1993 Volume 57 Issue 7 Pages 761-766
The relationship between microstructure and mechanical properties in air of various high Cr cast stainless steels were investigated in order to develop a new marine propeller material 1.5 times (265 MPa) greater in corrosion fatigue strength than nickel aluminum bronze. The results are summarized as follows.
(1) In order to achieve the target of tensile properties, it is necessary that microstructure of the new steel consists of martensitic, austenitic and ferritic phases.
(2) Concerning volume of metallographical phases, it is desirable to ensure 5∼30% volume of the austenitic phase and under 25% volume of the ferritic phase.
(3) Judging from the above-mentioned metallographical phases, the 18%Cr cast stainless steel containing C≤0.04%, Cr: 16∼18%, Ni: 5∼7%, Mo: 1% is almost proper for a new marine propeller material, which satisfies the intended tensile properties.
The characteristic of this 18%Cr cast stainless steel is that 0.2% proof stress of this steel is half of that of 12%Cr cast martensitic stainless steel, although this steel has almost the same tensile strength as that of 12%Cr cast martensitic stainless steel.
