Two refractory data sheets can look nearly identical and describe materials that behave completely differently in service. The difference is usually in which numbers were chosen, at which test conditions, and which were omitted. This checklist is written from the receiving end — for buyers and application engineers who need to compare quotations on substance rather than typography.
Chemistry: Purity Is Only Half the Story
Al₂O₃ or MgO content gets the headline, but impurities often matter more. In alumina products, check SiO₂ and Fe₂O₃: these form low-melting phases at service temperature and soften the hot face, so two 90% alumina bricks with different impurity profiles are different products wearing the same headline number. In magnesia-carbon, look past MgO purity to the CaO/SiO₂ ratio — the ratio, not just the MgO figure, governs how the magnesia behaves against slag. And in carbon products, ask for the ash chemistry, because the ash is what slag actually attacks once the carbon has done its job.
Physical Properties: Match the Test to the Failure Mode
- Bulk density and apparent porosity — porosity is the best available single predictor of slag penetration depth. Lower is generally better, but read it alongside density and strength: a very low porosity with low strength signals a body that may crack in service instead.
- Cold crushing strength — easy to quote and of limited use alone. It tells you about handling and installation survival, not hot performance. Treat a sheet that leads with CCS as a signal to ask about HMOR.
- Hot modulus of rupture — the number that actually matters for erosion and slag wash at temperature. If a supplier quotes only cold strength, ask for HMOR at your service temperature; the gap between the two is where many "equivalent" grades are not equivalent.
- Refractoriness under load — more useful than refractoriness (SK/сеger cone), because real linings carry load. Ask for RUL at 0.2 MPa, and for the creep rate where the application is sustained-load.
- Thermal shock resistance — where cycling dominates the duty. Ask how it was measured; the test conditions are the specification.
Application-Specific Numbers
- Carbon hearth block — pore size distribution, not total porosity. Average pore diameter and the share of pores below 1 μm govern iron penetration; a block that omits this data is asking to be judged on the wrong axis. Thermal conductivity at working temperature belongs beside it, verified per batch.
- Nitride-bonded SiC — nitrogen content, the measurable evidence that the nitride phase actually formed, plus residual free Si where specified.
- Stove grades — creep rate at a stated temperature, load and duration. A creep number without its test conditions is not a specification.
- Castables — strength after firing at service temperature, not only after drying, plus permanent linear change and water demand for placement.
- Flow-control items — dimensional inspection reports, because for SENs, plates and stoppers the interface fit is half the performance.
A Worked Example: Two Ladle Slag-Line Quotations
Consider a realistic comparison. Supplier A quotes a 14% C slag-line brick with CCS 40 MPa and no HMOR figure. Supplier B quotes 14% C with CCS 35 MPa, HMOR 10 MPa at 1400 °C, apparent porosity 15%, and the antioxidant package stated. On the traditional reading, A wins: higher cold strength, lower price. On the engineering reading, B wins before the price discussion starts: HMOR at temperature is the property that resists slag wash in the position that fails first, the porosity figure says something about penetration depth, and the antioxidant disclosure says the formulation was designed rather than assembled. If A's brick were genuinely superior, the HMOR figure would be its best argument — its absence is the information. Buyers do not need a laboratory to make this comparison; they need the discipline to ask for the number that governs the failure mode and to notice which supplier volunteers it. That single habit, applied across a full enquiry, eliminates most of the risk that hides behind identical-looking data sheets.
Red Flags
A complete grid with no blanks sometimes means numbers were filled in rather than measured. Missing test conditions next to quoted values is worse than a blank — it means the number cannot be reproduced or challenged. A quotation that under-specifies the application-critical property (creep for stoves, HMOR for ladles, pore structure for hearths) is pricing a different product than the one you need. None of these red flags is proof of a bad supplier; each is a reason to ask one more question and to notice how the answer feels.
Build Your Own One-Page Checklist
The fastest way to institutionalise this discipline is a one-page checklist per product family, built once and reused across every supplier. For each family, list the three properties that govern the failure mode, the test conditions they must be quoted at, and the batch documentation you expect at delivery. For ladle slag line: HMOR at service temperature, apparent porosity, antioxidant package. For stove checkers: creep at stated conditions, RUL, dimensional tolerance. For hearth carbon: pore size distribution, thermal conductivity at temperature, ash chemistry. For castables: fired strength, permanent linear change, water demand. The checklist changes the enquiry itself — suppliers receive the same property list from you and can no longer differentiate by omission. It also changes the internal conversation: when a cheaper quotation arrives missing the governing property, the discussion is no longer "should we take the discount" but "why is the number missing", and that discussion ends the same way every time.
What XZK Data Sheets Do Differently
We publish the figures we test consistently, state the test method — GB/T, ASTM or ISO — beside every number, and leave a cell blank when a property is not measured consistently for that grade. Every batch ships with a Certificate of Analysis tied to the pallet marking, so the sheet you compare in a negotiation is the sheet the receiving inspection can verify. If you are building a comparison across suppliers for an upcoming reline, send us the property list you care about — we will complete our column with test conditions stated, including the blanks. The product pages, from magnesia carbon brick to microporous carbon brick, follow this format, and the application pages state which property governs each duty.
