JP2597105B2 - Copper member surface hardening method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for hardening a surface of a copper or copper alloy member.

[Prior art] Copper or copper alloy members (hereinafter simply referred to as “copper members”) are used as members requiring good thermal conductivity or good electrical conductivity, but the copper members are soft and wear-resistant. Is scarce,
When this is applied to a sliding portion, the surface thereof is coated with a plating film such as chromium or nickel or a thermal spray coating to provide necessary wear resistance.

[Problems to be solved by the invention]

However, the plating film is as thin as about 500 μm or less. During use, cracks and peeling are likely to occur due to external loads such as mechanical stress, impact, and thermal stress, and the bonding strength with the base material is weak. Swelling at the bonding interface due to factors and peeling due to the swelling are likely to occur. On the other hand, the spray film can be formed with a relatively high film pressure, but as with the plating film, bonding with the base material is simple physical adhesion, There is a problem that cracks and peeling are likely to occur.

As another method, a mixture of metal and ceramic particles is used as a cladding material, and a cladding layer (composite cladding layer) having a composite structure composed of a metal matrix and ceramic particles as a dispersed phase is formed on a copper member surface by a welding cladding method. ) Is conceivable. This weld overlay is a method that has been proposed as a surface hardening method for copper members, and the composite overlay has a strong fusion bonding relationship with the base material and is excellent in peel resistance. Due to the dispersion strengthening action of the ceramic particles, it has a high degree of abrasion resistance which greatly surpasses the metal single-phase cladding layer.

However, even if this welding overlay method is used as a surface hardening method for a copper member, unlike a copper member, the melting point of the copper member is as low as 1000 to 1100 ° C., so that the welding heat cannot be sufficiently supplied. In addition, copper members have a thermal conductivity several times higher than steel members, and heat diffusion from the weld occurs rapidly, so it is possible to achieve sufficient penetration and fusion between the cladding material and the base metal. Can not. Therefore, the formed composite build-up layer contains defects such as poor penetration and non-uniformity of the composite structure. As a countermeasure, it is possible to heat the copper member to a high temperature (approximately 600 ° C or higher) to compensate for the lack of heat at the weld before the welding overlay is applied. When heated to a temperature, an oxide is generated on the welded portion and on the surface in the vicinity thereof, which causes welding defects such as blow holes in the welded portion. In addition, copper and copper alloys have a large coefficient of linear expansion (about 1.5 times that of mild steel), so if preheated to an excessively high temperature, deformation and distortion will occur in the member, which requires cumbersome post-treatment to correct it. Become.

For these reasons, it has been generally considered to be extremely difficult to weld and dispose a dissimilar material on the surface of a copper member.

An object of the present invention is to provide a method of hardening a copper member surface by welding overlay, which solves the above problem.

[Means and actions for solving the problems]

The method for hardening the surface of a copper member according to the present invention comprises the steps of: forming a nickel plating film having a thickness of 50 to 500 μm on the surface of the copper member, and then: C: 1% or less, Cr: 5 to 30%, Fe: 50% or less , Ti: 3% or less, Al: 3% or less, Mo: 20% or less, Co: 50
% Or less, W: 10% or less, Nb: one or more elements selected from 5% or less, a matrix metal consisting essentially of Ni, and a particle size of 50 to 50% mixed with the matrix metal as a dispersed phase. The present invention is characterized in that a weld overlay having a composite structure composed of 20 to 80% by weight of carbide ceramic particles of 200 μm is formed.

According to the method of the present invention, a nickel coating is first formed on the surface of a copper member prior to welding overlaying on the surface of the copper member. Thermal conductivity of nickel film is 0.201cal / deg ・ cm ・ sec
(0 ° C) and that of copper (0.989cal / deg · cm ·)
sec (18 ℃)), and its low thermal conductivity effectively suppresses the diffusion of heat from the welded part during welding overlaying. It serves to maintain the high temperature required for Further, the nickel film is excellent in oxidation resistance and serves as an antioxidant film on the surface of the copper member in a high-temperature state, thereby preventing the formation of oxides and welding defects such as blow holes due to the formation of oxides. The nickel film is
It is formed by plating or thermal spraying. The film thickness is preferably 50 μm or more in order to make the above-mentioned thermal diffusion suppressing effect sufficient. However, even if the thickness is too large, the effect is not increased, and not only the economic efficiency is impaired, but also the nickel content contaminates the build-up layer and causes a deterioration in the material properties of the build-up layer. To avoid these inconveniences,
Is the upper limit.

After the nickel film is formed on the surface of the copper member, a pre-heat treatment is performed if necessary, and then a weld overlay is applied. Since the surface of the copper member is coated with a nickel film having an effect of suppressing thermal diffusion, even when preheating is required, a heating temperature of about 400 to 500 ° C. is sufficient.

