Module 3 : Shipbuilding materials Flashcards

Question

Sourcing steel for ship building or repair

Answer 1

- Must come from an approved manufacturer - Will be inspected and certified prior to acceptance by classification society - Inspection would be destructive/ non-destructive techniques and chemical analysis - Information is marked on mill test certificate prior to shipping

Answer 2

- Options are A, B, D, and E - A : mild steel with carbon context at 0.15% - 0.23% - E has higher strength and more crack resistance due to increased carbon and manganese. - Can also have F : a grade conceived by classification societies, above grade E - Higher grades mean higher quality, can be used for high stress areas. Can have thinner plates but they're more expensive

Answer 3

- A designation for high tensile steel, used in conjunction with A, D, E and F - Each designation has a certain tensile yield strength: AH is 27S = 265 N/mm2 DH is 32 EH is 36 FH is 40 = 390 N/mm2

Answer 4

4 - digit code: 1. General category grouping steels 2. Presence of major elements that may affect properties of steel (if none, leave as 0) 3 & 4 : indicate carbon concentration as multiple of 0.01%

Answer 5

1XXX - Carbon Steels (most common, cheapest, easier to find) 2XXX - Nickel steels 3XXX - Nickel-chromium steels 4XXX - Molybdenum steels 5XXX - Chromium steels 6XXX - Chromium-vanadium steels 7XXX - Tungsten steels 8XXX - Nickel-chromium-molybdenum steels 9XXX - Silicon-manganese steels Price increases as category increases

Answer 6

- Composition - Production method (continuous casting, electric furnace, etc) - Finishing method (cold rolled, hot rolled, cold drawn) - Form or shape (bar, rod, tube, pipe, plate, sheet, structural, etc) - De-oxidation process (killed, semi-killed, etc) - Microstructure (ferritic, pearlitic, martensitic, etc) - Physical strength (ASTM standards) - Heat treatment (annealed, quenches, tempered, etc) - Quality nomenclature (commercial quality, drawing quality, pressure vessel quality, etc)

Answer 7

Classification societies lay down the grade of steel, thickness, and welding techniques for all shell and deck plating. Factors accounting for this decision are: loading, corrosion, erosion, and temperature. Grade "E" is often used for areas like the sheer strake, bilge strake, garboard strake, keel strake. Classification societies use classes O, I, II, and III The hull is broken down into sections that require certain classes of plating or sections to be used.

Answer 8

- Used extensively for areas where weight is a factor - Used in both plate and sectional form - Lightweight, good corrosion resistance - Will melt at low temperatures compared to steel - Can see galvanic action with other materials and must prevent contact with certain metals

Answer 9

- Commercially Pure - Heat- Treatable alloys - Non-heat-treatable alloys

Answer 10

The 1XXX series 99.000% pure or higher - Last 2 digits are % above 99 - Excellent corrosion resistance, excellent workability - High thermal and electrical conductivity - Commonly used for transmission or power grid lines 1350 for electrical applications 1100 for food packaging trays

Answer 11

2XXX series: copper is the principle alloying element and can be strengthened significantly through solution heat-treating - Good combination of high strength and toughness, but does not have the level of atmospheric corrosion resistance as other alloys - Generally painted or clad for exposure 2024 : aircraft alloy 6XXX series: Silicon and magnesium - Versatile, heat-treatable, highly formable, weldable, moderately high strength, excellent corrosion resistance - Architectural and structural applications 6061 : truck and marine frames 7XXX series: zinc primarily with a smaller amount of magnesium - Heat-treatable, very high strength 7050 & 7075 : aircraft industry

Answer 12

Method of strengthening alloys - Takes the solid, alloyed metal and heats it to a specific point - The alloy elements (called solute) are homogeneously distributed with the aluminum, putting them in a solid solution. - The metal is subsequently quenches (rapidly cooled) to freeze the solute atoms in place. These atoms consequently combine into a finely distributed precipitate.

Answer 13

3XXX series: manganese as major alloying element with smaller amounts of magnesium 3003 : general purpose, moderate strength & good workability; heat exchangers, cooking utensils 3004 : body of beverage cans 4XXX series: combined with silicon to lower the melting point of aluminum without producing brittleness - Excellent welding wire and brazing alloys 4043: welding 5XXX series: magnesium as primary alloying element - Moderate to high strength characteristics, good weldability and resistance to corrosion in the marine environment - Building and construction, storage tanks, pressure vessels, marine applications 5052 : electronics 5083 : marine applications 5005 : architectural applications 5182 : beverage can lid

Answer 14

Method of strengthening alloys - Occurs during rolling and is the action of "working" the metal to make it stronger - Builds up dislocations and vacancies in the structure, which then inhibits the movement of atoms relative to each other. - Magnesium will intensify this effect, resulting in even high strength

