Influence Of Magnesium On The Microstructure And Performance Of Cold Work Die Steel

Crl2MolVl cold work die steel is widely used in mould industry, which consumption in cold work die steel is in the first place in the cold. Cr12Mo1V1, belonging to the ledeburite high alloy steel, with the high carbon content and high chromium content, a large number of carbides and high-alloy degree martensit is in its substrate. This steel is characterized by high wear resistance, hardenability, high thermal stability, high flexural strength.During the solidification process, with segregation of the carbon and carbide-forming elements in the grain boundary, coarse eutectic carbides are produced and distribute in a continuous network, which separate steel substrate seriously. The presence of network carbide makes mold steel brittleness, low toughness, and almost can not be used in the cast condition. In order to break and refine eutectic carbides, improve the uniformity of carbides distribution, refine carbides granularity, metallargists usually do this work by forging, or by adding trace modification elements.In order to improve Cr12Mo1V1 mold steel thermoplastic, improve processing performance, the paper tries using Mg to modify this steel by adding nickel-magnesium, aluminum-magnesium alloy. By optical microscopy, electron microscopy and sweep surface temperature tensile testing machine, author analyses magnesium modification impact on mold cleanliness, microstructure and performance.Experimental results show that by magnesium modification, the size of inclusions decreases, the proportion of inclusions equivalent diameter less than 2 μm increases, inclusion average diameter decreases, Al2O3 inclusions transformed into MgO·Al2O3, stable MgO, MgS inclusions produced. Magnesium desulphurization, deoxidation reaction plays the role of purifying the liquid steel. Magnesium can refine the cast microstructure, reduce quantity of coarse dendrite, inhibit the growth of austenite grain.Experimental results show that. by magnesium desulfurization, deoxygenation, the liquid steel is purified. Magnesium alter the cast microstructure, reduce the number of coarse dendrites, inhibite austenite grain growth, grain evenly distribute.Magnesium modification, carbides distributed uniformly and semi mesh carbides replacing reticular carbides in die steel increase the continuity of the matrix. After quenching, the carbide refined improved the proportion of small carbides, and dispersed carbides replace large abnormal carbides.By magnesium modification on cold die steel, magnesium has no effect on the high temperature strength of the tool steel, but cold die steel thermoplasticity was improved. With the increase of temperature, thermal plasticity increased.