WO2013077113A1 - Ni-Cr-BASED BRAZING MATERIAL HAVING EXCELLENT WETTABILITY/SPREADABILITY AND CORROSION RESISTANCE - Google Patents

Abstract

Provided is a Ni-Cr-based brazing material having excellent wettability/spreadability and corrosion resistance, which can be brazed at a practicable temperature (1150˚C or lower) when used for joining a ferritic stainless steel by brazing, and has a good brazing property, good joint strength and good corrosion resistance against a base material. The brazing material is characterized by comprising, in mass%, 45.0% or less of Fe, 10.0 to 35.0% of Cr, 4.0% or less of Si, 6.5 to 10.8% of P, Si and P in the total amount of 9.0 to 11.8%, 0.3 to 5.0% of Cu, 0.01 to 0.10% of at least one selected from Al, Ca, Y and a misch metal, and a remainder made up by Ni and unavoidable impurities, wherein the total amount of Cr and Fe is 6.5 times or less larger than the content of P. The brazing material may additionally contain, as elements that do not affect the properties of the brazing material, Co and/or Mo in an amount of 15.0% or less, W and/or Mn in an amount of 5.0% or less, and C, B and Ti in the total amount of 0.3% or less, wherein the total amount of Co, Mo, W, Mn, C, B and Ti is 15.0 mass% or less.

Description

Ni-Cr brazing material with excellent wettability and corrosion resistance

The present invention is used for various heat exchanger applications such as general-purpose heat exchangers, EGR coolers, waste heat recovery devices, etc., and relates to a brazing material for joining members such as various stainless steels, and particularly excellent in corrosion resistance. In addition, the present invention relates to a nickel brazing material having good wetting and spreading properties for ferritic stainless steel.

Conventionally, nickel brazing materials used for joining various stainless steel members include BNi-2, BNi-5, and BNi-7 defined in JIS Z 3265 “Nickel brazing”. BNi-2 has an appropriate melting point and bonding strength, but has poor corrosion resistance and does not provide good wetting and spreading properties. Moreover, since it contains B, when it brazes, B will approach into the grain boundary of the stainless steel used as a base material, and the intensity | strength and corrosion resistance of a base material will fall. Although BNi-5 has moderate bonding strength and excellent corrosion resistance, it has poor wetting and spreading properties, so that the molten brazing material does not flow and may cause bonding failure. Moreover, since melting | fusing point is higher than other Ni brazing materials, and it is necessary to braze at high temperature, there exists a possibility that a deformation | transformation, deterioration, etc. may arise in a stainless steel base material by a heat effect. Although BNi-7 is excellent in wetting and spreading properties, the material strength is low, so there is a problem that equipment and members brazed with BNi-7 have low joint strength.

Patent Documents 1 to 6 show brazing materials containing Ni as a main component and containing Cr, Si, P, etc. (hereinafter referred to as Ni-based brazing materials in the prior art). These have an appropriate melting point and bonding strength, but cannot achieve both corrosion resistance and wettability with respect to ferritic stainless steel. Furthermore, the brazing materials containing Ni, Cr, Si, P, etc. mainly composed of Fe shown in Patent Documents 7 to 10 (hereinafter referred to as Fe-based brazing materials in the prior art) have an appropriate melting point and bonding strength. However, since Fe is the main component, it has poor wettability with respect to various stainless steels, and corrosion resistance is not sufficient.

Japanese Patent No. 3168158 Japanese Patent No. 3349222 Japanese Unexamined Patent Publication No. 2009-202198 JP 2010-269347 A Japanese Unexamined Patent Publication No. 2007-75867 JP 2011-110575 A WO2009 / 128174 Japanese Patent No. 4435826 JP 2008-12592 A Special table 2011-515223

Currently, various Ni and / or Fe brazing materials used in industrial use have various functions such as heat resistance / oxidation resistance, corrosion resistance, appropriate melting point, bonding strength, and various stainless steels. However, since there is no brazing material that has all of them, brazing materials are properly used depending on applications and environments.

Generally, nickel brazing filler metal has bonding strength, heat resistance, and corrosion resistance, and has been widely used for bonding materials such as various heat exchangers based on austenitic stainless steel. However, in recent years, ferritic stainless steel base materials not containing Ni have been actively applied for the purpose of cost reduction. On the other hand, the EGR cooler used for exhaust gas reduction measures for diesel engine vehicles contributes to the improvement of fuel efficiency when it is installed. However, the temperature of exhaust gas is higher in gasoline engine vehicles than in diesel engine vehicles. Therefore, when austenitic stainless steel is applied to the base material, there is a concern about deterioration of corrosion resistance and strength due to sensitization. Therefore, application of ferritic stainless steel has been studied. Therefore, the development of a brazing material having excellent wettability for ferritic stainless steel is required.

