Difference between EN8D and SAE4140 Grade Steels
Difference between EN8D and SAE4140 Grade Steels
A) Difference in Chemical Composition
Chemical Composition of EN8D Specification values in %
| C | Si | Mn | P | S |
| 0.40-0.45 | 0.10 – 0.35 | 0.70-0.90 | ≤ 0.050 | ≤ 0.050 |
Chemical Composition of 4140 Specification values in %
| C | Si | Mn | P | S | Cr | Mo |
| 0.38-0.43 | 0.10-0.35 | 0.75-1.00 | ≤ 0.035 | ≤ 0.035 | 0.8-1.10 | 0.15-0.30 |
B) Difference in Properties
a) En8D is a medium tensile low hardenability carbon steel typically supplied in black hot rolled or Normalised condition with a typical tensile strength range 570-700 MPa and Brinell hardness Range 170-210.
b) Whereas 4140 is a 1% chromium-molybdenum medium hardenability general purpose high strength steel generally supplied in hardened and tempered condition having tensile range of 850-1000 MPa.
C) Difference between Classification
a) En8D is medium carbon steel
b) AISI 4140 is a low alloy steel also referred to as chromium-molybdenum alloy steel
D) Applications
a) Applications of EN8D
EN8D is extensively used where more strength and wear resistance is required than low carbon mild steel and where higher strength of low alloy high tensile steel is not necessary. Example: Motor Shaft, axles, hydraulic rams and medium to high strength threaded fasteners are required
b) Applications of 4140
Medium-high stressed shafts and components where the use of carbon steel EN8D would not be appropriate. Reasons for using 4140 are the higher yield and fatigue strength, better through hardening of the material and superior impact properties compared to plain carbon steels like 1045.
These advantages are only achieved when 4140 is used in the heat-treated condition. Typical components include transmission shafts, spindles and small gears, high tensile threaded fasteners such as bolts, nuts and studs.