5CrMnMo Hot Work Tool Steel

Pada Aobo Steel, with over 20 years of experience in forging, we understand the demands placed on hot work tool steels. 5CrMnMo Hot Work Tool Steel is a reliable low-alloy option we frequently supply, known for its specific balance of properties.

1.  5CrMnMo Steel Overview and Chemical Composition

5CrMnMo Hot Work Tool Steel is classified as a low-alloy hot work die steel. Its performance characteristics stem from its specific chemical composition.

Based on standard GB/T1299-2000, the typical composition (weight %) is:

• Karbon (C): 0.50% – 0.60%
• Mangan (Mn): 1.20% – 1.60%
• Kromium (Cr): 0.60% – 0.90%
• Nikel (Ni): 1.40% – 1.80%
• Molibdenum (Mo): 0.15% – 0.30%
• Silikon (Si): ≤ 0.40% (some specifications allow 0.25-0.60%)
• Fosfor (P): ≤ 0,030%
• Belerang (S): ≤ 0,030%

Minor variations in ranges might exist depending on the specific standard edition.

2. 5CrMnMo Steel Applications

5CrMnMo Hot Work Tool Steel is a practical choice for manufacturing medium- to small-sized hot-forging dies, typically those with side lengths of up to 400 mm. Its good toughness makes it suitable for:

• Dies with complex shapes.
• Hammer forging dies are subject to significant impact.
• The working parts of hot work dies are subjected to high impact loads.
• Zinc, aluminum, and alloy die casting molds.
• Hot press molds and some plastic molds.
• Base material for certain shearing/punching tools and cold heading dies (can sometimes replace T10A, 9SiCr, Cr12MoV for larger sections).

3. Mechanical Properties and Comparison With 5CrNiMo

• Kekuatan: Slightly higher than 5CrNiMo steel.
• Toughness & Plasticity: Lower than 5CrNiMo at both room and elevated temperatures due to manganese replacing some nickel.
• Kemampuan pengerasan: Lower than 5CrNiMo.
• Ketahanan terhadap Kelelahan Termal: Poorer than 5CrNiMo at high working temperatures; shows greater sensitivity to overheating.

While 5CrMnMo Hot Work Tool Steel offers good value and performance for its target applications, its properties may make 5CrNiMo a preferred choice for larger or more demanding hot forging tasks. However, for very large section dies, other grades like 5Cr2NiMoVSi are often selected for superior hardenability.

4. Heat Treatment of 5CrMnMo Steel

Sesuai perawatan panas is crucial for achieving the desired performance from 5CrMnMo. Aobo Steel has extensive experience supplying steel that meets these processing requirements.

4.1 Penempaan

Follow process parameters similar to 5CrNiMo. Careful control of heating and cooling is necessary to prevent cracking. Slow cooling after forging (furnace cooling for large forgings to 150-200°C) is essential to prevent white spots.

4.2 Annealing

Isothermal annealing is recommended:

1. Heat to 850-870°C and hold for 4-6 hours.
2. Cool to isothermal temperature of 680°C, hold 4-6 hours.
3. Furnace cool to below 500°C, then air cool. Expected Hardness: 197-241 HBW (Pearlite + Ferrite structure).

4.3 Pendinginan

1. Heat to 840-860°C. Higher temperatures (around 900°C) can increase lath martensite, resulting in better toughness.
2. Oil quench. Cool down to 150-180°C before immediate tempering.
3. To minimize distortion and cracking, consider pre-cooling in air to 740-780°C (dark red) before oil quenching, or pre-cooling larger dies to 780-810°C. Isothermal quenching steps (e.g., oil quenching to 150-200°C, followed by an isothermal hold at 280°C) can also be beneficial.

4.4 Temperatur

Tempering adjusts final hardness and toughness. It relieves stress and stabilizes the structure.

1. General: 450-500°C, often performed twice.
2. Forging Die Bodies:
   
   • Small dies: 490-510°C (Hardness: 44-47 HRC)
   • Large dies: 560-580°C (Hardness: 34-37 HRC)
3. Die Tenons (for toughness):
   
   • Small dies: 620-640°C (Hardness: 34-37 HRC)
   • Medium dies: 640-660°C (Hardness: 30-35 HRC)
4. Penghilang Stres: A final stress relief treatment at 280°C for 2-3 hours is recommended after tempering.

5. Enhancing Performance

The service life of 5CrMnMo dies can be extended through:

• Optimized Heat Treatment: Techniques such as high-temperature quenching (around 900°C), pre-cooling before quenching, and isothermal quenching followed by double tempering can enhance toughness and reduce crack propagation.
• Perawatan Permukaan: Processes such as carbonitriding or rare-earth co-diffusion can significantly enhance surface hardness, wear resistance, and thermal fatigue resistance.
• Pemanasan awal: Always preheat dies to 200-250°C before use to minimize thermal shock and risk of fracture.