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Technical Paper

A Comparative Evaluation of Mechanical Properties and Machinability of Austempered Ductile Iron (ADI) and Microalloyed Steel

Austempered Ductile Iron (ADI) samples were heat treated to produce materials with tensile strengths in the range of 100 ksi to 170 ksi. Microalloyed steels were also produced with equivalent tensile and yield strength levels. These steels were evaluated for mechanical properties in terms of tensile and yield strength, ductility, impact toughness, fracture toughness and fatigue strength. Machinability was extensively evaluated through tests of drilling, turning and plunge machining. This paper reports on this comprehensive comparative evaluation of these two important classes of materials for use in the automotive industry.
Technical Paper

A Comparative Study on the Performance of Ventilated Brake Discs Manufactured in Different Advanced Materials

Two different aluminium alloy materials have been used to produce ventilated brake discs, on one hand, AS17G0.6 hypereutectic alloy and on the other hand, AS7G0.6 reinforced with 20% in wt. of SiC particles. The casting production technique used has been Low Pressure Casting (LPC) and some of the brake discs have been heat treated using a T6 treatment. Once the ventilated brake discs were produced and machined, they were tested in a dynamometer in order to compare the performance under service conditions of the aluminum alloy and grey cast iron (GCI) discs currently used in the market.
Technical Paper

A Comparison of Boundary Layer Treatments for Heat Transfer in IC Engines

Three different models, the law-of-the-wall, a modified law-of-the-wall, and an approximate one-dimensional solution to the energy equation are compared for the spatially-resolved prediction of engine heat tranfer. The multidimensional hydrodynamic code KIVA is used for the fluid mechanic simulation. Two different engine geometries are studied; one being a pancake-shaped chamber, and the other a bowl-in-piston geometry. The comparisons are done for a range of initial conditions of gas flow. Rates-of-pressure-rise were also varied to represent rates typical of those encountered in motored engines, and those found in fired engines. Comparisons with experimental results show that the heat transfer predictions using the law-of-the-wall may be in error when source terms such as the transient, work and chemical energy terms have a significant effect in determining the temperature profile in the boundary layer.
Technical Paper

A Comparison of Neural Networks and Wavelets Networks for Predicting Creep and Rupture Resistance of Ferritic Steels

This work is based in a model of neural and wavelets networks using published experimental data. The objective is to compare a neural and a wavelet network estimating the creep rupture strength based on chemical composition of Fe-2.25Cr-Mo and Fe-(9-12)Cr steels, and on its heat treatment temperature and life time. It will be determined the configuration that provides the best fit of the data.
Technical Paper

A Comparison of the Magnetic Properties of Hot Repressed and 7.4 g/cm3 Iron and 0.45% Phosphorus Iron Cores

Atomized iron powder was screened to narrow fractions and annealed. Intermetallic Fe3P powder was blended with the fractions to provide an alloy containing 0.45% phosphorus after sintering. Cores were pressed to a density of 7.4 g/cm3 and sintered at temperatures ranging from 1600°F (870°C) to 2600°F (1430°C) in hydrogen. Magnetic properties were determined from the sintered cores and compared with previous properties measured for iron and hot repressed 0.45% phosphorus iron. It was found that the induction at any density level was approximately 500 gausses (0.05 teslas) lower than for iron. Remanent magnetization was influenced by the size of the pores. If pores were large, remanent magnetization was 8 K gausses (0.8 teslas) and increased to 12 K gausses (1.2 teslas) as the pores become finer. Both maximum permeability and the coercive force were improved when 0.45% phosphorus was added.
Technical Paper

A Deep-Drawing, Hot-Dipped Galvanized Steel for Difficult Forming Applications

Formability of galvanized steel has been one of the key Issues In the automotive industry's transition to more corrosion resistant vehicle parts. This report describes a very ductile and formable grade of continuously annealed, hot dipped galvanized sheet steel that was specifically developed for difficult deep drawing or stretch-forming applications. The report also discusses performance of this grade in automotive stamping plants.
Journal Article

A Demonstration of Local Heat Treatment for the Preform Annealing Process

The preform annealing process is a two-stage stamping method for shaping non age-hardenable (i.e. 5000 series) aluminum sheet panels in which the panel is heat treated in between the two steps to improve overall formability of the material. The intermediate annealing heat treatment eliminates the cold work accumulated in the material during the first draw. The process enables the ability to form more complex parts than a conventional aluminum stamping process. A demonstration of local annealing for this process was conducted to form a one-piece aluminum liftgate inner panel for a large sport utility vehicle using the steel product geometry without design concessions. In prior work, this process was demonstrated by placing the entire panel in a convection oven for several minutes to completely anneal the cold work.
Technical Paper

