Method for making propellers of high-strength and high-toughness cast steel

Abstract

Abstract A HIGH STRENGTH, HIGH TOUGHNESS CAST STEEL FOR MARINE PROPELLLERS IS COMPRISED OF NOT MORE THAN 0.25% OF CARBON, NOT MORE THAN 1% OF SILICON, NOT MORE THAN 3% OF MANGANESE, FROM 5-20% OF CHROMIUM, FROM 1-8% OF COBALT, AND FROM 0.5-7% OF ONEOR BOTH OF MOLYBDENUM AND TUNGSTEN, AND THEREMAINDER CONSISTING OF IRON. IN ADDITION, THE CAST STEEL MAY CONTAIN UP TO 8% OF NICKEL AND UP TO 4% OF COPPER, DEPENDING ON THE CONDITIONS. THE METHOD OF MAKINGPROPELLERS OF CAST STEEL OF THE COMPOSITION SET FORTH ABOVE COMPRISES THE STEPS OF AFTER CASTING THE PROPELLER SLOWLY COOLING IT AT A RATE OF NOT MORE THAN 1*C. PER MINUTE, REHEATING THE CASTING TO BETWEEN 800* AND 1000*C. FORIMPROVING ITS STRENGTH, DUCTILITY AND TOUGHNESS, COOLING THE CASTING, AND THEN AGING IT AT 450-700*C. IN MAKING THE CASTING IT MAY BE CAST AS A SINGLE UNIT OR IN INDIVIDUAL SECTIONS, WHERE INDIVIDUAL SECTIONS ARE CAST, THE METHOD OF FORMING THE PROPELLER INCLUDES THE STEPS OF WELDING THE INDIVIDUAL SECTIONS, HEAT TREATING THE WELDED CASTING AT 800-1000* AND THEN SLOWLY COOLING THE CASTING. FURTHER, WHETHER THE CASTING IS FORMED AS A SINGLE UNIT OR FROM INDIVIDUAL SECTIONS, THE METHOD INCLUDES THE STEP OF ANNEALING AT 630-700*.

Inventors

• 👤 M Zama
• 👤 T Oda
• 👤 M Nakamura

Bibliographic Details