Lead block casting

The lead contains residual calcium and magnesium that must be removed by chlorination or treatment with caustic and niter. The molten lead is pumped or laundered to the casting kettles in which it is again treated with caustic and niter prior to mol ding, After a final drossing, the refined lead is cast into 45-kg pigs or 1- and 2-t blocks. 

Guss-beton, m. cast (or poured) concrete, -blase, /. flaw in a casting, blowhole, -blei, n. cast lead, -block, m. ingot, -bruch, m. broken castings, cast-metal scrap specif., cast-iron scrap. 

In the Trauzl lead block test (often called simply the lead block test) 10 grams of the explosive, wrapped in tinfoil and stemmed with sand, is exploded by means of an electric detonator in a cylindrical hole in the middle of a cylindrical block of lead, and the enlargement of the cavity, measured by pouring in water from a graduate and corrected for the enlargement which is ascribable to the detonator alone, is reported. For the standard test, the blocks are cast from chemically pure lead, 200 mm. in height and 200 mm. in diameter, with a central hole made by the mold, 125 mm. deep and 25 mm. in diameter The test is... 

The device consists of a lead block with linear dimensions three times as large as normal. The block has been used to obtain information about slurries the method is too expensive for practical work, since more than one ton of lead must be cast for each shot. 

As already stated, the detonator is placed into the cavity of the lead block (Figure 2.38). The block should be made of lead having precisely defined quality. It should be cast from soft lead at 390-400 "C. No tin or antimony... 

The lead block used for the determination of the strength of explosives should be made of soft lead, cast at a temperature 390-4(X) "C. The lead block test configuration is given in Figure 5.2. 

Before conducting the test, the lead block of the same casting should be calibrated. The calibration is performed with a pure picric acid whose density is 1 g/cm and charge volume is 10 cm. The net-expansion value of such an explosive charge, obtained in three shots, should ammmt to between 287 and 300 cm. However, the values between 280 and 310 cm can also be accepted. In that case, conversion of the net-expansion values obtained shmild be made. The conversion is obtained by multiplication of the calibration net-expansion value by the quotient of the mean value of the admissible calibration interval (294 cm ) and the obtained value. 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

Heavy dusts Heavy/wet sawdust, metal turnings, foundry tumbling barrels and shake-out, sand blast dust, wood blocks, brass turnings, cast iron boring dust, lead dust 4000-4500 20-23... 

D - Lead disks, each 2 mm thick E — Nickel steel block, 20 mm thick weighing 320g F — Hollow steel or cast iron cylinder... 

A — Solid lead cylinder. 25 mm in diam 25 mm high B — Steel plate, ca 25 mm thick C — Solid steel cylinder 100 mm in diam 128 mm high D — Solid steel cylinder, 100 mm in diam 8c 254 mm high E — Cast iron base block imbedded in cement F — Cavity for sample (l-2g) and priming compn (0.25g)... 

The molten tin is removed, cast into blocks (block tin), and subsequently purified by a number of refining processes, the most effective of which is an electrolytic process similar to that used in refining lead. 

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