Prospects for Titanium Armour Prof Malcolm Ward-Close

Transcription

1 Prospects for Titanium Armour Prof Malcolm Ward-Close Materials for Armour Systems Monday 23 June 2008 Source Public domain

2 Contents 01 A weight problem 02 Why/why not titanium armour? 02 Ballistic performance 03 Why is titanium expensive? 04 Prospects for cheaper titanium 05 Examples of titanium armour applications 06 Closing remarks 2

3 01 A weight problem Today Challenger II 62 t M1A2 Abrams 68 t Leopard II 55 t Leclerc MBT 53 t Leopard II Next generation US/UK Main battle tank <45 t Light combat vehicle 20 t (C-130 Hercules load limit 25 t) Source Public domain Source Public domain Source Public domain Leclerc 3

4 02 Why/why not titanium armour? Advantages Titanium is as strong as steel High ballistic mass efficiency 15-45% lighter than steel armour Good multi-hit capability full protection within shot diameter Extremely corrosion resistant 50 years+ in seawater Compatible with carbon fibre composite no galvanic corrosion, similar CTE Bio-compatible no hazardous debris Less acoustic noise than steel Non-magnetic Can be fabricated on existing facilities Lower cost than PMC s, MMC s or ceramics 4

5 02 Why/why not titanium armour? Disadvantages Titanium is expensive compared to RHA steel Titanium fabrication is more expensive than steel eg casting, forging, welding The price of titanium alloy plate fluctuates from year to year eg spot price of alloy plate increased from 25/kg to 80/kg in 2005/6, then fell back in 2007 Back-face spalling a spall liner is required to protect the crew 5

6 02 Why/why not titanium armour? Source Public domain For Challenger : steel - turret, hull, suspension 43 t = 35k titanium 25 t = 500k!! 6

7 03 Ballistic performance Mass efficiency compared to RHA steel, 50 mm titanium plate Ti-6Al-4V alloy CP titanium (unalloyed)

8 04 Why is titanium expensive? Low cost raw materials Ti 4 th most abundant metal in earth s crust TiCl 4 made for pigments industry High cost processes Kroll process week per batch Economy of scale = largest possible ingots Large cast ingots are expensive to forge Ti Ore Titanium tetrachloride Ti Alloy ingot Kroll Process Double or triple melt Alloying additions Titanium sponge Forge/roll Blend Cold press Titanium alloy scrap 8

9 04 Why is titanium expensive? Batch processing, <100,000 t/year Ti Sponge production Ingot melting Source Public domain Ingot forging 9

10 04 Why is titanium expensive? Cost breakdown 25 mm titanium alloy plate Plate fabrication $13 (48%) Ti sponge $10 (38%) Final arc melting $0.60 (2%) Primary arc melting $3.20 (12%) Total production cost $26.80/kg allowing for yields and scrap credits based on $7.25/kg sponge cost 10

11 05 Prospects for cheaper titanium Ingot melting - Cold hearth melting Electron beams / plas ma torches Cost reduction through : Slab casting higher yield Sponge / scrap feed lower conversion costs High levels of scrap Single melt eliminates 2 or 3 VAR melts Melting and refining hearths Continuous operation Ingot / slab w ithdrawal Courtesy Timet. Potential for 50-60% cost reduction for thick plate 11

12 05 Prospects for cheaper titanium Alloy sponge - Armstrong alloy powder process (ITP Inc.) Flowing Sodium AlCl 3 VCl 4 Ti-6-4 NaCl TiCl 4 Mixtures of chloride vapors produce alloys Courtesy ITP Inc. Process alloy powder directly to armour plate

13 05 Low-cost titanium alloy door made by ORNL for the US Joint Light Tactical Vehicle Courtesy ORNL 13

14 05 Examples of titanium armour applications M3 Bradley FV (23 t) Commanders hatch 500 kg each 150 kg saved 1600 produced M1A2 Abrams MBT (68 t) Turret blow off panels Armour skirts Commanders hatch GPS cover Engine top deck Source Public domain 14

15 06 Closing remarks Titanium is the only realistic option for significant weight reduction in military vehicles that is available now Cost is the major limiting factor High cost and price volatility are likely to continue over next 5 years Prospects for significant cost reduction in the 5-10 year time frame are good 15

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