1.2312 / 40CrMnMoS8-6 / P20+S – Pre-hardened mould steel with excellent machinability

Steel 1.2312 (P20+S) is a modified version of 1.2311 (P20) enriched with sulphur (S) for significantly improved machinability. It is supplied in a pre-hardened condition of 28–34 HRC, allowing immediate production of moulds without additional heat treatment.

It is ideal for plastic moulds that require good surface quality, fast machining and stable toughness.

Properties of 1.2312 (P20+S)

🔧 Excellent machinability thanks to sulphur addition
Sulphur improves chip formation, enabling faster machining and lower tool wear.

🔩 Pre-hardened condition 28–34 HRC
Allows immediate machining without hardening, saving time and production costs.

💥 Good toughness
Suitable for moulds exposed to pressure, vibration and medium mechanical stress.

✨ Good surface quality and polishability
Its polishability is slightly lower than 1.2311, but still very good.

🔥 Nitriding possible
The surface can be hardened up to 800–1000 HV, increasing mould life.

Chemical composition of 1.2312 (40CrMnMoS8-6)

Element	Content (%)
C	0.35 – 0.45
Mn	1.50 – 1.80
Cr	1.80 – 2.10
Mo	0.15 – 0.25
S	0.05 – 0.12
Si	0.20 – 0.40
P	≤ 0.030

Typical applications of 1.2312

🧩 Plastic moulds

• medium-sized and large moulds
• core components
• shaped inserts and segments

🛠️ Fast mould production

• moulds requiring high machining productivity
• repeated prototype and serial mould applications

⚙️ Mechanical engineering parts

• supporting mould components
• holders and structural blocks

Heat treatment (guideline values)

Note: This is rarely used, as the steel is supplied pre-hardened.

Process	Temperature	Note
Nitriding	480 – 520 °C	surface 800–1000 HV
Soft annealing	700 – 720 °C	hardness approx. 200 HB
Quenching and tempering	830 – 870 °C	less common

Mechanical properties

• Hardness in supplied condition: 28–34 HRC
• Hardness after nitriding: 800–1000 HV
• Excellent machinability
• Good toughness
• Stable thermal conductivity