Many bar and rebar mills still run high chrome or indefinite chill (ICDP) iron rolls in intermediate and finishing stands. HSS rolls cost more per roll, but often cost much less per ton rolled. Here is how to decide.
How the materials differ
Indefinite chill iron has graphite and carbides in an iron matrix. It resists thermal cracks well and is low cost, but wears relatively fast.
High chrome iron contains hard chromium carbides, so it wears more slowly than ICDP and gives a good surface, but it is less tolerant of thermal shock.
High speed steel (HSS) contains very hard vanadium, molybdenum and tungsten carbides in a tough steel matrix. It wears much more slowly than either iron and keeps the groove shape longer.
What mills usually see after switching
- Typically 2–4 times more tons per groove than cast iron in the same stand.
- Fewer roll and guide changes, so more rolling time.
- Better and more consistent bar dimensions and surface over the campaign.
Results depend on the stand, the product mix and how the rolls are cooled and reground.
Where HSS needs more care
Cooling. HSS is less forgiving of poor cooling than ICDP. Water volume, pressure and nozzle aim must be right, or thermal cracks and spalling appear.
Cobbles and overloads. A cobble can crack an HSS roll that an iron roll would survive. Stands with frequent cobbles may suit a tougher grade.
Regrinding. Remove the full fire-crack layer at each change. Leaving cracks to save material shortens the next campaign.
How to work out the payback
Compare cost per ton, not price per roll: (roll price ÷ total tons the roll rolls over its life) plus the value of the rolling time saved by fewer changes. Most mills start with one or two finishing stands, compare a few campaigns, then extend HSS to other stands.
And tungsten carbide?
For the highest-speed passes in wire rod blocks, tungsten carbide roll rings last longer still. HSS sits between cast iron and carbide: tougher than carbide, far longer-lasting than iron.
See our HSS rolls page, or send your stand data and we will propose grades for a trial.