Blanking and Piercing Dies
The largest by volume. What loads it is abrasive wear, and the usual form is flat and plate.
D2 Tool Steel (1.2379 / SKD11 / X153CrMoV12-1)
As a high-carbon, high-chromium cold work tool steel, D2 (1.2379) provides high wear resistance and excellent dimensional stability after heat treatment. Engineered with precise carbide distribution control, our D2 steel delivers superior edge retention and compressive strength for long-run stamping, blanking, and shearing dies.
- Chromium Held to 11.0–12.0%
- Measured Carbide Rating per Heat (MTC)
- Forging Ratio ≥ 4:1
- Hardness: Annealed ≤ 255 HB | 100% UT Tested
D2 Applications
As a D2 tool steel supplier we see the grade go into four families of cold tooling. It holds the position in cold work that H13 tool steel holds in hot work: the default, because wear resistance and compressive strength cover most of what cold tooling needs.
Forming and Roll Forming Tooling
Sustained rolling contact against strip; usually long round bar or heavy flats. What loads it is rolling contact, and the usual form is round bar.
Shear Blades and Slitting Knives
Edge retention is the entire requirement, and the edge is where carbide distribution and blank direction matter most. What loads it is edge retention; the thing to watch is banding direction.
Thread Rolling, Gauges and Wear Plates
Where dimensional stability after hardening matters as much as hardness — which decides the tempering route further down. What loads it is stability; the thing to watch is the tempering route.
D2 Composition: The 1.2379 Window
AISI D2, JIS SKD11 and EN ISO 4957 1.2379 are one grade here, and all three allow chromium anywhere between 11 and 13 percent. We use the lower half of that range.
Chromium: The Standards, and Our Window
AISI D211.0–13.0 %
JIS SKD1111.0–13.0 %
EN ISO 4957 1.237911.0–13.0 %
Fucheng D211.0–12.0 %
11.013.0
We hold chromium to 11.0–12.0 % inside the 1.2379 range, and the certificate reports the measured value.
That difference is not academic in a cold work die.
Move chromium towards 13 percent and carbide volume rises with it — and so does the coarseness of the network. Holding the top of the window down is the first of three controls on carbide size; remelting and forging reduction are the other two.
| Element | Window |
|---|---|
| Carbon | 1.45 – 1.60 % |
| Silicon | 0.10 – 0.60 % |
| Manganese | 0.20 – 0.60 % |
| Chromium | 11.0 – 12.0 % (standard 11.0 – 13.0) |
| Molybdenum | 0.70 – 1.00 % |
| Vanadium | 0.70 – 1.00 % |
| Phosphorus | 0.020 % max |
| Sulphur | 0.005 % max |
D2 Tool Steel Supplier Range: Sizes and Surface
The profile is weighted towards flat and plate rather than round, because that is what cold work tooling is — and most of it leaves ground.
On the shelf
From Stock
7–10 daysOne of five grades held finished, melted through certified before it went on the shelf.
Forged to order
From Production
25–35 daysRound bar 16 to 600 mm, flat and plate 20 to 500 mm thick by 200 to 1200 mm wide.
| Surface | Held to | Why it matters in D2 |
|---|---|---|
| Black forged and descaled | 3–6 mm per side | For most grades this is the economical way to hold volume. For D2 it puts the abrasive roughing work on your customer. |
| Peeled | Decarburised layer removed | The round-bar equivalent of the same decision — the slow work happens on our machines, not on their lathe. |
| Ground | ± 0.05 mm thickness | The condition most D2 ships in. Two parallel ground faces start producing features immediately, with no roughing pass. |
| Milled on six faces | 0.1 mm/m flatness | For customers who want the block squared as well as sized, ready to fixture. |
Why D2 Usually Ships Ground or Cut
Sawing and roughing a steel carrying this much chromium carbide is slow and consumes blades and inserts, so the work is done here on machines set up for it, and the plate arrives ready to produce features.
One caution: where your customer hardens after machining, a fine tolerance held beforehand will move, and in D2 how much it moves depends on the tempering route — covered below.
Marking
Every piece carries its heat number alongside the designation as you ordered it — D2, 1.2379 or SKD11 — so the certificate and the plate on your customer's bench match without a lookup.
