Precious Metal Pt70Rh30/Pt94Rh6 BN-Hard
Supply condition
ASTM E230 Type B
BN-Hard = bN hard-drawn
As-drawn negative leg for stiff, self-supporting elements; softens on first exposure to furnace temperature.
Values for the BN-Hard condition
Other Pt70Rh30/Pt94Rh6 tempers and conditions
Pt70Rh30/Pt94Rh6 is listed in 4 conditions; see the grade overview at Pt70Rh30/Pt94Rh6.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
BN annealed | Standard supply condition of the negative leg; softer and denser than BP, drawn to the same diameter for a matched pair. | 120 | 255 | 35 | 78 HV | 10.1 % IACS |
BP-AnnDefault BP annealed | Standard supply condition of the positive leg; annealed for stable EMF and easy junction welding. | 250 | 550 | 28 | 125 HV | 9.1 % IACS |
BN-HardThis page BN hard-drawn | As-drawn negative leg for stiff, self-supporting elements; softens on first exposure to furnace temperature. | 520 | 620 | 3 | 162 HB | 9.9 % IACS |
BP hard-drawn | Choose when the wire must stay straight/self-supporting during assembly; anneal or first heating to service temperature restores EMF. | 900 | 1,050 | 3 | 25 HRC | 8.8 % IACS |
What is Pt70Rh30/Pt94Rh6 BN-Hard?
Pt70Rh30/Pt94Rh6 BN-Hard is Pt70Rh30/Pt94Rh6 supplied in the BN-Hard condition — as-drawn negative leg for stiff, self-supporting elements; softens on first exposure to furnace temperature. Pt70Rh30/Pt94Rh6 BN-Hard has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 97% of precious metal grades. Elongation at break is 3% and the elastic modulus is 180 GPa (26.1 Msi). Pt70Rh30/Pt94Rh6 BN-Hard has a density of 20.6 g/cm³ (0.744 lb/in³), heavier than 95% of precious metal grades. It melts at 1,900°C (3,452 °F). BP-Ann is the default condition FabDigit quotes; BN-Hard is available on request or by drawing note.
Advantages
- High service temperature — 1,700°C (3,092 °F), better than 100% of precious metal grades
- Good corrosion resistance — 100/100, better than 98% of precious metal grades
- High strength — 520 MPa (75.4 ksi), better than 97% of precious metal grades
- Stiff — 180 GPa (26.1 Msi), better than 92% of precious metal grades
- Readily welded — 75/100, better than 78% of precious metal grades
Limitations
- High embodied carbon — 25,000 kg CO₂/kg, worse than 99% of precious metal grades
- Limited ductility — 3%, worse than 95% of precious metal grades
- Heavy — 20.6 g/cm³ (0.744 lb/in³), worse than 95% of precious metal grades
- Limited formability — 40/100, worse than 91% of precious metal grades
- Difficult to machine — 30/100, worse than 86% of precious metal grades
Pt70Rh30/Pt94Rh6 BN-Hard properties
Typical room-temperature values for Pt70Rh30/Pt94Rh6 BN-Hard; 20 are specific to this condition. Other listed values are Pt70Rh30/Pt94Rh6 reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
Pt70Rh30/Pt94Rh6 BN-Hard has a density of 20.6 g/cm³ (0.744 lb/in³), heavier than 95% of precious metal grades. It melts at 1,900°C (3,452 °F).
Mechanical9
Pt70Rh30/Pt94Rh6 BN-Hard has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 97% of precious metal grades. Elongation at break is 3% and the elastic modulus is 180 GPa (26.1 Msi).
Thermal6
Pt70Rh30/Pt94Rh6 BN-Hard is rated for continuous service to 1,700°C (3,092 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), worse than 82% of precious metal grades. Thermal expansion is 8.6 µm/m·K (4.78 µin/in·°F).
Electrical3
Pt70Rh30/Pt94Rh6 BN-Hard conducts electricity at 9.9 % IACS, worse than 79% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (100/100), better than 98% of precious metal grades.
Sustainability4
Producing a kilogram of Pt70Rh30/Pt94Rh6 BN-Hard takes about 300,000 MJ of energy and emits 25,000 kg of CO₂ — more than 99% of precious metal grades. Typical recycled content is 55%.
