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The study of the fracture behavior of the shaft with martensitic steel

Author: ZouWeiLong
Tutor: LiJian；WangMaoQiu
School: Kunming University of Science and Technology
Course: Metallurgical Engineering
Keywords: Martensitic steel Impact test Notched tensile Rotating bending fatigue Torsional fatigue
CLC: TG142.15
Type: Master's thesis
Year: 2008
Downloads: 96
Quote: 2
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Abstract

Large shaft parts to withstand tensile, impact and fatigue loads, and often there is the phenomenon of stress concentration, often used in high-performance carbon in Cr-Ni-Mo series and Cr-Ni-Mo-V Department of shafting forgings martensitic steel. The papers by notched tensile and impact test, and rotating bending and torsional fatigue testing, research new shaft martensitic steel the 25CrNi3MoV fracture behavior under different loads and commonly axis martensitic steel 18Cr2Ni4W and 34CrNiMo the fatigue fracture behavior. 1, the result of microstructure observation 25CrNi3MoV steel show that the 880 ° C after quenching 25CrNi3MoV steel prior austenite grain size of approximately 14μm. With the tempering temperature, carbide precipitation, grew up, the martensite lath community gradually disappear. Impact test results show that the U-shaped and V-impact fracture 25CrNi3MoV steel at room temperature and -30 ° C cold dimple fracture. With the tempering temperature, the increase in impact energy, the impact of the growing near the fracture stratified. Under normal temperature conditions, 25CrNi3MoV Steel (S4 Steel is the alloy composition of the lower limit S5 steel for the upper limit of the alloy composition) under different tempering temperature conditions are not sensitive to the U-shaped notch the basic impact energy equal; For the V-notch back at 600 ℃ when the fire S4 steel impact toughness than S5 steel S5 steel under low temperature conditions the impact toughness better than the S4 steel, and the U-notch impact toughness better than the V-notch impact toughness. 3, notched tensile test: stress concentration factor with notch root radius decreasing; 25CrNi3MoV steel notched tensile strength and notch sensitivity with the notch root radius decreases increasing; since the crack location is not in the notch root surface and in The sample internal stress is maximum position; notched specimen rupture maximum normal stress and the strain hardening exponent Related; fracture of the material for the hole fracture modes. 4, the rotating bending fatigue test results show that the tensile strength greater than 900MPa smooth specimen fatigue crack originated at the surface of aluminum oxide inclusions; tensile strength less than 900MPa, fatigue crack originated in the base body. New shaft with the martensitic steel 25CrNi3MoV steel rotating bending fatigue performance to better than the commercial use 34CrNiMo steel, and 18Cr2Ni4W of steel. The notched specimens fatigue crack originated in the surface of the substrate, there is more than one source of crack initiation. For smooth specimen rotating bending fatigue, the fatigue limit and tensile strength to meet the empirical formula σ _-1 of ≈ 0.5σ _b, and notched fatigue limit σ _-1N ≈ 0.5σ _-1. 5, torsion fatigue test results show that the torsional fatigue cracks originated in the internal matrix specimen fracture form off, that ductile fracture. With the increase of tensile strength and torsional fatigue limit also increases and the relation τ _-1 ≈ 0.5σ _-1.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > Microstructure and properties of steel > Analysis of the steel test
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