JPH10227301A - Pressure vessel and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the high strength of a pressure vessel while preventing occurrence of defects such as cracks and blow holes in a welded part, when the objective pressure vessel is manufactured by jointing together a plurality of divided bodies consisting of an Al alloy material by electron beam welding. SOLUTION: An upper divided body 12 and a lower divided body 14 are prepared by using an Al alloy having a composition which contains Si: 0.8-1.2%, Cu: 3.0-7.0%, Mn: 0.5-1.0%, Mg: 0.4-0.8%, and Ti: 0.1-0.2%, respectively in weight reference, and also has less than 0.8 of a content ratio (Mg/Si) of Mg and Si, and consists of the residue Al and an obligatory impurity. Then, these divided bodies 12, 14 are jointed together by electron beam welding, thereby a pressure vessel main body 10 can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure vessel made of an aluminum (Al) alloy completed by a joining method using electron beam welding, and a method of manufacturing such a pressure vessel. Without impairing weldability
The present invention relates to a technique for obtaining a pressure vessel made of an Al alloy having high strength.

[0002]

2. Description of the Related Art Electron beam welding is a method in which electrons accelerated in a vacuum are applied to a base material, which is an object to be welded, and the base material itself is heated to a high temperature by energy conversion due to the collision to perform fusion welding. Therefore, unlike a general arc welding method, it has a great feature that no filler metal is required. And, by adopting such electron beam welding, (1) deep penetration can be obtained,
(2) Less heat influence, (3) Less heat distortion, (4)
The advantage that there is no gas pollution can be enjoyed. Therefore, this electron beam welding method is superior in the quality of the welded parts compared to other welding methods, and is used in fields where high welding reliability is required, such as nuclear equipment, aircraft, automobiles and other transport equipment. It has been widely used for welding when manufacturing pressure vessels such as accumulators. In particular, when manufacturing an accumulator accommodating the diaphragm inside, by employing such an electron beam welding method, it is possible to reduce or avoid the thermal effect on the diaphragm, and thus, such Electron beam welding is a very advantageous welding technique.

[0003] As a material of the pressure vessel manufactured by the electron beam welding, a steel material has been conventionally used. In recent years, in order to reduce the weight of the pressure vessel, an Al material has been used. The use of alloy materials is being considered. However, in general, when electron beam welding is applied to an Al alloy material, there arises a problem that welding defects such as cracks and blowholes are easily generated in a welded portion due to the material and welding conditions. You may be hurried. In other words, when electron beam welding is applied to an Al alloy material, local distortion occurs due to rapid heating and quenching, which may cause cracking, or that steam generated during melting remains. Therefore, a blow hole may occur, and therefore, even when electron beam welding is employed, there is a possibility that welding defects similar to those of other welding methods may occur. As described above, when the electron beam welding method is applied to the Al alloy material, many problems still remain, and it has been difficult to realize Al alloying of the pressure vessel.

Therefore, the applicant of the present application has previously filed Japanese Patent Application No.
No. 173362 (JP-A-7-24585)
A method of manufacturing a pressure vessel excellent in electron beam weldability, in which defects such as cracks and blowholes do not occur in a welded portion, and an Al alloy material for manufacturing a pressure vessel that provides such a pressure vessel have been clarified. According to this, it is possible to manufacture a pressure vessel made of an Al alloy with high welding reliability using electron beam welding, and it is possible to respond to the need for reducing the weight of the pressure vessel.

[0005] However, the present inventors have further studied the Al alloy material for manufacturing a pressure vessel having such excellent characteristics.
For alloy materials, Al with excellent electron beam weldability
It has been clarified that, despite being made of an alloy material, the problem due to its low strength is still inherent.

That is, the pressure vessel manufactured using such an Al alloy material has a durable range of a low pressure range of 5 MPa class, and cannot be durable in actual use. . However, to be able to withstand actual use, its useful range must be at least 10
This is because it is required that the pressure is higher than the medium pressure type of the MPa class.

On the other hand, as a countermeasure, it is conceivable to increase the thickness of the pressure vessel in order to increase the strength of the obtained pressure vessel. However, when a target pressure vessel is formed by using such a thickened member, not only welding becomes difficult due to thickening, but also the welding quality is reduced. The problem is that there is a tendency to do so. Furthermore,
Increasing the thickness of the pressure vessel inevitably increases the weight of the member, and therefore, the effect of using the Al alloy material to reduce the weight of the pressure vessel is reduced. For these reasons, However, increasing the strength of the pressure vessel by increasing the thickness of the member has never been a preferable method.

[0008] As described above, in the pressure vessel proposed above, the strength of the Al alloy material used for its production was lower than that of the conventional steel material. In particular, the strength of the weld is inevitable to be lower than the base material, and also in terms of weldability, since it is generally inferior to steel materials, weldability is good,
It is desired to develop an Al alloy material having high strength.

