JP2014184476A - Composition for brazing and heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a composition for brazing which enables stainless steel to be excellently brazed at a relatively low temperature under an inert atmosphere (under an inert gas atmosphere or under a vacuum), and furthermore is excellent in application work efficiency, adhesion and storage stability; and a heat exchanger obtained by using the composition for brazing.SOLUTION: The composition for brazing used for brazing the stainless steel under the inert atmosphere contains (a) Ni-Cr-Si-P-based nickel brazing material powder, (b) butyl rubber, (c) a hydrocarbon -based organic solvent and (d) hardened castor oil, a blending rate of (b) the butyl rubber is set to 0.5 pts.mass-1.0 pts.mass, and a blending rate of (d) the hardened castor oil is set to 0.05 pts.mass-1.0 pts.mass, to 100 pts.mass of the composition for brazing.

Description

  The present invention relates to a brazing composition and a heat exchanger obtained by using the brazing composition.

  Conventionally, a heat exchanger made of stainless steel is used in an exhaust gas recirculation (EGR) system of an automobile. Such heat exchangers are assembled by brazing stainless steel with a brazing material such as a nickel brazing material.

  In brazing, a brazing paste containing a brazing material is generally used. For example, a brazing paste-like composition containing nickel brazing powder, butyl rubber, and an organic solvent is known.

  More specifically, for example, 85 parts by mass of nickel brazing filler metal powder (JIS: BNi-5) containing Ni, Cr and Si, 2.6 parts by mass of butyl rubber (Exxon Butyl 268 (manufactured by Exxon Chemical)), A brazing paste-like composition containing 0.4 parts by mass of hydrogenated castor oil (Disparon 305 (manufactured by Enomoto Chemical)) and 12 parts by mass of toluene has been proposed. Further, it has been proposed that such a brazing paste composition is heated to 1150 ° C. in an inert atmosphere such as an argon gas atmosphere furnace or a vacuum furnace and used for brazing stainless steel (for example, Patent Document 1 (Examples 7 and 8).

  On the other hand, in brazing, it is required to lower the heating temperature at the time of brazing from the viewpoint of suppressing deterioration of stainless steel and reducing the cost.

  In this regard, it is known that the heating temperature at the time of brazing can be lowered according to the Ni—Cr—Si—P type nickel brazing material in which phosphorus (P) is added to the nickel brazing material. As such a nickel brazing material, specifically, for example, Cr is contained in a proportion of 10 to 30% by weight, P is contained in a proportion of 2 to 11% by weight, and Si is contained in a proportion of 1 to 10% by weight. Has been proposed (for example, see Patent Document 2).

JP 2003-275895 A JP-A-9-225679

  However, in the brazing paste composition described in Patent Document 1, when the Ni-based heat-resistant brazing material described in Patent Document 2 is used as the nickel brazing material, the brazing property is inferior and coating dripping is likely to occur. Therefore, there is a problem that the coating workability is inferior.

  In addition, the brazing paste composition is required to have adhesion after coating and drying, storage stability (redispersibility after storage for a predetermined period), and the like.

  Accordingly, an object of the present invention is to satisfactorily braze stainless steel at a relatively low temperature in an inert atmosphere (inert gas atmosphere or vacuum), and further, coating workability, adhesion and storage. It is providing the brazing composition excellent in stability, and the heat exchanger obtained using the brazing composition.

  In order to achieve the above object, the brazing composition of the present invention is a brazing composition used for brazing stainless steel under an inert atmosphere, comprising: (a) Ni-Cr-Si- P-type nickel brazing filler metal powder, (b) butyl rubber, (c) hydrocarbon organic solvent, and (d) hardened castor oil, with respect to 100 parts by mass of the brazing composition, b) The blending ratio of butyl rubber is 0.5 parts by weight or more and less than 1.0 part by weight, and the blending ratio of the (d) hardened castor oil is 0.05 parts by weight or more and 1.0 part by weight or less. It is a feature.

  Further, in the brazing composition of the present invention, the Si content in the (a) Ni—Cr—Si—P-based nickel brazing powder is such that the (a) Ni—Cr—Si—P-based nickel It is preferable that the amount is 3.6 parts by mass or more and 4.4 parts by mass or less with respect to 100 parts by mass of the total amount of the brazing filler metal powder.

