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Technical Paper

A New Tool for Corrosion Inhibitor Research

2001-03-05
2001-01-1176
Electrochemical techniques such as repassivation potential measurements and electrochemical impedance spectroscopy (EIS) have become important tools in corrosion and corrosion inhibitor research. However, these techniques reflect the response of the total surface area of the exposed sample and cannot distinguish between types of localized corrosion e.g. pitting or crevice corrosion. Current density mapping (CDM) is a technique that uses a fine stainless steel needle, vibrating at a set frequency and scans over the surface of a sample in a plane micrometers above the sample surface. By mapping the current distribution over a surface, sites of localized corrosion can be characterized and the effect of a corrosion inhibitor monitored.
Technical Paper

Nanofluids for Vehicle Thermal Management

2001-05-14
2001-01-1706
Applying nanotechnology to thermal engineering, ANL has addressed the interesting and timely topic of nanofluids. We have developed methods for producing both oxide and metal nanofluids, studied their thermal conductivity, and obtained promising results: (1) Stable suspensions of nanoparticles can be achieved. (2) Nanofluids have significantly higher thermal conductivities than their base liquids. (3) Measured thermal conductivities of nanofluids are much greater than predicted. For these reasons, nanofluids show promise for improving the design and performance of vehicle thermal management systems. However, critical barriers to further development and application of nanofluid technology are agglomeration of nanoparticles and oxidation of metallic nanoparticles. Therefore, methods to prevent particle agglomeration and degradation are required.
Technical Paper

External Corrosion Resistance of CuproBraze® Radiators

2001-05-14
2001-01-1718
New technology for the manufacturing of copper/brass heat exchangers has been developed and the first automotive radiators are already in operation in vehicles. This new technology is called CuproBraze®. One of the essential questions raised is the external corrosion resistance with reference to the present soldered copper/brass radiators and to the brazed aluminium radiators. Based on the results from electrochemical measurements and from four different types of accelerated corrosion tests, the external corrosion resistance of the CuproBraze® radiators is clearly better than that of the soldered copper/brass radiators and competitive with the brazed aluminum radiators, especially as regards marine atmosphere. Due to the relatively high strength of the CuproBraze® heat exchangers, down gauging of fins and tubes in some applications is attractive. High performance coatings can ensure long lifetime from corrosion point of view, even for thin gauge heat exchangers.
Technical Paper

A New High Strength Aluminium Alloy for Controlled Atmosphere Brazing

2001-05-14
2001-01-1727
A new high strength aluminium alloy intended for tubes in automotive radiators has been developed. The material is an age hardening alloy containing Mg, Si, Cu, and Mn. Titanium is added for corrosion protection. The post-braze strength of the material is dependent on the cooling rate after brazing. With 1°C/s cooling rate between 400 and 200°C, the Rp0.2 will be about 75 MPa. The corrosion resistance of the material is excellent. It is more noble than standard fin materials and will be protected by sacrificial action. Any attack in the material will be forced into a lamellar mode due to the Ti addition.
Technical Paper

Rapid Electrochemical Characterisation of Corrosion Properties of Aluminium Brazing Sheet by Stepwise Dissolution Measurement

2001-05-14
2001-01-1693
For aluminium heat-exchangers one of the most accepted corrosion tests is the SWAAT. It is widely used by both aluminium producers and manufacturers of heat-exchangers. However, in alloy development programmes, as well as in production environments even faster characterisation of corrosion properties of aluminium brazing sheet would be advantageous. The Stepwise Dissolution Measurement (SDM), which is an electrochemical technique, was developed in our laboratory to enable rapid screening of corrosion properties of aluminium brazing sheet. Within approximately 6 hours it is possible to distinguish between Long Life (over 25 days SWAAT performance) and non Long Life materials. Cross section showed that the mode of attack in SDM is similar to the mode of attack in SWAAT exposure.
Technical Paper

