JPS5835249B2 - Cu alloy for seamless pipe manufacturing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Cu alloy suitable for use in manufacturing seamless pipes, which are components of heat exchangers and the like.

Generally, seamless pipes are used as structural components in heat exchangers such as room coolers, air conditioners, and refrigerators.
The seamless pipe has the following properties: (a) Cold drawing processability during pipe manufacturing; (b)
When assembling, bending workability and brazing are easy, (C)
When used, properties such as heat exchangeability, that is, thermal conductivity, are required, so phosphorus-deoxidized copper or oxygen-free copper is used as the material.

On the other hand, in recent years, there has been a strong demand for the heat exchangers to be smaller and more compact and to reduce costs. Although attention has been focused on reducing the thickness of seamless pipes, there is a problem in that thin seamless pipes made of phosphorus-deoxidized copper or oxygen-free copper cannot have the desired strength.

Therefore, a seamless pipe made of a Cu alloy whose strength has been improved by adding Fe to phosphorus-deoxidized copper has been proposed, and it is true that the addition of Fe makes the seamless pipe have the desired strength. However, on the other hand, due to the addition of Fe, (1) brazing properties are inferior to the above-mentioned seamless pipe made of phosphorus-deoxidized copper, (2) the crystal grains in the brazing part become coarser, and as a result, brazing (3) elongation is 40
% or more, and as a result, new problems arise such as the inability to perform bending work satisfactorily during assembly, which is not desirable from the standpoints of versatility and economy.

From the above-mentioned viewpoints, the present inventors have developed a seamless pipe that has high strength and sufficient elongation, and has no strength loss in its heat-affected zone even when brazed, and is particularly suitable for use in heat exchangers. In order to obtain a Cu alloy used in the production of
: 100-260 p, p, m, 02: 3-3
A Cu alloy with a composition containing 0p, p, m-1 and substantially no other alloy components has excellent cold resistance, which is especially required for manufacturing seamless pipes that are components of heat exchangers. It not only has properties such as drawing workability, bending workability, pressure resistance, and heat exchangeability, but also has sufficient strength and excellent brazing properties to cope with thinner walls that reduce costs, and also has excellent heat exchangeability. They found that it has sufficient elongation to alleviate constraints when designing containers.

This invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained.

■ Fe The Fe component has the effect of refining crystal grains and improving tensile strength and pressure resistance.
If the amount is less than 200 p, p, m, the desired effect cannot be obtained.

If it is contained above, the strength will increase too much and it will not be possible to secure an elongation of 40% or more, resulting in a decrease in drawing workability during pipe manufacturing and a decrease in bending workability during assembly. Since cracks may occur on the outside of the bend and wrinkles may occur on the inside, the content should be reduced to 50~2.
It was determined to be less than 00 p-p-m-.

■ P The P component refines crystal grains, improves strength and pressure resistance in coexistence with Fe, improves the drawing workability required during pipe manufacturing, and also improves the properties during brazing during assembly. It has the effect of preventing the strength reduction of the heat-affected zone, but if the content is less than 100 p, p, m, the desired effect cannot be obtained; on the other hand, 260 p, p, m
If the content exceeds 100 to 260p, p, m,
It was determined that

■ There is a close relationship between the 02 content and seamless pipe characteristics, and when the 02 content is reduced to 30p, p, m or less, the effects of the Fe and P components mentioned above become noticeable as a synergistic effect. Therefore, high strength and brazing, which can be made thinner, can prevent crystal grain coarsening or embrittlement in the heat affected zone, but if the content is less than 3p, p, m, However, it is technically difficult to
If the content exceeds , the above effect cannot be secured, so the content should be set at 3 to 30 p, p
, m.

Next, the Cu alloy of the present invention will be explained using Examples while comparing it with a comparative Cu alloy and a conventional Cu alloy.

Cu alloys 1 to 6 of the present invention and comparative Cu alloys having the compositions shown in Table 1 were prepared according to the usual melting and casting method.
Alloys 1-5 and conventional Cu alloys 1-3 were produced.

In addition, in comparative Cu alloys 1 to 5 in Table 1, /161
The Fe content is 1,45 is the Fe and P content, S3
, 4 are out of the scope of the present invention in terms of P content, and /i65 is out of the scope of the present invention in 02 content.

Moreover, in conventional Cu alloys 1 to 3 in Table 1, the 02 content is outside the range of the present invention.

Next, the above-mentioned present invention Cu alloys 1 to 6 and comparative Cu alloys 1 to
Seamless tubes with an outer diameter of 9.25 mm and a wall thickness of 0.35 mm were manufactured from 5 and conventional Cu alloys 1 to 3 by ordinary cold drawing.

The resulting seamless pipe (normal part), and the brazing of this seamless pipe using phosphor copper solder at a temperature of 730°C, are determined by the mechanical properties of the heat affected zone, pressure resistance, etc. The strength, grain size, and time required for stress corrosion cracking to occur in a stress corrosion cracking test in an ammonia atmosphere were measured, and the results are shown in Table 2.

As is clear from the results shown in Table 2, the present invention Cu
Seamless pipes made from alloys exhibit excellent mechanical properties, compressive strength, and stress corrosion cracking resistance in both normal and heat-affected zones, and have fine grain sizes; $5 Seamless pipes manufactured with Cu Alloy 1 have low elongation in both the normal part and the heat affected zone, and those made with Comparative Cu Alloy 2 have low mechanical properties and compressive strength in both the normal part and the heat affected zone. It has become a thing,
Similarly, the pipes made of Comparative Cu Alloys 3 and 4 suffered stress corrosion cracking in less than half the time of seamless pipes made of the Cu alloy of the present invention, and the pipes made of Comparative Cu Alloy 5 suffered from mechanical damage in the heat-affected zone. It is of inferior quality.

Furthermore, in the seamless pipes manufactured using conventional Cu alloys 1 to 3, the mechanical properties and compressive strength of the normal and heat-affected zones were extremely inferior to the seamless pipes manufactured using the Cu alloy of the present invention. Moreover, the grain size of the heat-affected zone is relatively coarse.

As mentioned above, the Cu alloy of the present invention has high strength (tensile strength) and elongation of 50% or more, does not lose strength even when subjected to heat effects such as brazing, and has excellent corrosion resistance. When used in the manufacture of seamless pipes, it is possible to reduce the wall thickness without any design restrictions, and therefore seamless pipes made of the Cu alloy of the present invention can be used particularly as constituent members of heat exchangers. In this case, it is possible to maintain excellent heat exchange characteristics over a long period of time, and
This brings about industrially useful effects such as making the heat exchanger smaller and more compact and contributing to cost reduction.

Claims (1)

[Claims] 1. Fe and P in Cu alloy for seamless pipe manufacturing. and 02 content, Fe: less than 50 to 200 p, p, m, P
: 100 to 260 p, p, m, 02 : 3 to 30 p, p, m, . A Cu alloy for seamless pipe production, characterized in that it contains substantially no other alloy components.