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K390 is a useful option for a knife that does plenty of abrasive cutting. It combines a high abrasive edge-retention rating with useful toughness, but it is not stainless. If you are happy to clean and dry the blade after use, that tradeoff may suit workshop tasks and frequent slicing.
What Is K390?
Böhler identifies K390 Microclean as a powder metallurgy cold-work tool steel. Its producer specification lists 9% vanadium and 4.2% chromium among the average alloy values. Those figures help identify the grade; they are not a recipe for predicting how a finished blade will cut.
Performance Ratings
For the science, we draw on Dr. Larrin Thomas of Knife Steel Nerds, who has kindly allowed us to share his ratings here. Our advice below puts those tradeoffs into everyday cutting and care.
| Property | Böhler K390 Microclean |
|---|---|
| Abrasive edge retention | |
| Toughness | |
| Corrosion resistance |
Heat treatment, hardness and geometry affect actual knives.
Explore Böhler K390 Microclean’s Tradeoffs
Choose a steel above to highlight its position and see all three exact ratings below. The full map fits your screen.
Non-stainless tool steel
Böhler K390 Microclean
- Abrasive edge retention
- 7.5
- Toughness
- 6
- Corrosion resistance
- 4
Same position; corrosion ratings may differ:
All 48 rated materials. Numbers group steels at identical coordinates; colors describe stainless classification, not corrosion scores. Neither direction means a universally better knife.
Böhler K390 Microclean’s ratings are shown above. Enable JavaScript to select another steel, or browse the full ratings table.
Wear Resistance Without Ignoring Edge Damage
The ratings put K390 at 7.5 for abrasive edge retention and 6 for toughness. That makes it interesting for repeated slicing, but an edge that chips needs a different diagnosis from one that slowly wears dull. Check the bevel and the task before assuming you need still more wear resistance. Thomas's K390 testing explores the balance across heat treatments.
Does K390 Rust?
Yes. K390 is non-stainless and carries a corrosion rating of 4 in this framework. Dry it after use and remove food, salt and other residue before putting it away. For longer storage, a light protective oil can help; choose one suitable for food contact if you use the knife to prepare food. A patina does not prevent further rust.
K390 or a Stainless Alternative?
For a dry workshop or regular cutting with time to clean up, K390's care requirements may be easy to accept. Around persistent moisture, a stainless alternative may be more convenient. MagnaMax shares its 7.5 edge-retention and 6 toughness ratings here, with a higher corrosion rating. Those scores help narrow the steel choice; the grind, handle and price help narrow the knife choice. See the wider steel tradeoffs.
The MagnaMax steel profile takes a closer look at that stainless alternative.
Composition
Our steel composition guide explains the elements and how to read these values.
Böhler K390 Microclean: Böhler K390 Microclean average composition, mass %; not a finished-blade assay. Böhler: K390 Microclean.
| Element | Böhler K390 Microclean |
|---|---|
| Carbon (C) | 2.47% |
| Chromium (Cr) | 4.2% |
| Molybdenum (Mo) | 3.8% |
| Vanadium (V) | 9% |
| Tungsten (W) | 1% |
| Cobalt (Co) | 2% |
| Silicon (Si) | 0.55% |
| Manganese (Mn) | 0.4% |
Compare Two Knife Steels
Sources and Update Notes
- Böhler: K390 Microclean · Average composition reported by Böhler; not a finished-blade assay.
- Dr. Larrin Thomas: K390 testing
- Dr. Larrin Thomas: rating framework · Toughness updated to 6 by direct author feedback, October 9, 2026.
