ADVANCED STEEL OFFERS AUTOMAKERS AGGRESSIVE ENGINE DOWNSIZING

Transcription

1 ADVANCED STEEL OFFERS AUTOMAKERS AGGRESSIVE ENGINE DOWNSIZING Andy Schmitter Nucor Corporation

2 Background and Scope The Bar Applications Group (BAG),a committee of the Steel Market Development Institute (SMDI), wanted to conduct a study to define engine performance and weight improvements that may be possible when an engine is designed using an increased number of steel components. The SMDI contracted with Mahle Powertrain to complete the study.

3 Background and Scope Project Scope Literature survey to quantify current steel usage in engines Review of MAHLE internal reports Brainstorm and information gathering with MAHLE Component Experts Determination of component weight saving potential Final Report MAHLE Powertrain (MPT) to focus on consideration of steel as an enabler e.g. Higher strength Smaller package Better heat management Friction Heavy duty engines not widely considered in this study steel content already high

4 Potential Component Evaluation List Engine Assembly Camshaft Valve Spring Valve Turbocharger Piston ring Piston Oil Pump Cylinder head Engine block Cylinder liner Connecting rod Bearings / bushings Crankshaft

5 Potential Component Evaluation List Focus on the Big Four Component/System Crankshaft Connecting Rods Camshaft Pistons Engine Block Piston Rings Springs Valves Cylinder Liners Ancillary Components Comments Currently cast iron, forged or machined steel. Powder metal FS, steel machined, steel FS. Small volume of Ti. Cast iron or assembled (assumed to be steel). Generally Al for light and medium duty. Stretch goal. Any steel block unlikely to be made using bar stock. Top and oil ring generally steel. Generally all produced from wire. Already steel although produced from wire. Generally already steel. Small volume of Ti. Generally cast iron. Light duty engines tending to parent Al. DI fuel pumps have high steel content. Brackets will likely be formed from flat sheet if steel. Pumps mix of steel and PM. Turbochargers

6 Literature Survey and Data Collection Camshafts and Connecting Rods

7 8 Cylinder Camshaft and Con-Rod Distribution 8 Cylinder Camshaft Distribution 8 Cylinder Con-Rod Distribution 5% 24% Cast % 22% 1% Powder Metal % Assembled % N/A% Forged Steel % N/A % 71% 77% Production Volume V90deg Chrysler 473,200 Ford 666,100 GM 1,307,200 European 238,000 Asian 196,500 Total Production 2,881,000

8 8 Cylinder Camshaft and Con-Rod Distribution For 8 cylinder engines steel camshafts appear to be very prevalent Likely due to the longer length of an 8 cylinder camshaft The high amount of cam in block ( OHV ) 8 cylinder engines may require more assembled camshafts also Powder metal connecting rods appear to be used in a majority of V-8 engines Low power density Lower engine speeds

9 6 Cylinder Camshaft and Con-Rod Distribution Production Volume Boxer Inline V( 60 ) V( 90 ) V( 11 ) Chrysler 0 109, , Ford 0 38,800 1,035, GM , European 12, , ,900 Asian 55, ,612, Total Production 5,150,000

10 6 Cylinder Camshaft and Con-Rod Distribution Several 6 cylinder configurations are readily available Only the two most common NA arrangements (90 o and 60 o ) were investigated closer The traditional 60 o V-6 sees a large use of Iron cast camshafts 90 o V-6 uses nearly 50% forged steel connecting rod Non-optimal layout Higher power density

11 4 Cylinder Camshaft and Con-Rod Distribution Production Volume Boxer Inline Chrysler 0 383,300 Ford 0 687,200 GM 0 896,000 European 0 400,400 Asian 230,100 3,436,500 Total Production 6,033,500

12 4 Cylinder Camshaft and Con-Rod Distribution In general 4-cylinder engines use mostly cast Iron camshafts Boxer or flat configurations use 100% steel camshafts but their market share is small A majority of both 4-cylinder engine configurations use forged steel connecting rods Increased occurrence of boosting Higher engine speeds common

13 Literature Survey and Data Collection Crankshafts

14 Steel Use in Current Engines I4 Crankshafts

15 Steel Use in Current Engines V6 Crankshafts

16 Steel Use in Current Engines V8/V10 Crankshafts

17 Steel Use in Current Engines Comments / Conclusions

18 Steel Component Use Pros and Cons

19 Steel Crankshaft Pros and Cons PROS(Compared to cast crank) Greater tensile strength Greater fatigue strength Smaller size/weight possible (in theory) enabling tighter package Machined steel crankshaft has advantages for low volume and prototype over cast iron CONS(Compared to cast crank) Cost of material/scrap rate of forging process Cost of forging process with finish machining Smaller size not always possible due to other factors e.g. oil film, bearing loads etc Typical Steels Used - EN40B / 4340 (machined), 42CrMo4 (forged) Steel cranks typically used where higher strength required e.g. high output turbocharged engines