[0009]

The present invention has been made in view of the above circumstances, and an object of the present invention is to join a plurality of divided bodies made of an Al alloy material by electron beam welding. Accordingly, in manufacturing a target pressure vessel, it is an object to prevent the occurrence of defects such as cracks and blowholes at a welded portion and to realize a high strength of the pressure vessel.

[0010]

In short, the present inventors have developed an Al alloy in the previously proposed Al alloy in order to develop an Al material having excellent electron beam weldability and high strength in order to solve the above problems. After a detailed study of the ingredients,
The following knowledge was obtained for Cu, which was conventionally considered as an impurity. That is, by containing a certain amount of Cu, the defect rate of the welded portion,
It decreases to a level where there is no problem in practical use, and with the addition amount of Cu, the base metal strength also increases, but when a certain amount of Cu is added, the strength of the Al alloy material is saturated. It becomes.

As a result of further studies based on those findings, the present invention has been completed. The gist of the present invention is that a plurality of divided bodies are joined by electron beam welding. Pressure vessel, and the plurality of divided bodies are divided by weight into Si: 0.8 to 1.2%, C
u: 3.0 to 7.0%, Mn: 0.5 to 1.0%, M
g: 0.4-0.8%, and Ti: 0.1-0.2%
And a content ratio of Mg to Si (Mg / Si) is 0.8 or less, and the balance is made of an Al alloy having a composition of Al and unavoidable impurities. .

That is, in the pressure vessel according to the present invention, by adding an appropriate amount of Cu as a strengthening element to the Al alloy material, which is a material of the pressure vessel, defects such as cracks and blow holes in a welded portion can be prevented. It can be made a pressure vessel with high strength while preventing generation.

Further, the present invention provides (a) S
i: 0.8 to 1.2%, Cu: 3.0 to 7.0%, M
n: 0.5 to 1.0%, Mg: 0.4 to 0.8%, and Ti: 0.1 to 0.2%, and the content ratio of Mg to Si (Mg / Si) is 0 Preparing a plurality of divided bodies for providing a target pressure vessel by using an Al alloy having a composition of 0.8 or less and a balance of Al and unavoidable impurities; and (b) dividing the plurality of divided bodies. A method of manufacturing the pressure vessel, characterized by including a step of forming the target pressure vessel by joining by electron beam welding, the method having a high strength. Pressure vessel can be manufactured with good weldability.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the Al alloy material used as a constituent material of a divided body for providing a pressure vessel by joining by electron beam welding includes S alloy.
i, Mn, Mg, and Ti are respectively contained at predetermined ratios as alloy components. Among these alloy components, Si is an effective element for securing strength and improving crack resistance, and it is necessary to contain Si at a ratio of 0.8% (weight basis; the same applies hereinafter) or more. In this case, the content must be increased up to 1.2% in order to reduce toughness. Mn is an element that enhances mechanical properties, and is required to be 0.5% or more.
If it exceeds 0%, the effect will not be improved and the cost will be increased. Further, it is necessary to contain Mg in an amount of 0.4% or more in order to secure the strength and the penetration depth of the weld. As an upper limit, it is contained.
Furthermore, Ti has an effect of refining crystal grains,
Addition of 0.1% or more is effective in preventing cracking. However, if it is too much, there is a problem in dispersibility and uniform quality is not obtained. Will be done.

In such an Al alloy material, Si
And Mg as main components to form Mg ₂ Si, and the strength is ensured. The balanced composition of Mg and Si is Mg: Si = 1.73: 1, and further, Regarding the content ratio of Mg and Si (Mg / Si), it is known that the addition of excess Si to the above-mentioned balance composition eliminates welding defects. Si content ratio (Mg
/ Si) is set to 0.8 or less.

In the present invention, a predetermined amount of Cu is further added and contained together with the alloy components as described above,
As a result, it has exhibited the desired excellent characteristics. That is,
This Cu is an element that lowers the weld defect rate and further increases the strength of the base material. By containing it in an amount of 3.0% or more, the defect rate of the welded portion is reduced to a level at which there is no practical problem. You can do it. Also, such C
When the content of u reaches a certain level, the increase in the strength of the base material saturates. On the other hand, when the content is too high, problems such as a decrease in corrosion resistance and stress corrosion cracking are caused. It must be contained up to 0.0%.

The balance excluding the above alloy components is as follows:
Although it will be composed of Al and unavoidable impurities,
Among various known impurities inevitably mixed into Al, as Fe increases, the ductility and impact value decrease, so that it is desirable to make it 0.4% or less. Also,
Cr is effective in improving stress corrosion cracking resistance, but when its content is large, quenching properties are impaired.
5% or less is desirable, and Zn evaporates during welding and tends to remain as blowholes.
It is desirable to make the following.

