JPH06173072A - Machine parts excellent in interline wear resistance - Google Patents

Abstract

PURPOSE:To provide machine parts such as a coil spring having low specific gravity and excellent interline wear resistance, suitably usable as the coil spring or the like for an automotive engine suction and exhaust valve, etc., and capable of reducing their weights and improving their durabilities. CONSTITUTION:This is the machin parts such as a coil spring obtd. by coating the surface of a base material constituted of a titanium allay or an aluminum alloy with an Ni-P electroplating layer. As for the surface of the base material, Ra is regulated to >=0.5mum and PPI50 to >=130, and as for the Ni-P plating layer, Vickers hardness Hv is regulated to 500 to 730, thickness to 0.5 to 15mum, P content to 0.5 to 7.0wt.% and plating stress to <=5kgf/mm<2>. The space between the base material and Ni-P plating layer is preferably applied with an Ni or Cu strike plating layer with 0.1 to 3mum thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical part having excellent resistance to abrasion between wires, and more specifically, it is formed by coating a surface of a base material made of a titanium alloy or an aluminum alloy with an electric Ni-P plating layer. Machine parts, especially titanium alloy wire,
The present invention relates to a mechanical component such as a coil spring which is coated with a P plating layer and has excellent resistance to abrasion between wires.

[0002]

2. Description of the Prior Art Intake and exhaust valves of gasoline engines for automobiles, diesel engines, etc.
A coil spring made of high carbon steel manufactured by aging treatment is used. In recent years, in response to the demand for CAFE compliance and the like, in order to meet the demand for improved fuel efficiency and weight reduction, the adoption of a coil spring (titanium alloy coil spring) made of a titanium alloy wire having a lower specific gravity than carbon steel has begun to be considered.

Since the titanium alloy has a low specific gravity as described above, its use as a constituent material for the coil spring is being studied to reduce its weight. However, its application is not limited to the coil spring, but also takes advantage of its excellent characteristics. Titanium alloys are being applied to various machine parts. For example, it is being applied to engine parts such as connecting rods and valve materials.
Further, aluminum alloys are also applied to various machine parts mainly for the purpose of weight reduction because of their low specific gravity.

[0004]

As described above, when titanium alloy or aluminum alloy is used as a constituent material of machine parts,
Although it is possible to reduce the weight, there is a problem that the interline wear resistance is poor due to the poor seizure resistance and wear resistance, which are disadvantages peculiar to titanium alloys.

For example, the above-mentioned conventional titanium alloy coil spring is lightweight because it is made of a titanium alloy wire and has excellent spring characteristics, but on the other hand, it has poor seizure resistance and wear resistance, which are disadvantages peculiar to titanium alloys. Therefore, there is a problem that the abrasion resistance between wires is inferior, and the improvement is necessary for practical use.

Therefore, in order to improve the inter-wire wear resistance of the above titanium alloy, an attempt has been made to increase the hardness by coating the surface of the titanium alloy wire of the coil spring with an electroless Ni-P plating layer having a P content of 10 wt%. Is made. Further, as a method of relieving the plating stress of the plating layer, a method of applying a residual stress by performing shot peening or honing is proposed. However, it has been found by experiments that none of these can improve the inter-wire wear resistance of titanium alloys. Further, it was also found that if the hardness of the plated layer was increased to about Hv: 900 by heating at 300 to 400 ° C. for about 1 hour after Ni-P plating, the abrasion resistance between wires deteriorated.

The present invention has been made in view of such circumstances, and its object is the problem of inter-line wear resistance of the conventional mechanical parts using a titanium alloy or an aluminum alloy as a constituent material. Providing machine parts that eliminate the above points and have low specific gravity and excellent wear resistance between wires, and in particular provide coil springs that have low specific gravity and excellent spring characteristics as well as excellent wear resistance between wires. Is what you are trying to do.

[0008]

In order to achieve the above object, the mechanical component according to the present invention has the following constitution. That is, the mechanical component according to claim 1 is a mechanical component in which the surface of a base material made of a titanium alloy or an aluminum alloy is coated with an electric Ni-P plating layer, and the surface of the base material is Ra:
0.5 μm or more and PPI ₅₀ : 130 or more,
The Ni-P plating layer has a Vickers hardness Hv of 500 to 730, a thickness of 0.5 to 15 μm, a P content of 0.5 to 7.0 wt%, and a plating stress of 5 kgf / mm ² or less. It is a machine component with excellent wear resistance.

