Material selection
Which tool steel: D2, H13, P20, 1.2316 or 1.2738?
Pick D2 for cold-work cutting and forming tools, H13 for hot-work dies, P20 or 1.2738 for plastic moulds, and 1.2316 when the plastic attacks the mould. Every hardness and strength figure here belongs to one temper, form or supplier, so quote the condition and the source with the grade.
- Pick D2 or H13 when you are making tools for metal. D2 is the cold-work grade (Uddeholm Sverker 21 data): very hard, but its sources disagree on toughness. H13 is the hot-work grade (Uddeholm Orvar Supreme, a premium ESR grade): 1,280 to 1,520 MPa yield, tested at 45 and 52 HRC. Commodity H13 may not meet these figures.
- Pick P20, 1.2738 or 1.2316 when the tool is a plastic mould you want to machine and polish without heat treatment. All three are supplied pre-hardened at roughly 280 to 330 HB. Choose 1.2738 for blocks above 400 mm and 1.2316 for PVC and plastics that release aggressive gases. P20 is the general choice and rusts unless protected.
- Unsure: ask what the tool touches. Cold metal points to D2, hot metal to H13, plastic to P20. Then ask the supplier for hardness at your tempering temperature, because hardness swings widely with temper in the Space Mushroom profiles.
Tool steels at a glance
| Material | yield strength (MPa) | hardness rockwell c (HRC) | thermal conductivity (W/(m·K)) |
|---|---|---|---|
| AISI D2 cold-work tool steel | no data | 35 to 65 | 20 |
| AISI H13 hot-work tool steel | 1,280 to 1,520 | 45 to 54 | 25 |
| P20 plastic mould steel | 827 to 862 | 28 to 51 | 32.5 |
| 1.2316 stainless plastic mould steel | no data | 30 to 48 | 23.5 |
| 1.2738 plastic mould steel | 826 | 28 to 51 | 29 to 34.5 |
- 1Does the tool cut, punch, roll or extrude cold metal, and does wear end its life?YesD2Use D2, and keep impact low: Uddeholm gives it rather limited cracking resistance, while Dörrenberg calls its toughness good, so ask the supplier for the toughness of your lot. The D2 profile holds no tensile or yield figure.
- 2Does the tool hold hot metal, as in die-casting, extrusion or forging?YesH13Use H13 at 42 to 53 HRC working hardness, depending on the job (Uddeholm). Keep tempering out of 425 to 550 °C, because temper brittleness there costs toughness.
- 3Is it a plastic mould that you want to machine and polish without heat treatment?YesP20, 1.2738 or 1.2316P20 is listed for large mould frames and bolsters. 1.2738 is the nickel-added choice for through-hardening above 400 mm (Dörrenberg; Industeel calls it medium-size). 1.2316 is for PVC and gas-releasing plastics.
- OtherwiseNot a toolIf the part is a shaft, gear or fixture and not a tool, a tool steel is probably the wrong class (general engineering knowledge, not in the Space Mushroom data).
How hard are D2, H13, P20, 1.2316 and 1.2738 at each temper?
Among the five, D2 is hardest as quenched and softens as the temper rises, with a small rise at 500 °C (secondary hardening). Uddeholm Sverker 21 gives 63 to 65 HRC before tempering after austenitising at 990 to 1080 °C. A thesis tempering curve, with no hardening temperature stated, gives 63 HRC after 100 °C, 61 after 200 °C, 58 after 300 and 400 °C, 59 after 500 °C, 56 after 550 °C, 51 after 600 °C and 35 after 700 °C. The 700 °C point is a curve value, not a service condition, because D2 is not tempered that high in practice (general engineering knowledge, not in the Space Mushroom data).
All H13 figures in this article are for Uddeholm Orvar Supreme, a premium ESR grade; commodity H13 may be lower in toughness and may not meet them (H13 profile). Before tempering it measures 53 HRC after 1025 °C and 54 HRC after 1050 °C; after a 2 + 2 hour temper at 610 °C it measures 45 HRC. The recorded states run 45 to 54 HRC HRC; working hardness by job is in the next section.
