Magnesia Hot Repairing Mass (Fettling) for BOF and EAF Lining Maintenance

Magnesia hot repairing mass is a fettling material — a granular magnesia mix charged onto a hot lining, where furnace temperature sinters it in place. It exists for a specific job: rebuilding worn areas of a converter or electric furnace without taking the vessel out of service. Where a gunning mix is sprayed onto a wall, a repairing mass is thrown or fed onto a hot surface, typically at the furnace bottom and banks, and left to sinter under the heat already present.

Why It Works Without Firing

The lining is already at temperature. A magnesia mass placed on it begins to sinter immediately at the contact surface, bonding to the existing hot face. That is the mechanism and also the constraint: the material must sinter fast enough to bond before it can run or be cut away by slag, and slowly enough that a worker has time to place it. Grain grading and the sintering additives are what set that window.

Where It Is Used

• BOF converter bottoms and banks — rebuilding areas eroded by slag and charging impact between campaigns, without a full reline.
• EAF bottoms and hot spots — maintaining the hearth and the areas in front of the electrodes where local wear is fastest.
• Ladle and vessel bottoms — local repair of eroded areas where a full reline is not justified.

What Makes One Mass Better Than Another

Three things decide whether a fettling campaign buys useful life or just delays the inevitable:

• Bonding to the existing hot face. A mass that does not bond sits as a loose layer and is gone within a heat or two. Adhesion to the residual lining is the property that matters most and the one least often specified.
• Sintering behaviour at the actual surface temperature. The repair area is not uniformly hot. Material placed on a cooler shoulder needs a different sintering response from material on a hot bottom, and a single grade used everywhere will under-perform somewhere.
• Slag resistance once sintered. A repair that resists placement but not slag simply relocates the wear.

Honest Limits

Fettling is maintenance, not a reline. It buys campaign time and it is very good value when the wear is localised — and it is the wrong tool when the lining is worn broadly or the vessel is close to the end of its campaign. If you send us wear measurements and the areas involved, we will say whether a repair campaign is likely to be worthwhile or whether it is time to plan the reline. We would rather tell you that than sell mass for a vessel that will not benefit.

Supply

Minimum order 5 metric tons, shipped in 7–14 days, with grading adjusted to the placement method (throwing, chute or gunning) and the areas being repaired. Batch test data covers MgO content, grain size distribution, bulk density and sintering behaviour, with a Certificate of Analysis per shipment. If you can tell us the vessel type, the zones being repaired and their surface temperatures, we will grade the mass for each zone rather than supplying one grade for the whole campaign.