Alternative Methods for Determining Microcleanliness: A Study Based on Hot Work Tool Steels

This study focuses on the development and comparison of standard a
nd alternative methods to evaluate the cleanliness of hot work tool steels
(for comparison reasons also other tool steels) used for dies on a microscopic level. The steels subjected to this study are hot working tool steels roduced by an electric arc furn ace and ladle furnace (abbreviation of the investigated materials: conv) . After re-melting by either an electric slag (abbrev. PESR) or a
vacuum arc furnace (abbrev. VAR), the forged or rolled specimen were taken as subject to investigate cleanliness with different methods. The typical
investigation method for non-metallic inclusions (NMI) is light optical microscopy (LOM) according to different standards such as ASTM E45, ISO 4967, DIN 50602, EN 10247, JIS G0555. For comparison, the alternative methods Gig
a Cycle Fatigue tests with automated SEM-EDS-investigations, electrolytic extraction and X-ray computed tomography (XCT) are applied. To obtain
comparative results from the standard and alternative methods, cylindrical
specimens with a circle diameter of ~ 2 mm and length ~20 mm used for XCT experiments were destructively investigated with automated LOM acc
ording to the LOM-standards as mentioned above and additionally statistical analysis on specific amount of NMI. Comparative results for the different pro
duction routes show a similar size of NMI within each method. Each method has its advantages and disadvantages concerning additional information, e.g. time for preparation and measurement and costs.