the solder is then cast into the desired shapes. During the entire operation of final casting the caster stirs every time he takes a ladleful from the pot. This work could be done much more rapidly at higher temperatures, and much more economically by the use of mechanical mixers, but the resulting solder would not be so thoroughly mixed, nor would it be so fluid. Mechanical mixing has a tendency to drive the oxide and dross back into the metals, thus diminishing the holding power of the solder. The scavenger must be chosen with great care, and the amount must be very accurately gaged; otherwise the scavenger becomes a constituent of the finished product, and, instead of being beneficial, is a detriment. We have found that in the grades of solder containing 46 per cent and less of tin, the addition of 2 per cent to 34 per cent of the best grades of antimony increases the fluidity and holding strength of the solder for working tin plate. Next to its use for containers, the largest consumption of solder has been on gasolene-motor radiators. The hand work on these radiators requires merely a free-flowing clean solder, but on the dipping work, where most of the solder is used, the greatest abuse has been practiced. As these radiators are composed of copper, low brass, or ordinary brass, no antimony whatever should be added to the solder used for this purpose. Also the affinity of tin and lead for zinc and copper will draw both of these metals from the radiators into the baths, and as both copper and zinc make solder sluggish, it does not take long (unless proper methods are employed for cleansing the baths) for the solder to become deteriorated. These baths can be thoroughly cleaned by a mixture of rosin and sulphur, but as this operation produces very disagreeable black smoke throughout the plant, some method should be devised for disposing of it. When sulphur is used for removing zinc and copper, a sufficiently high temperature should be employed to insure the complete combustion of the sulphur. The baths should then be allowed to settle for at least half an hour after such heating, and the top carefully skimmed to remove any sulphides present. It is important to note that the presence of any nonmetallic substance is injurious to solder, whether it has been added as a scavenger or is liberated from the original metals. The question is frequently asked, what is the strongest solder that can be made. Numerous experiments have been made, but the results are confusing. Tests of tensile strength, based upon wires and cast bars, indicate that the higher the tin, up to 75 per cent tin, 25 per cent lead, the greater the breaking strength; in the case of two pieces of tin plate soldered together, the maximum strength is given by a solder containing around 42 per cent tin. Other tests were made on square 5-gallon cans, completely filled with water and then capped; when dropped from a height of about 100 feet, the cans soldered with 46 per cent tin, 54 per cent lead, in no case broke at the seams, although the tin plate was ruptured. This was the only mixture that gave this result. Cans soldered with 47 per cent or more of tin, 53 per cent or less of lead, and with 45 per cent or less of tin, 55 per cent or more of lead, occasionally ruptured at the seams. These experiments were made most carefully and were afterward confirmed by subjecting the cans to air pressure. I am thus inclined to believe that, in round figures, 46 per cent tin, 54 per cent lead, is the strongest mixture that can be used for general soldering purposes, particularly if 4 per cent to 2 per cent of antimony be added to the mixture. The Bureau of Standards, with the approval of the War Industries Board, suggests that the highest grade of solder permitted should be 45 per cent tin, 55 per cent lead. For mechanical soldering, 40 per cent should be the highest tin ratio, and for most bath work it has been demonstrated that tin from 35 per cent to 38 per cent, according to the nature of the work, will give ample satisfaction, provided the solder is made properly.—“ Engineering." ELECTRIC HEATED INDUSTRIAL FURNACES BY GEORGE J. KIRKGASSER War conditions have greatly increased the use of the electric furnace, not only in work where it was already used, but where it had hardly been given more than a little consideration. Because of the comparatively short time that the electric furnace has been commercially used, methods of operation have not been so well standardized, but with the number of men now familiar with them, there will be an interchange of ideas that will help toward standardization. Where temperatures high enough to reduce steel to a molten condition are required the electric-arc furnace is employed, while for subsequent heat treatments, resistor-type furnaces are used, for in the latter process