AISI 4140H Alloy Steel (UNS H41400)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Applications

Introduction

Alloy steel is steel alloyed with different elements in total amounts between 1 and 50% by weight to enhance its mechanical properties such as strength, hardness, toughness and wear resistance. Low-alloy steels, on the other hand, are used to achieve better hardenability, which in turn enhances other mechanical properties.

AISI 4140H is an H-steel grade alloy steel, commonly called AISI 4140H chromium-molybdenum steel. The following datasheet will provide an overview of AISI 4140H alloy steel.

Chemical Composition

The chemical composition AISI 4140H alloy steels is outlined in the following table.

Element Content (%)
Iron, Fe 96.585 - 97.93
Chromium, Cr 0.75 - 1.2
Manganese, Mn 0.65 - 1.1
Carbon, C 0.37 - 0.44
Molybdenum, Mo 0.15 - 0.3
Silicon, Si 0.15 - 0.3
Sulfur, S ≤0.040
Phosphorous, P ≤0.035

Physical Properties

The following table shows the physical properties of AISI 4140H alloy steels.

Properties Metric Imperial
Density 7.85 g/cm3 0.284 lb/in3

Mechanical Properties

The mechanical properties of AISI 4140H alloy steels are displayed in the following table.

Properties Metric Imperial
Tensile strength 1150 MPa 167000 psi
Yield strength 1050 MPa 152000 psi
Modulus of elasticity 205 GPa 29700 ksi
Bulk modulus 140 GPa 20300 ksi
Shear modulus 80 GPa 11600 ksi
Poisson’s ratio 0.29 0.29
Elongation at break 17.50% 17.50%
Reduction of area 55% 55%
Hardness, Brinell 341 341
Hardness, Vickers 361 361
Hardness, Knoop 369 369
Hardness, Rockwell C 37 37
Hardness, Rockwell B 99 99

Thermal Properties

The thermal properties of AISI 4140H alloy steels are given in the following table

Properties Metric Imperial
Thermal expansion co-efficient (@0-100°C/32-212°F) 12.2 µm/m°C 6.78 µin/in°F
Thermal conductivity 42.6 W/mK 296 BTU.in/hrft².°F

Other Designations

Other designations that are equivalent to AISI 4140H alloy steels include the following.

  • B.S. 708 A 42
  • B.S. 708 M 40
  • B.S. 709 M 40
  • ASTM A304
  • SAE J1268
  • SS 2244
  • JIS SCM 4
  • JIS SCM 4 H
  • DIN 1.7225
  • AFNOR 42 CD 4
  • UNI 40 CrMo 4
  • UNI 38 CrMo 4 KB

Applications

The following are the list of applications of AISI 4140H alloy steels:

  • Oil industry
  • Automotive gears
  • Crank shafts
  • Gun barrels
  • Steering knuckles

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