Development of a High Strength Fin Stock Aluminium Alloy

2001-05-14
2001-01-1735
As part of the overall target in the automotive industry to decrease weight and production costs, the heat exchanger market has to develop more effective designs on an on-going basis. In turn this places demands on the material supplier to develop higher strength alloys, which enable down-gauging for lighter-weight structures, or the use of high pressure cycles, and/or an increased amount of fins for increased cooling efficiency. This increased performance must be achieved cost effectively and with brazing and corrosion performance equivalent to, or superior to, the existing material. In order to meet these demands Corus Aluminium has developed over the last few years new families of improved alloys for heat exchanger tubes and core plates, that are suitable for Vacuum and/or Controlled Atmosphere Brazing (CAB) [1]. To further complete this development a programme was started to develop a series of high strength alloys for the heat exchanger cooling fins.
Technical Paper

Electrochemical Tests with Copper/Brass Radiator Tube Materials in Coolants

2001-05-14
2001-01-1754
Corrosion behavior of brass CuZn15Fe, brass CuZn30 and aluminum in automotive coolants was studied with electrochemical methods. Two commercial glycols were used in the study. The tests indicate that both glycols provide the metals tested with good corrosion protection. Glycol with conventional inhibitor chemicals prevents corrosion of aluminum even with extensive anodic polarization. Although initiation of pitting could be observed in the same conditions with an inhibitor system based on organic acid technology, it is not very likely to have galvanic corrosion on aluminum by dissolved and deposited copper in automotive coolant systems.
Technical Paper

DAF Euro-4 Heavy Duty Diesel Engine with TNO EGR system and CRT Particulates Filter

2001-05-07
2001-01-1947
This paper reports on a study of the TNO venturi EGR system and the Johnson Matthey CRT particulates trap on a DAF 355 kW engine. The results obtained indicate that this EGR-CRT combination is an effective means to achieve EURO-4 emission level, while maintaining good fuel economy. EGR strategy, injection timing and air-fuel ratio were optimised in such a way that good regeneration conditions were obtained across most of the engine operating map. Also transient EGR control is optimised to combine low NOx emission during the ETC with good driveability and good engine out particulates emission. The size of the oxidation catalyst in the CRT was investigated. It appeared that the larger oxidation catalyst showed a better regeneration performance during a low temperature duty-cycle. Negative aspects of a larger oxidation catalyst are increased costs and increased NO2 emission (because of the catalyst ability to oxidise more NO into NO2).
Technical Paper

A development of diesel oxidation catalyst and the evaluation of its performance characteristic

2000-06-12
2000-05-0287
The new concept oxidation for diesel engine has been developed. It has been designed to use under circumstances of the "dry condition" of exhausted emission, which indicates low soluble organics and high dry soot concentration under high exhaust gas temperature. For the reliability and performance of catalysts in dry condition, several design concepts were established. First of all, extremely low sulfate formation on catalyst at high temperature conditions, and an improved soluble organic burning characteristics was required. A minimization of deposition of the particulate component, especially sulfate, was obtained from the adjustment of washcoat loading and material property. Six different types of catalysts have been prepared and tested in a laboratory. Diesel vehicle test showed the possibility that soluble organic could be removed mostly with minimal sulfate formation.
Technical Paper

Development of Creep-Resistant Magnesium Alloys for Powertrain Applications: Part 1 of 2

2001-03-05
2001-01-0422
A family of low-cost, creep-resistant magnesium alloys has been developed. These alloys, containing aluminum, calcium, and strontium are designated as “ACX” alloys. Developed for engine blocks and transmissions, the “ACX” alloys have at least 40% greater tensile and 25% greater compressive creep resistance than AE42, and corrosion resistance as good as AZ91D (GMPG 9540P/B corrosion test). These alloys are estimated to cost only slightly more than AZ91D and have as good castability. Creep data up to 200°C, tensile properties at room temperature and 175°C, corrosion results and microstructure analysis are presented and discussed. These alloys have the potential to enable the extension of the substantial weight reduction benefits of magnesium to powertrain components.
Technical Paper

