1. What is Material Grade C36000?
Material grade C36000 is a standardized free-cutting brass alloy defined by ASTM International under specification ASTM B16/B16M (Standard Specification for Free-Cutting Brass Rod, Bar, and Wire for Machined Parts). It is part of the ASTM "C-series" designations for copper alloys, where:
The letter "C" denotes a copper alloy;
The first three digits ("360") identify the specific alloy family (free-cutting brass with a precise copper-zinc-lead ratio);
The trailing two zeros ("00") indicate "standard purity" (no intentional variations in key elements like lead or zinc).
C36000 is renowned as the industry benchmark for free-cutting brass (with a machinability rating of 100%), thanks to its unique composition that balances exceptional machining performance, moderate strength, and good ductility. It is widely used to produce high-volume, precision-machined parts (e.g., nuts, bolts, plumbing fittings, electrical terminals) that require tight tolerances and smooth surface finishes. In casual industry terminology, C36000 is often shortened to "C360 brass"-the two terms refer to the exact same material.
2. What is Equivalent to C36000?
C36000 has standardized equivalents in major global material systems, ensuring consistent performance across international manufacturing. These equivalents match C36000's chemical composition, mechanical properties, and free-cutting characteristics. Key equivalents include:
| Standard/Region | Equivalent Grade | Specification Reference | Key Note |
|---|---|---|---|
| ISO (International) | CuZn36Pb3 | ISO 4032 (Brass and bronze rods, bars and sections) | "CuZn36" indicates 36% zinc; "Pb3" indicates 3% lead-mirroring C36000's core composition. |
| EN (European) | CW614N | EN 12164 (Copper and copper alloys - Rod, bar and wire for general purposes) | The most common European equivalent, used in automotive, electrical, and hardware applications. |
| JIS (Japanese) | C3601 | JIS H3250 (Brass plates, sheets and strips) / JIS H3300 (Brass rods) | Nearly identical to C36000; minor differences in lead content (2.0–3.5% vs. C36000's 2.5–3.7%) are negligible for most uses. |
| BS (British, obsolete) | CZ121 | Former BS 2874 (Copper and copper alloys - Rod, bar and wire) | Replaced by EN CW614N but still referenced in older designs; composition matches C36000. |
| DIN (German, obsolete) | CuZn36Pb3 | Former DIN 17660 (Copper and copper alloys - Rods and bars) | Now aligned with EN CW614N but retains the "CuZn36Pb3" designation, which is directly equivalent to C36000. |
Notably, these equivalents are "functionally interchangeable" for most applications (e.g., machining, general corrosion resistance), though minor regional variations in impurity limits may exist. Always confirm compatibility with specific application standards (e.g., aerospace, medical) if strict compliance is required.
3. What is the Chemical Composition of C36000?
The chemical composition of C36000 is strictly regulated by ASTM B16/B16M to ensure its signature free-cutting performance and consistent mechanical properties. The key elements and their weight percentage ranges are:
| Element | Weight Percentage Range | Role and Significance |
|---|---|---|
| Copper (Cu) | 60.0–63.0% | Base metal: Provides ductility, moderate corrosion resistance, and structural stability-critical for forming and service durability. |
| Zinc (Zn) | Remainder (~35.0–38.0%) | Primary alloying element: Boosts strength and hardness while reducing material cost; balances copper's softness to improve machinability. |
| Lead (Pb) | 2.5–3.7% | Free-cutting additive: Reduces friction between the alloy and cutting tools, prevents "galling" (tool sticking), and produces small, brittle chips that are easy to clear-this is what makes C36000 ideal for high-speed machining. |
| Iron (Fe) | Maximum 0.35% | Controlled impurity: Limited to avoid brittleness and minimize tool wear (excess iron forms hard particles that scratch cutting tools). |
| Nickel (Ni) | Maximum 0.50% | Minor impurity: No intentional addition (trace amounts come from raw materials but do not affect performance). |
| Other Impurities | Maximum 0.50% (total) | Includes elements like tin (Sn) or aluminum (Al); strictly limited to maintain composition consistency and prevent degradation of machinability or ductility. |
4. What is the Hardness of C36000?
The hardness of C36000 depends on its processing state (annealed, cold-worked, or as-cast), as cold working strains the alloy's crystal structure to increase hardness (at the cost of ductility). Below are typical hardness values for C36000 in its most common states, measured using the Brinell Hardness Test (HB)-the standard for brass alloys:
| Processing State | Typical Brinell Hardness (HB) | Key Context |
|---|---|---|
| Annealed | ~80–90 HB | Most common state for C36000. Annealing (heating to 600–700°C, then slow cooling) relieves internal stress, maximizes ductility, and ensures consistent, moderate hardness-ideal for machining parts that may need post-machining forming (e.g., bending small fittings). |
| Light Cold-Worked | ~100–110 HB | Achieved via minor cold working (e.g., light rolling or drawing). Hardness increases slightly to improve wear resistance, while retaining enough ductility for applications like electrical terminals. |
| Heavy Cold-Worked | ~120–140 HB | Result of significant cold working (e.g., heavy drawing or stamping). Maximizes hardness and strength for high-wear parts (e.g., heavy-duty fasteners), though ductility is reduced. |
For reference, annealed C36000 (~80–90 HB) is softer than stainless steel (e.g., 316 SS: ~150–180 HB) but harder than pure copper (~30–40 HB)-a balance that enables easy machining while ensuring finished parts withstand typical service loads without deformation. When specifying C36000, hardness is often tied to processing state, with annealed material being the default for most machining needs.