The mould steels are bought at working hardness. P20 is supplied at 280 to 325 HB, about 30 HRC. Four sources give 1.2738 at 280 to 330 HB; Industeel alone gives 30 to 35 HRC. 1.2316 is supplied at 280 to 325 HB; Abrams gives up to 48 HRC without tying that top figure to a heat treatment. At about 30 HRC, P20 wears fast against glass-filled resins (general engineering knowledge, not in the Space Mushroom data), so ask about a harder grade or a surface treatment for those.
The tempering charts for P20 and 1.2738 start from re-hardened steel, not the supplied block. After hardening from 840 to 870 °C, P20 measures 51 HRC as quenched, then 42, 36 and 28 HRC after tempers at 500, 600 and 700 °C (Swiss Steel 1.2311 sheet). 1.2738 gives 51, then 42, 39 and 28 HRC at the same tempers (Abrams).
Not like for like, and the bars cannot be split by state, so read the text for each condition. Each bar mixes as-quenched, tempered, supplied and vendor-stated values: D2's 35 HRC follows a 700 °C temper, P20 and 1.2738 reach 51 HRC only as quenched after re-hardening, and 1.2316's 48 HRC is a vendor statement tied to no heat treatment. 440C stores hardness under another property name and 4140 has no HRC value, so both are left out.
Data behind this chart
| Material | Low (HRC) | High (HRC) | Values |
|---|---|---|---|
| AISI D2 cold-work tool steel | 35 | 65 | 13 |
| AISI H13 hot-work tool steel | 45 | 54 | 6 |
| P20 plastic mould steel | 28 | 51 | 8 |
| 1.2738 plastic mould steel | 28 | 51 | 7 |
| 1.2316 stainless plastic mould steel | 30 | 48 | 1 |
What yield and compressive strength do they have, and how much ductility is left?
Only some have a tensile yield figure, and the figures are not like for like. H13 shows 1,280 MPa at 45 HRC and 1,520 MPa at 52 HRC at room temperature, from the centre of a 407 by 127 mm Orvar Supreme bar; tensile strength is 1,420 and 1,820 MPa at the same two hardnesses. Uddeholm does not state the heat treatment behind the 52 HRC column.
P20 and 1.2738 are pre-hardened and sit between 826 and 862 MPa. P20 shows 827 to 862 MPa yield and 965 to 1,030 MPa tensile (Smith Metal Centres, typical, about 300 HB). 1.2738 shows 826 MPa yield and 993 MPa tensile (Industeel, typical, 300 HB). H13's top figure is 1.8 times P20's top figure, but at 52 HRC against about 30 HRC, so it shows what hardness buys and not that one grade is better.
D2 has no tensile yield figure. Uddeholm Sverker 21 prints a compressive yield strength (Rc0.2) of 2,200 MPa at 62 HRC and 1,650 MPa at 50 HRC, approximate, tempering temperature not stated. 1.2316 has no yield figure either: Abrams gives an approximate 1,100 MPa tensile strength with no condition, and Dörrenberg's 950 to 1,100 MPa is converted from hardness, not tested.
Two reference steels show why conditions matter; neither is a tool steel. 4140 guarantees 740 MPa minimum yield for quenched and tempered bar of 10 to 100 mm and 665 MPa at 101 to 250 mm; typical values are 770 MPa at 50 mm and 570 MPa at 200 mm. We leave its 1,235 MPa value out of the chart: it is a research specimen tested in helium gas under pressure. For 440C, two datasheets print the same value, 1,896 MPa and 275 ksi, with 2 % elongation for bar hardened from 1900 °F and tempered at 600 °F.
Ductility and toughness are thin. P20 shows 20 % elongation (typical, 50 mm gauge). 1.2738 shows 17 % elongation and 25 J Charpy V at 20 °C, typical at about 300 HB; it is the only one of the five tool steels with an impact figure. For D2 the sources disagree in words: Dörrenberg calls its toughness good, Uddeholm Sverker 21 says rather limited cracking resistance, and Wikipedia says it is not as tough as lower-alloyed steels. For H13, Uddeholm says it can run 1 to 2 HRC harder, which slows heat checking, without loss of toughness. We cannot rank the five on toughness. A2 and S7 are usually named as tougher cold-work steels (general engineering knowledge, not in the Space Mushroom data); the A2 profile is below the full-grade bar, so we do not compare it.
