JP2023005976A - Composite sliding component and method for manufacturing the same - Google Patents

Abstract

To provide an iron-copper composite sliding component in which a high strength brass alloy layer excellent in abrasion resistance and seizure resistance is formed on a sliding surface of a ferrous material, and a method for manufacturing the same.SOLUTION: A composite sliding component has a body part composed of a ferrous material, a Zn-Fe alloy layer formed on the surface of the body part, and a high strength brass alloy layer which is joined to the surface of the alloy layer and is excellent in abrasion resistance and seizure resistance.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to an iron-copper-based composite sliding part, in which a high-strength brass alloy layer having excellent wear resistance and seizure resistance is formed on the sliding surface of an iron-based material, and a method for manufacturing the same.

Conventionally, bearing materials for high-load applications and sliding parts such as swash plates and piston shoes for axial piston pumps require high fatigue strength, wear resistance, and seizure resistance to withstand repeated loads. , JIS H3250 high-strength brass rods are used, but their strength is insufficient for recent high-speed and high-pressure hydraulic pumps. is used (Patent Document 1).
As wear-resistant high-strength brass alloys used for sliding parts such as swash plates and piston shoes of hydraulic piston pumps, aluminum and silicon are added to JIS high-strength brass to produce high-hardness manganese silicide (Mn ₅ Si ₃ ) is used.

Conventionally, when joining a wear-resistant high-strength brass alloy to a ferrous material, one of the following methods is used.
1) Brazing 2) Overlay welding 3) Casting 4) Thermal spraying 5) Sintering bonding 6) Diffusion bonding using phosphor bronze or nickel insert There are problems such as unsuitability for mass production and low bonding strength.

Patent Literature 1 discloses a method of joining a ferrous material and a wear-resistant high-strength brass alloy.
In the joining method of Patent Document 1, without using any insert material, the iron-based material is covered with flux or heated in a state where oxygen is blocked by a method such as a vacuum, so that the high-temperature iron-based material and the molten state are heated. The high-strength brass alloy is brought into direct contact and is rapidly cooled by shower water cooling, thereby suppressing the formation of a compound layer at the bonding interface.
However, when a high-temperature iron-based material is shower water-cooled, it undergoes martensitic transformation and is quenched to a high degree of hardness. .
However, alloy elements such as Al and Si, which have a high affinity with iron, form a compound layer with iron during tempering, which significantly reduces the bonding strength. Have difficulty.

JP-A-11-58034

Cast-in welding, in which a hot ferrous material covered with flux is brought into direct contact with a molten brass alloy, is a relatively easy joining method for ordinary brass.
However, in the case of wear-resistant high-strength brass alloys to which aluminum and silicon are added, there is a problem that a brittle intermetallic compound film of FeAl or FeSi system is generated at the joint interface, and the joint strength is significantly reduced. The challenge is to obtain a high bonding strength with iron-based materials without generating a film-like intermetallic compound.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a composite sliding part having excellent bonding strength between a ferrous material and a high-strength brass alloy, and a method for manufacturing the same.

A composite sliding part according to the present invention comprises a main body made of an iron-based material, a Zn—Fe-based alloy layer formed on the surface of the main body, and wear resistance and seizure resistance bonded to the surface of the alloy layer. It is characterized by having a high-strength brass alloy layer with excellent strength.
In this way, the brittle FeAl and FeSi-based intermetallic compounds generated by conventional casting welding are changed into a composite form in which the intermetallic compounds and the copper alloy are three-dimensionally intricate in the present invention to reduce brittleness. A composite sliding part made of a ferrous material with high joint strength and wear-resistant high-strength brass can be obtained.

