US3354290A

US3354290A - Forming projections on tubes

Info

Publication number: US3354290A
Application number: US446134A
Authority: US
Inventors: Robert E Monroe; Julius J Vagi
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-04-06
Filing date: 1965-04-06
Publication date: 1967-11-21
Anticipated expiration: 1984-11-21

Description

1967 R. E. MONROE ETAL 3,354,290

FORMING PROJECTIONS ON TUBES Filed April 6, 1965 3 Sheets-Sheet 1 F g- Fig- 1 15 7?] INVENTORS 1206 era! 5. jyarrroe' ulzius Va i BY J j Nov. 21, 1967 R. E. MONROE ETAL 3,354,290

FORMING PROJECTIONS ON TUBES 3 Sheets-Sheet 2 Filed April 6, 1965 T 4 f i Z a Z OWL Nov. 21, 1967 R. E. MONROE E'TAL 3,354,290

FORMING PROJECTIONS ON TUBES Filed April 6, 1965 3 Sheets-Sheet 5 United States Patent 3,354,290 I FORMING PROJECTIONS 0N TUBES Robert E. Monroe and Julius J. Vagi, Columbus, Ohio, assigno'rs to the United States of America as represented by the United States Atomic Energy Commission Filed Apr. 6, 1965, Ser. No. 446,134 2 Claims. (Cl. 219-152) ABSTRACT OF THE DISCLOSURE Apparatus for forming a projection on a tube by electrical-resistance heating and pressure. External projections on zirconium-alloy tubes used as jackets of nuclearfuel elements space the fuel elements from one another. The projections are formed by the concave recessed end of a Water-cooled copper-alloy electrode supplying pres sure and alternating current of high amperage and low voltage to the tube for a short time.

Contractual origin of the invention The invention described herein was made in the course of, or under, a contract with the US. Atomic Energy Commission.

This invention relates to the forming of projections on a metal piece by electrical resistance. More specifically, the invention relates to the forming of external projections on a refractory metal tube by electric-resistance heating and shaping.

In the nuclear-reactor field it is known to provide a plurality of rod-like fuel elements in a closely spaced parallel arrangement by means of spiral wires applied to the exteriors of the corrosion-resistant tubes jacketing the fuel elements. Various difficulties are encountered .in the application and use of the spiral spacing wires on the fuel elements. We .propose to form short localized spacing projections directly on the tubes from the tubes themselves. The dif- .ficulty arising from such a procedure lies in the fact that the material such as a zirconium alloy suitable for jacket tubesin a nuclear reactor has a high melting point and is difficult to shape without damage to its own metallic structure.

According to the :present invention, a zirconium-alloy tube on which projections are to be formed is supported internally on an expandable cooled copper-alloy mandrel and is pressed externally by a concave recessed end of a cooled dipper-alloy electrode. An alternating current of high amperage and low voltage is applied for a short time between the-electrode and mandrel across the :region of the tube wall where a projection is to be formed. The electrode is pressed against the tube wall for a short time that is somewhat longer than that during which the electric current is :permitted'to flow. An exterior projection is formed on the tube by flowing of metal of the tube wall into the recess-in the end of the'elcctrode.

In the drawings:

FIG. 1 is a perspective view of an electrode of the present invention showing the shaping end thereof;

FIG. 2 is aside view of theelectrode;

FIG. 3 is an elevation of the electrode;

'FIG. 4 is alongitudinal sectional'viewof the electrode taken on line'44 of FIG. 2;

FIG. 5 is a longitudinal sectional View of theelectrode -taken online'5-'5 ofFIG. 3;

FIG. dis a longitudinal sectional view of the mandrel of the present invention used to support a tubeinternally during shaping thereof;

FIG. 7 is a transverse sectional view of the mandrel taken on line 77 of FIG. 6;

3,354,290 Patented Nov. 21, 1967 FIG. 8 is a perspective view of the entire apparatus that includes the shaping electrode and the mandrel of the present invention;

FIG. 9 is a fragmentary perspective view of said apparatus;

FIG. 10 is a fragmentary sectional view showing a tube to be shaped and the shaping electrode before application thereof to the tube;

FIG. 11 is a sectional view similar to FIG. 10 after application of the electrode to the tube; and

FIG. 12 is a fragmentary sectional view showing a pro jection formed on a tube by the apparatus of the present invention.

As shown in FIGS. 1-5, inclusive a copper-alloy electrode 10 is of circular cylindrical shape and has at one end two conical surface portions 11, two circularly cylindrical convex surface portions 12, a circularly cylindrical concave surface portion 13, and a recess 14 formed in the surface portion 13. The conical surface portions 11 are formed about the axis of the electrode 10 by chamfering and are separated from one another by the convex surface portions 12. The surface portions 12 are formed by a machining operation subsequent to the chamfering operation about an axis perpendicular to the axis of the electrode 10 and are spaced from one another by the coucave surface portion '13. The surface portion 13 is formed in a machining operation subsequent to the operation forming the convex surface portions '12, about an axis perpendicular to the axis of the electrode 10, so as to be tangent to the original flat end of the electrode. Sharp edges at the intersections of the surface portion '13 with the surface portions 12 are removed by manual smoothing. Finally, the recess 14 is formed by pressing of a hardened drill rod against the concave surface portion 13,, and the disturbed metal around the recess 14 is machined. The internal corners of the recess 14 are formed on a radius, rather than sharp. The recess 14 is longer than it is wide, and its length extends parallel to the axis of the concave surface portion 13.

