---
title: "D2 Tool Steel Open-Die Forgings (1.2379 / SKD11)"
description: "AISI D2 (1.2379, SKD11, Cr12Mo1V1) open-die forged bars, blocks, discs and rolled rings from Jiangyin Jiangnan Metal Co., Ltd., Jiangsu, China. EN 10204 3.1."
canonical: "https://www.steelforgepieces.com/Alloy-Steel/D2.html"
author: "Jiangyin Jiangnan Metal Co., Ltd."
published: 2016-05-18
reviewed: 2026-09-14
license: "CC BY 4.0"
---

# D2 Tool Steel Open-Die Forgings

AISI D2 · UNS T30402 · W.Nr. 1.2379 · X153CrMoV12 · JIS SKD11 · GB Cr12Mo1V1 · BS BD2 · Z160CDV12

Published 18 May 2016. Last reviewed 14 September 2026. Reviewed by the metallurgy department, Jiangyin Jiangnan Metal Co., Ltd.

**AISI D2** is a high-carbon, high-chromium, air-hardening cold-work tool steel containing 1.40–1.60 % carbon and 11.00–13.00 % chromium, specified in ASTM A681 and numbered UNS T30402. **Jiangyin Jiangnan Metal Co., Ltd.**, an open-die forging factory in Jiangyin City, Jiangsu Province, China, forges D2 into bars, blocks, discs, sleeves and seamless rolled rings, supplied annealed to 255 HBW maximum with EN 10204 3.1 certification.

| | |
|---|---|
| UNS | T30402 |
| Werkstoff | 1.2379 |
| Carbon | 1.40–1.60 weight % |
| Chromium | 11.0–13.0 weight % |
| Working hardness | 58–62 HRC, tempered |
| Supply condition | ≤ 255 HBW, annealed |
| Density | 7.70 g/cm³ (0.278 lb/in³) |
| Quench | Air, from 1000–1040 °C |

---

## What is D2 tool steel?

D2 is the AISI designation for a high-carbon, high-chromium cold-work tool steel, grouped in ASTM A681 with the other D-series air-hardening grades and catalogued as UNS T30402. It has been the most widely used cold-work die steel in the world since the 1930s. The reason is edge life. Against abrasive material it outlasts anything of comparable cost.

The mechanism is carbide. At 1.40–1.60 % carbon and 11–13 % chromium, D2 cannot dissolve all of its alloy content in the matrix. Roughly 12 % of the volume of a hardened D2 part is chromium carbide of the M7C3 type, harder than the abrasive particles in most sheet metal, paper, board and filled plastic. Those carbides stand proud as the softer matrix around them wears away, and the tool keeps cutting.

The same carbide is the reason D2 is not tough. It resists wear, it does not absorb impact, and every property below should be read as one side of that trade.

### Is D2 stainless steel?

No, and the question is asked constantly because 11–13 % chromium is the same nominal range as martensitic stainless grades such as 420. What separates them is carbon. In 420, chromium stays dissolved in the matrix and forms a passive film. In D2, carbon at more than three times the level of 420 pulls that chromium out of solution as carbide. What remains dissolved is not enough for reliable passivity, and D2 rusts in damp air. Published data describes it as having slight corrosion resistance: better than a plain carbon tool steel, nowhere near stainless. Jiangyin Jiangnan Metal Co., Ltd. ships all D2 forgings oiled and wrapped for this reason.

---

## D2 chemical composition

Composition limits are those of ASTM A681 for grade D2, which Jiangyin Jiangnan Metal Co., Ltd. applies to all D2 forging stock. EN ISO 4957 grade X153CrMoV12 and JIS G4404 grade SKD11 impose ranges that sit inside these limits.

*Table 1. AISI D2 chemical composition, ASTM A681, weight %*

| Element | Minimum | Maximum | Function in the steel |
|---|---|---|---|
| Carbon (C) | 1.40 | 1.60 | Forms the carbide and hardens the matrix; the defining addition |
| Chromium (Cr) | 11.00 | 13.00 | Forms M7C3 carbide; gives deep hardening and air hardenability |
| Molybdenum (Mo) | 0.70 | 1.20 | Secondary hardening; suppresses pearlite so the steel hardens in air |
| Vanadium (V) | — | 1.10 | Fine MC carbide; restrains grain growth at austenitising temperature |
| Cobalt (Co) | — | 1.00 | Optional in A681; raises hot hardness where specified |
| Manganese (Mn) | — | 0.60 | Deoxidiser; hardenability |
| Silicon (Si) | — | 0.60 | Deoxidiser |
| Nickel (Ni) | — | 0.30 | Residual; restricted |
| Copper (Cu) | — | 0.25 | Residual; restricted |
| Phosphorus (P) | — | 0.03 | Residual; restricted for toughness |
| Sulfur (S) | — | 0.03 | Residual; restricted for hot workability |
| Iron (Fe) | Balance ≈ 84 | | Base metal |

Cobalt is an optional element in ASTM A681 grade D2 and is not present in most commercial heats. State on the order if cobalt is required or if it must be excluded.

