JPH0794702B2 - Method for manufacturing copper alloy spring material - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a thin copper alloy spring material of a plate, a strip or a wire, and in particular, it is cold worked at a working rate of 50% or more in an intermediate working step and sufficiently worked and hardened. The present invention relates to a method for producing a copper alloy spring material, the grain size of which is adjusted so as to be suitable for cold working for exhibiting higher physical properties.

[0002]

2. Description of the Related Art Copper alloy spring materials such as plates, strips or wires used in large quantities in electronic technology include brass for springs, phosphor bronze for springs, nickel silver for springs, beryllium copper alloy, titanium copper. Alloys are used. For these spring materials, brass, phosphor bronze, nickel silver, etc. are required to be softened and annealed by the material that has been hardened by cold working in consideration of the target plate thickness, physical property values, etc. Made by final cold working to bring out the characteristics of. At this time, the softening annealing is performed at 500 ° C. for 1 hour for brass and 5 for phosphorous copper.
It takes 1 hour at 50 ° C and 1 hour at 650 ° C for nickel silver.
Further, in the continuous reading type annealing, a temperature corresponding to each value is given within a desired residence time in the heating portion to recrystallize and the final cold working is performed so that a desired characteristic value is exhibited.
There is also a scene where phosphor bronze is blended with a metal element such as Ni to make the crystal grains uniform and fine so as to improve the characteristic value and used.

For precipitation-hardening type spring materials, the material which has been work-hardened by cold working as a standard precipitation material is subjected to softening annealing for solution treatment, and then subjected to forming processing such as pressing and homing, and then precipitation hardening treatment. Is used as a spring material. In order to obtain a higher degree of springiness, the material that has been cold worked after solution heat treatment and work-hardened to some extent is subjected to molding such as pressing and homing, and then precipitation hardening treatment is performed to exhibit high springiness. It's being used. There is also a mill-hardened material that is used after being subjected to solution treatment, followed by appropriate cold working, followed by an appropriate continuous precipitation hardening treatment, and subsequent forming such as pressing and homing. Although superior to bronze and nickel silver, it is inferior to the above standard precipitation materials.

[0004]

These spring materials are used in various parts in response to the development and progress of electronic technology, and in order to miniaturize the parts, the spring materials are made smaller and have higher performance. Accordingly, further improvement in workability and reliability of spring materials is desired. As part of this, various studies have been made and announced regarding the homogenization and miniaturization of the crystal grains that make up the metal material, but there are many problems among them.

This kind of spring material produces the required characteristics by cold working such as rolling and wire drawing, and the elastic strength,
It is designed and manufactured in consideration of the balance between physical property values showing values such as yield point, tensile strength and hardness, and moldability represented by elongation, Erichsen value, bendability and the like.

If the above-mentioned physical property value is increased, the molding workability is lowered accordingly, and if the molding workability is emphasized, the physical property must be lowered. Further, since the rolling and wire drawing in the final step are essentially cold working, the physical property value and the formability are different between the working direction and the vertical direction. That is, a large anisotropy occurs in the characteristic value for processing, and in the recent molding processing that requires high precision and fine performance, even if it can be bent in one direction, it can be bent in the direction perpendicular to it. There are various unfavorable problems such as accidents.

[0007]

Means for Solving the Problems The present inventor conducted research and investigation on the above-mentioned final softened and annealed material and found that an alloy such as phosphor bronze or nickel silver was heated to a recrystallization temperature and rapidly cooled by a conventional method. As a result, the average particle size of the crystal particles is 0.01
It was found that the particle size was as large as mm or more, and the mixed particles were composed of coarse particles and fine particles. Further, the same phenomenon was observed in the precipitation-hardened metal typified by beryllium-copper alloy as well as in the solution-treated material, and a study was conducted to eliminate or reduce this mixed grain state.

A heating furnace for recrystallizing and softening a plate, strip or wire of a relatively hard alloy of this kind, or for carrying out a solution treatment, is a conventional example in which a long product is continuously operated. Then, as shown in FIG. 2, the heating element 2 is arranged so as to surround the furnace core tube 1, the heat-resistant portion 3 is surrounded by the heat-generating portion 2, and the heat-retaining portion 4, the outer casing 5, etc. are surrounded by the heat-generating portion 3. A heating furnace is used.