  In the brazing composition of the present invention, the oxygen concentration in the (a) Ni—Cr—Si—P-based nickel brazing filler metal powder is such that the (a) Ni—Cr—Si—P-based nickel brazing powder is used. It is suitable that it is less than 500 ppm with respect to the total amount of material powder.

  Moreover, the heat exchanger of this invention is provided with the brazing part by said brazing composition, It is characterized by the above-mentioned.

  Since the brazing composition of the present invention contains Ni—Cr—Si—P-based nickel brazing powder, stainless steel is produced at a relatively low temperature in an inert atmosphere (inert gas atmosphere or vacuum). Can be brazed well.

  Moreover, since the butyl rubber and the hardened castor oil are mix | blended in the said ratio, the brazing composition of this invention can be equipped with the outstanding brazing property, application | coating workability, adhesiveness, and storage stability.

  Moreover, since the heat exchanger of the present invention includes the brazing portion of the brazing composition of the present invention, the heat exchanger can be manufactured with excellent coating workability and has excellent brazing properties and adhesion. Can do.

FIG. 1 is a schematic perspective view showing an embodiment of the heat exchanger of the present invention.

  The brazing composition of the present invention is a brazing composition used for brazing stainless steel, and comprises (a) Ni-Cr-Si-P-based nickel brazing powder, and (b) butyl rubber. , (C) a hydrocarbon-based organic solvent, and (d) hardened castor oil.

  (A) Ni—Cr—Si—P-based nickel brazing powder is obtained by alloying nickel (Ni), chromium (Cr), silicon (Si) and phosphorus (P) by a known method. Can do.

  In the (a) Ni—Cr—Si—P-based nickel brazing filler metal powder, the Cr content is, for example, with respect to 100 parts by mass of the total amount of the (a) Ni—Cr—Si—P-based nickel brazing powder. 25 parts by mass or more, for example, 35 parts by mass or less.

  If the content of Cr is in the above range, the melting point and wettability can be kept good, and the corrosion resistance and heat resistance can be improved.

  Moreover, Si content is 3 mass parts or more with respect to 100 mass parts of total amounts of (a) Ni-Cr-Si-P type nickel brazing filler metal powder, Preferably it is 3.6 mass parts or more. For example, it is 6 parts by mass or less, preferably 4.4 parts by mass or less.

  When the Si content is in the above range, brazing properties, particularly brazing properties in an inert gas atmosphere, can be improved.

  Moreover, P content is 4 mass parts or more with respect to 100 mass parts of total amounts of (a) Ni-Cr-Si-P-type nickel brazing filler metal powder, for example, 8 mass parts or less.

  If content of P is the said range, while maintaining corrosion resistance favorable, melting | fusing point can be adjusted to the target temperature.

  In (a) Ni—Cr—Si—P-based nickel brazing filler metal powder, the Ni content is appropriately set as the balance of the above components.

  The oxygen concentration in the (a) Ni—Cr—Si—P-based nickel brazing filler metal powder is, for example, less than 750 ppm relative to the total amount of the (a) Ni—Cr—Si—P-based nickel brazing filler metal powder. , Preferably, it is less than 500 ppm, More preferably, it is less than 300 ppm, Usually, it is 100 ppm or more.

  (A) When the oxygen concentration in the Ni—Cr—Si—P-based nickel brazing filler metal powder is in the above range, excellent brazing properties, particularly excellent brazing properties under an inert gas atmosphere can be ensured. .

  (A) Ni—Cr—Si—P-based nickel brazing filler metal powder may be used alone, and the content ratio of each element is different (a) Ni—Cr—Si—P-based nickel brazing filler metal powder May be used in combination of two or more.

  By using such a (a) Ni—Cr—Si—P-based nickel brazing powder, it is possible to satisfactorily braze stainless steel at a relatively low temperature in an inert atmosphere (inert gas atmosphere or vacuum). can do.

  (A) The average primary particle diameter of the Ni—Cr—Si—P-based nickel brazing powder is, for example, 10 μm or more, for example, 100 μm or less.

  (A) When the average primary particle diameter of the Ni—Cr—Si—P-based nickel brazing filler metal powder is in the above range, it is possible to ensure good dischargeability of the paste and improve brazing properties.

