Iron-based brazing filler metals

Abstract

A plurality of parts is brazed using an iron-based brazing filler metal. The parts generally include stainless steel, and the brazed assembly forms a heat exchanger characterized by effective corrosion resistance and low rates of leaching of nickel into fluids passing therethrough. The heat exchanger is especially suited for use in processing items intended to be ingested by humans or animals.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to brazing of metal parts, and more particularly, to a homogeneous, ductile iron-based brazing material useful in brazing stainless steels, and a method for brazing stainless steel components to form articles of manufacture, wherein the brazed stainless steel components reduce the propensity of nickel to leach from such articles in water. [0003] 2. Description of the Prior Art [0004] Brazing is a process for joining metal parts, often of dissimilar composition, to each other. Typically, a filler metal that has a melting point lower than that of the metal parts to be joined together is interposed between the metal parts to form an assembly. The assembly is then heated to a temperature sufficient to melt the filler metal. Upon cooling, a strong, leak-tight joint is formed. The assembled parts may either constitute a finished article of manufacture or may form a sub-component for use in a ...

AI Technical Summary

Benefits of technology

"The present invention provides a method for making heat exchangers and other articles of manufacture using an iron-based brazing filler metal composition. The brazed assemblies made using this method exhibit effective corrosion resistance and low rates of nickel leaching. The method involves joining parts together with the brazing filler metal, heating them to cause melting, and cooling them to produce a brazed joint that minimizes nickel leaching. The use of an iron-based brazing filler metal alloy is preferred for making heat exchangers and other assemblies that require low nickel leaching rates. The alloys of the invention are particularly suited for fabrication into flexible thin foil by rapid solidification techniques. The invention also provides a method for making the iron-based brazing filler metal in powder form."

Problems solved by technology

However, brazing manufacturing processes carried out at high temperatures may also adversely affect the propensity of the stainless steels to leach.

However, the corrosion resistance of heat exchangers having components brazed using copper as the brazing filler metal is poor.

Typically, such heat exchangers required frequent replacement, resulting in significant costs for the replacement device and the associated labor, as well as economic losses resulting from manufacturing downtime.

Unfortunately, it was also found that when such nickel-based brazing filler metals were used, an undesirably high amount of nickel often leached into water or other fluids flowing through such assemblies.

Not surprisingly, governmental regulations in some countries have imposed strict limitations on the amount of nickel which may be leached into fluids for human ingestion or consumption.

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