Study On The Micro-structures And Properties Of The Steel For Disc Cutter Rings Of TBM

With the development of economic and acceleration of urbanization in China.more and more tunnel projects such as subways will be constructed in future.Shield machines play an important role in tunnel projects.The work efficiency and the performances of the shield machines depend on the cutting tools qualities and the materials.At present,the hot working die steels are used as the cutter ring's material.Hot working die steels have lower strength and impact toughness,so these factors harm for cutting tools' service life.This paper studied on the effcct of ESR-CDS and multiple forging on H13 steel.Based on H13 steel's composition,this paper adjusted the compositions of experimental steels,including increased content of Mo and addition of Ni?W.This test steels was primarily melted in medium anti-vacuum induction furnace and then refined in an electroslag remelting continuous directionally solidified(ESR-CDS)furnace.Last the ingots forged by multiple forging to get the experimental steels.This paper studied the relations in detail among composition?properties and microstructure of experimental steels by series of experiments,including room and high temperature impact toughness?tensile and other tests of mechanical properties?metallographic microstructure?spectroscopy analysis under scan electron microscope(SEM)and electronic probe(EPMA)analysis.And this study discussed the effects of the ESR-CDS and multiple forging on the microstructure?segregation behaviors and mechanical properties and the effect of the composition on mechanical properties of the experimental steels.The main conclusions are shown as follows:1 The primary dendrites of the ingots are parallel to each other and have no disorderly dendrites from edge to centre of the ingots.So the ESR-CDS ingot has a lower level of segregation.2 The ESR-CDS and multiple forging is benefited to the transversal impact toughness that is greater than 400J of H13 steel.The multiple forging steels got uniform microstructure avoiding the banding structure.And the isotropy ratio of the steels are more than 0.85.The working life of ESR-CDS steels was increased 1.5?2 times.3 Increasing the content of Mo and reducing Si can enhance the impact toughness of H13 steel.Addition of Ni can enhance room temperature tensile strength especially.Addition of Mo and W can increase the stability and mechanical properties in high temperature.W is better than Mo in increasing the stability and Mo is well for the high temperature strength than W.The impact toughness of H13 steel is increased by 15%approximately by adjusting the compositions and increased by 45%by ESR-CDS and multiple forging.So the contribution of ESR-CDS and multiple forging is bigger to the mechanical properties.