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