JP2016008329A - Anodic oxidation treatment method for aluminum alloy member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anodic oxidation treatment method for an aluminum alloy member capable of hardening an oxide film while suppressing the complication of the management of anodic oxidation treatment conditions.SOLUTION: Provided is an anodic oxidation treatment method in which the surface of an aluminum alloy member 11 is subjected to anodic oxidation treatment to form an oxide film on the surface, in which after the surface of the aluminum alloy member 11 is subjected to trivalent chromate treatment, anodic oxidation treatment is performed. In this way, the oxide film can be hardened while suppressing the complication of the management of the anodic oxidation treatment conditions.

Description

  The present invention relates to a method for anodizing an aluminum alloy member.

  Of the parts constituting the master cylinder, anodizing treatment (alumite treatment) is performed on cylinder members that are aluminum products in order to improve wear resistance (see, for example, Patent Document 1).

JP 2008-56953 A

  When the anodizing treatment is performed on the aluminum alloy member, the surface of the aluminum alloy member is covered with a hard oxide film. If a harder oxide film is to be formed in order to further improve the wear resistance, the management of the current density, which is an anodizing treatment condition, and the temperature (bath temperature) of the anodizing solution are complicated. In other words, basically, to increase the hardness of the oxide film, the current density is increased and the temperature of the anodizing solution is increased. Since the hardness of the oxide film changes in a quadratic function, the hardness increases when it is appropriately raised, but it may decrease the hardness if it is not properly raised. Further, if the current density and the temperature of the anodizing solution are increased too much, the oxide film may be burned and the film may be destroyed.

  An object of this invention is to provide the anodizing method of the aluminum alloy member which can harden an oxide film, suppressing the management of anodizing treatment conditions becoming complicated.

  In order to achieve the above object, according to the present invention, the surface of the aluminum alloy member is anodized after the trivalent chromate treatment.

  According to the anodizing method for an aluminum alloy member according to the present invention, the oxide film can be hardened while suppressing the management of the anodizing conditions.

It is sectional drawing which shows the aluminum alloy member processed with the anodizing method of one Embodiment which concerns on this invention. It is sectional drawing which shows roughly the trivalent chromate processing apparatus for performing the anodizing method of the embodiment. It is sectional drawing which shows schematically the anodizing apparatus for performing the anodizing method of the embodiment.

  An embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows an aluminum alloy member 11 to be treated by the anodizing method of this embodiment.

  This aluminum alloy member 11 is a cylinder member constituting a master cylinder for a vehicle. A master cylinder for a vehicle is not shown in the figure, but a force corresponding to the operation amount of the brake pedal is introduced from the brake booster, and an internal piston is moved by the introduced force, and the brake hydraulic pressure corresponding to the operation amount of the brake pedal is Is generated.

  The aluminum alloy member 11 is an integrally molded product, and includes a cylindrical portion 13 having an opening 12 on one end side in the axial direction, a bottom portion 14 closing the opposite side of the cylindrical portion 13 with respect to the axial opening 12, and a cylinder It has a bottomed cylindrical shape having a mounting seat portion 15 projecting outward from the outer peripheral surface of the shape portion 13.

  The mounting seat portion 15 is a portion to which a not-illustrated reservoir tank for storing brake fluid is mounted, and is disposed at the upper portion of the aluminum alloy member 11 in the vertical direction when mounted on the vehicle. The mounting seat portion 15 has a mounting hole 21 on the bottom 14 side and a mounting hole 22 on the opening 12 side. The mounting holes 21 and 22 are formed at a predetermined depth from the opposite side to the cylindrical portion 13 in the mounting seat portion 15. The tubular portion 13 has a passage hole 23 for communicating the bottom of the attachment hole 21 on the bottom 14 side and the inside of the tubular portion 13, and the bottom of the attachment hole 22 on the opening 12 side and the inside of the tubular portion 13. And a passage hole 24 is formed. The two mounting holes 21 and 22 are fitted with two supply / discharge portions of the reservoir tank, whereby the inside of the reservoir tank and the inside of the aluminum alloy member 11 are connected via the passage holes 23 and 24. Can communicate with each other.

  Although not shown, the aluminum alloy member 11 is slidably fitted with a secondary piston on the bottom 14 side and a primary piston on the opening 12 side. The secondary piston forms a secondary pressure chamber that discharges the brake fluid to a predetermined wheel cylinder of the disc brake between the portion of the aluminum alloy member 11 on the bottom 14 side. The primary piston forms a primary pressure chamber for discharging brake fluid to another wheel cylinder of the disc brake between the secondary piston and the aluminum alloy member 11.

