Hot Work Tool Steel Introduction

Hot Work Die Steel: Types and Developments

Hot work die steel is crucial for manufacturing die materials used in the hot forming of metals. The three primary categories of hot work die steels are low alloy, medium alloy, and high alloy steels. Below, we explore the most commonly used grades and recent advancements in hot work die steels:

1. Low Alloy Hot Work Die Steel
   • Typical Grades: 5CrNiMo, 5CrMnMo
     Low alloy hot work die steels are characterized by their reduced alloy content, which provides a good balance between toughness and wear resistance.
2. Medium Alloy Hot Work Die Steel
   • Typical Grades: H13 (4Cr5MoSiV1), H11 (4Cr5MoSiV), H12 (4Cr5MoWSiV), H10 (4Cr3Mo3SiV)
     These grades are widely used for their excellent thermal fatigue resistance and wear resistance, making them suitable for various hot work applications.
3. High Alloy Hot Work Die Steel
   • Typical Grade: H21 (equivalent to 3Cr2W8V)
     High alloy steels are designed to withstand extreme conditions and are known for their high temperature strength and resistance to wear.

Recent Developments in High-Performance Hot Work Die Steels:

1. Base Steel
   • Features: This steel’s chemical composition is similar to the matrix structure of high-speed steel after quenching. It exhibits fine, dispersed carbides post-tempering, providing excellent toughness and thermal fatigue resistance.
2. Low Carbon High-Speed Steel
   • Features: By reducing the carbon content to 0.3%-0.6%, this steel maintains high red hardness while enhancing toughness and thermal fatigue properties. Examples include H25, H26, and H42 from the United States.
3. High Temperature Hot Work Die Steel
   • Features: These steels are designed for temperatures exceeding 700°C. They use austenite as the matrix structure and incorporate elements like vanadium, tungsten, and molybdenum. They offer improved strength and hardness but may have lower thermal conductivity and poor thermal fatigue resistance, making them unsuitable for chilling and heating conditions.
4. High Temperature Corrosion-Resistant Die Steel
   • Features: Developed for die casting molds and molds for pressed glass products, these steels improve resistance to liquid metal erosion and high-temperature oxidation.
5. High Hardenability Hot Work Die Steel
   • Features: For large forging dies, these steels have increased contents of Ni, Cr, and Mo to enhance hardenability, thermal strength, and toughness. Examples include 40NiCrMoV4 (4Ni4Cr2MoV) and 40NCD16 (4Ni4Cr2Mo) from the French NF-35-590 standard.
6. Medium Alloy High Strength and Toughness Hot Work Die Steel
   • Features: These steels optimize alloying elements to reduce production costs while enhancing strength and toughness. Examples include Sweden’s QRO80 and QRO90M, which feature MC carbide as the main strengthening phase.