JP3431358B2 - Joint - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dissimilar joint for a pipe when welding a vessel or a pipe made of an aluminum alloy to a stainless steel pipe. 2. Description of the Related Art In recent years, heat exchangers made of aluminum alloys are often used in plants that require corrosion resistance and are used at low temperatures, such as air separation units and LNG vaporizers. Further, since most of the ordinary pipes are made of stainless steel, it is necessary to join the aluminum alloy pipe and the stainless steel pipe coming out of the aluminum heat exchanger. Conventionally, it has been impossible to weld an aluminum alloy and stainless steel. When joining an aluminum alloy pipe and a stainless steel pipe, a flange is used for mechanical fastening or explosion crimping. In addition, there is a method in which a joint is prepared in advance by a joining method capable of joining an aluminum alloy and stainless steel, and the same type of metal is welded to each other using the joint as a medium. Above all, a method of preparing a joint in advance has an advantage that regular maintenance such as retightening is not required unlike the joining method using a flange because the entire joint has a welded integral structure. [0004] As a dissimilar material joint between aluminum and stainless steel using an explosion pressure bonding method, Japanese Patent Publication No. 52-1129 is known.
No. 3 discloses a joint in which a silver or silver alloy layer is interposed between a pure aluminum layer and a steel layer. When making a pipe joint using the joint disclosed in Japanese Patent Publication No. 52-11293, pure aluminum has a lower allowable stress than an aluminum alloy. It is necessary to make the thickness of the portion larger than the thickness of the aluminum alloy piping material. For example, JIS A50 as an aluminum alloy
83P-O material and JIS A11 as pure aluminum
Taking as an example the 00P-H112 material, the allowable stresses at room temperature or lower are 68.6 MPa and 22.54 MPa, respectively. Therefore, when the aluminum alloy pipe has an outer diameter of 50 mm and an inner diameter of 45 mm, pure aluminum has the same inner diameter. An outer diameter of 59 mm or more is required. [0005] On the other hand, pipe welding requiring strength is performed by butt welding, and the method of butt welding of members having different thicknesses is described in JIS B8.
As shown in 243 and the like, it is necessary to provide a taper in a thick plate portion. However, Japanese Patent Publication No. 52-112
If the pure aluminum layer of the joint of No. 93 is provided with a taper, the strength of the tapered portion is reduced. Therefore, a joint in which a silver or silver alloy layer is interposed between the pure aluminum and the steel layer is actually used. There is a problem that it cannot be used as a piping material. For this reason, welding of aluminum alloy pipe and stainless steel pipe is performed, for example, by Yoshihiko Mukai,
As shown in "Research on Deformation and Fracture Behavior of Explosion-Jointed Joints at Cryogenic Temperature" by Shin Nishimura ("ZEISEI", Result Report of Brittle Testing Laboratory, Low Temperature Center, Osaka University, Vol. 5, 1987) Silver / Stainless Steel 3
A joint consisting of a layer clad is used. [0007] Also, "Questions and Requests at the Second High-Pressure Gas Regulatory Meeting in Kyushu-Okinawa, 1983"
In the case of using pipe joints made by explosive crimping of stainless steel and aluminum alloy for pipe joints of specific equipment used at ultra-low temperature in (High Pressure Gas Explosives Control Monthly Report No. 234), the following 1. And 2. It is described that it can be used only when it is confirmed that there is no problem by conducting a test or the like. [0008] 1. And 2. To quote the test below, At the time of application, test data obtained by the manufacturer of the pressure-welded or explosion-fitted pipe joint for the tensile test, bending test, shear test, impact test, rotational bending fatigue test, etc. of the pressure-welded or explosion-fitted pipe joint shall be sent to the inspection organization. Submit.
2. The press-contact portion and the explosion-bonded portion are to be subjected to the tensile test specified in Article 49-2 of the Regulations and to pass the test. 1. Although the passing criteria for the strength as a joint in the test of the above are not specified, the above 2. There is a description in Article 49-2 of the Regulations, which indicates that the explosion joint is required to have the same strength as the welded joint. [0009] It is stipulated that the welded joint must pass a mechanical test specified in Article 44 of the High Pressure Gas Control Law Specific Equipment Inspection Regulations. In particular, regarding the impact test, in the impact test of the welded joint stipulated in Article 48 of the same regulation, the JI was tested at a temperature lower than the design temperature of the base material.
S Z2242 The minimum tensile strength of the material was 4 according to the Charpy impact test specified in the Metallic Material Impact Test Method.
In the case of 6 kg / mm ² or less, the case where the average value of the absorbed energy of three test pieces is 1.8 kg · m or more and the minimum value of one test piece is 1.4 kg · m or more is regarded as pass. [0010] However, the joint composed of the aluminum alloy / silver / stainless steel three-layer clad has a low absorption energy in the impact test, and cannot have the same strength as the welded joint. There was a problem that it could not be used for high-pressure gas identification equipment. It is an object of the present invention to address these problems and to provide a dissimilar joint between an aluminum alloy and steel or stainless steel having high joint strength and good impact characteristics at low temperatures. The Charpy impact test in this specification is a Charpy impact test defined in JIS Z2242 “Metallic material impact test method”, and the test piece is a No. 4 test in JIS Z2202 “Metallic material impact test piece”. Is a piece. The absorbed energy is the absorbed energy when the test piece is cooled in liquid nitrogen and then the Charpy impact test is quickly performed. In view of the above problems, the present inventors have inserted a pure aluminum layer at the aluminum alloy / silver / stainless steel three-layer clad aluminum alloy / silver interface. It has been found that the absorption energy of the entire joint is improved by absorbing the deformation due to the impact by the pure aluminum layer. That is, the present invention relates to a joint comprising an explosion pressure-bonded clad in which silver or a silver alloy is interposed between an aluminum alloy and stainless steel, wherein a pure aluminum layer is provided at an interface between the aluminum alloy layer and the silver layer or the silver alloy layer. Is inserted. The thickness of the pure aluminum layer is preferably about 5 to 15 mm in consideration of handling during the explosion compression bonding, but the upper limit of the thickness is not particularly required, and is about 500 μm, preferably 1 mm, for absorbing an impact on the joint. If it is above, desired absorption energy can be secured. The silver layer is preferably thin because it is expensive, and it is sufficient if the silver layer has a thickness necessary to suppress the formation of an interdiffusion layer formed at the joint interface due to the influence of welding heat. For example, a reaction product layer having a thickness of several tens of μm is observed at a silver / aluminum boundary in a material which is subjected to air cooling after holding at about 350 ° C. for 30 minutes to simulate welding heat input. Therefore, in order to prevent a direct reaction between aluminum and stainless steel, the thickness of the silver layer may be several tens μm, preferably 100 μm or more, and more preferably 70 μm or more.
