Cr12 tool Steel

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Cr12 tool steel is a grade under the Chinese national standard. It is a very classic high-carbon, high-chromium cold work die steel that combines high strength, wear resistance, and hardenability. Equivalent grades to Cr12 include American AISI D3, German W – Nr. 1. 2080, and Japanese JIS SKD1.

1. Composition(GB / T 1299—2000)

2. Mechanical Properties

Cr12 steel is classified as a high-carbon, high-chromium ledeburitic steel. Due to its high mass fraction of carbon, it exhibits lower impact toughness and a tendency for brittle fracture, coupled with a susceptibility to forming non-uniform eutectic carbides.

The high concentration of chromium in the steel promotes the formation of (CrFe)₇C₃ complex carbides, which in turn reduces the amount of cementite (Fe₃C). During the quenching heat treatment, a significant volume of these carbides dissolves into the austenite phase. Subsequent quenching transforms the austenite into high-hardness martensite. Upon tempering, a fine and dispersed precipitation of carbides occurs within the martensitic matrix, resulting in excellent wear resistance.

Through an appropriate heat treatment process, a microstructure with a combination of high strength and toughness can be achieved.

3. Forging Process

The primary objective of forging Cr12 steel is to break down and refine the coarse carbides inherent in the steel, ensuring they are distributed uniformly throughout the matrix. This process significantly improves the material’s overall strength and toughness. Furthermore, proper forging establishes a rational alignment of flow lines within the die, which helps to promote consistent and predictable dimensional changes (distortion) in all directions during the subsequent quenching process.

Regarding the heating procedure for forging, it is crucial to first preheat the workpiece before gradually increasing it to the final forging temperature. Attention must be paid to the proper placement of the workpiece within the furnace, and the material should be turned or flipped periodically to ensure uniform heating.

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4. Obróbka cieplna

4.1 Podgrzewanie wstępne

4.2 Hartowanie

4.2.1 Quenching Specification

4.2.2 Performance Comparison of Different Heat Treatment Processes

Note: All samples were tempered twice at 180°C, 1.5h each time.

4.2.3 Relationship between Quenching Temperature and Hardness

4.3 Hartowanie

Tempering Specification

Notatka: The tempering temperature is generally 180 ~ 200°C, with hardness ≥60HRC. To avoid cracks from EDM and grinding and to improve the toughness of the mold, it is often tempered below 400°C. The hardness after tempering is 54 ~ 58HRC. The temper brittleness range is 275 ~ 375°C, which should be avoided as much as possible during tempering.

Relationship between Tempering Temperature and Hardness

Notatka: 955°C oil quenching.

5. Aplikacje

It is predominantly selected for manufacturing components that require high wear resistance but are subjected to relatively low impact loads.

Specific applications include:

• Cold shearing blades and cutters
• Drill bushings
• Wskaźniki
• Dziurki
• Thread rolling plates and dies
• Stamping and punching dies
• Matryce do ciągnienia drutu
• Matryce do wytłaczania na zimno
• Coining and embossing dies
• Deep drawing dies