Eastern Tool
Steel Service, Inc.

1045 Delaum Rd.

P.O. Box 857

St. Marys, Pa 15857

Phone: (814) 834-7224
Fax: (814) 834-7225
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L-6 Tool Steel Data Sheet

AISI L-6 is a tough, high- strength tool steel suitable for general purpose applications. This grade is easily oil-hardened at low temperature.

Chemical Composition

Carbon 0.75%
Manganese 0.70%
Chromium 0.80%
Silicon 0.25%
Nickel 0.150%
Molybdenum 0.30%

Typical Applications

Form Rolls Brake Dies
Machine Tool Parts Chucks
Pinions Shear Blades

Cold Work Tool Steel Comparison Chart

Thermal Treatments

Note: Full hardness will only be attained in sections less than 3" thick

Preheat : 1250/1350F (675/730C), equalize

Austenize : 1500/1550F (815/840C), 15/30 minutes at temperature.

Quench : Oil to 150F (65C). For minimum distortion, parts may be removed from oil at about 400F(205 C), and air-cooled to hand warm.

Temper : 350/600F (175/315C), hold 2 hours minimum (4 hours preferred) at temperature air cool. Temper twice.

Cryogenic Treating : Refrigeration treatments may improve long term dimensional stability by transforming retained austenite. Refrigeration treatments should generally be performed after the first temper, and must be followed by a temper.

Hardness and Impact Toughness Data
Oil Quenched from 1500F(810C)

Tempering Toughness
Temperature HardnessCharpy C-Notch
Deg. FDeg. CHRCFt. Lbs.Joules
As quenched 64 -
300 150 64 15 20
400 205 61 43 58
500 260 59 38 52
600 315 57 68 92
700 370 54 - -

Surface Treatments

L-6 can be given standard surface treatments such as hard chrome plating if desired. Nitriding is not generally practical due to a substantial loss of core hardness.


A. Heat to 1375/1425F(745/775C), hold two hours, cool slowly, 50F(30C) per hour maximum, to below 1100F(600C), then air cool.
B. Heat to 1375/1425F(745/775C), hold 2 hours, cool to 1200/1250F(650/675C) 6 hours, then air cool.
Typical annealed hardness: 187/235 BHN.

Stress Relieving

Annealed Material: Heat to 1100/1300F(595/705C), hold two hours, cool in still air.
Hardened Material: Heat to 50F(15C) below original tempering temperature, hold two hours, cool in still air.


Use oil hardening (L-6, O-1) tool steel filler material.

Annealed Material:Preheat to 400/600F(205/315C). Maintain above 400F(205C) during welding. Reanneal or temper 1250/1300F(675/700C) 6 hours.

Hardened Material: Preheat to 50F(15C) below original tempering temperature (300F(150C) minimum). Maintain above 300F(150C) during welding. Cool to 150F(65C) after welding. Retemper twice 25F(15C) below original tempering temperature.

Physical Properties

Modulus of Elasticity
30psix10(6)(207 GPa)
Density0.284 lb/in3(7860 kg/M3)
Thermal Conductivity20 BTU/hr./ft./F34 W/m/ K)

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