High-surface-quality 1200 MPa-grade hot-dip galvanized dual-phase steel and production method thereof

Abstract

The invention relates to a high-surface-quality 1200 MPa-grade hot-dip galvanized dual-phase steel. The hot-dip galvanized dual-phase steel comprises the following chemical components of, in percentage by mass, 0.07%-0.10% of C, 0.25%-0.55% of Si, 1%-4% of Mn, less than or equal to 0.016% of P, less than or equal to 0.008% of S, 0.01%-0.05% of Als, less than or equal to 0.006% of N, 0.04%-0.08% ofTi, 0.015%-0.055% of Nb, 0.15%-0.45% of Mo, 0.008%-0.010% of B, and the balance Fe. The production method comprises the steps of continuous casting, hot rolling, cold rolling and galvanization, wherein in the hot rolling process, the coiling temperature is controlled by adopting a U-shaped coiling process, the coiling temperature of a head part and a tail part of a steel coil is 600 + / -20 DEG C,the coiling temperature of the middle section is 550 + / -20 DEG C, and the stability of the uncoiling performance is improved. According to the method, the production cost is remarkably reduced, the steel coil with stable mechanical property in the head part, middle part and tail part is obtained by combining the U-shaped coiling process and a pre-oxidation technology in a zinc plating furnace, thesurface quality of a steel strip is good and can reach the FB1 grade, and the production reliability is high.

Description

technical field [0001] The invention relates to a hot-dip galvanized dual-phase steel with a high surface quality of 1200MPa and a production method thereof, belonging to the technical field of galvanized ultra-high-strength dual-phase steel production. Background technique [0002] In recent years, the automobile manufacturing industry has researched and developed a series of new steel materials, and dual-phase steel is one of them. Composed of ferrite and martensite, dual-phase steel has the characteristics of low yield ratio, high initial work hardening rate, good strength and ductility through phase transformation strengthening, and is often used to manufacture structural reinforcements that withstand high loads. Ultra-high-strength galvanized dual-phase steel has the above characteristics and also has good corrosion resistance. Therefore, ultra-high-strength galvanized dual-phase steel has become the leading trend to solve energy-saving, environmental protection, and sa...

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Problems solved by technology

[0005] The patent application number 201811590444.X discloses a hot-dip galvanized steel sheet with a tensile strength greater than 1300MPa and its production method, using: C: 0.1-0.2%, Mn: 1.3-2.0%, S≤0.005%, P≤ 0.02%, Si: 0.2-0.3%, Als: 0.4-1.0%, Nb: 0.01-0.03%, Ti: 0.04-0.08%, B: 0.001-0.004%, Mo: 0.2-0.3%, Cr: 0.05-0.10 %, V: 0.01-0.02% of the high-aluminum composition system, and finally obtain a hot-dip galvanized steel sheet with a tensile strength greater than 1300MPa by controlling hot rolling, acid rolling, continuous hot-dip galvanizing, skin passivation and passivation processes, but the invention does not The precipitation of high-alloy elements in the subsequent production process due to the addition of high-alloy elements is not considered, and the subsequent coating performance and surface quality cannot be guaranteed. The problem of aluminum water plugging makes production more difficult

[0006] The patent application number 201811621827.9 discloses a cold-rolled composite steel with a tensile strength of 1200MPa and its preparation method, wherein the chemical composition of the composite steel is: C: 0.10-0.15%, Si: 0.1-0.5% , Mn: 1.5-2.6%, Cr: 0.4-0.7%, Mo: 0.2-0.5%, Nb: 0.02-0.05%, Ti: 0.02-0.05%, P≤0.02%, S≤0.015%, the balance is iron and other unavoidable impurity elements; and meet the following conditions at the same time: C+(Si+Mn) / 6+(Cr+Mo+V) / 5≤0.80 The tensile strength of the final cold-rolled multiphase steel product is above 1200MPa, and the yield strength reaches 900MPa Above, the elongation after fracture is more than 5%. Since it is a cold-rolled plate, the influence of the enrichment and precipitation of alloying elements on the coating is not considered, but the corrosion resistance is relatively reduced. More precise control with the phase ratio, so the technical requirements for annealing cooling rate and annealing cooling path control are more stringent

[0007] The patent application number 201110103690.X discloses a hot-dip galvanized steel sheet with a tensile strength greater than 1180 MPa. The chemical composition of the substrate is as follows: C: 0.08-0.12%, Si: 0.5-1.50%, Mn: 1.80- 2.50%, Cr: 0.10~0.80%, Mo: ≤0.50%, Al: 0.02~0.05%, Ti: 0.005~0.050%, Nb: 0.005~0.050%, P≤0.006~0.02%, S≤0.01%, N ≤0.005%, using a certain heat treatment process to finally obtain a hot-dip galvanized steel sheet with a tensile strength greater than 1180MPa. Excessive Si elements in this component will adversely affect welding performance and surface quality

[0008] The patent application number 201610542806.2 discloses a 1000MPa grade low-carbon hot-dip galvanized dual-phase steel and its preparation method: using C: 0.05-0.10%, Si: 0.20-0.60%, Mn: 1.40-1.90%, Cr: 0.20 ~0.70%, Mo: 0.20~0.50%, Al: 0.02~0.06%, Ti: 0.020~0.050%, Nb: 0.010~0.040%, B.0010~0.0030%, P≤0.015%, S≤0.005%, N ≤0.006%, through process control, a high-aluminum hot-dip galvanized dual-phase steel with a tensile strength greater than 1000MPa is obtained; this patent does not solve the problem of the influence of high-alloy element precipitation on the surface of galvanized sheets

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