Corten Steel Plate
Atmospheric corrosion resistant plate that builds its own protective rust instead of paint
Specifications
Alloy Steel Sheet
SKH55 Cobalt Alloyed High Speed Tool Steel
SKH55 tool steel under its M35 1.3243 and HS6-5-2-5 equivalents from one stock
SKH55 is the Japanese designation for the molybdenum cobalt high speed tool steel also catalogued as M35, 1.3243 and HS6-5-2-5. Tool rooms and cutting tool manufacturers working to JIS drawings call it out for drills, reamers, gear cutters, broaches and die steel where the edge has to hold its hardness while it is running hot. Buyers usually lose time proving that the grade on a Japanese drawing and the grade on a European mill certificate are the same steel, so this item is stocked and certified against all four designations at once. Thickness runs from 0-1000mm and the plate is supplied annealed for machining or quenched and tempered.
- Product Name — High speed steel
- Grade — M35 1.3243 HS6-5-2-5 SKH55
- Thickness — 0-1000mm
- Size — Customized size
- Technique — Annealed quenched and tempered
Why It Is Specified
Key Benefits of SKH55 high speed steel
One Grade Under Four Designations
SKH55 1.3243 HS6-5-2-5 and M35 describe the same molybdenum cobalt steel. Ordering against all four removes the substitution argument between your Japanese drawing and the mill certificate.
Cobalt Content Behind the Red Hardness
The 5% cobalt addition is what puts this grade ahead of M2 at temperature. The edge keeps cutting when friction heat would already have softened a cobalt free high speed steel.
Hardness Reached After Heat Treatment
Correctly heat treated SKH55 develops 64-66 HRC. That is the working hardness tool makers size their grinding allowance around.
Evenly Distributed Fine Carbides
Carbides in this conventional steel are small and evenly distributed, which is what lets a ground edge stay straight instead of chipping along a carbide band.
Annealed Or Hardened Delivery
Take it annealed when your shop machines the blank and heat treats in house, or quenched and tempered when you want to go straight to grinding.
Surface Condition To Suit the Next Operation
Raw material milling and grinding are all available, so you pay for stock removal only where your process actually needs it.
Problems It Solves
What This Material Removes From Your Process
Grade Equivalence Disputes At Goods Inward
A Japanese drawing says SKH55 and the certificate says 1.3243, and inspection stops the batch. The material is supplied and certified against SKH55 M35 1.3243 and HS6-5-2-5 together so the paperwork matches the drawing.
Edges Softening Under Cutting Heat
Cobalt free high speed steel loses hardness once the edge runs hot. The 5% cobalt in this grade is what gives it the red hardness to keep cutting.
Buying Bar Stock and Machining It Away
Cutting a blank out of oversize stock wastes an expensive alloy. Cut to size supply with milling or grinding leaves less metal to remove.
Uncertainty About Achievable Hardness
Heat treatment planning needs a target. This grade is documented to reach 64-66 HRC after heat treatment, so the shop can set its tempering schedule around a known figure.
Application Scenarios
Where It Is Used
Twist Drill and Reamer Blanks
Drill and reamer manufacturers cutting blanks from plate and bar where the finished tool has to survive dry or interrupted drilling.
Gear Cutters and Hobs
Gear cutting tools where a long tooth profile has to keep its form across a full production batch.
Broaches and Form Tools
Broaching and profile cutting instruments in which regrinding cost makes edge retention the deciding factor.
Cold Work Die Steel Components
Die steel applications listed for this grade where hardness and abrasion resistance matter more than toughness.
Tool Room Replacement Stock
Maintenance tool rooms holding SKH55 blanks so a worn special tool can be remade against the original JIS drawing.
Who It Is For
Buyers Who Specify This Product
- Cutting tool manufacturers buying SKH55 blanks for drills reamers and gear cutters
- Tool room supervisors sourcing plate to remake worn special tools against a JIS drawing
- Die and mould shops buying cobalt high speed steel for cold work die components
- Purchasing engineers at machine builders matching a Japanese grade call out to an available mill certificate
- Tool steel distributors holding SKH55 alongside its M35 and 1.3243 equivalents
- Sharpening and regrinding service shops that need matching stock for tool rebuilds
Technical Data
Specifications and Technical Features
Values below come from the product data published by Shandong Tianyu Metal Products. Confirm the exact grade and size against your order.
