ASTM E340-15 pdf free download.Standard Practice for Macroetching Metals and Alloys.
1.1 These procedures describe the methods of macroctching metals and alloys to reveal their macrostructure.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
3.1.3 Other applications of macroetching in the fabrication of metals are the study of weld structure, definition of weld penetration, dilution of tiller metal by base metals, entrapment of flux, porosity, and cracks in weld and heat affected zones, and so forth. It is also used in the heat-treating shop to determine location of hard or soft spots. tong marks, quenching cracks, case depth in shallow-hardening steels, case depth in carhurization of dies, effectiveness of stop-off coatings in carburization, and so forth. In the machine shop. it can be used for the determination of grinding cracks in tools and dies.
3.1.4 Macroetching is used extensively for quality control in the steel industry. to determine the tone of a heat in billets with respect to inclusions, segregation, and structure. Forge shops, in addition, use macroetching to reveal flow lines in setting up the best forging practice, die design. and metal flow. For an example of the use of macroetching in the steel forging industry see Method E38 1. Forging shops and foundries also use macroetching to determine the presence of internal faults and surface defects. The copper industry uses macroetching for control of surface porosity in wire bar. In the aluminum industry, macroetching is used to evaluate extrusions as well as the other products such as forgings. sheets, and so forth. Defects such as coring, cracks, and porthole die welds are identified.
4. Sampling
4.1 As in any method of examination, sampling is very important. When macroetching is used to solve a problem, the problem itself largely dictates the source of the sample as to the location on the work piece and the stage of manufacture; for example. when looking for pipe. the sample should represent the top of the ingot. or when looking for bursts or flakes, the sample should be taken as soon after hot working as possible.
4.2 When macroetching is used as an inspection procedure, sampling ought to he done in an early stage of manufacturing so that if the material proves faulty, no wasteful unnecessary work is done. However, the sample should not be taken so early that further working can introduce serious defects. In the steel industry, for example, the sample is usually taken after ingot breakdown and after most chances of bursts or flakes occurring have passed. Billets or blooms going into small sizes are sampled after initial breakdown.ASTM E340 pdf download.