Those in die casting industry know: If mold material is wrong, all design is wasted.
Die casting molds operate under harsh conditions of high temperature, rapid heating and cooling, high pressure friction, and repeated impacts. From small parts like cores and ejector pins to large parts like cavities and mold frames, material and heat treatment hardness of every component directly determine mold's lifespan, casting yield, are a core factor in controlling production costs.
Many on-site operators rely solely on experience to select materials. This can lead to minor issues like short-term thermal fatigue, aluminum adhesion, and wear, or even serious problems like cavity cracking and complete mold failure, resulting in huge losses. Today, we combine national industry standards, professional knowledge, and front-line practical experience to completely break down material selection requirements, steel properties, heat treatment parameters, and comparisons of domestic and international grades for all categories of die casting mold components, gating systems, sliding parts, and mold bases. Beginners can get started, and experienced operators can use it as a reference. We recommend saving and sharing!

Die-casting mold forming parts and gating systems are in constant contact with high-temperature molten metal, making them the most demanding in their working conditions. Sliding parts and support parts experience different stress patterns. Industry has established clear material selection standards for four types of parts, which are also primary principles for material selection.
1. Forming Parts & Gating System Parts (Cavity, Core, Sprue Bushing, Runner Cone, etc.)
These parts are in direct contact with high-temperature molten metal. Core performance requirements include:
- Excellent forging and machinability;
- High-temperature red hardness and high-temperature strength meet standards, resisting thermal deformation;
- Good thermal conductivity, strong resistance to thermal fatigue, low coefficient of thermal expansion, able to withstand repeated rapid heating and cooling;
- Resistance to high-temperature oxidation, high wear resistance, and resistance to molten metal corrosion;
- Good hardenability, minimal deformation after heat treatment.
2. Sliding Fit Parts (Guide Pillars, Guide Sleeves, Angled Pins, Wedge Blocks, etc.)
These parts do not come into high-temperature contact but experience continuous reciprocating friction and lateral forces. Requirements:
- High wear resistance and structural strength;
- Moderate hardenability, minimal deformation after heat treatment to ensure precise fit.
3. Structural Components such as Sleeve Plates and Support Plates
These components primarily bear clamping forces and injection pressure. Core requirements:
- Sufficient strength and rigidity to prevent deformation;
- Easy machining to reduce manufacturing costs.
4. Comprehensive Material Selection Principles
In actual material selection, it is not enough to only consider part's working condition; type of die-casting alloy, complexity of casting, dimensional accuracy, production volume, and cost budget must be considered comprehensively. Industry-recommended mainstream steels should be prioritized.

Hot work die steels are core base material for die casting molds. Based on domestic application history, R&D batches, and sources, industry uniformly classifies them into three main categories. A dedicated non-magnetic die steel is also included, and it's a key fundamental knowledge point emphasized in instructional videos.
1. Three Mainstream Categories of Hot Work Die Steels
- Established Classic Steel Grades: 5CrMnMo, 5CrNiMo, 3Cr2W8V, 8Cr3
With a long history of application, mature technology, and high cost-effectiveness, these remain commonly used materials for small-to-medium batch die casting and conventional castings.
- New Domestic Steel Grades: 5Cr4Mo3SiMnVAl, 3Cr3Mo3W2V, 5Cr4W5Mo2V, 4CrMnSiMoV
Optimized for high-temperature and thermal fatigue conditions in die casting, these steels offer superior high-temperature strength and crack resistance compared to traditional steels, making them suitable for mass production molds.
- Introducing Internationally Commonly Used Steel Grades: 4Cr3Mo3SiV (W10), 4Cr5MoSiV (H11), 4Cr5MoSiV1 (H13), 4Cr5W2VSi (W2)
These steels boast superior overall performance and are currently preferred choice for precision die casting, aluminum alloy die casting, and magnesium alloy die casting. They are also standard for high-end molds.
2. Special Use Material: 7Mn15Cr2A13V2WMo Non-magnetic Mold Steel
This steel combines non-magnetic properties with hot-work mold performance, making it suitable for die casting applications with specific anti-magnetic requirements. Its application scenarios are relatively niche.
3. General Performance Requirements for Hot Work Die Steel (Industry Mandatory Standard)
Die casting molds are subjected to repeated impact loads, high temperatures of 300~600℃, alternating hot and cold impacts, and frictional wear. Qualified hot work steel must meet following requirements:
High hardenability, resulting in uniform mechanical properties across large mold cross-sections; Excellent impact toughness and thermal fatigue resistance, preventing hot and cold cracking; Good thermal conductivity, rapidly dissipating heat and reducing thermal damage; High tempering stability and high-temperature strength, preventing high-temperature plastic deformation; Strong oxidation resistance and excellent machinability.
Industry standard for carbon content is controlled at 0.3%~0.5%, with addition of elements such as chromium, molybdenum, vanadium, and nickel to enhance overall performance. Molybdenum and tungsten effectively prevent high-temperature tempering brittleness in steel.

