For any blades from kitchen knives to mowers’ blades and industrial blades, do you have a problem about your stainless steel blade such as dullness, rusts? It is disappointing when stainless steel (meaning it does not rust) but it rusts. It is also stressful if your blade does not perform as you wish. Besides, dull blades are dangerous because extra force to cut may cause accidents. Regrettably, stainless blades, no matter how expensive, eventually become dull or rusted as you use. In this article, the author, who has 13 years of experience in procuring metal parts and materials for Toyota Motor Corporation and startup companies, will introduce the following with my experiences. we focus on blade stainless steels (martensitic stainless steels which contain high amount of carbon and become hard after heat treatment) and present the mechanism of cutting, the reasons to cause problems, the raw material effect on cutting performance, and the possible solutions for your individual problems.
Cutting is the process of separating one material into two or more pieces by using a sharp tool or instrument. The key to successful cutting is to apply force to the material and to overcomes the material’s resistance, resulting in a split or separation. This cutting process can be broken down to 4 elements; Edge Sharpness, Material Hardness, Force, and Safety.
Over time, as you use your blade, the above 4 elements change and cause problems. Most of your problems come from the 4 reasons; Edge Wear, Corrosion, Deforms or Chipping, and Heat.
From the raw material point of view, stainless steels play an important role of cutting elements for two aspects, chemical composition and raw material manufacturing processing.
If there is a stainless steel free of any changes of the cutting elements, the blade can keep the excellent performance. Unfortunately, we basically need to take a balance between the hardness and wear and corrosion resistance. This is due to the amount of carbon inside the stainless steel. If a stainless steel contains more carbon, hardness (cutting ability) increases, but it becomes more vulnerable for corrosion. Among chemical compositions, the carbon is the most important element for the blade performance.
Among conventional blade stainless steels such as SUS420J2 (X30Cr13 or 1.4028), 440A (X68Cr17 or 1.4109) or X65Cr13 & X68Cr13 (1.4037). The hardness and carbon content has positive correlation. At the same time, higher carbon content makes the stainless steels easier to corrode, and becomes hard and brittle like glass, making it more prone to chipping and other problems.
Mixing carbons, chromium, and other chemicals to form stainless steel is not enough for fine blade material. To maximize the hardness after heat treatment or avoid any deforms / chipping, the manufacturing process of steel mill is also important.
In general, to make good blade stainless steels, there are several elements to achieve high performance and quality such as impurity control (reduce unnecessary compositions or avoid their concentration), carbide size and distribution (make the particle of carbon small enough and well spread across the stainless steel), and precision control (if the material is evenly flat or straight, it will be easier for blade manufacturers to process). These are exactly the know-how of steel mills. Nippon Steel prohibits any photo or video shooting inside its plant to keep their production know-how in secret (reference).
To solve your problems about the blade from the raw material, we present the below table for your reference to reconsider material choice.
|Even sharpened blades do not cut well
|More hardenable material (higher amount of carbon (C))
|Blades are difficult to sharpen
|More workable material (reducing carbon (C) and adding other chemicals)
|Blade hardness after heat treatment is unstable
|Better Impurity managed material (reducing or dispersing impurities)
|Blades become dull or deforms quickly
|More wear resistant material (adding other chemicals)
|Blades cause damages or bumps on cut surface & Edge frequently has Chipping
|Better carbide managed material (smaller and more even distribution) or Metal coating on the blade edge
|Blades become corroded quickly
|More corrosion resistant material (reducing amount of carbon (C), and adding higher amount of chromium (Cr) or adding other chemicals)
To solve above problems, maybe we can help you find a solution. Our materials CB5 and CB6 from Japan performs exceptional hardness, wear and corrosion resistance with fine carbides. In fact, many blade manufactures do not have, or do not know options other than conventional SUS420J2 (X30Cr13 or 1.4028) and 440A (X68Cr17 or 1.4109) etc. This is not only in Japan, but also other countries as well. If you are looking for a solution to a real user’s blade problem, we may be able to help (see the product page here, but we can also find out what isn’t there).
CB5 and CB6, new steel grades invented for blade manufactures perform exceptional hardness for carbon content amount. It has high wear and corrosion resistance against water, dust, and chemicals.
As we have deep understanding and knowhow of martensitic stainless steel for blade applications, sometime we offer different from customers’ specified steel grades because we wish to optimize the balance between hardness (cutting ability) and durability (against wear, corrosion such as rust). Enserve is positioned to offer unique stainless steel such as CB5 and CB6 in your required specification (coil, plate, stamped, at annealed or quenched & tempered). CB6 is ready to offer samples and commercialization in relatively short period of time. We are confident about what we offer and proud of flexibilities for small MOQs.