Not like for like. H13 is Uddeholm Orvar Supreme at 45 and 52 HRC. P20 and 1.2738 are typical values at about 300 HB from two suppliers. D2 and 1.2316 have no tensile yield figure, and 4140 and 440C are reference steels; all four are covered in the text.
Data behind this chart
| Material | Low (MPa) | High (MPa) | Values |
|---|---|---|---|
| AISI H13 hot-work tool steel | 1,280 | 1,520 | 2 |
| P20 plastic mould steel | 827 | 862 | 1 |
| 1.2738 plastic mould steel | 826 | 826 | 1 |
Which tool steel suits hot-work, cold-work and mould jobs?
H13 is the hot-work steel. Uddeholm lists die-casting dies for tin, lead and zinc alloys at 46 to 50 HRC and for aluminium and magnesium alloys at 42 to 48 HRC, extrusion dies at 43 to 50 HRC by work material, and forging tools for steel at 50 to 52 HRC. Tempered at 250 °C, it gives 50 to 53 HRC for scrap shears and severe cold punching. Hot-work dies need preheating before use (general engineering knowledge, not in the Space Mushroom data). Its modulus falls from 210 GPa at 20 °C to 140 GPa at 600 °C, and we hold no hot yield strength or hot hardness for it.
D2 is the cold-work steel. Uddeholm lists blanking, punching, cropping, shearing and trimming tools, thread-rolling dies and cold-extrusion dies.
The mould steels are chosen on block size and plastic. P20 is listed for injection-mould cavities, cores and inserts, large mould frames and bolsters, and zinc die-casting dies. 1.2738 adds large mould blocks and hydroforming tools; Dörrenberg ties it to sections above 400 mm, while Industeel calls it medium-size, a conflict in the 1.2738 profile. 1.2316 is listed for moulds for corrosive plastics, extrusion tools and the food industry.
How well do D2, H13, P20, 1.2316 and 1.2738 conduct heat?
Among the five tool steels, D2 conducts least and 1.2738 most in the recorded values, but the sources do not always agree. H13 rises from 25 W/(m·K) at 20 °C to 29 at 400 °C and 30 at 600 °C. D2 is 20 at 20 °C in Uddeholm Sverker 21, while Dörrenberg prints 16,7, so D2 sits lowest on either figure.
Not like for like. D2 and H13 are Uddeholm values at 20 °C, hardened and tempered. The D2 bar rests on Uddeholm alone: Dörrenberg prints 16,7 W/(m·K) at 20 °C, lower still, with a decimal comma, so it is not charted. P20 is a 1.2311 data sheet, quenched and tempered at 23 °C. 1.2738 gives 29 W/(m·K) at 20 °C (Industeel) and 34.5 W/(m·K) at room temperature (Abrams). 1.2316 is at 23 °C with no heat treatment stated. 4140 is at 100 °C. 440C temperatures are mostly not stated. H13 also has 29 W/(m·K) at 400 °C and 30 at 600 °C.
Data behind this chart
| Material | Low (W/(m·K)) | High (W/(m·K)) | Values |
|---|---|---|---|
| Alloy steel AISI 4140 | 42.6 | 42.6 | 1 |
| 1.2738 plastic mould steel | 29 | 34.5 | 2 |
| P20 plastic mould steel | 32.5 | 32.5 | 1 |
| AISI H13 hot-work tool steel | 25 | 25 | 1 |
| Stainless steel 440C | 22.8 | 24.2 | 3 |
| 1.2316 stainless plastic mould steel | 23.5 | 23.5 | 1 |
| AISI D2 cold-work tool steel | 20 | 20 | 1 |
How are they heat treated and welded?
D2 and H13 are preheated, hardened, then tempered at least twice. D2 is hardened from 990 to 1080 °C, usually 1000 to 1040 °C, after a 650 to 750 °C preheat, and tempered twice at no less than 180 °C for at least 2 hours each time. H13 is hardened at 1020 to 1050 °C after a two-step preheat at 600 to 850 °C and tempered at least twice at 250 °C or above, with an interrupted quench where distortion or quench cracking is a concern.
