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US-12623308-B2 - Removable stop-off material for brazing

US12623308B2US 12623308 B2US12623308 B2US 12623308B2US-12623308-B2

Abstract

Provided herein is a stop-off material for a brazing process. The stop-off material includes a solvent, a thickener, and magnesium oxide. About 5 weight percent to about 60 weight percent of the stop-off material comprises the magnesium oxide. The stop-off material is configured to be removed from a surface after heating and via air pressure.

Inventors

  • KRISTINA PAVLOVNA DYSHKO
  • Warren Martin Andre Miglietti

Assignees

  • PRINCE & IZANT, LLC

Dates

Publication Date
20260512
Application Date
20240223

Claims (20)

  1. 1 . A stop-off material comprising: a solvent; a thickener, wherein the solvent and the thickener together form a solvent-thickener mixture, wherein 1 wt % to 3 wt % of the solvent-thickener mixture comprises the thickener; and magnesium oxide, wherein 5 wt % to 60 wt % of the stop-off material comprises the magnesium oxide.
  2. 2 . The stop-off material of claim 1 , wherein the solvent is water.
  3. 3 . The stop-off material of claim 1 , wherein the solvent is not water-based.
  4. 4 . The stop-off material of claim 1 , wherein 70 wt % to 80 wt % of the stop-off material comprises the solvent.
  5. 5 . The stop-off material of claim 1 , wherein about 20 wt % to about 40 wt % of the stop-off material comprises the magnesium oxide.
  6. 6 . The stop-off material of claim 1 , wherein about 25 wt % of the stop-off material comprises the magnesium oxide.
  7. 7 . The stop-off material of claim 1 , further comprising a second metal-oxide different than magnesium oxide.
  8. 8 . The stop-off material of claim 1 , wherein the solvent, the thickener, and the magnesium oxide form a paste.
  9. 9 . The stop-off material of claim 1 , wherein the solvent, the thickener, and the magnesium oxide form a preform.
  10. 10 . A stop-off material comprising: water; a thickener comprising a polymer, wherein the water and the thickener together form a water-thickener mixture, wherein 0.5 wt % to 3 wt % of the water-thickener mixture comprises the thickener; and magnesium oxide.
  11. 11 . The stop-off material of claim 10 , wherein about 20 wt % to about 40 wt % of the stop-off material comprises the magnesium oxide.
  12. 12 . The stop-off material of claim 1 , wherein about 30 wt % to about 40 wt % of the stop-off material comprises the magnesium oxide.
  13. 13 . The stop-off material of claim 1 , further comprising a cross-linking agent, wherein the solvent comprises water such that the solvent-thickener mixture is a water-thickener mixture, wherein the water-thickener mixture further comprises the cross-linking agent, and wherein about 2 wt % to about 7 wt % of the water-thickener mixture comprises the cross-linking agent.
  14. 14 . The stop-off material of claim 1 , wherein the thickener comprises a polymer.
  15. 15 . The stop-off material of claim 10 , wherein about 30 wt % to about 60 wt % of the stop-off material comprises the magnesium oxide.
  16. 16 . The stop-off material of claim 10 , wherein about 30 wt % to about 40 wt % of the stop-off material comprises the magnesium oxide.
  17. 17 . The stop-off material of claim 10 , further comprising a cross-linking agent, wherein the water-thickener mixture further comprises the cross-linking agent, and wherein about 2 wt % to about 7 wt % of the water-thickener mixture comprises the cross-linking agent.
  18. 18 . A stop-off material comprising: a water-thickener mixture comprising: water, a thickener, and a cross-linking agent, wherein about 2 wt % to about 7 wt % of the water-thickener mixture comprise the cross-linking agent; and magnesium oxide.
  19. 19 . The stop-off material of claim 18 , wherein the thickener comprises a polymer.
  20. 20 . The stop-off material of claim 18 , wherein 5 wt % to 60 wt % of the stop-off material comprises the magnesium oxide.

Description

RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Application No. 63/487,075 filed on Feb. 27, 2023, the entirety of which is incorporated herein by reference. TECHNICAL FIELD In general, the present invention relates to a stop-off material for brazing and methods for using and removing the stop-off material. BACKGROUND OF THE INVENTION Brazing is a method used to join two or more base materials together using brazing filler materials with liquidus temperatures above 450 degrees Celsius. At least one of the metal pieces may be partially coated with a stop-off material, which defines an area of the base material for the brazing filler material to flow. SUMMARY OF THE INVENTION In accordance with an embodiment of the present invention, a stop-off material is disclosed, which comprises a solvent, a thickener, and magnesium oxide. About 5 weight percent to about 60 weight percent of the stop-off material comprises the magnesium oxide. In accordance with another embodiment of the present invention, a stop-off material is disclosed. The stop-off material comprises a solvent, a thickener, and an amount of magnesium oxide such that the stop-off material is configured to be removed from a surface after heating via air pressure. In accordance with still another embodiment of the present invention, a method of brazing is disclosed. The method includes applying a stop-off material to a substrate to define a brazing area of the substrate. The stop-off material comprises magnesium oxide. A brazing filler material is applied to the brazing area of the substrate at a first temperature. The brazing filler material is heated to a second temperature greater than the first temperature. The second temperature is greater than a liquidus temperature of the brazing filler material. The substrate and brazing filler material are cooled to third temperature lower than the second temperature. The stop-off material is removed from the substrate. These and other objects of this invention will be evident when viewed in light of the drawings, detailed description and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein: FIG. 1 illustrates some embodiments of a stop-off material loaded in a syringe. FIGS. 2, 3A, 3B, 4, 5, 6, and 7 illustrate some embodiments of a method for using a stop-off material for brazing on a substrate and removing the stop-off material from the substrate after brazing. FIGS. 8, 9, 10, 11, and 12 illustrate some embodiments of another method for using a stop-off material for brazing two substrates together. FIGS. 13, 14, 15, and 16 illustrate some embodiments of yet another method for applying a stop-off material in cooling thru-holes to prevent a brazing filler material from filling the cooling thru-holes during brazing. FIG. 17 illustrates some embodiments of the stop-off material in a preform. FIG. 18 illustrates some embodiments of the stop-off material in preform inserted into cooling thru-holes before brazing. FIG. 19 provides a flow chart of some embodiments of the brazing method and stop-off material disclosed herein. DETAILED DESCRIPTION OF THE INVENTION With reference to the drawings, like reference numerals designate identical or corresponding parts throughout the several views. However, the inclusion of like elements in different views does not mean a given embodiment necessarily includes such elements or that all embodiments of the invention include such elements. The examples and figures are illustrative only and not meant to limit the invention, which is measured by the scope and spirit of the claims. Embodiments of the invention relate to methods and systems of a stop-off material and methods of using the stop-off material. Before brazing, a stop-off material may be applied to a substrate, such as a metal piece, to define a brazing area on the metal piece. The stop-off material defines a perimeter for a brazing area such that the stop-off material is not included in the brazing area. During brazing, the stop-off material prevents a brazing filler material from spreading past the defined brazing area. Brazing is conducted by joining two or more base materials together using brazing filler materials that have a liquidus temperature above 450 degrees Celsius. A liquidus temperature is the temperature at which a liquid-form of brazing filler material begins to solidify upon cooling. Thus, the stop-off material is formulated to withstand high temperatures while still preventing the brazing filler material from spreading onto the metal piece covered by the stop-off material. After brazing, the stop-off material may be removed to re-expose the metal piece. Removal of the stop-off material and re-exposure of the metal piece may