Mechanism of Void Formation during Brazing of Ni Paste Brazing Filler Metal

2021 ◽  
Vol 1016 ◽  
pp. 1218-1222
Author(s):  
Mana Sakai ◽  
Tatsuya Sasaki ◽  
Yasuyuki Miyazawa
Keyword(s):  
Stainless Steel ◽  
Filler Metal ◽  
Void Formation ◽  
Inert Atmosphere ◽  
Exhaust Gas ◽  
Vacuum Atmosphere ◽  
Brazed Joint ◽  
Egr Cooler ◽  
Debinding Process ◽  
Gas Recirculation

Automobiles are equipped with EGR (Exhaust Gas Recirculation) coolers to improve fuel economy and exhaust gas suppression performance. Inside the EGR cooler, the moisture in the gas is condensed by cooling the hot exhaust gas. This condensed water is highly corrosive because sulfur oxides dissolve. Therefore, stainless steel and Ni-based brazing metal having excellent corrosion resistance are used for the EGR cooler.Until now, stainless steel has been brazed under a vacuum atmosphere. However, there are increasing opportunities to braze stainless steel in an inert atmosphere gas at atmosphere for cost reduction and mass production. In this case, a paste-type brazing filler metal consisted of a powder brazing filler metal and a binder is used. As is well known, a debinding process that volatilizes the binder is needed. From previous research in this laboratory, it is clarified that the binder causes voids. In addition, it is said that the size and location of voids generated at the brazed joint affect the product performance. On the other hand, the detailed investigation about the influence which the installation position of a paste type brazing filler metal on the void formation process has not yet been made. Therefore, in this study, the arrangement method and influence on heating rate and debinder temperature on void formation were investigated by X-ray CT.

Corrosion Resistance Evaluation of a Stainless-Steel Brazed Joint in HCl Solution

2021 ◽  
Vol 1016 ◽  
pp. 997-1002
Author(s):  
Hikaru Nagata ◽  
Masa Ono ◽  
Yasuyuki Miyazawa ◽  
Yuji Hayashi ◽  
Yoshio Bizen
Keyword(s):  
Aqueous Solution ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Base Metal ◽  
Corrosion Behavior ◽  
Anodic Polarization ◽  
Filler Metal ◽  
Brazed Joint ◽  
In Situ Observations

To clarify the effect of the acid solution type on corrosion resistance, the corrosion behavior of stainless steel brazed joints in HCl aqueous solution was evaluated through electrochemical measurements. Anodic polarization curves of a ferritic stainless-steel base metal, Ni-based brazing filler metals, and a brazed joint were recorded. In addition, in situ observations were conducted to observe the corrosion behavior of each structure of the brazed joint. Corrosion potentials of the brazing filler metal were lower than that of the base metal. In situ observations of the brazed joint revealed the order of corrosion in aqueous hydrochloric acid. According to the electrochemical measurements, under an actual corrosive environment, the brazing filler metal can function as an anode and selectively corrode. In addition, the anodic polarization curve of the brazed joint showed values between those of the polarization curves of the brazing filler metal and the base metal, indicating that the corrosion resistance could be electrochemically evaluated in HCl aqueous solution.

Analysis of the Exhaust Gas Recirculation System Performance in Modern Diesel Engines

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Stefano d'Ambrosio ◽  
Alessandro Ferrari ◽  
Ezio Spessa
Keyword(s):  
Control Valve ◽  
Experimental Tests ◽  
Detailed Comparison ◽  
Exhaust Gas Recirculation ◽  
Valve Lift ◽  
Exhaust Gas ◽  
Flow Area ◽  
Tube Type ◽  
Egr Cooler ◽  
Gas Recirculation

Exhaust gas recirculation (EGR) is extensively employed in diesel combustion engines to achieve nitrogen oxides emission targets. The EGR is often cooled in order to increase the effectiveness of the strategy, even though this leads to a further undesired impact on particulate matter and hydrocarbons. Experimental tests were carried out on a diesel engine at a dynamometer rig under steady-state speed and load working conditions that were considered relevant for the New European Driving Cycle. Two different shell and tube-type EGR coolers were compared, in terms of the pressure and temperature of the exhaust and intake lines, to evaluate thermal effectiveness and induced pumping losses. All the relevant engine parameters were acquired along EGR trade-off curves, in order to perform a detailed comparison of the two coolers. The effect of intake throttling operation on increasing the EGR ratio was also investigated. A purposely designed aging procedure was run in order to characterize the deterioration of the thermal effectiveness and verify whether clogging of the EGR cooler occurred. The EGR mass flow-rate dependence on the pressure and temperature upstream of the turbine as well as the pressure downstream of the EGR control valve was modeled by means of the expression for convergent nozzles. The restricted flow-area at the valve-seat passage and the discharge coefficient were accurately determined as functions of the valve lift.

