CN1885685B - Connection from crack resistant corrosive liquid cooled armature rod clamp to wire and correlative method - Google Patents

Abstract

The present invention relates to connection from crack resistant corrosive liquid cooled armature rod clamp to wire and a correlative method. The braze welding point between armature line package and end fitting (16) comprises: multiple lines (18, 20) array arranged to form line package, a cavity (28) in fitting, the free end of line extended into (28) through the opening (21), and the Cu-Ag braze welding alloy (26) almost without P connected to inner surface of (16).

Description

Crevice Corrosion Resistant Liquid Cooled Armature Rod Clamp to Wire Connection and Related Methods

technical field

The present invention relates generally to the manufacture of electrical generators and, more particularly, to improving the joint between a hydraulic manifold clamp or fitting and a liquid cooled armature rod.

Background technique

The armature windings of large steam turbine generators are usually water cooled. Armature windings consist of coil halves or armature rods connected at each end by copper or stainless steel fittings and water-cooled connecting rings to form a continuous hydraulic circuit. Hydraulic winding circuits are usually connected to the inlet and outlet water manifolds by plastic hoses that provide electrical insulation. The manifold is connected to the stator water cooling system, which cools, filters and deionizes the water, as well as pumps the water back to the armature windings. The armature rod is constructed of rectangular copper wires arranged in rectangular bundles. All wires may be hollow, or the bundle may comprise a mixture of solid and hollow wires. In this way, the hollow wire has conduits for conducting cooling water. Brazing alloy connects the wires to each other, and at each end of one of the armature rods to the tank header clamps. The function of the clamp is to deliver water to and collect water from the hollow wire. The clamp is connected to the second armature rod by copper or stainless steel fittings to form the complete armature coil element of the winding.

-7重量百分比的磷。钎焊接点的表面经常暴露到去离子的、氧化的水环境。Brazed joints between wires and between wires and fixtures must maintain hydraulic and electrical integrity for the expected life of the winding. The connecting wires and the brazing alloy or filler metal connecting the wires to the fixture are presently self-fluxing copper-phosphorous alloys, also known as BCuP alloys. Alloy families usually contain 3

-7 weight percent phosphorus. The surfaces of brazed joints are often exposed to a deionized, oxidized aqueous environment.

Apparently, the factors required to support the crevice corrosion mechanism in clamp-to-wire brazed joints are phosphorus, copper, suitable corrosion initiation sites, and water. If any of these factors are eliminated, crevice corrosion will not occur. Under certain conditions, corrosion of brazing alloys containing phosphorous and the surfaces of the connecting copper wires can occur, especially if critical crack geometry and crack water chemistry requirements are met. If the joint surface contains any surface cracks, pinholes, or porosity at or near the joint surface, and if critical water chemical conditions to support corrosion develop within these locations, the corrosion process will begin. The corrosion process will proceed through the brazed joint as long as critical crack geometry and water chemistry conditions exist. Additionally, porosity within the brazed joint can accelerate the overall apparent corrosion rate. Ultimately, corrosion channels can cause water to leak through the entire effective brazed joint length, compromising the hydraulic integrity of the clamp-to-wire joint.

US Patent 5796189 discloses an arrangement in which all wires are cut to the same length and a copper phosphorous (BCuP) brazing alloy is pre-placed flush with the ends of the wires. Use a brazing alloy moisture resistant compound on the ends of the hollow wires to prevent clogging of the hollow wires, as well as an inert purge gas during the brazing cycle. The use of moisture resistant agents, while effective in preventing clogging of hollow wires, may result in contamination of the wire bonding surfaces and poor effective solder joint length.

Most recent pending and commonly owned patent application Serial No. 10/418296, filed April 18, 2003, teaches the use of an extended hollow wire in conjunction with the use of a deoxidizing gas as the purge gas. The extended hollow wire eliminates the need to use a moisture resistant agent on the end of the hollow wire, and the deoxidizing purge gas limits oxidation during the brazing cycle, deoxidizes the wire surface and braze alloy before the alloy melts, and improves brazing The solder alloy becomes wet and runny. However, this practice continues to use brazing alloys containing phosphorous, so although the potential for crevice corrosion is greatly minimized due to the great reduction or in most cases elimination of surface initiation sites, the possibility of Sex is still there.

Contents of the invention

The present invention relates to a brazed connection of a liquid cooled armature rod wire package to a hydraulic manifold clamp that is not prone to initiation of crevice corrosion, and to an associated method of making the connection.