The weld overlay on the copper member surface is performed by plasma welding, TIG welding, or the like, using a mixture of the metal component having the component composition and the carbide-based ceramic particles as a weld material (overlay material). Thus, a composite build-up layer comprising a metal matrix having the above-described component composition and carbide-based ceramic particles uniformly mixed as a dispersed phase with the metal matrix is formed.

The carbide-based ceramic particles in the dispersed phase in the composite overlay include, for example, chromium carbide (Cr ₃ C ₂ , Cr ₇ C ₃ etc.), niobium carbide (NbC), tungsten carbide (WC), titanium carbide (TiC), and carbide. Silicon (SiC) or the like.

The dispersed phase in the composite overlay was made of carbide-based ceramic particles because it was extremely hard, had good thermal stability and good wettability with the matrix metal, and was suitable as a dispersed phase. The reason why the matrix metal is limited to the Ni-based alloy having the above-described composition is that, within the range of the composition, the composite meat is excellent in high-temperature strength, heat resistance, oxidation resistance, impact resistance, etc. together with the ceramic ceramic particles. This is because an embossed layer can be formed.

Further, the ratio of the carbide-based ceramic particles in the composite structure of the composite cladding layer is set to 20% by weight or more because the composite cladding layer has sufficient high degree of wear and abrasion resistance by the dispersion strengthening action of the particles. On the other hand, the reason why the upper limit was set to 80% by weight is that if it exceeds this, the weldability becomes poor, it becomes difficult to form a homogeneous composite structure, and the toughness of the overlay layer is poor. Because it becomes. The particle size of the carbide-based ceramic particles is suitably in the range of 50 to 200 μm from the viewpoint of effectively exhibiting the dispersion strengthening action.

〔Example〕

Using a pure copper plate (width 50 mm x length 200 mm x plate thickness 30 mm) as a base material, the surface is sprayed with nickel to obtain a test material coated with a nickel film. After preheating, a 5 mm thick cladding layer (two cladding layers) is formed by a plasma powder welding cladding method (welding current: 120 to 160 A) using a separately prepared cladding material.
Was formed. As the overlay material, a mixed powder of a Ni-based alloy powder and chromium carbide particles (particle diameter: 100 μm) was used.

Further, as a comparative example, the same welding overlay as described above was performed after preheating using a material from which the nickel film was omitted. Table 1 shows the results. Test numbers (Nos. 1 to 3) are invention examples, Nos. 11 to 1
3 is a comparative example.

As shown in Table 1, the build-up layers (test Nos. 1 to 3) formed by the method of the present invention are free from blowholes and poor penetration, have a high surface hardness, are uniform, and are sound. It has a good build-up quality. On the other hand, N with the nickel coating omitted
In o.11, although the pre-heating temperature prior to welding was raised, poor penetration occurred, and the weld metal (facing layer) had blowholes. The variation in hardness is large. Also, even if a nickel film is provided as in No. 12, if the film thickness is too thin, the effect as a protective film is insufficient, so that the occurrence of blow holes cannot be prevented. As described above, when the thickness of the nickel film was unnecessarily increased, defects such as poor penetration and blowholes did not occur, but segregation occurred in the deposited metal due to melting and mixing of the nickel component into the deposited metal. As a result, the surface hardness is remarkably non-uniform, and in any case, the quality of the build-up layer according to the present invention is inferior.

[Effect of the Invention] According to the method of the present invention, on the surface of the copper or copper alloy member,
There is no penetration failure, no blowholes, etc., and a uniform composite overlay can be formed, and the heating temperature in the pre-heat treatment prior to welding work can be relatively low, so that deformation or distortion may occur in the member. Absent. Accordingly, the present invention provides a molding material, a tip member of a blast furnace ventilation branch pipe, an energizing roll, and surface modification of a copper or copper alloy member in various other uses.
It is extremely useful as a weld overlay method for hard facing, and its excellent welding quality enhances the stability and reliability as a structural member, and can guarantee durability superior to conventional materials.

Claims (1)

(57) [Claims] (1) After forming a nickel plating film having a thickness of 50 to 500 μm on the surface of a copper member, C: 1% or less, Cr: 5 to 30%, F:
e: 50% or less, Ti: 3% or less, Al: 3% or less, Mo: 20% or less, Co: 50% or less, W: 10% or less, Nb: 5% or less1
A matrix metal consisting of one or more kinds of elements and the balance substantially consisting of Ni; and a carbide-based ceramic particle 20 having a particle size of 50 to 200 μm mixed with the matrix metal as a dispersed phase.
A method for hardening a surface of a copper member, comprising forming a weld overlay having a composite structure of about 80% by weight.