In the mechanical component according to claim 2, a Ni or Cu strike plating layer having a thickness of 0.1 to 3 μm is provided on the surface of the base material, and an electric Ni-P plating layer is coated on the Ni or Cu strike plating layer. It is a machine component excellent in abrasion resistance between wires as described in 1. According to a third aspect of the present invention, in the machine component according to the first or second aspect, the base material is made of a titanium alloy wire and the machine component is a coil spring.

[0010]

As described above, the mechanical component according to the present invention is formed by coating the surface of a base material made of a titanium alloy or an aluminum alloy with an electric Ni-P plating layer. It is as lightweight as the mechanical parts made up of.

Moreover, since the surface of the base material is set to have Ra: 0.5 μm or more and PPI ₅₀ : 130 or more, the anchor effect can firmly adhere the base material and the electric Ni-P plating layer. It is difficult for the plated layer to peel off. Here, Ra and PPI ₅₀ are numerical values showing the surface condition such as surface roughness obtained as a result of surface roughness measurement as well known, Ra is the center line average roughness, and PPI ₅₀ is the reference level:
The number of peaks per inch (ie pe
ak per inch). The Ra and PPI ₅₀ are numerically limited as described above, but when Ra: less than 0.5 μm and / or PPI ₅₀ : less than 130, the adhesion between the base material and the plating layer is insufficient and the peeling of the plating layer occurs. This is because the possibility arises.

Further, the Ni-P plating layer is set to have Hv (Vickers hardness): 500 to 730, thickness: 0.5 to 15 μm, P content: 0.5 to 7.0 wt%, and plating stress: 5 kgf / mm ² or less. Therefore, the abrasion resistance between the wires is extremely excellent. This is based on the following findings obtained as a result of various experiments.

That is, it was found that the line-to-line wear of mechanical parts is wear that involves fatigue, and is the result of a decrease in the material surface accompanied by peeling due to the synergistic effect of wear and fatigue. For example, in the case of a coil spring, the spring wires come into contact with each other with a high surface pressure and separate from each other during use, so the surface of the spring wire is subjected to a kind of fatigue due to the change in the surface pressure, and therefore the wire-to-line wear of the coil spring causes fatigue. Is a result of the fact that the surface of the material is reduced with peeling due to the synergistic effect of wear and fatigue.

Generally, the fatigue property and toughness of a material are closely related to each other. When the toughness is improved, the fatigue strength is increased to improve the fatigue resistance. However, when the hardness is excessively increased, the toughness is decreased and the fatigue resistance is decreased. Deteriorates. Also, normal wear improves with increasing material hardness. Therefore, in order to improve the inter-wire wear resistance of mechanical parts, it is necessary not only to increase the hardness thereof but also to improve the hardness and toughness in a well-balanced manner. , Hv: 500 to 730, thickness: 0.5 to 15 μm, P content: 0.5 to 7.0 wt%, and plating stress: 5 kgf / mm ² or less, it was found that the interline wear resistance can be significantly improved.

Therefore, as described above, the Ni-P plating layer is formed with Hv:
500 to 730, thickness: 0.5 to 15 μm, P content: 0.5 to 7.0w
t% and plating stress: 5 kgf / mm ² or less. Therefore, the Ni-P plating layer can make the mechanical parts extremely excellent in the abrasion resistance between wires. The reason for limiting the numerical values as described above is as follows.

If the Hv is less than 500, the hardness is too low and the wear resistance decreases, and the interline wear resistance becomes insufficient. If it exceeds 730, the toughness of the plating layer becomes insufficient and the fatigue resistance deteriorates. As a result, the wear resistance becomes insufficient.

Regarding the thickness, a thinner one suppresses the shearing force acting between the base material and the plating layer and makes it difficult for the plating layer to peel off, so that the abrasion resistance between wires is remarkably improved.
If the thickness is less than 5 μm, the strength of the plating layer itself will be weak and it will be difficult to withstand fatigue due to contact between machine parts (spring wires, etc.) under high contact surface pressure. On the other hand, above 15 μm is expensive
In addition to the decrease in economic efficiency due to the increase in Ni, the weight of the plating layer increases, making it difficult to reduce the weight of mechanical parts.
If it exceeds m, the shearing force acting between the plating layer and the base material becomes large, so that the plating layer is easily separated.

