JPH09225679A - Ni base heat resistant brazing filter metal excellent in wettability and corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the Ni base heat resistant brazing filler metal which has good wettability able to braze at a low temp. and excellent corrosion resistance, in particular, for salt water by specifying a composition consisting of Cr, O, Si, and Ni. SOLUTION: The Ni base heat resistant brazing filler metal, which has a composition consisting of, by weight, 10-30% Cr, 2-11% P, 1-10% Si, and the balance Ni with inevitable impurities while satisfying 10-13% in total of (P+Si), and further contg; <=5% Mo, at need and excellent wetability/corrosion resistance, is obtained. The content of impurity elements in the brazing filler metal, which exert adverse effect on wettability/corrosion resistance, is regulated to <=5% Fe, <=1% Co, <=1% Cu, <=0.5% Mn, <=0.3% B, 0.15% C, <=0.5% in total of other elements and <=7% in total of impurities. By this method, the brazing filler metal, which can braze a stainless steel, etc., to form a strong oxide film on surface at a low temp. of about 1050 deg.C, is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-base heat-resistant brazing material having excellent wettability and corrosion resistance, which is used for brazing metals with each other, particularly stainless steel forming a strong oxide film on the surface. Is.

[0002]

2. Description of the Related Art Conventionally, the JIS standard (JIS Z326
The Ni-based heat-resistant brazing material specified in 5) is mainly used for brazing of stainless steel and the like, and has excellent oxidation resistance and corrosion resistance. Therefore, it has been widely used for brazing when manufacturing heat exchangers and gas turbines.

However, in recent years, in particular, the corrosion resistance under salt water environment is required, and the brazing material which can be brazed at a temperature as low as possible is required.
The following problems have arisen. BNi-5 Ni solder containing Si specified in JIS standard has good corrosion resistance and heat resistance, but since the liquidus temperature is high at about 1160 ° C, the brazing temperature needs to be higher than 1200 ° C. Therefore, the characteristics of the stainless steel to be joined may be deteriorated. BNi-1, 1A, 2, 3.4 containing B and BNi-6, 7 containing P have a low melting point, so they have the advantage that they can be brazed at a low temperature of about 1050 ° C, but have a difficulty in corrosion resistance to salt water, etc. There is.

[0004]

The object of the present invention is to lower the temperature (1050 ° C.) as low as possible when brazing metals, especially stainless steel etc. forming a strong oxide film on the surface.
The present invention is to provide a Ni-based heat-resistant brazing material which can be brazed at a certain degree), has good wettability, and particularly has excellent corrosion resistance to salt water.

[0005]

Means for Solving the Problems The inventors of the present invention can braze stainless steel or the like having a strong oxide film on the surface at a temperature as low as possible and have good wettability with a stainless steel base material. In order to find a Ni-based heat-resistant brazing filler metal composition with excellent corrosion resistance especially to salt water,
Regarding the components of the Ni-based brazing filler metal specified in the IS standard, we have reviewed the effectiveness of each component, made further improvements, and thought that we could solve the problem by constructing a new brazing filler metal composition .

As a result, by selecting P and Si as the melting point depressing elements based on Ni and limiting the addition amount of each and the total addition amount of P + Si, the alloy composition which becomes the target melting point is found, and Cr is added. It was found that salt water corrosion resistance is improved by adding Mo and Mo to the extent that they do not adversely affect the melting point and wettability. That is, in the present invention, Cr is 10 to 30%, P is 2 to 11%, and Si is 1 to 10% by weight.
%, The total of P + Si is 10 to 13%, 5% or less of Mo is included if necessary, and the balance is Ni and unavoidable impurities, which is a Ni-based heat-resistant brazing material excellent in wettability and corrosion resistance.
As unavoidable impurities, Fe 5% or less, Co 1% or less,
Cu 1% or less, Mn 0.5% or less, B 0.3% or less, C 0.15
%, The total of other elements is 0.5% or less, and the total of all impurities is 7% or less.

