MECHANICAL PROPERTIES ) 1400 3 30 300 Tensile strength Ti-10V-2Fe-3Al (STA) /g/cm 0.2%yield strength 2 Base material 1200 Welded portion(400˚C x 300min annealing) Ti-6Al-2Sn-4Zr-6Mo 2000 (STA) Heat-affected zone(400˚C x 300min annealing) Ti-15V-3Cr-3Sn-3Al 20 1800 1000 (STA) Ti-6Al-4V (Ann) Titanium alloy Ti-15V-3Cr-3Sn-3Al (ST) ( ) 250 KS120 Ti-9 Ann 1600 800 KS100 Ti-6Al-4V ELI (ST) Ti-15Mo-5Zr-3Al 10 1400 (STA) KS85 Steel-nickel alloy 600 Aluminum alloy 1200 KS70 Stress (MPa) Ti-5Al-2.5Sn ELI Ti-3Al-2.5V Commercially Magnesium alloy 200 KS50 pure titanium 1000 400 0 Specific strength [0.2% yield strength/density] (kgf/mm Tensile strength, 0.2%yield strength (MPa) Tensile 0 200 400 600 800 1000 KS40 800 Temperature (˚C) strength(MPa) Tensile 200 Fig.2:Specific strength of various materials 600 Commercially pure titanium Titanium alloy Commercially pure titanium (KS50) 400 0 1400 150 6 7 Fig.1:Tensile strength of commercially pure titaniums and various titanium Ti-15V-3Cr-3Sn-3Al (STA) 105 10 10 alloys, and 0.2% yield strength(Specified minimum values) 1200 200 Repetition frequency 1000 Fig.5:Fatigue characteristics of commercially pure titanium (KS50) base Ti-6Al-4V (Ann) 0 800 -300 -250 -200 -150 -100 -50 0 50 material and welded portion 600 SUS304 Temperature (˚C) 400 KS70 Ti-1.5Al Table 1:Representative characteristics of commercially pure titanium, titanium strength(MPa) Tensile 200 KS50 alloys, and steel base materials (Plate materials) 0 70 Representative values 0 100 200 300 400 500 600 Temperature (˚C) Portions Stress ratio Notch coefficient Base material 0 1.0 0.2% 1200 60 Material Tensile Tensile Vickers Erichsen Base material -1 1.0 direction yield Elongation 1400 strength hardness value 1000 Commercially pure titanium (KS50) Welded portion 0 1.0 strength (MPa) (%) (Hv) (mm) (MPa) Welded portion -1 1.0 800 50 1200 Base material 0 3.0 T 238 332 45.9 Base material -1 3.0 KS40 117 11.2 600 L 181 337 48.2 400 40 1000 T 272 387 41.6 KS50 144 10.3 L 222 391 38.7 200 0.2%yield strength(MPa) Elongation(%) 800 T 429 551 26.0 0 30 KS70 202 6.9 0 100 200 300 400 500 600 Temperature (˚C) Ti-15V-3Cr-3Sn-3Al (ST) Commercially pure titanium L 411 545 25.9 T 888 957 10.1 80 20 600 Ti-6Al-4V 320 - Ti-5Al-2.5Sn ELI Stress (MPa) L 905 959 10.3 60 400 T 615 661 23.0 10 Ti-3Al-2.5V 240 - L 501 654 20.0 40 Titanium alloy Titanium Ti-15V-3Cr T 789 828 19.8 Ti-6Al-4V ELI(ST) 200 260 7.9 0 -3Sn-3Al L 772 823 19.1 Elongation(%) 20 -300 -250 -200 -150 -100 -50 0 50 T 169 303 45.0 Temperature (˚C) 0 Mild steel 88 10.1 L 167 301 46.5 0 0 100 200 300 400 500 600 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 Temperature (˚C) Stainless steel T 263 648 58.0 Repetition frequency [-] (SUS 304) 168 13.0 L 264 662 55.7 Fig.3:Tensile characteristics of various commercially pure titaniums, various titanium Fig.4:Low temperature tensile properties of commercially pure titanium and Fig.6:Fatigue characteristics of Ti-6Al-4V base material and welded portion alloys and SUS304 under room temperature and high temperatures various titanium alloys Commercially pure titanium has a tensile strength ranging from 275 to titanium alloys. Low temperature characteristics pure titanium and titanium alloys exhibit almost no decline in fatigue 590 MPa, and this strength is controlled primarily through oxygen content The specific strength of titanium alloy is superior to other metallic Neither commercially pure titanium nor titanium alloys become brittle strength. and iron content. The higher the oxygen and iron content, the higher the materials in the temperature range up to 600ûC. (Fig. 2) even at extremely low temperatures. In particular, commercially pure strength. We are currently producing various titanium alloys from Ti- titanium and Ti-5A1-2.5Sn EL1 can be used even at 4.2 K (-269ûC). Toughness 3A1-2.5V with a tensile strength of 620 MPa, to Ti-15Mo-5Zr-3AI with High temperature characteristics (Fig. 4) The fracture toughness of titanium alloys range from 28 to 108MPa.m1/2 a tensile strength of 1250 MPa. Commercially pure titanium is stable for use in the temperature range up and is in negative correlation with tensile yield strength. Fracture (Tensile strengths listed above are KOBELCO's specified minimum values.) to approximately 300ûC due to its specific strength, creep resistance, and Fatigue characteristics toughness is dependent on microstructure, and thus fracture toughness is Fig.1 shows the tensile strength and yield strength of commercially other properties. On the other hand, titanium alloys exhibit high strength The fatigue strength (107 cycles) is roughly