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Thermal injury caused by ejection of liquid or semi-liquid slag droplets during metallurgical operations, particularly during bloom extraction and shingling (hammer consolidation) in bloomery smelting, and during tapping operations in blast furnaces and electric arc furnaces. Fayalitic slag at bloomery temperatures is liquid at ~1100–1200 °C; mechanical disturbance (hammer blows, tuyere back-pressure, or sudden gas release) can propel droplets over significant distances. Contact causes immediate deep thermal burns; slag adheres to skin and continues burning. [Source: General occupational health and safety knowledge for pyrometallurgical operations; Tylecote, R.F. (1992), ‘A History of Metallurgy’, 2nd ed., Institute of Materials, London, pp. 27–32 — describes bloom extraction and shingling context; specific burn injury data is common occupational medicine knowledge, uncited from specific study.]
Exposure routes
- Direct contact during bloom extraction from furnace
- Splatter during shingling/hammer consolidation of hot bloom
- Back-blast through tuyere ports if furnace pressure spikes
- Contact during slag-tapping operations (if furnace has tapping arch)
Mechanism
Liquid slag at ~1100–1200 °C is propelled by gas pressure release (from trapped steam or CO in bloom pores) or mechanical impact (hammer blow during shingling). Droplets travel and adhere to exposed skin or clothing, transferring thermal energy directly. Slag’s high heat capacity and adhesive properties (it sticks rather than bouncing off like water) cause deep partial or full-thickness burns even from small droplets. Damp ore or wet tools introduced near molten slag cause steam explosions that dramatically amplify ejection.
Mitigations
- Maintain dry conditions — never introduce wet ore, tools, or materials near molten slag
- Use long-handled tongs for bloom extraction to maximize distance from furnace
- Face and body protection (leather apron, face shield) for shingling operations
- Stand to the side of the blow direction during hammer work; avoid standing directly over the bloom
Severity
Deep thermal burns (partial and full thickness) from contact with liquid slag at >1100 °C; severity depends on exposed area and contact duration. Slag adhesion prolongs contact and worsens outcomes compared to equivalent water scalds. Eye contact at any distance causes severe injury. Can be fatal if large body surface area is affected.
Warning signs
- Visible liquid slag pooling at furnace base or tuyere ports
- Hissing/spattering sounds during operation indicate gas-slag interaction
- Steam rising from ore or charge indicates moisture — operation should pause
Connections
Incoming
- Has hazard ← Bloomery Iron Smelting — Liquid fayalitic slag at ~1100-1200 C is present throughout smelt and is violently disturbed during bloom extraction and shingling. Damp ore or tools amplify ejection risk via steam generation.
- Has hazard ← Fayalitic Slag — Fayalitic slag is liquid at ~1100-1200 C and is the direct agent in slag splatter burns. The hazard inheres in the material itself when in its molten state.
- Has hazard ← Iron Bloom — The iron bloom at extraction temperature (800-1100 C) contains occluded liquid slag; hammer blows during shingling expel this slag as droplets, causing splatter burns.
- Has hazard ← Wrought Iron — During shingling of the fresh bloom, liquid slag is mechanically expelled by hammer blows and can splatter onto operators. The hazard is most acute in the initial shingling phase when the bloom still contains a high proportion of occluded slag; it diminishes as the iron is progressively consolidated into wrought bar iron. Also relevant during forge-welding of wrought iron, where slag inclusions flux the weld but may be expelled as droplets.