Originally Posted by Rudebob

The use of “high tensile” is totally subjective and has no direct correlation to any specific mechanical properties that can be asserted to any material. It is a marketing term. Steel, even 1005 low carbon, is high tensile by comparison to most other non-metallic materials, and theoretically is valid. I mean a coat hanger is significant higher in tensile than pizza crust, right.

The term “low alloy steel”, however, usually refers to materials that have specific alloying elements (such as chrome, nickel, molybdenum, vanadium, etc.) within a range to provide desired mechanical properties, whether solution annealed, normalized or heat treated. However, even the term “low alloy steels” refers only to a class of material. Without specific alloy identification, one still knows very little regarding the actual mechanical strength (and condition) unless they actually test it.

The term “low carbon” steel usually means that mechanical properties are controlled primarily by carbon and manganese presence (although limits for sulfur, phosphorous and silicon are usually controlled as well).

I suspect the use of high tensile as is comes from some Asian countries is really more of a general term since the actual material types they use may change from different production runs, suppliers and such. They are not asserting any specific alloy, just that it is strong-well at least coat hanger strong.

Years back my company performed a failure instigation for an individual whose face looked like it went through a cheese grader. He had purchased a “mountain bike” from one of the major US “membership” warehouse stores. The frame and forks were labeled “chrome-moly”. However, the forks collapsed on a rough downhill run resulting in massive injuries. A quick chemical analysis of the forks showed the material to be low carbon steel (1018 if I remember correctly). I never heard how much received in the lawsuit, however, about 6 months later the same big box membership store was selling the same bike-this time labeled “high tensile steel”.

One other thing to keep in mind is that steel becomes much more difficult to weld once the carbon content gets to 0.40 percent or higher. At this point pre and/or post heat treatments usually need to be utilized to prevent cracking. This is the difference between 4130 and 4140 chrome-moly steel for example. I say this in that most production frames built with cost considerations in mind will utilize lower carbon steels as means of controlling costs from these additional processes. That means most of your “high tensile” low carbon steels are going to be limited on strength. For this reasoning, it is unlikely that high carbon “Spring temper”steels would be used.

'bob