JP2005272853A - Machine parts having oxide film, rolling equipment equipped with the machine parts, and surface treatment method for the machine parts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide machine parts which are composed of titanium, aluminum, magnesium or alloys composed thereof as principal components and are additionally excellent in resistance to corrosion and wear while lightness in weight and thermal conductivity are maintained. <P>SOLUTION: The machine parts are composed of a base material of the alloy consisting of one or more kinds of light metals or light metal elements as principal components and have the oxide films of the light metal elements of hardness above 8 Gpa on their surfaces. The light metal oxide films are formed by being subjected to an anodic electrolysis treatment in an alkaline solution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a machine part provided with a metal oxide film, and more particularly, to a wider range of machine parts, for example, engine parts, medical equipment parts, chemical fibers used in automobiles, ships, aircrafts, and the like. The present invention relates to machine parts that can be widely applied to machines used in high temperature, corrosive environments, boundary lubrication environments, such as parts of manufacturing machines, food machinery, semiconductor manufacturing equipment, and water supply / drainage pumps. The present invention also relates to a rolling device to which this mechanical component is applied.

  Light metals typified by titanium, aluminum, and magnesium, or alloys based on them are excellent in corrosion resistance and nonmagnetic properties. However, such an alloy is not at a sufficient level in terms of wear resistance. On the other hand, while stainless steel is excellent in wear resistance, its performance is not satisfactory for industrial use in terms of corrosion resistance and non-magnetic requirements.

  Therefore, for mechanical parts that require wear resistance in corrosive environments, use stainless steel at the expense of corrosion resistance, and use titanium alloys etc. when corrosion resistance is important. On the other hand, there was a case where selection was made at the expense of one of the performances.

  In order to solve this problem, attempts have been made to improve the wear resistance by improving the surface hardness of titanium, aluminum, magnesium and alloys based on these.

  For example, in the case of a titanium alloy, there is a precipitation effect treatment in which the α phase is finely precipitated in the β matrix by aging treatment after the solution treatment in the β phase region or the α + β two phase region. However, even if heat treatment is performed, the surface hardness obtained by precipitation hardening is at most about 6 Gpa.

  In addition, a heat treatment method is disclosed in which carbon, nitrogen, and oxygen are dissolved in the surface of titanium or a titanium alloy in carburizing, carbonitriding, or nitriding to improve surface hardness (see, for example, Patent Document 1). However, there is a problem that the processing depth per unit time is shallow, the surface hardness is only about 5 Gpa, and the processing takes time.

  On the other hand, aluminum and aluminum alloys, magnesium and magnesium alloys are used for cylinder pistons of reciprocating engines used in internal combustion engines and turbine blades of superchargers because of their high thermal conductivity and low specific gravity. These titanium-based, aluminum-based, or magnesium-based mechanical parts are subjected to heat treatment to impart strength to the material, and are then subjected to anodic electrolysis in an acidic solution, which is a kind of surface treatment, and several tens of μm on the surface. The oxide film is formed to increase the surface strength. Examples of such acidic solutions are typically sulfuric acid and oxalic acid. An anodic electrolysis treatment in an acidic solution for aluminum-based machine parts is commonly referred to as an alumite ™ treatment.

  As described above, in the anodic electrolysis treatment in an acidic solution, fine holes are formed on the surface after the treatment, and if the holes are not sealed, the corrosion resistance deteriorates. There is. Moreover, since the oxide film is a thin film having a thickness of several tens of μm at the maximum, it has various problems such as insufficient durability with respect to wear resistance.

By the way, in titanium, aluminum, magnesium, or an alloy containing these as main components, there is a method of forming an oxide film on the surface by an oxidation treatment in the atmosphere, but it has been reported that the surface strength remains at 5 GPa.
JP-B 61-2747

  SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a light-metal machine component that is lightweight and maintains thermal conductivity, and has excellent corrosion resistance and wear resistance, and a surface treatment method therefor. The purpose is to do. Another object of the present invention is to provide a rolling device comprising the mechanical component.

  As a result of intensive studies, the present inventors have completed the present invention based on the knowledge that the oxide film obtained by alkaline electrolytic treatment improves the surface hardness of mechanical parts. That is, according to the first aspect of the present invention, the light metal or the base material of the alloy mainly containing one or more light metal elements is provided, and the oxide film of the light metal element having a hardness of 8 GPa or more is provided on the surface thereof. The light metal oxide coating provides a mechanical part formed by anodic electrolysis in an alkaline solution.

