1. Hardness Units for Copper Alloys
Hardness of copper alloys is primarily measured using three standardized units, selected based on testing methods, application scenarios (e.g., quality control, material selection), and industry standards (ASTM, ISO, JIS):
| Testing Method | Unit Symbol | Definition & Application Scenario |
|---|---|---|
| Brinell Hardness (HB) | HB | Measured by pressing a hardened steel ball (10 mm diameter) into the material with a 3000 kgf load for 10-30 seconds. Suitable for soft to medium-hard copper alloys (e.g., pure copper, low-zinc brass) due to its large indentation area, which minimizes the impact of surface roughness. |
| Rockwell Hardness (HR) | HRB/HRC | - HRB: Uses a 1/16" (1.588 mm) steel ball indenter with a 100 kgf load. Ideal for medium-hard copper alloys (e.g., C26000 cartridge brass, C60600 aluminum bronze).
- HRC: Uses a conical diamond indenter with a 150 kgf load. Rarely used for copper alloys (reserved for high-hardness materials like quenched steel), but may apply to fully heat-treated high-strength copper-nickel alloys. |
| Vickers Hardness (HV) | HV | Uses a square-based diamond pyramid indenter with variable loads (10-1000 gf). Suitable for all copper alloy types, especially thin sheets, small components, or materials with uneven hardness (e.g., C17200 beryllium copper after heat treatment). Offers high precision and wide applicability across hardness ranges. |
2. Typical Hardness Ranges of Common Copper Alloy Grades
Hardness values below are based on annealed (O) or half-hard (H24) tempers (most common for industrial applications), referenced to ASTM B301 (brass), ASTM B124 (bronze), and ASTM B194 (copper-nickel) standards. Values may vary by heat treatment, cold working, and manufacturer processing.
| Alloy Grade | Common Name | Hardness Range (Annealed/O) | Hardness Range (Half-Hard/H24) | Testing Method | Key Notes |
|---|---|---|---|---|---|
| C11000 | Electrolytic Tough Pitch (ETP) Copper | HB 30-40 / HV 35-45 | HB 60-80 / HV 65-85 | HB/HV | Pure copper (99.9% Cu); soft, high conductivity; used in electrical components. |
| C26000 | Cartridge Brass (70Cu-30Zn) | HB 50-70 / HV 55-75 | HB 100-130 / HV 105-135 | HRB/HV | Most widely used brass; good formability and machinability; used in valves, fittings. |
| C28000 | Muntz Metal (60Cu-40Zn) | HB 60-80 / HV 65-85 | HB 120-150 / HV 125-155 | HRB/HV | Higher zinc content than C26000; stronger but less ductile; used in marine hardware. |
| C36000 | Free-Cutting Brass (61.5Cu-35.5Zn-3Pb) | HB 70-90 / HV 75-95 | HB 110-140 / HV 115-145 | HRB | Lead-containing for improved machinability; used in screws, nuts, and precision parts. |
| C60600 | Aluminum Bronze (90Cu-10Al) | HB 100-130 / HV 105-135 | HB 180-220 / HV 185-225 | HB/HRC | High strength and corrosion resistance; used in gears, bearings, and marine propellers. |
| C63000 | Nickel-Aluminum Bronze (85Cu-9Al-4Ni-2Fe) | HB 140-180 / HV 145-185 | HB 220-260 / HV 225-265 | HB/HRC | Superior wear resistance; used in pump impellers and industrial valves. |
| C71500 | Copper-Nickel (70Cu-30Ni) | HB 80-100 / HV 85-105 | HB 130-160 / HV 135-165 | HB/HV | Excellent corrosion resistance in seawater; used in ship hulls and heat exchangers. |
| C17200 | Beryllium Copper (98Cu-1.9Be-0.1Co) | HB 90-120 / HV 95-125 (Annealed) | HB 300-350 / HV 310-360 (Heat-Treated) | HV/HRC | Heat-treatable to high hardness; used in springs, electrical contacts, and aerospace components. |
| C51000 | Phosphor Bronze (95Cu-5Sn) | HB 80-110 / HV 85-115 | HB 150-180 / HV 155-185 | HB/HV | High fatigue strength; used in springs, washers, and musical instruments. |
