Ferrite-based tempering steel plate of which yield strength is 900MPa and production method

Abstract

The invention discloses a ferrite-based tempering steel plate of which the yield strength is 900Mpa and a production method. The ferrite-based tempering steel plate not only is prepared from chemicalcomponents of C, Si, Mn, P, S, Ti, Mo, Nb, Alt, Ca and N, but also an appropriate amount of Cr is added, and the balance is Fe. Steel ladle+vacuum dual refining smelting and pouring are adopted, a continuous casting billet is subjected to hot charging and hot conveying, the charging temperature of the continuous casting billet in a heating furnace is greater than 400 DEG C, the heating temperaturein the heating furnace is 1230 to 1280 DEG C, the hot rolling finish rolling temperature is 820 to 900 DEG C, a quick-cooling rate which is greater than 25 DEGC / s is adopted for cooling after rolling, the rolling temperature is 560 to 640 DEG C, a steel coil is cut and flattened along a transverse cutting line, and the cut and flattened steel plate is subjected to tempering at (500 to 650 DEG C) / (15 to 50 minutes) in a wide flat steel heat treatment line. The production method of hot continuous rolling, steel coil flattening and opening and steel plate tempering is adopted, a microscopic structure of steel is used as a ferrite matrix, strengthening mechanism is based on precipitation strengthening and refined crystalline strengthening, and the ferrite-based tempering steel plate is low-carbon steel, has good welding and extending plasticity and forming performance, and is suitable for being used on engineering machinery vehicles or automobile vehicles.

Description

technical field [0001] The invention relates to a ferrite-based tempered steel plate with a yield strength of 900 MPa and a thickness of 2.5-7.0 mm and a production method, which is a steel plate suitable for manufacturing engineering machinery vehicles or automobile vehicles. Background technique [0002] Advanced high-strength steel is a lightweight, cost-effective, and highly competitive material for vehicles. At present, the main grades of high-strength steel used in the construction machinery industry and the automotive and commercial vehicle industries are grades with a yield strength of 420-960MPa, of which 420-700MPa grades are acceptable The hot rolling process can also be produced by quenching and tempering heat treatment process, while the grade above 700MPa is basically produced by quenching and tempering heat treatment process. High-strength steel with a yield strength of 900MPa is widely used in construction machinery and coal machinery, and gradually begins to...

AI Technical Summary

Problems solved by technology

However, this kind of high-strength steel also has some disadvantages, mainly in the large fluctuations in strength and unstable mechanical properties; the precipitation strengthening effect is strong, and at the same time it is easy to form irregular Mao islands, and the toughness is relatively poor; the fine grains after welding Easy to grow, high welding loss rate

[0004] ZL201310412998.1 (CN103484764B) "Ti precipitation-strengthened ultra-high-strength hot-rolled sheet and its production method" has been checked, using low carbon (0.07-0.12wt%) plus Ti-B composite microalloying plus a certain amount of Ni, Cr , Mo or Cu composition design, obtained bainite + acicular ferrite Ti precipitation-strengthened ultra-high-strength hot-rolled coils, Kaiping Cheng steel plate adopts tempering process and hot straightening, and the flatness is 2mm / m , Rel≥900MPa and hot-rolled sheet with good formability; the disadvantage is that the cost is high because of the addition of Ni, Cr, Mo or Cu precious alloys; in addition, the structure type of bainite plus acicular ferrite is relatively Due to the type of ferrite structure, the cooling after hot rolling is fast, the shape of the plate is difficult to control, and the plasticity and formability are also poor.

[0005] Patent No. ZL201310111953.X (CN103194676B) "A 1000MPa grade ferritic steel and its preparation method", adopts the composition design of low carbon (0.085~0.090wt%) plus Ti microalloying plus Mo, on a 350mm two-roll rolling mill The microstructure with a single ferrite matrix plus a large number of carbide particles dispersion-strengthened was obtained through controlled cooling and isothermal 1-2h furnace cooling after coiling, and a 2-6mm thick Rel of 900MPa (Rm=1000MPa level) thermal Rolling thin plate; the disadvantage is that ① it is still in the laboratory stage and has not been tested in industrialized large-scale production; ② the production cost is high with the addition of precious alloy Mo (0.37-0.55wt%); ③ isothermal for 1-2 hours after coiling and furnace cooling The process is difficult to implement due to the lack of similar equipment in most iron and steel enterprises

The carbon content in the produced products is relatively high, and the increase of carbon content will significantly reduce the welding performance; in addition, the products are not processed by the tempering process, which has the disadvantages of large performance fluctuations and low impact toughness