JPS59118843A - Copper alloy for welded pipe - Google Patents

Abstract

PURPOSE:To obtain a Cu alloy for a welded pipe with superior corrosion resistance and weld crack resistance at the weld zone by adding specified amounts of Zn, P and Si to Cu and by regulating the grain size to a specified value or below by final annealing. CONSTITUTION:A Cu alloy ingot contg. 25-40% Zn, 0.005-0.70% P and 0.005- 1.0% Si is hot rolled, and it is cold rolled while suitably carrying out annealing. The grain size of the Cu alloy of the resulting plate is regulated to <=0.015mm. by final annealing. When the Cu alloy is formed into a pipe by welding, a welded Cu alloy pipe with superior corrosion resistance and weld crack resistance at the weld zone is obtd.

Description

[Detailed Description of the Invention] The present invention provides excellent corrosion resistance of welded parts. This invention relates to a steel alloy for welded pipes that has weld cracking resistance.

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.

Conventional. Lock-seam tubes have been 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 used. However, due to the uniqueness of the welded structure of copper alloy welded pipes, it has been said that the corrosion resistance of the welded part is significantly inferior to that of other parts, and this has been caused by the deterioration of the usage environment in recent years. Taken together, these are major constraints 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. It has a manufacturing drawback in that it is prone to weld cracking. Under these circumstances, the welded parts have excellent corrosion resistance,
In addition, materials with low weld cracking susceptibility are required.

The present invention was developed as a result of research conducted in view of these circumstances. Phosphorus 0.005-0.
70h%, silicon 0. 0 0 5~1. Ow
Copper alloy for welded pipes and zinc 25 to 40 w with improved corrosion resistance, including T-copper and the remainder copper and unavoidable impurities
T factor, phosphorus 0.005-0.70 wt factor, silicon 00
05-1. Developed a copper alloy for welded pipes with improved corrosion resistance and improved weld cracking resistance, which is adjusted so that the grain size is 0.015wn or less in the final annealing, which contains copper and unavoidable impurities. did.

Regarding the alloy components in the copper alloy for welded pipes of the present invention, their effects, addition amounts, and reasons for limiting the crystal grain size are explained. Copper and zinc are the basic materials of the present alloy, so they are important for corrosion resistance, workability, and mechanical strength. It also has excellent thermal conductivity. What is the reason for limiting the amount of zinc added to the above range?

This is because if the zinc content is less than 25 wt%, workability deteriorates, and if the zinc content exceeds 40 wt%, precipitation of β phase is observed in the copper-zinc alloy, resulting in poor corrosion resistance and cold workability. The reason why the amount of phosphorus added is set at 0.005 to 0.70 wt% is that if the amount of phosphorus added is less than 0.005 wt%, no improvement in the corrosion resistance of the welded part will be seen when welding.
Moreover, if the content exceeds 0.70 wt%, corrosion resistance improves, but signs of intergranular corrosion are observed. Addition of silicon to 0
005-1. The reason why it is set as Owt% is that if the amount of silicon added is less than 5wt% of CLOO, no improvement in the corrosion resistance of the welded part will be observed when welding, and no effect of grain refinement will be obtained. Also, the amount of silicon added is 1. This is because if the content exceeds Owt%, the effect of improving corrosion resistance is saturated, the effect of grain refinement is also saturated, and in addition, the manufacturability of the alloy is significantly reduced. Furthermore, the reason why the crystal grain size was limited to 0.015 mm 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. As a result of conducting various investigations into such phenomena, it was discovered that the effect of crystal grain size is large and that such phenomena can be largely suppressed by reducing the crystal grain size. Grain size is 0.01
The reason for limiting it to 5m+ is that the crystal grain size is 0.015+
This is because if it exceeds o+, weld cracking is likely to occur.

