A ti-v composite microalloyed ultrafine bainite non-quenched and tempered steel and its controlled forging and controlled cooling process and production process

Abstract

The invention discloses a Ti-V composite microalloyed ultrafine bainite non-quenched and tempered steel and its controlled forging and controlled cooling process and production process. The Ti-V composite microalloyed ultrafine bainite non-quenched and tempered steel Steel includes the following chemical composition in weight percentage: C 0.20‑0.30%, Si 0.20‑0.40%, Mn 1.90‑2.10%, P≤0.010%, S 0.030‑0.050%, Cr 0.40‑0.60%, V 0.10‑0.20%, Ti 0.030‑0.050%, Ni≤0.20%, Mo≤0.20%, Al 0.015‑0.045%, N≤0.0070%, the rest is Fe and unavoidable impurity elements, and Ti‑3.43*N≥0.017% and Ti×N ≤0.00016%; through high Ti content alloying design, supplemented by V‑N microalloying, compared with ordinary bainitic non-quenched and tempered steel, this steel has obvious bainite structure refinement, and obtains a tempered Sorbitite structure, the strength and toughness are greatly improved.

Description

technical field [0001] The invention belongs to the technical field of alloy structural steel, and in particular relates to a Ti-V composite microalloyed ultrafine bainite non-quenched and tempered steel and its controlled forging and controlled cooling process and production process. Background technique [0002] Traditional non-quenched and tempered steels generally add trace elements such as V, Nb, Ti to medium carbon (0.2-0.5% C) steel, and carry out controlled rolling (forging) and controlled cooling, so that V, Nb, Ti and other elements Precipitation of carbides and nitrides realizes the strengthening effect and obtains mechanical properties similar to quenching and tempering treatment, thereby eliminating the need for quenching and tempering treatment. In the cooling process after deformation, the precipitation strengthening effect of the carbonitride of V element is the strongest, and its strengthening effect is at a high level in a wide temperature range and does no...

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Problems solved by technology

Due to the low phase transformation temperature, the diffusion of alloying elements is inhibited during the phase transformation process, which makes it difficult to precipitate carbides of pinning dislocations, resulting in a high density of mobile dislocations in bainitic non-quenched and tempered steels, resulting in bainitic non-quenched and tempered steels. The yield strength of quenched and tempered steel is relatively low (≤0.70) under the general controlled forging and controlled cooling process conditions, which reduces the fatigue performance of bainite non-quenched and tempered steel

[0005] In order to improve the yield strength ratio of bainitic non-quenched and tempered steels, many bainitic non-quenched and tempered steels are tempered above 400°C. low steel strength

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