The metal strip 6 represented by an alloy plate or the like is heated by the furnace core tube in a reducing or inert gas atmosphere. In this heating, since the metal strip is not heated by directly contacting the furnace core tube, the heat efficiency is poor because it is received by convection and radiation from the tube wall. Generally, in order to uniformly heat and soften the material, the heating section The residence time is several minutes to several tens of minutes. When the heating time is long, the growth of crystal grains progresses with the lapse of time and fine particles remain around the coarsened crystal grains due to uneven growth degree, and a state called so-called coarse particles or mixed grains occurs, The spring characteristic value is reduced and at the same time the moldability is reduced.

The present applicant has filed an application for Japanese Patent Application No. 3-339584 "Heat treatment method for metal strips and heating furnace for heating" in order to solve the drawbacks of the conventional heating furnace. The heating section of this heating furnace is surrounded by a housing that accommodates a pair of heated boron nitride plates that are directly heated by a heat-generating book whose source is electric heat, and is filled with a reducing or inert gas atmosphere. . The metal strip is directly pressed by conduction heat while being sandwiched between a pair of boron nitride plates and continuously passes through the furnace. Is this case the metal strip is heated speed since due connexion heat thermal conductivity in direct contact with the boron nitride plate which is directly RECEIVING heat from the heating element of the electric heater is extremely fast
Is uniform. The present inventor has conducted various experiments using this heating furnace and found that a metal strip of this kind is uniformly kept at a desired recrystallization temperature and solution treatment temperature in an extremely short time of 6 to 10 seconds. It was found that it can be continuously increased.

The present invention is based on the results of experiments using the above heating furnace. The thickness or diameter of the copper alloy is 0.5 mm or less, which has been sufficiently work hardened by cold working at a working rate of 50% or more in the intermediate working step. A plate, a strip, or a wire is heated at a recrystallization temperature or higher for 20 seconds or less, and then rapidly cooled at a cooling rate of 200 ° C./second or more to obtain a crystal grain size of 0.01.
It is a method for producing a copper alloy spring material which is uniformly miniaturized to less than or equal to mm.

In the case of a beryllium copper alloy or a titanium copper alloy, the thickness or diameter of 0.5 m is also obtained by cold working with a working rate of 50% or more in the intermediate working step and sufficient work hardening.
A plate-shaped or strip-shaped or wire-precipitation-hardened copper alloy of m or less is heated at a temperature not lower than the solutionizing temperature for 20 seconds or less, and then 20
It is also a method for producing a copper alloy spring material in which the crystal grain size is uniformly refined to 0.01 mm or less by quenching at a cooling rate of 0 ° C./second or more.

[0013] processing hardening by working strain by new crystals are generated grow by heating annealing the work hardened metal material undergoing cold working here at moderate temperatures is reduced. The generation of this new crystal is called recrystallization, and the temperature at that time is called the recrystallization temperature. Further, the recrystallized crystal grains grow with the elapse of heating time, and become coarse particles or mixed particles in which coarse particles and fine particles are mixed. At that time, the heat is directly received from the heating body to promote recrystallization as uniformly as possible, and coarse particles generated with the growth of the crystal grains or to enter the mixed grain state. Moreover, fine crystal grains (0.
005 mm or less). The rapid cooling after heating is performed by a known method in a short time corresponding to the above heating time.