D2 Inspection Before Release
Every D2 heat passes eight inspection steps in our own quality department before it is released, in the order below. The results are printed on the EN 10204 3.1 MTC issued against the heat number stamped on the steel.
01Visual Inspection
Visual inspection of the bar or plate surface, by the inspectors in the quality department who work on dimensions and visual inspection.
02Dimensions and Tolerances
Every piece is measured against the size on the order: ground thickness to ± 0.05 mm, milled flatness to 0.1 mm per metre or better, cut lengths to ± 2 mm. A piece outside tolerance is held back at the dimensional check, not packed.
03Chemical Analysis
Every heat is analysed by optical emission spectrometry on our own spectrometers. The measured figures, not the window, are printed on the EN 10204 3.1 MTC — for D2, chromium held to 11.0–12.0 %.
04Hardness
Measured on our own Rockwell and Brinell testers. D2 is supplied annealed at 255 HB or below, and the reading for your batch is printed on the certificate, not quoted from a datasheet.
05Ultrasonic Testing
100% ultrasonic testing to SEP 1921 Class D/d or E/e, as your order names it. Every bar is inspected individually, with each bar’s own result held under its heat number.
06Magnetic Particle Testing
Magnetic particle testing covers surface and near-surface indications, and the result is reported on the certificate.
07Metallography and Grain Size
A sample from the heat goes through the metallography room and the grain size is rated, measured on your heat in the condition it is delivered rather than carried across from a catalogue.
08Carbide Distribution Rating
The carbide distribution is rated on the same sample and entered on the EN 10204 3.1 MTC beside the grain size line from step seven. How to read it is set out in the next section.
D2 Carbide Rating on the MTC
The most informative line on a D2 certificate. Steps one to seven describe a bar indistinguishable from a poor one; step eight is where a die that wears and a die that chips part company.
For each D2 heat a sample goes through the metallography room, the carbide distribution is rated, and that rating is entered on the batch's EN 10204 3.1 MTC beside the grain size line from step seven. Read it against the D2 you bought last year, from the same reported method: two documents that agree are evidence no description produces. Where your customer's specification names an acceptance level, put it on the order and the heat is judged against it.
How we report the two structure ratings, and why a measured value on your heat beats a published level, is set out under carbide distribution rating.
- Kept for ten years
- The rating stays retrievable against the heat number for ten years, so a reissue for material you sold three years ago is a lookup rather than a reconstruction.
Two Items You Can Add at Order Stage
Non-metallic inclusion rating, reported as a measured value. And a hardening test coupon: a sample from your heat, hardened and tempered to your customer's route, reported as achieved hardness and dimensional change — what it settles is under distortion and grinding cracks.
D2 Annealed Hardness and Tempering Routes
D2 reaches 58 to 62 HRC after hardening and tempering, across the usual working range — a property of the steel achieved by whoever heat treats it, not a condition we deliver. We deliver D2 annealed at 255 HB or below, never pre-hardened.
- Blanking and piercing: low temperature tempering, for the highest hardness the grade reaches.
- Coated, gauge and large tools: secondary hardening tempering, for dimensional stability and coating tolerance.
Recommended route — D2 / 1.2379 / SKD11
- 750–800 °C
- Preheat, stagedAnnealed D2 conducts heat poorly, so the preheat is staged before the section goes to austenitising temperature.
- 1000–1040 °C
- AustenitiseExecuted by your customer’s heat treater, on the route recommended here.
- Quench
- QuenchAfter the quench, the two tempering routes diverge.
- 180–250 °C
- Temper, at least twiceLow temperature tempering gives the highest hardness; secondary hardening tempering gives up a little peak hardness for stability and coating tolerance. Either way, a single temper leaves an unstable structure — a common origin of D2 tools that crack in service or in grinding.
Where the two routes part
Delivered Annealed, 255 HB or Below
D2 is hard to machine even when soft — 12 percent chromium carbides are abrasive whatever matrix holds them — so a batch at the top of the window costs a tool room real cutter life. Annealing has to spheroidise the network, carbides rounded rather than angular and connected, and a load that measures above the window is annealed again and measured again. The furnace uniformity and cooling rate that achieve it belong to the fine grain tool steel regime.
A recommended route, executed by your customer’s heat treater — not a condition we deliver.
Ultrasonic Testing on D2
Two targets matter more in D2 than in a hot work die block.
Coarse Carbide and Segregation Bands
The only inspection that sees the whole volume under a working face.
