Common Blade Alloying Elements

Common Blade Alloying Elements

Posted by Steven Tuckey on

When it comes to knife manufacturing, no task is more daunting than making sure you've chosen the best material for the assignment. If you're looking for the best steel for making knives, you want your blade to look amazing and perform well.

When metal is described as steel, it simply implies that iron and carbon make up the majority of their composition. The properties of the various types of steel can vary significantly depending on the inclusion of additional alloys or alloy mixtures.

Let's look at common alloying elements and their effects on kitchen knife making.

Carbon (C)

Knives made of high-carbon steel are incredibly easy to use and are popular among cooks of all skill levels. Users assert that they are highly durable and make the overall slicing procedure less taxing.

The basic varieties of steel are classified according to their carbon content:

Stainless Steel - Low Carbon Content

Knives made of stainless steel are used the most because of their corrosion resistance. They have a low carbon content but a high chromium concentration, which gives them corrosion resistance. Despite being corrosion-resistant, they are softer and easily blunt.

Carbon Steel Knives - High Carbon Content

The high carbon steel knife is a well-liked but less known type of knife. Due to its longevity and razor-sharp blades, professionals utilise it the most. It is robust and resistant to wear since it contains more than 1% carbon.

Knives with a high carbon content have an advantage over others because of their exceptional qualities, besides being fragile and less corrosion-resistant.

Effects:

  • Improves tensile strength and edge retention.
  • Enhances resistance to wear and abrasion and boosts hardness.
  • When the quantity increases, ductility reduces
  • Increases hardenability.
  • Blades have a more attractive appearance thanks to a fine polish and sturdy construction.

Chromium (Cr)

The element, chromium, contributes to the formation of a shield-like coating over the surface of the steel. Chromium can produce big, intricate carbides. Normally, steel is termed "stainless" if it has at least 13 percent chromium, but according to another definition, the steel must include at least 11.5 percent unbound chromium, which is chromium that is not ingrained in carbides. 

Despite its name, if it is not cared for properly, all steel can rust. Chromium in large doses reduces toughness. Chromium boosts wear resistance because it forms carbides. Sadly, it is generally never indicated how much free chromium is present in the steel.

Effects

  • Improves toughness, and tensile strength.
  • Improves resistance to wear, heat, and rust.
  • More than 11% chromium turns steel to "stainless" by forming an oxide coating on the surface.
  • Although the substance is softer, carbide inclusions reduce wear.
  • Additionally, higher chromium knives require less maintenance and cleaning.

Cobalt (Co)

For knife users who require a blade for a particular task, cobalt alloy blades can offer a variety of qualities.

Knife blades made of cobalt alloys have superior corrosion resistance than steel and a slicker surface for sharper, more precise cutting. Cobalt crystallises into a sturdy matrix structure that traps carbide grains for improved edge retention.

The two most well-known cobalt alloys are Talonite and Stellite. Chromium and a little quantity of molybdenum in the alloy react chemically with carbon to generate tiny carbide crystals during the production process.

These carbides are firmly held within the cobalt matrix, which gives the alloy its distinctive wear resistance. Cobalt Alloy 6BH (H = Hot Rolled Process) is another name for Talonite, and Cobalt Alloy 6B is another name for Stellite.

Effects:

  • Makes materials stronger and harder, allowing for higher temperature quenching.
  • In more intricate steels, amplifies the individual effects of other components.
  • Improves heat and corrosion resistance.

Manganese (Mn)

Manganese steel, commonly known as Mangalloy, is a steel alloy that contains 12-14% manganese and is frequently referred to as the utmost strain hardening steel. It helps the knife's hot working characteristics rendering it stronger during quenching. 

Effects

  • When applied in larger concentrations Manganese increases hardness and brittleness.
  • Increases wear resistance, tensile strength, and hardenability.
  • Deoxidizes and degasifies molten metal to remove oxygen. 
  • Based on the type and category of steel, manganese enhances or lowers corrosion resistance

Molybdenum (Mo)

Like chromium, molybdenum influences how well steel resists corrosion. Molybdenum is primarily utilised in austenitic and duplex stainless steels to improve corrosion resistance.

