Method Scope — Not a Feed Specification
ISO 4700 determines how much compressive load an individual fired iron ore pellet withstands before it fails. The material it describes is the indurated pellet — a finished product that has already been through a plant's thermal cycle.
That boundary is where most misreadings start. A crushing-strength result is frequently circulated with a pellet feed offer as though it vouched for the feedstock. It does not. This page sets out what the method covers, what sits outside it, and what to ask for instead.
This page explains the method's scope. It states no strength value, no acceptance limit and no test result of any kind.
What the method applies to
Read plainly, ISO 4700 answers a narrow question well. The difficulty is not in the method — it is in the assumption that a result obtained on pellets can be carried across to something else.
A plant buys feed and sells pellets. Those are two different materials, tested on different properties, at different points in the process. When a strength figure travels with a feed offer, it usually came from pellets produced somewhere else — on a different feed, in a different plant, under a different thermal cycle.
That does not make the figure worthless. It makes it a description of the pellets that were tested. The question a feed buyer has to answer is whether the material on offer will produce pellets of that quality in their own circuit — and the strength of a sample made elsewhere cannot settle that on its own.
The practical consequence: keep the tested object and the offered object separate. Ask what was tested, where it was produced and from which feed. Then ask for the feedstock's own characteristics, which are the ones that actually bear on whether it will suit your circuit.
Where the method stops
Each of these is a boundary the method draws. Crossing it does not make the figure wrong — it makes the claim attached to it unsupported.
Crushing strength is determined on indurated pellets that have already been through the plant's thermal cycle. It describes the product that went in for testing, so it cannot stand in for a feedstock's suitability. A strong result on one set of pellets says nothing about whether a different feed will ball or survive induration.
Applies to: fired pellet samples.
The method is written for pellets. Lumps, fines, sinter feed and concentrate are outside it, so a crushing-strength figure cannot be reported for them without leaving the method's scope. Where a sinter or lump charge needs a handling measure, that is a different determination with a different index.
Applies to: pellets only.
A crushing-strength result describes one mechanical property of the tested pellets. It does not establish chemistry, reducibility, swelling behaviour or how the pellets will perform in a particular furnace. Reading it as a general pass mark for a material conflates one measurement with a whole specification.
Applies to: one property among several.
Scope check
Say what the result was obtained on and what you are being offered. The check reports whether the two are the same object — and where they are not, what the figure can and cannot support.
Nothing is pre-selected. Both answers are needed before the check can say anything.
The check compares what a result was obtained on against what you are buying. Until both are stated there is nothing to compare, so no reading is offered.
Neighbouring methods
These are the determinations most often confused with each other on a certificate. Each answers a different question, and none of them substitutes for another.
| Method | Taken on | Reports |
|---|---|---|
| Crushing strength | Fired pellets | The compressive load an individual pellet withstands before failing. |
| Tumble and abrasion | Lump ore and sinter | How much a sized charge breaks down as it is tumbled and handled. |
| Total iron content | A prepared test portion of the ore | The total iron figure a grade claim or settlement is written against. |
| Sampling and preparation | A defined lot | Nothing about the ore — it is what makes a later result defensible at all. |
A comparison of scope, not a ranking. No method here is better than another — each is the correct one for the question it was written to answer, taken on the material it was written for.
The sampling, chemistry, physical and reduction methods that sit alongside this one, each with what it answers and what it does not certify.
Open the standards indexThe finished indurated product this method is written for, described as a product rather than as a feedstock.
See the pellet pageWhat to request
A strength figure on its own cannot be compared with another, and cannot be tied to a material. The parameters below are what make it a result rather than a number.
Strength varies with pellet size. A figure reported without the fraction it was taken on cannot be placed beside another figure, because the two may describe different portions of the size range.
The procedure is not frozen across editions. State which one was used, because two laboratories applying different editions are not doing the same thing even when the title matches.
A reported value rests on a population of individual pellet tests. Without the count, the figure has no stated basis for comparison with another laboratory's result.
This is the question that decides whether the result is relevant at all. Where they came from a different feed, in a different plant, the figure describes that material and not yours.
If you are buying feed, ask for its sizing and distribution with the method, each gangue component stated separately, loss on ignition, and moisture with its mass basis. Those are the properties that bear on the route.
A note on scope: this page explains what the method covers and what it does not. It states no strength value, no acceptance threshold and no test result, and nothing here should be read as a limit your plant ought to apply.
Buyer FAQ
These are the points buyers and plant teams raise once a crushing-strength result has been sent alongside an offer.
Qualified enquiry
Tell the commercial desk which material you are buying and what evidence you have, and the response can address the material rather than a test taken on something else.
State the material, the evidence you hold and the documents you still need. The full iron ore RFQ carries the fields for a qualified enquiry.