Manufacturability8
Pt70Rh30/Pt94Rh6 BN-Hard's machinability is poor (30/100, worse than 86% of precious metal grades); weldability very good (75/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Pt70Rh30/Pt94Rh6 BN-Hard
Is Pt70Rh30/Pt94Rh6 easy to machine?
Essentially never machined — the alloys are gummy and smear; product is cold-drawn wire, foil or tube made by drawing/rolling with frequent 1000–1200 °C anneals.
Can Pt70Rh30/Pt94Rh6 be welded?
Junctions are made by butt/spot resistance welding or oxy-gas bead fusion of the two legs; use clean tooling only, never steel or copper contact at heat.
Can Pt70Rh30/Pt94Rh6 be formed, bent or molded?
Both legs draw readily to 0.05 mm with intermediate bright annealing; BN (Pt-6Rh) is markedly softer, so drawing schedules for a matched pair are set separately.
What surface finishes work on Pt70Rh30/Pt94Rh6?
Supplied bright-annealed and used bare — no plating or coating; handle with clean gloves and protect with high-purity alumina insulators to avoid Si/C/P poisoning.
Pt70Rh30/Pt94Rh6 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Rhnegative leg BN (Pt94Rh6), supplied as a separate wire, Pt balance | 5.7 – 6.3 | 6 |
| Feimpurity limit, both legs | ≤ 0.01 | — |
| Siimpurity limit — Si causes embrittlement | ≤ 0 | — |
| Pdimpurity limit, both legs | ≤ 0.01 | — |
| Ptbalance, 99.99 % base purity; total metallic impurities <0.01 % for thermocouple grade | balance | — |
Pt70Rh30/Pt94Rh6 BN-Hard — frequently asked
What is Pt70Rh30/Pt94Rh6 BN-Hard used for?
Pt70Rh30/Pt94Rh6 BN-Hard is typically used for type B thermocouples, steelmaking temperature measurement and glass melting furnaces. In short: highest-temperature thermocouple pair; no cold-junction compensation needed; rated to 1700 °C.
What is the yield strength of Pt70Rh30/Pt94Rh6 BN-Hard?
Pt70Rh30/Pt94Rh6 BN-Hard has a typical yield strength of 520 MPa (75.4 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 97% of precious metal grades. Strength varies by condition: see the 4 listed tempers.
Is Pt70Rh30/Pt94Rh6 BN-Hard easy to machine?
Not especially — machinability is rated poor (30/100, worse than 86% of precious metal grades). Essentially never machined — the alloys are gummy and smear; product is cold-drawn wire, foil or tube made by drawing/rolling with frequent 1000–1200 °C anneals.
Can Pt70Rh30/Pt94Rh6 BN-Hard be welded?
Yes — weldability is rated very good (75/100). Junctions are made by butt/spot resistance welding or oxy-gas bead fusion of the two legs; use clean tooling only, never steel or copper contact at heat.
What surface finishes work on Pt70Rh30/Pt94Rh6 BN-Hard?
Supplied bright-annealed and used bare — no plating or coating; handle with clean gloves and protect with high-purity alumina insulators to avoid Si/C/P poisoning.
Can Pt70Rh30/Pt94Rh6 BN-Hard be formed, bent or molded?
Both legs draw readily to 0.05 mm with intermediate bright annealing; BN (Pt-6Rh) is markedly softer, so drawing schedules for a matched pair are set separately.
What is the maximum service temperature of Pt70Rh30/Pt94Rh6 BN-Hard?
Pt70Rh30/Pt94Rh6 BN-Hard is rated for continuous use to about 1,700°C (3,092 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Pt70Rh30/Pt94Rh6 BP-Ann and Pt70Rh30/Pt94Rh6 BP-Hard?
BP-Ann is the default condition — standard supply condition of the positive leg; annealed for stable EMF and easy junction welding. BP-Hard: choose when the wire must stay straight/self-supporting during assembly; anneal or first heating to service temperature restores EMF. Yield strength is 250 MPa in BP-Ann versus 900 MPa in BP-Hard.
Sources
- IEC 60584-1 Thermocouples — Part 1: EMF specifications and tolerances — IEC (2013)
- ASTM E230/E230M Standard Specification for Temperature-EMF Tables for Standardized Thermocouples — ASTM International (2017)
- Platinum-rhodium alloys for thermocouples and high-temperature applications — Johnson Matthey / Heraeus (2021)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (precious metals) — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.