JP2017512654A - Boric acid free flux - Google Patents

Abstract

The invention described herein generally relates to boric acid free flux compositions in which boric acid and / or borax replaces a molar equivalent of potassium tetraborate tetrahydrate. In some embodiments, phthalocyanine pigments are used to cause a color change at the activation temperature. [Selection figure] None

Description

  This application is a continuation-in-part of US application Ser. No. 13 / 838,485, filed Mar. 15, 2013, which is fully incorporated by reference.

  The invention relates to a boric acid free paste flux composition according to claim 1, a low temperature boric acid free paste flux composition according to claim 6, a high temperature boric acid free paste flux composition according to claim 7, and a boric acid free powder according to claim 8. 15. A flux composition, a high temperature boric acid free powder flux composition according to claim 11, a low temperature boric acid free powder flux composition according to claim 12, a method for producing a boric acid free flux according to claim 13, and a boric acid free according to claim 15. The present invention relates to a flux manufacturing method. The invention described herein generally relates to boric acid free brazing flux compositions.

  In general, brazing flux removes oxides and contaminants from the base material to ensure good quality brazing bonds. The choice of flux depends on the type of filler material, heat source and application method, as well as the base material used. By brazing and heating them in the presence of a filler metal having a liquidus higher than 425 ° C. to 450 ° C. (about 800 ° F. to 840 ° F.) and lower than the solidus of the base material Similar and dissimilar materials are combined. During brazing, the filler material flows between the adapted bonding surfaces by capillary action. The lowest temperature on the surface of the brazed component that occurs without the process being disturbed is the so-called working temperature. That is the specific amount of filler metal in question. The filler material can be an alloy or a pure metal. In general, the heat from brazing is not as harmful as the heat from welding. Furthermore, brazed joints typically have higher strength than soft solder joints. The choice of flux plays an important role in most brazing processes, and bond quality can be compromised by the use of inappropriate flux.

  The molten filler metal must be in direct contact with the base metal so that a bond with the base metal can be formed. Therefore, the type of oxide layer present on any engineered metal surface must first be released and removed. If brazing occurs in air, this is accomplished by coating the brazing site with the flux during a melt flow where the oxide dissolves, decreases or decomposes above the activation temperature of the flux. .

  When heated, the flux dissolves the surface oxide and protects the cleaned surface from reoxidation, transfers heat from the heat source to the bond, removes the oxide product, and contacts the filler material. To wet the base material. The brazing flux, paste or powder is activated at a temperature lower than that required to melt the filler metal. Because the flux is in intimate contact with the binding surface, they are liquid or gas at the brazing temperature. They remove only surface oxides and discoloration. Other contaminants must be removed mechanically or chemically prior to brazing.

  Flux is typically categorized by form (powder, liquid or paste), base materials and filler materials with which they can be used, heat source, application method and active temperature range. The silver brazing flux contains boric acid and potassium borate in combination with a complex potassium fluoroborate and fluoride compound. Up to 40% fluoride in the flux content imparts these fluxes with their characteristically low melting point and high capacity for metal oxide dissolution. High temperature fluxes based on boric acid and alkali borates sometimes contain small additions of elemental boron or silicon dioxide to increase activity and protection.

  The melting point and effective temperature of the flux must be compatible with the working temperature of the brazing filler metal used, so that the flux is about 50-100 ° C. below the working temperature of the filler metal used. At this temperature and should be fully effective from this temperature. Furthermore, the melt flux should form a dense uniform coating on the workpiece that remains intact at the required brazing temperature and during the brazing period.

  Assuming a pure metal surface, the liquid filler material spreads in a thin layer on the base material surface and wets it. The filler material adheres to the base metal surface by slight alloying of the base metal and the filler material. The filler material extends on the bonding surface and, after solidifying, forms a bond that can be loaded by the base metal.

  The brazing flux consists essentially of a salt mixture capable of dissolving the metal oxide in the molten state. These fluxes are substantially in particular inorganic boron compounds such as alkali borates and fluoroborates containing boric acid, and in particular halides such as alkali halides, for example alkali fluorides.

  Regulation (EC) No 1272/2008 of the European Parliament and of the Council on classification, labeling and packaging of substances and mixtures as toxic, according to European Union This requires special labeling that leads to consumer efforts to find boric acid-free alternatives.The appropriate boric acid-free brazing flux maintains market share and Must be developed to achieve.

