JPH11264039A - Brass material containing tin and excellent in mechanical property, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a brass material contg. Sn and having excellent mechanical characteristics. SOLUTION: This brass material contains, by weight, 28 to 36% Zn and 0.1 to 5.0% Sn, in which (100-(the Zn content %)/(100+(the Sn content %) is regulated to >=0.640, and has the ratio of the minimum bend radius in which wrinkles are not generated, tensile strength and elongation are equal to those of the conventional Sn-nonadded copper or above. In this producing method, a brass ingot having the above compsn. is subjected to working immediately before final annealing at a working ratio of >=60%, is subjected to final annealing at 350 to 550 deg.C and is subjected to finish working at a working ratio of 5 to 40%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brass material containing Sn which is excellent in mechanical properties, specifically, tensile strength, elongation and bending workability, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a material for a terminal or a material for a connector, a brass strip excellent in formability (bending workability), spring characteristics and conductivity has been press-formed. The brass strip is manufactured by performing finishing and working after performing working and annealing on the brass ingot. The manufactured brass strip is plated with Sn.

[0003] It is extremely important to reuse a brass scrap material to which Sn plating has been applied (hereinafter referred to as scrap material) from the viewpoint of effective use of resources.

If the scrap material is reused as it is, it is inevitable that Sn is mixed in the brass strip produced by reuse. However, the brass strip component standard is JI
Table 1 shows one type of brass strip, which is specified in SH8821 and is a typical example. Table 1 does not specify the Sn content. Therefore, although the Sn content is desirably a small amount in principle, it is actually left to the manufacturer in consideration of problems in actual production technology.

[0005]

[Table 1]

Further, brass containing a large amount of Sn added for the purpose of improving corrosion resistance is known, and it is conceivable to reuse scrap material as a raw material for producing this Sn-added brass strip. However, Sn-added brass is inferior in mechanical properties such as elongation, bending workability and cold workability required for terminal materials and connector materials. We cannot expect much.

The mechanical properties of Sn-added brass are inferior because
(1) The added Sn causes a β phase to be generated during annealing.
(2) This is because the β phase is transformed into the γ phase depending on the annealing conditions. When the β phase is formed to form a (α + β) two-phase structure, the tensile strength increases, but the elongation and bending workability deteriorate. Further, since the γ phase significantly deteriorates the cold workability, it may be impossible to work to a strip shape.

In order to reuse the scrap material, the following method for removing Sn has been conventionally performed.

(1) Oxygen-containing gas is blown into a molten metal in which a scrap material is dissolved to perform oxidative refining, and float Sn as tin oxide.

(2) The scrap material is heated in an oxygen gas atmosphere to generate a composite oxide of Sn and Zn in the Sn plating layer.

However, in the above method (1), at the same time as Sn floats as tin oxide, Zn is also partially oxidized and floats as zinc oxide to be removed. Will drop. Further, in the method (2), oxygen diffuses into the brass base material coated on the Sn plating layer and abnormally generates zinc oxide, so that it is impossible to reuse the scrap material. .

[0012]

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to include Sn so that scrap materials can be reused for effective use of resources, and excellent mechanical properties.
More specifically, it is an object of the present invention to provide a brass material having excellent tensile strength, elongation and bending workability and suitable for a terminal material, a connector material, and the like, and a method for producing the same.

[0013]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies. As a result, even if Sn is positively contained as an additive element, (1) the composition ranges of Zn and Sn are limited. By doing so, the formation of β phase can be suppressed and an α single phase structure can be obtained. (2) By limiting the processing conditions and annealing conditions, a uniform fine structure and good bending workability can be obtained. (3) It has been found that, according to the above (1) and (2), excellent mechanical properties equal to or higher than that of a conventional brass material can be obtained.

That is, in the first invention, Zn is 28-36.
Wherein wt%, and the Sn 0.1 to 5.0 wt%, the balance being Cu and inevitable impurities, Zn content (wt%) and C _Zn, and Sn content (wt%) and C _Sn When (100−C _Zn ) / (100 + C _Sn ) ≧ 0.640
And the tensile strength is 550 MPa or more,
The brass material has excellent mechanical properties including Sn having an elongation of 6% or more and a minimum bending radius ratio at which no wrinkles occur (hereinafter, referred to as a minimum bending radius ratio) of 0.95 or less. here,
The minimum bending radius ratio means the ratio (R / t) between the minimum bending axis radius of curvature (R) at which no wrinkles occur and the brass strip thickness (t), and indicates the ease of wrinkling (ratio of the ratio). The higher the value, the easier the wrinkles).