Since various heat exchangers including EGR coolers require joint strength and corrosion resistance, BNi-2, BNi-5, Ni-based brazing materials of prior literature, and Fe-based brazing materials of prior literature are currently used. Yes. However, when ferritic stainless steel is applied to the base material, the wettability of the brazing material is lower than that of austenitic stainless steel, so there may be poor bonding due to slight fluctuations in brazing conditions and brazing environment. . In addition, among the prior art Ni-based brazing materials or the prior art Fe-based brazing materials, there are brazing materials that have good wetting and spreading properties with respect to ferritic stainless steel, but they have improved bonding strength and corrosion resistance. I have a problem. Therefore, the development of Ni brazing filler metal that has bonding strength and corrosion resistance and has good wet spreadability with respect to ferritic stainless steel has been an issue.

In the present invention, in studying the alloy composition for developing a nickel brazing material excellent in corrosion resistance and wettability, the following target values are set and all the conditions are satisfied.
(Target value)
(1) Liquidus temperature (melting point) → 1120 ° C or less (2) Fracture strength (material strength) → 700N / mm ² or more (3) Brazing (wet spread test for SUS444) → Area after brazing 750 mm ² or more (4) Sulfuric acid corrosion resistance (corrosion loss in 30% sulfuric acid) → 1.0 mg / m ²・ s or less

The alloy of the present invention (Ni-Cr brazing filler metal) satisfying all the above target values is excellent in wetting spreadability and corrosion resistance, Fe 0-35.0 mass%, Cr 18.0-35.0 mass%, Si 1.0- 4.0 mass%, P 6.5-9.5 mass%, Si and P in total 9.2-11.8 mass%, Cu 0.3-5.0 mass%, Al, Ca, Y, Misch metal (alloy containing multiple rare earth elements) ) Is contained in an amount of 0.01 to 0.10% by mass, the balance is made of Ni and inevitable impurities, and the total amount of Cr and Fe is 6.5 times or less of the P content.
Here, the inevitable impurities are impurities that are inevitably mixed in the manufacturing process of each raw material, although not intentionally added. Examples of such impurities include Mg, S, O, and N. , V, Zr, Sn, etc., and the sum of these is usually 0.3% by mass or less, and does not affect the function of the present invention.

In addition, the Ni-Cr brazing filler metal of the present invention has a Si content of 0 to less than 1.0% by mass, Fe of 10.0 to 45.0% by mass, Cr of 10.0 to 30.0% by mass, and P of 8.5 to 10.8% by mass. In addition, Si and P in total 9.0 to 11.0% by mass, Cu 0.3 to 5.0% by mass, Al, Ca, Y, and one or more kinds of misch metal 0.01 to 0.10% by mass, the balance being Ni and inevitable impurities And the total amount of Cr and Fe is not more than 6.5 times the P content.

Furthermore, the present invention provides at least one element selected from Co, Mo, W, Mn, C, B, and Ti as an element that does not affect the characteristics of the Ni—Cr brazing material having the above characteristics. And the Co and / or Mo content is 15.0 mass% or less, the W and / or Mn content is 5.0 mass% or less, and the total content of C, B, and Ti is 0.3 mass% or less. The total content of Co, Mo, W, Mn, C, B, and Ti is 15.0% by mass or less.

Next, the reason why the range of each component of the Ni-Cr brazing material (hereinafter referred to as the present invention brazing material) having excellent wettability and corrosion resistance according to the present invention is limited will be described.

Fe dissolves in the Ni solid solution to improve the material strength. However, when the addition amount increases, the function of P is inhibited and the wet spreading property is lowered. When Si was 1.0 to 4.0% by mass and the P content was 6.5 to 9.5% by mass, the upper limit was defined as 35.0% by mass so as not to reduce the wetting and spreading property. In this case, the Fe content may be 0% by mass. In addition, when Si is 0 to less than 1.0% by mass and the P content is 8.5 to 10.8% by mass, the lower limit of the Fe content is specified to 10.0% by mass to provide material strength. The upper limit value of Fe was set to 45.0% by mass so as not to lower the wet spreading property. Furthermore, the total amount of Cr and Fe is specified to be 6.5 times or less of P because the function of P is inhibited and the wetting and spreading property is lowered when the total amount of Cr is increased.