A Design Tool for Tuning and Optimizing Carburizing and Heat Treat Processes

A software tool has been developed to aid designers and process engineers in the development and improvement of heat treat processes. This tool, DANTE™, combines metallurgical phase transformation models with mass diffusion, thermal and mechanical models to simulate the heating, carburization, quenching and tempering of steel parts. The technology behind the DANTE software and some applications are presented in this paper.
Technical Paper

A Development of the High-toughness Nitriding to Reduce Heat Treatment Distortion of AT Annulus Gear

In terms of reducing the gear noise of automatic transmission, improvement of heat treatment distortion of the annulus gear is very important, because annulus gear is very sensitive heat treatment due to thin walled ring-like shape. Nitriding is very effective method to meet the both requirements for heat treatment distortion and durability of the annulus gear, as compared with conventional carburizing. However, conventional nitriding has problems to be applied for annulus gear, such as brittleness of compound layer and low adhesion strength between compound layer and matrix. In this research, we developed the high toughness nitriding and greatly improved the problems as mentioned above, by controlling gas pressure and temperature.
Technical Paper

A Formable-Strengthenable Sheet Steel

High-strength cold-rolled sheet steels offer a potential to accomplish weight savings through gage reductions. However, the reduced formability which accompanies increased strength presents difficulties in the application of these steels for sheet metal stampings which require the formability equivalent of deep-drawing steels. A new deep-drawing sheet steel is being developed which overcomes the formability limitations of high-strength cold-rolled steels. Parts made from this steel can be uniformly strengthened to a high yield strength, up to 120,000 psi (827 MPa). Strengthening is accomplished by a 1200°F (921°K) heat treatment in a controlled atmosphere which results in internal nitridation. The nitrides formed by the alloying elements in the steel provide precipitation hardening. No distortion of the parts results from the heat treatment. The effect of heat-treating variables on tensile properties, weldability, fatigue, and toughness, are discussed.
Technical Paper

A Highly Formable Aluminum Alloy-5182-SSF

The best combination of strength and formability of any aluminum alloy is offered by the 5000 series (Al-Mg) alloys containing 4 to 5% magnesium, e.g. 5182. In the conventional annealed state (-0 temper) necessary for maximum formability, this alloy suffers from the formation of type A Luder lines (stretcher strains) when plastically deformed a small amount (<1%). Such Luder lines are similar to those commonly encountered in steel and are unacceptable in outer panels. The conditions under which Luder lines form are discussed. The introduction of 5182-SSF has completely avoided these problems with a stretcher-strain free (SSF) material which exceeds the formability of 5182-0.
Technical Paper

A Method for Reliability Improvement of Torsion Spring for Exhaust Valve

The exhaust valve plays a role of reducing the mechanical noise and vibration of vehicle by smooth discharging of the vehicle emissions after combustion process in exhaust system of engine. The torsion spring is one of the most core components in exhaust valve, which generates variable torque for control of opening and closing angle of exhaust valve. Its performance represents all over the performance of exhaust system of vehicle. As it were, the failure of torsion spring means the failure of all exhaust system. So, as well as performance, the reliability of the torsion spring is very important. To secure the reliability is same to secure the security and comfort of passengers including driver. This paper proposed two methods for improvement of torque and reliability characteristics of torsion spring. One is improvement of heat treatment condition for getting of more constant torque characteristic of torsion spring.
Technical Paper

A New Approach to Design High Porosity Silicon Carbide Substrates

Diesel particulate filters (DPF) are now a mandatory part in diesel exhaust aftertreatment systems in order to achieve compliance with current emission legislations. However future demands for further NOx and CO₂ reductions combined with a maximum amount of allowed particle numbers per ccm lead to special requirements for the DPF substrate material. On the one hand high filtration efficiency of soot particles in the nanometer scale has to be reached and on the other hand high porosities and large pore sizes have to be realized to support catalytic coating. In order to have a base material composition which can easily be modified to meet current and future demands a new SiC substrate, called XP-SiC, was developed. The technology of the XP-SiC is based on a reaction forming process of coextruded silicon and carbon particles to SiC. This new manufacturing process leads to a unique microstructure with a sponge-like appearance and a high porosity in the range of 50% - 70%.
Technical Paper

A New Concept in Formable High Strength Steel

A new approach to forming high strength steels is proposed and its feasibility demonstrated. The proposed method involves relationship between steel composition and heat treatment which allows specific steels to be formed at low strength levels and subsequently strengthened, without distortion, by a martensitic transformation. The steel chosen to demonstrate the concept could be formed at 40 ksi yield strength and subsequently strengthened by a short heat treatment to yield strengths in excess of 100 ksi.
Technical Paper

