Aug 9 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat treatment
Tempering
Annealing
Cold Working
Welding
Forging
Forming
Machinability
Heat Treatment
Applications
Introduction
Low alloy special purpose steels or group L steels contain small quantities of chromium, nickel, vanadium, and molybdenum. L2 and L6 form the group L steels.
The L6 tool steels contain 0.70% carbon with a quenched hardness of about 64 HRC. The alloying elements in these tools steels are chromium and molybdenum, and 1.50% nickel to increase toughness. These tool steels can maintain hardness above 60 HRC for sections of 75 mm (3 in.) thickness.
The sections below provide an overview of L6 tool steels.
Chemical Composition
The chemical composition of L6 tool steels is outlined in the following table.
|
Element |
Content (%) |
|
Nickel, Ni |
1.25-2.00 |
|
Chromium, Cr |
0.60-1.20 |
|
Carbon, C |
0.65-0.75 |
|
Silicon, Si |
0.5 |
|
Molybdenum, Mo |
0.5 |
|
Manganese, Mn |
0.25-0.80 |
|
Vanadium, V |
0.20-0.30 (a) |
|
Copper, Cu |
0.25 |
|
Phosphorus, P |
0.03 |
|
Sulfur, S
|
0.03 |
|
Iron, Fe |
Balance |
Physical Properties
The following table shows the physical properties of L6 tool steels.
|
Properties |
Metric |
Imperial |
|
Density |
7.86 g/cm³ |
0.284 lb/in³ |
|
Melting point |
2590°F |
1421°C |
Mechanical Properties
The mechanical properties of L6 tool steels are displayed in the following table.
|
Properties |
Metric |
Imperial |
|
Poisson's ratio |
0.27- 0.30 |
0.27- 0.30 |
|
Elastic modulus |
190-210 GPa |
27557-30457 ksi |
Other Designations
Equivalent materials to L6 tool steels are:
-
UNS T61206
-
ASTM A681
-
DIN 1.2713
-
SAE J437
-
SAE J438
Fabrication and Heat treatment
Tempering
L6 tool steels are tempered between 177 to 538°C (350 to 1000°F) for Rockwell C 62 to 45 range.
Annealing
L6 tool steels are annealed at 788°C (1450°F) and cooled slowly at a maximum of 4°C (40°F) per hour.
Cold Working
Conventional methods are used for cold working of L6 tool steels.
Welding
L6 tool steels are generally weldable in nature.
Forging
L6 tool steels are forged at 1079°C (1975°F) down to 871°C (1600°F). These steels should not be forged below 843°C (1550°F).
Forming
Conventional methods are used for forming of L6 tool steels.
Machinability
L6 tool steels have extremely good machinability that is rated at 90% in comparison with the machinability of W group water hardening low alloy steels that are rated 100% as a baseline.
Heat Treatment
L6 tool steels are heated slowly to 816°C (1500°F) and then held for 10 to 30 min. This is followed by water or oil quenching.
Applications
L6 tool steels are used in springs, bearings, chuck parts or rollers.