  In addition, the measuring method of an average primary particle diameter applies to the Example mentioned later.

  In addition, the blending ratio of (a) Ni—Cr—Si—P-based nickel brazing filler metal powder is, for example, 91.2 parts by mass or more with respect to 100 parts by mass of the total amount of the brazing composition. It is 93.2 mass parts or less.

  (A) When the blending ratio of the Ni—Cr—Si—P-based nickel brazing powder is within the above range, the viscosity of the brazing composition can be adjusted to a range suitable for coating.

  (B) Butyl rubber is contained in the brazing composition as a binder resin, and examples thereof include known butyl rubber, specifically, a homopolymer of isobutylene or a copolymer of isobutylene and isoprene.

  Such (b) butyl rubber is not particularly limited and can be obtained by a known method.

  (B) The polystyrene-reduced weight average molecular weight of butyl rubber by gel permeation chromatography (measurement conditions are in accordance with Examples described later) is, for example, 160,000 or more, preferably 200,000 or more, more preferably. 400,000 or less, for example, 4,500,000 or less, preferably 4,000,000 or less, and more preferably 1,200,000 or less.

  (B) If the weight average molecular weight of butyl rubber is more than the said minimum, the outstanding workability | operativity can be obtained and the improvement of storage stability can be aimed at. Moreover, if the weight average molecular weight of (b) butyl rubber is below the said upper limit, the outstanding workability | operativity can be obtained and also the outstanding productivity in continuous production can be ensured.

  Such (b) butyl rubber can also be obtained as a commercial product. Specifically, for example, the trade name “OPanol B30” (manufactured by BASF, weight average molecular weight 200,000), the trade name “ Opanol B50 "(BASF, weight average molecular weight 308,000), trade name" Opanol B80 "(BASF, weight average molecular weight 748,000), trade name" Opanol B100 "(BASF, weight average molecular weight 1) , 120,000), trade name “Opanol B150” (BASF, weight average molecular weight 2,560,000), trade name “Opanol B200” (BASF, weight average molecular weight 4,180,000), and the like. It is done.

  These (b) butyl rubbers can be used alone or in combination of two or more.

  The blending ratio of (b) butyl rubber is 0.5 parts by mass or more, preferably 0.7 parts by mass or more and less than 1.0 parts by mass with respect to 100 parts by mass of the total amount of the brazing composition. The amount is preferably less than 0.8 parts by mass.

  (B) If the mixing | blending ratio of a butyl rubber is more than the said minimum, while providing the outstanding adhesiveness, the improvement of storage stability can be aimed at. Moreover, if the blending ratio of (b) butyl rubber is less than the above upper limit, excellent brazing property and coating workability can be ensured.

  Further, when the blending ratio of (b) butyl rubber is within the above range, (b) Ni—Cr—Si—P-based nickel brazing powder is used and brazing is performed at a relatively low temperature condition. ) The butyl rubber can be thermally decomposed well, and excellent brazing properties can be obtained.

  On the other hand, when the blending ratio of (b) butyl rubber is less than the lower limit, there is a problem that the adhesiveness of the brazing composition is poor and the storage stability is poor. In addition, when the blending ratio of (b) butyl rubber is equal to or more than the above upper limit, the brazing property when brazing at a relatively low temperature, particularly the brazing property under an inert gas atmosphere is inferior. There is a problem that workability is inferior.

  (C) Examples of hydrocarbon-based organic solvents include aliphatic hydrocarbon-based / alicyclic hydrocarbon-based (naphthene-based) organic solvents such as n-hexane, cyclohexane, methylcyclohexane, and octane, such as toluene and xylene. And aromatic hydrocarbon organic solvents (hydrocarbon organic solvents having an aromatic ring). Further, examples of the hydrocarbon-based organic solvent include a hydrocarbon-based organic solvent having a hydroxyl group such as methyl alcohol, ethyl alcohol, and isopropyl alcohol.

  (C) The hydrocarbon organic solvent can be used alone or in combination of two or more.

  On the other hand, hydrocarbon organic solvents having an aromatic ring may be inferior in occupational health, safety, environmental conservation, and odor.

