L6 Tool Steel Properties and Applications

L6 tool steel is a low-alloy hot work tool steel valued for its excellent toughness and good hardenability. It has a long history of use and remains a solid choice for specific tooling and component needs where impact resistance and strength are critical.

1. L6 steel Chemical Composition

The typical composition of L6 tool steel includes:

• Carbon (C): 0.65-0.75%
• Manganese (Mn): 0.25-0.80%
• Silicon (Si): 0.25%
• Chromium (Cr): 0.60-1.20%
• Nickel (Ni): 1.25-2.00%
• Molybdenum (Mo): Up to 0.50% (in some variants)

2. L6 tool steel Characteristics

• High Toughness: The significant nickel content is key to L6’s high toughness and impact resistance.
• Good Hardenability: Nickel and chromium ensure L6 hardens well, achieving significant hardness even in larger sections, with hardness levels of over 60 HRC possible in sections up to 3 inches (75 mm) thick. As-quenched hardness can reach around 64 HRC.
• Moderate Abrasion Resistance: L6 offers fair wear resistance, suitable for many applications, although less than that of higher-alloy grades. Carbon content contributes to low-temperature wear resistance.
• Machinability: The nickel content makes L6 slightly less machinable than nickel-free grades, such as L2.
• Temperature Limitation: L6 has relatively low resistance to softening at high temperatures, resulting in low hot hardness, making it unsuitable for high-temperature service.

3. Heat Treatment Guidelines for L6 tool steel

Correct heat treatment unlocks the full potential of L6 steel. 

3.1 Forging

• Forge L6 between 980°C and 1090°C (1800°F to 2000°F).
• Aim to finish forging above 845°C (1550°F).
• Note: Grades containing molybdenum require slow cooling after forging due to high hardenability.

3.2 Annealing & Hardening

• Annealing after forging is recommended before hardening.
• L6 is typically considered an oil-hardening steel. Standard hardening temperature is around 870°C (1600°F).
• For large sections, water quenching can sometimes be used to create a hard outer case and a tougher core.

3.3 Tempering & Hardness

• Temper L6 tool steel after hardening to achieve the target balance of toughness and hardness for your specific application.
• Depending on the tempering parameters, final hardness typically ranges from 45 HRC to 62 HRC. Surface hardness after oil quenching can reach up to 65 HRC.

4. Common Applications for L6 Tool Steel

L6 tool steel’s blend of toughness and moderate wear resistance makes it a versatile choice for:

4.1 Tooling & Dies

• General-purpose tools and dies require good toughness.
• Shear blades, blanking dies, forming dies, punches.
• Press-brake dies, trimming dies.
• Cold-heading and bending dies.
• Massive dies for hammer forging (excellent impact resistance).
• Popular in automotive metal stamping dies.

4.2 Knives & Cutting Tools

• Woodworking saws and knives, especially where toughness is paramount.

4.3 Machine Components

• Parts requiring good strength and toughness include arbors, cams, chucks, collets, spindles, clutch parts, gears, and ratchets.

4.4 Other Uses

• Rock drills and heavy-duty shears.

5. How L6 tool steel compares to Other Steels

Selecting the right steel is crucial. Here’s how L6 compares:

• vs. O1 Tool Steel: L6 offers significantly higher toughness but exhibits lower abrasion resistance compared to O1.
• vs. L2 Tool Steel: L6 generally offers better hardenability due to its nickel content.
• vs. P-Type Mold Steels: For plastic injection molds, specialized P-type steels are usually the preferred choice.
• vs. 4140/4150 Alloy Steels: While 4140/4150 are sometimes used for simpler fixtures or short-run dies, L6 is a dedicated tool steel grade that offers superior performance for more demanding tooling.

6. Equivalent grades

• Germany: DIN 1.2714/DIN 55NiCrMoV7 (older designation, but still sometimes used)   

• Japan: JIS SKT4

• China: GB/T 1299: 5CrNiMo 

7. Why choose L6 tool steel?

Select L6 tool steel when your application demands high toughness, good strength, and reliable hardenability, and where moderate wear resistance is acceptable. It is a proven performer for a variety of impact-prone tools, dies, and structural components.

Contact Aobo Steel today to discuss your L6 tool steel requirements. With our extensive experience and reliable supply chain, we can provide the quality materials you need.