METHOD OF FORMING A SEALED JOINT BETWEEN A TUBULAR ARTICLE AND A SHEET ARTICLE

Abstract

A method of forming a sealed joint between a tubular article (10) and a thin sheet article (14) wherein the articles (10, 14) are made of metallic materials that are capable of fusion welding together. One step in the method involves locating an end of the tubular article in a collar (20) surrounding a hole (12) formed in the thin sheet article (14). An end (22) of the tubular article (14) is positioned to lie substantially flush with a proximal end (24) of the collar (20). Next the ends (22, 24) of the collar and the tubular article are fusion welded forming a circumferential bead (26) creating an integral joint. Consequently in effect the previously separate a tubular article (10) and a thin sheet article (14) become a single piece.

Claims

1. A method of forming a sealed joint between a tubular article and a sheet article wherein the articles are made of metallic materials that are capable of fusion welding together, the method comprising: locating an end of the tubular article in a collar surrounding a hole formed in the thin sheet article wherein an end of the collar lies substantially flush with a proximal end of the tubular article; and, fusion welding an end of the collar to the proximal end of the tubular article about the full circumference of the collar.

2. The method according to claim 1 wherein the fusion welding is performed to create a volume of molten material that solidifies to form a continuous smooth bead of material that joins the end of the collar and the proximal end of the tubular article.

3. The method according to claim 2 wherein one of the sheet article and the end of the tubular article located in the collar has a higher rate of thermal energy conduction than the other away from an a region adjacent to where the bead is formed.

4. The method according to any one of claims 1 to 3 wherein a circumferential wall of the tubular article at the proximal end has a thickness greater than that of a wall of the collar.

5. The method according to any one of claims 1 to 4 wherein the thin sheet article has a thickness of up to about 3 mm.

6. The method according to any one of claims 1 to 5 comprising forming a recessed seat about the tubular article for seating the collar.

7. The method according to claim 6 comprising forming the recessed seat with a depth in the order of the thickness of a wall of the collar.

8. The method according to any one of the claims 4 to 7 wherein the thickness of the circumferential wall is at least 1.5 times the thickness of a wall of the collar.

9. The method according to any one of the preceding claims comprising coupling a heat sink to the tubular portion.

10. The method according to any one of claims 1 to 8 comprising reducing the thickness of the tubular article wall near the end of the tubular article to a thickness similar to the thickness of the wall of the collar.

11. The method according to any one of the preceding claims comprising forming, or otherwise providing, the collar to extend in an axial direction for a length of up to 30% of the diameter of the collared hole.

12. The method according to any one of claims 1 to 11 wherein the tubular article is a socket, pipe, tube or conduit.

13. The method according to any one of claims 1 to 12 wherein the tubular and thin sheet articles are made of stainless steel.

14. A sheet metal article comprising: a hole provided with a collar, the collar having a free end; a tubular article with an end located in the collar, the end of the tubular article lying substantially flush with the free end of the collar; and, a bead of metal formed by fusion welding of the tubular article and the free end of collar creating a fusion joint between the tubular article and the hole collar about the full circumference of the collar.

15. The sheet metal article according to claim 14 wherein the sheet metal article is a tank.

16. The sheet metal article according to claim 15 wherein the tank is a water tank for an integral collector storage solar hot water system

17. The sheet metal article according to any one of claims 14-16 wherein the collar extends in an axial direction for a length of up to 30% of the diameter of the hole.

18. The sheet metal article according to any one of claims 14-17 wherein the thin sheet article has a thickness of up to about 3 mm.

19. The sheet metal article according to any one of claims 14-18 wherein the tubular article is provided with a recessed seat in which the collar is seated.

20. The sheet metal article according claim 19 wherein the recessed seat has a depth in the order of the thickness of a wall of the collar.

21. The sheet metal article according to any one of claims 14-20 comprising arranging the thickness of the tubular article wall near the end of the tubular article to be of a thickness similar to the thickness of the wall of the collar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Notwithstanding any other forms which fall within the scope of the method as set forth in the Summary, a specific embodiment will now be described by way of example only, with reference to the accompanying drawings in which:

[0037] FIG. 1 is a partial cut-away perspective view of a penetration in a sheet metal wall in relation to which an embodiment of the disclosed method may be applied;

[0038] FIG. 2 is an enlarged view of detail A from FIG. 1; and,

[0039] FIG. 3 is an open and in line for assembly view of the two parts to be welded together.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENT

[0040] FIG. 1 depicts a tubular article in the form of a threaded socket 10, which penetrates through a hole 12 of a sheet article. The sheet article is a sheet metal wall 14 of a stainless steel tank 16 used in, for example, an integral collector storage solar hot water system. The socket 10 in this example is a DN15 threaded socket. While the tubular article is exemplified in this embodiment as a socket 10, it may take other forms such for example a pipe or tube, one end of which is to be joined to the wall 14 of tank 16. The sheet wall 14 is relatively thin, for example, having a having a thickness up to or less than about 3 mm. In a specific embodiment sheet article has a thickness of about 0.55 mm.

[0041] The hole 12 is surrounded by or formed with a circumferential collar 20. The collar 20 extends in an axial direction for a distance D1 from the plane of the wall 14.

