1.2714 Hot Mold Steel
1.2714 is a high-quality hot work tool steel known for its excellent combination of high-temperature strength, thermal fatigue resistance, and wear resistance. It is specifically designed for demanding hot-forming applications where tools are subjected to repeated heating and cooling cycles, high pressure, and abrasive wear. This grade is widely used in the die casting, forging, and extrusion industries.
Basic Information
Definition: 1.2714 is a chromium-nickel-molybdenum alloy hot work steel that maintains its mechanical properties at temperatures up to 600–650°C. It is characterized by good hardenability, uniform hardness distribution, and resistance to heat checking, making it suitable for large and complex mold components.
Corresponding Standards: Defined by DIN (Germany) as 1.2714, it is equivalent to grades such as AISI L6 (USA) and GB 5CrNiMo (China) in terms of application, though with slight compositional variations for enhanced hot-work performance.
Key Characteristics: High toughness at elevated temperatures, good thermal conductivity, excellent wear resistance, and dimensional stability during heat treatment.
Chemical Composition
The composition of 1.2714 is carefully balanced to optimize hot-work performance, with key elements as follows:
Element Content Range Role in the Steel
Carbon (C) 0.50–0.60% Provides a foundation for hardness and carbide formation, ensuring strength and wear resistance at high temperatures.
Chromium (Cr) 0.50–0.80% Enhances hardenability, oxidation resistance, and thermal stability; improves resistance to scaling at elevated temperatures.
Nickel (Ni) 1.50–2.00% Significantly improves toughness and impact resistance, especially at high temperatures, reducing the risk of thermal cracking.
Molybdenum (Mo) 0.40–0.60% Boosts high-temperature strength, creep resistance, and hardenability; reduces temper brittleness.
Manganese (Mn) 0.60–0.90% Enhances hardenability and strength; refines grain structure during heat treatment.
Silicon (Si) 0.20–0.40% Acts as a deoxidizer; improves strength and oxidation resistance at high temperatures.
Phosphorus (P) ≤0.030% Strictly controlled to avoid brittleness, especially under thermal stress.
Sulfur (S) ≤0.030% Minimized to prevent reduced toughness and hot cracking during processing.
Physical Properties
Density: Approximately 7.85 g/cm³ (consistent with most alloy tool steels).
Melting Point: Around 1450–1500°C.
Thermal Conductivity: ~35–40 W/(m·K) at room temperature; maintains stable heat dissipation at high temperatures.
Coefficient of Thermal Expansion: ~11.0×10⁻⁶/°C (20–500°C), minimizing thermal distortion during cyclic heating and cooling.
Elastic Modulus: ~210 GPa at room temperature; retains ~80% of modulus at 600°C, ensuring structural stability under heat.
Mechanical Properties
1.2714’s mechanical properties are optimized for hot-work applications, with a focus on balancing strength, toughness, and heat resistance:
Annealed State (for Machining)
Hardness: ≤241 HB (machinable with conventional tools).
Tensile Strength: ~700–800 MPa.
Elongation: ~18–22% (good ductility for complex mold shaping).
After Hardening + Tempering (for Hot-Work Use)
Tempering Temperature Hardness Tensile Strength (20°C) High-Temp Strength (600°C) Impact Toughness (Charpy V-Notch)
500°C (932°F) 45–48 HRC ~1400–1600 MPa ~900–1000 MPa ~35–45 J
550°C (1022°F) 42–45 HRC ~1200–1400 MPa ~800–900 MPa ~45–55 J
600°C (1112°F) 38–42 HRC ~1000–1200 MPa ~700–800 MPa ~55–65 J
Thermal Fatigue Resistance: Excellent—resists microcracking from repeated heating and cooling cycles, critical for long die life in hot forging and die casting.
Wear Resistance: Good at high temperatures, due to carbide formation, ensuring durability in abrasive conditions.
Heat Treatment Process
Proper heat treatment is essential to maximize 1.2714’s performance in hot-work applications:
Annealing
Purpose: Soften the steel for machining and ensure a uniform microstructure.
Process: Heat to 830–860°C, hold for 3–4 hours, then cool slowly (≤30°C/hour) to 600°C, followed by air cooling. Results in hardness ≤241 HB.
Austenitizing (Heating for Hardening)
Temperature: 830–860°C (1526–1580°F).
Hold Time: 1–2 hours (depending on part thickness) to ensure uniform austenitization.
Quenching
Cooling Medium: Oil quenching to achieve a martensitic structure, with as-quenched hardness of 50–55 HRC.
Result: Ensures full hardening while minimizing distortion.
Tempering
Temperature Range: 500–600°C (932–1112°F), with holding time of 2–3 hours (double tempering recommended to eliminate retained austenite and reduce internal stress).
Effect: Balances hardness and toughness; higher temperatures increase toughness and thermal stability while slightly reducing hardness.
Processing Performance
Machinability: Good in the annealed state (≤241 HB) using high-speed steel or carbide tools. Proper cutting parameters are recommended to avoid work hardening.
Weldability: Moderate; requires preheating to 300–400°C and post-weld tempering to prevent cracking. Welding is primarily used for mold repair.
Formability: Cold formability is limited due to moderate strength in the annealed state. Hot forming is possible at 1100–1150°C, followed by annealing to restore machinability.
Forging Performance: Excellent—can be forged into complex shapes at 1050–1150°C, with slow cooling to avoid cracking.
Application Fields
1.2714 is widely used in hot work mold applications requiring resistance to thermal shock and high pressure:
Hot Forging Molds:
Dies for forging automotive components (e.g., crankshafts, connecting rods, gears) and large mechanical parts.
Upsetting dies and forming tools for high-strength steel forging.
Die Casting:
Molds for medium to large aluminum and zinc alloy die castings, including automotive housings and industrial components.
Extrusion Tools:
Dies for hot extrusion of non-ferrous metals (e.g., aluminum, copper alloys) and low-carbon steel.
Other Hot Work Applications:
Hot shear blades, pressure casting molds, and die inserts subjected to repeated thermal cycles.
In summary, 1.2714 hot mold steel is valued for its balanced combination of high-temperature strength, toughness, and thermal fatigue resistance, making it a reliable choice for demanding hot forming processes in automotive, machinery, and metallurgical industries.