An example of a piston shoe to which the present invention is applied is shown in FIG.
A wear-resistant high-strength brass alloy 2 containing manganese and silicon is fusion-bonded to the sliding surface of a shoe body 1 made of chromium-molybdenum steel with high fatigue durability.
The metallographic structure of the bonding interface has a bonding layer in which FeSi-based columnar intermetallic compounds and copper alloys are three-dimensionally intricate.
Shoe body 1 rotatably accommodates spherical portion 12 in accommodation recess 31 formed in first end portion 51 of piston 5 and is joined by caulking. is slid at a high speed of 10 m/s.
The shoe surface is lubricated by introducing a portion of the piston hydraulic pressure through the first through hole 3 and the second through hole 32 provided in the center of the piston, and by sealing with the annular projection 21, the oil pressure balance on the piston shoe surface is maintained. there is

The shoe of the axial piston pump is required to have a high hardness swash plate made of carburized steel, which is the mating material, and slidability and wear resistance under high pressure. High-strength brass alloys with added components are preferable, but when these molten copper alloys are brought into direct contact with high-temperature ferrous materials and welded using high-pressure air cooling so as not to cause martensite transformation, Fe The study by the inventors of the present invention revealed that brittle film-like precipitates such as Si--Mn compounds are generated to cause peeling defects on the joint surface, resulting in a marked decrease in joint strength.
Al also has a high affinity with Fe, and is known to deposit an Al—Fe-based brittle intermetallic compound layer on the joint surface.

Therefore, in the present invention, when the surface of an iron-based material is plated with zinc, zinc dissolves into the copper alloy due to contact with the molten copper alloy, and the solute concentration gradient in the vicinity of the contact surface increases. It was found that the crystals solidify and grow as columnar crystals, not as crystals.
Although the details will be described later, FIG. 2(a) is a hot-dip galvanized iron base made of an iron-based material and then contacted with a molten high-strength brass, and FIG. 2(b) is a hot-dip galvanized Instead of , it is electroplated with Cu.
In order to generate a concentration gradient sufficient for columnar crystal growth, the thickness of the zinc plating is preferably 15 microns or more. For example, hot-dip galvanization can easily provide a thick zinc plating.
However, if the zinc film thickness is too large, the zinc equivalent of the brass alloy in the vicinity of the contact surface will become too high, and δ copper will crystallize and the joint strength will decrease, so the zinc plating should be 300 microns or less. preferable.

By making the surface of the iron substrate, which is the joint interface, a Zn-Fe-based alloy layer, the surface area of the iron that becomes the heterogeneous solidification nucleus of the Fe-Si-based compound is reduced, and the space between the Fe-Si-based compounds that grow columnar crystals. becomes sparse.
A composite of a metal and a compound in which the gaps between the columnar crystals are filled with a copper alloy significantly improves the fragility of the intermetallic compound generated at the bonding interface, resulting in high bonding strength.

On the other hand, in hot-dip galvanizing, zinc diffuses into the iron substrate during the plating process to form a Zn--Fe alloy layer.
In particular, the thickness of the alloy layer can be increased by allowing it to cool after hot-dip galvanizing.
The Zn—Fe alloy layer can also be obtained by heat treatment at 350° C. to 500° C. after electrogalvanization, but it can also be obtained by heating to a temperature (800° C. or higher) at which the flux melts in the welding process. .
Among the Zn—Fe alloy layers, the composition of the alloy layer called the ζ layer is presumed to be FeZn ₁₃ , which is an alloy layer with relatively low bonding between iron and zinc.
When zinc comes into contact with the molten copper alloy and dissolves into the copper alloy, an iron skeleton remains, and the copper alloy wets and penetrates into these voids, forming a three-dimensionally intricate bonding layer of iron and copper alloy. be.
FIG. 3(a) shows an enlarged photograph of the joint in FIG. 2(a), and FIG. 3(b) shows an analysis (distribution) image of Cu—Kα.
This bonding layer significantly improves the bonding strength and improves the quality of bonding between ferrous materials and high-strength brass alloys.

Direct contact between a molten high-strength brass alloy and a high-temperature iron-based material avoids the formation of brittle intermetallic compounds with alloy elements such as Al and Si, which have a high affinity for iron melted from the contact surface. However, the intermetallic compound is formed in the form of a film, which significantly reduces the bonding strength.
In the sliding part according to the present invention, the intermetallic compound generated on the joint surface is changed into a composite of copper alloy and compound, and a joint layer in which iron and copper alloy are three-dimensionally intricate is formed. Excellent quality.

