JPH0724904B2 - Hot forging method for beryllium copper alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hot forging method for a high-strength beryllium copper alloy.

(Prior Art) A processed material of beryllium copper alloy is widely used as a highly reliable mechanical component other than a conductive spring material, by taking advantage of excellent properties such as high strength, high conductivity, and corrosion resistance. As such a high-reliability mechanical part, it is necessary to break the coarse crystal structure during casting by hot forging in order to improve reliability and ultrasonic flaw detection, and to make uniform and fine crystal grains. To be done. This is because the mechanical properties are inferior in a non-uniform structure such as the state where grain flows are left, directionality occurs in the material, and it is difficult to perform flaw detection with simple ultrasonic waves and problems such as defects cannot be checked. Is. As a measure of the crystal grain size for this purpose, the average grain size is preferably 2 mm or less.

In order to obtain such crystal grains, conventionally, hammer forging with a total forging ratio of 8 or more has been performed on a beryllium copper alloy material in the range of 650 to 800 ° C. (Note that the wrought ratio is a term expressing the amount of deformation or the degree of processing applied to a material by forging. In Japan, in JIS, the absolute value of the strain in the three principal directions given to the material is the absolute value. It is defined as the deformation ratio corresponding to the maximum strain.) However, hammer forging has problems of noise and vibration, and in order to obtain a sufficient crystal refining effect to the inside of the material, it is extended and set up. However, there is a problem that it takes a lot of man-hours because it is necessary to repeat the forging so as to obtain a total forging ratio of 8 or more in consideration of the direction such as lateral stretching. There is also a method of performing press forging to prevent noise and vibration, but since press forging is slower in giving a processing strain than hammer forging, even if the same temperature conditions and forging ratio as hammer forging are given. There is a drawback that a sufficient crystal refining effect cannot be obtained.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and beryllium copper which can be efficiently refined to 2 mm or less with a minimum number of steps by a crystal of a beryllium copper alloy by a press forging method. It has been completed to provide a method for hot forging of alloys.

(Means for Solving the Problems) The present invention made to solve the above problems is in terms of% by weight.
Beryllium copper alloy material containing Be 1.6-2.0%, Co + Ni 0.2-0.6%, and the balance substantially Cu at 450 ℃ or more 700
It is characterized in that it is press-forged at a forging ratio of 2.5 or more at a temperature of ℃ or less and then reheated to a temperature of 700 ° C or more and 840 ° C or less.

The beryllium copper alloy used in the present invention is JIS C1700, C17 which is commercially available as a high-strength beryllium copper alloy.
It corresponds to 20 beryllium copper alloys of normal composition. The reason why the material is limited in the present invention is that it is industrially most practical in view of mechanical strength, electrical conductivity, economical efficiency and the like. If Be, Co, and Ni are less than the above numerically limited range, the desired strength cannot be obtained. Conversely, if the content exceeds this range, not only the property improvement corresponding to the increase cannot be obtained, but cracking occurs during forging. Becomes easier to enter. As for Co and Ni, if Co is contained at 0.2% or more, the desired characteristics can be obtained even if Ni is hardly contained. However, when Co is less than 0.2%, Ni can be used to cover that amount. It is possible.

In the present invention, such a beryllium copper alloy material is subjected to hot press forging and reheating treatment as described above. The forging temperature is above 450 ℃ and below 700 ℃, but this is 45
This is because if the temperature is lower than 0 ° C, forging becomes extremely difficult due to deterioration of workability and cracks easily occur, and if the forgeability is taken into consideration, the temperature is preferably 500 ° C or higher. Also 700 ℃
If it exceeds, the effect of refining the crystal is hardly obtained.

The reason for setting the forging ratio to 2.5 or more is that a uniform refined state cannot be obtained below this. However, even if a total forging ratio of more than 10 is not obtained, the characteristics are not improved, and the number of man-hours is increased. Therefore, the forging ratio of 2.5 to 10 is preferable. In addition, forging in one heating has a forging ratio of 8
The following is preferable, and if it exceeds 8, there is a possibility that crystal growth or coarsening may occur at the time of reheating in a later step.

Next, the beryllium copper alloy material is reheated to a temperature of 700 ° C or higher and 840 ° C or lower. If this temperature is less than 700 ° C., a uniform refined state due to recrystallization cannot be obtained. However, after 70
There is no problem if it is heated in the range of 0 ° C to 840 ° C. When the reheating temperature exceeds 820 ° C, partial crystal growth and coarsening occur. Note that this reheating step is the usual final solution treatment (700-800 ° C) that is applied to the beryllium copper alloy.
May be combined with water cooling after heating.