great accuracy and exactness of temperature control must be maintained. The electric furnace is a metallurgical appliance in which any desire1 temperature up to the point of fusion of the best refractory materials obtainable can be attained and perfectly controlled. At these high temperatures chemical reactions take place much more rapidly than in other processes, and the most refractory metals and alloys can be reduce to fluidity. An electric-arc furnace for steel making usually consists of a steel tank lined inside with refractory materials and fitted with working doors, spouts and tilting arrangements for teeming; regulatable carbon or graphite electrodes of a suitable section are inserted through the roof or walls. A high-tension electrical supply is transformed down to a low pressure for operating the furnace. Arc furnaces are of two principal kinds: one known as the arc-radiation type, in which heat is radiated from the arc; and the arc-resistance or arc-conduction type, in which there is radiation of heat from the arc, and heat also generated as a result of the resistance due to the flow of the current in the furnace. PRODUCTION OF ELECTRIC STEEL. What are said to be the first patents on the electric arc steel furnace were recorded about 40 years ago, an Englishman, William Siemens, being the inventor. As with other patents, the patentee could not by any stretch of imagination realize to what extent the electric furnace would be used in the steel industry. The world's output of electric steel has multiplied more than tenfold since 1914. In that year there were about 30 electric furnaces in the United States and Canada, while t the beginning of 1918 there were 300 such furnaces in use in these countries with an annual output of about 2,000,000 tons. The Illinois Steel Co. of South Chicago has the largest output of electric steel in the country, employing three 25-ton and two 15-ton furnaces of the Heroult type. The first, a 15-ton furnace, was installed in 1909. The products of this first furnace, steel rails, were laid on 14 railroad lines and the results showed that the electric steel was more ductile at low temperatures than either the openhearth or the Bessemer steel. Subsequent tests showed this also. Now the capacity of the plant is 16,000 to 17,000 tons of electric steel per month. The electric furnaces manufacturing steel in England are now pro ducing about 40 times the pre-war output, and it is now possible to dc. without the large imports of Swedish iron and steel which were formerly considered necessary to maintain the output of high-class products. Furthermore, the approaching exhaustion of the high-grade ores of Cumberland may be looked upon with equanimity, as electricity makes possible the use of the inferior ores of Cleveland and the Midlands to manufacture steel of great purity. The electric furnace has not only proved that it offers many advantages in steel making over the older processes, but has also shown that in making many classes of steel it is an absolute necessity. Electric steel is free from dissolved gases which is due in a measure to the perfect control over the temperature of the steel by the operator. By raising the temperature until the steel is in an exceedingly fluid state, the gases are permitted to escape, after which the temperature can be regulated for casting so that the desired grain can be produced in the setting of the ingot. In practically all cases the electric furnace is used not for the manufacture of steel directly from cold metal, but more as an electric refining process. Making steel directly from the cold metal requires a large consumption of current which makes the cost prohibitive. Usually it is used to finish metal previously made by the Bessemer or openhearth process. Very often in steel plants, the openhearth furnace is used for preliminary melting and an electric furnace for deoxidizing and desulphurizing, and for making any other changes needed to secure a steel according to analysis. In what is known as the "Triplex" system, the Bessemer converter is used for decarbonizing and desiliconizing the metal; the openhearth furnace is then used for dephosphorizing it and the electric furnace completes the work of deoxidizing and desulphurizing. BASIC OR ACID OPERATION. The basic process of furnace operation is the more costly because of the present high cost of refractories. The use of basic slag serves to remove impurities from the metal, just as in the basic openhearth steel furnace. Phosphorus, oxygen and sulphur may be removed, which permits using relatively cheap raw materials. With acid operation no phosphorus or sulphur is removed and more care is needed to hold the elements between desired limits. In lining basic furnaces, magnesite or dolomite is used up to about the slag line and above