An Intelligent Catalyst

2001-03-05
2001-01-1301
The catalyst of the crystalline ceramics known as a perovskite-type oxide was designed and controlled at the atomic level in order to create a new function for self-regeneration of precious metals in a usage ambience without auxiliary treatment. We have already reported that a catalyst with Pd supported on the perovskite-type oxide has higher activity than a catalyst with Pd supported on alumina. It was also found that Pd supported on the perovskite catalyst is finely dispersed [1, 2 and 3] The object of this study was to investigate the mechanism of self-regeneration by using hyper-analytical facilities. XAFS analysis, at SPring-8 (8 GeV), revealed that Pd is in six-fold coordinations with oxygen in a perovskite crystal, which indicating that Pd occupies the B site of the unit formula of ABO3 in the perovskite crystal structure under oxidation atmosphere.
Technical Paper

Regeneration Behavior and Transient Thermal Response of Diesel Particulate Filters

2001-03-05
2001-01-1342
The diesel particulate filter (DPF) is effective for particulate removal from diesel engine exhaust under a variety of conditions, but development of regeneration strategies remains an ongoing challenge, primarily because of low exhaust temperatures. This paper addresses two issues related to DPF regeneration: the thermal response of DPFs during regeneration events and the soot oxidation (i.e., regeneration) rate at varying temperature, flow rate, oxygen content, and unsteady inlet temperature. The experiments are performed in a laboratory reactor, which provides gas temperature and composition similar to diesel engine exhaust. The catalyzed and uncatalyzed DPFs used in this study are first loaded with soot on an engine dynamometer at a fixed load and engine speed. During constant temperature regeneration experiments, the change in pressure drop is monitored to determine the extent of regeneration.
Technical Paper

Development of Quad-layer Clad Brazing Sheet for Drawn Cup Type Evaporator: Part 2

2001-03-05
2001-01-1254
We have achieved significant weight reduction for the MS (Multi-Tank Super Slim Structure) Evaporator (1)currently in production at DENSO CORPORATION. The evaporator of HVAC unit, located in the instrument panel, is a component of the aluminum heat exchanger used in automotive air conditioners. The new evaporator uses thinner quad-layer sheet material, thanks to optimization of the electrical potential among its outer filler metal, intermediate anodic layer and core. The evaporator is thus lighter than conventional evaporators, but retains equivalent corrosion resistance.
Technical Paper

Development of Quad-layer Clad Brazing Sheet for Drawn Cup Type Evaporators: Part 1

2001-03-05
2001-01-1253
Having a light weight, a good heat conductivity and a good brazability, aluminum alloy is widely used for automotive heat exchanger systems. The major problem with Aluminum is perforation of the tube by pitting corrosion and corrosion protection is necessary in the field. In radiator and condenser systems using the the Nocolok brazing process given good corrosion resistance using cathodic protection with sacrificial anode made of Zn-sprayed onto tube or low corrosion potential fins etc. On the other hand, in drawn-cup type evaporators, that are fabricated from brazing sheet tubes in vacuum brazing method and then covered low electro-conductive drain water film in operation, the effect of cathodic protection by the anode fin is limited to a very small area. Therefore, this has been studied to improve self-corrosion resistance of the core in the brazing sheet tube.
Technical Paper

Detailed Chemical Kinetic Modeling of Diesel Spray Combustion with Oxygenated Fuels

2001-03-05
2001-01-1262
This paper confirms a structure for the soot formation process inside a burning diesel jet plume of oxygenated fuels. An explanation of how the soot formation process changes by the use of oxygenated fuel in comparison with that for using a conventional diesel fuel, and why oxygenated fuel drastically suppresses the soot formation has been derived from the chemical kinetic analysis. A detailed chemical kinetic mechanism, which is combined with various proposed chemical kinetic models including normal paraffinic hydrocarbon oxidation, oxygenated hydrocarbon oxidation, and poly-aromatic hydrocarbon (PAH) formation, was developed in present study. The calculated results are presented to elucidate the influence of fuel mixture composition and fuel structure, especially relating to oxygenated fuels, on PAH formation. The analysis also provides a new insight into the initial soot formation process in terms of the temperature range of PAH formation.
Technical Paper

Development of High Corrosion Resistant Stainless Steels for Automotive Mufflers Based on Condensate Corrosion Test and Field Investigation

