阅读说明：本技术 轴构件以及轴构件的制造方法 (Shaft member and method for manufacturing shaft member ) 是由 喜多昭彦 小泽诚也 森孝弘 井口昭司 松本修 于 2018-12-27 设计创作，主要内容包括：实施方式的轴构件具备：轴状的基材,以钢为材料；低磷镀层,层积于所述基材并且含有磷,所述磷的含量为4.5质量％以下；以及基底镀层,作为电解镍磷镀层或高磷镀层而形成,层积在所述基材与所述低磷镀层之间,因此能够实现轴构件的高强度化,进而能够实现轴构件的小型化。(The shaft member of the embodiment is provided with: a shaft-shaped base material made of steel; a low-phosphorus plating layer which is laminated on the base material and contains phosphorus, wherein the content of the phosphorus is less than or equal to 4.5 mass%; and an undercoat plating layer formed as an electrolytic nickel-phosphorus plating layer or a high-phosphorus plating layer and laminated between the base material and the low-phosphorus plating layer, whereby the shaft member can be made stronger and can be made smaller.)

1. A shaft member is provided with:

a shaft-shaped base material made of steel;

a low-phosphorus plating layer which is laminated on the base material and contains phosphorus, wherein the content of the phosphorus is less than or equal to 4.5 mass%; and

and a base plating layer formed as an electrolytic nickel-phosphorus plating layer or a high-phosphorus plating layer and laminated between the base material and the low-phosphorus plating layer.

2. The shaft member according to claim 1,

the base material is high-carbon steel or high-carbon alloy steel.

3. The shaft member according to claim 2,

the carbon content in the high-carbon steel or the high-carbon alloy steel is 0.85-1.10 mass%.

4. The shaft member according to any one of claims 1 to 3, wherein,

the thickness of the base plating layer is set to be thinner than that of the low-phosphorous plating layer.

5. The shaft member according to any one of claims 1 to 3, wherein,

the phosphorus content in the low-phosphorus coating is 1.0-1.5 mass%.

6. The shaft member according to any one of claims 1 to 5, wherein,

the surface of the shaft member is the low-phosphorous plating.

7. A method of manufacturing a shaft member, comprising:

a degreasing step of performing electroless degreasing or anodic electrolytic degreasing for a predetermined time on a base material made of steel and constituting the shaft member; and

and a plating step of performing low-phosphorus plating containing phosphorus and having a phosphorus content of 4.5 mass% or less.

8. The manufacturing method of a shaft member according to claim 7, wherein,

and a base plating step of performing electrolytic nickel-phosphorus plating or high-phosphorus plating between the degreasing step and the plating step.

Technical Field

The present invention relates to a shaft member and a method of manufacturing the shaft member.

Background

Ideally, mechanical components such as shaft members and gear members have hard surfaces and high wear resistance, and have viscosity inside to be able to withstand an impact load.

As the alloy steel used for this purpose, chromium molybdenum steel such as SCM420H, which is one of alloy steels for machine structural use, is known.

The SCM420H is a case hardening steel, has excellent temper resistance and mechanical properties, and also has toughness, and is therefore widely used for automobile parts such as crankshafts and flywheels.

Disclosure of Invention

Problems to be solved by the invention

However, in order to use the case hardening steel as a shaft member, it is desired to achieve an improvement in wear resistance of the surface.

Therefore, the surface of the case hardening steel is usually subjected to plating treatment.

Specifically, for example, the following structure is adopted: SCM420H (case hardened steel) as a base material was subjected to electrolytic degreasing as a pretreatment, and after electroless nickel-phosphorus plating of medium phosphorus or high phosphorus was performed, a shaft member was formed by baking to remove hydrogen in order to secure strength.

Here, electroless nickel-phosphorus plating in the case where the phosphorus content in the electroless nickel-phosphorus plating film is less than 4.5% is defined as low phosphorus (plating), medium phosphorus (plating) in the case where the phosphorus content is 4.5% or more and less than 10.5% is defined as medium phosphorus, and high phosphorus (plating) in the case where the phosphorus content is 10.5% or more is defined as high phosphorus (plating).

However, in the above conventional shaft member, the electroless nickel-phosphorus plating of medium phosphorus or high phosphorus sometimes generates much Ni in the plating layer at the time of baking₃P, the plating becomes brittle. That is, in applications where the internal stress is increased due to a bending load, as in the case where the shaft member is used for a pinion shaft for a differential, miniaturization cannot be achieved in order to ensure fatigue strength. Further, the miniaturization of the device using the shaft member cannot be achieved. Further, if baking is not performed, most of the plated structures become amorphous structures, and the hardness of the plating may decrease, which may deteriorate the wear resistance of the pinion shaft.

On the other hand, although the electroless nickel-phosphorus plating of medium phosphorus or high phosphorus has good adhesion to the substrate, when the electroless nickel-phosphorus plating of low phosphorus is used in order to avoid embrittlement of the plating layer, the adhesion may be reduced and the plating may be easily peeled from the substrate.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a shaft member and a method for manufacturing a shaft member, which can maintain adhesion to a base material, can increase strength of the shaft member, and can further reduce the size of the shaft member.

Means for solving the problems

Drawings

FIG. 1 is a cross-sectional view of a differential.

Fig. 2 is a state diagram showing a crystalline state of nickel-phosphorus plating applied to the shaft member of the embodiment.

Fig. 3 is a manufacturing flow chart of the shaft member of the embodiment.

FIG. 4 is an explanatory view of an example and a comparative example.

The shaft member of the embodiment is provided with: a shaft-shaped base material made of steel; a low-phosphorus plating layer which is laminated on the base material and contains phosphorus; and a base plating layer formed as an electrolytic nickel-phosphorus plating layer or a high-phosphorus plating layer and laminated between the base material and the low-phosphorus plating layer.

In addition, the method for manufacturing a shaft member according to an embodiment includes: a degreasing step of performing electroless degreasing or anodic electrolytic degreasing for a predetermined time on a base material made of steel and constituting the shaft member; and a plating step of performing low-phosphorus plating having a phosphorus content of 4.5 mass% or less.

Effects of the invention

According to the above structure, Ni can be suppressed₃The generation of P suppresses embrittlement and also suppresses the formation of an amorphous structure, and can improve the wear resistance and increase the strength of the shaft member while maintaining the adhesion to the base material, and further can achieve miniaturization of the shaft member.