The Effect of Ni on the Formation of Bainite in Fe-Ni Lateritic Steels through Semi-continuous Cooling Method
The formation of bainite in steel alloys is affected not only by temperature, holding time, and cooling method but also by steel alloy’s main alloying element. In iron-nickel (Fe-Ni) lateritic steels, the steelmaking process from nickel pig iron (NPI) gives various Ni contents. In this study, fi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Universitas Indonesia
2020-01-01
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| Series: | International Journal of Technology |
| Subjects: | |
| Online Access: | http://ijtech.eng.ui.ac.id/article/view/3178 |
| Summary: | The formation of bainite in steel alloys is
affected not only by temperature, holding time, and cooling method but also by
steel alloy’s main alloying element. In iron-nickel (Fe-Ni) lateritic steels,
the steelmaking process from nickel pig iron (NPI) gives various Ni contents.
In this study, five Fe-Ni alloys with various Ni contents were subjected to
semi-continuous austempering. The holding temperatures were 535°C (T1) and
360°C (T2). All alloys were held for 1800 s. Both holding temperatures were
determined through the average temperatures of bainite start (Bs) and
martensite start (Ms) of each alloy. Observations of the microstructures using
an optical microscope and Scanning Electron Microscope (SEM) showed the
formation of one or more phases in the alloys. These phases are ferrite as the
matrix, degenerated pearlite (DP), lamellar pearlite (LP), and plate-like
bainite. In Fe-Ni alloys with Ni content of 0.01 to 2.2 wt% Ni, after holding
at either T1 and T2, a mixture of DP and LP in the ferrite matrix is more
pronounced. Some plate-like bainite is gradually formed in the 3.3% Ni alloy
after holding at T1 and T2. As the Ni content increases to as much as 4.5 wt%
Ni, pearlite is no longer visible and is replaced by plate-like bainite in the
ferrite matrix. These results indicate that the variation of Ni in Fe-Ni alloys
with Ni content less than and equal to 4.5 wt% results in different shapes of
bainite, which then affects the mechanical properties of the alloy. |
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| ISSN: | 2086-9614 2087-2100 |