  According to a preferred aspect of the mechanical component according to the present invention, the light metal is made of titanium, aluminum, or magnesium, and the base material is made of an alloy containing at least one of these light metal elements as a main component. It is characterized by.

  According to a preferred aspect of the mechanical component according to the present invention, the base material further contains one or more metal elements selected from the group consisting of vanadium, chromium, molybdenum, zirconium, and tin. Features.

  According to a second aspect of the present invention, there is provided a rolling device having a rotation guide function or a linear motion guide function, part or all of which comprises the mechanical parts.

  According to the third aspect of the present invention, a mechanical part made of a base material of a light metal or an alloy mainly composed of one or more light metal elements is subjected to an anodic electrolysis treatment in an alkaline solution, and the surface thereof is 8 GPa or more. A surface treatment method for a machine part, wherein the light metal oxide film having a hardness of 5 mm is formed.

  The term “main component” used in the present invention refers to a component having the largest content compared to other components with respect to the total weight in the alloy, for example, a component having a content of 50% by mass or more. Refer to it.

  The oxide film formed by anodic electrolysis in the present invention is a machine that has a particularly high surface hardness and excellent corrosion resistance and wear resistance as compared with conventional atmospheric oxidation methods and anodic oxidation methods using acidic solutions. Parts can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. The following embodiment is an example for explaining the present invention, and is not intended to limit the present invention only to this embodiment. The present invention can be implemented in various forms without departing from the gist thereof.

  The mechanical component according to the present invention is based on a light metal such as titanium, aluminum, or magnesium, or based on an alloy mainly composed of one or more of these. The mechanical component according to the present invention has a metal oxide film containing, as essential components, a metal element and oxygen as main components of the equipment on the surface, and the hardness of the metal oxide film is 8 Gpa or more.

  Specific examples of the titanium alloy as an alloy used in the present invention include Ti-6Al-4V, Ti-4.5Al-3V-2Fe-2Mo, and Ti-15V-3Cr-3Sn-3Al. Also, pure titanium having high purity such as α titanium can be used, and titanium added with other metal elements, such as α + β titanium, for example, 90% by mass of titanium, 6% by mass of aluminum, and vanadium 4 A titanium alloy added with mass% can also be used.

  Other examples of alloys used in the present invention include aluminum alloys, specifically, Al-Mn alloys (3000 series), Al-Si alloys (4000 series), Al-Mg alloys (5000 series). Al-Mg-Si alloy (6000 series), Al-Zn-Mg alloy (7000 series), Al-Cu alloy (2000 series), and the like. Among these aluminum alloys, an Al—Mg—Si alloy (6000 series) is preferable.

  Another example of the alloy used in the present invention is a magnesium alloy. Specifically, AZ91D, AM60B, AM50A, AS41B (JIS standard), etc. can be used.

  In addition, the substrate composed of the alloy used in the present invention preferably contains one or more metal elements selected from vanadium, chromium, molybdenum, zirconium, and tin. When an alloy containing one or more metal elements selected from vanadium, chromium, molybdenum, zirconium, and tin is subjected to anodic electrolysis in an alkaline solution, these metals are also oxidized, together with the main component oxide, An oxide film is formed on the surface. The oxide film containing the additional metal element reinforces various effects to be described later of the oxide film composed of the main component.

  The content of vanadium, chromium, molybdenum, zirconium, and tin is 50% by mass or less and preferably 0.001% by mass or more in the metal material constituting the substrate. If the content exceeds 50% by mass, the effect of strengthening the oxide film composed of the main component cannot be expected to be further improved, and the cost is high. On the other hand, if the content is less than 0.001% by mass, the improvement is achieved. The degree of is not enough.

  Forming the metal oxide film according to the present invention on the substrate surface is achieved by anodic electrolysis in an alkaline solution.

  The film formed by such an anodic electrolytic treatment is a dense crystalline oxide film having no pores, and has a surface hardness of 8 GPa or more. Further, the thickness of the oxide film can be set to several tens to several hundreds μm by adjusting the amount of electricity. Here, the existence ratio of the pores in the metal oxide film is very small, and the oxide film having a thickness of several tens to several hundreds μm is the same quality as a so-called ceramic, and has wear resistance and corrosion resistance. Is excellent. However, when the surface hardness exceeds 30 GPa, the oxide coating itself becomes brittle, which is not preferable.

