Hot Work Tool Steel｜High Strength, Heat Resistant for Die Casting & High-Temperature Applications

In the mold and machinery industries, where components are constantly exposed to high heat such as in die casting or hot forging, the durability and heat resistance of the tool steel directly determine production efficiency and mold life. However, many manufacturers continue to face problems such as cracking, surface burning, and premature wear of molds. These are often caused by thermal fatigue repeated heating and cooling that gradually weakens the steel structure and shortens mold life.

Key Industry Challenges

In hot metal forming or casting operations, molds frequently encounter temperatures exceeding 600°C. Conventional steel cannot maintain its structure under such extreme heat. Their microstructure softens, leading to loss of hardness and deformation, and often causing quenching cracks during rapid cooling cycles.

Root Cause of the Problem

Ordinary steels lack key alloying elements such as Molybdenum (Mo) and Vanadium (V), which are essential for thermal stability and high-temperature strength. Without them, steel cannot withstand rapid temperature changes (thermal shock), resulting in cracking, softening, and severe wear during long-term use at elevated temperatures.

Yamaichi’s Solution

Yamaichi Special Steel (Thailand) supplies premium-grade Hot Work Tool Steel SKD61 and SKD61 MODIFY, manufactured in compliance with JIS G4404 (Japan Industrial Standard). Both grades are refined through the ESR (Electro Slag Remelting) process, which ensures a fine-grain microstructure, minimal inclusions, and high material purity. As a result, these steels offer superior heat resistance, thermal shock durability, and extended die life, outperforming conventional hot work steels.

Characteristics of YAMAICHI Hot Work Tool Steel

1. SKD61 — The Global Standard for Hot Work Tool Steel

• Composition: Chromium–Molybdenum–Vanadium (Cr–Mo–V Alloy Steel)
• Hardness after heat treatment: HRC 48–52
• Excellent balance of hardness and toughness
• High resistance to heat checking and thermal cracking
• Superior polishability and surface finish
• Compatible with surface treatments such as Nitriding / PVD / CVD
• Idea for Die casting molds, forging dies, core pins, inserts, cavity blocks, and other hot-working components

2. SKD61 MODIFY — Enhanced Grade for Longer Tool Life

• Improved alloy composition for better balance of toughness and hardness
• Refined through High Purity ESR Process
• Offers 20–30% higher toughness than standard SKD61
• Reduces risk of thermal fatigue cracking and post-treatment stress
• Excellent surface polishability and texturing capability
• High corrosion resistance under cooling or lubricant exposure
• Idea for High-pressure die casting molds (HPDC), large forging dies, and components exposed to continuous heat

Why Choose Yamaichi Hot Work Tool Steel

• Japan Quality Manufacturing with certified consistency
• ISO 9001:2015 Certified
• ESR / VAR refined for microstructural purity and stability
• Outstanding high-temperature strength and impact resistance
• In-house Heat Treatment Service under the Yamaichi Group
• Cut-to-Length and Precision Grinding available for ready-to-use materials

Practical Applications

• Aluminum Die Casting Manufacturers:

Use SKD61 MODIFY for core inserts and cavity blocks to extend mold life

• Forging Mold Producers:

Use SKD61 for upper and lower dies requiring strength and high heat resistance

• High-Temperature Machinery Component Makers:

Use SKD61 for sleeves, hot runners, and guide pins exposed to continuous heat

Hot Work Tool Steel from Yamaichi Special Steel (Thailand) deliver the perfect combination of hardness, heat resistance, and durability, making them ideal for die casting, forging, and high-temperature precision components. Engineered with Japanese metallurgical technology, Yamaichi steels help manufacturers achieve longer mold life, stable performance, and reduced maintenance costs.

※ For more information, please contact us below or download our brochure.

Glossary

• ESR (Electro Slag Remelting): Refining process for cleaner, inclusion-free steel
• Thermal Fatigue: Fatigue caused by repeated heating and cooling cycles
• Thermal Shock: Stress from sudden temperature change
• Nitriding: Surface hardening process using nitrogen diffusion
• PVD / CVD: Thin-film coating processes that enhance surface hardness and heat resistance
• Hot Work Tool Steel: Steel designed for molds or tools used at elevated temperatures

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