This section compiles material selection and heat treatment hardness standards for all types of parts, considering different die-casting alloys (zinc alloy, aluminum-magnesium alloy, copper alloy). It can be directly referenced for machine setup, mold design, and mold repair in workshop.
(I) Parts in Contact with Molten Metal (Molded Parts + Gating System)
1. Cavity Inserts, Cores, and Slider Forming Parts - Zinc Alloy Die Casting: 4Cr5MoVSiI (H13), 3Cr2W8V, 5CrNiMo, 4CrW2Si
- Aluminum and Magnesium Alloy Die Casting: 4Cr5MoV1Si (H13), 3Cr2W8V
- Copper Alloy Die Casting: 3Cr2W8V, 3Cr2W5Co5MoV, 4Cr3Mo3W2V, 4Cr3Mo3SiV, 4Cr5MoV1Si
- Heat Treatment Hardness: Zinc/Aluminum/Magnesium Alloy Molds 43~47HRC; Copper Alloy Molds 38~42HRC
2. Sprue Bushings, Gating Inserts, and Runner Cones (Gating System)
- Zinc Alloy Die Casting: 4Cr5MoVSi, 3Cr2W8V
- Aluminum and Magnesium Alloy Die Casting: 3Cr2W8V
(II) Sliding Fit Parts (Guide Posts, Guide Sleeves, Angled Pins, Bent Pins, Wedge Blocks)
General Materials: T8A, T10A
Heat Treatment Hardness: 50~55HRC
(III) Push Rods, Reset Rods
1. Push Rods: Zinc alloy: 4Cr5MoV1Si, 3Cr2W8V; Aluminum and Magnesium alloy: T8A, T10A, Hardness 45~50HRC
2. Reset Rods: General T8A, T10A, Hardness 50~55HRC
(IV) Mold Frame Structural Parts (Sleeve Plates, Support Plates, Seat Plates, Push Rod Fixing Plates, etc.)
- Conventional Selection: 45# Steel; Heavy-Duty Application: Q235, Cast Steel
- Heat Treatment Requirements: Quenching and Tempering, Hardness... 28~32HRC
Supplementary Process Specifications: For die-cast zinc, aluminum, and magnesium alloy parts, soft nitriding/nitriding treatment is recommended after quenching: nitriding depth controlled at 0.08~0.15mm, surface hardness HV≥600, which can significantly improve wear resistance and corrosion resistance of mold, extending its service life.
Important Note: Materials listed first in the table are preferred choices; refer to this order when selecting materials.

Many companies use a mix of domestic and imported materials. Different countries have different steel grade naming conventions. This comparison table is essential for mold procurement, mold repair, and material replacement, covering mainstream grades from China, US, Russia, Japan, Germany, Sweden, etc.:

 

Supplementary Explanation: US H13 corresponds to domestic 4Cr5MoSiV1, with superior overall performance, and is currently the most widely used in high-end die-casting.

Precise Material Selection Based on Die-Casting Alloy: Copper alloys have the highest die-casting temperature and are the most corrosive. Direct use of ordinary zinc alloy mold steel is strictly prohibited; high-tungsten, high-chromium hot-work steel must be selected. For mass production of aluminum alloys, H13 series is preferred, balancing lifespan and cost.
Strictly Adhere to Hardness Standards: Excessive hardness in formed parts easily leads to cracking, while insufficient hardness easily leads to deformation and sticking to mold. Insufficient hardness in sliding parts will cause rapid wear; heat treatment must be performed according to HRC parameters.
Do Not Omit Nitriding Process: For mass-produced molds, nitriding of forming surface is the most cost-effective way to extend life. Depth and hardness must strictly adhere to standards of 0.08~0.15mm and HV≥600.
Avoid Blindly Using High-Hardness Steel for Mold Base Components: Clad plates and support plates only require heat treatment. Excessive quenching increases processing difficulty and costs, which is unnecessary.
Selection of materials for die-casting molds follows three core principles: "part working conditions + die-casting alloy + industry standards."
For high-temperature components in contact with molten metal, hot-work die steel is primary choice, with control over red hardness, thermal fatigue performance, and heat treatment hardness. Carbon tool steel is used for sliding friction parts to ensure precise fit. For mold frame structural components, strength and ease of machining are paramount.
3Cr2W8V and H13 (4Cr5MoSiV1) are currently two main steels used in die-casting industry, suitable for over 90% of mass production conditions. A comparison table of domestic and international steel grades can solve problem of replacing imported and domestic materials. Thoroughly understanding these standards can reduce mold damage and casting defects at source, resulting in clear cost reduction and efficiency improvements.