Cr dissolves in a Ni solid solution serving as a substrate (matrix) to impart corrosion resistance and heat resistance, but if the content is less than 10.0% by mass, sufficient effects cannot be obtained. On the other hand, if it exceeds 35.0% by mass, a large amount of P and an intermetallic compound are formed, and the material strength is lowered and the wetting and spreading property is also lowered. Therefore, Cr is set in the range of 10.0 to 35.0% by mass. The Cr content must be adjusted according to the content of Si and P contained in the brazing filler metal of the present invention. The Si content is 1.0 to 4.0% by mass and the P content is 6.5 to 9.5% by mass. In this case, the Cr content must be set in the range of 18.0 to 35.0% by mass. When the Si content is 0 to less than 1.0% by mass and the P content is 8.5 to 10.8% by mass, the Cr content is It is necessary to set it in the range of 10.0 to 30.0% by mass.

Si dissolves in Ni to form a eutectic phase, contributing to the melting point drop of the brazing filler metal. However, if the content exceeds 4.0 mass%, the liquidus temperature rises and exceeds the target value. It is necessary to adjust the liquidus temperature by reducing the P content, and as a result, the wet spreading property is deteriorated. Therefore, the Si content is 4.0% by mass or less. Si may be 0% by mass depending on the P content.

P, like Si, dissolves in Ni to form a eutectic phase, which contributes to lowering the melting point of the brazing material and improves wetting spreadability, but wetting spreadability with a content of less than 6.5% by mass Becomes worse. On the other hand, when the content exceeds 10.8% by mass, hypereutectic is formed, and the strength is greatly reduced, so that the target bending strength cannot be obtained. The P content must be adjusted according to the Si content. When the Si content is 1.0 to 4.0 mass%, the P content is in the range of 6.5 to 9.5%, and the Si content is In the case of 0 to less than 1.0% by mass, the P content was set in the range of 8.5 to 10.8% by mass.

Furthermore, regarding Si and P, by limiting the total amount of Si and P, the melting point and material strength can be controlled in particular. That is, when the Si content is 1.0 to 4.0% by mass, the melting point increases when the total amount of Si and P is less than 9.2% by mass, exceeding the target liquidus temperature. On the other hand, when the total amount of Si and P exceeds 11.8% by mass, hypereutectic is formed, and the material strength is significantly reduced, so that the target bending strength cannot be obtained. For this reason, the total amount of Si and P is set in the range of 9.2 to 11.8% by mass. When the Si content is 0 to less than 1.0% by mass, the melting point increases when the total amount of Si and P is less than 9.0%, exceeding the target liquidus temperature. When the total amount of Si and P exceeds 11.0% by mass, hypereutectic is formed, the material strength is significantly reduced, and the target bending strength cannot be obtained. For this reason, the total amount of Si and P is set in the range of 9.0 to 11.0% by mass.

Cu is a solid solution in Ni solid solution and improves the corrosion resistance especially against sulfuric acid, but its effect is insufficient with a content of less than 0.3% by mass, and when it exceeds 5.0% by mass, wetting spreadability and material strength decrease. Therefore, the Cu content is set in the range of 0.3 to 5.0% by mass.

Al, Ca, Y, and misch metal contribute to the deoxidation action of the molten brazing filler metal and have an effect of improving wet spreadability, but if it is less than 0.01% by mass, the effect is small, and if it exceeds 0.1% by mass The total amount of Al, Ca, Y, and misch metal was determined to be in the range of 0.01 to 0.1% by mass because the viscosity of the molten brazing material was lowered and the wet spreadability was deteriorated. Examples of the misch metal that can be used in the present invention include high-purity Nd and In, as well as La-52Ce-15Nd-6Pr alloy and Pr-25Nd alloy.

In the brazing material of the present invention, as additive elements that do not adversely affect the physical properties, Co is 15.0 mass% or less, Mo is 15.0 mass% or less, W is 5.0 mass% or less, Mn is 5.0 mass% or less, C, B, Ti In order not to impair the wetting spreadability, melting point, material strength, and corrosion resistance, the upper limit of the total of Co, Mo, W, Mn, C, B, and Ti is included. It was set to 15.0% by mass.

Since the brazing filler metal of the present invention has the following characteristics, it can be applied to a wide range of applications as a nickel brazing filler metal having excellent corrosion resistance, wettability and material strength.
-The liquidus temperature is 1120 ° C or less, and brazing can be performed using a general-purpose industrial atmospheric furnace.
・ Because the bending strength is 700N / mm ² or more, it has moderate bonding strength as a nickel brazing material.
For-wetting area after brazing for SUS444 substrate has a 750 mm ² or more, wet well the ferritic stainless steel, spread flow, has excellent brazing workability.
・ In 30% H ₂ SO ₄ (60 ° C) corrosion test, corrosion weight loss is 1.0mg / m ² · s or less, so it has excellent corrosion resistance to sulfuric acid.