Aspect of Sliding Part Piston Shoe According to the Present Invention A cross-sectional view of a shoe of an axial piston pump to which the present invention is applied is shown. A high-strength brass alloy layer is formed on the sliding surface between the main body and the swash plate. A structure photograph showing the form of intermetallic compounds generated at the joint interface. is the joint surface where the is cast and welded. A change is seen in the form of the intermetallic compound generated at the joint interface. Scanning electron micrographs showing a bonding layer in which a copper alloy is three-dimensionally intricate a) is an enlarged photograph of a compound layer and a bonding layer, and b) is a distribution of copper in the same field of view. The compound layer forms a composite with copper, and a bonding layer in which iron and copper are three-dimensionally intricate can be confirmed on the underlying iron base. Diagram showing the manufacturing method of casting welding Table showing the components of the high-strength brass alloy used in this example Diagram showing the shear test method Table showing evaluation results of weldability

When molten metal of high-strength brass containing aluminum or silicon is brought into contact with a high-temperature iron-based material that has been covered with conventional flux such as borax and heated in the air, in a reducing atmosphere, or in a vacuum so as not to oxidize, Since a brittle iron-based compound layer is formed on the contact surface with the molten metal, the bonding strength is low and the sliding parts are easily peeled off during use. The compound layer is film-like and is produced by a diffusion reaction during the cooling process after solidification of the brass alloy.
Conventionally, there have been attempts to suppress the diffusion of iron by plating copper or nickel. can't. Therefore, in joining high-strength brass and iron-based materials, composite sliding parts are manufactured without melting the copper alloy by a method such as brazing and without bringing the high-temperature iron and copper alloy into direct contact.
In contrast, the present invention is based on a new idea of improving the bondability by changing the form of the compound that is produced, rather than suppressing the production of the compound in casting welding.

The amount of silicon and manganese contained in the high-strength brass alloy is related to the thickness of the compound layer generated between the iron-based materials. , Mn: 2.0 to 5.0%, and Si: 0.5 to 2.0%, strong bonding with ferrous materials is achieved.
Manganese combines with silicon to form a needle-like intermetallic compound of Mn ₅ Si ₃ in the metal structure, which improves the wear resistance and seizure resistance of high-strength brass alloys.
If the manganese content is less than 2.0%, a needle-shaped intermetallic compound sufficient for improving wear resistance cannot be obtained, and if the manganese content is more than 5.0%, a brittle intermetallic compound layer is formed at the joint. Bonding strength is reduced.
If the silicon content is less than 0.5%, a needle-shaped intermetallic compound sufficient for improving wear resistance cannot be obtained, and if it exceeds 2.0%, a fragile intermetallic compound layer is formed at the joint. and the bonding strength decreases.

In order to obtain the properties required for the high-strength brass alloy to be welded to the composite sliding parts, the reasons for selecting the other elements to be added to the high-strength brass alloy and the limits of the amount of addition are as follows.
Cu: 55.0-65.0%
Copper is the main component of the alloy, and if it exceeds 65.0%, the tensile strength, hardness, and wear resistance of a high-strength brass alloy cannot be obtained. On the other hand, if it is less than 55.0%, the zinc equivalent of the brass alloy is too large, the elongation is lowered, and the toughness is insufficient. Preferably, Cu: 58.0 to 63.0%.
Al: 0.5-2.0%
Although Al is not an essential component in the present invention, Al dissolves in copper and increases the tensile strength and hardness of the brass alloy.
If it is less than 0.5%, the effect is low, and if it is more than 2.0%, a brittle intermetallic compound layer is formed at the joint and the joint strength is lowered.
Pb: 0.5-4.0%
Although Pb is not an essential component in the present invention, lead improves the machinability and seizure resistance of the brass alloy.
On the other hand, it is designated as an environmentally hazardous element by the RoHS Directive, etc., and its addition must be limited to a small amount.
If the content is less than 0.5%, the effect is low.
Currently, the RoHS Directive allows less than 4.0% lead in copper alloys.
Sn: 1.0% or less Sn is not an essential component in the present invention, but even a small amount of Sn prevents dezincification corrosion of high-strength brass.
However, if Sn is contained in an amount of 1% or more, a Cu ₄ Sn phase appears and embrittles the brass alloy.
P: 0.1% or less In the present invention, P is not an essential component, but the molten metal containing P does not contain slag and has high fluidity, so it has the effect of facilitating removal of the flux used during joining. .
However, if the content exceeds 0.1%, the brass alloy is hardened and voids are likely to occur, so the content should be 0.1% or less.
Zn: Balance Zinc is a main component of the alloy together with copper, and determines tensile strength, hardness, and wear resistance as a high-strength brass alloy. The amount of zinc in the alloy is controlled by the content of copper.

