Grade 2 titanium

Identity and ordering basis

Nippon Steel's comparison gives JIS Class 2 oxygen ≤0.20% and proof stress ≥215 MPa, versus ASTM/ASME Grade 2 oxygen ≤0.25% and proof stress 275–450 MPa. Use the ordered standard, product form and certificate to evaluate a cross-system substitution. Nippon Steel grade comparison

Grade 2 is a commercially pure titanium grade identified by UNS R50400. ATI markets it as ATI 40/CP Grade 2; TIMET identifies TIMETAL 50A as equivalent to ASTM Grade 2. Those producer names do not establish the provenance of generic stock. ATI product identity, TIMETAL 50A datasheet

Commercially pure does not mean chemically pure titanium. TIMET's composition table permits oxygen ≤0.25%, iron ≤0.30%, nitrogen ≤0.03% and carbon ≤0.08%, with titanium remainder and additional impurity limits. Its hydrogen entry has a product-form qualification. TIMET composition table

Specify the exact product standard and edition, form, dimensions, delivery condition, surface requirements and inspection documentation. A grade number alone does not establish whether the item is plate, seamless tube, welded pipe, bar or a finished fitting. Keep heat/lot traceability after cutting and forming; a catalogue description cannot certify an unidentified offcut.

Nippon Steel’s table compares the specifications by product and test requirement. Nippon Steel standards table, page 14

Strength: minimum, typical and allowable are separate

ATI's plate entry lists tensile strength ≥345 MPa, yield strength 275–450 MPa and elongation ≥20%, alongside ASTM B265 and ASME SB-265. Confirm the purchase-standard applicability, dimensions and test requirements before treating the web summary as acceptance criteria. ATI plate data

TIMET's named-product data illustrate a different type of information:

The typical row must not silently replace the specified minimum. TIMETAL 50A introduction and Tables 2–4

Corrosion screening and exposure limits

TIMET describes seawater piping, reactor vessels and heat exchangers among 50A applications. That identifies candidate service, not approval of every medium, temperature or equipment geometry. TIMET application overview

Nippon Steel's corrosion table shows why concentration and temperature belong in a compatibility statement. Its general titanium entries rate 30% hydrochloric acid at 24°C and 10% hydrochloric acid at 80°C with the category corresponding to >1.27 mm/year. The table also flags local corrosion for several hot chloride solutions. It is a general screening table, not a Grade 2 component-life prediction or a substitute for the actual process assessment. Nippon Steel corrosion tables, pages 19–20

Record composition, impurities, aeration, temperature, pressure, deposits and cleaning cycles. Include startup, shutdown and upset conditions. Review crevices, gasket interfaces and mating materials as part of the assembly; an open-surface exposure result does not establish behavior inside every joint. Require process-specific evidence where loss of containment or long inaccessible service makes an unsupported assumption consequential.

Forming, welding and surface condition

TIMET's fabrication handbook calls for clean joints and filler wire and separates primary torch shielding, trailing shielding and root-side backup shielding. It warns that excess torch gas can create turbulence and reduce protection. Its welding guidance therefore cannot be reduced to “use argon” with one universal flow setting. TIMET design and fabrication handbook, welding section

Qualify shielding for the actual joint, access and equipment. Include tack welds and starts/stops, then inspect against the selected procedure and acceptance standard. Surface color is useful process feedback, but does not replace required mechanical tests or nondestructive examination.

The handbook discusses galling in sliding contact and warns that surface treatments must remain compatible with the corrosive environment. It also discourages carbon-steel brushes because embedded iron can impair corrosion performance. TIMET surface treatment and maintenance sections

For formed parts, establish stock condition, rolling direction, tooling, bend geometry and the inspection stage. Use representative trials for critical shapes. Define whether an intermediate anneal or final stress relief is needed through the qualified process; do not copy a catalogue heat-treatment cycle onto every thickness, assembly or finish. For machined parts, qualify tooling and coolant on the actual stock and operation rather than inheriting a universal speed/feed recipe from the grade name.

Reconciled expansion example

TIMET lists density 4.51 g/cm³ and a mean thermal-expansion coefficient of 8.6 × 10⁻⁶/K over 20–100°C. TIMET physical properties

For an unconstrained 1,000 mm member initially at 20°C, the estimated expansion to 100°C is:

ΔL = 1,000 × 8.6 × 10⁻⁶ × 80 = 0.688 mm.

This original calculation uses the coefficient over its stated interval. It excludes temperature gradients, constraints, joint motion and property scatter. It is a preliminary clearance estimate, not a restrained thermal-stress calculation. Do not extend that coefficient unchanged to an arbitrary high-temperature range.

Source versions and related reference

The TIMETAL 50A PDF footer identifies ©2000, TMC-0159. The fabrication handbook ends with ©1997, HQ-10/97-BG104-4M. These are historical technical references, not current code editions. ATI's product page and the inspected Nippon Steel catalogue text do not provide a clearly verified technical revision date here. Obtain current order-specific documents and construction requirements before procurement or procedure approval.

Grades, tempers and conditions