JP2016138330A - Metal material having surface shape allowing low friction coefficient - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal material used for a machine element component and a press molding and having a surface shape allowing a low friction coefficient.SOLUTION: The metal material allowing a low friction coefficient has flat projections having an area larger than that of a true contact portion generated by plastic deformation of the projections of surface projections and depressions of the metal material having a relative slide under a load without plastically deforming a bulk. The metal material having a surface shape allowing a low friction coefficient is manufactured by plastically or mechanically processing, etc., such as rolling and drawing the metal material having the flat projections having an area larger than that of the true contact portion. The area of the flat projections of the metal material is 1.2A or more to an area A of the true contact portion generated by plastic deformation at the initial stage.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a metal material having a surface shape that enables a low coefficient of friction used in machine element parts and press molding.

  In the mechanical element part and the press molding, a frictional force is acting on the true contact surface of the contact interface in which the two metal materials slide relative to each other under a load that does not cause plastic deformation. Machine element parts are often used under harsh conditions, and press molding often uses a high-strength metal material, resulting in a very high load acting between two objects and seizure. Decided to do.

  In order to reduce the load applied between two objects in machine element parts and press molding, a contrivance has been made to reduce the frictional force acting on the true contact surface. Specifically, a method of performing a composite hard film treatment on the surface of a metal material, a method of imparting high lubricity to the lubricating oil used, a method of controlling the geometric shape of the metal surface, etc. have been proposed.

JP 2000-144378 A JP 2003-253290 A

  However, among these methods, the method of controlling the geometric shape of the metal surface is difficult to provide a tribologically quantitative basis for suppressing the frictional force of the real contact area of the contact portion. In terms of trobbology, it is important to understand the interaction between lubricating oil and surface microdeformation in order to suppress frictional force. The present invention is to quantitatively understand the interaction between lubricating oil and surface microdeformation and to provide a metal material having a surface shape that enables a low coefficient of friction.

Means for Solving the Invention

Means for solving the above problems are as follows.
Under a load where the bulk of the two objects is not plastically deformed, the convex and concave portions of the metal surface are plastically deformed at the contact interface of the two objects under relative slip, and the load load is supported at the generated true contact portion. Under this condition, the contact surface pressure acting on the true contact portion is loaded with a surface pressure nearly three times higher than the yield stress Y of the metal material, and seizure is likely to occur as the true contact area increases.

  Therefore, in order to suppress seizure in machine element parts and press molding, in order to reduce the frictional force acting on the true contact portion and to enable a low friction coefficient, the oil film thickness of the lubricating oil interposed between the true contact surfaces is reduced. It is necessary to increase For this purpose, it is preferable to prepare a metal material having a flat convex area larger than the area of the true contact portion caused by plastic deformation of the convex portion at the contact interface that is relatively sliding under a certain load. If the same load is applied to the flat area, the contact surface pressure will be much lower than three times the yield stress of the material, and the oil film thickness of the lubricating oil interposed between the true contact surfaces will increase. A low coefficient of friction can be possible.

Effect of the invention

  The metal material of the present invention prepares a metal material having an area of a flat convex portion larger than the area of the true contact portion caused by plastic deformation of the convex portion of the surface unevenness, and reduces the surface pressure acting on the contact area. Thus, the oil film thickness of the lubricating oil interposed between the true contact surfaces is increased, and a low friction coefficient is made possible by reducing the frictional force acting on the contact surfaces.

    The present invention is described in detail below. In order to suppress seizure in machine element parts and press molding, to reduce the frictional force acting on the true contact part and to enable a low coefficient of friction, in order to enable a low coefficient of friction, the convex part at the contact interface that is relatively sliding under a certain load. When the same load is applied to the flat area of a metal material having a flat convex area larger than the area of the true contact caused by plastic deformation, the contact pressure is considerably lower than three times the yield stress of the material. And a low friction coefficient can be achieved by increasing the oil film thickness of the lubricating oil interposed between the true contact surfaces.

  Specifically, a plain steel plate having a surface roughness of 0.86 Raμm and a yield stress of 125 MPa was repeatedly slid using a lubricating oil having a viscosity of 80 cSt under a vertical load of 500 kgf (surface pressure of 25 MPa) and a sliding speed of 170 mm / s. The relationship between the friction coefficient and the number of sliding times is shown in FIG. As the number of sliding increases, the friction coefficient decreases. In this phenomenon, the true contact area increases as the number of sliding operations increases, the surface pressure applied to the true contact area decreases, and the friction coefficient decreases as the oil film thickness of the lubricating oil intervening at the contact interface increases. ing. By using a metal material having a flat convex area larger than the real contact area caused by plastic deformation of the convex and concave parts of the surface of the metal material, the surface pressure acting on the contact area is reduced, and the real contact It is an aspect of the present invention to enable a low coefficient of friction by increasing the oil film thickness of the lubricating oil interposed between the surfaces and reducing the frictional force acting on the contact surface.

  In the present invention, when the area of the true contact portion caused by the initial plastic deformation of the convex portion of the surface unevenness of the metal material that is sliding relative to the bulk under a load that does not undergo plastic deformation is A, the area of the true contact portion is The area of the large flat convex portion means a range larger than 1.2A.

  In the present invention, manufacturing a metal material having a flat convex area larger than the area of the true contact portion means that the metal material is manufactured by plastic processing or machining such as rolling or drawing. .

  Examples of the present invention will be specifically described below. High tensile strength steel plate with a dull surface irregularity with a tensile strength of 590 MPa and a surface roughness of 0.74 Raμm, and the same high tension with flat convexities of flat bottom ratios of 18.6%, 27.1% and 35.8% by skin pass rolling The steel sheet was slid once using a lubricating oil having a viscosity of 16 cSt under conditions of a vertical load of 450 kgf (surface pressure of 88 MPa) and a sliding speed of 0.42 mm / s.

  FIG. 2 shows the friction coefficient and flattening rate of four types of high-tensile steel plates. The coefficient of friction decreases from 0.22 for high-strength steel sheets with random surface irregularities, and decreases as the flatness ratio increases and decreases to 0.17 for high-tensile steel sheets with a flatness ratio of 35.8%. Yes. It shows that the flat bottom ratio of the convex part of the high-tensile steel plate increases and the friction coefficient decreases.

When a normal steel plate with random surface irregularities is repeatedly slid using a lubricating oil with a viscosity of 80 cSt under a vertical load of 500 kgf (surface pressure of 25 MPa) and a sliding speed of 170 mm / s, the true contact area increases with the number of sliding times. Drawing explaining that the oil film thickness of the lubricating oil intervening at the contact interface increases as the surface pressure increases and the friction coefficient decreases with the number of sliding Drawing explaining that the flat bottom ratio of the convex portion of the high-tensile steel sheet increases and the friction coefficient decreases when four types of high-tensile steel sheets with different flat bottom ratios slide once.

Claims (2)

  Featuring a metal material having a flat convex area larger than the area of the true contact part caused by plastic deformation of the convex part of the surface irregularity of the metal material that is relatively sliding under a load where the bulk does not undergo plastic deformation Metal material that enables a low coefficient of friction.   2. The low friction according to claim 1, wherein a metal material having a flat convex area larger than the area of the true contact portion is produced by plastic processing such as rolling or drawing or mechanical processing. Metal material with a surface shape that allows modulus.

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