[0015] The second invention is a method for producing a brass material by performing working and annealing on a brass ingot, and (1) the ingot is made of Zn.
8-36 include weight% and Sn 0.1 to 5.0 wt%, the balance being Cu and inevitable impurities, the C _Zn
And the above C _Sn are (100−C _Zn ) / (100 + C _Sn ) ≧
The relationship of 0.640 is satisfied, (2) the working rate of the working immediately before final annealing is 60% or more, (3) the annealing temperature of the final annealing is 350 to 550 ° C., (4) the finishing processing A method for producing a brass material containing Sn and having excellent mechanical properties, characterized in that the working ratio is 5 to 40%.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION (1) First invention The brass material containing Sn of the first invention and having excellent mechanical properties is β
The formation of a phase is suppressed to form an α single phase structure. Therefore, the Zn content is 28 to 36% by weight, the Sn content is 0.1 to 5.0% by weight, and the C _Zn and the C
_Sn and (100−C _Zn ) / (100 + C _Sn ) ≧ 0.64
0 must be satisfied. If the Sn content is less than 0.1% by weight, the reuse rate of the scrap material decreases. On the other hand, if the Sn content exceeds 5.0% by weight,
The value of (100−C _Zn ) / (100 + C _Sn ) is 0.640
If it is less than 3, the β phase is likely to be generated, and the elongation is 6%.
Or the minimum bending radius ratio tends to exceed 0.95.

Further, the brass material of the first invention has a uniform and fine recrystallized grain structure in the final annealing, and then has good bending workability in the finishing work.
It has excellent mechanical properties equal to or better than that of the additive-free brass material. That is, the tensile strength is 550 MPa or more, the elongation is 6% or more, and the minimum bending radius ratio is 0.95 or less.

(2) Second Invention The method for producing a brass material containing Sn and having excellent mechanical properties according to the second invention is one method for producing the brass material according to the first invention.

In the method for producing a brass material according to the second invention, in order to produce a brass material from a brass ingot, the brass ingot is worked to a desired working rate. As the processing proceeds, the workability decreases. If a desired processing rate is obtained without hindering the processing, finishing processing is performed after annealing. If the desired processing rate cannot be obtained by one processing, the second processing is performed after annealing to improve the workability. In this way, finishing is performed after the processing and annealing are repeated. At this time, the processing rate of the processing immediately before the final annealing, the annealing temperature of the final annealing, and the processing rate of the finishing processing are important.

The processing just before the final annealing is performed in order to obtain a uniform and fine recrystallized grain structure in the final annealing. The processing rate of this processing is 60% or more. When the working ratio is less than 60%, recrystallization only occurs in the final annealing without recrystallization, or even if recrystallization occurs, recrystallized grains do not become fine but have a mixed grain structure.

The final annealing is performed to obtain a uniform and fine recrystallized grain structure as described above. The final annealing temperature is 350 ℃
If it is lower than 550 ° C., recrystallization does not occur. On the other hand, if it exceeds 550 ° C., coarsening of crystal grains (secondary recrystallization) becomes remarkable.

The processing rate of the finishing processing is 5 to 40%. Finishing is performed to obtain good bending workability. If the processing rate is less than 5%, the tensile strength is 550MP.
a. On the other hand, if it exceeds 40%, the elongation is reduced and the ductility is reduced by the addition of Sn as compared with the Sn-free material, so that the bending workability is significantly deteriorated.

[0023]

EXAMPLES Examples 1 to 6 and Comparative Examples 1 to 5
In order to obtain the brass composition shown in (1), a scrap material and a raw material for replenishing components were blended and dissolved. During the dissolution, the molten metal was analyzed, and if there was any deviation from the brass composition shown in Table 2, a component replenishing raw material was further added to adjust the components.

The molten metal whose components had been adjusted was cast in a horizontal continuous casting machine to form a coiled ingot having a thickness of 16 mm and a width of 655 mm, and cooled to room temperature.

After the coil-shaped ingot is chamfered to a thickness of 14 mm, primary cold rolling, primary annealing, pickling, secondary cold rolling,
Next annealing and finish rolling were performed in this order to produce a brass strip.

Here, Examples 1 to 6 and Comparative Examples 1, 2, and 4
In the first cold rolling, the thickness is from 14 mm to 2.5 m
m, primary annealing for 4 hours in the air at 500 ° C., pickling using sulfuric acid, and secondary cold rolling to a thickness of 2.5 m.
m to 0.3 mm (rolling ratio 88%), and secondary annealing was performed at 500 ° C. (Examples 1 to 6, Comparative Examples 1 and 2) and 60 ° C.
Continuous annealing was performed at 0 ° C. (Comparative Example 4), and finish rolling was performed so that the final thickness was 0.25 mm (rolling ratio 20%).