Therefore, in an Al alloy material having such a composition, Cu is added at a predetermined content to a conventionally known component composition as a component design having excellent electron beam weldability. As a result, the welding strength and the strength of the Al alloy material can be improved without impairing the electron beam weldability. Therefore, when such an Al alloy material is subjected to electron beam welding, generation of defects such as cracks and blowholes in a welded portion is effectively prevented, and high welding strength is ensured. .

In the method for manufacturing a pressure vessel according to the present invention, first, a plurality of divided bodies for providing a target pressure vessel using an Al alloy material having the above-described composition are formed in the same manner as in the prior art. Then, the target pressure vessel is obtained by joining the plurality of divided bodies by electron beam welding.

Here, taking a vehicle accumulator as an example of the pressure vessel as an example, specifically, first, in the vehicle accumulator shown in FIG. 1, reference numeral 10 denotes a pressure vessel body having a substantially spherical shape. Yes, it consists of an upper split 12 and a lower split 14. Further, the lower divided bodies 12 and 14 are formed and prepared by means such as press forming using an Al alloy material having excellent electron beam weldability as described above. is there. An annular mounting bracket 16 is fixed by caulking to the inner peripheral surface of the opening of the lower divided body 14, whereby the peripheral edge is sandwiched between the mounting bracket 16 and the lower divided body 14. The diaphragm 18 in the form of a film is attached to the diaphragm 1.
An oil chamber 20 is formed between the lower part 8 and the wall of the lower divided body 14.

Then, the upper divided body 12 and the lower divided body 14 are assembled in a state where the openings thereof abut each other, and the assembled parts are integrally joined by a normal electron beam welding technique. The pressure vessel main body 10 is formed. Therefore, the pressure vessel body 1
In the manufacture of No. 0, the characteristics of electron beam welding are: (1) deep penetration can be obtained, (2) little heat effect, (3) little distortion due to heat, (4) no contamination by gas And so on. in addition,
The upper and lower divided bodies 12 and 14 have excellent electron beam weldability in terms of material, and furthermore, contain an appropriate amount of Cu as an element for reducing the welding defect rate. Thus, the occurrence of cracks, blowholes, and the like can be prevented well, so that high welding quality and excellent reliability can be ensured.

A gas chamber 22 is formed inside the pressure vessel body 10 between the diaphragm 18 and the wall of the upper divided body 12. A gas plug 24 is attached to the wall of the upper split body 12 so as to communicate with the gas chamber 22, and a wall of the lower split body 14 is connected to the oil chamber 20 so as to communicate with the oil chamber 20.
By attaching the plug 28 having the oil port 26, an intended accumulator (pressure vessel) is formed.

As described above, according to the method of the present invention, it is possible to manufacture a practical pressure vessel made of an Al alloy by electron beam welding.
Since an appropriate amount of Cu is contained, the strength of the Al alloy pressure vessel can be advantageously increased without increasing the wall thickness of the pressure vessel. As a result,
A pressure vessel having high welding reliability, light weight and high strength can be obtained.

[0024]

Hereinafter, typical examples of the present invention will be described to clarify the present invention more specifically. However, the present invention imposes no restrictions on the description of such examples. It goes without saying that you don't receive anything. In addition, the present invention, in addition to the following examples, in addition to the above specific description, various modifications based on the knowledge of those skilled in the art, unless departing from the spirit of the present invention,
It should be understood that modifications, improvements and the like can be made.

First, at the ratios shown in Table 1 below, Si, Cu,
Various Al alloy materials containing Mn, Mg, Zn, and Ti (alloy Nos. 1 to 10) were prepared, welding evaluation samples were prepared from each material, and the samples were welded by electron beam welding. . The main welding conditions at that time were: acceleration voltage: 60 kV, beam current: 43 mA, welding speed: 14
mm / sec and the resulting penetration depth was about 8 mm. Then, after the welding, the welded portion of each sample is cut, a defect in a cross section of the welded portion is observed, and a defect length in a sheet thickness direction is measured to obtain a defect rate: [defect length /
Penetration depth] × 100 (%) was determined, and the results are shown in Table 1 below.

Further, a conventional Al for electron beam welding is used.
As a typical example of the alloy material, No. No. 1 is used as a typical example of the Al alloy material for electron beam welding according to the present invention. Using the alloy No. 7, the tensile strength, the fatigue strength, the proof stress, and the elongation of each of the base metal and the welded portion were measured, and the results are shown in Table 2 below.