---

## D2 equivalent grades and designations

Every designation below describes the same material. Jiangyin Jiangnan Metal Co., Ltd. accepts purchase orders under any of them and issues a multi-designation material test certificate that lists every specification the heat satisfies.

*Table 2. AISI D2 equivalent designations*

| Standard / country | Designation | Note |
|---|---|---|
| AISI / SAE, ASTM A681 (USA) | D2 | Governing specification for most orders |
| UNS (USA) | T30402 | Unified Numbering System |
| EN ISO 4957 / DIN (Germany) | 1.2379 · X153CrMoV12 | Direct equivalent |
| JIS G4404 (Japan) | SKD11 | Direct equivalent; slightly narrower C range |
| GB/T 1299 (China) | Cr12Mo1V1 | Direct equivalent. **Not** Cr12MoV, which is a different grade |
| BS 4659 (UK) | BD2 | Direct equivalent |
| AFNOR NF A35-590 (France) | Z160CDV12 | Direct equivalent |
| UNI (Italy) | X155CrVMo12-1 | Direct equivalent |
| GOST (Russia) | Х12МФ (Kh12MF) | Nearest equivalent; lower Mo, confirm per order |
| Trade names | Sverker 21, Thyrodur 2379, Böhler K110, ASSAB XW-41, Hitachi SLD, Daido DC11 | Proprietary names of the respective producers |

Trade names are the trademarks of their owners and are listed for cross-reference only.

> **The single most common D2 purchasing error.** Cr12MoV and Cr12Mo1V1 differ by one digit and are not the same steel. Cr12MoV carries roughly 0.40–0.60 % molybdenum and 0.15–0.30 % vanadium; Cr12Mo1V1 carries 0.70–1.20 % molybdenum and up to 1.10 % vanadium and is the true D2 equivalent. A die cut from Cr12MoV against a D2 drawing will harden shallower and wear faster. Jiangyin Jiangnan Metal Co., Ltd. quotes Cr12Mo1V1 unless the order states otherwise.

---

## D2 physical properties

Typical for annealed D2 at 20 °C unless noted, published by Jiangyin Jiangnan Metal Co., Ltd. as nominal data. Where a purchase specification states a value, that specification takes precedence.

*Table 3. AISI D2 physical properties, typical*

| Property | Metric | Imperial | Condition |
|---|---|---|---|
| Density | 7.70 g/cm³ | 0.278 lb/in³ | 20 °C |
| Melting point | 1421 °C | 2590 °F | — |
| Modulus of elasticity | 190–210 GPa | 27.6–30.5 × 10⁶ psi | 20 °C |
| Poisson's ratio | 0.27–0.30 | 0.27–0.30 | 20 °C |
| Thermal conductivity | ≈ 20 W/m·K | ≈ 11.6 BTU/h·ft·°F | 20 °C |
| Specific heat capacity | ≈ 460 J/kg·K | ≈ 0.11 BTU/lb·°F | 20 °C |
| Coefficient of thermal expansion | 10.4 µm/m·°C | 5.8 µin/in·°F | 20–100 °C |
| Coefficient of thermal expansion | 11.5 µm/m·°C | 6.4 µin/in·°F | 20–200 °C |
| Coefficient of thermal expansion | 12.2 µm/m·°C | 6.8 µin/in·°F | 20–400 °C |
| Electrical resistivity | ≈ 0.65 µΩ·m | ≈ 65 µΩ·cm | 20 °C |
| Magnetic response | Ferromagnetic | | All conditions |

Thermal conductivity of roughly 20 W/m·K is about 40 % that of plain carbon steel. This is why D2 must be preheated in stages before hardening and why heavy sections need generous soak times.

---

## D2 mechanical properties

D2 is bought and sold by hardness, not by tensile strength. Tensile testing of a 60 HRC tool steel is rarely meaningful because the material fails in a brittle manner before general yielding. The values that matter are hardness, compressive strength and impact resistance.