  The cylindrical portion 13 is formed with a bottom-side sliding inner diameter portion 28 in which the secondary piston is slidably fitted to the inner peripheral portion on the bottom portion 14 side. Is moved in the axial direction. The cylindrical portion 13 is formed with an opening-side sliding inner diameter portion 29 in which the primary piston is slidably fitted to the inner peripheral portion on the opening 12 side. Is moved in the axial direction.

  In the intermediate position in the axial direction in the formation range of the bottom sliding inner diameter portion 28, an annular shape that is recessed radially outward from the bottom sliding inner diameter portion 28 at the opening position into the tubular portion 13 of the passage hole 23. The passage groove 31 is formed. Further, in the formation range of the bottom sliding inner diameter portion 28, a circumferential groove 32 is formed on the bottom portion 14 side of the passage groove 31, and a circumferential groove 33 is formed on the opening 12 side of the passage groove 31. Each of the circumferential grooves 32 and 33 has an annular shape and is recessed outward in the radial direction from the bottom sliding inner diameter portion 28.

  At the intermediate position in the axial direction in the formation range of the opening-side sliding inner diameter portion 29, an annular shape that is recessed radially outward from the opening-side sliding inner diameter portion 29 at the opening position into the cylindrical portion 13 of the passage hole 24. A passage groove 36 is formed. Further, in the formation range of the opening-side sliding inner diameter portion 29, a circumferential groove 37 is formed on the bottom 14 side of the passage groove 36, and a circumferential groove 38 is formed on the opening 12 side of the passage groove 36. These circumferential grooves 37 and 38 are both in an annular shape and are recessed radially outward from the opening-side sliding inner diameter portion 29.

  An annular cup seal is disposed in the circumferential groove 32, and an annular partition seal is disposed in the circumferential groove 33. When the secondary piston moves forward toward the bottom 14 and the pressure in the secondary pressure chamber becomes higher than the pressure in the reservoir tank (atmospheric pressure), the cup seal disposed in the circumferential groove 32 is formed between the secondary piston and the aluminum alloy member 11. While the gap is sealed, the secondary piston is retracted to the opposite side of the bottom 14 by the biasing force of the spring, and when the pressure in the secondary pressure chamber becomes lower than the pressure in the reservoir tank, liquid is supplied to the secondary pressure chamber from the reservoir tank. Is possible. The partition seal disposed in the circumferential groove 33 always seals the gap between the secondary piston and the aluminum alloy member 11.

  An annular cup seal is disposed in the circumferential groove 37, and an annular partition seal is disposed in the circumferential groove 38. The cup seal disposed in the circumferential groove 37 is formed between the primary piston and the aluminum alloy member 11 when the primary piston advances toward the bottom portion 14 and the pressure in the primary pressure chamber becomes higher than the pressure (atmospheric pressure) in the reservoir tank. While the gap is sealed, the primary piston is retracted to the opposite side of the bottom 14 by the biasing force of the spring, and when the pressure in the primary pressure chamber becomes lower than the pressure in the reservoir tank, Allows replenishment. The partition seal disposed in the circumferential groove 38 always seals the gap between the primary piston and the aluminum alloy member 11.

  That is, the aluminum alloy member 11 is a sliding member having a bottom-side sliding inner diameter portion 28 and an opening-side sliding inner diameter portion 29 that slide relative to the piston.

  The surface of the aluminum alloy member 11 is anodized to form an oxide film on the surface. In the anodizing method of this embodiment, the surface of the aluminum alloy member 11 is pretreated as the pretreatment. A trivalent chromate treatment, which is a chemical conversion treatment, is performed to form a trivalent chromate film on the surface. FIG. 2 schematically shows a trivalent chromate treatment apparatus 41 that performs trivalent chromate treatment on the surface of the aluminum alloy member 11.

  The trivalent chromate treatment apparatus 41 maintains the temperature of the trivalent chromate treatment tank 42 storing the trivalent chromate treatment liquid L1 and the temperature of the trivalent chromate treatment liquid L1 in the trivalent chromate treatment tank 42 at a predetermined maintenance temperature. And a temperature adjusting unit 43 for adjusting the temperature. The temperature adjusting unit 43 is provided at the bottom position of the trivalent chromate treatment tank 42 so as to form the bottom. Specifically, the temperature adjustment unit 43 is a heater that heats the trivalent chromate treatment liquid L1 so as to reach a set maintenance temperature. The trivalent chromate treatment tank 42 has such a size that the entire aluminum alloy member 11 that performs the trivalent chromate treatment can be immersed in the trivalent chromate treatment liquid L1.

