the cylinder cool, the blast tempera- ture, and other visual and audio clues. Additionally, analyzing the outputs (iron, slag and emissions) gives a picture of how the furnace is melting. For the iron, you measure temperature, chemistry and volume. Are you getting too much or too little iron based on the current melting conditions? Slag is monitored through floor testing and lab analysis, and stack gas analysis provides information on the cupola furnace emissions.
Making and keeping records gives
the operator the power to look at what has changed in the process that led to an unexpected and unwanted result and make adjustments accordingly.
Checking Composition
Fig. 2. The chill test is a visual indicator of iron’s chemical composition. The chill on the left shows more white iron in the corners of the wedge than the chill on the right, indicating the iron on the left is trending more toward white iron than gray iron.
Continuous measuring and record- ing of data is preferred, although not practical for all. At the least, consistent sampling should be used to keep tabs on how the furnace operates. Te fundamental requirement is that the sample is representative of the whole, or the test results become meaningless and misleading. For iron, several methods are avail- able to obtain compositional infor- mation, and they don’t always seem to agree. Te composition of the iron coming out of the cupola can be mea- sured in spectrometer and combus- tion lab tests and via thermal analysis. In addition, operators can conduct chill tests on the shop floor—it’s a simple test to use in between the other tests and gives a visual indica- tion of the potential of the metal to solidify as white iron rather than gray iron (Fig. 2). Changes in operational conditions
can affect each of the tests differently. When the test results disagree with each other or what you are expecting to come out of the furnace, it is an indication that something has changed and needs to be investigated. Tests on the iron give you the com-
Fig. 3. This chart illustrates a blast rate sweet spot for a cupola furnace. 28 | MODERN CASTING August 2016
position of your end product. Testing the composition of your slag may give you clues as to why the iron composi- tion or element recoveries might be out of whack. Cupola operations have to balance
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60