Published: Jan 1982
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A new low-carbon 16Cr-5Ni stainless martensitic cast steel (S + C 4405) is presented as an advancement of CA6NM with improved corrosion resistance, excellent ductility, less susceptibility to hardening cracks, and good weldability, filling the gap between CA6NM and CF8M. The chemical composition is balanced so that a homogeneous microstructure consisting of annealed martensite with small amounts of δ-ferrite and finely dispersed austenite is obtained after hardening and tempering. Because of limited δ-ferrite, the impact values obtained correspond to CA6NM, and limited austenite still allows yield strength values comparable to those of CA6NM.
Due to its excellent ductility combined with good fabricability, the material is also suitable for cryogenic applications down to −200°C. Furthermore, favorable fatigue tests, and particularly test results in artificial seawater, show a remarkable improvement over CA6NM. Pitting- and crevice-corrosion tests by the International Nickel Co. multiple-crevice tetrafluoroethylene washer method suggest a corrosion resistance between that of CA6NM and CF8M and that this steel is suitable for seawater application in connection with cathodic protection. Stress-corrosion cracking in hydrogen sulfide-containing media was investigated according to the National Association of Corrosion Engineers Specification MR-01-75, and the resistance of 16Cr-5Ni under sour-gas conditions was found to be superior to that of CA6NM. The castability of this alloy was found to be favorable and comparable to that of CA6NM.
These characteristics are important for the following applications: offshore engineering, seawater desalination, chemical and petrochemical industries, shipbuilding, cryogenics, power generation, food industry, paper machine construction, and especially for pumps, compressors, fittings, centrifuges, waterturbines, and ship propellers.
stainless martensitic cast steel, high ductility, good weldability, low-temperature application, seawater corrosion, sour-gas service, corrosion fatigue, aceticacid test
Chief metallurgist, Schmidt & Clemens Alloy Steel Works, Lindlar,