  The entire aluminum alloy member 11 is immersed in the trivalent chromate treatment liquid L1 in the trivalent chromate treatment tank 42 for a predetermined time while controlling the temperature adjusting unit 43 so as to maintain the trivalent chromate treatment liquid L1 at a predetermined temperature. Thereby, a trivalent chromate film is formed on the surface of the aluminum alloy member 11.

  FIG. 3 shows an anodizing apparatus 51 that forms an oxide film on the surface of an aluminum alloy member 11 that has been trivalent chromated by the trivalent chromate apparatus 41 by anodizing the surface. The trivalent chromate treatment apparatus 41 and the anodization treatment apparatus 51 constitute a surface treatment facility for performing the anodization treatment after the trivalent chromate treatment is performed on the aluminum alloy member 11.

  The anodizing apparatus 51 includes an anodizing liquid tank 52 that stores the anodizing liquid L2, an agitation unit 53 that agitates the anodizing liquid L2 in the anodizing liquid tank 52, and an anodizing liquid tank 52. A plurality of temperature adjusting parts 54 and 54 for adjusting the anodic oxidation liquid L2 to be maintained at a predetermined maintenance temperature, and a current supply part for supplying current to the anodic oxidation liquid L2 in the anodizing liquid tank 52. 55.

  The anodizing solution tank 52 is sized so that the entire aluminum alloy member 11 to be anodized can be immersed in the anodizing solution L2.

  The agitating unit 53 agitates the anodizing solution L <b> 2 by ejecting air from the bottom of the anodizing solution tank 52 in a bubble shape. The agitation unit 53 includes a compressor 61 that takes in outside air, an air passage 62 that guides compressed air discharged from the compressor 61 to the anodizing solution tank 52, and an anodizing solution tank 52 that sends the compressed air guided through the air passage 62. And a jet part 63 for jetting into a anodic oxidation treatment liquid L2 from a fine hole (not shown) formed on the entire surface extending in the horizontal direction at the bottom.

  The temperature control units 54 and 54 are provided on the side wall of the anodizing solution tank 52. Specifically, the temperature control units 54 and 54 are coolers that cool the anodizing treatment liquid L2 so as to reach a set maintenance temperature.

  The current supply unit 55 is electrically connected to the rectifier 71 and the cathode terminal 72 of the rectifier 71, and is a plurality of cathode electrodes 73 and 73 disposed so as to be immersed in the anodizing solution L <b> 2 in the anodizing solution tank 52. And have. The cathode electrodes 73 and 73 are disposed so as to sandwich the aluminum alloy member 11 to be anodized. The aluminum alloy member 11 is electrically connected to the anode terminal 74 of the rectifier 71, and the aluminum alloy member 11 to be anodized becomes the anode electrode.

  When the aluminum alloy member 11 that has been subjected to trivalent chromate treatment by the trivalent chromate treatment device 41 is subjected to anodization treatment by the anodization treatment device 51, the aluminum alloy member 11 is electrically connected to the anode terminal 74 of the rectifier 71. In a connected state, the anode electrode is disposed between the cathode electrodes 73 and 73 of the anodizing solution tank 52 and is entirely immersed in the anodizing solution L2.

  In this state, the temperature adjusting units 54 and 54 are controlled so as to maintain the anodizing treatment liquid L2 at a predetermined temperature, and air is jetted out from the jetting unit 63 in a bubble shape by the stirring unit 53 to thereby generate the anodizing treatment liquid L2. While stirring, a current is supplied at a predetermined current density for a predetermined time between the cathode electrodes 73 and 73 and the aluminum alloy member 11 as the anode by the current supply unit 55. Then, the anodizing treatment liquid L2 that contacts the entire surface of the aluminum alloy member 11 forms an oxide film on the entire surface of the aluminum alloy member 11.

  An oxide film is formed on the surface of the aluminum alloy member 11 by the above anodic oxidation treatment. Thereafter, among the surfaces of the aluminum alloy member 11, the surfaces of the bottom-side sliding inner diameter portion 28 and the opening-side sliding inner diameter portion 29 on which the piston slides are subjected to a polishing process for smoothing.

