Are “HC” Spikes “High Carbon”?
The carbon content of railroad spikes is a widely debated and openly discussed topic amongst the blacksmithing and knifemaking communities, so lets explore some facts.
Often I hear that “you should only make knives out of the HC Spikes” “HC stands for High Carbon” and “HC spikes make great knives”. While I can’t argue their edge retention or hardness properties when forged into a knife (in THIS article), we can easily solve some myths about their carbon content and material composition.
There is no such thing as a “High Carbon Steel” railroad spike, but there is such thing as an “HC” “Higher Carbon” spike! This is just a term used within the railroad industry for when to use specific spikes on specific sections of tracks (HC spikes are often used in tight bends).
It is generally accepted by most sources that anything from 0.3% Carbon to about 0.6% carbon is considered a “Medium Carbon steel”, and anything above 0.6% carbon a “high carbon steel”. For example- 1045, a steel that is widely recognized as a medium carbon steel, (AISI1045 describes it as “Medium Carbon steel”) has a carbon content of 0.420-0.50%.
While another example material, 1075 (AISI1075) (UNSG10750) is described as “high carbon steel” and contains a carbon content of 0.70-0.80%
Railroad spikes are made by multiple factories, and are held to a standard in regards to metallurgical composition and physical properties, by an organization Called “ASTM International”, formerly known as “American Society for Testing and Materials” for non standard track spikes, and AREMA (American Railway Engineering and Maintenance- Of- Way Association) standard for standard track spikes.
ASTM A65-07 dictates the specifics of standards for railroad infrastructure including the carbon content and labeling of spikes. “Grade 2” spikes must be marked with HC (Higher Carbon) spikes and must have AT LEAST 0.30 points of carbon, with an acceptable variance of 0.03%. This means that an HC spike can have as little as 0.27 points of carbon, a little lower in carbon then 1045 steel (AISI Standard) referred to as "medium Carbon Steel", containing 0.42-0.50 points of carbon.
METALLURGICAL LAB ANALYSIS
My supplier of railroad spikes (Keystone Spike) who manufactures spikes entirely in the USA using US Steel from Gerdau Ameristeel US has been kind enough to include the actual certification sheets for their Medium Carbon and their “HC” spikes (See attached). This is not open to speculation of carbon percentages, this is an actual metallurgical assessment of the materials from this batch of spikes on a certified test report.
Here you can see that the “MC” spikes contained 0.19% Carbon (essentially “Mild Steel”/ “Low Carbon Steel”) and the “HC” spikes contained 0.34% Carbon (Essentially the low end of “Medium Carbon Steel”).
As you can see, under no circumstances would you consider an “HC” spike to be “HIGH CARBON STEEL”, a phrase commonly used in the knife making world to refer to materials such as 1095 (AISI1095) which contains 0.90-1.03% Carbon, about three times as much carbon as the “HC” Spikes measured and lab certified to contain.
If you’re looking to purchase some brand new railroad spikes straight from the source, with a receipt that will hold up in court and a proper chain of custody (Not receiving stolen goods, picking them up on your own, etc)- Keystone Spike is the best source I know of. To purchase a bucket (120 spikes) costs $1 a spike (plus shipping) at the time of this article. We’ve had great luck with their products over the years, they’re consistently and a pleasure to deal with- give them a call to order some spikes.
www.keystonespikes.com
Tell Bob, “Craig sent you”!
Conclusion
”HC” Spikes are “higher carbon” than “MC” spikes, but are by no means anywhere near “high carbon” by any other industry standard, and should not be considered to be “high carbon” in comparison to knife steels. In the real world, they’re Mild steel at best and most similar in almost all material compositions (As elemental compositions other then Carbon content matter) to A36, commonly known as “mild steel”. (ASTMA36) but to stick to only one standard- we’ll call it “low carbon steel” and compare it to 1018 steel (AISI1018) (Carbon content of 0.18%).
In conclusion, an MC Spike is slightly lower strength than steel you’d get at Home Depot, and an HC spike is VERY similar, but potentially “SLIGHTLY” stronger…….than steel from the isle in Home Depot. In the end- you’re making a mild steel/low carbon steel knife, and arguing otherwise.
I have specifically avoided stating whether or not HC spikes can be hardened, whether a forged blade from an HC spike will “hold a good edge”, or opinion on whether or not they are “good” steel.
These topics will be discussed in the future, with testing and data.
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Resources:
https://www.azom.com/article.aspx?ArticleID=6130
https://www.azom.com/article.aspx?ArticleID=6559
https://www.astm.org/Standards/A29.htm
https://www.azom.com/article.aspx?ArticleID=6561
www.keystonespikes.com
https://www.azom.com/article.aspx?ArticleID=6117
https://www.azom.com/article.aspx?ArticleID=6115