Grade 4 Titanium CNC Machining Services — CP-Ti (UNS R50700)

Engineering Challenge

Grade 4 carries roughly 60% more tensile strength than Grade 2 but lower ductility (typically 15% elongation vs 25%). Machined sections optimized for GR2 — sharp internal corners, deep draws, aggressive flanges — can crack or chip during machining or service. Cold-forming operations that work for GR2 (bending, flaring, stamping) need larger bend radii and intermediate anneals for GR4.

Our Machining Approach

We confirm bend radii, draw depths, and minimum corner radii against the agreed specification and the material condition (annealed vs as-rolled) at the RFQ stage. Cutting parameters are tuned to keep the cutting-zone temperature below the alloy over-aging range. In-process inspection verifies that as-machined geometry is within drawing tolerance before the next operation, so geometry drift is caught early.

Engineering Outcome

Components that meet drawing tolerance without edge chipping, cracking, or excessive springback at the agreed strength level. Final tolerance and property targets are confirmed after CAD, drawing, material condition, and inspection method review.

Engineering Challenge

Grade 4 weldments are more sensitive to contamination, joint fit-up, and shielding-gas coverage than Grade 2. The higher oxygen content reduces weld-metal ductility, and embrittlement from atmospheric pickup (oxygen, nitrogen, hydrogen) is a real risk. Machined weld preps that look acceptable to the eye can introduce fit-up gaps that the welder cannot compensate for.

Our Machining Approach

We machine weld preps to tighter geometric tolerance than for Grade 2 (root-face flatness, groove angle, land thickness) and verify dimensions at the agreed inspection locations. The surface-preparation step (degrease, pickling) is scheduled before welding to remove the oxygen-rich alpha-case layer from the heat-affected zone. The WPS / WPQ reference is reviewed at the RFQ stage.

Engineering Outcome

Weld prep geometry that meets the agreed WPS tolerance band, with a contaminant-free joint surface ready for welding. Welding and WPS / WPQ qualification remain the customer or designated fabricator responsibility.

Engineering Challenge

Like Grade 2, Grade 4 chips are long and stringy when cut with the wrong tool geometry, leading to wrap-around, re-cut, and surface scratching. Corrosion performance in chloride service depends on an intact passive film; iron, carbon-steel, or abrasive embedment from prior work can seed pitting.

Our Machining Approach

We use sharp, positive-rake carbide tooling with chip-breaker geometry suited to CP-Ti, lower cutting speeds than for Ti-6Al-4V, and high-pressure coolant directed at the cutting edge. Where the order scope requires it, we segregate CP-Ti work from carbon-steel / 316L / aluminum work, use dedicated tooling, workholding, and consumables. Surface preparation per ASTM B600 (alkaline cleaning + acid pickling) is scheduled per the agreed inspection plan.

Engineering Outcome

Predictable chip evacuation, surface free of iron and abrasive embedment, with the passive oxide film intact at the point of shipment. Corrosion performance remains subject to the customer qualification of the finished component in its service environment.