Answer 15

F (fabricated) no special control over thermal conditions or strain-hardening used O (annealed) to obtain lowest strength temper H (strain-hardened) subjected to application of cold work after annealing (or after hot forming), or to a combination of cold work and partial annealing or stabilizing W (solution heat-treated) unstable temper application only to alloys which spontaneously age at room temperature after solution heat treatment T (thermally treated to produce stable tempers) applies to products which are thermally treated, with or without supplementary strain-hardening, to produce stable tempers other than F, O or H

Answer 16

- High resistance to corrosion - Light in comparison to most other metals (about 8x lighter than steel) - Non-magnetic (will not interfere with sensitive navigational equipment) - Totally recyclable

Answer 17

- Not as strong as steel - Melts at lower temperatures - High coefficient of expansion - High thermal coefficient - Expensive to manufacture as well as build into structures - Often highly reactive to other metals (galvanic) - Painting of aluminum requires special process (aluminum oxide coating and immediately prime)

Answer 18

- Means of obtaining certain desirable properties or to remove undesirable properties of steel - Limited by the size of the hull or components - Steel will pass through a transformation temperature range (will show as colours) during which the internal metallurgical structure (grain structure) changes and there is a pronounced effect on the properties of the metal - Lower transformation temperature : steel constituents begin to dissolve into each other - Higher transformation temperature : dissolving process is complete, but structure will coarsen with time and temperature

Answer 19

- Area or the portion of the base metal that was not melted during brazing, cutting or welding but whose microstructure and mechanical properties were altered by the intense heat - The extent and magnitude of property change depend primarily on the base material, the weld filler material, and the amount and concentration of heat input by the welding process. - This alteration can be detrimental, causing stresses that reduce the strength of the base metal, leading to catastrophic failure

Answer 20

1. Preheating 2. Annealing 3. Normalizing 4. Quenching 5. Tempering 6. Stress Relieving 7. Case hardening

Answer 21

- Preheating is done by raising the temperature of the parent metal above ambient temperature - Effective at reducing cracking of the parent and weld materials - Slower cooling rate of the HAZ due to smaller temperature gradient between HAZ and surrounding parent metal. - Reduces hydrogen in the weld by evaporating any moisture off the metal prior to welding as well as allowing for better hydrogen diffusion due to slower cooling rate - Temperatures may range from 20 to 200, but generally 100 is sufficient for most welding procedures. - When applied, should extend along the full length of the area to be welded and for a distance of 75 mm in any direction from the joint edge

Answer 22

- Will help refine the structure of the metal and provide more even distribution of various elements - Helps improve the ductility but will adversely affect the strength and hardness - Full process involves raising the metal temperature to above the upper transformation temperature (850-900 C), maintaining this temperature for a period of time, then allowing to cool slowly in a furnace

Answer 23

- Similar to annealing but the metal is permitted to cool more rapidly in still air - Tensile strength is reduced, but will improve notch resistance - Care must be exercised to not cause distortion or structural failure of welded structures

Answer 24

- Method used to harden metals - Temperature is brought above the upper transformation temperature, held there for a period of time after which the metal is rapidly cooled by immediate immersion into a liquid medium (water or oil) - Rapid cooling process traps the grain in the position attained by the increased temperature - Significantly increase in hardness, but likely increase in brittleness so very durable to erosion but easily breakable when subjected to certain directional loads

Answer 25

- Typically conducted after the metal has been quenched - Metal temperature is increased below its lower transformation temperature, held for a period of time, then rapidly cooled again in water or oil. - Will remove some hardness obtained during the quenching treatment but greatly improves the ductility of the metal

Answer 26

- Post-welding heat treatment - Uniform heating of the metal to below the lower transformation temperature then allows to cool slowly in a uniform manner (probably still or circulating air). - Will help maintain specific characteristics such as tensile strength - Often called "process annealing"

Answer 27

AKA Carburizing - Used to increase the surface hardness of metals - Typically for machinery components that require high surface hardness but still need to be relatively ductile overall (such as a cutting edge or a shaft) - Steel is wrapped in carbon-rich material then placed in a furnace and heated to a specific temperature range. The temperature is maintained for a period of time to allow the carbon atoms to penetrate the metal surface

Answer 28

1. Casting - where molten metal is poured or forced into suitably shaped moulds 2. Forging - shaping the metal when it is hot (but not molten) 3. Extruding - forcing a metal through a suitably shaped die (usually rods or tubes) when the metal is hot 4. Sintering - suitable metal powder is heated and compressed in a die to produce a particular shape of metal with certain qualities (not seen on ships!) 5. Machining - process used to achieve a finished product (includes lathe, milling, bending, rolling, grinding, drilling, etc)

Answer 29

1. Storage 2. Heat treatment / De-scaling 3. Sand blasting 4. Priming / Painting 5. Plate cutting 6. Shaping 7. Welding 8. Assembly