Copper alloy C70250 (CuNi3SiMg) CuNi3SiMg

spore: profile
id: copper-c70250
spore_version: 0.2
family: copper-alloys
name: Copper alloy C70250 (CuNi3SiMg)
abbreviation: CuNi3SiMg
role: precipitation-hardened spring and connector alloy
category: metals
type: copper-alloys
summary: |
  Copper alloy C70250 (UNS C70250, CuNi3SiMg) is a precipitation-hardened copper alloy with 2.2 to 4.2 wt% nickel and 0.25 to 1.2 wt% silicon, per Aurubis. Aurubis gives a tensile strength of 655 to 830 MPa and a yield strength of 590 to 760 MPa in temper TM02, with an electrical conductivity of at least 23 MS/m (40 %IACS) in the soft condition.
best_for: 'Springs and connectors that need strength and electrical conduction together, without beryllium: 655 to 830 MPa tensile strength in temper TM02 and at least 40 %IACS in the soft condition'
weakest_at: Electrical and thermal conduction, which is well below that of pure copper, and machining, which Fisk rates poor and Aurubis does not recommend
identity:
  formula: 'Copper alloy: Cu rest (Cu plus named elements 99.5 % minimum), Ni 2.2 to 4.2, Si 0.25 to 1.2, Mg 0.05 to 0.30, Zn up to 1.0, Pb up to 0.05, Fe up to 0.20, Mn up to 0.10 wt% (Aurubis US). Nominal Cu 96.3, Ni 3.0, Si 0.7 (Fisk). Nominal Ni 3, Si 0.65, Mg 0.15 (KME).'
  source: aurubis-us
  where: Composition table of the Aurubis C70250 datasheet 18 08 US, and nominal composition of the Fisk Alloy page and the KME datasheet
  designations:
    - system: UNS
      code: C70250
      source: aurubis-us
      where: 'Header, Comparable standards: UNS C70250'
    - system: ASTM
      code: B422
      source: olin-c7025
      where: Title block, ASTM B422 beside the alloy number
    - system: EN name
      code: CuNi3Si
      note: KME prints EN CuNi3Si; Kemper says EN not standardised
      source: kme-cunisi
      where: Alloy Designation table, EN row
    - system: Trade name
      code: PNA 370
      note: Aurubis designation
      source: aurubis-pna370
      where: Header, Aurubis designation
    - system: Trade name
      code: C7025
      note: Aurubis designation
      source: aurubis-us
      where: Header, Aurubis designations
tags:
  environments: []
  stresses: []
  applications:
    - electronics-and-chips
    - mechanisms
properties:
  - benchmark: density
    label: Density, Aurubis PNA 370 datasheet
    value: 8.82
    unit: g/cm3
    scope: material
    conditions:
      temperature: not stated
      temper: not stated
      unit_in_source: g/cm³
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-pna370
    where: Physical properties table, Density column
  - benchmark: density
    label: Density, KME datasheet typical value
    value: 8.8
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
      temper: annealed (typical values, per KME)
      unit_in_source: g/cm³
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: kme-cunisi
    where: Physical Properties table, Density row
  - benchmark: density
    label: Density, Fisk Alloy listing
    value: 8.94
    unit: g/cm3
    scope: material
    conditions:
      temperature: not stated
      temper: not stated
      unit_in_source: gm/cm³
    method: Value printed on a supplier product page
    status: ground
    note: The Fisk value is higher than the Aurubis and KME values. The sources disagree and all three are recorded.
    source: fisk-c70250
    where: Physical properties, Metric units, Density
  - benchmark: melting_point
    label: Melting point, Aurubis PNA 370 datasheet
    value: 1095
    unit: °C
    scope: material
    conditions:
      temperature: not stated
      pressure: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    note: Aurubis's two datasheets give different melting points, 1095 °C and 1062 °C. Both are recorded.
