大型特殊鋼材の軟化焼鈍への等温變態の應用 I

概要

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The purpose of this study was to save fuels, equipments and labours reguired for full annealing of low alloy steel thick forgings. In this first report, theory of isothermal annealing and fundamental studies carried out on small spacimens were given. The steel used was a medium C low Ni-Cr-Cu-Mo steel contg. 0.30∿0.35%C, 0.6∿1.0%Mn, 1.0∿1.8%Ni, 1.0∿1.3%Cr, 0.2∿0.4%Cu and 0.4%Mo. To determine the S-curve of this steel, thermal expansion was measured and microstructure and hardness of specimens quenched after isothermal heating were investigated. The results obtained were summarized as follows : (1) This steel can be full annealed within 5 hrs. if its supercooled austenitic state is kept and transformed at 660∿670℃, 6 hrs. at 650∿680℃ and 9 hrs. at 640℃ (2) The isothermally annealed steel is satisfactorily softened and its Brinnel hardness number is below 200. (3) The microstructure of the isothermally annealed steel is quite different from that of the ordinary annealing, but the time required for heating in the quenching operation those steels was not varied between these two different annealing structures. (4) That different annealing process has no influence on the mechanical properties of the steel after hardening and tempering.
社団法人日本鉄鋼協会の論文
1949-10-25