DIN 1.2312 40CrMnMoS8-6 P20+S Plastic Mould Steel

Product Overview

DIN 1.2312 (40CrMnMoS8-6) is a premium pre-hardened plastic mould steel compliant with DIN 17350 German standard, renowned as the industry workhorse for high-precision plastic mould manufacturing. Its American standard equivalents are ASTM A681 P20+S/P21, engineered with a balanced chemical composition that delivers exceptional machinability, superior polishability, and uniform hardness distribution across the entire material cross-section.

Infused with chromium and manganese, this steel grade boasts enhanced hardenability and wear resistance, while a precisely controlled sulfur content further optimizes its machining performance—eliminating the need for additional heat treatment before processing due to its pre-hardened state. This characteristic drastically reduces production lead times and manufacturing costs, making it the first choice for mould makers producing plastic parts with stringent surface quality requirements. It is widely applied in automotive, electronics, consumer goods, and engineering plastic processing industries, with proven reliability in mass production and prototype manufacturing scenarios.

Steel Grade Equivalents

The following table lists the official equivalent grades of DIN 1.2312 across major international standards, ensuring seamless material selection for global manufacturing projects:

Product Features

Chemical Composition

The strict chemical composition control of DIN 1.2312 ensures consistent material performance, with all elements within the standard range to avoid performance deviations caused by component fluctuations:

Hardness & Hardenability

DIN 1.2312 is supplied in two main heat treatment states, with hardness values meeting industrial mould manufacturing requirements, and uniform hardenability ensuring no hardness difference in large-size mould components:

Supply Specifications & Tolerance

We provide a full range of product forms of DIN 1.2312, with strict dimensional tolerance and straightness control to meet the precision requirements of different mould processing links. All products are available in stock with regular sizes, and custom forging/rolling of non-standard sizes is supported with short lead times:

Product Type & Size Range

Dimensional Tolerance & Straightness

In-Stock Sizes

• Hot Rolled Bar (Φmm): 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 120, 130, 140, 150, 160, 170, 180, 190

• Hot Forged Bar (Φmm): 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400

Note: Stock sizes are updated daily. For real-time stock availability and non-standard size customization, please contact our sales team directly.

Quality Inspection: Ultrasonic Test

All DIN 1.2312 products undergo strict ultrasonic flaw detection in accordance with international standards to ensure zero internal defects (e.g., cracks, inclusions) that may affect mould service life:

• Test Standard: EN10228-3 Class III / Sep 1921-84 D/D

• Inspection Scope: 100% full-length detection for all bars and plates

• Qualified Criterion: No detectable internal defects in the effective working area of the material

Steel Making & Forging Process

We adopt advanced smelting and forging processes to ensure the purity and internal structure uniformity of DIN 1.2312, laying a solid foundation for excellent mechanical properties:

1. Steel Making Process

All processes adopt vacuum degassing and refining to reduce gas and impurity content in the steel:

• EF+LF+VD (Electric Furnace + Ladle Refining + Vacuum Degassing)

• EAF+LF+VD (Electric Arc Furnace + Ladle Refining + Vacuum Degassing)

• EF+LF+VD+ESR (Added Electroslag Remelting for ultra-high purity)

• EAF+LF+VD+ESR (Added Electroslag Remelting for ultra-high purity)

ESR process is recommended for moulds with mirror surface requirements or long service life requirements.

2. Forging Processing

Precise forging temperature control ensures the steel's grain refinement and eliminates casting defects:

• Put the 1.2312 ingot into the heating furnace for uniform preheating

• Heat the ingot to the initial forging temperature: 1050-1100℃ (uniform temperature distribution)

• Forging operation with the minimum forging temperature not lower than 850℃ (avoid cold forging cracks)

• Slow cooling in sand or furnace after forging (reduce internal stress, prevent deformation and cracking)

Heat Treatment

The heat treatment process of DIN 1.2312 is strictly standardized, and the following processes are recommended for different application scenarios to ensure the optimal performance of the material:

1. Soft Annealing

Suitable for large and complex moulds that require a lot of machining, reducing machining difficulty and tool wear:

• Heat the steel to 780-820℃ in a controlled atmosphere furnace

• Soak at this temperature for sufficient time (based on material thickness: 1-2h/50mm)

• Furnace cooling at a rate of ≤30℃/h to approximately 500℃

• Air cooling to room temperature (final hardness ≤285HB)

2. Quenching and Tempering

The standard heat treatment process for the supplied state, ensuring balanced hardness and toughness:

• Heat the steel to 840-850℃ in a furnace with uniform temperature

• Soak for heat preservation (ensure the entire material is heated through)

• Oil quenching (rapid cooling to obtain martensite structure, ensure hardness)

• Temper at 500-600℃ (eliminate quenching stress, improve toughness)

• Air cooling to room temperature (final hardness HRC28-32)

It normally suppolied in the quenched and tempered condition with a hardnedd of about 300HB

3. Heat Treatment Time for Test Pieces (Salt Bath)

The following time parameters are for reference of small test pieces; the heating time of actual large-size moulds needs to be appropriately extended:

Total heating time of test pieces in a salt bath

Note: For heating in air furnace or other non-salt bath equipment, the heating time should be extended by 2-3 times according to the material thickness. The above parameters are not applicable to thick-walled mould tools (>200mm).