    source: aurubis-pna370
    where: Physical properties table, Melting point column
  - benchmark: melting_point
    label: Melting point, Aurubis US datasheet
    value: 1062
    unit: °C
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 1944 °F
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Physical properties table, metric row under the 1944 °F value, Melting point column
  - benchmark: melting_point
    label: Melting point, solidus (Fisk Alloy)
    value: 954
    unit: °C
    scope: material
    conditions:
      temperature: not stated
      pressure: not stated
      unit_in_source: 1,750 °F
    method: Value printed on a supplier product page
    status: ground
    source: fisk-c70250
    where: Physical properties, Metric units, Melting Point (Solidus)
  - benchmark: melting_point
    label: Melting point, liquidus (Fisk Alloy)
    value: 1049
    unit: °C
    scope: material
    conditions:
      temperature: not stated
      pressure: not stated
      unit_in_source: 1,920 °F
    method: Value printed on a supplier product page
    status: ground
    source: fisk-c70250
    where: Physical properties, Metric units, Melting Point (Liquidus)
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 20 °C, Aurubis US datasheet
    value: 169
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: W/mK
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Physical properties table, Thermal cond. at 20 °C column, metric row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 20 °C, Fisk Alloy listing
    value: 170
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: W/m·K
    method: Value printed on a supplier product page
    status: ground
    source: fisk-c70250
    where: Physical properties, Metric units, Thermal Conductivity
  - benchmark: thermal_conductivity
    label: Thermal conductivity, KME typical value
    value: 190
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 20 °C
      temper: annealed (typical values, per KME)
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: kme-cunisi
    where: Physical Properties table, Thermal conductivity row
  - benchmark: electrical_conductivity
    label: Electrical conductivity, minimum, soft condition (Aurubis PNA 370)
    value: 23
    bound: lower
    unit: MS/m
    scope: material
    conditions:
      temper: soft condition only (the datasheet says the specified conductivity applies to the soft condition only)
      temperature: not stated
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: aurubis-pna370
    where: Physical properties table, Electrical cond. column (value 23 with a greater-than-or-equal sign)
  - benchmark: electrical_conductivity
    label: Electrical conductivity, minimum, soft condition (Aurubis PNA 370, %IACS)
    value: 40
    bound: lower
    unit: '%IACS'
    scope: material
    conditions:
      temper: soft condition only
      temperature: not stated
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: aurubis-pna370
    where: Description paragraph, 'min. 40% IACS'
  - benchmark: electrical_conductivity
    label: Electrical conductivity, Aurubis US datasheet
    value: 23.4
    unit: MS/m
    scope: material
    conditions:
      temperature: 20 °C
      temper: not stated
      note_in_source: the same row gives 40 %IACS
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Physical properties table, Electrical cond. column, metric row
  - benchmark: electrical_resistivity
    label: Electrical resistivity, annealed (Fisk Alloy)
    value: 4.31
    unit: µΩ·cm
    scope: material
    conditions:
      temperature: 20 °C
      temper: annealed
      unit_in_source: µΩ·cm
    method: Value printed on a supplier product page
    status: ground
    source: fisk-c70250
    where: Physical properties, Metric units, Electrical Resistivity (Annealed)
  - benchmark: elastic_modulus
    label: Modulus of elasticity, Aurubis PNA 370 datasheet
    value: 130
    unit: GPa
    scope: material
    conditions:
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-pna370
    where: Physical properties table, Young's modulus column
  - benchmark: elastic_modulus
    label: Modulus of elasticity, Aurubis US datasheet
    value: 131
    unit: GPa
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: kN/mm2 and x1000 ksi (19)
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Physical properties table, Mod. of elasticity column, metric row
  - benchmark: cte
    label: Coefficient of thermal expansion, 20 to 300 °C, Aurubis PNA 370
    value: 17.6
    unit: ppm/K
    scope: material
    conditions:
      temperature: 20 to 300 °C
      unit_in_source: 10-6/K
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-pna370
    where: Physical properties table, alpha at 20 to 300 °C column
  - benchmark: cte
    label: Coefficient of thermal expansion, 20 to 300 °C, Olin Brass
    value: 17.6
    unit: ppm/K
    scope: material
    conditions:
      temperature: 20 to 300 °C (68 to 572 °F)
      unit_in_source: PPM/ºC
    method: Value printed in a manufacturer technical letter
    status: ground
    source: olin-c7025
    where: Physical Properties table, Coeff. of Thermal Expansion, 68-572 ºF (20-300 ºC) row, metric column
  - benchmark: specific_heat
    label: Specific heat capacity at 20 °C, Aurubis PNA 370
    value: 0.399
    unit: kJ/(kg·K)
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: kJ/kgK
    method: Value printed in a manufacturer datasheet
    status: ground
    source: aurubis-pna370
    where: Physical properties table, cp at 20 °C column
  - benchmark: specific_heat
    label: Specific heat capacity at 20 °C, Aurubis US
    value: 0.38
    unit: kJ/(kg·K)
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: kJ/kgK
    method: Value printed in a manufacturer datasheet
    status: ground
    note: The Aurubis US sheet gives a lower value than the Aurubis PNA 370 sheet. Both are recorded.
