C26800 brass, also known as 60/40 yellow brass, is a two-phase alpha-beta copper-zinc alloy that has become a cornerstone of precision engineering and CNC machining. Its unique metallurgical structure—combining a ductile alpha phase with a harder beta phase—delivers an exceptional balance of mechanical strength, corrosion resistance, and machinability. With a nominal composition of 60–63% copper and the balance zinc, this alloy offers a tensile strength range of 380–650 MPa depending on temper, making it ideal for components from electrical connectors to marine hardware. At Dongguan Stirling Metal Products Co., Ltd., we combine over 15 years of metallurgical expertise with advanced CNC machining capabilities to produce C26800 parts that consistently meet or exceed ASTM B36/B36M and SAE J461 standards.
1. C26800 Basic Information
C26800 is classified as a duplex brass, containing both alpha (face-centered cubic) and beta (body-centered cubic) phases. This dual-phase structure provides a unique combination of high strength and excellent hot workability, with a nominal copper content of 60–63% ensuring optimal phase balance. The alloy is commonly supplied in rod, bar, sheet, and tube forms, with typical tempers including half-hard (H02), hard (H04), and spring hard (H06). Its density of 8.4 g/cm³ and moderate melting point of approximately 920°C make it suitable for a wide range of forming and machining operations. The beta phase content, which increases with lower copper levels, enhances hot workability and machinability but reduces ductility, making C26800 particularly well-suited for high-speed CNC machining where chip control is critical.
2. Chemical Composition
The precise chemical composition of C26800 is critical to its performance, as even minor deviations can significantly alter mechanical properties and corrosion resistance. The following table provides the standard composition ranges as per ASTM B36/B36M and SAE J461 specifications:
| Element | Content (%) | Role in Alloy |
|---|---|---|
| Copper (Cu) | 60.0 – 63.0 | Primary alloying element; provides strength and corrosion resistance; controls alpha/beta phase ratio |
| Zinc (Zn) | Balance | Strengthens via solid solution; improves machinability and reduces cost |
| Iron (Fe) | ≤ 0.15 | Refines grain structure; limits to avoid brittleness and intergranular corrosion |
| Lead (Pb) | ≤ 0.08 | Trace impurity; higher levels degrade ductility and hot workability |
| Tin (Sn) | ≤ 0.05 | Minor addition for corrosion resistance, especially in marine environments |
| Nickel (Ni) | ≤ 0.05 | Trace element; stabilizes beta phase and improves strength |
| Other Elements (Total) | ≤ 0.15 | Includes Al, Si, Mn, etc.; controlled to avoid adverse effects on properties |
Note: The copper content is tightly controlled between 60–63% to maintain the optimal alpha-beta phase balance. Lower copper (<60%) increases beta phase content, enhancing hot workability but reducing ductility and corrosion resistance. Higher copper (>63%) shifts toward single-phase alpha brass, improving cold formability but reducing strength and machinability. For CNC machining, a copper content of 61–62% is often preferred to maximize chip breakage and tool life.
3. Mechanical & Physical Properties
C26800 exhibits a robust set of mechanical and physical properties that make it suitable for demanding applications. The following tables provide comprehensive data for typical tempers, based on ASTM B36/B36M and internal testing at Dongguan Stirling Metal Products Co., Ltd.:
Mechanical Properties (Typical Values at Room Temperature)
| Property | Half-Hard (H02) | Hard (H04) | Spring Hard (H06) | Unit |
|---|---|---|---|---|
| Tensile Strength (Rm) | 380 – 450 | 450 – 550 | 550 – 650 | MPa |
| Yield Strength (Rp0.2) | 160 – 250 | 250 – 350 | 350 – 450 | MPa |
| Elongation (A50) | 35 – 45 | 15 – 25 | 5 – 10 | % |
| Hardness (Rockwell B) | 60 – 75 | 75 – 90 | 90 – 100 | HRB |
| Hardness (Vickers) | 110 – 140 | 140 – 170 | 170 – 200 | HV |
| Modulus of Elasticity | 105 | 105 | 105 | GPa |
| Poisson’s Ratio | 0.34 | 0.34 | 0.34 | – |
| Shear Strength | 240 – 280 | 280 – 340 | 340 – 400 | MPa |
| Fatigue Strength (10⁷ cycles) | 120 – 150 | 150 – 180 | 180 – 210 | MPa |
Physical Properties
| Property | Value | Unit |
|---|---|---|
| Density | 8.4 | g/cm³ |
| Melting Point (Liquidus) | 920 | °C |
| Melting Point (Solidus) | 895 | °C |
| Thermal Conductivity (at 20°C) | 120 | W/m·K |
| Electrical Conductivity (at 20°C) | 26 | %IACS |
| Specific Heat Capacity | 380 | J/kg·K |
| Thermal Expansion Coefficient (20–300°C) | 20.5 × 10⁻⁶ | /°C |
| Electrical Resistivity (at 20°C) | 6.6 × 10⁻⁸ | Ω·m |
| Magnetic Permeability | < 1.01 | µ (non-magnetic) |
Note: Mechanical properties vary significantly with temper. For CNC machining, half-hard (H02) or hard (H04) tempers are most commonly specified, as they offer an optimal balance of strength and chip formation characteristics. The spring hard (H06) temper is used for applications requiring high elastic limits, such as springs and clips.
