Introduction
Most global mold manufacturers struggle with a critical material selection dilemma: choosing between pre-hardened mold steel and quenched & tempered mold steel for injection mold production. Industry research shows that 42% of mold factories suffer irreversible losses due to improper mold steel selection.
The common losses include delayed urgent orders caused by unnecessary 7-10 days heat treatment for simple low-volume molds using H13/S136 quenched steel, high scrap rate up to 27% for thin-walled complex cavities due to quenching deformation, and squeezed profit margins from inflated overall costs (material + heat treatment) for ordinary mass-production plastic molds.
Most engineers only recognize the high hardness and wear resistance of quenched steel, while ignoring the core advantages of pre-hardened steel: no heat treatment required, easy welding, low deformation risk and lower machining costs. Combined with overseas original steel technical data and actual measurement data of 150 mass-production mold projects from 2025 to 2026, this article comprehensively analyzes the applicable scenarios of the two types of mold steel, helping mold manufacturers select materials correctly and avoid heavy rework and scrap losses.
1 Fundamental Differences in Production Logic and Supply Status
1.1 Pre-hardened Mold Steel (P20/1.2312/718H/NAK80)
Pre-hardened mold steel is fully quenched and high-temperature tempered in advance at the steel mill, with a stable delivery hardness of 28–40HRC. The delivered blanks can be directly processed through CNC machining for roughing and finishing without secondary heat treatment. Most internal forging stress is released during smelting, greatly reducing the deformation risk of thick plates and special-shaped parts, and enabling easy modification and welding in later stages. As a high-end intermediate pre-hardened steel, NAK80 features a maximum delivery hardness of 40HRC, with polishing and wear resistance performance between ordinary pre-hardened steel and quenched steel.
1.2 Quenched Mold Steel (H13/S136/D2)
Quenched mold steel is supplied in an annealed soft state (18–22HRC), only allowing rough machining with a 0.2~0.3mm finishing allowance reserved. After roughing, it must be sent for vacuum quenching and tempering to reach a high hardness of 48–62HRC. Although quenched steel delivers excellent wear resistance, corrosion resistance and mirror polishing performance, the heat treatment process generates uncontrollable internal stress, easily causing plate warpage and cavity cracking. The overall production lead time is extended by 1~2 weeks, and finishing processes such as hard milling, EDM and grinding are required after hardening, resulting in significantly higher machining costs.
2 Full-dimensional Quantitative Comparison: Pre-hardened Steel vs Quenched Steel
Unified test conditions: 1000×600×120mm mold steel, identical CNC equipment, tested under ABS and 30% glass-filled PA66 injection molding conditions
| Comparison Dimension | Pre-hardened Mold Steel (P20/718H/NAK80) | Quenched Mold Steel (H13/S136/D2) | Impact & Gap |
| Hardness Range | 28–40HRC, max 40HRC for NAK80 | 48–62HRC after heat treatment | Quenched steel owns superior wear resistance and polishing performance |
| Total Mold Lead Time | 7–10 days, no heat treatment waiting | 14–22 days, 3~7 days occupied by heat treatment | Quenched steel doubles lead time, unable to support urgent orders |
| Heat Treatment Deformation Rate | ≤0.05mm/m, no secondary quenching process | 0.05–0.15mm per 100mm thick plate | 27% scrap rate for complex cavities, scrap loss of $5,000–$15,000 for thick plates |
| Raw Material Cost | Benchmark 100% | +35% higher than pre-hardened steel | Higher procurement cost for quenched steel blanks |
| Additional Heat Treatment Cost | 0 | +15%~25% of total mold cost | Extra fixed outsourcing expense for quenching & tempering |
| Later Mold Modification & Welding Difficulty | Easy welding, low cracking risk at room temperature | High difficulty, 250℃ pre-heating & post-weld tempering required | 60% more working hours for quenched steel mold repair |
| Service Life (Unfilled ABS/PC) | 300,000–500,000 shots (P20/718H/NAK80) | 1,000,000–2,000,000 shots (H13/S136) | Quenched steel service life is 2~4 times that of ordinary pre-hardened steel |
| Service Life (30% GF PA66) | Obvious gate wear after 50,000–100,000 shots (P20) | Stable 500,000–1,000,000 shots without scratch (H13) | Quenched steel is mandatory for glass-filled abrasive molding |
| Maximum Mirror Polishing Grade | SPI B-1 (P20/1.2312); SPI A-2 (NAK80) | SPI A-1 mirror finish (Ra＜0.012μm, S136) | Quenched stainless steel is exclusive for optical & high-gloss cosmetic molds |
| Conventional CNC Machining Cost | Benchmark 100%, processable with standard tools | +40% higher, requiring hard milling tools / EDM processing | Higher consumable and programming costs for quenched steel finishing |
Core Conclusions
Pre-hardened steel reduces comprehensive costs by 30% and outperforms quenched steel for ordinary shell molds, medium and low-volume production, short-cycle products (within 2 years) and urgent orders. Quenched high-hardness steel is mandatory for glass-filled abrasive molding, PVC corrosive materials, medical optical parts and long-term mass production over 500,000 shots. As an intermediate material, NAK80 balances moderate polishing performance and wear resistance, ideal for non-glass-filled consumer electronics and medical molds with annual output below 500,000 shots.
3 Targeted Material Selection Standards for 5 Injection Molding Scenarios
Scenario 1: Home Appliance & Daily Necessity Shells (ABS/PP Unfilled, <500K Shots/Year)
Recommended Steel: P20 steel / 1.2312 pre-hardened steel
Reason: No heat treatment required to shorten lead time, smooth cutting reduces CNC machining costs, easy for later modification and welding. It delivers the lowest comprehensive production cost for molds without strict high-gloss appearance requirements.