this silica, magnesia, and chrome brick is provided; while for the roof, silica is used. For acid operation, silica is used for the entire lining. Acid operation has been used to a great extent because of the abundance of shell turnings, steel clippings, and punchings from steel shipyards, etc. It is a little quicker than the basic, as it is not necessary nor possible to refine the charge. In Canada electric pig iron is made from steel scrap, the scrap being used in this way rather than being turned into refined steel, because of the shortage of low phosphorus pig iron. About 500 kw. hours of power per ton is average current consumption in this process. Dr. John A. Matthews, president of the Halcomb Steel Co., Syracuse, N. Y., recently said: "The electric furnace requires for successful operation less labor per ton than is necessary for crucible steel, but it calls for metallurgical skill in order to produce the best results. Easy oxidizing metals like vanadium, chromium and manganese, are readily handled and less of them required to give the content desired in the steel. Sulphur and phosphorus can be readily eliminated and the yield of sound steel increased. "With the electric furnace, alloy steels are made in the furnace itself rather than in the ladle, and in this way there is better opportunity for increasing the solution, diffusion and homogeneity in the product. All DIAGRAM SHOWING ELECTRICAL CONNECTIONS AND CURRENTS SET UP IN THE MOLTEN METAL IN A GREAVES-ETCHELL FURNACE of these things make for high quality, and quality is the first consideration. In addition to this, the electric furnace performs an economic function because of its adaptability for handling and recovering alloy values contained in scrap. This was of especial importance during the war, when alloys had to be conserved. The alloy content of chromium, manganese and vanadium in scrap used in the open-hearth steel is only recovered to a very small extent, and not only is the alloy value lost but the oxides formed are frequently a source of trouble in the final product." The superiority of electric steel castings over those made by any other process has been conclusively proved by the extremely severe conditions to which they have been subjected under specialized war conditions. The castings produced can be finished off dead mild and a one-inch square bar can be bent as cast, no expensive annealing operations being necessary. The carbon contents usually vary between 0.2 per cent and 0.25 per cent, while the sulphur and phosphorus are each reduced below 0.015 per cent and the manganese and silicon are adjusted to suit the work. The tensile properties of ordinary electric cast steel are: Yield point, 25 tons per square inch. Reduction of area, 50 per cent. Elongation, 30 per cent. The maximum tensile stress can be readily increased to even 100 tons per square inch by the introduction of special elements such as nickel, chromium and vanadium. Steel from the electric furnace is finished off under a reducing atmosphere of carbonic oxide and a slag out of which the metallic oxides have been reduced, and is singularly free from blow-holes when properly cast. This is due to the elimination of the gases that molten steel usually holds in solution and the ease with which the steel can be poured into small and intricate castings, flowing smoothly and setting perfectly. Electric steel castings can be made as cheaply as malleable iron castings, while the former are lighter for the same strength. HEROULT FURNACES. Heroult furnaces are of the arc-resistance type, the electrodes for introducing the current being placed above the bath and the current passing from one electrode to the metal and from the metal to the next electrode. The bath is thus heated by radiation from the arc and by the resistance of the steel and slag to the flow of current. The steel shell is lined with a refractory material, the nature of which depends on whether the furnace is to be basic or acid in its operation. The 25-ton furnace of this type at the Duquesne plant of the Carnegie Steel Co. requires 175 kw. hours per ton of steel and operates basic on hot metal. The three electrodes are of 12-inch graphite and are used up to the extent of about four pounds per ton of steel. Three phase current received at 6,600 volts is transformed to 100 volts at the furnace. Six heats are made per day of 24 hours, and each heat averages about 21⁄2 hours. GREAVES-ETCHELLS FURNACE. In principle, the "Greaves-Etchells" Furnace is a combined arc-resistance furnace. Two phases of a three-phase low-tension supply are connected to their respective upper graphite or carbon electrodes, while the third phase is connected to the bottom of the hearth. The current flowing through the hearth generates a considerable amount of heat immediately below the |