First semi-annual progress report on development of superplastic steel processing: A joint R and D effort between industry and a national laboratory: Caterpillar Inc. , Peoria, IL; Ladish Co. , Inc. , Cudahy, WI; North Star Steel Company, Monroe, MI; Lawrence Livermore National Laboratory, Livermore, CA

Technical Report · Thu Sep 15 04:00:00 EDT 1988

OSTI ID:6556354

The influence of aluminum content and thermomechanical processing steps in developing fine microstructures in ultrahigh carbon steels (UHCS) was examined. It was shown that ultrafine pearlitic structures, containing no proeutectoid carbide networks, can be obtained by the addition of at least 1.5% aluminum. Hot-working (HW) followed by slow cooling from the austenite region (above A/sub cm/) will lead to a carbide-network-free pearlitic structure. Spheroidized structures, with the elimination of any pre-existing carbide networks, can be obtained either by a thermomechanical treatment or by a thermal treatment alone. These are: (1) warm working (WW) involving a divorced-eutectoid transformation with associated deformation (DETWAD), and (2) heat treating involving a divorced-eutectoid transformation (DET), which requires heating to a low austenitizing temperature followed by isothermal transformation just below the A/sub 1/ temperature. This retardation will provide a wide window of time and temperature for processing with a number of possible combinations of DET and DETWAD steps. Results of superplasticity studies on the UHCS-Al alloys reveal that superplastic behavior is enhanced by aluminum additions and by increasing the amount of deformation during DETWAD processing. Preliminary studies on the cold-rolling characteristics of the UHCS-1.6Al alloy reveal that it can be cold-rolled to 50% in the fully pearlitic condition without annealing, and to over 60% in the fully spheroidized condition. A modified Fe-C diagram is proposed for the UHCS-1.6Al. Aluminum is shown to raise the liquidus and solidus temperatures, to increase the solubility of carbon in austenite, to increase the A/sub 1/ temperature, and to introduce a three-phase region of ferrite, austenitic, and carbide.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6556354
• Report Number(s): UCID-21610-88; ON: DE89006469
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
AUSTENITE
CARBON ADDITIONS
CARBON STEELS
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
DECARBONIZATION
DOCUMENT TYPES
FABRICATION
FERRITE
HOT WORKING
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS WORKING
MECHANICAL PROPERTIES
MICROSTRUCTURE
PEARLITE
PLASTICITY
PROGRESS REPORT
SPHEROIDS
STEELS