Main Content
The global plastic mold steel market continues to expand steadily. In 2026, the overall market size of plastic mold steel has exceeded 15.2 billion US dollars. As a classic low-alloy pre-hardened tool steel, P20 mold steel (AISI P20, DIN 1.2311) accounts for 41.7% of the global general-purpose plastic mold steel shipments. It dominates the mid-to-low-end injection mold, die-casting mold and mold base markets, and has become the preferred material for 70% of small and medium-sized mold manufacturers worldwide. Combining authoritative material parameters, field processing data and practical industry experience, this article elaborates on the core advantages, application boundaries, processing specifications and selection strategies of P20 steel, helping engineers and purchasers avoid material selection mistakes and control production costs efficiently.
1 Basic Introduction & Standard Chemical Composition
P20 is a representative pre-hardened low-alloy mold steel. It is delivered after complete quenching and tempering heat treatment, so secondary overall heat treatment is not required before processing. Its balanced hardness, toughness and machinability make it widely used in plastic molding and light-duty die-casting industries.
The standardized chemical composition of commercial P20 steel is strictly controlled within the following range, and each element jointly optimizes the comprehensive mechanical performance of the material:
· Carbon (C): 0.28% - 0.40%
· Chromium (Cr): 1.40% - 1.60%
· Manganese (Mn): 0.60% - 1.00%
· Molybdenum (Mo): 0.15% - 0.25%
· Silicon (Si): 0.20% - 0.40%
Chromium and molybdenum enhance the wear resistance and oxidation resistance of P20 steel, while manganese and carbon stabilize the overall toughness and structural strength. The uniform material structure ensures stable performance in long-term cyclic production. The standard delivery hardness is 28 - 32 HRC, and high-grade modified models such as P20HH and P20PH can reach 32 - 34 HRC, which can meet basic polishing and engraving requirements for plastic products.
2 Core Performance & Field Test Data
Based on the long-term detection data from third-party material testing institutions and workshop processing feedback, we sort out the practical performance indicators of P20 steel, and quantify its advantages and limitations in actual production.
2.1 Mechanical Strength & Toughness
The tensile strength of standard P20 steel is 980 - 1020 MPa, and the yield strength is 780 - 810 MPa. It maintains stable structural integrity under frequent mold opening and closing impact. In conventional injection molding working conditions, it will not crack or collapse due to mechanical fatigue. Compared with high-hardness mirror mold steel, its toughness is 15% higher, which is more suitable for molds with complex structures and thin-walled parts.
2.2 Superior Machinability for CNC Machining
Machinability is the most prominent advantage of P20 steel. It supports multiple processing methods including milling, drilling, turning and EDM. When matched with coated carbide tools for standard CNC machining, the recommended cutting speed for rough machining is 80 - 100 m/min, and the speed for finish machining can be increased to 100 - 120 m/min. The feed per tooth is controlled at 0.05 - 0.25 mm.
Field statistics show that the cutting resistance of P20 is 20% lower than that of S136 and NAK80. The tool loss rate is reduced by about 25%, and the processing cycle of complex cavities is shortened by 18% - 22%. This feature greatly improves the delivery efficiency of small and medium-sized mold projects.
2.3 Wear Resistance & Service Life
The alloy elements inside P20 provide moderate wear resistance. When processing general plastics such as ABS, PP and PE, the service life of the mold is stably maintained at 100,000 to 500,000 shots. After nitriding surface reinforcement (treatment depth 0.1 mm), the surface hardness rises to 65 - 68 HRC, and the wear resistance is increased by more than 3 times, extending the mold life to over 1 million shots.
It should be noted that if it is used to process plastics with glass fiber content exceeding 20%, the wear speed will accelerate significantly, and the service life will be reduced by 40% - 50% without surface reinforcement.
2.4 Corrosion Resistance Performance
P20 is not stainless steel. Although chromium brings slight anti-oxidation ability, its overall corrosion resistance is weak. In the production environment of PVC and halogen-containing flame-retardant plastics, the cavity will rust within less than 10,000 shots. It is only suitable for conventional non-corrosive plastic production scenarios.
