복합조직강의 연속어닐링과정에서 미세조직과 집합조직의 변화 = Research Change in Microstructure and Texture during Continuous-Annealing in Dual-Phase Steels

다국어 초록 (Multilingual Abstract)

The variation in microstructure and texture during continuous annealing was examined in a series of 1.6% Mn-0.1% Cr-0.3% Mo-0.005% B steels with carbon contents in the range of 0.010 to 0.030%. It was found that microstructure of hot band consisted of ferrite and pearlite as a consequence of high coiling temperature, and eutectoid carbon content was between 0.011% and 0.016%. Martensite ranged in volume fraction from 1.5% to 4.0% when annealed at 820oC according to the typical continuous annealing cycle. The critical martensite content for the continuous yielding was about 4% from stress-strain curves. The continuous yielding was obtained in the 0.030% carbon steel and 0.010% to 0.020% carbon steels revealed some yield point elongation ranging from 0.8% to 2.2% in as-annealed conditions. Higher tensile strength in the higher carbon steel is due to both increase in the martensite volume fraction and ferrite grain refinement. Decreasing the carbon content to 0.01% strengthened the intensities of γ-fiber textures, resulting in the increase in the rm value, which was caused by the lower volume fraction of martensite. The higher carbon steels showed the lower rm value of about 1.0.