A pre-hardened plastic mould steel (AISI P20 / DIN 1.2311) supplied already hardened and tempered to about 28 – 35 HRC, so it can be machined and put straight to work in injection and compression moulds.
What Is P20 Plastic Mold Steel?
P20 is the standard pre-hardened plastic mould steel. It is delivered in the hardened-and-tempered condition, so the toolmaker machines it directly without a hardening step that would distort the cavity — a big time saver for injection moulds.
It is used for injection and compression moulds, die-casting tools for low-melting alloys, jigs and fixtures. For extra surface wear it is commonly nitrided. It is not stainless.
Supply Forms and Sizes
Every form is available soft-annealed (for further forming and machining) or heat-treated to your hardness window.
| Form | Condition | Size Range | Typical Use |
|---|---|---|---|
| Pre-hardened plate | Q&T, 28 – 35 HRC | 10 – 300 mm | Mould plates, bases |
| Pre-hardened block | Q&T | 100 – 600 mm | Large mould sections |
| Round bar | Q&T | 20 – 300 mm | Cores, ejector housings |
| Pre-machined blank | Q&T | custom | Mould cavities |
Chemical Composition (AISI P20 / DIN 1.2311)
| C | Mn | Si | Cr | Mo | P max | S max |
|---|---|---|---|---|---|---|
| 0.30 – 0.40 | 0.60 – 1.00 | 0.20 – 0.80 | 1.40 – 2.00 | 0.30 – 0.55 | 0.030 | 0.030 |
Heat analysis is reported on the mill certificate for every lot. If your drawing calls for tighter limits than the standard, flag it at enquiry — ladle-refined heats usually meet it without a surcharge.
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Elastic modulus (E) | ~200 GPa |
| Shear modulus (G) | ~79 GPa |
| Thermal conductivity | ~40 W/m·K at room temperature |
| Coefficient of thermal expansion | ~12 ×10⁻₆ /K (20 – 200 °C) |
Mechanical Properties
Typical values for pre-hardened P20 (supplied condition). The mill certificate is the binding document.
| Condition | Tensile Strength | Yield Strength | Elongation | Hardness |
|---|---|---|---|---|
| Pre-hardened | 950 – 1100 MPa | ≥ 750 MPa | ≥ 12 % | 28 – 35 HRC |
| Nitrided surface | — | — | — | ≥ 600 HV surface |
Equivalent Grades
| Standard | Designation |
|---|---|
| USA AISI | P20 |
| Germany DIN | 1.2311 |
| China GB/T 1299 | 3Cr2Mo (similar) |
| Japan JIS | PDS3 (similar) |
Heat Treatment and Processing
Preheat slowly, then raise to the grade forging range. Work above the lower limit and cool slowly after forging to avoid cracks.
Not required — supplied pre-hardened. Softening anneal 710 – 740 °C only if heavy re-machining is planned.
User does not re-harden in normal use; supplied at 28 – 35 HRC.
Supplied tempered; optional nitriding or PVD for surface wear after machining.
After machining or forming, 200 – 350 °C for 1 – 2 hours, air cool, to stabilise dimensions and relieve residual stress.
Heat-treated bars and plates are supplied with the hardness and test certificate you specify. For critical parts we can control decarburisation depth and supply a spheroidized or soft-annealed structure on request.
Applications of P20 Plastic Mold Steel
The main use for plastic part production.
Rubber and composite tooling.
For zinc and similar low-melting alloys.
Stable, machinable tooling bodies.
Stable, machinable tooling bodies.
Low-stress forming dies.
P20 Plastic Mold Steel vs Alternative Grades
| Grade | vs P20 Plastic Mold Steel | Choose It When |
|---|---|---|
| P20 | — | Pre-hardened plastic moulds, no distortion from user hardening. |
| H13 | Hot-work, higher temp | Moulds running hot or high wear |
| 4140 | Lower alloy, cheaper | General engineering where pre-hard not needed |
| 1.2738 (P20+Ni) | Higher toughness | Large sections needing more through-hardness |
Quality Control and Mill Certificates
Every shipment ships with an EN 10204 3.1 mill certificate covering heat chemical analysis, hardness and the mechanical test on record. On request we add: ultrasonic test on heavy bar and plate, magnetic particle inspection on machined surfaces, and third-party inspection (SGS / BV) before loading. Dimensional tolerances follow the relevant EN / ASTM / JIS standard or your drawing.
Frequently Asked Questions
What is P20 mould steel used for?
Injection and compression plastic moulds, low-melt die-casting tools, jigs and fixtures — anywhere a pre-hardened, machinable mould steel saves the distortion of user hardening.
Is P20 pre-hardened?
Yes. It is supplied hardened and tempered to about 28 – 35 HRC, ready to machine.
What is P20 equivalent to?
DIN 1.2311, China 3Cr2Mo and JIS PDS3 are the same pre-hardened mould steel.
Can P20 be nitrided?
Yes. Nitriding or PVD coatings are commonly added for extra surface wear on the cavity.
What is the minimum order quantity?
Mill lots typically start at 500 kg per item; common plate sizes are often from stock.
Related Products
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