Steel N690 Co

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N690

Stainless steel N690CO, is a steel used a lot in cutlery both industrial and by many makers for the high hardness and wear resistance, good corrosion resistance.

Matches of N690 or SEL code –> 1.4528 or EN –> X105CrCoMo18-2

This is not the first steel to use to make knives but over time it is definitely a steel that you have to insert into your set of materials.

N690 is a steel produced by Bohler-Uddeholm and is a martensitic steel with chromium and cobalt, molybdenum and vanadium.

Bohler-Uddeholm says that the N690 is suitable for making very hard cutting tools, with excellent wire holding properties, such as:

  • knife blades,
  • sharp surgical instruments,
  • rotating knives for the meat processing industry,
  • fulcrums of plates and blades,
  • corrosion-resistant roller bearings,
  • needles for valves and pistons for refrigeration machines,

with excellent wire sealing properties.

Steel N690 Co coltellimania.com

N690 and the comparison with the 440C

I want to give you some examples of alternative steel that you may have used or that you want to use as an alternative.

N690 is very similar to 440C steel but has a carbon content of 1.08% while 440C steel has a carbon content of between 0.95% and 1.07%.

N690 is a superior quality stainless steel and that is why it is a very common alloy in many good quality industrial knives.

    • It is a durable and wear-resistant knife steel.
    • It is also a very hard steel and can be hardened to a very high level of hardness even if it is difficult to sharpen with field or improvised instruments.
    • The finish of the surface is fine but is not suitable for mirror finishes.

N690 is sometimes compared to 440C steel.

Many knife manufacturers however do not believe that the 440C is the best steel for comparison with N690.

N690 is a much better steel and is very similar to VG10.

N690 steel is so good for knife production that many major knife manufacturers use only N690 steel.

This steel has the right carbon content and the right cobalt content.

The key to the hardness of the N690 is the addition of cobalt in the steel matrix.

Cobalt creates uniformity in the structure inside the steel.

The value of cobalt in a knife blade is that it produces a wire (thin edge) with excellent edge retention.N690

Chemical composition:

N690Co
CSiMnCrMoVCo
1.080.400.4017.301.100.101.50
  • carbon 1.08,
  • chromium 17.3,
  • cobalt 1.5,
  • manganese 0.40,
  • molybdenum 1.10,
  • silicon 0.40,
  • vanadio 0.10
Steel N690 Co coltellimania.com
“Periodic table detail for the elements cobalt, nickel and copper. Image uses an altered public domain periodic table as the source document. Part of a series covering all the elements”

N690CO stainless steel,with the addition of molybdenum, vanadium and cobalt, perhaps one of the best compounds in a stainless steel, specially designed to cut.

Features:

    • high wear resistance.
    • high wire maintenance.
    • high corrosion resistance.
    • Hardness up to 63 HRC but consider that on knives you get to 58 HRC go further does not make sense on a knife.

This steel is not recommended for beginners, its degree of difficulty in working is average.

Provided annealed (soft), to facilitate work, since hardened once is a very difficult job.

I assure you that to finish it once hardened you will make go away (consume) several tapes and abrasive paper.

It is not suitable for making mirror surface finishes!

 

Table heat treatment:

Forging:900 to 1050 oC. Heating to 800 oC for 20-25 minutes. Very slow cooling in the oven or insulation materials (sand, salt, mica).

Normalization: 800 to 850 oC. To eliminate structural tensions caused by forging or roughing. Favorite time, 1 hour.

Temperate (oil): from 1045 to 1080 oC. Heating to 950 ºC, stabilized temperature, thermal jump to the temple, temperature reached, maintenance of at least 4 minutes per millimeter. Cooling in oil at 180 – 200 oC to reduce heat shock, keep cool for 25 to 35 minutes. Hardness from 61 to 63 HRC.

Discovery: double temper. Slow heat to the temperature of the find.

The temperature reached the core of the bar in about 14 minutes per mm, the minimum recommended time is 1 hour.

Tempering and finding are recommended in a controlled atmosphere with professional ovens.

Temperatures, times or form of realization of the blade depending on the needs can vary so experiment in the hardening process.

Knowing the thermal treatment of the N690Co therefore is not enough for you to achieve the desired result.

N690 table

Typical heat treatment

I provide you with a typical heat treatment that will make the blade useful a little for all uses and with an adequate hardness but that must always be verified.

