US3852873A — Method for manufacturing and brazing various appa…

Claim 1

Independent Claim 278 words

METHOD FOR MANUFACTURING AND BRAZING VARIOUS APPARATUSES AND PARTICULARLY HEAT EXCHANGERS, WHEREIN: THE PARTS OF THE APPARATUS ARE MADE FROM THIN SHEETS OF A BASIC ALUMINUM ALLOY CONTAINING SILICON AND MAGNESIUM ABLE TO FORM A MAGNESIUM SILICIDE COMPOUND MG2SI; THE APPARATUS IS ASSEMBLED AND SUBMITTED TO ACTION OF A CLEANING SOLVENT OF THE GREASY PRODUCTS, THE APPARATUS IS HEATED IN PRESENCE OF AN ALUMINIUM BRAZING ALLOY CONTAINING AT LEAST 7% AND AT MOST 15% OF SILICON IN PRESENCE OF METALS AND METAL SALTS CAUSING REMOVAL OF THE OXIDES COVERING THE BASIC ALLOY AND WETTING THEREOF BY THE BRAZING ALLOY, THE APPARATUS IS HEATED TO A TEMPERATURE WITHIN THE RANGE OF 580* TO 600*C, WHEREBY AT A SAME TIME THE MAGNESIUM SILICIDE IS COMPLETELY SET IN A SUPERSATURATED STATE SOLUTION IN THE BASIC ALLOY KEEPING A SOLID STATE AND THE BRAZING ALLOY IS MELTED AND WETS SAID BASIC ALLOY, AS SOON AS WETTING OF SAID BASIC ALLOY BY THE BRAZING ALLOY IS PERFORMED, THE APPARATUS IS QUICKLY COOLED AT A SPEED OF AT LEAST 1*C PER SECOND SUBSTANTIALLY UP TO THE AMBIENT TEMPERATURE, WHEREBY THE MAGNESIUM SILICIDE OF SAID BASIC ALLOY IS KEPT IN SUPERSATURATION STATE WHILE SAID BRAZING ALLOW IS SOLIDIFIED AND HARDENED, THEN THE APPARATUS IS AGAIN HEATED UP TO A TEMPERATURE AT LEAST EQUAL TO 180*C AND AT MOST EQUAL TO 250*C UP TO THE POINT TO CAUSE A TEMPER CAUSING THE MAGNESIUM SILICIDE TO PRECIPITATE WHILE PROVIDING AN HARDENING OF SAID BASIC ALLOY, AND THE APPARATUS IS LASTLY COOLED BACK TO THE AMBIENT TEMPERATURE, WHEREBY THE BRAZING OF THE PARTS CONSTITUTING IT IS PERFORMED ALONG WITH THE HEAT TREATMENT HARDENING THE ALLOY CONSTITUTING SAID APPARATUS.

Claim 2

Dependent Claim 278 words

METHOD FOR MANUFACTURING AND BRAZING VARIOUS APPARATUSES AND PARTICULARLY HEAT EXCHANGERS, WHEREIN: THE PARTS OF THE APPARATUS ARE MADE FROM THIN SHEETS OF A BASIC ALUMINUM ALLOY CONTAINING SILICON AND MAGNESIUM ABLE TO FORM A MAGNESIUM SILICIDE COMPOUND MG2SI; THE APPARATUS IS ASSEMBLED AND SUBMITTED TO ACTION OF A CLEANING SOLVENT OF THE GREASY PRODUCTS, THE APPARATUS IS HEATED IN PRESENCE OF AN ALUMINIUM BRAZING ALLOY CONTAINING AT LEAST 7% AND AT MOST 15% OF SILICON IN PRESENCE OF METALS AND METAL SALTS CAUSING REMOVAL OF THE OXIDES COVERING THE BASIC ALLOY AND WETTING THEREOF BY THE BRAZING ALLOY, THE APPARATUS IS HEATED TO A TEMPERATURE WITHIN THE RANGE OF 580* TO 600*C, WHEREBY AT A SAME TIME THE MAGNESIUM SILICIDE IS COMPLETELY SET IN A SUPERSATURATED STATE SOLUTION IN THE BASIC ALLOY KEEPING A SOLID STATE AND THE BRAZING ALLOY IS MELTED AND WETS SAID BASIC ALLOY, AS SOON AS WETTING OF SAID BASIC ALLOY BY THE BRAZING ALLOY IS PERFORMED, THE APPARATUS IS QUICKLY COOLED AT A SPEED OF AT LEAST 1*C PER SECOND SUBSTANTIALLY UP TO THE AMBIENT TEMPERATURE, WHEREBY THE MAGNESIUM SILICIDE OF SAID BASIC ALLOY IS KEPT IN SUPERSATURATION STATE WHILE SAID BRAZING ALLOW IS SOLIDIFIED AND HARDENED, THEN THE APPARATUS IS AGAIN HEATED UP TO A TEMPERATURE AT LEAST EQUAL TO 180*C AND AT MOST EQUAL TO 250*C UP TO THE POINT TO CAUSE A TEMPER CAUSING THE MAGNESIUM SILICIDE TO PRECIPITATE WHILE PROVIDING AN HARDENING OF SAID BASIC ALLOY, AND THE APPARATUS IS LASTLY COOLED BACK TO THE AMBIENT TEMPERATURE, WHEREBY THE BRAZING OF THE PARTS CONSTITUTING IT IS PERFORMED ALONG WITH THE HEAT TREATMENT HARDENING THE ALLOY CONSTITUTING SAID APPARATUS.

