CYLINDER HEAD
BYTRISHUL S. PATIL
IntroductionCylinder head is an important part of IC EngineCylinder head sits above the cylinders on topIt forms the combustion chamber of IC EngineIt houses parts like valves, spark plugs and fuel
injectorsIt also houses integral ducts and passages for
engines` coolantNumber of cylinder heads is a function of the engine
configurationEfficiency of the engine depends on the cylinder head
CYLINDER HEAD
Material SelectionMaterial selection depends upon the various factors Material must possess high strength, modulus of
elasticity, abrasion resistance, and corrosion resistanceThe material should posses low density, thermal
expansion thermal conductivityGood machinability and castability of the metal alloy are
also important factorsThe alloys must possess good vibration damping to
absorb the shuddering of the moving partsExcellent castability, and high strength-to-weight ratioHigh strength is a particular concern in diesel engines
Materials UsedGenerally different alloys are used
Alloys such as gray cast iron alloys, compacted graphite cast iron, aluminum alloys, magnesium alloys are used
Two materials are widely used cast iron, aluminium and aluminium alloys like Al–Si–Mg, Al–Si etc
Advantages & DisadvantagesAluminium
Advantages: Lightweight, repairable, easier to port, and more forgiving of high compression ratios
Disadvantages: Cost, proper fastener tightening procedures to avoid thread damage, high coefficient of (thermal) expansion when engine reaches its normal operating temperature
Cast IronAdvantages: Inexpensive,
durable, required in many oval track classes, less coefficient of (thermal) expansion
Disadvantages: Heavy, less forgiving of high compression ratios, and more expensive to port.
Manufacturing Processes
Generally casting processes are used
Green sand moulding, Lost foam casting, Gravity die casting etc
Green Sand MouldingA combination of silica sand, clay, and water
poured in one-half of the block pattern with a wood or metal frame
Mold is then compacted by squeezing or jolting, and the process is repeated for the other half of the mold
Then, molten cast iron, aluminum, or magnesium alloy is poured into the combined molds and solidifies
The molds are removed, and the cylinder block is cleaned and inspected
Green Sand Moulding
Heat TreatmentMostly T6 Heat Treatment is used
It increases the strength of the alloy by as much as 30%
The process occurs in two phases 1. Quench Phase 2. Precipitation
T6 Heat Treatment Quench Phase
Alloy is heated to 920 degrees Fahrenheit for 9 hours causing the copper to become dissolved in aluminum, forming a "Single Phase Alloy“
Slow air cooling, the copper will tend to reconstitute, or reform itself within the alloy
Rapid water quenching, the reformation of the copper is retarded and the aluminum, supersaturated with copper, is locked into the "Single Phase Alloy" state.
T6 Heat Treatment Precipitation
The alloy is heated to 350 degrees Fahrenheit for 10 hours and then allowed to air cool
Copper combines with the aluminum in a process called "precipitation hardening" to form a copper aluminum crystal
These copper aluminum crystals gives the alloy its strength
Strength of the alloy depends on size of these crystals
T6 Heat Treatment
Microstructures
Mechanical Testing
Mechanical Testing
Thank you
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