L6 Steel | 55NCDV7 | 5ХНМ | 5CrNiMo

L6 steel is an AISI L‑series low‑alloy Ni‑Cr‑Mo tool steel. With 0.65–0.75% carbon and 1.25–2.00% nickel, it features excellent toughness, deep hardenability and good wear resistance. It is ideal for complex tools that tend to crack with water‑hardening steel.

Different from most tool steels, L6 tool steel offers great impact resistance and stable oil‑hardening performance. It can reach 61–62 HRC after oil quenching with minimal distortion. Its high nickel content ensures superior toughness for parts under hardness and shock load requirements.

L6 steel equivalent: DIN 1.2713 (55NiCrMoV6), DIN 1.2714 (55NiCrMoV7), JIS SKT4, GB 5CrNiMo, BS BH224‑5, AFNOR 55NCDV7 and GOST 5ХНМ.

Supply Range & Tolerances

1. Round Bar

Hot Rolled / Forged: Diameter Φ16mm – Φ500mm
Forged: Diameter Φ50mm – Φ400mm (larger sizes available upon request)
Length: 2000mm – 5800mm (customizable)
Tolerances: Compliant with ASTM A681 or DIN EN ISO 4957, or to your specified requirements
Surface conditions: Black skin, peeled, turned, or ground finish

2. L6 Steel Flat Bar / Plate

3. Forgings / Special Shapes of AISI L6

L6 Steel Equivalent

Standard System	Country/Region	Equivalent Grade	Common Search Terms
AISI / ASTM	USA	L6, UNS T61206	L6 steel, L6 tool steel, AISI L6, L6 material, AISI L6 steel
DIN / EN	Germany	1.2713, 55NiCrMoV6	1.2713 steel, DIN 1.2713, 55NiCrMoV6
DIN / EN	Germany	1.2714, 55NiCrMoV7	1.2714 steel, DIN 1.2714, 55NiCrMoV7
JIS	Japan	SKT4	SKT4 steel, JIS SKT4
GB	China	5CrNiMo	5CrNiMo steel, Chinese L6 equivalent
BS	UK	BH224-5	BH224-5 tool steel
AFNOR	France	55NCDV7	55NCDV7 steel
GOST	Russia	5ХНМ, 5KHNM	5ХНМ steel, 5KHNM steel

L6 Steel Composition

Standard	C	Si	Mn	P	S	Cr	Ni	Mo
ASTM A681-2008(R2015)	0.65-0.75	0.10‑0.50	0.25‑0.80	≤0.030	≤0.030	0.60‑1.20	1.25‑2.00	≤0.50

The high nickel content in L6 material provides exceptional toughness and deep hardenability. Chromium and molybdenum enhance hardenability and wear resistance.

L6 Steel Properties

MECHANICAL PROPERTY	METRIC VALUE	IMPERIAL VALUE
Hardness (Annealed)	≤ 241 HB	≤ 241 HB
Hardness (Quenched & Tempered)	57 – 62 HRC	57 – 62 HRC
Tensile Strength (σb)	655 – 2090 MPa	95 – 303 ksi
Yield Strength (σ0.2)	380 – 440 MPa	55 – 64 ksi
Elongation (δ5)	21 – 25 %	21 – 25 %
Reduction of Area (ψ)	55 %	55 %

The L6 steel is typically supplied in the annealed condition with a maximum Brinell hardness of 241 HB. After oil quenching at 830–870°C and tempering, it achieves a working hardness of 57–62 HRC. Tensile and yield strength values vary widely depending on heat treatment condition — from annealed (lower values) to hardened and tempered (higher values). AISI L6 steel exhibits very high impact toughness compared to other common oil‑hardening grades, with Charpy impact values (V‑notch) of approximately 1 ft·lb when tempered at 400°F. Unit conversions: 1 MPa ≈ 0.145 ksi.

Delivery Condition of L6 Steel

Black Surface, Bright Surface, Turned Surface, Grinded Surface, Poblished surface.

L6 Tool Steel Application

Dies of Various Types: Blanking dies, forming dies, embossing dies, swaging dies.
Punches: Heavy-duty punches, piercing punches, stamping punches.
Shear Blades: Shear blades, slitting shears, trimming dies.
Cold Forming Tools: Cold forming tools, coining dies, forming rolls.
Machine Parts: Pinions, arbors, spindles, lead and feed screws.
Clutch & Drive Components: Clutch parts, pawls, dogs, knuckle pins.
Springs & Bearings: Springs, bearings, rollers.
Plastic Molds: Plastic moulds, moulds for forging.
Tooling Components: Hobs, collets, chuck parts, stamp dies.
Hot Work Applications: Hammer dies, forging bolsters, extrusion die backers.

