Grain quality question

[Bühlmann]

I had a little W1 I wanted to use to make an inexpensive starter file guide for plunge lines. Measured 2” between machine screws.Took it to critical temperature in my little gas forge and quenched in room temp water. Upon cleaning up I saw tons of fine linears at the surface and a few that clearly wrapped around the edges. I was pretty certain I was doomed, but I finished up and tested hardness with my file set. The 65 HRC didn’t scratch a bit. Cool. Put it on a scrap piece of 1075 stock to test with a round file to make a practice plunge. As soon as I put the tiniest amount of even torque on the screws she snapped. Dammit. Oh well. Below is a few pics of the grain structure I thought I’d post to try and learn what anyone may say about the size and disposition of the grains. Pure curiosity on my part, as I’m totally cherry on destructive testing. Let me know the good and bad:

https://imgur.com/9r9TJOf

https://imgur.com/pES8vpH

Pieces are around 0.75” wide by 0.25” thick.

 

[weo]

That looks like pretty big grain to me. Here's a picture I got somewhere a year or so ago that's my standard response to the grain question:

 

[Stacy E. Apelt - Bladesmith]

Extremely coarse grain.
Too hot.
Water is quite brutal for a quenchant.
You have to temper after HT.

Use a magnet to determine when it converts to austenite and heat a shade brighter red -100°F more. Quench in oil. Temper at 350°F for a file guard, 400-450°F for a blade, 500-650°F for a spring.

Do some test coupons at colors starting at non-magnetic and see what the results are as to hardness and grain.

Hedre is data on working W1:

W1 Tool Steel - Water-Hardening Tool Steel (UNS T72301)

Water-hardening tool steels are also known as group W steels. This group consists of three types, namely, W1, W2, and W3. The main alloying element found in group W steels is carbon.

www.azom.com

 

[Bühlmann]

Thank you, guys. Heat control in a forge is definitely something I’m experiencing a learning curve on. I’m trying to look for the decalescence, but I clearly missed it on these. looks exactly like the "Bad Heat Control" photo above! Looking back on it and comparing what I remember seeing with a color chart I was wayyyyy too hot, as Stacy said. The good news is I didn't have a bunch of time invested, and I learned a good lesson. Time to give 'er another go. Thank you for the references.

 

[Joseph Bandeko]

Knife Steel Nerds - Metallurgy and Testing of Knives and Steel

Articles and original research for knife makers and enthusiasts about steel metallurgy and knife design.

knifesteelnerds.com