[0027]

[Table 1]

[0028] * 1: T6 treated * 2: As welded (no post heat treatment)

As is clear from the results shown in Table 1 above, S
i, Cu, Mn, Mg, and Ti are all within the range specified in the present invention, and the Mg / Si component ratio is 0.8 or less (alloys Nos. 6 to 8). In (2), the defect length in the welded portion can be made as small as possible, and the defect rate is also kept low. In addition, since it also has sufficient tensile strength, it can be seen that it has excellent weldability, high strength, and high reliability.

On the other hand, in the case of the alloy whose Cu content is out of the specified range of the present invention, a large defect occurs in the welded portion, resulting in a defect rate exceeding an allowable value (Alloy No. 2 to No. 2). 5) Inconveniences such as low tensile strength and inability to obtain sufficient strength occur (alloy No. 1), indicating that the reliability is low.

Specifically, as shown in Table 2, by adding an appropriate amount of Cu, the alloy No.
In alloy No. 7, Compared to 1, while maintaining the quality of the weld, the tensile strength at the weld was 35%,
In the fatigue strength, an improvement in strength of 46% can be seen.

For comparison, alloy No. 1 was used as an Al-Zn-Mg alloy. 9 and alloy no. 10 were prepared and subjected to similar welding tests. As a result, in these alloys, since the content of Zn and Mg components having high vapor pressure is high, blowhole defects were found in the welded portions during electron beam welding. Are likely to occur, and therefore the defect length and defect rate are high, which indicates that when such an alloy is used, it is difficult to ensure welding quality.

FIG. 2 shows alloy No. FIG. 3 is a graph showing the relationship between the Cu content and the tensile strength of each of the alloys Nos. 1 to 8, and FIG. 3 is a graph showing the relationship between the Cu content and the defect rate. As is apparent from FIG. 2, the tensile strength of the Al alloy material increases with the Cu content, but when the content exceeds 7%, the increase in the tensile strength becomes a saturated state. . Further, as is clear from FIG. 3, the defect rate in the welded portion is such that when the Cu content is less than 2%, the defect rate increases as the content increases, but the content exceeds 3%. Then, the defect rate is settled at a low level below the target value.

[0034]

As is apparent from the above description, in the present invention, a plurality of divided bodies are prepared using an Al alloy material having a predetermined alloy composition, and these divided bodies are formed by an electron beam welding technique. By joining, an intended pressure vessel with high strength realized without impairing the electron beam weldability can be manufactured. Therefore, based on the characteristics of the Al alloy material, it is possible to satisfactorily increase the strength of the base material while effectively preventing the occurrence of welding defects due to electron beam welding and preventing a decrease in welding quality. It is possible to obtain a pressure vessel having a durable range of 10 MPa class medium pressure type or higher without requiring a thicker member, and therefore,
This makes it possible to manufacture a pressure vessel made of an Al alloy with high welding reliability that can meet the need for weight reduction.

The pressure vessel obtained in this way is not inferior in the weldability, the strength of the welded portion, the strength of the base material, etc., as compared with a pressure vessel manufactured using a conventional steel material. Therefore, the weight is advantageously reduced while having sufficient strength.

[Brief description of the drawings]

FIG. 1 is a half sectional explanatory view showing an accumulator for a vehicle as an example of a pressure vessel manufactured according to the present invention.

FIG. 2 is a graph showing the relationship between the Cu content and the tensile strength of each Al alloy obtained in the examples.

FIG. 3 is a graph showing the relationship between the Cu content of each Al alloy and the defect rate obtained in the examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pressure vessel main body 12 Upper divided body 14 Lower divided body 16 Mounting bracket 18 Diaphragm 20 Oil chamber 22 Gas chamber 30 Welded part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidetoshi Uchida 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries, Ltd. (72) Inventor Shinichi Komazawa 5-11-3, Shimbashi, Minato-ku, Tokyo No. Sumitomo Light Metal Industries Co., Ltd. (72) Inventor Masaki Kumagai 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries Co., Ltd.

Claims (2)

[Claims] 1. A pressure vessel obtained by joining a plurality of divided bodies by electron beam welding, wherein the plurality of divided bodies are based on weight:
1.2%, Cu: 3.0 to 7.0%, Mn: 0.5 to
1.0%, Mg: 0.4-0.8%, and Ti: 0.
1 to 0.2%, and the content ratio of Mg to Si (Mg
/ Si) is 0.8 or less, and the balance is made of an Al alloy having a composition of Al and unavoidable impurities. 2. Si: 0.8 to 1.2% by weight,
Cu: 3.0 to 7.0%, Mn: 0.5 to 1.0%, M
g: 0.4-0.8%, and Ti: 0.1-0.2%
And an Al alloy having a composition ratio of Mg and Si (Mg / Si) of 0.8 or less and a balance of Al and unavoidable impurities to provide a target pressure vessel. A method for manufacturing a pressure vessel, comprising: a step of preparing a divided body; and a step of joining the plurality of divided bodies by electron beam welding to form the target pressure vessel.