JPH04268033A - Production of beryllium-copper alloy - Google Patents

Abstract

PURPOSE:To keep a molten alloy at <=1,100 deg.C at the beginning of casting when a Be-Cu alloy contg. 1.5-2.0wt.% Be is produced. CONSTITUTION:The amt. of beryllium carbide contained in a Be-Cu alloy product contg. 1.5-2.0wt.% Be in the alloy is reduced by keeping a molten alloy at <=1,100 deg.C at the beginning of casting.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for casting beryllium-copper alloys. More specifically, the present invention relates to a method for producing a beryllium copper alloy that makes it possible to reduce carbides contained in the beryllium copper alloy.

0002

2. Description of the Related Art Beryllium copper alloys have excellent electrical conductivity and high strength, and are therefore used as switch parts or electrical components of automobiles. Such beryllium copper alloys are generally produced by melting-degassing-casting or continuous casting. During the manufacturing process, carbon is mixed in from the furnace or scrap and dissolved into the molten metal, and is present in the form of carbides (mainly beryllium carbide) in the beryllium-copper alloy. Since such carbides are hard and brittle, it is known that they reduce the machinability of beryllium copper alloy materials containing carbides. In the conventional manufacturing method of beryllium copper alloy, in order to melt additive components such as cobalt, the alloy components of beryllium copper alloy are melted at a temperature of 1150 to 1200°C.
Molten metal is poured into the mold at the same temperature. In this case, carbides are considered to be present in the molten metal in the same way as oxide-based nonmetallic inclusions that are generated during melting, and the molten metal is floated and filtered to remove nonmetallic inclusions. A method of removing carbides is by tration. However, this method could not sufficiently reduce carbides in the beryllium-copper alloy.

0003

Although conventional methods have not been able to sufficiently reduce the amount of carbides in beryllium-copper alloys, it is an object of the present invention to effectively reduce the amount of carbides. That is, an object of the present invention is to provide a method for producing a beryllium copper alloy with excellent machinability, which makes it possible to reduce the amount of carbides, particularly beryllium carbide, in the beryllium copper alloy.

0004

[Means for Solving the Problems] The present invention provides a method for producing a beryllium-copper alloy containing 1.5 to 2.0% by weight of beryllium based on the total weight of the alloy, the casting start temperature being 1,100°C. It is characterized by the following. In this specification, the casting start temperature refers to the temperature of the molten metal at the outlet of the ladle through which the molten metal is poured into the mold.

The present invention was made based on the following findings. As mentioned above, carbides in conventional beryllium-copper alloys are thought to exist before the melting process of beryllium-copper alloys, and attempts have been made to remove them together with non-metallic inclusions by a method called flotation/filtration. It had been done. The present inventor conducted a detailed study of the melting process, injection process, and cooling process for the purpose of reducing carbides, and found that carbon is dissolved in the molten metal, and that the carbon combines with beryllium during cooling to form beryllium. Crystallizes as carbide,
It was discovered for the first time that it exists in beryllium-copper alloys. Therefore, a detailed study of the cooling process revealed that by casting at a temperature of 1,100°C or less at the start of casting, the amount of carbides in the beryllium-copper alloy was reduced, resulting in excellent machinability. A beryllium-copper alloy having the following properties was obtained, and the present invention was completed.

[0006] When melting the alloy components at a temperature below 1,100°C, it is sufficient to tap the metal as is, but depending on the desired alloy composition, it is necessary to melt the alloy components at 1,1
Melting may be carried out at temperatures higher than 00°C. In such a case, after melting, lower the temperature to below 1.100 °C and float the separated carbides (hereinafter referred to as
(referred to as pretreatment), degassing and casting are performed at the same temperature or lower but at a similar temperature. Those that perform such pretreatment also fall within the scope of the present invention.

First, the relationship between beryllium content in beryllium copper alloy and carbon solubility will be explained. Be in copper alloy
When carbon is added, the carbon dissolves into the alloy. Therefore,
By changing the Be content variously, the beryllium copper alloy was made into 1,
It was melted at 200°C and the solubility of carbon in the molten metal was examined. For the measurement, a sample for analysis was taken from the molten metal and analyzed using infrared absorption spectroscopy. The results are shown in Figure 1. From the same table, it can be seen that when Be is 1.5% by weight or less, the solubility of carbon is 50 ppm or less. The inventor has discovered that when the molten metal contains 50 ppm or more of carbon, Be2C (beryllium carbide) crystallizes during cooling and appears in the beryllium copper alloy product.

