Heat Treating W-1

[Jay Ramirez]

I Recently picked up some 3/4 W-1 Drill Rod from Grainger yesterday, ive got no experience with W-1 only used 5160. Anybody know how to heat treat this steel. I use a charcoal side blowing forge. Thanks Jay

[Jerrod Miller]

Have you seen this thread? As stated there, the spec is extremely broad, but generally the carbon on W1 is around 1%, meaning it is REALLY close to 1095. There is also this thread. If you do a site search with Google you'll get a lot of results. Don't bother with the built in forum search tool.

 

In Google: site:bladesmithsforum.com heat treat

[Jay Ramirez]

Awesome Thanks Jerrod

[stuart davenport]

That TTT chart for W1 speaks quite a bit! You've got way less than one second for your quench medium to do it's job, as Jerrod mentioned...just like 1095 and W2. Warm canola oil at 130°F will work in a pinch, but likely will not provide max hardness, especially on stock thicker than 1/8". A brine solution, followed by a warm canola oil, is a pretty safe way to beat the pearlite nose on these steels. 3 seconds into the brine (distilled or purified water with a 10% salt solution), and then finish the quench in 130°F canola oil. FAST commercial oils like P50 simulate the speed of water without the risk, and if you're going to be using shallow hardening steels quite often, it is your greatest friend (or similiar oils like DT48). As a side note...if you ever work with the Hitachi Yasuki steels, White Paper and Blue Paper, these are about the only steels that I would recommend an actual brine quench. Their Mn count is so low, you must have a super fast quench, and because these steels are so pure, brine quenching is not as risky. But I digress.

 

Forged W1 heat treat, a good start would be to do as follows (I like recipes. The "why" can be asked at any time and I'd be MORE than happy to talk steel and heat treating!)

 

Since we have forged, we MUST normalize first. And then thermal cycle to take care of aus grain.

W1 recommended normalizing temp for a 1.0% carbon content: 1600°F, soak for 10 minutes, air cool only

To thermal cycle: usuall three cycles is plenty, some guys go thru a dozen or so (way overkill to me, and can reduce hardenability. Play around with temps and number of cycles if you like)

1550°F for 10 minutes, air cool

1500°F for 10 minutes, air cool

1450°F for 10 minutes, air cool or quench

1400°F for 10 minutes, air cool or quench

Notice "air cool or quench". I think it has been shown in Cr bearing carbon steels, like 5160 and 52100, that quenching refines grain slightly (very slightly) better than simply air cooling...but with risk!!! I do NOT do multiple quenches on any steel, usually. Air cool in still air refines grain structure quite well without risks of distortion or other issues that cannot be detected visually. Simply put....it's YOUR shop...YOUR call to quench a few times or just once during hardening.

To harden: 1475°F for 10 minutes, quench (brine) or (brine for 3 seconds then oil) or (Parks 50 at room temp) or (canola at 130°F)

Once able to handle at room temp, you can check your file test, but be sure there will be a decarb layer to get thru, especially if unprotected during all that cycling.

Max hardness after quench will be 66-67. Temper at 300°F one hour for 63. Temper at 400°F one hour for 61. Temper at 500°F one hour for 59 (Blue brittle range....be careful here) (numbers provided by Buffalo Precision) At least two temper cycles.

Edited December 12, 2015 by stuart davenport

[Jay Ramirez]

Wow Stuart thats SUPER helpful!!! I was just gonna do an oil quench but ill try the 3 second quench in Brine then in veg oil .Should i do a vertical quench or horizontal quench, Any diference BTW I temper over my forge would it still be somewhat accurate or would it be better to temper in a toaster oven And Why do i have to hold the hardening temp for 10 minutes Thanks

Edited December 13, 2015 by Holcan Knife and Tool

[Jerrod Miller]

Vertical vs. horizontal is typically determined by blade geometry and maker's preference (and equipment available). Toaster oven is likely to be a bit more accurate, especially if you add some mass to it (like a brick) to prevent it from swinging too far either way on the temp. The 10 minute soak is intended to dissolve carbides (and with 1% C there is a bit of them). 10 minutes is longer than needed for simple iron carbides like in W1, but it does ensure that you get all you need. The tougher carbides like V, W, Mo, and Cr need both more time and more temperature than iron.

 

When I heat treat W1 I go by re/decalescence. I actually do this for all steels, partly because I do not care to ensure thermal uniformity in my forge to just let things soak and trust getting an even heat, partly because watching the phase transformation is so fricking cool. I enjoy watching it enough and heat treat so infrequently that I end up normalizing a bunch (phase change to black, not completely cool). I very rarely get any single soak longer than a minute and haven't noticed a performance issue. But then again I haven't done much extreme performance testing of W1. And I quench in 130ish canola oil, but have had to try a quick water quench followed by the canola on occasion.

[stuart davenport]

Couldn't have said it any better than Jarrod did! Soak times are usually not recommended, because they aren't needed, on eutectoid steels. Like 1084 or 15n20. With those steels, hit the target temp, let the blade equalize (I guess technically we could say soak it for ONE minute), then quench.

 

However, with HYPER eutectoid steels like W1, there is extra carbon (and it is tied up with iron....making the iron carbide cementite). How do we heat treat with a steel that has extra carbon? Well, the first thought is to go higher in temperature. And yes, this can put more carbon into solution. But by going higher in temp (talking 1530°f plus), not only will the martensite not get any harder, you'll have TOO much carbon in solution, and this translates to retained austenite. Like A2 for example. Austenizing temp for that steel is 1750°F, and in order to achieve max hardness by RA reduction, a sub zero or cryo is a MUST. Plus, you'll likely have your aus grain blown way too big, especially if there are basically zero alloying ingredients in the steel....like W1. A2 has alloying to help prevent that. W2 is a bit better than W1 in that regard, the Vanadium in W2 really helps to pin the grain boundaries, so little to no grain growth is noticed, even at higher hardening temps. But RA still is a problem in that situation.

 

We do good to remember that carbon in solution is not JUST temp dependant, but TIME dependant as well. But MUCH more temp dependant for sure. So in order to keep our aus grain small (since we don't have cool alloys to help us with W1), we do extended soaks at a somewhat lower aust temp. This allows carbon to come into solution without grain growth, without retained austenite.

 

Edited to add....I forgot that W1 should have a little V in there as well. Even just .1% is enough to help prevent grain growth.

Edited December 14, 2015 by stuart davenport

[Jerrod Miller]

For more on soak times, see this thread.