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Guide to Characteristics and Production Applications of Common Materials for High-Pressure Die Casting Mold Bases. Ensure the Life of HPDC Molds

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aCatTech’s Guide to Characteristics and Production Applications of Materials for HPDC Mold Bases

In the overall structure of high-pressure die casting molds, the mold base (including mold frames, mold feet, and other components) is the basic framework that supports the normal operation of the mold. The selection of mold base materials is directly related to the overall performance of the mold. Appropriate mold base materials can significantly extend the mold life, ensure the stability of the production process, and reasonably control production costs. Improper material selection may lead to premature mold damage, production interruptions, and a substantial increase in the company’s operating costs.

Here we focuse on three key materials widely used in high-pressure die casting mold bases: P20, S50C, and H13 ESR. It conducts in-depth analysis of their characteristics, applicable application scenarios, and matters needing attention in production applications, providing comprehensive and practical references for mold design, manufacturing, and production personnel.

Analysis of Core Material Characteristics

P20 Mechanical Properties

P20 material has a stable hardness of 28-32HRC in the pre-hardened state, and this hardness range gives it relatively balanced mechanical properties. Its tensile strength can reach 850-1000MPa, enabling it to withstand large static and dynamic loads and not easily fracture when subjected to complex forces such as clamping force and impact force. At the same time, it has a certain degree of toughness, with an impact toughness value of approximately 25-35J/cm². It can effectively absorb energy when encountering instantaneous impacts, avoid brittle fracture, and ensure the structural integrity of stress-bearing components of the mold base.

P20 Machinability

P20 material has excellent machinability and is very suitable for various mechanical processing techniques. In cutting processes, whether turning, milling, or planing, relatively smooth machined surfaces can be obtained, and the surface roughness can be easily controlled below Ra1.6μm. Drilling operations are also smooth, with less wear on the drill bits, high drilling efficiency, and the hole wall accuracy can meet the assembly requirements of mold base components. In addition, P20’s polishing performance is particularly outstanding. After rough polishing and fine polishing processes, the surface can achieve a mirror-like effect, which can meet the needs of decorative mold pads and other components that have certain requirements for surface quality.

P20 Heat Treatment Characteristics

P20 material is in a pre-hardened state when leaving the factory, which brings great convenience to mold manufacturing. In the manufacturing process of conventional mold bases, there is no need for secondary heat treatment, which greatly shortens the production cycle and reduces the risk of mold deformation caused by heat treatment. However, this pre-hardened state also determines that its hardness cannot be further increased through subsequent heat treatment processes, thus limiting its application in some special working conditions where higher material hardness is required.

P20 Wear Resistance and Fatigue Resistance

During high-pressure die casting, the stress-bearing components of the mold base are frequently subjected to cyclic loads. P20 material has certain wear resistance and fatigue resistance. Its wear rate is relatively low, and it can maintain the dimensional accuracy of components for a long time under normal use conditions. In terms of fatigue resistance, after multiple load cycles, fatigue cracks are not easily generated inside the material, which can reliably ensure the long-term stable operation of the stress-bearing components of the mold base and is suitable for scenarios subject to large forces such as clamping force and impact force.

S50C Mechanical Properties

The hardness range of S50C material is usually between 180-230HBW, with moderate strength and good plasticity. Its tensile strength is approximately 600-700MPa, and the yield strength is around 300-400MPa, which can meet the basic strength requirements of structural support components. At the same time, its elongation after fracture can reach 15%-20%, with good plastic deformation capacity, making it easy to be made into various complex-shaped structural components through cold working processes. Compared with P20 material, S50C has lower hardness but better plasticity, which is more advantageous in the manufacturing of some structural components that require a certain degree of deformation capacity.

S50C Machinability

S50C material has excellent cold forming properties and can be easily processed into various specifications of profiles and parts through cold rolling, cold drawing, cold bending, and other processes. Moreover, the machined parts have high dimensional accuracy and good shape stability. In terms of welding performance, it is an easily weldable material. Firm welded joints can be obtained using conventional welding methods such as arc welding and gas welding, and the strength of the welded joint after welding can reach more than 80% of the base metal strength, making it suitable for manufacturing structural components that need to be assembled by welding. These excellent machining properties enable S50C material to adapt to the processing needs of various types of structural components.

