Slag Notch for Furnace Hearth - Industrial Component

Product Specifications

Technical details and manufacturing context for Slag Notch

Definition

The slag notch is a critical component of industrial furnace hearths, specifically engineered to provide a controlled exit point for molten slag—the waste byproduct formed during metal smelting or refining processes. Located at the appropriate level in the hearth wall, it allows for the periodic or continuous tapping of slag to maintain optimal furnace operation, prevent overflow, and separate impurities from the molten metal bath. The notch is typically a refractory-lined aperture with a removable plug or gate. During operation, accumulated slag floats on top of the denser molten metal. When the slag level reaches a predetermined height, the plug is removed or the gate is opened, allowing the slag to flow out by gravity through a runner or launder system for disposal or further processing, before the opening is resealed. The slag notch is designed to operate under high temperatures (1400–1600 °C) and pressures (1.0–1.6 MPa), with a nominal diameter typically ranging from 50 to 200 mm. It is constructed with refractory materials such as high-alumina or magnesia-carbon brick, encased in a steel retaining ring. Cooling water flow (10–30 m³/h) and pressure (0.3–0.6 MPa) are required to prevent overheating of the frame. Sealing surface flatness must be ≤0.05 mm to ensure leak-tightness, and the leakage rate is specified as ≤0.1% (Class A). The refractory material grade (A–C per ISO 10081-1) affects service life. The weight ranges from 500 to 2000 kg, and actuation torque for manual or hydraulic operation is 200–800 N·m. These parameters are reference ranges; actual values must be confirmed with the manufacturer for specific applications. Standards such as ISO 6708, ISO 17584, and ISO 10081-1 are referenced for verification. The slag notch is essential for efficient slag removal, preventing furnace damage, and ensuring metal quality.

Working Principle

The slag notch operates on the principle of density separation. Molten slag, being less dense than the molten metal, accumulates on top of the metal bath. The notch is positioned at a height corresponding to the slag layer. When slag reaches the notch level, the plug or gate is opened, allowing slag to flow out by gravity through a runner or launder. The opening is then resealed to maintain furnace integrity. The refractory lining protects the structure from high temperatures and chemical attack, while cooling water prevents overheating of the frame. The sealing surface ensures minimal leakage, and the actuation mechanism allows controlled tapping.

Common Materials

Refractory brick (e.g., high-alumina, magnesia-carbon), Steel casing/retaining ring

Technical Parameters

Parameter	Typical range	Notes & selection driver
Nominal Diameter	50–200 mm	Matches furnace tapping rateISO 6708
Operating Temperature	1400–1600 °C	Refractory lining required
Cooling Water Flow Rate	10–30 m³/h	Prevents overheating of frame
Cooling Water Pressure	0.3–0.6 MPa	Ensure adequate flow
Sealing Surface Flatness	≤0.05 mm	Critical for leak-tightnessISO 17584
Refractory Material Grade	A–C	Higher grade for longer lifeISO 10081-1
Weight	500–2000 kg	Affects installation and support
Leakage Rate	≤0.1 %	Class A per ISO 5208 Measured at the stated test pressure
Actuation Torque	200–800 N·m	For manual or hydraulic operation

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Refractory Lining Part
Forms the internal, wear-resistant surface of the notch, containing the molten slag and resisting erosion/corrosion.

Material: High-alumina or basic refractory brick/monolithic
Steel Casing/Retaining Ring Part
Provides structural support and containment for the refractory lining, and facilitates mounting to the hearth structure.

Material: Heat-resistant steel (e.g., carbon steel plate)
Tapping Plug/Gate
A removable or operable closure mechanism to open and seal the notch for controlled slag tapping.

Material: Refractory plug or steel gate with refractory facing
Water Cooling System
Circulates water through the notch frame so the steelwork survives beside flowing slag.

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Frequently Asked Questions

What is the primary function of a slag notch?

The slag notch provides a controlled opening in the furnace hearth to remove molten slag, which is a waste byproduct of metal smelting. It helps maintain furnace operation and separate impurities from the metal bath.

What materials are used in slag notch construction?

Slag notches are typically lined with refractory brick such as high-alumina or magnesia-carbon, and have a steel casing or retaining ring for structural support.

What are typical operating parameters for a slag notch?

Typical parameters include operating temperatures of 1400–1600 °C, pressures of 1.0–1.6 MPa, and nominal diameters of 50–200 mm. Cooling water flow is 10–30 m³/h at 0.3–0.6 MPa. These are reference ranges; actual values must be confirmed.

How is the slag notch sealed to prevent leakage?

The sealing surface flatness must be ≤0.05 mm, and the leakage rate is specified as ≤0.1% (Class A). The plug or gate must be properly seated and maintained to ensure leak-tightness.

Data Basis

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pressure:	0-0.5 bar (atmospheric to slight positive pressure)
flow rate:	Variable, controlled by opening size and slag viscosity
temperature:	1200-1600°C (typical molten slag range)
slag concentration:	100% molten slag (no dilution required)

Slag Notch

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