The above-described press forging → reheating step may be performed at any stage, for example, press forging under the conditions of the present invention to form an intermediate shape and then forging to a final shape at a temperature of 650 to 800 ° C. of conventional conditions. The same uniform fine structure can be obtained by performing the conventional forging at 650 to 800 ° C. up to the intermediate shape and performing the forging up to the final shape under the conditions of the present invention. As described above, the desired fine crystal structure can be obtained by adding the conditions of the present invention to the necessary minimum in the conventional forging process at a temperature of 650 ° C. or higher, which is relatively easy to forge.

The forging direction in the present invention may be only one direction,
In order to obtain a more uniform crystal structure more efficiently, it is preferable to add forging in two directions such as stretching and upsetting.

The beryllium copper alloy material obtained under the above conditions is the same as conventional products, and is subjected to the age hardening treatment after the usual solution treatment (including the case where it also serves as reheating), so that the beryllium copper alloy is required to have the required mechanical properties. Characteristic can be obtained.

Examples of the present invention will be shown below.

(Example) Example 1 A cast product having a weight% of 1.8% Be, 0.25% Co, 0.1% Ni and the balance substantially Cu and having an outer dimension of 230 mmφ x 300 mm ^H was prepared. Press forging was performed under the various conditions shown. These forged products were subjected to solution treatment by heating at 780 ° C. for 3 hours and then water cooling, and the macrostructure of the cross section of the central part was observed. The results are shown by symbols in Table 1. ◎
Indicates that a uniform fine recrystallized structure with a maximum crystal grain size of 1.5 mm or less was obtained, ○ indicates a uniform fine recrystallized structure with a maximum crystal grain size of 2 mm or less, and △ indicates a recrystallized microstructure. Partially grown and coarsened, and x indicates that coarse crystals remained at the time of casting or they were extended but did not have a uniform recrystallization structure. In this embodiment, the forging direction is only the extension direction.

When the sample thus obtained by the method of the present invention was age-hardened at 315 ° C. for 5 hours,
The hardness was in the range of RC35-40, and it was possible to obtain beryllium-copper alloy material with no problem characteristics.

Example 2 A cast product of the same beryllium copper alloy as that used in Example 1 was forged under the conditions (1) to (3) shown in Table 2, and then reheated to 780 ° C. and allowed to cool, as in Example 1. Was evaluated. Was a conventional hammer forging, and the forging ratio was insufficient and the structure was non-uniform. Shows the case where the temperature was lowered by hammer forging, in which cracks occurred during forging and the crystal became partially coarse after reheating. Is the method of the present invention, which is more favorable than that of Example 1 having the same forging ratio (4.0). This is because the direction of training changed in Example 2.

Further, the press forging under the above conditions was reheated under the conditions shown in Table 3 to evaluate the structure. Recrystallization at 680 ° C is insufficient. However, after this 700
A good crystal structure can be obtained by heating above 840C. When reheating at 850 ° C, the recrystallized structure became coarsely grown. In each case, no difference due to cooling conditions was observed.

Example 3 Fourth example of combining the process of the present invention with conventional high temperature forging conditions
Shown in the table. In each case, a good uniform fine structure was obtained.

(Effects of the Invention) As described above, the present invention is capable of hot forging a beryllium copper alloy material by a press forging method to obtain a uniform fine crystal structure, and has high reliability and ultrasonic flaw detection. An excellent beryllium copper alloy material can be obtained with a small number of steps. Further, according to the present invention, since hot forging can be performed by using a press forging method with less vibration and noise, it is preferable from the viewpoint of working environment. Therefore, the present invention is a method of hot forging a beryllium copper alloy that eliminates the conventional problems and has a great contribution to the industrial development.

Claims (1)

[Claims] 1. Be 1.6 to 2.0% by weight, Co + Ni 0.2 to 0.6
%, The beryllium copper alloy material with the balance being substantially Cu is press forged at a forging ratio of 2.5 or more at a temperature of 450 ° C or more and 700 ° C or less, and then reheated to a temperature of 700 ° C or more and 840 ° C or less. A method for hot forging a beryllium copper alloy, which is characterized by the above.