Beryllium / copper alloy ring and method for its manufacture

Abstract

A method for producing a beryllium / copper alloy ring, comprising the following steps: providing a columnar forged material made of a beryllium / copper alloy; opening a hole from the center of an upper surface of the columnar forged material in a direction parallel to a central axis of the columnar forged material to produce a ring intermediate; performing ring forging on the ring intermediate, thereby enlarging the hole to achieve a reduction of 63% or more to produce a ring-forged product, wherein the reduction is described by the following expression: P = 100 × (T - t) / T, where P represents the reduction (%), T represents a thickness (mm) of the ring intermediate, and t represents a thickness (mm) of the ring-forged product;and performing solution annealing and precipitation hardening on the ring-forged product to produce the beryllium / copper alloy ring, wherein the ring-forged product has an outer diameter ranging from 620 mm to 2045 mm and an inner diameter ranging from 460 mm to 1875 mm.

Description

Technical field

[0001] The present invention relates to a beryllium / copper alloy ring and a method for its manufacture. Background area

[0002] Previously, a ring casting process was used to produce an alloy strip, such as an amorphous foil for a transformer. The ring casting process involves forging a block obtained by melt casting an alloy or similar material to create a forged material. This forged material is then subjected to steps of hole opening, hole enlargement (i.e., ring forging), solution annealing, and precipitation hardening.

[0003] The alloy strip is obtained by dripping molten alloy onto the surface of the casting ring while the resulting ring is rotated at high speed. The molten alloy is then drawn off the ring as it quenches and solidifies. In this process, the ring's surface is rapidly heated while in contact with the molten alloy and then quenched after the molten alloy is drawn off. This means the ring undergoes repeated expansion and contraction. Therefore, to withstand the large temperature changes resulting from such a heating cycle, the casting ring must possess, for example, high hardness (strength), excellent thermal conductivity, minimal degradation at high temperatures, and a uniform microtexture.To micronize the crystal grains of a ring for casting, increasing the degree of forging of a forged material in a forging step was carried out as a conventional procedure. Additionally, a ring made of, for example, a beryllium / copper alloy was used for casting, as one exhibiting excellent thermal conductivity or similar properties.

[0004] For example, patent literature 1 (JP3977868B) discloses a quench support used for the rapid solidification of a molten alloy to produce a strip, wherein the quench support has a microcrystalline or amorphous texture, and wherein a quench surface consists of a thermally conductive alloy, and the texture of the thermally conductive alloy is substantially homogeneous. This quench support may contain a beryllium / copper alloy, which is a precipitation-hardening copper alloy, or the like.

[0005] Furthermore, patent literature 2 (JP3194268B) discloses a quenching surface for rapidly solidifying a molten alloy into a ribbon, which has a microcrystalline or amorphous texture. This quenching surface is made of a thermally conductive alloy having a microstructure consisting of fine, equiaxial, recrystallized grains, wherein the grains have a mean size of 200 µm or less, are not larger than 500 µm, and exhibit a dense Gaussian grain size distribution. A beryllium / copper alloy or the like is used as the casting ring having such a quenching surface.

[0006] Furthermore, patent literature 3 (W02012 / 096238A1) discloses a method for the continuous casting of copper or a copper alloy, wherein a depth d (mm) of a surface defect of a coarse drawing line of the copper or copper alloy produced by a strip and wheel process satisfies expression (I). Expression (I) specifies d ≤ r × 0.1, where d represents the depth of a surface defect of a coarse drawing line and r represents a radius (mm) of the coarse drawing line. It is described that a beryllium / copper alloy or the like is preferred as an alloying material forming a casting ring. List of prior art patent literature [Patent Literature 1] JP3977868B [Patent Literature 2] JP3194268B [Patent Literature 3] WO2012 / 096238A1 Summary of the invention

[0007] However, when a conventional beryllium / copper alloy ring is used to create an alloy strip, as described above, a problem arises: due to repeated thermal expansion and contraction during the casting process, cracks appear on the ring's surface. One known method for reducing these cracks is micronizing the crystal grains that make up the beryllium / copper alloy. For example, micronizing the crystal grains can be achieved by increasing the degree of forging in a forging step performed after casting and before opening a hole in the beryllium / copper alloy ring production process, thereby reducing cracking to some extent. However, there is a limitation to micronizing the crystal grains by increasing the degree of forging, and further improvements are desirable.Furthermore, increasing the degree of forging leads to an increase in production costs.