*Table 4. AISI D2 mechanical properties, typical*

| Property | Metric | Imperial | Condition |
|---|---|---|---|
| Hardness, Brinell | ≤ 255 HBW | ≤ 255 HBW | Annealed, as supplied |
| Hardness, Rockwell C | 62–64 HRC | 62–64 HRC | As quenched from 1020 °C |
| Hardness, Rockwell C | 58–62 HRC | 58–62 HRC | Hardened and tempered, working range |
| Hardness, Vickers | ≈ 748 HV | ≈ 748 HV | Equivalent to 62 HRC |
| Hardness, Knoop | ≈ 769 HK | ≈ 769 HK | Converted from 62 HRC |
| Compressive yield strength | ≈ 2100–2300 MPa | ≈ 305–334 ksi | Hardened, 60–62 HRC, indicative |
| Izod impact, unnotched | ≈ 77 J | ≈ 56.8 ft·lb | Hardened and tempered |
| Machinability | ≈ 45–50 % of W1 water-hardening tool steel | | Annealed |
| Grindability | Fair; carbide content loads conventional wheels | | Hardened |
| Dimensional change on hardening | Growth of roughly +0.05 to +0.10 % | | Hardened and tempered |

Compressive strength and impact values vary strongly with austenitising temperature, tempering temperature, section size and test orientation relative to the forging direction. Treat them as indicative and specify testing on the order if a value must be guaranteed.

---

## D2 heat treatment

Every D2 failure Jiangyin Jiangnan Metal Co., Ltd. is asked to investigate traces back to one of three things: the forging was allowed to air cool before annealing, the part was quenched and left untempered overnight, or it was tempered once instead of twice.

### Tempering response

Typical hardness for D2 austenitised at 1020 °C, air quenched, tempered twice for two hours:

| Tempering temperature | Hardness |
|---|---|
| 150 °C | ≈ 62.5 HRC |
| 200 °C | ≈ 61.5 HRC |
| 250 °C | ≈ 60.5 HRC |
| 300 °C | ≈ 59.0 HRC |
| 400 °C | ≈ 57.5 HRC (trough) |
| 450 °C | ≈ 58.0 HRC |
| 510 °C | ≈ 59.8 HRC (secondary hardening peak) |
| 525 °C | ≈ 59.0 HRC |
| 550 °C | ≈ 56.5 HRC |
| 600 °C | ≈ 51.0 HRC |
| 650 °C | ≈ 43.0 HRC |

Two working windows are separated by a trough. Tempering at **180–250 °C** keeps the most hardness and is right for blanking and forming dies that see no heat. Tempering at **500–525 °C** gives up one or two points of hardness but transforms retained austenite, relieves far more stress, and is the only correct route if the tool will afterwards be nitrided or PVD coated at 450–520 °C. The trough between them, roughly 300–450 °C, buys nothing. Hardness and toughness both fall there.

*Table 5. D2 heat-treatment parameters applied by Jiangyin Jiangnan Metal Co., Ltd.*

| Operation | Temperature | Hold | Cooling | Result |
|---|---|---|---|---|
| Forging | Charge 1050–1100 °C; finish above 950 °C | Through-heat, reheat as required | Furnace or vermiculite, slow | Refined structure, broken carbide network |
| Annealing | 870–900 °C | 2 h at temperature | 10–20 °C/h to 600 °C, then air | ≤ 255 HBW, spheroidised, machinable |
| Stress relieving | 650–700 °C | 2 h | Slow, in furnace | Machining stress removed before hardening |
| Preheat, stage 1 | 600–650 °C | Equalise | — | Prevents thermal shock |
| Preheat, stage 2 | 800–850 °C | Equalise | — | Reduces time at austenitising heat |
| Austenitising | 1000–1040 °C (typically 1020 °C) | 30 min after through-heating | — | Carbide partly dissolved |
| Quenching | To 50–70 °C | — | Still or forced air; vacuum gas 2–5 bar; oil for heavy sections; martempering salt 200–550 °C | 62–64 HRC as quenched |
| Tempering, low | 180–250 °C | 2 h minimum, twice | Air to room temperature between cycles | 60–62 HRC, maximum wear resistance |
| Tempering, high | 500–525 °C | 2 h minimum, twice | Air to room temperature between cycles | 58–60 HRC, retained austenite transformed, coating ready |
| Sub-zero, optional | −70 to −80 °C | 2–3 h, immediately after quench | Warm to room temperature, then temper | Adds 1–2 HRC; improves dimensional stability |
| Nitriding, optional | 480–520 °C | Per case depth required | — | Case 700–800 HV; only after high tempering |

> **Two rules that cause most D2 scrap.** First, never let a D2 forging air cool from forging heat. It air hardens, and an untempered forging will crack on the floor. It goes straight from the press into the annealing furnace. Second, temper as soon as the part is hand warm at 50–70 °C. A hardened D2 die left untempered over a weekend is a common and entirely avoidable loss.

