ISO 4968:2022

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 4968
ISO/TC 17/SC 7
Steel — Macrographic examination by
Secretariat: AFNOR
sulfur print (Baumann method)
Voting begins on:
2021-12-20
Acier — Examen macrographique par empreinte au soufre (méthode
Baumann)
Voting terminates on:
2022-02-14
RECIPIENTS OF THIS DRAFT ARE INVITED TO
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OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 4968:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2021

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ISO/FDIS 4968:2021(E)
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  © ISO 2021 – All rights reserved

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ISO/FDIS 4968:2021(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 1
5 Principle and aim of the test .1
6 Test paper and reagents . 2
6.1 Photographic paper . 2
6.2 Reagents . 2
7 Fixing solution .2
8 Test piece . 2
9 Sampling . 3
10 Machining . 3
11 Procedure . 3
12 Test report . 4
Annex A (informative) Classification of sulphur print test results . 5
iii
© ISO 2021 – All rights reserved

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ISO/FDIS 4968:2021(E)
Foreword
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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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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 7, Methods of
testing (other than mechanical tests and chemical analysis).
This second edition cancels and replaces the first edition (ISO 4968:1979), which has been technically
revised.
The main changes are as follows:
— in the Scope, the applicable steels for this method are specified as from 0,005 % to 0,40 %, and this
method may also be applied to cast irons;
— type and concentration of recommended reagents have been explicitly specified for steels with
different sulphur content, respectively, to improve test effect and efficiency;
— method to remove extra acid solution and bubbles, and method to drain have been added in detail;
— classification of test results as positive segregation, negative segregation and central segregation,
with examples in Annex, has been added.
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.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 4968:2021(E)
Steel — Macrographic examination by sulfur print
(Baumann method)
1 Scope
This document specifies a method (Baumann) for the macrographic examination of steel by means of
contact printing using silver salts and acid.
The method is applicable to steels of which the sulphur content is less than 0,40 %. This method can
also be applied to cast irons.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
4 General
4.1 The sulphur print test is essentially a qualitative test. It is inadvisable to evaluate the sulphur
content of a given steel merely on the basis of its sulphur print.
4.2 Experience shows that the degree of darkening of the photo-sensitive emulsion is not always
in proportion to the quantity of sulphides present in the metal. Certain factors may influence the
macrographic attack to a greater or lesser extent; as examples, the following may be quoted:
— the chemical composition of the steel: the presence of certain elements modifies the type and shape
of the sulphides and consequently the appearance of the image obtained, for example concentrations
of titanium greater than 0,1 % give prints which do not reveal sulphides;
— the surface condition of the sample: the presence of surface cold working may alter the image
obtained;
— the sensitivity of the photographic paper.
4.3 The use of the test, and the conditions for interpreting the results observed, depend on the
particular case: details are laid down in product standards or shall be subject to special agreement.
5 Principle and aim of the test
5.1 The aim of macrographic examination by sulphur printing is to detect, by printing on photo-
sensitive papers previously soaked in acid, the position o
...