US3645435A

US3645435A - Means for joining metallic tubes by explosive bonding

Info

Publication number: US3645435A
Application number: US871140*A
Authority: US
Inventors: Alfred E Doherty Jr; Louis H Knop
Original assignee: Aerojet General Corp
Current assignee: Aerojet Rocketdyne Inc
Priority date: 1965-08-19
Filing date: 1969-07-24
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28

Abstract

Disclosed is means for the explosive bonding of metallic tubing sections to one another. The portions of the tubes to be bonded are maintained in intimately contacting relationship, and an explosive charge is provided in proximity thereto. This charge, when detonated, creates shock waves which cause the sections to be driven together, creating the bond. Additional axial or circumferential support means may be provided to constrain the tubing sections during bonding. The means for maintaining the intimately contacting relationship may comprise this support means, the explosive charge, or a combination thereof.

Description

I; m ,w in, 4 l 11 1 Lil Patent [is] mniiinnty, ,ii 1 nt 1 [54] Miiifiii' ifi ii 311% ,H UNiNiiN G MIE'IALLHQ 3,411,687 11/1968 Riley ct n1 'ii'iUiEiliEEi EXET ILUFQWE BUNHIiHNG 3,419,951 1/1969 Carlson 3,432,912 3/1969 Doherty, 11'. ct a1. [721 1mm: g ggfifg g li-gg gfii 3,477,262 11/1969 Schmidtke @1111.

[73] Assignee: Aemjct-Gcncmi finirpni'ntinn, El Monte, Primary Campaign] Calif. Assistant E.mminer-R. J. Craig A I Att0mey-Edwa1rd O. Ansell, D. Garden Any [22] filed. $1111 21 1, 11%) L Koandakjim [21] Appi. 1 10.: $711,149

[57] Aififiii'it/Wi itcintnti 1U nmaiicntinn I q Disclosed 15 means for the enpiasivc bonding; 111 111 1 i P 431,024, 19, 1965* ing sections to one another. The pontienn mi 11 3,535,!15 l. bonded are maintained in intimntciy contacting; i" D and an explosive charge is provided in proximity t1 Uta. "Bi! 228/3, 29/421 Chm-g8 h d t t d emes ghoul: wzivcs wiiici i 1 r sections to be driven togetliei', crcatlng the 1101' {38] them at ficni'cii ..29/421E,470.l,486,228/3 axial or circumfmemial Support Imam may I m [56] mewmwwr Cited! constrain the tubing sections during bonding. The nic J maintaining the intimately contacting relationship mn'y nit-- UMTED STATES PATENTS Qrisedtlhis slgpport means, the explosive charge, 01' n cmniiitm non ereo 3,140,537 7/1964 Popoff ..29/42l 3,409,969 1 1/1968 Simona et a] ......228/3 X 41 Ciainns, 9 Marni/ting Wigwam PAIENTEDHZB 29 m2 3 6W5 43 5 WEE? OF H mmmmmmmmmmmmmmmmmmmmmmmmmmm m W as? 52 m M Q WATP mm H. mm E ALFRED momma.

w M W TTOWNEVS MEANS ll' 'tfllil .ll U il' lllhlG METAMLHC 'illJlBlEb BY ElllPlLtllSlWE h'U l lBllNG This is a division of application Ser. No. 481,023, filed Aug. l9, i965 now US. Pat. No. 3,535,767.

This invention relates generally to the bonding of metal tubes to one another, and more particularly to such articles for use in cryogenic environments and a method and apparatus for the manufacture thereof.

in the prior art, when a section of tubing must be added to an existing section the ends have been butted together and the abutted ends brazed or welded by heat, or by electrical or resistance welding techniques. These prior art techniques are both time consuming and inefficient. Furthermore, if the section to be added is not of the same metal as that to which it is added, great complication develops because of the differences between the two different metals in melting points, plasticization and other characteristics.

Moreover, in the case where joined metal tubes are to carry cryogenic materials, or are disposed in exceptionally low temperature environments, the manner of joining the tubes is especially critical. Where the materials of the different tubes and the weldment are identical, there is still formed what is termed a heat-affected zone that is structurally weaker than the tubes themselves at very low temperatures, particularly when exposed to vibrations and shocks. This condition is further aggravated where tubes of different metals are joined in that not only are the specific heats usually different, producing a considerable heat-affected zone, but also there may be no satisfactory weld material for satisfactorily joining a specified set of metals.

