炭素鋼の高温変形挙動におよぼす温度, ひずみ速度と炭素含有量の影響

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High temperature tensile deformation of carbon steels containing from 0.036 to 1.09 wt% C was studied in the temperature range 873 to 1373 K over a wide range of strain rates between 1 and 10^<-5>s^<-1>. The shape of true stress-true strain (σ-ε) curves in the austenite (γ) range is expressed solely in terms of the first stress peak (σ_p) or Z in the following equation, and the relation is almost independent of C content. σ_p can be correlated with temperature (T) and strain rate (ε) by the following equation in the range of stresses below 110∿120 MPa ; Z=ε・exp(Q/RT)=A・σ^m_p in which A, m, and Q decrease with C content. The activation energies for deformation (Q) are nearly the same as those for self-diffusion. These results being almost the same as those of 0.16% C steel reported previously, it is concluded that the high temperature deformation of carbon steels in the γ range is controlled by the dynamic recrystallization process assisted by the diffusion of vacancy. σ_p in the γ range decreases with C content in the whole range of Z used. This solid solution softening is considered to be attributed to the enhanced dynamic recrystallization process caused by increased diffusivity of vacancy due to the addition of C in the γ range. The flow stress maximum (α ; ferrite) or the first stress peak (γ), σ_p, of mild steel (or iron) changes discontinuously near the A_3 point, and σ_p at a Z is always larger in the γ range than in the α range. This is considered to be attributed to the differences of vacancy diffusivity and of the dynamic restoration process (i.e., recrystallization in the γ and recovery in the α) which may be caused by the difference in the stacking fault energy. The flow stress in the initial work hardening region (σ_ε) is larger in the γ range than in the α range in the lower Z, but σ_ε in the both ranges can be expected to become equal with an increase in Z. This is caused by the difference of strain hardening behavior in the both ranges and the lower strain rate (or Z) dependence of σ_ε in the γ range.
社団法人日本鉄鋼協会の論文
1981-09-01

炭素鋼の高温変形挙動におよぼす温度, ひずみ速度と炭素含有量の影響

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