ISO 11257:2022

Iron ores for shaft direct-reduction feedstocks - Determination of the low-temperature reduction-disintegration index and degree of metallization

This document specifies a method to provide a relative measure for evaluating the degree of size degradation and degree of metallization of iron ores, when reduced under conditions resembling those prevailing in shaft direct-reduction processes. This document is applicable to lump ores and hot-bonded pellets.

Minerais de fer pour charges utilisées dans les procédés par réduction directe — Détermination de l'indice de désintégration par réduction à basse température et du degré de métallisation

General Information

• Status: Published
• Publication Date: 21-Mar-2022
• ICS: 73.060.10 - Iron ores
• Technical Committee: ISO/TC 102/SC 3 - Physical testing
• Drafting Committee: ISO/TC 102/SC 3 - Physical testing
• Current Stage: 6060 - International Standard published
• Start Date: 22-Mar-2022
• Due Date: 30-Sep-2022
• Completion Date: 22-Mar-2022

Relations

• Revises: ISO 11257:2015 - Iron ores for shaft direct-reduction feedstocks - Determination of the low-temperature reduction-disintegration index and degree of metallization
• Effective Date: 17-Jul-2021

Overview - ISO 11257:2022 (low‑temperature reduction-disintegration index)

ISO 11257:2022 specifies a laboratory method to evaluate iron ores (lump ores and hot‑bonded pellets) as feedstocks for shaft direct‑reduction processes. The standard defines a rotating‑tube, isothermal low‑temperature reduction test (760 °C) using a controlled reducing gas to produce two comparative metrics: the reduction‑disintegration index (D_R) - the mass percentage of material finer than 3.15 mm after reduction - and the degree of metallization (M) derived from chemical analysis of metallic and total iron.

Key topics and technical requirements

• Test scope: Applicable to lump ores and hot‑bonded pellets; results intended for quality control, contracts and research comparisons.
• Sample preparation:
  • Follow ISO 3082 for sampling and preparation.
  • Test sample ≥ 2.0 kg (dry basis); oven‑dry at 105 °C ± 5 °C to constant mass.
  • Prepare at least four test portions ≈ 500 g each, weighed to 1 g.
  • Typical size ranges specified for pellets and lump ores (e.g., pellets: 50% - 16.0 mm +12.5 mm and 50% - 12.5 mm +10.0 mm).
• Apparatus and test conditions:
  • Rotating reduction tube (no lifters), internal dia. 130 mm ± 1 mm, length 200 mm; tube rotated at 10 r/min ± 1 r/min.
  • Furnace to reach and maintain 760 °C ± 5 °C.
  • Sieves per ISO 3310 (3.15 mm mesh used for D_R).
• Reducing atmosphere and flows:
  • Reducing gas composition (volume fraction): CO 36% ±1, CO2 5% ±1, H2 55% ±1, CH4 4% ±1.
  • Reducing gas impurities limited (O2 ≤ 0.1%, H2O ≤ 0.2%); reducing gas flow 13 L/min ± 0.5 L/min for 300 min.
  • Nitrogen used for heating/cooling with specified flow controls.
• Measurements and calculations:
  • After reduction, sieve at 3.15 mm and determine mass percentage <3.15 mm → reduction‑disintegration index (D_R).
  • Determine total and metallic iron (methods such as ISO 16878 referenced) to calculate degree of metallization (M).
• Safety: Explicit warnings about toxic/explosive gases (CO, H2) and requirements for ventilation and operator precautions.

Applications - who uses ISO 11257:2022

• Iron ore producers and pellet manufacturers for product quality control.
• Direct reduced iron (DRI) plant engineers and feedstock selection teams.
• Materials testing laboratories performing comparative reducibility and disintegration assessments.
• Buyers, contract managers and R&D groups evaluating ore behaviour under shaft direct‑reduction conditions.

Related standards

• ISO 3082 (sampling/sample preparation)
• ISO 3310‑1/2 (test sieves)
• ISO 16878, ISO 5416, ISO 2597‑1/2 (metallic and total iron determination)
• ISO 11323 (vocabulary for iron ore and DRI)

Keywords: ISO 11257:2022, low‑temperature reduction‑disintegration index, degree of metallization, shaft direct‑reduction, iron ores, hot‑bonded pellets, lump ores, rotating tube test, reducing gas composition.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 11257
Fourth edition
2022-03
Iron ores for shaft direct-reduction
feedstocks — Determination of
the low-temperature reduction-
disintegration index and degree of
metallization
Minerais de fer pour charges utilisées dans les procédés par réduction
directe — Détermination de l'indice de désintégration par réduction à
basse température et du degré de métallisation
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Sampling, sample preparation, and preparation of test portions .2
5.1 Sampling and sample preparation . 2
5.2 Preparation of test portion . 2
6 Apparatus . 2
7 Test conditions .4
7.1 General . 4
7.2 Reducing gas . 4
7.2.1 Composition . 4
7.2.2 Purity . 4
7.2.3 Flow rate . 4
7.3 Heating and cooling gas . 4
7.4 Temperature of the test portion . 4
8 Procedure .4
8.1 Number of determinations for the test . 4
8.2 Reduction . 4
8.3 Sieving . 5
8.4 Chemical analysis . 5
9 Expression of results . 5
9.1 Calculation of the reduction-disintegration index (D ) . 5
DR
9.2 Calculation of the degree of metallization (M) . 6
9.3 Repeatability and acceptance of test results . 6
10 Test report . 6
11 Verification . 7
Annex A (normative) Flowsheet of the procedure for the acceptance of test results .8
Bibliography . 9
iii
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
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Attention is drawn to the possibility that some of the elements of this document may be the subject of
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expressions related to conformity assessment, as well as information about ISO's adherence to
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron,
Subcommittee SC 3, Physical testing.
This fourth edition cancels and replaces the third edition (ISO 11257:2015), which has been technically
revised to include ISO 16878 as a reference for the metallic iron determination.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This document concerns one of a number of physical test methods that have been developed to
measure various physical parameters and to evaluate the behaviour of iron ores, including reducibility,
disintegration, crushing strength, apparent density, etc. This method was developed to provide a
uniform procedure, validated by collaborative testing, to facilitate comparisons of tests made in
different laboratories.
The results of this test have to be considered in conjunction with other tests used to evaluate the quality
of iron ores as feedstocks for direct reduction processes.
This document can be used to provide test results as part of a production quality control system, as a
basis of a contract, or as part of a research project.
v
INTERNATIONAL STANDARD ISO 11257:2022(E)
Iron ores for shaft direct-reduction feedstocks —
Determination of the low-temperature reduction-
disintegration index and degree of metallization
CAUTION — This document can involve hazardous operations and equipment. document does
not purport to address all of the safety issues associated with its use. It is the responsibility of
the user of this document to establish appropriate safety and health practices and determine
the applicability of regulatory limitations prior to its use.
1 Scope
This document specifies a method to provide a relative measure for evaluating the degree of size
degradation and degree of metallization of iron ores, when reduced under conditions resembling those
prevailing in shaft direct-reduction processes.
This document is applicable to lump ores and hot-bonded pellets.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2597-1, Iron ores — Determination of total iron content — Part 1: Titrimetric method after tin(II)
chloride reduction
ISO 2597-2, Iron ores — Determination of total iron content — Part 2: Titrimetric methods after
titanium(III) chloride reduction
ISO 3082, Iron ores — Sampling and sample preparation procedures
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3310-2, Test sieves — Technical requirements and t
...