  In addition, the hydrocarbon organic solvent having a hydroxyl group may be inferior in storage stability. For example, when water coexists, it reacts with the brazing filler metal powder over time to improve storage stability and safety. In some cases, it may be lowered or brazing may be lowered.

  Therefore, (c) the hydrocarbon-based organic solvent is preferably a hydrocarbon-based organic solvent having no aromatic ring and hydroxyl group, specifically, an aliphatic hydrocarbon-based / alicyclic hydrocarbon-based (naphthene-based) organic A solvent is mentioned.

  If an aliphatic hydrocarbon / alicyclic hydrocarbon (naphthene) organic solvent is used, occupational health, safety, environmental conservation, odor, and storage stability can be ensured.

  In addition, the boiling point of the (c) hydrocarbon-based organic solvent is, for example, 150 ° C. or higher, preferably 180 ° C. or higher, from the viewpoint of smoothness of work by suppressing odor.

  Such a hydrocarbon organic solvent is also available as a commercial product. Specifically, for example, the trade name “EXSOL D80” (manufactured by Exxon Mobil, naphthenic hydrocarbon organic solvent, boiling point (initial Boiling point) 205 ° C.).

  (C) The blending ratio of the hydrocarbon-based organic solvent is not particularly limited, but is appropriately set so that the viscosity of the brazing composition falls within the range described below.

  (C) If the blending ratio of the hydrocarbon-based organic solvent is within the above range, excellent coating workability can be obtained.

  (D) Hardened castor oil is contained in the brazing composition as a thixotropic agent.

  (D) The mixture ratio of hardened castor oil is 0.05 mass part or more with respect to 100 mass parts of total amounts of the composition for brazing, and is 1.0 mass part or less.

  (D) If the mixture ratio of hardened castor oil is more than the said minimum, the outstanding workability | operativity can be obtained and the improvement of storage stability can be aimed at. Moreover, if the blending ratio of (d) hardened castor oil is not more than the above upper limit, excellent brazing properties can be ensured.

  On the other hand, when the blending ratio of (d) hardened castor oil is less than the above lower limit, there is a problem that the coating workability is poor and the storage stability is also poor. Further, when the blending ratio of (d) hardened castor oil exceeds the above upper limit, there is a problem that the brazing property, in particular, the brazing property under an inert gas atmosphere is inferior.

  The brazing composition may contain, for example, an antioxidant (for example, dibutylhydroxytoluene), a corrosion inhibitor (for example, benzotriazole), an antifoaming agent (for example, silicon oil, glycerin) as necessary. Etc.), various additives such as viscosity modifiers (for example, wax, fatty acid amides, polyamides, etc.) excluding hardened castor oil, and colorants can be contained within a range not impairing the effects of the present invention.

  And the composition for brazing can be obtained as a paste-like composition by mixing and stirring said each component by a well-known method in the above-mentioned ratio.

Viscosity V _{10 rpm at} 25 ° C. measured by a spiral pump viscometer (measurement sample amount 150 mL) of the brazing composition obtained is, for example, 70 Pa · s or more, preferably 77 Pa · s or more. For example, it is 90 Pa · s or less, preferably 82 Pa · s or less.

If viscosity _V10rpm is the said range, the improvement of coating workability | operativity and storage stability can be aimed at.

Further, the viscosity V _{30 rpm at} 25 ° C. measured by a spiral pump viscometer (measurement sample amount 150 mL) of the brazing composition is, for example, 35 Pa · s or more, for example, 50 Pa · s. It is as follows.

Further, the viscosity V 3 _{rpm at} 25 ° C. of the brazing composition measured by a spiral pump viscometer (measurement sample amount 150 mL) with a stirring speed of 3 _rpm is, for example, 114 Pa · s or more, for example, 160 Pa · s. It is as follows.

Then, a viscosity V at ₃₀ ° C. measured by a spiral pump viscometer with a stirring speed of 30 rpm (measured sample amount 150 mL) and a viscosity V of _{30 rpm} measured at 25 ° C. with a spiral pump viscometer with a stirring speed of 3 rpm (measured sample amount of 150 mL). The thixo value calculated by the following formula (1) from the viscosity V of 3 _rpm is, for example, 0.51 or more.

