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French National Laboratory of Physics and Mechanics
March. I917.]
CURRENT TOPICS.
383
ished by machining the rear surface of the blade to a true helicoidal surface and finishing by hand the front face so that it will be perfec.tly smooth. The propellers of merchant vessels, however, generally have blades of cast iron or cast steel and are given no finish whatever, except trimming off the rough places with chisel or file. In addition, as is well known, iron and steel propellers often suffer by pitting, so that they present an extremelv rough surface to the water. With the object of determining the relative efficiency of a smooth finished propeller and a propeller left with the rough surfaces of the original casting, four propellers, I6 inches in diameter, were tested at a uniform speed of 5 knots. Two of the propellers were of bronze, one of cast iron and one of cast steel. One of the bronze propellers was finished perfectly smooth; the others were left as they came from the mold, with only the ordinary cleaning. The test showed that the propellers with a rough surface had a maximum efficiency of about 63 per cent. whereas the polished propeller had an efficiency of about 72 per cent. Another test was made to determine the effect of a still rougher surface, such as exists on a propeller that becomes badly pitted or on which barnacles and other sea growths accumulate, by varnishing the polished bronze propeller and applying to the sticky varnish a layer of granulated cork, such as is used for cork paint in ship work. The efficiency of the artificially roughened propeller which had been about 72 per cent. in its polished condition was reduced to 3(; per cent.
A Rapid Process for Determining the Acidity of Corn. (U. S. Department of dgriculture. Circular 68.)--The test to determine the acidity of corn, which previously required I6 to 18 hours, can be made in less than one hour by the use of improved apparatus developed by H. J. Besly and G. H. Baston of the office of Grain Standardization, Bureau of Plant Industry. Under the new method an electric mechanism, similar to those seen on soda fountains, is used to mix finely ground corn and alcohol. Thirty minutes of mixing, it is found, will extract from the corn an amount of acid-reacting substances comparable to the amount extracted through digestion in 86 per cent. alcohol at room temperature for I8 hours. The methods for making acidity determinations of corn with this apparatus are described in detail in circular 68, Office of the Secretary, recently published by the U. S. Department of Agriculture.
French National Laboratory of Physics and Mechanics. ANON. (Metallurgical and Chemical Engineering, vol. xvi, No. 4, P. I86, February 15, I917.)--The Genie Civil, has resolved chanical laboratory for the ward industrial uses. The
Academic des Sciences, according to the to establish a national physical and mepurpose of scientific research directed tolaboratory will be controlled by a council,
384
CURRENT TOPICS.
[J. F. I.
of which half the members will be nominated by the Academy, onefourth by the State Department, and the remainder by the chief industrial associations. The executive control will be in the hands of a small technical committee. Existing laboratories engaged in similar work will be affiliated to the National Laboratory, and will work in close relationship to the latter. Substantial funds will have to be provided for the working expenses of the laboratory and for the assistance of the affiliated institutions.
Manganese Steel Castings. W . S . McKI~J~. (The Iron Trade Review, vol. lx, No. 7, P. 413, February I5, IgI7.)--Manganese steel was developed originally in England, largely through the efforts of Sir Robert Hadfield. It has been manufactured on a commercial scale for nearly 26 years. The first manganese steel castings made in the United States were turned out in 1892. Originally it was considered impossible to make manganese steel castings successfully weighing o~;'er a few hundred pounds, but at the present time large rolling-mill pinions, crusher heads, and similar castings weighing up to 30,000 pounds each are being produced regularly, and it does not appear that the limit of weight has been reached by a considerable margin. As manufactured at present, manganese steel is similar in analysis to ordinary converter metal, except that it is high in carbon and unusually high in manganese. In ordinary commercial castings the proportions of the latter metal range from II to I 3 ~ per cent. This combination of constituents gives the finished castings certain distinctive physical properties. Heat treatment is a very essential part of the process. The necessity for heat treatment limits the thickness of section which it is possible to cast successfully. Originally the castings were made with comparatively thin sections, but researches during the past few years have made it possible to increase the thickness of section, so that at present castings with walls up to 5 ~ inches in thickness are handled satisfactorily. Manganese steel made by Robert W. Hunt ,& Co., Chicago, has an elastic limit of 53,400 pounds, tensile strength of lO8,4oo pounds per square inch, an elongation of 33.7 per cent. in 2 inches, and a reduction in area of 38.6 per cent. This steel does not owe its wear-resisting qualities to its hardness. When subjected to the Brinell test, it shows an average hardness number of 200. The electrical resistance of manganese steel is about 3.4 times that of ordinary Bessemer steel. It is non-magnetic, and advantage is taken of this property in the use of this material for shields or bottom plates of lifting magnets. If the castings require finishing, s.pecial equipment is necessary. Ordinary machining methods are unsuccessful, and grinding must be employed. Holes more than ~ inch in diameter are cored and ground to size. When it is necessary to drill smaller holes or to cut th.reads, soft steel or wrought-iron inserts are set in the molds at desired points like chaplets and the metal is cast around them.