3 Main Application Fields & Industry Distribution
Relying on high cost performance and stable performance, P20 steel has formed a clear application layout in the global mold industry. According to 2026 downstream industry material consumption statistics, the market share of each application field is as follows.
3.1 Injection Molding Molds (48%)
This is the largest application scenario of P20 steel. It is widely used to produce molds for home appliance shells, daily plastic products and ordinary auto interior parts. More than 75% of mid-range home appliance injection molds worldwide choose P20 as the cavity material. As a mainstream injection mold steel, it balances production cost and service life perfectly for mass-produced ordinary plastic parts.
3.2 Die-casting Molds (27%)
P20 is a cost-effective choice for low and medium-pressure die-casting molds of aluminum, zinc and magnesium alloys. Its excellent strength can ensure that the mold does not deform under high temperature and pressure, and it is favored by small die-casting processing factories.
3.3 Tooling & Fixture Components (16%)
A large number of jigs, fixtures, stamping dies and auxiliary tooling parts adopt P20 steel. Its easy processing feature allows manufacturers to quickly produce customized tooling with complex shapes and fine structures.
3.4 Mold Base & Structural Parts (9%)
Major mold bases, ejector plate and sliders of various plastic molds and die-casting molds use P20 to replace high-priced mold steel. This measure can reduce the material cost of a single large mold base by more than 30%.
4 P20 vs Mainstream Mold Steels: Performance & Cost Comparison
Mold manufacturers often struggle with the selection among P20, 718H, NAK80 and S136. The table below integrates the 2026 international market unit price, processing cost and actual service life data to present the differences of various steels in a straightforward way (the processing cost of P20 is taken as the benchmark 1.0).
| Steel Grade | Delivery Hardness (HRC) | Maximum Polishing Grade | Corrosion Resistance | Standard Service Life (Shots) | Global Unit Price (USD/kg) | Machining Cost Coefficient | Core Application Scenarios |
| P20 | 28~32 | 2000~4000 Grit | Poor | 100,000~500,000 | 2.4~3.5 | 1.0 | Ordinary injection molds, mold bases, tooling parts |
| 718H | 35~40 | 6000~8000 Grit | Poor | 300,000~1,000,000 | 3.3~4.9 | 1.5 | Medium-gloss plastic parts, modified plastic molds |
| NAK80 | 40~42 | 10000~15000 Grit | Medium | 500,000~1,000,000 | 7.1~8.5 | 2.0 | High-mirror transparent parts, cosmetic packaging molds |
| S136 | 48~52 | 8000~12000 Grit | Excellent | 400,000~800,000 | 10.0~12.8 | 2.2 | Corrosive plastic, food and medical grade molds |
Combined with the table data, we can draw targeted selection suggestions:
· In terms of cost: The unit price of NAK80 is about 2.4 to 2.8 times that of P20, and S136 is 3.6 to 4 times higher. For medium-sized molds with a material consumption of 500kg, the material cost gap can reach 3,800 to 5,100 US dollars.
· In terms of working conditions: For non-corrosive and low-gloss product molds with medium output, P20 is the most cost-effective option; for corrosive plastics and high-cleanliness products, S136 must be selected instead of P20.
· In terms of processing efficiency: P20 has the lowest processing difficulty, which is the core reason why it is popular in factories with tight delivery schedules.
5 Standard Processing, Heat Treatment & Daily Maintenance Specifications
Although P20 steel is easy to process, standardized operation is the key to maximizing its performance and extending its service life. We summarize the general specifications summed up by global mold workshop operation experience.
5.1 Mechanical Processing Rules
For CNC roughing, reserve a margin of 0.3~0.5mm on a single side, and 0.02~0.05mm for finishing. Use water-soluble cutting fluid for cooling throughout the process to control the tool temperature and reduce thermal deformation. After wire cutting and EDM processing, workpieces larger than 300mm must be tempered at 250~300℃ for 2 to 4 hours to remove internal stress, so as to avoid later cracking and dimensional deviation.
5.2 Heat Treatment Taboos & Surface Strengthening
P20 is delivered in a pre-hardened state. Overall quenching is strictly prohibited. Industry data shows that the cracking and deformation rate will exceed 80% if overall secondary heat treatment is carried out. If higher wear resistance is required, local nitriding treatment is the preferred solution. For molds exposed to slight corrosive materials, chrome plating can be used for temporary protection.