[0008] The inventors of the present invention have discovered that a beryllium / copper alloy ring in which crystal grains are micronized can be produced by performing ring forging on a forged material in which a hole is opened (specifically a ring intermediate product), which enlarges the hole with a reduction degree of a predetermined value or greater.

[0009] Accordingly, it is an object of the present invention to provide a beryllium / copper alloy ring in which crystal grains are micronized, and a method for producing the beryllium / copper alloy ring.

[0010] According to one aspect of the present invention, a method for producing a beryllium / copper alloy ring is provided, comprising the following steps: Providing a column-shaped, forged material made from a beryllium / copper alloy; Opening a hole from the center of an upper surface of the columnar forged material in a direction parallel to a central axis of the columnar forged material to produce a ring intermediate product; Performing ring forging on the ring intermediate product, thereby enlarging the hole to achieve a reduction of 63% or more, in order to produce a ring-forged product, wherein the reduction is described by the following expression: P = 100 × (T - t) / T, where P represents the reduction (%), T represents a thickness (mm) of the ring intermediate product, and t represents a thickness (mm) of the ring-forged product; and Performing solution annealing and precipitation hardening on the ring-forged product to produce the beryllium / copper alloy ring.

[0011] According to another aspect of the present invention, a beryllium / copper alloy ring is created which consists of a beryllium / copper alloy, wherein the beryllium / copper alloy has a mean crystal grain size of 20 µm or smaller. List of characters Fig. Figure 1 is an optical micrograph of a cross-section of a beryllium / copper alloy ring prepared in Example 1 (Comparison Example). Fig. Figure 2 is an optical micrograph of a cross-section of a beryllium / copper alloy ring that was prepared in Example 2 (Comparison Example). Fig. Figure 3 is an optical micrograph of a cross-section of a beryllium / copper alloy ring that was prepared in Example 3. Fig. Figure 4 is an optical micrograph of a cross-section of a beryllium / copper alloy ring prepared in Example 4. Fig. Figure 5 is an optical micrograph of a cross-section of a beryllium / copper alloy ring that was prepared in Example 5. Fig. Figure 6 is an optical micrograph of a cross-section of a beryllium / copper alloy ring prepared in Example 6. Fig. Figure 7 is an optical micrograph of a cross-section of a beryllium / copper alloy ring that was prepared in Example 7 (Comparison Example). Description of the embodiments

[0012] The present invention relates to a beryllium / copper alloy ring and a method for producing it. The beryllium / copper alloy ring produced by the method of the present invention consists of a beryllium / copper alloy, and the crystal grains forming the beryllium / copper alloy are micronized. As described above, cracks can occur during the casting of an alloy strip on a conventional beryllium / copper alloy ring; however, the cracks can be significantly reduced by micronizing the crystal grains forming the beryllium / copper alloy by a greater margin than those of the conventional beryllium / copper alloy. The beryllium / copper alloy preferably has a mean crystal grain size of 20 µm or less, more preferably 17 µm or less, and even more preferably 15 µm or less.From the perspective of crack reduction, the beryllium / copper alloy is more advantageous when the mean crystal grain size is smaller. Therefore, the lower limit for the mean crystal grain size is not particularly restricted and is typically 5 µm or more, more typically 7 µm or more, and again typically 10 µm or more. It should be noted that the mean crystal grain size is determined by the procedure described later in the Examples section. Producing such a beryllium / copper alloy ring with a small mean crystal grain size—specifically, a beryllium / copper alloy ring in which the crystal grains are micronized—was limited and difficult using conventional methods.However, according to the method for producing a beryllium / copper alloy ring of the present invention, the beryllium / copper alloy ring in which the crystal grains are micronized can be produced by carrying out ring forging with a high degree of reduction on a ring intermediate product.

[0013] The size of the beryllium / copper alloy ring of the present invention is not particularly limited and can be suitably determined according to the intended use. In the case of the intended use for a ring for casting, the beryllium / copper alloy ring of the present invention preferably has a size with an outer diameter in the range of 320 to 2045 mm and an inner diameter in the range of 265 to 1875 mm, more preferably an outer diameter in the range of 620 to 2045 mm and an inner diameter in the range of 460 to 1875 mm, and even more preferably an outer diameter in the range of 830 to 2045 mm and an inner diameter in the range of 680 to 1875 mm.

