Electric heating – Metal heating – For deposition welding
Patent
1983-05-16
1985-06-04
Rutledge, L. Dewayne
Electric heating
Metal heating
For deposition welding
219 7612, 427 49, 427319, B23K 904, B23K 3530
Patent
active
045216630
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for depositing filler materials on heavily worn surfaces on parts of machines and equipment made of carbon and manganese bearing alloys of iron, in particular such as are employed in the carbon processing industry, especially in the production of electrodes for the fused salt electrolytic production of aluminum by the Hall-Heroult process, in order to protect these against wear, and relates too to a wear resistant alloy.
The preparation of the mass for making electrodes, in particular anodes for the fused salt electrolytic production of aluminum via the Hall-Heroult process, involves large amounts of carbonaceous material such as, for example, various types of coke, anode butts, tar, and pitch binder being transported, broken, ground-down, classified and mixed. The equipment employed for this e.g. crushers, grinding mills, mixers, transporting equipment etc. are subject to intensive wear, which is countered, sometimes via very different methods and measures.
In the case of machine and equipment parts made of ferrous materials, flame spraying and cladding with ceramic materials is known, as well as the deposition of wear resistant materials by means of electric arc welding.
One of the best known methods for preventing premature fracture of highly mechanically stressed parts is the application of composite layers, in particular deposit welding of hard materials on a tough base material. In each case it is necessary to adapt the composition of the protective layer for each particular application. In this connection the type of physical action such as abrasion and/or disruption, adhesion and chemical properties--in particular with respect to tribochemical reactions--of the material causing the wear, and especially the operating temperature, are all of importance.
A detailed description of the state of the art of wear prevention technology is presented in Aufbereitungs-Technik No. 10, 1979--the method of deposit welding in particular is dealt with on pages 562-565.
Deposit welding is a protective measure in which a so-called buffer layer is deposited first on the ferrous base material--for which purpose e.g. tubular electrode rods or wire about 3 mm in diameter are employed with a welding current of 300-350 ampere. The actual wear resistant coating is deposited on the buffer layer.
In the carbon processing industry, in particular for the manufacture of electrodes for aluminum production, the equipment used for processing carbon in the form of petroleum coke, pitch coke and anthracite and for comminuting or crushing carbonaceous blocks etc. made from the above mentioned raw materials and pitch and tar type binders, is subjected to wear preventive measures using the above mentioned state of the art of deposit welding, for example for base material made of ferrous alloys containing carbon and manganese, and making use of filler rods of the following composition:
C.perspectiveto.5.5%
Cr.perspectiveto.20.5-23.0%
Mn.perspectiveto.0.5%
Si.perspectiveto.0.5%
Mo.perspectiveto.6.0-8.0%
Nb.perspectiveto.6.0-8.0%
W.perspectiveto.2.0%
V.perspectiveto.1.0%
Fe=remainder percentage).
With this commercially available additive (e.g. from Kestra Schweisstechnik GmbH & Co. KG, 404 Neuss, West Germany) a hardness of 59-64 Rockwell C is achieved at ambient temperatures or 40-44 Rockwell C at a working temperature of 600.degree. C. Using this or a similar material and suitable welding equipment a wear resistant layer can be produced with good adhesion between the substrate material and the protective layer.
The reduction in wear produced by the deposited layer is however not adequate in practice. Under continuous operating conditions--as is normal in the industry in question--the wear resistant layer is in fact quickly worn away. This makes it necessary to renew the protective coating after only a few weeks, which leads to high maintenance costs and, due to the undesired down-time of the equipment, to high operating costs.
The object of the present invention is to improve the wear resistance of mach
REFERENCES:
patent: 3231709 (1966-01-01), Foley
Frumin et al., "Surfacing with Large Diameter Cored Wire", Autom. Welding (GB), vol. 25, pp. 42-46, 6-72.
Cary, H., "The Arc Welding Processes-Using CV Power," Modern Welding Tech., Prentice-Hall, Inc., NJ, 1979, pp. 154-157.
Rutledge L. Dewayne
Swiss Aluminum Ltd.
Yee Debbie
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