As shown in FIGS. 4 and 5, the electrode 10' is cooled by a coolant such as water entering through a line 14a inserted through the end of the electrode opposite that provided with the

surfaces

11, 12, and 13. The coolant leaves the line 14a at .its open end and flows back and out of the electrode in an annular space between the .line 14a and a closed-end 'bore 14b formed in the electrode and loosely containing the line 14a.

As shown in FIGS. 6 and 7, a mandrel 15 comprises a copper-alloy sleeve 16, a copper-alloy tube 17, a stainless-steel rod 18, a stainless-steel stationary wedge 19, a stainless-steel adjustable wedge 20, .and a stainless-steel nut 21 fixedly inserted in the wedge '20 and engaging a threaded portion 22 in one end of the rod 18. The

wedges

19 and 20 engage the interior of one end of the sleeve 16 which end has diametrally opposed .slots 23. The stationary wedge 19 is fixed and sealed to the sleeve 16. The wedge 19 is sealed to, andhas a threaded connection with, the tube 17. The rod 18 is fixed against longitudinal movement with respect to the stationary wedge 19 and the tube 17 by a shoulder 24 on the rod and a collar 25 secured inside the tube. The adjustable wedge '20 .is free to move longitudinally with respect to the sleeve 16 and is prevented from rotating by engagement of an inclined surface 26 on the adjustable wedge with an inclined sur- "face 27 on the stationary wedge 19. When the rod ,lSis rotated by manipulation of a'knurled'knob 28 on the end of the rod remote from the threaded portion 22, the adjustable wedge 20 is moved lengthwise of the sleeve ,16 with respect to the stationary "wedge '19, since neither the wedge 20 nor the nut 21 attached thereto can rotate. Movement of wedge 20 to the right as viewed 'in FIG. 6 acts through engagement of inclined surfaces 26 and 27 to expand the mandrel or more particularly the end of the sleeve 16 having the slots 23 for internal-gripping purposes. For release of the mandrel 15 from gripping, the rod 18 is rotated so as to move the adjustable wedge to the left as viewed in FIG. 6.

Between the sleeve 16 and the tube 17 there is an annular space 29 through which a liquid coolant such as water flows to the left as viewed in FIG. 6 after having entered the annular space 29 from an inlet line 30 which is connected to the sleeve 16 near its end that appears at the right in FIG. 6. The coolant leaves the annular space 29 by way of side openings 31formed in the tube 17 near its end connected with the stationary wedge 19. The coolj ant, on passing through openings 31, enters an annular space 32 formed between the tube 17 and the rod 13. The coolant flows in the annular space 32 to the right as viewed in FIG. 6 and leaves through an outlet line 33 connected to the end of the tube 17 adjacent the knob 28. The end of the rod 18 carrying the knob 28 extends from the tube 17 through an internal collar 34 with which the rod has rotational sealing engagement. The adjacent ends of the sleeve 16 and the tube 17 are held in spaced relation to one another by an end cap 35 which closes the adjacent end of the annular space 29. The end cap 35 is fixed to the sleeve 16 and tube 17 by

set screws

36 and 37.

As shown in FIGS. 8 and 9, the apparatus of which the electrode 10 and the mandrel 15 form part is a 50 kva. single-phase 60-cycle alternating current spot welder, although the apparatus is not used in the present invention for welding, but for shaping. The end of the mandrel 15 adjacent the knob 28 is carried in a bracket 38 carried on a horizontal member 39 which is carried on the upper end of a post 40 and braced by a diagonal member 41 connected with the lower end of the post. A tube 42 to be shaped is applied to the end of the mandrel 15 remote from the knob 28 and rests in a horizontal insulating trough 43 carried by the horizontal member 39. The electrode'10 is fixedly carried in a sleeve member 44 attached to a plunger 45, which is connected to a piston (not shown) shiftable in an hydraulic cylinder 46.

