4340anneal.jpg

4340 Heat Treated

4340 Annealed

4340heat.jpg

PACIFIC 4340 is available in two conditions: heat treated (quenched and tempered) to high strength or annealed for ease of machining and subsequent heat treatment. It is a nickel-chromium-molybdenum medium carbon alloy steel with deep hardenability. It can be through hardened in large sections. When properly hardened, 4340 exhibits a good combination of strength, ductility and toughness; this is the material to which other ultra-strength steels are compared. PACIFIC 4340 Heat Treated bars are hardened to 285/331 HB and meet ASTM A 434, Class BD. 4340 is weldable but only with proper precautions; because of its high hardenability, it requires both preheat and post heat in virtually all welding applications. It can be induction hardened or nitrided after quenching and tempering.

Chemical Composition

Heat Analysis - ranges and limits %

C

.38/.43

Mn

.60/.80

P

.035 Max

S

.040 Max

Ni

1.65/2.00

Cr

.70/.90

Mo

.20/.30

Typical Properties

Approximate - not  for specification

Over 2-1/2" thru 4"

Tensile (psi)

140,000

Yield (psi)

110,000

Elongation

14%

Over 4" thru 7"

Tensile (psi)

135,000

Yield (psi)

105,000

Elongation

14%

Over 7" thru 9-1/2"

Tensile (psi)

130,000

Yield (psi)

100,000

Elongation

14%

Processing Temperatures

Typical

Forge

2200°F Max

Normalize

1550/1650°F

Case Harden

1475/1550°F

Anneal 

1475/1575°F Max

Temper

1200°F & 400°F

Shapes and Conditions Available
  • ​Hot Rolled Annealed Rounds through 3" Diameter

  • Rough Turned Oversize Annealed Rounds from 3-1/4" through 17-1/2" Diameter

  • Rough Turned Oversize Heat Treated Rounds from 3-5/8" through 10" Diameter