JPS59179744A - Copper alloy for welded tube - Google Patents

Abstract

PURPOSE:To manufacture a Cu alloy plate 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, Sn and Si to final annealing so as to regulate the grain size 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, 0.05-1.0% Sn and 0.005-1.0% Si is worked into a sheet by hot rolling and cold rolling, and the cold rolled Cu alloy plate is subjected to final annealing under conditions which regulate the grain size of the Cu alloy plate to <=0.015mm.. When the resulting Cu alloy plate 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 remarkable for the tubes used in patent radiators.

Traditionally, 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 adopted. 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. Considering the deterioration of the usage environment in recent years, this has a manufacturing drawback in that weld cracks are likely to occur when high-frequency induction welding or high-frequency resistance welding is used as an inclined welding method when manufacturing copper alloy welded pipes. Under these circumstances, there is a demand for materials that have excellent corrosion resistance in welded areas and have low weld cracking susceptibility.

The present invention was developed as a result of research conducted in view of these circumstances.
Zinc 25-40 wt%, Shino, oos~α070
wt%, tin 0.05-1. Owt%, silicon α00
5-1. Steel alloy for welded pipes with improved corrosion resistance consisting of Owt4, balance steel and unavoidable impurities, zinc 25-40 wt%, phosphorus 0.005-0.07
0 wt section, tin α05~1. Owt%, silicon α00
5-1. A steel alloy for welded pipes with improved corrosion resistance and improved weld cracking resistance, which is adjusted so that the grain size is less than [1L015 days] in the final annealing, which contains copper and unavoidable impurities. developed.

The effects of the alloy components in the copper alloy for welded pipes of the present invention, the amount added, and the reason for limiting the crystal grain size will be explained. Copper and zinc are the basic components of the alloy of the present invention, and have excellent workability, mechanical strength, and thermal conductivity.

The reason why the amount of zinc added was limited to the above school area is that zinc
If the zinc content is less than 40 wt%, the processability will be poor, and if the zinc content is less than 40 wt%,
This is because if it exceeds wt%, precipitation of β phase in the copper-zinc alloy is observed, resulting in poor corrosion resistance and cold workability. The reason why the amount of phosphorus added is set to 1005 to 0.070 wt% is that if the amount of phosphorus added is less than 5 wt% Q, OO, no improvement in corrosion resistance is observed.

Moreover, if the content exceeds 0.070 wt%, corrosion resistance improves, but signs of intergranular corrosion are seen. The amount of tin added is 0.05 to 1. The reason why it is set as Owt% is that if the amount of tin added is less than 0.05 wt%, no improvement in the corrosion resistance of the welded part will be seen when welding, and if it exceeds 1.0wt%, the effect of improving corrosion resistance will be saturated. be. The reason why the amount of silicon added is set to a005 to t Owt% is that if the amount of silicon added is less than o, o o s wt%, no improvement in the corrosion resistance of the welded part will be observed, and if t Owt96 is This is because if it exceeds this, the effect of improving corrosion resistance will be saturated. As mentioned above, the addition of phosphorus adds corrosion resistance to the material, and the addition of tin and silicon adds corrosion resistance to the welded part when welded to the material. Furthermore, the reason why the crystal grain size was limited to 0.015 m or less will be described. As a result of investigating the cause of weld cracking caused by high-frequency induction welding or high-frequency resistance welding, the present inventors found that grain boundaries become brittle when in contact with molten base metal, and weld cracking occurs when subjected to a light impact. I found out that.

As a result of conducting various investigations into such phenomena, it was found that the influence of the crystal grain size is large and that decreasing the crystal grain size significantly reduces the sensitivity to such phenomena compared to K.

The reason why the grain size is limited to 0.015 m or less is that if the grain size exceeds α015, weld cracking is likely to occur.

Examples Table 1 Alloys with various compositions shown in Table 1 were melted, hot rolled, and cold rolled with appropriate annealing to form plates of 1-thickness 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 1 inch thick alloys having the various compositions shown in Table 1.

