Flame Hardened Medium Carbon Steel Qualities

15 June 2018

While medium carbon steel clearly isn’t as hard as a high-carbon alloy, those lenient mechanical qualities can be enriched. By exposing the steel to flame hardening equipment, a heat treatment technique that uses a focused cone of combusted gas, we fortify the material and reinforce its generally weaker microcrystalline bonds. A mild steel workpiece is approaching the flame now, so let’s do a before and after comparison.

When Oxy-Gas Meets Medium Carbon Steel

As mentioned in several past articles, flame hardening technology is a targeted high-temperature heat treatment process, one that uses a focused, unwavering open flame to selectively surface harden different types of metal. In this case, we’re transporting a medium carbon steel workpiece towards the flame. Locked in place, the procedure begins. The oxy-gas head traverses the length of the part, the metal reaches its critical transformative temperature, and then it’s rapidly quenched. A hardening depth of around 3 – 5mm is certainly feasible here, but it’s difficult to go any deeper without introducing a secondary source of carbon.

Flame Hardened Qualities

For medium carbon steel, the open flame surface is harder and stronger than the “before” material, but the hardness depth is inflexible. Transformed until the lower carbon content gifts the alloy with moderate strength and a reasonable amount of wear resistance, the heat treated parts processed here tend to end up in the light-to-medium industrial sector. Axles and transmission rods exit the equipment ready to endure substantial loading factors, as do shafts, spindles and gear tooth areas. As long as the flame head covers every square millimetre of the medium carbon workpiece, it will gain all of the qualities required to satisfy these parts taxing applications.

Supported by Numerical Data

The first relevant number here is the amount of carbon incorporated into the steel. Medium carbon workpieces typically add between 0.3 and 0.65 percent of this heat-transformative element, so the formerly soft metal receives a hard but possibly slender shell. Somewhere in the region of HRC 54 to HRC 60 (Rockwell Hardness) is entirely possible when that flame gets to work. As for varying that fixed value, quenching fluid types are known to enhance the process. Furthermore, specially adjusted twin flame heads have an advantage. Spaced just-so, the twin flame heads introduce more carbon into the operation, so the heat treated hardening depth deepens.

An investigation into flame head geometries yields positive results. Although the lower carbon content in that medium grade steel alloy forms a thinner case depth, that quality does become controllable when the head array is adjusted. Last of all, additional manganese and alternative quenching fluids are known to improve the qualities of medium grade steels. At the end of the day, this heat treatment procedure equips medium carbon steel components with a moderately hardened surface, with exteriors that are also relatively wear resistant.

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