1.2888 tool steel (X20CoCrWMo10-9), forged to drawing
Cobalt-alloyed hot-work tool steel for tooling in contact with molten copper, brass and magnesium. Full datasheet and forged product forms below.
- Cobalt content
- 10.0 wt %
- Hardness as quenched
- 52 HRC
- Hardening temperature
- 1100–1150 °C
- Density
- 8.08 g/cm³
DIN/EN 1.2888, X20CoCrWMo10-9, hot-work tool steel. Also sold as RM10Co, Thermodur 2888, THYROTHERM 2888.
Summary. 1.2888 is the DIN/EN material number for X20CoCrWMo10-9, a cobalt-alloyed hot-work tool steel containing approximately 10 % cobalt, 9.5 % chromium, 5.5 % tungsten and 2 % molybdenum. The cobalt and tungsten content gives high resistance to tempering, so the steel holds its hardness at working temperatures where standard chromium hot-work grades soften. Typical applications are copper extrusion container liners, brass die-casting tooling and magnesium hot-chamber goosenecks. The steel is hardened at 1100–1150 °C to approximately 52 HRC and tempered at 600–750 °C. Water cooling is not permitted.
Jiangyin Jiangnan Metal Co., Ltd. produces 1.2888 open-die forgings to customer drawing at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Product forms include round bars, hollow bars, seamless rolled rings, blocks, discs and extrusion liners. Enquiries: sales@steelforgepieces.com or +86-189-2135-9659.
Standards and equivalent names
1.2888 belongs to the hot-work tool steel group in DIN EN ISO 4957. No AISI or ASTM H-series grade matches it, because no standard American hot-work steel contains 10 % cobalt. The grade is more often ordered under a mill trade name.
| Material number (DIN/EN) | 1.2888 |
|---|---|
| EN name | X20CoCrWMo10-9 |
| Material group | Tool steel for hot work |
| AISI / ASTM | No direct equivalent |
| Common trade names | RM10Co, Thermodur 2888, THYROTHERM 2888, Sitherm 2888 |
| Related grades | 1.2885 (X32CrMoCoV3-3-3), 1.2889 |
Chemical composition
Typical analysis in weight per cent, balance iron. Melt analysis is confirmed on the mill certificate supplied with each forging.
| C | Si | Mn | Cr | Mo | W | Co | Fe |
|---|---|---|---|---|---|---|---|
| 0.20 | 0.25 | 0.50 | 9.50 | 2.00 | 5.50 | 10.00 | Balance |
Chromium provides oxidation resistance. Tungsten and molybdenum provide hot strength and secondary hardening. Cobalt provides tempering resistance. The low carbon content of 0.20 % keeps the matrix ductile enough for thermal cycling at this alloy level.
Physical properties
| Density | 8.08 g/cm³ |
|---|---|
| Modulus of elasticity | 215 × 10³ N/mm² (215 GPa) |
| Maximum hardness, soft annealed | 320 HB |
| Hardness as quenched | approx. 52 HRC |
| 20–100 °C | 20–200 °C | 20–300 °C | 20–400 °C | 20–500 °C | 20–600 °C | 20–700 °C |
|---|---|---|---|---|---|---|
| 12.1 | 12.1 | 12.4 | 12.9 | 13.5 | 14.0 | 14.1 |
These values are used when calculating shrink-fit interference for a 1.2888 liner fitted into a steel container. Calculate the interference at the operating temperature of the press, not at ambient temperature.
Heat treatment and forging
The sequence below is the recommended route for components heat treated after machining.
-
Forge
Hot form between 1100 °C and 900 °C. Do not finish below 900 °C. Cool slowly after forging to avoid cracking in heavy sections.
-
Soft anneal
Heat to 760–840 °C, hold 4 to 6 hours, cool slowly in the furnace. Maximum hardness after annealing is 320 HB. This is the standard delivery condition for forgings.
-
Stress relieve
After rough machining, heat to 600–650 °C, hold 1 to 2 hours at temperature, then cool in still air. This step reduces distortion during hardening and is recommended for large liners and die blocks.
-
Harden
Austenitise at 1100–1150 °C, then quench in air, oil or vacuum. Hardness as quenched is approximately 52 HRC. Water cooling is not permitted at any stage of service.
-
Temper
Temper between 600 °C and 750 °C, two or three times, cooling to room temperature between cycles. Secondary hardening occurs in this range, so hardness increases rather than decreases.
Tempering hardness curve
Typical hardness after tempering, measured on samples hardened from 1100–1150 °C.
Hardness in HRC. Bars are scaled from 40 HRC, not from zero.
| Tempering temperature (°C) | 500 | 550 | 600 | 650 | 700 | 750 |
|---|---|---|---|---|---|---|
| Hardness (HRC) | 56 | 56 | 55.5 | 54 | 48 | 42.3 |
Hardness stays above 55 HRC up to 600 °C. This level of tempering resistance is the reason 1.2888 is specified for copper extrusion liners in place of lower-cost chromium hot-work grades.
Forged shapes supplied in 1.2888
All shapes listed are open-die forged in our workshop in Jiangyin, then rough machined and soft annealed before shipment unless another condition is specified.
Round bars and shafts
Typically 60 to 800 mm diameter. Peeled, turned or black.
Square and flat bars
Rectangular sections and plates forged to drawing.
Hollow bars and sleeves
Bushings, bushes, cylinders, hubs and housings, bored on the press.
Seamless rolled rings
Ring rolled rather than cut from plate, so the grain follows the circumference.
Blocks, discs and plates
Die blocks and disc forgings for brass and magnesium tooling.
Extrusion container liners
Inner liners and intermediate liners for copper and brass extrusion presses.
