A kind of 780mpa heat-based coating dual-phase steel and preparation method thereof
A dual-phase steel and coating technology, which is applied in the field of 780MPa heat-based coating dual-phase steel and its preparation, can solve the problems of low strength level and insufficient corrosion resistance, and achieve improved corrosion resistance, simplified process flow, and good plasticity Effect
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[0083] According to another typical embodiment of the present invention, a kind of preparation method of 780MPa heat-based coating dual-phase steel is provided, such as image 3 Shown, described preparation method comprises:
[0084] S1. Obtain the slab of the 780MPa grade heat-based coating dual-phase steel;
[0085] S2. Heating the slab to 1230°C-1270°C and keeping it warm for 120min-180min;
[0086] S3. The slab after heat preservation is hot-rolled to obtain a hot-rolled coil;
[0087] S4. Cooling the hot-rolled coil after rolling, coiling, pickling and hot-dip galvanizing / zinc-magnesium-aluminum to obtain the 780MPa grade hot-based coating dual-phase steel;
[0088] Wherein, the post-rolling cooling includes:
[0089] Water cooling the hot-rolled coil to 620°C-670°C at a cooling rate ≥30°C / s, and then air-cooling for 6s-10s;
[0090] After the air cooling is completed, water-cool to 460°C-500°C at a cooling rate of ≥20°C / s.
[0091] In the present invention, by impro...
Embodiment approach
[0098] As an optional implementation manner, the coiling includes:
[0099] The hot-rolled coil cooled after rolling is coiled, the coiling temperature is 460°C-500°C, and after the coiling is completed, it is cooled in a slow cooling pit, and the average cooling rate is ≤15°C / h.
[0100] In this application, the coiling temperature is 460°C to 500°C. The purpose of controlling the coiling temperature is to obtain the ideal bainite ratio and strength. When the coiling temperature is greater than 500°C, the phase transition will easily enter the pearlite region, which will lead to bainite. When the proportion of bainite is reduced, the strength of hot-rolled sheet is insufficient; when the coiling temperature is lower than 460°C, the carbon enrichment degree of bainite is high, and martensitic structure is easy to appear, resulting in the increase of hardness difference between adjacent phases, which affects the forming of steel sheet performance.
[0101] As an optional imple...
Embodiment
[0114] A 780MPa grade heat-based coating dual-phase steel, prepared by the following method:
[0115] (1) Obtain a slab with a thickness of 220mm~250mm, in terms of mass fraction, the chemical composition of the slab is:
[0116] C: 0.04% to 0.08%, Si: 0.5% to 0.8%, Mn: 1.4% to 2.1%, Al: 0.02% to 0.50%, Nb: 0.04% to 0.07%, Ti: 0.05% to 0.14%, Cr: 0 to 0.25%, Cu: 0 to 0.01%, Ni: 0 to 0.01%, B: 0 to 0.001%, P: 0 to 0.015%, S: 0 to 0.001%, and the rest is Fe and unavoidable impurities.
[0117] (2) Heating the slab to 1230° C. to 1270° C. and keeping it warm for 120 minutes to 180 minutes.
[0118] (3) Hot rolling: the rough rolling start temperature of the hot rolling is 1160°C, the rough rolling end temperature is 1110°C, the finish rolling start temperature is 1040°C, and the finish rolling temperature is 890°C-930°C.
[0119] (4) Cool the hot-rolled coils obtained by hot rolling after rolling: water-cool the hot-rolled coils at a cooling rate of ≥30°C / s to 620°C-670°C, and ...
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