JP5638887B2 - Method for producing copper alloy material and copper alloy part - Google Patents

Description

  The present invention relates to parts used in electronic equipment, precision machines, automobiles, etc., in particular, parts manufactured by cutting, and copper alloy materials and copper alloy parts used therefor.

  The size and number (density) of the compounds (crystallized substances, precipitates) in the copper alloy have a great influence on the performance, particularly in an aging precipitation type alloy. For example, Patent Document 1 proposes to use a copper alloy having crystallized substances and / or precipitates having a predetermined size and number (density). When cutting is performed on this alloy, the cutting waste is likely to be cut and the machinability is improved. In Patent Document 2, the compound size can be controlled by defining the cooling rate in the mold from the casting temperature to the solidification temperature.

JP 2010-106363 A JP-A-10-219374

The amount of the compound in the copper alloy can be determined if the amount of the component constituting the crystallized product or the compound forming the precipitate is defined. Therefore, if the size can be controlled, the number (density) of individual compounds can be controlled as a result. Several methods for controlling the size of such compounds (crystals and precipitates) have been proposed so far. Examining the contents of Patent Document 1 also means that the crystallized material size can be determined by controlling DAS (Dendrite Arm Spacing): d or cooling rate at casting: R. d and R have a relationship satisfying the following formula, and controlling either has the same meaning.
d (μ) = a × R (° ^C./sec)−b
(A and b are constants determined by the material. For example, in the case of 7% phosphor bronze, a = 68.3, b = 0.33)

However, according to the confirmation of the present inventor, in the method described in Patent Document 1, when cooling is performed from a molten state, a compound (Ni—Si—Ti based crystallized product, Ti—C based crystallized product) is obtained. It has been found that other components such as copper may solidify thereafter. This is thought to be due to the transformation of the parent phase from a molten state to a solid and the formation of a solid matrix.
Moreover, in the method of patent document 2, since casting temperature is not clear, it is unclear how long it has been in a molten state after the copper alloy is poured into the mold. Therefore, the compound generated in the mold may be coarsened by growth, coalescence, aggregation, etc., and the size of the compound in the copper alloy material (after solidification) cannot be controlled.
In view of the problems included in the above-described conventional technology, an object of the present invention is to provide a copper alloy material excellent in machinability by controlling the size of a compound generated before solid matrix formation (solidification). A further object of the present invention is to provide a copper alloy part obtained by cutting the copper alloy material.

  As a result of intensive studies, the present inventors have used a specific aging precipitation type copper alloy, the temperature at which the molten copper alloy is poured into the mold, and it is necessary to complete solidification in the mold after pouring. By defining the residence time in the mold, which is the time, a copper alloy material having a desired compound size and number density, excellent machinability, and excellent strength and conductivity can be obtained. It came to make this invention.

That is, the said subject was solved by the following means.
(1) A method for producing a copper alloy material containing Ni, Si, Ti, and C, the balance being inevitable impurities and copper,
Under the conditions A and B below, Ni—Si—Ti crystallization is performed by controlling the residence time in the mold from the time when the molten copper alloy is poured into the mold until solidification is completed in the mold. after generating the objects and Ni-Si crystallized products were pushed out hot, water quenching is, performs cold drawing is dissolved the Ni-Si crystallized products to the matrix rows further aging To produce precipitates ,
A method for producing a copper alloy material characterized by obtaining the following structural characteristics of C in the copper alloy after melting and casting and obtaining the characteristics of D and E below .
A: The content of Ni, Si, Ti in the molten copper alloy satisfies the following formula (1) B: In the melting casting, the casting is performed at a temperature equal to or higher than the melting point of the compound in the copper alloy material, and the mold said mold residence time t when poured into satisfies the equation (2) C: the copper alloy after the melting and casting, eutectic compounds and / or precipitate over an average diameter of 1 micron is 1500 / mm ² may be present or D: tensile strength of the copper alloy material after the aging heat treatment is not less than 500 MPa E: that the conductivity of the copper alloy material after the aging heat treatment is 25% IACS or more <formula (1)>
(I) 1.5 ≦ {[Ni] -15 / 6 × [Ti]} / {[Si] -7 / 6 × [Ti]} ≦ 2.5
(Ii) [Ni] -15/6 [Ti]> 1.5atm%
(Iii) [Ni] <7.4 atm%
(Iv) 0.05 ≦ (Ti) ≦ 2.0 mass%
[*] ... atm% of element *, (*): mass% of element *
<Formula (2)>
(I) t (seconds) <{1500 / N} ^{(1 / 0.19)}
(Ii) N = α + β × [Ti (atm%)] + 10000γ × [C (atm%)]
(Iii) α = −300, β = 4000, γ = 10
(2) The method for producing a copper alloy material according to (1), wherein the molten copper alloy contains 0.05 to 1.5 mass% of Sn.
( 3 ) A copper alloy part formed by cutting a copper alloy material produced by the method for producing a copper alloy material according to (1) or (2) .

