EP1812615A2 - Metaux d'apport de brasage a base de fer - Google Patents

Metaux d'apport de brasage a base de fer

Info

Publication number
EP1812615A2
EP1812615A2 EP05824771A EP05824771A EP1812615A2 EP 1812615 A2 EP1812615 A2 EP 1812615A2 EP 05824771 A EP05824771 A EP 05824771A EP 05824771 A EP05824771 A EP 05824771A EP 1812615 A2 EP1812615 A2 EP 1812615A2
Authority
EP
European Patent Office
Prior art keywords
filler metal
brazing filler
brazing
iron
brazed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05824771A
Other languages
German (de)
English (en)
Inventor
Anatol Rabinkin
Nicholas J. Decristofaro
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Metglas Inc
Original Assignee
Metglas Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Metglas Inc filed Critical Metglas Inc
Publication of EP1812615A2 publication Critical patent/EP1812615A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K1/00—Soldering, e.g. brazing, or unsoldering
    • B23K1/0008—Soldering, e.g. brazing, or unsoldering specially adapted for particular articles or work
    • B23K1/0012—Brazing heat exchangers
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C45/00—Amorphous alloys
    • C22C45/02—Amorphous alloys with iron as the major constituent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D7/16—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D9/0031—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other
    • F28D9/0037—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other the conduits for the other heat-exchange medium also being formed by paired plates touching each other
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F3/00—Plate-like or laminated elements; Assemblies of plate-like or laminated elements
    • F28F3/02—Elements or assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with recesses, with corrugations
    • F28F3/025—Elements or assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with recesses, with corrugations the means being corrugated, plate-like elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
    • F28F9/02—Header boxes; End plates
    • F28F9/0219—Arrangements for sealing end plates into casing or header box; Header box sub-elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
    • F28F9/02—Header boxes; End plates
    • F28F9/04—Arrangements for sealing elements into header boxes or end plates
    • F28F9/16—Arrangements for sealing elements into header boxes or end plates by permanent joints, e.g. by rolling
    • F28F9/18—Arrangements for sealing elements into header boxes or end plates by permanent joints, e.g. by rolling by welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/04—Tubular or hollow articles
    • B23K2101/14—Heat exchangers

Definitions

  • 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.
  • Brazing is a process for joining metal parts, often of dissimilar composition, to each other.
  • a filler metal that has a melting point iower than that of the metai 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 further manufacturing operation.
  • brazing filler metal for a specific application depends on a variety of factors, including requirements related to the components to be joined and to the conditions under which the assembly ultimately must operate.
  • Brazing filler metals are characterized by their solidus and liquidus temperatures.
  • solidus refers to the highest temperature at which a metal or alloy is completely solid
  • liquidus refers to the lowest temperature at which the metal or alloy is completely liquid.
  • the brazing filler metal In any brazing process, the brazing filler metal must possess a solidus temperature that is high enough to provide the brazed assembly with adequate integrity to meet the desired service requirements and yet have a liquidus that is low enough to be compatible with the temperature capabilities of the parts being joined.
  • brazed assemblies must operate under environmental conditions that are conducive to corrosion, especially in the vicinity of the brazement.
  • the propensity of a given system to corrode is strongly influenced by the gases or liquids to which the system is exposed and by typical operating temperatures.
  • One class of devices which are frequently assembled using brazing as a joining technique is heat exchangers. These devices are known in a variety of configurations.
  • heat exchangers allow heat to be transferred across an interface that separates one circulating fluid from another circulating fluid. It is generally essential that the fluids, either of which can be gaseous or liquid, be kept separate.
  • brazed joints which define, at least in part, the interface maintain structural integrity under a full range of operating conditions and for a prolonged service life.
  • heat exchangers find utility is in the processing of materials which are ultimately intended for human ingestion and consumption. These include foodstuffs, as well as fluids such as water, beverages, juices,, and the like.
  • the metallic materials used for the construction of heat exchangers appointed for such applications are of critical importance. Such metallic materials not only need to provide excellent operative characteristics with regard to heat transfer, but also must be compatible with the substances to which they are exposed.
  • One particular concern is the requirement that there be no undesired leaching or desolution of any elemental or molecular component species of the materials of construction that is harmful or adds undesirable taste to the fluids. If a harmful species or an undesirable taste is present, then it is imperative that any leaching of causative materials be minimized.
