Open-die forgings, seamless rolled rings and forged bars to drawing
X20CoCrWMo10-9
Material No. 1.2888. Also written X20CoCrWMo109 and X20CoCrWMo10.9. Trade names RM10Co and SITHERM 2888.
X20CoCrWMo10-9 (DIN material number 1.2888) is a cobalt-alloyed hot work tool steel containing about 10 % cobalt, 9.5 % chromium, 5.5 % tungsten and 2 % molybdenum. It is used for tooling that must stay hard and resist molten metal erosion at high temperature, including copper and brass extrusion dies, extrusion container liners, and goosenecks and chambers for magnesium die casting.
X20CoCrWMo10-9 is the DIN/EN name and 1.2888 is the corresponding German material number. Both refer to the same steel and both appear in enquiries and mill certificates. There is no direct AISI or UNS equivalent for this grade. Its alloy content is higher than that of the AISI H-series hot work steels, so drawings normally call out the DIN designation.
Designations for X20CoCrWMo10-9 hot work tool steel
System
Designation
DIN / EN
X20CoCrWMo10-9
Werkstoff-Nr.
1.2888
AISI / UNS
No direct equivalent
Common trade names
RM10Co, SITHERM 2888
Spelling variants in enquiries
X20CoCrWMo109, X20CoCrWMo10.9, X20 CoCrWMo 10 9, DIN 1.2888
Steel group
Tool steel for hot work
Chemical composition
Cobalt and tungsten are the elements that keep this steel hard at service temperature. Chromium and molybdenum provide hardenability and resistance to tempering.
X20CoCrWMo10-9 / 1.2888 chemical composition, weight %
Element
Typical %
Specified range %
Carbon (C)
0.20
0.17–0.23
Silicon (Si)
0.25
0.15–0.35
Manganese (Mn)
0.50
0.40–0.60
Phosphorus (P)
—
0.035 max
Sulfur (S)
—
0.035 max
Chromium (Cr)
9.50
9.00–10.00
Molybdenum (Mo)
2.00
1.80–2.20
Tungsten (W)
5.50
Reported per heat on the mill certificate
Cobalt (Co)
10.00
9.50–10.50
Iron (Fe)
Balance
—
Typical values for the grade. The analysis of each heat is stated on the EN 10204 3.1 mill test certificate supplied with the order.
Physical properties
Average values at ambient temperature.
Physical properties of X20CoCrWMo10-9 at 20 °C
Property
Metric
Imperial
Density
8.08 g/cm³
0.292 lb/in³
Modulus of elasticity
215 GPa (215 × 10³ N/mm²)
31.2 × 10⁶ psi
Maximum annealed hardness
320 HB
320 HB
Coefficient of linear thermal expansion
Mean coefficient of linear thermal expansion of X20CoCrWMo10-9, 10⁻⁶ K⁻¹
Range
20–100 °C
20–200 °C
20–300 °C
20–400 °C
20–500 °C
20–600 °C
20–700 °C
10⁻⁶ K⁻¹
12.1
12.1
12.4
12.9
13.5
14.0
14.1
Expansion increases by about 17 % between 100 °C and 700 °C. This helps the tool hold dimensional accuracy during long production runs.
Heat treatment
The following sequence is normally applied to X20CoCrWMo10-9 tooling. Holding times depend on section thickness. Soak the part through-section at temperature before each step.
Soft annealing
Heat to 760–840 °C (1400–1545 °F), hold 4 to 6 hours, then cool slowly in the furnace. This gives a maximum hardness of 320 HB for machining.
Stress relieving
After rough machining, heat to 600–650 °C (1110–1200 °F), hold 1 to 2 hours at temperature and cool in air. This reduces distortion during hardening.
Hardening
Austenitise at 1100–1150 °C (2010–2100 °F), then quench in air, oil or vacuum. Hardness after quenching is about 52 HRC.
Tempering
Temper at 600–750 °C (1110–1380 °F), two or three times, cooling to room temperature between cycles. Tempering in the 500–600 °C band gives a secondary hardness peak of about 56 HRC.
