ASTM B863 Grade 7 Titanium Wire
- Standard: ASTM B863
- Grade: Grade 7 (CP Titanium + 0.12-0.25% Pd)
- UNS: R52400
- Supply form: Coil, spool or straight cut length
- Condition: Annealed or cold-worked, as ordered
- Diameter Range: Ø0.03–Ø7.0 mm
Customizable sizes are available, while specific product parameters should be confirmed per the applicable standard edition and order.
Product Overview
ASTM B863 Grade 7 titanium wire is palladium-bearing commercially pure titanium-base wire with UNS designation R52400. Its base chemistry and room-temperature mechanical level are similar to Grade 2, with 0.12-0.25% palladium added to stabilize passivity in reducing media and reduce susceptibility to crevice corrosion in certain chloride environments. The room-temperature structure is predominantly alpha titanium; palladium is not added primarily for strength.
The principal value of Grade 7 is improved corrosion resistance in specific environments, not universally higher strength than Grade 2. It is used for corrosion-resistant wire components in chemical, marine, brine, heat-exchanger and electrochemical equipment. Selection must still consider acid concentration, temperature, chloride content, crevices, flow, dissolved oxygen, galvanic contact and hydrogen-charging conditions.
| Specification | Details |
| Industrial Standard | ASTM B863 |
| Grades | Gr7 |
| Diameter Range | Ø0.03–Ø7.0 mm |
| Typical Diameters | Ø0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.0 mm |
| Supply Form | Coil / Spool or straightened and cut wire |
Grade-equivalence note: Grade 7 is sometimes informally called TA9 in the Chinese market. ASTM Grade 7 and Chinese GB/T grades must be certified to their own specifications and should not be declared fully equivalent without a clause‑by‑clause comparison.
Main Characteristics
- Improved resistance in reducing media: Palladium supports cathodic reactions and helps the surface maintain or recover passivity, giving Grade 7 better performance than Grade 2 in certain reducing acids and low-pH chloride environments.
- Improved crevice-corrosion resistance: In some hot chloride, brine, deposit and gasket-crevice conditions, Grade 7 has more favorable critical limits than unalloyed CP titanium, but it is not immune at every temperature or concentration.
- Grade 2-type strength and formability: Grade 7 generally retains useful ductility for coiling, weaving and bending. Mechanical behavior is governed mainly by oxygen, iron, grain size, cold work and final annealing.
- Good weldability: Qualified fusion or resistance welding may be used with full inert-gas shielding of hot metal. Filler-wire supply requires separate compliance with AWS A5.16 ERTi-7 or the customer consumable specification.
- Low density and useful low-temperature behavior: Density is approximately 4.50-4.51 g/cm³. Qualified design data must be used for actual low-temperature service.
- Not significantly strengthened by conventional heat treatment: Annealing restores ductility and relieves drawing stress. Grade 7 and Grade 7H have the same chemistry, but Grade 7H carries a higher minimum tensile-strength requirement and the designations are not automatically interchangeable.
Chemical Composition
The following limits apply to ASTM B863 Grade 7. Values are mass percentages. Formal acceptance is governed by the contract edition and the producer’s certified report.
| Element | ASTM B863 Grade 7 requirement |
| Palladium, Pd | 0.12-0.25% |
| Nitrogen, N | ≤0.03% |
| Carbon, C | ≤0.08% |
| Hydrogen, H | ≤0.015% |
| Iron, Fe | ≤0.30% |
| Oxygen, O | ≤0.25% |
| Residual elements, each | ≤0.10% |
| Residual elements, total | ≤0.40% |
| Titanium, Ti | Balance |
Technical references: ASTM B863 grade scope, TIMETAL 50A Grade 2 base-property data, and METALCOR/BIBUS Grade 7 technical information.
- Palladium: The specified range is 0.12-0.25%. Its main role is to help maintain passivity in selected reducing media and crevice conditions, not to act as a principal strengthening addition.
- Oxygen, iron and nitrogen: Control strength, hardness and ductility. Their limits follow the Grade 2-type base chemistry.
- Hydrogen: Must be strictly controlled. Pickling, cathodic protection and electrochemical service can promote hydrogen pickup; palladium does not eliminate hydride or embrittlement risk.
- Titanium content: ASTM states Titanium: Balance. Do not publish a fixed minimum titanium percentage unless it is supported by the actual heat analysis or an additional guarantee.
