COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF TITANIUM GRADE 4 FASTENERS
Titanium Grade 4 (UNS R50700) is the absolute strongest classification of Commercially Pure (CP) Titanium. It serves as the ultimate bridge between the severe formability of the lower CP grades and the immense strength of alloyed titanium (like Grade 5). This exceptional strength is achieved by intentionally maximizing the allowable interstitial Oxygen and Iron content, which stiffens the alpha-phase crystal structure to yield mechanical properties that rival mild steel.
Because it contains no Aluminum or Vanadium, Grade 4 retains the phenomenal, uncompromised corrosion resistance of pure titanium. It is totally immune to chloride stress-corrosion cracking, pitting in marine environments, and degradation in oxidizing acids. UNS R50700 fasteners are the mandatory choice for applications demanding the absolute highest structural yield possible without sacrificing the biocompatibility or chemical inertness of unalloyed titanium, making them essential in aerospace airframes, severe chemical processing, and critical load-bearing medical implants.
■ Product Overview & Specifications
| Material Classification | Commercially Pure (CP) Titanium - Highest Strength Grade |
|---|---|
| UNS Designation | R50700 |
| Microstructure | Single-Phase Alpha Matrix |
| Magnetic State | Completely Non-Magnetic |
| Density | 4.51 g/cm³ (0.163 lb/in³) — Exceptionally Lightweight |
| Size Range | Metric: M4 to M36 | Imperial: #8 to 1-1/2" |
| Primary Attribute | Maximum Yield Strength of all Unalloyed Titanium Grades |
■ Proprietary Datasheet Download (GATED)
Titanium Grade 4 (CP) — Complete Technical Datasheet
Contains detailed high-load structural shear thresholds, dynamic fatigue limits for aerospace applications, and specialized machining parameters for hard CP titanium.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
In high-stress aerospace and biomedical applications, the precise management of Oxygen and Iron dictates the metal's performance limit. Exceeding the maximum allowed limits causes catastrophic embrittlement. Ananka ensures every Grade 4 fastener lot is backed by rigorous, aerospace-grade Vacuum Arc Remelting (VAR) certification.
- EN 10204 Type 3.1: Validates the critical 0.40% maximum Oxygen limit (driving the high strength), ensures Hydrogen remains strictly limited to prevent embrittlement, and confirms the annealed mechanical yield limits.
- EN 10204 Type 3.2: Available upon request for commercial aviation structures, naval submarine components, and critical surgical implant manufacturing requiring third-party testing oversight.
■ Chemical Composition
Grade 4 represents the physical limit of strengthening unalloyed titanium via interstitial elements. It allows the highest concentration of Oxygen (up to 0.40%) and Iron (up to 0.50%) of any CP grade. This deliberate inclusion creates a highly rigid, strong alpha-phase matrix without resorting to heavy alloying elements like Aluminum or Vanadium.
| Titanium (Ti) | Oxygen (O) | Iron (Fe) | Carbon (C) | Nitrogen (N) | Hydrogen (H) |
|---|---|---|---|---|---|
| Balance (~98.9) | 0.40 Max | 0.50 Max | 0.08 Max | 0.05 Max | 0.015 Max |
■ Mechanical Properties
| Mechanical Property | Typical Limits (Annealed Temper) |
|---|---|
| Tensile Strength | 80,000 psi (550 MPa) Minimum |
| Yield Strength (0.2% Offset) | 70,000 - 85,000 psi (480 - 585 MPa) |
| Elongation (in 2 inches) | 15% Minimum |
| Hardness (Brinell) | ~ 230 HB (approx. 98 HRB) |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASTM Specifications | ASTM B348 (Rod/Bar), ASTM F467 / F468 (Fasteners) |
| Common Trade Names | CP Titanium Grade 4, Unalloyed Titanium |
| Medical Specifications | ASTM F67 (Unalloyed Titanium for Surgical Implant) |
| European Equivalent | EN 3.7065 (Ti4) |
■ Applications & Industries
- Aerospace Structures: High-strength mounting brackets, engine firewall fasteners, and hydraulic system bolting where the strength-to-weight ratio of steel is unacceptable but Grade 5's lower ductility is a concern.
- Biomedical Engineering: Load-bearing spinal fixation screws, heavy orthopedic bone plates, and dental implants requiring maximum structural integrity and 100% biocompatibility.
- Aggressive Chemical Processing: Heavy flange bolts and pressure-vessel studs for reactors handling hot nitric acid, wet chlorine, and organic chlorides at elevated temperatures.
■ Compatible Fastener Assemblies
| Mating Bolts/Studs | Internal Threads (Nuts) | Washers / Gaskets |
|---|---|---|
| Grade 4 CP Titanium Heavy Hex Bolts | Grade 4 CP Titanium Hex Nuts | Grade 4 Flat Washers / PTFE |
■ Torque & Installation Guidelines
Due to its high structural rigidity, Grade 4 Titanium can withstand aggressive torque loads comparable to many carbon steels. However, because it remains an unalloyed titanium, the risk of severe thread galling (cold-welding) is extremely high under heavy friction. Generous application of premium dialectric anti-seize pastes or specialized Teflon dry-films is absolutely mandatory before applying torque.
| Nominal Diameter | Threads Per Inch (UNC) | Max Target Torque (in-lbs) — Lubricated | Max Target Torque (ft-lbs) — Lubricated |
|---|---|---|---|
| 1/4" | 20 | 65 - 75 | ~ 5.5 |
| 5/16" | 18 | 140 - 160 | ~ 12.5 |
| 3/8" | 16 | 250 - 280 | ~ 22.0 |
| 1/2" | 13 | 520 - 580 | ~ 46.0 |
■ Frequently Asked Questions
1. Why choose Grade 4 over Grade 5 (Ti-6Al-4V) if Grade 5 is stronger?
It comes down to a balance of strength, ductility, and absolute corrosion resistance. Grade 5 is significantly stronger due to Aluminum and Vanadium, but those alloys reduce its ductility (making it more brittle) and slightly decrease its corrosion resistance in certain highly specific, extreme chemical environments. Grade 4 offers the absolute highest strength possible while remaining 100% commercially pure, making it tougher and more chemically inert than Grade 5.
2. Can Titanium Grade 4 fasteners be cold-headed?
Generally, no. The high oxygen and iron content that gives Grade 4 its strength also makes it quite rigid and difficult to form at room temperature. If you attempt to aggressively cold-head Grade 4 wire into a bolt head, the metal is highly likely to crack. Fasteners made from Grade 4 are predominantly manufactured via CNC machining from solid bar stock or through hot-forging processes.
3. Is Grade 4 Titanium safe for human implantation?
Yes, absolutely. Grade 4 is fully recognized by ASTM F67 as an approved material for surgical implants. Because it contains no Vanadium (which is mildly toxic and present in Grade 5), it is heavily favored for high-load orthopedic implants, such as hip joint replacements and spinal rods, where both extreme strength and perfect biocompatibility are required.
