Rotor shaft of steam turbine
AssigneeHitachi, Ltd.
InventorsTakatoshi Yoshioka, Seishin Kirihara, Masao Siga, Takehiko Yoshida, Katsukuni Hisano, Toshimi Tan, Masahiro Kobayashi
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Abstract
A steam turbine rotor shaft comprising the main body of the rotor shaft made of a high Cr steel of martensite structure, and a journal having a plurality of built-up welding layers formed successively said main body, the outer surface portion of the journal being made of steel containing 0.5 to 3 wt % of Cr, and a method of producing same.
Claims16
A steam turbine rotor shaft comprising:
- a main body of the rotor shaft made of a high Cr steel having a matrix of tempered martensite structure in which carbides are precipitated and consisting essentially of, by weight, 0.1 to 0.3% of C, 0.4 to 1.2 wt % of Mn, not more than 0.6 wt % of Si, not more than 1.2 wt % of Ni, 8 to 13% of Cr, 0.5 to 1.5 of Mo, 0.03 to 0.15% of Nb, 0.1 to 0.3% of V, 0.04 to 0.2% of N and the balance of Fe;
- and
- a journal having a plurality of built-up welding layers formed successively on said main body, with the radially innermost layer having the highest Cr content and the radially outermost layer having the lowest Cr content;
- the outermost layer having an outer surface portion with a composition consisting essentially of, by weight, 0.01 to 0.2% of C, 0.1 to 1.0% of Si, 0.1 to 1.5% of Mn, 0.5 to 3% of Cr, not more than 1.1% of Ni, not more than 1.5% of Mo, and the balance Fe.
A method of producing a steam turbine rotor shaft having a main body made of high chromium steel having a matrix of tempered martensite structure in which carbides are precipitated and consisting essentially of, by weight, 0.1 to 0.3% of C, 0.4 to 1.2 wt % of Mn, not more than 0.6 wt % of Si, not more than 1.2 wt % of Ni, 8 to 13% of Cr, 0.5 to 1.5 of Mo, 0.03 to 0.15% of Nb, 0.1 to 0.3% of V, 0.04 to 0.2% of N and the balance of Fe which main body has a journal portion at which a journal is to be formed, comprising the steps of preheating at least the journal portion of the main body, outermost layer having an outer surface portion with a composition consisting essentially of, by weight, 0.01 to 0.2% of C, 0.1 to 1.0% of Si, 0.1 to 1.5% of Mn, 0.5 to 3% or Cr, not more than 1.5% of Mo, and the balance Fe, holding a weld zone at a predetermined temperature to reduce the hydrogen content of the weld zone, cooling the weld zone from the predetermined temperature to cause the martensite transformation of the weld heat-affected zone of the main body, and effecting stress relief annealing.
Dependencies are inferred from the claim text.