If the P content is less than 0.5 wt%, the hardness of the plating layer is insufficient, the wear resistance is reduced, and the interline wear resistance is insufficient. If it exceeds 7.0 wt%, the toughness of the plating layer is insufficient. If it becomes sufficient, the fatigue resistance deteriorates, and as a result, the abrasion resistance between wires becomes insufficient. This is because if the plating stress exceeds 5 kgf / mm ² , plating peeling easily occurs when tensile stress acts on the plating layer of the mechanical component. The above is the reason for the numerical limitation.

As is clear from the above description, the mechanical component according to the present invention has a low specific gravity and an excellent resistance to inter-line wear, and is sufficient for ensuring excellent durability and weight reduction. Will be able to meet.

When the base material is a titanium alloy, in order to make the surface Ra: 0.5 μm or more and PPI ₅₀ : 130 or more, chemical etching with a hydrofluoric acid salt such as NH ₄ F.HF or NaF.HF is performed. do it. After such etching, it is desirable to perform electrolytic treatment in a phosphoric acid or sulfuric acid solution for surface smut removal, or activation treatment with hydrofluoric acid or the like.

The electric Ni-P plating layer may be provided so as to cover the entire surface of the base material, or may be provided only at a portion where machine parts (spring wires, etc.) contact each other. However, in order to further reduce the weight, it is effective and desirable to cover only the minimum necessary portion where the abrasion resistance between wires is a problem.

It is desirable to provide a Ni or Cu strike plating layer having a thickness of 0.1 to 3 μm between the substrate and the electric Ni-P plating layer. Such a plating layer can be obtained by subjecting a base material to Ni or Cu strike plating having a thickness of 0.1 to 3 μm as an undercoat, and coating an electric Ni—P plating layer on the Ni or Cu strike plating. When the strike plating layer is provided in this way, the shear stress at the interface between the Ni-P plating layer and the base material, which has a compressive stress, is relieved, so that the adhesion between the base material and the Ni-P plating layer is further improved. .

The present invention can be applied to various machine parts, and particularly to a coil spring whose base material is a titanium alloy wire. This coil spring is formed by coating the surface of a coil-shaped titanium alloy wire with an electric Ni-P plating layer, is lightweight like the conventional titanium alloy coil spring, has excellent spring characteristics, and has excellent wire resistance. It has characteristics such as abrasion resistance, and can satisfy requirements for ensuring excellent durability and reducing weight.

[0024]

[Example] After hot working, wire drawing, aging, etc., Φ
A coil spring type made of 3.0 mm titanium alloy wire was manufactured, degreased, washed with water, chemically etched with hydrofluoric acid, washed with water, activated with hydrofluoric acid, and then electroplated with Ni-P to obtain Ni- The P plating layer was covered. In this _{plating, NiSO 4 · 6H 2 0:} 200g / l ( liter), NiCl _{2
· 6H 2 0: 50g / l} , H 3 PO 3: 4~40g / l, H 3 PO 4: 50g / l, H 3
BO ₃ : 0.5 to ₃ g / l, saccharin: 0.1 to 1.0 g / l bath temperature: 60 ± 5 ° C, pH: 1 ± 0.5 It was carried out at 5 to 30 A / dm ² . The composition (type) of the titanium alloy, the P content of the Ni-P plated layer, the thickness and plating stress, and the heating conditions of the coil spring after plating were changed as shown in Table 1.

[0025]

[Table 1]

Next, regarding the coil spring made of the titanium alloy wire coated with the Ni-P plated layer, the hardness of the surface layer was measured, and the peeling resistance evaluation test and the resistance against the titanium alloy wire of the base material and the Ni-P plated layer were performed. A line wear test was conducted. In addition, the abrasion resistance test between wires is performed under the conditions of fluctuation range of contact surface pressure (stress) between spring wires: 60 ± 40 kgf / mm ² , number of repetitions: 1 × 10 ⁷ times, and the coil spring surface condition after the test. Was visually observed to evaluate the abrasion resistance between wires.

A coil spring (not covered with the Ni-P plating layer) made of a titanium alloy wire was also manufactured. Furthermore, a coil spring was also produced in which Ni or Cu strike plating was applied before the Ni-P plating layer coating, and thereafter, the same electric Ni-P plating layer coating as described above was performed. And
The same measurements and tests as above were performed on these coil springs.