[Thixo value] = Log ₁₀ (V 3 _rpm ) / Log ₁₀ (V _{30 rpm} ) (1)
If the thixo value is in the above range, excellent coating workability can be obtained, and brazing and storage stability can be improved.

  Since the brazing composition of the present invention contains Ni-Cr-Si-P-based nickel brazing filler metal powder, as will be described later, the stainless steel is better brazed at a relatively low temperature in an inert atmosphere. Can be attached.

  Moreover, since the butyl rubber and the hardened castor oil are mix | blended in the said ratio, the brazing composition of this invention can be equipped with the outstanding brazing property, application | coating workability, adhesiveness, and storage stability.

  Hereinafter, a method for brazing stainless steel using the above brazing composition will be described in detail.

  In this method, first, the brazing composition is applied to a member made of stainless steel (hereinafter referred to as a stainless member) (application step).

  The application method is not particularly limited, and known methods such as dispenser, screen printing, brush coating, spray coating, roll coater, bar coater, doctor blade, etc. can be employed.

  In addition, the amount of brazing composition applied and the shape of the coating area (linear coating, dot coating, etc.) are not particularly limited, and the viscosity of the brazing composition and the structure to be brazed are taken into consideration. And it sets suitably so that sufficient joint strength may be obtained after brazing.

  Next, a separate stainless steel member is prepared and brought into contact with the stainless steel member coated with the brazing composition via the brazing composition, and assembled into a predetermined structure (contact process).

  In this method, the brazing composition can be dried, if necessary, after the coating step, before or after assembling the members into a predetermined structure.

  In this method, the brazing composition is heated under an inert atmosphere (heating step).

Specifically, as the inert atmosphere, for example, an inert gas atmosphere such as argon gas, helium gas, nitrogen gas, or a vacuum atmosphere (vacuum degree: 133 × 10 ⁻³ Pa (10 ⁻³ torr) or less) is used. Can be mentioned.

  Also, the brazing temperature (heating temperature) is relatively low, specifically, usually above the melting point of the brazing material (the above (a) Ni-Cr-Si-P-based nickel brazing powder), For example, it is 960 degreeC or more, for example, 1200 degreeC, Preferably, it is 1000 degrees C or less.

  When the brazing temperature is in the above range, deterioration due to brazing of stainless steel can be suppressed and cost reduction can be achieved.

  Thereby, a stainless steel member can be brazed (joined).

  In such a brazing method, since the above brazing composition is used, the stainless steel member can be brazed with excellent coating workability, brazing performance and brazing performance.

  Therefore, the brazing composition and the brazing method described above are used in the manufacture of various equipment including a stainless steel member, for example, a stainless steel heat exchanger provided in an exhaust gas recirculation (EGR) system of an automobile. Preferably used.

  FIG. 1 is a schematic perspective view showing an embodiment of the heat exchanger of the present invention.

  In FIG. 1, a heat exchanger 1 is an EGR cooler mounted on a vehicle such as an automobile and provided for cooling a part of exhaust gas and returning it to an intake system of an engine. A gas tube 3 and a pair of end plates 4 are provided.

  The shell 2 is a pipe member through which cooling water passes, and is formed in a rectangular tube shape extending in the longitudinal direction. The shell 2 includes a cooling water inlet pipe 8 on one side in the longitudinal direction, and a cooling water outlet pipe 9 on the other side in the longitudinal direction.

  Specifically, an opening is formed in the side wall on one side in the longitudinal direction of the shell 2, and a cooling water inlet pipe 8 for supplying cooling water to the shell 2 is joined to the opening. Yes. An opening is also formed in the other side wall of the shell 2 in the longitudinal direction, and a cooling water outlet pipe 9 for discharging the cooling water from the shell 2 is joined to the opening.

  A plurality of (for example, six) gas tubes 3 are flat tube members through which EGR gas passes, and are formed so as to extend along the direction in which the shell 2 extends. They are arranged in parallel at intervals.

  The pair of end plates 4 are plate-like members formed in substantially the same shape as the cross-sectional shape of the shell 2, and are fitted into openings on both sides in the longitudinal direction to close the shell 2. The end plate 4 is penetrated by the gas tube 3 to fix the gas tube 3 in the shell 2.

  In addition, a pair of header members 5 are provided at both longitudinal ends of the shell 2.

