4140 is an oil hardening steel with relatively high hardenability.  This grade is capable of good strength and wear resistance.  It possesses excellent toughness and good ductility.  It also has the ability to resist stress and creep at prolonged high temperatures up to 1000F.  The chromium content provides good hardness penetration and molybdenum imparts uniformity of hardness and high strength.  These grades are especially suitable for forging because they have self-scaling characteristics.

 

TYPICAL ANALYSIS

 

  C             Mn                      P                   Si               Cr                    Mo
0.38    0.75/1.00      0.035 Max     0.04 Max   0.80/1.10      0.15/0.20

 

TYPICAL APPLICATIONS

Drill collars, bolts, couplings, axle shafts, sprockets, trailer axles, piston rods ,rams, hydraulic shafts, spindles, precision lead screws, reamer bodies.


MECHANICAL PROPERITES (Annealed)

TENSILE STRENGTH (KSI)                                    140
YIELD STRENGTH   (KSI)                                        90
ELONGATION (% IN 2”)                                        20
REDUCTION IN AREA (%)                                    45
BRINELL HARNESS                                              285

MACHINABILITY

This material has machinability rating in the annealed condition of approximately 66% of 1212.  Surface cutting speed is approximately 120 feet per minute.

WELDABLITY

Difficult to weld, but can be welded by any of the common welding processes providing the section is preheated and stress relieved after welding.  The grade of welding rod to be used depends upon thickness of section, design, service requirements, etc.


THERMAL TREATMENTS                           DEGREES
Forging                                                          Heat to 2100 – 2200 F
Annealing                                                      Heat to 1450 – 1550 F.
                                                                      Cool slowly in furnace
                                                                      Average Brinell Hardness 187
                                                                      Heat to 1600 – 1700 F. Cool in air
Normalizing                                                    Average Brinell Hardness 285

Hardening                                                      Standard Hardening range is between
1525 – 1625                                                  Quenched in oil.  A wide range of mechanical properties can be obtained by tempering                                                                       between 400 – 1300 F