2001-03-05
2001-01-0640
Automotive exhaust gas condensate causes severe corrosion inside mufflers. Corrosive condensate became a problem following the introduction of three-way catalytic converters in exhaust systems. The authors previously established a new laboratory test method that simulates condensate corrosion. This test method contributed to the development of new stainless steels for automotive mufflers. The addition of molybdenum (Mo) and copper (Cu) to ferritic stainless steels was found to be effective in improving condensate corrosion resistance, and the effect was arranged using the index [%chromium (Cr)+3×%Mo+1.5×%Cu]. A field test was carried out to investigate the corrosion behavior of mufflers under actual conditions. Aluminized steels showed severe damage by general corrosion. On the other hand, 19%Cr-Cu ferritic stainless steel exhibited excellent corrosion resistance. The corrosion behavior in the field test showed good agreement with the results of the laboratory test.
Technical Paper

A Vehicle Micro Corrosion Environmental Study of Field and Proving Ground Tests

2001-03-05
2001-01-0646
This paper presents the progress of an ongoing vehicle micro corrosion environment study. The goal of the study is to develop an improved method for estimating vehicle corrosion based on the Total Vehicle Accelerated Corrosion Test at the Arizona Proving Ground (APG). Although the APG test greatly accelerates vehicle corrosion compared to the field, the “acceleration factor” varies considerably from site-to-site around the vehicle. This method accounts for the difference in corrosivity of various local corrosion environments from site-to-site at APG and in the field. Correlations of vehicle microenvironments with the macroenvironment (weather) and the occurrence of various environmental conditions at microenvironments are essential to the study. A comparison of results from APG versus field measurements generated using a cold rolled steel based corrosion sensor is presented.
Technical Paper

Development of Pitting Resistant Steel for Transmission Gears

2001-03-05
2001-01-0827
It was found that pitting resistance of gears is strongly influenced by resistance to temper softening of carburized steel. The investigation about the influence of chemical compositions on hardness after tempering revealed that silicon, chromium and molybdenum are effective elements to improve resistance to temper softening and pitting resistance. Considering the production of gears, molybdenum is unfavorable because it increases hardness of normalized or annealed condition. Developed new steel contains about 0.5 mass% of silicon and 2.7 mass% chromium. The new steel has excellent pitting resistance and wear resistance. Fatigue and impact strength are equivalent to conventional carburized steels. Cold-formability and machinability of the new steel are adequate for manufacturing gears because of its ordinary hardness before carburizing. The new steel has already been put to practical use in automatic transmission gears. Application test results are also reported.
Technical Paper

High Frequency Fatigue Crack Propagation Behavior of a Spheroidal Graphite Cast Iron

2001-03-05
2001-01-0831
Owing to the combination of high strength and good ductility, spheroidal graphite cast iron (SGI) has been widely used in the automotive industry. The application of the damage-tolerance design approach to the mechanical parts subjected to high frequency vibration loading necessitates a more reliable determination of crack propagation threshold. In this study, the fatigue crack propagation behavior of a SGI (ferrite in matrix with about 5% pearlite) was investigated experimentally at a frequency of 20 kHz and the stress ratio of R=-1 and R=0.1. The propagation threshold was determined at a very slow rate of 10-11 m/cycle. The results of these tests have been compared with those of conventional fatigue test. Effects of cyclic loading frequency have been discussed. It is shown that the threshold stress intensity value is smaller at ultrasonic frequency. The observations of the fracture surface at SEM show that there is less oxidation at very high frequency in all propagation regimes.
Technical Paper

THE ROLE OF “CRATERING” IN THE PROCESSING AND PROPERTIES OF GALVANNEALED STEEL SHEET

2001-03-05
2001-01-0084
Craters in galvannealed coatings on steel sheet are depressions caused by non-uniform diffusive growth. Correlations have been sought between “crater” densities in galvannealed sheet steel and friction, powdering, and paint adherence, as relevant to the appearance, corrosion resistance and processing of auto body panels. Crater densities were established on a series of samplings from major producers, and related to frictional measurements from a binder-radius simulator, powdering levels from bend testing, and paint adherence assessments from a stone-chipping test. Results suggest that increased crater density decreases powdering, but does not aid in lubrication. In fact, decreased powdering could be correlated with increased friction levels. A strong correlation was found between increased crater density and increased paint adherence.
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