Steel properties

ALTA D2 is a high carbon-chromium tool steel (Cr-Mo-V, Cr12% version, ledeburite organization). This is a very commonly used cold work tool steel, comes with high wear resistance (higher than D3, 1.2080), good cutting power, very good firmness in the pressure, lower toughness (but higher than D3, 1.2080). This ALTA D2 tool steel shows good dimensional stability at the heat treatment, suitable for hardening to the secondary hardness (the possibility of nitriding). 

Applications

² Precision stamping dies, cold extrusion forming dies, drawing dies, punching dies, forging dies

² Cutting tools, measuring tools, industrial cutting knives, blades, work-rolls

² High-speed blanking molds of silicon steel sheets

² Heavy-load stamping dies, cold shearing blades, wire rolling plates

² Thread rolling die and wear-resistant slider

Chemical composition

Chemical Composition per %

Heat treatment

1).  1.2379, D2 steel has a relatively stable residual austenite, which starts to decompose at around 400℃ and ends at around 600~650℃. When high tempering (above 400℃) be taken, tempering times must be performed twice or more.

2).  Large modules need to go through high-temperature tempering (more than twice), which can greatly reduce the risk of cracking and deformation during wire cutting.

3).  For molds that need to be nitrided, high-temperature quenching (1070~1090℃) + multiple high-temperature tempering (550℃) can be used, and the final heat treatment hardness can be maintained above 60HRC.

** This steel is also suitable for ultra-cryogenic (-160℃) heat treatment. Hardness improved by 1~2HRC, but the impact toughness, wear resistance and pitting corrosion resistance performance get significantly improve (retained austenite is transformed into martensite, and the martensite after ultra-cryogenic treatment will precipitate dispersed carbides in the tempered structure).

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Product images

Features

² High wear resistance

² High hardenability and good dimensional stability

² Good compressive strength

² Good high temperature oxidation resistance

² Good rust resistance after quenching and polishing

Research of matrix strengthening and toughening heat treatment process for 1.2379, D2 tool steel

(tested sample EAF+LF+VD+ESR, composition : C%1.57, Si%0.25, Mn%0.28, Cr%11.35, Mo%0.75, V%1.01)

Conclusion :
1)    Cyclic phase transformation austenitizing treatment can effectively improve the impact toughness of 1.2379, D2 steel, but the number of cyclic passes and austenitizing temperature have a significant impact on the mechanical properties. The optimal number of cycles is 2, and the first pass is austenitizing. The tempering temperature is 1050℃ for the best effect.

2)    Cyclic phase transformation austenitization can refine carbide particles and improve carbide morphology. As the number of cyclic phase transformation austenitization passes increases and the austenitization temperature increases, the refining effect of carbides will be increased more significantly.

3)    Cyclic phase transformation austenitization can refine the austenite grain size, but the austenitization temperature should not be too high. Too high austenitization temperature will cause grain growth and fail to achieve grain refinement effect.

4)    Through the tempering matrix strengthening and toughening heat treatment process of 1050 ℃ ×30 min OQ+1030 ℃ ×30 minOQ+(500~540 ℃) ×1 h×2 AC, 1.2379, D2 steel can obtain a hardness of ≥60 HRC and significant impact toughness Improved excellent comprehensive mechanical properties.

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