• Korean Journal of Materials Research
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• v.33 no.5
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• pp.214-221
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• 2023

As a filler metal for lowering the melting point of Ag, many alloy metal candidates have emerged, such as cadmium, with zinc, manganese, nickel, and titanium as active metals. However, since cadmium is known to be harmful to the human body, Cd-free filler metals are now mainly used. Still, no study has been conducted comparing the characteristics of joints prepared with and without cadmium. In addition, studies have yet to be conducted comparing the typical characteristics of brazing filler metals with special structures, and the joint characteristics of brazing filler metals with available frames. In this study, the characteristics of junctions of silver-based intercalation metals were compared based on the type of filler metal additives, using a special structure, a filler metal sandwich structure, to protect the internal base metal. The general filler metal was compared using the structure, and the thickness of the filler metal according to the thickness was reached. A comparison of the characteristics of the junction was conducted to identify the characteristics of an intersection of silver-based brazing filler metal and the effect on joint strength. Each filler metal's collective tensile strength was measured, and the relationship between joint characteristics and tensile joint strength was explored. The junction was estimated through micro strength measurement, contact angle measurement with the base metal when the filler metal was melted, XRD image observation, composition analysis for each phase through SEM-EDS, and microstructure phase acquisition.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.179-183
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• 2007

A plate heat exchanger (PHE) normally uses vacuum brazing technology for connecting plates and fins. However, the reliability of high temperature brazing, especially with nickel-based filler metals containing boron the formation of brittle intermetallic compounds (IMCs) in brazed joints is of major concern. since they considerably degrade the mechanical properties. This research was examined the vacuum brazing of commercially SUS304 stainless steel with BNi-2 (Ni-Cr-B-Si) filler metal, and discussed to determine the influence of brazing temperatures on the microstructure and mechanical strength of brazed joints. In the metallographic analysis it is observed that considerable large area of Cr-B intermetallic compound phases at the brazing layer and the brazing tensile strength is related to removal of this brittle phase greatly. The mechanical properties of brazing layer could be stabilized through increasing the brazing temperature over $100^{\circ}C$ more than melting temperature of filler metals, and diffusing enough the brittle intermetallic compound formed in the brazing layer to the base metal.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.142-146
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• 2007

Vacuum brazing method has been coming to an important process as one of the new fabricating techniques of metals and alloys. In this study, a vacuum brazing of SUS304 stainless steel with BNi-2 filler metal was carried out in $1{\times}10^{4}$ Torr of vacuum atmosphere. The formation of brittle intermetallic compounds in brazed joints between SUS304 stainless steel and BNi-2 filler metal is a major concern, since they considerably degrade the mechanical properties of joints. To obtain enough stable joining strength, it is necessary to understand the unique properties of brazing process with Ni-based filler metals containing boron. So, in this research we investigated the performance of SUS304/BNi-2 brazed system and the brazed joint properties were evaluated at room temperature by using tensile test. Metallurgical and fractographic analysis were used to characterize the microstructure, the mechanisms of brazing, and joint failure modes.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.4
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• pp.210-216
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• 2009

Stainless steel EGR cooler of diesel engine is widely used to prevent the corrosion due to the content of sulfur in diesel fuel. The strength of brazed joint between stainless steel materials is very important. It is essential to observe the spreading ratio of the filler metals under the condition of deoxidation or vacuum during heating process. In this experiment, spreading ratio was tested to find the optimum brazing condition for stainless steel using brazing filler metals of FP-613, BNi-2 and BNi-5 on sus304 and sus410. Anti-corrosion tests were also performed on the above filler metals with solution of 5% $H_2SO_4$, 65% $HNO_3$ and 5% $NH_4OH$. Consequently FP-613 has good ability for anti-corrosion with 30% of chromium content compared with other filler metals. The optimum brazing conditions are occurred at $960^{\circ}C$ for 90 min. and at $1090^{\circ}C$ for 50 min. at the same degree of vacuum, $2{\sim}3{\times}10^{-3}$ Torr.

• Journal of Welding and Joining
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• v.9 no.4
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• pp.17-27
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• 1991

The direct brazing technology which could be used for the simplification of brazing process and the improvement of brazed joint quality was studied with $Al_2O_3$ and stainless steels. The brazing of $Al_2O_3$ to STS304 or STS430 was performed under different brazing conditions such as brazing filler metal, temperature, heating rate and brazing time. Microstructural observation and chemical analysis be SEM/EPAM were carried out to verify the quality of brazed joints. 4-point bending strength of brazed joints was also measured to find the optimal brazing conditions. The results showed that, in brazing of $Al_2O_3$, the mixed oxide layer resulted from the reaction between Ti in filler metal and oxide layer on the material surface to be brazed was found to be bery important for the joint quality. The width of oxide layer varied with the brazing conditions such as brazing time, heating rate and chemical composition of filler metals. The strength of brazed joints was more affected by the type of materials and their thermal properties than by brazing heat cycle.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.66-70
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• 2014