S50C Application Characteristics

S50C material exhibits excellent stability in positioning, supporting, and guiding components. When used as a supporting component, its rigidity can ensure that the component does not undergo significant deformation when bearing loads, ensuring the stability of the overall mold structure. In positioning and guiding functions, the material has good dimensional stability and can maintain high accuracy after long-term use, ensuring positioning accuracy and smooth guiding, and effectively avoiding the impact on the normal operation of the mold due to component loosening or displacement.

H13 ESR Mechanical Properties

After quenching and tempering, H13 ESR material can usually reach a hardness of 44-48HRC, with extremely high strength and hardness. Its tensile strength can reach 1800-2000MPa, and it is not prone to plastic deformation when bearing large loads. It has excellent high-temperature strength. In a working environment of 200-300℃, the strength decreases slightly, which can meet the use requirements of wear-resistant components in the mold base that are in a relatively high-temperature environment for a long time.

H13 ESR Heat Treatment Sensitivity

H13 ESR material is very sensitive to heat treatment process parameters. Small changes in quenching temperature and holding time will have a great impact on its performance. If the quenching temperature is too high (exceeding 1050℃), it will cause coarse grains in the material, significantly reducing toughness, and components are prone to brittle fracture during use; if the quenching temperature is too low (below 1020℃), the hardness potential of the material cannot be fully exerted, resulting in insufficient wear resistance. Excessively long holding time will cause grain growth, while excessively short holding time will result in insufficient austenitization of the material, affecting the final performance. Therefore, it is necessary to strictly control the heat treatment process parameters to ensure that the material performance meets the use requirements.

H13 ESR Applicability Boundaries

H13 ESR material is mainly applicable to components in the mold base that are not in contact with the material flow but have high wear resistance requirements. For some parts that bear large frictional loads, such as lifters and wear plates, its excellent wear resistance can meet long-term use needs. However, due to its relatively high cost, using H13 ESR material in ordinary structural components with low wear resistance requirements will increase costs, and in such cases, P20 or S50C materials can be considered.

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Description of Typical Application Scenarios of Materials

Detailed Application Scenarios of P20

P20 Stress-Bearing Components

Mold base plates, spacers, cylinder brackets, etc., are typical components in the mold base that bear large forces. Mold base plates need to bear the clamping force from the die casting machine during the die casting process, which can usually reach several thousand tons. The tensile strength and toughness of P20 material can effectively resist this huge pressure, ensuring that the plates do not deform or fracture. As components supporting the upper and lower molds, spacers need to bear the weight of the mold itself and the pressure transmitted during the die casting process. The hardness and rigidity of P20 material can ensure its long-term stable support. Cylinder brackets are subject to large pushing and pulling forces when the cylinder is working. The mechanical properties of P20 material can meet its force requirements, ensuring the normal operation of the cylinder.

P20 Test Mold Components

In the mold testing stage, some temporary components of the mold base often use P20 material. The main purpose of mold testing is to inspect the overall structure and operation of the mold, and there are relatively low requirements for the service life of components. P20 material is easy to process and relatively low in cost, and can quickly produce temporary components required for mold testing, such as some auxiliary supports and positioning blocks. After mold testing, if modifications to the mold structure are needed, the processing and modification of P20 material components are also more convenient, which can effectively shorten the mold testing cycle and reduce mold testing costs.

P20 Decorative Mold Pads

Decorative mold pads have certain basic requirements for precision and surface quality. P20 material can achieve high dimensional accuracy through precision machining, with tolerances controlled within ±0.01mm, meeting the fitting requirements between the pads and other components. At the same time, its good polishing performance can make the surface of the pads achieve high smoothness, avoiding wear or scratches caused by rough surfaces when in contact with other components, and ensuring the overall accuracy of the mold.

Detailed Application Scenarios of S50C

S50C Stress-Bearing Components

Structural support components such as spacers, feet, and centralized water blocks have clear requirements for stability and rigid support. Spacers need to fix the distance between the upper and lower molds to ensure the dimensional accuracy of the mold cavity. The rigidity of S50C material can meet this requirement, and it does not undergo significant deformation when bearing pressure. Feet are used to fix the mold on the die casting machine workbench and need to bear the weight of the entire mold. The strength of S50C material can ensure the stable support of the feet, avoiding mold shaking during operation. Centralized water blocks have complex water channels inside for mold cooling, and they need to bear the pressure of the cooling liquid. The sealing performance and strength of S50C material can ensure that the water blocks do not leak and have a stable structure.