    source: aurubis-us
    where: Physical properties table, Specific heat cap. at 20 °C column, metric row
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, temper TM02 (Aurubis US)
    value: 655
    value_high: 830
    bound: range
    unit: MPa
    scope: material
    conditions:
      temper: TM02
      product_form: not stated
      unit_in_source: 95-120 ksi
    method: Range printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Mechanical properties table, Tempers TM02 row, Rm metric column
  - benchmark: yield_strength
    label: Yield strength Rp0.2, temper TM02 (Aurubis US)
    value: 590
    value_high: 760
    bound: range
    unit: MPa
    scope: material
    conditions:
      temper: TM02
      product_form: not stated
      unit_in_source: 85-110 ksi
    method: Range printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Mechanical properties table, Tempers TM02 row, Rp0.2 metric column
  - benchmark: elongation
    label: Elongation, temper TM02 (Aurubis US), minimum
    value: 7
    bound: lower
    unit: '%'
    scope: material
    conditions:
      temper: TM02
      gauge_length: 2 in. (column header Elongation 2)
      basis: minimum
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Mechanical properties table, Tempers TM02 row, Elongation 2 column
  - benchmark: vickers_hardness
    label: Vickers hardness HV, temper TM02 (Aurubis US)
    value: 210
    value_high: 240
    bound: range
    unit: HV
    scope: material
    conditions:
      temper: TM02
      product_form: not stated
    method: Range printed in a manufacturer datasheet
    status: ground
    source: aurubis-us
    where: Mechanical properties table, Tempers TM02 row, Hardness HV column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, temper R690 (EN 1652, KME)
    value: 690
    value_high: 860
    bound: range
    unit: MPa
    scope: material
    conditions:
      temper: R690 (EN 1652 temper)
      product_form: strip
      thickness: up to 0.5 mm for bending values only
    method: Range printed in a manufacturer datasheet
    status: ground
    source: kme-cunisi
    where: Mechanical Properties table (EN 1652), Tensile Strength Rm, row R690
  - benchmark: yield_strength
    label: Yield strength Rp0.2, temper R690, minimum (KME)
    value: 655
    bound: lower
    unit: MPa
    scope: material
    conditions:
      temper: R690 (EN 1652 temper)
      product_form: strip
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: kme-cunisi
    where: Mechanical Properties table (EN 1652), Yield Strength Rp0.2 minimum, row R690
  - benchmark: yield_strength
    label: Yield strength Rp0.2, temper R690, minimum (Aurubis PNA 370)
    value: 650
    bound: lower
    unit: MPa
    scope: material
    conditions:
      temper: R690
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    note: The Aurubis PNA 370 sheet gives 650 MPa as the minimum for R690, while KME gives 655 MPa. Both are recorded.
    source: aurubis-pna370
    where: Mechanical properties table, row R690, Yield strength column
  - benchmark: elongation
    label: Elongation A50, temper R690, minimum (KME)
    value: 5
    bound: lower
    unit: '%'
    scope: material
    conditions:
      temper: R690
      gauge_length: A50 mm
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: kme-cunisi
    where: Mechanical Properties table, Elongation A50mm minimum, row R690
  - benchmark: soft_annealing_temperature
    label: Soft annealing temperature range (KME, not a canonical benchmark)
    value: 250
    value_high: 650
    bound: range
    unit: °C
    scope: material
    conditions:
      time: 1 to 3 h
      purpose: soft annealing (KME process data)
    method: Range printed in a manufacturer datasheet
    status: ground
    source: kme-cunisi
    where: Fabrication Properties table, row Soft Annealing
  - benchmark: stress_relief_temperature
    label: Stress relieving annealing temperature range (KME, not a canonical benchmark)
    value: 150
    value_high: 200
    bound: range
    unit: °C
    scope: material
    conditions:
      time: 1 to 3 h
      purpose: stress relieving annealing (KME process data)
    method: Range printed in a manufacturer datasheet
    status: ground
    source: kme-cunisi
    where: Fabrication Properties table, row Stress Relieving Annealing
corrosion:
  - environment: Natural and industrial atmospheres, maritime air, drinking and service water
    headline: Good corrosion resistance in atmospheres (manufacturer statement, no rate printed).
