Jiangyin Jiangnan Metal Co., Ltd.
JIS SKD61 Tool Steel (AISI H13 / DIN 1.2344): Properties and Open-Die Forgings
SKD61 is the Japanese Industrial Standard (JIS G 4404) designation for 5% chromium hot-work tool steel, equivalent to AISI H13, DIN 1.2344 (X40CrMoV5-1) and GB 4Cr5MoSiV1. The Cr-Mo-V chemistry gives hot strength, resistance to thermal fatigue and air-hardenability with low distortion, which is why it remains the default grade for die casting dies, aluminium extrusion tooling and hot forging dies. Delivery condition is annealed at 229 HBW maximum. Working condition is quenched and tempered at 38 to 52 HRC.
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory in Jiangyin, Jiangsu Province, China, forges SKD61 into round bars from 80 to 1,200 mm diameter, blocks, discs, rings, seamless rolled rings, hollow bars and sleeves at 20 kg to 20 tonnes per piece, supplied with an EN 10204 3.1 certificate and ultrasonic testing.
- Standard
- JIS G 4404
- Steel type
- 5% Cr-Mo-V hot-work
- Equivalents
- H13, 1.2344, 4Cr5MoSiV1
- Annealed hardness
- 229 HBW max
- Working hardness
- 38 to 52 HRC
- Max service temp.
- 540 to 600 °C
- Density
- 7.80 g/cm³
- Delivery
- Annealed or Q+T
1. What is SKD61 tool steel?
SKD61 is a chromium-molybdenum-vanadium hot-work tool steel defined in JIS G 4404, Alloy tool steels. Nominal composition is 0.40% C, 1.0% Si, 5.0% Cr, 1.2% Mo and 1.0% V.
Chromium and molybdenum carry the hardenability and the resistance to tempering. Vanadium forms fine carbides that stay stable at working temperature and take the abrasive wear. Silicon at around 1% lifts oxidation resistance and hot strength.
What this buys the toolmaker is a steel that hardens in air, so heavy sections come through with little distortion, and that holds hardness through thousands of heating and quenching cycles without cracking. Most other hot-work grades on the market are described by how they differ from SKD61, which makes it the usual starting point when a die material is being chosen.
Standard delivery is soft annealed at 229 HBW maximum, so the block is machined first and hardened afterwards. Large open-die forged blocks and sleeves can also be supplied pre-hardened and tempered to a hardness band, which saves the toolmaker a heat-treatment cycle and the distortion risk that comes with it.
2. SKD61 equivalent grades and cross reference
Every major standard lists this steel under its own designation. The table below is the cross reference printed on our mill certificates.
| Region / standard | Designation | Number |
|---|---|---|
| Japan, JIS G 4404 | SKD61 (SKD-61) | n/a |
| USA, ASTM A681 / AISI | H13 | UNS T20813 |
| Germany, DIN / EN ISO 4957 | X40CrMoV5-1 | 1.2344 |
| China, GB/T 1299 | 4Cr5MoSiV1 | n/a |
| UK, BS 4659 | BH13 | n/a |
| France, AFNOR NF A35-590 | Z40CDV5 | n/a |
| Italy, UNI | X35CrMoV05 KU | n/a |
| Spain, UNE | X40CrMoV5 | F.5318 |
| Sweden, SS | 2242 | n/a |
| Russia, GOST | 4Kh5MFS | n/a |
| India, IS | T35Cr5MoV1 | n/a |
| Common trade names | Orvar Supreme, W302, Thyrotherm 2344, Vidar, DAC | n/a |
3. Chemical composition of SKD61
All three standards are shown together because buyers order against whichever one their drawing cites.
| Element | JIS SKD61JIS G 4404 | AISI H13ASTM A681 | 1.2344EN ISO 4957 |
|---|---|---|---|
| Carbon, C | 0.35 to 0.42 | 0.32 to 0.45 | 0.35 to 0.42 |
| Silicon, Si | 0.80 to 1.20 | 0.80 to 1.20 | 0.80 to 1.20 |
| Manganese, Mn | 0.25 to 0.50 | 0.20 to 0.50 | 0.25 to 0.50 |
| Chromium, Cr | 4.80 to 5.50 | 4.75 to 5.50 | 4.80 to 5.50 |
| Molybdenum, Mo | 1.00 to 1.50 | 1.10 to 1.75 | 1.20 to 1.50 |
| Vanadium, V | 0.80 to 1.15 | 0.80 to 1.20 | 0.85 to 1.15 |
| Phosphorus, P | 0.030 max | 0.030 max | 0.030 max |
| Sulfur, S | 0.030 max | 0.030 max | 0.020 max |
| Nickel, Ni | residual | 0.30 max | residual |
| Copper, Cu | residual | 0.25 max | residual |
| Iron, Fe | Balance | ||
Melt practice and cleanliness
For die casting and other critical tooling we hold P and S well below the standard limits and can supply electro-slag remelted material. The two routes we run are:
- EAF + LF + VD, standard quality, for general hot-work tooling.