S50C Positioning and Guiding Components

Positioning and guiding components such as positioning plates, guide rods, and limit posts have extremely high requirements for accuracy retention. Positioning plates are used to ensure the accurate position of the upper and lower molds during clamping, and their positioning accuracy directly affects the dimensional accuracy of die castings. The dimensional stability of S50C material can maintain positioning accuracy for a long time, avoiding positioning deviations caused by wear or deformation. Guide rods guide the movement direction during mold opening and closing, requiring good straightness and surface finish. After precision machining and grinding, S50C material can meet the guide accuracy requirements and is not prone to large wear during long-term use. Limit posts are used to limit the maximum opening and closing distance of the mold to prevent damage to mold components due to excessive movement. The strength of S50C material can bear the impact force during limiting, ensuring accurate and reliable limiting.

S50C Versatility

S50C material has good cross-scenario adaptability and can be used for both structural components and decorative mold pads, etc. In terms of structural components, its machinability and mechanical properties can meet the needs of different structural designs, whether simple support blocks or complex connection structures, which can be made through appropriate processing techniques. In decorative mold pads, after processing, its dimensional accuracy and surface quality can meet basic requirements, and the cost is relatively low. Therefore, in some scenarios where the surface quality requirements are not particularly high, it can replace P20 material, reducing mold manufacturing costs.

Detailed Application Scenarios of H13 ESR

H13 ESR Non-Material Flow Contact Components

Non-material flow contact components such as lifters and wear plates mainly bear losses caused by motion friction. Lifters need to slide relative to other components during mold opening and closing, and large wear will occur on the friction surfaces. The high hardness and wear resistance of H13 ESR material can reduce this wear, extending the service life of lifters. Wear plates are usually installed in the sliding parts of the mold to reduce friction and protect the mold body. Wear plates made of H13 ESR material can bear long-term frictional loads, ensuring the smooth operation of sliding parts and reducing mold maintenance costs.

H13 ESR Relationship Between Mold Testing and Service Life

The recommended service life ranges of H13 ESR material in mold base components of small and medium-sized molds and large molds are different. For small and medium-sized molds, due to their relatively small overall size, the loads borne by the components are relatively small, and the service life of components made of H13 ESR material can usually reach 10,000-20,000 cycles. This is because the die casting frequency of small and medium-sized molds is relatively high, but the force per die casting is small, and the wear and fatigue accumulation of the material are relatively slow. For large molds, the mold base components are larger in size and bear greater loads, and the service life of H13 ESR material components is generally 5,000-10,000 cycles. Large molds have a longer die casting cycle and greater force per die casting, resulting in more severe material wear and fatigue, so the service life is relatively shorter. These service life ranges are obtained by comprehensively considering factors such as material performance, mold size, and working conditions, which can provide references for mold design and use.

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Matters Needing Attention and Solutions in Material Production Applications

Matters Needing Attention in P20 Production

P20 Processing Difficulties

When cutting P20 material in the pre-hardened state, appropriate cemented carbide tools should be selected, such as YT15, YW1, etc. These tools have high hardness and wear resistance and can bear the cutting resistance of P20 material. The selection of cutting parameters is also crucial. For an end mill with a diameter of 20mm, the cutting speed can be controlled within the range of 1200-1500r/min, and the feed rate is 0.12-0.15mm/r. Excessively high speed will cause a sharp increase in tool temperature, accelerating tool wear; excessively large feed rate will increase cutting force, easily causing tool chipping and rough part surfaces.

P20 Assembly Risks

Stress concentration problems are prone to occur during the assembly of stress-bearing components made of P20 material, especially in the threaded processing parts of tie rods and cylinder connecting rods. The root of the thread is a high-risk area for stress concentration. If the thread processing accuracy is not high, such as non-standard thread form and excessive surface roughness, it will lead to increased stress concentration, and thread fracture may occur when stressed. Therefore, when processing threads, the thread accuracy grade should reach 6g or higher, the surface roughness should be controlled below Ra3.2μm, and at the same time, processes such as rolling should be used to improve the strength and wear resistance of the thread surface.

P20 Solutions

To avoid stress concentration, key parts should adopt fillet transition design during the design of stress-bearing components, with a fillet radius of generally not less than 3mm, to disperse stress through the smooth transition of the fillet. After processing, the components should be subjected to aging treatment. The parts are heated to 150-180℃, kept warm for 4-6 hours, and then slowly cooled to room temperature. Aging treatment can eliminate internal stress generated during processing, improve the dimensional stability of parts, and reduce deformation and cracking caused by internal stress release during use.