The P20 and 1.2738 sheets both warn of stress corrosion cracking after oil hardening unless the quench is interrupted at about 300 to 400 °C. Stress relief is 500 to 550 °C for both (Abrams: 550 to 600 °C). Simold's about 650 °C for P20 would soften a pre-hardened block (an inference in the profile). 1.2316 is hardened from 1020 to 1050 °C. Its soft anneal at 760 to 800 °C, to a maximum of 230 HB, is not a stress-relief step: do not reheat a pre-hardened 1.2316 block into that range, or it softens.
Weld notes differ in kind. D2: working temperature 200 to 250 °C, with matching consumables if the tool will be polished. H13: working temperature 325 to 375 °C with TIG or MMA, cooling at 20 to 40 °C per hour for the first 2 to 3 hours, and 50 to 55 HRC in the weld afterwards. P20 (Abrams, 1.2311 sheet): preheat 315 to 370 °C, cool slowly to 40 to 65 °C, reheat to 540 °C for one hour per 25 mm of weld depth, and never exceed 565 °C. 1.2738 (Abrams): preheat 316 to 371 °C, cool to 100 to 150 °C, reheat to 538 °C with the same hold, never exceed 566 °C.
Each source names its own tempering range to avoid, because of temper brittleness: for H13 it is 425 to 550 °C, where toughness falls.
What traps catch buyers of these tool steels?
The first trap is unlike numbers. Dörrenberg prints a 229 HB maximum for soft-annealed 1.2344 (its H13 grade, annealed at 750 to 800 °C); Uddeholm prints about 180 HB typical after its own 850 °C cycle. A maximum and a typical value are different things, so ask which the supplier guarantees. P20 and EN 1.2311 are also not identical: the P20 profile prints 0.28 to 0.40 percent carbon and 0.35 to 0.45 percent for 1.2311, so check which one a data sheet describes. The P20 tempering, conductivity, stress-relief and weld figures here come from 1.2311 sheets.
Corrosion is the second. D2 is not stainless. P20 rusts unless protected, and Abrams gives 1.2738 only a certain degree of resistance; it is not stainless, with 1.8 to 2.1 percent chromium. 1.2316 has a passive chromium layer, but its corrosion data are qualitative and no test is printed. The H13 profile holds no corrosion statement.
Surface treatment is the third. A nitrided H13 layer is brittle, and Uddeholm does not recommend case depths above 0.3 mm for hot work. After EDM, remove the white re-cast layer and give D2 or H13 an extra temper about 25 °C below the previous one. After hard-chromium plating, temper H13 or 1.2738 at 180 °C for about 4 hours, starting within 4 hours of plating, to limit hydrogen embrittlement.
Premium and commodity grades are the fourth. The H13 profile holds only Uddeholm Orvar Supreme, sold as Superior AISI H13 per NADCA#207 Grade B, and no data for other H13 qualities. The P20 profile records Aços Formosa pointing PVC to 420-series stainless steels. Ask suppliers for their data sheets.
Terms used
- Cold-work steel
- a tool steel for cutting, punching and forming other metal at room temperature, where wear and chipping decide tool life.
- Hot-work steel
- a tool steel for dies that touch hot metal, as in die-casting, extrusion and forging.
- Pre-hardened
- supplied already hardened and tempered, so a block can be machined and polished without a further heat treatment.
- HRC and HB
- Rockwell C and Brinell hardness scales. A higher number is harder. The Space Mushroom profiles store them separately and hold no conversion between them.
- Tempering
- reheating hardened steel to a lower temperature to trade some hardness for toughness.
- Temper brittleness
- a loss of toughness after tempering in a temperature range that each data sheet names for its steel (425 to 550 °C for H13).
- Heat checking
- a net of fine surface cracks from repeated heating and cooling of a hot-work tool.
- Compressive yield strength
- the stress at which a metal starts to deform for good when it is squeezed. Uddeholm prints it as Rc0.2, the stress for 0.2 percent permanent shortening.
- ESR
- electroslag remelting, a refining step that gives cleaner steel (general engineering knowledge, not in the Space Mushroom data).
- EDM
- electrical discharge machining, which cuts by sparks and leaves a hard white re-cast layer.