At least one aspect of the present invention provides superior performance to achieve desirable flux characteristics in which no boric acid (H ₃ BO ₃ ) or borax (NaB ₄ O ₅ (OH) · 4H ₂ O) is present in the flux. Exists.

またこの課題は、おおよその重量％で以下を含んでなる低温ホウ酸フリーペーストフラックス組成物によって解決される。上記組成物は、合計１００％の量で添加される。

またこの課題は、おおよその重量％で以下を含んでなる高温ホウ酸フリーペーストフラックス組成物によって解決される。上記組成物は、合計１００％の量で添加される。

またこの課題は、以下を含んでなるホウ酸フリー粉末フラックス組成物によって解決される。

またこの課題は、おおよその重量％で以下を含んでなる高温ホウ酸フリー粉末フラックス組成物によって解決される。上記組成物は、合計１００％の量で添加される。

またこの課題は、おおよその重量％で以下を含んでなる低温ホウ酸フリー粉末フラックス組成物によって解決される。上記組成物は、合計１００％の量で添加される。

A boric acid free paste flux composition according to claim 1, a low temperature boric acid free paste flux composition according to claim 6, a high temperature boric acid free paste according to claim 7, in order to achieve the desired flux characteristics and overcome the above disadvantages. A boric acid free powder flux composition according to claim 8, a high temperature boric acid free powder flux composition according to claim 11, a low temperature boric acid free powder flux composition according to claim 12, and a boric acid free flux according to claim 13. And a method for producing a boric acid-free flux according to claim 15. Preferred embodiments of the invention are the subject matter of the dependent claims. The present invention describes various flux compositions that do not contain boric acid and optionally include a color change pigment, such as a phthalocyanine pigment, at the activation temperature. This problem is solved by a boric acid free paste flux composition comprising:

This problem is also solved by a low temperature boric acid free paste flux composition comprising, in approximate weight percent, the following: The composition is added in a total amount of 100%.

This problem is also solved by a high temperature boric acid free paste flux composition comprising, in approximate weight percent, the following: The composition is added in a total amount of 100%.

This problem is also solved by a boric acid free powder flux composition comprising:

This problem is also solved by a high temperature boric acid free powder flux composition comprising, in approximate weight percent, the following: The composition is added in a total amount of 100%.

This problem is also solved by a low temperature boric acid free powder flux composition comprising, in approximate weight percent, the following: The composition is added in a total amount of 100%.

Containing in one embodiment, water and potassium hydrogen fluoride _(KHF 2), fumed silica _(SiO 2), potassium tetraborate _{(K 2 B 4 O 7 ·} 4H 2 O) and potassium fluoroborate (KBF ₄₎ A boric acid free paste flux composition is described.

  For high temperature applications, boric acid free paste flux compositions often contain boron.

For low temperature applications, one embodiment of a boric acid free paste flux composition is based on weight percent water (total remaining up to 100%), wetting agent, preferably UDYLITE 62 (0.1-1%), potassium hydrogen fluoride _{(KHF 2) (12~16%)} , fumed silica _{(SiO 2) (0.1~4%)} , potassium tetraborate tetrahydrate _{(K 2 B 4 O 7 ·} 4H 2 O ) (26-35%), potassium fluoroborate (KBF ₄ ) (26-35%) and pigment (phthalocyanine) (0.1-2%).

For high temperature applications, another embodiment of the boric acid free paste flux composition is based on weight percent water (total remaining up to 100%), wetting agent, preferably UDYLITE 62 (0.1-1%). , potassium hydrogen fluoride _{(KHF 2) (12~16%)} , fumed silica _{(SiO 2) (0.1~4%)} , potassium tetraborate tetrahydrate _{(K 2 B 4 O 7 ·} 4H 2 O) (26 to 35%), containing potassium fluoroborate _(KBF 4) (26 to 35%) and boron (0.1% to 2%).

Respect powder applications, boric acid-free powder flux compositions, potassium tetraborate tetrahydrate _{(Κ 2 Β 4 O 7 ·} 4H 2 O), potassium fluorosilicate _(K 2 SiF ₆₎ and potassium fluoroborate (KBF ₄ ) is included.

  For high temperature applications, the boric acid free powder flux will contain boron.