Main Applications

DIN 1.2312 is a versatile plastic mould steel with excellent comprehensive performance, and its application covers almost all plastic mould types and low-temperature die-casting insert scenarios, especially suitable for moulds with high requirements on machinability and surface quality:

1. Plastic Moulds

• Compression Moulds & Blow Moulds: For processing PVC, ABS, PP, PE, PC, PS and other general and engineering plastics

• Injection Moulds: Mass production of plastic parts for automotive interiors, electronic housings, daily consumer goods

• Requirement Match: Suitable for plastic parts with Ra0.8-Ra1.6 surface roughness, and can be polished to mirror surface (Ra0.05-Ra0.1) with special process

2. Low-Temperature Die-Casting Inserts

• Applicable to zinc/aluminum alloy die-casting inserts (working temperature ≤300℃)

• Not Applicable: High-temperature alloy die-casting (e.g., magnesium, copper alloy) with working temperature >300℃

3. Mould Bases & Precision Components

• Core/cavity inserts, ejector pins, sliders, guide pillars, guide bushes and other precision mould components

• Mould frames and structural parts for medium and small size moulds

• Key application industries: Automotive manufacturing, 3C electronics, home appliances, packaging, toy manufacturing

4. Prototype & Low-Cost Moulds

• Rapid manufacturing of prototype moulds for product development and testing

• Low-cost mass production moulds for small and medium batch plastic parts

Comparative Analysis: DIN 1.2312 vs Other Common Mould Steels

To help customers select the most suitable material, we compare DIN 1.2312 with the most commonly used P20 (standard grade), 1.2311 and S50C mould steels in terms of performance, cost and application, clarifying the advantages and applicable scenarios of each grade:

FAQ

We have sorted out the most frequently asked questions by customers about DIN 1.2312 in the process of material selection and use, with professional and detailed answers to solve your doubts:

Q1: What is the difference between DIN 1.2312 and P20+S? Are they the same material?

A1: DIN 1.2312 (40CrMnMoS8-6) is the German standard grade, and P20+S is its American standard (ASTM A681) equivalent grade—they are essentially the same material with consistent chemical composition and performance. The "S" in P20+S means the steel contains a certain amount of sulfur to improve machinability, which is the core characteristic of this grade.

Q2: Can DIN 1.2312 be polished to a mirror surface?

A2: Yes. DIN 1.2312 has good polishability, and can be polished to Ra0.05-Ra0.1 mirror surface after proper surface treatment (e.g., grinding + fine polishing). For moulds with strict mirror surface requirements, we recommend choosing the ESR smelting process grade to ensure the material has no internal inclusions and achieve a perfect mirror effect.

Q3: Do I need to perform additional heat treatment on DIN 1.2312 before use?

A3: No. DIN 1.2312 is supplied in a pre-hardened state (HRC28-32), which can be directly used for machining mould core/cavity and other components without secondary quenching and tempering. Only for complex large-size moulds that require a lot of machining, soft annealing can be performed to reduce machining difficulty.

Q4: Can DIN 1.2312 be welded? What welding process is recommended?

A4: Yes, DIN 1.2312 has good weldability and is suitable for mould repair and modification welding. It is recommended to use argon arc welding with matching welding rods (e.g., SKD61 welding rods), and preheat the welding area to 200-300℃ before welding, and perform stress relief tempering at 500-550℃ after welding to avoid welding cracks and deformation.

Q5: What is the difference between DIN 1.2312 and P21? Which one is more suitable for my mould?

A5: P21 is a low-alloy alternative grade of DIN 1.2312, with lower carbon and alloy content (no molybdenum), so its hardness, wear resistance and hardenability are lower than DIN 1.2312. DIN 1.2312 is recommended for engineering plastic moulds, high-precision inserts and mass production moulds; P21 can be selected for low-cost light-duty plastic moulds (e.g., small toy moulds, low-batch packaging moulds) to save material costs.

Q6: How to choose the smelting process of DIN 1.2312 (EF+LF+VD vs ESR)?

A6: Choose according to the mould requirements:

• EF+LF+VD: Suitable for general plastic moulds with normal surface quality requirements, with high cost performance.

• ESR (Electroslag Remelting): Recommended for moulds with mirror surface requirements, long service life or large-size moulds, with ultra-high material purity, no internal defects and more uniform internal structure.

Q7: What is the difference between 1.2311 and 1.2312?

A7: 1.2311 is the standard P20 grade with no added sulfur. 1.2312 is the "free-cutting" version with added sulfur for maximum machinability. Choose 1.2311 when you need maximum polishability and toughness. Choose 1.2312 when your priority is fast machining and reduced production costs for large or complexly machined components.

Q8: For which plastic materials is 1.2312 most commonly used?

A8: It is an excellent choice for molding non-corrosive and mildly abrasive plastics such as ABS, PP (Polypropylene), PE (Polyethylene), Polystyrene, and PVC. It is also used for engineering plastics like PC (Polycarbonate) and POM, provided the production volume doesn't require the higher wear resistance of a harder steel.

Inquire Now: We will provide you with the most professional material solutions and the most competitive prices with sincere service and reliable quality!