题 3-10 . (omega )_(c)=0.85% 的碳钢加热到900℃,在空气中保温1h后外层碳浓度降-|||-至零。-|||-(1)推导脱碳扩散方程的解,假定 gt 0 时, x=0 处, rho =0 。-|||-(2)假如要求零件外层的wc为0.8%,表面应车去多少深度?( _(C)^y=1.1times -|||-^-7(cm)^2/s )