  • Heat exchangers of the "shell-and-tube,” “plate/plate,” and “plate/fin” types are most usually encountered.
  • a larger diameter housing typically referred to as a "shell” encompasses one or more small diameter tubes or pipes.
  • a first fluid i.e., liquid, gas
  • a second fluid liquid, gas
  • plate/plate and plate/fin type heat exchangers again a physical member, namely one or more plates separate a first fluid from a second fluid while heat transfer occurs across the plate.
  • metals are most commonly used due to their high strength and effective heat transfer characteristics.
  • the individual parts, which are used to make up such types of heat exchangers are joined by brazing. It is imperative that the heat exchanger maintain a physical integrity, and retain the isolation of the fluids from each other and the outside world.
  • the heat exchanger and the joints that secure the internal components must be resistant to any potential detrimental effects which might result from contact with one or both of the fluids.
  • Stainless steels which contain up to about 20% nickel, are very commonly utilized, for stainless steels exhibit desirable properties, including low leaching rates into fluids or gases, and generally effective corrosion resistance.
  • brazing manufacturing processes carried out at high temperatures may also adversely affect the propensity of the stainless steels to leach.
  • elemental copper was used as a brazing filler metal since copper featured low leaching of nickel into fluids, especially water.
  • corrosion resistance of heat exchangers having components brazed using copper as the brazing filler metal is poor.
  • brazing filler metals with compositions based primarily on nickel and chromium could be employed to join stainless steel parts used in such assemblies.
  • nickel-based brazing filler metals were used, an undesirably high amount of nickel often leached into water or other fluids flowing through such assemblies.
  • nickel-based brazing filler metals include a significant proportion of nickel, nickel-based brazing filler metals are believed to be the source of the undesired nickel leachate. For this reason, use of nickel-based brazing filler metals should be avoided in applications where nickel leaching into a fluid presents a concern, as is the case when materials passing through the heat exchangers are to be used for human ingestion or consumption. 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. It is to one or more of these technical needs that the present invention is directed.
  • the present invention provides a method to fabricate heat exchangers and other articles of manufacture by brazing components thereof with an iron-based brazing filler metal composition.
  • Brazed assemblies advantageously exhibit effective general corrosion resistance and low rates of leaching of nickel into fluids passing through either side of the heat exchanger.
  • the heat exchanger is highly suited for exposure to items intended for ingestion by humans or animals.
  • the present invention provides a method to manufacture assemblies, especially assemblies which include parts comprising stainless steels.
  • Such assemblies comprise parts joined using iron-based brazing filler metals.
  • the assemblies are characterized by general corrosion resistance and by low leaching rates of nickel.
  • the method comprises: juxtaposing at least two parts to define one or more joints therebetween; supplying to the one or more joints an iron-based brazing filler metal composition that is a ductile, amorphous brazing foil; heating the juxtaposed parts and the brazing filler metal to cause melting of the iron-based brazing filler metal; and cooling the melted iron-based brazing filler metal to produce a brazed joint that minimizes an amount of nickel leaching into a fluid contacting the brazed joint.
  • the heating and cooling operations are generally carried out either in a protective gas atmosphere or in a vacuum.
  • an iron-based brazing filler metal alloy is used.
  • the iron-based brazing filler metal having essentially a composition with the formula Fe a Cr b B c Si d X e , wherein X is molybdenum or tungsten and incidental impurities, wherein the subscripts "a”, “b”, “c”, “d”, “e” are all in atom percent, and wherein “b” is between about 0 and 5, “c” is between about 10 and about 17, “d” is between about 4 and about 10, “e” is between about 0 and about 5, and a sum "a"+”b” +"c"+"d”+”e” is approximately equal to 100.
  • the iron-based brazing filler metal is especially suited for fabricating heat exchangers and other assemblies of the invention which require low nickel leaching rates.
  • the iron-based brazing filler metal is prepared in the form of a homogeneous, ductile ribbon or strip.
