KNIFE STEELS INTRODUCTION

 

 
 
 
 

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- KNIFE STEELS INTRODUCTION -

This information refers to the various types of knife steels that we use to make our knives.

   ELMAX STEEL: Produced by Bohler-Uddenholm, ELMAX steel is a Powder Metalurgy (PM) high chromium-vanadium-molybdenum-alloyed steel made of 1.7% carbon, 18% chromium, 0.3% manganese, 1% molybdenum, 0.8% silicon, and 3% vanadium. This composition allows for the metal to have a high wear resistance, high compressive strength, superior corrosion resistance and a very good dimensional stability or the ability to retain its size and form even after taking abuse. Also, the PM process combined with the high chromium content imparts Elmax with good grindability and excellent polishability.

This gives the knife the desired traits of superior edge retention and an ease of sharpening, which is often the reason that people are attracted to such stainless steel knives. The steel's "Superclean" production process combined with small sized powder and carbides guarantee trouble-free grinding and polishing. When hardened to 57-59 HRC, though the steel can actually be hardened up to 62 HRC, the knife has a good edge holding ability as well as a less-commonly found impact resistance and grinds very easily. Therefore, ELMAX steel can take more abuse than other metals, and come out unscathed.

On a CATRA (Cutlery Allied Trades Research Association) Edge Retention Test, when tested for Rockwell C Hardness, Uddenholm's ELMAX scored higher than the other tested stainless steels, including Aisi M4, Aisi 440C, Bohler M390 Superclean, and Uddenholm Vanadis 4, at an impressive 62 HRC. In its TCC (total cards cut) test, which measures how many silica impregnated cards that a knife with each steel type can cut through at a time, ELMAX scored a 930.7, higher than most other steels, and second only to Bohler's M390 Superclean.

In an impact toughness test, the toughness of ELMAX steel at 61 HRC is better than any competitor's stainless blade steel even at 57 HRC, despite a lower HRC typically providing more toughness.

What many love about this steel is that, although it is a stainless steel and has the better qualities of stainless steel, it also has qualities of a carbon steel alloy. Carbon steel, unlike stainless steel, is easier to sharpen and achieve a good edge.

Knife steels Introduction 1

   M390 STEEL: M390 (Bohler-Uddeholm) martensitic Chromium steel is a 3rd generation PM stainless steel that offers good wear resistance with excellent corrosion resistance through the use of high chromium and vanadium content. The PM process combined with the high chromium content imparts M390 with good grindability and excellent polishability. Its high austenizing temperature imparts M390 with a high attainable hardness of RC 58-62. It has been developed for knife blades requiring good corrosion resistance and very high hardness for excellent wear resistance. 1.9% carbon, 20% chromium, 1% molybdenum, 4% vanadium, 0.7% silicon, 0.3% manganese and 0.6% tungsten are added for excellent sharpness and edge retention. It can be polished to an extremely high finish. It hardens and tempers to 60-62 HRC.

M390 is a fine grained alloy, popular choice for high end folders and small fixed blades. Excellent performance with both, coarse and high polished edges. You still need about 15° per side edge to get the best performance and edge holding. Working hardness can reach 62HRC, and most of the production knives are in 60-62HRC range. Overall, it is one of the best performers as far as corrosion and wear resistance go and because of that it is a popular choice for high end and limited edition knives. Aside from a very good edge holding ability, maintaining the edge is very easy. And one more thing worth noticing, there's no stubborn burr forming during sharpening, therefore, there's no risk to form a wire edge either.

Unlike other stainless steels, most carbides are formed by vanadium and molybdenum, leaving more ‘free chromium’ to fight corrosion. Bohler calls this steel “Microclean”.

Knife steels Introduction 4

RWL 34 STEEL: RWL 34 is a premium powder metallurgy cutlery steel manufactured by Damasteel AB. RWL 34 has a strong following in Europe. This is not surprising given it's impressive performance and European origin. It is named after the world famous knife maker Robert W Loveless (January 2, 1929 – September 2, 2010).

Essentially a powder metallurgy variant of ATS-34, RWL 34 has very similar composition as ATS-34/154CM, but because of it is manufactured from rapidly solidified powders, the microstructure of the steel is much more uniform. This gives the steel much higher strenth and resistance to cracking.

RWL 34 is a particularly successful steel with very high strength and toughness combined with extreme edge sharpness that is easy to maintain. RWL 34 most appreciated features among knife makers are the ease to work with and the ability to mirror finish polish.