    effect: Aurubis PNA 370 lists resistance to natural and industrial atmospheres, maritime air, drinking and service water, non-oxidizing acids, alkaline solutions and neutral saline solutions. Aurubis US describes good corrosion resistance in industrial atmospheres. KME describes good corrosion resistance in natural atmosphere. No corrosion rate is printed in any of these sources.
    rating: low
    conditions:
      basis: manufacturer statements; no test conditions or corrosion rates given
    source: aurubis-pna370
    where: Corrosion resistance section
  - environment: Stress corrosion cracking
    headline: Not susceptible to stress corrosion cracking (Kemper and Aurubis US).
    effect: Kemper's processing table lists stress crack corrosion as none. Aurubis US says the alloy is resistant against stress corrosion cracking. KME says it is insensitive to stress corrosion cracking.
    rating: none
    conditions:
      basis: manufacturer statements; no test data given
    source: kemper-khp7025
    where: Processing information table, row Stress crack corrosion
  - environment: Ammonia, halide, cyanide and hydrogen sulphide solutions and atmospheres, oxidizing acids, sea water at high flow rates
    headline: Not resistant to these environments (Aurubis PNA 370); no rate given.
    effect: Aurubis PNA 370 lists these as environments in which the alloy is not resistant. The sheet gives no corrosion rate or test condition.
    rating: unknown
    conditions:
      basis: manufacturer statement; no rate or test condition printed
    source: aurubis-pna370
    where: Corrosion resistance section, 'is not resistant to' sentence
risks:
  hazards:
    - text: Wieland's copper alloy safety data sheet (SDS No. 00001.0001, revision 6/1/15) says the health hazards apply only in fume or dust form. Its OSHA classification lists skin irritation (H315) and respiratory irritation (H335) for fume or dust, and states that in solid form the material is not hazardous. The sheet covers UNS/CDA alloy numbers C10000 to C15599, which does not name C70250, so this is a related family sheet, not a sheet for this grade.
      ghs:
        - H315
        - H335
      source: wieland-sds
      where: Section 2, Hazard identification, and Section 3 regulatory status
    - text: The same sheet says that under 29 CFR 1910.1200 the product is considered hazardous, and lists dust or fume hazards as carcinogen, irritant, lung, blood, kidney, reproductive and developmental toxin, neurotoxin and sensitizer. The two statements apply to different forms (solid versus dust or fume).
      ghs: []
      source: wieland-sds
      where: Section 2, Other Hazards, and Section 3 OSHA regulatory status
  failure_risks:
    - mode: Loss of spring force in relaxation
      trigger: Sustained stress at temperatures up to 150 °C
      consequence: KME calls the relaxation properties excellent up to 150 °C because of NiSi precipitation. The Aurubis sheet plots residual stress against Larson-Miller parameter with no rate printed, so the loss of contact force cannot be quantified from these sources.
      severity: moderate
      source: kme-cunisi
      where: Characteristics paragraph, and Relaxation Properties section
    - mode: Softening from overheating
      trigger: Heating in the soft annealing range of 250 to 650 °C for 1 to 3 h
      consequence: Soft annealing softens the material, so an unplanned excursion into this range lowers the strength of the spring temper. KME gives no strength figure after such heating.
      severity: moderate
      source: kme-cunisi
      where: Fabrication Properties table, Soft Annealing row
    - mode: Attack in ammonia or sulphide environments
      trigger: Exposure to ammonia, halide, cyanide or hydrogen sulphide solutions or atmospheres, oxidizing acids or sea water at high flow rates
      consequence: Aurubis PNA 370 lists these as not resistant. No rate or time to failure is given.