  • the alloys of the present invention include substantial amounts of boron and silicon, which are present in the crystalline solid state in the form of hard and brittle borides and suicides. Accordingly, the alloys of the invention are particularly suited for fabrication into flexible thin foil by rapid solidification techniques. Foil produced in such a manner is a metastable material having at least a 50% glassy structure and a thickness ranging from about 18 - 50 ⁇ m (approximately 0.0007 to 0.002 inches). Use of a thin flexible and homogeneous foil as a filler metal is especially beneficial for brazements wherein the mating surfaces have wide areas with narrow clearances and for brazing joints having complex shapes.
  • the alloys of the present invention may also be produced in powder form by gas or water atomization of the alloy or by mechanical comminution of a foil comprised thereof. Other methods, such as rolling, casting, and other powder metallurgical techniques may be also be used to prepare such alloys.
  • Fig. 1 is a perspective view of a portion of a shell-and-tube heat exchanger in a partially disassembled state, along with a brazing foil preform adapted for use in brazing the components of the heat exchanger in accordance with an embodiment of the present invention
  • Fig. 2 is a cross-sectional view of a heat exchanger of the plate and fin type brazed using iron-based brazing filler metal in accordance with an embodiment of the present invention.
  • Fig. 3 is a cross-sectional view of a heat exchanger of the plate-plate type brazed using iron-based brazing filler metal in accordance with an embodiment of the present invention.
  • the present invention is directed to methods to manufacture assemblies which include brazed metal components, wherein the manufactured assemblies are advantageously characterized by low leaching rates of nickel into fluids which flow through the manufactured assembly and general corrosion resistance.
  • the invention further provides an iron-based brazing filler metal suitable for such a manufacturing process.
  • an iron-based brazing filler metal alloy is used.
  • the iron-based brazing filler metal has essentially a composition with the formula Fe a Cr b B c Si d Xe, wherein X is molybdenum or tungsten, and incidental impurities, wherein the subscripts "a”, “b”, “c”, “d”, “e” are all in atom percent, and wherein” b" is between about 0 and 5, “c” is between about 10 and about 17, “d” is between about 4 and about 10, “e” is between about 0 and about 5, and a sum "a”+”b” +"c"+"d”+”e" is approximately equal to 100.
  • the brazing filler metal In any brazing process, the brazing filler metal must have a melting point high enough to provide joint strength meeting service requirements of the brazed metal parts. Too high a melting point may weaken or sensitize the base metal. Additionally, too high a melting point may erode the base metal in the vicinity of the joint region.
  • a filler material must also be compatible, both chemically and metallurgically, with the materials being brazed.
  • Iron-based brazing filler metals particularly useful in the methods and assemblies of the present invention are metal alloys which may be produced in various forms, including, but not limited to, powders, foils, ribbons and wires, according to well known techniques. Methods commonly used to fabricate alloys in powder form include gas or water atomization, as well as mechanical pulverization. Alloys of the present invention are most generally formed into ductile foils, ribbons or wire by rapid solidification. Prod uction of metal alloys by rapid solidification typically entails quenching a melt of the requisite composition by rapidly cooling at a rate of at least about 10 3o C/sec, although higher rates are known and more commonly used.
  • the iron-based brazing filler metal of the present invention is in the form of a ductile foil which may be readily handled.
  • the iron-based brazing filler metal of the present invention is conveniently prepared in a variety of shapes that conform to contours used in the assembly of complex part assemblies. Formation into complex shapes may occur by bending or stamping the ductile foil.
  • the brazing foil of the invention is essentially homogeneous in composition, that is to say, that it includes no binders, such as organic binders which would provide the potential for void formation or the deposition of contaminating residues during brazing.
  • the homogeneous composition of the foil results in liquidus and sol ⁇ dus temperatures that are uniform throughout, further promoting uniform melting and the formation of a strong, uniform, void-free brazed joint.
  • Rapidly solidified products produced from homogeneous melts of the alloys are usually homogeneous in the solid state.
  • the products may be glassy or crystalline, depending upon the alloy compositions and processing parameters.
  • products that are at least 50% glassy usually exhibit sufficient ductility to enable foil, ribbon and wire forms of the alloys to be bent to a radius as small as ten times a thickness of the foil, ribbon or wire without fracture.
  • the iron -based brazing filler metals of the present . invention are metal alloys which are formed by rapidly solidifying a melt of the metal alloy at quenching rates of at least about 10 5o C/sec.