According to the invention, a variety of end configurations of the pipe or tubing ends to be joined together may be employed. The ends of the pipes or tubes to be joined have male and female end configurations so as to mate together in intimate contact. The configuration of the ends may be angled to form cones, or flares, of a shallow or steep angle; they may be offset in appropriately matched steps; they may be joined by an external collar in an undercut portion of the outside diame ter, or they may be joined upon an internal collar fitted into an undercut on the inside diameter. Furthermore, the joined ends may be of the same metal or of different metals as may be the case with cryogenic containers, tubings or vessels, or for other uses.

However the ends may be configured for the junction thereof according to this invention, the fusion or bonding of the ends being joined is accomplished generally by the utilization of the force provided by detonation of an explosive charge located either external to, or within the confines of the interior of the tubing members being joined.

The inner or outer surfaces of the pipe or tubing over the area to be joined is so constrained that the detonation force is confined to the area being joined. This is accomplished by providing the parts with an external force collar or internal mandrel to withstand the explosive force of the shock wave generated by the detonation of the charge. if the explosion occurs outside the structure, an inner mandrel is used to take up the effect of the inwardly directed force. if the explosive force is generated within the tubing, then an outer restraining collar or die is provided to take up the outwardly directed force and to provide a forming guide to the pipe ends being joined.

Accordingly, it is an object of this invention to provide a bonded tubular metal article suitable for use at cryogenic temperatures.

Another object is the provision of a tubular article formed by bonding at least a pair of tubes to one another wherein bonding is accomplished without resort to intermediary welding materials.

Still another object is the provision of a tube-to-tube bonded article wherein portions of the tubes are configured for being mutually fit together with contacting surfaces thereof directly joined by surface alloying effected through the medium of an explosive force.

It is another object of this invention to provide rap means and method for the explosive joining together oftn sections wherein an explosive charge is placed within i side of the area of the tubing sections to be joined propriate restraining means provided in or about t sections opposite the location of the charge.

it is a further object of this invention to provide enplr. ive welding means and method for the joining of tubing sections; of either similar or dissimilar metals.

it is a still further object of this invention to provide in for explosively welding together the abutting ends of to members, the abutting ends being configured in compler tary forms so as to interfit with one another.

These and further objects of the invention will be it clearly understood from the specification which follows it taken together with the accompanying drawings am in t light of the appended claims. it should be clearly understnr that the illustrative examples shown in the figures representative of the manner in which the invention can implemented and should not be construed as limiting the invention to the specific embodiments shown, since in accordance with the teachings herein, those skilled in the art to which the invention appertains will be: able to devise other ern bodiments and applications thereof within the ambit of the appended claims.

IN THE DRAWINGS H6. 1 is a longitudinal sectional view of two sections of tnbing, or pipe, showing one form of interfitting pattern with constraining die therearound and an explosive charge device in the center;

FIG. 2 is a longitudinal sectional view of a typicaljnnction between two sections of pipe or tubing being joined by the technique of this invention showing another interfitting pat tern therebetween wherein the explosive charge means not rounds the pipe and a central mandrel forms the die;

FlG. 3 is a longitudinal sectional view of a further elnbnrliment wherein another interfitting pattern is employed between two pipe or tubing ends being joined and explosive charge devices are used both internally and externally;

FIG. 4 is a longitudinal sectional view of a pair of pipe tubing ends prepared for joining by the techniques of this in vention wherein a predetermined male and female mating configuration is used on the ends of the respective pipes: or tubes being joined;

FIG. 5 is a longitudinal sectional view of sections of pipe prepared for joining by the techniques of this invention wherein an internal cylinder interfits with the interiorly undercut ends of the pipes to be joined;

FIG. 6 is a longitudinal sectional view of pipes similar to that of H6. 5 wherein the cylinder is external to the pipes and the undercut is on the peripheries of the pipes exterior;

H0. '7 is a longitudinal sectional view of an arrangement of inner and outer pipes being joined, employing means similar to that shown in H6. l;

H6. 8 is a longitudinal sectional view of pipes being joined to show a further employment of the technique of the invert tion utilizing means shown in H6. 2; and

H6. 9 is a longitudinal sectional view of pipes similar to that in FIG. 3 wherein the technique shown in H6. 1 is employed.

in the illustrations herein above listed, any combination of elements that is shown in any particular figure may be rear ranged to incorporate similar elements from any other of the figures and still be within the spirit of the invention. That is, appropriate combinations of internal, external or both int. d and external explosive charge elements, or combinations of explosive charge elements with an inner mandrel, or external die elements may be used in any combination as desired or required by selecting appropriate groups from the different figures.

