High-strength and high-toughness bainite spring steel and manufacturing method thereof

Abstract

The invention provides high-strength and high-toughness bainite spring steel and a manufacturing method thereof. The spring steel comprises the following chemical components, by mass, of 0.25%-0.4% of C, 1.5%-2.5% of Si, 1.0%-2.0% of Mn, 1.0%-2.0% of Cr, 0.2%-0.5% of Mo, 0%-0.15% of V, 0%-0.10% of Ti, no more than 0.03% of P, no more than 0.01% of S and the balance Fe and inevitable impurities, and the metallographic structure of the spring steel is mainly a bainite structure or a bainite / martensite dual-phase structure. The preparation method of the spring steel comprises the steps that residual harmful elements of adjusted molten steel are controlled in smelting, specifically, O is smaller than or equal to 15 ppm, H is smaller than or equal to 1.5 ppm, and N is smaller than or equal to 60 ppm; then the adjusted molten steel is poured into a steel ingot; and after hot-rolling forming or forging forming, normalizing heat treatment and tempering heat treatment at the temperature of 200-400 DEG C are conducted in sequence, or tempering heat treatment is directly conducted at the temperature of 200-400 DEG C, and thus a spring for a vehicle and engineering machinery is prepared. By matching with the corresponding low-pollution and environment-friendly manufacturing process, the spring steel meets the high-performance requirement and is especially suitable for a heavy-load automobile or engineering machinery.

Description

technical field [0001] The invention belongs to the technical field of spring steel and its preparation, in particular to a bainite spring steel with high strength, high toughness and excellent fatigue resistance and a manufacturing method thereof. Background technique [0002] In recent years, with the needs of the development of my country's national economy, in construction machinery, automobiles, and railway operations, efforts have been made to increase the load and speed of engineering vehicles, automobiles, and freight trains in order to increase transportation capacity and improve transportation efficiency. Reduce shipping costs. As a common consumable for auto parts and railway vehicles, springs are also used in large quantities. With the demand for vehicle load and transportation speed increase, the performance requirements for springs in vehicles are also further improved, so the comprehensive performance requirements for spring steel are also increased. [0003]...

AI Technical Summary

Problems solved by technology

In these patent applications, the final heat treatment process used for spring steel is oil quenching + medium and high temperature tempering, and the obtained structure is mainly tempered troostite, although there are differences in strength, toughness and fatigue resistance. The focus has been improved, but the disadvantage is that because they still use the traditional heat treatment process, not only the process is complicated, but also the requirements for energy saving and environmental friendliness cannot be met.

Images