  • Such quenching rates typically produce alloys which are at least about 50% glassy and, as a result, are sufficiently ductile so as to enable the alloys to be stamped into complex shapes. More typically, the alloys of the present invention are at least about 80% glassy. Most typically, the alloys are substantially fully glassy (i.e., at least 90% glassy), and thus exhibit a significantly elevated degree of ductility.
  • the alloys provided by the present invention are particularly suited for use as brazing filler metals in the methods described herein. Most generally, the alloys are produced in foil form and are useful regardless of whether the foil is glassy or microcrystalline. Alternatively, the alloys may be prepared in the form of a foil with a crystalline solid solution or glassy metal structure, and in both cases, may be heat treated to obtain therein a fine-grained crystalline structure that promotes longer die life when stamping of complex shapes is contemplated.
  • the foils of the present invention typically are between about 18 to 50 micrometers (about 0.0007 inches and about 0.002 inches) thick. In many instances, the foil thickness corresponds approximately to the desired gap between parts to be brazed.
  • the brazing filler metals of the present invention are particularly useful for the joining of metal parts, and particularly, stainless steel parts.
  • Stainless steels are most frequently used in processing of fluids, including foodstuffs such as juices or other beverages, such as water, which are ultimately intended for human consumption.
  • Exemplary grades of such stainless steels include: steel S31603 according to UNS Classifications, as well as type 316L stainless steel, which is described as typically having approximately 0.03 wt. % carbon, 2.00 wt. % manganese, 1.0 wt. % silicon, 10 to 14 wt. % nickel, 16 to18 wt. % chromium, 2 to 3 wt. % molybdenum, 0.1 wt.
  • % nitrogen and iron as the balance to 100 wt. %. It is contemplated that other materials benefiting from the teaching herein may also be used in accordance with the invention to afford reduced nickel leaching rates and increased corrosion resistance.
  • such materials include other grades of stainless steel, as well as other corrosion resistant alloys, such as those including nickel.
  • brazing filler metals of the present invention include an iron-based brazing filler metal alloy that comprises essentially a composition with the formula Fe a Cr b B c Si d X e , wherein X is molybdenum or tungsten, and incidental impurities, wherein the subscripts "a”, “b”, “c”, “d”, “e” are all in atom percent and, and wherein “b” is between about 0 and 5, “c” is between about 10 and about 17, “d” is between about 4 and about 10, “e” is between about 0 and about 5, and a sum "a"+”b” +"c"+"d”+”e” is approximately equal to 100.
  • the typical brazing filler metal is readily quenched into a significantly ductile metal strip and exhibits low liquidus temperatures that are generally below liquidus temperatures of materials to be brazed. Moreover, heat exchangers and other similar assemblies brazed using the typical brazing filler metal are characterized by rates of nickel leaching that are advantageously lower than average leaching rates and by general corrosion resistance.
  • a brazing method is used to manufacture devices such as heat exchangers and other equipment comprising brazed parts.
  • the devices are selected to process materials for human ingestion or human consumption and are characterized by reduced leaching rates of nickel into fluids in contact with the devices.
  • the method includes the operations of: juxtaposing at least two parts to define one or more joints therebetween; supplying to the one or more joints an iron-based brazing filler metal in the form of a ductile, amorphous brazing foil; heating the juxtaposed parts and the brazing filler metal to cause melting of the brazing filler metal; and cooling the melted brazing filler metal to produce at least one brazed joint that minimizes an amount of nickel leaching into a fluid contacting the brazed joint.
  • FIG. 1 a partially disassembled state of a portion of a heat exchanger 80 of conventional shell-and-tube form is illustrated.
  • the heat exchanger 80 comprises a shell 82 and a plurality of tubes 84, each having an end 86 extending through a suitably dimensioned passage through a plate 90.
  • one fluids flows through tubes, while another fluid flows through the inside portion of shell 82 not occupied by tubes 84.
  • Heat is exchanged in a conventional manner across the interface defined by the combined external surface area of tubes 84 located within shell 82.
  • the diameter of the plate 90 is selected to fit within the inside diameter of the shell 82.
  • Edge 92 of plate 90 is generally formed with a slight taper to facilitate insertion into shell 82 during assembly.
  • the outer diameter of the plate 90 should have a small clearance relative to the inner diameter of the shell 82.
