Steel for Fasteners Containing Niobium Grade 10.9 Rail Transit Mobile Equipment and Its Heat Treatment Process

Abstract

The invention provides vanadium-contained 10.9-level steel for a fastener for rail transit mobile equipment. The steel mainly comprises following chemical elements including, by mass percentage, 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, 0.30% to 0.60% of Ni, 0.20% to 0.30% of Mo, 0.015% to 0.045% of Als, 0.03% to 0.06% of Nb, not larger than 0.010% of P, not larger than 0.005% of S and not larger than 0.0015% of T[O]. The autstenitic grain size of steel obtained after heat treatment of the fastener is larger than 10.0 level, and according to the structure of the steel obtained after heat treatment of the fastener, a small amount of small pro-eutectoid ferrite is dispersed and distributed on a tempered sorbite base body, wherein, the amount of the pro-eutectoid ferrite is smaller than or equal to 5%, and the size of the pro-eutectoid ferrite is smaller than or equal to 5 micrometers. The longitudinal mechanical property of the fastener obtained after heat treatment can meet the standard requirement.

Description

Technical field [0001] The invention belongs to the field of alloy steel, in particular the steel used for fasteners for 10.9 grade rail transportation mobile equipment and its heat treatment process. 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 performance 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 level of high-strength fasteners such as high-strength bolts is generally divided into four levels, 8.8, 9.8, 10.9 and 12.9, and is usually quenched and tempered medium carbon steel or medium carbon alloy steel. [0003] With the rapid and heavy load of rail transit, the impact and vibration of key component...

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 for fasteners of grade 10.9 and grade 12.9 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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