ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2025 20 TABLE 1 — CHEMICAL COMPOSITION OF THE NARROW-GAUGE RAIL, DECAUVILLE TYPE %C %Si %Mn %P (max) %S (max) %Cr %Mo %Ni %Al %Co %Cu %Nb 0.52 0.055 0.92 … … 0.050 < 0.003 0.12 0.003 0.026 0.098 0.020 EXPERIMENTAL RESULTS The micrograph of the Decauville type narrow-gauge rail in Fig. 3 shows the different sectors named head, web, and flange. A ferrite matrix (light zone) combined with pearlite (dark zone) of a hypoeutectoid steel with a medium carbon content (0.52 %C) is observed according to what was revealed by the chemical composition analysis, that is to say that the material of this historical Decauville rail would be a structural steel that is used in the manufacture of long products and structural profiles[5]. In the micrographs cited, the grain of the material can be seen with signs of cold deformation due to the stresses or loads acting on the rail. These grain deformations are called “saw teeth.” In the corresponding macrographs shown in Fig. 5, a perfect delineation of the fibers of the constituent material, formed by ferrite and pearlite bands, can be clearly observed in the area of the edge of the profile. No gaps, sink holes, bubbles, or anything to indicate poor quality of the rail material and the Aires to the West,” was opened to public service. It connected the Parque Station (today where the Teatro Colón is located) and the Floresta station, a distance of 10 km, that was covered in approximately half an hour. The trains were driven by locomotive, christened as 2-2-0ST from the factory. This distribution of numbers and letters is the locomotive’s wheelset (2 front wheels, 2 drive wheels, none at the rear and a saddle tank (ST) above the boiler). The Raúl Scalabrini Ortiz Railway Museum and Cultural Center, also known as the Haedo Railway Museum is a Civil Association whose purpose is to rescue, preserve, and restore the rolling stock of our country for educational and tourism purposes. It had its origins as a headquarters of the Argentine Railway Club, founded in 2003. The site where the museum is located was originally a coal elevator where steam locomotives refueled and emptied their ash bins. EXPERIMENTAL PART The sample received for the study is shown in Fig. 3. It was sanded using a sequence of 60, 80, 120, 360, 500, 1200, and 2500 grains/cm2 sandpapers. Next, it was polished to a mirror finish. Micrographs were taken with etching in different sectors as shown in Fig. 4. The etching lasted for approximately 10 s with 2% Nital reagent. Later, a metallic micrograph was observed in three different sectors of change in dimension of said rail, named as head, web, and flange, shown in Fig. 4, using a metallographic microscope. The sanding process for the macro- graphic procedures was carried out again following a sequence of 60, 80, 120, 360, 500, 1200, and 2500 grits grains/cm2 and then polished with alumina to eliminate the attack previously carried out with the 2% Nital reagent as shown in Fig. 5. The chemical composition was studied using a portable spectrometer with plasma spectroscopy and is listed in Table 1. A study of hardness measurements was carried out in the three different areas of the specimen using a microhardness tester on the HV scale and the results are listed in Table 2. Fig. 3 — Narrow-gauge rail profile, Decauville type. TABLE 2 — MICROHARDNESS PROFILE OF THE NARROW-GAUGE RAIL, DECAUVILLE TYPE Head Web Flange Microhardness profile, HV 263 214 198 236 212 180 241 201 208 259 197 239 204 187 239 Average, HV 240 202 212 Equivalence, HRB 98 92 96
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