Additionally, steel's hardenability, toughness, and tensile strength can all be improved by molybdenum. Reducing the necessary chill rate during the heating process raises the hardenability to produce robust and durable steel. 

As molybdenum boosts resistance to chloride-induced corrosion, it can also lessen the danger of steel pitting. The "A" class of tool steels, maraging steels like Grade 250, and many stainless steels are standard steel grades with higher molybdenum content.

Nickel (Ni)

Nickel is a significant and necessary alloying ingredient in the latest stainless steel grades. The inclusion of nickel causes the creation of austenitic structures, which provide their grades with the necessary strength, ductility, toughness, and cryogenic temperatures. It also renders the material significantly less magnetic. While the entire role of nickel does not affect the establishment of a passive surface layer, it always improves resistance to acid assault, notably with sulphuric acid.

Niobium (Nb)

Niobium is employed in a few knife steels, its presence has a major impact on the final qualities. Fundamentally, niobium is added for the same reasons as vanadium: to generate hard MC carbides, where M can be V, Nb, Ti, or other elements. Hard carbides can help with grain size refinement, carbide structure refinement, and wear resistance.

Carbides are hard particles that contribute to the wear resistance of steel. The more carbide is present the lower the toughness of the steel. The carbides are hard but brittle which is why toughness is reduced. 

Harder carbides are better at contributing to wear resistance. So a low volume of very hard carbides can give a better balance of properties than a larger volume of softer carbides. 

Nitrogen (N)

Metal cryogenic treatment is a technique in which metals are purposely subjected to freezing temperatures for an extended and regulated length of time. During the production process, the metal is first heated to transition from a solid to a liquid form.

The material is then exposed to liquid nitrogen during the cryogenic treatment phase. Finally, it is kept at temperatures as low as -300 degrees Fahrenheit.

The fundamental advantage of cryogenic freezing is that the metal's atoms rearrange, increasing the metal's martensite structure and decreasing its austenite structure. Martensite is a strong crystalline structure, whereas austenite structures are softer and more ductile, meaning they may twist under tensile stress without shattering.

Cryogenic treatment has several advantages for knife and blade production and care because of the particular arrangement that metal develops during liquid nitrogen freezing.

Effects:

  • Wear and tear resistance is improved.
  • Sensitivity to stress is improved
  • Improves resistance to oxidation, corrosion, and water
  • Improves sharpening

Sulfur (S)

When steel is high in sulfur and low in manganese, sulfur—which is typically regarded as an impurity—has a negative impact on the impact properties. Sulfur increases machinability, however, it decreases the transverse ductility and notched impact toughness while having no impact on the longitudinal mechanical properties. 

Its concentration in steels is restricted to 0.05 percent, but it is incorporated to free cutting steels in amounts up to 0.35 percent with the manganese content raised to counteract any negative effects since alloying additions of sulfur in amounts between 0.10 percent and 0.30 percent will tend to improve a steel's machinability. 

Such materials can be described as "free-machining" or "resulfurized." Sulfur is typically added to free-cutting steels up to a maximum of 0.35 percent to increase machinability.

Even though sulfur hurts steel at some stages, steel grades benefit from any sulfur concentration lower than 0.05 percent.

Vanadium (V)

Approximately 85% of vanadium production is used as a ferro-vanadium or steel enhancer. Early in the 20th century, it was discovered that steel with modest levels of vanadium had a significant boost in strength.

The advantages of using vanadium as an alloying element during the steelmaking process include:

  1. Its versatility, 
  2. Its high regeneration during additions,
  3. Its good cast-ability, 
  4. Its high dissolution rate during heating up of the cast steel, 
  5. The lack of additional roll forces needed with vanadium alloyed steel, and 
  6. Its strong reaction during heat treatment.

Effects:

  • Increases strength, wear resistance and increases toughness.
  • Improves corrosion resistance by contributing to the oxide coating.
  • Carbide inclusions are very hard.
  • Expensive.
  • Increases chip resistance.

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