With reference to Flt}. ll, it may be seen that a typical pair of pipe ends lb, ill. have been machined so that too and of pipe tapers outwardly from the inner diameter to the outer diameter thereof to form a female member as indicated at 12, and the end of pipe ll tapers oppositely as shown at 13 to form a male member so that the ends 112 and 13 can be interfitted as illustrated. The angle of the

tapered ends

12 and 13 may be small, as shown, or may be larger thereby using a shorter length of the pipes being joined. The angles of the female end 12 and male end 13 are matched to insure a direct, flush and intimate contacting relationship between the metal tapering surfaces.

About the outer portions of the pipes 10, H in the region of the tapered junctions I2, 13 there is provided a supporting element 17 and concentrically therewith within the pipes an explosive charge 16 is disposed. There is also provided a booster 19, a cord explosive M, an initiator l5 and leads 18 for connection to external detonation means to detonate the charge '16.

Upon detonation of the charge 1 6 the mating surfaces 12, 113 are subjected to extremely high pressure which causes a true bond to be produced between the contacting surfaces. It can be shown that a bond so produced is relatively free of heat-affected zones and has increased qualities of strength at the extremely low temperatures encountered in conveying liquefied gases, for example.

In FIG. 2, pipe ends 20, 21 are to bejoined. Pipe end 20 has its outer diameter undercut as at 23 to form a male member, and pipe end 21 has its inner diameter undercut as at 22 to form a female member.

Undercuts

22, 23 are so dimensioned as to interfit for an intimate contacting relationship between the male and female members. A mandrel 27 is inserted as a supporting element in the inner diameter of joined

pipes

20, 21 which mandrel is of such geometry as to be in even contacting relation to the inner surfaces of the pipes. An explosive charge 24 surrounds the outer diameter of the

junction

22, 23 of

pipes

20, 21. Plane wave generators 26, initiator 25 and leads 28 for connection to external detonating means serve as means for effecting detonation of the charge 24.

As shown in FIG. 3, the explosive charges may be inserted in the interior as at 35 and on the exterior as at 34 of the pipes 30, 3k to be joined. Another

interfitting configuration

32, 33 is shown in FIG. 3 that differs from the arrangement of FIG. 1 in having a substantial extent of mating surfaces generally parallel to the peripheral surfaces of the pipes. Respective

plane wave generators

36 and 37 are connected to the interior explosive charge 35 and the exterior explosive charge 35 and the exterior explosive charge 34, the

plane wave generators

36, 37 leading to a common initiator 38 which is connected by leads 39 to an external detonating means such that the exterior and interior

explosive charges

34 and 35 may be simultaneously detonated to effect bonding of the mating surfaces 32, 33 of the pipes and together.

Further examples of the preparation of pipe sections for joining in the manner of the invention are shown in FIGS. 4-6. The pipe ends 40, M in FIG. 4 include V-groove 42 forming the female member which receives a suitably shaped male portion 43. Any of the explosive elements and mandrel or restraining collar devices shown in the preceding figures and discussed above, can be combined to bond the pipe ends 40, till together.

A collar 52, MG. 5, is fitted into appropriately dimensioned undercuts 54, 55 in the inner surface of

tube sections

50, 51 to be joined. The opposed end surfaces of the

tube sections

50, 51 are in abutting engagement as at 53 along the portions thereof disposed radially outwardly of the collar 52 and the groove defined by the undercuts 5d, 55 in which the collar 52 is matingly received. Similarly, in FIG. 6, a collar 62 may be disposed in outer surrounding relationship to pipe ends 60, 61 to be fitted together. The outer diameters of pipes 60, 611 are respectively provided with recesses 64, 65 which define a groove for receiving the collar 62. The opposed end surfaces of the

pipes

60, 61 are in abutting engagement as at 63 along the portions thereof disposed radially inwardly of the collar 62 and the groove defined by the recesses 64, 65 in which the collar 62 is matingly received.

Where it is desired to join a pipe of larger diameter 7%? to one of smaller diameter 7'1, as shown in FEG. 7, or where the inner pipe 71 is to be a cladding for the outer pipe '76 er similarly if the outer pipe 70 is to be a cladding for the inner pipe 71, the arrangement shown in FllG. 7 may be empioyed. While only an inner explosive charge 72 is shown in FZG. 7, an outer explosive charge, such as shown in FIG. 2, or combinations of inner and outer explosive devices, as in MG. 3, may equally well be used here. As illustrated in PEG. 7, an outer die or collar 74 is provided in the exemplary structure shown. Booster 77, initiator 75, and leads 76 make up the explosive train for actuating the charge 72 and effecting bonding of the pipes.

