).
This modified layer is strengthened by the so-called Petch's law, and its abrasion resistance is greatly improved as compared with the base metal.

According to the present invention, a modified layer having a thickness of about 0.5 to 5 mm can be formed on the inner surface of a cylinder. The present invention is particularly effective when applied to the processing of a metal member made of a low melting point metal such as aluminum, an aluminum alloy, and a magnesium alloy. Applicable to processing.

Processing can usually be carried out in the air. However, for an active material such as a titanium alloy, an inert gas atmosphere such as argon, an atmosphere such as vacuum, or a material such as copper which is slightly active is used. In this case, the reaction can be performed in a nitrogen or carbon dioxide gas atmosphere. Further, processing can be performed by utilizing plastic flow caused by frictional heating not only in a gas but also in a liquid such as water or oil. In this case, the effect of making the crystal grains finer is even greater.

In the present invention, the strength of the inner surface of the cylinder under pressure by a pressure rod is refined by plastic working or mechanically divided by plastic flow to refine the structure, and the strength is enhanced by Petch's law. In addition to this, the impurities in the inner surface layer can be finely and uniformly dispersed, thereby improving the strength.

Further, defects such as cracks and pores in the inner surface of the cylinder generated during the production of the metal member can be compressed and sealed by plastic deformation and pressing force, so that a sound structure can be obtained and residual compression remains on the inner surface of the cylinder. Since the stress can be applied, the fatigue life of the inner surface of the cylinder can be improved. Further, according to the present invention, advantages such as simple processing equipment and easy control and operation of processing can be obtained.

In the present invention, the pressure rod having a softening temperature higher than the softening temperature of the metal member can be used. For example, when the metal member is made of an aluminum alloy, a pressure rod made of stainless steel can be used.

In the present invention, the pressure rod can be brought into pressure contact with the inner surface of the cylinder by a variety of methods and can be relatively rotated. However, a pressure rod having an outer diameter larger than the diameter of the inner surface of the cylinder is used. A method of forming the modified layer by plastically flowing the surface layer of the inner surface of the cylinder by inserting it into the opening from the opening while relatively rotating the inner layer relative to the inner surface of the cylinder and moving the inner layer relatively in the axial direction is preferable. (Claim 3).

According to this method, the reformed layer can be easily formed on the inner surface of the cylinder only by pushing the rod into the opening while rotating the pressure rod relative to the inner surface of the cylinder.
The pressure rod may be cylindrical (solid), cylindrical (hollow), or polygonal such as solid or hollow hexagonal, in addition to the columnar (solid) rod. Further, by providing irregularities of a specific shape on the surface, more effective frictional heat can be generated, and strong plastic flow can be promoted.

[0016]

Next, embodiments of the present invention will be described in detail. FIG.
As shown in the figure, the opening is formed by rotating the pressure rod 16 made of the SKD 61 at a high speed with respect to the cylindrical inner surface 14 of the metal member 10 made of Al-Si alloy (AC8A) (in this example, with the bottom 12). Push in axially from 18,
The inner surface 14 of the cylinder was reformed.

The diameter of the inner surface 14 of the cylinder is 20 mmφ, the outer diameter of the pressure rod 16 is 23 mmφ, the rotation speed of the pressure rod 16 is 1500 rpm, and the pushing speed is 0.2 mm / sec.
And As a result, the surface layer of the inner surface 14 of the cylinder was softened under pressure to generate a plastic flow, whereby a high-strength modified layer 20 having a dense structure was formed on the inner surface 14 of the cylinder.

The cross section of the processed portion was cut out (indicated by K in FIG. 2) to examine the structure of the modified layer 20 and observed with a microscope. As a result, the modified layer formed along the surface of the inner surface 14 of the cylinder was observed. Reference numeral 20 denotes a structure in which the crystal grains are finer and the structure is denser than the structure of the base metal (shown in the reference photograph (a)) (shown in the reference photograph (b)), and the modified layer thereof 20 was solid-phase bonded or fused well with the base metal.

The embodiment of the present invention has been described in detail above, but this is merely an example. For example, the present invention can be applied to the processing of a metal member having the cylindrical inner surface 14 having no bottom portion 12 as described above, and can be carried out in variously modified aspects without departing from the gist thereof. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method according to an embodiment of the present invention.

FIG. 2 is a view showing a cut-out portion of a modified layer formed in the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal member 14 Inner surface of cylinder 16 Pressure rod 18 Opening 20 Modified layer

Claims (3)

[Claims] A metal member made of a pure metal or an alloy having an inner surface of a cylinder is relatively rotated while a pressure rod is pressed along the inner surface of the cylinder to soften a surface layer of the inner surface of the cylinder due to frictional heat generation. Plastic flow,
A method for modifying a cylindrical inner surface of a metal member, comprising forming a modified layer having a dense structure. 2. The method according to claim 1, wherein the pressing rod has a softening temperature higher than a softening temperature of the metal member. Column inner surface modification method. 3. The method for modifying the inner surface of a cylinder of a metal member according to claim 1, wherein the pressure rod having an outer diameter larger than the diameter of the inner surface of the cylinder is used. Inserting into the inside of the cylindrical inner surface from the opening thereof while rotating relative to the cylindrical inner surface and moving the surface relative to the axial direction to plastically flow the surface layer of the cylindrical inner surface to form the modified layer. A method for modifying a cylindrical inner surface of a metal member.