Tough-pitch copper

Zahkupfer, n. tough-pitch copper, tough pitch. Zahl,/. number numeral (numerieal) value. Zahlapparat, m. coimtlng apparatus, coimter. zahlbar, a. payable, due. zahlen, v.t. i. pay. 

A 99.5% Cu—0.5% Te alloy has been on the market for many years (78). The most widely used is alloy No. CA145 (number given by Copper Development Association, New York), nominally containing 0.5% tellurium and 0.008% phosphorous. The electrical conductivity of this alloy, in the aimealed state, is 90—98%, and the thermal conductivity 91.5—94.5% that of the tough-pitch grade of copper. The machinahility rating, 80—90, compares with 100 for free-cutting brass and 20 for pure copper. 

If the fire-refined copper is to be cast into anodes for electrorefining, the oxygen content of the copper is lowered to 0.05—0.2%. If the copper is to be sold directly for fabrication, the oxygen level is adjusted to 0.03—0.05%, which is the range for tough-pitch copper. The principal reactions of fire refining are... 

Fig. 12. Decrease in copper conductivity in the presence of the indicated impurities (a) tough-pitch copper and (b) oxygen-free copper.

One disadvantage of tough pitch coppers is the embrittlement that is liable to occur when they are heated in atmospheres containing hydrogen. For many purposes, therefore, and particularly where fabrication is involved, deoxidised coppers are preferred. The usual deoxidising agent is phosphorus, and specifications require residual phosphorus contents of between... 

The behaviour of the phosphorus-deoxidised and tough pitch coppers was in general very similar. At the less corrosive sites, copper was, with few exceptions, the best material, but most of the alloys lost not more than about twice as much weight, with maximum depths of attack usually not more than two or three times as great as with copper. At the other sites copper was also usually rather better than the alloys, but some of the alloys were occasionally superior. 

The British Non-Ferrous Metals Research Association carried out two series of tests, the results of which have been given by Gilbert and Gilbert and Porter these are summarised in Table 4.12. In the first series tough pitch copper tubes were exposed at seven sites for periods of up to 10 years. The two most corrosive soils were a wet acid peat (pH 4-2) and a moist acid clay (pH 4-6). In these two soils there was no evidence that the rate of corrosion was decreasing with duration of exposure. In the second series phosphorus-deoxidised copper tube and sheet was exposed at five sites for five years. Severe corrosion occurred only in cinders (pH 7 1). In these tests sulphides were found in the corrosion products on some specimens and the presence of sulphate-reducing bacteria at some sites was proved. It is not clear, however, to what extent the activity of these bacteria is a factor accelerating corrosion of copper. 

Blister copper, produced from sulfide ores by matte smelting and converting, is refined to the grade known as tough pitch copper by a multistage operation known as fire refining. 

ELECTROLYTIC TOUGH PITCH COPPER WROUGHT ALLOY... 

Tough-pitch copper, of 99.85% purity, is used in chemical and general engineering applications where the highest conductivity is not... 

The tendency of copper to dissolve oxygen when the metal is heated in air leads to rupture of the metal along grain boundaries by formation of steam when the metal is subsequently heated in hydrogen. Cast tough-pitch copper containing... 

C11300, C11400, C11500, C11600 Silver-bearing tough pitch copper 99.90 Cu, 0.04 0, Ag(f) F,R,W,T,S G-E... 

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