[0014] The composition of the beryllium / copper alloy ring of the present invention is not particularly limited, and the beryllium / copper alloy typically contains Be in an amount preferably in the range of 0.2 to 2.0 wt.%, more preferably in the range of 0.4 to 2.0 wt.%, and again more preferably in the range of 1.8 to 1.9 wt.%, the remainder consisting of Cu and unavoidable impurities. The beryllium / copper alloy may further contain an optional element such as Ni, Co, Fe, or Zr. In particular, the inclusion of Zr can reduce cracking. That is to say, the beryllium / copper alloy preferably also comprises Zr.

[0015] The method for producing a beryllium / copper alloy ring of the present invention comprises (1) providing a column-shaped forged material made of a beryllium / copper alloy and successively performing a hole opening step (2), a hole enlargement step (3), a solution annealing step, and a precipitation hardening step (4). Providing a column-shaped, forged material

[0016] First, a columnar forged material made from a beryllium / copper alloy is provided. The columnar forged material can be prepared by a known method and is not particularly restricted, preferably by a melt casting step, a treatment step to maintain the firing temperature, and an intermediate forging step.

[0017] In the melt casting step, the beryllium / copper alloy is melted and poured into a mold to cool and solidify, resulting in a solid block. The melting temperature in this case is preferably in the range of 1100 °C to 1250 °C.

[0018] In the treatment step to maintain the firing temperature, the block is preferably held at 800 °C to 850 °C for 6 hours or longer.

[0019] In the intermediate forging step, upsetting and pre-blocking of the billet are repeated to perform the forging, resulting in a columnar forged material of an easily machinable size. The temperature in this case is preferably in the range of 530 to 760 °C. The degree of forging is preferably in the range of 18 to 25. The size of the columnar forged material is preferably 450 to 850 mm in diameter × 200 to 600 mm in height. Hole opening step

[0020] A hole is opened from the center of the upper surface of the columnar, forged material in a direction parallel to the central axis of the columnar, forged material to produce an intermediate ring. The method for opening the hole can be carried out by any method as long as a desired hole can be opened; however, opening the hole is preferably carried out, for example, by punching with a die. The size of the intermediate ring is not particularly limited and can be suitably determined according to the intended use.In the case of intended use for a ring for casting, the intermediate ring product preferably has a size with an outer diameter in the range of 330 to 815 mm and an inner diameter in the range of 150 to 250 mm, more preferably an outer diameter in the range of 400 to 815 mm and an inner diameter in the range of 150 to 250 mm, and even more preferably an outer diameter in the range of 465 to 815 mm and an inner diameter in the range of 160 to 250 mm.

[0021] In the hole-opening step, the columnar, forged material is preferably heated. The temperature of the columnar, forged material is preferably in the range of 550 to 800 °C, more preferably in the range of 550 to 780 °C, and even more preferably in the range of 550 to 750 °C. Such heating facilitates opening a hole in the columnar, forged material. Hole enlargement step

[0022] The hole is enlarged to achieve a reduction of 63% or more by performing ring forging on the intermediate ring to produce a ring-forged product. The reduction is described by the following expression: P = 100 × (T - t) / T, where P represents the reduction (%), T represents the thickness (mm) of the intermediate ring, and t represents the thickness (mm) of the ring-forged product. The thickness T of the intermediate ring is described here by the following expression: T = (Do - D l ) / 2, where Do represents the outer diameter of the ring intermediate and D l represents the inner diameter of the intermediate ring product; and the thickness t of the ring-forged product is described by the following expression: t = (do - d l ) / 2, where d o represents the outer diameter of the ring-forged product and d lThis represents the inner diameter of the ring-forged product. The reduction ratio is 63% or more, preferably 65% ​​or more, more preferably 70% or more, and again more preferably 73% or more. The beryllium / copper alloy ring, in which the crystal grains are micronized, can be produced in this way by carrying out ring forging with a high reduction ratio on the intermediate ring product. Therefore, the upper limit of the reduction ratio is not particularly restricted and is typically 90% or less, more typically 85% or less, and again typically 80% or less.

[0023] As described above, micronization of the crystal grains can be achieved by increasing the degree of forging in the forging step performed after casting and before hole opening in the process of producing a beryllium / copper alloy ring, thereby maintaining a certain degree of crack reduction. However, there was a limitation to micronizing the crystal grains by increasing the degree of forging. Furthermore, increasing the degree of forging leads to increased production costs. These problems are advantageously solved by performing ring forging with a high degree of reduction in the hole enlargement step.

[0024] The temperature at which the ring forging is carried out is preferably in the range of 530 to 780 °C, more preferably in the range of 530 to 750 °C, and even more preferably in the range of 530 to 720 °C. Lowering the working temperature in this way allows for more effective micronization of the crystal grains that form the beryllium / copper alloy ring.