- EAF + LF + VD + ESR, premium quality, for large die blocks and critical die casting dies. Lower sulphur, finer and more even carbide distribution, better transverse toughness.
Cleanliness and structure are reported to ASTM E45 Method A for inclusions and ASTM E112 for grain size, and against the annealed-microstructure and segregation charts of the NADCA special quality die steel criteria where the order calls for it.
4. Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density (20 °C) | 7.80 g/cm³ | 0.282 lb/in³ |
| Melting range | 1,427 °C approx. | 2,600 °F approx. |
| Specific heat (20 °C) | 460 J/kg·K | 0.11 Btu/lb·°F |
| Electrical resistivity (20 °C) | 0.52 µΩ·m | 313 Ω·cmil/ft |
| Magnetic | Ferromagnetic in all delivery conditions | |
5. Mechanical properties
Strength figures follow the heat treatment, not the grade on its own. The values below apply to material quenched and tempered into the 44 to 52 HRC range and tested at 20 °C.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, ultimate | 1,200 to 1,590 MPa | 174,000 to 231,000 psi |
| Tensile strength, yield (0.2%) | 1,000 to 1,380 MPa | 145,000 to 200,000 psi |
| Reduction of area | 50% approx. | 50% approx. |
| Modulus of elasticity (20 °C) | 215 GPa | 31,200 ksi |
| Modulus of elasticity (500 °C) | 180 GPa approx. | 26,100 ksi approx. |
| Poisson's ratio | 0.27 to 0.30 | 0.27 to 0.30 |
| Annealed hardness (as delivered) | 229 HBW max | 229 HBW max |
| Hardness after hardening (as quenched) | 52 to 56 HRC | 52 to 56 HRC |
| Typical working hardness | 38 to 52 HRC | 38 to 52 HRC |
6. Thermal properties
Conductivity and expansion both shift with temperature and both feed into heat-checking life, so they are listed against temperature rather than as single figures.
| Property | Value | Temperature |
|---|---|---|
| Coefficient of thermal expansion | 10.4 × 10⁻⁶ /K | 20 to 100 °C |
| Coefficient of thermal expansion | 11.5 × 10⁻⁶ /K | 20 to 400 °C |
| Coefficient of thermal expansion | 12.2 × 10⁻⁶ /K | 20 to 600 °C |
| Thermal conductivity | 24.3 W/m·K | 20 °C |
| Thermal conductivity | 28.6 W/m·K | 215 °C |
| Thermal conductivity | 29.0 W/m·K | 600 °C |
| Maximum continuous service temperature | 540 to 600 °C | n/a |
7. Heat treatment of SKD61
Critical points are Ac1 at about 860 °C and Ms at about 340 °C. SKD61 hardens in air, so any hot-worked or hardened section has to be annealed or tempered before it is allowed to reach room temperature unsupported.
| Operation | Temperature | Practice | Result |
|---|---|---|---|
| Forging / hot working | 1,050 to 1,100 °Cfinish above 900 °C | Heat slowly and soak through. Reduction ratio 3:1 minimum. Cool slowly in furnace or insulation | Cast structure broken down, wrought grain flow |
| Soft annealing | 860 to 900 °C | Soak 2 to 4 h, cool 10 to 20 °C/h to 700 °C in the furnace, then air | 229 HBW max, machinable |
| Stress relieving | 650 to 700 °C | After rough machining. Soak 2 h, cool slowly in furnace to 500 °C | Distortion control before hardening |
| Preheating | 750 to 850 °C | One or two equalising steps before austenitising | Less thermal shock, lower cracking risk |
| Hardening (austenitising) | 1,000 to 1,050 °C | Soak 15 to 30 min after through-heating. Vacuum, controlled atmosphere or salt | Full austenitising, carbides in solution |
| Quenching | to 50 to 70 °C | Pressurised nitrogen in vacuum, air or air blast, hot oil, or salt at 500 to 550 °C for heavy sections | 52 to 56 HRC as quenched |
| Tempering | 550 to 650 °C | Two tempers minimum, 2 h minimum per 25 mm of thickness, full cool to room temperature between tempers | 38 to 52 HRC working hardness |
| Gas nitriding (optional) | 480 to 540 °C | Below the last tempering temperature. Case 0.1 to 0.3 mm | Surface 1,000 to 1,200 HV |
Tempering response
| Tempering temperature | Typical hardness | Typical use |
|---|---|---|
| As quenched | 52 to 56 HRC | Never put into service untempered |
| 550 °C | 50 to 54 HRC | Aluminium extrusion dies, shear blades |
| 570 °C | 48 to 52 HRC | Extrusion tooling, plastic mould inserts |
| 590 °C | 46 to 49 HRC | Aluminium die casting dies |
| 610 °C | 43 to 46 HRC | Large die casting dies, hot forging dies |
| 630 °C | 40 to 43 HRC | Hot forging dies, high-toughness work |
| 650 °C | 36 to 40 HRC | Dummy blocks, containers, holders |
8. SKD61 forged product forms and size range
Everything listed below is open-die forged from ingot or continuous-cast bloom at our Jiangyin works, then annealed, rough machined and inspected before it ships. We work to customer drawings, so the figures below are press and lathe capacity rather than a stock list.
