FIRST LAYER OR UPPER LAYER WELDING SECTION OF HIGH Cr STEEL TURBINE ROTOR, OVERLAY WELDING MATERIAL FOR WELDING SECTION, AND METHOD FOR MANUFACTURING OVERLAY WELDING SECTION

Abstract

The present invention relates to a multilayer overlay welding section in which a first layer of an overlay welding section to be formed on the bearing contact surface of a high Cr steel turbine rotor includes C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%, Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5% with a remainder including Fe and unavoidable impurities, a multilayer overlay welding section in which, in addition to the above layer, an upper layer welding section includes C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 2.5%, Cr: 1.0 to 4.0%, and Mo: 0.5 to 1.5%, and a welding material therefor and a process for producing the multilayer overlay welding section.

Description

TECHNICAL FIELD[0001]The present invention relates to a multilayer overlay for forming a Cr-containing steel overlay on a surface with which bearings of a high Cr steel turbine rotor come into contact.BACKGROUND ART[0002]Since a high Cr steel is excellent in high-temperature strength and low-temperature toughness, the steel has been increasingly used as a material for high-pressure and medium-pressure turbine rotors of generators. However, the contact surface with the bearings of the high Cr steel turbine rotor is prone to develop seizure at the bearings during its use, so that there is a concern of inviting damage. Therefore, there has been proposed a method for preventing the generation of seizure by overlay welding a low alloy steel on the bearing part of the rotor (e.g., see Patent Document 1).[0003]Heretofore, with regard to such a kind of overlay welding, mainly welding materials and welding methods for submerge arc welding have been developed.[0004]For example, Patent Documen...

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Benefits of technology

[0024]According to the upper layer welding section of the present invention, ferrite is not formed at the boundary part between the first layer and the upper layer, also it is possible to suppress stress relief annealing cracks, and bearings can be prevented from seizing with satisfying strength and toughness required for the bearing part.

[0025]Furthermore, the strength balance among the base material, the first layer, and the upper layer is made most suitable by combining the first layer welding section according to the first invention and the second in

Problems solved by technology

However, since the welding material used in the first layer welding material described in Patent Document 2 contains no Cr, accumulation of strain occurs in the first layer at shape discontinuous parts such as a thrust part during stress relief annealing and there is a possibi

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