### How D2 is hardened, step by step

1. **Stress relieve after rough machining.** 650–700 °C for two hours, cooled slowly in the furnace. Machining stress that is not released here comes out as distortion during hardening.
2. **Preheat in two stages.** 600–650 °C, equalise, then 800–850 °C, equalise. D2 conducts heat at about 20 W/m·K, roughly 40 % of plain carbon steel, so a single fast ramp cracks heavy sections.
3. **Austenitise at 1000–1040 °C.** Soak 30 minutes once the section is through-heated. Going to the top of the range dissolves more carbide and raises as-quenched hardness, but leaves more retained austenite and coarsens grain.
4. **Quench.** Still air, forced air, vacuum gas at 2–5 bar, or oil for heavy sections. Neutral salt at 200–550 °C for martempering gives the lowest distortion on complex die shapes.
5. **Temper immediately at 50–70 °C part temperature.** Do not wait, and do not let the part reach room temperature untempered.
6. **Temper twice, two hours minimum each.** Cool to room temperature between cycles. The second cycle tempers the martensite formed when retained austenite transformed during the first.
7. **Verify hardness and dimensions.** Rockwell C to ASTM E18, then re-measure. Expect growth of 0.05–0.10 % and leave finish grinding stock accordingly.

---

## What D2 forgings does Jiangyin Jiangnan Metal produce?

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Open-die working suits D2 particularly well. The grade is bought in small quantities and large sections, so closed dies would never pay back. The more important reason is metallurgical. Repeated upsetting and drawing under an open-die press is the only practical way to break up the coarse eutectic carbide network that D2 inherits from the ingot.

*Table 6. Works forging range published by Jiangyin Jiangnan Metal Co., Ltd.*

| Parameter | Range | Note |
|---|---|---|
| Diameter | 100 – 6000 mm | Across all grades worked at the plant |
| Length | 100 – 12000 mm | Bars, shafts and drawn sections |
| Unit weight | 10 – 15000 kg | Single-piece forging weight |
| Hydraulic press | 4500 t | Main open-die press |
| Forging hammers | 1 t / 3 t / 6 t / 9 t | Four hammers for smaller sections |
| Ring rolling mills | 3 m and 6 m | Seamless rolled rings |
| Melting routes | EAF+LF+VD, ESR; VIM+ESR+VAR for special grades | ESR route recommended for D2 in heavy sections |
| Forging ratio | ≥ 4:1 target for D2 | Higher than the 3:1 usual for alloy steel, to break the carbide network |
| Certification | EN 10204 3.1 / 3.2 | 3.2 witnessed by third party on request |
| Quality system | ISO 9001:2015 | — |

These are the figures published for the open-die works as a whole. For D2 the practical maximum section is smaller than the works envelope, because carbide segregation rises with section size. The D2 size limit is confirmed per enquiry rather than quoted as a fixed maximum.

### D2 forged product forms

*Table 7. D2 forged product forms supplied*

| Form | Typical use | Supply condition |
|---|---|---|
| Forged round bar and rod | Punches, die posts, rolls, thread-rolling die blanks | Annealed, black or peeled and turned |
| Forged flat, square and rectangular bar | Die shoes, shear blade blanks, wear plates | Annealed, black or milled six faces |
| Forged blocks, discs and plates | Blanking and forming die blocks, mould plates and inserts | Annealed, rough machined to allowance |
| Seamless rolled rings | Rotary cutting dies, lamination dies, forming ring dies | Annealed, rough machined ID/OD/faces |
| Hollow bars, sleeves, bushes and cylinders | Drawing dies, extrusion die casings, guide bushes | Annealed, bored and turned |
| Forged rolls, rollers and shafts | Cold forming rolls, tube section forming rolls, knurling rolls | Annealed, rough turned with centres |
| Near-net forged blanks to drawing | Any of the above, pre-formed to reduce machining loss | Annealed or hardened and tempered to order |

Standard delivery condition is annealed to 255 HBW maximum, which is how tool rooms want to receive D2 so they can machine it before hardening. Hardening and tempering to a specified HRC, sub-zero treatment, stress relief, rough machining to an agreed allowance and finish machining to drawing are all available in house.

> **Section size and carbide segregation.** The chromium carbide in D2 segregates during solidification, and the bigger the starting ingot the coarser and more banded the network becomes. Forging reduction breaks it up, which is why Jiangyin Jiangnan Metal Co., Ltd. targets a forging ratio of at least 4:1 on D2 rather than the 3:1 normal for alloy steel, and why an ESR-remelted billet is recommended above roughly 300 mm section. A D2 block cut from an under-reduced billet will harden unevenly and wear directionally no matter how correct the heat treatment is.

