Most enquiries that reach this page do not carry a grade. They carry a mold: a resin, a shot-count expectation, a cavity that has to come off the polisher looking a certain way, and a stack of plates that has to be machined by a date already promised.
Fucheng supplies plastic injection mold steel as three stocked grades: 1.2316 for resins that attack steel, 1.2085 pre-hardened for plates and bases that go straight to the machine, and 420 for cavities that have to polish out. All three are melted, electroslag remelted, forged, treated, finished and inspected inside our own works.
Send the resin, the shot-count band, the cavity and plate sections, and whether the cavity has to reach a mirror. A grade recommendation with the stock position comes back within 24 hours on a working day. Or work the selection route below and arrive with the grade already picked.
Three questions decide which of the three grades goes on the order, and they are asked in this order because each one closes off part of the range.
Cavity and core blocks, mirror work.
PVC, halogen-bearing flame-retardant compounds and some acetal formulations release acidic products at melt temperature, and they reach the cavity face, the vents and the parting line.
The cooling side attacks separately, from the water: untreated circuits in a mold that stands between programmes pit and scale from the inside, and blocked cooling shows up as warped parts long before anyone opens the mold to look. Where either condition applies, the grade is 1.2316, at 15.5 to 17.5 % chromium with 1.00 to 1.30 % molybdenum behind it.
Large plates, mold bases and heavy cavity blocks are usually machined once and put to work, because a hardening cycle after the cavity is cut puts every hour of that machining at risk.
Tooling that will be hardened goes out annealed at 245 HB or below and comes up to roughly 48 to 52 HRC in 1.2316, or 48 to 54 HRC in 420, in the hardener's own furnace.
Transparent parts, optical surfaces and cosmetic medical housings print every defect in the steel onto every shot, and the answer there is 420, electroslag remelted.
The 0.05 to 0.10 % sulphur that makes 1.2085 cut so freely is present as sulphides, and sulphides are what open up as pinholes at the fine stages of polishing, which is why 1.2085 earns its place on plates, bases and textured or technical surfaces rather than on a mirror cavity.
No to all three
| The mold in front of you | Grade | Delivery condition |
|---|---|---|
| Corrosive resin, cavity hardened afterwards | 1.2316 | Annealed, 245 HB or below |
| Corrosive resin, mirror cavity | 420 | Annealed for hardening, or pre-hardened 30 – 34 HRC |
| Transparent or optical cavity, high shot count | 420 | Annealed for hardening |
| Mold base, plates, large cavity block, no hardening step | 1.2085 | Pre-hardened 29 – 33 HRC |
| Textured or technical surface, free machining priority | 1.2085 | Pre-hardened 29 – 33 HRC |
Mold base, plates, large cavity block.
Where two answers pull against each other — a corrosive resin and a mirror cavity in the same tool — the technical desk works it in writing, on your side of the enquiry, and comes back with the grade, the delivery condition and whether the section is on the shelf or goes to production.
1.2316, 1.2085 and 420 all sit inside the 8,000 tonnes we hold finished. A plastic injection mold steel enquiry for common sections is a stock question here, not a production queue.
Six lines turn a mold description into a grade and a delivery date, and they are the six the desk works from.
The six the desk works from.
Glass-filled and mineral-filled compounds.
| Line | What it decides |
|---|---|
| Resin and filler content | Corrosion route: 1.2316, or chromium alone |
| Shot-count band | Whether hardened working hardness is worth a hardening cycle |
| Cavity and plate sections | Stock band or production, and the pre-hardening route |
| Surface target: mirror, textured, technical | 420 against 1.2085 |
| Delivery condition: annealed or pre-hardened | Which line the steel runs down here |
| Who hardens, if anyone | Machining allowance and added test items |
Filler content. Glass-filled and mineral-filled compounds wear a cavity from the gate outward regardless of how corrosive the resin is, and that changes the working hardness worth aiming for rather than the grade family. Say the loading and it is answered on the first reply.
These molds run high cavity counts against surfaces that have to stay clean and stay identical from cavity to cavity over the life of a validated tool, which puts the load on surface condition and on the steel behind every block being the same.
We supply 420 for those cavities, electroslag remelted, with non-metallic inclusion rating available as an added test item and the heat number carried on every piece.
PMMA and polycarbonate cavities transfer everything: a pinhole in the steel is a pinhole in every part until the cavity is repolished.
