EFS · Extra Fine Structure
EFS is the grain refining regime we run on our hot work, cold work and plastic mould grades. Two controlled operations produce it, both on our own presses and our own bogie hearth furnaces, and both signed off before anything ships.
Heavier sections start from a larger ingot, so the ratio itself never has to move. Our ingot range of 3 to 12 tonnes exists for exactly that.
Thirteen of fourteen
Thirteen of the fourteen grades we produce run the EFS regime, across three families. M2 is a high speed steel and is supplied outside that regime, on the same melting, electroslag, inspection and certification route.
Order in the designation your customer uses. Equivalents are one grade here, quoted once and certified once, with cross-references to AISI, DIN and W-Nr, JIS, GB, ASSAB and BÖHLER confirmed in writing on the first reply so you can forward the mapping.
| Grade | Also called | Family | EFS regime |
|---|---|---|---|
| H13 | 1.2344, SKD61 | Hot work | Yes |
| 1.2367 | — | Hot work | Yes |
| H11 | 1.2343 | Hot work | Yes |
| H10 | 1.2365 | Hot work | Yes |
| 1.2714 | — | Hot work, forging dies | Yes |
| D2 | 1.2379, SKD11 | Cold work | Yes |
| DC53 | — | Cold work | Yes |
| D3 | 1.2080 | Cold work | Yes |
| D6 | 1.2436 | Cold work | Yes |
| O1 | 1.2510 | Cold work, oil hardening | Yes |
| 1.2316 | — | Plastic mould, corrosion resistant | Yes |
| 1.2085 | — | Plastic mould, pre-hardened | Yes |
| 420 | 1.2083, 3Cr17 | Plastic mould, mirror finish | Yes |
| M2 | 1.3343 | High speed | Supplied outside EFS |
Reduction, then the curve
Three things come out of the regime: high cleanliness, uniform grain size through the section, and toughness at the level European tool steel buyers work to.
Cleanliness is set upstream, in our own melting and electroslag shops, and the EFS regime works on what that ingot delivers. Reduction under the press breaks up the as-cast structure and the carbide banding that solidification leaves behind. The controlled annealing curve that follows fixes the grain size and the carbide morphology at delivery. What your customer receives is a bar produced to a written regime for that grade, repeatable on the next heat and the one after it.
A uniform structure responds the same way from bar to bar and batch to batch, so the hardness that comes back from the tool room furnace lands where their route says it should.
Distortion is easier to predict when carbides are distributed rather than banded, which matters most on cold work sections that get through-hardened and ground afterwards.
Finer, more evenly distributed carbides take a better edge on cutting and blanking tools, and polish more evenly on the plastic mould grades.
These are material properties of the structure we deliver in the annealed condition. Hardening, tempering and finishing happen in your customer's shop, on their route, so the numbers that end up in the finished tool come from that process working on our structure.
Two operations
Deformation under the press is what redistributes the carbides that solidification laid down. The controlled cool is what decides the form they keep.
Load bearing — 4 : 1 minimum
The number the regime controls, and the number that moves instead when the section gets heavier.
The minimum forging ratio we hold is 4:1. It is issued per grade and per section by our metallurgical and process engineers, before the order reaches the shop floor, together with the ingot size the bar is to be started from.
Reduction is what does the work. An as-cast ingot has a coarse solidification structure and, in the high carbon high chromium grades, eutectic carbide banding laid down as it froze. Deformation under the press is what breaks that structure down and redistributes those carbides. The forging ratio is the measure of how much deformation the bar has actually had, which is why it is the number the regime controls rather than the press tonnage or the number of passes.
When the section gets heavier, what changes is the ingot, not the ratio.
Heavier sections are started from a larger ingot so the same reduction is still available at the end of the route. Our ingot range of 3 to 12 tonnes exists for that, poured in our own two 15-tonne induction furnaces and remelted in our own electroslag shop before it ever reaches a press. Because the ingot is ours to choose, the ratio does not have to move to make a big diameter.
For you, the result is that a 600 mm round and a 60 mm round of the same grade come out of the same regime and land in the same rating band. Your customer's hardening route behaves the same way on both, and you are not managing two different materials under one grade name.
Ask what ingot a 600 mm round in your grade is started from, and what reduction that gives. A mill that buys its ingots in can name a diameter and a delivery date. The ingot size sits in someone else's melt shop, which is where that decision was made.
Three lines, two shifts
Send a section and three answers come back: which line, which ingot, what reduction.
Three forging lines run on two shifts, and fifty-two people work on them. The radial precision forging machine holds the small diameters, and it is also what sets dimensional accuracy and surface on Ø 16 to 150 mm, so small sections are forged to size rather than turned down from something larger.
Eight bogie hearth furnaces
Forging sets the structure. The annealing curve is what fixes it.
Eight bogie hearth furnaces run the annealing area. Each has a chamber of 6,000 by 2,000 by 1,500 mm and takes a 30 tonne load, and a cycle runs about three days. Chamber temperature uniformity is held to plus or minus 5 °C, which is what keeps the whole load on the same curve rather than the bars nearest the burners running ahead of the bars in the middle.
The curve itself is written per grade by the same engineers who issue the forging ratio. After the soak, the load is cooled under control at no more than 20 °C per hour down below 600 °C before the furnace can be opened. That cooling rate is the part of the regime that decides carbide morphology and the machinability of the bar your customer puts on the mill, and it is the reason a load stays in the furnace for days rather than hours.