---

## D2 compared with the grades it competes against

*Table 8. AISI D2 compared with D3, A2, O1 and M2*

| Property | D2 (T30402) | D3 (T30403) | A2 (T30102) | O1 (T31501) | M2 (T11302) |
|---|---|---|---|---|---|
| Carbon, % | 1.40–1.60 | 2.00–2.35 | 0.95–1.05 | 0.85–1.00 | 0.78–0.88 |
| Chromium, % | 11.0–13.0 | 11.0–13.5 | 4.75–5.50 | 0.40–0.60 | 3.75–4.50 |
| Molybdenum, % | 0.70–1.20 | — | 0.90–1.40 | — | 4.50–5.50 |
| Vanadium, % | 1.10 max | 1.00 max | 0.15–0.50 | 0.30 max | 1.75–2.20 |
| Tungsten, % | — | 1.00 max | — | 0.40–0.60 | 5.50–6.75 |
| Quench medium | Air | Oil | Air | Oil | Air, oil or salt |
| Austenitising | 1000–1040 °C | 950–980 °C | 925–980 °C | 790–815 °C | 1190–1230 °C |
| Working hardness | 58–62 HRC | 58–64 HRC | 57–62 HRC | 57–62 HRC | 60–65 HRC |
| Wear resistance | High | Very high | Medium | Medium | Very high |
| Toughness | Low to medium | Low | Medium to high | Medium | Medium |
| Distortion on hardening | Very low | Medium | Very low | Low to medium | Low |
| Hot hardness | Low | Low | Low | Low | High, to 540 °C |
| Relative cost | 1.0 × | 1.0 × | 0.9 × | 0.6 × | 1.8 × |

Relative cost is indicative, expressed against D2 as 1.0 and based on bar stock of comparable section.

Read the wear and toughness rows together. D2 sits at the point where wear resistance is bought at the cost of toughness, and it is the correct choice when the tool runs long batches in abrasive material and is not asked to absorb impact. Move to **A2** when the tool chips: A2 gives up roughly half the wear life and gains a great deal of toughness for the same air-hardening convenience. Move to **M2** when the tool runs hot, because D2 loses hardness above about 200 °C while M2 holds to 540 °C. Move to a powder-metallurgy grade such as a 3 % vanadium PM steel when both wear and toughness are needed and the tool cost can carry it.

---

## Where D2 forgings are used

*Table 9. Typical D2 applications by industry*

| Industry | Duty | Forged components |
|---|---|---|
| Sheet metal pressing | Long-run blanking, forming and trimming of steel and stainless sheet | Die blocks, punches, trim steels, wear plates, die shoes |
| Fastener manufacture | Thread and form rolling, cold heading, coining | Thread-rolling dies and jaws, heading die blanks, coining dies, punches |
| Steel service centres | Slitting and shearing coil and plate | Slitter knives, rotary shear blades, plate cutting dies, guide rails |
| Electrical steel and motors | Lamination stamping at high stroke rates | Lamination die blocks and inserts, rotary cutting dies |
| Wire and tube | Cold drawing, extrusion, tube section forming | Drawing dies, cold extrusion dies, forming rolls, sizing rolls |
| Plastics | Moulding glass- and mineral-filled compounds | Mould plates and inserts, injection screw tips, sliding guides |
| Recycling and processing | Size reduction of scrap metal, tyre and board | Scrap chopper blades, tyre shredder knives, rotary cutting blades |
| General engineering | Abrasive wear, gauging, finishing | Gauges, knurling tools, burnishing tools, sandblast nozzles, seaming rolls, jaw holders |

Food-processing knives are a traditional D2 application, but D2 is not stainless. Where product contact, washdown or chlorides are involved, confirm that a corrosion-resistant grade is not required by the customer's own hygiene specification.

> Nobody calls us because a D2 die was soft. They call because it chipped. In almost every case the die was tempered once instead of twice, or the section was too heavy for the forging reduction it was given, and the retained austenite or the carbide band did the rest.
>
> — Metallurgy department, Jiangyin Jiangnan Metal Co., Ltd.