In Comparative Example 3, the thickness of the first cold rolling was set to 14 mm to 0.5 mm, and the first annealing was performed by 5 mm.
4 hours in air at 00 ° C, pickling using sulfuric acid, secondary cold rolling with thickness from 0.5mm to 0.3mm (rolling ratio 40%), secondary annealing at 500 ° C continuously Annealing and finish rolling resulted in a final thickness of 0.25 mm (rolling ratio 20%).

Further, in Comparative Example 5, the primary cold rolling had a thickness of 14 mm to 3.8 mm, the primary annealing was at 500 ° C. for 4 hours, and the pickling was sulfuric acid.
The next cold rolling has a thickness of 3.8 mm to 0.45 mm (rolling ratio 88%), the secondary annealing is continuous annealing at 500 ° C., and the finish rolling has a final thickness of 0.25 mm.
(Rolling ratio 45%).

Table 2 shows the main production conditions among these production conditions.
Shown in

The brass strip thus prepared was subjected to a tensile test and 90 °
A W bending test was performed to evaluate mechanical properties. The tensile strength and elongation were measured by a tensile test, and the minimum bending radius ratio was measured by a 90 ° W bending test. The minimum bending radius ratio is measured when the brass strip is set so that the rolling direction of the brass strip is perpendicular to the axis of the bending axis (Good way).
When the above is set to be parallel (Bad wa
y).

Table 3 shows the measurement results.

[Reference Examples 1 and 2] In order to prepare conventional 70/30 brass strips containing no Sn (Reference Example 1) and 65/35 brass strips (Reference Example 2), these brass were dissolved. went.
Since the molten metal was cast on a horizontal continuous casting machine, the same tests as in Example 1 were conducted thereafter.

Table 2 shows the main conditions for forming the strip, and Table 3 shows the measurement results.
Shown in

[0034]

[Table 2]

[0035]

[Table 3]

Examples 1 to 3 are reference examples 1 which are conventional brass.
(70/30 brass), and the tensile strength of Examples 4 to 6 is higher than that of Reference Example 2 (65/35 brass).
Bending workability, which is important when used as a material for terminals or a material for connectors, is comparable.

In Comparative Example 1, since the amount of Sn added was too small, the mechanical properties were almost the same as those in Reference Example 2, but the reuse rate of the scrap material was low.

In Comparative Example 2, (100-C _Zn ) / (100
+ C _Sn ) ≧ 0.64, so that although tensile strength is excellent, elongation and bending workability are inferior.

Comparative Examples 3, 4 and 5 are all inferior in bending workability due to insufficient secondary rolling reduction, excessively high secondary annealing temperature, and excessive finish rolling reduction, respectively.

[0040]

As described above, the brass material containing Sn of the present invention and having excellent mechanical properties and the method for producing the same have excellent tensile strength, elongation and bending workability, and are suitable for terminal materials and connector materials. It can be seen that a brass material suitable for such purposes can be provided by reusing the scrap material, that is, effectively using resources and at low cost.

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Claims (5)

[Claims] 1. A Zn of 28 to 36 wt%, and Sn comprises 0.1 to 5.0 wt%, the balance being Cu and inevitable impurities, Zn content (wt%) and C _Zn, Sn
When the content (% by weight) is C _Sn , (100-C _Zn )
/ (100 + C _Sn ) ≧ 0.640, brass excellent in mechanical properties including Sn having a tensile strength of 550 MPa or more, an elongation of 6% or more, and a minimum bending radius ratio of 0.95 or less Wood. 2. A method for producing a brass material by performing working and annealing on a brass ingot, and then performing a finishing work on the brass ingot, wherein (1) the ingot contains 28 to 36% by weight of Zn and Sn hints 0.1-5.0 wt%, the balance being Cu and inevitable impurities, Zn content (wt%) C _Zn
When the Sn content (% by weight) is C _Sn , (10
0-C _Zn ) / (100 + C _Sn ) ≧ 0.640. (2) The working ratio of the working immediately before final annealing is 60%.
As described above, (3) the annealing temperature of the final annealing is set to 350 to 55
0 ° C. (4) The finishing rate of the finishing process is 5 to 40%
A method for producing a brass material containing Sn and having excellent mechanical properties. 3. The method for producing a brass material containing Sn and having excellent mechanical properties according to claim 2, wherein the brass ingot is produced using a brass scrap material to which Sn plating has been applied as a melting raw material. 4. A brass material containing Sn produced by the method according to claim 2 and having excellent mechanical properties. 5. A brass material containing Sn according to claim 1 or 4 and having excellent mechanical properties, which is used for a terminal or a connector.