[0007]

In the present invention, the reason why each component range is limited as described above will be described below. In the following% display, weight% is shown. Cr forms a solid solution in Ni and Ni-
It becomes a Cr solid solution and improves the oxidation resistance, heat resistance and corrosion resistance of the alloy, and particularly in the case of the brazing alloy composition of the present invention, it is effective as an element for improving the corrosion resistance to salt water, but 10%
If less than 30%, the effect is small, and if over 30%, wettability with stainless steel deteriorates. For the above reasons, Cr is 10 to 30
Limited to%.

P and Si have a large effect on the melting point of the alloy due to the eutectic reaction with the Ni-Cr solid solution, and thus have an important effect on the brazing property, and at the same time, are components that also affect the corrosion resistance. In the case of the brazing alloy composition of the present invention, the limitation of the total addition amount of P and Si plays an important role in determining the melting point of the alloy. That is, if the total of P + Si is less than 10%, the hypoeutectic tendency becomes strong, the liquidus temperature rises, and the width with the solidus line widens, so that the brazing property deteriorates. If the total amount of P + Si exceeds 13%, the hypereutectic tendency becomes strong, the liquidus temperature rises, and the alloy becomes brittle. P and Si tend to interact and counteract the melting point and corrosion resistance of the alloy.

Therefore, P and S depend on each balance.
The individual addition amount of i is limited. That is, when P is less than 2% and when Si is more than 10%, the melting point of the alloy increases and brazing cannot be performed at the target temperature. Also, Si is 1
%, And P exceeds 11%, the corrosion resistance of the alloy deteriorates and the toughness decreases. For the above reasons, P is 2-11
%, Si is 1 to 10%, and the total of P + Si is 10 to 13
Limited to%.

Although the above Ni-Cr-P-Si alloy composition also has good wettability and corrosion resistance, the addition of Mo further improves the corrosion resistance.
Can be added. However, when Mo exceeds 5%, the effect is small, the melting point rises, and the brazing property deteriorates. For the above reasons, Mo is limited to 5% or less.

In the Ni-based brazing alloy of the present invention, it may be unavoidably mixed in during manufacture, but it is acceptable to allow the inclusion of the following elements as impurities that do not adversely affect the wettability and corrosion resistance. it can. That is, Fe 5% or less, Co
1% or less, Cu 1% or less, Mn 0.5% or less, B 0.3% or less, C 0.15% or less, the total of other elements is 0.5% or less, and the total of all impurities is 7% or less. The Ni-based brazing material alloy of the present invention is useful because it can be used in the form of foil, rod, etc. in addition to the powder produced by the usual atomizing method.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Representative examples and comparative examples of the present invention will be described below.

EXAMPLES Table 1 shows the results of alloy compositions, melting points, brazing tests, and salt spray tests of brazing test pieces of Examples and Comparative Examples of the present invention. The test method for each property is as follows.

(1) Measurement of melting point (liquidus line, solidus line) The alloys of Examples and Comparative Examples were melted in an electric furnace in an argon gas atmosphere, and the melting point was measured by a thermal analysis method. 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 and solidus temperatures were read from the cooling curve.

(2) Brazing Test The alloys of Examples and Comparative Examples were melted in an electric furnace in an argon gas atmosphere, and the melt was cast into a graphite mold to obtain a rod-shaped cast piece of 5 mmφ, which was about 5 mm. Was cut at a height of 1 to obtain a brazing material sample. Next, as shown in FIG.
A brazing material sample was placed on a stainless steel base material, and a brazing heat treatment (hereinafter referred to as brazing) was performed at 1050 ° C. for 30 minutes in a vacuum of 10 ⁻⁴ to 10 ⁻³ torr. After brazing, as shown in FIG. 1 (b), the area S of the brazing material melted and expanded was measured, and the area S was divided by the cross-sectional area So of the sample before brazing, that is, the brazing coefficient W ( = S / So), and the braze alloy SU
It was used as an index of wettability with respect to the S304 stainless steel base material.

