700MPa-grade thermal forming axle housing steel and preparation method thereof

Abstract

The invention discloses 700MPa-grade thermal forming axle housing steel. The 700MPa-grade thermal forming axle housing steel is prepared from the following chemical components in percentage by mass: 0.17%-0.27% of C, 0.30%-0.50% of Si, 1.2%-1.8% of Mn, less than or equal to 0.02% of P, less than or equal to 0.009% of S, less than or equal to 0.1% of Ti, less than or equal to 0.2% of Cr and the balance of Fe and inevitable impurities, wherein the mass fraction of Si and Mn meets the condition that Si / Mn is more than or equal to 0.23 and less than or equal to 0.27. The invention further discloses a preparation method. The preparation method comprises the steps of adopting the chemical components for smelting, continuous casting, heating, rough rolling, finish rolling, curling and machining treatment with the heating temperature of 1180 DEG C-1220 DEG C and the heating time of 150 min-200 min to obtain the 700MPa-grade thermal forming axle housing steel. The mechanical properties before and after heat treatment are excellent, and a plate obtained after heat treatment is free of obvious microscopic banded structures and has excellent impact toughness.

Description

technical field [0001] The invention relates to the technical field of steel preparation, in particular to a 700MPa grade thermoformed axle housing steel and a preparation method thereof. Background technique [0002] The axle housing is the structure that mainly supports the load of the vehicle, and its lightweight research is of great significance to the lightweight of the medium and heavy trucks. At present, my country's automobile industry has widely used hot-rolled axle housing steel plates to produce axle housings through hot stamping + welding, replacing cast axle housings with complex manufacturing processes, low production efficiency, and high cost. [0003] Automobile axle housings have used hot-rolled plate substitutes (such as 610L, Q460, etc.) for mass production, but the substitutes have the problem that the material strength is significantly reduced after hot stamping, which is manifested in the obvious grains of the plates after hot stamping. Coarsening, fin...

AI Technical Summary

Problems solved by technology

At present, my country's automobile industry has widely used hot-rolled axle housing steel plates to produce axle housings through hot stamping + welding, replacing cast axle housings with complex manufacturing processes, low production efficiency, and high cost.

[0003] Automobile axle housings have used hot-rolled plate substitutes (such as 610L, Q460, etc.) for mass production, but the substitutes have the problem that the material strength is significantly reduced after hot stamping, which is manifested in the obvious grains of the plates after hot stamping. Coarsening, the fine grain strengthening effect of the plate disappears, and the automobile axle housing products cannot meet the service conditions

Therefore, the special hot-formed axle housing steel designed and developed according to market demand is mainly based on precipitation strengthening (V(C,N)). and heating and holding time) and the cooling conditions of the axle housing after hot stamping (such as: air cooling cooling rate) change greatly, the precipitation amount, precipitation position and precipitation size of V (C, N) precipitates fluctuate greatly, after hot stamping The mechanical properties of the axle housing steel cannot be stably controlled, and the casting slab containing V axle housing steel is very easy to form surface transverse cracks, resulting in abnormal structure at the edge of the plate

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