  According to the present embodiment described above, since the anodizing treatment is performed after the trivalent chromate treatment is performed on the surface of the aluminum alloy member 11, the oxide film is suppressed while controlling the anodizing treatment conditions becomes complicated. Can be hardened.

  In the present embodiment described above, the portions (the bottom sliding inner diameter portion 28 and the opening side sliding inner diameter portion 29) that slide with other parts and require wear resistance are the surfaces of the aluminum alloy member 11. Are provided only on the inner surface 11a on the inner side, and are not provided on the outer surface 11b on the outer side. For this reason, the trivalent chromate treatment may be performed only on the inner surface 11a of the aluminum alloy member 11, and then the anodic oxidation treatment may be performed only on the inner surface 11a. In other words, at least the inner surface 11a of the aluminum alloy member 11 may be anodized after the trivalent chromate treatment.

  Further, in the present embodiment described above, the bottomed cylindrical cylinder member of the vehicle master cylinder has been described as an example of the aluminum alloy member 11, but relative to other members (particularly metal members). As long as the sliding member is slidable, it can be applied to other various aluminum alloy members such as a piston of a disc brake caliper for a motorcycle. When applied to any aluminum alloy member, a trivalent chromate treatment may be performed on at least a portion that slides relative to another member, and then an anodization treatment may be performed.

  The anodizing method for an aluminum alloy member of the present embodiment described above is an anodizing method for forming an oxide film on the surface by anodizing the surface of the aluminum alloy member. After trivalent chromate treatment on the surface, anodic oxidation treatment is performed. Thereby, an oxide film can be hardened, suppressing that the management of anodizing treatment conditions becomes complicated.

As shown in Table 1, as an example of the present invention, a trivalent chromate treatment was performed on the plate-like test piece of an AC2A aluminum alloy member by the above-described trivalent chromate treatment apparatus 41 under the following conditions. .
A first trivalent chromate treatment liquid (trivalent chromium-zirconate-based treatment liquid) having a concentration of 160 [mL / L] and a second trivalent chromate treatment liquid (trivalent) having a concentration of 50 [mL / L]. Chromium-zirconate treatment solution) is appropriately mixed to obtain a trivalent chromate treatment solution L1 having a pH of 3.5, which is used.
The temperature adjusting unit 43 is controlled so that the temperature of the trivalent chromate treatment liquid L1 in the trivalent chromate treatment tank 42 is maintained at 30 [° C.].
-Trivalent chromate processing time shall be 3.0 [min].

Next, the test piece after the trivalent chromate treatment was anodized under the following conditions by the anodizing apparatus 51 of the above embodiment. This anodizing process is the same process as a comparative example which will be described later, and can be executed without complicated management of anodizing process conditions.
-An aqueous sulfuric acid solution having a concentration of 343.6 [g / L] is used as the anodizing solution.
The temperature adjusting units 54 and 54 are controlled so that the temperature of the anodizing solution L2 in the anodizing solution tank 52 is maintained at 0.0 [° C.].
A current is supplied at a current density of 4.0 [A / dm ² ] by the current supply unit 55.
The anodizing time (that is, the current supply time by the current supply unit 55) is set to 18.5 [min].

  In the example in which the anodizing treatment was performed under such conditions, the hardness (HV) of the oxide film was 401.3.

  As a comparative example, anodizing treatment was performed on the same test piece as in the example by the anodizing apparatus 51 under the same conditions as in the example without performing the trivalent chromate treatment.

  In the comparative example in which the anodic oxidation treatment was performed without performing the trivalent chromate treatment, the hardness (HV) of the oxide film was 362.2.

  In other words, even if anodization is performed under the same conditions, in the example in which trivalent chromate treatment was performed as the previous step, the hardness (HV) of the oxide film was 401.3, and trivalent chromate treatment was performed in the previous step. In the comparative example which was not performed, the hardness (HV) of the oxide film was 362.2. Therefore, it turns out that the direction which performed trivalent chromate treatment as a previous process increases hardness compared with the case where trivalent chromate treatment is not performed in a previous process.

11 Aluminum alloy member 11a Inner surface 41 Trivalent chromate treatment device 51 Anodization treatment device L1 Trivalent chromate treatment solution L2 Anodization treatment solution

Claims (1)

An anodizing method for forming an oxide film on the surface by anodizing the surface of an aluminum alloy member,
A method for anodizing an aluminum alloy member, wherein the surface of the aluminum alloy member is anodized after trivalent chromate treatment.

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