Do not water cool X20CoCrWMo10-9 tooling in service. The grade is specified for dry or air cooled operation. Water cooling causes thermal fatigue cracking in a steel of this alloy content.
Tempering temperature vs hardness
Hardness remains almost unchanged up to 650 °C and drops sharply above 700 °C. This is the main reason the grade is selected over conventional hot work steels for copper and brass tooling.
Typical tempering response of X20CoCrWMo10-9 (1.2888) after hardening from 1100–1150 °C.
Tempering temperature and resulting hardness, X20CoCrWMo10-9
Tempering temperature
500 °C 932 °F
550 °C 1022 °F
600 °C 1112 °F
650 °C 1202 °F
700 °C 1292 °F
750 °C 1382 °F
Hardness, HRC
56
56
55.5
54
48
42.3
Typical values. Actual hardness depends on section size, austenitising temperature and the number of tempering cycles.
Forging X20CoCrWMo10-9
Hot forming temperature is 1100–900 °C (2010–1650 °F). Preheat slowly and uniformly, because the high alloy content makes this grade sensitive to thermal shock. Soak the billet through-section before the first pass and stop forging before the steel falls below 900 °C. Cool slowly in the furnace or in an insulating medium after forging, then soft anneal before machining.
We forge this grade on open-die hammers and presses at our works in Jiangyin. Reheats are scheduled so that every pass finishes inside the temperature window. Forging ratio and upsetting sequence are set according to the loading direction of the finished part. This is important for extrusion liners and rolled rings, where the working stress is circumferential.
X20CoCrWMo10-9 compared with H13 and 1.2367
Most enquiries for this grade come from plants where H13 tooling has failed early. 1.2888 contains less carbon and no vanadium, and adds 10 % cobalt and 5.5 % tungsten. The result is a much higher temperature before hardness begins to fall.
Hot work tool steel comparison, typical composition and use
Grade
1.2888 X20CoCrWMo10-9
1.2344 H13 / X40CrMoV5-1
1.2367 X38CrMoV5-3
Carbon %
0.20
0.40
0.38
Chromium %
9.50
5.20
5.00
Molybdenum %
2.00
1.40
3.00
Tungsten %
5.50
—
—
Cobalt %
10.00
—
—
Vanadium %
—
1.00
0.55
Hot hardness retention
Highest of the three
Moderate
High
Water cooling in service
Not permitted
Common practice
Common practice
Typical use
Copper and brass extrusion, magnesium die casting, steel extrusion
Aluminium die casting, general hot work dies
Heavy duty aluminium die casting, hot forging dies
1.2888 is normally selected when the tool face runs above about 600 °C, when the worked metal is copper, brass or magnesium, or when H13 tooling is failing by softening and washout instead of by cracking. For aluminium die casting with water cooled channels, H13 or 1.2367 is cheaper and more suitable.
Applications
X20CoCrWMo10-9 is specified where the tool sees both high temperature and contact with molten or near-molten metal:
Extrusion tooling for copper, copper alloys and steel, including dies, mandrels and special dies
Extrusion container inner liners and intermediate liners for copper extrusion presses
Brass extrusion dies and die casting tools of all kinds for brass
Goosenecks and shot chambers for magnesium die casting
Hot shear blades, hot punches and dummy blocks running at sustained high temperature
All of these applications require resistance to high temperature wear and to erosion by molten metal, together with hardness retention over long production runs.
X20CoCrWMo10-9 forged forms we supply
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Zhouzhuang Town, Jiangyin, Jiangsu Province, China. We produce X20CoCrWMo10-9 (1.2888) forgings to customer drawing or specification in the following forms.
Forged product forms available in X20CoCrWMo10-9 / 1.2888
Form
Covers
Bars
Forged round bars and rods; square, rectangular and flat bars
Extrusion container inner liners and intermediate liners, extrusion dies, dummy blocks for copper and brass presses
Die casting parts
Gooseneck and chamber blanks for magnesium die casting
Delivery condition
Soft annealed, 320 HB maximum, for customers who machine and heat treat in house
Quenched and tempered to an agreed hardness between 42 and 56 HRC
Black forged, rough machined with machining allowance, or finish machined to drawing
To quote quickly, please send: the grade (X20CoCrWMo10-9 or 1.2888), outside diameter × inside diameter × length or block dimensions, quantity, delivery condition and target hardness, any NDT requirement, and the drawing if you have one. Email sales@steelforgepieces.com or WhatsApp 0086-189-2135-9659.
