Category 

Steel

Class 

Alloy steel

Type 

Standard

Common Names 

Chromium-molybdenum steel

Designations 

France: AFNOR 40 CD 4 , AFNOR 42 CD 4 
Germany: DIN 1.7225 
Italy: UNI 38 CrMo 4 KB , UNI 40 CrMo 4 , UNI G 4O CrMo 4 
Japan: JIS SCM 4 , JIS SCM 4 H 
Sweden: SS 2244 
United Kingdom: B.S. 708 A 42 , B.S. 708 M 40 , B.S. 709 M 40 
United States: AMS 6378 , AMS 6379 , AMS 6381B , AMS 6382 , AMS 6382G , AMS 6390 , AMS 6390A , AMS 6395 , ASTM A322 , ASTM A331 , ASTM A505 , ASTM A519 , ASTM A547 , ASTM A646 , MIL SPEC MIL-S-16974 , SAE J404 , SAE J412 , SAE J770 , UNS G41400

 Read more: Mechanical Properties

Properties

 Conditions 

T (°C)

Treatment

Density (×1000 kg/m3)

7.7-8.03

25

Poisson’s Ratio

0.27-0.30

25

Elastic Modulus (GPa)

190-210

25

Tensile Strength (Mpa)

655.0 

25 

annealed at 815°C  more

Yield Strength (Mpa)

417.1 

Elongation (%)

25.7 

Reduction in Area (%)

56.9 

Hardness (HB)

197 

25 

annealed at 815°C more

Impact Strength (J)
(Izod)

54.5 

25 

annealed at 815°C  more

Thermal Properties

Properties

 Conditions 

T (°C)

Treatment

Thermal Expansion (10-6/ºC)

12.3 

20-100 more

oil hardened, tempered 600°C 

Thermal Conductivity (W/m-K)

42.7 

100 more

Specific Heat (J/kg-K)

473 

150-200 more

Electric Properties

Properties

 Conditions 

T (°C)

Treatment

Electric Resistivity (10-9W-m)

222 

20 

4140 is an alloy steel that is supplied in either the annealed or prehardened condition. The prehardened condition is heat treated to a medium hardness (HRC 28/32) and is designated as 4140 HT. 4140 annealed is supplied in the soft condition and can be hardened to RC 54. 4140 annealed is designated as 4140 Ann or simply 4140. 4140 HT is supplied in many forms such as hot rolled or turned, ground and polished rounds and block or DCF plate to be used as a holder material for high strength structural components.

Typical Chemistry
Carbon 0.42%
Silicon 0.30%
Molybdenum 0.20%
Manganese 1.00%
Chromium 1.00%

Typical Applications
Support Plates Filler Blocks
Punch Holders Structural Parts
Clamps Base Plates
Gages Molds
Brake Dies Jigs
Fixtures Tool Holders
High-Strength Parts
Annealed Hardness: BHN 185/200.

Thermal Treatments.  

Annealing: 1550F (840C), hold 2 hours, slow cool 50F(30C)/hr. max. to 1200F (650C), then air or furnace cool. Hardness BHN 185/200.

Stress Relieving:

Annealed Material: 1100-1300F (595-740C), hold 2 hrs, air cool.

Hardened Material: 50-100F (30-55C) below last tempering temperature, hold 2 hrs, air cool.

Straightening: Best done warm 400-800F (205-425C)

Hardening: (Atmosphere or Vacuum Furnace)

Preheat: 1250-1300F (675-705C), equalize

High Heat: 1550-1600F (840-870C), soak 10 to 30 minutes. For vacuum hardening, use the high side of the high heat range and soak times.

Quench: Oil quench to hand warm, 150F (650C). Temper immediately. Water quenching from 1550F (840C) may be used for simple shapes and larger sections. Note vacuum furnaces must have oil quench capability to achieve comparable results.

Temper: Tempering at 400-1200F (205-650C) for 1 hour per inch (25mm) of thickness at temperature is recommended (2 hrs min). Air cool to room temperature.  

Welding

Medium carbon steel filler material.

Annealed Material:
Preheat: 400F (205C)
Postheat: 500-600F (260-315C)

Hardened Material:
Preheat: 50F (30C) less than last tempering temperature.
Postheat: 50F (30C) less than last tempering temperature.

Physical Properties

Modulus of Elasticity …………………..29 psi x 106(200 GPa)
Specific Gravity ………………………………………………(7.81)
Density ………………………………….0.282 lb/in3(7810 kg/m3) 

 Technical Data

AISI 4140 is a chromium molybdenum quality alloy steel. AISI 4140 is primarily supplied in the hardened and tempered condition to 18-22HRc range. AISI 4140 offers good ductility, shock resisting characteristics combined with resistancee to wear. AISI 4140 is suitable for a variety of applications in the oil and gas sector. This material can be supplied to AISI steel standards