Study On Microstructure And Properties Of Nitrogen - Containing M35 High Speed ​​Steel

The amount for usage of M35 is increasing for reason of its typical respect for high speed steel(short for HSS). However M35 HSS can hardly meet the using requirements in domestic market because of existed flaws as follows. Such as poor wear resistance, brittleness, appeared big carbide particles and serious segregation. Nitrogen for the superiority of wide addition and easy preparation from environment was widely used in stainless steel, low alloy steel, ball bearing steel and refractory steel. Moreover nitrogen functioned well in strengthening and toughening doing good in grain refinement, improving of hot working property, corrosion resistance and fatigue resistance. Even so, lots of disputes about what the role nitrogen played in HSS can be heard without end. Some research showed element nitrogen in M41 HSS were good for enhancing macro-hardness, modifying organization, promoting secondary hardening effect. While reports about M35 HSS with nitrogen were real in steel filed. In this paper, Micro-structure, mechanical properties and hot working properties were investigated by means of Gleeble thermal simulated test machine, metallographic microscope, scanning electron microscopy, transmission electron microscopy, XRD diffraction instrument, tensile testing machine, MTS testing machine and other equipment. Besides the paper try to investigate how element nitrogen effect the performance of M35 HSS. The results show as follows:Optimal deformation temperature is 1100℃, deformation rate is 0.1S-1 and optimal thermal plastic interval is 1075℃～1150℃ when nitrogen content in M35 HSS is 124 ppm; Optimal deformation temperature is 1050℃, deformation rate is 0.1s-1 and optimal thermal plastic interval is 1050℃～1100℃ when nitrogen content of M35 HSSis641ppm.Reduction of area from 83.7% reduce to 67.1%, Re-crystallization activation energy from 375.25MPa reduce to 333.04MPa, Optimal thermoplastic interval from 1100℃ reduce to 1050℃, austenite grain level on the quenching state from grade 10.57 increase to grade 11.7, carbide particles type are’t varied but those size on the annealing state change from 19.09μm to 14.29μm with the correspondence of increasing of nitrogen content in M35 HSS from 124 ppm raise to 641 ppm.When nitrogen content in M35 HSS from 124 ppm increase to 641 ppm, the solid solution of alloy in M35 HSS is weakened in the quenching treatment, carbide precipitation is reduced in tempering craft. The craft also lead to hardness falled off 1.7HRC. Besides cold working plasticity, impact toughness and red hardness were cut down while bending strength is heightened when the nitrogen content increase.Through the analysis of organization and performance for the M35 HSS in this paper, we can find when nitrogen content is 124 ppm, the performance is better in M35 HSS on the whole.