The brazing filler metal of the present invention is prepared by adjusting and blending Ni as a base and the components Fe, Cr, Si, P, Cu, Al, etc., and Mo, Co, Mn, etc. at a predetermined mass% if necessary. After the molten metal is completely melted in the crucible of the melting furnace, the molten alloy is powdered by the atomizing method or melt pulverization method, or cast into a predetermined mold to obtain a rod shape or plate shape be able to.

In particular, the alloy powder produced by the atomizing method is adjusted to a particle size suitable for the intended construction method, but as a method of installing the brazing material of the present invention on a stainless steel base material, a binder and powder are sprinkled and applied to the base material surface. A method, a method of applying a paste in which a binder and powder are mixed, a method of installing by processing into a sheet or foil, a method of spraying and installing a powder, and the like can be selected.

Example brazing material and comparative example brazing material of the present invention prepared and mixed as described above, and melted (liquidus temperature), bending strength, wetting spreadability, corrosion resistance to sulfuric acid by the following methods Evaluated.

(1) Melting point (liquidus temperature) measurement: 100g of ingot with the composition of each alloy was melted by heating to about 1500 ° C in an argon stream using an electric furnace, and then naturally cooled in the furnace The melting point temperature was measured by a thermal analysis method in which the temperature of the alloy was continuously measured. That is, a thermal analysis curve was drawn on a recorder connected to a thermocouple inserted in the center of the melt, and the liquidus temperature was read from the cooling curve.

(2) Folding strength test: After the metal was melted by the same method as (1) above, the molten metal was cast into a quartz glass tube and then machined to about φ5 × 35 mm to obtain a test piece. Next, place a test piece on a bending strength test jig (three-point support, distance between supports 25.4 mm (JIS Z 2511: metal powder-a jig described in the method for measuring the strength of green compacts by bending test)). The load at the time of breaking with a tester was measured, and the bending strength (N / mm ² ) of the alloy was calculated from the shape of the test piece and the breaking load.

(3) Wet spreadability test: The round bar having a diameter of about 5 mm obtained in the above (2) was cut to 0.5 g (about 2 mm thickness) to obtain a test piece. Next, a test piece was placed on a SUS444 stainless steel substrate degreased with acetone, and a brazing treatment was performed at 1150 ° C. for 30 minutes in an atmosphere of 10 ⁻³ Pa region. In the evaluation, the area “A” where the brazing material after brazing wetted and spread on the base material was measured to evaluate the wettability.
The evaluation index is shown below.
“A ≧ 1000mm ² : ○”
“1000 mm ² > A ≧ 750 mm ² : △”
"A <750mm ^2: ×"

(4) Corrosion test in 30% sulfuric acid; after melting the metal in the same way as (1) above and casting the molten metal in a shell mold, machine this cast piece to about 10 x 10 x 20 mm A test piece was obtained. Next, a 30% sulfuric acid aqueous solution was prepared in a 300 cc beaker, and a test piece was put therein to conduct a corrosion test by a total immersion method. The test conditions were a test temperature of 60 ° C. and a test time of 6 hours. Then, the unit area before and after the test and the mass reduction amount per unit time were calculated to be the corrosion weight loss (mg / m ² · s), and the corrosion resistance against sulfuric acid was evaluated.
The index is shown below.
“Corrosion weight loss ≦ 0.5mg / m ²・ s ： ○”
"0.5mg / m ² · s <corrosion weight loss ≤ 1.0mg / m ² · s: △"
"Corrosion weight loss> 1.0mg / m ² · s: ×"

Table 1 shows examples of the present invention, and Tables 2 and 3 show comparative examples.