  In the copper alloy material of the present invention, an aging precipitation type copper alloy is excellent in strength and conductivity, and is excellent in machinability. Moreover, the copper alloy material of the present invention can be suitably used as a material for parts such as electronic equipment manufactured by cutting.

FIG. 3 is a graph schematically showing the change in order to explain the definition of the residence time in the mold. FIG. 2A is a graph plotting the results of Examples and Comparative Examples, FIGS. 2A and 2B show the relationship of the formula <1>, FIG. 2C shows the relationship of the formula <3>, and FIG. 2D shows the relationship of the formula <2>. Indicate

In the precipitation hardening type copper alloy according to a preferred embodiment of the present invention, the Ni—Si—Ti crystallized product is formed in a specific state by cooling from a molten state. With this Ni-Si-Ti crystallized product, the cutting waste is easily finely divided when cutting is performed, and the machinability is improved. When further cooled, a solid matrix is formed, and when the content ratio of Ni and Si is controlled, a Ni—Si crystallized product (Ni ₂ Si) is generated in the matrix. In the heat treatment after casting, the crystallized material is once dissolved in the matrix and then precipitated, and the strength and conductivity of the copper alloy are improved by precipitation strengthening. Incidentally, the Ni-Si precipitate _(Ni 2 Si: precipitate for precipitation strengthening) does not contribute to improvement of the machinability.
Here, the crystallized product is a compound generated in the process of solidification of the molten metal during the casting of the copper alloy, and the precipitate is a compound generated in a solid state of the matrix in the heat treatment after casting. In the present specification, these generic names may be referred to as crystallized substances and / or precipitates or simply compounds.

  As a method of finely dispersing a crystallized product, there is a method of forming a crystallized product around another compound. This is because before the desired crystallized product (Ni-Si-Ti-based crystallized product in this embodiment) is formed, another compound is charged or formed in the molten metal, and the crystal is used as the nucleus. This is a method of forming a product. In the present embodiment, the other compound needs to have a higher melting point than the target crystallization product, and specifically, a non-metal element-containing compound such as carbide, sulfide, boride, oxide, or nitride is effective. It is. This nonmetallic element-containing compound is a Ti—C compound in the present invention. As a method for forming this Ti—C compound, there are a method in which the compound is directly charged into a molten metal as a powder, or a method in which carbon is added as it is (for example, a carbon rod is immersed). When a large amount of Ti—C compound is formed in the molten metal, a crystallized product is formed using the Ti—C compound as a nucleus.

  The Ni-Si-Ti-based crystallized product formed around the Ti-C compound stays in the molten matrix, but in the meantime, becomes coarse due to agglomeration and coalescence. This coarsening proceeds until the solidification of the matrix is complete, and the crystallized size increases in proportion to the time it takes for the solidification.

[Condition A] In the present invention, the content of Ti which is a constituent element of the Ni-Si-Ti-based crystallized substance contributing to the machinability is 0.05 mass% or more and 2.0 mass% or less (the following formula (iv )), And more preferably 0.1 to 1.5 mass%. If it is more than the said lower limit, the number of the crystallized matter formed will be large and machinability will be improved. Moreover, since it is not saturated and the electrical conductivity does not fall that the effect of a machinability improvement is below the said upper limit, it is preferable.

