EAF Roof & Delta Castable for Arc Radiation Zones
Al₂O₃ ≥80–85% · Cr₂O₃ 2–5% · BD ≥2.80–2.90 g/cm³ · CCS ≥30–40 MPa · Service to 1720–1750 °C — built for arc radiation.
Specifications of XZK EAF Roof Castable
Manufactured strictly in accordance with ASTM, ISO, and YB/T metallurgical refractory standards.
| Property | XZK-CastE80 | XZK-CastE85 |
|---|---|---|
| Max Service Temperature (°C) ≤ | 1720 | 1750 |
| Al₂O₃ (%) ≥ | 80.0 | 85.0 |
| Cr₂O₃ (%) | 2 – 5 | 2 – 5 |
| Bulk Density 110 °C × 24 h (g/cm³) ≥ | 2.80 | 2.90 |
| Bulk Density 1600 °C × 3 h (g/cm³) ≥ | 2.80 | 2.90 |
| Crushing Strength 110 °C × 24 h (MPa) ≥ | 30 | 30 |
| Crushing Strength 1600 °C × 3 h (MPa) ≥ | 40 | 40 |
| Modulus of Rupture 110 °C × 24 h (MPa) ≥ | 6.0 | 6.0 |
| Modulus of Rupture 1600 °C × 3 h (MPa) ≥ | 8.0 | 8.0 |
| Permanent Linear Change 1600 °C × 3 h (%) | 0.2 – 0.6 | — |
Values are typical production averages, not guaranteed minima. A batch-specific Certificate of Analysis is issued for every shipment; third-party inspection (SGS / BV / TÜV) can be arranged on request.
| Property Reported Above | ASTM | ISO | GB/T |
|---|---|---|---|
| Chemical composition — MgO, Cr₂O₃, SiO₂, Fe₂O₃, Al₂O₃ | ASTM C572 | ISO 12677 | GB/T 5070 |
| Apparent porosity and bulk density | ASTM C20 | ISO 5017 | GB/T 2997 |
| Cold crushing strength | ASTM C133 | ISO 10059-1 | GB/T 5072 |
| Hot modulus of rupture (elevated temperature) | ASTM C583 | ISO 5013 | GB/T 3002 |
| Permanent linear change on heating | ASTM C113 | ISO 2478 | GB/T 5988 |
Every value in the tables above is determined by the method stated in this reference table, and the method is identified on the batch Certificate of Analysis. Where a property is not covered by a directly corresponding ISO method, the ASTM or GB/T method is applied as the reference method and stated accordingly. Third-party verification (SGS / BV / TÜV) can be arranged on request.
About XZK EAF Roof Castable
EAF roof castable is specified for a duty that behaves differently from the rest of the furnace. The roof and delta are heated mainly by radiation from the arc, not by contact with steel or slag. Radiant load damages refractory differently, and a castable chosen for slag resistance alone will underperform there.
Radiation Is a Different Failure Mode
In the roof and delta, the surface absorbs intense radiant energy and runs hotter than the material behind it. That gradient plus the on-off cycling of the arc produces thermal stress, surface spalling and gradual loss of the hot face. Resistance to corrosion hardly enters into it.
Chrome oxide additions at 2–5% improve tolerance of exactly that combination — radiant load plus thermal cycling — which is why Cr₂O₃ appears in roof grades and not in, say, a ladle bottom castable.
Grade Selection
- XZK-CastE80 — 80% Al₂O₃, service to 1720 °C, density 2.80 g/cm³. Standard roof duty.
- XZK-CastE85 — 85% Al₂O₃, service to 1750 °C, density 2.90 g/cm³. High-power furnaces and aggressive melting practice.
Both hold bulk density stable after firing at 1600 °C — the roof does not shrink away from the shell — with crushing strength ≥40 MPa and modulus of rupture ≥8.0 MPa at 1600 °C.
Precast Delta Sections
The delta is the most complex geometry in the roof and the most awkward to cast in situ. Precasting it to drawing removes site variability, improves consistency, and shortens roof change time. On plants where roof change is on the critical path, that time saving is usually worth more than the material cost difference.
Handling and Compliance
Chrome-bearing refractories carry handling and disposal obligations in some jurisdictions, particularly around hexavalent chromium under certain service conditions. We supply full material safety documentation with every order and will advise on compliant handling for your market.
Supply
Minimum order 5 metric tons for standard grades and 10 metric tons for custom formulations, shipping in 7–14 days; precast delta sections quoted to drawing. Batch test data covering density before and after firing, hot strength, permanent linear change and chemistry ships with every lot, along with installation and heat-up guidance.
Where This Grade Sits in the Lining System
Monolithic materials fail more often on installation than on specification. Water demand, mixing time, vibration and the first heat-up curve decide the outcome before the lining ever sees metal — which is why installation parameters are issued with the material instead of being left to site practice.
XZK supplies eaf roof castable as one zone of a zoned package rather than as a standalone item: the grades normally zoned alongside it — among them magnesia dry ramming mass — are documented on the monolithic refractories page, and the vessel-level architecture — where each zone starts and ends, and which mechanism actually limits the campaign — is set out on the electric arc furnace page.
The ABINSK Electric Steel Works EAF and ladle programme reference documents how this class of material performed in full service, with the measured campaign figures rather than datasheet values.
