JIS Standard Oilless Bearings: Selecting the Right Bronze Material (CAC406, CAC703, CAC304) for Precision Machinery
Navigating the Nuances of JIS Bronze for Oilless Bearings
For engineers specifying components in precision machinery, material selection is paramount. When a drawing calls for a JIS standard bronze like CAC406 (BC6), CAC703 (AlBC3), or the high-strength CAC304 (HBsC4) for oilless bearings, it’s not just a designation; it’s a statement about expected performance. Understanding the underlying metallurgical properties and their implications for real-world applications is crucial, especially when sourcing globally. This article delves into these prominent JIS bronze alloys, offering a detailed comparison, technical insights, and guidance on acceptable international equivalents.
JIS H5120: The Foundation of Japanese Bronze Casting
At the heart of Japanese bronze casting for industrial applications lies JIS H5120, the Japanese Industrial Standard that specifies the requirements for copper and copper alloy castings. This standard is fundamental for oilless bearings because it ensures the base material possesses the correct metallurgical structure necessary to effectively support solid lubricant embedding technology. Without a precisely controlled casting, the integration of graphite or other solid lubricants, which define an oilless bearing’s self-lubricating properties, would be compromised. JIS H5120 provides a framework for consistent quality, ensuring that the bronze matrix can reliably house and release lubricants under operational stress.
1. CAC406 (BC6): The Machining-Friendly “Workhorse” Casting Bronze
CAC406, also commonly known as BC6 or often referred to as “85-5-5-5” gunmetal due to its approximate composition, is a leaded tin bronze widely utilized in bushing and general machine parts. Its popularity stems from its engineering as a practical, machinable bronze casting alloy. The balanced chemical composition of CAC406 is specifically designed to meet real-world manufacturing demands, making it a versatile choice for various industrial applications.
Composition Snapshot of CAC406 (BC6)
Typical published ranges for CAC406 (BC6) highlight its balanced alloy content :
|
Element
|
Composition Range (wt%)
|
|
Cu
|
83.0–87.0
|
|
Sn
|
4.0–6.0
|
|
Pb
|
4.0–6.0
|
|
Zn
|
4.0–6.0
|
This chemistry is critical for its performance characteristics. The tin (Sn) content contributes to strength and corrosion resistance, while lead (Pb) significantly enhances machinability and acts as a solid lubricant, improving wear properties. Zinc (Zn) improves castability and mechanical properties, making it a robust and cost-effective material.
Mechanical Properties of CAC406 (BC6)
CAC406 exhibits a set of mechanical properties that underscore its role as a reliable workhorse :
|
Property
|
Typical Value (min)
|
|
Tensile Strength
|
195-245 MPa
|
|
Yield Strength
|
100-140 MPa
|
|
Elongation
|
10-15%
|
|
Hardness (Brinell)
|
60-70 HB
|
Common Applications of CAC406
•Injection molding machines: Linkages, guides, and wear points.
•Automotive tooling/molds: Wear plates, bushings, and sliding components.
•Maintenance replacement: General industrial equipment where cost-effectiveness is key.
2. CAC703 (AlBC3): Aluminum Bronze for Strength and Corrosion Resistance
In contrast to the general-purpose nature of CAC406, CAC703, also known as AlBC3, belongs to the aluminum-bronze family. Engineers typically opt for CAC703 when applications demand superior strength, enhanced corrosion resistance, and improved deformation resistance under heavy loads.
Composition Snapshot of CAC703 (AlBC3)
The chemical composition of CAC703 reflects its high-strength aluminum bronze positioning :
|
Element
|
Composition Range (wt%)
|
|
Cu
|
78.0% minimum
|
|
Al
|
8.5–10.5
|
|
Fe
|
3.0–6.0
|
|
Ni
|
3.0–6.0
|
|
Mn
|
0.1–1.5
|
Mechanical Properties of CAC703 (AlBC3)
CAC703 boasts significantly higher mechanical properties compared to CAC406 :
|
Property
|
Typical Value (min)
|
|
Tensile Strength
|
590-660 MPa
|
|
Yield Strength
|
245-280 MPa
|
|
Elongation
|
13-15%
|
|
Hardness (Brinell)
|
150-180 HB
|
Common Applications of CAC703
•Precision machinery: Components experiencing intermittent high loads.
•Corrosive environments: Equipment exposed to moisture or seawater.
•Heavy-duty industrial parts: Valve guides, pump components, and gears.
3. JIS CAC304 (High Tensile Brass) – The High-Load Specialist
For heavy-load, low-speed applications such as bridge supports or dam gate rollers, JIS CAC304 (often called High Tensile Brass or Manganese Bronze, formerly HBsC4) is the material of choice. It is engineered to withstand extreme pressures where other alloys might fail.
Key Performance Advantages
•Load Bearing: It possesses the highest tensile strength among common copper alloys, making it capable of supporting massive structural loads.
•Durability: Its high wear resistance makes it the ideal carrier for solid lubricants in environments where oil film formation is impossible.
Mechanical Properties of CAC304 (HBsC4)
|
Property
|
Typical Value (min)
|
|
Tensile Strength
|
755 MPa
|
|
Yield Strength
|
410 MPa
|
|
Elongation
|
12%
|
|
Hardness (Brinell)
|
200 HB
|
JIS Bronze Material Comparison Table
To help our global partners find the correct replacement, here is how JIS grades compare to other international standards:
|
JIS Grade (H5120)
|
Former JIS Code
|
ASTM Equivalent
|
DIN Equivalent
|
Characteristics
|
|
CAC406
|
BC6
|
C83600
|
Excellent machinability
|
|
|
CAC603
|
PbC3
|
C93200
|
Classic bearing bronze
|
|
|
CAC703
|
AlBC3
|
C95400 / C95800
|
CuAl10Fe3Mn2
|
High strength, anti-corrosion
|
|
CAC304
|
HBsC4
|
C86300
|
CuZn25Al5
|
Ultra-high load capacity
|
CAC406 vs. CAC703: Fast Selection Table for Engineers
Use this as a shortlist tool before you go deep into PV calculations and validation testing.
|
Item
|
CAC406 (BC6)
|
CAC703 (AlBC3)
|
|
Alloy Family
|
Tin/lead bronze casting
|
Aluminum bronze casting
|
|
Design Intent
|
Easy machining + general service
|
Higher strength + environmental resistance
|
|
Chemistry Highlights
|
Sn/Pb/Zn present
|
Al/Fe/Ni present
|
|
Common Industries
|
Injection molding, tooling
|
Harsh service, heavier loads
|
|
Global Sourcing
|
Cross-referenced to “bearing bronze”
|
Cross-referenced to “aluminum bronze”
|
Why VIIPLUS for Your JIS-Standard Project?
Understanding the nuance between BC6, AlBC3, and HBsC4 is what sets a specialized supplier apart. We provide a full range of oilless bearings manufactured from JIS-compliant alloys, ensuring seamless integration into Japanese-designed equipment.
From China to Tokyo, we provide the technical expertise and material certifications required to ensure your machinery runs longer without the need for manual lubrication. Our commitment to quality and deep understanding of JIS H5120 standards make us the ideal partner for your precision machinery needs.
Self-Lubricating Bronze Bushings (Standard & Custom) – Bronze Oilless
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