FBinNY 

I haven't stayed on top of this for years, but to my knowledge all bicycle chains have tensile strength ratings of 1100-1200kg. I remember that there's a standard for them at 1,000 or 1100kg but don't remember if it's an old US or European industrial standard, or a national standard. In all likelihood it's now an ISO standard and is somewhere in that range.

But comaring tensile load ratings is pointless because tensile chain failure (plates failing under load) is extremely rare. When it happens, it's usually the result of heat treat and/or tolerance issues causing outer plates to stress crack at the pins. Another cause is embrittlement caused by exposure to various ions, mainly hydrogen and chlorine, in cleaning solutions, but this too is rare.

99% of chain failures happen in the two step process I described earlier. Shifting forces plates outward to and beyond the end of the pin, and at a later time a peak tension load snaps the chain. The evidence is clear, 1 plate intact but detached at one end, and the other bent when the pin slides free.

Traditionally chains have been made of carbon steel plates, with bearing grade pins and bushings, but the current bushingless design and thinner plates today narrows the options. Alloy steel is used for the plates, but heatreating for maximum tensile strength is limited by the need to maintain ductility and toughness. The inner plate also has to be heat treated to a balance the wear properties against toughness (opposite ends of the scale) which is one reason wear life is down compared to 30 years ago (smaller contact area being the main other reason).