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Titanium ASTM Grade
What is Titanium ASTM B381 Gr 23 (6AL - 4V ELI)
Grade 12 titanium welds well but is reactive; therefore, precautions are necessary when welding it. Such precautions include preparation before welding, shielding during welding, and proper heat input to eliminate the possibility of oxidation, embrittlement, or cracking in weldments. When this is done, Grade 12 titanium can be welded into strong, reliable components that retain the inherent corrosion resistance and mechanical properties of the base material.
Composition:
- Titanium (Ti): The balance.
- Aluminium (Al): 6%, strengthening this alloy and reducing the final weight.
- Vanadium (V): 4% higher tensile strength and improves corrosion.
- ELI: Extra Low Interstitial This reduces the quantities of oxygen and nitrogen, which improve ductility fracture toughness, and weld ability.
Applications:
The Titanium ASTM B381 Grade 23 is used widely in high-performance applications, including.
Aerospace: For components like airframe parts, turbine blades, engine parts due to high strength-to-weight ratio with resistance to high temperature.
Medical: In implants, such as joint replacements and dental implants, especially because this is non-biodegradable and holds low reactivity of rejection of the human body. Chemical treatment: For items that are exposed to corrosive environments, such as heat exchangers and reactors.
Properties:
Strength: The Titanium Grade 23 has excellent strength while weighing lighter compared to nearly all other alloys, thus widely applied in aerospace and structural applications.
It has excellent resistance to corrosion, especially on those aggressive environments like saltwater, chlorine, and high-temperature conditions.
Definition of Titanium ASTM B381 Grade 23 (6AL-4V ELI)
This alloy, titanium ASTM B381 Grade 23, or more commonly known as 6AL-4V ELI, is the extra low interstitial titanium alloy characterized by the author with 6% aluminium and 4% vanadium and minimized values of the interstitial elements oxygen, nitrogen, and carbon. The ELI designation represents improved ductility, fracture toughness, and biocompatibility in critical applications, such that superior mechanical properties combined with corrosion resistance are insured in such applications.
Composition: Bal Ti, Al (6%), V (4%), having reduced interstitials.
It is said that this ELI grade possesses toughness accompanied by a high strength-to-weight ratio.
Resistance to Corrosion: Excellent resistance to a variety of corrosion environments, including saltwater and aggressive chemicals.
Biocompatibility: Low interstitial content makes it safe for use in medical implants, hence minimizing the chances of the body rejecting it.
Machinability of Titanium ASTM B381 Grade 23 (6AL-4V ELI)
Titanium ASTM B381 Grade 23 (6AL-4V ELI) is stiff to machine compared to many other materials using standard techniques with regular tools. This is primarily because of low thermal conductivity and tends to galling, in addition to being a highly strong material. Comparatively, it is easier to machine than commercial-pure titanium grades but needs proper techniques and tools for good results.
Cutting Tools: Use carbide-tipped tools or coated cutting tools, to withstand the toughness of such an alloy, and minimize tool wear.
Sensitive tools with good heat resistance are critical since work hardening should be avoided.
Cutting Speed: Cuts at lower cutting speeds (30-50 m/min) to minimize the generation of heat, which may damage the tool and affect the quality of surface.
Feed Rates: Feeds should be moderate to high to allow for proper chip removal, thus preventing excessive heat build-up.
Cooling and Lubrication: A high-pressure coolant system will help prevent overheating and will make for smooth machining.
Coolants with anti-galling capabilities may improve surface finish as well as extended tool life.
Work Hardening: Avoid overpassing or dwelling since this alloy tends to work-harden and the subsequent cuts tend to be severe.
Chip Control: The alloy tends to produce long, continuous chips that interfere with machining. Chip-breaking tools can be more effective in improving efficiency.
Surface Finish: Titanium Grade 23 can achieve excellent surface finishes with careful control of machining parameters and the use of finishing tools.
The shielding gas should be applied both during the welding process and in order to back-purge the root of the weld to prevent oxidation on the underside. Input Heat Control The most critical feature of titanium welding is that the heat input must control. High heat input causes distortion, embrittlement, and cracking in the weld area. Thus, low heat input and high welding speed must ensure in order to minimize the heat input to the base material.
Post-Weld Treatment:
This Grade 12 titanium, generally speaking, does not require post weld heat treatment; but, it can be used when residual stresses in the material need to be relieved and its properties enhanced. The weld may be protected from oxidation on the inside by using argon or helium for back purging to keep one surface of the weld and the other surface under inert atmosphere.
Chemical Composition
| Element | Titanium, Ti | Aluminum, Al | Vanadium, V | Iron, Fe | Carbon, C | Nitrogen, N | Hydrogen, H | Other, each | Other, each |
|---|---|---|---|---|---|---|---|---|---|
| Content (%) | 88.09 – 91 | 5.5 – 6.5 | 3.5 – 4.5 | ≤ 0.25 | ≤ 0.080 | ≤ 0.030 | ≤ 0.0125 | ≤ 0.10 | ≤ 0.40 |
Conclusion
Titanium ASTM B381 Grade 23 (6AL-4V ELI) is one of the top class premium products that offer extraordinary strength and lightweight properties, as well as superior corrosion resistance and biocompatibility. The ELI grade raises its extra toughness and ductility to take it up to perfect use in hard applications, especially those in aerospace, medical, and chemical processing industries.