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The metallurgical phase transformations in ROQ-tuf AD690 due to the MMA welding process
Author(s)
Daames, Sherwyn
Date Issued
2002
Type
Thesis
Publisher
Peninsula Technikon
Abstract
Phase transformations in steel are of profound commercial importance due to the fact that
they influence the physical and mechanical properties of the end product. During the casting
process, which occurs at temperatures in excess of 1500°C, the microstructure of the steel is
austenitic. During slow cooling the austenite will decompose into lower temperature
microstructures such as ferrite, pearlite or hard, brittle cementite, the latter becoming
increasingly present the higher the carbon content of the steel. Steel manufacturers, however,
make use of additional forming processes such as rolling, quenching and reheat or tempering
to impart specific mechanical or metallurgical properties to a particular steel. If the cooling
rate is increased, as would be the case during a quenching process, the austenite will
decompose forming a needle like microstructure called bainite in addition to the other
microstructures. A further increase in the cooling rate will result in the diffusionless
transformation of part of the austenite to form martensite, a hard brittle microstructure. If heat
was now to be applied to the steel, as in a tempering process, some of the martensite formed
during the quenching process will again transform into a softer microstructure such as
pearlite or ferrite.
they influence the physical and mechanical properties of the end product. During the casting
process, which occurs at temperatures in excess of 1500°C, the microstructure of the steel is
austenitic. During slow cooling the austenite will decompose into lower temperature
microstructures such as ferrite, pearlite or hard, brittle cementite, the latter becoming
increasingly present the higher the carbon content of the steel. Steel manufacturers, however,
make use of additional forming processes such as rolling, quenching and reheat or tempering
to impart specific mechanical or metallurgical properties to a particular steel. If the cooling
rate is increased, as would be the case during a quenching process, the austenite will
decompose forming a needle like microstructure called bainite in addition to the other
microstructures. A further increase in the cooling rate will result in the diffusionless
transformation of part of the austenite to form martensite, a hard brittle microstructure. If heat
was now to be applied to the steel, as in a tempering process, some of the martensite formed
during the quenching process will again transform into a softer microstructure such as
pearlite or ferrite.
Additional information
Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2002
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Metallurgical phase transformations in ROQ-tuf AD690.pdf
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