Corrosion-resistant medium-nickel steels
Equipment for chemico-pharmaceutical plants is predominantly made of structural steels highly doped with nickel, such as 12KhlSN10T, 08KhlSN10T, and 10Khl7N13M2T (Russian State Standard GOST 563272, average nickel contents 10 13 wt.%). The wide application of these alloys is explained by their high corrosion resistance with respect to many aggressive technological media, commercial availability, good workability, practical traditions, etc. However, these steels are rather expensive because of the large content of nickel, which is the high-cost component. Expenditures related to the purchase and maintenance of this equipment account for one of the most significant items in the product cost. A reduction in the product cost can be reached by replacing the high-cost high-nickel steels by less expensive medium-doped alloys, such as 08Kh22N6T and 08Kh21N6M2T (av. Ni 6 wt.%), whose corrosion resistance to many technolo#cal reaction media is comparable to that of the highnickel counterparts. At present, there are many traditional and new mediumnickel compositions that are successfully used in contact with aggressive media. The new alloys are characterized by the presence of copper, molybdenum, and some other elements improving the anticorrosion and mechanical characteristics. The medium-nickel steels are extensively used abroad in the production of equipment for chemico-pharmaceutical, chemical, and some other industries. Most of these steels are available from well-known metallurgical companies such as Shikoku Metal Industries Co. Ltd. and Kobe Seiko She K. K. (Japan), Allegheny Ludlum Steel Corp., Armco Steel Corp., and Carpenter Technology Corp. (USA), Marmesman AG,
Recent Trends of Development of Stainless Steels Highly Resistant to Corrosion
近年化学工 業,原 子力工業,石 油掘削 など各種産業分 野 の発展に伴 い,金 属材料の使用環境 はます ま す 多 様 化,過 酷化する趨勢 にある.こ のよ うな過酷 な腐食環境 においてはステ ン レス鋼 が代表的 な耐食材料 として多用 されて きたが,そ れ で も孔食,す きま腐食,応 力腐 食割 れ,硫 化物応力割れ,粒 界腐食,全 面腐食 などの種々の 形態の腐食事故 を生 じてお り1)~3),それに よる経済的損 失には 莫大な ものがある4)~6).一 方,そ の 防止対 策 と して使 用条件 に 対 して 過剰品質 の 高価 な 代替材料を使 用す ることは現実的 でない.こ のよ うな背景か らそれぞ れの 使 用環境 に 対応 した ステ ンレス鋼の 必要性が認識 され,膨 大な数 の高耐食性 ステ ンレス鋼が開発 されてい る7)~10). 一般 に腐食 現象 は乾食 と湿食 に大別 できるが ,本 稿で は腐食 事例 の比較的 多い湿食 に限定 し,最 近約10年 間 における高耐食性 ステ ンレス鋼開発 の動 向を概説す る. なお,ス テ ン レス鋼 が使用 の対象 となる環境 の種類は莫 大であるが,こ こでは最近特に材料 面で進歩のあつた代 表的 な使用環境 として低 ・中濃度塩化物,海 水,酸 性油 井,高 温純水お よび硝酸を取 り上げ概略を述べた. 表 1 はそれ らの環境用に開発 され た高耐食性 ステ ンレス鋼の 代表組成を示 した ものである.
Research and Development Programme on ‘Corrosion and Corrosion Protection’ in the German Federal Republic
Abstract After stressing the economic importance of corrosion research, the main subjects of corrosion research undertaken under the auspices of the German Joint Corrosion Association (AGK) during the period 1958–1973 are listed.Based on these experiences a Research and Development Programme on ‘Corrosion and Corrosion Protection’ for the period 1974–1978 has been evolved, financed by the Federal Government, with the DECHEMA acting as Project Director. The research is done by member associations of AGK, co-ordinated under the Project Director and Steering Committee. Organisational and Flow Charts are given.Great stress is laid on the dissemination of information and on bridging the gulf between research and its application, particularly by means of the ready exchange of practical information and the giving of advice. A biennial ‘Korrosionum’ is planned, incorporating lectures, discussions, and exchange of information on case histories.