KR20210027632A - Brazing filler metal powder - Google Patents

Abstract

The present invention relates to brazing filler metal powder and a brazing paste having the same. The powder comprises: 30-80 wt% of Ni; 5-40 wt% of Cr; 5-30 wt% of Fe; and 5-20 wt% of P.

Description

Brazing filler metal powder {BRAZING FILLER METAL POWDER}

The present invention relates to a brazing filler metal powder having a low melting point, high spreadability and high corrosion resistance.

Brazing is one of the welding technologies. When it is joined below 450℃, it is called soldering, and when it is joined above 450℃, it is called brazing. The brazing agent is divided into nickel (Ni)-based alloys and copper (Cu)-based alloys. In the case of the nickel (Ni)-based alloy brazing agent, it has high high temperature strength, excellent corrosion resistance and high temperature oxidation resistance, and is thus widely used in the aerospace and power plant industries. However, nickel-based alloy brazing agents are more expensive than copper-based, and problems such as corrosion occur depending on the use environment. In the case of BNi-2 (Ni-Cr-B-Fe-Si), which is a general-purpose product, boron (B) is essential to improve low melting point and fluidity. However, when the content of boron exceeds 50 ppm, boride is formed, and when it exceeds 100 ppm, Fe ₂ B or Cr ₂ B is formed, thereby reducing the corrosion resistance of the brazed metal. A chromium (Cr) deficient layer may be formed due to excess boron at the boundary, resulting in pitting or crevice corrosion.

As an alternative to this, Korean Patent No. 1,812,618 (Patent Document 1) discloses an iron-chromium-based brazing filler powder made of chromium, nickel, copper, silicon, phosphorus, manganese and iron. However, the conventional brazing filler metal such as Patent Document 1 has the effect of improving the corrosion performance and securing cost competitiveness by using iron (Fe), but the spreadability, which is an important performance of the brazing filler material, is low, and leaks, pinholes, unfilled and There is a limitation that causes the same spreading failure.

Therefore, it is necessary to research and develop a brazing filler material having a low melting point, excellent spreadability and corrosion resistance, and excellent cost competitiveness.

Korean Patent Registration No. 1,812,618 (published on June 26, 2012)

Accordingly, the present invention provides a brazing filler material powder having excellent fairness when bonding in a post-treatment process by having a low melting point, high corrosion resistance, and high spreadability. In addition, it provides a brazing filler material powder capable of producing an economical brazing paste in terms of cost by using an iron (Fe) alloy, which is an inexpensive alloy.

The present invention is a brazing filler powder comprising 30 to 80 parts by weight of nickel (Ni), 5 to 40 parts by weight of chromium (Cr), 5 to 30 parts by weight of iron (Fe) and 5 to 20 parts by weight of phosphorus (P). to provide.

The brazing filler metal powder according to the present invention has a low melting point and high corrosion resistance, and has high spreadability, which is advantageous for the bonding temperature in the post-treatment process. In particular, the brazing filler metal powder can secure sufficient spreadability required for the exhaust system heat exchanger parts, and can exhibit excellent corrosion resistance in an environment of condensate generated during cooling. In addition, the brazing filler metal powder includes an iron (Fe) alloy, which is a low-cost alloy, and has an advantage in that it is possible to economically manufacture a brazing paste in terms of cost.

1 is a SEM photograph of the results of corrosion resistance measured in Test Example.
2 is a side view and a front view of a specimen prepared in Test Example.

Hereinafter, the present invention will be described in detail.

Brazing filler powder

The brazing filler powder according to the present invention includes nickel, chromium, iron and phosphorus.

Nickel (Ni)

Nickel has oxidation resistance and serves to improve the corrosion resistance of the filler powder containing it.

The nickel may be included in the brazing filler powder in an amount of 30 to 80 parts by weight, or 35 to 75 parts by weight based on 5 to 40 parts by weight of chromium. When the content of nickel is within the above range, the filler material powder including the same has excellent corrosion resistance and excellent economic efficiency.

Chromium (Cr)

Chromium plays a role in improving the corrosion resistance of the filler metal powder.