EAF Roof Castable — Production & Application Scenarios
Premium raw materials, CNC pressing, high-temp firing, and on-site installation.
Advantages of Choosing XZK EAF Roof Castable
Chrome Oxide for Arc Radiation
The roof and delta take direct radiant heat from the arc, and radiation damages refractory differently from convection or conduction. Cr₂O₃ additions at 2–5% improve resistance to that radiant load and to the associated thermal cycling.
Service to 1750 °C
XZK-CastE85 is rated to 1750 °C with density stable at 2.90 g/cm³ after firing at 1600 °C, so the roof does not shrink or soften under sustained arc exposure.
Thermal Cycling Tolerance
Roofs swing hard in temperature between power-on and power-off, especially with frequent scrap charging. Modulus of rupture ≥8.0 MPa at 1600 °C reflects the hot strength needed to survive those cycles.
Precast Delta Sections
Delta sections and roof shapes can be precast to drawing, which removes site variability and shortens roof change time.
Specific Applications of EAF Roof Castable
Proven performance across diverse heavy industrial thermal equipment.
EAF Roof & Delta Section
The roof centre and delta area around the electrodes, where arc radiation is most intense.
Electrode Surround Areas
Zones immediately around electrode ports, subject to radiation, off-gas velocity and mechanical disturbance.
Other High-Radiation Zones
Ladle and vessel roofs and covers with similar radiant duty.
400+ Furnaces Trust XZK Refractory Solutions
Over 75% of our international steel and kiln clients continue multi-year long-term procurement partnerships.
Roof delta life improved and the change-out intervals became predictable, which matters more to us than the absolute number.
Density held after firing and the roof did not shrink away from the shell the way the previous material did.
Precast delta sections cut our roof rebuild time significantly.
Chrome content and hot strength were both within the specified range on every batch.
Frequently Asked Engineering Questions
Click any question to expand; only one answer is shown at a time.
Why chrome oxide in an EAF roof castable?
The roof is heated primarily by radiation from the arc rather than by contact with steel or slag. Chrome oxide improves resistance to that radiant load and to the severe thermal cycling that comes with power-on and power-off sequences. It is the radiant duty, not corrosion, that these grades are built for.
CastE80 or CastE85?
By peak roof temperature. CastE80 is rated to 1720 °C and CastE85 to 1750 °C, with slightly higher density. On high-power furnaces with aggressive melting practice, CastE85 usually justifies the difference.
Do you supply precast delta sections?
Yes, to drawing. Precasting removes site variability and shortens roof change time, which on many plants is worth more than the material cost difference.
Are there handling considerations for chrome-bearing material?
Chrome-bearing refractories are regulated in some markets, particularly around hexavalent chromium under certain service and disposal conditions. We supply full material safety documentation and will advise on compliant handling for your jurisdiction.
What is the MOQ and lead time?
5 metric tons for standard grades and 10 metric tons for custom formulations, shipping in 7–14 days. Precast delta sections are quoted to drawing.
What test data is supplied?
Bulk density before and after firing, crushing strength and modulus of rupture at 1600 °C, permanent linear change, and chemistry including Cr₂O₃. Batch COA ships with every lot.
Do you provide installation guidance?
Yes — water addition, mixing, vibration, curing and a heat-up curve suited to roof sections, which are particularly sensitive to moisture removal during first heat.
How is it packed?
25 kg moisture-barrier bags on ISPM-15 pallets with container desiccant. Big-bag options available.
Related Refractories & Lining Materials
Explore complementary refractory brick grades and monolithic materials for your furnace relining.
Get Your EAF Roof Castable Quote within 12 Hours
Please specify your refractory requirements by referring to the following aspects:
- ✓ Target Application: Furnace type, lining position (slag line, hearth, roof)
- ✓ Technical Specs: Operating temperature, slag chemistry, chemistry requirements
- ✓ Quantity & Dimensions: Tonnage requirement, standard or custom CAD drawing
- ✓ Delivery Terms: FOB Qingdao/Tianjin, CIF destination port
Why Steel Plants Choose XZK Refractories
Zonal Engineering, Not Just Bricks
Every proposal is a zone-by-zone material schedule matched to your furnace profile and operating practice — so all zones reach end-of-life together.
Source Factory Consistency
Fully automatic CNC batching and zero-defect quality control keep batch-to-batch variation at laboratory level.
Proven Global References
Supplied to Baosteel, Shougang, Hyundai Steel, JSW, Severstal, MMK and 400+ furnace projects across 60+ countries.
Full-Lifecycle Service
Lining design, masonry supervision, heat-up curves and failure analysis — plus EPC turnkey delivery for new builds and relines.
Send Us Your Furnace Drawing
Our engineers will return a zonal lining proposal with material schedule and quotation within 48 hours — even for non-standard shapes.
- Free material feasibility review
- Zonal architecture & installation drawings
- Heat-up curve & masonry guidance
Strict ISO 9001 Process Control Across All 6 Workshops
Every batch of raw materials is chemically assayed. Finished refractory shapes undergo density, ultrasonic non-destructive testing, and pre-assembly gap verification prior to global packaging.
- Raw material ICP chemical assay on every incoming batch
- Density, porosity and cold crushing (CCS) tests per ASTM / ISO
- Ultrasonic non-destructive testing of finished shapes
- Pre-assembly gap verification before seaworthy packaging