First of all you have to wrap the knife in the ” candy ” and if you want but I advise you to also put in charcoal or cigarette butts that acts as a reducing atmosphere (eliminate the oxygen that remains in the spaces even if you have crushed the candy well.

  • Now be careful — > not forge but buy ready-made drawn bars.
  • The “knife” — > put it in the oven not yet hot.

1 – Do 2 pre-tempered stretches, one at 830 degrees for 50 minutes, the other at 800 degrees for 50 minutes (values obtained by studying the behavior of phonons in this type of stainless steel). You don’t have to go back to room temperature. You can consider it as a stop at 800/850 degrees then arrived at this temperature, reset the values on the keyboard of your electric oven and start towards the highest degrees. The more you perform the procedures calmly, the better the temper will come.

2 – Austenitization at 1070 degrees for 15 minutes (increases by 0.8 minutes per millimeter of thickness) and turning off in oil at about 70 degrees. Attention, at 1100 degrees funds all over, and ruin your knife.

3 – Make 2 tempers at 200 degrees of an hour each if you want to privilege hardness and good resilience. Number 2 Finds at 250 degrees by one hour each for general use.

The two refills are recommended for less risk of breakage

The N690 is similar to the 440c , hardens 1070 degrees for 5/15 min. , tempering 250 degrees for 1 hour and a half at 250 degrees hardness 60 HRC
Now beyond the tables my experience with this steel is Cordusal and hardens at 1050 ° C leaving in the oven the blade for example 5 mm thick for 7 minutes and 1/2, shutdown between aluminum plates with forced air.
Tempering at 230°C for 1.5 h or two for 45 minutes.
It is advisable to “study” the tempering and tempering diagram, to understand the possibilities that you have.
This steel has a range of usable temperatures, you can harden it between 1030 and 1080 and the diagram itself tells you that if you exceed 250 ° C in tempering, the hardness drops drastically, while after 300 ° C it returns to rise.
Tempering is a science and these tips have been valuable gifts from the experience of many makers who have shared their experiences.

 

Steel N690 Co coltellimania.com

Knives from famous brands using N690 Co:

N690

The average price of a 1 meter bar of N690

  • Width 3.0X30X1000 mm. Laser cut (30.00 euros)
  • Width 3.0X50X1000 mm. laser-cut (49.00 euros)
  • Width 3.0X65X1000 mm. (62.00 euros)
  • Width 3.5X30X1000 mm. (28.84 euros)
  • Width 4.0X40X1000 mm. laser-cut (49.00 euros)
  • Width 4.0X50X1000 mm. laser-cut (61.50 euros)
  • Width 4.0X65X1000 mm. (83.00 euros)
  • Width 5.5X40X1000 mm. (52.52 euros)
  • Width 5.5X40X1000 mm. laser-cut (61.50 euros)
  • Width 5.5X50X1000 mm. (65.40 euros)
  • Width 5.5X50X1000 mm. laser-cut (76.51 euros)
  • Width 5.5X65X1000 mm. (89.00 euros)
  • Width 6.5X50X1000 mm. (laser cut) (93.73 euros)
  • Width 6.5X60X1000 mm. (laser cut) (111.24 euros)
  • Width 6.5X70X1000 mm. (134.00 euros)
  • Width 7.0X50X1000 mm. (87.55 euros)
  • Width 7.0X50X1000 mm. (laser cut) (101.00 euros)
  • Thickness 7,0X60X1000 mm. ( laser cut ) (119,00 €)
  • Width 7.0X100X1000 mm. (laser cut) (197.99 USD)
These prices are indicative and vary in thickness and width

The material is cut by mechanical process and for this reason it can have curvatures (not flat) but some suppliers make laser cutting but the price of the bar changes by about 15 Euros more.

Steel N690 Co coltellimania.com

Conclusions

If you want to make a knife depending on the use you have to make of this cutting tool, which you are going to build, you will have to in addition to the shape, the handle, etc. favor some features rather than others.

One of these features is steel but if you want to use the N690Co rest assured that on average you are not wrong, you are using a quality steel.

Are You Experience?

Andrea


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Andrea F

Maker and Enthusiast of Knifemaking. Other: Engineer / Professional Blogger / Bass Player / Instructor of Boxing / Muay Thai / Brazilian Jiu Jitsu / Grappling / CSW / MMA / Self Defence / FMA / Dirty Boxing / Silat / Jeet Kune Do & Kali / Fencing Knife / Stick Fighting / Weapons / Firearms. Street Fight Mentality & Fight Sport! State Of Love And Trust!

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