The chromium may be included in the brazing filler powder in an amount of 5 to 40 parts by weight, or 10 to 38 parts by weight based on 30 to 80 parts by weight of nickel. When the content of chromium is within the above range, a sufficient effect of improving corrosion resistance can be obtained, and there is an effect that is not disadvantageous in strength reduction and recrystallization characteristics during post-treatment of brazing bonding. If the content of chromium is less than the above range, sufficient corrosion resistance improvement cannot be expected, and if it exceeds the above range, properties such as strength of the base material may be deteriorated during post-treatment.

Iron (Fe)

Iron plays a role in improving the corrosion resistance of the brazing filler powder.

The iron may be included in the brazing filler powder in an amount of 5 to 30 parts by weight, or 6 to 20 parts by weight based on 30 to 80 parts by weight of nickel. When the iron content is within the above range, the effect of improving the strength compared to the iron content is excellent, the economy of the filler material is improved by replacing some of the expensive nickel with iron, and the increase in the bonding temperature during post-treatment causes an increase in the cost of the brazing process. Thus, it is possible to prevent the problem of lowering the corrosion resistance. If the iron content is less than the above range, it is difficult to obtain a sufficient strength improvement effect during post-treatment and economic benefits through replacement of expensive nickel materials, and if it exceeds the above range, economical efficiency is secured, but brazing due to improvement of the bonding temperature during post-treatment The cost of the process may increase and the corrosion resistance of the brazed base metal may decrease.

Phosphorus (P)

Phosphorus improves the strength and fluidity of the alloy powder, and improves the spreadability of the paste containing the same.

The phosphorus is 5 to 20 parts by weight, or 6 to 18 parts by weight based on 30 to 80 parts by weight of nickel The content may be included in the brazing filler powder. When the phosphorus content is within the above range, it has a sufficient melting point lowering effect and excellent spreadability to prevent the problem of lowering the fluidity in the bonding process, and the problem of lowering the bonding strength of the bonding surface due to excessive fluidity, and the phenomenon of unfilling due to excessive spreadability. It can be prevented from occurring. When the content of phosphorus is less than the above range, it is difficult to sufficiently lower the melting point of the filler powder and secure the spreadability, which may cause a problem of lowering the fluidity in the post-treatment bonding process. In addition, when the content of phosphorus exceeds the above range, the fluidity of the filler material is improved, but the problem of lowering the bonding strength of the bonding surface due to excessive fluidity in the post-treatment process, and when the bonding part tolerance is large due to wide spreadability, the tolerance is sufficiently filled. There may be problems that cannot be done.

Liquidity granting system

The brazing filler powder may further include at least one fluid imparting agent selected from the group consisting of silicon (Si) and tin (Sn). At this time, the fluidity imparting agent serves to improve the strength and fluidity of the alloy powder, and improve the spreadability of the paste containing the same. In particular, tin can improve the diffusion of the filler material to the base material, and silicon can improve the fluidity and strength of the filler material.

The fluidity imparting agent may be included in the brazing filler powder in an amount of 1 to 5 parts by weight, 1.5 to 4.5 parts by weight, or 2 to 4 parts by weight based on 30 to 80 parts by weight of nickel. When the content of the fluidity imparting agent is within the above range, an alloy powder having excellent strength, fluidity and spreadability can be obtained. On the other hand, since silicon may cause a problem of forming inclusions or lowering strength by forming a silicide on the surface after bonding, it is recommended to be cautious in use.

In this case, the total amount of the fluidity imparting agent and phosphorus may be included in the brazing filler powder in an amount of 6 to 25 parts by weight or 6 to 20 parts by weight based on 30 to 80 parts by weight of nickel. When the total amount of the fluidity imparting agent and phosphorus is within the above range, the fluidity and spreadability of the filler material is appropriate, so that the workability is easy, and the problem that the tolerance of the joint is not filled can be prevented.

impurities

The brazing filler powder may contain inevitable impurities in a very small amount. The inevitable impurities may be included in a very small amount or less than 1.0% by weight so as not to affect properties such as melting point, spreadability, and corrosion resistance of the brazing filler powder.

The brazing filler metal powder according to the present invention having the above-described composition may have a melting point of 800 to 1,010°C, 830 to 995°C, or 840 to 970°C.

