ISSN:
0947-5117
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Description / Table of Contents:
Carburization of centrifugally cast tubes in the petrochemical industries and explication of this behaviour by laboratory tests with chromium nickel steels and chromium nicked materials in the temperature range 800 to 1150°CThe carburization behaviour of the tubes used under the conditions of petrochemical cracking processes depends in a first line on the temperature. Up to 1000°C carbon pickup is low, but above 1050°C heavy carbon pickup and increasing carburization depth must be counted with. This temperature dependence is due to the fact that at 1050°C equilibrium is attained between chromium oxide and carbide, so that the oxide is no longer stable and the original protective effect of the oxide layer is lost. It is for this reason that pre-oxidation of the tubes has not only favourable effects: during cooling cracks may form in the oxide layer, so that carburization of a surface layer may set in at temperatures as low as 800°C. Carburization is delayed by high Cr, Ni and Si contents: for uses at 1100°C at least 28% Cr, 32% Ni and 2.5% Si are required.
Notes:
In einer Crackanlage zur Äthylenherstellung kohlten Schleudergußrohre aus G-X 40 NiCr 35 25 (W.-Nr. 1.4857), die von zwei Herstellern geliefert worden waren, trotz praktisch gleicher Betriebsbedingungen verschieden schnell und stark auf. Zur Klärung dieses unterschiedlichen Verhaltens wurden mehrere ausgebaute Rohre im Vergleich zu Ersatzrohren eingehend untersucht. Die hierbei zwischen den Rohren der beiden Hersteller festgestellten Qualitätsunterschiede werden im einzelnen beschrieben und hinsichtlich ihrer Bedeutung für das Aufkohlungs verhalten erörtert.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/maco.19770281002
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