FIG. 8 shows a pair of end contoured pipes Hi S1 arranged with an explosive charge 82 in surrounding relationship. An undersized mandrel 83 is situated within the tubes 52b, iii to provide a space 87 along at least one side thereof. Detonation actuation means 84, 85 and 86 are provided as in the previously described embodiments.

Similarly, FIG. 9 illustrates

pipes

90, 91 joined together with an explosive charge 92 contained within. A backstop die 93 is maintained about the outer pipes 91 in slightly spaced relation thereto as at 97. Conventional detonation means )4, 95 and 96 are also supplied.

With reference to all of the figures, the basic concept of the invention is seen to be the preparation of the ends of pipes to be joined into predetermined male and female mating configurations which are brought into full contacting relationship with one another by press fitting, for example. Although full reasons are not known, it is believed that the initial contacting relation has a salutary effect on the explosively formed bond.

The technique of the invention also enables cladding the interior or exterior of pipes with a complementary metal layer, or of joining pipes of different diameters where the inner diameter of one matches the outer diameter of the other. That is, the form of the invention of FIG. 7 can be utilized for end connection or for the bonding of entire lengths of tubing to each other.

Because the bonding of the invention is accomplished by explosive shock waves and the attendant very high pressures so generated, pipes of the same or dissimilar metals can be joined into an integral unit of great strength. This is believed to be a direct function and result of the application of very high pressures in an extremely short time, as compared to the relatively low melting and fusion achieved by conventional welding methods. It is this feature which is also believed to make metal bonds formed in accordance with the practice of the invention ideal for use in a cryogenic environment. Thus, these bonds do not exhibit the characteristics of a heat-affected area associated with conventional welds.

Implementation of the invention can be accornpiished without heavy or complex machinery. No specialized tooling or materials is necessary to support the members being espiosively bonded. For example, central mandrels can be mad-e of steel, wood, plastics, rubber, ice, or fluids. Simiiar materials may also be used for the outer constraining and backstop means. Moreover, explosives may be of the castablc types formed into appropriate cylindrical or other shapes as required.

While a particular embodiment of the invention has been illustrated and described, it will be understood that the invention should not be construed as being limited thereto, but only to the scope of the claims.

We claim:

ll. Means for the explosive bonding of tubing sections to one another, comprising:

a supporting element disposed in relation to said tubing sections so as to maintain, in intimately contacting engagement, the portions of said tubing sections to be bonded, and to form a die for and to support the joint formed therebetween;

an explosive charge disposed in proximity to said portions of said tubing sections and said supporting element and arranged so as to be opposite said supporting element with said sections therebetween; and

means for detonating said explosive charge, whereby, when said charge is detonated, said portions of said tubing sections are forced together against said supporting element, bonding, said sections together.

2. Means as defined in claim ll, wherein said supporting element is disposed about said tubing sections as an external circurnferential die therefor, and said explosive charge element is disposed within said tubing sections.

3. Means as defined in claim ll, wherein said supporting ele ment is disposed within said tubing sections as a mandrel, and said explosive charge element circumferentially surrounds said tubing sections.

Means for explosive bonding of pipe or tubing sections together, comprising:

Claims

1. Means for the explosive bonding of tubing sections to one another, comprising: a supporting element disposed in relation to said tubing sections so as to maintain, in intimately contacting engagement, the portions of said tubing sections to be bonded, and to form a die for and to support the joint formed therebetween; an explosive charge disposed in proximity to said portions of said tubing sections and said supporting element and arranged so as to be opposite said supporting element with said sections therebetween; and means for detonating said explosive charge, whereby, when said charge is detonated, said portions of said tubing sections are forced together against said supporting element, bonding said sections together.

2. Means as defined in claim 1, wherein said supporting element is disposed about said tubing sections as an external circumferential die therefor, and said explosive charge element is disposed within said tubing sections.

3. Means as defined in claim 1, wherein said supporting element is disposed within said tubing sections as a mandrel, and said explosive charge element circumferentially surrounds said tubing sections.

4. Means for explosive bonding of pipe or tubing sections together, comprising: A first explosive element disposed circumferentially about the sections in proximity with the portions thereof to be bonded; a second explosive element being disposed axially within said sections in proximity with the portions thereof to be bonded; means for maintaining, in intimately contacting engagement, the portions of said sections to be bonded; and means for simultaneously detonating said explosive elements to bond said portions of the sections to one another.