Steel for Fasteners Containing Niobium 12.9 Grade Rail Transit Mobile Equipment and Its Heat Treatment Process

Abstract

The invention provides a fastener used for niobium-containing 12.9-grade rail transit mobile equipment. The fastener is mainly prepared from the following chemical elements of, by mass percentage (%): 0.33-0.38% of C, 0.05-0.10% of Si, 0.70-0.90% of Mn, 0.70-0.90% of Cr, 0.60-0.90% of Ni, 0.20-0.30% of Mo, 0.015-0.045% of Als, 0.03-0.06% of Nb, less than or equal to 0.010% of P, less than or equal to 0.005% of S, and less than or equal to 0.0015% of T[O]; the austenitic grain size of the steel obtained after heat processing is greater than 10.0 grade; and the structure of the steel obtained after heat processing is characterized in that a small amount of fine proeutectoid ferrite is distributed on a tempered sorbite matrix in a dispersed way, the content of the proeutectoid ferrite is less than or equal to 3%, and the size is less than or equal to 5 micrometers.

Description

technical field [0001] The invention belongs to the field of alloy steel, in particular to grade 12.9 steel for fasteners used in rail transit mobile equipment and a heat treatment process thereof. Background technique [0002] Fasteners are also called standard parts in the market, which is a general term for a type of mechanical parts used when two or more parts (or components) are fastened and connected into a whole. It is characterized by a wide variety of specifications, different performances and uses, and a high degree of standardization, serialization, and generalization. Fasteners are the most widely used mechanical basic parts and are in great demand. The strength levels of high-strength fasteners such as high-strength bolts are generally divided into four grades: 8.8, 9.8, 10.9 and 12.9, and they are usually quenched and tempered medium carbon steel or medium carbon alloy steel. [0003] With the high-speed and heavy-duty rail transit, the impact and vibration o...

AI Technical Summary

Problems solved by technology

In order to ensure the low-temperature impact resistance and fatigue resistance of fasteners, at present, high-alloy structural steels such as 4340, 40CrNiMo and 18Cr2Ni4WE are mostly used in steels for 12.9-grade and 12.9-grade fasteners for high-speed and heavy-duty rail transit mobile equipment in my country. Difficulty, high consumption of precious alloys such as Ni and Mo, high production cost, and most of them are imported

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