Delivered condition
Delivered hardness is the check that the annealing regime ran as written.
| Grade | Delivered condition | Hardness |
|---|---|---|
| H13, H11, H10, 1.2367 | Annealed | ≤ 235 HB |
| 1.2714 | Annealed | ≤ 250 HB |
| D2, D3, D6, DC53 | Annealed | ≤ 255 HB |
| O1 | Annealed | ≤ 220 HB |
| 1.2316, 420 | Annealed | ≤ 245 HB |
| M2 | Annealed | ≤ 269 HB |
| 1.2085 | Pre-hardened | 29 to 33 HRC |
| 420 | Pre-hardened | 30 to 34 HRC |
Hardness is measured on our own Rockwell and Brinell testers and reported on the certificate for your heat.
No concession shipment
The heat is re-annealed and re-tested. Quality holds the release until the reading falls inside, and no concession shipment is offered instead.
Load bearing — two lines
Every batch ships with an EN 10204 3.1 Material Test Certificate. Two lines on it report what the EFS regime produced in your material.
A sample is cut from the heat and prepared on our metallography sample line, then rated under one of two metallurgical microscopes by the eight people who staff the physical and chemical laboratory and the metallography room. That is step seven and step eight of the eight-step inspection every heat goes through before quality signs the certificate.
Both numbers are measured on that heat, so they move from heat to heat with the material. What you are reading is a measurement of the steel in front of you, taken on the sample that came out of it.
Five results sit on one document, under one heat number, issued by an authorised inspection representative in our quality department.
When your customer asks what they are buying, that document is the answer, and it carries our name on it rather than yours. Ask for a sample EN 10204 3.1 MTC on any grade you buy, and read the structure lines on it before you quote anything.
Before you quote
Name a grade you buy and a real certificate comes back, structure lines and all, within 24 hours on a working day.
Request the Sample CertificateTen years of records
Send us a heat number and the record comes back out, years later.
That is what makes the certificate useful after delivery rather than only at the moment of shipment. We pull the record for that heat, including the metallography result and the individual ultrasonic result for that bar, and recheck it against what was reported.
Records are held for ten years, so a heat number from three years ago still resolves. If your customer has their own laboratory run the same checks, the certificate states the methods used, so those readings and ours line up item by item rather than being two sets of numbers that cannot be compared.
Order of operations
Melting sets the composition on our own spectrometers. Electroslag remelting then rebuilds the ingot through a layer of molten slag, taking sulphur and non-metallic inclusions out and giving a solidification pattern that a conventionally cast ingot does not have. All fourteen grades go through our ten electroslag furnaces, and the arithmetic behind that word is set out on our ESR tool steel refining page.
Forging and annealing follow, and that is where the EFS regime is executed. Cleanliness comes from the melt route; grain size and carbide distribution come from reduction and the annealing curve.
Two stages, one document
Cleanliness comes from the melt route. Grain size and carbide distribution come from reduction and the annealing curve. Both are reported under one heat number.
Sixteen engineers
Who writes the forging ratio and the annealing curve, and who is allowed to refuse to release the material.
Regimes are written by our sixteen metallurgical and process engineers. They set the forging ratio and the ingot size for each grade and section, and the annealing curve for each grade, and they issue that regime before an order reaches production.
Inspection criteria and release rules are set by the quality department, not by production. Quality reports to the general manager, its own targets do not include output or delivery dates, and its manager holds stop authority and the authority to refuse release. Production cannot overturn a refusal to release.
Buyers who want to watch the regime being executed are welcome to book a works visit, and what you can see on the route through the six areas is set out on our about page.
Issued per grade, not per house
The regime targets something different in each family, which is why the ratio and the curve are issued per grade rather than as one house setting.
Hot work
In H13, 1.2367, H11, H10 and 1.2714 the structure question is toughness in heavy sections that are cycled hot and cold. These are the grades most often ordered in the upper part of our diameter range, where holding 4:1 depends on starting from a larger ingot. Grain size uniformity from surface to core is what keeps the response to hardening the same across a thick block.
Cold work
In D2, DC53, D3, D6 and O1 the structure question is carbide banding. These grades solidify with a coarse eutectic carbide network, and reduction is what breaks it up and redistributes it. In D2 we also hold chromium to 11.0 to 12.0 per cent inside the 1.2379 range, a composition decision made in our own melt shop rather than an inherited one, and it works with the reduction rather than against it. Distortion in hardening and edge behaviour in blanking both track the carbide picture, and D2 buyers can have a hardening test sample taken from the same heat.
Plastic mould
In 1.2316, 1.2085 and 420 the structure question is uniformity through the thickness of a plate that will be cavity-machined and then polished. A banded structure shows the bands on the polished surface. 1.2085 and 420 also come pre-hardened, which puts the structure through the quench and temper line as well.
Ø 16 to 600 mm
Every heat, before release
Steps seven and eight are where the EFS regime is verified on the material itself.
Step five is 100% ultrasonic testing to SEP 1921 Class D/d or E/e, bar by bar, with the result for each bar filed under the heat number. How that works, and how a disagreement over a test result is settled, are set out on our homepage.
Five lines — reply T+24 h
Five lines, and the first reply is a complete one, inside 24 hours on a working day.
Feasibility line by line, the forging line and ingot size for each section, the grade mapping confirmed in writing, and the documents that will ship with the batch.
Reply T+24 h
You get the route, the ingot size and the reduction it gives, within 24 hours on a working day. Ask for a sample EN 10204 3.1 MTC at the same time and read the grain size and carbide distribution lines on it.
Or write to wonderful@fcstoolsteel.com · +86-18972782802 on WhatsApp. Mon–Fri 09:00–18:00 (GMT+8).