International Standards for Estimating Nonmetallic Inclusions in Steel and the High-Priority Problems of Improving State Standard GOST 1778–70

Foreign metallographic standards are updated every 2–5 years and include an image analyzer, which was used for the first time more than 20 years ago. All valid modern standards are based on quantitative metallography methods, since visual estimation using the rating charts method contrary to direct stereological measurement by means of an image analyzer cannot provide unity of measurements. The status of State Standard GOST 1778–70 has been analyzed; until now, it is used in the revision of 1970, and high-priority problems of its improvement are formulated with allowance for the world experience of development of standard practice for determining the nonmetallic inclusions in steel. Herewith, the use of an automatic image analyzer should be available for all estimation methods described in State Standard GOST 1778–70 together with the visual estimation by methods Sh and manual measurements using methods K, P, and L. The practice of direct stereological measurements of the volume fraction, size, number, shape, and distribution of nonmetallic inclusions in steel should become one of the methods of State Standard GOST 1778. The names of rating charts (OT (DO = dot oxides), SN (NDS = non-deformable silicates), SKh (BS = brittle silicates), etc.) should be considered conditional, since optical metallography cannot estimate the chemical composition of the complex multiphase deoxidation products retained in the finished metal after secondary steelmaking. Interlaboratory round-robin tests, which are required for objective assessment during acceptance tests performed by the manufacturers and consumers of metal products, should become regular practice for provision of measurements unity.