JPS59179745A - Copper alloy for welded tube - Google Patents

Abstract

PURPOSE:To manufacture a Cu alloy sheet for a welded tube having superior corrosion resistance and weld crack resistance at the weld zone by subjecting a cold rolled sheet of a Cu alloy contg. Zn, P and Sn to final annealing so as to regulate the grainsize to a specified value. CONSTITUTION:When a tube for a radiator is manufactured by welding, a Cu alloy contg. 25-40% Zn, 0.005-0.070% P and 0.05-1.0% Sn is worked into a sheet by hot rolling and cold rolling, and the cold rolled Cu alloy sheet is subjected to final annealing under conditions which regulate the grain size of the Cu alloy sheet to <=0.015mm.. When the resulting Cu alloy sheet is welded to manufacture a tube for a radiator, a Cu alloy tube having superior corrosion resistance and weld crack resistance at the weld zone can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copper alloy for welded pipes having excellent corrosion resistance and weld cracking resistance in welded parts.

In recent years, thin-walled copper alloy pipes have come to be welded by high-frequency resistance welding or high-frequency induction welding. This tendency is particularly noticeable for tubes used in radiators.

Traditionally, lock-seam tubes were used for radiators, but due to demands for cost reduction and increased production efficiency, welded tubes made by high-frequency resistance welding or high-frequency induction welding are increasingly being adopted. However, copper alloy welded pipes have the disadvantage that the welded portion has significantly lower corrosion resistance than other parts due to the uniqueness of its welded structure. Considering the deterioration of the usage environment in recent years, this is a major restriction on the use of copper alloy welded pipes. Furthermore, when high-frequency induction welding or high-frequency resistance welding is used as a welding method when manufacturing copper alloy welded pipes, there is a manufacturing difficulty in that weld cracking is particularly likely to occur due to the characteristics of the welding method. Under these circumstances, there is a need for materials with excellent corrosion resistance in welded parts and low susceptibility to weld cracking.

Copper alloy for welded pipes containing 0.070%, tin Q, 05-1.0%, residual copper and inevitable impurities, improved corrosion resistance, and zinc 25-40%, phosphorus 0005-007
The final annealing results in a crystal grain size of 0.015-1.0%, tin of 0.05-1.0%, and the remainder consisting of steel and unavoidable impurities.
We have developed a steel alloy for welded pipes with improved corrosion resistance and improved weld cracking resistance, adjusted as follows.

Regarding the alloy components in the steel alloy for welded pipes of the present invention, their effects, addition amounts, and reasons for limiting the crystal grain size will be explained.

Copper and zinc are the basic materials for the alloy of the present invention, and have excellent workability and mechanical strength.

It also has excellent fuel conductivity. The reason why the amount of zinc added is limited to the above range is that when the zinc content is less than 25 parts, workability deteriorates, and when the zinc content exceeds 40 parts, precipitation of β phase in the copper-zinc alloy is observed.

This is because corrosion resistance and cold workability are poor.

The reason why the amount of phosphorus added is 0.005 to 1070% is that if the amount of phosphorus added is less than α005, no improvement in corrosion resistance will be observed, and if it exceeds 0.070%, corrosion resistance will improve, but the two-grain boundary bottom This is because there are signs of eclipse. The reason why the amount of tin added is set to 0.05 to 1.0 is that the amount of tin added is 0.00
This is because if it is less than 5%, no improvement in corrosion resistance, especially in the welded part when welded, will be observed, and if it exceeds a ratio of 1.0, the effect of improving corrosion resistance will be saturated. As described above, the addition of tin adds corrosion resistance to the material, and the addition of tin adds corrosion resistance to the welded part when welded to the material.

Furthermore, the reason why the crystal grain size is limited to 0.015+n+a or less will be described. As a result of investigating the causes of weld cracking caused by high-frequency induction welding or high-frequency resistance welding, the present inventors found that when in contact with molten base metal, the grain boundaries become brittle, and when subjected to a light impact, weld cracking occurs. We found that this occurs. Therefore, as a result of conducting various investigations into these phenomena, the influence of crystal grain size is large.

It has been observed that by reducing the grain size, the susceptibility to such phenomena is significantly reduced.

The reason why the crystal grain size was limited to 15 mm or less.

If the grain size exceeds 0.015 cm, weld cracking force is likely to occur.