What to check before you order
- Ask for the grade, the designation (P20 or EN 1.2311) and the supplier's data sheet, and say whether each number is a minimum, a typical value or converted from hardness.
- For D2 and H13, ask for the hardening temperature, the tempering temperature and the delivered hardness. For H13 confirm that no temper falls between 425 and 550 °C, the temper-brittleness range where toughness is lost, and ask whether the quoted properties are for a premium ESR grade or commodity H13.
- For pre-hardened blocks (P20, 1.2738, 1.2316), ask for delivered HB at the block centre, and say if the block is thicker than 400 mm.
- For welded repairs, ask the supplier for a procedure for your exact grade. Among the tool steels, the profiles hold weld notes for D2, H13, P20 and 1.2738 only.
What do we not know yet?
- No hot yield strength, hot hardness or heat-checking resistance is stored for any of the five tool steels, and the H13 values are for one premium ESR grade only.
- D2 has no tensile or yield strength, and 1.2316 has no yield strength, only an approximate tensile figure. The 1.2316 tempering diagram has no readable values.
- Toughness cannot be compared. Only 1.2738 has a tool-steel impact figure, and no wear rate is stored for any of the five.
- Weld data are missing for 1.2316, and the P20 and 1.2738 notes come from 1.2311 and 1.2738 data sheets, not qualified welding procedure specifications.
- Machinability cannot be compared: only P20 and 1.2316 have a rating, on different scales.
- Cost, polish quality and mould life are not stored, and the profiles rest on between two and eight sources each (H13 on two, P20 on about eight).
Questions people ask
Is D2 or H13 harder?
D2 reaches the higher hardness in the Uddeholm data. Sverker 21 D2 measures 63 to 65 HRC and Orvar Supreme H13 53 to 54 HRC before tempering. Tempered, D2 tools run 54 to 62 HRC, while H13 measures 50 to 53 HRC after 250 °C, 50 to 52 HRC after 575 °C and 45 HRC after 610 °C. The ranges overlap, so the job decides.
What is the difference between P20 and 1.2738?
1.2738 is a nickel-added P20 for large blocks. Dörrenberg says its nickel improves through-hardening above 400 mm. Typical yields are close, 826 MPa for 1.2738 and 827 to 862 MPa for P20, but come from different suppliers. P20 rusts unless protected; 1.2738 has only a certain degree of corrosion resistance (Abrams).
Is 1.2316 stainless?
Yes, 1.2316 is a stainless martensitic mould steel with 15.5 to 17.5 percent chromium, but its corrosion data are qualitative. Abrams describes a passive layer, and no corrosion test is printed.
Can P20 be hardened further?
Yes, but you give up the pre-hardened advantage. The Swiss Steel 1.2311 sheet hardens P20 from 840 to 870 °C to 51 HRC as quenched, and every temper then lowers it (the full curve is in the hardness section). Re-harden only when the face needs more hardness than the supplied 280 to 325 HB, and expect the 1.2311 sheet to stand in for P20.
Does D2 rust?
Yes, it can. D2 has about 12 percent chromium, but most is tied up in carbides, so it is not stainless, and the stock is usually slightly oil coated against rust. Uddeholm says nitriding increases corrosion resistance, but gives no test value.
How does a tool steel compare with 4140 on strength?
A guaranteed minimum and a typical value are different kinds of number, so compare like with like. 4140 guarantees 740 MPa minimum yield at 10 to 100 mm. H13 shows 1,280 to 1,520 MPa as Uddeholm test values at 45 to 52 HRC; the mould steels show 826 to 862 MPa typical.
How this was made
Each material is a profile in the Space Mushroom database, drafted by AI assistants from cited pages; a script checks that each value appears in the source it cites, and each profile page lists its sources. Every number in this article is either resolved from those profiles when the page is built or checked against them, so it cannot drift from the data. Ranges run across the conditions each source reports (temper, form, heat treatment). A named human reviewer has not yet signed this article. Related: AISI D2 cold-work tool steel, AISI H13 hot-work tool steel, P20 plastic mould steel, 1.2316 stainless plastic mould steel, all collections, standards.
Last checked 25 October 2026. Next review when a profile changes.