| Product form | Size range | Typical end use |
|---|---|---|
| Round bars, rods, shafts | Ø80 to 1,200 mm, up to 6,000 mm long | Punches, stems, mandrels, insert stock |
| Square and rectangular flat bars | 50 to 800 mm thick, up to 1,500 mm wide, up to 6,000 mm long | Die blocks, bolsters, holders |
| Blocks, discs, plates | Thickness 50 to 800 mm, diameter or width up to 1,500 mm | Die casting die blocks, cavities, inserts |
| Forged rings and seamless rolled rings | OD 200 to 4,000 mm, wall from 40 mm, height to 1,000 mm | Shrink rings, containers, liners |
| Hollow bars, sleeves, bushings, cylinders | OD 100 to 1,500 mm, ID from 50 mm, length to 4,000 mm | Die casting shot sleeves, extrusion liners, barrels |
| Unit weight | 20 kg to 20,000 kg per piece | |
Delivery condition and surface
- Heat treatment: soft annealed at 229 HBW maximum as standard, or quenched and tempered to a specified hardness band, normally held to ±2 HRC.
- Surface: black forged, shot blasted, rough turned or milled with 3 to 6 mm machining allowance, or finish machined to drawing.
- Marking and packing: hard stamped or paint marked with grade, heat number, piece number and order number. Steel band or wooden case for sea freight.
9. Quality, testing and certification
SKD61 forgings are released against the standards below. Tell us on the enquiry which of them your drawing calls for and the inspection is quoted with the material.
| Scope | Standard / method | Status |
|---|---|---|
| Grade chemistry | JIS G 4404, ASTM A681, EN ISO 4957, GB/T 1299 | Standard |
| Mill test certificate | EN 10204 3.1, with ladle and product analysis, hardness, heat-treatment record, dimensions | Standard |
| Ultrasonic examination | ASTM A388, SEP 1921 class on request, EN 10228-3 | Standard on blocks and bars from 100 mm |
| Microcleanliness | ASTM E45 Method A, DIN 50602 | On request |
| Grain size | ASTM E112 | On request |
| Annealed microstructure and segregation | NADCA #207 / #229 acceptance charts | On request, die casting |
| Impact toughness | Charpy, notched or unnotched, per the applicable NADCA grade | On request |
| Hardness survey | HBW or HRC, multi-point on faces and cross-section | Standard on Q+T material |
| Third-party inspection | SGS, BV, TÜV, customer witness | On request |
For die casting dies the reference document is the North American Die Casting Association specification for special quality die steel and heat treatment, originally NADCA #207 and now consolidated into NADCA #229. It defines acceptance grades A through G, with Grade A corresponding to Premium Grade H13 and Grade B to Superior Grade H13. Name the grade and class you need and we melt, forge and certify to it.
