826M40 is a 2.5% Ni-Cr-Mo high hardenability, high tensile strength steel.

826M40 is generally supplied in the Hardened and Tempered condition in the tensile range of 1000 – 1150Mpa (V Condition) but can be heat treated to 925 – 1550Mpa dependent on section size (U – Z Condition). It could also be supplied in the annealed condition suitable for pre-heat treatment machining.

This grade is very popular and widely used in most industry sectors where high strength and moderate impact properties are essential in fairly large components.

Typical applications include axles, shafts, rolls, die holders and rams. Pre-hardened and tempered 826M40 can be further surface hardened by flame or induction hardening or nitriding.

RELATED SPECIFICATIONS 826M40 – 2.5% Ni-Cr-Mo Steel
BS970 – 1955 EN26
DIN 40NiMoCr10 4
W.Nr. 1.6745
TYPICAL CHEMICAL COMPOSITION
Carbon 0.40%
Silicon 0.25%
Manganese 0.60%
Phosphorous <0.040%
Sulphur <0.040%
Chromium 0.65%
Molybdenum 0.55%
Nickel 2.55%
Mechanical Property Requirements – BS970 Part 3 1991
Condition Rulling Section Tensile Strength Mpa Yield (0.2%) Mpa Elongation % Izod Ftlbs Charpy J Hardness HB
U 250 925/1075 725 12 25 28 269/331
U 150 925/1075 740 12 35 42 269/331
V 250 1000/1150 820 12 25 28 293/352
V 150 1000/1150 835 12 35 42 283/352
W 250 1075/1225 910 11 20 22 311/375
W 150 1075/1225 925 11 30 35 311/375
X 150 1150/1300 1005 10 25 28 341/401
Y 150 1225/1375 1080 10 25 28 363/429
Z 100 1550 Min
 1125 7 10 11 444 Min
FORGING
Forging Temperature for this material should be 850 – 1200oC

Soak times should be kept to a minimum to avoid heavy scaling, but sufficient time should be given to allow centre to achieve furnace temperature.

After forging pieces should be allowed to cool in still air.
HEAT TREATMENT
Annealing – Heat to 790-840oC for a time commensurate with ruling section and furnace cool.
Hardening – Heat to 820 – 850oC for a time commensurate with ruling section and quench in Oil, Water or Polymer.

Note: If water quench is to be used, although not recommended, care must be taken to ensure that all sharp corners are removed prior to heat treatment.
Tempering should be done immediately whilst the material is still hand warm

Tempering – Re-heat to 450 – 660oC as required, dependent on final required properties. Hold for a time commensurate with the ruling section and cool in still in air.

Tempering below 450oC could lead to temper embrittlement.
MACHINING
826M40 has good machinability in the quenched and tempered condition, dependent on condition, and operations such as sawing, turning, broaching, milling etc can be accomplished satisfactorily using standard machine tool manufacturers recommended speeds and feeds.
WELDING
Welding of 826M40 in the hardened and tempered condition is not advised and should be avoided if possible, as the mechanical properties will be altered in the heat affected zone. If welding is required it should be done using low hydrogen electrodes, while the material is in the annealed condition, and the work piece should be stress relieved (640 – 660oC) immediately after cooling to hand warm, prior to hardening and tempering.

If welding in the quenched and tempered condition, the work piece should be stress relieved at 15oC below the original tempering temperature.

Pre-heat temperature should be at least 370oC