Hello all, Looking to heat treat this blade soon. Basically I’m looking for confirmation that I am on the right track. Hardening is 800c (1472f) no issues there pretty straight forward. Looking at the chart though it seems that somewhere between 200c (392f) and 300c (572f) is where I need to be in the temper. I were shooting for 58-59 HRC I’m looking at somewhere between 250c -275c (482f-527f). So basically looking for confirmation and consensus that I am reading it correctly. Thanks for looking. Fig. 3 & 4 Are for the Blue. The HRC is high on most sites because it’s used a lot for chisels/ woodworking tools and 190c (374f) is recommended. Blade is also a belt finish experiment strictly using only Scotchbrite belts after 120G bevel grind. Belts used were the Norton Brown (Coarse) Maroon (Medium) Green (Fine) Blue (Very-Fine) it was etched in FC for 5 mins, neutralized with Windex, treated with Brasso and a 3000g pad, then soaked in WD-40 and wiped clean.
Looks good Griff. That was a pretty tiny graph until I realized I could click on it. I would go 800°C for hardening and 260°C (spot on 500°F) on the temper according to Fig.4. It's pretty tight in there. Are you going to use the heat-treat oven for tempering as well? Good looking blade so far. Can't wait to see it when it's done. Dan
Yeah Dan I’ll take her to 260c/ 500f on the temper and use the Paragon, won’t trust this one to the stove lol. Thanks for the input as always, much appreciated
Hi Griff, Knife Steel Nerds has a good write-up on tungsten steels if you haven't read it yet: https://knifesteelnerds.com/2018/03...uper-the-facts-about-tungsten-alloyed-steels/ Unfortunately, there doesn't seem to be much information on toughness vs hardening/tempering temps (sometimes there's a real gem of a heat treat if you decrease both the recommended austenizing and tempering temps a bit). In the absence of this information, I think what you're doing is the best option. Do you have a hardness tester? Magnus
I use the HRC Files Magnus, and these tech sheets are from the supplier of the steel, it’s the high temper cycles for this particular steel that had me doubting myself. I know there are some other carbon steels like this, M4 for instance, just always want a second and third opinion haha. Thanks for the link, I’ll make use of their information for sure. Cheers!
So update, blade hardened beautifully, file skated. 500F temper produced a Blue/Purple effect. Now couple of things, oil residue, coatings (atp) can skew coloration, and a temper this high would yield an interesting colour as it is. HRC files are showing its above the 55 and below 60, but again I am suspicious. My concern is that the ‘tech sheets’ were again referencing large cross sections and the supplier is simply passing it along and it’s not valid for a roughly 5/32 thick knife (at its thickest point). With possible tempering issues aside, I am very impressed with how thin I was able to grind the edge post HT and how straight everything stayed. So I plan on sharpening a 15 per side degree test-bevel on it and do an edge roll test. Should it fail I am going to re-heat-treat and temper at coin toss of 450f- 475f.
Hi Griff, Thanks for sharing the details with us. It's great to see what people are doing and learning new things along the way. I wouldn't normally think of purple/blue as a colour for the RHC 60 range. To me, purplish is heading towards a spring. However, I wonder if different steel constituents could yield different oxide film colours. In hindsight, it may have been smart to temper at lower temperature for the first cycle, say 200°C. Then check with the hardness file. If it the RHC was on the high side, then the second cycle could be bumped up a bit to get to the desired hardness. Dan
Yeah we will see Dan. With it being a Suminagashi billet too, and layers with different steel, who knows...it could be that the mild steel jacket was effected, and I am okay with the spine having a spring temper. If the edge doesn’t roll I will finish her, sharpen it, and call it a win and a keeper
