Process

Description

Abrasive Jet Machining

Cutting hard brittle materials through a process similar to sand blasting. Abrasive jet machining, however, can use much finer abrasives carried at high velocities (500-3000 fps) by a liquid or gas stream. The process can result in wastewater from solution dumps, spills, leaks or wash downs of work area. Wastes may contain abrasive fines, metals and oils.

Casting

Filling shaped containers or molds with molten metal so that upon solidification, the shape of the mold is reproduced. Types of casting methods: stationary casting (or pig casting, air cooled in molds); direct chill casting (continuous solidification of the metal while it is being poured); continuous casting (sheet or strip); semi-continuous casting (molten metal is poured down a trough and into vertical billet molds).

Cladding

Creating a composite metal containing two or more layers that have been bonded together. Bonding may have been accomplished by roll bonding (co-rolling), solder application (brazing), or explosion bonding.

Drawing

Fulling the metal through a die or succession of dies to reduce its diameter. alter the cross-sectional shape, or increase its hardness. Typically used to manufacture tube, rod, bar, and wire. May be conducted hot or cold. Intermediate annealing is frequently required between draws to restore the ductility lost by cold working of the drawn product.

Electrical Discharge Machining

Removal of metal from the workpiece surface with stringent dimensional control. The machining action is caused by the formation of an electrical spark between an electrode, shaped to the required contour, and the workpiece. Rinsing of machined parts and work area cleanups can generate wastewaters which also contain base materials. These wastewaters contribute to the common metals and oily waste types.

Electrochemical

Machining

Process based on the same principles used in electroplating except the workpiece is the anode and the tool is the cathode. Electrolyte is pumped between the electrodes and a potential applied which results in removal of the metal. In addition to standard chemical formulations, inorganic and organic solvents are sometimes used as electrolytes for electrochemical machining and with the basis material being machined, can enter waste streams via rinse discharges, bath dumps, and floor spills. Waste generated can contain metals, cyanide, and solvents depending upon specific process.

Electron Beam Machining

Thermoelectric process whereby heat is generated by high velocity electrons impinging on part of the workpiece. At the point where the energy of the electrons is focused, it is transformed into sufficient thermal energy to vaporize the material locally to alter or cleave surfaces. The operation is generally under vacuum.

Extruding

Applying high pressures to a cast metal billet, forcing the metal to flow through a die orifice. ‘Iwo types: direct and indirect. Heat treatment is often used after extrusion to attain the desired mechanical properties.

Forging

Deformation of metal, usually hot, with compressive force into desired shapes with or without dies. Five types: closed die, open die, rolled ring, impacting, and swaging. In each, pressure is exerted on dies or rolls, forcing the heated stock to take the desired shape. The first three are hot working, the other two are cold.

Impact Deformation

Applying impact force to a workpiece such that it is permanently deformed or shaped. Wastes containing metals and oils may result from cleaning the impacted parts.

LASER Beam Machining

Process whereby a highly focused monochromatic collimated beam of light is used to remove material at the point of impingement on a workpiece. Laser beam machining is a thermoelectric process with material removal largely accomplished by evaporation, although some material is removed in the liquid state at high velocity.

Plasma Arc Machining

Removal of material from shaping of a workpiece by a high velocity jet of high temperature ionized gas. A gas (e.g., nitrogen, argon, or hydrogen) is passed through an electric arc causing it to become ionized and raised to temperatures in excess of 16,649 oC (300,000 oF). The relatively narrow plasma jet melts and displaces the workpiece material in its path.

Pressure Deformation

Applying force (at a slower rate than at impact force) to permanently deform or shape a workpiece Cleanup wastes may contain metals and oils.

Rolling

Reducing cross-sectional area of metal stock, or otherwise shaping metal products, through the application of pressure by rotating rolls. Cylindrical rolls produce flat shapes; grooved rolls produce rounds, squares, and structural shapes. Employs hot or cold working techniques depending on the kind of metal or alloy. Hot rolling is generally rolling at temperatures above the recrystallization temperature. Cold rolling is defined as rolling below the recrystallization temperature of the metal. Heat treatment is usually required before and between stages of the rolling process. Annealing is typically required between passes or after cold rolling to keep the metal ductile and remove the effects of work hardening.

Sand Blasting

Removing stock, including surface films, from a workpiece by the use of abrasive grains pneumatically impinged against the workpiece. Waste blasting media can contain metals and residues from the surface of the metal.

Thermal Cutting

Cutting, slotting or piercing a workpiece using an oxyacetylene oxygen lance or electric arc cutting tool. Water may be used for rinsing or cooling of parts and equipment following this operation.

Ultrasonic Machining

Mechanical process designed to effectively machine. It hard, brittle materials. removes material by the use of abrasive grains which are carried in a liquid between the tool and the work, and which bombard the work surface a high velocity and are agitated using high energy ultrasonic waves.