Hot Tops (Steel Mill Ingot Insulation) — Asbestos Exposure Crosswalk
What This Equipment Is
In traditional ingot-cast steel making — the dominant production method before continuous casting displaced it in the 1970s–1980s — molten steel was poured into cast-iron ingot molds and allowed to solidify before stripping the mold and reheating the ingot for rolling. To control the solidification gradient and minimize internal defects, the top of each mold was fitted with a “hot top” — an insulating cap that kept the upper steel molten longer, allowing impurities and shrinkage cavities to concentrate at the top where they could be cropped off the finished ingot.
For decades, the dominant hot-top product family was asbestos-bearing insulating board — pressed asbestos / silica composite panels cut to fit the mold rim and stacked into hot-top boxes. Major brand names included Carey Marvelous Hot Top, Foseco hot-top products, and various Johns-Manville and Combustion Engineering offerings.
Why Hot-Top Work Was Among the Heaviest Steel-Mill Asbestos Exposures
Hot tops were consumables. A single ingot pour destroyed the hot top. A medium-sized melt shop pouring 50–100 ingots per shift consumed hot-top material in volume continuously, around the clock, every shift.
The exposure pathway was extreme:
- Cutting and fitting hot-top boards to mold-rim dimensions in a dusty cut-and-fit shop — workers ran band saws and abrasive cutters through asbestos boards all shift
- Placing the hot top on the mold immediately before pour — handling broken board, brushing off dust
- Stripping the destroyed hot-top assembly off the cast ingot — hammering, prying, and shoveling the asbestos rubble back to a recycle bin or dumpster
- Cleanup of the pouring bay — sweeping accumulated asbestos dust and broken board across the deck
Steel-mill workers in cast-house, mold-yard, stripping-shop, and hot-top fabrication areas were directly exposed every shift for entire careers. Mesothelioma rates among long-tenure steel-mill workers in hot-top-using mills are well documented in epidemiology.
Manufacturers Named in Hot-Top Litigation
- Carey Canada / Philip Carey Manufacturing — Marvelous Hot Top brand
- Foseco International — hot-top products
- Johns-Manville — hot-top board and shaped components
- Combustion Engineering — hot-top products
- A.P. Green Refractories — hot-top related refractory
- Harbison-Walker Refractories — hot-top related refractory
- Eagle-Picher — insulating board
Documented Product References
Images sourced from publicly available product-identification reference materials. Inclusion does not constitute a finding of liability against any company.
Trust Funds That May Apply
- Combustion Engineering 524(g) Asbestos PI Trust
- Manville Personal Injury Settlement Trust
- Carey Canada Asbestos PI Trust
- A.P. Green Industries Asbestos PI Settlement Trust
- Harbison-Walker Refractories / RHI Asbestos PI Trust
- Eagle-Picher Industries PI Settlement Trust
Trades Most Exposed at Hot-Top Work
Steel-mill cast-house and mold-yard workers, stripping-shop crews, hot-top fabrication workers, melt-shop laborers, ingot mold setters, crane operators in the pouring bay, ironworkers and millwrights on cast-house maintenance.
Jobsites in the Network Documenting Hot Tops
- Every traditional ingot-cast Missouri steel mill (operating in the ingot-cast era)
- Steel-mill jobsites across the state-site network and adjacent Illinois, Indiana, and Ohio sites
- See companion pages: Refractory Brick, Refractory Mortar, Industrial Furnaces
Compiled from publicly filed asbestos litigation, EPA / OSHA / NIOSH records, steel-mill industry publications, and academic epidemiology on steel-mill asbestos exposure cohorts. Product and company references reflect what has been alleged or documented in publicly filed litigation. This page does not constitute a finding of liability against any company. Not legal advice; consult a licensed attorney about your specific situation.