As an H13 tool steel supplier to distributors and stockholders, we run melting, electroslag remelting, EFS grain refining, forging, annealing, finishing and eight-step inspection inside one works. H13 tool steel is one of the five grades we hold finished in stock, which is what puts the common sections on a 7 to 10 day dispatch window rather than a production lead time.
H13 tool steel sits where hot hardness, thermal fatigue resistance and toughness balance well enough to cover most hot work tooling without moving to a specialised grade. Three families account for most of the H13 that leaves here.
The largest family. Aluminium and magnesium die casting subjects the die face to a thermal cycle thousands of times, and the grade has to hold hardness at temperature while resisting the crack network that develops from repeated expansion and contraction. It remains the default for cavity blocks, cores and inserts.
Extrusion loads a die continuously rather than cyclically, so the demand shifts towards hot strength and wear resistance at the bearing surfaces, with nitriding usually applied afterwards. H13 is standard across flat dies, porthole dies and mandrels.
Particularly in small and medium sizes and for inserts within larger die sets, where toughness matters as much as hot hardness.
Hot shear blades, extrusion tooling for non-ferrous metals and hot work punches, off the same lines with the same certificate behind them.
A distributor's catalogue has to answer whatever designation the customer uses — and here the three are one grade.
= one grade, one regime, one certificate
The same four documents sit behind all three names, so the designation never quietly becomes two products with different process histories. On the certificate this is visible rather than assumed: the EN 10204 3.1 MTC carries the designation as you ordered it alongside the measured composition for that heat, so a document raised against an order written as SKD61 can be forwarded to a customer working in AISI.
The failure this prevents is the one where a customer specifies SKD61, a supplier maps it internally to something adjacent, and the substitution becomes visible only when the die behaves differently from the last one.
Several hot work grades look interchangeable on a summary table and are not interchangeable in a die running a thermal cycle. We do not substitute silently: a designation outside our fourteen gets a written comparison naming which of ours sits closest, what differs and what that difference means for the tool.
Whichever of the six your customer wrote in, the mapping is already made and comes back with the first reply.
The alloying elements are the grade definition and every H13 producer works to them. The two at the bottom are the ones worth reading twice.
Phosphorus and sulphur are residuals, and the window we hold on them is tighter than the grade standard requires. That window is what electroslag remelting delivers.
A sulphur maximum of 0.005 percent is achievable because every heat is remelted through slag rather than cast directly, and it matters because sulphide inclusions are where thermal fatigue cracks initiate. Every heat is analysed by optical emission spectrometry and those readings, not the window, appear on your certificate.
The common practice is to reserve remelting for premium grades. Ours are remelted without exception, H13 included.
Every one of our fourteen grades goes through electroslag remelting, and this matters most for anyone comparing H13 tool steel offers. Remelting fixes what is in the steel; forging then decides the structure.
The electrode is remelted a droplet at a time through a molten slag layer, and the slag strips sulphur and oxide inclusions out as it passes — the mechanism behind the 0.005 percent sulphur maximum. In a hot work die, inclusions are crack initiation sites, which is why a die can craze early while every bulk property on the certificate reads correctly.
A conventionally cast ingot solidifies outside in, concentrating the last liquid — and the porosity it carries — at the centre. Remelting solidifies progressively from the bottom upward, so there is no trapped final liquid at the core.
Composition at the top and bottom of the ingot ends up far closer together, which shows up as consistency between bars cut from the same heat and between one order and the next.
EFS is not a separate shop or a proprietary machine: a forging ratio control regime plus a grade-specific annealing regime, issued in writing before the heat is scheduled.
The ratio is a minimum of 4:1, issued per order against the section. This is where the 3 to 12 tonne ingot range does its work: a heavy H13 section is produced from a larger ingot specifically so the ratio stays at or above 4:1.
The easy way to produce a Ø 500 mm H13 bar is to forge it from an ingot only slightly larger, reaching the dimension with far less reduction. It meets its dimensional and composition requirements; its centre never receives the work needed to refine the structure.
A shortcut invisible on any certificate that does not report structure — which is why heavy sections are the ones that fail in service.
Steps seven and eight are metallography with grain size and carbide distribution rating. In H13 tool steel these are the closest thing on a certificate to a prediction of how the die will behave, because uniform fine grain and evenly distributed carbides are what resist the crack network that ends a hot work tool's life.
A printed figure looks like the firmer commitment. At first glance it is stronger than “we report what we measured.” It is not.
Samples are prepared and examined in the inspection centre and the ratings for that heat are written onto the EN 10204 3.1 MTC shipping with your batch.
The difference is whether the number moves. For a distributor that is the difference between a claim you repeat to your customer and a document you forward, and it means the ratings on two of your certificates can be read against each other.
If your customer requires an acceptance level rather than a report, state it on the order and it becomes the standard the batch is judged against.