Here the attack is chemical and it is continuous, on the cavity face, in the vents where products concentrate, and on the water side of the plate.
Three different molds, three different reasons for the same question at the desk: what is the resin, and what does the surface have to do.
Corrosion in a plastic mold shows up in three places, and they fail on different clocks.
The two corrosion-resisting grades here answer that differently.
| Grade | Chromium | Molybdenum | Delivered |
|---|---|---|---|
| 1.2316 | 15.5 – 17.5 % | 1.00 – 1.30 % | Annealed, 245 HB or below |
| 420 | 12.5 – 14.5 % | — | Annealed 245 HB or below, or pre-hardened 30 – 34 HRC |
1.2316 carries both the higher chromium and the molybdenum, and molybdenum raises resistance to localised pitting specifically — the pinpoint attack that starts in a vent or a water line rather than as general dulling across a face.
That is why a PVC or flame-retardant tool goes to 1.2316 even where 420 would be adequate on every other count, and why 420 stays the answer where the requirement is mirror polishing rather than chemical attack.
Comparative corrosion ratings for either grade. What goes on the certificate is the measured composition of your heat, taken by optical emission spectrometry during melting and again on the finished product, against the standard window above.
Pinholes do not appear when polishing starts.
They appear at the fine stages, after the cavity has every one of its machining hours already in it, because the abrasive has finally reached deep enough to open non-metallic inclusions sitting under the surface and pull them out.
What is left is a pit that cannot be polished away, only cut away — and cutting it away means taking the whole cavity surface down and starting again, or scrapping the block. Nothing at the roughing or the first polishing stages predicts it.
That is why every 420 heat here is remelted. Two 15-tonne induction furnaces feed a shop of ten electroslag furnaces running 3 to 12 tonne ingots, and electroslag remelting is what strips the inclusion population and the segregation that a cast ingot carries.
Our EFS grain refining practice is applied across the hot work, cold work and plastic mould grades on top of that.
Both pages carry the process detail; what matters at the order stage is what you can check yourself.
Ten electroslag furnaces, 3 to 12 tonne ingots.
With a mirror-grade 420 order we send an unpolished coupon cut from the same heat as your blocks. There is no polishing operation in this works and we make no claim about what level it reaches — the coupon arrives as steel, and your own polisher takes it down with your own compounds, on your bench, past #2000 where pinholes declare themselves.
If it goes quiet and clean, that heat behaves on your process. If it does not, you know before the cavity is cut rather than after, and nothing has been spent.
The coupon arrives as steel.
The 0.05 to 0.10 % sulphur in 1.2085 is deliberate: it is what makes a heavy plate machine at the rate it does. Those same sulphides are what surface as pinholes above roughly #2000.
Any offcut of 1.2085 already in your warehouse, from any source, will show it in twenty minutes of polishing — which is the same evidence that puts 420 on the mirror cavity line and keeps 1.2085 on the plates and bases where its machinability pays.
Twenty minutes of polishing.
Non-metallic inclusion rating is available as an added item on any heat, rated by whichever method you specify: ASTM E45, DIN 50602 or ISO 4967. The measured rating goes on the EN 10204 3.1 for that heat.
We do not print an acceptance class that was not agreed with you first, and the way to test that is to ask loosely.
What comes back from here is three questions: which standard, which inclusion types, and where your line sits. Then we measure to that and report it.
ASTM E45 · DIN 50602 · ISO 4967.
One more thing decides whether a mirror job behaves consistently: a mold is several pieces, not one.
Each piece marked with its own heat number.
Four lines, and a grade recommendation with the stock position comes back within 24 hours on a working day, written so you can forward it to the tool room that asked.
Pre-hardened plastic injection mold steel leaves here at a measured hardness inside a stated window.
That condition is produced on our own quench and temper line, not bought in pre-hardened. Two pit furnaces, 4,000 mm deep by 1,600 mm diameter, take the heavy plate and block sections that this work needs, which is what lets the pre-hardened band cover the full flat range up to 500 mm thick and 1200 mm wide rather than thin plate only.
The spread between surface and core widens as sections get heavier, so send the thickest piece on your list and the desk tells you which route the material takes rather than leaving you to find it at the first cut. That is also where a heavy block moves from pre-hardened supply to annealed supply plus hardening.
4,000 mm deep by 1,600 mm diameter.
The reading for your batch, not a datasheet.
Machined once, and go to work.
