14C28N Stainless Steel

B/U: Bohler / Uddeholm

Bohler and Uddeholm are two large steel companies based in Europe. Both companies make high quality steel alloys and are subsidiaries of Voestalpine.

Cross Grain:

Steel is toughest when it is cut with the grain. However, we occasionally get pieces that were cut across the grain. We call this “cross grain”. The cross grain billets are discounted.

CRA: Cold Rolled Annealed

Cold rolled steel has a nice finish. The surface is bright and smooth. It can be darker on the edges of the sheet showing some heat coloring from annealing. Cold rolled alloys have minimal runout. The steel is annealed (soft).

CRHT: Cold Rolled Heat Treated

Cold rolled heat treated applies to only some 15N20. The steel is heat treated to approximately HRC 45. This alloy is used extensively for sawmill bandsaw blades. The sawmills require the steel be heat treated.

Even though this 15N20 is heat treated, it is not full hard. It is easy to work with metal working tools. When drilling this 15N20, It is important to keep constant pressure and use a lubricant.

ESR: Electroslag Remelt

Electroslag remelting is a process of remelting and refining a steel alloy to make it cleaner. The result is very clean steel. The steel is annealed (soft).

FG: Flat Ground

The AKS definition of flat ground is +- .001 inch runout across 12 inches. The surface of the steel is ground until it is bare steel with a uniform grind pattern. The front and back of the billet are parallel.

FGHT: Flat Ground Heat Treated

Flat ground heat treated applies to only some 15N20. The steel is heat treated to approximately HRC 45. This alloy is used extensively for sawmill bandsaw blades. The sawmills require the steel be heat treated.

Even though this 15N20 is heat treated, it is not full hard. It is easy to work with metal working tools. When drilling this 15N20, It is important to keep constant pressure and use a lubricant.

The AKS definition of flat ground is +- .001 inch runout across 12 inches. The surface of the steel is ground until it is bare steel with a uniform grind pattern. The front and back of the billet are parallel.

HRA: Hot Rolled Annealed

Hot rolled steel has mill scale and is dirty on the surface of the steel. The mill scale is easily removed by multiple processes such as pickling or sand blasting. The steel is annealed (soft).

HRDA: Hot Rolled Descaled Annealed

The steel is heated and run between rollers to achieve the desired thickness. As the steel cools, scale forms on the surface of the sheet. The scale is removed by sand blasting or shot blasting. After blasting, the surface of the sheet has a rough finish. The steel is annealed (soft).

HRPA: Hot Rolled Pickled Annealed

The steel is heated and run between rollers to achieve the desired thickness. As the steel cools, scale forms on the surface of the sheet. The scale is removed by immersing the sheet in a bath of acid. The process is called pickling. The acid removes the scale. After pickling, the surface of the sheet has a rough finish. The steel is annealed (soft).

PESR: Pressurized Electroslag Remelt

PG: Precision Ground

The AKS definition of precision ground is less than .001 inch runout across 12 inches.

PM: Particle Metallurgy

Alloys using particle metallurgy processes are made from powdered metal. The powder is put in a can and pressed into a solid billet in a hot isostatic press.

CPM: Crucible Particle Metallurgy

Crucible is a steel company based in USA. They produce multiple steel alloys. Some of the alloys are made using the Crucible Particle Metallurgy i.e. CPM process.

The first step in the CPM process is heating the steel until it is a liquid. The liquid is sprayed through a small nozzle and forms into a powder. The steel powder is packed into a steel container that is welded shut. The container containing the powder is placed into a hot isostatic press or HIP. The HIP heats the container and compresses the steel powder into a solid billet. After the billet cools the container is removed. The remaining billet has a consistent composition.

The major advantage of the CPM process is producing alloys that would not be possible using traditional steel production processes.

CG: Cross Grain

Steel is toughest when it is cut with the grain. However, we occasionally get pieces that were cut across the grain. We call this “cross grain”. The cross grain billets are discounted.

Imitation Alloys

We are continually asked why our AEB-L outperforms other alloys with the same name and/or composition. Hopefully the following information will provide clarification.

There are multiple alloys with the same name/composition as AEB-L. We call these alloys "imitations”.

AEB-L is made by Voestalpine/Bohler/Uddeholm (VBU). They have been making it for more than 100 years. VBU continually refines the composition and manufacturing processes. Other companies copy AEB-L, but their manufacturing processes are not the same. We asked Bernie Iacampo of Voestalpine to explain the differences between VBU AEB-L and the imitations. He wrote the following:

"Hot rolled material tends to have a larger grain size, more segregation and a more uneven secondary carbide distribution. The combined effect of this is to make the material less flat and more uneven in properties (i.e. harder and softer regions.)

The advantage of cold rolling and annealing is that the material becomes recrystallized with a more even and finer grain size, the carbide distribution is improved and segregated areas get broken down. This means that the hardening process gives a more even set of properties and has better flatness. The more cold reduction that is given, the better the consistency of the structure.” [emphasis added]

Dr. Larrin Thomas noticed the performance difference when he tested AEB-L and imitations. He wrote the following:

“When it comes to steels of identical composition the differences come down to impurity levels (like phosphorus and sulfur) and microstructure, especially carbide size and distribution, that results from hot rolling and annealing. Uddeholm has that dialed in for AEB-L as does Sandvik with 13C26.” [emphasis added]

What does this mean to knifemakers? Feedback we’ve received regarding imitation alloys is the toughness is lower, more chipping occurs and the edge holding is mediocre.

The alloy discussed so far is AEB-L. However, there are also imitations of 15N20 and 26C3. VBU uses the same production processes on these alloys that they perform on AEB-L. The result is the same superior performance compared to imitations.