Scenario 2: Glass-filled Nylon/PPS Abrasive Structural Parts (Long-term Mass Production)
Recommended Steel: Quenched H13 hot work mold steel
Reason: High vanadium alloy greatly improves anti-abrasion performance, preventing gate and core erosion caused by high-velocity glass fiber flow. P20 is only suitable for prototype molds within 10,000 shots, with severe parting line erosion and texture peeling in mass production.
Scenario 3: Transparent PC/PMMA, Cosmetic & Medical Consumables (Corrosion-resistant & High-gloss)
Recommended Steel: Quenched S136 stainless mold steel
Reason: 13.5% high chromium forms a stable anti-rust passivation layer, supporting top-tier SPI A1 mirror polishing and resisting acid corrosion from PVC and disinfectants. No pre-hardened steel can replace its anti-corrosion and high-gloss performance.
Scenario 4: Consumer Electronics & Medical Small Parts (Medium Volume, Moderate Mirror Requirement)
Recommended Steel: NAK80 pre-hardened steel
Reason: Higher hardness and better polishing performance than P20, no additional heat treatment needed. It perfectly balances machining efficiency and appearance quality for medium-end small molds without fiber filling or corrosion.
Scenario 5: Large Mold Base, Bottom Plate & Support Structural Parts (No Appearance Requirement)
Recommended Steel: 1.2312 free-cutting pre-hardened steel
Reason: Sulfur-added design reduces cutting resistance, saving 27% of CNC roughing time. No polishing or quenching treatment is required, making it the most cost-effective choice for structural mold components.
4 Four Common Mold Steel Selection Mistakes Made by 90% of Mold Factories
Mistake 1: Higher Hardness Equals Better Performance for All Molds
Higher hardness reduces steel toughness and increases welding cracking risk. Blindly adopting quenched steel for ordinary non-abrasive products leads to wasted costs on raw materials, heat treatment and repeated repairs. Quenched steel is only worthwhile for abrasive, corrosive and high-gloss molding scenarios.
Mistake 2: Pre-hardened Steel Cannot Be Used for Mass Production
Optimized chromium-molybdenum formulation of 718H and NAK80 pre-hardened steel supports stable production of 500,000 shots for ordinary ABS plastic, fully meeting medium-volume production demands. Upgrading to quenched steel is only necessary for glass-filled materials and annual output over 500,000 shots.
Mistake 3: Quenching Deformation Can Be Fixed by Finishing
Quenching internal stress causes integral plate warpage, which cannot be repaired if the finishing allowance is insufficient, resulting in direct steel scrap. Thick plates over 100mm face double scrap risks.
Mistake 4: Directly Use P20 for Small-batch Glass-filled Prototypes
P20 can barely serve prototypes within 10,000 shots but suffers obvious gate and core wear, easily causing defective products. The cost-effective solution is to adopt P20 base matched with H13 quenched gate inserts.
5 One-stop Mold Steel Supply & Processing Service (ASIATOOLS)
ASIATOOLS provides full-range in-stock mold steel solutions. We offer 24-hour custom cutting and fast delivery for pre-hardened steel including P20, 1.2312 and NAK80, and support one-stop vacuum heat treatment for H13 and S136 annealed blanks, with all materials certified by EN 10204 official material reports. Our professional engineering team provides free customized material selection guidance based on plastic type, production volume and surface requirements. Verified by European home appliance and medical mold clients, our pre-hardened steel shortens mold lead time by 40% and reduces overall production costs by 28%. We also provide one-stop pre-processing services such as six-sided precision milling, supporting global sea freight and cross-border delivery.
FAQ (Google People Also Ask Optimization)
Q1: Can pre-hardened mold steel be re-quenched for higher hardness?
A: It is not recommended. Pre-hardened steel has undergone stabilized high-temperature tempering. Secondary quenching will trigger massive internal stress, causing severe cavity deformation and cracking. High hardness requirements must be met with original annealed blanks for professional heat treatment.
Q2: Is P20 pre-hardened steel applicable for mass production of 30% glass-filled nylon molds?
A: Not recommended for mass production. Glass fiber is highly abrasive, and low-hardness P20 suffers obvious gate wear and texture peeling after 20,000–50,000 shots. It is only acceptable for prototypes within 10,000 shots, preferably matched with H13 quenched gate inserts to reduce wear.
Q3: How to control heat treatment deformation of quenched steel?
A: Standard four-step deformation control process: 1. Reserve 0.2~0.3mm finishing allowance on key surfaces before heat treatment; 2. Adopt vacuum heat treatment to avoid surface decarburization; 3. Perform double tempering to fully release internal stress; 4. Conduct low-temperature stress relief after roughing to reduce final quenching deformation.
Q4: What are the pros and cons of NAK80 pre-hardened steel versus H13 quenched steel?
A: Advantages of NAK80: No heat treatment required, shorter lead time, lower machining cost and easy modification, supporting SPI A-2 mirror finish. Disadvantages: Limited wear resistance, unable to meet long-term mass production demands over 500,000 shots or glass-filled/corrosive molding scenarios, where H13 performs far better.
Q5: What is the total cost gap between pre-hardened steel and quenched steel?
A: For the same specification plate, quenched annealed blank costs 35% higher in raw material, plus an additional 15%-25% heat treatment fee, resulting in an overall mold cost increase of about 50%.
Q6: How to solve welding cracking of quenched steel during mold modification?
A: Preheat the steel integrally at 250℃ before welding, adopt professional matching welding materials, and perform low-temperature tempering after welding to eliminate stress. However, the complex process greatly increases working hours. Pre-hardened steel is the preferred choice for molds requiring frequent modification.