AA-GMA69-2002.pdf
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1、G ar 1 1 Copyright The Aluminum Association Inc. Provided by IHS under license with AA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 02:57:14 MDTNo reproduction or networking permitted without license from IHS -,-,- Guidelines for Handling Molten Aluminum Third Edit
2、ion Editor: Seymour G. Epstein Technical Consultant Editorial Board Michael K. Anderson Christian M. Bickert J. Martin Ekenes Seymour G. Epstein E Robert Hubbard John E. Jacoby Charles D. Johnson Vincent J. Newberry Jake J. Niedling Warren S. Peterson Donald C. Pierce Greg Rawls Ray T. Richter Clark
3、 Weaver Wagstaff, Inc. Pechiney, Inc . Hydro A l Dross processing operations and equipment are not discussed. Emphasis is placed on large-scale melting and casting practices for the production of process ingot. Slabs or billets are subsequently mechanically worked into forms such as sheet, plate, fo
4、il, forgings, extrusions, or T-bars, sow and Remelt Scrap Ingot (RSI). These are then remelted at another site. More attention is also given to scrap melting operations. Terminology used in these guidelines reflects that employed in the industry. 2.1 .I: Aluminum-Lithium Alloys These Guidefinesdo no
5、t cover procedures for the additional hazards involved in melting and casting aluminum-lithium alloys. For information, see Aluminum Association Pub- lication T4, Safe also hydrated lime. Some appreciation of the magnitude of the release of energy when aluminum is converted to its oxide can be reali
6、zed by noting that the energy release in this reaction per pound of aluminum is about three times that from a pound of trinitrotoluene (TNT). Section 6 Suggested Purchase Specifications for Charge Materiais Purchase orders offer the first opportunity to control the presence of harmful contaminants i
7、n materials to be added to melting furnaces. It is suggested that purchase orders specify in writing that aluminum, aluminum scrap, alloying materials, and fluxes be relatively free of water and contain no volatile materials, or other oxidizing agents which can cause an explosion when charged into a
8、 melting furnace. An exception is the purchase of aluminum scrap in the form ofbofigs, * g S , Saw Chips, fines, Pit cledgs, etc. Which can contain oil and water. Extreme care must be taken in processing these forms of scrap. Section 7 heiving, hspection, Storage, Drying of Scrap and AU Other Compon
9、ents of the Furnace Charge As in the case of the proposed purchase specifications noted in Section 6, the goal in Section 7 is to provide guidance for each facility to devise and implement a system that covers a l l plant functions and cast shop related activities to anticipate and prevent water and
10、 other hazardous contaminants being present on and in materials added to the melting furnaces. Recommended actions are given in Sections 12-1 9. For more detailed descriptions, refer to Aluminum Association Publication GSR, Guidelines for AZuminum Scrap Receiving and Inspection, Second Edition (2002
11、). 12 Copyright The Aluminum Association Inc. Provided by IHS under license with AA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 02:57:14 MDTNo reproduction or networking permitted without license from IHS -,-,- Section 8 Melting, Melt ktment and Tiruisfer, and Cas
12、ting Processes This section provides general information on these processes for those readers not closely associated with or directly involved in handling molten aluminum. More detailed information and recommendations on melting and casting operations are given in Parts V and VI. Since the initial f
13、iidefines were issued, a large number of improvements have been made in controlling and automating melting and casting operations. Also, new systems have been devised for removing dissolved gas (hydrogen) and non-metallic particles from the liquid metal. In general, these new controls, systems, and
14、equipment are proprietary; details are available from the manufacturers and, frequently, in the open literature such as the LightMeta2.s volumes published by The Minerals, Metals and Materials Society (TMS). 8.1: Melting Large scale melting of aluminum is usually done in reverbatory or “open hearth”
15、 refractory-lined furnaces, with capacities that in some cases exceed 200,000 pounds (100 Metric Tonnes (MT). Some furnaces are topcharged, in which case the charge falls directly into molten metal that may be in the furnace or onto an unmelted charge of metal. Some furnaces are charged from floor l
16、evel, through doors or into a side well adjoining the hearth. In the latter case, the charge does not fall into the main body of molten metal but into a small well or connecting pool of metal. In some installations, the aluminum is melted in one furnace (melting furnace), and transferred to a second
17、 furnace (holding furnace) for further processing such as composition adjustments, fluxing and close control of temperature prior to casting. In the primary aluminum industry, it is usual to find melting holding furnaces where metal from the potrooms (or cell lines) is transferred into the furnace t
18、ogether with process metal scrap. These furnaces are frequently of the tilting variety to provide good control over temperature and flow of metal to the casting machine and to permit rapid and complete draining. In the secondary aluminum industry, rotary salt furnaces, side well furnaces and inducti
19、on furnaces are used to melt lighter gauge secondary scrap. Drosses are typically processed in a rotary salt furnace where salt is used to separate metallic oxides from the molten metal. I figurn 3: Charping fumacehm 7ianshrCtucib/e 8.2: Transfer of Molten Aluminum For direct chill (DC) casting, mol
20、ten aluminum is usually transferred by gravity from the melting h a c e to the holding furnace and to the mold. In stationary rnaces, the metal flow rate from a tap hole in the furnace is controlled by tapered plugs, whereas with a tilting furnace the flow rate is a function of tilt rate. After leav
21、ing the furnace, the metal flows through slightly sloping refractory lined troughs, or launders, toward the casting * As indicated previously, process ingot is a casting which is subsequently mechanically worked into shapes such as sheet, forgings, extrusions, wire, etc. 13 Copyright The Aluminum As
22、sociation Inc. Provided by IHS under license with AA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 02:57:14 MDTNo reproduction or networking permitted without license from IHS -,-,- machine. The system usually includes one or more flow rate or molten metal level con
23、trol devices. In some instances, special pumps may be used to move the liquid metal. To process the metal, the melt may be treated in the furnace with a fluxing agent. Processing may also be accomplished by “in line” systems as the metal flows from the h a c e to the casting station. Examples of met
24、al processing include removal of hydrogen, trace a l k a l i removal, inclusion removal and alloying. A typical melting, holding and casting process is shown schematically on the flowsheet in Figure 4. Molten metal may also be moved from one funiace to another or to a casting station by means of cru
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