      severity: high
      source: aurubis-pna370
      where: Corrosion resistance section
  side_effects: []
  handling:
    - text: Use dust and fume controls when cutting, welding, melting or grinding the alloy. Avoid breathing dust or fumes (P261) and keep them off the skin and clothing (P262), per the Wieland sheet.
      source: wieland-sds
      where: Section 2, precautionary statements
    - text: After contact with dust or fumes, wash the skin with plenty of water and remove contaminated clothing before reuse, per the Wieland sheet's first aid section.
      source: wieland-sds
      where: Section 4, First aid measures
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Electronic connectors, contacts, lead frames and terminals
    example: Aurubis lists contact springs, lead frames, electronic connectors and automotive electrical connectors as typical uses. Olin adds semiconductor leadframes and CPU sockets.
    source: aurubis-us
    where: Typical uses row; Olin introduction paragraph
  - application: mechanisms
    device: Relay and contact springs
    example: KME rates relay springs as a particularly well-suited application, and lists switches and relays among its main applications. Aurubis PNA 370 lists contact springs and relays among typical uses.
    source: kme-cunisi
    where: Preferred Applications table; Main Applications paragraph
  - application: electronics-and-chips
    device: Beryllium-free replacement for some beryllium copper alloys
    example: Olin says the alloy can often be substituted directly for some Be-Cu alloys. Fisk says it has the qualities of some beryllium coppers without containing any beryllium.
    source: olin-c7025
    where: Introduction paragraph; Fisk overview paragraph (fisk-c70250)
supply:
  - subject: Copper (about 96 % of the alloy; Fisk prints Cu 96.3 nominal)
    abundance: 'USGS mine production 2025e, copper content, thousand metric tons: Chile 5,300; Congo (Kinshasa) 3,200; Peru 2,700; China 1,800; Russia 1,300. World total 23,000. Reserves for the world total are 980,000 thousand t.'
    producers:
      - country: Chile
        year: 2025
      - country: Congo (Kinshasa)
        year: 2025
      - country: Peru
        year: 2025
      - country: China
        year: 2025
      - country: Russia
        year: 2025
    critical_lists:
      - list: U.S. Final 2025 List of Critical Minerals (copper added), per USGS Mineral Commodity Summaries 2026
        listed: true
    recycling: 'USGS: old (post-consumer) scrap gave an estimated 160,000 tons of copper in 2025, and about 760,000 tons were recovered from new scrap. Scrap contributed about 30% of U.S. copper supply.'
    substitutes:
      - 'USGS: aluminum substitutes for copper in electrical equipment and power cable.'
      - 'Olin: the alloy can often be substituted directly for some Be-Cu alloys.'
    source: usgs-mcs2026-copper
    where: World Mine and Refinery Production and Reserves table; Recycling; Substitutes; Events, Trends, and Issues
  - subject: Silicon (alloying element, 0.25 to 1.2 wt%)
    abundance: Silicon was added to the U.S. 2025 critical minerals list. Supply shares for silicon were not looked up in this run.
    critical_lists:
      - list: U.S. Final 2025 List of Critical Minerals (silicon added), per USGS Mineral Commodity Summaries 2026
        listed: true
    source: usgs-mcs2026-copper
    where: Events, Trends, and Issues, second paragraph
documents:
  - title: Aurubis technical datasheet C70250 (CuNi3SiMg), 18 08 US
    type: datasheet
    url: https://www.aurubis.be/en/dam/jcr:168e88f6-00e4-41a8-9f07-246f75e99273/c70250-cuni3simg-us.pdf
  - title: Aurubis material datasheet CuNi3SiMg, PNA 370, EN_2026_01
    type: datasheet
    url: https://www.aurubis.com/en/dam/jcr:ecd0d61d-f7f8-4a87-9fe6-c08c681323a1/PNA%20370_CuNi3SiMg_C70250-En.pdf
    year: 2026
  - title: Olin Brass Alloy C7025 technical data, ASTM B422
    type: datasheet
    url: https://www.wieland-rolledproductsna.com/wp-content/uploads/2018/08/Olin-Brass-Mill-Products-Technical-Letter-Alloy-C7025_0.pdf
    year: 2013
  - title: KME CuNi3Si1Mg (C70250) industrial rolled datasheet
    type: datasheet
    url: https://www.kme-archiv.com/fileadmin/DOWNLOADCENTER/COPPER%20DIVISON/4%20Industrial%20Rolled/3_Datasheets/3_Datasheets_new_2019/CuNi3Si_04_2019.pdf
    year: 2019
  - title: Fisk Alloy C70250 product page
    type: datasheet
    url: https://fiskalloy.com/product/c70250/
  - title: Kemper KHP 7025 (CuNi3SiMg) alloy page
    type: datasheet
    url: https://www.kemper-group.com/en-en/rolled-products/alloys/khp7025-(cuni3simg)/
  - title: 'USGS Mineral Commodity Summaries 2026: copper'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.pdf
    year: 2026
  - title: Wieland copper alloy safety data sheet, SDS No. 00001.0001
    type: sds
    url: https://www.wieland.com/fr/content/download/12648/file/Safety-Data-Sheet_Copper-alloy.pdf
    year: 2015
gaps:
  - No safety data sheet for C70250 itself was found. The hazard entries use Wieland's copper alloy sheet, whose synonym line covers a range of copper alloy UNS/CDA numbers that does not name C70250. The three Fisk Alloy safety sheets checked cover other alloys.
