Copper Alloy C51900 H08-SR
Heat-treated state
UNS C51900 · EN CuSn6, CW452K
Pick for formed springs that must hold load: a 180–230 °C bake raises the elastic limit and cuts stress relaxation.
Values for the H08-SR condition
Other C51900 tempers and conditions
C51900 is listed in 10 conditions; see the grade overview at C51900.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Soft annealed | Pick for deep drawing, severe forming or coining before final heat treatment. | 180 | 380 | 60 | 95 HB | — |
Quarter hard | Pick when moderate bending or forming is still needed but higher strength than annealed is wanted. | 340 | 450 | 35 | 128 HB | 15 % IACS |
Light-drawn wire/rod | Pick for wire and small rod that must still be coiled or headed after drawing. | 400 | 500 | 22 | 150 HB | 15 % IACS |
H02Default Half hard | Default stocked strip temper: balanced strength and bendability for contacts, clips and washers. | 450 | 520 | 20 | 155 HB | 15 % IACS |
Full hard | Pick for flat springs and contacts with only gentle bends, where higher elastic limit matters. | 530 | 600 | 10 | 175 HB | 14.5 % IACS |
Extra hard | Pick where near-spring strength is needed but full spring temper is too brittle to form. | 590 | 655 | 7 | 193 HB | 14 % IACS |
Spring hard | Standard temper for connector springs, diaphragms and clips loaded in bending fatigue. | 630 | 695 | 5 | 200 HB | 14 % IACS |
Extra spring hard | Highest cold-rolled strength; use for flat springs bent only along the rolling direction. | 670 | 730 | 3 | 210 HB | 14 % IACS |
H08-SRThis page spring temper, stress-relieved (low-temperature bake) | Pick for formed springs that must hold load: a 180–230 °C bake raises the elastic limit and cuts stress relaxation. | 670 | 710 | 5 | 19 HRC | 14 % IACS |
Hard drawn | Pick for helical compression/extension springs and woven mesh needing maximum wire strength. | 690 | 760 | 4 | 218 HB | 14 % IACS |
What is C51900 H08-SR?
C51900 H08-SR is C51900 heat treated to H08-SR — pick for formed springs that must hold load: a 180–230 °C bake raises the elastic limit and cuts stress relaxation. C51900 H08-SR has a yield strength of 670 MPa (97.2 ksi) and a tensile strength of 710 MPa (103 ksi) — stronger than 96% of copper alloy grades. Elongation at break is 5% and the elastic modulus is 117 GPa (17 Msi). C51900 H08-SR has a density of 8.8 g/cm³ (0.318 lb/in³), heavier than 58% of copper alloy grades. It melts at 910°C (1,670 °F). H02 is the default condition FabDigit quotes; H08-SR is available on request or by drawing note.
Advantages
- High strength — 670 MPa (97.2 ksi), better than 96% of copper alloy grades
Limitations
- Limited service temperature — 150°C (302 °F), worse than 96% of copper alloy grades
- Limited ductility — 5%, worse than 93% of copper alloy grades
- Limited formability — 15/100, worse than 79% of copper alloy grades
C51900 H08-SR properties
Typical room-temperature values for C51900 H08-SR; 19 are specific to this condition. Other listed values are C51900 reference data and may not represent this condition. Bars are the position among copper alloy grades.
Physical3
C51900 H08-SR has a density of 8.8 g/cm³ (0.318 lb/in³), heavier than 58% of copper alloy grades. It melts at 910°C (1,670 °F).
Mechanical14
C51900 H08-SR has a yield strength of 670 MPa (97.2 ksi) and a tensile strength of 710 MPa (103 ksi) — stronger than 96% of copper alloy grades. Elongation at break is 5% and the elastic modulus is 117 GPa (17 Msi).
Thermal6
C51900 H08-SR is rated for continuous service to 150°C (302 °F). It conducts heat at 67 W/m·K (38.7 BTU/hr·ft·°F), worse than 56% of copper alloy grades. Thermal expansion is 18.5 µm/m·K (10.3 µin/in·°F).
