Process of galvanizing for consecutively producing two different

Details Process of galvanizing for consecutively producing two different Process of galvanizing for consecutively producing two different

1985-11-15

1987-02-24

Bueker, Richard

Coating processes

Immersion or partial immersion

Molten metal or fused salt bath

4274342, C23C 100, B05D 118

Patent

active

046456945

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process of galvanizing for consecutively producing two different coatings on a metal band.
Coating of a metal band with a zinc alloy is at present effected by means of an installation called a galvanizing line along which the band moves and undergoes various treatments. An unwinding station at the beginning of the line is successively followed by a cleaning station, a pre-heating station with or without control of atmosphere, a so-called laboratory station where heating of the band is generally continued in a highly reducing atmosphere, possibly a cooling station and finally a bath of molten zinc alloy. On leaving the bath, the band is dried and cooled before being wound or conducted through subsequent treatment stations (such as for example heat treatment or surface treatment stations . . . ).
It will be readily appreciated that such a galvanizing line is a complex installation intended for continuous mass production of a single product. Now, it may be advantageous to be able to manufacture products whose coatings are different. On the same galvanizing line, in addition to the adjustment of all the treatment stations upstream of the bath of alloy, this modification requires the emptying of the tank containing this bath, which is a delicate, long and therefore expensive operation, taking into account in particular the heating means employed (induction) which function correctly only in the presence of a bath in the tank. In addition, the correctly emptied tank must be subjected to an extremely thorough cleaning, in certain cases, in order thereafter to be able to receive the new coating alloy which may possibly not tolerate, even at a very low concentration, one or more of the elements constituting the preceding alloy.
The manufacture of two different products has therefore often required the use of two galvanizing lines, each especially provided for one or the other of the products. It will be readily appreciated that this solution involves considerable investment which can be justified only by intensive mass production. Furthermore, two tanks have been provided on the same line, which may be alternately put into service by translation transverse to the direction of advance of the metallic band. However, this solution presents the drawback of immobilizing large quantities of molten metal and of having to maintain in the molten state one bath out of use whilst the other is being used, with the energy consumption that this represents.
It is an object of the invention to propose another solution for the successive production, on the same galvanizing line, of two different products, i.e. coated with different alloys, by means of a galvanizing process. The arrangements of the invention advantageously allow a change of bath with a minimum of handling of molten metal, a maximum of safety, particularly for the device for maintaining temperature, and finally in a relatively short time, i.e. without appreciable influence on the production capacity and therefore on the cost price of the finished product.
To this end, the invention relates to a process for consecutively producing on a single production line at least two metal band products coated with different metal alloys, the production line comprising in particular a fixed tank of molten alloy in which the metal band advances.
According to one of the principal features of the invention, this process consists, in order to pass from the first to the second product, in placing in the bath of said fixed tank a removable tank of smaller volume containing one of the said alloys different from that contained in the fixed tank, in maintaining the temperature of the bath of the removable tank by regulating the temperature of the bath of the fixed tank and in advancing said metal band in the bath of the removable tank, and, to pass from the second to the first product, in withdrawing said removable tank, the metal band then advancing in the fixed tank.
In this process, it is advantageous to constitute at least one start of bath in the remo

REFERENCES:
patent: 3758333 (1973-09-01), Herman
Smith, IBM Tech. Dis. Bul., vol. 8, No. 11, Apr. 1966, p. 1639.

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