Claim 3

Dependent Claim 87 words

Method as set forth in claim 1, wherein the proportion of silicon and magnesium comprised in the basic alloy is selected in such a way that all Mg2Si binary system which is formed thereby is set in solution in the aluminium at the melting temperature of the brazing alloy, whereby the magnesium silicide forms with the aluminium a quasi-binary system at said brazing temperature and the magnesium silicide is entirely utilized as an hardening element upon precipitation thereof after a tempering step performed at the brazing end.

Claim 4

Dependent Claim 24 words

Method as set forth in claim 1, wherein magnesium silicide in the aluminium alloy is within the range of 0.3 to 1.9% in weight.

Claim 5

Dependent Claim 87 words

Method as set forth in claim 1, wherein the brazing alloy contains between 7 and 15% of silicon and preferably between 10 and 12%, whereby the melting temperature of said alloy is lower than 580*C, and wherein the basic alloy comprises between 0.30 and 0.80% of magnesium and 0.20 to 0.50% of silicon and preferably 0.45 to 0.65% of magnesium and 0.37 to 0.47% of silicon, whereby the melting temperature of said basic alloy is comprised between 615* and 625*C with a burning point higher than 600*C.

Claim 6

Dependent Claim 31 words

Method as set forth in claim 1, wherein the basic alloy comprises substantially no copper, the highest limit being lower than 0.05% in weight and preferably lower than 0.02% in weight.

Claim 7

Dependent Claim 43 words

Method as set forth in claim 1, wherein the assembled apparatuses are submitted after the degreasing operation to a cleansing operation by passing in an acid or alkaline bath then to a drying operation and a heating operation up to the brazing temperature.

Claim 8

Dependent Claim 147 words

Method as set forth in claim 1, wherein brazing is performed in presence of flux deposited through dipping, through wet spraying, through a dry spraying, and wherein a cooling step which follows immediately the brazing is quickly performed to cause both keeping in solution of the magnesium silicide in the basic alloy, quick solidification and hardening of the brazing alloy, and a heat shock causing removal of the flux from the portions covered by the flux; said apparatus having been cooled substantially up to the ambient temperature and then submitted to a washing operation in a hot acid bath and to a rinsing operation in an aqueous bath at a temperature slightly higher than temperature of the acid bath; whereby traces of flux are eliminated simultaneously with the progressive start of a tempering treatment through which the magnesium silicide is caused to precipitate in the basic alloy.

Claim 9

Dependent Claim 65 words

Method as set forth in claim 7, wherein the quick cooling following immediately the brazing step is performed by blowing gas up to a temperature close to 300*C, then by spraying liquid up to the ambient temperature, whereby the heat shock causing the removal of the flux occurs only at a temperature about 300*C thus eliminating the risks of deforming the parts of the apparatus.

Claim 10

Dependent Claim 74 words

Method as set forth in claim 7, wherein the quick cooling is performed by a liquid spraying according to a cycle causing a quick decrease of the basic alloy temperature, then a heat shock at a temperature about 300*C, said spraying being firstly performed in a very thin atomization form, then under a liquid form sprayed in increasing quantity, said liquid having an aqueous base and containing additives reducing heat absorption power of water.

Claim 11

Dependent Claim 38 words

Method as set forth in claim 1, wherein the brazing alloy contains additives, especially alkaline and alkaline-earth metals, to increase wetting of said alloy, whereby at least the cleaning operation preceeding the fluxing operation is no more required.

Claim 12

Dependent Claim 96 words

Method as set forth in claim 1, wherein brazing is performed without flux, the apparatuses being raised at a temperature within 600*C in presence of magnesium in metal form brought through diffusion under vacuum, through pulverulent form, through suspension in a volatile support, or as additive to the brazing alloy then comprising up to 15% of silicon and 5 to 10% of magnesium to form a ternary alloy having a melting point of about 550*C, the brazing operation being then performed under a vacuum close to 10 4 mm of mercury or under a neutral atmosphere.

Claim 13

Dependent Claim 23 words

Method as set forth in claim 7, wherein the tempering treatment is made in a stove at a temperature between 180* and 240*C.

Claim 14

Dependent Claim 27 words

Method as set forth in claim 7, wherein the tempering treatment is performed together with drying the apparatuses when they have been submitted to the washing operation.

Claim 15

Dependent Claim 54 words

Method as set forth in claim 7, wherein the tempering treatment is performed in two steps, a first one consisting in a slow temperature increase up to a point comprised between 180* and 240*C and a second one consisting in keeping the apparatuses at the temperature point to which said apparatuses have been raised.

Claim 16

Dependent Claim 27 words

Method as set forth in claim 14, wherein the first step of the tempering treatment is performed within a time interval comprised between 20 and 60 minutes.

Claim 17

Dependent Claim 35 words

Method as set forth in claim 14, wherein the second step of the tempering treatement is performed at a temperature within the range of 210* to 225*C for a period of 15 to 30 minutes.

Claim 18

Dependent Claim 61 words

Method as set forth in one of claim 1, wherein the sheets of basic alloy are submitted, before forming the parts, to at least one work-hardening followed by a heat treatment of at least partial restoration performed at a temperature between 250* and 290*C and during a time in relation with a type of mechanical work said sheets have to stand.

Claim 19

Dependent Claim 57 words

Method as set forth in claim 1, wherein the brazing alloy is selectively brought on the sheets of basic alloy through plating upon the manufacturing of said sheets or brought furtherly through bringing the brazing alloy in the form of mixture, or powder especially sprayed with a flame blow-pipe simultaneously with a spraying of an anhydrous flux.

Claim 20

Dependent Claim 14 words

Method as set forth in claim 1, wherein the brazing alloy contains no copper.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1977-12-09	1978-06-10	1978-12-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1981-12-09	1982-06-10	1982-12-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1985-12-09	1986-06-10	1986-12-10	$7700.00	Window Closed / Lapsed

Method for manufacturing and brazing various apparatuses and particularly heat exchangers

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