Carburization and its prevention in ethylene cracking furnace tubes. [0. 4C-25Cr-20Ni]

Conference · · TMS (The Metallurgical Society) Paper Selection; (USA)

OSTI ID:5393467

Saori, M; Ohta, S ^[1]

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1. Kobe Steel, Ltd. (Japan)

The centrifugally cast HK-40 (0.4C-25Cr-20Ni) heat-resisting alloy tube has been widely used for ethylene cracking furnace tube. Carburization is the most detrimental factor which determines the tube life. Carburization resistance of heat-resistant alloys strongly depends on the tightness and adherence of surface oxide film. Carburization takes place at the point where the oxide scale spalls. Solid pack carburization test at 1100 C on certrifugally cast alloy tubes containing 25-36 wt.% of chromium and 18-34 wt. % of nickel revealed the effective improvement of carburization resistance by increasing chromium and silicon contents. Chromium, in particular, greatly improved the tightness and adherence of oxide film. Addition of W., Mo and Nb also improved carburization resistance. These elements remained in the chromium-depleted layer just below the surface, and resultant decrease of carbon solubility in this layer improved carburization resistance. Decrease of thermal expansion coefficient and increase of volume due to formation of a large amount of chromium carbides cause cracks in inner carburized and outer uncarburized layers of tube respectively. Appearance of carburization-induced magnetism is the result of decrease of chromium in matrix due to formation of chromium carbides. Twenty-two and seven weight percent decrease of chromium drastically increase the magnetic permeabilities of HK-40 and HP (0.5C-25Cr-35Ni) alloys respectively.

• OSTI ID: 5393467
• Report Number(s): CONF-840909--
• Conference Information: Journal Name: TMS (The Metallurgical Society) Paper Selection; (USA) Journal Volume: 56
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400* -- Petroleum-- Processing
36 MATERIALS SCIENCE
360105 -- Metals & Alloys-- Corrosion & Erosion
ADHESION
ALKENES
ALLOY-HK-40
ALLOYS
AUSTENITIC STEELS
CARBIDES
CARBON
CARBON COMPOUNDS
CARBURIZATION
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMICAL REACTORS
CHROMIUM ALLOYS
CHROMIUM CARBIDES
CHROMIUM COMPOUNDS
CHROMIUM-NICKEL STEELS
COATINGS
CORROSION RESISTANCE
CORROSION RESISTANT ALLOYS
CRACKING
CRACKS
DECOMPOSITION
ELEMENTS
ETHYLENE
HARDENING
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HIGH ALLOY STEELS
HYDROCARBONS
IRON ALLOYS
IRON BASE ALLOYS
LAYERS
MAGNETIC PROPERTIES
MAGNETISM
MATERIALS
MODIFICATIONS
MOLYBDENUM ADDITIONS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
NONMETALS
OPTIMIZATION
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
PROTECTIVE COATINGS
PYROLYSIS
QUANTITY RATIO
SILICON ALLOYS
SOLUBILITY
STAINLESS STEELS
STEEL-CR25NI20
STEELS
SURFACE HARDENING
SURFACE PROPERTIES
SURFACE TREATMENTS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN ADDITIONS
TUNGSTEN ALLOYS