[0014]

1 is a vertical sectional view of a heating furnace for a copper alloy spring material of the present invention, and FIG. 2 is a transverse sectional view of a conventional heating furnace.
In FIG. 1, reference numeral 7 denotes a housing, which is a case of an atmosphere in which a heating main part is housed and filled with a reducing gas or an inert gas. 8 is a cooling chamber formed in the wall of the inlet 14 of the metal strip 13 to be heated, 9 is a pair of heat insulating materials symmetrically provided in the thickness direction of the metal strip 13 passing through, and 11 is provided inside the heat insulating material. A pair of heating elements such as an electric heater is provided, and the pair of boron nitride plates 12 are directly provided inside the heating elements.
The metal strip 13 moves from the carry-in port 14 of the housing to a cooling unit (not shown) through the space between the boron nitride plates and the carry-out port 15. The pair of boron nitride plates presses the passing metal strip by means not shown. Therefore, the thin metal strip 13 that passes through the heating furnace is pinched by the boron nitride plate that has been heated to a predetermined temperature and receives heat immediately by heat conduction, so that the recrystallization temperature or solution treatment occurs within a very short time of 20 seconds or less. It is heated to a temperature higher than the processing temperature.

Table 1 shows phosphor bronze for springs, nickel silver for springs, general phosphor bronze, and beryllium copper alloys having a thickness of 0.2 mm and finally softened and annealed according to the examples of the present invention and the conventional examples. As shown in the table, in the conventional example, the softening annealing requires 1 hour, and the grain size at that time is 0.01 mm to 0.015 mm.
Met. However, according to the method of the present invention, it takes only 6 seconds to complete the softening annealing, and the grain size is only 0.003.
It was only ~ 0.005 mm.

[Table 1]

Table 2 shows the results of rolling the above copper alloy material with a workability of 20% according to the method of the present invention and 30% according to the conventional example. According to this, tensile strength, elongation, bending,
In the spring limit value , the imbalance in the direction perpendicular to the machining direction is improved.

[Table 2]

Further, in the case of the precipitation hardening treatment of the above beryllium copper alloy, it took 2 hours to heat it to 315 ° C. until the precipitation hardening, but according to the method of the present invention, it takes only 30 to 60 minutes. According to the method of the present invention thus treated, the tensile strength is 135 kg / mm ² , the elongation is 8%, and the spring limit value is 9
5 kg / mm ² and conventional tensile strength 130 k
g / mm ² , elongation 2%, spring limit value 90 kg / mm ² compared to the improvement.

[0018]

As described above, according to the present invention, since the metal strip can be heated in an extremely short time, coarse particles and mixed particles are less likely to occur and the conventional diameter is about 0.03 mm to 0.005 mm.
Although it was a mixed grain of 0.005 mm to 0.003 m
m and the grain size is uniform, resulting in an elongation of 4 to 1.5.
It was greatly improved, and the molding processability was extremely good.

The work hardening degree increased by 30% or more as the crystal grain size was reduced, and the physical property values such as tensile strength, spring characteristics, and fatigue resistance were improved by 30% or more. With the precipitation hardening type metal, the processing time for precipitation hardening was shortened by 50% or more, and the strain deformation due to precipitation was greatly reduced. Further, the degree of cold work due to the homogenization and refinement of the crystal grain size can be reduced by 30% or more, and the anisotropy of material properties, which is a problem in the molding process, is greatly improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a heating furnace used in the present invention.

FIG. 2 is a cross-sectional view of a conventional heating furnace.

[Explanation of symbols]

 7 Housing 8 Cooling Chamber 9 Heat Insulating Material 11 Heating Element 12 Boron Nitride Plate 13 Metal Strip 14 Carry In Port 15 Discharge Port

Claims (2)

[Claims] 1. A plate, strip or wire having a thickness or a diameter of 0.5 mm or less of a copper alloy which has been cold worked at a working rate of 50% or more in an intermediate working step and is sufficiently work hardened at a recrystallization temperature of 20 or more. The grain size is 0.01 m by heating within a second and then quenching at a cooling rate of 200 ° C./sec or more.
A method for producing a copper alloy spring material, which comprises uniformly refining to m or less. 2. A precipitation hardening type copper alloy having a thickness or a diameter of 0.5 mm or less, which has been sufficiently work hardened by cold working at a working rate of 50% or more in an intermediate working step, to a solutionizing temperature or more. Heating in 20 seconds at 200 ° C /
The crystal grain size is reduced to 0.
A method for producing a copper alloy spring material, which comprises uniformly miniaturizing the alloy to a size of 01 mm or less.