  • This clearance between the shell 82 and the plate 90 is usually at least slightly larger than the thickness of the brazing foil preform 10. The reason for the clearance is that it is contemplated that the tabs 14 depending from the major planar face 18 of the preform 10 are placed in contact with the edge 92 of the plate 90 prior to the brazing operation.
  • the perforations 16 present and passing through the planar face 18 are also selected and arranged to coincide with the placement and dimensions of the ends of the tubes 86.
  • the assembly of heat exchanger 80 comprises the operations of positioning brazing foil preform 10 against a primary face 94 of plate 90; folding tabs 14 to contact or at least to extend alongside the tapered edge 92; and orienting preform 10 such that perforations 16 correspond suitably with positioned tube ends 86 and the plate 90. Thereafter, the assemblage is inserted into the shell 82; and the assemblage is brazed in accordance with specific requirements necessary for the materials of construction of the assembly, and with regard to the iron-based brazing filler metal of which the brazing foil preform 10 is composed.
  • Fig. 2 illustrates a heat exchanger 15 of a plate-fin type, comprising a plurality of plates 1 and fins 2.
  • Assembly of the heat exchanger 15 comprises the operations of: preparing a requisite number of preforms, each being a preselected sheet of brazing filler metal of a preselected size comprising an iron-based brazing filler metal; and disposing a preform between each of the adjacent fins and plates to be joined by brazing.
  • the assemblage is then brazed in accordance with specific requirements necessary for the materials of construction of the assembly, and with regard to the iron-based brazing filler metal comprising the brazing preform.
  • a fillet 4 of the brazing filler metal is present in substantially a full area of contact between adjacent plates 1 and fins 2.
  • Fig. 3 depicts a heat exchanger 25 of a plate-plate type, comprising a plurality of plates 1.
  • the assembly of heat exchanger 25 comprises the operations of: preparing a predetermined number of preforms, each having a preselected size of a sheet of brazing filler metal comprising an iron-based brazing filler metal; and disposing a preform between each of the adjacent plates 1 to be joined by brazing.
  • This assemblage is then brazed in accordance with specific requirements necessary for the materials of construction of the assembly, and with regard to the iron-based brazing filler metal which comprises the brazing preform.
  • a fillet 4 of the brazing filler metal is present in substantially a full area of contact between adjacent plates 1.
  • the iron-based brazing filler metal comprises essentially a composition with the formula Fe a Cr b B c SiciXe, wherein X is molybdenum or tungsten, and incidental impurities, wherein the subscripts "a”, “b”, “c”, “d”, “e” are all in atom percent, and wherein “b” is between about 0 and 5, “c” is between about 10 and about 17, “d” is between about 4 and about 10, “e” is between about 0 and about 5, and a sum "a"+”b” +"c"+"d”+”e" is approximately equal to 100.
  • the heating and cooling of the juxtaposed parts to cause the brazing thereof occurs in a closed oven in a presence of a protective gas such as argon, helium, or nitrogen.
  • a protective gas such as argon, helium, or nitrogen.
  • heating and cooling may occur in a closed oven under vacuum conditions as well, and in certain instances, such conditions are typical.
  • the brazing conditions are typically used in industry to achieve a high joint strength and integrity when using filler metals containing oxygen-active elements such as boron, silicon, and phosphorus.
  • Manufactured assemblies, and especially heat exchangers manufactured according to the methods described herein are characterized by reduced leaching rates of nickel into water-based fluids passed therethrough when compared to assemblies manufactured in accordance with known methods comprising brazing using nickel and nickel-chromium based filler metals. While it is to be understood that any reduction in nickel leaching, particularly into a liquid such as water is to be considered to fall within the scope of the present invention, a reduction on the order of at least 50%, typically at least about 70%, and most typically a reduction of at least about 85%, is attained.
  • S uch percentages are based upon a comparison of nickel leaching rates under identical test conditions of two identical heat exchangers (or other manufactured assembly) which have been similarly manufactured, but wherein one is manufactured in a process which includes the use of an iron-based braze filler metal and an optional, post-brazing conditioning operation described herein, and the other is manufactured conventionally, such as using a nickel or nickel/chromium-based braze filler metal.
  • optional post-brazing conditioning may include annealing by heating to a temperature below solidus for a predetermined period of time to improve microstructure and associated ductivity of a joint.
  • Corrosion may occur over a large part of a given surface, or may be localized in a region, such as a region in and around a brazement.
