Gunmetal (LG2) — Bronze Grade Specification, Properties & Equivalents

Gunmetal (LG2), conforming to IS 319 Grade II specifications, is a vital leaded bronze alloy extensively used across India's industrial landscape. Renowned for its excellent machinability, good strength, and decent corrosion resistance, LG2 finds critical applications in pressure castings, valve components, pipe fittings, and general engineering parts requiring a reliable, cost-effective material. Procurement engineers and fabricators in Mumbai, Pune, and Chennai frequently specify Gunmetal (LG2) for its balance of performance and economic viability. Its consistent quality and availability make it a go-to choice for manufacturing components that need to withstand moderate pressures and temperatures while being easily workable. The alloy's specific composition, detailed below, ensures it meets the demanding requirements of various sectors, from plumbing to heavy machinery. Understanding the nuances of Gunmetal (LG2) is crucial for ensuring optimal performance and longevity in manufactured goods.

Chemical Composition of Gunmetal (LG2)

Chemistry Standards for Gunmetal (LG2)

Element	Weight % (Max)
Copper (Cu)	80.0 - 83.0
Tin (Sn)	5.0 - 7.0
Lead (Pb)	4.0 - 6.0
Zinc (Zn)	4.0 - 6.0
Iron (Fe)	0.10
Nickel (Ni)	0.50
Antimony (Sb)	0.50
Phosphorus (P)	0.10
Sulphur (S)	0.10
Total Other Impurities	1.0

Mechanical Properties of Gunmetal (LG2)

Property	Minimum Value
Ultimate Tensile Strength (UTS)	270 MPa
Yield Strength (YS) (0.2% offset)	150 MPa
Elongation at Break (%)	15%
Brinell Hardness (HB)	70 - 90
Density	8.50 g/cm³
Modulus of Elasticity	100 GPa

Available Forms of Gunmetal (LG2) in India

Shape	Typical Sizes Available	Standard Lengths
Round Bars / Rods	10 mm – 150 mm Diameter	3-meter, 6-meter
Hexagonal Bars	12 mm – 100 mm A/F	3-meter, 6-meter
Sheet / Plates	3 mm – 50 mm Thickness	Custom Cut
Casting Ingots	Various sizes for foundries	As per order
Sand Castings / Machined Parts	Customizable	As per requirement

Real-world Applications of Gunmetal (LG2)

Valves & Fittings: Manufacturing high-pressure valve bodies, stems, and assorted pipe fittings for fluid control systems.
Pump Components: Producing impellers, casings, and wear rings for pumps handling water and industrial fluids.
Marine Hardware: Fabricating corrosion-resistant components for ships and offshore equipment exposed to saltwater.
Automotive Parts: Used in bushings, bearings, and hydraulic system components requiring good wear resistance.
Plumbing & Sanitaryware: Casting basic taps, mixers, and connectors for water distribution systems.
Machine Tool Components: Production of gears, bushes, and sliding elements in machinery.
Electrical Engineering: Some applications in switchgear components where conductivity and durability are key.
General Engineering: Broad use in creating custom parts, flanges, and connectors for diverse industrial assemblies.

Machinability & Weldability of Gunmetal (LG2)

Gunmetal (LG2) is specifically prized for its excellent machinability, a key attribute for Indian fabricators working with this alloy. Its lead content acts as a chip breaker, allowing for high cutting speeds and efficient material removal with standard machining tools like HSS or carbide. When machining Gunmetal (LG2), recommended speeds typically range from 60-120 m/min for turning and 40-80 m/min for milling, depending on the tool and depth of cut. Generous coolant flow is advised to manage heat and ensure a good surface finish. Weldability for Gunmetal (LG2) is considered fair to good under controlled conditions. Using TIG or MIG welding with a filler rod of similar composition (e.g., Cu-Sn-Pb-Zn) is common. Preheating Gunmetal (LG2) to around 150-250°C can help reduce stress, especially for thicker sections. Post-weld heat treatment is generally not required for typical applications, but stress relieving at 300-400°C might be employed for critical components to improve ductility and reduce residual stresses after welding Gunmetal (LG2).

Heat Treatment & Processing of Gunmetal (LG2)

Gunmetal (LG2) is typically supplied in the

Sourcing Gunmetal (LG2) in India

Gunmetal (LG2) is readily available across major industrial hubs in India, with significant stock typically found in Mumbai, Pune, and Chennai. While large Indian steel manufacturers like SAIL or Jindal do not produce this alloy directly, numerous specialized non-ferrous foundries and rerollers, such as those in the local Gujarat and Maharashtra clusters, are key manufacturers. Minimum Order Quantities (MOQ) can vary; for standard bar forms, MOQs might start from 50-100 kg, while custom castings require larger commitments. The pricing for Gunmetal (LG2) typically falls within the INR 450 – 650 per kg band, fluctuating with global copper prices and specific order volumes. Most reputable suppliers will provide a Material Test Certificate (MTC) as per IS 319 standards, detailing the chemical composition verified by spectrometry and mechanical test results. Full traceability and third-party inspection are common requests that reliable suppliers can accommodate for Gunmetal (LG2) orders.

International Equivalents for Gunmetal (LG2)

Standard	Code
IS	319 Grade II
BS	249 Part 2 CZ121 Pb3
EN	CW602N (approximate)
SAE	660 / SAE 67 (similar alloys)
JIS	BC6 (similar copper-tin bronze)
ASTM	B584 UNS C84400 (similar casting alloy)

FAQs about Gunmetal (LG2)

What are the main uses of Gunmetal (LG2) in India?

Gunmetal (LG2) is predominantly used in India for manufacturing valve components, pump parts, pipe fittings, pressure castings, and general engineering items. Its excellent machinability, good strength, and corrosion resistance make it ideal for applications involving moderate pressures and temperatures, particularly in plumbing, marine hardware, and automotive systems. Fabricators value LG2 for reliable fluid handling and mechanical components.

What is the typical hardness of Gunmetal (LG2) supplied in India?

The typical Brinell hardness for Gunmetal (LG2) supplied in India, as per IS 319 Grade II specifications, ranges between 70 and 90 HB. This hardness level ensures a good balance between wear resistance and machinability, making LG2 suitable for components like bushings, bearings, and valve seats that require durability without compromising ease of fabrication.

Can Gunmetal (LG2) be welded?

Yes, Gunmetal (LG2) can be welded using techniques like TIG or MIG, typically employing a filler rod of similar composition. Preheating Gunmetal (LG2) to about 150-250°C helps reduce stress during welding. While not always necessary, a post-weld stress relief heat treatment at 300-400°C can enhance the ductility and integrity of the welded joint for critical Gunmetal (LG2) parts.

What kind of mechanical properties can I expect from Gunmetal (LG2)?

Gunmetal (LG2) offers a respectable combination of mechanical properties. You can expect an Ultimate Tensile Strength (UTS) of around 270 MPa, a Yield Strength (YS) of approximately 150 MPa, and an elongation of at least 15%. These figures, coupled with its moderate hardness, confirm Gunmetal (LG2)'s suitability for components requiring both strength and formability.

What are the common forms of Gunmetal (LG2) available from Indian suppliers?

Indian suppliers typically offer Gunmetal (LG2) in various forms to meet diverse manufacturing needs. Common forms include round bars and rods (diameters from 10mm to 150mm), hexagonal bars, and sheets or plates (thicknesses from 3mm to 50mm). Foundries also procure LG2 in the form of casting ingots. Custom-cast or machined components made from Gunmetal (LG2) are also readily available upon request.

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