Plastic injection molding is one of the most widely used production processes in the manufacturing industry, and mold steel is the core material of injection molds. Choosing the right mold steel for plastic injection molds directly affects mold life, product quality, and production costs. With the continuous development of the plastic industry, there are more and more types of mold steel, which makes it difficult for many purchasers and manufacturers to make choices. This 2026 complete guide will detail the key factors for choosing plastic injection mold steel, recommended grades for different scenarios, common mistakes, and selection steps, helping you choose the most suitable mold steel for your injection production.

Key Factors for Choosing Plastic Injection Mold Steel

When choosing plastic injection mold steel, you need to comprehensively consider the following key factors to ensure that the selected steel meets the production needs:

1. Plastic Material Properties

The properties of the plastic material to be processed are the most important factor, especially corrosion resistance and viscosity:

• Corrosive Plastics (PVC, PC, flame-retardant plastics): Need mold steel with good corrosion resistance, such as S136, 2083, NAK80 (with certain corrosion resistance).
• Non-Corrosive Plastics (ABS, PP, PE): Ordinary pre-hardened mold steel can meet the requirements, such as P20, 718H, P20HH.
• High-Viscosity Plastics (PC, PMMA): Need mold steel with good wear resistance and polishability, such as S136, NAK80, 718H.

2. Product Surface Quality Requirements

The surface quality of plastic products directly determines the choice of mold steel, especially the polishability of the steel:

• Ordinary Surface (no high-gloss requirement, such as plastic toys, daily necessities): P20, P20HH, 45# steel (low cost, general polishability).
• High-Gloss Surface (such as electronic shells, cosmetic packaging): NAK80, S136, 718H (excellent polishability, can achieve mirror effect).
• Matte Surface (such as automotive interior parts, household appliance shells): 718H, P20HH (can be processed into matte surface, good toughness).

3. Production Batch & Mold Service Life Requirements

The production batch of plastic products determines the wear resistance and service life requirements of the mold steel:

• Small Batch (less than 100,000 pieces): P20, 45# steel (cost-effective, can meet short-term use requirements).
• Medium Batch (100,000-500,000 pieces): 718H, P20HH, 2083 (good wear resistance, long service life).
• Large Batch (more than 500,000 pieces): S136, NAK80, H13 (excellent wear resistance and corrosion resistance, suitable for long-term continuous production).

4. Mold Structure Complexity

Complex mold structures (such as thin-walled parts, intricate cavities, sliding blocks) have higher requirements on the machinability and toughness of mold steel:

• Simple Structure (such as flat products, simple cavities): P20, D2 (easy to process, low cost).
• Complex Structure (such as thin-walled parts, multi-cavity molds): 718H, NAK80, DC53 (good machinability, high toughness, not easy to crack during processing).

5. Budget Constraints

Budget is an important factor for many manufacturers. It is necessary to choose mold steel with high cost-effectiveness according to the budget:

• Low Budget: P20, 45# steel, ordinary hot work mold steel (meet basic production requirements).
• Medium Budget: 718H, P20HH, 2083 (balance of performance and cost).
• High Budget: S136, NAK80, DC53, H13 (excellent performance, long service life, suitable for high-end production).

Recommended Mold Steel Grades for Different Plastic Injection Scenarios

According to the above key factors, we have sorted out the most suitable mold steel grades for different plastic injection scenarios, which can help you quickly select:

1. Ordinary Non-Corrosive Plastics (ABS, PP, PE) – Cost-Effective Scenario

• Recommended Grades: P20, P20HH
• Features: Pre-hardened, easy to process, moderate hardness and toughness, cost-effective.
• Applications: Plastic toys, daily necessities, low-precision electronic accessories, small to medium batch production.

2. High-Gloss Non-Corrosive Plastics (ABS, PP) – High-Quality Scenario

• Recommended Grades: 718H, NAK80
• Features: Excellent polishability, high precision, good toughness, suitable for large batch production.
• Applications: Electronic product shells, automotive interior parts, household appliance shells, high-gloss cosmetic packaging.

3. Corrosive Plastics (PVC, PC, Flame-Retardant Plastics) – Corrosion-Resistant Scenario

• Recommended Grades: 2083 (cost-effective), S136 (high-end)
• Features: Good corrosion resistance, excellent polishability, wear resistance, can avoid mold rust.
• Applications: PVC pipes, PC lenses, flame-retardant electronic shells, medical plastic products.

4. High-Viscosity Plastics (PC, PMMA) – Wear-Resistant Scenario

• Recommended Grades: S136, NAK80, H13
• Features: High wear resistance, excellent polishability, good high-temperature resistance, suitable for long-term continuous production.
• Applications: PMMA lenses, PC optical parts, high-precision plastic components.

5. Complex Structure Molds (Thin-Walled, Multi-Cavity) – High-Toughness Scenario

• Recommended Grades: 718H, NAK80, DC53
• Features: Good machinability, high toughness, not easy to crack during processing, stable dimensional accuracy.
• Applications: Thin-walled plastic parts, multi-cavity injection molds, complex electronic product shells.

Step-by-Step Selection Process for Plastic Injection Mold Steel

To help you avoid mistakes and select the most suitable mold steel, here is a step-by-step selection process:

1. Clarify Plastic Material: First determine the type of plastic to be processed (corrosive or non-corrosive, high-viscosity or low-viscosity), which is the basis for selection.
2. Confirm Product Requirements: Clarify the surface quality (ordinary, high-gloss, matte) and production batch of the plastic product.
3. Analyze Mold Structure: Judge the complexity of the mold structure and whether it needs high toughness and machinability.
4. Determine Budget Range: According to the production cost budget, screen the mold steel grades within the budget.
5. Consult Professionals: If you are unsure, consult a professional mold steel supplier or engineer to get customized selection advice.

Common Mistakes to Avoid When Choosing Plastic Injection Mold Steel

1. Blindly Pursuing High-End Steel: Using high-cost S136 or NAK80 for ordinary plastic products with small batches, resulting in waste of cost. P20 or 718H is sufficient for most ordinary scenarios.
2. Ignoring Corrosion Resistance: Using ordinary mold steel (such as P20) for corrosive plastics (such as PVC), leading to mold rust, shortened service life, and affecting product quality.
3. Neglecting Toughness for Complex Molds: Choosing mold steel with insufficient toughness (such as D2) for complex structure molds, leading to mold cracking during processing or use.
4. Only Focusing on Cost, Ignoring Service Life: Choosing low-cost but low-wear-resistance mold steel for large-batch production, resulting in frequent mold replacement and increased production costs in the long run.

We provide a full range of plastic injection mold steel grades, including P20, 718H, NAK80, S136, 2083, etc., with complete quality certificates and free custom cutting, milling, and grinding services. Our professional engineer team can provide you with free selection advice according to your plastic material, product requirements, and budget. Contact us now to get a free quote and detailed material data sheet!

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