P20+S|1.2312

Category

Plastic mold steel
Delivery condition

Hot rolled&forged
Supply form

Flat bar, Square bar, Plate/Block ,Round bar

Introduction:

1.2312 is a sulfur-alloyed modification of 1.2311, designed for enhanced machinability. The addition of sulfur improves cutting performance, making it ideal for machining large or complex molds with reduced tool wear and production time.

Chemical composition:

Corresponding international common brands				Hardness	Chemical Composition (%)
CHINA	US	JAPAN	GERMNAY	Hardness	C	Si	Mn	P	S	Cr	Ni	Mo	V
3Cr2Mo+S	P20+S	-	1.2312	HRC:28-36	0.35-0.45	0.3-0.5	1.4-1.6	≤0.03	≤0.1	1.8-2.1	-	0.15-0.25	-

Characteristics:

Similar to 1.2311 but with added sulfur (~0.05-0.10%).
This improves machinability significantly, especially in large and complex molds.
Still supplied pre-hardened (28-36 HRC).
Slightly reduced toughness and polishability compared to 1.2311 due to sulfur inclusions.

Applications:

Large plastic injection molds where machining efficiency is critical.
Mold parts that do not require mirror polishing or high-grade surface finish.
Suitable for automotive parts, appliance housings, etc.

Mechanical Properties

Tensile Strength	Yield Strength	Hardness	Elongation	Compressive Strength	Elastic Modulus
965-1030 MPa	827-862 MPa	30 HRC	20%	862 MPa	190-210 GPa

Heat Treatment & Processes

01
Hardening

Heat the steel evenly to 820–840°C until the whole section reaches temperature. Then quench in oil to cool.
02
Normalizing

Heat the steel uniformly to about 900°C to achieve a normalized structure.
03
Annealing

Heat P20 steel to 770–790°C, hold it well at temperature, and then let it cool slowly inside the furnace.
04
Tempering

Heat the steel evenly and hold it for at least 1 hour per 25 mm of thickness at the chosen tempering temperature. Allow it to cool in still air.

Tempering °C after Quenching	100oC	200oC	300oC	400oC	500oC	600oC
Hardness(HRC)	51	50	48	46	42	36
Tensile Strength (Mpa)	1730	1670	1570	1480	1330	1140

Nitriding

Tools machined from pre-hardened P20+S Plastic Mold Steel may be nitrided to give a wear resistant case of approximately Rockwell C60 surface hardness with a case depth of 0.35mm to 0.5mm. Nitriding also increases the corrosion resistance. After nitriding at 525°C in ammonia gas the surface hardness of the tool will be approximately 650HV.

Temperature	525oC	525oC	525oC
Time(hours)	20	40	60
Approx. Depth of Case(mm)	0.3	0.35	0.5

01
Case Hardening

P20+S plastic mold steel can be case hardened to achieve a surface hardness of 55–59 HRC.
02
Hard Chromium Plating

After hard chromium plating, the steel should be tempered at 180°C for 4 hours to prevent hydrogen embrittlement.
03
Induction Hardening

Induction or flame hardening can produce a hardness of 50–55 HRC. Air cooling is preferred, but smaller parts may need forced cooling. Temper the steel immediately after hardening.