Microstructure and mechanical properties of a 3Cr-1.5Mo steel
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I.
INTRODUCTION
T H E steel most frequently used for pressure-vessel applications for elevated-temperature service (to 482 ~ in a hydrogen environment is 2.25Cr- 1Mo steel. For higher process efficiencies in future coal-conversion plants, chemicalprocessing plants, and petrochemical-refining plants, it will be desirable to operate at higher temperatures and pressures than those now in use. To meet these more-stringent requirements, improved pressure-vessel steels are being studied. One way to meet the higher strength requirements is to produce a higher strength 2.25Cr-lMo steel. This could be accomplished by placing restrictions on the chemical composition and by employing appropriate heat-treating procedures ( e . g . , quench and temper). An alternative approach involves the microalloying of the 2.25Cr-lMo composition with vanadium, titanium, niobium, boron, plus variations in the chromium and molybdenum compositions. Several microalloyed low-chromium Cr-Mo steels have been proposed and investigated. These include a V-Ti-Bmodified 2.25Cr-1Mo steel ~'2 and several 3Cr-1.5Mo steels containing small amounts of vanadium. 3-s In the present paper, studies on the 3Cr-l.5Mo-0.1V steel developed by Wada and coworkers 3'4 at Climax Molybdenum Company Research Laboratories, Ann Arbor, Michigan, will be discussed.
II.
EXPERIMENTAL
The 3Cr-1.5Mo-0. IV-0.1C (compositions are in weight percent) steel used was melted by Carpenter Technology Company, Reading, PennsylvaniaP The chemical compositions of the argon-oxygen-decarburized (AOD) 8-ton commercial heat (A9349) is given in Table t. Using standard rolling practice, Lukens Steel Company, Coatsville, Pennsylvania, processed the ingot to plates that measured 0.1 x 1.7 x 3.9 m (4 x 67 x 154 in.), after which they R.L. KLUEH is Research Metallurgist, Metals and Ceramics Dwislon, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6376. A . M . NASRELDIN is Metallurgist, Metallurgy Department, Nuclear Research Center, Atomic Energy Establishment, Cairo, Egypt. Manuscript submitted October 27, 1986.
METALLURGICAL TRANSACTIONS A
Table I. Chemical Composition of 3Cr-I.5Mo-0.1V Steel Plate
Element
Content, Wt Pct
C Mn Si Ni Cr Mo V S P AI Sn Sb Cu N
0.12 0.84 0.27 0.14 2.86 1.48 0.09 0.002 0.011 0.004 0.002
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