Production of aluminum-silicon alloys in an electrolytic cell

Claim 1

The method of operating an aluminum reduction cell to produce an aluminum-silicon alloy, including the steps of feeding alumina and silica into a molten salt bath of the cell and passing electric current through the bath, wherein: a. said feeding of alumina comprises introducing approximately equal incremental amounts of alumina effective in the aggregrate to supply the cell's alumina requirements, b. said feeding of silica comprises introducing approximately equal incremental amounts of silica effective in the aggregate to supply the cell's corresponding requirements of silica to produce an alloy of the desired silicon content, and c. these incremental feeding operations are conducted on a coordinated basis such that at times substantially only alumina is added to the bath and the feeding of silica is deferred, while at other times both alumina and silica are added to the bath.

Claim 2

The method of operating an aluminum reduction cell to produce an aluminum-silicon alloy, including the steps of feeding alumina and silica into a molten salt bath of the cell and passing electric current through the bath, wherein: a. said feeding of alumina comprises introducing approximately equal incremental amounts of alumina effective in the aggregrate to supply the cell's alumina requirements, b. said feeding of silica comprises introducing approximately equal incremental amounts of silica effective in the aggregate to supply the cell's corresponding requirements of silica to produce an alloy of the desired silicon content, and c. these incremental feeding operations are conducted on a coordinated basis such that at times substantially only alumina is added to the bath and the feeding of silica is deferred, while at other times both alumina and silica are added to the bath.

Claim 15

The method of operating an aluminum reduction cell to produce an aluminum-silicon alloy, including the steps of feeding alumina and silica into the molten salt bath of said cell and passing electric current through the bath, which method comprises: introducing incremental amounts of alumina into the bath n times during each 24-hour period of operation, wherein n is an integer from 4 to 15, with each such amount representing about 1/nth of the cell's daily requirement of alumina; and introducing incremental amounts of silica effective in the aggregate to supply the cell's corresponding daily requirements of silica to produce an alloy of the desired silicon content, with each such amount not exceeding about 2 percent of the weight of the molten bath, the number of said incremental feedings of silica being no more than n-2, for n ≦ 6; and being only about n-4, for 6< n<15.

Claim 16

The method of operating an aluminum reduction cell to produce an aluminum-silicon alloy, including the steps of feeding alumina and silica into the molten salt bath of said cell and passing electric current through the bath, which method comprises: introducing incremental amounts of alumina into the bath n times during each 24-hour period of operation, wherein n is an integer from 4 to 15, with each such amount representing about 1/nth of the cell's daily requirement of alumina; and introducing incremental amounts of silica effective in the aggregate to supply the cell's corresponding daily requirements of silica to produce an alloy of the desired silicon content, with each such amount not exceeding about 2 percent of the weight of the molten bath, the number of said incremental feedings of silica being no more than n-2, for n ≦ 6; and being only about n-4, for 6< n<15.

Claim 20

The method of operating an aluminum reduction cell to produce a hypereutectic aluminum-silicon alloy, including the steps of feeding alumina and silica into a molten salt bath of the cell and passing electric current through the bath, comprising: repeatedly feeding into the bath of said cell both alumina and silica at substantially uniform intervals in the range of about 1 to 4 hours over at least a major portion of each daily period of operation, each such feeding being effect to introduce about 1/nth of the cell's daily requirement of alumina and a larger fraction up to about one-half of the cell's daily requirement of silica to obtain an alloy of the deisred silicon content, discontinuing said feedings of alumina and silica at least once daily and continuing to operate the cell without feeding long enough to reduce the total bath oxide content to a level effective to control ridge formations, there being for each feeding cycle prior to said continuing operation without feeding a total of n feedings to supply alumina, where n is an integer from 4 to 15, of which no more than (n-2) include a feeding of silica, for n ≦ 6, and of which only about (n-4) include a feeding of silica, for 6<n<15.

Claim 21

The method of operating an aluminum reduction cell to produce a hypereutectic aluminum-silicon alloy, including the steps of feeding alumina and silica into a molten salt bath of the cell and passing electric current through the bath, comprising: repeatedly feeding into the bath of said cell both alumina and silica at substantially uniform intervals in the range of about 1 to 4 hours over at least a major portion of each daily period of operation, each such feeding being effect to introduce about 1/nth of the cell's daily requirement of alumina and a larger fraction up to about one-half of the cell's daily requirement of silica to obtain an alloy of the deisred silicon content, discontinuing said feedings of alumina and silica at least once daily and continuing to operate the cell without feeding long enough to reduce the total bath oxide content to a level effective to control ridge formations, there being for each feeding cycle prior to said continuing operation without feeding a total of n feedings to supply alumina, where n is an integer from 4 to 15, of which no more than (n-2) include a feeding of silica, for n ≦ 6, and of which only about (n-4) include a feeding of silica, for 6<n<15.

Claim 22

The method of operating an aluminum reduction cell to produce an aluminum-silicon alloy, including the steps of feeding alumina and silica into a molten salt bath of said cell and passing electric current through the bath, wherein said feeding comprises: spreading out a measured charge of silica with loose alumina on the crust of said cell, so as to minimize the development of high-silica crust formations; breaking an underlying portion of the crust to introduce the silica and a related quantity of alumina into the bath; and periodically omitting to deposit a charge of silica and breaking in a portion of the crust to feed substantially only alumina into the bath.

Claim 23

The method of operating an aluminum reduction cell to produce an aluminum-silicon alloy, including the steps of feeding alumina and silica into a molten salt bath of said cell and passing electric current through the bath, wherein said feeding comprises: spreading out a measured charge of silica with loose alumina on the crust of said cell, so as to minimize the development of high-silica crust formations; breaking an underlying portion of the crust to introduce the silica and a related quantity of alumina into the bath; and periodically omitting to deposit a charge of silica and breaking in a portion of the crust to feed substantially only alumina into the bath.