[0025] The size of the ring-forged product is not specifically limited and can be suitably determined according to the intended use. In the case of intended use as a ring for casting, the ring-forged product preferably has an outer diameter in the range of 320 to 2045 mm and an inner diameter in the range of 265 to 1875 mm, more preferably an outer diameter in the range of 620 to 2045 mm and an inner diameter in the range of 460 to 1875 mm, and even more preferably an outer diameter in the range of 830 to 2045 mm and an inner diameter in the range of 680 to 1875 mm. Solution annealing step and precipitation hardening step

[0026] Solution annealing and precipitation hardening are performed sequentially on the ring-forged product to produce a beryllium / copper alloy ring with the desired properties. The beryllium / copper alloy is an aging-hardenable alloy and can therefore exhibit the desired thermal refining properties (e.g., high strength) through solution annealing and subsequent precipitation hardening.

[0027] Solution annealing can be carried out by heating the ring-forged product at a predetermined solution annealing temperature for a predetermined time and subsequently quenching it with water. A preferred solution annealing temperature is in the range of 700 to 950 °C, more preferably in the range of 730 to 920 °C, and even more preferably in the range of 760 to 900 °C. The holding time at the solution annealing temperature is preferably in the range of 120 to 240 minutes, more preferably in the range of 120 to 180 minutes, and even more preferably in the range of 120 to 150 minutes.

[0028] Precipitation hardening can be carried out by holding the ring-forged product at a predetermined precipitation hardening temperature for a predetermined time after solution annealing. A preferred precipitation hardening temperature is in the range of 280 to 450 °C, more preferably in the range of 300 to 450 °C, and even more preferably in the range of 320 to 450 °C. The holding time at the precipitation hardening temperature is preferably in the range of 120 to 600 minutes, more preferably in the range of 180 to 300 minutes, and even more preferably in the range of 180 to 240 minutes.

[0029] Surface machining can be performed on the ring-forged product and / or the beryllium / copper alloy ring before and after precipitation hardening. The advantages of this are that oxidized surfaces of the ring-forged product and / or the beryllium / copper alloy ring can be removed, and the sizes of the ring-forged product and / or the beryllium / copper alloy ring can be manufactured to the desired dimensions by performing surface machining. Examples

[0030] The present invention is described in more detail with reference to the following examples. Examples 1 to 7

[0031] Beryllium / copper alloy rings were prepared and evaluated according to the following procedures. Pour

[0032] A beryllium / copper alloy (Be content: 1.86 to 1.87 wt.%, Co content: 0.24 to 0.25 wt.%, Fe content: 0.02 to 0.03 wt.%, the remainder: Cu and unavoidable impurities, UNS No. C17200) was provided for Examples 1 to 5 and 7, and a beryllium / copper alloy (Be content: 1.86 to 1.87 wt.%, Co content: 0.24 to 0.25 wt.%, Fe content: 0.02 to 0.03 wt.%, Zr content: 0.2 wt.%, the remainder: Cu and unavoidable impurities, UNS No. C17200) was provided for Example 6. Each beryllium / copper alloy was melted at a temperature in the range of 1130 to 1170 °C to produce molten metal, and the molten metal was poured into a mold. The ingot that came out of the mold was cooled with water. Treatment to maintain firing temperature

[0033] A treatment to maintain the firing temperature was carried out by keeping the obtained blocks at a temperature in the range of 800 to 850 °C for 6 hours or longer. Intermediate forges

[0034] Following treatment to maintain the firing temperature, upsetting and pre-blocking of each block was carried out at a temperature in the range of 668 to 749 °C in such a way that the degree of forging was in the range of 18 to 25 in order to produce a columnar forged material with a diameter in the range of 440 to 460 mm × a height in the range of 110 to 460 mm. Hole opening

[0035] A hole with a diameter of 160 to 250 mm was opened at a temperature of 550 to 748 °C from the center of the upper surface of the columnar forged material in a direction parallel to the central axis of the columnar forged material. In this case, the center of the upper surface of the columnar forged material was punched by applying pressure with a press. This resulted in ring-shaped intermediate products, each with a size shown in Table 1. Hole expansion

[0036] Each hole was enlarged by ring forging each intermediate ring at a temperature shown in Table 1, such that the degree of reduction was as shown in Table 1. In this process, a core bar was inserted into the hole opened by pressing, and the hole was enlarged while each intermediate ring was held and pressed and rotated from the outside. This resulted in ring-forged products, each with a size shown in Table 1. Solution annealing and precipitation hardening

