| In order to clarify the effects of small addition of silicon content on the grain size refinement in ferrite-martensite duplex steel, the average grain size, distribution of martensite phase and mechanical properties of this steel were investigated in this work. The results obtained are as follows; 1. The average grain size of the duplex steel containing Si below 0.2 wt% decreases with increasing Si content but the duplex steels exhibit different effects of grain size refinement depending upon the types of heat treatment cycle. 2. The duplex steel containing 0.1 wt% Si has the finest grain size (about 1 ㎛), and exhibits excellent mechanical properties (260 MPa yield strength, 640 MPa tensile strength, 28% total elongation and 25% uniform elongation). 3. The finer the starting structure, the finer the grain size of the duplex steel. 4. The grain size of the duplex steel decreases with increasing intercritical annealing temperature for a given holding time. |
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