Water-base aluminum-brazing composition and process of brazing

• US 20060102691A1
• Filed: 06/16/2003
• Published: 05/18/2006
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: Harima Chemicals Incorporated, Sumitomo Light Metal Industries Limited (UACJ Corporation)
• Original Assignee: Harima Chemicals Incorporated, Sumitomo Light Metal Industries Limited (UACJ Corporation)
• Inventors: Hisatomi, Yuji, Taninaka, Ichiro, Hasegawa, Yoshiharu, Sanada, Ryoichi, Toyama, Taketoshi
• Granted Patent: US 7,534,309 B2
• Time in Patent Office: Days
• US Class Current: 228/101
• CPC Class Codes: B23K 1/0012 Brazing heat exchangers
• CPC Class Codes: B23K 2101/006 Vehicles
• CPC Class Codes: B23K 2101/14 Heat exchangers
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 35/288 with Sn or Zn
• CPC Class Codes: B23K 35/3605 Fluorides
• CPC Class Codes: B23K 35/3612 with organic compounds as principal constituents
• CPC Class Codes: B23K 35/3613 Polymers, e.g. resins
• CPC Class Codes: F28F 1/126 consisting of zig-zag shaped fins F28F1/105 takes precedence
• CPC Class Codes: F28F 21/084 from aluminium or aluminium alloys

Abstract

An aqueous aluminum brazing composition containing an organic binder and zinc-based flux which prevents precipitation of the zinc-based flux having a large specific gravity while securing excellent brazeability. The thixotropic index of the brazing composition is adjusted to 1.01-1.20 by adding (meth)acrylic acid/(meth)acrylate copolymer emulsion to the brazing composition as a precipitation inhibitor in an amount of 0.03-1.50 wt % of 100 wt % of the brazing composition. Since the (meth)acrylic acid/(meth)acrylate copolymer emulsion is used as the precipitation inhibitor in a specific amount instead of other types of compounds used for powder-containing paint such as ultrafine particle silica, poly(meth)acrylate, or polyvinyl alcohol, precipitation of the zinc-based flux can be prevented without impairing brazeability.

Claims

1. An aqueous aluminum brazing composition which comprises a zinc-based flux, an organic binder, and (meth)acrylic acid/(meth)acrylate copolymer emulsion as a precipitation inhibitor in an amount of 0.03-1.50 wt % of 100 wt % of the brazing composition, the brazing composition having a thixotropic index calculated by dividing a logarithm of viscosity of the brazing composition measured at 25°

C. and 10 rpm by a logarithm of viscosity of the brazing composition measured at 25°

C. and 100 rpm by using an EH-type viscometer of 1.01-1.20.

2. The brazing composition according to claim 1, wherein the zinc-based flux is a K—

Zn—

F-type zinc fluoride.

3. The brazing composition according to claim 1, further comprising metal silicon powder as a brazing filler metal.

4. The brazing composition according to claim 1, further comprising a reaction inhibitor which inhibits a reaction between zinc and a carboxyl group in the organic binder or the precipitation inhibitor.

5. The brazing composition according to claim 4, wherein the reaction inhibitor is an amino alcohol having a boiling point of 120-200°

C.

6. An aluminum material coated with a brazing composition which is produced by applying the brazing composition according to any of claim 1 to the aluminum material and drying the brazing composition, thereby causing a dried residual component in the brazing composition to adhere to a surface of the aluminum material.

7. The aluminum material according to claim 6, wherein an average thickness and a maximum thickness of a film of the brazing composition are respectively 2-15 μ

m and 30 μ

m or less.

8. The aluminum material according to claim 6, wherein an average particle diameter of the zinc-based flux is 30 μ

m or less.

9. An aluminum brazing method comprising assembling the aluminum material according to claim 6 into a specific structure, and heating the structure to a brazing temperature to form a zinc diffusion layer on the surface of the aluminum material.

10. An automotive heat exchanger manufactured by using the brazing method according to claim 9.