ASTM A 604 Standard Practice for Macroetch Testing of Consumable Electrode Remelted Steel Bars and Billets

Scope:

This test method is used to examine the bars, billets, and blooms of carbon alloy and stainless steel which have been consumable electrode remelted. In this method, the consumable electrode remelting process is defined as the steel remelting process. This practice and involving comparison macrographs apply to steel bars and a billet size of 225 in².

Test procedure:

In this test method acid or other corrosive agent is used to develop the character of the suitably prepared specimen. Then the specimen is etched and then the section is compared visually as well as at very low magnification. The material reacts differently depending on the chemical composition, method of manufacture, heat treatment and many other variables.

Video 01:MACROSTRUCTURE ETCHING and EVALUATION, Quick Simple Explanation in 11 Minutes

Test Specimen:

The specimen is 1⁄4 to 1 inch thick, cut to reveal a transverse surface.

Data:

After Macroetching four distinct classes are defined as follows 

Class 1: Freckles: Circular or near-circular dark etching areas generally enriched with carbides and carbide-forming elements

Class 2: White Spots: Light etching areas, having no definitive configuration or orientation which are generally reduced in carbide or carbide-forming elements

Class 3: Radial Segregation: Dark etching with elongated, radially or spirally oriented areas that are typically carbide enriched occurs most frequently at the mid-radius. In some materials, this condition can be mistaken for freckles.

Class 4: Ring Pattern: One or more concentric rings evidenced by a differential in etch texture associated with minor composition gradients and ingot solidification.

Conclusion:  

ASTM A 604 gives guidelines for macro etching of steels and alloys prepared by Consumable electrode vacuum-melted and electro-slag remelting which may have discontinuities. This discontinuity is determined by the macro etching of these materials.