Four Families and Three Designation Systems
The four families of copper material are separated by which element is deliberately added to the copper base. Pure copper, also called red copper, keeps copper above roughly 99.7 % and is designated T, TU, TP or TUP in China. Brass adds zinc and is designated H, as in H62 and H65. Bronze adds a principal element that is neither zinc nor nickel, mainly tin, aluminium or silicon, and is designated Q, as in QSn6.5-0.1. Cupronickel adds nickel and is designated B, as in BFe10-1-1. The same materials are known internationally by the five-digit numbers of the Unified Numbering System, where C11000 is electrolytic tough pitch copper, C27200 is 63 % brass, C51000 is 5 % tin phosphor bronze and C70600 is 90-10 cupronickel. European practice uses the EN 1412 numbering system with symbols such as Cu-ETP, CuZn37 and CuNi10Fe1Mn. The three systems are not mechanically interchangeable: the same chemistry can carry different designations, and the composition limits in GB/T 5231, ASTM B152/B152M, ASTM B36/B36M, ASTM B103/B103M, ASTM B122/B122M and EN 1412 must be read from the actual standard before a substitution is approved.
Chemistry That Separates the Families
| Material | Chinese designation | UNS number | Principal composition |
|---|---|---|---|
| Pure copper | T2 | C11000 | Cu 99.90 % min, oxygen 0.02-0.04 % |
| Brass | H62 | C27200 | Cu 60.5-63.5 %, Zn balance |
| Phosphor bronze | QSn6.5-0.1 | C5191 type | Sn 6.0-7.0 %, P 0.10-0.25 %, Cu balance |
| Aluminium bronze | QAl10-4-4 | C63000 type | Al about 10 %, Fe and Ni additions |
| Cupronickel | BFe10-1-1 | C70600 | Ni 9.0-11.0 %, Fe 1.0-1.8 %, Cu balance |
| Cupronickel | BFe30-1-1 | C71500 | Ni 29-33 %, Fe 0.4-1.0 %, Cu balance |
Property Comparison
| Property | Pure copper | H62 brass | Phosphor bronze | 90-10 cupronickel |
|---|---|---|---|---|
| Density, g/cm3 | 8.96 | 8.43 | 8.86 | 8.94 |
| Electrical conductivity, % IACS | 100-101 | 27-28 | about 15 | about 9 |
| Tensile strength, soft temper | 220-260 MPa | 340-430 MPa | 310-380 MPa | 275-380 MPa |
| Tensile strength, hard temper | 300-380 MPa | 520-620 MPa | 640-720 MPa | 480-550 MPa |
| Colour | reddish | yellow | dull gold | silvery white |
| Best-known strength | conductivity | formability and cost | spring and wear | seawater corrosion |
These are typical values for material in the stated temper rather than guaranteed minima, and they illustrate why substitution across families almost always requires requalification of the part.
How to Choose Between Them
Selection follows the dominant requirement. If the part must carry current with minimum loss, pure copper is the only sensible answer, and the choice reduces to oxygen content and temper. If the part must be formed deeply, spun or flanged at low cost, brass is the practical choice, with higher copper content giving better cold ductility. If the part must act as a spring, contact or wear surface, phosphor bronze or a related tin bronze is used because it holds load over many cycles. If the part must survive chlorides and fast water flow, cupronickel takes over: 90-10 material is the workhorse, and 70-30 cupronickel is chosen for higher flow velocities and higher pressures. Where high strength and wear resistance are combined with seawater exposure, aluminium bronze is used instead, at the cost of poorer conductivity and machinability.
Identification and Incoming Inspection
Colour gives a first indication only and cannot be relied upon for acceptance. Practical identification combines density measurement, magnetic response, spark or chip appearance during machining, and above all instrumental analysis. Standard practice is spectrometric chemical analysis to GB/T 5121 or ASTM E478, tensile testing to ASTM E8, hardness to ASTM E18, and electrical conductivity by eddy-current testing to ASTM E1004, with resistivity measured to ASTM B193 where a certificate value must be reproduced. For coins and similar legacy parts, the historical position is that copper coins were cast from the alloys available at the time: yellow coins were copper-zinc alloys, blue or grey-green coins were copper-tin alloys, and later periods used brass in place of bronze. Modern coinage and token blanks are ordered to a defined alloy rather than to a colour, and the same instrumental verification applies.
Frequently Asked Questions
Q: Is red copper always pure copper?
A: The term covers material with copper above about 99.7 %, but grades such as TP2 contain deliberate phosphorus additions and remain classified in the pure copper group.
Q: What is the difference between brass and bronze?
A: Brass is a copper-zinc alloy, while bronze is a copper alloy whose principal addition is neither zinc nor nickel, most commonly tin, aluminium or silicon.
Q: Which of the four families conducts electricity best?
A: Pure copper, at 100-101 % IACS; H62 brass reaches 27-28 %, phosphor bronze about 15 % and 90-10 cupronickel about 9 %.
Q: How can cupronickel be distinguished from stainless steel in the warehouse?
A: By density, which is about 8.9 g/cm3 for cupronickel against about 7.9 g/cm3 for austenitic stainless steel, and by spectrometric analysis, which is the acceptance test in any dispute.
Q: Which family should be used for a seawater pipeline?
A: Cupronickel BFe10-1-1 (C70600) for general seawater service, BFe30-1-1 (C71500) where higher velocity and pressure apply, or aluminium bronze where wear resistance dominates.