Next, the relationship between beryllium copper alloy molten metal temperature and carbon solubility will be explained. FIG. 2 is a graph showing the relationship between molten metal temperature and carbon solubility obtained for a beryllium-copper alloy when the beryllium content is 2.0% by weight. From the same figure, the content of beryllium is 2.
It can be seen that even if the carbon content is 0% by weight, the solubility of carbon can be reduced to 50 ppm or less if the temperature of the molten metal is 1,100°C. Here, the content of beryllium is 2.0% by weight.
is considered to be the maximum value that the beryllium content of ordinary beryllium alloys can take. Further, there is no particular restriction on the lower limit of the casting start temperature, and it is considered that it is sufficient as long as the alloy is in a molten state. Therefore, about 970°C will be adopted as the lower limit. From the above results, in the manufacturing method of beryllium copper alloy, the Be content is set to 1.5 to 2.0% by weight, and the casting start temperature is set to 1.
, 100° C. or lower, a beryllium-copper alloy without carbide crystallization can be obtained. B
Additives other than e include Co, Ni, Mn,
Of course, it is also good to add Mg, Al, etc.

[0009]

EXAMPLES The present invention will be explained below with reference to Examples. Experimental example 1 1.86% Be -0.25% under the following conditions
A beryllium steel alloy containing Co was produced by a melting-degassing-casting process using a die casting method, and the amount of carbide crystallized in the alloy was measured by the method described below. The results are also shown in Table 1. From the above results, although 143 carbide crystals/cm2 were observed in the comparative example, the beryllium copper cast by the method of the present invention, which has a casting start temperature of 58°C lower than the comparative example and a casting start temperature of 1100°C or less. No crystallization of beryllium carbide was observed in the alloy. The amount of beryllium carbide was measured using an optical microscope with a magnification of 400 times, and the amount of beryllium carbide was measured in 100 fields of view of the cross section of the alloy, and the amount was calculated per unit area, and the average value of these values was taken.

Example 2 The alloy components of beryllium copper alloy shown in Table 2 were mixed and melted, and continuous casting was performed to produce a billet with a diameter of 200 mm. Note that the melting temperature at this time was 1100°C or lower. Then, the amount of beryllium carbide was measured by the same method as in Example 1. Table 2 shows the relationship between casting temperature and beryllium carbide content. As can be seen from Table 2, according to the method of the present invention, the amount of beryllium carbide in the beryllium copper alloy can be reduced to zero. On the other hand, the casting start temperature was set at 1,100°C.
In a comparative example with a higher value, 123 to 141 pieces/c
A large amount of carbide (m2) was observed to crystallize.

Example 3 Under the following conditions, 1.83%Be-0.23%Co
beryllium copper alloy was produced by melting-degassing-pretreatment-casting process. Melting was performed at 1100° C. or higher, and casting was performed by continuous casting into a slab with a thickness of 130 mm and a width of 500 mm. Pretreatment was performed by removing slag on the surface of the molten metal using a sludge remover after degassing. In the conventional method, crystallization of 136,178 carbides/cm2 was observed, but in the present invention, in which pretreatment was performed at 1100° C. or lower after melting and casting was started, no crystallization of carbide was observed. According to the present invention, a carbide-free beryllium copper alloy can be obtained even if melting starts at 1100° C. or higher.

As explained above, in the method for producing a beryllium copper alloy containing 1.5-2.0% by weight of beryllium according to the present invention, the casting start temperature is set at 1,100% by weight.
By keeping the temperature below 0.degree. C., the amount of beryllium carbide crystallized in the alloy can be made substantially zero. Therefore, according to the present invention, a highly practical beryllium copper alloy with excellent machinability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between beryllium content in a molten beryllium-copper alloy and carbon solubility at 1200°C.

FIG. 2 is a graph showing the relationship between temperature and carbon solubility of a molten beryllium copper alloy.

Claims (2)

[Claims] Claim 1: Contains 1.5 beryllium in the total weight of the alloy.
- A method for producing a beryllium copper alloy containing 2.0% by weight, characterized in that the casting start temperature of the molten metal is 1,100°C or less. [Claim 2] The alloy composition of the beryllium copper alloy is 1.1.
When melting at a temperature higher than 0.0°C, the molten metal is
2. A manufacturing method according to claim 1, characterized in that the temperature is lowered to 100 DEG C. or less to thereby remove separated carbides, followed by casting.