Regard high temperature applications, an embodiment of the boric acid-free powder flux compositions, in weight percent basis, potassium tetraborate tetrahydrate _{(Κ 2 Β 4 O 7 ·} 4H 2 O) (44~54%), fluoro It will contain potassium silicate (K ₂ SiF ₆ ) (1-3%), potassium fluoroborate (KBF ₄ ) (44-54%) and boron (0.1-2%).

For low temperature applications, another embodiment of the boric acid free powder flux composition is potassium tetraborate tetrahydrate (Κ _{2 ４ 4} O ₇ · 4H ₂ O) (44-54%), on a weight percent basis, It will contain potassium fluorosilicate (K ₂ SiF ₆ ) (1-3%), potassium fluoroborate (KBF ₄ ) (44-54%) and pigment (phthalocyanine) (0.1-2%).

The present invention includes the step of replacing boric acid present in the boric acid-containing flux with a substantially similar molar amount of potassium tetraborate tetrahydrate (Κ _{2 ４ 4} O ₇ · 4H ₂ O). And a method for producing boric acid-free flux. The method optionally also includes the step of adding a phthalocyanine pigment that causes a color change at the activation temperature of the flux.

The present invention further comprises the step of replacing the borax present in the borax-containing flux with a substantially similar molar amount of potassium tetraborate tetrahydrate (Κ _{2 ４ 4} O ₇ · 4H ₂ O). The manufacturing method of the boric acid free flux which comprises. The method optionally also includes the step of adding a phthalocyanine pigment that causes a color change at the activation temperature of the flux.

  These and other objects of the invention will become apparent upon consideration of the detailed description and the appended claims.

  The best mode for carrying out the invention will be described for the purpose of illustrating the best mode known to the applicant at the time of filing the present invention. The examples are only illustrative and are not intended to limit the invention as considered by the claims and spirit.

  As used herein, the term “approximately” or “about” means within the stated range with a tolerance of 10%.

  The brazing flux composition is boric acid free, provides good wettability, and changes color from visible spectrum color to clear at the activation temperature.

  The present invention will be described in a series of non-limiting but illustrative examples.

Boric acid has a melting temperature of about 336 ° F. (169 ° C.) and melts initially during heating in the brazing process. This allows the boric acid brazing flux to begin to melt at low temperatures well before the brazing temperature is reached, thereby protecting the joint surface from further oxidation. In addition, this low melting temperature is a hot / hot rod with a boiling / dehydrogenation temperature combination of about 532 ° F. (300 ° C.), that is, the flux melts and then congeals and heated brazing. Useful for creating brazing flux that adheres to the rod. When boric acid reaches 842 ° F. (450 ° C.), it completely dehydrates (or decomposes the released H ₂ O) and protects the base metal and filler metal surface throughout the remaining brazing process. Boron oxide remains. Replacing boric acid in a brazing flux requires the replacement of boric acid with one or more compounds that can substantially replicate the above properties.

  Some compounds have attributes that will lead to boric acid substitution. These options will minimally include a combination of potassium carbonate and diammonium phosphate and ammonium fluoroborate or ammonium fluorosilicate and potassium tetraborate tetrahydrate. In general, the sodium salt is not considered as a possible substitution, primarily because of the “sodium glare” encountered when heated to the brazing temperature. In addition, the sodium borate salt has the EU “regulation (EC) No 1272/2008 of the European Parliament and of the Council on classification, labeling and packing of substances, As such, it was excluded from further consideration.

  Potassium carbonate provides protection at temperatures above 1600 ° F. (871 ° C.) and, by combining potassium carbonate with diammonium phosphate (DAP), provides protection from oxidation above 302 ° F. (150 ° C.). Will make it possible. However, while meeting some substitution criteria, this combination was determined to be impractical for dry powder flux due to the liquefaction of potassium carbonate, the tendency of the flux to absorb moisture. The high dissolution partial pressure of ammonia from DAP requires that the flux be stored in a sealed container when it is not used in order to retain the chemical and physical properties of the flux. Ammonia release is a problem with ammonia fluoroborate and fluorosilicates, and water increase is not a problem, but paste flux is produced by rapid dissolution of ammonia from its anionic counterpart in aqueous solution In that case, the release of ammonia worsens. While these flux formulations provide adequate performance, better alternatives have been pursued based on at least two factors: (1) unpleasant ammonia gas from flux application to heating, and (2) Possible change in flux properties due to hygroscopic renewal over time.

