Preparation method for 2400MPa class low-cost nano bainitic steel

Abstract

The invention discloses a preparation method for 2400MPa class low-cost nano bainitic steel, belonging to the field of metal materials. The steel is C-Si-Mn-Al high and medium carbon alloy, without addition of expensive alloy elements of Cr, Mo and the like. The preparation method comprises the following steps: carrying out heat preservation to a forging block for 0.5-1 hour at 900-1000DEG C, and then directly feeding in a salt bath hardening furnace for preserving heat for 3-6 hours, thus being capable of producing carbide-free nano bainite with tensile strength of 2400MPa class. According to the method, the component optimization of reducing Mn and increasing C and Si is carried out, the preparation technology is simplified, the high-temperature dispersion annealing and hot rolling processes are not required, the forging block is directly subjected to low-temperature isothermal heat treatment, to obtain the final product, so that the production cost can be greatly lowered.

Description

technical field [0001] This technology involves a 2400MPa low-cost nano-bainite steel and its preparation process, which mainly involves the preparation of an ultra-high-strength nano-bainite steel at a relatively low cost. The structure is lamellar bainitic ferrite lath with a thickness of ≤100nm and film-like carbon-rich retained austenite distributed between the laths, and no cementite is precipitated in the structure. Put the forged billet directly into the furnace and keep it warm in the single-phase austenite zone for complete austenitization, and then put it into the salt bath quenching furnace between the starting temperature of bainite transformation and the starting temperature of martensitic transformation Isothermal heat treatment is carried out at a lower temperature, and finally the billet is water-cooled to room temperature. Background technique [0002] Since the development of bainitic steel, it has been widely used in structural materials because of its go...

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Problems solved by technology

[0008] This kind of nano-bainite steel has excellent mechanical properties, but to obtain this structure usually requires the addition of a large amount of expensive alloying elements, and requires long-term high-temperature diffusion annealing before austempering. The general preparation process is: Homogenization annealing → furnace cooling to room temperature → heating to a certain temperature for austenitization → long time isothermal heat treatment → cooling to room temperature, the preparation time of this process is too long and the preparation cost is too high

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