IS 318 HTB3 Aluminium Brass Casting – Grade 3

IS 318 HTB3 (High Tensile Brass Grade 3) is the Indian standard aluminium brass casting grade, equivalent to C87200 (USA) and CC770S (EN 1982). The aluminium addition (2–5%) creates alpha + kappa phase microstructure that delivers high strength (420 MPa), excellent erosion-corrosion resistance, and improved seawater resistance compared to standard yellow or naval brass. IS 318 HTB3 is used for high-velocity pump impellers, structural marine hardware, and castings requiring higher strength combined with lead-free compliance.

Alloy Overview

IS 318 HTB3 (Cu 65–70%, Zn ~25%, Al 2–5%) gains its high strength through kappa phase (AlCu₃) intermetallic precipitation in the alpha matrix and the strengthening effect of the aluminium solid solution. Erosion-corrosion resistance is markedly better than HTB2 naval brass at high fluid velocities, making HTB3 preferred for pump impellers in abrasive or high-velocity service. The alloy is essentially lead-free (Pb max 0.30%), meeting most lead-reduced specification requirements.

Material Composition – IS 318

Element	Min %	Max %	Typical %	Role
Copper (Cu)	65.0	70.0	67.5	Primary matrix
Zinc (Zn)	Balance	Balance	~25.5	Strength, castability
Aluminium (Al)	2.0	5.0	3.5	Strengthener, kappa phase, corrosion
Manganese (Mn)	0.5	3.0	1.5	Strengthener, grain refiner
Iron (Fe)	0.5	2.5	1.0	Grain refiner
Nickel (Ni)	–	1.0	0.3	Toughness
Lead (Pb)	–	0.30	–	Low-lead
Tin (Sn)	–	0.20	–	Minor
Silicon (Si)	–	0.10	–	Impurity
Phosphorus (P)	–	0.05	–	Deoxidant

Mechanical Properties

Property	Sand Cast	Die Cast	Standard
Tensile Strength (MPa)	420 min	490 min	IS 318
Yield Strength (MPa)	160	200	IS 1608
Elongation (%)	18%	20%	IS 1608
Hardness (HB)	90–120		IS 1756
Density (g/cm³)	8.42		–
Electrical Conductivity (%IACS)	8–12		–
Melting Range (°C)	880–1000		–
Machinability (%)	30		CDA scale

International Equivalent Grades

Standard	Designation	Name
India (IS 318)	HTB3	Aluminium Brass Grade 3
USA (ASTM B584)	C87200 / CDA 872	Silicon/Al Brass Casting
Europe (EN 1982)	CC770S	CuZn25Al5-C
Germany (DIN)	CuZn22Al3-C (nearest)	Al-Sondermessing
UK (BS 1400)	HTB3 (nearest)	High Tensile Brass 3
Japan (JIS H5111)	HBsC3 (nearest)	High Strength Brass 3
ISO	CuZn25Al5-C	Aluminium Brass Casting

Applications

IS 318 HTB3 castings: high-velocity pump impellers (erosion-corrosion resistant); marine propellers for performance vessels; structural marine hardware requiring strength above HTB2 naval brass; desalination plant components; industrial pump and valve bodies for abrasive slurries; offshore structural connectors.

Pricing

US$ 11.50 per kilogram (CIF, indicative). MOQ: sample 1 pc; production 50 pcs.

Quality

IS 318 HTB3; EN 1982 CC770S; C87200 (nearest); ISO 9001:2015; spectrometric analysis; mechanical property certificates; carbide tooling required for machining. ISO 9001:2015. EN 10204 3.1 MTR.