Matters Needing Attention in S50C Production

S50C Processing Accuracy

The dimensional tolerance control of positioning components made of S50C material, such as positioning plates and positioning rods, is strict. The flatness tolerance of the positioning plate should be controlled within 0.02mm/m, and the thickness tolerance is ±0.01mm. The fit clearance between the positioning rod and the matching hole is usually 0.005-0.01mm, using transition fit or small clearance fit to ensure positioning accuracy. Excessively large fit clearance will lead to inaccurate positioning; excessively small clearance will increase assembly difficulty and may even cause jamming.

S50C Performance Limitations

The wear resistance of S50C material is relatively insufficient, and it is prone to wear under long-term friction conditions. To improve its wear resistance, surface nitriding treatment can be performed. Nitriding treatment involves placing the parts in a nitriding furnace, introducing ammonia gas into the furnace at a temperature of 500-550℃, so that nitrogen atoms penetrate into the part surface to form a nitrided layer with a thickness of 0.1-0.3mm, and the hardness of the nitrided layer can reach 500-800HV. Surface nitriding treatment can significantly improve the wear resistance of the part surface, while the core still maintains good toughness, meeting the use requirements of components.

S50C Solutions

To ensure the accuracy of key mating surfaces, the grinding process should be optimized. Select a grinding wheel with a grain size of 80-120#, control the grinding speed at 30-35m/s, and the feed rate at 0.01-0.02mm per pass. At the same time, use sufficient cooling fluid to avoid burns on the part surface. Before assembly, establish a strict accuracy verification process, and use precision measuring tools such as dial indicators and micrometers to conduct a comprehensive inspection of the dimensional, shape, and positional accuracy of positioning components to ensure that unqualified parts do not enter the assembly process and ensure the assembly quality of the mold.

Matters Needing Attention in H13 ESR Production

H13 ESR Heat Treatment Control

To solve the problems caused by improper temperature during the heat treatment of H13 ESR material, a stepwise heating process can be adopted. Specifically, first, slowly heat the material from room temperature to 600-650℃, and keep it warm for a period of time (such as 1-2 hours) to make the internal temperature of the material uniform and reduce thermal stress; then increase the temperature to 850-900℃, and keep it warm again (such as 2-3 hours) to further refine the grains; finally, heat up to the quenching temperature (usually 1020-1050℃), keep it warm for an appropriate time, and then perform quenching treatment. This stepwise heating method can effectively control grain growth, ensuring that the material maintains good toughness while obtaining high hardness.

H13 ESR Service Life Matching

Different heat treatment parameters and use and maintenance cycles should be formulated according to the size of the mold to achieve a reasonable match of mold service life. For H13 ESR components of small and medium-sized molds, the quenching temperature can be controlled at 1030℃, the tempering temperature is 520℃, and tempering is performed three times, with each holding time of 2 hours to obtain high hardness and toughness. The use and maintenance cycle can be set to conduct a comprehensive inspection every 10,000 productions, mainly checking the wear and dimensional accuracy of components. For H13 ESR components of large molds, the quenching temperature can be slightly lower, 1020-1030℃, and the tempering temperature is 540℃, also tempering three times to improve the toughness of the material. The use and maintenance cycle is shortened to once every 5,000 productions to timely detect and replace severely worn components, ensuring the normal operation of the mold.

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Die-casting Mold’s Mold Base Materials Common Problems and Solutions

Matching of Materials and Die Casting Processes

The temperature and pressure of the die casting process will affect the performance of mold base materials. In high-temperature die casting processes, the working temperature of the mold is high, which will reduce the strength and hardness of the mold base material. Therefore, materials with good heat resistance, such as H13 ESR material, should be selected to avoid component deformation due to high temperature. In high-pressure die casting processes, the mold base bears large pressure, and materials with high strength and toughness, such as P20 material, should be selected to ensure that components can bear high-pressure effects. When selecting materials, it is necessary to comprehensively consider the material properties according to specific die casting process parameters such as temperature and pressure to ensure that the material matches the process.

