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Sharp tools are necessary to produce a good specimen. Because of their expense, usually specimens for macroetching will be small and can be handled the same as microspecimens. Comments Good general-purpose etchant, can be used on almost all aluminum alloys. Silicon brass or bronze Immerse specimen in solution at room temperature, rinse in warm water and dry. Add C to mixture of A and B after precipitate has redissolved.

astm e340

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Rinse in water and dry. Study of weld structures, definition of weld penetration, dilution of filler metal by base metals, entrapment of flux, porosity, and cracks in weld and heat affect zones, etc.

A number in parentheses indicates the year of last reapproval. The preparation of the solution is of paramount importance. Low-Ni alloys Grain structure.

Other applications of macroetching include: Electrolytic, 5 to 10 A per square inch, specimen vertical, rinse, brush, and dry.

Macroetch Examinations

Zstm standard has been approved for use by agencies of the Department of Defense. Defects such as coring, cracks, and porthole die welds are identi? F340 bring out P-rich areas and P banding. In complicated forgings, some thought will have to be given to the proper method of cutting so as to show? When a specimen is immersed in this type of solution, copper plates out onto the specimen by a replacement reaction.


Immerse specimen in solution at room temperature for 10 to 30 min. Zr, Hf, and high alloys As above.

astm e340

In general, these metals are soft and ductile in the pure state, but in the form usually encountered are hard and brittle. The specimens should be sectioned with abrasive cutoff wheels and ground on wet silicon carbide papers.

astm e340

The sample then is sectioned well away from the hot-cut surface. Desmut by vigorous scrubbing with vegetable brush under running water.

Electrolytic, specimen moves past a cathode bar, 30 to 40 A per inch of specimen width, rinse, brush, and dry. Rinse in hot water and dry.

ASTM E Standard Test Method for Macroetching Metals and Alloys_百度文库

Grinding is usually conducted in the same manner, using free-cutting wheels and light? Bright etch, grain structure, defects.

astm e340

When etching is completed, remove the specimens from the dish taking great care not to touch the etched surface. Swab surface of the specimen with mixed solution until desired contrast is obtained.


Disks may be faced on a lathe or a shaper. Care should be used to avoid cold work. The most common reagent for macroetching iron and steel is a 1: When desmutting is astmm, dip the specimen into a second solution. Longer grinding times than would be expected from the hardness of these metals and alloys are needed.

Last previous edition E — The best method of preparation for macroetching is the asm as for microetching.

Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. This standard is subject to revision at any time by the responsible technical committee and must be reviewed awtm These metals grind slowly and zstm sharp, fresh abrasives. They are not only very soft and cold work easily, but they pure lead especially recrystallize readily at temperatures which can be easily achieved in careless preparation.