Steel Strip for Knife Blades

Blade Steel: Carbon vs. Stainless

The first decision in blade steel selection is carbon steel vs. stainless steel. This is not a quality decision — it is an application decision. Each category exists because different blade products operate in different environments and serve different user expectations.

Carbon blade steels (SK5, 75Cr1) are candidates for utility and industrial blades. Select hardness, edge geometry and surface protection for the cutting task. Edge retention, sharpening effort and cost depend on the specific grade, processing and blade design.

Stainless blade steels (such as SUS420 and SUS440C) are candidates where corrosion resistance matters. Stainless does not mean corrosion-proof or automatically food-contact or medical compliant. Verify grade designation, heat treatment, surface condition and intended-use requirements.

Grade Comparison for Blade Applications

Grade	Type	Hardness reference	Typical candidate uses	Selection note
SK5	Carbon	Hardness to be agreed	Utility knives, industrial blades, box cutters	Validate sharpness, edge retention and sharpening requirements on the finished blade.
75Cr1	Carbon + Cr	Confirm for the finished blade	Knife and industrial blade candidates	Chromium-alloyed carbon steel whose suitability depends on heat treatment and blade geometry.
SUS420 (420J2)	Stainless	Hardness to be agreed	Kitchen knives (economy), food processing blades	Verify corrosion resistance and food-contact requirements for the finished product.
SUS440C	Stainless	Confirm for the finished blade	Corrosion-sensitive blade candidates	High-carbon stainless candidate; corrosion and edge performance depend on processing and service conditions.

Performance Requirements by Blade Type

Blade Product	Recommended Grade	Typical Thickness	Key Requirement
Utility/box cutter blades	SK5	0.3 – 0.6mm	Low cost, high hardness, easy snap-off fracture at score lines
Industrial cutting blades	SK5, 75Cr1	0.5 – 1.5mm	Wear resistance, consistent edge geometry across long blade runs
Kitchen knives (mass market)	SUS420	1.0 – 2.5mm	Validate corrosion resistance, food-contact compliance and cleaning instructions
Kitchen knives (premium)	SUS440C, 75Cr1	1.5 – 3.0mm	Edge retention for professional use, mirror polishability
Surgical/medical blades	SUS420, SUS440C	0.2 – 0.5mm	Validate sterilization compatibility, corrosion resistance and applicable medical requirements
Craft/hobby knives	SK5	0.3 – 0.8mm	Ultra-sharp edge for precision cutting, low cost for disposable blades

Surface Finish for Blade Strip

Blade applications may place high demands on surface quality because the strip surface can become part of the visible blade. State the required finish and roughness so feasibility can be reviewed:

Bright annealed (BA): Specify surface appearance, roughness and defect acceptance criteria. Confirm compatibility with subsequent hardening and finishing.
2B or polished finish: These are distinct finish descriptions. Name the required finish, appearance reference, roughness and measurement method rather than treating 2B as a mirror finish.
Blue/Gold tempered: Specify appearance separately from hardness. Oxide color is not a hardness test or a verified corrosion-protection rating.
Satin/Hairline: Directional brush finish. Specified for decorative blades where a non-reflective surface is preferred for aesthetics or to hide minor scratches in use.

How Edge Geometry Relates to Steel Grade

Hardness, toughness, carbide structure and blade geometry jointly affect edge performance:

Hardness: Treat published grade values as reference data only. Specify and validate the finished-blade target for the actual heat treatment.
Edge geometry: Edge angle and thickness must be designed together with hardness, toughness and intended cutting material.
Application validation: Kitchen, outdoor, surgical and industrial blades have different corrosion, hygiene, impact and cutting requirements.

Blade Strip Specification Review

Precision Thickness

State the required thickness tolerance, measurement locations and sampling method. Feasibility is confirmed against grade, condition and width.

Heat Treatment Options

State whether annealed or hardened-and-tempered strip is required, together with the target hardness and acceptance test.

Custom Slitting

State the slit width, width tolerance, burr limit and edge condition required by the blanking or grinding process.

Surface Quality

Controlled decarburization, pitting and surface roughness requirements can be agreed for applications where the strip surface becomes the finished blade surface.

Quality Points for Blade Steel Buyers

Decarburization control: Define an acceptance limit, test method and sampling plan appropriate to the blade thickness and final edge.
Inclusion cleanliness: Hard oxide inclusions can affect the cutting edge during sharpening. Define the required cleanliness method and acceptance rating in the order specification.
Carbon and microstructure uniformity: Agree the spheroidization and hardness-uniformity criteria, then verify them using the specified sampling and test method.
Traceability: State the required inspection certificate and source-to-coil identifiers, especially for regulated or food-contact applications.

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