Phosphor Bronze
Phosphor bronze is a tin bronze with a small phosphorus addition that increases strength, hardness, wear resistance and fatigue resistance. It is used for worm wheels, bushes, springs, electrical contacts and heavy-duty bearings.
What it is
Grades such as PB1 (cast, about 10% tin) and PB2 (about 12% tin) are standard for gears and bearings; wrought phosphor bronze (C51000) is used for springs and electrical contacts because it combines strength with good conductivity and elasticity.
It runs smoothly against hardened steel and resists seizure under high loads.
Typical applications
- Worm wheels and gears
- Heavy-duty bushes and bearings
- Springs and spring contacts
- Electrical connectors
- Marine and pump parts
Materials & grades
- PB1 (cast)
- PB2 (cast)
- C51000 / C52100 (wrought)
- Continuous cast phosphor bronze bar
Points to consider
- PB2 has higher tin for harder, more wear-resistant gears.
- Needs good lubrication at high loads.
- Pair with hardened, ground steel worms and shafts.
- Wrought grades suit springs and contacts; cast grades suit bearings.
Frequently asked questions
Why are worm wheels made of phosphor bronze?
It runs well against hardened steel worms with low friction and good wear and seizure resistance.
What is the difference between PB1 and PB2?
PB2 contains more tin, making it harder and more wear resistant, suited to heavily loaded gears.
Is phosphor bronze used for springs?
Yes. Wrought phosphor bronze is used for springs and electrical contacts for its strength and elasticity.