Low Carbon Steel - Metallographic Sample Preparation

Metallographic preparation of low carbon steel alloys can be easily accomplished through the utilization of OnPoint Abrasives' consumables and procedures. Below, we present step-by-step instructions for preparing metallographic samples of low carbon steel alloys.

Recommendations for Sectioning: Achieving optimal outcomes in the resurfacing process relies on precise cutting techniques. To minimize subsequent grinding phases, it is strongly advised to cut the specimen as close as possible to the Point of Interest (POI).
 
For low carbon steel alloys, our top-tier recommendations involve the use of either MultiSec abrasive blades or our General Purpose diamond blade. The MultiSec abrasive blade is made of aluminum oxide particles within a rubber bond, resulting in a thin, high-speed cutting blade that effectively maintains the specimen's integrity.

In scenarios where conventional metallurgical sectioning is unfeasible, particularly with delicate specimens such as thin wires or foil-like materials, fundamental cutting tools like scissors, paper cutters, or bolt shears are more appropriate. It's worth noting that for small samples like biomedical device components, a common approach is to solely rely on grinding procedures to achieve the desired depth, bypassing the need for initial sectioning.

Recommendations for Mounting: To create optimal metallographic mounts for low carbon steel, consider employing PhenoMount phenolic powder for compression specimen mounting. Available in black, red, and green, phenolic provides a cost-effective option that works well with low carbon steel.

For low carbon steel specimens requiring castable mounting, we suggest using our EpoPro liquid epoxy system. The use of a vacuum impregnation chamber during the castable mounting process effectively eliminates unwanted air bubbles from the epoxy material, ensuring penetration into the intricate recesses and geometries of the low carbon steel specimen. This method is highly recommended for casting metallographic samples, although it may not be necessary in all instances.

Recommendations for Grinding and Polishing: OnPoint's grinding and polishing guidelines serve as a valuable reference for preparing samples for metallographic analysis. Our procedure for low carbon steel is tailored for use on an automated polisher featuring Central Force capability. This procedure involves a contra-directional pattern between the working wheel and specimen holder.
 
When using polishers exclusively equipped with Individual Force capability or when opting for manual polishing, the operator should initiate the procedure from step number 2. Adjustments are also required in these cases, with the recommendation of adopting a complementary directional pattern.
 
In this section, we present two methods for preparing your specimen for analysis: the Traditional Method and the Advanced Method.
 
The Traditional Method employs a series of Silicon Carbide grinding papers to initially planarize and then grind the surface to approximately 3-5 microns (1200 grit), followed by polishing steps using suspensions and cloths. This method is effective for general-purpose metallography, although it may introduce some relief or rounding of the specimen's edges when viewed at high magnifications.

Our Advanced Method uses one or two steps of SiC grinding paper to initially planarize the mounted specimen. This is followed by a series polishing steps that utilize diamond, alumina, and colloidal silica suspensions along with polishing cloths. The less aggressive approach of this method preserves the specimen's edge and produces ultra-flat results. This can be critical for analysis such as coating thickness measurements or samples that are examined near the specimen's edge. Furthermore, the addition of colloidal silica at intervals during the final polishing step produces enhanced grain boundaries during etching. It is viewed by many that the "advanced" methods of preparation offer superior results and higher consistency when compared to traditional methods.