  - PubChem could not be read in this run (the page returned a browser check), so no ECHA or GHS classification record was added for this alloy or for copper.
  - Only the tempers TM00, TM02, TM03 (Aurubis US, Olin) and R620, R650, R690 (Aurubis PNA 370, KME) were read in full. The highest EN 1652 temper shown by Kemper was not recorded.
  - Kemper's datasheet gives strength ranges for the same EN 1652 temper designations that differ from KME's ranges. Kemper strength values were not recorded; the KME values were kept.
  - Stress relaxation rates were not recorded. KME and Aurubis publish relaxation data as plots only. Sundwiger and Wieland datasheets found in search were not readable.
  - Fisk's modulus of elasticity entry is in a unit that does not match the other sources and was not recorded. Fisk's conductivity entries are in units that were not converted, so they were not recorded.
  - Vickers hardness (HV) and soft annealing and stress relief temperatures are recorded under benchmark names that are not in the canonical list (vickers_hardness, soft_annealing_temperature, stress_relief_temperature).
  - Electrical resistivity and conductivity of the spring tempers were not found as numbers. KME says cold deformation lowers conductivity without giving a value.
  - Corrosion rates in micrometres per year, and salt spray or atmospheric exposure results, were not found in any source read.
  - The EN number (1.xxxx) and the CW112C designation were not printed in any source read. KME prints 'EN CuNi3Si' while Kemper states 'EN not standardised'; the KME name is recorded with that conflict noted.
  - Nickel and magnesium supply (producers, shares and critical lists) were not looked up. Only copper and silicon are covered in the supply section.
  - Radiation tolerance, outgassing and flight heritage were not looked up. No space application or flight record was found in the sources read.
  - The Aurubis sheets give specific heat as 0.399 and 0.38 kJ/kgK, and melting point as 1095 and 1062 °C; both are recorded as printed, and the disagreement is noted on each row.