A Comprehensive Physics-Based Model for Medium-Duty Diesel Engine With Exhaust Gas Recirculation

2007 ◽  
Author(s):  
Alok A. Joshi ◽  
Scott James ◽  
Peter Meckl ◽  
Galen King ◽  
Kristofer Jennings
Keyword(s):  
Heat Transfer ◽  
Exhaust Gas Recirculation ◽  
Boost Pressure ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
Transfer Effects ◽  
Variable Geometry Turbine ◽  
Heat Transfer Effects ◽  
Egr Cooler ◽  
Gas Recirculation

Physics-based models of diesel engines with exhaust gas recirculation and a variable geometry turbine (EGR/VGT) have been developed extensively in the control system design community. However, these models omit the heat transfer effects of the charge-air cooler and the recirculated exhaust gas cooler in order to avoid the added complexity in model order for online implementation. Generally, there is no need to include these effects if the purpose of the model is to control the target variables, such as boost pressure and air-to-fuel ratio. In this paper, after surveying the existing state of physics-based models for the EGR/VGT subsystem, a comprehensive model of the EGR/VGT subsystem is developed. This model includes heat transfer effects in the coolers, pressure drops across air filters and pipes, and mass flow rate calculations for a variable geometry turbine and an exhaust gas recirculation control valve. The purpose and scope of this work is offline modeling-for-diagnostics. Such models, though complex, will assist in the fault sensitivity analysis of a subsystem while avoiding any destructive testing when a major design modification in the EGR/VGT subsystem is proposed. For example, the impact of charge-water or EGR cooler degradation on the boost pressure and the air-to-fuel ratio can be studied with such models to further help in designing diagnostic reasoning strategies. Simulation performed using the proposed physicsbased model demonstrates a dominant failure effect of an EGR cooler coolant leak over a charge-water cooler water leak on the properties of the intake air.

scholarly journals Development of Low Silver AgCuZnSn Filler Metal for Cu/Steel Dissimilar Metal Joining

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 198 ◽  
Author(s):  
Peng Xue ◽  
Yang Zou ◽  
Peng He ◽  
Yinyin Pei ◽  
Huawei Sun ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Shear Strength ◽  
Penetration Depth ◽  
Aging Process ◽  
Filler Metal ◽  
Aging Treatment ◽  
304 Stainless Steel ◽  
Dissimilar Metal ◽  
Brazed Joints ◽  
Brazed Joint

The microstructure and properties of a Cu/304 stainless steel dissimilar metal joint brazed with a low silver Ag16.5CuZnSn-xGa-yCe braze filler after aging treatment were investigated. The results indicated that the addition of Ce could reduce the intergranular penetration depth of the filler metal into the stainless steel during the aging process. The minimum penetration depth in the Ag16.5CuZnSn-0.15Ce brazed joint was decreased by 48.8% compared with the Ag16.5CuZnSn brazed joint. Moreover, the shear strength of the brazed joint decreased with aging time while the shear strength of the AgCuZnSn-xGa-yCe joint was still obviously higher than the Ag16.5CuZnSn joint after a 600 h aging treatment. The fracture type of the Ag16.5CuZnSn-xGa-yCe brazed joints before aging begins ductile and turns slightly brittle during the aging process. Compared to all the results, the Ag16.5CuZnSn-2Ga-0.15Ce brazed joints show the best performance and could satisfy the requirements for cost reduction and long-term use.

A Simplified Model for Deposition and Removal of Soot Particles in an Exhaust Gas Recirculation Cooler

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
A. Reza Razmavar ◽  
M. Reza Malayeri
Keyword(s):  
Maximum Velocity ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Rolling Moment ◽  
Soot Particles ◽  
Exhaust Gases ◽  
Particulate Fouling ◽  
Efficient Performance ◽  
Egr Cooler ◽  
Gas Recirculation

Nitrogen oxides (NOx) emissions from diesel engines can profoundly be suppressed if a portion of exhaust gases is cooled through a heat exchanger known as exhaust gas recirculation (EGR) cooler and returned to the intake of the combustion chamber. One major hurdle though for the efficient performance of EGR coolers is the deposition of various species, i.e., particulate matter (PM) on the surface of EGR coolers. In this study, a model is proposed for the deposition and removal of soot particles carried by the exhaust gases in a tubular cooler. The model takes thermophoresis into account as the primary deposition mechanism. Several removal mechanisms of incident particle impact, shear force, and rolling moment (RM) have rigorously been examined to obtain the critical velocity that is the maximum velocity at which the particulate fouling can profoundly be suppressed. The results show that the dominant removal mechanism changes from one to another based particle size and gas velocity. Based on particle mass and energy conservation equations, a model for the fouling resistance has also been developed which shows satisfactory agreement when compared with the fouling experimental results.