CURRENT TOPICS.
383
ished by machining the rear surface of the blade to a true helicoidal surface and finishing by hand the front face so that it will be perfec.tly smooth. The propellers of merchant vessels, however, generally have blades of cast iron or cast steel and are given no finish whatever, except trimming off the rough places with chisel or file. In addition, as is well known, iron and steel propellers often suffer by pitting, so that they present an extremelv rough surface to the water. With the object of determining the relative efficiency of a smooth finished propeller and a propeller left with the rough surfaces of the original casting, four propellers, I6 inches in diameter, were tested at a uniform speed of 5 knots. Two of the propellers were of bronze, one of cast iron and one of cast steel. One of the bronze propellers was finished perfectly smooth; the others were left as they came from the mold, with only the ordinary cleaning. The test showed that the propellers with a rough surface had a maximum efficiency of about 63 per cent. whereas the polished propeller had an efficiency of about 72 per cent. Another test was made to determine the effect of a still rougher surface, such as exists on a propeller that becomes badly pitted or on which barnacles and other sea growths accumulate, by varnishing the polished bronze propeller and applying to the sticky varnish a layer of granulated cork, such as is used for cork paint in ship work. The efficiency of the artificially roughened propeller which had been about 72 per cent. in its polished condition was reduced to 3(; per cent.
A Rapid Process for Determining the Acidity of Corn. (U. S. Department of dgriculture. Circular 68.)--The test to determine the acidity of corn, which previously required I6 to 18 hours, can be made in less than one hour by the use of improved apparatus developed by H. J. Besly and G. H. Baston of the office of Grain Standardization, Bureau of Plant Industry. Under the new method an electric mechanism, similar to those seen on soda fountains, is used to mix finely ground corn and alcohol. Thirty minutes of mixing, it is found, will extract from the corn an amount of acid-reacting substances comparable to the amount extracted through digestion in 86 per cent. alcohol at room temperature for I8 hours. The methods for making acidity determinations of corn with this apparatus are described in detail in circular 68, Office of the Secretary, recently published by the U. S. Department of Agriculture.
French National Laboratory of Physics and Mechanics. ANON. (Metallurgical and Chemical Engineering, vol. xvi, No. 4, P. I86, February 15, I917.)--The Genie Civil, has resolved chanical laboratory for the ward industrial uses. The
Academic des Sciences, according to the to establish a national physical and mepurpose of scientific research directed tolaboratory will be controlled by a council,
384
CURRENT TOPICS.
[J. F. I.
of which half the members will be nominated by the Academy, onefourth by the State Department, and the remainder by the chief industrial associations. The executive control will be in the hands of a small technical committee. Existing laboratories engaged in similar work will be affiliated to the National Laboratory, and will work in close relationship to the latter. Substantial funds will have to be provided for the working expenses of the laboratory and for the assistance of the affiliated institutions.
Manganese Steel Castings. W . S . McKI~J~. (The Iron Trade Review, vol. lx, No. 7, P. 413, February I5, IgI7.)--Manganese steel was developed originally in England, largely through the efforts of Sir Robert Hadfield. It has been manufactured on a commercial scale for nearly 26 years. The first manganese steel castings made in the United States were turned out in 1892. Originally it was considered impossible to make manganese steel castings successfully weighing o~;'er a few hundred pounds, but at the present time large rolling-mill pinions, crusher heads, and similar castings weighing up to 30,000 pounds each are being produced regularly, and it does not appear that the limit of weight has been reached by a considerable margin. As manufactured at present, manganese steel is similar in analysis to ordinary converter metal, except that it is high in carbon and unusually high in manganese. In ordinary commercial castings the proportions of the latter metal range from II to I 3 ~ per cent. This combination of constituents gives the finished castings certain distinctive physical properties. Heat treatment is a very essential part of the process. The necessity for heat treatment limits the thickness of section which it is possible to cast successfully. Originally the castings were made with comparatively thin sections, but researches during the past few years have made it possible to increase the thickness of section, so that at present castings with walls up to 5 ~ inches in thickness are handled satisfactorily. Manganese steel made by Robert W. Hunt ,& Co., Chicago, has an elastic limit of 53,400 pounds, tensile strength of lO8,4oo pounds per square inch, an elongation of 33.7 per cent. in 2 inches, and a reduction in area of 38.6 per cent. This steel does not owe its wear-resisting qualities to its hardness. When subjected to the Brinell test, it shows an average hardness number of 200. The electrical resistance of manganese steel is about 3.4 times that of ordinary Bessemer steel. It is non-magnetic, and advantage is taken of this property in the use of this material for shields or bottom plates of lifting magnets. If the castings require finishing, s.pecial equipment is necessary. Ordinary machining methods are unsuccessful, and grinding must be employed. Holes more than ~ inch in diameter are cored and ground to size. When it is necessary to drill smaller holes or to cut th.reads, soft steel or wrought-iron inserts are set in the molds at desired points like chaplets and the metal is cast around them.