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Standard Test Method f A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. Scope 1. The SI equivalents of inch-pound units may be approximate. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
For speci? Referenced Documents 2. Metallographic specimens and chemical analyses will provide the necessary detailed information about speci?
Current edition approved May 10, Published August Replaces portions of Method E 3. Originally published as E — Last previous edition E — The information provided about variations in chemical composition is strictly qualitative but the location of extremes in segregation will be shown. Chemical analyses or other means of determining the chemical composition would have to be performed to determine the extent of variation. Macroetching will also show the presence of discontinuities and voids, such as seams, laps, porosity,?
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 carburization of dies, effectiveness of stop-off coatings in carburization, etc. In the machine shop, it can be used for the determination of grinding cracks in tools and dies. Forge shops, in addition, use macroetching to reveal? For an example of the use of macroetching in the steel forging industry see Method E 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, etc. Defects such as coring, cracks, and porthole die welds are identi? Sampling 4.
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 Copyright? 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? Billets or blooms going into small sizes are sampled after initial breakdown. Material going into forging billets or die blocks is sampled near?
Sampling may be done systematically or on a random basis. The use of torch cutting or hot cutting should be used only when necessary to cut a sample from a large piece.
The sample then is sectioned well away from the hot-cut surface. An example of permissible use of torch cutting is the excising of a piece from a large plate and then cutting a sample for macroetching 4 to 5 in. Samples cut too close to the end, however, may have false structures because of? Disks from large blooms are sometimes cut into smaller pieces for ease in handling. Forgings may also be cut parallel to the long dimension to show?
In complicated forgings, some thought will have to be given to the proper method of cutting so as to show? Macroetching of an unprepared specimen will show surface defects such as shuts,? In extrusions, coring and coarse grain are more commonly found in the back end of the extrusion. An ideal length would be the circumference of the last roll, but this may be inconveniently long.
Several samples totaling some given fraction of the circumference can be used; however, there is always a chance then that a defect arising from faulty rolls would not be detected. When seeking information on laminations, a transverse section is used. In many cases, however, to reduce the size of the specimen, only a section out of the center of the plate may be taken.
Careful preparation is usually rewarded with highly detailed structures giving a large amount of information. Welds involving dissimilar metals will produce problems in etching.
The best method is to etch the least corrosion-resistant portion? Occasionally an intermediary etchant may be required. The boundaries between etched and unetched portion will give an idea of weld penetration and dilution. Because the machined or ground part is often the? In this case, other methods such as dye penetrant methods may be more desirable.
Preparation 5. Any method of presenting a smooth surface with a minimum amount of cold work will be satisfactory. Disks may be faced on a lathe or a shaper. The usual procedure is to take a roughing cut, then a?
This will generate a smooth surface and remove cold work from prior operations. Sharp tools are necessary to produce a good specimen. Grinding is usually conducted in the same manner, using free-cutting wheels and light?
Where necessary, details are given in the tabulation of procedures. Any grease, oil, or other residue will produce uneven attack. Once cleaned, care should be taken not to touch the sample surface or contaminate it in any way. Solutions 6. In most cases a good grade of reagent should be used but need not be chemically pure or of analytical quality. The so-called technical grades are usually satisfactory. The solution should be clean and clear, free of suspended particles, scum, etc.
Many of the etchants are strong acids. In all cases, the various chemicals should be added slowly to the water or solvent while stirring. In the cases where hydro? Procedure 7. Etching should be done in a well-ventilated room, preferably under a fume hood. The solution should be mixed and placed in a corrosion resistant tray or dish and brought to the operating temperature. The specimen or specimens should be placed in a tray of stainless steel screen or on some non-reactive support.
Glass rods often are placed on the bottom of the acid container and the specimens laid directly on the rods. When etching is completed, remove the specimens from the dish taking great care not to touch the etched surface. When desmutting is required, dip the specimen into a second solution. After rinsing the specimen with hot water, blow dry with clean compressed air.
E — 00e1 Saturate a large wad of cotton held in stainless steel or nickel tongs with the etchant and sweep over the surface of the specimen. An effort should be made to wet the entire surface as soon as possible. After the initial wetting, keep the swab saturated with solution and frequently sweep over the surface of the specimen to renew the solution. When the structure has been suitably developed, rinse the specimen, either with a swab saturated with water, or better still, by pouring water over the specimen.
After rinsing with hot water, blow the specimen dry with compressed air. Details of the procedure not discussed here are covered in the sections for the various metals and their alloys.
In fact, the progress of etching should be closely watched and etching stopped when the preferred structural details have been revealed. Specimens should be etched to develop structure. Generally, a light etch is better than a heavy etch; overetching can often lead to misinterpretation. The actual time to develop a structure properly may be quite different from the one suggested.
All these methods will cause cold work at the surface and will generate heat. The temperature rise can be enough to cause changes in structure. For these reasons sharp tools and generous lubrication are necessary for sectioning.
Again sharp tools and copious lubrication are required. In these cases the specimen is periodically removed from the solution, cooled in running water, and reimmersed in the etchant. This procedure is repeated until the desired degree of etching is obtained.
Warning—Before starting any work involving beryllium, a review of hazards and plans for handling should be made. A number of references on beryllium are available. First, beryllium is a rather brittle metal and sectioning can be difficult. Cut-off wheels with the designation C46FR70 have been the most successful.
Secondly, beryllium does not grind easily; hence, specimens should be as small as possible to minimize grinding time.
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade TBT Committee. Standard Practice for. Macroetching Metals and Alloys 1. A number in parentheses indicates the year of last reapproval. This standard has been approved for use by agencies of the U. Department of Defense. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
ASTM E340 (2015).pdf
Historical Version s - view previous versions of standard. More E Metallographic specimens and chemical analyses will provide the necessary detailed information about specific localities but they cannot give data about variation from one place to another unless an inordinate number of specimens are taken. The information provided about variations in chemical composition is strictly qualitative but the location of extremes in segregation will be shown. Chemical analyses or other means of determining the chemical composition would have to be performed to determine the extent of variation.