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P20+S 1.2312 PX5 plastic mold steel

1.2312 plastic mold steel delivers superior machinability, uniform hardness, and good polishability. Pre-hardened for direct use, ideal for high-volume plastic molds, mold bases, and general forming components.

Standard: AISI P20+S, DIN 1.2312, JIS PX5
Technique: EAF + LF + VD, forged, multi-directional forging ratio ≥4, quenched and tempered (pre-hardened), controlled sulfur addition for improved machinability
Shape: Round, Flat, Plates, Blocks
Heat treatment: Supplied in pre-hardened condition, hardness 28–32 HRC (quenched and tempered). Annealed supply available on request
Surface Treatment: Turned, milled / ground, sawn ends. Black (hot-rolled / forged surface) available for large sections
Tolerance: flat bars & plates thickness: +0.5/-0.0 mm (turned); forged blocks: ±0.2 mm
MOQ: 1 Ton

We supply DIN 1.2312 in various custom sizes

Chemical Composition (%)

Grade	C	Si	Mn	P (≤)	S	Cr	Mo	Ni
1.2312 (40CrMnMoS8-6)	0.35–0.45	0.30–0.50	1.40–1.60	0.030	0.05–0.10	1.80–2.00	0.15–0.25	≤0.40
P20+S	0.28–0.40	0.20–0.80	0.60–1.00	0.030	0.05–0.12	1.40–2.00	0.30–0.55	0.25–0.55
PX5	0.35–0.42	0.20–0.40	0.90–1.20	0.025	0.05–0.10	1.80–2.00	0.30–0.50	—

Main characteristics of 1.2312 tool steel

P20+S | 1.2312 | PX5 tool steel applications

1.2312 steel for Plastic Injection Mould

Excellent machinability and consistent pre-hardened hardness make 1.2312 ideal for fast, high-quality production of plastic injection moulds with reduced cycle time.

1.2312 steel for Mould Base & Die Carrier

The controlled sulphur content ensures superior chip breaking and smooth machining, enabling complex mould bases and die carriers to be produced efficiently and to tight tolerances.

1.2312 steel for Wear Plates & Structural Components

Pre-hardened 1.2312 offers uniform hardness and good wear resistance, allowing direct use in wear plates and structural components without additional heat treatment.

Our Production Technology For 1.2312 (40CrMnMoS8-6 / P20+S) Prehardened Plastic Mold Steel

Ultrasonic testing (UT) 100% as per EN 10228-3 Class 3 or SEP 1921 Class D/d
Micro Cleanliness as per ASTM E45 or DIN 50602
Delivery condition: Quenched and tempered (prehardened), hardness 280 – 325 HB (28 – 34 HRC)
Polishability: Technical polishing possible, but not suitable for high-gloss optical surfaces or fine etching

mechanical properties & heat treatment of 1.2312 steel

Heat temperature	Start forging temperature	Finish forging temperature	Cooling method
1050 – 1100 °C	1050 – 1000 °C	≥ 850 °C	Pit, sand, or furnace cooling

Annealing

Hardening

1.2312 (P20+S) is generally used in the prehardened delivery condition; rehardening is only required for specific applications where higher hardness is needed (e.g., extending mold life beyond 800,000 cycles). For rehardening applications, the following parameters apply
Pre-heating (required): Preheat to 500 – 600°C and hold for 2–4 hours to ensure uniform temperature distribution
Austenitizing temperature: 830 – 880°C.
Preferred range: 840 – 870°C.
Alternative range: 860 – 880°C
Holding time: After temperature equalization, hold for at least 2 hours (or min. 1 minute per mm of section thickness)
Quenching media:
Oil (preferred) — quench immediately after holding
Polymer
Warm bath at 180 – 220°C (martempering) — as an alternative for complex shapes
Hot bath at 180 – 220°C
Cooling procedure: Quench in oil to 50–100°C, then remove and air cool to room temperature
Hardness after quenching: approx. 51 – 52 HRC

Stress relieving

Perform after rough machining or heavy stock removal, especially for tools with complex shapes or unbalanced crosssections, to reduce the risk of distortion during final heat treatment
For quenched and tempered (prehardened) material: heat carefully to 500 – 550°C
For soft annealed material: heat carefully to 600 – 650°C
Hold at temperature for 1 – 2 hours (or min. 2 minutes per mm of section thickness)
Air cool after holding
This operation is recommended to eliminate residual stresses induced by mechanical working and to reduce distortion during further processing

Tempering

Temper immediately after the workpiece cools to handwarm temperature (approx. 50–70°C). Delayed tempering may cause cracking
Number of tempers: Minimum 2 times. After each tempering cycle, air cool to room temperature before the next tempering
Holding time: Soak for at least 3 minutes per mm of section thickness (minimum 2 hours per cycle)
Cooling method: Air cool after each tempering cycle
Tempering temperature selection:
180 – 220°C (low-temperature tempering) — For applications requiring maximum hardness after rehardening, to prevent cracking and maintain hardness ≥48 HRC.
550 – 620°C (standard tempering range after hardening from 830–880°C) — Produces balanced mechanical properties in rehardened condition.
640 – 680°C — Common tempering range for standard applications

Why Choose NSPM as Your 1.2312 Tool Steel Supplier

Source Direct

Direct mill cooperation ensures stable supply, competitive pricing, and consistent quality. Global resource integration and strong supply chain management guarantee reliable material sourcing and long-term availability.

Stock Ready

50,000+ tons inventory across 11 warehouses enables fast delivery. Flexible cutting, short lead times, and ready stock support urgent demands and improve customers’ production efficiency.

Expert Team

600+ professionals, including R&D specialists and technical engineers, provide application-driven support. Fast response and deep tooling knowledge ensure accurate solutions for diverse industrial needs.

Fully Inspected

Strict quality control system with full traceability, UT testing, and heat treatment records. Certified standards (ISO, CE) ensure every material meets high-performance and reliability requirements.

Full-Chain Machining

From steel supply to precision machining, heat treatment, and equipment manufacturing, NSPM offers integrated solutions that enhance accuracy, efficiency, and overall tooling performance.