Common Metal Materials: Traits and How to Choose (SUS304, A5052, S45C, with Density)

Choosing a material balances cost, strength, corrosion resistance, and machinability. This article compiles the traits, density, and applications of representative metals used in machining.

Quick reference of metals

Material	Density (approx.)	Traits	Main uses
SUS304	7.9	Excellent corrosion resistance, non-magnetic. Gummy, a bit hard to machine	Food, medical, wet areas
SUS303	7.9	More free-cutting than 304, slightly less corrosion-resistant	Stainless parts needing machinability
A5052	2.7	Aluminum. Light, corrosion-resistant, good machinability	General, sheet metal, jigs
A2017 (duralumin)	2.8	High-strength aluminum, poorer corrosion resistance	Light parts needing strength
S45C	7.8	Medium-carbon steel. Hardenable, strong	Shafts, machine parts
SS400	7.85	General structural steel. Cheap, weldable	Frames, structures
C3604 (free-cutting brass)	8.5	Very easy to cut, conductive	Terminals, small parts

Key points for choosing

• Need corrosion resistance → stainless (SUS304) or aluminum (A5052)
• Need strength/hardness → S45C (with heat treatment)
• Need light weight → aluminum (A5052; A2017 for strength)
• Prioritize machinability → free-cutting brass (C3604), SUS303
• Cost-first, structural → SS400

Machinability cautions

• Stainless is gummy and work-hardens → mind sharpness, depth of cut, chip handling
• Aluminum cuts easily but is prone to built-up edge → high speed, sharp tools
• Free-cutting grades (C3604, SUS303) add sulfur, etc. to ease cutting
• Density directly drives weight and material cost (important for quoting)

FAQ

Q. What's the difference between SUS304 and SUS303? A. 303 improves machinability at the cost of slightly lower corrosion resistance than 304. Choose by application.

Q. Is all aluminum light and strong? A. Light, yes, but strength varies by grade. For strength, A2017 (duralumin); for corrosion resistance/general use, A5052.

Q. What is density used for? A. Volume × density gives weight. Weight × unit price gives material cost, so density is base data for quoting.

Conclusion

Choose by "function (corrosion, strength, weight) × cost × machinability." Know the density and your weight/material-cost quotes stay accurate.

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