. The Bell System technical journal . 30,000 0% This same figure shows the tensile strengths obtained when five,six, and seven die reductions are used to produce line wire of .104diameter from the same supply. Here the elongation loss is about thesame in each case, but the tensile strength is greater with the heavier DEVELOPMENTS IN MANUFACTURE OF COPPER WIRE 207 reductions. The five die arrangement is satisfactory according to theresults shown on the curve, but the heavy reduction at the first dieoften results in rough or slivered wire. The six die arrangement,therefore, gi
. The Bell System technical journal . 30,000 0% This same figure shows the tensile strengths obtained when five,six, and seven die reductions are used to produce line wire of .104diameter from the same supply. Here the elongation loss is about thesame in each case, but the tensile strength is greater with the heavier DEVELOPMENTS IN MANUFACTURE OF COPPER WIRE 207 reductions. The five die arrangement is satisfactory according to theresults shown on the curve, but the heavy reduction at the first dieoften results in rough or slivered wire. The six die arrangement,therefore, gives the greatest factor of safety. The seven die arrange-ment is less satisfactory since the elongation and tensile strength in thefinished wire are so close to the requirements. 30^ 1^ Lbs. 25^ 20^ 10 \afL 5 Lbs. 5% 0 ^. 22 23 24 25 26 11 28 29 30 31 3Z 33 34 35 36 37 35 39 40 Die Size1 2 3 4 5 6 7 6 3 10 II 12 13 14 )5 )6 Reduction Fig. 17 The use of reductions for the finer sizes of cable and magnetwire provides flexibility since a change in the size of wire can be ac-complished simply by increasing or reducing the number of dies were conducted to determine the gain by using heavier reduc-tions and annealing the wire before redrawing, and Fig. 17 shows theincreased reduction possible at the first die when the metal is this test, an annealed No. 22 gauge wire of 31 per cent elongation 208 BELL SYSTEM TECHNICAL JOURNAL was reduced to No. 24, two gauges, in one draw. The soft copper per-mitted a double reduction at the first die, but the elongation droppedduring the operation to less than 1 per cent; the second reduction onthis test was from No. 24 to No. 26 gauge and the pull required for thispass practically coincides with the breaking strength of the wire. Wiredrawing un
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