In the present invention, the Ni content is set as follows.
(I) 1.5 ≦ {[Ni] -15 / 6 × [Ti]} / {[Si] -7 / 6 × [Ti]} ≦ 2.5
(Ii) [Ni] -15/6 [Ti]> 1.5atm%
(Iii) [Ni] <7.4 atm%
(Iv) 0.05 mass% ≦ (Ti) ≦ 2.0 mass%
[*] ... atm% of element *, (*): mass% of element *

  First, regarding the formula (ii) and (iii), [Ni] -15/6 [Ti]> 1.5 atm% (atomic%, see FIG. 2 described later) and [Ni] <7.4 atm% ( Atomic%). The amount of [Ni] -15/6 [Ti] is the amount of Ni remaining in the matrix after the formation of the Ni-Si-Ti-based crystallized product, and when this amount exceeds the lower limit, Ni-Si precipitates. The amount of precipitation hardening due to the material is large and sufficient strength is ensured. When the amount of Ni is less than the above upper limit value, grain boundary reaction type precipitation does not occur during heat treatment, the amount of coarse crystallized material does not increase excessively, and the strength is preferably maintained at a sufficiently high level.

Regarding formula (i), it is derived experimentally as in the examples described later, and a desired effect can be obtained by setting this range. Explaining this technical significance, including estimation, the amount of [Si] -7/6 [Ti] in the formula (1) is a Ni—Si—Ti-based crystallized product (Ni ₁₅ Si ₇ Ti ₆ ). The amount of Si remaining in the matrix later, and the value {[Ni] -15/6 [Ti]} / {[Si] -7/6 [Ti]} is the [Ni] in the matrix at that time. ], [Si] ratio. The [Ni] and [Si] form a crystallized product as Ni ₂ Si during casting, and once precipitated by solid solution by heat treatment, it precipitates and contributes to improvement of strength and conductivity. Therefore, when the value {[Ni] -15/6 [Ti]} / {[Si] -7/6 [Ti]} is in the range of 1.5 to 2.5 close to 2, the desired strength and conductivity Get a rate.

  The Si content may be determined in accordance with the above conditions, but the atomic ratio of Ni-Si-Ti-based crystallized substances contributing to machinability is 15: 7: 6, Ni contributing to strength and conductivity. It is known that the contribution is the largest when the atomic ratio of the Si-based precipitate is 2: 1, and it is preferable to take this into consideration. Considering the above points, specifically, Si is preferably contained at 0.3 to 1.8 mass%, and more preferably 0.35 to 1.7 mass%.

  Sn is an optional additive element, and improves the strength by dissolving in a matrix. The reason why the content is specified to be 0.05 to 1.5 mass% is that the effect is not sufficiently obtained when the content is less than 0.05 mass%, and the conductivity is decreased when the content exceeds 1.5 mass%.

[Condition B]
In the present invention, casting is performed at a temperature equal to or higher than the melting point of the compound in the copper alloy material, and the condition is that the residence time t in the mold when poured into the mold satisfies the formula (2). Here, the residence time in the mold is the time required from when the molten copper alloy is poured into the mold until solidification is completed in the mold.
<Formula (2)>
(I) t (seconds) <{1500 / N} ^{(1 / 0.19)}
(Ii) N = α + β × [Ti (atm%)] + 10000γ × [C (atm%)]
(Iii) α = −300, β = 4000, γ = 10

Here, the meaning of the expression (2) will be described. Expression (2) is also a relational expression derived experimentally as shown in the examples described later (see also FIG. 2D). Considering the relational expression and the alloy material or its structural behavior, it is considered that the following technical significance is obtained including the estimation. That is, as described above, when the molten metal is supplied to the mold and cooled, a Ni—Si—Ti based crystallized product is generated around the Ti—C based compound. N in the formula (ii) is the number density of the crystallization product immediately after the formation of the Ni—Si—Ti-based crystallization product. This number density increases with the amount of Ti-C compound, which is the crystallized product generation site. Therefore, the value of N is considered to be proportional to the amount of Ti and the amount of C, and the inventor investigated experimentally. However, equations (ii) and (iii) were derived. In addition, as described above, the number density of crystallized substances decreases with the mold residence time in order to reduce the coalescence of the crystallized substances while the crystallized substances are retained in the mold after generation. When the number density of the ingot having an internal residence time of t seconds was experimentally determined, it was N / t ^ 0.19. This value affected the machinability, and in order to improve the machinability, it was necessary to be 1500 pieces / mm ² or more, and the formula (i) was derived.