  Next, a surface treatment method for forming a metal oxide film according to the present invention on a machine part will be described. As disclosed in US Pat. No. 5,616,229, in addition to the incomplete rectification method, the energization method in the anodic electrolysis treatment in an alkaline solution is a direct current method, a constant current method, a constant voltage method, a PR method, a pulse Any of the law and the AC / DC tatami mat method may be used. Among these energization methods, the incomplete rectification method, the pulse method, or the AC / DC folding method is preferable. These three methods change the direction of current flow (voltage polarity) at predetermined time intervals, thereby reducing electrode polarization and temperature rise. Therefore, the current density can be improved and the film can be thickened. However, the proportion of mechanical parts that are anodes (the product of the absolute value of current or voltage and time) must exceed 50%.

  In addition, when performing an anodic electrolysis process, it is preferable to mask a base material partially and to perform the surface treatment based on the anodic electrolysis process by this invention only in a desired position.

The voltage range used in the anodic electrolysis treatment used in the present invention is preferably ± 100 V to ± 2000 V, and the current density range is preferably 5 to 200 A / dm ³ . If the voltage during the anodic electrolytic treatment exceeds ± 2000 V, the equipment cost tends to be relatively high, and it tends to be difficult to obtain a uniform oxide film. On the other hand, if the voltage is less than ± 100 V, the effect of reducing the polarization effect is difficult to obtain, and therefore, a uniform oxide film is difficult to be formed. Also, if the current density during anodic electrolysis exceeds 200 A / dm ³ , a uniform oxide film is less likely to be formed than a relatively large equipment cost, while the current density is less than 5 A / dm ^3. This is not preferable because it takes too long to obtain an oxide film having a required thickness.

  Next, specific examples of the alkali compound for obtaining the alkaline solution used for the anodic electrolytic treatment can be used without particular limitation as long as it is a substance that exhibits alkalinity when dissolved in water, but preferably sodium hydroxide. And metal hydroxides typified by potassium hydroxide and the like. Also, composite oxide salts and the like can be suitably used for sodium silicate, sodium aluminate, sodium titanate and the like. More preferably, a metal hydroxide and sodium silicate may be used in combination.

  A preferable pH range of the alkaline solution used for the anodic electrolysis according to the present invention is pH 8-13. If the pH is less than 8 or exceeds 13, a uniform oxide film cannot be formed.

  There are no particular restrictions on the equipment content of the anodizing treatment used in the present invention, but preferably, the alkaline solution described above is placed in a corrosion-resistant and conductive container such as stainless steel, and the pH, temperature, stirring speed, etc. are adjusted. After appropriate management, a mechanical part to be coated with an oxide film is immersed in the solution so as not to touch the container, and a predetermined voltage is applied between the container and the part for a predetermined time.

  The conditions for the anodic electrolytic treatment according to the present invention can be appropriately adjusted within a preferred range depending on the material, shape, desired film thickness, etc. of the parts to be treated. The anodic electrolytic treatment uses an alkaline solution. Therefore, in general, when an acidic solution is used in an anodic electrolytic treatment of aluminum, amorphous alumina is formed on the surface, whereas in the present invention, crystalline alumina is formed on the surface by using an alkaline solution. Since the crystalline alumina is a so-called ceramic, it is presumed to be excellent in corrosion resistance and wear resistance.

  Furthermore, when the base material constituting the mechanical component according to the present invention is made of an alloy containing vanadium, chromium, molybdenum, zirconium or tin, or is contained as an impurity, it is a main component constituting the base material. In addition to the improvement in strength caused by the oxide film of the metal element, an oxide film made of vanadium, chromium, molybdenum, zirconium, and tin is also formed during the anodic oxidation. As a result, the corrosion resistance, abrasion resistance, peel resistance, etc. of the coating film made of such metal are improved.

The anodic electrolysis treatment according to the present invention is a treatment method in which the direction of the current voltage changes in a predetermined time, such as a pulse method, and is formed at the time of anodic electrolysis by the action of a voltage current of ± 100 V or more and 5 A / dm ³ or more. The coated film is repeatedly melted and recrystallized on the extreme surface, whereby it becomes a denser film, and the corrosion resistance, wear resistance, peel resistance and the like are further improved.