  Potassium tetraborate is also found in brazing flux. It easily dissolves metal (not easily soluble) oxides at high temperatures, almost as much as potassium pentaborate (another substitution option) at a fraction of the cost. It was chosen as an option to be considered for boric acid substitution. Anhydrous potassium tetraborate alone does not melt to 1500 ° F. (816 ° C.), is hygroscopic and converts to tetrahydrate upon prolonged moisture exposure. The hydrating action of powdered anhydrous potassium tetraborate flux causes uncontrolled changes in flux properties over time and imposes unnecessary conditions and / or processing during manufacture. Hydration is an exothermic process that creates manufacturing challenges. While the anhydrous powdered potassium tetraborate flux performs adequately, the flux that does not melt to the interface is hot enough to form additional oxide that would then need to be removed. In addition, this flux will not fully “hot rod” due to the high melting temperature. For all these reasons, potassium tetraborate tetrahydrate was chosen as the preferred substitution over anhydrous potassium tetraborate as an alternative to boric acid.

  The invention is illustrated by a series of non-limiting examples.

Example # 1
In one embodiment of the present invention, the composition comprises water, potassium tetraborate tetrahydrate, potassium hydrogen fluoride, boron, UDYLITE (Udylite 62 is Enthone®, 350 Frontage Road, West Haven, CT A black high temperature paste flux comprising a mixture of fumed silica in the following weight percent:

Example # 2
In another embodiment of the present invention, the low temperature boric acid free paste flux comprises a mixture of water, potassium hydrogen fluoride, potassium tetraborate tetrahydrate, potassium fluoroborate, pigment, UDYLITE and fumed silica in the following weight: Included in%.

  Copper phthalocyanine green no. 7 was utilized as a visual indicator of activation temperature in several compositions. It decomposes in the temperature range of 1022 ° F. (550 ° C.) to 1650 ° F. (900 ° C.), depending on the concentration of acceptable oxidant. The test revealed a reliable correlation between the color change of the low temperature brazing flux from green to transparent and the brazing temperature at the joint surface. Furthermore, this color change did not seem to depend on the pigment concentration.

Example # 3
In another embodiment of the present invention, the high temperature boric acid free powder flux comprises a mixture of potassium tetraborate tetrahydrate, potassium fluorosilicate, potassium fluoroborate and boron in the following weight percent.

Example # 4
In another embodiment of the present invention, the low temperature borate free powder flux comprises potassium tetraborate tetrahydrate, potassium fluorosilicate, potassium fluoroborate and pigment in the following weight percent:

As mentioned above, phthalocyanine pigments are aromatic macrocycles that form coordination complexes with many elements of the periodic table. These complexes are intensely colored and promote color conversion at the temperatures utilized in the reaction. As mentioned above, phthalocyanine pigments are aromatic macrocycles that form coordination complexes with many elements of the periodic table. These complexes are intensely colored and promote color conversion from a colored state in the visible spectrum to a state that is essentially colorless at temperature at the temperature utilized in the reaction. A phthalocyanine macrocycle is shown below, in which a metal ion is typically coordinated to a nitrogen atom within a 5-membered ring.

  The above composition is useful for brazing metallic materials based on copper, silver, nickel and iron based alloys. Without being bound by any one theory or operating mechanism, the flux is used to remove the oxide layer and to allow the base material to be wetted. The activated flux forms a layer on the workpiece and removes surface oxides. The color change at the activation temperature is an obvious feature not seen when compared to commercially available flux.

  The above flux compositions and combinations were tested and all met the AWS A5.31 M / A5.31: 2012 test standards for moisture content, particles, adhesion, flowability, erosion, flow, life and viscosity. .

  The boric acid free fluxes listed in Tables I to IV give excellent performance and are effective alone as brazing fluxes. As discussed below, boric acid free flux often provides better results than commercially available standard fluxes that are not boric acid free.

  In addition, the following tests were performed on an additional series of fluxes synthesized using the compositions identified in Tables 1-6, according to the performance criteria identified and defined below, and in Tables 1a-6a Characterized.

Oxide Removal All boric acid free flux dissolved all oxide from the base metal surface.