When the thickness is 0 μm or more, even if the heat treatment is performed at a higher temperature for a long time, it is enough to secure a desired tensile strength. In addition, from the viewpoint of material cost, the thickness may be about 3 mm at most, preferably 2 mm or less. The value of the absorbed energy in the Charpy impact test is 1.4 according to the description of the high pressure gas specification rule.
kg / m or more, preferably 1.8 kg / m or more. The energy absorbed by pure aluminum is about 10 kg · m. The pure aluminum layer and the silver layer or the silver alloy layer to be inserted between the aluminum alloy and the stainless steel may be sequentially joined by explosive compression bonding, or the silver layer or the silver alloy layer and the pure aluminum layer may be joined first. May be joined, and a thinner intermediate material may be prepared by rolling the material, and then inserted. Embodiments of the present invention will be described below with reference to embodiments. Embodiment 1 Aluminum alloy (JIS A5052P)
-O, plate thickness: 50mm) and industrial pure aluminum (JI
SA1100P-H24, plate thickness: 5 mm), silver plate (plate thickness: 1.2 mm), and stainless steel (JIS SUS30)
4L, a plate thickness: 40 mm) was formed by an explosion pressure bonding method. JISZ from clad after making
No. 4 test piece described in 2202 “Impact test piece of metal material” was prepared, and the test piece was sufficiently cooled in liquid nitrogen according to the Charpy impact test of JISZ2242 “Method of impact test of metal material”. The test was performed. Table 1 shows the absorbed energy in the impact test. From Table 1, it was found that all cases had an absorbed energy of 1.8 kg · m or more and had excellent impact characteristics. Embodiment 2 As in Embodiment 1, an aluminum alloy (J
IS A5052P-O, plate thickness: 50 mm), industrial pure aluminum (JIS A1100P-H24), silver plate (plate thickness: 1.0 mm), and stainless steel (JIS SUS)
304L, plate thickness: 40 mm)
The plate thickness of industrial pure aluminum was changed to 1, 2, 3, and 4 mm, and a total of four sheets were produced by an explosion pressure bonding method. Further, a test piece was prepared from each of the formed claddings in the same manner as in Example 1, and a Charpy impact test was performed in the same manner as in Example 1.
Table 2 shows the absorbed energy in the impact test. From Table 2, it was found that all the cases had an absorption energy of 1.8 kg · m or more and had excellent impact characteristics. Example 3 Pure aluminum for industrial use (JIS A110)
0P-H24, thickness: 15 mm) and silver plate (thickness: 0.7)
mm) was produced by explosive pressure bonding, and then cold-rolled to produce an aluminum / silver explosion rolled cladding having a thickness of (2 + 0.1) mm. Then, an aluminum alloy (JIS A5052PO, plate thickness: 50 mm) and stainless steel (JIS SUS304L, plate thickness: 40 mm)
And the explosion rolled cladding was inserted between them to form a four-layer cladding by an explosion pressure bonding method. From the clad after creation,
A Charpy impact test was performed in the same manner as in Example 1 and Example 2. As a result, the absorbed energy in the impact test was almost the same as the result obtained when the thickness of pure aluminum was 2 mm in Example 2, and in all cases, 1.8 kg ·
It has an absorbed energy of at least m and has excellent impact properties. Comparative Example Aluminum alloy (JIS A5083P-
O), silver plate (plate thickness: 1.0 mm) and stainless steel (JI
S SUS304L) was formed by an explosion pressure bonding method. A test piece was prepared from the clad after the preparation in the same manner as in the above example, and after sufficiently cooling the test piece in liquid nitrogen, a Charpy impact test was performed. Table 3 shows the absorbed energy in the impact test. From Table 3, the three-layer clad made of aluminum alloy, silver and stainless steel is
All had an absorption energy of less than 1.4 kg · m, and it was found that the impact characteristics were extremely low. [Table 1] [Table 2] [Table 3] According to the present invention, a pure aluminum layer is inserted into the aluminum / silver interface of a joint composed of three layers of aluminum alloy / silver / stainless steel so that deformation caused by impact is absorbed by the pure aluminum layer. As a result, it has become possible to provide a joint made of aluminum alloy / pure aluminum / silver / stainless steel having excellent impact properties even at low temperatures. The joint according to the present invention provides extremely high reliability for aluminum alloy-stainless steel connections exposed to low temperature environments such as air separation devices.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 20/08

Claims (1)

(57) [Claim 1] In a joint consisting of an explosion pressure-bonded clad in which silver or a silver alloy is interposed between an aluminum alloy and stainless steel, the joint between the aluminum alloy layer and the silver layer or the silver alloy layer is provided. A joint characterized by having a pure aluminum layer inserted at the interface.