GR1 vs GR2 vs GR5 Titanium: Machinability & Formability Guide

The machinability and formability of titanium rods differ sharply across ASTM B348 GR1, GR2 and GR5, because all fabrication behaviour follows from the mechanical properties of each grade. This guide gives the numbers you need for tooling, cutting speeds, coolant, bend radii and heat treatment.

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GR1 machines most easily: low strength and high ductility give excellent chip formation, but the long, stringy chips demand effective chip control. GR2 behaves like GR1 with slightly more strength and is the industry baseline for machining titanium. GR5 is significantly harder to machine: its higher strength, work-hardening tendency and low thermal conductivity concentrate cutting heat at the tool edge, causing rapid wear unless conditions are managed.

Tooling: sharp, positive-rake carbide tools with wear-resistant coatings (AlTiN, TiAlN or diamond-like coatings).

• Coolant: high-pressure coolant at 70–100 bar for chip evacuation and heat control; flood coolant is insufficient for production machining.
• Cutting speeds: 30–60 m/min for turning GR5; 60–90 m/min for GR1/GR2, with higher feed rates to avoid work hardening.
• Engagement: avoid dwell and light cuts that promote work hardening; keep continuous engagement where possible.

GR1 offers the highest formability: elongation above 24%, and it can be severely bent, drawn or formed without cracking - the choice for complex deep-drawn shapes. GR2 cold-forms well at 20–24% elongation but requires larger bend radii (2–3 times material thickness) than GR1, and springback is more pronounced than in steel. GR5 has limited cold formability at 10–15% elongation; cold forming is restricted to simple bends with generous radii, and complex shapes are normally hot formed at 650–815 °C.

Bend radii: GR1: 1–2× thickness; GR2: 2–3×; GR5: 3–5× or hot forming.

Annealing: stress-relief annealing at 650–760 °C after cold work exceeding about 50% reduction for GR1/GR2.

Surface protection: prevent iron contamination from tooling or work surfaces - embedded iron causes galvanic corrosion in service.

Cleaning: remove all lubricants and contaminants before welding or heat treatment to prevent hydrogen absorption and embrittlement.

Specify GR1 when maximum formability and ductility are the priority (liners, deep-drawn parts, heat-exchanger components); GR2 as the general baseline for corrosion service with moderate strength; and GR5 when high strength-to-weight ratio is the driver (aerospace, medical implants, high-stress industrial parts), accepting its higher fabrication cost and more demanding machining and forming practice.

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FAQ:

Which is better, grade 2 titanium or grade 5 titanium?

Neither grade is universally "better"-it depends entirely on your application. Grade 5 is much stronger and harder, making it better for high-stress structural uses, aerospace, and scratch-resistant items like watch cases. Grade 2 is purer, more ductile, cheaper, and offers superior corrosion resistance in harsh marine or chemical environments

What is the difference between Grade 1 and grade 2 titanium?

Grade 1 and Grade 2 titanium are both commercially pure unalloyed metals, sharing identical corrosion resistance and density. The primary difference is that Grade 1 is softer and more ductile with maximum formability, while Grade 2 contains slightly more oxygen and iron, making it stronger, harder, and the general "workhorse" industry standard.

Is grade 5 or grade 2 titanium more expensive?

Titanium Grade 2 vs Grade 5: Cost Comparison.Grade 2 is generally easier to process, and weld, and less expensive than Grade 5.

How hard is grade 2 titanium?

Grade 2 titanium has a typical hardness of around 80 HRB on the Rockwell scale, 145–200 on the Brinell scale, and roughly 145 on the Vickers scale. As a commercially pure metal, its hardness offers a balance of moderate strength and high formability.