20 Forged Steel Connecting Rod Pros and Cons PROS (compared to PM Rod) Longer fatigue life Higher strength Newer fracture split steel rods stronger than PM Good potential for material reduction and weight saving Good cap shift control No real size limitation CONS (Compared to PM Rod) Higher cost (gap closing) Post-forge machining and scrap level (PM Near net shape after forming process requires less machining and scrap) Used to need machined rod and cap joint whereas PM easily fracture split (newer forging steels fracture split) Early fracture split C70 steel rods offered little strength advantage over PM Typical steels used C70, 36MnVS4, 46MnVS6mod

21 Steel Camshaft Pros and Cons PROS (Assembled cam compared to cast iron cam) Greater fatigue life Higher strength (smaller journals possible) Greater stiffness Greater flexibility in lobe geometry Ground before final assembly (cleaner) Selective properties of assembled components e.g. hardened DI fuel pump lobe, sintered trigger wheel etc. Lighter weight CONS (Assembled cam compared to cast iron cam) Hi cost

22 Steel Camshaft Weight Saving Potential Huge potential for weight saving compared cast iron camshaft approx. 50 % less weight

23 Steel Piston Pros and Cons PROS (compared to cast aluminum pistons) Higher cylinder pressure limit Higher piston temperature limit Reduced top land height possible (reduced crevice volume) May offer friction advantages particularly in iron block/liner engines CONS (compared to cast aluminum pistons) Highercost Weight (current) Cooling oil flow requirement due to higher piston temperature Potential to increase detonation sensitivity in gasoline applications

24 Market Trends Turbocharging and Downsizing Turbocharging Significant growth of gasoline turbo share in Europe NAFTA is following this trend, first with partly importing engines, followed by a growing local production Also increasing gasoline turbo growth in China Japanese OEMs with partly increasing TC share Gasoline Turbo Share* * by Vehicle Production Region

25 Market Trends Turbocharging and Downsizing Downsizing Increasing number of development projects for 2-cyl. engines, 3-cyl. engines also applied in D- segment cars of premium brands (e.g. BMW 3 series) Downsizing in NAFTA on a higher level in, but limited due to higher vehicle mass V8 -> V6, V6 -> I4 Increasing share of 3-cylinder engines in China expected Worldwide Downsizing Scenario

26 General Market Trends Power Cylinder Unit (PCU) Increase of Temperature and Cylinder Pressure Increasing maximum specific power and peak cylinder pressure for LV gasoline engines, LV diesel engines and also for medium and heavy duty diesel engines Higher piston temperatures expected Engine Block Significant worldwide increase of gasoline aluminum blocks (62% in % in 2017) Moderate increase of aluminum diesel engine blocks (18% in % in 2017) which could increase if the European OEMs enforce plans to increase their aluminum diesel engine share. Spray coated aluminum blocks provide advantages regarding engine size reduction, less scrap rates, recycling, etc. Even though traditional liners will still be used in the coming engine generation, spray coating will be the trend at numerous customers towards 2020 Pistons Steel piston share will increase significantly for HD engines Rising share of steel pistons also for diesel passenger cars expected Due to improvements in the casting process as well as design optimization there is no advantage for forged aluminum pistons compared to the cast piston

27 Conclusions Engine designers will always favor the lowest cost solution that satisfies the requirements For steel components to be adopted in larger quantities they need to act as enablers for something e.g. more highly stressed downsized engines Increasing trend of extreme downsizing and hence higher specific component loading favorable for the implementation of Steel components. Steel crankshaft distribution unlikely to change in current engine ranges due to design constraints and cost implications Trend to more extreme levels of downsizing will increase steel crankshaft adoption due to high specific component loading and desire for compact, lightweight engines Real potential for optimized steel connecting rods offering light weight, near PM cost with higher strength

28 Conclusions Real potential for steel camshafts offering lighter weight, flexibility of individually assembled components and little additional cost Technology trends predict significant adoption Future engine development to meet legislative targets (CAFE 54.5 MPG) will dictate the use of alternative materials including high strength steel to reduce whole vehicle mass Engine downsizing is predicted to be the biggest technology path to achieving lower fuel consumption As engines get increasingly downsized steel content will increase (although physical size will likely decrease) Real potential for increased volume of steel pistons in the light duty diesel market with some breakthrough into the highly downsized gasoline market

29 Next Steps Original idea to take a current engine and analyze weight saving with high steel content Based on this Phase I study the potential weight saving of using steel components in an existing engine is likely to be low (and largely based upon camshaft weight saving) Needs complete redesign of engine from clean sheet to optimize for weight Engine downsizing trend will continue Ever more extreme downsizing with the goal to completely de-throttle the engine for maximum efficiency Will increase loading on components as cylinder pressures increase. Fuel economy benefits will come through engine operating point efficiency gains (de-throttling) and overall vehicle mass reduction Compact lightweight engines result in lower whole vehicle mass Steel will be the enabler for an increasingly extreme downsized engine particularly as it can be implemented in the harsh environment of the PCU.