  FIG. 1 shows a schematic view of an apparatus for carrying out an anodic electrolysis process used in the present invention. In the anodizing apparatus to which the present invention is applied, electric power is supplied from the power supply apparatus 10 to the workpiece 11 through the ammeter (A) through the lead wire 12. A voltmeter (V) 14 is installed in parallel with the lead wire 12 between the counter electrode 13 of the stainless steel container.

In the method for producing an oxide film of the present invention, an applied voltage of about 600 V is applied to a counter electrode 13 of a stainless steel container in an alkaline electrolyte 15 with a base material that is an object to be processed 11 as an anode, and about 70 A / In this method, electrolysis conditions with a current density of dm ³ are applied for 30 minutes from the power supply device 10.

  The following examples and comparative examples of the present invention are illustrative, and the present invention is not limited to the following specific examples. Those skilled in the art can implement the present invention by making various modifications to the embodiments shown below, and such modifications are included in the scope of the claims of the present application.

Example 1
When a titanium alloy (Ti-15Mo-5Zr alloy) was connected to the anode and electrolytic treatment was performed at 50 A / dm ³ by an AC / DC superposition method with an applied voltage of 600 V, an alloy oxide film was formed on the surface of the titanium alloy. And a thickness of 20 μm. The electrolytic bath was composed of potassium hydroxide and sodium titanate, and had a pH of 10 to 11 and a liquid temperature of 45 to 55 ° C.

Comparative Example 1
A rutile type titanium oxide layer was formed by atmospheric oxidation treatment of the same titanium alloy (Ti-15Mo-5Zr alloy) as in Example 1. The oxide coating was 20 μm thick.

Comparative Example 2
An alloy oxide film was formed on the surface of the same titanium alloy as in Example 1 (Ti-15Mo-5Zr alloy) using an acidic bath with an applied voltage of 40 V and direct current electrolysis. The electrolytic bath was oxalic acid and the pH was adjusted to 1-2. The resulting oxide film thickness was 10 μm.

  In order to examine the wear resistance of the machine parts obtained in Example 1 and Comparative Examples 1 and 2, a comparative experiment using a ball-on-disk was performed. Specifically, the surface of the object to be processed obtained in the previous examples and comparative examples is used against the disk, the SUJ2 ball is pressed with a constant load, and the contact surface pressure is 1.8 GPa. Rotated at a speed of / s for 2 hours.

  When the shape of the wear depth after the test was measured with a surface roughness meter, the results were 5 μm in Example 1, 18 μm in Comparative Example 1, and 15 μm in Comparative Example 2.

Example 2
An aluminum alloy (JIS name 6N01; Al—Mg—Si alloy) was attached to the anode in the same manner as in Example 1 and subjected to electrolytic treatment for 40 minutes. The electrolytic voltage was 400 V, the current density was 50 A / dm ³ , and the pulse electrolysis method was adopted. The electrolytic bath was adjusted with a hydroxide solution and metaphosphoric acid to obtain an alkaline solution having a pH of 10 to 11. The liquid temperature was maintained at 45 to 55 ° C., and anodic electrolysis was performed. As a result, an alloy compound layer having a thickness of 20 μm was formed on the surface. When the hardness of the cross section was measured with a microphotometer, it was 12 GPa.

Comparative Example 3
Using the same aluminum alloy as in Example 2, the surface was subjected to anodic electrolysis (electrolysis voltage: 30 V, current density: 5 A / dm ² , acidic solution adjusted to pH 1-2 with oxalic acid solution by direct current electrolysis). An oxide film having a thickness of 10 μm was formed. When the hardness was measured in the same manner as in Example 2, it was 5 GPa.

  FIG. 2 shows an example of a ball screw as a linear motion rolling device to which part or all of the mechanical parts according to the present invention are applied. The ball screw 20 is one moving member and a screw shaft 22 in which a spiral screw groove 21 is formed on the outer peripheral surface serving as a guide surface thereof, and the other moving member and an inner surface serving as a guide surface thereof. A nut 25 having a spiral thread groove 24 opposed to the thread groove 21 formed on the peripheral surface 23, a large number of balls 26 that are rolling elements interposed between the opposed thread grooves so as to be freely rollable, and And a tube-type circulation path 27 through which the balls 26 are circulated.

