Machining swarfs

Titanium, which was in commercial production in 1950, is thermodynamically a very reactive metal (machining swarf can be ignited in a similar fashion to that of magnesium ribbon) but this is offset by its strong tendency to passivate i.e. to form a highly stable protective oxide film. 

In spite of this limitation, the method is very useful, because it provides a means of forming a ceramic of one of the most common and inexpensive oxides. As discussed before, iron oxide is a component of lateritic soils and red mud, high-volume iron mine tailings, and machining swarfs. Thus, useful products of several mineral waste streams can be formed by the process described in this chapter. Development of ceramics using red mud and swarfs is discussed in Chapter 14. 

M.J. Hess and S.K. Kawatra, Environmental beneficiation of machining wastes. Part I. Materials characterization of machining swarf, J. Air Waste Mgmt, 49 (1999) 207-212. 

S.K. Kawatra and M.J. Hess, Environmental beneficiation of machining wastes. Part II. Measurement of the effects of moisture on the spontaneous heating of machining swarf, J. Air Waste Mgmt, 49 (1999) 477-481. W.D. Kingery, Fundamental study of phosphate bonding in refractories. II. Cold-setting properties, J. Am. Ceram. Soc., 33 [5] (1950) 242-250. 

CBPC matrix composites can incorporate a high volume of industrial waste streams such as fly ash, mineral waste such as iron taUings and Bayer process residue from the aluminum industry (red mud), machining swarfs from the automobile industry, and forest product waste such as saw dust and wood chips. Table 14.1 lists some of these waste streams and potential products or applications. 

Swarf - The residue created from metal fab-ricatimi. In machining, swarf is synonymous with chips. 

Sheet and block may be machined with little difficulty providing care is taken to avoid overheating and to collect the inflammable swarf. 

Metalworking fluids contain mineral oils (refer to p. 80) or synthetic lubricants they are used neat or in admixture with water. They may contain small amounts of biocides, stabilizers, emulsifiers, coiTosion inhibitors, fragrances and extreme pressure additives. The formulations render them suitable for application to metal being worked, generally from a recirculatory system, to provide lubrication, corrosion protection, swarf removal and cooling of the tool and machined surface. 

The main function of most lubricants is to reduce friction and wear between moving surfaces and to abstract heat. They also have to remove debris from the contact area, e.g. combustion products in an engine cylinder, swarf in metal-cutting operations. Sometimes they have to protect the lubricated or adjacent parts against corrosion, but this is not a prime function of most lubricants. On the other hand, many lubricants do contain corrosion inhibitors and some lubricating oils, greases, mineral fluids and compounds are specially formulated to prevent the corrosion of machinery or machine parts, particularly when these components are in storage or transit. These temporary protectives are described in Section 17.3. 

It should be noted that swarf from a zirconium-titanium alloy containing approximately 50% by weight of each element is prone to pyrophoricity in air. It has also been reported that when zirconium is welded to titanium, the welded zone is much more sensitive to corrosion than either of the parent metals. If, therefore, it is proposed to use my construction in which zirconium is welded to titanium, caution should be observed in the machining of welds, and the corrosion behaviour of the weld should be checked by prior testing in the environment with which the construction will be employed. 

Piping circuits will usually contain a small quantity of dirt, scale and swarf, no matter what care is taken to keep these out. A strainer is fitted in the compressor suction to trap such particles before they can enter the machine. Such strainers are of metal mesh and will be located where they can be removed for cleaning. In some configurations two strainers may be fitted. 

Storage of uranium foil in closed containers in presence of air and water may produce a pyrophoric surface [1], Uranium must be machined in a fume hood because, apart from the radioactivity hazard, the swarf is easily ignited. The massive metal ignites at 600-700°C in air [2]. The finely divided reactive form of uranium produced by pyrolysis of the hydride is pyrophoric [3], while that produced as a slurry by reduction of uranium tetrachloride in dimethoxyethane by potassium-sodium alloy is not [4],... 

Swarfs, machining waste from steel -50 Recycling metal values... 

The most common metal swarfs are iron-based [9,10] and produced by the machine tool and automobile industries. The resulting fine Fe particles oxidize in storage and form magnetite and hematite. Because they also contain flammable machine oils, this oxidation makes them pyrophoric and hence a liability. Because the particle surfaces are coated with oil, they cannot be incorporated in conventional cement. As demonstrated by Wagh and Jeong [3], the acid phosphate in the CBPC process acts like a detergent and exposes the surface of these particles to the acid-base reaction and binds them. 

Aluminum home scrap in the form of swarf is produced in considerable amounts during the trimming of ingots and blocks by milling for sheet and foil manufacturing, in large machining centers, for example in automobile wheel and motor production,... 

The flow diagram of a complete processing system is shown in Fig. 6.9-20. The vi-bro-screen feeders in front of the centrifuges and the press eliminate and by-pass large pieces that might damage the machines. Fig. 6.9-21 shows processed aluminum swarf and briquettes produced with a punch-and-die press. 

Do not attempt to adjust the coolant supply or remove swarf when the machine is running. 

Eye injuries and cuts from machine cleaning and swarf removal. 

While machining metals such as steel, wheel loading (embedment of swarf) will be caused. 

Would Mr. Thompson say whether any special procedures were employed to collect swarf arising from the machining ... 

After finishing the process, machines must be regularly maintained and lubricated. Swarf must be removed from the working zone. Solvents are used to clean processed metal products and skin from mineral oils. 

The best means of keying the insert is to machine on to it a coarse knurl. Great care is needed to ensure no swarf remains, and that there are no burrs - both are potential sources of stress concentration, crack initiation and premature failure. 

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