10. Applications of SKD61 forgings
Die casting
- Die casting dies, cavities, cover and ejector die halves for aluminium, magnesium and zinc alloys
- Shot sleeves, plungers, gooseneck parts
- Cores, core pins, inserts, slides, ejector pins and nitrided ejectors
Aluminium extrusion
- Extrusion dies, die holders, backers and bolsters
- Extrusion stems, dummy blocks, containers and liners
- Mandrels and shrink rings
Hot forging and hot forming
- Hot forging dies and die inserts, stamping dies, trimming tools
- Forming punches, hot gripper and header dies, bolt and nut dies
- Hot shear blades and scrap shears
- Tools and dies for hollow bodies, screws, nuts, rivets and bolts
Plastics and general tooling
- Plastic mould cavities and dies, worms and cylinders for plastics processing
- Press dies and die inserts, rolls for profiling tools
- Wear-resisting parts, cold heading die casings, severe cold punching tools
11. SKD61 compared with other hot-work grades
| Grade | Equivalent | Against SKD61 | Choose it when |
|---|---|---|---|
| SKD61 | H13, 1.2344 | The reference | General die casting, extrusion and hot forging. Best availability and price |
| SKD6 | H11, 1.2343 | Lower C and V, tougher, slightly less hot wear resistance | Large dies where cracking rather than wear ends tool life |
| SKD7 | H10, 1.2365 | 3% Cr with higher Mo, better temper resistance above 600 °C | Hot extrusion and forging tools running very hot |
| 1.2367 | X38CrMoV5-3 | Higher Mo, better hot strength and thermal fatigue life | High-pressure die casting, long-run aluminium dies |
| SKD61 ESR | Premium / Superior H13 | Same chemistry, cleaner and more isotropic | Critical dies, heavy cross-sections, NADCA grades B to E |
| SKD5 / SKD8 | H21, H19 | Tungsten alloyed, much higher hot hardness, lower toughness | Brass and copper-alloy hot work |
12. Machining, EDM, welding and surface treatment
Machining
Machine in the annealed condition at 229 HBW maximum. Machinability runs at roughly 50 to 60% of a 1% carbon steel benchmark. Use rigid setups, positive rake carbide tooling and plenty of coolant, because SKD61 work-hardens locally wherever a tool is left to rub. Hard machining at 44 to 50 HRC is workable with ceramic or coated carbide tooling, with finishing allowances of 0.3 to 0.5 mm.
EDM
Spark erosion leaves a re-hardened white layer and tensile residual stress on the surface. Stone or polish it off, then temper the tool again 20 to 30 °C below its last tempering temperature. Skipping that step is one of the commonest causes of early heat checking in die casting cavities.
Welding
Repair welding is routine provided the procedure is controlled:
- Grind the defect out completely and check with dye penetrant.
- Preheat the whole tool to 350 to 450 °C and hold that temperature throughout welding.
- Weld with a matching hot-work filler of H13 type, or a tougher buffer layer with an H13 cap.
- Cool slowly, in insulation, to about 80 °C.
- Temper at 20 to 30 °C below the last tempering temperature of the tool, 2 h minimum.
Surface treatment
- Gas or plasma nitriding at 480 to 540 °C gives a case of 0.1 to 0.3 mm at 1,000 to 1,200 HV. This is the usual treatment for extrusion dies and ejector pins. Keep the case thin on die casting cavities, because a thick brittle case brings heat checking on sooner.
- PVD coatings such as CrN and TiAlN are applied below the tempering temperature and are used on extrusion and forming tools.
- Shot peening puts the surface into compression and is worth doing after EDM and on forging dies.
13. How to order: RFQ checklist
Send the following to sales@steelforgepieces.com and a quotation normally comes back within 24 hours:
- Grade and governing standard. SKD61 to JIS G 4404, H13 to ASTM A681, or 1.2344 to EN ISO 4957.
- Product form and dimensions. Drawing, sketch or finished size with the machining allowance you want left on.
- Quantity and piece weight.
- Delivery condition. Annealed, or quenched and tempered to a hardness band.
- Melt route. Standard EAF+LF+VD, or ESR.
- Testing and certification. EN 10204 3.1, UT class, NADCA grade, third-party inspection.
- Destination port and Incoterms, such as FOB Shanghai, CIF or DAP.
14. Frequently asked questions about SKD61
Is SKD61 the same as H13?
The trade treats SKD61 and AISI H13 as equivalent and they are interchangeable in most tooling work, but the two specifications are not written to the same limits. JIS G 4404 holds SKD61 to C 0.35 to 0.42% and Mo 1.00 to 1.50%. ASTM A681 allows H13 a wider band, C 0.32 to 0.45% and Mo 1.10 to 1.75%. Material certified to SKD61 will normally pass as H13. Material certified to H13 can fall outside the SKD61 limits, so state the standard you are ordering to.
What hardness can SKD61 reach?