sources:
  aurubis-us:
    title: Technical Datasheet C70250 (CuNi3SiMg), Aurubis, 18 08 US
    id: UNS C70250; Aurubis designations C7025 and PNA370
    url: https://www.aurubis.be/en/dam/jcr:168e88f6-00e4-41a8-9f07-246f75e99273/c70250-cuni3simg-us.pdf
    kind: datasheet
  aurubis-pna370:
    title: Material Datasheet CuNi3SiMg, Aurubis PNA 370, EN_2026_01
    id: Comparable standards UNS C70250; Aurubis designation PNA 370
    url: https://www.aurubis.com/en/dam/jcr:ecd0d61d-f7f8-4a87-9fe6-c08c681323a1/PNA%20370_CuNi3SiMg_C70250-En.pdf
    year: 2026
    kind: datasheet
  olin-c7025:
    title: Olin Brass Alloy C7025 (C70250) technical data, ASTM B422
    id: ASTM B422
    url: https://www.wieland-rolledproductsna.com/wp-content/uploads/2018/08/Olin-Brass-Mill-Products-Technical-Letter-Alloy-C7025_0.pdf
    year: 2013
    kind: datasheet
  kme-cunisi:
    title: KME CuNi3Si1Mg (C70250), Industrial Rolled, High Performance Alloys datasheet
    id: EN CuNi3Si; UNS C70250; DIN CEN/TS 13388
    url: https://www.kme-archiv.com/fileadmin/DOWNLOADCENTER/COPPER%20DIVISON/4%20Industrial%20Rolled/3_Datasheets/3_Datasheets_new_2019/CuNi3Si_04_2019.pdf
    year: 2019
    kind: datasheet
  fisk-c70250:
    title: C70250 High Performance Alloy (CuNi3Si1), Fisk Alloy product page
    id: ASTM B422; ASTM B888
    url: https://fiskalloy.com/product/c70250/
    kind: web
  kemper-khp7025:
    title: KHP 7025 (CuNi3SiMg), Gebr. Kemper rolled products alloy page
    id: 'Standard designation: EN not standardised / UNS C70250'
    url: https://www.kemper-group.com/en-en/rolled-products/alloys/khp7025-(cuni3simg)/
    kind: datasheet
  usgs-mcs2026-copper:
    title: 'USGS Mineral Commodity Summaries 2026: Copper'
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.pdf
    year: 2026
    kind: report
  wieland-sds:
    title: Wieland copper alloy safety data sheet, SDS No. 00001.0001 (revision 6/1/15)
    id: UNS/CDA Alloy Nos. c10000 to c15599 (except 15815)
    url: https://www.wieland.com/fr/content/download/12648/file/Safety-Data-Sheet_Copper-alloy.pdf
    year: 2015
    kind: datasheet
story:
  recipe:
    line: Copper alloy C70250 is copper with nickel and silicon, plus small additions of magnesium, made to temper by cold working and heat treatment at the mill (Fisk). In heat treatment the nickel and silicon form NiSi precipitates (KME), which give the strength and the stress relaxation resistance.
    parts:
      - name: Copper
        symbol: Cu
        share_note: balance (rest)
        role: The matrix. Copper carries the electrical and thermal conduction, and the alloy keeps its conductivity at 40 %IACS minimum in the soft condition.
        source: aurubis-us
        where: 'Composition table, Cu row: rem, with Cu plus named elements 99.5 % minimum'
      - name: Nickel
        symbol: Ni
        share_percent: 2.2
        share_high: 4.2
        role: Forms NiSi precipitates with silicon during heat treatment, which hardens the alloy.
        source: aurubis-us
        where: Composition table, Ni column
      - name: Silicon
        symbol: Si
        share_percent: 0.25
        share_high: 1.2
        role: Combines with nickel to form the NiSi precipitates.
        source: aurubis-us
        where: Composition table, Si column
      - name: Magnesium
        symbol: Mg
        share_percent: 0.05
        share_high: 0.3
        role: A minor addition. KME gives 0.15 wt% as the nominal magnesium content.
        source: aurubis-us
        where: Composition table, Mg column
  risk_groups:
    - title: Solid alloy
      level: 0
      verdict: Not hazardous in solid form
      lead: The Wieland copper alloy safety data sheet says the solid metal is not hazardous. No sheet for C70250 itself was found.
      points:
        - label: Solid form
          line: The Wieland sheet's OSHA statement says that in solid form the material is not hazardous. Its family sheet covers C10000 to C15599, which does not name C70250.
        - label: Processing
          line: Cutting, welding, melting and grinding produce dust and fume that carry the alloy's component elements into the air.
    - title: Dust and fume
      level: 2
      verdict: Irritant dust and fume while processing
      lead: The health hazards apply to dust or fume, not to the solid metal, according to the Wieland sheet.
      points:
        - label: Hazard statements
          line: H315 causes skin irritation and H335 may cause respiratory irritation, for dust or fume (Wieland sheet).
