Blow Bars
High Chrome Blow Bars: Choosing Chrome Content and Hardness
Last updated November 2026 · By SKS Steel Zambia, Foundry & Machine Shop, Kalulushi
High chrome blow bars are a popular upgrade for impact crushers working on abrasive rock. They wear slowly, but they are less forgiving than manganese if something hard gets into the crusher. This guide explains what high chrome means, how hardness and toughness trade off, and how to decide.
What High Chrome Means for a Blow Bar
High chrome blow bars are made from high chromium white iron. The chromium forms hard carbides in the iron, which is what resists abrasion. Grades are commonly described under the ASTM A532 standard, and the chromium level is often quoted somewhere in the range of about 11 to 30 percent, depending on the grade.
After casting, the bar is heat treated to develop its hardness. Hardness is often quoted at roughly 600 to 700 HB for a heat treated bar. Exact numbers depend on the grade and the heat treatment, so ask for the hardness record with your bars.
Hardness vs Toughness: The Trade-off
Higher hardness means better wear life on abrasive rock, but lower impact toughness. A high chrome bar can chip or crack if the crusher takes uncrushable metal or very large feed. Manganese steel is softer when new but tough, and it work hardens as it is struck.
- Choose high chrome for clean, abrasive, pre-screened feed, often in secondary or tertiary crushing.
- Choose manganese for mixed or large feed, or where tramp metal is a real risk.
- Check the feed first. A bar that wears slowly but breaks is more costly than one that wears faster and survives.
Read our full comparison in Manganese Steel vs High Chrome Iron Wear Parts.
Want to trial high chrome blow bars?
Send the crusher model and a drawing or worn bar. We recommend the grade.
Chat on WhatsAppHigh Chrome vs Manganese Blow Bars at a Glance
| Factor | High chrome | Manganese steel |
|---|---|---|
| Wear resistance on abrasive rock | High | Moderate |
| Impact toughness | Lower | High |
| Best feed | Clean, abrasive, pre-screened | Mixed, large, possible tramp metal |
| Breakage risk | Higher if tramp metal enters | Lower |
| Hardness | Hard as supplied, often 600 to 700 HB | Softer as cast, hardens in service |
General guidance only. Actual life depends on rock, crusher settings and bar design.
Ordering High Chrome Blow Bars
To quote blow bars we need the following:
- Crusher make and model, for example the PF series
- A drawing, or a worn bar to copy
- Feed type, top size and tonnes per hour
- Your current bar material and how long it lasts
SKS casts high chrome and manganese blow bars, heat treated in house with hardness recorded per batch, cast to your drawing or worn sample. See the blow bars page and our guide to blow bars for PF series crushers. If a bar is failing early, this troubleshooting guide can help.
Signs Your Blow Bars Are Too Hard or Too Soft
The failure pattern tells you which way to move.
- Chipping or cracking: the material is too hard for the feed or tramp metal is present.
- Rapid, even thinning: the material is too soft for the abrasion.
- Mushrooming at the edge: common in softer manganese before it work hardens.
A Simple Trial Plan
- Fit one full set of the new grade in the same crusher.
- Record tonnes processed until the set is worn.
- Photograph the bars at each stop.
- Compare with the previous set before changing other crushers.
Frequently Asked Questions
High chrome bars are harder and resist abrasion better, but are more brittle. Manganese bars are tougher and work harden under impact, so they cope better with large or mixed feed.
Heat treated high chrome bars are often quoted at roughly 600 to 700 HB, depending on grade and heat treatment. Ask your supplier for the hardness record.
Yes. We cast high chrome and manganese blow bars in Kalulushi, heat treated in house, cast to your drawing or worn sample. Send your crusher model on WhatsApp for a quote.
Need high chrome blow bars for your crusher?
Send us the crusher model and a drawing or worn bar. We will confirm the grade and lead time.
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