Examples Alloys having the various compositions shown in Table 1 were melted, hot rolled and appropriately annealed, then cold rolled to form a 1 m thick plate, and finally annealed at various temperatures. The crystal grain size was adjusted to the one shown in Table 1 and subjected to the test. The welded parts to be subjected to the corrosion resistance test were manufactured by butt T welding of alloys of one thickness each having the various compositions shown in Table 1. Corrosion resistance test was carried out by dissolving 1 yst/l of sodium bicarbonate, 1.6 t/l of sodium sulfate, and 1.6 t/l of sodium chloride in 1 ton of water.
7! of air was blown into the sample, and the sample was immersed in this solution for 240 hours. The maximum dezincification corrosion depth that occurred at that time was measured for the welded part, and the corrosion resistance was evaluated based on this in mR%, and 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 of one thickness and the compositions shown in Table 1 in a ring as shown in Figure 1. This is processed into a shape, immersed in molten metal of the same composition maintained at +50°C, melting point, for 3 seconds, and then taken out and placed in a holding furnace, with the attached metal melted, as shown in Figure 2. Added a shock. The cross section of the deformed ring was observed under a microscope to confirm the presence or absence of intergranular fracture, and this was used to evaluate resistance to weld cracking. The results are shown in Table 6.

As can be seen from Tables 2 and 3, it was found that the alloys of the present invention had excellent corrosion resistance in the welded areas against dezincification corrosion, and the weld cracking resistance was improved.

In other words, the maximum dezincification corrosion depth of the welded parts of the comparative alloys (sample numbers 1 to 5) is 240μ to 325μ, whereas the maximum dezincification corrosion depth of the nine invention alloys (sample numbers 6 to 15) is 240μ to 325μ. It can be seen that the welded portion has a resistance of 43μ to 83μ, which indicates that the dezincing corrosion resistance of the two invention alloys is extremely excellent.

The alloys of the present invention have excellent dezincification corrosion resistance as described above, but those with a grain size of 0.015 mm or less (sample numbers 7 to 10.14) can be welded as shown in Figure 2. In crackability tests.

There is no cracking due to only ductile deformation, and weld cracking is improved. On the other hand, a crystal grain size exceeding 0.015 mm 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 (Unit wt section) Table 2 Table 5

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an alloy pipe with a thickness of one body 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 10+Wn) 2: Free falling body (weight 200gW) 3: Support stand 4: Heating and holding furnace a: Pipe inner diameter (g20) b: Purive outer diameter (c322-) C : Falling distance of falling object 2 (50 mm) Patent applicant: Japan Mining Co., Ltd. Patent attorney (7569) Keishite Namikawa Continued amendment Written by Jθ, March 1982, Commissioner of the Japan Patent Office Kazuo Wakasugi 1, of the case Indication Patent Application No. 226667 No. 2 of 1980, Relationship with the case of the person amending the name of the invention: Copper Alloy for Welded Pipe 5 Patent Applicant 4, Agent Address: 2-10 Toranomon, Minato-ku, Tokyo 105 Phone: 582-2111 Address: 2-10 Toranomon, Minato-ku, Tokyo No. 1 Japan Mining Co., Ltd. 5, date of amendment order Voluntary 8″−°−+6
, Target of amendment "Column for detailed explanation of the invention in the specification" Contents of Z amendment (1) In the fourth line of page 6 of the specification, the phrase "Processed into a ring shape" was replaced with "Processed into a pipe shape." Correct it to J. (2) “Cross section of the ring” on page 6, lines 8 to 9.
(3) In the 4th line of the 7th page of the same page, ``Sample numbers 7 to 10,
Correct 14J to r sample number 7-11, 14J.

Claims (2)

[Claims] (1) Zinc 25-40 wt. Phosphorus 0. 0
05-0.70wt%, silicon 0. 0 O 5
~1. Contains O wt%. Copper alloy for welded pipes consisting of residual steel and unavoidable impurities. (2) The grain size is 0 in the final annealing. Zinc 25-40 wt% adjusted to be 0.15■ or less
, Rin0005~0. 7 0 wt, silicon 0
005-1. Copper alloy for welded pipes, containing 50% by weight and the balance consisting of copper and unavoidable impurities.