Incendivity of some coal-cutter materials by impact-abrasion in air-methane
Test equipment that simulated frictional impacts between coal-cutter bits and mineral inclusions at a coal face during operation of a continuous coal mining machine was used to study the incendivity of impacts between various rocks, metals, and hard-metal alloys in an explosive mixture of air-7 pct natural gas. Quartzitic sandstone was found to be the most incendive of several rocks tested. Limestone concretions from a coal seam, known locally as ''sulfur balls,'' sparked furiously but were not incendive. Among the metals tested, the type of steel used in commercial coal-cutter tools was the most incendive material tested. A 17-4PH stainless steel was less incendive and appears to be the most promising high-strength steel alloy, reasonably economical, for use in coal-cutter bits. Some hard-metal alloys, primarily titanium and zirconium diboride composites, were also evaluated as possible replacements for the conventional cobalt-bonded tungsten carbide used in the tip of coal-cutter bits. The metal-bonded diborides were generally less incendive (but more brittle) than the conventional tungsten carbide. Carbonitride coatings on tool bits were also tested but found to have no advantage. The source of ignition during frictional impact between metal and rock was studied. Immediately after impact, a yellow flash was observed and a smear of metal near its melting point occurred on the rock. This hotspot on the rock, rather than the yellow flash or sparks or metal fragments, was observed to be the cause of the ignition.
- Research Organization:
- Bureau of Mines, Albany, Oreg. (USA). Albany Metallurgy Research Center
- OSTI ID:
- 7264734
- Report Number(s):
- BM-RI-7930
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
03 NATURAL GAS
COAL MINES
FIRE PREVENTION
CUTTING TOOLS
SAFETY ENGINEERING
NATURAL GAS
IGNITION
ABRASION
AIR
CARBONITRIDES
COMPOSITE MATERIALS
FRICTION
ROCKS
ENERGY SOURCES
ENGINEERING
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
MINES
TOOLS
016000* - Coal
Lignite
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012000 - Coal
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034000 - Natural Gas- Combustion