It can be either a weld line or a quench line or both. We recently had a photo on here of an axe with a double line, one darker than the other. They couldn't both be the weld line. I suspect one was the weld line and the other showed the depth of quench.
Exactly.Out of the two,the "quench" line would be closer to the edge,and it'd be Straight(naturally,more or less, representing a level of quenching fluid).
These two axes show an unmistakable difference in material.The higher Carbon in the steel insert makes it etch darker.
Wrought Iron,(WI),is not really an exact term,metallurgy-wise for sure,but even as a trade-term,as it changed around with the times...It used to mean generally that the steel in question was obtained by means of the so-called "Puddling" process;and the carbon-content,as well as any other specifics,differed widely,to say the least...
Eventually the term WI grew to mean low-C,malleable steel of whatever level of refinement(early in the 20-th c. it was still obtainable in "refined",to "5-x refined" grades,from some producers,and i believe it was finally discontinued in the US in 1969),but still all that was applied but loosely,and the chem.composition of WI has remained fairly random.....