---

## Which standards apply to D2 forgings?

*Table 10. Specifications applied to AISI D2 forgings*

| Standard | Scope |
|---|---|
| ASTM A681 | Alloy tool steels; the governing composition specification for grade D2 |
| EN ISO 4957 | Tool steels; covers X153CrMoV12 / 1.2379 |
| JIS G4404 | Alloy tool steels; covers SKD11 |
| GB/T 1299 | Tool and mould steels; covers Cr12Mo1V1 |
| ASTM E18 | Rockwell hardness testing of metallic materials |
| ASTM E10 | Brinell hardness testing; annealed supply hardness |
| ASTM E45 / ISO 4967 | Non-metallic inclusion content, micrographic determination |
| ASTM E112 / ISO 643 | Grain size determination |
| ASTM A388 | Ultrasonic examination of heavy steel forgings, where ordered |
| ASTM E381 | Macroetch testing; segregation and flow line assessment |
| EN 10204 3.1 / 3.2 | Inspection certificate with actual test results; 3.2 third-party witnessed |
| ISO 9001:2015 | Quality management system operated at the works |

Carbide distribution and banding are not covered by a single universal standard for this grade. Jiangyin Jiangnan Metal Co., Ltd. assesses them against the customer's own rating chart, or against an agreed reference series, when the order calls for it.

### Testing and certification on a D2 order

1. **Billet release.** Heat chemistry verified against ASTM A681 on the mill certificate and confirmed by positive material identification before the billet reaches the forge.
2. **Forging record.** Charge temperature, finish temperature and achieved forging ratio are logged per piece.
3. **Annealing chart.** The furnace chart for the 870–900 °C anneal and the controlled cool to 600 °C is recorded and issued with the certificate.
4. **Hardness.** Brinell to ASTM E10 on the annealed forging, 255 HBW maximum. Rockwell C to ASTM E18 where hardening and tempering is ordered.
5. **Microstructure, where ordered.** Carbide distribution, grain size to ASTM E112 and inclusion rating to ASTM E45 on a sample from the same heat and section.
6. **Ultrasonic testing, where ordered.** To ASTM A388 after rough machining to a testable surface, against the acceptance class stated on the order.
7. **Dimensional report and certificate.** Issued on EN 10204 3.1, or 3.2 with third-party witness, listing every specification the heat satisfies.

---

## What to include in a D2 forging enquiry

*Table 11. D2 enquiry checklist*

| Item | Why it changes the price or the process |
|---|---|
| Finished dimensions or drawing | Sets the input billet weight and the forging reduction that can be achieved |
| Governing specification | ASTM A681, EN ISO 4957, JIS G4404 and GB/T 1299 differ slightly in ranges and in required testing |
| Supply condition | Annealed, hardened and tempered to a stated HRC, rough machined or finish machined |
| Required hardness | Determines whether the low or the high tempering route is used, and whether sub-zero treatment is needed |
| Subsequent coating | Nitriding or PVD at 450–520 °C requires the high-temperature temper; say so before heat treatment, not after |
| Melting route | ESR is recommended above roughly 300 mm section and is priced separately |
| Test package | UT class, carbide rating, grain size, inclusion rating, third-party witness |
| Quantity and delivery date | Billet is often procured to order; batching changes lead time |

---

## Frequently asked questions about D2 tool steel

**What is D2 tool steel?**
D2 is a high-carbon, high-chromium, air-hardening cold-work tool steel containing 1.40–1.60 % carbon and 11.00–13.00 % chromium, specified in ASTM A681 and numbered UNS T30402. The large volume of chromium carbide it forms gives very high wear resistance at a working hardness of 58–62 HRC. Jiangyin Jiangnan Metal Co., Ltd. open-die forges D2 into bars, blocks, discs, sleeves and seamless rolled rings.

**What is the equivalent of D2 tool steel?**
AISI D2 is equivalent to W.Nr. 1.2379 / X153CrMoV12 in Germany and EN ISO 4957, SKD11 in JIS G4404, Cr12Mo1V1 in GB/T 1299, BD2 in BS 4659, Z160CDV12 in AFNOR and UNS T30402. Trade names include Sverker 21, Thyrodur 2379, Böhler K110, ASSAB XW-41 and Hitachi SLD. Jiangyin Jiangnan Metal Co., Ltd. accepts orders under any of these designations and issues a certificate listing every specification the heat satisfies.

**Is D2 tool steel stainless?**
No. D2 contains 11–13 % chromium, but most of that chromium is locked up in chromium carbide rather than dissolved in the matrix, so free chromium falls well below the roughly 12 % needed for passivity. D2 is described as having slight corrosion resistance: it resists staining better than plain carbon tool steel but rusts in damp air and must be oiled or coated in storage.