  Each of the pair of header members 5 includes a plate-like flange portion 6 having a through-hole, and a rectangular tube-like square tube that extends from the flange portion 6 toward the shell 2 side and gradually increases in diameter toward the shell 2 side. Part 7. Such a rectangular tube portion 7 of each header member 5 and the plurality of gas tubes 3 communicate with each other.

  Although not shown in detail, the flange portion 6 of one header member 5 is connected to piping from the engine exhaust system of the vehicle, and the flange portion 6 of the other header member 5 is connected to the engine intake system of the vehicle. Connected to the pipe.

  In such a heat exchanger 1, cooling water is supplied into the shell 2 (around the gas tube 3) via the cooling water inlet pipe 8, passes through the shell 2, and then passes through the cooling water outlet pipe 9. Discharged outside.

  At the same time, high-temperature EGR gas is supplied from the engine exhaust system into the gas tube 3 through the one header member 5. The EGR gas passes through the gas tube 3 and is cooled by cooling water flowing around the gas tube 3, and then is discharged from the gas tube 3 through the other header member 5 and introduced into the engine intake system. Is done.

  In such a heat exchanger 1, the above-described members, that is, the shell 2, the gas tube 3, the end plate 4, the header member 5, the cooling water inlet pipe 8, and the cooling water outlet pipe 9 are each made of stainless steel. Each of these members is brazed (joined) by the brazing composition described above.

  That is, said heat exchanger 1 is provided with the brazing part by the brazing composition of this invention. Therefore, the above-described heat exchanger 1 can be manufactured with excellent coating workability, and can be provided with excellent brazing properties and adhesion.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example. “Part” and “%” are based on mass unless otherwise specified. Moreover, the numerical value of the Example shown below can be substituted for the numerical value (namely, upper limit value or lower limit value) described in embodiment.

The measuring method of the physical property used in an Example, a comparative example, etc. is shown below.
<Average primary particle size>
A laser diffraction / scattering particle size distribution analyzer MT3000II (manufactured by MICROTRAC) was used. Using isopropyl alcohol (IPA; refractive index 1.38) as a solvent, measured by the DV value of the sample (a value related to the integrated scattered light amount of particles captured by a detector placed in front of the laser) A sample is prepared so that the standard of the microtrack for determining the concentration is in the range of 0.01 to 1.0, and after irradiating with ultrasonic waves using an ultrasonic device (output 40 W) for 3 minutes, a flow rate of 80 % (40 cc / min) while circulating (measurement conditions: particle permeability... Reflection).
<Weight average molecular weight (Mw) measurement by gel permeation chromatography>
The sample was dissolved in tetrahydrofuran, the sample concentration was set to 1.0 g / L, and the sample was measured by gel permeation chromatograph (GPC) equipped with a differential refractive index detector (RID) to obtain the molecular weight distribution of the sample.

Thereafter, the weight average molecular weight (Mw) of the sample was calculated from the obtained chromatogram (chart) using standard polystyrene as a calibration curve. The measurement apparatus and measurement conditions are shown below.
Data processor: Part number HLC-8220GPC (manufactured by Tosoh Corporation)
Differential refractive index detector: RI detector column built in part number HLC-8220GPC: Part number TSKgel SuperHZM-H (manufactured by Tosoh Corporation) 2 mobile phases: tetrahydrofuran column Flow rate: 0.35 mL / min
Sample concentration: 1.0 g / L
Injection volume: 10 μL
Measurement temperature: 40 ° C
Molecular weight marker: Standard polystyrene (Standard material manufactured by POLYMER LABORATORIES LTD.) (Used by POLYSTYRENE-MEDIAUM MULTICULAR WEIGHT CALIBRATION KIT)
<Viscosity>
The viscosity of the sample at 25 ° C. (viscosity V ₁₀ rpm at a stirring speed of 20 _rpm ) was measured under the following conditions using a spiral pump viscometer (PCU-205, manufactured by Malcolm).
Stirring speed: 10rpm
Sample size: 150cc
Sample container: High resist container manufactured by Kinki Container Co., Ltd.
The viscosity of the sample at 25 ° C. (viscosity V _{30 rpm at} a stirring speed of _{30 rpm} , viscosity V 3 _{rpm at} a stirring speed of 3 _rpm ) was measured using a spiral pump viscometer (PCU-205, manufactured by Malcolm) under the following conditions. And thixo value was computed by following formula (1).
Stirring speed: 30 rpm and 3 rpm
Sample size: 150cc
Sample container: High resist container manufactured by Kinki Container Co., Ltd. [Thixo value] = Log ₁₀ (V 3 _rpm ) / Log ₁₀ (V _{30 rpm} ) (1)
Examples 1-10 and Comparative Examples 1-5
In accordance with the formulation shown in Tables 1 and 2, Ni-Cr-Si-P-based nickel brazing filler metal powder, butyl rubber and hardened castor oil are blended, and a hydrocarbon-based organic solvent (Exol is used so that the total amount becomes 100 parts by mass. D80, manufactured by ExxonMobil Co., Ltd.) was mixed and stirred to obtain a brazing composition.