A New High Strength CAB Evaporator Plate Alloy with High Corrosion Resistance

A new evaporator plate alloy identified as FA7857 has been developed by Sapa. This alloy which is intended for CAB brazing, has been developed to meet the market needs for a material with good formability prior to brazing and a low susceptibility to filler liquid core penetration (sometimes termed LFM) during brazing. The excellent formability in the annealed condition, with an elongation of 26% and an Erichsen cup height of 9.2mm, makes this material highly suitable for pre-stretching prior to evaporator plate forming and brazing. An appropriate pre-stretch is 5% which eliminates the risk of LFM, while improving the uniformity of flow of the filler metal and the final corrosion performance. In SWAAT corrosion tests, brazed samples of the two-side clad sheet remained unperforated after 42 days of testing.
Technical Paper

A New Method of Reliability Testing for C-MOS VLSI's Evaluation

This paper presents a new method of reliability testing for C-MOS VLSI's evaluation, i.e. a means to verify the future reliability prediction. In this method, VLSI's under testing are stressed by soft x-ray irradiation and subsequently annealed at moderate temperature and then they are classified according to the time required to recover the computer action of VLSI's to the previous level. This method offers a new technology for future reliability testing in higher accuracy of C-MOS VLSI's used in automotive electronics system compared to the conventional technique so called burn-in.
Technical Paper

A New Microalloyed, Multi-Phase Steel for High Strength Forging Applications

Forged components to be used in high strength applications have traditionally been heat treated after forging. This processing route unfortunately suffers from many technical and economical shortcomings. The first attempt to overcome these difficulties led to the development of medium carbon microalloyed steels for bar applications in the early 1970's. While these steels did not require heat treatment, their strengths were limited. Furthermore, the notch toughness of these steels was rather poor. The limitation on strength and toughness have hindered their acceptance as a substitute for the conventional QT steels, especially in safety critical components. In addition, these shortcomings eliminate the possibility of downsizing through redesign. Since the tempered martensite and the microalloyed ferrite-pearlite steels have obvious limitations, an alternative microstructure had to be developed.
Technical Paper

A New Polycarbonate and Glass Laminate and Its Affects on the Relationship Between Residual Tensile Stresses and Impact Resistance of Windshields

Current windshield manufacturing processes produce residual tensile stresses near the edges of windshields. This residual tensile stress reduces the ability of the windshield to withstand suddenly applied external loading over a short time interval near the edge. Present manufacturing processes can reduce some of the residual tensile stress produced during the annealing process, but currently it is technically difficult to eliminate. However, an innovative and more cost-effective solution for the residual tensile stress problem has been proposed. Application of a thin film of polycarbonate around the perimeter of the windshield allows the energy generated during impact loading to be dissipated without the need to change the windshield's material properties.
Technical Paper

A Non-Distorting Heat Treatment Which Provides Both Wear and Corrosion Resistance

For structural components that require improved fatigue and wear resistance, shallow case carbonitriding has traditionally been specified by the automotive industry. A typical specification might call for .003 to .010 inch case depth consisting of clear martensite and a surface file hardness of Rc 58 file hardness. A problem with this treatment has been excessive distortion in precision components such as fine blanked stampings, screw machine parts, and powder metal parts. In many cases, these parts have to be finish ground or sized in some manner to return the parts to print tolerances. Another problem has been a severe loss of fatigue strength because of over-casing. This embrittles parts with thin cross sectional thicknesses. Lindberg Corporation has developed the Lindure process to provide an alternative to carbonitriding. Lindure is a gaseous nitrocarburizing treatment which takes place at temperatures below the lower critical (AC1) where the austenite transformation begins.
Technical Paper

A Novel Approach for Rapid Solidification Processing of High Strength PM Aluminum Alloys

Incremental spray casting has been applied to the consolidation of advanced high strength aluminum alloys requiring rapid solidification processing. The conditions for incremental spray casting are described and compared with the spray rolling process as proposed originally by A. R. E. Singer. Microstructures and tensile properties of the aluminum alloys 7075, 7091, and PM64 prepared by incremental spray casting and subsequently rolled and heat treated are presented and compared with their conventionally prepared counterparts. This process provides a direct route from pre-alloyed melt stock to sheet bar; it is a promising alternative to conventional powder metallurgy methods for producing a dense, rapidly solidified deposit of high strength PM aluminum alloy. At the present time the process is limited to producing deposit thicknesses of about 1 to 2 cm. Improved methods of extracting heat from the solidifying deposit are required for scaleup to thicker sections.