Next, the pre-welding treatment of iron-based materials, which is performed to improve the joint strength, will be described.
A zinc layer having a thickness of 15 μm or more is formed on the joining surface of the ferrous material by an appropriate method such as a hot dipping method, an electroplating method, or a metal spraying method.
If the thickness of the zinc layer is insufficient, the solute concentration gradient at the bonding interface will not increase, and the morphology of the film compound layer will not change.
In the case of the hot-dip plating method, an alloy layer with zinc is formed when the zinc layer is formed. However, when the zinc layer is formed by a method other than the hot-dip plating method, heat treatment is performed at 350 to 500° C. for 30 minutes or longer. , forms an alloy layer with zinc on the iron surface.
The alloy layer formed at this time is an alloy layer of relatively low bonding strength of iron and zinc called ζ phase.

Iron-based materials with a zinc layer and an alloy layer should be exposed to a temperature just above the melting point of brass alloy (880°C) for 30 minutes or more (adjusted according to the volume of the product) after taking anti-oxidation measures such as covering the joint surface with flux. ) Preheat, pour and weld molten high-strength brass alloy.
When the molten brass alloy comes into contact with an alloy layer with low bonding between iron and zinc, zinc elutes into the molten brass alloy to form a porous iron matrix, and the brass alloy gets wet and penetrates into the iron. form a three-dimensionally intricate complex.
Since this composite is a continuum with the welded brass alloy, it serves as a bonding layer to increase the adhesion strength of the welded brass alloy.

On the other hand, the zinc layer on the surface of the iron-based material is eluted in contact with the molten brass alloy, increasing the solute concentration gradient at the joint interface.
As a result, the film-like Fe--Si--Mn compound produced on the surface of the iron turns into columnar crystals that solidify and grow toward the molten brass alloy.
In addition, the surface of the iron-based material alloyed with zinc has little formation of heterogeneous solidification nuclei, and the brass alloy and the compound remaining in the gaps between the sparsely grown columnar crystals form a composite, making the compound layer fragile. improved sexuality.
This increases the adhesion strength of the welded brass alloy.

As the ferrous material used in the present invention, mild steel, carbon steel, alloy steel, spheroidal graphite cast iron, and the like can be appropriately used depending on the application.

<Example>
Next, assuming application to the piston shoe shown in FIG. 1, high-strength brass was cast and welded to chromium-molybdenum steel to evaluate bonding.
The sample used for casting and welding was made by lathing a sump with an inner diameter of φ45 mm on a SCM440H round bar of φ50 mm as a ferrous material, and then (1) hot-dip galvanized (hot-dip Zn) with a thickness of 50 μm, (2) Electrogalvanizing (electrical Zn) with a thickness of 25 μm, and as a comparative example (3) electrolytic copper plating (electrical Cu) with a thickness of 15 μm were applied.
The electrogalvanized sample (2) was heat treated at 350-500°C.