        - label: Precautions
          line: Avoid breathing dust or fumes (P261). Do not get them in the eyes, on the skin or on clothing (P262).
  why: Copper alloy C70250 (UNS C70250, CuNi3SiMg) is a precipitation-hardened copper alloy for springs, connectors and lead frames. Aurubis gives a tensile strength of 655 to 830 MPa and a yield strength of 590 to 760 MPa in temper TM02, with an electrical conductivity of at least 23 MS/m (40 %IACS) in the soft condition. Pure copper conducts better; this alloy trades some conduction for strength and spring behaviour. Olin says it can often replace some beryllium copper alloys.
  uses:
    - where: Connectors and contacts
      line: Aurubis lists contact springs, lead frames, electronic connectors and automotive electrical connectors as typical uses. Olin adds semiconductor leadframes and CPU sockets.
    - where: Relay and switch springs
      line: KME rates relay springs as particularly well-suited applications, and lists switches and relays among its main applications.
    - where: Replacement for beryllium copper
      line: Olin says the alloy can often be substituted directly for some Be-Cu alloys. Fisk says it has some of the qualities of beryllium coppers without containing any beryllium.
  can_do:
    - label: Strength
      benchmark: ultimate_tensile_strength
      value: 655 to 830 MPa
      line: In temper TM02 the tensile strength is 655 to 830 MPa, and the yield strength is 590 to 760 MPa (Aurubis US datasheet).
    - label: Conductivity
      benchmark: electrical_conductivity
      value: 23 MS/m minimum
      line: In the soft condition the minimum electrical conductivity is 23 MS/m, or 40 %IACS (Aurubis PNA 370 datasheet). Aurubis says this applies to the soft condition only.
    - label: Heat conduction
      benchmark: thermal_conductivity
      value: 169 W/(m·K) at 20 °C
      line: Thermal conductivity is 169 W/(m·K) at 20 °C in the Aurubis US datasheet, 170 W/(m·K) in the Fisk listing and 190 W/(m·K) as a typical value in the KME datasheet.
    - label: Spring relaxation
      line: KME says the relaxation properties are excellent even at temperatures up to 150 °C. Aurubis gives relaxation only as a plot, so no relaxation rate is recorded here.
    - label: Stress corrosion
      line: Kemper lists stress crack corrosion as none, and Aurubis US says the alloy is resistant against stress corrosion cracking.
  compare: C70250 is a precipitation-hardened copper alloy. It gives up some of the conduction of pure copper in exchange for much higher strength and good stress relaxation resistance, and it keeps the spring behaviour that copper alone lacks. Olin and Fisk both present it as a beryllium-free substitute for some beryllium copper alloys, and the beryllium copper profile in this collection can be read against these claims. The table compares it on the three benchmarks the collection uses.
  compare_rows:
    - label: Electrical conductivity
      benchmark: electrical_conductivity
    - label: Tensile strength
      benchmark: ultimate_tensile_strength
    - label: Density
      benchmark: density
  handling:
    - The solid alloy is not hazardous in solid form under the Wieland copper alloy safety data sheet. Dust and fume from cutting, welding, melting and grinding are the hazard.
    - Avoid breathing dust or fumes (P261) and keep them off skin and clothing (P262).
    - Keep the alloy away from ammonia, halide, cyanide and hydrogen sulphide solutions, oxidizing acids and sea water at high flow rates (Aurubis PNA 370).
    - Soft annealing is 250 to 650 °C for 1 to 3 h and stress relief is 150 to 200 °C for 1 to 3 h (KME). Heating in these ranges changes the temper.
  good_for:
    - 'Spring contacts and connectors that need strength and conduction together: 655 to 830 MPa tensile strength in TM02 and at least 40 %IACS in the soft condition.'
    - A beryllium-free alternative for some beryllium copper connectors, as Olin and Fisk describe it.
  watch_out:
    - Conductivity is lower in cold-worked and hard tempers. Aurubis says the specified conductivity applies to the soft condition only.
    - Not resistant to ammonia, halide, cyanide or hydrogen sulphide solutions and atmospheres, oxidizing acids or sea water at high flow rates (Aurubis PNA 370).
    - Machinability is rated poor by Fisk and not recommended by Aurubis US.
  verdict: C70250 is the choice for springs and connectors that need strength and conduction without beryllium, as long as the part avoids ammonia and sulphide environments.
review:
  status: draft
  method: assistant
  checked_values: 30
  unreachable: 0
  caveats: 0
  note: Values read in this run from the Aurubis, Olin, KME, Fisk and Kemper pages and the USGS summary. Sundwiger and Wieland datasheets for other copper alloys were not readable.