Details of each component in the table are described below.
<Ni-Cr-Si-P-based nickel brazing powder>
Ni-Cr-Si-P brazing powder A: In 100 parts by weight of brazing filler metal powder, Ni 60.8 parts by weight, Cr 29.7 parts by weight, Si 3.5 parts by weight, P 6.0 parts by weight, oxygen concentration 170 ppm, average primary Particle size 33μm
Ni-Cr-Si-P brazing filler metal powder B: In 100 mass parts of brazing filler metal powder, Ni 60.4 mass parts, Cr 29.9 mass parts, Si 3.6 mass parts, P6.1 mass parts, oxygen concentration 200 ppm, average primary Particle size 30μm
Ni-Cr-Si-P brazing filler metal powder C: In 100 parts by weight of brazing filler metal powder, Ni 60.4 parts by mass, Cr 29.6 parts by mass, Si 4.0 parts by mass, P 6.0 parts by mass, oxygen concentration 230 ppm, average primary Particle size 31μm
Ni-Cr-Si-P brazing filler metal powder D: In 100 mass parts of brazing filler metal powder, Ni 59.8 mass parts, Cr 29.6 mass parts, Si 4.4 mass parts, P6.2 mass parts, oxygen concentration 250 ppm, average primary Particle size 29μm
Ni-Cr-Si-P brazing filler metal powder E: In 100 parts by weight of brazing filler metal powder, Ni 59.6 parts by weight, Cr 29.8 parts by weight, Si 4.5 parts by weight, P6.1 parts by weight, oxygen concentration 300 ppm, average primary Particle size 29μm
Ni-Cr-Si-P brazing filler metal powder F: In 100 parts by weight of brazing filler metal powder, Ni 60.4 parts by mass, Cr 29.6 parts by mass, Si 4.0 parts by mass, P 6.0 parts by mass, oxygen concentration 510 ppm, average primary Particle size 22μm
<Binder>
Butyl rubber: “Opanol B80” (BASF, weight average molecular weight 748,000)
Polysaccharide thickener: Water-soluble binder, trade name “Metroze 65SH” (manufactured by Shin-Etsu Chemical Co., Ltd.)
<Hydrocarbon organic solvent>
Naphthenic hydrocarbon solvent: Trade name “Exor D80” (Exxon Mobile)
Water + water-soluble solvent: Mixed solvent of water and water-soluble solvent (trade name “propylene glycol” (Asahi Glass Co., Ltd.)) (water: water-soluble solvent (mass ratio) = 76: 24)
<Hardened castor oil>
Hardened castor oil: Trade name “Castor hardened oil”
[Evaluation]
Using the brazing composition obtained in each Example and each Comparative Example, a test piece for evaluation was produced and evaluated according to the following criteria.

  Specifically, first, in the center in the width direction orthogonal to the longitudinal direction of a 25 mm × 60 mm stainless steel plate (SUS-430 compliant with JIS standard), the width is about 5 mm and the height is about 2 mm. An application composition was applied.

  Next, a stainless steel plate of 25 mm × 60 mm (SUS-430 compliant with JIS standard) is perpendicular to the first stainless steel plate (inverted T-shape) so as to come into contact with the applied brazing composition. Standing, fixing with a stainless steel wire, and drying at 200 ° C. for 0.5 hour, a test piece for brazing evaluation was prepared.

