Effects of straining, aging, and stress-relieving on mechanical properties of steels for Arctic service
Armco Steel Corp. tested the effects of straining, straining + aging, and straining + aging + stress-relieving on the tensile and Charpy V-notch properties of 3 new grades of steel developed for Arctic pipe and fittings. The tests were conducted on Climax Molybdenum's Mn-Mo-Cb steel, International Nickel's IN-787, and Armco's VNT-QT (quenched and tempered) at 25/sup 0/F (-4/sup 0/C), -20/sup 0/F (-29/sup 0/C), and -80/sup 0/F (-62/sup 0/C) to provide additional guidance in selecting the best steels currently available for Arctic pipeline construction. The results indicate that IN-787 and Climax Mn-Mo-Cb steels in either the as-rolled or as-rolled + age-hardened conditions are condidate grades for Arctic applications by displaying the required 50 ft-lb C/sub v/ impact energy absorption characteristics at +25/sup 0/, -20/sup 0/, in the heat-affected zones of welds and after 3% uniaxial straining + 550/sup 0/F (288/sup 0/) aging. The as-rolled IN-787 could be used for -20/sup 0/F and as-rolled Mn-Mo-Cb only for 25/sup 0/F (4/sup 0/C). If these steels were age-hardened during stress-relieving to develop full precipitation strengthening after forming, both grades could be used through -20/sup 0/F service temperatures. Normalizing or water quenching + tempering will be needed for Arctic values and fittings. Straining + aging tests on heat-treated IN-787 and Mn-Mo-Cb demonstrated that both steels were capable of meeting the proposed -80/sup 0/F toughness requirements. Stress-relieving after straining + aging would rise the strengths without affecting the use of either normalized or quenched + tempered IN-787 and Mn-Mo-Cb in fittings. It would also provide Armco VNT-QT sufficient toughness after 3% straining and aging at 550/sup 0/F to meet -20/sup 0/F Arctic requirements. Stress-relieving may further improve the toughness of VNT-QT to extend its use at -80/sup 0/F.
- OSTI ID:
- 5763843
- Journal Information:
- J. Eng. Ind.; (United States), Journal Name: J. Eng. Ind.; (United States) Vol. 97; ISSN JEFIA
- Country of Publication:
- United States
- Language:
- English
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022000 -- Petroleum-- Transport
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03 NATURAL GAS
032000 -- Natural Gas-- Transport
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36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
AGING
ALLOYS
ARCTIC REGIONS
COBALT ALLOYS
CONSTRUCTION
CONTROL EQUIPMENT
EQUIPMENT
FLOW REGULATORS
IRON ALLOYS
IRON BASE ALLOYS
LOW TEMPERATURE
MANGANESE ALLOYS
MECHANICAL PROPERTIES
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
PIPE FITTINGS
PIPELINES
POLAR REGIONS
STEELS
STRAIN AGING
STRAINS
STRESS RELAXATION
VALVES