[0037] Each ring-forged product underwent solution annealing by heating it to a temperature in the range of 700 to 800 °C for 120 minutes, followed by water cooling and surface cutting. The solution-annealed ring-forged product then underwent precipitation hardening by holding it at a temperature in the range of 300 to 350 °C for 120 to 180 minutes, followed by surface cutting. This resulted in beryllium / copper alloy rings, each with an outer diameter shown in Table 1. Evaluation

[0038] The following evaluation was carried out on the beryllium / copper alloy rings obtained. <Berechnung der mittleren Kristallkorngröße>

[0039] The mean crystal grain size of each beryllium / copper alloy ring was calculated using a sectioning method. This involved examining a surface obtained by slicing the beryllium / copper alloy ring in the thickness direction with an optical microscope and analyzing the microtexture of the resulting cross-section. Specifically, three lines were drawn on the photographed microtexture image, and the arithmetic mean of the values ​​obtained by dividing the number of crystal grains crossed by each line along its length was used to calculate the mean crystal grain size. The results are shown in Fig. 1 to Fig. 7 and is shown in Table 1.

[0040] Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 and Fig. 7 correspond to examples 1, 2, 3, 4, 5, 6 and 7. [Table 1] Table 1 Hole opening step Hole enlargement step Beryllium / copper alloy ring Size of the ring intermediate product (after opening the hole) (mm) Ring forging temperature (°C) Size of the ring-forged product (after enlarging the hole) (mm) Degree of reduction P (= 100 × (T - t) / T) (%) Outer diameter (mm) Average crystal grain size (µm) Outer diameter D o Inner diameter D l Thickness T Outer diameter d o Inner diameter d l Thickness t Example 1* 470 200 135 750 840 730 55 59 810 20,0 Example 2* 490 200 145 750 1070 945 62,5 57 1030 21,3 Example 3 470 160 155 720 840 730 55 65 810 16,8 Example 4 585 250 167,5 750 1240 1115 62,5 63 1200 18,8 Example 5 815 250 282,5 750 2025 1870 77,5 73 1980 14,8 Example 6 585 250 167,5 750 1240 1115 62,5 63 1200 19,1 Example 7* 470 250 110 750 840 730 55 50 825 27,7 * provides a comparative example T = (DO − DI) / 2, t = (dO − dI) / 2

[0041] The results shown in Table 1 indicate that the mean crystal grain size of the beryllium / copper alloy ring is smaller the greater the degree of reduction P. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 3977868 B [0004, 0006] JP 3194268 B [0005, 0006] WO 2012 / 096238 A1

[0006]

Claims

[1] Method for producing a beryllium / copper alloy ring comprising the following steps: Providing a column-shaped, forged material made from a beryllium / copper alloy; Opening a hole from the center of an upper surface of the columnar forged material in a direction parallel to a central axis of the columnar forged material to produce a ring intermediate product; Performing ring forging on the ring intermediate product, thereby enlarging the hole to achieve a reduction of 63% or more, in order to produce a ring-forged product, wherein the reduction is described by the following expression: P = 100 × (T - t) / T, where P represents the reduction (%), T represents a thickness (mm) of the ring intermediate product, and t represents a thickness (mm) of the ring-forged product; and Performing solution annealing and precipitation hardening on the ring-forged product to produce the beryllium / copper alloy ring. [2] Method for producing a beryllium / copper alloy ring according to claim 1, wherein the ring forging is carried out at a temperature in the range of 530 to 780 °C. [3] Method for producing a beryllium / copper alloy ring according to claim 1 or 2, wherein the ring forging is carried out at a temperature in the range of 530 to 720 °C. [4] Method for producing a beryllium / copper alloy ring according to any one of claims 1 to 3, wherein the ring intermediate product has an outer diameter in the range of 330 to 815 mm and an inner diameter in the range of 150 to 250 mm. [5] Method for producing a beryllium / copper alloy ring according to any one of claims 1 to 4, wherein the ring-forged product has an outer diameter in the range of 320 to 2045 mm and an inner diameter in the range of 460 to 1875 mm. [6] Method for producing a beryllium / copper alloy ring according to any one of claims 1 to 5, wherein the beryllium / copper alloy further comprises Zr. [7] Beryllium / copper alloy ring consisting of a beryllium / copper alloy wherein the beryllium / copper alloy has a mean crystal grain size of 20 µm or less. [8] Beryllium / copper alloy ring according to claim 7, wherein the beryllium / copper alloy further comprises Zr.