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Home » FAQs » Comparative study on impact fracture behavior of domestic 4Cr5Mo2SiV modified steel and imported similar hot work die steel
Comparative study on impact fracture behavior of domestic 4Cr5Mo2SiV modified steel and imported similar hot work die steel
2017-06-17 15:50:30

 Hot working die steel needs good strength and toughness ratio, and impact toughness has always been an important reference index, and improving the impact toughness of materials has been the focus of this research. Domestic 4Cr5Mo2SiV steel is improved due to lower Si and 4Cr5MoSiV1 on the basis of the content of V, high performance heat to increase the content of Mo for die steel, because of its thermal fatigue cracking, good thermal shock cracking, thermal wear and plastic deformation performance, and has become the best choice of casting, forging, heat extrusion die steel. High performance heat is the same kind of imported steel, chromium molybdenum, vanadium steel, pure iron by adding pure smelting alloy elements necessary to, and all through the ESR process, so it has very high purity, but also has a very high wear resistance at high temperature and high temperature toughness and thermal high mutation it is suitable for the fabrication of complex structure, large precision casting die. To this end, some researchers have compared the microstructure and impact toughness of domestic 4Cr5Mo2SiV modified steel and imported similar steel, and analyzed the gap between domestic material quality control level and imported materials.

4Cr5Mo2SiV improved steel sample is taken from a steel plant in China, and its manufacturing process is as follows: induction melting, electrode rod annealing, electroslag remelting, ESR ingot annealing, high temperature homogenization, multi direction forging and annealing. Imported steel material annealed specimens from a foreign steel production, sample is 1030 DEG C vacuum oil quenching, and then to the 101A-1 type drying box to stress annealing in S2-5-12 type heat treatment furnace at 600 DEG C for 2h, air cooling after heating to 605 DEG C for 2h, will eventually control sample hardness in the range of 44 to 46HRC.
The inclusions, segregation and spheroidization of annealed specimens of two kinds of materials were examined under optical microscope. Grain grading is done by comparison with NADCA#207-2006 and GB/T 6394-2002 standards. Test the impact toughness of the material in accordance with GB/T 229-2007. After the impact test, the specimen was clamped off, and the fracture surface was observed by scanning electron microscope (SEM). Then the specimens were dissected along the longitudinal direction, and then the microstructure was observed by light microscope and scanning electron microscope. Measure the hardness near the impact zone according to the GB/T 4340 standard. Test results show that:
(1) although the quality control of domestic 4Cr5Mo2SiV steel improved well and meet quality standards, but compared with the imported steel, microstructure uniformity and zonal segregation control was less than that of imported steel. It shows that the heat treatment process of domestic steel still has room for further improvement.
(2) the formation of particle micro crack brittle oxide modified 4Cr5Mo2SiV steel has become the inclusion of dimple fracture, decrease the toughness of a material, thus improving the purity of the material, the inclusion control at a higher level can improve the impact toughness of materials.

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