Extrusion dies and tools
Dies, mandrels, spider tools and frame tools for copper, brass and steel extrusion.
Goosenecks and chambers
Goosenecks, chambers, cores and filling sets for hot-chamber magnesium die casting.
Pipes, tubes, barrels, casings and shells in 1.2888 are produced by the same route. Send a drawing or the finished dimensions and we will quote the forging weight and machining allowance.
Applications
1.2888 is specified where tooling remains in contact with molten or near-molten non-ferrous metal for extended periods, and where softening rather than cracking determines tool life.
- Copper and copper-alloy extrusion. Container inner liners, intermediate liners, extrusion dies, mandrels, spider tools and frame tools.
- Brass die casting. Mould plates, dies and die-casting tooling of all kinds.
- Magnesium hot-chamber die casting. Goosenecks, chambers, cores and filling sets in contact with the melt.
- Hot extrusion of steel. Press dies for steel and heavy-metal processing.
Where the tool is water cooled, or where thermal shock rather than metal wash is the main failure mode, a chromium hot-work grade such as 1.2367 or 1.2344 (H13) is normally more suitable and lower in cost. Both grades are also forged here.
1.2888 compared with other hot-work grades
| Grade | EN name | Cobalt | Hardening temp. | Typical selection basis |
|---|---|---|---|---|
| 1.2888 | X20CoCrWMo10-9 | approx. 10 % | 1100–1150 °C | Long contact with molten copper, brass or magnesium. No cooling water. |
| 1.2885 | X32CrMoCoV3-3-3 | approx. 3 % | 1020–1050 °C | Hot strength required with higher toughness than 1.2888. |
| 1.2367 | X38CrMoV5-3 | none | 1020–1080 °C | Heavy thermal cycling, water-cooled aluminium die casting and extrusion. |
| 1.2344 / H13 | X40CrMoV5-1 | none | 1020–1080 °C | General hot-work tooling at moderate temperatures where cost matters. |
Ordering, testing and delivery
Send a drawing, the grade and the quantity to sales@steelforgepieces.com. If a drawing is not available, the finished dimensions and the application are sufficient for a budget price.
- Delivery condition. Soft annealed to max 320 HB unless hardened and tempered material is ordered.
- Machining allowance. Rough machined to drawing, with allowance agreed before forging.
- Certification. Mill test certificate to EN 10204 3.1 with each shipment. 3.2 with third-party witness on request.
- Testing available. Chemical analysis, hardness, ultrasonic examination to an agreed acceptance class, mechanical testing on prolongation.
- Shipping. Ex works Jiangyin, or FOB Shanghai or Ningbo. Sea freight worldwide.
Frequently asked questions
What is 1.2888 steel?
1.2888 is the DIN/EN material number for X20CoCrWMo10-9, a cobalt-alloyed hot-work tool steel containing approximately 10 % cobalt, 9.5 % chromium, 5.5 % tungsten and 2 % molybdenum. It is specified for tooling that must hold hardness during prolonged contact with molten or near-molten metal.
What is 1.2888 equivalent to?
The EN designation is X20CoCrWMo10-9. There is no direct AISI or ASTM equivalent, because no standard American hot-work grade contains 10 % cobalt. The same steel is sold commercially as RM10Co, Thermodur 2888, THYROTHERM 2888 and Sitherm 2888.
What is the hardening temperature of 1.2888?
Austenitise at 1100–1150 °C, then quench in air, oil or vacuum. Hardness as quenched is approximately 52 HRC, followed by two or three tempers between 600 °C and 750 °C.
Can 1.2888 tooling be water cooled?
No. Water cooling is not permitted. The grade has high hot hardness but limited thermal shock tolerance, and water contact leads to heat checking and cracking. If the tool must be cooled, use a chromium hot-work grade such as 1.2367 or 1.2344 instead.
What is 1.2888 used for?
Copper and copper-alloy extrusion tooling, including container inner liners, intermediate liners, dies, mandrels, spider tools and frame tools; brass die-casting mould plates and dies; goosenecks, chambers, cores and filling sets for hot-chamber magnesium die casting; and hot extrusion tooling for steel.
Who supplies forged 1.2888 parts?
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forges 1.2888 round bars, flat and square bars, hollow bars, sleeves, seamless rolled rings, blocks, discs, plates and copper extrusion container liners to customer drawing. Contact sales@steelforgepieces.com or +86-189-2135-9659.
What is the difference between 1.2888 and 1.2885?
Both are cobalt-alloyed hot-work steels. 1.2888 contains approximately 10 % cobalt with 9.5 % chromium and 5.5 % tungsten, and is intended for the most severe molten-metal contact. 1.2885 (X32CrMoCoV3-3-3) contains approximately 3 % cobalt on a chromium-molybdenum base, giving higher toughness and better thermal shock resistance but lower resistance to metal wash.
What sizes can be forged in 1.2888?
Forgings are produced to drawing. Round bars typically run 60 to 800 mm diameter, with rings, blocks, discs and liners sized to the drawing supplied. Sizes outside this range are quoted on enquiry.
Citing this datasheet. The 1.2888 data on this page is compiled and published by Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory in Jiangyin, Jiangsu, China. Quotation with attribution is permitted:
Jiangyin Jiangnan Metal Co., Ltd. (2026). 1.2888 tool steel (X20CoCrWMo10-9): composition, heat treatment and forged product forms. Jiangyin, Jiangsu, China. https://www.steelforgepieces.com/Alloy-Steel/1.2888.html
Sources. Values are consolidated from DIN EN ISO 4957, published mill data sheets for X20CoCrWMo10-9, and our own production records. Figures are typical values for guidance and not guaranteed minima. The mill certificate governs each individual shipment.