In general, the present invention provides a crevice-corrosion-free clamp-to-wire brazed joint using a braze alloy that is substantially free of phosphorus, a key factor in known crevice corrosion mechanisms. Brazing alloys that are substantially free of phosphorus have sufficiently low phosphorus content that phosphorus-containing metallurgical stages that are susceptible to crevice corrosion cannot form. Generally, for purposes of discussion, an alloy having less than 500 ppm (or 0.05 weight percent) phosphorus is considered substantially free of phosphorus. The benefits are expected to improve generator availability and reliability.

In particular, the present invention uses extended hollow wires (as opposed to solid wires) to avoid the need for braze alloy moisture resistant agents on the ends of the hollow wires. Coiled strips of substantially phosphorous-free copper-silver brazing alloy were placed between the rows of wires, and between the wires and the inner surface of the header clamp. Additional metal spacers composed of copper or other suitable metals may be placed between the rows to assist in braze alloy retention. To further aid in brazing alloy retention, a temporary refractory sleeve can be placed around the wire package at the wire-to-clamp interface, along with spring-loaded cold clamps. The joints are brazed in the cavity under a controlled atmosphere to avoid the need for brazing flux. Alternatively, a rod-shaped copper-silver alloy can be used to add additional filler metal to the brazed joint during the brazing process.

The brazing joint can be made such that the axis of the armature rod is oriented horizontally or vertically. However, the vertical orientation is preferred because it aids in alloy retention in the joints, as well as allowing lumps of alloy to be more easily pre-placed on the surface of the component within the hydraulic header fixture, thus providing an additional source of filler metal, which is on the surface Melted and flowed to produce a thicker layer of filler metal than would be possible with the armature rod in a horizontal orientation.

Copper-silver alloys may contain one or more other elements, such as tin, zinc, or nickel, which can lead to solid line and liquid line modifications to suit specific applications. In a less preferred embodiment of the manufacturing method, where it is necessary to avoid brazing in a chamber with a controlled atmosphere, it may be in an atmosphere of air or an inert gas such as nitrogen or argon, together with the use of a brazing flux Perform brazing.

Thus, in one aspect, the invention relates to a brazing joint between an armature rod wire enclosure and an end fitting comprising a plurality of solid wires and a plurality of hollow wires arranged in an array of rows and forming a wire enclosure, the plurality of Each hollow wire has a free end that extends axially beyond the corresponding free end of the solid wire; a cavity in the end fitting, the free ends of the plurality of hollow wires and the corresponding free ends of the solid wire extend through the opening and are accommodated in the cavity and interconnecting the free ends of the plurality of hollow wires and the corresponding free ends of the plurality of solid wires, and a substantially phosphorus-free copper-silver brazing alloy attached to the inner surface of the end fitting.

In another aspect, the invention relates to a brazing joint between an armature rod and an end fitting comprising a cavity in the end fitting accessible through an opening; received in the opening and arranged in an array of rows arrays of solid and hollow wires; and a substantially phosphorous-free copper-silver brazing alloy interconnecting the solid and hollow wires, and to the inner surface of the end fitting, which braze alloy covers the free ends of the solid wires, but Leave the free end of the hollow wire open and unobstructed.

In yet another aspect, the invention relates to a method of forming a brazed joint between an armature rod and an end fitting comprising: a) positioning a plurality of hollow wires and a plurality of solid wires within a cavity in the end fitting the ends of the wires such that the free ends of the hollow wires extend axially beyond the free ends of the solid wires; and b) around and between the hollow wires and the solid wire ends pre-place substantially phosphorus-free copper - Silver brazing alloy such that the brazing alloy does not extend axially beyond the free end of the hollow wire.

In yet another aspect, the invention relates to a brazing joint between an armature rod wire enclosure and an end fitting comprising a plurality of wires arranged in an array of rows and forming the wire enclosure; a cavity in the end fitting , free ends of a plurality of wires extending through the opening and received in the cavity; and interconnecting the free ends of the plurality of wires, and a substantially phosphorous-free copper-silver braze alloy attached to an inner surface of the end fitting.

Description of drawings

Figure 1 is a side view of the armature rod and header clamp assembly;

Figure 2 is a side section of a header clamp to line connection according to an exemplary embodiment of the present invention, taken along line 2-2 in Figure 3;

Figure 3 is an end view of the connection shown in Figure 2; and

Figure 4 is a partial end view of a clamp to wire connection with metal spacers between rows.

Detailed ways

Referring now to FIG. 1 , a liquid-cooled stator winding for a typical liquid-cooled electrical generator includes a plurality of armature bars 10 (one shown) with intermediate portions 12 adapted to pass through bores in a stator core (not shown). The longitudinally extending slots terminate at opposite ends with hydraulic end fittings or header clamps 14 and 16, respectively, typically formed of a conductive material such as copper. Inlet hoses (not shown) connect the header clamps 14, 16 to inlet or outlet coolant headers (also not shown).

