Copper Alloy C51000 · finish state
Copper Alloy C51000-M20
Properties of the M20 condition, compared with the other C51000 tempers.
Mill-condition hot-rolled C51000 phosphor bronze plate/bar: soft, ductile and highly formable, with strength only slightly above the fully annealed state.
What is C51000-M20?
C51000-M20 is C51000 supplied in the M20 condition — mill-condition hot-rolled C51000 phosphor bronze plate/bar: soft, ductile and highly formable, with strength only slightly above the fully annealed state. C51000-M20 has a yield strength of 180 MPa (26.1 ksi) and a tensile strength of 350 MPa (50.8 ksi) — weaker than 58% of copper alloy grades. Elongation at break is 48% and the elastic modulus is 110 GPa (16 Msi). C51000-M20 has a density of 8.86 g/cm³ (0.32 lb/in³), heavier than 67% of copper alloy grades. It melts at 950°C (1,742 °F). O is the default condition FabDigit quotes; M20 is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 48%, better than 96% of copper alloy grades
- Forms and bends easily — 85/100, better than 83% of copper alloy grades
C51000-M20 properties
Typical room-temperature values for C51000-M20 — 36 properties are specific to this condition; the rest are grade-level values shared by every C51000 temper. Each bar shows where the value sits among the copper alloy grades in FabDigit's library — further right is higher.
Physical3
C51000-M20 has a density of 8.86 g/cm³ (0.32 lb/in³), heavier than 67% of copper alloy grades. It melts at 950°C (1,742 °F).
Mechanical11
C51000-M20 has a yield strength of 180 MPa (26.1 ksi) and a tensile strength of 350 MPa (50.8 ksi) — weaker than 58% of copper alloy grades. Elongation at break is 48% and the elastic modulus is 110 GPa (16 Msi).
Thermal6
C51000-M20 is rated for continuous service to 200°C (392 °F). It conducts heat at 69 W/m·K (39.9 BTU/hr·ft·°F), worse than 56% of copper alloy grades. Thermal expansion is 17.8 µm/m·K (9.89 µin/in·°F).
Electrical3
C51000-M20 conducts electricity at 15 % IACS, worse than 54% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is good (65/100), better than 57% of copper alloy grades.
Sustainability4
Producing a kilogram of C51000-M20 takes about 62 MJ of energy and emits 3.8 kg of CO₂ — more than 76% of copper alloy grades. Typical recycled content is 35%.
Manufacturability8
C51000-M20's machinability is poor (30/100, worse than 66% of copper alloy grades); weldability fair (45/100); formability excellent (85/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other C51000 tempers and conditions
C51000 is also supplied in 8 other conditions. The full side-by-side table is on the C51000 overview.
- ODefaultPick for deep drawing, severe bending or forming before a final stress-relief/age.140 MPa yield · 80 HB
- H10Maximum-strength strip for the highest contact forces in thin gauges; forming essentially limited to flat blanking.630 MPa yield · 95 HRB
- H08Standard temper for contact springs, diaphragms and clips; stress-relieve after forming to hold load.600 MPa yield · 93 HRB
- H06Step between hard and spring temper for flat springs with only straight-line forming.560 MPa yield · 91 HRB
- H04Use for high-strength flat stock, hard-drawn wire and rod where forming is limited to gentle bends.515 MPa yield · 87 HRB
- H02Most common general-purpose strip temper for stamped parts needing strength plus mild bending.415 MPa yield · 78 HRB
- H01Compromise temper when moderate strength must survive a fairly sharp form.310 MPa yield · 60 HRB
- M20Mill-condition hot-rolled C51000 phosphor bronze plate/bar: soft, ductile and highly formable, with strength only slightly above the fully annealed state.180 MPa yield · 70 HB
- O60Fully recrystallised soft-anneal temper per ASTM B601 O60, giving the lowest strength and maximum ductility for deep drawing, bending and forming of C51000 strip, wire and rod.140 MPa yield · 60 HB
Working with C51000-M20
Is C51000 easy to machine?
Gummy and abrasive to tooling — rating ~20 % of free-cutting brass; use sharp positive-rake carbide, high speed, light feed and good coolant, or switch to C54400 for turned parts.
Can C51000 be welded?
Best joined by soft soldering (excellent) or brazing/GTAW with phosphor-bronze filler; oxyacetylene welding is not recommended and hot-short cracking plus tin oxide inclusions must be controlled.
Can C51000 be formed, bent or molded?
Excellent cold formability in O/H01 tempers (deep draws, coining); harder tempers need generous bend radii, grain-direction control and a 175–230 °C stress-relief bake after forming to limit springback and relaxation.
What surface finishes work on C51000?
Not anodizable; takes bright tin, nickel, silver and gold plating readily, buffs to a warm bronze luster, and may be chemically blackened or lacquered for decorative use.
C51000 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 |
|---|---|---|
| Sn | 4.2 – 5.8 | 5 |
| Pdeoxidizer, raises strength | 0.03 – 0.35 | 0.15 |
| Zn | ≤ 0.3 | — |
| Fe | ≤ 0.1 | — |
| Pb | ≤ 0.05 | — |
| CuCu + named elements 99.5 % min; Ag counted as Cu | balance | — |
C51000-M20 — frequently asked
What is C51000-M20 used for?
C51000-M20 is typically used for electrical connector contacts, precision strip springs and spring clips, switch and relay blades, diaphragms, bellows and fasteners and washers. In short: best spring-tempered bronze.
What is the yield strength of C51000-M20?
C51000-M20 has a typical yield strength of 180 MPa (26.1 ksi) and a tensile strength of 350 MPa (50.8 ksi) — weaker than 58% of copper alloy grades. Strength varies by condition: see the 9 listed tempers.
Is C51000-M20 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 66% of copper alloy grades). Gummy and abrasive to tooling — rating ~20 % of free-cutting brass; use sharp positive-rake carbide, high speed, light feed and good coolant, or switch to C54400 for turned parts.
Can C51000-M20 be welded?
With care — weldability is rated fair (45/100). Best joined by soft soldering (excellent) or brazing/GTAW with phosphor-bronze filler; oxyacetylene welding is not recommended and hot-short cracking plus tin oxide inclusions must be controlled.
What surface finishes work on C51000-M20?
Not anodizable; takes bright tin, nickel, silver and gold plating readily, buffs to a warm bronze luster, and may be chemically blackened or lacquered for decorative use.
Can C51000-M20 be formed, bent or molded?
Excellent cold formability in O/H01 tempers (deep draws, coining); harder tempers need generous bend radii, grain-direction control and a 175–230 °C stress-relief bake after forming to limit springback and relaxation.
What is the maximum service temperature of C51000-M20?
C51000-M20 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C51000-O and C51000-H10?
O is the default condition — pick for deep drawing, severe bending or forming before a final stress-relief/age. H10: maximum-strength strip for the highest contact forces in thin gauges; forming essentially limited to flat blanking. Yield strength is 140 MPa in O versus 630 MPa in H10.
Can FabDigit make parts in C51000-M20?
Yes — C51000-M20 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM B103/B103M — Phosphor Bronze Plate, Sheet, Strip and Rolled Bar — ASTM International (2019)
- ASTM B139/B139M — Phosphor Bronze Rod, Bar and Shapes — ASTM International (2017)
- C51000 alloy datasheet — Copper Development Association (copper.org) (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- EN 1654 / CW451K CuSn5 strip for springs and connectors — CEN (2019)
- GB/T 2059 / GB/T 2049 (2017)
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.