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The inconel and candy of the knife maker.
The knife maker candy is called inconel, and it is the “tight-fitting dress” for the knife when it goes into tempering.
Now it is not something necessary but if you want to take the level and quality of tempering to the next level this is a way.
The aim is to create a knife dress trying to let out all the air inside what in jargon is called “candy”.
Also consider that there are “fine techniques” of performing the process of hardening knives called “candy”.
These blade seals are used to prevent carbon from being dispersed.
The candy consists of wrapping the knife in an inconel material isolating it and helping to preserve the amounts of carbon during the reclamation phase.
The inconel is hardening steel 0.05 mm thick is an element that is often seen using by makers who perform the hardening themselves.
Mainly in cutlery two types are used:
The 321 and 309 which are both valid but with a small difference in the maximum operating temperature.
The 309 is best suited to temperatures above 1050°C.
Specialized companies
Personally sometimes I bring to harden my knives in a specialized company that operates in the automotive sector that in addition to tempering certifies the hardness in HRC achieved by each knife.
This is useful to make qualitative comparisons on the same knife, same material and see the quality level achieved.
Now the Rockwell certification in HRC is fundamental because it is an objective value.
But when you use your hardening oven or that of your friend, the wrapping of the blade in hardening steel (candy) is essential because you have to harden the blade in the absence of oxygen.
The reason to make candy
The reason is because at high temperatures in the presence of oxygen the steel decarmatizes which means that it loses surface carbon forming small camolatures.
The camolatures are quite deep holes that are difficult to remove thus ruining the surface and this loss of carbon compromises the final properties of the steel.
Sheets of steel for hardening
To avoid this you have to make candy with tempering sheets or there are also compounds resistant to high temperatures made specifically for these applications.
I have a friend who uses this technique a lot and has never had problems, always if you apply it with due care but you have to do some tests or get explained.
How to make candy
Wrap the blade or blades in the inconel and before closing the package insert into the gaps (holes in the shank, blade curvature) of the combustible material (paper, cotton, cigarette filters).
Close the candy very well, beating the edges with the hammer so that it is airtight.
With a wooden spatula shape the inconel around the blade you have inserted by making the blade adhere well to minimize empty spazo.
The shutdown
Reached the temp. of hardening and the established time, remove the candy from the oven, quickly cut the edge of the inconel and immerse the blade in the oil (possibly hot).
Keep in mind that attaching the inconel to the blade (with the wooden tool), on the one hand helps to limit any decarburization of the steel, but on the other hand makes it difficult to extract the blade from the candy.
For the shutdown depends on what requires the steel or with hardening oil possibly hot 60 ° C or even in the air but this is also a delicate but fundamental phase of the container that must be wide to allow either the total horizontal or vertical immersion.
My advice is to do cold blade movement tests by passing from the cold oven to the container filled with water several times to understand the sensation (excluding heat).
If you do the shutdown with air you can also not extract the blade from the Inconel but it is a different type of shutdown / thermal shock and depends on the type of steel.
If the inconel is very thin and very well adhered, you could venture to turn off the blade and candy together but I do not guarantee the good quality of the shutdown.
Ps. In water I do not recommend it because the too abrupt thermal shock can create the torsion of the blade especially on some steels.
Pss. Tempering is essential to do it at the right temperature which can be from 250 ° C for about 1 hour and 1/2 and that you can do it using a home oven but other steels require temperatures from 550 ° C for about 1 hour and 1/2 and that therefore you must use the hardening oven or have 2.
Here too there are several theories about making the discovery immediately or that you can do even the day after nothing changes.
Turning off in hot oil with candy
You can not immerse the knife inside the candy to harden it but you must always pull it out, otherwise there are points of the steel sheet that adhere to the blade and others do not.
If you don’t, this creates a non-homogeneous cooling and you have a “spot” temper.
The resulting blade is all hardened but not uniformly, so before immersing in oil / water / etc. you have to pull the blade out of the sealed candy.
It is not a simple operation since you have a glowing piece in your hand.
Technique to extract the glowing knife from the candy
Important safety (gloves, shoes/mask/apron/etc.)
- With pliers pull the blade out of the oven.
- Take the scissors with the other hand and cut the inconel sheet at the bottom of the shank and open it for a few cm above the back of the shank.
- I support the scissors, and with the other pliers I grab the blade in the middle of the shank.
- With free pliers remove the blade from the candy and immediately cool.
- When you do the extraction pull to extract but without making twisting movements otherwise you risk bending the blade.
- You have to do it in less than 10 seconds..
Where to find it
The alternative is the CONDURSAL Z1100
The
CONDURSAL Z1100
is sold in jars of 2.5 kg each and costs about 150 euros shipped but you can find it at Rockblade in smaller formats at a price clearly proportionate to the quantity.
- Bring the grain blade 400
- Remove the blade and apply the mixture with a brush (just one pass)
- You dry it well (even with a hair dryer to do before) and put it in the oven!
if you put it in a hot oven at 600 degrees you will see that when you turn off part of the product it crumbles and the rest or remove it by boiling water or with a sandpaper bottarella always 400 … maybe with a bit of svitol. - When the first pass the paper is kneaded a little because the product melts
Personally I prefer this method to candy, I use it and both solutions perform the work but I feel good with this method, my choice is the cordusal.
Attention! degrease the knife very well and if when you apply it it gives you a “rinsed” effect it is not good.
When hanging the knife be careful that they do not create especially on the tips of the drops and accumulations of materials.
With a brush paint the knife with an even layer, some soak it but it is a waste of material.
Let it dry as if it were nitro paint, about 40 minutes, do not pile material even in the holes, it takes flame
and the brush after wash it with nitro thinner.
Let the knife dry well even more than 40 minutes, in short, it must be dry, put it maybe once dry in the oven at 50 degrees for 3/4 minutes and you are affixed.
Conclusions
The hardening phase is fundamental and doing tests to find the best way is important.
Consider that a wrong hardening and throw the knife.
Consider that you need to reach the HRC hardness values of the steel table.
It is a science but with the means available today even in your laboratory you can achieve high levels of temper.
Are you experience?
Andrea
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