Examples P alloys with various compositions shown in Table 1 were melted, hot rolled and appropriately annealed, and then cold rolled to form a plate with a thickness of 1 ml.Finally, annealed at various temperatures, the first The crystal grain size was adjusted to the one shown in the table and used for the test. The welded parts to be subjected to the corrosion resistance test were manufactured by butting together 1fi thick alloys having the various compositions shown in Table 1 and performing T-welding and G-welding. Corrosion resistance test was carried out by adding 1.3 y of sodium bicarbonate to 1 t of water, 1.5 t of sodium sulfate, and 1.5 t of sodium chloride. The solution in which lrf/l was dissolved was maintained at a temperature of 88°C, and the speed was increased at 100 m/min.
7! of air was blown into the sample, and the sample was immersed in this solution for 240 hours. The depth of dezincification corrosion that occurred at that time was measured for the welded part and the base metal part, and the corrosion resistance was evaluated based on this. The results are shown in Table 2.

A test for resistance to weld cracking caused by embrittlement of grain boundaries when in contact with molten base metal was carried out using alloys with a thickness of 1 mm with the compositions shown in Table 1 as shown in Figure 1. Processed into a tube shape, it is immersed for 3 seconds in molten metal of the same composition maintained at +50°C, melting point, and then taken out and placed in a holding furnace, where the attached metal is melted, as shown in Figure 12. Added a shock. The cross section of the deformed wedge was observed under a microscope to confirm the presence or absence of single grain boundary fracture, and this was used to evaluate resistance to weld cracking. The results are shown in Table 3.

In other words, the maximum dezincification corrosion depth in the welds for the comparative alloys (sample numbers 1 to 5) is 270 to 364μ, while the maximum dezincification corrosion depth in the welds for the invention alloys (sample numbers 6 to 20) is 270 to 364μ. It can be seen that the dezincing corrosion resistance of the alloy of the present invention is extremely excellent.

Furthermore, although the alloys of the present invention have excellent dezincification corrosion resistance as described above, those with a grain size of 0.015+++m or less (sample numbers 7 to 14) were simply Only ductile deformation occurs, no cracking occurs, and weld cracking resistance is improved. On the other hand, the grain size is 0.015
If it exceeds m, it is not preferable because it causes grain boundary destruction.

Therefore, the grain size is adjusted depending on the use of the pipe.The alloy of the present invention has extremely excellent properties as a copper alloy for welded pipes.

Table 1 Table 2 Table 3

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an alloy pipe with a thickness of 1 cm 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 with thickness 1■ (length 10m) 2: Free-falling object (weight 200gw) 3: Support stand 4: Heating and holding furnace a: Pipe inner diameter (e2o cod) b: Pipe outer diameter (g22■) C: Falling distance of falling object 2 (50m+) Patent applicant Nippon Mining Co., Ltd. Agent Patent attorney (7569) 'Namiyo Keishi Figure 1 Figure 2 Procedures Amendment Written June 79, 1980 Commissioner of the Patent Office Wakasugi Mr. Kazuo 1. Display of the case Patent Application No. 52752 filed in 1982 2. Name of the invention Steel alloy for welded pipes 5. Relationship to the amendment case Patent applicant address 2-10-1 Toranomon, Minato-ku, Tokyo Name Nippon Mining Co., Ltd. Co., Ltd. Representative: Yoshin Sasaki 4th Director: 105 Phone: 582-2111 Address: 2-10-1-5 Toranomon, Minato-ku, Tokyo Date of amendment order: Voluntary action 6, subject of amendment: ``Detailed explanation of the invention in the specification'' Contents of the amendment (1) Page 3 of the specification, 3rd line from the bottom: “Corrosion resistance is less than”
If the value is less than 1, the corrosion resistance of the welded part will be corrected to 1 when welded. (2) On page 3, line 3 of the specification, the phrase "Improvement of corrosion resistance, especially of the welded parts" will be corrected to "of the welded parts when welded." (3) Delete the following from lines 5 to 8 on page 4 of the specification cylinder: “As stated above, this is added.” Masu. (4) Delete "and base material" on the third line from the bottom of page 5 of the specification. that's all

Claims (2)

[Claims] (1) Zinc 25-40wt1. l) N [1,00
5~α070wt%. A copper alloy for welded pipes containing 05 to 1.0 wt1 of tin, with the remainder being steel and unavoidable impurities. (2) Zinc 25 to 40 wt%, j9 α0 adjusted so that the grain size is 10150 or less in the final annealing.
05~α070wt, tin [LO5~1. (l it
Including chi. Copper alloy for welded pipes free of residual steel and unavoidable impurities.