JPH03170646A - Manufacture of copper alloy having fine crystalline grains as well as low strength - Google Patents

Abstract

PURPOSE:To obtain the brass-series copper alloy having low strength and excellent in formability as well as excellent in stress corrosion cracking resistance, weld cracking resistance and solderability by subjecting a brass-series copper alloy to cold rolling at a specified amt. or above of draft and thereafter refining its grain size into specified value or below by final annealing. CONSTITUTION:A brass-series copper alloy contg., by weight, 25 to 45% Zn or furthermore contg., at need, total 0.005 to 2.0% of one or >=2 kinds among the group constituted of Pb, Fe, Sn, Al, Mn, Ni, P, As, Te, Cr, Co, Zr, V, Be, Cd, Si, B, In, Ti, Mg, Hf and Ge is cold-rolled at >=75% draft and is thereafter subjected to final annealing to regulate its grain size to <=0.015mm. Or, the alloy is furthermore subjected to 1 to 15% cold rolling to improve its solderability. The brass-series copper alloy having reduced cracks in the weld zone, excellent in stress corrosion cracking resistance, furthermore free from the increase of strength in accordance with the refining of its crystallinity and excellent in formability can be obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to radiators used in automobiles, etc. as materials for heat exchangers such as condensers, feed water heaters, distillers, coolers, and water supply devices. The present invention relates to a method for producing brass and brass-based copper alloys that are optimal as materials for tanks, chives, fins, etc.

[Prior Art] As a copper alloy material conventionally used for radiators, bitter copper is known, which is composed of 5% by weight of Cu[i] and 35% by weight of Zn. However, the radiator is in constant contact with the cooling medium, and while the car is running, it is exposed to exhaust gas, salt-containing atmosphere, and SO2 gas from factory exhaust, and these corrosive environments cause brass to undergo stress corrosion. Cracking and dezincification corrosion occur, which has become a major problem. Furthermore, in recent years, copper alloy welded tubes made by high-frequency induction welding or high-frequency resistance welding have been adopted, especially for radiator tubes, in place of the conventional lock-seamed tubes made by caulking, in order to reduce costs and improve production efficiency. It's here.

However, copper alloy welded pipes have the disadvantage that the welded part has significantly lower corrosion resistance than other parts due to the uniqueness of its welded structure.

[Problems to be Solved by the Invention] The present inventors have conducted various studies on the above-mentioned problems, and have found that making the grain size finer reduces cracking in welds and improves corrosion resistance, especially stress corrosion cracking resistance. It has become clear that this is an effective method for improving However, making the crystal grains of copper alloys finer improves their strength, but this has led to problems such as the load on tubes, fins, etc. during forming, the accumulation of mold wear, and a decrease in formability. .

Under these circumstances, the present invention aims to provide a material with fine crystal grains and excellent formability that does not suffer from an improvement in strength due to the refinement of the crystal grains.

[Means for Solving the Problems] The present invention provides Zn: 25 to 45% by weight or further Pbx
Fe. SnSAl, Mn, Nix PsA s s
T e s C r % C o 1Z r SV s
B e sCd, St, BS In, TiSMg, H
f, one or two or more from the group consisting of Ge at 0.005
After cold rolling an alloy material containing ~2.0% by weight and the balance consisting of Cu and unavoidable impurities at a working degree of 75% or more, the grain size is reduced to 0.0% by final annealing. A method for producing brass or brass-based copper alloy with fine crystal grains and low strength, characterized by having a crystal grain size of 5 mm or less, and an alloy material having the above composition.
After cold rolling with a working degree of % or more, the grain size is 0 in the final annealing.
．． After adjusting it so that it is 0.015 mm or less, further l-1
This manufacturing method is characterized by performing 5% cold rolling.

The reasons for limiting the alloy components and other structural requirements constituting the present invention will be explained.

Cu and Zn are the basic materials of the alloy constituting the present invention, and have excellent workability and mechanical strength, as well as excellent thermal conductivity. The reason why the Zn content is set to 25 to 45% by weight is that if the Zn content is less than 25% by weight, workability or solderability will deteriorate, but if it exceeds 45% by weight, the Cu-Zn alloy will This is because the precipitation of the β phase becomes significant, resulting in poor corrosion resistance and cold workability.

P b % F e SS n s A 1 , M n
SN is P sAs, TeS Crs Co, Z
r. VS Be, Cd, SiS B% InSTi,
0 of one or two or more from the group consisting of MgSHf, Ge
．． The reason for containing 0.005 to 2.0% by weight is to improve the corrosion resistance of the material and welded parts.
This is because even if the content exceeds %, the effect will be saturated and the processability will deteriorate.

Furthermore, the reason why the working degree of cold rolling before final annealing is set to 75% or more is to reduce the strength after final annealing 1=11 and improve formability, and if the working degree is less than 75%, this effect will be reduced. This is because it is not recognized.

The reason for reducing the crystal grain size to 0.015 mm or less by final annealing is that reducing the crystal grain size is effective in improving corrosion resistance, especially stress corrosion cracking resistance, and that welding caused by high-frequency induction welding or high-frequency resistance welding Cracking is caused by grain boundaries becoming brittle when in contact with molten base metal, but by reducing the grain size it is possible to suppress this phenomenon in Daifuku. . This is because if the grain size exceeds 0.015+lla+, weld cracking is likely to occur and deterioration of stress corrosion cracking resistance is observed.

In the present invention, the reason why cold rolling is performed at a working degree of 1 to 15% after final annealing is to improve solderability by performing cold rolling, but the working degree is 1%. If it is less than that, no improvement in solderability is observed, and
This is because if it exceeds 15%, the mechanical strength increases and the moldability during processing with a radiator tube deteriorates.