Activation Range All boric acid free fluxes are fully active, for low temperature (green) and high temperature flux (black), 1050 ° F to 1600 ° F (566 ° C to 871 ° C) and 1050 ° F to 1050 ° F, respectively. The oxide is removed through a range of 1800 ° F. (566 ° C. to 982 ° C.).

Hot lodging “Hot lodging” is a piece of brazing rod (filler) coating by dipping the hot end into a powder flux. This is applicable only to powder flux. Both powder fluxes were "hot rod" very well.

Activation Range Flux Flowability The flowability test was performed according to AWS A5.31 M / A5.31: 2012. The flowability was good for both boric acid free powder and paste.

Brazing odor and fuming Through all boric acid free flux brazing processes, there was very little unpleasant odor and fuming.

Activation Indicator The colored fluxes in Tables 2 and 4 were the only flux with a visual indicator of the activation temperature actually tested.

In determining the performance of the brazing flux formulation, seven criteria were selected.
(1) Hot rod—The ability of the powder brazing flux to adhere to the hot brazing rod / wire.
(2) Flux flow—how well the molten flux spreads or “wets out” across the heated surface of the base metal, more specifically, the molten flux enters the brazed coupling capillary. How well it flows along and adjacent to the interface.
(3) Metal flow—Metal flow is a decisive criterion for the performance of a brazing flux that reduces the surface tension of the melted melt at the base metal surface, which is generally How well the entire heated surface of the base metal will spread or “wet out”; more specifically, the molten filler material will be along the brazed coupling capillary and close to the interface It is measured by how well it flows adjacently.
(4) Irritating odor—the amount of fumes and soot released and how irritating, sharp or pungent they are.
(5) Flux composition-uniformity and ease of application.
(6) Flux residue—ease of removal of flux residue.
(7) Hot clean—easy to remove flux residue using only hot water.

  Each criterion is evaluated as having a subjective value of 1-5 for the flux formulation. Here, 1 is “undesirable” and 5 is “desirable”.

  In the following examples, tests were performed on 8 powders and 3 paste flux test formulations combined with various components and / or at various ratios. Of these formulations, six contained boric acid to confirm some benchmarks. SSP-4 was selected as the baseline for the powder flux (Tables 1 and 1a) and SSWF was selected as the baseline for the paste flux (Tables 2 and 2a). None of the initial tests were for boron-containing (high temperature) flux. It was hypothesized that a successful low temperature flux could be used as a base for the high temperature flux. Experience with prior art compositions demonstrates this. In addition, the green phthalocyanine pigment, besides providing a visual indicator to the worker, is present at a concentration that is considered very low to be any effective on the performance of the flux. Not included in the functional test of low temperature flux.

Initial powder flux:

Initial paste flux:

  Potassium tetraborate is a common component of brazing flux. This makes it a natural consideration for the substitution of boric acid because it easily dissolves metal (not easily soluble) oxides at high temperatures, and for these reasons it is actually a first choice chemical. It was. Anhydrous potassium tetraborate alone does not melt to 1500 ° F. (816 ° C.), is hygroscopic and converts to tetrahydrate upon prolonged moisture exposure. The hydrating action of powdered anhydrous potassium tetraborate flux causes uncontrolled changes in flux properties over time and imposes unnecessary conditions and / or processing during manufacture. Hydration is an exothermic process that creates manufacturing challenges. A flux that does not melt to the interface while the anhydrous powdered potassium tetraborate flux performs adequately is hot enough to form some additional oxide that would then need to be removed. In addition, this flux will not fully “hot rod” due to the high melting temperature. For these reasons, potassium tetraborate tetrahydrate was selected as a preferred embodiment over anhydrous potassium tetraborate. In both powder and paste flux, boric acid was replaced with potassium tetraborate tetrahydrate. This substitution was initially a molar ratio of about 1: 1 borate content for both fluxes, but then adjusted for the infiltrant to achieve optimal performance.

Testing low temperature (green) powder boric acid free flux formulations:

Testing high temperature (black) powder boric acid free flux formulation:

Testing low temperature (green) paste boric acid free flux formulations:

Test of high temperature (black) paste boric acid free flux formulation:

  The invention has been described with reference to the preferred and alternative embodiments. Obviously, modifications and changes will become apparent upon reading and understanding this specification. It is intended to include all such modifications and changes as long as they come to the scope of the appended claims or their equivalents.

