3Cr2Mo Tool Steel for Molds

1. Overview

3Cr2Mo Tool Steel, also known as P20, is a versatile chromium-molybdenum tool steel widely used interchangeably with it. Its primary application is in mold manufacturing, particularly for plastic injection molds and die casting molds that handle lower-melting-point alloys. You may find this grade specified under various international standards, sometimes with slight variations in designation. At Aobo Steel, we supply high-quality 3Cr2Mo manufactured to meet precise specifications.

2.  3Cr2Mo Tool Steel Chemical Composition (Typical Weight%)

• Carbon (C): 0.28 – 0.40%
• Silicon (Si): 0.20 – 0.80%
• Manganese (Mn): 0.60 – 1.00%
• Chromium (Cr): 1.40 – 2.00%
• Molybdenum (Mo): 0.30 – 0.55%
• Phosphorus (P): ≤ 0.030%
• Sulfur (S): ≤ 0.030%
• Copper (Cu): ≤ 0.30%

Note: The exact composition may vary slightly depending on the specific standard required (e.g., ISO 4957/EN ISO 4957 grade 35CrMO7 may have minor differences). Always specify the standard needed for your application. This grade is distinct from the related 3Cr2MnNiMo steel.

3.  3Cr2Mo Tool Steel Key Properties and Advantages

3Cr2Mo / P20 is most commonly supplied in a pre-hardened condition, offering practical advantages for mold producers.

3.1 Pre-Hardened Condition

Delivered hardened and tempered, typically to 28-36 HRC. This allows mold makers to machine directly, bypassing the need for post-machining heat treatment and avoiding associated risks, such as distortion, cracking, or surface decarburization.

3.2 Machinability

Provides good machinability in its pre-hardened state (typically up to 30 HRC), facilitating the production of complex mold geometries.

3.3 Polishability

This steel grade allows for an excellent surface finish. High levels of polish, including mirror finishes (surface roughness Ra 0.05-0.10 μm or lower), can be achieved, which is critical for producing high-quality plastic parts.

3.4 Hardenability and Toughness

3Cr2Mo offers good through-hardenability, ensuring relatively uniform hardness even in larger mold sections. It provides a solid combination of hardness and toughness, which can be fine-tuned through tempering processes.

3.5 Surface Treatment Compatibility

Suitable for various surface treatments, including nitriding, carburizing, boronizing, and chrome plating. These treatments enhance surface hardness, wear resistance, and corrosion resistance, significantly extending mold life. Nitriding, for example, is often used to achieve long production runs.

3.6 Weldability

Possesses reasonable weldability, allowing for effective mold repairs and modifications when necessary.

4.  3Cr2Mo Tool Steel Applications

3Cr2Mo / P20 is a reliable choice for:

• Medium to large-sized precision plastic injection molds (e.g., molds for TV housings, appliance panels, large containers).
• General-purpose plastic molds are designed for a long service life, especially when enhanced with surface treatments such as nitriding.
• Die casting molds are used for low-melting-point alloys, such as zinc, tin, and certain aluminum alloys.

For more demanding applications, such as high-volume aluminum die casting or extremely large and high-performance plastic molds, alternative grades like 4Cr5MoSiV1 (H13) or 3Cr2MnNiMo (P20+Ni / 1.2738) may be better suited.

5. Equivalent Grades

6. Summary

3Cr2Mo (P20) steel is a standard in the mold industry. Its pre-hardened state, combined with good machinability, excellent polishability, and suitability for surface enhancements, makes it a cost-effective and dependable material for a wide range of mold applications.

Your 3Cr2Mo Supplier – Aobo Steel

Aobo Steel brings over 20 years of forging experience to the production of tool steels, such as 3Cr2Mo. If you require a consistent supply of high-quality P20 or need technical support with material selection for specific challenges such as wear, surface finish, or toughness, please contact us. We focus on providing solutions.