In addition, the brazing filler powder has excellent corrosion resistance in which very little corrosion or corrosion does not occur on the surface in a condensed water environment of pH 1 to 2. Therefore, it is very suitable as a material for brazing pastes such as automotive EGR cooler parts that require high corrosion resistance.

The brazing filler metal powder according to the present invention as described above has a low melting point and high corrosion resistance, and has high spreadability, which is advantageous for the bonding temperature in the post-treatment process. In particular, the brazing filler metal powder can secure sufficient spreadability required for the exhaust system heat exchanger parts, and can exhibit excellent corrosion resistance in an environment of condensate generated during cooling. In addition, the brazing filler metal powder includes an iron (Fe) alloy, which is a low-cost alloy, and has an advantage in that it is possible to economically manufacture a brazing paste in terms of cost.

The content of each component of the filler material powder according to the present invention as described above may be an amount based on 100 parts by weight of the filler material powder.

Brazing paste

In addition, the brazing paste according to the present invention includes the brazing filler powder and the binder as described above.

The paste may include 50 to 98 parts by weight, 65 to 95 parts by weight, or 80 to 90 parts by weight of brazing filler powder and 2 to 50 parts by weight, 5 to 35 parts by weight, or 10 to 20 parts by weight of a binder. When the content of the brazing filler material powder in the paste is within the above range, the viscosity of the paste is appropriate, so workability is easy, and the content of the filler material is small, so that the problem of generating pores or not filling the surface during brazing can be prevented.

At this time, the binder is easily melted and dissolved to impart adhesion to the paste, and serves to adjust the viscosity and viscosity of the paste. The binder may include at least one selected from the group consisting of an aqueous binder and an oily binder.

The aqueous binder is decomposed in a drying furnace by 60 to 70% by weight and serves to hold the filler material so that it does not escape during the brazing process, but is completely decomposed in a brazing furnace, and does not change the appearance or characteristics of the product after brazing. I can. The aqueous binder is not particularly limited as long as it is commonly used in a brazing paste, and may include, for example, water and a water-soluble resin. Specifically, the aqueous binder may include 80 to 95 parts by weight of water and 5 to 20 parts by weight of a water-soluble resin.

The water-soluble resin may include at least one selected from the group consisting of acrylic resins, alkyd resins, urethane resins, vinyl acetate resins, and urea resins. At this time, the physical properties (eg, weight average molecular weight, etc.) of the water-soluble resin are not particularly limited as long as they are generally usable for a brazing paste.

In addition, the oily binder is not particularly limited as long as it is a conventional one capable of adjusting the drying speed and flowability of the paste according to the intended use. For example, the oily binder may include an oily solvent and an oily resin. Specifically, the oily binder may include 80 to 95 parts by weight of an oily solvent and 5 to 20 parts by weight of an oily resin.

The oily solvent may include at least one selected from the group consisting of acetate-based, benzene-based, ketone-based, ester-based, and carbonate-based. Specifically, the oily solvent may include at least one selected from the group consisting of dipropylene glycol methyl ether (DPM), butyl glycol acetate, toluene, xylene, methyl isobutyl ketone, acetone, and dimethyl carbonate.

In addition, the oily resin may include at least one selected from the group consisting of an epoxy-based resin, a silicone-based resin, a polyurethane-based resin, a polyester-based resin, and a polyvinyl alcohol-based resin. At this time, the physical properties (eg, weight average molecular weight, etc.) of the oily resin are not particularly limited as long as they are generally usable for a brazing paste.

The paste has a spreading rate of 180 to 350%, or 200 to 310%, measured using the base material STS-316 by the method described in KS B 0873, and a shear strength of 50 to 80 MPa, 60 to 80 MPa, or 65 to Can be 80 MPa.

