1. Ice Breaker Hulls Ameralys Correa UW-Milwaukee
Materials
Picture 1 shows one of the Unites States Icebreaker Vessels: The Healy.
Why Use Steel in the First Place?
Problem #1: Toughness in Low Temperatures
Problem #2: Corrosion
Other Improvements:
Ice applies strong compressive forces against the hull of the ship.
Cold Temperatures decrease the steel’s toughness.
Figure 4. There is a decrease in the 1018 steel’s ability to absorb impact energy at colder temperatures.
Figure 5. Iron hulls need alloying for arctic sea conditions as shown by their limited use in salt water.
Connecting sheets with welding over using rivets also strengthens hulls.
Figure 6. Alloying is needed, for the very weldable steels have limited use in salt water due to corrosion.
Salt water causes corrosion by ionizing with the ions on the steel hull.
Corrosion decreases fracture toughness, thus, ice can create a hole and sink the ship.
Figure 1. Steels maintain high compressive strengths in the (non-sea) polar temperatures: -76F to 32F (-60C to -0C).
Figure 2. Steels can withstand more forces without plastic deformation in the (non-sea) polar temperatures.
Figure 3. Steels can resist more deformation in the (non-sea) polar temperatures.
Picture 2 shows corrosion to a steel hull.
Solution: Impressed Current Cathodic Protection
References
Brandon R. Reynolds. Jan
Callister, WD., Materials Science and Engineering: An Introduction. Section 8.6
CES Edu Pack
Donald L. Canney Jan
Paul Kah. Pavel Layus. Jukka Martikainen
Polar Discovery
Stew Magnuson. June
University of Illinois Urbana-Champaign
ICCP creates a false anode and a power source to react with the salt water.
ICCP provides electrons so that the iron in the steel is saved from reacting with the salt water.
This method is in development because the low conductivity of arctic seas limits the distribution of current on hull’s surface.
Solution: Alloying With Other Metals
Solution: Zinc Protective Coatings
Grain Growth Inhibitors:
Aluminum, Nickel, Titanium, Nitrogen
Face Center Cubic:
Nickel, Calcium Aluminum, Copper
Hexagonal Close Packed Crystal Structures:
Titanium and Zirconium
FCC and HCP pack closer than BCC, thus, making the steel stronger
Zinc is more reactive than Iron.
Zinc provides electrons to react with salt water.
Zinc most be replaced once used up.