Alliedsignal Inc.

Other

Honeywell International Inc.

Allied Corporation

Metglas, Inc.

Metzlas, Inc.

Anatol Rabinkin

Nicholas J DeCristofaro

Amitava Datta

A plurality of parts are brazed using an iron/chromium filler metal. The parts are preferably composed of stainless steel. The brazed assembly forms a heat exchanger characterized by good corrosion resistance and low rates of leaching of Ni, which are further improved by a post-brazing conditioning step in an oxygen-containing atmosphere at a temperature of about 150&#xb0; to 600&#xb0; C. The preferred brazing filler metal consists essentially of a composition having the formula FeCrCoNiMoWBSiwherein the subscripts are in atom percent and total 100%, 'b' is about 5 to 20, 'c' ranges from 0 to about 30, &#x201c;d&#x201d; is 0 to about 20, &#x201c;e&#x201d; is 0 to about 5, &#x201c;f&#x201d; is 0 to about 5, &#x201c;g&#x201d; is about 8 to 15, &#x201c;h&#x201d; is about 8 to 15, the balance being incidental impurities of up to about 1 percent by weight of the total composition.

Iron-chromium base brazing filler metals

Methods for the manufacture of assemblies which included brazed components and in which nickel/chromium-based filler metals are used wherein the manufactured assemblies are characterized by low leaching rates of nickel in water and water-based fluids, are disclosed. More specifically, there are disclosed methods for the manufacture of a heat exchanger or other assembly which method includes a brazing step, as well as a post-brazing conditioning step for treating the heat exchanger or other assembly. The manufactured heat exchangers and other assemblies are particularly useful in the handling of materials intended for human consumption such as water, beverages or food as the manufactured heat exchangers or other assemblies are characterized by reduced leaching rates of nickel into fluids passed through the heat exchanger. Brazing compositions useful in such manufactured assemblies are also described.

Heat exchanger manufacturing methods and brazing filler metal compositions useful therein, characterized by low nickel leaching rates

A plurality of parts are brazed using an iron/chromium brazing filler metal. The parts are preferably composed of stainless steel and the brazed assembly forms a heat exchanger characterized by good corrosion resistance and low rates of leaching of Ni into fluids passing therethrough. The heat exchanger is especially suited for use in processing items intended to be ingested by humans or animals. Leaching rates and corrosion resistance are further enhanced by a post-brazing conditioning step wherein the assembly is heated in an oxygen-containing atmosphere to a temperature ranging from about 150&deg; to 600&deg; C. The preferred iron/chromium brazing filler metal consists essentially of a composition having the formula Fe Cr Co Ni Mo W B Si wherein the subscripts &ldquo;a&rdquo;, &ldquo;b&rdquo;, &ldquo;c&rdquo;, &ldquo;d&rdquo;, &ldquo;e&rdquo;, &ldquo;f&rdquo;, &ldquo;g&rdquo;, and &ldquo;h&rdquo; are in atom percent and wherein, &ldquo;b&rdquo; ranges from about 5 to 20, &ldquo;c&rdquo; ranges from 0 to about 30, &ldquo;d&rdquo; ranges from 0 to about 20, &ldquo;e&rdquo; ranges from 0 to about 5, &ldquo;f&rdquo; ranges from 0 to about 5, &ldquo;g&rdquo; ranges from about 8 to 15, &ldquo;h&rdquo; ranges from about 8 to 15, and the sum &ldquo;a&rdquo;&plus;&ldquo;b&rdquo;&plus;&ldquo;c&rdquo;&plus;&ldquo;d&rdquo;&plus;&ldquo;e&rdquo;&plus;&ldquo;f&rdquo;&plus;&ldquo;g&rdquo;&plus;&ldquo;h&rdquo;&equals;100, the balance being incidental impurities present in an amount up to about 1 percent by weight of the total composition.

A process is disclosed for brazing plate/plate and plate/fin multi-channeled structures using an amorphous brazing foil as a brazing filler metal between the parts in order to form uniform joints having optimal dimensions, shape and strength. The parts are assembled in an unconstrained stack, and a controlled load is applied to the top of the stack. The stack is then heated to a temperature at which the interlayer melts and reacts with the base metal to form the joints. The stack is cooled resulting in a brazed structure having the desired characteristics, wherein the brazed joints are optimally formed and the strength of the structure is equal to the underlying strength of the base metal.

Process for manufacturing of brazed multi-channeled structures

Preformed articles of an amorphous metal foil which are particularly adapted to be used in the manufacture of an assembly having brazed joints, especially a heat exchanger. Methods for the manufacture of a heat exchanger or other assembly having brazed joints, which method includes the process step of providing a preformed article formed of a brazing foil composition of an amorphous metal alloy in contact with one or more elements of said heat exchanger or other assembly.

