ASTM B320-2019 pdf free download

ASTM B320-2019 pdf free download.Standard Practice for Preparation of Iron Castings for Electroplating
1. Scope
1.1 This practice is intended to assist electroplaters in establishing and maintaining a satisfactory pre-electroplating cycle for malleable iron, gray iron, nodular iron, and white iron castings. It is also intended to indicate certain foundry practices which will facilitate subsequent finishing. Most ofthe practices that follow have been based on experience with malleable and gray iron. However, since they are related to the other forms, the same practices will probably apply. Nodular iron is also known as spheroidal or ductile iron, which is defined as cast iron with the graphite substantially in spherical shape and substantially free of flake graphite. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in 2.1. 1.3 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Foundry Practices
3.1 The seacoal content of the molding and facing sands should be maintained at the maximum practicable limits to minimize the occlusion of sand in the surfaces of the castings. 3.2 Upon removal from the molds, castings should be subjected to an abrading action (such as tumbling, grit blasting, or shot blasting) to remove as much as practicable of the occluded molding sand. Residual sand and scale may be removed, if necessary, by treatment in various proprietary descaling baths. These are usually based on fused caustic soda, some of which use chemical oxidizing or reducing agents and others employ electrochemical action as well. This is particu- larly important in the case of castings that will be annealed, to prevent the burning on of sand during this operation. Castings that will be warped or damaged by a blasting operation may be pickled in a solution containing 200 to 250 mL/L of sulfuric acid to remove occluded molding sand. See Warning state- ment in 2.1. 3.3 Annealed castings should be given an additional abrad- ing as described in 3.2 to remove any scale that may have been formed, as well as graphitic carbon that may be present at the surface.
5. Cleaning Solutions and Equipment
5.1 The various solutions used for the treatment of mal- leable and gray iron castings should be maintained by chemical analysis so far as is practicable, such as determining the free acid and iron concentrations of the acid baths and using tests recommended by the manufacturer, the effective components of the proprietary cleaning solutions. 5.2 All solutions should be discarded before they lose their effectiveness, based on tests and experience. 5.3 When the amount ofsoil is excessive, particularly where no precleaning is done, it may be desirable to double the cleaning and pickling facilities. Thus, while the first ofany two particular solutions becomes heavily contaminated, the second remains relatively clean and effective for further use. When the first of a pair of solutions is discarded, it is replaced by the second solution and a fresh second solution is prepared. This system also reduces the possible carry-over of contaminants such as oil and grease into subsequent solutions. 5.4 Where doubling the facilities is impossible or impracticable, similar economies may be obtained to a degree by providing cleaner and pickle tanks with overflow dams, sumps and pumps with which the solution may be recirculated. The pump intake should be located approximately half-way down the sump to preclude returning either settled-out solid dirt or surface oil and grease to the processing tank. The outlet should be near the bottom of the processing tank at the end opposite to the overflow dam so as to create some solution turbulence (for mechanical scrubbing benefits) and to ensure flow of contaminated solution to the dam.