Heat hardening equipment

Several pellet hardening processes are used commercially, and these are summarized below. 

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Pellet cooling is usually done on the same machine used for heat hardening whereas sinter is cooled in separate equipment. 

The patching mix may be processed in an asphalt hot-mix plant and transported to the various patching sites in a heated vessel. Alternatively, the patching mix may be produced by remelting previously made hardened mix in a mobile heated vessel equipped with an agitator. The latter process is particularly adaptable for use during the winter in areas where hot-mix plants are not normally operational. 

Carburization damage is mainly associated with high-temperature exposure to carbon dioxide, methane, and other hydrocarbons. Heat-treating equipment used for gas carburization (surface hardening) of steels is also vulnerable. An insidious aspect of carburization is its nonuniform nature. Just as for other forms of localized corrosion, it is extremely difficult to predict and model localized carburization damage. As a rule of thumb, carburization problems only occur at temperatures above 815°C, because of unfavorable kinetics at lower temperatures. Carburization is therefore not a common occurrence in most refining operations because of the relatively low tube temperatures of most refinery-fired heaters. 

Typical apphcations for the nickel—copper alloys are in iadustrial plumbing and valves, marine equipment, petrochemical equipment, and feedwater heat exchangers (see Piping systems). The age-hardened alloys are used as pump shafts and impellers, valves, drill parts, and fasteners (see Pumps). 

Martensitic Stainless Steels. The martensitic stainless steels have somewhat higher carbon contents than the ferritic grades for the equivalent chromium level and are therefore subject to the austenite—martensite transformation on heating and quenching. These steels can be hardened significantly. The higher carbon martensitic types, eg, 420 and 440, are typical cutiery compositions, whereas the lower carbon grades are used for special tools, dies, and machine parts and equipment subject to combined abrasion and mild corrosion. 

Both thermoplastics and thermosets can be formed by compression moulding (Fig. 24.5). The polymer, or mixture of resin and hardener, is heated and compressed between dies. The method is well suited to the forming of thermosets (casings for appliances, for instance) and of composites with a thermosetting matrix (car bumpers, for example). Since a thermoset can be removed while it is still hot, the cycle time is as short as 10 seconds for small components, 10 minutes for large tliick-walled mouldings. Pressures are lower than for injection mouldings, so the capital cost of the equipment is much less. 

The nickel silvers generally are classified as brasses. Cupronickels fall more into basic copper-nickel alloys. Possible minor ingredients are manganese, iron, and zinc. These alloys can be used for severe drawing, spinning, and stamping operations because Ihey do not harden readily. They also are extensively used for condenser lubes and plates, heat exchangers, and other process equipment. 

Material is cold drawn seamless mechanical tubing or similar high quality seamless steel tube. Use an inside micrometer and an auto engine cylinder hone to enlarge and polish the bore to 2.38" +. 005". This is CRITICAL and is the most important operation of the entire project. Inside mikes and cylinder hones are available from local equipment rental shops. Cut the tube to length, square and deburr ends and crown the muzzle (.1875" half round). Thread 1.75" of the base end of the barrel w/2A TPI outside threads. Heat treat or case harden the finished barrel if possible. This will increase strength and reduce wear. Screw the barrel into the basecap (assembly A-B).Paint the outside of the completed assembly w/ olive drab enamel. 

Precipitation hardening stainless steels are those alloys ending with the sufBx PH (i.e., precipitation hardening), for example, 17 PH (17Cr-4Ni-4Cu) (UNS S17400). They are hardenable by heat treatment. They are most often used for springs, valve stems, the internals of rotating equipment. 

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