5.3 Daily Use & Anti-rust Maintenance
The mold temperature is controlled at 40~80℃ during injection production to prevent the hardness of P20 from decreasing due to long-term high temperature. After daily shutdown, clean the residual plastic materials in the cavity and apply anti-rust oil in time. For molds stored for more than 7 days, vacuum sealing and moisture-proof treatment are required. Statistics prove that standardized maintenance can increase the overall service life of P20 molds by 15%~20%.
6 Our P20 Mold Steel Products & Supporting Services
As a reliable global supplier specializing in P20 / 1.2311 plastic mold steel and comprehensive machining solutions, we maintain abundant inventory and full-range product specifications to serve mold manufacturers across over 30 countries worldwide. Our products strictly conform to AISI and DIN international standards, covering diverse supply forms to meet various production demands. Below are our core strengths:
First, reliable material quality and standardized production. Our P20 (1.2311) pre-hardened mold steel is produced via hot rolling and forging processes, featuring uniform hardness throughout cross-sections. Every batch of goods comes with complete official inspection documents. We conduct rigorous quality checks to eliminate internal defects like pores and cracks, ensuring the finished steel delivers stable toughness, polishability and photo-etching performance for long-term mold operation.
Second, ample stock, full sizes and efficient delivery. We keep more than 2000 tons of P20 mold steel in permanent stock. Our available products include flat bars, square bars, steel plates, blocks and round bars. Ranging from conventional to customized dimensions, all standard specifications can be delivered promptly. We also offer professional pre-processing services such as customized cutting, chamfering, drilling, milling and grinding, which greatly save customers’ secondary processing time and costs.
Third, integrated one-stop services. Beyond raw material supply, we provide full technical guidance and customized machining support. Our experienced technical team offers free professional advice on material selection and processing parameters. Supported by complete production equipment, we are capable of high-precision CNC machining, including custom fabrication of mold cavities, mold bases and other tooling components. This all-in-one service model effectively shortens the entire mold manufacturing cycle for our partners.
7 FAQ
Q1: Does pre-hardened P20 steel need overall secondary heat treatment?
A: No. P20 has completed quenching and tempering before leaving the factory, and the hardness meets the standard use requirements. Overall secondary quenching will lead to a high probability of cracking and deformation. If you need to improve local performance, you can only adopt surface strengthening processes such as nitriding and chrome plating.
Q2: What is the difference between P20 and 718H? How to make a reasonable selection?
A: 718H is an upgraded version of P20. Its delivery hardness, polishing performance and toughness are better than P20. Its unit price is 30% to 40% higher than P20, and the service life under conventional working conditions is increased by 60% to 100%. For ordinary matte daily necessities and home appliance molds, choose P20 for cost control; for plastic parts with medium and high surface gloss and long-term mass production, 718H is more suitable.
Q3: Why is P20 mold prone to rust? What are the practical anti-rust solutions?
A: P20 has limited chromium content and no inherent anti-corrosion ability. The most cost-effective solutions are: Clean the cavity and apply anti-rust oil after daily work; use vacuum sealing for long-term stored molds; conduct local chrome plating for molds contacting slightly corrosive plastics. It is not recommended to use P20 to process PVC and other highly corrosive plastic materials for a long time.
Q4: How much will the service life decrease when P20 processes glass fiber reinforced plastics? How to fix this problem?
A: When processing plastics with glass fiber content of 20% to 30%, the service life of untreated P20 molds will be reduced by 40% to 50%. Nitriding surface treatment can effectively solve this problem. The surface hardness after treatment is increased to 65 HRC or above, and the wear resistance is increased by 3 times, which can restore the normal service life of the mold.
Q5: What are the differences in processing efficiency between P20, NAK80 and S136?
A: Taking the processing time of P20 as the benchmark (1.0), the processing time of 718H is about 1.15 times, NAK80 is 1.25 times, and S136 is 1.22 times. P20 has the lowest cutting resistance and tool loss, so it has obvious advantages in mass processing and urgent delivery orders.