Mechanical Properties
ASTM B863 includes tensile, elongation and hardness requirements for Grade 7 wire. Properties vary with diameter and delivery condition. Formal acceptance must therefore follow the ordered annealed or cold-worked condition, applicable size range, test method and the official tables of the specified standard edition.
| Property | Product-page technical statement | Acceptance basis |
| Tensile strength | Depends on diameter and annealed/cold-worked condition | Applicable ASTM B863 table and purchase order |
| Elongation | Depends on diameter, gauge length and condition | Applicable ASTM B863 table and purchase order |
| Hardness | The specification includes applicable requirements; one value cannot cover every condition | Applicable grade, condition and test method |
| Yield strength | Minimum values defined for annealed condition; cold‑worked values vary with cold reduction & wire diameter, no universal fixed value | Specify condition, diameter and acceptance requirements in purchase order if yield strength is required |
Representative Annealed Grade 7 Properties (METALCOR/BIBUS reference data, NOT ASTM B863‑26 wire guaranteed acceptance values)
| Property | Representative annealed Grade 2-base/Grade 7 reference |
| Ultimate tensile strength | Representative approx. 485 MPa |
| 0.2% yield strength | Representative approx. 345 MPa |
| Elongation | Representative approx. 28% |
| Reduction of area | Representative approx. 57% |
Important: The values above are representative annealed Grade 7 data and are not ASTM B863 wire acceptance values. Diameter, cold reduction and final annealing materially affect strength, elongation and hardness. Quotations, contracts and MTRs should identify diameter, tolerance, condition, surface, coil weight or cut length, and inspection requirements.
HTN Supply and Quality Documentation
HTN organizes ASTM B863 Grade 7 palladium-bearing titanium wire supply to customer purchase requirements. Material is produced by qualified titanium-mill resources. Original mill reports, heat traceability, palladium content, full chemistry and property records can be supplied as agreed. HTN reviews the edition, Grade 7/7H designation, heat number, documents, diameter, tolerance, condition, surface, coil weight or cut length, and can arrange independent retesting, PMI, cut-to-length service, clean packaging and third-party inspection.
Typical Applications
- Corrosion-resistant mesh, filters and mist eliminators for chlor-alkali, salt and chemical-process equipment;
- connection wire, locating wire and mesh for heat exchangers, reactors, condensers and seawater systems;
- racks, baskets, cathode or connection components for plating, anodizing and electrochemical equipment;
- wire parts for high-chloride brine, wet chlorine and qualified acidic process environments;
- corrosion-resistant fastening and support components where gaskets, deposits or structural crevices are expected;
- fine-wire parts for pharmaceutical, high-purity chemical and pollution-control equipment;
- welding filler wire when AWS A5.16 ERTi-7 or the customer consumable specification is met;
- special wire assemblies made to customer drawings for validated corrosion conditions.
Application boundary: ASTM B863 Grade 7 wire is not automatically implant grade, aerospace grade or qualified welding filler. Filler use additionally requires AWS A5.16 ERTi-7. Medical, aerospace and pressure-equipment uses require the applicable material and design specifications, drawings and quality system. Grade 7H must be explicitly ordered when its higher-strength designation is required.
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Fabrication and Machining Characteristics
Drawing and Dimensional Control
Grade 7 draws similarly to Grade 2: it has relatively low thermal conductivity, noticeable elastic recovery and a tendency to adhere to tooling. Use clean dies, suitable lubrication, controlled area reduction and scheduled intermediate anneals. Segregate palladium-bearing heats and revert to prevent mix-ups.
Cold working
Annealed wire provides useful coiling, weaving and bending capability. Cold drawing increases strength and hardness while reducing ductility; final reduction must match subsequent forming, diameter and ordered properties.
Annealing and heat treatment
Annealing restores ductility, reduces drawing stress and stabilizes the alpha structure. Actual time and temperature depend on diameter, cold reduction and the qualified process. Vacuum or inert atmosphere helps limit oxidation and contamination.
Welding and joining
GTAW/TIG, resistance welding or another qualified method may be used with complete inert-gas shielding of the weld, root and hot heat-affected zone. Filler wire must separately satisfy AWS A5.16 ERTi-7 chemistry, cleanliness, dimensions and procedure requirements; ASTM B863 compliance alone does not qualify ERTi-7.