  Next, the test piece was inserted into a box-type brazing furnace (A-BC-M type (manufactured by Noritake TCF)) and heated from 30 ° C. to 1200 ° C. over about 20 minutes in an argon atmosphere. And brazing.

Further, brazing was performed in the same manner as described above except that the atmosphere in the brazing furnace was vacuum (5 × 10 ⁻³ Pa).
<Brassability>
The brazing composition of the test piece was visually observed to evaluate the brazing property. The criteria for evaluation are as follows.
○: The brazing residue was not seen, and the brazing was sufficiently spread.
Δ: Some unmelted wax was seen and the wet spread was slightly insufficient, but brazing was possible.
X: The wax was hardly melted and was not brazed.
<Applicability (1) Application workability>
At the time of application of the brazing composition, the application dripping from the nozzle tip of the dispenser and the application failure of the brazing composition were visually evaluated. The criteria for evaluation are as follows.
◯: Stable application was possible without application dripping or application interruption.
(Triangle | delta): Application | coating dripping and application | coating cut-off were seen a little, and adjustment was needed for stable application | coating one by one.
X: Application dripping and application interruption were frequently observed, and stable application was not possible.
<Applicability (2) Adhesiveness>
After the brazing composition was applied and dried, the following drop test was performed before heating in the brazing furnace.

That is, after measuring the mass (A) of the member after coating and drying, it was dropped freely from a height of 20 cm, the mass (B) of the dry paste remaining on the member was measured, and the mass change ((A−B) × 100 / A) was calculated. The criteria for evaluation are as follows.
○: No peeling was confirmed in the drop test after coating and drying. (Mass change within 1%)
Δ: Some peeling was confirmed in the drop test after coating and drying. (Mass change less than 5%)
X: Peeling was confirmed in the drop test after coating and drying. (Mass change 5% or more)
<Storage stability (redispersibility)>
The brazing composition was stored for 2 months under a stationary storage condition of 23 ° C., and the dispersibility of each component was compared with the initial state (dispersibility immediately after production of the brazing composition). The criteria for evaluation are as follows.
○: Almost no change compared to the initial state.
Δ: Slight phase separation was observed compared to the initial state, but it easily returned to the initial state when stirred.
X: Phase separation was remarkable compared to the initial state, and it was difficult or did not return to the initial state even after stirring.

Production Example 1
In the production of the heat exchanger (see FIG. 1), the brazing composition obtained in Example 1 was used.

  Specifically, the brazing composition was applied to a stainless steel member, which is a member of the heat exchanger, with a dispenser.

  Subsequently, a stainless steel member, which is a member of the heat exchanger, was prepared separately, fixed so as to be in contact with the application portion of the brazing composition, and dried at 350 ° C. for 1 hour. Next, it is inserted into a box-type brazing furnace (A-BC-M type (manufactured by Noritake TCF)) and heated from 30 ° C. to 1100 ° C. over about 30 minutes in an argon atmosphere to braze. Carried out.

Also, other members were brazed in the same manner, and a heat exchanger provided with a brazed portion (a brazed portion by the brazing composition of Example 1) was obtained.

Claims (4)

A brazing composition used for brazing stainless steel under an inert atmosphere,
(A) Ni-Cr-Si-P-based nickel brazing powder,
(B) butyl rubber;
(C) a hydrocarbon-based organic solvent;
(D) containing hardened castor oil;
For 100 parts by weight of the brazing composition,
The blending ratio of the (b) butyl rubber is 0.5 parts by mass or more and less than 1.0 part by mass,
The composition for brazing, wherein the blending ratio of the (d) hardened castor oil is 0.05 parts by mass or more and 1.0 part by mass or less. The Si content in the (a) Ni—Cr—Si—P-based nickel brazing filler metal powder is:
It is 3.6 to 4.4 mass parts for brazing with respect to 100 mass parts of the total amount of said (a) Ni-Cr-Si-P type nickel brazing filler metal powders. Composition. The oxygen concentration in the (a) Ni—Cr—Si—P-based nickel brazing powder is:
The brazing composition according to claim 1 or 2, which is less than 500 ppm based on the total amount of the (a) Ni-Cr-Si-P-based nickel brazing filler metal powder. A heat exchanger comprising a brazing portion made of the brazing composition according to claim 1.