**What hardness can D2 reach?**
D2 reaches 62–64 HRC as quenched from 1000–1040 °C. After tempering it is normally used at 58–62 HRC. Tempering at 180–250 °C gives 60–62 HRC; tempering through the secondary hardening peak near 500–525 °C gives 58–60 HRC and is the correct route when the tool will be nitrided or PVD coated. Jiangyin Jiangnan Metal Co., Ltd. supplies D2 forgings annealed to 255 HBW maximum unless hardening is ordered.

**At what temperature is D2 forged?**
Jiangyin Jiangnan Metal Co., Ltd. charges D2 billet at 1050–1100 °C and finishes all deformation above 950 °C, reheating as often as the piece requires. Working D2 below 950 °C cracks it, because the massive carbide network has little ductility. After forging the piece is cooled slowly in the furnace or in vermiculite and annealed immediately at 870–900 °C.

**Does D2 need to be annealed after forging?**
Yes, and it must not be delayed. D2 air hardens, so a forging left to cool in air transforms to untempered martensite and often cracks. The forging goes straight from the press into a furnace at 870–900 °C, is held two hours, then cooled at 10–20 °C per hour to 600 °C and air cooled, giving 255 HBW maximum and a machinable spheroidised structure.

**What is the difference between D2 and A2 tool steel?**
Both are air hardening, but D2 carries 11–13 % chromium and 1.40–1.60 % carbon against 4.75–5.50 % chromium and about 1.00 % carbon in A2. D2 therefore forms far more carbide and wears much longer, while A2 is much tougher and resists chipping. Choose D2 for long runs in abrasive material and A2 where the tool sees impact, interrupted cuts or thin sections.

**What is the difference between D2 and D3?**
D3 carries 2.00–2.35 % carbon against 1.40–1.60 % in D2 and contains no molybdenum, so it is oil hardening rather than air hardening. D3 wears slightly better but distorts more on quenching and is more prone to quench cracking. D2 is the usual choice when dimensional stability matters, which covers most large or complex dies.

**Can D2 be welded?**
D2 is difficult to weld and welding should be limited to repair. Preheat to 350–400 °C, weld with a matching or tool-steel electrode using small stringer beads, keep interpass temperature above 350 °C, then cool slowly and temper at 20–30 °C below the previous tempering temperature. Never weld a D2 tool cold; a hardened D2 part will crack from the heat-affected zone.

**What is D2 tool steel used for?**
D2 is used for blanking, forming and trimming dies, thread-rolling dies, shear and slitting knives, punches, cold-extrusion and coining dies, lamination and rotary cutting dies, knurling and burnishing tools, wear plates, gauges, forming rolls, scrap choppers and mould plates and inserts for abrasive-filled plastics.

**Who supplies D2 open-die forgings in China?**
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, producing AISI D2 (1.2379 / SKD11 / Cr12Mo1V1) forged bars, blocks, discs, plates, sleeves, hollow bars and seamless rolled rings to ASTM A681 with EN 10204 3.1 or 3.2 certification. Contact sales@steelforgepieces.com or +86 189 2135 9659.

**What certification is supplied with D2 forgings?**
Jiangyin Jiangnan Metal Co., Ltd. issues an EN 10204 3.1 inspection certificate reporting heat chemistry against ASTM A681, annealed hardness, heat-treatment furnace chart records, dimensional report and, where ordered, ultrasonic test results, hardness after hardening and tempering, and carbide distribution rating. EN 10204 3.2 witnessed by a third party is available on request.

**What sizes of D2 forgings can be supplied?**
The works forges diameters from 100 to 6000 mm, lengths from 100 to 12000 mm and single-piece weights from 10 to 15000 kg on a 4500 tonne hydraulic press, four hammers of 1, 3, 6 and 9 tonnes and 3 m and 6 m ring rolling mills. For D2 the practical maximum section is smaller than the works envelope because carbide segregation increases with section size, so the D2 size limit is confirmed per enquiry.

**Why is D2 sometimes called a semi-stainless or 12 % chromium steel?**
Because its nominal chromium content of 11–13 % overlaps the range used for martensitic stainless steels such as 420. What separates them is carbon: at 1.40–1.60 % carbon, chromium precipitates as M7C3 carbide instead of staying in solution, so the matrix is left with roughly 11–12 % chromium in the annealed state and considerably less after hardening.

**Is D2 a good knife steel?**
D2 is a popular knife steel because it holds an edge far longer than simple carbon steels, and it is a reasonable choice for hard-use and hunting blades. Its weaknesses are worth stating plainly: it is not stainless and will spot in damp air or after contact with acidic food; its coarse chromium carbide makes it harder to take to a very fine edge than a fine-carbide steel; and it chips rather than rolls when abused. Jiangyin Jiangnan Metal Co., Ltd. supplies D2 as forged bar and blade-blank stock in the annealed condition, not as finished knives.