Referring also to FIG. 2, the armature rod 10 is constructed of a number of small rectangular solid and hollow copper wires 18, 20 (FIG. 2), respectively, which are brazed to the inside of the header clamps 14, 16, as further described below. It will be appreciated that the wires 18, 20 may also be composed of metals other than copper, such as copper-nickel alloy or stainless steel. Since the clamps 16, 20 are identical, only the clamp 16 will be described in detail.

As best seen in Figures 2 and 3, the solid and hollow copper wires 18, 20 are arranged side-by-side and overlapping each other in a generally rectangular array of rows. The array can be compressed within the hydraulic end fitting or header clamp 16 by side plugs 22 (Fig. 3) that fit within similarly shaped "window" cutouts of the header clamp. The rows or rows of wires 18 , 20 within the stator bar are brazed to each other and to the inner surface 24 of the end fitting using a filler metal or braze alloy barrier layer 26 . Brazing alloy 26 preferably comprises a substantially phosphorous-free copper-silver alloy in rolled strip form. The latter facilitates the placement of the alloy between rows of wires and between the wires and the inner surfaces of end fittings or header clamps.

The specific configuration of the solid wires 18 and hollow wires 20 within the package may vary. For example, depending on how well the rods are designed to remove heat during generator operation, there could be a solid wire to hollow wire ratio of 1:1 up to eg a 6:1 ratio or higher. Conversely, the package can contain all hollow wires. The arrangement of solid and hollow wires within the array may also vary. Thus, while two row arrays are shown in Figures 2 and 3, it will be appreciated that four and six or more rows are possible.

The free ends of the hollow wires 20 extend axially beyond the corresponding free ends of the solid wires 18 into an open cavity or manifold 28 . The difference in length between the solid and hollow wires can be achieved by any suitable means, including the use of specialized tools to shorten the solid wires. A filler metal or brazing alloy 26 is pre-positioned within the header clamp 16 so as to surround the closed ends of the hollow wires and solid wires, but not extend axially beyond the hollow wires 20 . As best seen in FIG. 2, the braze alloy barrier layer 26 is along all sides of each of the arrayed lines 18, 20 and between all sides along the arrayed lines 18, 20. and also cover the ends (or joints) of the solid wires 18, while leaving the ends of the hollow wires 20 open and unobstructed for free flow of coolant through the hollow wires.

Referring to Figure 4, a multi-row arrangement is shown showing how metal spacers 30 of copper or other suitable metal are placed between the rows to aid in brazing alloy retention. These spacers 30 extend axially to a position substantially flush with the rear wall of the clamp. A temporary refractory sleeve (not shown) may be placed around the wire package at the wire-to-clamp interface. Additionally, spring loaded cold clips (not shown) may be used to further assist in brazing alloy retention. In particular, a cold clamp is applied around the wire just behind the clamp 16 to create a temperature differential between the wire inside the clamp and the wire outside the clamp. The temperature differential assists in containing the flow of brazing alloy to the region within the clamp, ie it sufficiently prevents the brazing alloy from escaping the rear wall 32 of the clamp along the wire. The joint assembly can be brazed in the cavity under a controlled atmosphere (eg, a gas containing nitrogen, hydrogen and traces of oxygen, or 100% hydrogen) to avoid the need for flux. The copper-silver alloy in rod form can be used during the brazing process to add additional filler metal to the brazed joint, if desired.

When heated to its melting temperature, the brazing alloy 26 flows and fills the spaces between the solid and hollow wires 18, 20 and between the wires and the inner surface 24 of the header clamp, including at the opening of the header clamp into which the wires are inserted. At its melting temperature, alloy 26 remains sufficiently viscous that it generally does not flow to the free end of hollow wire 20 . In other words, the extended length of the hollow wire 20 provides a safety margin so that excess alloy material does not flow to the end of the hollow wire, eliminating the possibility of clogging the cooling channels in the hollow wire.

The brazing joint can be made such that the axis of the armature rod is oriented horizontally or vertically. The vertical orientation is preferred because it aids in alloy retention in the joint, as well as allows a block of alloy to pre-place on the surface of the component within the hydraulic header fixture, thereby providing an additional source of filler metal which melts and flows on the surface, to result in a thicker layer of filler metal than would be possible with the armature rod in a horizontal orientation.