  The tube-type circulation path 27 is formed of a tube having a substantially U-shaped outer shape, and ball rolling in the nut 25 is performed at both end portions 28 from a tube mounting hole 29 penetrating the nut 25 in the tangential direction of both screw grooves 21 and 24, respectively. It is inserted into the space and fixed to the outer surface of the nut 25 with a stopper 30. The ball 26 that rolls in the spiral ball rolling space moves around the screw grooves 21 and 24 a plurality of times, and is then scooped up at one end 28 of the tube-type circulation path 27 to be tube-type circulation path 27. , And the circulation from the other end (not shown) back to the ball rolling space in the nut 25 is repeated.

  By using parts such as rolling elements, screw shafts, and nuts as machine parts subjected to anodic electrolysis according to the present invention, the corrosion resistance and wear resistance of the rolling device are improved.

  FIG. 3 is a cross-sectional view of a deep groove ball bearing to which a mechanical component according to the present invention is applied. A deep groove ball bearing 40 shown in FIG. 3 includes an outer ring 42 having a deep groove type outer ring raceway 41 on an inner peripheral surface, an inner ring 44 having a deep groove type inner ring raceway 43 on an outer peripheral surface, the outer ring raceway 41 and the inner ring raceway 43. And a plurality of balls 46 which are provided so as to be able to roll while being held by a cage 45.

  When the deep groove ball bearing 40 is operated, the balls 46 revolve while rotating between the outer ring raceway 41 and the inner ring raceway 43 as the outer ring 42 and the inner ring 44 rotate relative to each other. . And the probability that abrasion damage, such as peeling, between the rolling surfaces of the balls 46 and the tracks 41 and 43 will be extremely high. For this reason, the mechanical component according to the present invention is used for the ball 46, and this has the effect of reducing wear damage due to the improvement in corrosion resistance and wear resistance.

  In the embodiment of the present invention illustrated in FIG. 2 and FIG. 3, suitable materials, film thicknesses, and the like are often different depending on the shape and use of the apparatus and the type of parts to be applied, and they have corrosion resistance and wear resistance. Of course, since it may be considered to affect the durability, dust generation and the like, the material, the anodic electrolytic treatment conditions, and the like can be appropriately selected within a preferable range.

  Since the oxide coating according to the present invention is basically electrically insulative, for example, by forming the oxide coating according to the present invention on the outer ring outer surface or the inner ring outer surface of a rolling bearing, the bearing is electrically insulated. It can be given. A preferred specific example of the bearing using the electrical insulation of the oxide film according to the present invention is a bearing for an inverter motor or the like.

FIG. 1 is a schematic view of an apparatus for performing an anodic oxidation process that is an anodic electrolytic process according to an embodiment of the present invention. FIG. 2 is a view showing an example of a ball screw which is a linear motion rolling device to which a mechanical component according to the present invention is applied. FIG. 3 shows a cross-sectional view of a deep groove ball bearing to which a mechanical component according to the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electric power supply apparatus, 11 ... To-be-processed object, 12 ... Lead wire, 13 ... Counter electrode, 14 ... Voltmeter, 20 ... Ball screw, 21 ... Screw groove, 22 ... Screw shaft, 23 ... Inner peripheral surface, 24 ... Screw Groove, 25 ... nut, 26 ... ball, 27 ... circulation path, 28 ... both ends, 29 ... tube mounting hole, 30 ... clasp, 40 ... deep groove ball bearing, 41 ... outer ring raceway, 42 ... outer ring, 43 ... inner ring raceway 44 ... Inner ring, 45 ... Cage, 46 ... Ball

Claims (5)

  It is made of a base material of a light metal or an alloy containing at least one kind of light metal element as a main component, and has an oxide film of the light metal element having a hardness of 8 GPa or more on its surface. The light metal oxide film is an anode in an alkaline solution. Machine parts formed by electrolytic treatment.   The machine part according to claim 1, wherein the light metal is made of titanium, aluminum, or magnesium, and the base material is made of an alloy containing at least one of these light metal elements as a main component.   The machine part according to claim 1 or 2, wherein the base material further contains one or more metal elements selected from the group consisting of vanadium, chromium, molybdenum, zirconium, and tin.   A rolling device having a rotation guide function or a linear motion guide function, part or all of which comprises the mechanical component according to any one of claims 1 to 3. A mechanical component made of a base material of a light metal or an alloy mainly composed of one or more light metal elements is subjected to an anodic electrolysis treatment in an alkaline solution, and the light metal oxide film having a hardness of 8 GPa or more is formed on the surface thereof. A method for treating the surface of a machine part.

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