The hot water reservoir of each sample is filled with flux such as borax, heated in a furnace at 910° C. for 35 minutes to melt the flux, and as shown in FIG. The high-strength brass alloy 2a having the composition shown in FIG. 5 was poured.
The molten flux 4a is swept away from the joint surface and replaced with a high-strength brass alloy without coming into contact with air.
After pouring the copper alloy, it was immediately cooled from the bottom surface with high-pressure air so that solidification progressed directionally from the joining surface into the molten metal.
In the table of FIG. 5, Examples 1 to 5 are brass alloys that do not substantially contain Al, and Example 6 suppresses the Pb content and uses a brass alloy containing 1.62% Al. However, all were within the range set in the present invention, and the joint was close to that shown in Fig. 2(a).
On the other hand, Comparative Examples 7 and 10, which were electroplated with Cu, had a joint structure similar to that shown in FIG. 2(b).

Evaluation after casting and welding was performed by penetrant testing and shear strength testing.
In the penetrant testing, the copper alloy welded sample was longitudinally cut, and the presence or absence of flaw detection reaction (defective welding) at the joint interface was visually examined according to the test method of JIS Z2343.
The pass/fail judgment was based on three or less flaw detection reactions with a length of less than 1.6 mm.
In the shear strength test, a sample welded with copper alloy was machined into a test piece having a cross section of 5 mm square, and a die set shown in FIG. P was added, the load required for shearing the joint interface was measured, and the shear strength was obtained by dividing it by the cross-sectional area.
The evaluation results are collectively shown in FIG.

In Examples 1 to 6 to which the present invention was applied, all penetrant testing passed, and a shear strength of 120 N/mm ² or more was obtained.
On the other hand, in Comparative Examples 7 to 10, the flaw detection reaction length at the bonding interface was large, and in the shear test, the copper alloy was peeled off with a very small force, so the shear strength could not be obtained.

1 Shoe body 2 High-strength brass alloy 3 First flow hole 4 Swash plate 5 Piston 12 Spherical part 21 Annular projection 31 Accommodating recess 32 Second flow hole 51 First end 61 Movable punch 62 Fixed die P Load

Claims (7)

A main body made of an iron-based material, a Zn-Fe-based alloy layer formed on the surface of the main body, and a high-strength brass alloy layer having excellent wear resistance and seizure resistance joined to the surface of the alloy layer. A composite sliding component characterized by: The high-strength brass alloy contains the following mass%, Cu: 55.0 to 65.0%, Mn: 2.0 to 5.0%, Si: 0.5 to 2.0%, and further Al: 0 .5 to 2.0%, Pb: 0.5 to 4.0%, Sn: 1.0% or less, P: 0.1% or less, containing one or more, the balance being Zn and unavoidable 2. The composite sliding part according to claim 1, wherein the sludge is an organic impurity. A method for manufacturing a composite sliding component according to claim 1 or 2,
forming a Zn--Fe alloy layer on the surface of the iron-based material; and contacting the high-strength brass alloy in a molten state thereon to dissolve zinc in the high-strength brass alloy. A method for manufacturing a composite sliding part, characterized by: The step of forming the Zn-Fe-based alloy layer includes forming a zinc layer having a thickness of 15 μm or more on the surface of the iron-based material by hot-dip galvanization to form a Zn-Fe-based alloy layer under the interface. 4. The method of manufacturing a composite sliding component according to claim 3, wherein: The step of forming the Zn-Fe-based alloy layer includes forming a zinc layer having a thickness of 15 μm or more on the surface of the iron-based material, performing heat treatment at 350 to 500 ° C., and forming a Zn-Fe-based alloy under the interface. 4. The method of manufacturing a composite sliding component according to claim 3, wherein layers are formed. After forming a Zn-Fe alloy layer on the interface between the zinc layer and the iron material, the joint surface is covered with flux, heated to a temperature at which the flux melts, and the molten high-strength brass alloy is poured and welded. 6. The method of manufacturing a composite sliding part according to claim 4, further comprising the steps of: A composite sliding part or a manufacturing method thereof according to any one of claims 1 to 5, characterized in that said zinc layer has a thickness in the range of 15 to 300 µm.

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