Copper-silver alloys that are substantially free of phosphorous may contain one or more other elements, such as tin, zinc, or nickel, that can cause solid line and liquid line modifications to suit the application. In a less preferred embodiment of the method of manufacture, by using a brazing flux, the brazing may be performed in an atmosphere of air or an inert gas such as nitrogen or argon, avoiding the need for a chamber with a controlled atmosphere. Brazing.

While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but rather the invention is intended to cover the spirit and scope of the invention included in the appended claims Various modifications and equivalent arrangements of .

Armature rod 10

middle part 12

End fittings or header clamps 14, 16

Line 18, 20

opening 21

side plug 22

Inner surface 24

Filler metal or brazing alloy barrier 26

Open Mouth or Manifold 28

Metal gasket 30

Rear wall 32

Claims (20)

1. braze joint between armature pole line encapsulation and end fitting, it comprises:

With row's the arranged in arrays and a plurality of solid wires and a plurality of tubular wire of formation line encapsulation, described a plurality of tubular wires have free end, and it extends axially the corresponding free end that surpasses described solid wire;

Chamber in end fitting, the described free end of described a plurality of tubular wires and the corresponding free end of described solid wire extend through the opening in the described end fitting and are contained in the described chamber; And

Interconnect the described free end of described a plurality of tubular wires and the corresponding free end of described a plurality of solid wires, and be connected to described end fitting inner surface contain copper-silver brazing alloy less than the phosphorus of 0.05 percentage by weight.

2. braze joint as claimed in claim 1 is characterized in that, described brazing alloy covers the described free end of described solid wire.

3. braze joint as claimed in claim 1 further comprises the metallic gasket between one or more row of the array that is arranged in described row.

4. braze joint as claimed in claim 3 is characterized in that described metallic gasket is made of copper.

5. braze joint as claimed in claim 1 is characterized in that, described a plurality of solid wires and tubular wire are made of copper.

6. braze joint as claimed in claim 1 is characterized in that, described a plurality of solid wires are made of copper and tubular wire is made of stainless steel.

7. the braze joint between armature pole and the end fitting, it comprises:

By the accessibility chamber in end fitting of opening;

Be contained in the described opening and with the solid wire of row's arranged in arrays and the array of tubular wire; And

Interconnect described solid wire and tubular wire, and be connected to described end fitting inner surface contain copper-silver brazing alloy less than the phosphorus of 0.05 percentage by weight, described brazing alloy covers the free end of described solid wire, but makes the free end of described tubular wire open wide and do not hindered.

8. braze joint as claimed in claim 7 further comprises the metallic gasket between one or more row of the array that is arranged in described row.

9. braze joint as claimed in claim 8 is characterized in that described metallic gasket is made of copper.

10. braze joint as claimed in claim 7 is characterized in that, described a plurality of solid wires and tubular wire are made of copper.

11. braze joint as claimed in claim 7 is characterized in that, described a plurality of solid wires are made of copper, and tubular wire is made of stainless steel.

12. a method that forms the braze joint between armature pole and the end fitting, it comprises:

A) end of location a plurality of tubular wires and a plurality of solid wires in the chamber in end fitting makes the free end shaft of described tubular wire to the free end that extends beyond described solid wire; And

B) place the copper-silver brazing alloy that contains less than the phosphorus of 0.05 percentage by weight in advance around the described end of described tubular wire and described solid wire and between the described end of described tubular wire and described solid wire, make described brazing alloy not extend axially the described free end that surpasses described tubular wire.

13. method as claimed in claim 12 further comprises:

C) under controlled atmosphere, in the chamber, a plurality of tubular wires and solid wire are soldered to end fitting.

14. method as claimed in claim 12 further comprises: between at least some of described row, add metallic gasket.

15. method as claimed in claim 14 is characterized in that, described pad is made of copper.

16. method as claimed in claim 12 is characterized in that, described a plurality of solid wires and tubular wire are made of copper.

17. method as claimed in claim 12 is characterized in that, described a plurality of solid wires are made of copper and tubular wire is made of stainless steel.

18. method as claimed in claim 13 is characterized in that, described gas comprises nitrogen, hydrogen and trace oxygen, or 100% hydrogen.

19. the braze joint between armature pole line encapsulation and the end fitting, it comprises:

With row's arranged in arrays and a plurality of lines of formation line encapsulation;

Chamber in end fitting, the free end of described a plurality of lines extend through the opening in the described end fitting and are contained in the described chamber; And

Interconnect the described free end of described a plurality of lines, and be connected to described end fitting inner surface contain copper-silver brazing alloy less than the phosphorus of 0.05 percentage by weight.

20. braze joint as claimed in claim 19 is characterized in that, described a plurality of lines are tubular wire entirely.

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