[Condition C]
In the present invention, the alloy material is required to have 1,500 / mm ² or more of crystallization and / or precipitates having an average diameter of 1 micron or more, and more preferably less than 30000 / mm ^2. preferable. By setting the upper limit value or less, it is possible to avoid a decrease in the strength of the material.
[Condition D]
In the present invention, the alloy material is required to have a tensile strength of 500 MPa or more, more preferably 550 to 1200 MPa, after being formed into a predetermined shape suitable for cutting. By setting it to the above lower limit value or more, it can be preferably used as an electric / electronic component. If the above upper limit is exceeded, the material may be too hard and wear of the cutting tool during cutting may be accelerated.

[Condition E]
In the present invention, it is a condition that the conductivity of the alloy material is 25% IACS or more, and more preferably 27% IACS or more. By using more than the said lower limit, it can utilize suitably as an electrical / electronic component. In the present invention, unless otherwise specified, the conductivity means a value obtained by the measurement method employed in Examples described later.

In addition, the following points can be mentioned as matters considered as a preferred embodiment of the present invention.
C has a function of forming a Ti—C compound and finely dispersing a Ni—Si—Ti crystallized product. As the amount of C increases, the Ti—C compound increases and the Ni—Si—Ti-based crystallized product becomes finer. The required amount of C is determined by the residence time during casting. In this regard , reference can be made to the following formula <3> obtained by modifying the above formula <1> (see also FIG. 2C described later).
Formula <3>
10000 [C (atm%)] <{1500 * [t (seconds)] ^-0.19 −α−β × [Ti (atm%)]} / γ
α = −300, β = 4000, γ = 10
For example, if t = 1 second,
10000 [C (atm%)] <180−400 × [Ti (atm%)]

  When further described as one embodiment of the copper alloy material of the present invention, when this is poured into a mold in a molten state, it is cooled (rapidly cooled) just above the temperature (liquidus temperature) at which a solid matrix is formed, and Ti—C A Ni-Si-Ti-based crystallized substance is generated around the compound. The distribution (size, number) of Ni-Si-Ti-based crystals at this point depends on the amount of Ni, Si, Ti, and C, but the time until the matrix temperature is completely solidified (= residence in the mold) Time, see Fig. 1). This is because the agglomeration and coalescence of the crystallized substances proceed and stay coarse in the molten matrix (the size is large and the number is reduced). If the coarsening proceeds excessively, the contribution of the Ni—Si—Ti based crystallized product to the machinability is lost (decreased), which is allowed depending on the distribution of the generated Ni—Si—Ti based crystallized product. The residence time is determined (if the number of Ni-Si-Ti-based crystallized products generated is not enough, solidification must be completed quickly. Does not require immediate completion of clotting.) As a method for controlling the solidification completion time, one simple method is to change the size of the ingot to be produced. The present invention is not construed as being limited by the above description.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

  Alloys having the compositions shown in Table 1 were melted in a high-frequency melting furnace, and each billet was cast while changing the residence time in the mold. Here, the inner dimension of the mold was set to 25φ to 150φ × 750 mm, and the residence time in the mold was controlled using a mold capable of heating with heater and air cooling or water cooling. The billet was hot extruded at 900 ° C. and immediately quenched in water to obtain a round bar. Next, the round bar was drawn out cold to produce a round bar having a diameter of 10 mm, and further subjected to aging heat treatment at 450 ° C. for 2 hours.