Claims (16)

water and,
Potassium hydrogen fluoride (KHF ₂ ),
Fumed silica (SiO ₂ );
Potassium tetraborate _{(K 2 B 4 O 7 ·} 4H 2 O),
A boric acid-free paste flux composition comprising potassium fluoroborate (KBF ₄ ). In the boric acid free paste flux composition according to claim 1,
A boric acid-free paste flux composition, further comprising boron. In the boric acid-free paste flux composition according to claim 1 or 2,
A boric acid-free paste flux composition further comprising an infiltrant and / or a phthalocyanine pigment. In the boric acid free paste flux composition according to any one of claims 1 to 3,
A boric acid-free paste flux composition, wherein the phthalocyanine pigment changes from colored to colorless at a temperature of about 500 to 600 ° C. In the boric acid-free paste flux composition according to any one of claims 1 to 4,
Phthalocyanine pigments,
An infiltrant;
A boric acid-free paste flux composition, further comprising boron. In approximate weight percent,
The remaining water,
0.1-1% infiltrant,
12 to 16% of potassium hydrogen fluoride and (KHF _2),
0.1 to 4% fumed silica (SiO ₂ );
26 to 35% of potassium tetraborate tetrahydrate and _{(K 2 B 4 O 7 ·} 4H 2 O),
26 to 35% of potassium fluoroborate and (KBF _4),
A low-temperature boric acid-free paste flux composition comprising 0.1 to 2% of a pigment (phthalocyanine), wherein the composition is added in a total amount of 100%. Composition. In approximate weight percent,
The remaining water,
0.1-1% infiltrant,
12 to 16% of potassium hydrogen fluoride and (KHF _2),
0.1 to 4% fumed silica (SiO ₂ );
26 to 35% of potassium tetraborate tetrahydrate and _{(K 2 B 4 O 7 ·} 4H 2 O),
26 to 35% of potassium fluoroborate and (KBF _4),
A high-temperature boric acid-free paste flux composition comprising 0.1 to 2% boron, wherein the composition is added in a total amount of 100%. Potassium tetraborate _{(K 2 B 4 O 7 ·} 4H 2 O),
Potassium fluorosilicate (K ₂ SiF ₆ );
A boric acid-free powder flux composition comprising potassium fluoroborate (KBF ₄ ). The boric acid-free powder flux composition according to claim 8,
A boric acid-free powder flux composition further comprising boron and / or a phthalocyanine pigment. The boric acid-free powder flux composition according to claim 8 or 9,
A boric acid-free powder flux composition, wherein the phthalocyanine pigment changes from colored to colorless at a temperature of about 500 to 600 ° C. In approximate weight percent,
44 to 54% of potassium tetraborate tetrahydrate and _{(K 2 B 4 O 7 ·} 4H 2 O),
1-3% potassium fluorosilicate (K ₂ SiF ₆ ),
44 to 54% of potassium fluoroborate and (KBF _4),
A high temperature boric acid free powder flux composition comprising 0.1 to 2% boron, wherein the composition is added in a total amount of 100%. In approximate weight percent,
44 to 54% of potassium tetraborate tetrahydrate and _{(K 2 B 4 O 7 ·} 4H 2 O),
1-3% potassium fluorosilicate (K ₂ SiF ₆ ),
44 to 54% of potassium fluoroborate and (KBF _4),
A low-temperature boric acid-free powder flux composition comprising 0.1 to 2% of a pigment (phthalocyanine), wherein the composition is added in a total amount of 100%. Composition. Characterized in that the boric acid present in boric acid-containing flux contains substantially similar molar amount of steps to replace the potassium tetraborate tetrahydrate _{(K 2 B 4 O 7 ·} 4H 2 O) A method for producing boric acid-free flux. The method of claim 13, wherein
Adding a phthalocyanine pigment which causes a color change at the activation temperature of the flux. Characterized in that the borax present in borax-containing flux contains substantially similar molar amount of steps to replace the potassium tetraborate tetrahydrate _{(K 2 B 4 O 7 ·} 4H 2 O) A method for producing boric acid-free flux. The method of claim 15, wherein
Adding a phthalocyanine pigment which causes a color change at the activation temperature of the flux.