  • the manufactured assemblies and heat exchangers of the present invention exhibit effective general corrosion resistance. That is, such assemblies are resistant to a wide variety of localized and generalized manifestations of corrosion, including generalized or localized removal of material, surface oxidation, rusting, pitting, and the like.
  • the particular mechanism that operates in a given situation depends on the materials used in constructing an assembly, the materials to which the assembly is exposed, and a time, temperature, and duration of that exposure.
  • manufactured assemblies, and especially heat exchangers constructed according to the methods described herein are characterized by superior resistance to corrosion in water- based fluids when compared to assemblies constructed using copper-based filler metals. While it is to be understood that any improvement in resistance to corrosion is to be considered to fall within the scope of the present invention, a reduction on the order of at least 20%, typically at least about 40%, and most typically a reduction of at least about 60%, is attained. Such percentages are based upon a comparison of the corrosion rates under identical test conditions of two identical heat exchangers (or other manufactured assembly) which have been similarly manufactured, but wherein one is manufactured in a process which includes the use of an iron-based brazing filler metal.
  • the general corrosion resistance of the heat exchangers and other assemblies produced according to the process described herein advantageously leads to a substantially longer expected service life of the assembly.
  • the increased service life not only lessens the risk of failure during operation, but also reduces the expected frequency of replacement or maintenance of such heat exchangers and other assemblies and the attendant disruption of service.
  • inventive heat exchangers and other assemblies manufactured according to the methods described herein include the cooling of drinking water or other beverages.
  • the methods described herein may be used in manufacture of other devices or articles useful both within the technical area related to in food and beverage processing, as well as outside of such a technical area.
  • the present invention has utility not only in the manufacture of heat exchangers, but also in any application where it is desired to reduce an amount of nickel which may leach from an assembly comprising brazed metal parts and to maintain an advantageous effective general corrosion resistance.
  • the invention additionally relates to a process for joining two or more metal parts, and particularly two or more stainless steel parts, comprising the operations of: juxtaposing the at least two parts to define one or more joints therebetween; supplying to the one or more joints an iron- based brazing filler metal having a melting temperature less than that of any of the parts and having a composition that is a ductile, amorphous brazing foil; heating the juxtaposed parts and the brazing filler metal to cause melting of the brazing filler metal; and cooling the melted brazing filler metal to produce at least one brazed joint that minimizes an amount of nickel leaching into a fluid contacting the brazed joint.
  • the iron-based brazing filler comprises essentially a composition with the formula Fe a Cr b B 0 Si d X e , wherein X is molybdenum or tungsten, and incidental impurities, wherein the subscripts "a”, “b”, “c”, “d”, “e” are all in atom percent, and wherein “b” is between about 0 and 5, “c” is between about 10 and about 17, “d” is between about 4 and about 10, “e” is between about 0 and about 5, and a sum "a"+”b” +"c"+"d”+”e” is approximately equal to 100.
  • Strips of about 2.5 to 25 mm (about 0.10 to 1.00 inch) width and about 18 to 50 ⁇ m (about 0.0007 to 0.002 inch) thick are formed by squirting a melt of a preselected composition, such as the composition with the formula Fe a Cr b B c Si d X e noted above, by overpressure of argon onto a rapidly rotating copper chill wheel (surface speed about 3000 to 6000 ft/min.).
  • a preselected composition such as the composition with the formula Fe a Cr b B c Si d X e noted above
  • argon onto a rapidly rotating copper chill wheel (surface speed about 3000 to 6000 ft/min.).
  • Metastable, ductile, homogeneous ribbons of substantially glassy alloys comprising essentially the compositions (atom percent) set forth in Table I are produced, wherein "bal.” for iron indicates a balance (100% minus the values stated for other components of the composition).
  • the liquidus and solidus temperatures of selected ribbons having compositions set forth in Table I are determined by a Differential Thermal Analysis (DTA) Technique.
  • DTA Differential Thermal Analysis
  • the individual samples are heated side by side with an inert reference material at a uniform rate, and a temperature difference between the individual sample and the inert reference material is measured as a function of temperature.
  • a resulting curve conventionally known as a thermogram, is a plot of relative changes in the temperatures of the sample and the reference materials during simultaneous heating vs. temperature, from which the beginning of melting and end of melting, which represent the solidus and liquidus temperatures, respectively, are determined. Values thus determined are set forth in Table Il below.
