Hand Tools Archive

Subject:
Re: Narex chisels = chrome manganese

Steve Voigt
I looked into it too. Here's an abstract from one article:

Traditionally it have been reported that bainite microstructure has better impact properties than tempering martensite at the same hardness level. In this work a comparative study was performed using samples of 2 different steels: SAE 4140 and SAE O1 (tool steel) under different heat treatment conditions: austempering; quenching and tempering followed or not by a cryo bath. At the total 47 samples were Charpy impact tested. Hardness, microscopy (optical and SEM) and fractography analysis were performed. No matter the steel analyzed, better performances were obtained for the tempering martensite followed by the cryo bath.

I should add that I haven't read the actual paper (it's paywalled) and I don't have the technical chops to evaluate the claim, but I thought it was interesting. Reading the Narex page on heat treating, it seems pretty clear that they chose the isothermal route not to make a better tool, but because it's easier to manufacture (once it's set up). Same reason that other companies go the A2 route; it's done for ease of production, not tool quality. All the claims about how wonderful the steel is are just rationalization for a more profitable process.

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