Bronze process

NbjSn superconductors with multifila-mentary geometry, which is needed for electromagnet applications, are easily fabricated by the so-called bronze process, which has led to the wide-spread commercial application of NbjSn (Smathers, 1990). In the bronze process Nb rods are inserted in a bronze rod or tube which is... 

The external diffusion process is based upon the fabrication of a Nb-Cu-Ta composite in a manner analogous to the processing used for NbTi. The surface of a wire strand is plated or dip-coated with Sn which is then diffused and reacted to form NbaSn. The cost of this process is lower than that of current bronze processes, since the use of a Cu matrix removes the need for repeated anneals during drawing, and multiple extrusions are not required. Because the amount of Sn is not restricted to 13 wt.% of the matrix, a high overall critical current density can be achieved without the need for thin reaction layers and very fine filaments (--2 pm in diameter). Thus, a single extrusion with several hundred filaments, compared with thousands for the bronze process, is all that is required to obtain a high critical current density in an external diffusion conductor. 

Bronze process The initial rod composite contains Nb rods surrounded by Cu—Sn alloy rods (13-15 wt%Sn) in a suitable arrangement such that after processing into wire form the diffusion-reaction treatment leads to the formation of Nb3Sn at the interface of Nb and Cu—Sn. The initial composite, if composed in a suitable configuration, has excellent deformation properties such that a geo-... 

Bronze process External diffusion Internal diffusion... 

Bronze process Internal Tin (IT) process Powder-in-tube process (PIT)... 

Bronze disease necessitates immediate action to halt the process and remove the cause. For a long time, stabilization was sought by removal of the cuprous chloride by immersing the object in a solution of sodium sesquicarbonate. This process was, however, extremely time-consuming, frequentiy unsuccesshil, and often the cause of unpleasant discolorations of the patina. Objects affected by bronze disease are mostiy treated by immersion in, or surface appHcation of, 1 H-henzotriazole [95-14-7] C H N, a corrosion inhibitor for copper. A localized treatment is the excavation of cuprous chloride from the affected area until bare metal is obtained, followed by appHcation of moist, freshly precipitated silver oxide which serves to stabilize the chloride by formation of silver chloride. Subsequent storage in very dry conditions is generally recommended to prevent recurrence. 

In the sheet-forming process, stainless steel, bronze, nickel-base alloys, or titanium powders are mixed with a thermosetting plastic and presintered to polymerize the plastic. Sintering takes place in wide, shallow trays. The specified porosity is achieved by selecting the proper particle size of the powder. Sheet is available in a variety of thicknesses between 16 x 30 mm and as much as 60 x 150 cm. A sheet can be sheared, roUed, and welded into different configurations. 

Secondary Recovery. Metal returning from the store of metal in use is referred to as old scrap, in contrast with scrap generated within the copper fabrication process, which is called new scrap (see Recycling). In 1990 the amount of the U.S. copper supply derived from old scrap was 24% of the total copper consumed. About 40% of old scrap is used for producing refined copper most of the remainder is used in the production of brass and bronze ingots (see Copper alloys). About 75% of new scrap is consumed by brass mills, with most of the remainder used in the production of refined copper. Some estimates suggest that as much as 60% of the copper produced is ultimately recycled for reuse. Old scrap combined with new scrap from fabricating plants accounts for about 40% of the metallic input to domestic copper furnaces. 

Ejectors are available in many materials of construction to suit process requirements. If the gases or vapors are not corrosive, the diffuser is usually constructed of cast iron and the steam nozzle of stainless steel. For more corrosive gases and vapors, many combinations of materials such as bronze, various stainless-steel alloys, and other corrosion-resistant metals, carbon, and glass can be used. 

Secondary Brass and Bronze Production Plants Primary Emissions from Basic Oxygen Process Furnaces for Which Construction Commenced after June 11, 1973... 

Bronzes are somewhat similar to brasses in mechanical properties and to high-zinc brasses in corrosion resistance (except that bronzes are not affected by stress cracking). Aluminum and silicon bronzes are very popiilar in the process industries because they combine good strength with corrosion resistance. 

An example where one metal melts before the densihcation process, is the formation of bronze from a 90 10 weight percentage mixture of copper and tin. The tin melts at a temperature of 505 K, and the liquid immediately wets the copper particles, leaving voids in the compact. The tin then diffuses into the copper particles, leaving further voids due to dre Kirkendall effect. The compact is therefore seen to swell before the hnal sintering temperature of 1080 K is reached. After a period of homogenization dictated by tire criterion above, the alloy shrinks on cooling to leave a net dilatation on alloy formation of about 1%. 

In the so-called Dormagen process developed by IG Farben the cotton was first preheated with 30-40% of its own weight with glacial acetic acid for 1-2 hours. The pretreated material was then fed to the acetylisers, which consisted of horizontal bronze cylinders. For every 100 parts of pretreated cellulose there was added the following acetylating mixture, previously cooled to 15-20°C ... 

---