  • Alloys of the present invention may be used as filler metals to braze stainless steels. Such alloys will melt and flow at temperatures that will not damage the stainless -steel-based metal parts and, at the same time, are convenient for industrial brazing processing. As may be seen from Table II, the amounts of boron and silicon may be varied to adjust the liquidus and solidus temperatures of the brazing filler metal material to desired liquidus and solidus temperatures.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Abstract

Selon l'invention, une pluralité d'éléments est brasée à l'aide d'un métal d'apport de brasage à base de fer. Les éléments comprennent généralement de l'acier inoxydable et l'ensemble brasé forme un échangeur de chaleur caractérisé par une résistance à la corrosion efficace et de faibles taux de lixiviation de nickel dans des fluides passant par l'échangeur de chaleur. L'échangeur de chaleur est notamment approprié pour être utilisé dans le traitement d'articles conçus pour être ingérés par des humains ou des animaux.
EP05824771A 2004-11-01 2005-11-01 Metaux d'apport de brasage a base de fer Withdrawn EP1812615A2 (fr)

Applications Claiming Priority (2)

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US10/977,944 US20060090820A1 (en) 2004-11-01 2004-11-01 Iron-based brazing filler metals
PCT/US2005/039408 WO2006050334A2 (fr) 2004-11-01 2005-11-01 Metaux d'apport de brasage a base de fer

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US (1) US20060090820A1 (fr)
EP (1) EP1812615A2 (fr)
JP (1) JP2008518786A (fr)
KR (1) KR20070085596A (fr)
TW (1) TW200628258A (fr)
WO (1) WO2006050334A2 (fr)

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JP5215174B2 (ja) * 2005-05-26 2013-06-19 アルファ ラヴァル コーポレイト アクチボラゲット ステンレス鋼の物品をろう付けする方法
DE102005039803A1 (de) * 2005-08-22 2007-05-24 Vacuumschmelze Gmbh & Co. Kg Hartlotfolie auf Eisen-Nickel-Basis sowie Verfahren zum Hartlöten
US7392930B2 (en) * 2006-07-06 2008-07-01 Sulzer Metco (Us), Inc. Iron-based braze filler metal for high-temperature applications
US8894780B2 (en) * 2006-09-13 2014-11-25 Vacuumschmelze Gmbh & Co. Kg Nickel/iron-based braze and process for brazing
DE102007028275A1 (de) * 2007-06-15 2008-12-18 Vacuumschmelze Gmbh & Co. Kg Hartlotfolie auf Eisen-Basis sowie Verfahren zum Hartlöten
US9316341B2 (en) 2012-02-29 2016-04-19 Chevron U.S.A. Inc. Coating compositions, applications thereof, and methods of forming
DK2644312T3 (en) 2012-03-28 2019-02-25 Alfa Laval Corp Ab Hitherto unknown soldering concept
US10940565B2 (en) 2014-02-21 2021-03-09 Oerlikon Metco (Us) Inc. Low-melting nickel-based alloys for braze joining
DE102015010310A1 (de) * 2015-08-08 2017-02-09 Modine Manufacturing Company Gelöteter Wärmetauscher und Herstellungsverfahren
EP3266559A1 (fr) * 2015-03-05 2018-01-10 Hitachi Metals, Ltd. Poudre de brasage en alliage et composant assemblé
EP3507046B1 (fr) 2016-09-01 2020-11-11 Linde GmbH Procede de fabrication d'un bloc d'echangeur de chaleur a plaques consistant en l'application ciblee de materiau a braser, en particulier sur des ailettes et barres laterales
US20200166293A1 (en) * 2018-11-27 2020-05-28 Hamilton Sundstrand Corporation Weaved cross-flow heat exchanger and method of forming a heat exchanger
JP7442238B1 (ja) 2023-06-09 2024-03-04 東京ブレイズ株式会社 ろう材及びろう付用部材、並びにそれらの製造方法

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KR20070085596A (ko) 2007-08-27
JP2008518786A (ja) 2008-06-05
TW200628258A (en) 2006-08-16
WO2006050334A3 (fr) 2007-02-01
US20060090820A1 (en) 2006-05-04
WO2006050334A2 (fr) 2006-05-11

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