The tube 42 is placed on the mandrel 15, with the portion of the tube to be processed located on the end of the sleeve 16 which has slots 23. The grip of the mandrel 15 is tightened by turning of rod 18 and the resultant shifting of the adjustable wedge 20. Now the electrode 10 is moved down against the tube 42 and pressed thereagainst with an appreciable force for a short time, and during a part of this time an alternating current is applied between the electrode 1 and the sleeve 16 of the mandrel 15 through the region of the tube 42 lying therebetween. As a result of the intense heat generated in this region of the tube 42 and the pressure applied thereagainst, there are, as shown in FIGS. 11 and 12, a thinning of the tube at this region contacted by the electrode and a thickening of the tube into a projection 47 formed in and determined by the recess 14 in the electrode 10. T heprojection 47 is parallel to the tube 42. The cooling water applied to the electrode 10 and the mandrel and the heat conductivity of these parts due to the large amount of copper present in them keep electrode and mandrel cool enough to resist deformation during the shaping operation. Other projections 47 are formed on the tube 42 by repetition of the application'of pressure and electric current to the tube 42 after release of the tube 42 by the mandrel, shifting of the tube on the mandrel, and retightening of the mandrel. I

Successful results were achieved with the apparatus of the present invention in the forming of external projections on tubes 42 formed of an alloy composed of 1.10- 1.70% by weight tin, 0.l20.18% by Weight iron, 0.05- 0.15% by weight chromium, and the remainder substantially all zirconium, the tube 42 having an outer diameter of l and a wall thickness of 0.056". The electrode 10 used was formed of an alloy composed of 5 7% by weight of chromium and the balance substantially allcopper, having a Rockwell hardness of 83B and an electrical conductivity of 85% (I.A.C.S.) and being of RWMA Class 2. An example of such an alloy is Mallory 3, manufactured by Mallory Metallurgical Co., Indianapolis, Indiana. The electrode 10 had a diameter of A3"; conical surface portions 11 formed in'a 45 chamfer so as to reduce the width of the electrode to at the widest portion of the concave surface portion 13 as viewed in FIG. 2; a radius of for the concave surface portion 13; a radius of /3" for the convex surface portions 12; and length, width, and depth of .125, .062", and .032", re spectively, for the recess 14 in the electrode. The sleeve 16 and tube 17 of mandrel 15 were formed of a hard copper alloy, an example of which is one composed of 1.0% by weight of cadmium and the balance substantially copper, having a Rockwell hardness of 70B and an electrical conductivity of (I.A.C.S.) and being of RWMA Class 1, such as Elkaloy A, manufactured by Mallory Metallurgical Co. The forming load was 500 lbs. The current setting was 25,000 amperes. The actual current was 12,00014,000 amperes, and the actual voltage, 4.2-4.5 volts. The heating time was 3 cycles. The time for applying load was 60 cycles.

The electrode 10 may also be formed of an alloy composed of 1-3% by weight beryllium, 5% cobalt, and the balance substantially all copper.

The tube 42 may also be so processed that the projections 47 extend other than parallel to the tube 42. This is accomplished by angular shifting of the electrode 10 about its own axis in the sleeve member 44 or by a forming of the electrode so that the recess 14 therein does not extend parallel to the axis of the surface portion 13.

It is understood that the invention is not to be limited by the details given herein but that it may be modified within the scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for forming an exterior short localized projection on a zirconium-alloy tube, said method comprising supporting the tube on "a water-cooled copperalloy mandrel directly engaging the interior of the tube, applying with appreciable pressure for a short time against the exterior of the tube a water-cooled copperalloy electrode having a concave cylindrical surface portion having a recess, the said surface portionengaging the tube exterior, and applying for a shorter time an alternating current of low voltage and high amperage between the electrode and the mandrel across the tube to form the said projection on the tube by thinning of the region of the tube wall engaged by the said surface portion of the electrode and flowing and thickening of the tube wall in the said recess in the said surface portion, the said thinning, flowing, and thickening of the tube wall being due to pressure against and electrical-resistance heating of the tube wall.

2. The method specified in claim 1, 5000 lbs. of pressure being applied by the electrode against the tube for 60 cycles, the current being at 60 cycles and having a value of 12000 to 12400 amperes at 4.2 to 4.5 volts applied for 3 cycles, the tube having an outer diameter of 1" and a wall thickness of .056.

References Cited UNITED STATES PATENTS 1,261,943 4/1918 Lashar 2l9-91 1,435,919 11/1922 Fay 219 1,504,367 8/ 1924 Meadowcroft 219-91 1,607,262 11/1926 Ledwinka 219-91 2,989,618 6/1961 French 21991 X RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

B. A. STEIN, Assistant Examiner.

Claims

1. A METHOD FOR FORMING AN EXTERIOR SHORT LOCALIZED PROJECTION ON A ZIRCONIUM-ALLOY TUBE, SAID METHOD COMPRISING SUPPORTING THE TUBE ON A WATER-COOLED COPPERALLOY MANDREL DIRECTLY ENGAGING THE INTERIOR OF THE TUBE, APPLYING WITH APPRECIABLE PRESSURE FOR A SHORT TIME AGAINST THE EXTERIOR OF THE TUBE A WATER-COOLED COPPERALLOY ELECTRODE HAVING A CONCAVE CYLINDRICAL SURFACE PORTION HAVING A RECESS, THE SAID SURFACE PORTION ENGAGING THE TUBE EXTERIOR, AND APPLYING FOR A SHORTER TIME AN ALTERNATING CURRENT OF LOW VOLTAGE AND HIGH AMPERAGE