Typical Physical Properties
The following are representative values for Grade 7 or its Grade 2-type base near room temperature and are not mandatory lot-acceptance requirements of ASTM B863 .
| Physical property | Typical value |
| Density | Approx. 4.50-4.51 g/cm³ |
| Elastic modulus | Approx. 105-120 GPa; some sources cite about 108 GPa |
| Thermal conductivity near 20°C | Reported approx. 17-21.8 W/(m·K) |
| Electrical resistivity near 20°C | Approx. 0.50-0.53 μΩ·m |
| Mean CTE, 20-100°C | Reference approx. 8.6×10⁻⁶/K |
| Mean CTE, 20-300°C | Reference approx. 9.5×10⁻⁶/K |
| Specific heat | Approx. 0.52 kJ/(kg·K) |
| Beta transus | Typically approx. 915-920°C |
| Reference melting point | Approx. 1670°C |
| Magnetism | Essentially non-magnetic |
Physical-property references: METALCOR/BIBUS Grade 7 and TIMETAL 50A base data. Reported thermal conductivity and beta-transus values can differ with chemistry, condition and method; confirmed data should be used for engineering calculations.
Corrosion Resistance
Grade 7 relies on a stable titanium-oxide passive film, with palladium helping to maintain passivity in selected reducing acids, low-pH chlorides and crevice conditions. This is particularly useful in chemical-process, brine, seawater and heat-exchanger service, but performance remains dependent on temperature, concentration, crevice geometry, contamination, flow, potential and hydrogen-charging conditions.
Environments in Which Grade 7 Generally Performs Well
- Seawater, salt spray and humid air;
- neutral chloride and brine solutions;
- many oxidizing acid environments;
- nitric acid and some oxidizer-containing process streams;
- many organic acids and organic compounds;
- alkaline media;
- wet chlorine and hydrated halogen environments;
- many food, pharmaceutical and high-purity-water systems.
Environments Requiring Careful Evaluation
- Strong reducing acids under oxygen-starved conditions;
- hot concentrated hydrochloric or sulfuric acid;
- fluoride-containing media or hydrofluoric acid;
- tight crevices in hot concentrated chloride or sulfate solutions;
- anhydrous methanol or halide-contaminated methanol;
- red fuming nitric acid;
- molten chloride salts;
- cathodic-protection or electrochemical conditions that may promote hydrogen absorption;
- dissimilar-metal contact with an unsuitable galvanic design.
Engineering caution: Grade 7 is not immune to every corrosive environment. Fine wire and mesh may also be affected by crevices, deposits, contacting metals and cleaning residues. Evaluate crevice corrosion in hot chloride service and control hydrogen pickup during pickling, heat treatment and electrochemical use.
Typical Production Process for Grade 7 Titanium Wire
- Raw-material selection and charge preparation: Select qualified titanium sponge, controlled clean revert and palladium-bearing input, accurately controlling palladium together with oxygen, iron, nitrogen, hydrogen and other elements.
- Electrode preparation: Homogenize, compact and weld the consumable electrode while preventing local noble-metal segregation and contamination from iron particles, oil and moisture.
- Vacuum melting and ingot production: Use a qualified vacuum-melting route to achieve chemistry uniformity and cleanliness. ASTM B863 does not prescribe one identical VAR count for every Grade 7 wire order; special melting requirements belong in the purchase order.
- Ingot conditioning and breakdown: Crop unsuitable ends, remove surface defects, and forge or roll to billet or rod while verifying palladium distribution and heat traceability.
- Hot processing to wire rod: Forge and hot roll under controlled conditions to manage microstructure, oxidation, dimensions and surface quality.
- Pickling, conditioning and multi-pass drawing: Remove scale and defects, draw through successive dies, and schedule intermediate anneals according to reduction while controlling hydrogen pickup and surface notches.
- Intermediate and final annealing: Restore ductility, lower residual stress and obtain the ordered annealed condition. For cold-worked supply, final reduction is controlled to achieve the required strength and hardness.
- Surface finishing: Pickling, mechanical cleaning, polishing or another approved cleaning method may be used. Pickling and heat treatment must control hydrogen pickup, oxidation and foreign contamination.
- Straightening, coiling and cutting: Supply on coils or spools, or as straight cut lengths, and inspect diameter, roundness, straightness of cut lengths, coil quality and surface condition.
- Inspection and traceability: Verify chemistry, tensile properties, elongation, hardness, dimensions and surface quality, maintaining traceability from heat and lot to spool or package and material-test documentation.
Melting and inspection note: ASTM B863 requires finished wire to meet applicable chemistry, performance, dimensional and quality requirements. It does not prescribe the same number of VAR melts for every Grade 7 product. Double or triple VAR, tight roundness, special roughness, cleanliness, nondestructive testing, EN 10204 3.1 documentation and third-party inspection must be confirmed in the purchase order when required.