4. Corrosion Resistance
C26800 demonstrates excellent corrosion resistance in a variety of environments, though its performance is inferior to that of higher-copper brasses (e.g., C26000, C28000) in highly aggressive media. Key performance data based on ASTM G1 and field testing:
- Atmospheric Environment: Outstanding resistance to rural, industrial, and marine atmospheres. Corrosion rate typically < 0.5 µm/year in rural atmospheres and < 2 µm/year in marine atmospheres. In industrial environments with SO₂ exposure, a protective patina forms, reducing corrosion to < 1 µm/year.
- Fresh Water: Excellent resistance in potable water and most fresh water systems. Corrosion rate < 1 µm/year at flow rates up to 2 m/s. In soft water (low hardness), dezincification may occur; use of inhibited grades (e.g., C26800 with 0.02–0.05% As) is recommended.
- Seawater: Good resistance in static or low-flow seawater (corrosion rate 5–15 µm/year). Susceptible to dezincification in stagnant or high-temperature seawater (>60°C). For continuous immersion, a corrosion allowance of 0.5–1.0 mm is recommended.
- Acids and Alkalis: General corrosion resistance in dilute acids (pH > 4) and alkalis (pH < 11). Not recommended for concentrated sulfuric (>50%), nitric (>10%), or hydrochloric acids (>5%). In dilute sulfuric acid (pH 2–4), corrosion rate is 20–50 µm/year.
- Stress Corrosion Cracking (SCC): Susceptible to SCC in ammonia-containing environments, particularly under tensile stress. Stress relief annealing at 250–300°C for 1 hour is recommended for components under tensile stress > 50% of yield strength. In ammonia-free environments, SCC is rare.
For applications requiring enhanced corrosion resistance, surface treatments such as chromate conversion coating (MIL-DTL-5541, Type II) or electroless nickel plating (AMS 2404, 25–50 µm thickness) are commonly applied. At Dongguan Stirling Metal Products Co., Ltd., we offer in-house surface finishing to meet specific environmental requirements.
5. Typical Applications
C26800’s combination of strength, machinability, and corrosion resistance makes it suitable for a diverse range of industries. The following table summarizes key applications and material requirements:
| Industry | Application | Key Requirements | Typical Temper |
|---|---|---|---|
| Electrical | Connectors, terminals, switchgear components, busbars | Electrical conductivity (26% IACS), machinability, strength | H02, H04 |
| Shipbuilding | Propellers, valve bodies, pump impellers, heat exchanger tubes | Corrosion resistance in seawater, strength, weldability | H02, annealed |
| Automotive | Radiator cores, oil cooler tubes, carburetor parts, brake components | Thermal conductivity, formability, corrosion resistance | H02, H04 |
| Watch Parts | Precision gears, pinions, decorative bezels | Excellent machinability, tight tolerances (±0.005 mm), aesthetic finish | H02 |
| Lock Hardware | Lock cylinders, keys, latch mechanisms | Wear resistance, machinability, dimensional stability | H04, H06 |
| CNC Machining Parts | Medical devices, aerospace fittings, industrial automation components | High machinability, tight tolerances (±0.01 mm), surface finish | H02, H04 |
| Plumbing | Faucet bodies, valves, pipe fittings | Corrosion resistance in potable water, pressure rating | H02, annealed |
In addition to these, C26800 is used in musical instruments (e.g., saxophone keys, trumpet valves), decorative hardware, and architectural fittings where its golden color and corrosion resistance are valued.