equivalent to 50% of the tensile higher in materials with acicular structures. pure titanium and various titanium alloys and Table 1 shows the ten- in the temperature range up to approximately 500ûC. (Fig. 3) strength, and welding does not cause a significant decline in fatigue sile characteristics of commercially pure titanium and representative strength. (Figs. 5 and 6) In addition, even in seawater, both commercially CORROSION RESISTANCE Tantalum Boiling point Table 2:Comparison of corrosion resistance of various heat exchanger materials 23˚C 100 1.4 8m/s, sea water Zirconium Commercially pure titanium Corrosion resistance rank Hastelloy B 150h Purity of Sand diameter < 50 m Ti-015Pd alloy Material sea water General Pitting Crevice Stress corrosion corrosion corrosion corrosion cracking Erosion 1.2 T-15Mo-5Zr-3Al alloy Clean 1 1 1 1 2 Ti-5Ta alloy 10 Titanium Contaminated 1 1 1 1 2 Naval brass AKOT 1.0 Clean 2 2 2 1 3 Commercially pure titanium AKOT Al brass Hastelloy C Contaminated 2 4 4 4 3 Clean 1 2 2 1 3 0.8 Monel 1 70/30 Cu-Ni Contaminated 2 4 4 4 3 Clean 1 1 2 1 2 Aluminum brass Zirconium Hastelloy C Stainless steel 0.6 Contaminated 1 2 3 2 2 Corrosion rate (mm/year) Ti-0.15Pd Chloride concentration Corrosion resistance rank: 1=Excellent 2=Good 3=Ordinary 4 =Inferior 90/10 cupronickel Monel 0.1 Corrosion rate (mm/year) 0.4 Inconel Table 3:Environment causing titanium stress corrosion cracking 316 Stainless steel 0.2 Aluminum bronze 70/30 304 Stainless steel 0.01 Environment Susceptible titanium materials Cupro- 024681012 Methanol containing halogen or acid Commercially pure titanium nickel Oxidizing Non-oxidizing HCl (mass %) Non-aqueous solution 0 Fuming red nitric asid Ti-6Al-4V Commercially pure titanium Fig.7:Corrosion resistance range of various metals Fig.8:Corrosion resistance of commercially pure titanium and corrosion resistant (Each metal shows excellent corrosion resistance in the arrow-marked range) titanium alloys in hydrochloric acid solution Brine High strength titanium alloy 0 5 10 15 Aqueous solution High temperature and high pressure Sand content in seawater (g/l) Commercially pure titanium bromide solution Fig.11:Sand erosion resistance of commercially pure titanium and copper Ti-015Pd alloy High temperature chloride Molten halogen salt High strength titanium alloy alloys in running sea water 250 Liquid metal Hg, Cd High strength titanium alloy Commercially pure titanium AKOT 1 104ûC 200 Susceptible to crevice corrosion Magnesium Velocity: 2.4 ~ 3.9m/sec Zinc 0.5 Beryllium PdO/TiO2 Temperature: 10 ~ 27˚C Aluminum alloy Cadmium coated titanium Activated condition Mild steel/Cast iron Low alloy steel 82ûC 150 Austenitic nickel cast iron Aluminum bronze Immune to crevice corrosion Naval brass, bronze, red brass Tin Copper Temperature (˚C) Temperature Solder(50/50) Admiralty brass, aluminum brass 0.1 54ûC Manganese bronze 100 Silicon bronze Tin bronze(G&M) Corrosion rate (mm/year) 0.05 Stainless steel(410,416) 32ûC 316 Stainless steel German silver 90~10 Cupronickel 80~20 Cupronickel Stainless steel(430) 50 Lead 70~30 Cupronickel Nickel, aluminum bronze Nickel -chrome alloy 600 (inconel 600) 304 Stainless steel Silver solders Nickel 200 0.01 Silver 0 Stainless steel(302,304,312,347) 0102030405060 0.001 0.01 0.1 1 10 Nickel-copper alloy 400,K-500 NaOH (mass %) CI- concentration (mass %) Stainless steel(316,317) 20 alloy (Carpenter 20) Source:LaQue, F. L.,"The behavior of nickel-copper alloys in seawater", Nickel-iron-chrome alloy 825 (Inconel 825) Fig.9:Corrosion rate of commercially pure titanium deaerated NaOH solution Fig.10:Boundary of crevice corrosion of various titanium materials and Ni-Cr-Mo-Cu-Si alloy B (Hastelloy B) Journal of the American society of naval engineers, Titanium vol. 53, February 1941, #1, pp.22-64 stainless steel in chloride solution Ni-Cr-Mo alloy C (Hastelloy C) Platinum Tokushuko, Vol.41, No.5, P38 Graphite +0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6 (1) General properties Potential (V vs SCE) Titanium is normally an active metal, but exhibits extremely high Please note that titanium is corroded by alkali of high temperature and Fig.12:Natural potential of various metals in running seawater corrosion resistance because a passive film of titanium oxide is high concentration. (Fig. 9) generated and is maintained in many environments. (3) Corrosion resistance against chloride solutions Titanium is optimal in oxidizing environments in which this passive film Unlike stainless steel and copper alloys, titanium is not subject to pitting (5) Erosion resistance (7) Reactivity to gas is formed.