SKD61 is delivered annealed at 229 HBW maximum. Hardening from 1,000 to 1,050 °C gives about 52 to 56 HRC as quenched. It is then tempered at least twice at 550 to 650 °C down to a working hardness of 38 to 52 HRC. Die casting dies normally run at 44 to 48 HRC, hot forging dies at 40 to 46 HRC and aluminium extrusion tooling at 46 to 50 HRC. Gas nitriding takes the surface to roughly 1,000 to 1,200 HV.
What is the maximum working temperature of SKD61?
About 540 to 600 °C in continuous service. Past roughly 600 °C the tempered martensite softens quickly. Keep the service temperature at least 50 °C below the final tempering temperature. If the process runs hotter than that, specify DIN 1.2367 (X38CrMoV5-3), H10, or a tungsten-alloyed grade such as H21.
What product forms and sizes of SKD61 forgings are available?
Jiangyin Jiangnan Metal Co., Ltd. open-die forges SKD61 as round bars from Ø80 to Ø1,200 mm, square and rectangular blocks, discs and plates, forged and seamless rolled rings up to 4,000 mm OD, and hollow bars, sleeves and cylinders, at unit weights from about 20 kg to 20 tonnes. Material goes out black forged, rough turned, milled or finish machined to drawing.
Why is SKD61 used for die casting dies?
A die casting die is cycled between molten aluminium and die spray thousands of times, so it needs hot strength, toughness and resistance to heat checking at once, and it has to harden in air without distorting. SKD61 covers all four at a price the volumes can carry. It is also the base grade behind Premium Grade and Superior Grade H13 in the NADCA acceptance criteria for special quality die steel, #207, now consolidated into #229.
Can SKD61 be welded?
Yes, with a controlled repair procedure. Preheat the whole tool to 350 to 450 °C and hold it there while welding, use a matching hot-work filler, cool slowly in insulation to about 80 °C, then temper 20 to 30 °C below the last tempering temperature of the tool. Welding without preheat or without a post-weld temper usually cracks the heat-affected zone.
How should SKD61 be forged?
Heat slowly and evenly to 1,050 to 1,100 °C, work with a total reduction of at least 3:1 to 4:1 to break down the cast structure, and stop forging above 900 °C. Cool slowly in the furnace or in insulation, then anneal at 860 to 900 °C straight away. SKD61 hardens in air, so a forging left to cool in still air without annealing will crack.
What certificates are supplied with SKD61 forgings?
An EN 10204 3.1 mill test certificate with heat number, ladle and product chemical analysis, delivery hardness, heat-treatment record and dimensional report. Ultrasonic testing to ASTM A388 or SEP 1921, microcleanliness to ASTM E45, grain size to ASTM E112, annealed microstructure assessment and third-party inspection by SGS, BV or TÜV are quoted on request.
Who supplies open-die forged SKD61 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, manufacturing SKD61 / H13 / 1.2344 forged bars, blocks, rings, sleeves and discs to customer drawings. Call +86-189-2135-9659 or write to sales@steelforgepieces.com.
What is the difference between SKD61 and SKD61 ESR?
The nominal chemistry is identical. ESR material is electro-slag remelted after the first melt, which cuts sulphur and inclusion content, refines and evens out the carbide distribution and lifts transverse impact toughness. ESR is specified for critical die casting dies and for heavy cross-sections where the centre of the block has to perform as well as the surface. For general hot-work tooling, conventionally melted and forged SKD61 does the job.
15. Manufacturer of record
Jiangyin Jiangnan Metal Co., Ltd.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. It manufactures forged bars, blocks, discs, rings, seamless rolled rings, hollow bars and sleeves in JIS SKD61 / AISI H13 / DIN 1.2344 hot-work tool steel, along with carbon steel, alloy steel, stainless steel and nickel alloys, to customer drawings and international standards, and exports worldwide.
- Company Jiangyin Jiangnan Metal Co., Ltd.
- Business Open-die forging factory: forged bars, blocks, rings, sleeves, discs
- Address No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Phone +86-189-2135-9659
- E-mail sales@steelforgepieces.com
- Website www.steelforgepieces.com
- Languages English, Chinese, Japanese
Citing this datasheet. The data on this page is compiled by the engineering department of Jiangyin Jiangnan Metal Co., Ltd. from JIS G 4404, ASTM A681, EN ISO 4957, GB/T 1299 and NADCA #207/#229, and checked against our own mill certificates.
Jiangyin Jiangnan Metal Co., Ltd. "JIS SKD61 (AISI H13 / DIN 1.2344) Hot-Work Tool Steel: Properties, Equivalents and Forged Product Forms." steelforgepieces.com, updated 18 September 2026. https://www.steelforgepieces.com/Alloy-Steel/SKD61.html