| Product Name | High speed steel |
|---|---|
| Grade | M35 1.3243 HS6-5-2-5 SKH55 |
| Thickness | 0-1000mm |
| Size | Customized size |
| Technique | Annealed quenched and tempered |
| Hardness After Heat Treatment | 64-66 HRC |
| Carbon C | 0.82-0.95 |
| Tungsten W | 5.50-6.50 |
| Chromium Cr | 3.80-4.50 |
| Molybdenum Mo | 4.75-5.25 |
| Vanadium V | 1.75-2.15 |
| Surface | Raw material milling grinding |
| Processing Service | Bending welding decoiling cutting punching |
| Place of Origin | China |
Technical Features
- Grade SKH55 with equivalents M35 1.3243 and HS6-5-2-5
- Molybdenum tungsten cobalt vanadium alloyed high speed tool steel
- Hardness up to 64-66 HRC after heat treatment
- Thickness 0-1000mm in customized size
- Delivery condition annealed or quenched and tempered
- Surface raw material milling or grinding
- Processing covers bending welding decoiling cutting and punching
- Mill test certificate issued with the material
Materials
- Molybdenum cobalt high speed tool steel to SKH55 and its M35 1.3243 and HS6-5-2-5 equivalents
- Cobalt addition of 5% giving the grade its red hardness over M2
- Tungsten and molybdenum carbide forming alloys at 5.50-6.50 W and 4.75-5.25 Mo
- Vanadium at 1.75-2.15 for abrasion resistance in the cutting edge
Certification
- Mill test certificate supplied with the material
Manufacturing
How It Is Made and Processed
Melting and rolling to high speed steel plate stock
Annealing to leave the material machinable
Quenching and tempering where hardened delivery is ordered
Milling or grinding the surface to the ordered condition
Cutting blanks to the ordered size
Optional bending welding decoiling and punching
Marking and export packing
Quality Control
Checks Before It Ships
- Chemical composition checked against the C W Cr Mo V limits for the grade
- Mill test certificate issued for SKH55 and its stated equivalents
- Thickness verified within the 0-1000mm ordered range
- Surface condition inspected against the ordered raw milled or ground finish
- Blank dimensions checked against the cutting list before packing
Customization
What We Can Change on Your Order
- Blanks cut to your tool drawing instead of standard plate sizes
- Annealed or quenched and tempered delivery condition
- Raw milled or ground surface as required by your next operation
- Punching and bending carried out before shipment
- Certificate issued naming the equivalents your drawing uses
Comparison
SKH55 high speed steel Against the Alternatives
| HSS M2 high speed steel | SKH55 carries 5% cobalt which M2 does not, so it holds hardness better as the cutting edge heats up. |
|---|---|
| Carbon tool steel | Carbon tool steel loses its edge quickly at temperature while this grade is specified for its red hardness and reaches 64-66 HRC after heat treatment. |
| Solid carbide tooling | Carbide is harder but brittle and expensive to blank. SKH55 can be cut punched welded and reground in a normal tool room. |
Use Guide
Specifying Handling and Welding Notes
- Order annealed stock if your shop machines the blank and heat treats it in house
- Plan the heat treatment around the documented 64-66 HRC so grinding allowance is set correctly
- State the surface you need because milling or grinding adds cost you may not require
- Give the finished blank size so less of an expensive alloy is machined away
- Keep the mill test certificate with the tool record when the drawing calls SKH55 rather than M35
- Store blanks dry and protected because ground surfaces mark easily in transit
Questions Buyers Ask
SKH55 high speed steel FAQ
Is SKH55 the same steel as M35?
Yes. SKH55 is the Japanese designation and M35 1.3243 and HS6-5-2-5 cover the same molybdenum cobalt high speed steel. The certificate can name the equivalents your drawing uses.
What hardness will it reach after heat treatment?
This grade is documented to generate 64-66 HRC after heat treatment. The result depends on the heat treatment cycle your shop or heat treater runs.
What thickness can you supply?
Thickness runs from 0-1000mm and size is cut to your requirement, so blanks can be supplied close to the finished tool dimension.
Do you supply it annealed or already hardened?
Both. Annealed is the usual choice when you machine the blank yourself, and quenched and tempered when you want to go straight to grinding.
What surface conditions are available?
Raw material milling and grinding. Pick the one that matches your next operation so you are not paying for stock removal twice.
Can we test a piece before ordering a batch?
Samples are available. Send the thickness and blank size you want to machine and we will confirm what can be released.
Do you issue a mill test certificate?
Yes. A mill test certificate is issued against the grade and ships with the material.
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