30% Silicon Copper

Fluidity Improver Deoxidizer Phosphorus-Free Treatment Silicon Source for Brass Alloys

Silicon copper master alloy (70% Cu, 30% Si) for fluidity improvement and deoxidation in brass and copper-nickel alloys. Broken slab and lump forms.

Solidus

1,472°F (800°C)

Liquidus

1,580°F (860°C)

Density

0.252 lbs/in³ (6.97 g/cm³)

Primary Elements

Cu · Si

Nominal Composition

30% Si, 70% Cu

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Product Overview

30% Silicon Copper is a copper-silicon master alloy with a nominal composition of 70% Cu and 30% Si. Silicon additions to copper alloys serve two primary functions: improving fluidity and castability of brasses and copper-nickel alloys, and acting as a deoxidizer in applications where phosphorus deoxidation is undesirable. Silicon dramatically reduces the surface tension of molten copper alloys improving flow into thin sections and reducing misrun and cold shut defects in complex castings. As a deoxidizer silicon copper can substitute for phosphorus deoxidation in applications where residual phosphorus would be harmful — for example in copper alloys intended for welding where phosphorus promotes hot cracking in the heat-affected zone. Silicon copper is also added to brasses and nickel silvers to improve fluidity in thin-section investment and die castings. It is the silicon source for manufacturing silicon brass (C87500) and related silicon-bearing copper alloys. Supplied in broken slab and lump forms for foundry charge addition.

Available Forms

1/2" x 14" Mesh Broken Pieces, Broken Slabs

Product Code

4710

Technical Info

Thermal Properties

Melting Point (Solidus)1,472°F (800°C)

Melting Point (Liquidus)1,580°F (860°C)

Physical Properties

Density (imperial)0.252 lbs/in³

Density (metric)6.97 g/cm³

Primary ElementsCu · Si

Lead FreeNo — contains lead

Key Features

Fluidity ImproverDeoxidizerPhosphorus-Free TreatmentSilicon Source for Brass Alloys

Solubility Note

Dissolves readily in molten copper alloy heats; add with gentle stirring at standard pouring temperatures. Avoid overaddition as excess silicon reduces ductility.

Nominal Composition

70% Cu
30% Si

Frequently Asked Questions

Common technical inquiries regarding 30% Silicon Copper

Silicon copper is preferred over phosphorus copper when the finished alloy will be welded or brazed. Residual phosphorus above approximately 0.02% promotes liquid metal embrittlement and hot cracking in copper alloy weld heat-affected zones making phosphorus-deoxidized alloys problematic for structural welded fabrications. Silicon does not cause this issue. Silicon deoxidation is also specified when the copper alloy will be used in electrical applications as phosphorus reduces conductivity more severely than silicon at equivalent addition levels.

Silicon in brass increases tensile strength and hardness while reducing ductility — up to approximately 3-4% Si strength gains outweigh ductility losses for most casting applications. Above 4% Si brittleness increases significantly and the alloy becomes difficult to machine cleanly. The C87500 silicon brass composition at 4% Si represents a practical upper limit for general casting use. For fluidity improvement alone additions of 0.5-1% Si provide significant casting improvement with minimal mechanical property penalty.

30% Silicon Copper is chemically stable and presents no special handling hazards in solid form. During melting silicon-copper additions generate silicon fume if the addition is made to an overheated melt — maintain melt temperature within the recommended range and avoid excessive superheating. The broken slab and lump forms can produce sharp edges during handling — use appropriate cut-resistant gloves. Store in a dry location; moisture does not degrade the product but can cause minor spatter when charged into a molten heat.