Electrical3
C51900 H08-SR conducts electricity at 14 % IACS, worse than 56% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 69% of copper alloy grades.
Sustainability4
Producing a kilogram of C51900 H08-SR takes about 62 MJ of energy and emits 4.2 kg of CO₂ — more than 76% of copper alloy grades. Typical recycled content is 40%.
Manufacturability7
C51900 H08-SR's machinability is poor (30/100, worse than 67% of copper alloy grades); weldability poor (30/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C51900 H08-SR
Is C51900 easy to machine?
Machinability only ~20 % of free-cutting brass — gummy, work-hardening chips; use sharp positive-rake tools, high speed, light feeds and flood coolant.
Can C51900 be welded?
Solder and braze excellently and resistance-weld well; oxyacetylene and TIG/MIG welding are poor because of tin oxide and hot-shortness, so avoid fusion joints in springs.
Can C51900 be formed, bent or molded?
Excellent cold formability in O60/H01; hard and spring tempers must be bent with the bend axis transverse to rolling and often need a 180–230 °C post-form stress relief to set the shape.
What surface finishes work on C51900?
Not anodizable; readily electroplated with tin, nickel, silver or gold after cyanide-free cleaning, and polishes to a bright bronze finish (bright-dip or lacquer to stop tarnish).
C51900 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 | 5 – 7 | 6 |
| Pdeoxidizer; raises strength | 0.03 – 0.35 | 0.2 |
| Zn | ≤ 0.3 | — |
| Fe | ≤ 0.1 | — |
| Pb | ≤ 0.05 | — |
| CuCu + named elements 99.5 % min | balance | — |
C51900 H08-SR — frequently asked
What is C51900 H08-SR used for?
C51900 H08-SR is typically used for springs & contacts, connectors and bushings. In short: spring-grade phosphor bronze.
What is the yield strength of C51900 H08-SR?
C51900 H08-SR has a typical yield strength of 670 MPa (97.2 ksi) and a tensile strength of 710 MPa (103 ksi) — stronger than 96% of copper alloy grades. Strength varies by condition: see the 10 listed tempers.
Is C51900 H08-SR easy to machine?
Not especially — machinability is rated poor (30/100, worse than 67% of copper alloy grades). Machinability only ~20 % of free-cutting brass — gummy, work-hardening chips; use sharp positive-rake tools, high speed, light feeds and flood coolant.
Can C51900 H08-SR be welded?
Not readily — weldability is rated poor (30/100). Solder and braze excellently and resistance-weld well; oxyacetylene and TIG/MIG welding are poor because of tin oxide and hot-shortness, so avoid fusion joints in springs.
What surface finishes work on C51900 H08-SR?
Not anodizable; readily electroplated with tin, nickel, silver or gold after cyanide-free cleaning, and polishes to a bright bronze finish (bright-dip or lacquer to stop tarnish).
Can C51900 H08-SR be formed, bent or molded?
Excellent cold formability in O60/H01; hard and spring tempers must be bent with the bend axis transverse to rolling and often need a 180–230 °C post-form stress relief to set the shape.
What is the maximum service temperature of C51900 H08-SR?
C51900 H08-SR is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C51900-H02 and C51900-O60?
H02 is the default condition — default stocked strip temper: balanced strength and bendability for contacts, clips and washers. O60: pick for deep drawing, severe forming or coining before final heat treatment. Yield strength is 450 MPa in H02 versus 180 MPa in O60.
Can FabDigit make parts in C51900 H08-SR?
Yes — C51900 H08-SR is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. 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)
- EN 1654 / EN 1652 — Copper and copper alloys, strip for springs and connectors (CuSn6, CW452K) — CEN (2019)
- GB/T 2059 / GB/T 2040 — (QSn6.5-0.1) — SAC (2017)
- C51900 alloy datasheet — Copper Development Association (copper.org) (2023)
- CuSn6 Werkstoff-Datenblatt — Deutsches Kupferinstitut (2005)
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys — 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.