1.2316 plastic tool steel is a high-quality German standard corrosion-resistant plastic mold steel, belonging to the chromium-molybdenum alloy system. It is specially designed for plastic injection molding applications, where molds are exposed to corrosive plastics, additives, or cleaning agents. Renowned for its excellent corrosion resistance, polishability, and machinability, 1.2316 is widely used in the production of high-precision and aesthetically demanding plastic molds. Below is a detailed overview:
Chemical Composition
The typical chemical composition of 1.2316 plastic tool steel is as follows:
Carbon (C): 0.40–0.45% (provides hardness and wear resistance through heat treatment)
Chromium (Cr): 16.00–18.00% (the primary element for corrosion resistance, forming a passive oxide layer on the surface)
Molybdenum (Mo): 1.00–1.50% (enhances corrosion resistance, especially in harsh environments, and improves hardenability)
Silicon (Si): ≤1.00% (aids in deoxidation and improves mechanical properties)
Manganese (Mn): ≤1.00% (enhances hardenability and reduces brittleness)
Phosphorus (P): ≤0.030% (minimized to avoid embrittlement and reduce machining defects)
Sulfur (S): ≤0.015% (controlled to ensure good polishability and toughness)
Key Properties
1.2316 steel is tailored to meet the specific demands of plastic mold manufacturing, with properties that prioritize durability, precision, and surface quality:
Excellent Corrosion Resistance
The high chromium content (16–18%) forms a dense chromium oxide film on the surface, effectively resisting corrosion from corrosive plastics (e.g., PVC, POM), plasticizers, flame retardants, and cleaning agents. This makes it ideal for molds used in medical, food packaging, and chemical plastic products.
Superior Polishability
It can achieve a high-gloss surface finish (up to mirror polish) due to its low sulfur content and fine, uniform microstructure. This is critical for plastic parts requiring high aesthetic quality, such as automotive interior trim, electronic product casings, and cosmetic packaging.
Good Machinability
Despite its high chromium content, 1.2316 maintains reasonable machinability in the annealed state, allowing for precise processing of complex mold cavities and cores.
Hardenability and Dimensional Stability
It can be hardened to moderate hardness levels with uniform properties across thick sections. Heat treatment causes minimal distortion, ensuring dimensional accuracy in finished molds.
Wear Resistance
After proper heat treatment, it exhibits good wear resistance, extending mold life even in high-volume production of abrasive plastics (e.g., filled with glass fibers or minerals).
Physical Properties
Density: ~7.85 g/cm³
Thermal Expansion Coefficient: ~10.5×10⁻⁶/K (at 20–100°C)
Thermal Conductivity: ~25 W/(m·K) (at room temperature)
Melting Point: ~1400–1450°C
Mechanical Properties (After Heat Treatment)
Hardness: Typically 45–50 HRC (adjustable via tempering; higher hardness for wear resistance, lower for improved toughness).
Tensile Strength (Rm): ~1600–1900 MPa
Yield Strength (Rp0.2): ~1400–1700 MPa
Elongation (A): ~8–12%
Impact Toughness (Charpy V-notch): ≥20 J/cm² (at room temperature, depending on heat treatment).
Heat Treatment Process
Proper heat treatment is essential to optimize 1.2316’s corrosion resistance, hardness, and dimensional stability:
Annealing
Purpose: Soften the steel for machining, reduce internal stress, and improve machinability.
Process: Heat to 800–850°C, hold for 2–4 hours, then furnace cool slowly (≤50°C/hour) to below 500°C before air cooling.
Result: Hardness ≤230 HBW, ensuring ease of cutting and grinding.
Quenching
Purpose: Harden the steel by forming martensite, enhancing strength and wear resistance.
Preheating: Heat to 600–650°C, then to 800–850°C (to avoid thermal shock and ensure uniform heating).
Austenitizing: Heat to 1020–1050°C, hold for 30–60 minutes (based on section thickness) to fully dissolve chromium carbides.
Cooling: Quench in oil or air (oil quenching for deeper hardness; air quenching for minimal distortion in complex molds).
Tempering
Purpose: Relieve quenching stress, reduce brittleness, and balance hardness with toughness while preserving corrosion resistance.
Process: Temper at 200–250°C (for high hardness) or 450–500°C (for better toughness), hold for 2–4 hours per 25mm thickness, then air cool. Double tempering is recommended to ensure stability.
Result: Hardness adjusted to 45–50 HRC with optimal corrosion resistance and mechanical performance.
Application Fields
1.2316 plastic tool steel is widely used in plastic mold manufacturing, particularly in applications requiring corrosion resistance and high surface quality:
Corrosive Plastic Molds: Ideal for molds processing PVC (polyvinyl chloride), POM (polyoxymethylene), and plastics containing corrosive additives (e.g., flame retardants, plasticizers).
High-Gloss Plastic Parts: Used for molds producing automotive interior/exterior trim, electronic device casings, cosmetic packaging, and household appliance components that require a mirror-like surface finish.
Medical and Food-Grade Molds: Suitable for manufacturing plastic parts in medical devices, food packaging, and pharmaceutical containers, where corrosion resistance and cleanliness are critical.
Large or Complex Molds: Applied in large-sized injection molds (e.g., automotive bumpers, refrigerator liners) due to its good hardenability and dimensional stability.
Abrasive Plastic Molds: Used for molds processing filled plastics (e.g., glass fiber-reinforced plastics) thanks to its balanced wear resistance.
1.2316 steel’s combination of corrosion resistance, polishability, and processability makes it a top choice for high-performance plastic molds, ensuring long service life and consistent part quality in demanding applications.