What Titanium Grade 4 Is
Titanium Grade 4, UNS R50700, is the strongest of the four commercially pure grades. Its strength comes mainly from a higher oxygen content, limited to 0.40 percent maximum, which hardens the alpha structure without the addition of alloying elements. Grade 4 therefore keeps the corrosion resistance and biocompatibility of pure titanium while approaching the strength of some titanium alloys.
Composition and Mechanical Properties
Grade 4 is essentially unalloyed titanium with iron up to 0.50 percent, carbon, nitrogen and hydrogen held to low limits and oxygen at 0.40 percent maximum. In bar form under ASTM B348 it requires a minimum tensile strength of 550 MPa, a minimum yield strength of 483 MPa and 15 percent elongation. Sheet and strip under ASTM B265 follow the same strength minimums.
Medical Implant Standards
For surgical fixation devices Grade 4 is supplied under ASTM F67, the standard for unalloyed titanium for surgical implant applications, and ISO 5832-2. These standards tighten the impurity limits and add microstructure and inclusion controls appropriate for implant material. The same grade appears in both industrial and medical specifications, but the supply route, testing and documentation differ.
Applications in Surgery
Grade 4 is widely used for bone screws, plates, pins and dental implant bodies where strength and osseointegration are both required. Its elastic modulus is closer to that of bone compared with cobalt-chromium and stainless steel, which reduces stress shielding. The material is also chosen for maxillofacial and trauma fixation systems.
Bar Supply Forms and Surface Conditions
Medical-grade bar is supplied in round, square and hexagon sections with machined, ground or peeled surfaces. The surface is free of scale, cracks and contamination, and each heat is traceable through a certificate that reports composition, mechanical results and the implant standard invoked. Bars are packed to protect the surface during transport.
Frequently Asked Questions
Q: What is UNS R50700?
A: UNS R50700 is the unified numbering system designation for titanium Grade 4, the strongest commercially pure grade.
Q: Why is Grade 4 used for medical implants?
A: It combines the biocompatibility of pure titanium with higher strength, which suits bone screws, plates and dental implant bodies.
Q: Which standards govern medical-grade Grade 4?
A: ASTM F67 and ISO 5832-2 define the requirements for unalloyed titanium for surgical implant applications.
Q: How strong is Grade 4 bar?
A: ASTM B348 requires a minimum tensile strength of 550 MPa and a minimum yield strength of 483 MPa.
Q: What oxygen limit applies to Grade 4?
A: Oxygen is limited to 0.40 percent maximum, and this oxygen content is the main source of its higher strength.
Q: Is the same grade used for industrial parts?
A: Yes, Grade 4 is also used industrially for fasteners, pump components and marine hardware where high CP strength is required.