6. CNC Machining Performance
C26800 is renowned for its excellent machinability, earning a machinability rating of 80% relative to free-cutting brass (C36000, rated 100%). The following parameters are recommended for optimal CNC machining, based on extensive testing at Dongguan Stirling Metal Products Co., Ltd.:
Recommended Cutting Parameters
| Operation | Cutting Speed (m/min) | Feed Rate (mm/rev) | Depth of Cut (mm) | Tool Material | Coolant Type |
|---|---|---|---|---|---|
| Turning (Roughing) | 150 – 250 | 0.15 – 0.30 | 2.0 – 4.0 | Carbide (K10-K20) | Water-soluble (5-10%) |
| Turning (Finishing) | 200 – 300 | 0.05 – 0.15 | 0.2 – 1.0 | Carbide (K10) or CBN | Oil-based for mirror finish |
| Milling (Roughing) | 120 – 200 | 0.10 – 0.25 (per tooth) | 1.0 – 3.0 | Carbide (K20-K30) | Water-soluble (5-10%) |
| Milling (Finishing) | 180 – 250 | 0.05 – 0.12 (per tooth) | 0.2 – 0.5 | Carbide (K10) or HSS | Oil-based for surface quality |
| Drilling | 80 – 150 | 0.05 – 0.20 | N/A | HSS or Carbide (K20) | Water-soluble (5-10%) |
| Threading | 50 – 100 | 0.10 – 0.20 | N/A | HSS or Carbide | Oil-based |
| Parting/Grooving | 100 – 180 | 0.05 – 0.15 | 1.0 – 3.0 | Carbide (K20) | Water-soluble (5-10%) |
Key Machining Characteristics
- Chip Formation: Produces short, broken chips (favorable for chip evacuation). Use of chip breakers is recommended for high-speed operations. At cutting speeds > 250 m/min, chip length is typically 2–5 mm.
- Coolant: Water-soluble coolant (5–10% emulsion) is recommended to reduce tool wear and improve surface finish. For high-speed operations (>200 m/min), oil-based coolants can extend tool life by 20–30% and achieve surface finishes of Ra < 0.2 µm.
- Surface Finish: Typical Ra values of 0.4–1.6 µm achievable with proper parameters. For mirror finishes (Ra < 0.2 µm), use diamond tools (PCD) with cutting speeds > 300 m/min and feed rates < 0.05 mm/rev.
- Tool Wear: Carbide tools typically achieve 30–60 minutes of cutting time before flank wear reaches 0.3 mm. For high-volume production, PCD (polycrystalline diamond) tools can extend tool life to 200+ hours, reducing downtime and cost per part.
- Work Hardening: Minimal work hardening compared to stainless steels. However, excessive feed rates (>0.3 mm/rev) or dull tools can cause surface hardening (up to 20% increase in hardness), reducing tool life and surface quality.
- Dimensional Tolerances: Typical tolerances of ±0.01 mm are achievable on CNC lathes and machining centers. For high-precision applications, tolerances as tight as ±0.005 mm can be held with proper tooling and machine setup.
7. Why Choose Dongguan Stirling Metal Products Co., Ltd.
Dongguan Stirling Metal Products Co., Ltd. combines over 15 years of metallurgical expertise with state-of-the-art CNC machining capabilities to deliver C26800 components that meet the highest quality standards. Our commitment to precision and reliability is reflected in every project:
- Material Integrity: All C26800 materials are sourced from ISO 9001-certified mills and supplied with full Material Test Certificates (MTC) per EN 10204 3.1. We perform in-house chemical analysis (using OES) and mechanical testing (tensile, hardness, and elongation) to verify compliance with ASTM B36/B36M and customer specifications.
- CNC Machining Excellence: Our facility is equipped with 5-axis CNC machining centers (Mazak, DMG MORI), Swiss-type lathes (Citizen, Star), and multi-spindle automatics (Index, Tornos), capable of holding tolerances as tight as ±0.005 mm. We specialize in complex geometries, thin-wall sections, and high-volume production runs (100–100,000+ pieces).
- Surface Treatment Capabilities: In-house finishing options include mechanical polishing (to Ra 0.1 µm), electropolishing, chromate conversion coating (MIL-DTL-5541, Type II), electroless nickel plating (AMS 2404, up to 50 µm), and passivation. All processes are certified to ISO 9001 and AS9100D.
- Quality Assurance: 100% inspection using CMM (Coordinate Measuring Machines, Zeiss), optical comparators, and surface roughness testers (Mitutoyo). Statistical Process Control (SPC) is implemented for all critical dimensions, with CpK values typically > 1.33.
- Lead Times: Rapid prototyping in 3–5 working days, with production quantities delivered in 7–15 working days. Expedited services available for urgent requirements, with lead times as short as 24 hours for simple parts.
- Cost Efficiency: Our vertical integration—from material procurement to final inspection—reduces supply chain costs by 15–20% compared to traditional subcontracting models. We offer competitive pricing for both low-volume prototypes and high-volume production runs.
Whether you require a single prototype or a high-volume production run, Dongguan Stirling Metal Products Co., Ltd. is your trusted partner for C26800 brass components. Contact us today for a free quote and technical consultation.
