High-strength and high-toughness wind power gear steel and preparation method thereof

Abstract

The gear steel comprises the following chemical components in percentage by mass: 0.12 to 0.23 percent of C, 0.17 to 0.42 percent of Si, 1.7 to 2.5 percent of Mn, 0.4 to 1.25 percent of Cr, 0.5 to 1.45 percent of Mo, 0.35 to 0.75 percent of Ni, 0.1 to 0.35 percent of V, 0.002 to 0.007 percent of B, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, less than or equal to 0.01 percent of Cu, less than or equal to 0.015 percent of Al, less than or equal to 0.008 percent of Ti, less than or equal to 0.02 percent of N, less than or equal to 0.002 percent of O and the balance of Fe and inevitable impurity elements. The preparation method comprises the procedures of molten steel smelting, refining and deoxidizing, continuous casting, rolling, quenching and tempering which are conducted in sequence, the soft argon blowing time in the refining and deoxidizing procedure is larger than or equal to 30 min, the final secondary cooling water amount in the continuous casting procedure is controlled to be 0.5-0.9 L / kg steel, and through steelmaking component control, temperature control, slag charge control, refining and deoxidizing control, argon blowing control, alloy optimization control and low residual element control, the production efficiency of the steel is improved. And through the controlled rolling and controlled cooling process, the transverse performance, ductility, toughness and compactness are guaranteed, the overall hardness, tensile strength, yield strength and impact toughness are improved, the strength and toughness of the wind power gear steel are both considered, and the tooth breaking risk is avoided.

Description

technical field [0001] The invention belongs to the technical field of wind power gear steel, and particularly relates to a high-strength and toughness wind power gear steel and a preparation method thereof. Background technique [0002] The gears in the wind turbine transmit the power generated by the wind rotor under the action of the wind to the generator and make it obtain the corresponding speed. Due to the high-frequency line contact of the tooth surface and the development of wind power to high speed, high load and low noise The requirements for gear steel's wear resistance, toughness, fatigue strength under alternating bending stress and resistance to tooth surface contact fatigue damage have been continuously improved. The existing use of CrMoH steel as gear steel is due to the fact that mold slag, nozzle deposits, oxidation products, etc. in the mold are brought into the molten steel during continuous casting to cause slag entrainment or lower slag inclusion defect...

AI Technical Summary

Problems solved by technology

At present, CrMoH steel is used as gear steel, because mold slag, nozzle sediment, oxidation products, etc. in the crystallizer are brought into the molten steel during continuous casting production, resulting in slag entrainment or lower slag inclusion defects, the composition of the steel grade is difficult to meet the mechanical performance requirements of the steel. Defects such as pores and inclusions in the process of steelmaking and casting will reduce the uniformity and compactness of the as-cast structure and make rolling sensitive. The large fluctuations in the content of aluminum and titanium will cause the slag in the converter to be unstable, and the surface of the slab is prone to blisters, inclusions and cracks. Defects, stopper rod blowing argon to crystallize the liquid level and mold heat transfer wall temperature fluctuate greatly, resulting in thin and uneven thickness of the billet shell at the outlet of the crystallizer, resulting in cracks and leaks

[0003] Due to the process conditions, the temperature in the solid-liquid two-phase region is high, and the impurity elements are separated and crystallized at the solid-liquid and boundary, when the medium superheated molten steel solidifies, the solute is precipitated from the larger lens and the overlap of the center of the columnar crystal in the later stage of solidification. The accumulation of elements leads to inclusions, center segregation and center porosity. The uneven distribution of solute elements in the center of the slab reduces the mechanical properties of the steel, especially the transverse properties, ductility, toughness and compactness. The pearlite band and elongated Coarse dispersion of inclusions affects notch toughness at low temperatures in the Charpy transition temperature range, which is not conducive to subsequent rolling and improvement of steel carbide network and suppression of abnormal structures such as martensite; improper rolling and cooling control can easily make ferrite grains Coarseness reduces the toughness of the steel, and the surface hardness is adjusted by nitriding, quenching and tempering to achieve the strength and wear resistance of the designed tooth surface. However, during the quenching process, the martensite substructure is coarse, and it is difficult to form stable austenite islands to reduce crack propagation. The hindrance effect reduces the toughness, making it difficult to balance the strength and toughness of wind power gear steel, resulting in the risk of broken teeth

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