Mat.No. 1.3255, DIN S18-1-2-5, AISI T4
Designation by Standards Mat. No. DIN EN AISI 1.3255 S18-1-2-5 HS18-1-1-5 T4 Chemical Composition (in weight %) C Si Mn Cr Mo Ni V W Others 0.79 max. 0.45 max. 0.40 4.15 0.65 - 1.55 18.00 Co: 4.75 Description This alloy is a High Speed, tungsten type tool steel. It is a deep hardening alloy capable of Rockwell C 64 hardness. Applications Generally used as cutting tools, broaches and cold extrusion punches, turning, planing and milling cutters for roughing work. Physical proper...
Designation by Standards
Chemical Composition (in weight %)
|0.79||max. 0.45||max. 0.40||4.15||0.65||-||1.55||18.00||Co: 4.75|
This alloy is a High Speed, tungsten type tool steel. It is a deep hardening alloy capable of Rockwell C 64 hardness.
Generally used as cutting tools, broaches and cold extrusion punches, turning, planing and milling cutters for roughing work.
Physical properties (avarage values) at ambient temperature
Modulus of elasticity [103 x N/mm2]: 217
Density [g/cm3]: 8.70
Thermal conductivity [W/m.K]: 19.0
Electric resistivity [Ohm mm2/m]: 0.65
Specific heat capacity[J/g.K]: 0.46
Coefficient of Linear Thermal Expansion 10-6 oC-1
Heat to 820-850oC, cool slowly in furnace to 550oC then air. This will produce a maximum Brinell hardness of 265.
Stress relieving to remove machining stresses should be carried out by heating to 600-650oC, holding for one hour at heat, followed by air cooling. This operation is performed to reduce distortion during heat treatment.
Harden from a temperature of 1260-1290oC followed by oil, air quenching or warm bath at 550oC. Hardness after quenching is 63-66 HRC.
Tempering temperature: 2x 560-580oC. Hardness after tempering is 64-65 HRC.
Tempering Temperature (oC) vs. Hardness (HRC)
Click the image to enlarge the diagram.
Hot forming temperature: 1150-900oC.
In the annealed condition the alloy may be cold worked by conventional methods.
Machinability of T4 is only fair. It ranks as 55% that of the W group water hardening simple tool steels.
Although this alloy contains appreciable amount of tungsten it is still not a corrosion resistant alloy. it will rust unless adequately protected.
The alloy may be welded but has a high tungsten content. Consult the alloy supplier for information relative to welding methods.
Forms manufactured: Please see the Dimensional Sales Program.
The information and data presented herein are typical or average values and are not a guarantee of maximum or minimum values. Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to make his own evaluation and are not intended as warranties, either express or implied, of fitness for these or other puposes. There is no representation that the recipient of this literature will receive updated editions as the become available.