Testing refractories ASTM standards

Table 10.20. ASTM standards for testing refractories ASTM standard Description...

Manual of ASTM Standards on Refractory Materials, 8th Edition. American Society for Testing and Materials, Philadelphia. PA. 1957. 

It is well known that corrosion of refractories used in the superstructure of glass melting furnaces can occur due to reaction with components of raw batch (also known as batch carryover) such as silica sand and soda ash and also from vapor phase species, such as NaOH. While there is a standard test available from ASTM for corrosion of refiectories from vapors (C987), there is no standard test available for testing corrosion from batch carryover. The ASTM standard, C987, requires the use of either alumina or platinum crucible for melting batch components that produce vapors, such as sodium carbonate. For the purpose of this study, the authors chose to prepare crucibles directly from the fusion-cast AZS and vibro-cast AZS products. 

ASTM C16-96. Standard test method for load testing refractory brick at high temperatures. 

ASTM C768-99. Withdrawn standard ASTM C768-99 standard practice for drip slag testing refractory materials at high temperature (withdrawn 2004). 

There are two standard methods for determining the thermal shock resistance of refractory materials. For brick shapes, thermal shock resistance is measured by Ribbon Thermal Shock Testing (ASTM C-1100), and for monolithic refractories the standard method is ASTM C-1171. These tests clearly differentiate among refractory materials about their resistance to thermal shocks. 

C71 -00 Standard Terminology Relating to Refractories. Annual Book of ASTM Standards Vol. 15.01. West Conshohocken, PA American Society for Testing and Materials, 2001. 

In addition to the above-mentioned standards, a number of specifications exist, unfortunately. These specifications come from the petrochemical industry and deviate from EN and ASTM standards especially in regard to the shape of the test pieces. Here, too, harmonization would be in the best interest of all parties involved. Figure 2 demonstrates how many test pieces a producer of unshaped refractories has to prepare. 

Measurement methods vary. Both horizontal and vertical measuring techniques exist, and test piece sizes vary between 114 mm long x 38 mm x 38 mm in the ASTM standard test (3), which combines thermal expansion with a refractoriness under load test, down to small rectangular prisms of 55 mm x 10 mm x... 

Refractoriness. Refractoriaess is determined by several methods. The pyrometric cone equivalent (PCE) test (ASTM C24) measures the softening temperature of refractory materials. Inclined trigonal pyramids (cones) are formed from finely ground materials, set on a base, and heated at a specific rate. The time and temperature (heat treatment) requited to cause the cone to bend over and touch the base is compared to that for standard cones. 

The standard ASTM PCE test is relative and used extensively only for alumina—siUca refractories and raw materials (see Table 5). However, the upper service limit is generally several hundred degrees below the nominal PCE temperature because some load is generally appHed to the refractory duriag service. In addition, chemical reactions may occur that alter the composition of the hot face and therefore the softening poiat. The relationship between PCE numbers and temperature is described ia ASTM C24. 

ASTM C 417 Standard Test Method for Thermal Conductivity of Unfired Monolithic Refractories, December 1993, Revised 1998. 

ASTM C860 Standard Practice for Determining the Consistency of Refractory Castable Using the Ball-in-Hand Test, April 2000. 

ASTM. 2000. Standard test methods for apparent porosity, liquid absorption, apparent specific gravity, and bulk density of refractory shapes by vacuum pressure. ASTM Stand. (C830). 

ASTM 0134-95(1999), Standard Test Methods for Size, Dimensional Measurements, and Bulk Density of Refractory Brick and Insulating Firebrick, 1999. 

While corrosion testing of metallic materials is the focus here, planning and design of environmental perfoirnance tests for nonmetaUic materials, such as paints, plastics, ceramics, and refractories is similar. Specific corrosion test methods have been developed by ASTM International [70-12], NACE International [73], and the International Organization for Standardization (ISO) [74]. 

Hot-plate Spalling Test. A spalling test designed specifically for the testing of silica refractories it was standardized in ASTM - C439, now withdrawn, though a description still appears for information in the ASTM Annual Book of Standards. 

Refractoriness-under-Load. The ability of a material to withstand specified conditions of load, temperature and time. Details of variations in this test will be found in the following national standards Britain-B.S. 1902 USA-ASTM-C16 Germany-DIN 51064 France-AFNOR B49-105. B.S. 1902 specifies a dilatometer method (Pt. 4.8)... 

In Comparative Tests the same constant heat flow is established through the specimen to be measured, and a standard sample of known conductivity. The different temperature gradients across the two samples are compared. (B.S. 1902 Pt. 5.8 specifies a test of this type for refractories, Pt.6 Section 6 a guarded hot-plate test up to 1200 C for ceramic fibre products ASTM C408 one for ceramic whitewares, using a copper standard from 40 to 150°C. 

The wear resistance of refractories is determined according to ASTM C-704-01 [56]. This test method measures the relative abrasion resistance of various refractory samples under standard conditions at room temperature. The abrasion resistance of a refractory material provides an indication of its suitability for service in abrasion or erosive environments. 

The hardness determination of refractories is limited by its heterogeneous coarse-grained structure. The hardness values characterize small volumes of the material. There is no standard for the determination of the hardness for refractories for research purposes, it is possible to use ASTM Cl 327-08 [59] and ASTM C1326-13 [60] for structural ceramics. Many publications describe the determination of the fracture toughness of ceramics by measurement of cracks around the indented areas during hardness testing [61-63]. 

ASTM C914-95 (1999). Standard test method for bulk density and volume of solid refiac-tories by wax immersion. ISO 5018 1983 Refractory materials - determination of true density. 

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