ISO 4968-1979 pdf free.Steel — Macrographic examination by sulphur print (Baumann method).
1.Scope and field of application:This International Standard specifies a method (Baumann) forthe macrographic examination of steel by means of contactprinting using silver salts and sulphuric acid.The method is applicable to non-alloy and alloy steels1) ofwhich the sulphur content is less than 0,1 %.2)
2.General:
2.1 The sulphur print test is essentially a qualitative test. It isinadvisable to assess the sulphur content of a given steelmerely on the basis of its sulphur print. Experience shows that the degree of darkening of thephoto-sensitive emulsion is not always in proportion to thequantity of sulphides present in the metal. Certain factors mayinfluence the macrographic attack to a greater or lesser extent;as examples, the following may be quoted :
—the chemical composition of the steel : the presence ofcertain elements modifies the type and shape of thesulphides and consequently the appearance of the imageobtained,for example concentrations of titanium greaterthan o,1 % give prints which do not reveal sulphides;
— the surface condition of the sample : the presence ofsurface cold working may alter the image obtained;
— the sensitivity of the photographic paper.
2.2.The use of the test,and the conditions for interpretingthe results observed, depend on the particular case : details arelaid down in product standards or shall be subject to specialagreement.
3Principle and aim of the test
3.1.The aim of macrographic examination by sulphur printingis to detect,by printing on photo-sensitive paper3) previouslysoaked in sulphuric acid solution, the position of areas contain-ing sulphur inclusions found in the metal in various chemicalforms and with various shapes : iron sulphide,manganesesulphides,mixed sulphides, oxy-sulphides etc.
3.2The distribution of the sulphur-rich areas is revealed bythe locai release of hydrogen sulphide，causing darkening ofthe sensitive emulsion due to the chemical conversion of thesilver halides to silver sulphide.
3.3By examining the distribution and size of the sulphur in-clusions detected by this process it is possible to make someasessment of the degree of uniformity of the metal from thesection examined.Thus sulphur printing reveals chemical ir-regularities (segregations : for example those of a non-rimmingfree-cutting steel) and may reveal certain physical irregularities(for example cracks and porosity). Furthermore,sulphur prin-ting may be used sometimes to distinguish rimming steel fromkilled steel and may also draw attention to certain areas wheretests (for example,mechanical tests) or sampling for analysismay need to be carried out.ISO 4968 pdf download.