Vanadium-containing 12.9 grade steel for fasteners used in rail transit mobile equipment and its heat treatment process

Abstract

The invention provides a vanadium-containing 12.9-grade steel for a fastener applied to rail transit mobile equipment. The steel mainly comprises the following chemical elements in percentage by mass: 0.33% to 0.38% of C, 0.05% to 0.10% of Si, 0.70% to 0.90% of Mn, 0.70% to 0.90% of Cr, 0.60% to 0.90% of Ni, 0.20% to 0.30% of Mo, 0.015% to 0.045% of Als, 0.06% to 0.10% of V, 0.006% to 0.010% of [N], smaller than or equal to 0.010% of P, smaller than or equal to 0.005% of S and smaller than or equal to 0.0015% of T[O]. The thermally-treated steel is larger than 10.0 grades in austenitic grain size; the structure of the thermally-treated steel is a small amount of small proeutectoid ferrite dispersed on a tempered sorbite base body, wherein the amount of the proeutectoid ferrite is smaller than or equal to 3%, and the size of the proeutectoid ferrite is smaller 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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