Heat-resistant 12.9-grade fastener steel for rail transit and heat treatment process thereof

Abstract

The invention discloses heat-resistant 12.9-grade fastener steel for rail transit. The 12.9-grade fastener steel comprises the following components in percentage by weight: C 0.25%-0.35%, Si 0.20%-0.50%, Mn 0.50%-0.70%, Cr 1.10%-1.40%, Mo 0.60%-0.80%, V 0.20%-0.40%, W 0.80%-1.20%, Al 0.015%-0.040%, Co 0.40%-0.80%, P <=0.015%, S <= 0.015%, O <= 0.0015%, N <= 0.006%, the balance Fe and other unavoidable impurities. The invention also discloses a heat treatment process of the 12.9-grade fastener steel, after heat treatment, the normal-temperature mechanical property and the 450-DEG C high-temperature mechanical property of the steel reach 12.9 grade, the steel has low notch sensitivity and good delayed fracture resistance, and is suitable for manufacturing heat-resistant 12.9-grade high-strength bolts for rail transit.

Description

technical field [0001] The invention belongs to the technical field of steel for fasteners, and in particular relates to a heat-resistant grade 12.9 steel for fasteners used in rail transit and a heat treatment process thereof. Background technique [0002] Fasteners are the basic industry of my country's equipment manufacturing industry. Domestic railway construction has maintained rapid development. Not only the new railways and the transformation of existing lines have provided new market demand for high-speed EMUs, high-power locomotives, and heavy-duty trucks, but also in-service The upgrading of equipment also provides market space for fasteners. In recent years, the development of high-strength fastener steels with special properties is a hot topic. [0003] Chinese patent CN 106086652 A discloses a high-strength heat-resistant cold-heading steel wire rod and its production method. The high-strength bolts made of the obtained wire rod serve at high temperatures, can m...

AI Technical Summary

Problems solved by technology

[0003] Chinese patent CN 106086652 A discloses a high-strength heat-resistant cold-heading steel wire rod and its production method. The high-strength bolts made of the obtained wire rod serve at high temperatures, can maintain good strength and toughness indicators, and have good durability. High temperature stability, strength and thermal strength, but the steel in this method does not have excellent low temperature toughness, so it is not suitable for fasteners used in rail transit across cold regions

Chinese patent CN 106929623 B discloses a preparation method of a 10.9-grade high-strength bolt steel hot-rolled round wire rod. Through a reasonable preparation method, the high-strength fastener bolt steel hot-rolled round wire rod produced by this patent has a clean High degree of hardness, good hardenability, suitable strength and hardness, excellent ductility and cold heading and upsetting deformation ability, the disadvantage is that the steel does not have significant heat resistance, and is not suitable for tight conditions that need to experience high temperature conditions. Firmware, while the steel grade only reaches 10.9

Chinese patent CN 103173694 B discloses a method for manufacturing high-temperature resistant fasteners. The invention also introduces a method for manufacturing high-temperature-resistant fasteners. The fasteners produced have good plasticity, high hardness, and high strength. However, the method A large number of precious metal elements are added, the production cost is extremely high, and it is not suitable for mass promotion and use in the rail transit industry

[0004] To sum up, although there is a certain technical accumulation in heat-resistant fasteners and high-strength fasteners in China, there are few researches on heat-resistant fasteners for the rail transit industry.

Images