[Example] Next, embodiments of the present invention will be described.

Alloys having various compositions shown in Table 1 were melted and cast in a high-frequency melting furnace in air or an inert atmosphere, and after hot rolling, cold rolling and annealing were repeated to obtain intermediate thickness materials. This is 5
After annealing at 00° C. for 30 to 60 minutes, the sheets were cold rolled at the working degree shown in Table 1 to form a plate having a thickness of 0.8 slw. This was further heat treated at 500°C for 60 to 900 seconds to adjust the crystal grain size shown in Table 1. Further, some of the samples were further cold rolled.

As an evaluation of such samples, Table 1 shows the strength of the material, Erichsen value, stress corrosion cracking test results, resistance to weld cracking, and solderability.

The stress corrosion cracking test was conducted using a JIS conical cup test tool type 17 cylindrical flat bottom punch with a drawing ratio of 2.
0 cup was made and exposed to an ammonia atmosphere of pHlO made from sodium hydroxide and ammonium chloride, and the time until cracking started was measured.

A test for resistance to weld cracking was carried out by processing the alloys shown in Table 1 into a vibrator 1 shape as shown in Fig. 1 (inner diameter a: 20 mm, outer diameter b: 2211 mm).
Length: 10mm), melting point of the same composition +50℃
The pipe 1 is immersed for 3 seconds in the molten metal held in the heating and holding furnace 4, and then taken out and placed in the holding furnace with the attached metal melted, as shown in FIG. 3, and a free-falling object weighing 200 gw was dropped at a falling distance c: 50 tm to apply an impact. The cross section of the vibrator deformed at that time was observed under a microscope to confirm the presence or absence of intergranular fracture, and this was used to evaluate the resistance to melt cracking.

Also, the solderability is 80IImm in diameter and BOIFll in height.
In a cylindrical crucible, a solder consisting of 20% Sn and 80% Pb was heated to 230°C to form a molten metal, and a sample (width lOII 1% length 50av with a clean surface) was poured into the melt at a descending speed of 25a+m/sec. The time required for the buoyant force exerted on the sample from the solder bath and the force drawn into the solder bath to reach equilibrium was measured and evaluated.

As is clear from Table 1, the alloy of the present invention obtained satisfactory results in all properties, but the comparative alloy No.
Nos. 17 to 24 are alloy Nos. 17 to 24 of the present invention, respectively. 1, 2, 4, 8
．． Although the alloy composition and grain size are the same as 7.8 and 11.12, the degree of work before final annealing is lower, so the tensile strength is higher and the Erichsen value is lower than the invention alloy. Also, comparative alloy No. 25 to 29 are alloy Nos. 25 to 29 of the present invention, respectively. l.
Although the alloy composition and degree of work before final annealing are the same as those of 2, 5, and 10.15, the grain size is larger, so the stress corrosion cracking resistance is poorer than that of the present alloy, and the grain boundary was observed in the weld cracking test. The weld cracking resistance is poor. Also, comparative alloy No. Samples Nos. 30 and 31 have poor moldability and solderability due to their low Zn content. Furthermore, the invention alloy No. ．．
9.12 and comparative alloy 24 are invention alloy No. 2.8.
11 and comparative alloy No. 23, the solderability is improved by cold rolling the skin bath.

[Effects of the Invention] As detailed above, the present invention has low strength and excellent formability, and also has stress corrosion cracking resistance, weld cracking resistance, and solderability, and is suitable for use in heat exchangers, especially heat exchangers. We can provide the best material for copper alloys for radiator tanks, plates, and tubes.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an alloy pipe with a thickness of 0.8 mm used in the weld cracking resistance test, and FIG. 2 is a schematic explanatory diagram of the weld cracking resistance testing apparatus. 1... Alloy pipe, 2... Free falling body, 3... Support stand, 4... Heating and holding furnace.

Claims (4)

[Claims] (1) An alloy material consisting of Zn: 25 to 45% by weight, balance Cu and unavoidable impurities is cold rolled at a working degree of 75% or more, and then final annealed to reduce the grain size to 0.015mm or less. A method for producing brass with fine crystal grains and low strength. (2) Zn: 25 to 45% by weight and Pb, Fe, Sn,
Al, Mn, Ni, P, As, Te, Cr, Co, Zr
, V, Be, Cd, Si, B, In, Ti, Mg, Hf, Ge, 0.005 to 2.0% by weight of one or more from the group consisting of Ge, and the balance consists of Cu and inevitable impurities. After cold rolling the alloy material with a working degree of 75% or more, the grain size is reduced to 0.015 by final annealing.
A method for producing a brass-based copper alloy having fine crystal grains and having low strength, characterized in that the grain size is less than mm. (3) After cold rolling an alloy material consisting of Zn: 25 to 45% by weight, balance Cu and unavoidable impurities at a working degree of 75% or more, the grain size was adjusted to 0.015 mm or less by final annealing. A method for producing brass having fine crystal grains and low strength, characterized in that the method further comprises cold rolling by 1 to 15%. (4) Zn: 25 to 45% by weight and Pb, Fe, Sn,
Al, Mn, Ni, P, As, Te, Cr, Co, Zr
, V, Be, Cd, Si, B, In, Ti, Mg, Hf, Ge, 0.005 to 2.0% by weight of one or more from the group consisting of Ge, and the balance consists of Cu and inevitable impurities. After cold rolling the alloy material with a working degree of 75% or more, the grain size is 0.015 mm in the final annealing.
A method for producing a brass-based copper alloy with fine crystal grains and low strength, which comprises adjusting the following properties and then cold-rolling the alloy by 1 to 15%.