Testing and documents
The following can be supplied with any X20CoCrWMo10-9 order. Please state the requirement at enquiry stage so that it is scheduled into production.
EN 10204 3.1 mill test certificate covering heat number, chemical analysis and hardness
Spectrographic chemical analysis against the composition table above
Hardness testing, HRC or HB, at agreed positions
Ultrasonic testing to SEP 1921 or ASTM A388 acceptance classes
Grain size and microstructure examination
Dimensional inspection report against the drawing
Third party inspection by SGS, BV or TÜV can be arranged on request. The inspection body and the acceptance criteria must be agreed before production starts.
Frequently asked questions
What is X20CoCrWMo10-9 steel?
X20CoCrWMo10-9 is a cobalt-alloyed hot work tool steel with material number 1.2888. It contains about 0.20 % carbon, 9.5 % chromium, 5.5 % tungsten, 2 % molybdenum and 10 % cobalt. The cobalt and tungsten give it high hardness retention at elevated temperature and resistance to erosion by molten metal.
What is the material number for X20CoCrWMo10-9?
The material number is 1.2888. X20CoCrWMo10-9 is the DIN/EN designation and 1.2888 is the German Werkstoffnummer for the same steel. Enquiries also arrive written as X20CoCrWMo109 or X20CoCrWMo10.9, which refer to the same grade.
Is there an AISI or UNS equivalent to 1.2888?
No. There is no direct AISI or UNS equivalent to X20CoCrWMo10-9. Its cobalt and tungsten content places it above the AISI H-series hot work steels, so drawings and specifications normally call out the DIN designation X20CoCrWMo10-9 or the material number 1.2888 directly.
What is X20CoCrWMo10-9 used for?
It is used for extrusion tooling for copper, copper alloys and steel, including special dies and extrusion container inner and intermediate liners; die casting tools of all kinds for brass; and goosenecks and chambers for magnesium die casting. It is suitable for tooling that must resist high temperature wear and molten metal erosion.
What hardness can X20CoCrWMo10-9 reach?
About 52 HRC as quenched from 1100–1150 °C. After tempering, hardness is about 56 HRC at 500–550 °C, 55.5 HRC at 600 °C, 54 HRC at 650 °C, 48 HRC at 700 °C and 42.3 HRC at 750 °C. In the soft annealed condition the maximum hardness is 320 HB.
How is X20CoCrWMo10-9 heat treated?
Soft anneal at 760–840 °C for 4 to 6 hours with slow furnace cooling. Stress relieve after rough machining at 600–650 °C for 1 to 2 hours, then air cool. Harden from 1100–1150 °C with air, oil or vacuum quenching. Temper at 600–750 °C, two or three times, cooling to room temperature between cycles.
Why choose 1.2888 instead of H13 (1.2344)?
1.2888 holds its hardness at much higher temperature because of its 10 % cobalt and 5.5 % tungsten, and it resists erosion by molten metal better than H13. It is the usual choice for copper and brass extrusion and for magnesium die casting. H13 remains the cheaper and better option for aluminium die casting and general hot work dies.
Can X20CoCrWMo10-9 tooling be water cooled?
No. The grade is specified for use without water cooling. Water cooling a steel of this alloy content causes thermal fatigue cracking on the tool face. Tools in this grade are run dry or air cooled.
What is the forging temperature for X20CoCrWMo10-9?
Hot forming is carried out between 1100 °C and 900 °C. Preheat slowly and soak through-section, stop forging before the steel falls below 900 °C, then cool slowly in the furnace and soft anneal before machining.
Who supplies open-die forgings in X20CoCrWMo10-9?
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, produces X20CoCrWMo10-9 (1.2888) forged bars, rings, blocks, sleeves and extrusion liners to customer drawing. Contact sales@steelforgepieces.com or 0086-189-2135-9659.
