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Atlas 4140
Through-Hardening Low Allow Steel Bar 4140
Colour code: Jade (Band) – Bluebell Introduction Atlas 4140 is a Chromium-Molybdenum through-hardening steel of medium hardenability. It is a general purpose high-tensile steel with medium strength level and good impact properties. Related Specifications Material stocked by Atlas complies with grade AS1444 Grade 4140 and/or ASTM A434 (A29)Grade 4140 and/or Euronorm EN 10083 grade 42CrMo4 (Material Number 1.7225/17227). Chemical Composition C Si 0.37-0.44 0.10-0.35
Specification values in %

Mn 0.65-1.10

P ≤ 0.040

S ≤ 0.040

Cr 0.75-1.20

Mo 0.15-0.30

Ni --

Conditions of Supply – Mechanical Properties Atlas 4140 is supplied in the hardened and tempered condition. The level of hardness is selected to give usefulstrength while still maintaining the ability to machine the material into finished components.
Diameter (mm) Heat Treated Condition Tensile Strength (MPa) 930 – 1080 850 – 1000 850 – 1000 0.2% Proof Stress (MPa) 740 min 665 min 665 min Impact Elongation (% in 50mm) 12 min 13 min 13 min Izod or Charpy (J) (J) 47 min 42 min 54 min 50 min not guaranteed Hardness (HB) 269 - 331 248 – 302 248 – 302

upto 180 incl AS1444 Condition U >180 to 250 incl AS1444 Condition T >250 to 450 incl AS1444 Condition T

Atlas 4140 can be re-heat-treated to higher strength or tempered back to lower strength levels than those supplied as standard. Assistance with heat treatment should be sought from reputable heat treatment companies. Conditions of Supply – Surface Finish and Machining Allowance Atlas 4140Black is supplied with +/- tolerances according to DIN 1013 or better. Atlas 4140 Bright is supplied cold drawn with h10 tolerance for bar diameters up to 25mm; bars with diameters 25 to 75mm are supplied as cold drawn with h10 tolerance or peeled with k12 tolerance, diameters 75-220mm are supplied peeled to k12, sizes 220mm are supplied peeled to -0/+2mm.

Revised April 2006

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AtlasSpecialty Metals
Through-Hardening Low Allow Steel Bar 4140
Machining Allowances for Atlas 4140 round bar (mm on diameter) part length part length part length part length 120mm 120mm 0-50 1.5mm 1.5 + 6mm/m 1.0mm 1.0 + 4mm/m 50-100 2.3mm 2.3 + 6mm/m 1.0mm 1.0 + 4mm/m 100-150 4.5mm 4.5 + 6mm/m 1.0mm 1.0 + 4mm/m 150-210 6.5mm 6.5 + 6mm/m 1.5mm 1.5 + 4mm/m 210-450 1.5mm 1.5 + 6mm/m Hot-rolling surfacedefects are retained in cold drawing. For bright bar in the range of cold drawing (up to 50mm) it is essential to take machining allowance into account. Peeled bar is generally free of surface defects. A certain allowance for surface defects is recommended however, as minor defects are permitted by the various national standards (AS, EN, etc.). Heat Treatment Annealing 850°C Normalising 850 –920°C Hardening 850 – 860°C Quenching medium Oil Tempering 500 – 680°C Bar diameter (mm) Black (hot rolled or forged) Bright (drawn or peeled bar)

Tempering Diagram 4140
typical values for 30 mm section 1600 Tensile Strength and 0.2% Proof Stress (MPa)
Tensile Strength Izod Im pact

100 90 80 70

Proof Stress

Elongation (A%), Red of Area (Z%) and Izod Impact (J)

HardeningComponents should be heated slowly to 850 to 860°C, held until uniform, then quenched vigorously in oil (or polymer with an equivalent quench rate to between 80 to 110°C). Polymer quenchants have similar cooling capacities to oil, while having the advantage of a being less likely to ignite. Tempering While still warm, re-heat to tempering temperature, hold one hour per 25mm of section (2 hours minimum)and cool in air. Select tempering temperatures according to the required mechanical properties (refer to tempering curve). Holding in the temperature range 230 to 370°C should be avoided due to possible temper embrittlement (“Blue Brittleness”). For yield strengths above 1380MPa: temper ½ to 2 hours at between 175 and 230°C, while for yield strengths below 1380MPa temper in the temperature range...
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