JPS6151019B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an Al alloy bellows, and in particular has improved cyclic expansion and contraction fatigue strength. In general, bellows are made by forming the peripheral wall 2 of a thin cylinder 1 into a bellows-like shape 3 to make it easy to expand and contract or bend in the axial direction, as shown in Figure 1.Bellows are used as expansion joints in piping systems to absorb expansion and contraction due to thermal expansion. It is used in It is also attached to vacuum equipment and used to move things inside without breaking the airtightness from the outside. As described above, the bellows is required to have durability and fatigue resistance against repeated expansion and contraction in the axial direction. Traditionally, austenitic stainless steel and phosphor bronze have been mainly used for bellows, but recently in the ultra-high vacuum field, Al or Al alloys have been used for piping because they emit less gas or gas.
Also, in the nuclear power field, Al or Al alloys have come to be used for piping because they quickly reduce residual radioactivity from exposure. For the same reason, it has become necessary to use Al or an Al alloy for the bellows of such piping systems and equipment, and it has been put into practical use in some cases. Purity 99.5wt for Al or Al alloy bellows
% (hereinafter wt% is simply abbreviated as %) of pure Al
(JIS1050), Al-2.5%Mg-0.2%Cr alloy (JIS5052 equivalent), Al-1.2%Mn-0.1%Cu alloy (JIS3003 equivalent), Al-1.2%Mn-1.0%Mg alloy (JIS3004 equivalent), Al -0.6%Si-1.0%Mg-0.3%
A Cu-0.2% Cr alloy (equivalent to JIS6061) is used. All of these were selected because of the bellows' bellows-like formability, but they have the disadvantage of low material strength, especially fatigue strength due to repeated expansion and contraction of the bellows, and are equivalent to the bellows made of austenitic stainless steel mentioned above. In order to maintain the service life of the bellows, it is necessary to increase the number of bellows by a considerable number.
As a result, not only the length of the bellows became longer, but also the weight increased. In view of this, the present invention was developed as a result of various studies.
We have developed an Al alloy bellows that has approximately 6 times the durability and fatigue properties as an austenitic stainless steel bellows, and has approximately the same durability and fatigue properties as an austenitic stainless steel bellows. .1
~1.0%, Ti0.01~0.5%, Zr0.01~0.5%, V0.01
It is characterized by being made of a heat-treated Al alloy consisting of ~0.5% Al, the balance being Al and normal impurities. In other words, the bellows of the present invention is produced by adding Cu to Al to improve its strength (tensile strength, yield strength, fatigue strength) through heat treatment, and by adding Mn to refine the crystal grains without impairing workability. At the same time with Al
A fine intermetallic compound of Mn is precipitated and contributes to strength improvement, and small amounts of Ti, Zr, and V are added to further refine the crystal grains without significantly impairing workability, and to improve the strength of the fine intermetallic compound with Al. Made of a heat-treated Al alloy that precipitates intermetallic compounds to improve the cyclic expansion and contraction fatigue strength of the bellows. In the bellows of the present invention, the Al alloy composition is limited as described above for the following reasons. The Cu content was limited to 4.0% to 7.0%, which is 4.0%.
If it is less than 7.0%, sufficient strength will not be obtained, and if it exceeds 7.0%, the strength improvement effect will be saturated and large intermetallic compounds will crystallize, making moldability difficult. The Mn content was limited to 0.1-1.0% because
This is because if it is less than 0.1%, the effect of improving fatigue strength is not recognized, and if it exceeds 1.0%, an enormous intermetallic compound of Al and Mn will crystallize, resulting in a decrease in workability. Also
The reason why the content of Ti, Zr, and V was limited to 0.01 to 0.5% each is because if any of these is less than 0.01%, no improvement in fatigue strength will be observed, and if it exceeds 0.5%, the crystallized substances will become coarse. This is because moldability becomes difficult. The bellows of the present invention has the above-mentioned structure, and the usual method is to form a thin-walled cylinder with predetermined dimensions and form the peripheral wall into a predetermined bellows shape by bulge processing.
During this time, it is produced by solution treatment at a temperature of 520 to 540°C for 1 minute to 3 hours, water quenching, and tempering at a temperature of 150 to 190°C for 2 to 48 hours. For example, after a thin-walled cylinder is solution-treated and water-quenched, the peripheral wall is bulged and then tempered, or the peripheral wall of a thin-walled cylinder is bulged and then solution-treated, water-quenched, and tempered. administer. The bellows of the present invention manufactured in this manner exhibits approximately 6 times more durability and fatigue characteristics than conventional bellows made of Al or Al alloy, and is approximately equivalent to that of conventional austenitic stainless steel bellows. It exhibits the above durability and fatigue properties, compared to conventional
Approximately 60% more compact (in terms of length) with the same durability life as Al or Al alloy bellows.
becomes possible. Although the bellows of the present invention has been described with reference to an expansion joint, it is not limited to this, and the same effect can be achieved even if the bellows is used in a pressure switch, a backless valve, etc. The present invention will be described below with reference to Examples. Example (1) Bellows outer diameter 55.5 using the materials shown in Table 1
mm, bellows inner diameter 43.5mm, bellows wall thickness 0.225
A bellows with a length of 36 mm and a number of bellows threads of 16 was created. The mechanical properties of these bellows were measured, and the number of repetitions until breakage was measured by a repeated fatigue test due to expansion and contraction. These results are also listed in Table 1. The bellows of the present invention and the comparative bellows have a diameter of 55.5
The tube was processed into a thin-walled tube with a wall thickness of 0.3 mm, solution-treated at a temperature of 535°C for 5 minutes, water quenched, formed by cold bulge processing, and then tempered at a temperature of 160°C for 24 hours. In addition, the conventional bellows has a diameter of 55.5 mm and a wall thickness of
It was processed into a 0.3 mm thin-walled tube, which was then subjected to bulge processing to create a bellows. The test conditions were a bellows internal pressure of 1 Kg/cm ² G, and a repeated expansion and contraction speed.
The test was carried out at 90 cycles/min, at room temperature, and at a stretching amount of 10 mm.