(A) to (m) of comparative example brazing materials shown in Table 2 are brazing materials having compositions outside the claimed scope of the present invention. In Comparative Example (a), Cr exceeded the upper limit of the claim, and in Comparative Example (k), Fe was lower than the lower limit of the claim and C exceeded the upper limit of the claim. The target value is not satisfied. In Comparative Example (b), the total amount of Cr and Fe exceeded 6.5 times the content of P, and in Comparative Example (d), the total amount of P and Si and P was below the lower limit of the claims, comparison Example (f) shows the total amount of Cu and Co and Mn exceeding the upper limit of the claims, Comparative Example (g) shows that Al exceeds the upper limit of the claims, and Comparative Example (h) shows a combination of Ca and Y. The total amount exceeded the upper limit of the claims, and in all cases, the wet spreadability did not satisfy the target. In Comparative Example (c), Si exceeded the upper limit of the claim, B exceeded the upper limit of the claim, and Comparative Example (m), Mn exceeded the upper limit of the claim. Not meeting the goal of wettability. In Comparative Example (e) and Comparative Example (i), the total amount of P and Si and P exceeded the upper limit of the claims, and none of them satisfied the liquidus temperature and bending strength targets. In Comparative Example (j), Cr and Cu are below the lower limit of the claims, and the corrosion resistance against sulfuric acid does not satisfy the target. In Comparative Example (l), the total amount of P and Si and P is below the lower limit of the claims, and the total amount of Fe and Cr exceeds 6.5 times the P content. Sex does not meet the goal.

The comparative brazing materials (A), (B), and (C) shown in Table 3 are typical nickel brazing materials defined in JIS Z 3265, and the comparative brazing materials (D) to (W) are “ Patent No. 3168158 ”,“ Patent No. 3349522 ”,“ JP 2009-202198 ”,“ JP 2010-269347 ”,“ JP 2007-75867 ”,“ JP 2011-110575 ”,“ WO 2009/128174 ” The Ni-based brazing material of the prior art or the Fe-based brazing material of the prior art described in “Patent No. 4435826”, “Japanese Patent Laid-Open No. 2008-12592”, and “Special Table 2011-515223”, respectively. None of these brazing materials satisfy all of the target values such as the liquidus temperature, the bending strength, the wet spreadability, and the corrosion resistance against sulfuric acid.

On the other hand, the brazing filler metals 1 to 15 of the present invention satisfy all the target values of the liquidus temperature, the bending strength, the wetting spreadability and the corrosion resistance against sulfuric acid, as is clear from Table 1. As a brazing material, it has an appropriate melting point, material strength, brazing property, and excellent corrosion resistance.

In addition, the brazing filler metal of the embodiment of the present invention shows good brazing properties against various stainless steels other than SUS444, nickel-base heat-resistant alloys and corrosion-resistant alloys such as Inconel and Hastelloy.

In addition to vacuum, the brazing atmosphere exhibits good brazing properties even in a reducing hydrogen atmosphere, an inert argon atmosphere, or a nitrogen atmosphere.

Furthermore, the brazing filler metal of Example has good corrosion resistance against sulfuric acid, various acids such as nitric acid and ammonia water.

As described above, the nickel brazing material of the present invention has an appropriate melting point, excellent material strength and corrosion resistance, and has good wetting and spreading properties in ferritic stainless steel, and austenitic stainless steel and nickel alloy members. Because brazing is good in brazing, not only EGR coolers, but also a wide range of brazing equipment parts such as environment- and energy-related heat exchangers, waste heat recovery equipment, and hot water supply parts Can be widely used as a bonding material.

Claims (3)

0 to 35.0 mass% Fe, 18.0 to 35.0 mass% Cr, 1.0 to 4.0 mass% Si, 6.5 to 9.5 mass% P, 9.2 to 11.8 mass% in total with Si and P, and 0.3 to Cu 5.0% by mass, containing at least one of Al, Ca, Y, and Misch metal in an amount of 0.01 to 0.10% by mass, the balance being Ni and inevitable impurities, and the total amount of Cr and Fe is 6.5 times the content of P Ni-Cr brazing material with excellent wet spreading and corrosion resistance, characterized by the following: The Si content is 0 to less than 1.0% by mass, Fe is 10.0 to 45.0% by mass, Cr is 10.0 to 30.0% by mass, P is 8.5 to 10.8% by mass, and Si and P are 9.0 to 11.0% in total. %, Cu 0.3-5.0% by mass, Al, Ca, Y, and one or more types of misch metal are contained 0.01-0.10% by mass, the balance consists of Ni and inevitable impurities, and the total amount of Cr and Fe is P Ni-Cr brazing material with excellent wettability and corrosion resistance, characterized by being 6.5 times or less the content of. Containing at least one element selected from Co, Mo, W, Mn, C, B, and Ti as an element that does not affect the properties, and a Co and / or Mo content of 15.0% by mass or less, W and / or Mn content is 5.0 mass% or less, C, B, Ti total content is 0.3 mass% or less, Co, Mo, W, Mn, C, B, Ti total content is The Ni-Cr brazing material having excellent wettability and corrosion resistance according to claim 1 or 2, wherein the content is 15.0% by mass or less.