Determination of Resistance to Abrasion at Ambient Temperature – in Order to Establish Better Comparability Between Laboratories, Existing Standards Have to Be Revised
1 Hochschule Koblenz, 56203 Höhr-Grenzhausen/Germany
2 RHI AG, 8700 Leoben/Austria
3 DIFK GmbH, 56203 Höhr-Grenzhausen
Volume 5, Issue 2, Pages 59 - 64
In order to gain a deeper understanding how highly accelerated particles affect the surface of a refractory material during service, two test methods, ASTM C 704 and EN ISO 16282 were established. In the past imprecise data obtained by these methods lead to unjustified complaints of the refractory user industry when a third party laboratory cross checked the specified values for the abrasion resistance. The economic impact for the refractory producers as well as for the consumers is tremendous and painful. In order to enhance the reproducibility of this test, the latest revisions of ASTM C 704 in 2009 and 2012 result in a more rigid definition of the testing device. However the authors propose a different route to perform blast abrasion tests which generate highly reproducible abrasion values even if the tests are performed in different laboratories. The key to obtain rigid test values is that prior to the test the pressure supply for blast gun has to be adjusted till the abrasion volume for a standard float glass sample yields the exact value of 9,3 cm3 ± 0,3 %. The properties of the standard float glass plates are defined in ASTM C 704-12. As a consequence it is proposed that the standard air pressure should no longer be defined at 4,5 bar but shall be adjustable. The effectiveness of this measure was constrained by a round robin test that was performed in accordance to ISO 5725 in 2012. In this test 10 laboratories were involved and 6 different refractory materials were tested. The tests were performed according to ASTM C 704-09 with a standard air pressure of 4,5 bar. A second test series was conducted in which the test conditions were modified that way that the air pressure was adjusted till the abrasion result for a standard float glass sample yields the exact value of 9,3 cm3 ± 0,3 %. The results of both test runs were compared with each other and with the precision date published in ASTM C 704-09 and ASTM C 704-12 (latest revision). The major outcome of the round robin test is that the precision of results can be significantly enhanced if the air pressure is calibrated prior to the test by using a standard float glass sample. Due to the wear inside the venturi system it is necessary to readjust the air pressure with float glass samples frequently. It is recommended to do this every 20 tests. If the air pressure is adjusted properly the detailed layout of the apparatus dimension has no significant influence on the precision of the results. The gained results are robust enough to recommend a revision of the actual EN ISO 16282.
blast abrasion, refractory wear, interlaboratory comparison, round robin test results
Göller Verlag GmbH