For each round bar (alloy material) thus obtained, [1] tensile strength, [2] conductivity, and [3] machinability were examined by the following methods. The measurement method for each evaluation item is as follows.
[1] Tensile strength Three were measured according to JIS Z 2241 and the average value (MPa) was shown.
[2] Conductivity Using a four-terminal method, two samples were measured for each sample in a thermostatic chamber controlled at 20 ° C. (± 1 ° C.), and the average value (% IACS) was shown.
When the tensile strength investigated in [1] is 500 MPa or more and the conductivity investigated in [2] is 25% IACS or more, the performance evaluation is “good”, and otherwise the evaluation is “poor”.
[3] Cutting performance A cutting experiment was performed using a general-purpose lathe, and the form of the cutting waste was observed. It is good if the cutting waste is divided to a length of 10 mm or less, and the cutting waste is divided, but the length is more than 10 mm and 20 mm or less, the cutting waste is divided, but the length is 20 mm. Exceeded items (including those in which the cutting waste is not divided) were not allowed. It is good and good that there is no practical problem. The cutting conditions were a cutting speed of 30 m / min, a feed speed of 0.1 mm per rotation, and a cutting allowance of 0.2 mm. The tool was made of cemented carbide and no cutting oil was used.

  The results are shown in Tables 1 and 2. Tables 1-1 to 1-4 are examples of the present invention, and Table 2 is a comparative example. Comparative examples 1 to 29 are examples in which the components are outside the scope of the present invention or the residence time in the mold exceeds the threshold value. FIG. 2 illustrates the threshold values represented by the formulas <1> to <3> together with the components of Examples 3-1 to 40 and Comparative Examples 1 to 29.

  The alloy materials of the examples have a performance evaluation (strength, electrical conductivity), a machinability evaluation of “◯”, and good. On the other hand, in Comparative Examples 1 to 11, although the components are within the scope of the present invention and the performance is satisfied, the residence time in the mold is compared with the threshold value defined from the components (Ni, Si, Ti, C amount). This is an example where the actual value of becomes large and the cutting evaluation becomes impossible (the crystallized material becomes coarse). Comparative Examples 12 to 29 are examples in which the performance is “x” because the components are outside the scope of the present invention.

Claims (3)

A method for producing a copper alloy material containing Ni, Si, Ti, and C, the balance being inevitable impurities and copper,
Under the conditions A and B below, Ni—Si—Ti crystallization is performed by controlling the residence time in the mold from the time when the molten copper alloy is poured into the mold until solidification is completed in the mold. after generating the objects and Ni-Si crystallized products were pushed out hot, water quenching is, performs cold drawing is dissolved the Ni-Si crystallized products to the matrix rows further aging To produce precipitates ,
A method for producing a copper alloy material characterized by obtaining the following structural characteristics of C in the copper alloy after melting and casting and obtaining the characteristics of D and E below .
A: The content of Ni, Si, Ti in the molten copper alloy satisfies the following formula (1) B: In the melting casting, the casting is performed at a temperature equal to or higher than the melting point of the compound in the copper alloy material, and the mold The residence time t in the mold when poured into the mold satisfies the formula (2) C: The copper alloy after melting and casting has 1500 crystallization and / or precipitates having an average diameter of 1 micron or more. / mm ² may be present or D: tensile strength of the copper alloy material after the aging heat treatment is not less than 500 MPa E: that the conductivity of the copper alloy material after the aging heat treatment is 25% IACS or more <formula (1)>
(I) 1.5 ≦ {[Ni] -15 / 6 × [Ti]} / {[Si] -7 / 6 × [Ti]} ≦ 2.5
(Ii) [Ni] -15/6 [Ti]> 1.5atm%
(Iii) [Ni] <7.4 atm%
(Iv) 0.05 ≦ (Ti) ≦ 2.0 mass%
[*] ... atm% of element *, (*): mass% of element *
<Formula (2)>
(I) t (seconds) <{1500 / N} ^{(1 / 0.19)}
(Ii) N = α + β × [Ti (atm%)] + 10000γ × [C (atm%)]
(Iii) α = −300, β = 4000, γ = 10 The method for producing a copper alloy material according to claim 1, wherein the molten copper alloy contains 0.05 to 1.5 mass% of Sn. Copper alloy parts copper alloy material produced by the production method of the copper alloy material according to claim 1 or 2 is formed by cutting.

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