670 架空大口径ガス配管の内面腐食深さと耐用年数の推定 : 工業用配管の防食管理第 5 報(耐食性, 材料, 日本鉄鋼協会第 109 回(春季)講演大会)670 Estimation of internal corrosion depth and durable years of over-head pipe-line system : Corrosion control for industrial pipe-line V(PRODUCTS AND PROPERTIES, The 109th ISIJ Meeting (April, 1986))