Four vacuum melted low carbon steels, two based on 2%Cr-2%Mn and one each on 4%Mn and 4%Cr were solution treated in the range 1150 degree C to 1300 degree C and controlled rolled. The steels were finish-rolled between 950 degree C and 800 degree C and finally air cooled to room temperature. The mechanical and toughness properties were studied as a function of chemical composition, solution temperature and finish rolling temperature. Measurements were made of the mean free distance, which was correlated with the strength data. The best combination of properties was found for the niobium containing chromium steels with 0. 2% proof stresses greater than 900Nmm** minus **2 and DBTT less than minus 20 degree C. NbC particles were observed to outline a boundary network in the 2%Cr steel, but a more uniform finer dispersion was present in the 4%Cr steel. When the mfd was plotted as a function of strength the relationship sigma yp -15. 4 (2. 1Mn%-2. 0Cr%) equals 135 plus 24d** minus ** one-half was found, with r equal to 0. 83. This is regarded as a first attempt in understanding the factors controlling the strength of acicular steels.
|Publication status||Published - 1986|