[0042] In one embodiment of the method the hole 12 and collar 20 are already provided or pre-exists in the wall 14. However in an alternate embodiment the method may include a step of forming the hole 12 and/or collar 20 in the tank wall 14, say through a dimpling operation or with a tee-extractor plumbing tool.

[0043] Irrespective of whether the hole 12/collar 20 pre-exists or are created as part of an embodiment of the method, the method entails locating an end 22 of the socket 10 in the collar 20. Optionally, one of the collar 20 and socket 10 may have a higher rate of thermal energy conduction than the other away from an interface region 23 between the collar 20 and the socket 10.

[0044] Fusion welding entails partially melting both of the collar 20 and the socket 10 so that on cooling and re-solidification the melted portions form a single integral structure or bead 26. Fusion welding is applicable to materials of similar composition and melting points. In this example this is achieved by ensuring that the tank wall 14 and the socket 10 are made of the same type of material, such as for example stainless steel.

[0045] The end 22 of the socket 10 is positioned to lie flush with an end 24 of the collar 20. With the ends 22 and 24 being substantially flush with each other a sealed joint is formed between the collar 20 and the socket 10 by the fusion welding.

[0046] The fusion welding creates a fusion joint at the previously free and separate ends 22 and 24 of the collar 20 and socket 10. The fusion joint is manifested by a bead 26 of material made from molten material sourced from the ends of the collar 20 and the socket 10. The bead 26 extends circumferentially about the radial faces of the ends 22 and 24. That is, the bead 26 forms an integral joint at the free ends 22 and 24 so that in effect the previously separate two articles become a single piece. The bead 26 has a very small volume, which enables rapid heating and cooling of the weld. In combination with the smooth bead surface this produces a corrosion resistant and high quality joint.

[0047] The end 22 of the socket 10 has a circumferential wall 28. The heat transfer characteristics of the circumferential wall 28 and/or the collar 20 are such that the weld temperature is reached rapidly, yet sufficient heat is drawn from the ends 22 and 24 so as to minimise or reduce the high temperature exposure time thereby reducing heat tint for stainless steel. In this way the one or both of the socket 10 and wall 14 can act as a heat sink. This can be achieved by arranging the thickness of the wall 28 and the wall of the collar 20 to be similar to each other. Here “similar” is intended to mean that the respective wall thicknesses are either substantially the same or that the thicker of the two walls is no more than one and half to two times the thickness of the thinner of the two walls.

[0048] For example in the illustrated embodiment, but not necessarily all embodiments, the socket 10 can act as a heat sink by arranging, at the interface region 23, the thickness T.sub.1 of the circumferential wall 28 to be similar to (in this instance about 1.5 times) the thickness T.sub.2 of a wall of the collar 20. In this manner the wall 28 can provide an appropriate thermal resistance between the ends 22 and 24 and the more massive portion of socket 10.

[0049] By providing such a ratio of relative thickness the socket 10 acts as a heat sink sufficient to minimise or reduce heat tinting but not sufficient so as to adversely affect the fusing together of the socket 10 and sheet 14. Thinning the wall thickness of the socket adjacent to the weld site 26, as shown in FIG. 2, may allow an increase in the relative thermal capacity of the heat sink on the socket side.

[0050] In this embodiment as shown in FIG. 2 a recessed seat 30 is formed in the circumferential wall 28 of the socket 10. The recess seat is provided for seating the inner circumferential surface of the collar 20. The seat 30 and an inner diameter of the collar 20 may be arranged so as to provide a slight interference fit. In the present embodiment the recessed seat 30 is formed to a depth R≧T.sub.2. However it should be understood that a recess is not an essential requirement in order to practice embodiments of the method.

[0051] For some, but not necessarily all embodiments the collar 20 can be provided or otherwise formed so that its axial length D.sub.1 is up to about 30% of the diameter of the hole 12. For example in one specific embodiment the distance D.sub.1 may be 15% of the hole diameter.

[0052] In one specific example of an application of the disclosed method, the method may be applied to produce a DN15 threaded socket penetration in a wall of a 0.55 mm thick Grade 316 open vented hot water storage tank. In such an embodiment the hole 12 has a diameter of 25 mm and the collar 20 extends for a distance D.sub.1 of about 3 mm. The fusion welding of the collar 20 and socket 10 may be performed with a high-speed pass of a gas tungsten arc welder without addition of any filler wire or with a laser-welding machine.

[0053] Whilst a specific embodiment has been described it should be appreciated that the method may be embodied in other forms. For example the method may entail forming the hole 12 and collar 20 by an extrusion process. Also, embodiments of the method may be practiced by providing a removable heat sink, which is inserted into the socket 10 prior to the fusion process and removed subsequent thereto. Further, while stainless steel is mentioned as a possible material from which the articles 10 and 14 may be made other materials can be used. Also it is not critical that materials from which the articles are made be identical. They merely require similar composition and melting points. For example the tank 16 and/or wall 14 may be made from USN No. S44400 Grade ferritic stainless steel while the socket 10 may be made from USN No. S31603 Grade low carbon austenitic stainless steel. Also while in the specific embodiment the wall 14 is states as having a thickness of about 0.55 mm, other thickness are possible, such as: any thickness less than 3 mm; or any range of thickness between 3 mm and 0.1 mm, including any sub range within that range such as 0.3 mm to 1 mm.

[0054] In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence of addition of further features in various embodiments of the method as disclosed herein.