[Table] As is clear from Table 1, the bellows of the present invention has far superior expansion and contraction cyclic fatigue strength compared to conventional bellows made of Al or Al alloy, and almost superior to conventional austenitic stainless steel bellows. It can be seen that it has the same or higher cyclic fatigue strength. Example (2) Using the present invention product No. 1 and conventional products No. 15 to 18 in Table 1, EJMA (Standard of The
Expansion Joint Manufacturers Associa―
The calculated stress due to expansion and contraction was calculated using the formula of tion, Inc). The results are shown in FIG. Further, this was confirmed by conducting a fatigue test in the same manner as in Example (1) until the bellows broke. The result is the second
Shown in the table.

【table】

[Table] As is clear from Figure 2 and Table 2, there is a clear correspondence between the EJMA calculated stress values and the actual measured values, and the product of the present invention is far superior to the conventional bellows made of Al or Al alloy. Even when compared with conventional bellows made of austenitic stainless steel, it can be seen that although it is somewhat inferior in terms of a large amount of expansion and contraction, it is conversely superior in terms of a small amount of expansion and contraction. Example (3) Material of the invention product No. 1 shown in Table 1, conventional product No. 15
~18 materials were used to create bellows with a bellows diameter of 55.5 mm, a bellows inner diameter of 43.5 mm, and a wall thickness of 0.225 mm, varying the number of bellows and the length. A repeated expansion/contraction fatigue test was conducted to determine the number and length of bellows required to pass 1×10 ⁵ repetitions. The result is the third
Shown in the table.

[Table] As is clear from Table 3, the bellows of the present invention has a significantly superior durability fatigue life.
It can be seen that a compact design as a bellows is possible. In this way, according to the bellows of the present invention, the conventional bellows
Compared to Al or Al alloy bellows, it has far superior durability and fatigue strength due to repeated expansion and contraction, and not only improves the life of the bellows, but also has remarkable industrial effects such as making it possible to make the bellows lighter and more compact. be.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing the structure of a general bellows, and FIG. 2 shows fatigue curves of the bellows of the present invention and a conventional bellows in an expansion/contraction cyclic fatigue test.

Claims (1)

[Claims] 1 Cu4.0~7.0wt%, Mn0.1~1.0wt%, Ti0.01
~0.5wt%, Zr0.01~0.5wt%, V0.01~0.5wt%,
Heat treatment type consisting of balance Al and normal impurities
Al alloy bellows characterized by being made of Al alloy.