ASTM B505 Tin Bronze UNS C90300 Tube & Rod

C90300 is a designation for a type of Tin Bronze casting alloy, also commonly known by its historical name, “Navy G” Bronze (or SAE 620).

It’s a high-strength, wear-resistant alloy with good corrosion resistance, making it suitable for heavy-duty, low-speed applications.

C90300 is a highly durable Tin Bronze alloy, commonly available in rod and tube (hollow bar) forms, and is widely used for components requiring high strength, excellent wear resistance, and good corrosion resistance.

Its low lead content ( $Pb$ max $0.30%$ ) also makes it suitable for many modern plumbing and potable water applications.

Key Characteristics and Composition

Alloy Type: High Tin Bronze, part of the Copper-Tin (Cu-Sn) alloy family.
Key Properties:
- High Strength: Possesses good tensile, yield, and compressive strength.
- Wear Resistance: Highly resistant to wear and impact.
- Corrosion Resistance: Offers good resistance to corrosion, especially in saltwater (marine) and potable water applications.
- Machinability: Has a moderate machinability rating (typically $30%$ of free-cutting brass).

Approximate Nominal Chemical Composition (by weight):

Copper ( $Cu$ ): $\approx 87.5%$ (range of $86.0%$ to $89.0%$ )
Tin ( $Sn$ ): $\approx 8.3%$ (range of $7.5%$ to $9.0%$ )
Zinc ( $Zn$ ): $\approx 4.0%$ (range of $3.0%$ to $5.0%$ )

Lead ( $Pb$ ): Max

0.30%

(making it a lead-free option for many modern applications, including potable water systems)

Key Properties and Composition

Property	Value (Continuous Cast, Min.)	Comment
UNS Designation	C90300	Also known as Navy G or SAE 620.
Nominal Composition	Cu $87.5%$ , Sn $8.3%$ , Zn $4.0%$	High Tin content provides strength and corrosion resistance.
Lead Content ( $Pb$ )	$0.30%$ max	Considered “lead-free” for most potable water standards.
Tensile Strength	$44 ksi$ ( $303 MPa$ )	Provides high structural integrity.
Yield Strength	$22 ksi$ ( $152 MPa$ )	Excellent for load-bearing parts.
Brinell Hardness	$70 BHN$ (typical)	Indicates good wear resistance.
Machinability Rating	$30%$	Moderate, compared to free-cutting brass ( $100%$ ).

Applications for Rod and Tube

The primary use of C90300 rod (solid bar) and tube (hollow bar) is for machining into critical wear and pressure-tight components. Rods are used for solid components, and tubes are used to minimize material waste when producing bushings or rings.

Component Type	Application Details
Bearings & Bushings	Used in heavy-load, low-speed applications (e.g., machinery, construction equipment, bridge bearings, trunnion bearings). Its high wear resistance and low coefficient of friction are key.
Gears	Ideal for industrial gears and worm wheels due to its strength and ability to withstand heavy loads and impacts.
Valve/Pump Parts	Used for valve bodies, stems, pump impellers, and steam fittings due to its pressure tightness and corrosion resistance, particularly in marine and potable water systems.
Seal Rings	Used where good wear resistance and low friction are required in sealing applications.

Fabrication

C90300 is readily fabricated using several common joining techniques, although specific care is needed for brazing:

Soldering: Excellent suitability.
Brazing: Good suitability (requires care to avoid strain and cool slowly, as it is performed within the hot-short range).
Welding (Arc/Gas Shielded): Fair suitability.
Casting Methods: Rod and tube are typically made via Continuous Cast (ASTM B505) or Centrifugal Cast (ASTM B271) methods to ensure a dense, high-quality structure.