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Piston Ring Casting Process Lowers Friction, Increases Durability Te pursuit of stronger, lighter

segment of Federal-Mogul Corp., Southfield, Mich., has developed an automated vertical molding process that produces stronger, more wear- resistant piston rings. Additionally, Federal-Mogul has created a casting simulation process that provides more precise data for optimal material flow, pressure and filling of molds. “Te thermal, mechanical and

components in the commercial automotive market has led casting suppliers to emphasize innovation in an effort to reduce fuel consumption and CO2

emissions. Te powertrain

tribological demands on components around the combustion chamber, par- ticularly piston rings, have increased,” said Steffen Hoppe, director of tech- nology, rings and liners. “While engine friction can be reduced through the use of thinner piston rings, a stronger material is necessary to maintain the proper bending strength.” With a traditional stack casting

process, horizontal arrangements of multiple molds are stacked above each other in layers, which can com- promise the runner system’s design because pressure and flow varies in different levels. Stack casting’s one- piece molds also reduce the range of available design options for the piston rings. In response to these limitations,

Federal-Mogul developed a vertical casting process to improve mate- rial flow at its facility in Burscheid, Germany. Te new casting form al- lows for feeding around the complete circumference of the casting, which improves graphite uniformity in the cast gray iron. Additionally, extensive monitoring and increased in-process documentation of parameters im- prove consistency. Federal-Mogul developed a new

casting simulation method using high-speed cameras that overcomes the limitations of conventional finite element (FE) modeling. “FE simula- tion has one major drawback,” Hoppe said. “No matter how fine a network is selected, the macro process is still simulated. How close the simulation is

Series production of cast iron and cast steel piston rings on new casting line at Federal- Mogul in Burscheid, Germany.

to reality always depends on how well the simulation parameters are chosen and set.” The new Federal-Mogul tech-

nique, called Slow-Motion Cast- ing Simulation (SMCS), provides a more detailed analysis of mold filling that allows for more precise

optimization of the gating and feeder systems. SMCS improves the tracking of the melt’s flow at differ- ent temperatures and casting speeds. SMCS allows the metalcaster to

develop a highly refined cast steel. Traditionally, high strength mar- tensitic gray cast iron containing nodular graphite, with strength up to 1,200 MPa, is used for diesel engine rings. Federal-Mogul’s new cast steel material, GOE70, is characterized by a martensitic matrix structure with embedded chromium carbides and strengths of 1,800 MPa. Piston rings made from GOE70

were subjected to endurance tests on heavy-duty diesel engines and showed exceptionally low side face wear and high robustness, reducing exhaust gas blow-by and decreasing oil consump- tion. Series production of rings made from GOE70 began in 2012, with the first application on a highly loaded heavy-duty engine. “Trough the development of

innovative technologies that provide enhanced control of key process pa- rameters, we have achieved improved product quality and increased strength and wear resistance,” Hoppe said.

Automated molding and pouring processes ensure the quality of cast iron rings in mass production. April 2014 MODERN CASTING | 45

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