Both are performed and reported as measured values on the certificate — the practical answer when a customer specifies a third-party acceptance standard.
Name the items your customer's specification calls for; we test them and report the measured values against your heat, on a document they can check.
It is the only step that sees the centre of the bar. Everything else is measured on a surface or a small sample.
The reading belongs to the specific bar rather than a batch, recorded against the heat number within a ten-year retention period, so a question three years from now is answered by retrieving that piece's own reading.
Held back rather than shipped, with no concession shipment. The route for nonconforming material and disputes is set out once, on the home page.
See the measured composition, the grain size rating and the carbide distribution rating we actually report for an H13 heat, before you order anything. Returned within 24 hours on a working day.
Not whether we make H13 — which sizes are on the floor.
Already melted, remelted, forged, annealed, inspected and certified before it went on the shelf.
Melting, remelting, forging, annealing, finishing, eight inspection steps.
The ordering decision most often left to default, and the one that decides how much of what you buy your customer pays to cut away.
| Surface | Allowance | What it is | Who it suits |
|---|---|---|---|
| Black forged and descaled | 3–6 mm per side | As it comes from forging and annealing, scale removed. The allowance covers the scale and the decarburised layer beneath it. | Customers doing substantial roughing anyway |
| Peeled | Layer already gone | Round bar with the decarburised layer removed on our machines rather than the customer's. | Smaller tool rooms set up for finish machining |
| Ground | ± 0.05 mm thickness | Surface grinders to 2,000 × 800 mm, gantry grinders to 4,000 × 1,300 mm — the full 1200 mm plate width. | Goes straight to the machining centre |
| Milled on six faces | 0.1 mm/m flatness | A rectangular block on CNC gantry mills with 4,000 × 1,500 mm travel. | Die block work |
Decarburisation matters more in H13 tool steel than in most grades a distributor stocks: the surface layer has lost carbon, will not harden to the same level as the bulk, and a die face machined into it behaves differently from the steel underneath. All four are cut to your lengths at ± 2 mm.
If your customer is hardening after machining, a fine tolerance held before heat treatment will move during it.
Where an order specifies a tolerance that will not survive it, the technical desk raises it before anything is cut.
Everything on the certificate is worthless if the bar on your rack cannot be connected back to it.
We deliver H13 annealed. The tool is hardened by whoever makes it — so here is what we can usefully tell you about that stage.
H13 tool steel takes 44 to 52 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. Die casting dies commonly sit lower in that range where toughness does more of the work; extrusion tooling often sits higher.
A recommended route, not a specification we impose or verify.
What we can do is answer the question. Behind the technical desk sit sixteen metallurgical and process engineers who write the regimes we anneal to.
A die crazes at a fraction of the expected cycle count and the customer comes back to you. You are between two parties, and you need to establish what happened rather than assert that your material was fine.
Inclusions or centre unsoundness acting as initiation sites, or a coarse structure. What settles this is already on your certificate, issued before anybody knew there would be a dispute.
Under-tempering, a single temper where a double was needed, austenitising outside the range, or a quench that induced stress. The most common origin in practice, and testable at the customer's end.
A die running hotter or faster than the grade suits, inadequate cooling, or a design concentrating thermal load. Where the duty exceeds what H13 handles, the useful outcome is a grade change rather than a claim.
Open it with the heat number. What to send is listed on the contact page; how a remaining disagreement is settled is under nonconforming material and disputes.
Material questions route to the quality department, independently of whoever sold you the steel.
A distributor who can tell a customer when to leave H13 is worth more than one who ships whatever was written on the order. For blanking, trimming and cold forming dies the move is out of the hot work family altogether, to D2 cold work tool steel.
All four are in our fourteen-grade range: same melt shop, same furnaces, same minimum ratio, same eight steps. Moving between them changes the metallurgy and nothing else.
The enhanced thermal crack resistance grade: aggressive die casting duty, large dies with a severe thermal gradient, and tools where H13 has already crazed sooner than the cycle count justified.
The lower-carbon relation within the same family, trading hot strength for impact resistance.
Where hot strength does more of the work than toughness — running continuously hot rather than cycling.
Heavy forging die blocks: mechanical toughness under repeated impact in a large section.
Tell us the tool, the working conditions and the section size and we will say which of the fourteen to put against it, in writing.
Six lines and we answer completely on the first reply, within 24 hours on a working day. If you are unsure about the surface, tell us what your customer does first when the material arrives and we will tell you which one saves them the most. For a fuller brief or a sample certificate, use the H13 tool steel quote request on the contact page.
Working days, Monday to Friday 09:00–18:00 GMT+8. We supply distributors, stockholders, wholesalers and large-scale procurement buyers.
Or write directly: wonderful@fcstoolsteel.com
WhatsApp: +86-18972782802