C51100 Bronze

Alloy Designation

C51100 belongs to the Tin-Phosphor Bronze series. Its international common name is CUSn4, conforming to Chinese National Standard GB/T 4423-1992 and American ASTM B103/B103M. With 3.5%-4.5% Sn and 0.20%-0.40% P, this copper-based alloy is industrially recognized as "Pressure Gauge Bronze" or "Instrument Bronze" due to its exceptional mechanical and processing properties.

Key Features

• C51100 phosphor bronze exhibits outstanding physical and mechanical characteristics ideal for precision engineering:

• Optimal Strength-Elasticity Balance: Maintains good plasticity while delivering tensile strength exceeding 410 MPa, making it perfect for elastic components and precision springs.

• Superior Wear Resistance: Low friction coefficient and high resistance to abrasive wear under sliding friction conditions.

• Excellent Corrosion Resistance: Performs well in atmosphere, freshwater, seawater, and various chemical media.

• Special Physical Properties: Non-magnetic, cryogenic toughness (down to -200°C), and spark-free upon impact.

• Favorable Processability: Excellent cold/hot workability for precision forming and forging.

• Versatile Fabrication: Good weldability and brazeability for complex part manufacturing.

Common Forms & Dimensions

Table 1: Product Forms & Specifications

Form	Size Range	Temper	Standard
Sheet/Plate	Thickness: 0.1-100mm Width: 100-2000mm	O60, H02, Y2	ASTM B103
Strip	Thickness: 0.05-2.0mm Width: 10-600mm	H04, H06, H08	GB/T 4423
Bar	Diameter: Ø5-200mm	H02, Y2, T6	ASTM B103
Tube	OD: Ø3-150mm Wall: 0.2-15mm	Annealed, Hard	GB/T 4423
Wire	Diameter: Ø0.1-12mm	Soft, 1/2 Hard	ASTM B103
Forging/Flange	Custom per drawings	Soln.+Aged	–

Chemical Composition

Table 2: Chemical Composition (wt%)

Element	Req.	Typical	Impurity Max	Function
Cu	Bal.	≥95.5	–	Matrix, conductivity
Sn	3.5-4.9	4.0-4.5	–	Strength & corrosion res.
P	0.20-0.40	0.25-0.35	–	Deoxidizer, wear res.
Pb	≤0.05	≤0.02	0.05	Machinability
Fe	≤0.10	≤0.02	0.10	Strength enhancer
Total Impurities	≤0.1	≤0.05	0.1	–

Physical Properties

Table 3: Physical Properties

Property	Value	Condition	Unit
Density	8.86-8.92	20°C	g/cm³
Electrical Conduct.	≥15	Annealed	%IACS
Thermal Conduct.	70-75	20°C	W/(m·K)
CTE	18.0×10⁻⁶	20-300°C	K⁻¹
Elastic Modulus	110-115	Tensile	GPa

Mechanical Properties

Table 4: Mechanical Properties (Room Temp)

Property	Annealed (O60)	1/4 Hard (H02)	Test Std.
Tensile Strength	≥325 MPa	≥410 MPa	ASTM E8
Yield Strength	≥150 MPa	≥350 MPa	ASTM E8
Elongation (δ10)	≥25%	≥12%	GB/T 228.1
Hardness (HV)	80-100	120-150	ASTM E92

(Tables for semi-hard/hard tempers omitted for brevity)

Core Advantages

• 40% higher wear resistance vs. brass

• Superior cold workability with 15-30% pass reduction

• Corrosion rate <0.01 mm/year in harsh environments

• Non-magnetic (μ<1.01) and spark-free

• Excellent weldability and brazeability

Applications

• Elastic components: Springs, contact reeds

• Pressure measurement: Bourdon tubes, sensors

• Wear parts: Bearings, bushings, thrust washers

• Precision instruments: Gears, optical components

• Electrical: Connectors, relay parts

• Chemical: Pump valves, corrosion-resistant parts

Processing Guidelines

Hot working: 750-780°C (avoid >800°C grain growth)

Cold working: 15-30% reduction per pass, intermediate anneal at 600-650°C

Prevent tin inverse segregation:

• Cooling rate >15°C/min

• Add 0.02-0.2% rare earth elements

Heat treatment:

• Stress relief: 260-300°C × 1-2h (critical for springs)

• Aging: 320-340°C × 2-3h (enhances elasticity)

Key Application Scenarios

• Instrumentation: Pressure gauge tubes (0.1% FS accuracy)

• Mechanical bearings: Medium-speed PV≤2.5 MPa·m/s applications

• Marine/chemical: Seawater valve bushings (10+ year service)

• Electronics: High-cycle connectors (>100k mating cycles)

• Safety tools: Non-sparking wrenches for explosive environments

FAQ

Q1: C51100 vs QSn6.5-0.1?

A1: C51100 (4% Sn) offers balanced strength/formability; QSn6.5-0.1 (6.5% Sn) provides higher strength at 30% higher cost with poorer hot workability.

Q2: Seawater corrosion resistance?

A2: Corrosion rate: <0.015 mm/year (static), <0.03 mm/year (flowing ≤2m/s). Use cathodic protection for long-term immersion.

Q3: Solving "tin sweat" defect?

A3: Counter tin inverse segregation by:

1. Increasing cooling rate >15°C/min

2. Adding 0.02-0.1% rare earths

3. Homogenization: 650°C×8h + 750°C×4h

Q4: Post-cold working heat treatment?

A4: Essential for springs: 260±10°C×1-2h stress relief. Optional for structural parts unless >30% reduction.

Q5: Welding precautions?

A5: Recommended:

• TIG welding with Sn-bearing filler (SCu5210), 200-250°C preheat

• Brazing with BAg-5 or phosphor copper filler

• Post-weld annealing at 500-550°C

Reference Standards

• China: GB/T 4423-1992, GB/T 5231-2012

• USA: ASTM B103/B103M-2019, ASTM B139/B139M-2013

• International: ISO 427:2016, EN 12163:2016

This translation maintains all technical details, tables, and specifications while adapting terminology to international engineering standards. Critical industry terms (e.g., tempers O60/H02, IACS conductivity) follow ASTM conventions.