JPH03258433A - Hot forging method for beryllium copper alloy - Google Patents

Abstract

PURPOSE:To efficiently form the finer crystals of the alloy with min. stages by press-forging a Be-Cu alloy material at a specific temp. and forging ratio, then reheating the alloy material. CONSTITUTION:The casting material of the Be-Cu alloy consisting, by weight %, of 1.8 to 2.0% Be, 0.2 to 0. 6% Co+Ni and the balance Cu is practically prepd. This Be-Cu alloy is press forged at >=2.5 forging ratio at 450 to 700 deg.C. The material is thereafter reheated to 700 to 840 deg.C. The uniform and fine crystal structure is formed in this way, by which the Be-Cu alloy material having excellent reliability and ultrasonic flaw detectability is obtd. with the fewer stages.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for hot forging a high-strength beryllium copper alloy.

(Prior Art) Beryllium-copper alloy processed materials are widely used as highly reliable mechanical parts as well as conductive spring plates due to their excellent properties such as high strength, high conductivity, and corrosion resistance. For such high-reliability mechanical parts, it is necessary to use hot forging to break the coarse crystal structure during casting and create homogeneous, fine crystal grains in order to improve reliability and ultrasonic flaw detection. It is said that This is because a non-uniform structure, such as a state where grain flow lines remain, has poor mechanical properties, and the material becomes directional, making simple ultrasonic flaw detection difficult and causing problems such as the inability to check for defects. As a guideline for the crystal grain size for this purpose, it is preferable that the average grain size is 2 mm or less.

In order to obtain such crystal grains, conventionally, helium copper alloy materials were hammer forged at a temperature of 650 to 800° C. with a total forging ratio of 8 or more. However, in addition to the problem of noise and vibration, hammer forging requires a total of 8 or more, taking into consideration the directionality of stretching, upsetting, cross-grain stretching, etc., in order to obtain sufficient crystal refinement effects even inside the material. There was a problem in that it was necessary to repeat training to obtain the training ratio of , which required a large number of man-hours. There is also a method of press forging to prevent noise and vibration, but press forging has a slower rate of applying strain than hammer forging, so
Even if the temperature conditions and forging ratios similar to those of hammer forging were given, a sufficient crystal refinement effect could not be obtained.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and makes it possible to efficiently refine the crystals of beryllium copper alloy to <2m+ or less using a press forging method with a minimum of man-hours. It was completed to provide a method for hot forging copper alloys.

(Means for Solving the Problems) The present invention has been made to solve the above problems.
Be 1.6-2.0%, Co+Ni 0.2-0.
A beryllium-copper alloy material containing 6% Cu and the remainder substantially Cu is press-forged at a temperature of 450°C or higher and 700°C or lower with a forging ratio of 2.5 or higher, and then heated to 700"C or higher 8
It is characterized by being reheated to a temperature of 40°C or lower.

The beryllium copper alloy used in the present invention is JIS C1, which is commercially available as a high strength beryllium copper alloy.
700 and C1720, which correspond to beryllium copper alloys of normal composition. The reason why the present invention is limited to this material is that it is industrially most practical in terms of mechanical strength, electrical conductivity, economical efficiency, etc. If Be, Co, and Ni are less than the above numerical limit range, the desired strength cannot be obtained, and conversely, if the content exceeds this range, not only will the properties not improve commensurate with the increased amount, but cracks may occur during forging. becomes easier to enter. Regarding Co and Ni, if Co is contained at 0.2% or more, the desired characteristics can be obtained even if Ni is hardly contained, but if Co is less than 0.2%, the amount is replaced by Ni. It is something that can be enjoyed.

In the present invention, such beryllium copper alloy material is subjected to hot press forging and reheating treatment as described above. The forging temperature is 450°C or more and 700°C or less, because if it is less than 450°C, forging becomes extremely difficult due to deterioration of workability and cracks are likely to occur.
Considering forgeability, the temperature is preferably 500°C or higher. Moreover, if the temperature exceeds 700°C, the effect of making the crystals finer will hardly be obtained.

The reason why the forging ratio is set to 2.5 or more is because a uniformly refined state cannot be obtained if it is less than this. But in total 1
Even if a training ratio exceeding 0 is given, no improvement in characteristics will be obtained, but only an increase in the number of man-hours, so a training ratio of 2°5 to 10 is preferable. In addition, for forging in one heating process, it is preferable to set the forging ratio to 8 or less. The material is 700℃ or higher 840℃
reheated to a temperature below °C. If this temperature is less than 700°C, a uniformly refined state cannot be obtained by recrystallization.