Balance Between Cost and Performance

When selecting mold base materials, it is necessary to seek a balance between cost and performance. H13 ESR material has excellent performance but relatively high cost, and is suitable for key components with high requirements for wear resistance and service life, such as lifters and wear plates. P20 material has moderate performance and relatively low cost, and is suitable for ordinary components with large forces, such as mold base plates and spacers. S50C material has the lowest cost and can be used for structural support components and positioning and guiding components with low performance requirements. In practical applications, materials should be reasonably selected according to factors such as the importance of components, working conditions, and production batch to meet the use requirements while minimizing costs as much as possible.

Comprehensive Comparison and Summary

Comparison Table of Core Properties of Three Materials

Material	Hardness	Machinability	Wear Resistance	Application Scenarios
P20	Pre-hardened 28-32HRC	Good cutting, drilling, and polishing performance, surface roughness can be controlled below Ra1.6μm	Has certain wear resistance, can meet the wear requirements of conventional stress-bearing components	Stress-bearing components such as mold base plates, spacers, cylinder brackets; test mold components; decorative mold pads
S50C	180-230HBW	Excellent cold forming and welding performance, can be processed into complex shapes	General wear resistance, needs to be improved through surface nitriding treatment, surface hardness after nitriding reaches 500-800HV	Structural support components (spacers, feet, etc.); positioning and guiding components (positioning plates, guide rods, etc.); cross-scenario adaptation
H13 ESR	44-48HRC after quenching and tempering	Relatively difficult to process, requires high tools and processes, needs to use cemented carbide tools	Excellent wear resistance, suitable for components bearing large frictional loads	Non-material flow contact wear-resistant components (lifters, wear plates, etc.)

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Future Requirements for Material Properties in High-Pressure Die Casting Molds

With the development of the high-pressure die casting industry towards high efficiency, precision, and long service life, higher requirements are put forward for the performance of mold base materials. Future mold base materials need to have a longer service life to adapt to the needs of large-scale continuous production, reduce the number of mold replacements, and improve production efficiency. At the same time, materials need to have better stability, and can maintain stable mechanical properties and dimensional accuracy during long-term use and complex working conditions to ensure the consistency of die casting quality. In addition, with the improvement of environmental protection requirements, materials should also have certain recyclability and environmental friendliness.

Material Selection Principles for Die-casting Tools's Mold Base

When selecting mold base materials, comprehensive judgment should be made according to mold type (small and medium-sized / large), service life requirements, and component functions. For small and medium-sized molds with small production batches and service life requirements within 10,000 cycles, P20 and S50C materials can be preferred; for large production batches and service life requirements exceeding 10,000 cycles, key wear-resistant components should select H13 ESR material. Due to the large loads borne by large molds and high requirements for material strength and stability, P20 material can be used for stress-bearing components, S50C material for support and positioning components, and H13 ESR material for wear-resistant components. For components with large forces, P20 material is preferred; for positioning and support components, S50C material is a cost-effective choice; for non-material flow contact wear-resistant components, H13 ESR material is the first choice.

Key Production Control Points

In the mold base production process, processing accuracy, heat treatment process (for H13 ESR), and assembly adaptability are key control points. In terms of processing accuracy, the key dimensional tolerances of all materials need to be controlled within ±0.01mm, and the surface roughness should be controlled below Ra1.6μm (for general components) or Ra0.8μm (for precision components) according to use requirements. The heat treatment of H13 ESR material must be carried out in strict accordance with process parameters to ensure that the quenching temperature is 1020-1050℃, the holding time is reasonable, and the tempering temperature and times meet the requirements. During assembly, it is necessary to ensure reasonable fit clearance between components, accurate positioning, avoid stress concentration, and conduct comprehensive accuracy verification to ensure that the mold assembly quality meets the use requirements.

Optimization Directions of Existing Materials

For P20 material, it can be optimized by adjusting the alloy composition, such as appropriately increasing the content of alloying elements such as nickel and chromium to improve its strength and wear resistance while maintaining good machinability. For S50C material, grain refinement treatment can be carried out, such as adopting controlled rolling process to improve its strength and toughness and reduce surface treatment procedures. The optimization focus of H13 ESR material is to further improve purity, reduce the content of inclusions through optimizing the electro-slag remelting process, and improve material uniformity; at the same time, new heat treatment processes should be studied to further improve its toughness while ensuring hardness, and expand its application range. Through these optimization measures, the performance of existing materials can be continuously improved to meet the development needs of high-pressure die casting molds.

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