In Ti active brazing of YSZ to STS 430 using Ag-Cu Filler Metal, the effect of Ti contents on the shear bonding strength were investigated together with the effect of brazing temperature and holding time. The addition of Ti in Ag-Cu Filler Metal increased the bonding strength up to 4.68% Ti, followed by the decrease with further addition. This seems to be caused by formation of TixOy at the reaction layer. Brazing temperature was optimized at $960^{\circ}C$ among a given temperature ranges. The addion of Sn to Ag-Cu filler metal brought the decrease of its melting temperature its melting temperature without a significant decrease of bonging strength.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.539-544
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• 2002

Titanium and titanium alloy are excellent in corrosion resistance and specific intensity, and also in the biocompatibility. On the other hand, the brazing is bonding method of which productivity and reliability are high, when the complicated and precise structure of the thin plate is constructed. However, though conventional titanium-based brazing filler metal was excellent in bond strength and corrosion resistance, it was disadvantageous that metal structure and mechanical property of the base metal deteriorated, since the brazing temperature (about 1000 C) is considerably high. Authors developed new brazing filler metal which added Zr to Ti-Cu (-Ni) alloy which can be brazed at 900 C or less about 15 years ago. In this paper, the development of more low-melting-point brazing filler metal was tried by the addition of the fourth elements such as Ni, Co, Cr for the Ti-Zr-Cu alloy. As a method for finding the low-melting-point composition, eutectic composition exploration method was used in order to reduce the experiment point. As the result, several kinds of new brazing filler metal such as 37.5Ti-37.5-Zr-25Cu alloy (melting point 825 C) and 30Ti-43Zr-25Cu-2Cr alloy (melting point: 825 C) was developed. Then, the brazing joint showed the characteristics which were almost equal to the base metal from the result of obtaining metallic structure and strength of joint of brazing joint. However, the brazing filler metal composition of the melting point of 820 C or less could not be found. Consequentially, it was clarified that the brazing filler metal developed in this study could be practically sufficiently used from results such as metal structure of brazing joint and tensile test of the joint.

• International Journal of Korean Welding Society
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• v.2 no.2
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• pp.14-18
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• 2002

Titanium and titanium alloy are excellent in corrosion resistance and specific intensity, and also in the biocompatibility. On the other hand, the brazing is bonding method of which productivity and reliability are high, when the complicated and precise structure of the thin plate is constructed. However, though conventional titanium-based brazing filler metal was excellent in bond strength and corrosion resistance, it was disadvantageous that metal structure and mechanical property of the base metal deteriorated, since the brazing temperature ( about $1000^{\circ}C$ ) is considerably high. Authors developed new brazing filler metal which added Zr to Ti-Cu (-Ni) alloy which can be brazed at $900^{\circ}C$ or less about 15 years ago. In this paper, the development of more low-melting-point brazing filler metal was tried by the addition of the fourth elements such as Ni, Co, Cr for the Ti-Zr-Cu alloy. As a method for finding the low-melting-point composition, eutectic composition exploration method was used in order to reduce the experiment point. As the result, several kinds of new brazing filler metal such as 37.5Ti-37.5-Zr-25Cu alloy (melting point: $825^{\circ}C$) and 30Ti-43Zr-25Cu-2Cr alloy (melting point: $825^{\circ}C$) was developed. Then, the brazing joint showed the characteristics which were almost equal to the base metal from the result of obtaining metallic structure and strength of joint of brazing joint. However, the brazing filler metal composition of the melting point of $820^{\circ}C$ or less could not be found. Consequentially, it was clarified that the brazing filler metal developed in this study could be practically sufficiently used from results such as metal structure of brazing joint and tensile test of the joint.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.1
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• pp.47-52
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• 2003

The metallurgical and mechanical experiments of Titanium frame were conducted to investigate the optimum brazing and the improved brazed joints by filler metals has been developed by using other filler metals at brazing process. The filler metal is used in form of a metallic glass. The optimum brazing conditions were obtained from microstructural observation of brazed joints chemical analysis by means of X-ray micro-analysis and heating method.

• Journal of Welding and Joining
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• v.17 no.4
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• pp.26-31
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• 1999

An attempt was made in this study to investigate the brazing characteristics of Zr-Be binary amorphous alloys for the development of a new brazing filler metal for joining Zircaloy-4 nuclear fuel cladding tubes. This study was also aimed at the feasibility study of rapidly solidified amorphous alloys to substitute the conventional physical vapor-deposited(PVD) metallic beryllium. The $Zr_{1-x}Be_{x}$($0.3\leq$x$\leq0.5$) binary amorphous alloys were produced in the ribbon form by the melt-spinning method. It was confirmed by x-ray diffraction that the ribbons were amorphous. The amorphous. the amorphous alloys were used to join bearing pads on Zircaloy-4 nuclear fuel cladding tubes. Using Zr-Be amorphous alloys as filler metals, it was found that the reduction in the tube wall thickness caused by erosion was prevented. Especially, in the case of using $Zr_{0.65}Be_{0.35}$ and $Zr_{0.7}Be_{0.3}$ amorphousalloys, the smooth and spherical primary $\alpha$-Zr particles appeared in the brazed layer, which was the most desirable microstructure from the corrosion-resistance standpoint.