As described above, the brazing paste according to the present invention includes alloy powder having a low melting point and high corrosion resistance, and has excellent spreadability, and is particularly suitable for exhaust system heat exchanger parts as it can secure sufficient spreadability required for exhaust system heat exchanger parts. Do. In addition, the brazing paste has excellent corrosion resistance in an environment of condensate generated during cooling, and is economical in terms of cost, including alloy powder including iron (Fe) alloy, which is an inexpensive alloy.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

[Example]

Examples 1 to 21 and Comparative Examples 1 to 10. Preparation of brazing filler material powder

A brazing filler powder (alloy powder) containing each component was prepared in the composition as shown in Table 1 below.

division Alloy component (parts by weight) Melting point(℃) Ni Cr P Fe Si Sn Example 1 59 25 6 10 - - 968 Example 2 53 25 12 10 - - 956 Example 3 47 25 18 10 - - 956 Example 4 56 25 12 7 - - 955 Example 5 48 25 12 15 - - 992 Example 6 35 25 12 28 - - 1,001 Example 7 71 7 12 10 - - 970 Example 8 58 20 12 10 - - 962 Example 9 40 38 12 10 - - 965 Example 10 57 25 6 10 2 - 964 Example 11 51 25 12 10 2 - 958 Example 12 45 25 18 10 2 - 957 Example 13 52 25 12 10 One - 957 Example 14 50 25 12 10 3 - 951 Example 15 48 25 12 10 5 - 947 Example 16 69 7 12 10 2 - 959 Example 17 56 20 12 10 2 - 958 Example 18 38 38 12 10 2 - 959 Example 19 52 25 12 10 - One 957 Example 20 50 25 12 10 - 3 955 Example 21 48 25 12 10 - 5 951 Comparative Example 1 75 3 12 10 - - 984 Comparative Example 2 33 45 12 10 - - 1,056 Comparative Example 3 28 25 12 35 - - 1,100 Comparative Example 4 85 7 - 3 5 - 970 Comparative Example 5 60 25 3 10 2 - 988 Comparative Example 6 75 25 - - - - 1,399 Comparative Example 7 76 14 10 - - - 930 Comparative Example 8 18 29 6 40.5 6.5 - 1,050 Comparative Example 9 18 29 3 43.5 6.5 - - Comparative Example 10 18 20 - 55.5 6.5 - -

As shown in Table 1, the powders of Examples 1 to 21 had a low melting point of less than 1,010°C.

Test Example: Evaluation of Paste Properties

A paste was prepared by mixing 85 parts by weight of the brazing filler powder prepared in Examples and Comparative Examples and 15 parts by weight of KD Braz of Kyungdong M-Tech Co., Ltd. as a binder. Thereafter, a specimen brazed using the paste was prepared, and the physical properties were measured in the following manner, and the results are shown in Tables 2 and 3.

(1) corrosion resistance

Corrosion resistance is made by using STS-316 as the base material and using the paste to braze the two base materials in a T-shape with aqua regia (nitric acid: hydrochloric acid: distilled water in a volume ratio of 1:1:1) ) After 18 hours immersion, the surface of the specimen was observed with a scanning electron microscope (SEM) to evaluate the degree of corrosion. The measured SEM picture is shown in Fig. 1, and the corrosion resistance evaluation was carried out as a relative evaluation.

(2) spread rate

STS-316 material of 50mmX50mm (width X length) was used as the base material, and after producing a specimen in the shape as shown in FIG. 2, the length before and after brazing was measured by the method specified in KS B 0873, and the following Equation 1 was used. The spread rate was calculated.

(3) Shear strength

After grinding and cleaning the brazing surface with No. 400 sandpaper, the thickness of the shear test specimen is 3.2mm, and the spacing of the brazing part is 0.1mm. The shear load and the joint area of the brazing part were measured. Thereafter, the shear strength was calculated using Equation 2 below.

division Corrosion resistance division Corrosion resistance Example 1 O Example 15 O Example 2 O Example 16 0 Example 3 O Example 17 O Example 4 O Example 18 O Example 5 O Example 19 O Example 6 O Example 20 O Example 7 0 Example 21 O Example 8 O Comparative Example 1 X Example 9 O Comparative Example 2 O Example 10 O Comparative Example 3 O Example 11 O Comparative Example 4 X Example 12 O Comparative Example 5 O Example 13 O Comparative Example 6 O Example 14 O

Spread rate (%) Shear strength (MPa) Example 2 253.85 79.26 Example 3 276.92 65.61 Example 5 238.46 72.66 Example 6 207.69 72.23 Example 15 300 78.56 Comparative Example 4 30.77 82.23 Comparative Example 6 - Cannot be produced Comparative Example 7 161.54 45.14 Comparative Example 8 53.85 42.32 Comparative Example 9 15.38 44.96 Comparative Example 10 7.69 40.41

As shown in Tables 1 to 3, the brazing filler powders of Examples 1 to 21 had a low melting point, and were excellent in corrosion resistance, spreading rate, and shear strength.