However, if it is later heated to a temperature of 700"C or more and B40"C or less, there will be no problem. Furthermore, if the reheating temperature exceeds 820'C, partial crystal growth or coarsening will occur.

Note that this reheating step may also serve as the usual final solution treatment (heating to 700 to 800° C. and then water cooling) performed on beryllium copper alloys.

The process of press forging → reheating as described above may be performed at any stage; for example, after press forging is performed under the conditions of the present invention to form an intermediate shape, the process is performed at 650 to 800 °C under conventional conditions.
A similar uniform microstructure can be obtained by forging the material up to the final shape at a temperature of 200° C., or by forging the intermediate shape at 650 to 800° C. in the conventional manner, and then performing the forging up to the final shape under the conditions of the present invention.

In this way, the desired fine crystal structure can be obtained even by adding the necessary minimum conditions of the present invention to the conventional forging process at a temperature of 650° C. or higher, where forging is relatively easy.

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

The beryllium-copper alloy material obtained under the above conditions is subjected to an age hardening treatment after normal solution treatment (including reheating) in the same way as conventional products. characteristics can be obtained.

Examples of the present invention are shown below.

(Example) Example 1 In weight%, Be 1.8%, Co 0.25%, Ni
0.1%, the remainder substantially consists of Cu, and the outer dimension is 230
A cast product of wrφ×30Qm+′ was prepared and press forged under various conditions shown in Table 1. These forged products were subjected to solution treatment by heating at 780° C. for 3 hours and then cooling with water, and the macrostructure of the cross section of the center was observed. The results are shown in Table 1 using symbols. ◎ means the maximum grain size is 1
．． A uniform fine recrystallized structure of 5 or less is obtained, ○
△ means that the recrystallized structure has partially grown and become coarse, × means coarse crystals at the time of casting. In this case, the crystal structure is not a uniform recrystallized structure, but only remains or is elongated. In this example, the forging direction is only the stretching direction.

When the samples thus obtained by the method of the present invention were subjected to age hardening treatment at 315°C for 5 hours, all of them had hardness in the HRC range of 35 to 40, indicating that they had satisfactory properties as a beryllium copper alloy material. did it.

Table 1 (Relationship between temperature and forging ratio during press forging) * is 45
Cracking occurs during forging after the temperature drops below 0°C Example 2 The same beryllium copper alloy casting used in Example 1 was forged under the conditions of ■ to ■ shown in Table 2, and then heated to 780°C. The same evaluation as in Example J was performed on the product that was reheated and allowed to cool. ■ is conventional hammer forging,
The training ratio was insufficient and the organization was uneven. (2) shows the case where the temperature was lowered during hammer forging, and cracks occurred during forging, and after reheating, the structure became partially coarsened. Method (2) is the method of the present invention, and the result was even better than that of Example 1 with the same training ratio (4,0). This is because the direction of training is changed in Example 2.

Table 2 (Effects of Forging Methods) In addition, the press forged products under the conditions (2) were reheated under the conditions shown in Table 3, and their structures were evaluated. 680
Recrystallization is insufficient by reheating at ℃.

However, a good crystal structure can be obtained by heating at a temperature of 700° C. or more and 840° C. or less after this. When reheated at 850° C., the recrystallized structure grew coarsely.

In any case, no difference was observed depending on the cooling conditions.

Table 3 (Example 3 of heated strips after forging under condition ① of Example 2)
Shown in the table. In all cases, a good uniform fine structure was obtained.

Table 4 (Example of application of combinations of conditions of the present invention) (Effects of the invention) As explained above, the present invention hot forges a beryllium copper alloy material by a press forging method to obtain a uniform fine crystal structure. As a result, a beryllium-copper alloy material with excellent reliability and ultrasonic flaw detection properties can be obtained with a small number of man-hours. Further, according to the present invention, hot forging can be performed using a press forging method with less vibration and noise, which is preferable from the viewpoint of the working environment. Therefore, the present invention greatly contributes to the development of industry as a hot forging method for beryllium-copper alloys that eliminates the problems of the conventional method.

Claims (1)

[Claims] Be 1.6-2.0%, Co+Ni 0.2-0 in weight%
．． 6% and the remainder is substantially Cu at a temperature of 450°C or more and 700°C or less.
Press forged with the above forging ratio, then heated to 700℃ or above 84
A method for hot forging beryllium copper alloy, characterized by reheating to a temperature of 0°C or lower.