How to choose plastic mold steel

Choosing plastic mold steel is a critical process in mold manufacturing. The classification of plastic molds is generally based on their longevity, divided into five grades: Grade 1 lasts over a million cycles; Grade 2 lasts between 500,000 and 1 million cycles; Grade 3 lasts from 300,000 to 500,000 cycles; Grade 4 lasts from 100,000 to 300,000 cycles; and Grade 5 lasts below 100,000 cycles.

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For Grades 1 and 2, mold steel typically requires a hardness after heat treatment of around HRC 50. Since plastic is prone to wear, this can affect tolerance. It is essential to select steel that not only exhibits good performance after heat treatment but also provides excellent cutting qualities at high hardness levels. Often, imported raw materials from the Pearl River Delta are preferred.

Common selections include S136 from Sweden, 420 and H13 from the USA, and 083 from Europe, as well as Japanese options like SKD61 and DC53 (the latter used under special conditions). Moreover, the raw plastic materials and any added fillers significantly influence the choice of mold steel, especially when glass fiber is involved, as it can severely wear down the mold cavity surface.

Some plastic materials exhibit acid corrosion, and certain additives or modifiers—such as glass fiber—can lead to mold degradation. Therefore, the selection of plastic materials is crucial. For highly corrosive plastics, options like S136 and Grade 420 are recommended. For less corrosive materials, S136, 420, SKD61, NAK80, PAK90, and 718M should be chosen. Examples of strong acid plastic materials include PVC, POM, and PBT, while weak acid materials include PC, PP, PMMA, and PA.

Additionally, the product's appearance requirements greatly impact the selection of plastic mold materials. If high transparency is necessary, materials like S136, 718 S, NAK80, or PAK90 should be used; in contrast, S136 and 420 are recommended for molds requiring high transparency.

While it is essential to meet product requirements, cost must also be a consideration. For instance, S136 typically costs significantly more—around 55-60 yuan per kilogram—compared to other options. Making an incorrect choice can lead to significant financial losses.

Pre-hardened mold steels are available in grades such as S136H, H, 718H, and 083H, with hardness levels ranging from HB270 to HB340. For lower specification molds, S50C and 45# steel are often utilized, which can go directly into the mold cavity.

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Here are 4 essential tips for selecting the right 718H steel:

When selecting materials for advanced applications, choosing the right steel is paramount. Among various grades, 718H steel is recognized for its applications in sectors such as aerospace, oil and gas, and power generation. Its distinctive composition and properties render it suitable for high-stress environments. This article outlines four key tips for selecting the appropriate 718H steel, emphasizing its functional attributes, advantages, and practical applications.

## 1. Understanding the Chemical Composition of 718H Steel

The first step in selecting 718H steel is understanding its chemical makeup. This grade is a nickel-based superalloy consisting of approximately 50% nickel, 18% chromium, and trace amounts of titanium, molybdenum, and aluminum. This specific formulation enhances its resistance to corrosion and heat, making it ideal for applications requiring prolonged exposure to high temperatures. Moreover, the alloy demonstrates exceptional fatigue strength and thermal stability, ensuring both longevity and reliability under varied conditions.

## 2. Assessing Mechanical Properties

Next, focus on the mechanical properties of 718H steel. It possesses outstanding tensile strength, yield capacity, and ductility, all crucial for high-performance applications. The yield strength can surpass 1,100 MPa (approximately 160,000 PSI), enabling it to endure substantial loads without deforming. Furthermore, its ductility simplifies machining and forming, which is beneficial for producing complex components. Always evaluate these attributes concerning the specific needs of your application to ensure optimal performance.

## 3. Considering Production Flexibility

A significant advantage of 718H steel is its production flexibility. This material is highly workable, accommodating various fabrication techniques, including forging, casting, and additive manufacturing. Its versatility makes it suitable for a broad spectrum of applications—from turbine blades in jet engines to downhole components in drilling operations. Additionally, its ability to maintain mechanical properties post-machining facilitates rapid prototyping and design iterations, improving overall production efficiency.

## 4. Analyzing Application-Specific Requirements

Finally, consider the distinct requirements of your application when choosing 718H steel. Different environments necessitate varying degrees of corrosion resistance or thermal stability. For instance, aerospace applications demand materials that can withstand extreme temperatures while retaining their strength. Conversely, in the oil and gas industry, enhanced corrosion resistance is vital due to the hostile conditions involved. Careful examination of operating conditions and aligning them with the unique properties of 718H steel will yield better decisions and optimized performance outcomes.

## Conclusion and Future Outlook

In summary, selecting the right 718H steel entails understanding its composition, evaluating mechanical properties, considering production flexibility, and analyzing specific application requirements. As industries increasingly strive for higher efficiency, precision, and adaptability, 718H steel remains a leading choice for numerous applications. By following the tips presented in this article, you can make informed decisions that align with your project objectives.

Looking ahead, advancements in materials like 718H steel will likely continue, fostering innovation across multiple sectors. Stay updated on developments in material science to ensure your choices remain relevant and effective in addressing emerging challenges.

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