Table 1 shows the results of the hardness measurement and the abrasion resistance test between wires. In this table, Experiment Nos. 1-5 and No. 1
Nos. 1 to 16 are coil springs according to the embodiments of the present invention, while Nos. 6 to 10 and Nos. 17 to 91 are Ni-P.
The coil spring covers the plating layer, but is a coil spring according to a comparative example. In addition, Experiment Nos. 20 to 21 are coil springs according to a comparative example which are not covered with the Ni-P plating layer and are made of a titanium alloy.

In each case, the hardness is Hv: 500 or more, but among the coil springs according to the comparative examples, those of Experiment Nos. 6 and 19 have the Ni—P plating layer embrittled by the heat treatment and the hardness thereof is extremely high. In addition, since Nos. 20 to 21 do not cover the Ni-P plating layer, the abrasion resistance between wires is poor and it is extremely inferior. On the other hand, in the comparative example,
Experiments Nos. 7 to 10 and Nos. 17 to 18 have improved interline wear resistance, but the hardness, thickness, and plating stress of the Ni-P plated layer according to the present invention are Since the stress exceeds the upper limit value, the interline wear resistance does not reach the level (level marked with ◯ or more) capable of achieving the object of the present invention, and is at an insufficient level (Δ).

On the other hand, the experiment according to the embodiment of the present invention
All of Nos. 1 to 5 and Experiments No. 11 to 16 were excellent in interline wear resistance. Also, these are Ni
The peel resistance of the -P plating layer was also excellent and sufficient.
In addition, among those related to the examples of the present invention, Experiment No. 4
5 and Experiment Nos. 13 to 15 have a thickness of 0.1 to 3 μm Ni or Ni between the titanium alloy wire of the base material and the Ni-P plating layer.
Since the Cu strike plating layer was provided, the peeling resistance was further excellent. However, in Experiment No. 16, since the thickness of the strike plating layer exceeded 3 μm, the effect of improving the peel resistance by the strike plating layer was not recognized.

When the present invention is applied to engine parts such as connecting rods and valve materials instead of the coil springs,
The same tendency result as in the case of the coil spring was obtained.

[0032]

Since the mechanical part according to the present invention has the above-mentioned structure and functions, it has a low specific gravity and excellent interline wear resistance, and therefore is durable and lightweight. Therefore, it can be used as a mechanical part, and thus can be suitably used as a mechanical part for automobiles, etc., and its weight can be reduced, and the durability can be greatly improved. Among them, it can be suitably applied to a coil spring based on titanium alloy, and the coil spring has a low specific gravity and excellent spring characteristics, and is extremely excellent in resistance to wire wear compared to conventional titanium alloy coil springs. Therefore, it can be used as a lightweight coil spring with excellent durability, and thus can be suitably used as a coil spring for gasoline engine intake / exhaust valves for automobiles, etc. There is an effect that it can be improved.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hidetoshi Nishimoto 1-3-18 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo Kobe Steel Works, Ltd. Kobe Head Office (72) Inventor Yoshinori Terada Chuo-ku, Osaka-shi, Osaka Bingo Town 4-chome 1-3 Kobe Steel Co., Ltd. Osaka Branch Office (72) Inventor Tawaraya Tadashi 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Kobe Steel Co., Ltd. Tokyo Main Office (72) Inventor Yasunori Wada Hyogo Prefecture 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi Kobe Steel Co., Ltd. Kobe Research Institute

Claims (3)

[Claims] 1. A mechanical component comprising a base material made of a titanium alloy or an aluminum alloy, the surface of which is coated with an electric Ni-P plating layer, wherein the surface of the base material has a Ra of 0.5 μm or more and PP.
I ₅₀ : 130 or more, the Ni-P plating layer is Vickers hardness Hv: 500 to 730, thickness: 0.5 to 15 μm, P
Content: 0.5-7.0wt%, and plating stress: 5kgf / mm
Mechanical parts with excellent wear resistance between wires, characterized by having been set to ² or less. 2. The surface of the substrate has a thickness of 0.1 to 3 μm.
A Ni or Cu strike plating layer is provided on which electrical
The mechanical component having excellent wear resistance between wires according to claim 1, which is covered with a Ni-P plating layer. 3. The mechanical component having excellent wear resistance between wires according to claim 1, wherein the base material is made of a titanium alloy wire, and the mechanical component is a coil spring.