• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.6
• /
• pp.827-834
• /
• 2009

The cooling heat transfer coefficient of $CO_2$ in a brazing type small diameter tube was investigated experimentally. The main components of the refrigerant loop are a receiver, a $CO_2$ compressor, a mass flow meter, an evaporator and a brazing type small diameter tube as a test section. The mass flux of $CO_2$ is $400{\sim}1600$ [kg/$m^2s$], the mass flowrate of coolant were varied from 0.15 to 0.3 [kg/s], and the cooling pressure of gas cooler were from 8 to 10 [MPa]. The cooling heat transfer coefficients of the brazing type small diameter copper tube is about $4{\sim}11.7%$ higher than that of the conventional type small diameter copper tube. In comparison with test results and existing correlations, correlations failed to predict the cooling heat transfer coefficient of $CO_2$ in a brazing type small diameter copper tube. therefore, it is necessary to develope reliable and accurate predictions determining the cooling heat transfer coefficient of $CO_2$ in a brazing type small diameter copper tube.

• Journal of the Korean Society for Heat Treatment
• /
• v.2 no.4
• /
• pp.69-72
• /
• 1989

• Proceedings of the KWS Conference
• /
• v.43
• /
• pp.43-45
• /
• 2004

Brazing between cemented carbides and steel for tool investigated by copper alloy brazing filler. Copper alloy filler was high liquidus temperature($990^{\circ}C$), therefor the shank(steel) occurred softening. Because brazing sample was necessary to heat treatment after brazing process. This experiment, influence of austenite time and purge temperature on heat treatment were investigated. As a result, these treatments obtained to high deflective strength In case of austenite time was short and purge temperature was low. Especially, nitride precipitated brazing layers was strongly influenced by the deflective strength.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.1083-1091
• /
• 1988

Vacuum brazing is the most modern brazing process and is at present, far from being completely understood. By brazing under high vacuum, in an atmosphere free of oxidizing gases, a superior product with greater strength, ductility and uniformity can be obtained. In this study, the influence of brazing parameters such as base metal characteristics, joint clearance and brazing time were described in relation to the metallurgical phenomena and shear strength of vacuum-brazed joints between carbon steels and 304 stainless steel (SUS 304) brazed by copper filler metal. In copper brazing of SUS 304 to a medium carbon steel(M.C.S) the columnar Fe-Cr-Ni-Cu-C alloy structure was formed and grew from the M.C.S side and at the same time, the surface of M.C.S. was decarbonized. The driving force for the formation and growth of columnar structure was the difference of carbon content between base metals. As the joint clearance is narrower and brazing time is longer, the formation and growth of columnar phase and decarburization of carbon steels were more noticeable. Because of decarburization of carbon steels, the shear strength of brazed joints were reduced as the formation of columnar structure was increased.

• Journal of Welding and Joining
• /
• v.7 no.3
• /
• pp.36-43
• /
• 1989

The furnace brazing in a Ar of copper to martensitic stainless steel(13.5Cr) using Cu-(5~8%)P-(0~8%)Sn powders was investigated. Shear strength, wettability, reacted layer, defect ratio at the stainless steel interface was evaluated. As Sn was added to the Cu-P powders, defect ratio and P content at the stainless steel interface decreased. And also as Sn was added, defect form at the stainless steel interface changed from the continuous layer to the discrete type, and shear strength of the brazed joint increased.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.7 no.4
• /
• pp.73-79
• /
• 2003

The tensile strength test and the analysis for the section of brazing were performed in the cases of materials used for combustion chamber of regeneratively cooled liquid rocket engine. BNi-2 and BNi-7 based on nickel were used for brazing as filler metal. The properties of material and filler metal were analyzed by tensile strength test and metal microscope for 12 specimens. The tensile-strength of brazing for chrome-copper alloy and other kinds of alloy was higher than that of chrome-zirconium-copper alloy and other kinds of alloy The tensile strength in the case of BNi-2 as filler metal was higher than that of BNi-7 because the wetting property of BNi-2 was better than that of BNi-7.

• Journal of Ocean Engineering and Technology
• /
• v.15 no.3
• /
• pp.49-57
• /
• 2001

One of the most important considerations to braze Cu-Al dissimilar materials is control of brittle metallic compound which makes it difficult to obtain a sound brazed joint. Nowdays, several attempts were made to control the metallic compound. But effective method for controlling metallic compound was not established. In this point of view, commercially pure aluminum and copper were used as base metal and Al-Si-X and Zn-Al-X alloy systems were developed as filler metal. Brazing was carried out to find optimum conditions for Cu-Al dissimilar joint. The results obtained in this study were summarized as follows: 1) The joint brazed by Al-Si-X filler metal showed good brazeability and mechanical properties. The tensile strength of the joint brazed over solidus temperature was more than 90% of Al base metal. Especially, the joint brazed at liquidus temperature was fractured in the Al base metal. 2) Fluorides fluxes(a mixture of potassium fluoro-aluminates) were used to improve surface cleanliness of base metal and wettability of Al-Si-X filler metal. It was melted at the temperature about 1$0^{\circ}C$ lower than that of the filler metal, and made appropriate brazing environment. Therefore, it could be a proper selection as flux.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.555-560
• /
• 2002

Brazing of Al to Cu using AI-Si-Mg-Bi brazing alloy has been carried out in the vacuum furnace. In the bonded interlayer, there were two kinds of intermetallic compounds. One of these intermetallic compounds was e phase and the other was b phase. The growth of b phase was controlled by diffusion Al into Cu. Deformation behavior of Al-Cu brazing joint was brittle without deformation of the base metal. Shear strength of the joint was only about 20MPa. The shear specimen broken in the intermetallic compound, which was mainly e phase. Shear strength did not depend on the bonding temperature.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.7
• /
• pp.112-117
• /
• 2003

The brazing of copper alloys and duplex stainless steels is an indispensable manufacturing technology for thrust chambers with regenerative cooling. For setting up the optimized brazing conditions, C18200 copper alloy plate with machined cooling channels and S31803 stainless steel plate are brazed with AMS4764 filler metals of which thickness is 50${\mu}m$ and 80${\mu}m$ They are tested by X-ray radiography, strength/leakage and fracture tests, and fracture surface inspection. The results obtained by the suggested conditions are that the specimen brazed with filler metal thickness of 50${\mu}m$ has good strength properties and brazed zone. However, the specimen with filler metal thickness of 80${\mu}m$ has the brazed zone with cooling channel obstruction and enlargement.

• Proceedings of the KWS Conference
• /
• 1999.05a
• /
• pp.103-106
• /
• 1999