Forging Discontinuities
Folds or laps, wherever enough reduction is applied to matter.
Centre Unsoundness
Sound outside, unsound inside.
The Regime
- Coverage
- 100% UT, one piece at a time
- Standard
- SEP 1921 Class D/d or E/e, from your order
- Where
- Sets and signatories: the tool steel factory page
D2 Distortion and Grinding Cracks
Two complaints account for most D2 disputes, and both are resolvable if the line between what the mill controls and what the heat treater controls is drawn before the argument starts.
Distortion After Hardening
Every steel moves during hardening. In D2 the amount depends on the residual stress the material arrived with, the section symmetry, the quenching practice, and how much retained austenite the tempering route leaves. The low temperature route leaves more of it, and retained austenite that transforms later — in service, or under a coating cycle — moves the tool a second time, after it was ground to size.
Ours
A properly spheroidised annealed structure, a uniformly worked structure from adequate reduction, and hardness inside the delivered window.
Theirs
The furnace, the fixturing, the quench, the section geometry the customer designed, and which tempering route they chose.
Grinding Cracks
Almost always a thermal event at the grinding wheel acting on a material state that could not tolerate it: insufficient tempering, high retained austenite, or grinding heat with inadequate coolant. Carbide banding concentrates stress along the bands, which is why the cracks in D2 so often run in one direction — the direction the edge orientation section describes — and why a crack that follows the banding points first at the material state, not at the wheel.
Ours
A well-broken carbide structure and material delivered correctly annealed.
Theirs
The tempering route, the number of tempers, and the grinding practice.
The Test That Settles It in Advance
Rather than leave that as an argument about probability, a hardening test coupon can be added at order stage. We take a sample from your heat, harden and temper it to the route your customer intends, and report the measured hardness achieved and the dimensional change.
Your customer then knows, before a single plate is machined, what hardness that route delivers on that heat and how much the material moves.
A distributor who supplies the coupon result with the material is supplying a decision, not just a plate.
- Origin: the material
- Coarse carbides or a poorly broken structure providing initiation sites. Addressed by the carbide and grain size ratings already on your certificate.
- Origin: the heat treatment
- Under-tempering, or retained austenite left by a low temperature route on a tool that needed stability. The most frequent origin in practice, testable on the failed tool.
- Origin: the tool
- Clearance too tight, an edge radius concentrating load, or a grade too hard for the duty — a grade change rather than a claim.
If a D2 Tool Still Fails
A failed tool is opened as a batch query — heat number, certificate number, the piece, photographs — and the quality department rather than your commercial contact takes it from there; the procedure, third-party retest included, is on the home page, and a query is opened through the contact page.
D2 Alternatives: DC53, D3, D6, O1
Four cold work grades sit either side of D2 on the wear–toughness line, and knowing when to leave D2 is worth more to a customer than reliable supply of it.
For hot work — die casting, extrusion and forging dies — the answer is never a harder cold work grade: it is H13 tool steel for hot work, which has a page of its own.
DC53
Toughness end- Move when
- D2 is chipping rather than wearing
- Instead of
- Specifying harder D2
For tooling working thicker or higher strength sheet, slender or unsupported sections, and progressive dies where one chipped station stops the whole tool.
D3
1.2080- Move when
- Wear resistance is the entire requirement
- Needs
- A well supported tool
Higher carbide volume and no molybdenum, so it holds an edge against abrasion and tolerates less impact.
D6
1.2436- Move when
- Wear resistance has to go further still
- Needs
- A well supported tool
The highest wear resistance option in this family, where edge life dominates every other consideration.
O1
1.2510- Move when
- Stability through a simple oil hardening route matters more
- Suits
- Tool rooms treating their own
Smaller tooling where stability through a straightforward oil hardening route matters more than maximum wear life, and tool rooms treating their own without controlled atmosphere equipment.
How to use it
Send the sheet grade and thickness, the tool geometry and the stroke count the tool is costed on, and the technical desk names the grade in writing — DC53, D3, D6, O1, or D2 as it stands — within 24 hours on a working day.
What to Send Us for a D2 Quote
Response in 24h on working days.
- Stocked From stock · 7–10 days
- Full range Ø 16 – 600 mm
Email: wonderful@fcstoolsteel.com
WhatsApp: +86-18972782802