Thermodynamic Performance Simulation of Diesel EGR Cooler with Finned Tube

2010 ◽  
Vol 97-101 ◽  
pp. 3345-3348
Author(s):  
Yan Song Wang ◽  
Hui He ◽  
Zhen Hua Xu ◽  
Jiang Hua Liu
Keyword(s):  
Finned Tube ◽  
Finite Element Models ◽  
Exhaust Gas ◽  
Performance Simulation ◽  
Pressure Fields ◽  
Thermodynamic Performance ◽  
Cooling Tube ◽  
Egr Cooler ◽  
Gas Recirculation ◽  
Pressure Boundary Conditions

Exhaust gas recirculation (EGR) cooler plays an important role in reducing the nitrogen oxides (NOx) emission of diesel engines. By using the CFDesign software, in this paper, the finite element models are established for analyzing the thermodynamic performance of an EGR cooler. The temperature, velocity and pressure fields of the fluids in the EGR cooler are simulated and verified. Based on these models, furthermore, the thermodynamic performance of the EGR cooler with different structures of cooling tube are analyzed, compared and discussed. The results show that, under the fixed pressure boundary conditions, the EGR cooling efficiency can be significantly increased by properly design the fin number of the cooling tube in EGR coolers.

Development and performance estimation of an exhaust gas recirculation cooler with dimpled rectangular tubes

2011 ◽  
Vol 225 (3) ◽  
pp. 384-397
Author(s):  
Y-H Seo ◽  
S-C Heo ◽  
T-W Ku ◽  
J Kim ◽  
B-S Kang
Keyword(s):  
Heat Exchange ◽  
Structural Integrity ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Exhaust Gas ◽  
Core Tube ◽  
Egr Cooler ◽  
Gas Recirculation ◽  
Rectangular Tubes

In this study, an exhaust gas recirculation (EGR) cooler with dimpled rectangular tubes, whose heat exchange effectiveness is higher than that of a conventional cooler, is developed. To maximize the heat transfer between the exhaust gas and coolant, the dimples are formed on the surface of the heat exchange tubes. A dimpled-tube manufacturing process is established that comprises: dimple shape forming, edge bending, centre v-notch bending, compression, and plasma welding. The high effectiveness of the dimple-type EGR cooler is confirmed by the effectiveness-NTU method and experimental approaches under normal operating conditions. It is also important to verify the structural integrity, in view of the practical uses of the dimple-type EGR cooler. In order to confirm the safety of the EGR cooler, finite element analyses are carried out for each component, such as the oval core tube with a dimpled shape. The structural integrity under thermal stress and pressure, which are caused by gas and coolant flows in the shell and tubes, is evaluated through thermal and structural analyses.

scholarly journals Microstructure and Properties of Si3N4 Ceramics and 304 Stainless Steel Brazed Joint with Cu/Ag-Cu/Ti Laminated Filler Metal

2018 ◽  
Vol 37 (6) ◽  
pp. 597-602 ◽  
Author(s):  
X. P. Xu ◽  
Q. M. Liu ◽  
C. Z. Xia ◽  
J. S. Zou
Keyword(s):  
Stainless Steel ◽  
Bending Strength ◽  
Filler Metal ◽  
Interfacial Microstructure ◽  
304 Stainless Steel ◽  
Four Point Bending ◽  
Maximum Value ◽  
Brazed Joint ◽  
Cu Foil ◽  
Cu Interlayer

AbstractSi3N4 ceramics and 304 stainless steel were joined by the Cu/Ag-Cu/Ti laminated filler metal. Interfacial microstructure of brazed joint and effect of brazing temperature and thickness of Cu foil on mechanical properties were studied in this paper. Research results showed that the interfacial microstructure of the brazed joint might be 304 stainless steel/TiFe2/Ag-Cu eutectic+Cu(s,s)/Cu(s,s)/Cu(s,s)+Ag-Cu eutectic/Cu3Ti+TiN/Si3N4 ceramics. With the increasing of the brazing temperature, four-point bending strength of the brazed joint initially increased, then decreased. The bending strength reached the maximum value of 53 MPa at 1153 K when the thickness of Cu foil was 500 μm. The bending strength reached the maximum value of 57 MPa with 1 mm thickness Cu interlayer under the brazing temperature of 1153 K.

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