HARDENABILITY RESPONSE OF ALADJA ST 60-2 STRUCTURAL STEEL QUENCHED IN FATTY BASE LOCAL OILS
HARDENABILITY RESPONSE OF ALADJA ST 60-2 STRUCTURAL STEEL QUENCHED IN FATTY BASE LOCAL OILS
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Date
1991-07
Authors
GBADAMASI, IBRAHIM
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Abstract
The suitability of three types of locally produced fatty
oils, as quenchants was investigated in this research work.
Palm oil, shea butter oil and ground nut oils were used in
quenching "ST 60-2" plain carbon steel produced by Delta
Steel Company, Aladja. The quench characteristics of the
steel as determined by the Jominy End Quench Test compare
favourably with the established data for similar grade of
steel. Based on the Grossmann test procedure, hardenability
of the steel was estimated by measuring the centre hardness
of bars with various diameters quenched in these investigated
oils.
The quench severity of each oil under investigation was
determined using the technique developed by Detroit Diesel
Engine division of the General Motors Company (U.S.A.)
Experimental results indicate a strong dependence of the
cooling properties of the oils on their chemical
compositions. The presence of reactive (Polar) carboxylic
group in addition to the fatty acid content of the oils,
contribute to strong molecular adhesion of the oils to metal.
This adhesion affects the heat extraction properties of the
oil.
The iodine content which reflects the degree of
saturation is plausibly the most influential chemical
constituent which determines quench severity of the oils
under investigation.
Palm oil which is rated as the best with a quench
severity (H) value of 0.12 - 0.15 is capable of generating a
hardness value equal to that of 50% martensite at the centre
of a bar of 10.2mm maximum diameter as revealed by the
Grossmann test. Shea butter and groundnut oils gave similar
result with quench severity values of 0.08 - 0.10 and a
hardenable bar diameter of 9mm.
Microstructural examination of the quenched bars were
further used to corroborate hardness measurements.
Microstructural examination revealed, principally,
ferrite - pearlite structure in all the quenched steel
rounds. The observed increase in hardenability in quenched
steel rounds in various media can be attributed to the
formation of finer and, therefore, stronger ferrite
pearlite structure. Definitely, the steel will respond
favourably to alloying elements for martensite formation.
Description
A thesis submitted to the postgraduate school, Ahmadu Bello
University, Zaria, in partial fulfillment of the requirements
for the award of the degree of Master of Science in
Production Engineering.
Department of Mechanical Engineering,
Faculty of Engineering,
Ahmadu Bello University,
Zaria.
July, 1991
Keywords
HARDENABILITY,, RESPONSE,, ALADJA,, STRUCTURAL,, STEEL,, QUENCHED,, FATTY BASE,, LOCAL OILS