Brazing foil performs and their use in the manufacture of heat exchangers

A nickel-chromium-based brazing alloy has a composition consisting essentially of about 9.5 to about 16.5 atom percent chromium, 0 to about 5 atom percent iron, about 10 to about 15 atom percent silicon, about 6 to less than 7 atom percent boron, and 0 to about 5 atom percent molybdenum, the balance being essentially nickel and incidental impurities. The alloy is especially suited for use as a brazing filler metal for joining stainless steel and/or superalloy at temperatures above 1100 degree(s) C. Such a filler metal has a thickness ranging from about 65 to 100 micrometers and a width ranging from 100 to 250 millimeters and more. Honeycomb structures and thin corrugated fin/plate structures particularly suited for use in manufacture of plate-type heat exchangers formed at least in part from stainless steels and/or superalloys are brazed using a unique process. The process is characterized by a long holding time at brazing temperature, and combines brazing and diffusion annealing in one technological step. Brazements produced by the process exhibit complete disappearance of central eutectic line and brittle intermetallic compounds from the joint microstructure. The brazements further exhibit joint ductility, as well as high strength and fatigue and corrosion resistance.

Nickel-chromium-based brazing alloys

This invention relates to brazing metals composed of cobalt-chromium-palladium-based alloys containing transition metals such as cobalt, nickel, tungsten, molybdenum and certain metalloids; and more particularly to multicomponent alloys containing cobalt, chromium, palladium, nickel, tungsten, molybdenum, boron, and silicon, which are especially useful for brazing metals at high temperatures to produce high strength, high oxidation and high temperature and corrosion-resistant brazements. Alloys of the present invention have a composition represented by the formula:

Cobalt-chromium-palladium-based brazing alloys

A palladium-based alloy is disclosed having a composition consisting essentially of nickel in the range of about 3 to about 30 atom percent, silicon in the range of about 15 to about 20 atom percent, the balance being palladium plus incidental impurities. The alloys of the present invention are particularly suited for joining stainless steels employed in orthodontic devices at brazing temperatures less than about 900.degree. C.

Low melting nickel-palladium-silicon brazing alloy

A palladium-based alloy is disclosed having a composition consisting essentially of nickel in the range of about 3 to about 30 atom percent, silicon in the range of about 15 to about 20 atom percent, the balance being palladium plus incidental impurities. The alloys of the present invention are particularly suited for joining stainless steels employed in orthodontic devices at brazing temperatures less than about 900.degree. C. The alloys are typically produced in the form of a foil having a thickness of at least about 150 .mu.m.

Low melting nickel-palladium-silicon brazing alloys

A brazing process is disclosed for joining two or more metal parts. The metal parts are brazed by interposing between the parts to be joined a brazing paste composed of a homogeneous microcrystalline rapidly solidified alloy powder having a composition consisting essentially of about 15 to 40 weight percent copper, 0 to 32 weight percent zinc, 0 to 24 weight percent cadmium, 0 to 3 weight percent nickel and 0 to 10 weight percent tin, the balance being silver and incidental impurities, and a phase structure such that the largest dimension of any precipitated phase ranges from about 0.01 to 0.1 micrometer, heating the powder to melt the powder, and thereafter cooling the parts to produce a brazed product. The brazing process can be carried out at lower temperatures as compared to prior art processes employing conventional BAg-alloy powders.

Method of brazing employing bag-group homogeneous microcrystalline

A flexible multilayered brazing material is disclosed comprising at least one layer of ductile brazing foil defining a core body having two major surfaces and at least one minor surface, and at least one layer of ductile brazing foil substantially covering said two major surfaces and at least one minor surface. In particular, the layer(s) and the covering foil are each at least about 50% amorphous, with the covering foil being, most preferably, helically wrapped around the layers. The multilayered brazing materials enable brazing of large gaps and wide gaps formed by juxtaposed parts to be brazed. Processes for producing the flexible multilayered brazing material are also disclosed.

Flexible multilayered brazing materials

A brazing foil is composed of metastable material having a microcrystalline structure and a composition consisting essentially of about 15 to 40 weight percent copper, 0 to 32 weight percent zinc, 0 to 24 weight percent cadmium, 0 to 3 weight percent nickel and 0 to 10 weight percent tin, the balance being silver and incidental impurities. The foil is clean, homogeneous, brittle and is especially adapted for comminution into powder.

Homogeneous, metastable BAg-group brazing alloys

A nickel-palladium-based brazing alloy is disclosed having a composition consisting essentially of about 38 to about 55 atom percent palladium, about 19 to about 34.5 atom percent iron, about 11 to about 20 atom percent silicon, the balance being essentially nickel and incidential impurities. These alloys are especially suited for use as brazing filler metals in joining stainless steels and/or superalloys at temperatures above about 1000.degree. C. A process for brazing honeycomb structures formed at least in part from stainless steels and/or superalloys is also disclosed.

Nickel-palladium based brazing alloys

Nickel based alloy compositions are disclosed comprising between about 25 and about 35 atom percent palladium, about 10 to about 13 atom percent of at least one of boron and silicon, from about 5 to about 20 atom percent cobalt, up to about 5 atom percent molybdenum, the alloys exhibiting a liquidus temperature of less than about 950.degree. C. The alloys are particularly suited for brazing stainless steel and cemented carbide joints. Also disclosed are brazing processes utilizing the alloys.

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Morris Plains, NJ, United States of America

Anatol Rabinkin