RWL 34 COMPOSITION: C-1.05%, Si-0.50%, Mn-0.50%, Cr-14%, Mo-4%, V-0.20%

Knife steels Introduction 4

   N690 STEEL: N690 steel is a stainless martensitic steel  with cobalt, molybdenum and vanadium addition, produced by a small Austrian steel plant that also provides steel for surgical instruments. The Austrian Bohler Company says that the N690 can be made into hardened cutting tools with excellent edge-holding property, such as knive blades, cutting surgical instruments, rotary knives for the meat processing industry, plate and knive-edge fulcrums, corrosion resistant roller bearings, valve needles and pistons for refrigerating machines, with excellent edge-holding property. This steel is very similar to 440C steel, and it has 1.07% carbon content. N690 composition is as follows: carbon 1.07%, chromium 17%, cobalt 1.5%, manganese 0.40%, molybdenum 1.10%, silicon 0.40% and vanadium 0.10%. 440C steel has a carbon content ranging from 0.95% – 1.07%. N690 is a high end stainless steel with an alloy that is common in many good knives. It is a durable knife steel that is wear resistant. It is also a very hard steel. N690 contains the important martensitic chromium steel composition with cobalt, molybdenum and vanadium. It can be hardened to a very desirable hardness level. The surface finish is fine ground or polished.

N690 is sometimes compared to 440C steel. Many knife makers however do not believe that 440C is the best steel for comparison to N690. N690 is a much better steel and it is very similar to the VG10.

N690 steel is so good for making knifes that many prominent knife manufacturers use only N690 steel. This steel has the right carbon content and the right cobalt content. The key to the hardness of N690 is the addition of cobalt in the steel matrix. Cobalt creates uniformity in the structure within the steel. The value of cobalt in a knife blade is that it produces a fine edge with excellent edge retention.

Knife steels Introduction 2

    440C STEEL: 440C stainless steel (once the most popular stainless steel among knife makers) is a high-carbon martensitic chromium steel designed to provide stainless properties with maximum hardness. It also has high strength, moderate corrosion resistance and wear resistance. It resistscorrosion from fresh water steam, crude oil, gasoline, and resists staining from fruit and food acids. Maximum resistance is obtained by hardening and polishing.

It is used in the hardened plus tempered condition. It is a bearing steel, and used in rolling contact stainless bearings, e.g. ball and roller bearings. It is also used to make knife blades. When heat-treated, 440C stainless steel attains a very high hardness of 58–60 HRC. It is a 400 series stainless steel, and has the highest carbon content in the 400 stainless steel series. Actually, it is very similar to the 440B grade but with a slightly higher carbon content. It attains a higher hardness than that of 440B but with a slight reduction in its corrosive properties.

440C has a carbon (C) content of 0.95–1.20%, chromium (Cr) content of 16.00–18.00%, molybdenum (Mo) content of 0.75%, Manganese (Mn) content of 1.0%, and silicon (Si) content of 1.0%.

Knife steels Introduction 3

   D2 STEEL: First appeared during WW II, semi-stainless tool steel made of 1.55% carbon, 12% chromium, 0.3% manganese, 1% molybdenum, and 0.8% vanadium. It is very popular even today. Pretty much every steel manufacturer makes it and it's quite popular with knifemakers, custom and factory alike. Composition-wise it's almost a stainless steel. Resists rust pretty well, good edge holding and good toughness. Rockwell hardness range (depending on the manufacturer) is HRC 57-62, with blades typically hardened to the upper range. Since D2 is a tool steel, it’s susceptible to staining and corrosion. However, when compared with other tool steels, the elevated chromium content of the formulation has garnered D2 a reputation for superior corrosion and stain resistance. The effects of environmental attacks (blood, body fluids, salty water and ambient moisture) on this steel are restrained if reasonable care is used.

With minimal care, D2 can remain free from corrosion and staining for the lifetime of the blade.

D2 does have some other drawbacks as blade steel. It can be difficult to polish properly, with many manufacturers opting to avoid attempts at mirror polishing simply because it takes too much time and effort with little to gain. Furthermore, since D2 blades are typically Rockwell hardened to HRC 60-61, some users will encounter difficulties with edge reestablishment. At the same time, once a D2 blade has been sharpened properly, it will hold its edge much longer than blades with a lower Rockwell hardness.

 
 

JN VARIOUS STEELS INTRODUCTION


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VARIOUS KNIFE STEELS INTRODUCTION