Heat Treatment & Processing of AISI L6

L6 Steel Heat Treatment

Soft Annealing: Heat to 670-700°C, hold adequately, then cool slowly in furnace. Resulting hardness ≤250 HB, optimized for batch machining.
Stress Relieving: Heat to approximately 650°C, hold for 1-2 hours, then air cool. Recommended after rough machining to minimize distortion.
Preheating: Preheat at 649°C (1200°F) before austenitizing to avoid thermal shock.
Austenitizing (Heating): 830-870°C. Soak time: 10-30 minutes. Protect against oxidation and decarburization.
Quenching (Cooling): Oil quench (40-60°C) is the primary method. L6 tool steel can also be water or brine quenched. Quench to 50-70°C, then temper immediately. Hardness after quenching: 57-61 HRC.
Tempering: Double tempering is recommended to eliminate retained austenite and ensure dimensional stability. Temper at 205-425°C for 50-62 HRC, or at higher temperatures for improved toughness. Cryogenic treatments may improve long-term dimensional stability.

Tempering Temp	As Quenched	148°C	204°C	260°C	315°C	371°C	426°C	482°C	537°C
Hardness (HRC)	65	62	60	57	55	53	50	46	43

For maximum wear resistance in blanking and shearing tools, temper at 204°C (60 HRC). For improved toughness in impact applications, temper at higher temperatures.

Processing Guide:

Forging: Heat uniformly to 1050-1100°C. Start forging at 1050°C, finish above 850°C. Do not forge below 843°C. After forging, cool slowly in lime or insulating media, then anneal.
Machining: Annealed L6 steel (≤250 HB) offers excellent machinability rated at 90% compared to W-group steels. Hardened parts require grinding with CBN wheels.
Polishing: This grade offers good polishability for most tooling applications.
Welding: L6 material is generally weldable. Consult supplier for proper procedures.
Nitriding: Gas or plasma nitriding can be applied to enhance surface hardness and wear resistance.
Corrosion Resistance: This is a steel alloy and is not corrosion resistant. Protect from rusting.

Quality Inspection & Control of L6 Steel

Full-process control:

Raw material and manufacturer control
Test : Chemical composition, mechanical properties, UT(ultrasonic testing), specification, surface condition, straightness, etc.
Packing: Wooden case or pallet or VCI plastic film

Why Purchase L6 Material from Keyspark Steel?

Fully Customizable: Dimensions, heat treatment, and hardness – all adjustable per batch order.
Certified Quality: Each batch comes with MTC certificate (EN 10204 3.1/3.2) , full chemical and mechanical test report.
ESR Option: Premium quality with Electro-Slag Remelting available for critical applications.
Stable Production: Large forging and rolling capacity ensures consistent quality across orders.
Long-Term Supply: Reserved production slots for regular customers – no interruptions.
Neutral Packaging: Oiled, wrapped, and strapped.

FAQ of L6 Steel

Q1: What is L6 steel?

A: L6 is oil‑hardening chromium‑nickel tool steel. It contains 1.25‑2.00% nickel to get very high impact toughness. While it keeps high hardness, it has good hardenability and stable size after heat treatment. It fits precision workpieces with complex shapes.

Q2: What are the equivalent standards of L6 steel?

A: Matching standards for L6 material: UNS T61206 (USA), GB 5CrNiMo (China), JIS SKT4 / SKS51 (Japan), DIN 1.2713 (55NiCrMoV6) (Germany), EN 55NiCrMoV7 (Europe).

Q3: What is the chemical composition of L6 steel?

A: Typical composition (mass): C 0.65‑0.75 %, Si 0.10‑0.50 %, Mn 0.25‑0.85 %, P ≤0.030 %, S ≤0.030 %, Cr 0.60‑1.20 %, Ni 1.25‑2.00 %, Mo ≤0.50 %, V 0.20‑0.30 %.

Q4: What hardness can L6 steel achieve after heat treatment?

A: Annealed (delivery condition) hardness of AISI L6: 183‑262 HB. Hardness after quench and temper: 45‑64 HRC. As‑quenched hardness is about 64 HRC. Different temper temperatures bring different hardness: temper at 300°F gives about 62.5 HRC; temper at 600°F gives about 56 HRC; temper at 900°F gives about 45 HRC. It can keep hardness above 60 HRC for 75 mm thick sections.

Q5: How is L6 steel heat treated?el best suited for?

Forging: start forging at 1079°C, stop forging above 843°C.
Annealing: heat to 760‑788°C and cool slowly (≤28°C/h).
Preheat: 649°C.
Quenching: heat to 815‑870°C, then oil quench.
Tempering: 177‑538°C.

You must temper right after quenching to avoid cracking.

Q6: What are the main applications of L6 steel?

A: AISI L6 steel works for parts that need both high toughness and good wear resistance: blanking dies, forming dies, coining dies; punches, mandrels, shear blades; clutch parts, pawls, spring collets; forming rolls, thread‑rolling dies; saw blades, lathe lead screws.