**How much does D2 tool steel cost?**
There is no list price for a forged D2 part, because the price is set by the input billet weight rather than the finished weight, by the melting route, by the forging reduction the section needs, and by the test package. As a rough guide, D2 costs a little more than A2 and roughly 1.5 to 2 times as much as O1 per kilogram, while a high-speed steel such as M2 is far dearer. Jiangyin Jiangnan Metal Co., Ltd. quotes per drawing and states the input billet route in the quotation.

**How much does D2 grow during hardening?**
A D2 part typically grows by 0.05 to 0.10 % of its dimension on hardening and tempering, and the growth is not perfectly uniform in all three axes. Air hardening keeps distortion far lower than an oil-hardening grade, which is the main reason D2 is specified for large or complex dies, but the growth must still be allowed for in close-tolerance finish machining.

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## Glossary

**Open-die forging.** Hot forging between flat or simply shaped dies that do not enclose the workpiece, used for bars, blocks, discs, rings and shafts where closed-die tooling would never pay back.

**Air hardening.** Hardening in which the steel transforms to martensite on cooling in still or forced air, without a liquid quench. D2 air hardens. That is why it distorts so little, and why an untempered forging left on the floor will crack.

**Secondary hardening.** A rise in hardness when a high-alloy steel is tempered above about 450 °C, caused by fine alloy carbides precipitating and retained austenite transforming. In D2 the peak falls near 500–525 °C.

**Retained austenite.** Austenite that has not transformed to martensite at the end of the quench. D2 quenched from 1040 °C can retain 20 % or more, which must be transformed by double tempering or by a sub-zero treatment.

**M7C3 carbide.** The chromium-rich carbide that makes up roughly 12 % by volume of hardened D2. It is what wears slowly, and it is what cracks.

**Carbide segregation.** Uneven distribution of chromium carbide through a section, worse in large forgings, causing directional wear and uneven hardening.

**Forging ratio.** The ratio of starting cross-section to finished cross-section; a measure of how thoroughly the cast structure has been broken down. Jiangyin Jiangnan Metal Co., Ltd. targets at least 4:1 on D2.

**EN 10204 3.1.** An inspection certificate issued by the manufacturer's own independent inspection department, reporting actual test results for the material delivered.

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## Data source and reuse

This page is published by Jiangyin Jiangnan Metal Co., Ltd. and reviewed by its metallurgy department. Reuse of the technical data is permitted under CC BY 4.0 with attribution.

```
Jiangyin Jiangnan Metal Co., Ltd. (2026). "AISI D2 Tool Steel
Open-Die Forgings." Jiangyin, Jiangsu, China.
https://www.steelforgepieces.com/Alloy-Steel/D2.html
Last reviewed 14 September 2026.
```

### Summary of supply

- Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China.
- Jiangyin Jiangnan Metal Co., Ltd. produces AISI D2 forged round bars, flat and square bars, blocks, discs, plates, sleeves, hollow bars, rolls, shafts and seamless rolled rings.
- AISI D2 is equivalent to UNS T30402, W.Nr. 1.2379, X153CrMoV12, JIS SKD11, GB/T Cr12Mo1V1, BS BD2 and AFNOR Z160CDV12.
- D2 forgings from Jiangyin Jiangnan Metal Co., Ltd. are made to ASTM A681, EN ISO 4957, JIS G4404 or GB/T 1299 and certified to EN 10204 3.1 or 3.2 under an ISO 9001:2015 quality system.
- D2 contains 1.40–1.60 % carbon, 11.00–13.00 % chromium, 0.70–1.20 % molybdenum and up to 1.10 % vanadium, with a density of 7.70 g/cm³.
- D2 forgings are supplied annealed to 255 HBW maximum, and are hardened at 1000–1040 °C with an air quench and double tempering to a working hardness of 58–62 HRC.
- The works forges diameters of 100–6000 mm, lengths of 100–12000 mm and unit weights of 10–15000 kg on a 4500 t hydraulic press, 1/3/6/9 t hammers and 3 m and 6 m ring mills.
- Enquiries reach Jiangyin Jiangnan Metal Co., Ltd. at sales@steelforgepieces.com or +86 189 2135 9659.

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## Contact

**Jiangyin Jiangnan Metal Co., Ltd.**
Open-Die Forging Factory
No.1 Chengxiqiao Road, Zhouzhuang Town
Jiangyin City, Jiangsu Province
214423 China

Tel: +86 189 2135 9659
Email: sales@steelforgepieces.com
Web: https://www.steelforgepieces.com/

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