ASTM E381-20 pdf free download.Standard Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings.
1.1 Macroetching, which is the etching of specimens for macrostructural examination at low magnifications, is a frequently used technique for evaluating steel products such as bars, billets, blooms, and forgings.
1 .2 Included in this method is a procedure for rating steel specimens by a graded series of photographs showing the incidence of certain conditions. The method is limited in application to bars, billets, blooms, and forgings of carbon and low alloy steels.
1 .3 A number of different etching reagents may he used depending upon the type of examination to be made. Steels react differently to etching reagents because of variations in chemical composition, method of manufacture, heat treatment and many other variables. Establishment of general standards for acceptance or rejection for all conditions is impractical as some conditions must be considered relative to the part in which it occurs.
3. Terminology
3.1 Definitions—For definitions of terms used in this method, see Terminology E7.
3.2 I)efinitions of Ternis Specific to This Standard:
3.2. 1 Terminology Applicable Only to Ingot cast Product:
3.2.1. 1 splash—a nonuniform etch pattern where irregularly-shaped areas exhibit a different etch contrast than surrounding areas. Splash is normally associated with molten steel which solidifies and oxidizes during initial pouring and which is not completely redissolved by the remaining molten steel.
3.2.1.2 hun tears—subsurface cracks normally parallel to the surface of the ingot mold wall.
3.2.1 .3 flute cracks—cracks perpendicular to the surface of the ingot mold wall which may, or may not, extend to the surface of the product.
3.2.1.4 hurst—a single or multi-rayed crack normally located at the center of the wrought product.
3.2.2 Definitions Applicable Only to Continuously cast
Prodi.tcts:
3.2.2.1 chill wne—rapidly cooled metal with a fine structure at the surface of the product which is normally continuous around that surface.
3.2.2.2 cliii! cone crack—any crack which is located partially or completely in the chill zone and may extend to the surface of the product.
3.2.2.3 diagonal crack—a crack which lies completely or partially in the diagonal regions of a non-round product where adjacent columnar or dendritic growth patterns intersect.
3.2.2.4 subsuiface crack—a crack perpendicular to and just beneath the chill zone.
3.2.2.5 mid-radius crack—a crack perpendicular to the surface of the product located approximately halfway between the surface and center of the product.
3.2.2.6 center crack—a crack with an aspect ratio of approximately 3 or greater located at, or near, the center of the product.
3.2.2.7 star crack—a star-shaped or multi-rayed crack at the center of the product.
3.2.2.8 scattered porositv—multiple round or irregularlyshaped pores uniformly distributed about the central portion of the product.ASTM E381 pdf download.