On the other hand, the paste of Comparative Example 1 containing a small amount of chromium was poor in corrosion resistance. In addition, the pastes of Comparative Example 2 containing an excess of chromium and Comparative Example 5 containing a small amount of phosphorus had a high melting point. In addition, the alloy powder of Comparative Example 3 containing an excess of iron had a very high melting point of more than 1,010°C. In addition, the paste of Comparative Example 4 containing no phosphorus was poor in corrosion resistance, and the spreading rate was remarkably insufficient. Furthermore, the alloy powder of Comparative Example 6 that does not contain phosphorus and iron has a remarkably high melting point, and it is impossible to prepare a specimen through brazing with a paste containing the same. In particular, it was confirmed that Example 2 contained phosphorus and iron, so that the spreadability was remarkably improved and the shear strength was excellent compared to Comparative Example 6.

In addition, as confirmed through Examples 2 to 6, as the iron content increased, the spreading rate gradually decreased. On the other hand, in Comparative Example 8 containing iron as a main component, after brazing, the spreadability was markedly decreased, and spread unevenly, and the shear strength was significantly insufficient. In addition, as confirmed through Comparative Examples 8 to 10, when the phosphorus content was small or phosphorus was not included, the spreadability became worse and non-uniform.

In addition, as shown in FIG. 1, in Comparative Example 4, due to the low chromium content, surface oxidation was confirmed after the corrosion test, and crack corrosion occurred in a part of the joint by the oxide. In addition, in Comparative Example 8 containing iron as a main component, local corrosion occurred at the brazing bonding interface after the corrosion test. On the other hand, in Examples 2 and 15, it was confirmed that there was no surface corrosion and joint corrosion even after the corrosion test.

Claims (14)

Brazing filler powder comprising 30 to 80 parts by weight of nickel (Ni), 5 to 40 parts by weight of chromium (Cr), 5 to 30 parts by weight of iron (Fe) and 5 to 20 parts by weight of phosphorus (P). The method according to claim 1,
The brazing filler metal powder further comprises at least one fluid imparting agent selected from the group consisting of silicon (Si) and tin (Sn). The method according to claim 2,
The powder comprises 1 to 5 parts by weight of a fluidity imparting agent, brazing filler powder. The method according to claim 2,
The total amount of the fluidity imparting agent and phosphorus is 6 to 25 parts by weight, brazing filler powder. The method according to claim 1,
The powder comprises 35 to 75 parts by weight of nickel, 10 to 38 parts by weight of chromium, 6 to 20 parts by weight of iron (Fe) and 6 to 18 parts by weight of phosphorus, brazing filler powder. The method according to claim 1,
The powder has a melting point of 800 to 1,010 ℃, brazing filler powder. A brazing paste comprising the brazing filler material powder and a binder of any one of claims 1 to 6. The method of claim 7,
The paste is a brazing paste containing 50 to 98 parts by weight of a brazing filler material powder and 2 to 50 parts by weight of a binder. The method of claim 8,
The binder is a brazing paste containing at least one selected from the group consisting of an aqueous binder and an oily binder. The method of claim 9,
The aqueous binder comprises water and a water-soluble resin, a brazing paste. The method of claim 10,
The water-soluble resin comprises at least one selected from the group consisting of acrylic resins, alkyd resins, urethane resins, vinyl acetate resins, and urea resins. The method of claim 9,
The oily binder comprises an oily solvent and an oily resin, a brazing paste. The method of claim 12,
The oily solvent includes at least one selected from the group consisting of acetate-based, benzene-based, ketone-based, ester-based and carbonate-based,
The oily resin comprises at least one selected from the group consisting of an epoxy-based resin, a silicone-based resin, a polyurethane-based resin, a polyester-based resin, and a polyvinyl alcohol-based resin. The method of claim 7,
The paste is a brazing paste having a spreading ratio of 180 to 350%, and a shear strength of 50 to 80 MPa, as measured using the base material STS-316 by the method described in KS B 0873.

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