Corrosion resistance test was carried out by adding 1.5t of sodium bicarbonate to 1L of distilled water and adding sodium sulfate to 1L of distilled water. A solution containing 1.6 t/l of sodium chloride and St/ was maintained at a temperature of 88°C, and the rate was 100-1/min.
Air was blown into the sample, and the sample was immersed in the solution for 240 hours. The maximum dezincification corrosion depth 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 of 1 mm thickness with various compositions shown in Table 1 in pipes as shown in Figure 1. This was 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. Shocks were applied as shown. The cross section of the deformed pipe was then observed under a microscope.

The presence or absence of intergranular fracture was confirmed, and resistance to weld cracking was evaluated based on this. The results are illustrated in Table 3.

Δ Excellent resistance to dezincification corrosion of welds It was found that the weld cracking resistance was improved.

In other words, the maximum dezincification corrosion depth of the welded part of the comparative alloys (sample numbers 1 to 5) was 260 to 384μ, whereas
In the alloys of the present invention (sample numbers 6 to 20), the maximum dezincification corrosion depth was 52 to 97μ at the welded portion, indicating that the dezincification corrosion resistance of the two inventive alloys was extremely excellent.

In addition, although the present invention alloys have excellent dezincification corrosion resistance as described above, those with crystal grain sizes of 0.015 mm or less (sample numbers 7 to 14) showed no resistance in the weld cracking test shown in Fig. 2. There is no cracking due to the simple ductile deformation, and the weld crackability is improved. On the contrary, the grain size is Q, Q15w
A K exceeding n 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 steel alloy for welded pipes.

Table 1 (Unit wt section) Table 2 Table 6

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an alloy pipe with a thickness of 1 strip used for a weld cracking resistance test, and FIG. 2 is a schematic explanatory diagram of a weld cracking resistance testing apparatus. 1: Alloy pipe with thickness 1fi (length 10 gourd) 2: Free falling body (weight 200gw) 3: Support stand 4: Heating and holding furnace a: Pipe inner diameter (g20fi) b: Pipe outer diameter (■221!m1) ) C: Falling distance of falling object 2 (50 scales) Patent applicant Nippon Mining Co., Ltd. Agent Patent attorney (7569) Keishi Junyo Figure 1 Figure 2 Procedures Amendment Written by the Commissioner of the Japan Patent Office June 72, 1982 Kazuo Wakasugi 1, Indication of the case Patent Application No. 52751 of 1980, Name of the invention Copper Alloy for Welded Pipe 5 Relationship to the Amendment Case Patent Applicant Address 2-10-1 Toranomon, Minato-ku, Tokyo Name Japan Acupuncture Co., Ltd. Representative Yoshin Sasaki 4, Agent 105 Telephone 582-2111 Address 2-10-1 Toranomon, Minato-ku, Tokyo & Subject of amendment "Detailed description of the invention in the specification" l Contents of the amendment (1) On the bottom line of page 3 of the specification, the phrase ``Corrosion resistance'' will be corrected to ``Corrosion resistance of welded parts when welded.'' (2) Delete the statement “The above description is added as described above” in lines 11 to 14 on page 4 of the specification cylinder. Masu. (3) In the 3rd line of page 6 of the specification tube, the words "welded part and base metal part" will be corrected to "welded part". that's all

Claims (1)

[Claims] (1) Zinc 25-40wt%, #) (LO05
~an 70 wt%. Tin 0.05-1. Owt staff, silicon 0005~1. O
Copper alloy for welded pipes, including wt%, with the balance being steel and unavoidable impurities. Zinc 25-40 wt., phosphorus 0.0.
OO5~[lLO70wt, tin 0.05~1,0vr
tq6r silicon 0.005-1. A steel alloy for welded pipes, containing 0.0% by weight, with the balance consisting of steel and unavoidable impurities.