(3) Salt spray test of brazing test piece The brazing test piece after brazing by the above method is subjected to a salt spray test in accordance with JIS Z2371 "Salt spray test method" The presence or absence of rust on the surface and at the interface with the base material was observed and used as an index of salt water corrosion resistance. The test time was set to 48 hours (the state was observed every 6 hours on the way), and after 48 hours, those without rust were evaluated as “good”. In addition,
No. a, b, c and e of the comparative example alloys were not brazed at 1050 ° C., so the salt spray test was not conducted. BNi-5 was subjected to a salt spray test on a test piece brazed at 1200 ° C.

As shown in Table 1, the example alloys of the present invention are
In the brazing test at 1050 ° C., the brazing expansion coefficient is as large as 40 or more, which shows that the wettability to the SUS304 stainless steel base material is good. In addition, as a result of the salt spray test, no rust was found on the surface of the brazing filler metal or the interface with the base metal after 48 hours, indicating that the salt water corrosion resistance is good.

On the other hand, in the comparative alloys, No. a to e are compositions outside the range of the alloy of the present invention. No. a and b
Although the solidus temperature is low, the liquidus temperature is high and brazing cannot be performed at 1050 ° C. No. c does not melt and braze at 1050 ° C because both solidus and liquidus temperatures are high. No. d has a melting point at an appropriate temperature of 1050 ° C., but has good brazing property, but has a large amount of P and a small amount of Si, and thus has poor salt water corrosion resistance. No.e is M
Since the amount of o is large, the liquidus temperature becomes high and the wettability with the stainless steel base material is poor.

In the comparative alloys, BNi-7,
Nos. 5 and 2 are Ni-based brazing alloy compositions defined in the conventional JIS. BNi-7 and BNi-2 have low melting points and show good brazing properties at 1050 ° C., but as a result of the salt spray test, red rust is generated within 24 hours and the salt water corrosion resistance is poor. B
Ni-5 cannot be brazed at 1050 ° C because of its high melting point.
The example alloys of the present invention have good wettability not only for austenitic stainless steel base materials such as SUS304 and 316, but also for ferritic and martensitic stainless steel base materials such as SUS410 and 430. Show. In addition, it has been confirmed that the brazing atmosphere exhibits good brazing properties in a reducing hydrogen atmosphere or an inert argon atmosphere in addition to vacuum.

[0019]

[Table 1]

[0020]

As described above in detail, the Ni-based heat-resistant brazing filler metal of the present invention has a low melting point and is low in temperature as Ni brazing at about 1050 ° C. on various stainless steels that form a strong oxide film on the surface. It can be brazed, has good wettability, and has an effect of exhibiting good corrosion resistance against salt water, and is a great invention in that it contributes to industrial development.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a brazing test of a brazing alloy.

[Explanation of symbols]

 So: cross-sectional area of brazing material sample S: spreading area of alloy after brazing W: brazing spreading coefficient (S / So) 1: base material (SUS304 stainless steel) 2: brazing material sample before brazing (5φ x approx. 5mm) 3: Melted and expanded brazing alloy after brazing

Claims (3)

[Claims] 1. By weight%, Cr is 10 to 30%, and P is 2 to 11
%, Si is 1 to 10%, and the total of P + Si is 10 to 13%,
The balance is Ni-based heat resistant brazing material with excellent wettability and corrosion resistance, consisting of Ni and unavoidable impurities. 2. A Cr content of 10 to 30% and a P content of 2 to 11 by weight.
%, Si is 1 to 10%, and the total of P + Si is 10 to 13%, Mo
Is a Ni-based heat-resistant brazing material having excellent wettability and corrosion resistance, containing 5% or less of Al and the balance Ni and unavoidable impurities. 3. An impurity element which does not adversely affect wettability and corrosion resistance, in terms of weight%, Fe 5% or less, Co 1%
Below, Cu 1% or less, Mn 0.5% or less, B 0.3% or less,
C 0.15% or less, the total of other elements is 0.5% or less,
The total of all impurities is 7% or less, claim 1, claim 2
Ni with excellent wettability and corrosion resistance described in any of
Base heat resistant brazing material.