The reason this condition exists at all is the sequence it removes. A mold base and a set of plates bought pre-hardened are machined once and go to work; there is no hardening cycle after the cavity geometry is in the steel, so there is no distortion to chase, no cracked water-line corner and no re-machining of a block that already carries days of spindle time.
A mold order is a parts list, so what matters is which parts of it come off the shelf. Plastic injection mold steel is stocked here as flat product first, because that is the shape a base, a plate and most cavity blocks start as.
| Part of the mold | What is held | Typical route |
|---|---|---|
| Base and support plates | 1.2085 pre-hardened flat, common thicknesses | Shelf, 7 – 10 days |
| Cavity and core blocks, mirror work | 420 flat and round, common sections | Shelf, 7 – 10 days |
| Cavity blocks for corrosive resins | 1.2316 flat and round, common sections | Shelf, 7 – 10 days |
| Heavy or off-band sections | Up to 500 mm thick, 1200 mm wide, Ø 600 mm | Made for the order, 25 – 35 days |
Add 2 days where the list is sawn to length, 5 days where faces are ground or milled, and work to drawing is quoted per drawing.
A size drawn down by a large set is replaced out of our own melt shop rather than bought in, so the same parts list answers at the same speed the next time it comes round.
Steel leaves in one of four surface conditions, and the choice is worth making per line rather than per order, because it decides how much work the tool room does before it starts on the mold.
| Operation | What it holds |
|---|---|
| Cut-to-length | ±2 mm |
| Ground thickness | ±0.05 mm |
| Milled surfaces, flatness | 0.1 mm per metre |
For plates and bases those figures are the ones that decide whether a stack goes straight onto the machine or through a squaring operation first, and six-face milled plate is bought here for exactly that reason.
Precision sawing, grinding, milling and machining to drawing are all run in our own finishing bays, so a cut list and a surface spec travel on the same order as the steel and under the same heat number.
Straight onto the machine, or through a squaring operation first.
Sawing, grinding, milling, machining to drawing.
Every batch ships with an EN 10204 3.1 material test certificate, signed by a quality department that reports to the general manager rather than to production, and written to survive being forwarded to a tool room that will test the steel again.
Non-metallic inclusion rating by ASTM E45, DIN 50602 or ISO 4967, and the quench test sample for material that will be hardened downstream.
Grain size, carbide distribution and inclusion rating are reported as measured. We do not declare a default acceptance class on any of them, because a class printed without agreement is a specification commitment made on your customer's behalf by someone who has not seen their part.
Tell us the class the tool room works to and the material is measured and reported against it.
Records are kept for ten years against the heat number. When a block behaves unexpectedly two years into a programme, the file for that heat still exists and the handling of nonconforming material and disputed results is set out in full on the home page.
Three grade choices arrive already made that will not survive the mold they are meant for, and each one costs at a different point.
It machines beautifully, which is usually how it got onto the drawing, and it fails at the last operation before the mold ships.
The sulphides come out as pinholes at the fine polishing stages, and by then the block carries its full machining cost.
It polishes and it holds hardness, and it pits — in the vents first, then the water side.
The tool comes back for welding and repolishing early in its life, and the argument about who pays for that lands on whoever supplied the steel.
Every hour of cavity work is at risk in the quench, and a crack at a water-line corner or a distortion beyond the polishing allowance writes off the block, not just the cycle.
We supply distributors, stockholders and wholesalers, and the tool rooms and molders they serve remain their accounts.
A set is not held whole while one plate waits.
Plastic mold grades move differently from the rest of the range: they go out as mold sets rather than as bar, they are asked for by resin as often as by grade name, and the person asking usually needs an answer the same day.
Mixed lists are handled line by line rather than as one order. Stocked sections are confirmed against the 7 to 10 day window and the rest is scheduled to production, so a set is not held whole while one plate waits. A first order can run as a trial before a programme depends on the supply, and it is answered on the same terms as a repeat.
A first order can run as a trial.
Hot work, cold work and plastic mould grades.
Send the resin, the shot-count band, the section list and the surface target, and a grade recommendation, the stock position and the lead time come back within 24 hours on a working day.
Add the mirror requirement to the enquiry and the unpolished coupon from your heat is arranged with the order.
Working days, Monday to Friday 09:00–18:00 GMT+8. We supply distributors, stockholders, wholesalers and buyers procuring at scale.
Or write directly: wonderful@fcstoolsteel.com
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