High hole expansion and high plasticity 980mpa grade duplex galvanized steel sheet and preparation method thereof

Abstract

The invention provides a 980MPa grade dual-phase steel galvanized steel sheet with high hole expansion and high plasticity and a preparation method thereof. The composition of the steel sheet in terms of weight percentage is as follows: C: 0.13%-0.18%, Si: 0.5%-1.4%, Mn: 2.2%~2.5%, P≤0.02%, S≤0.005%, Ti:≤0.03%, Al: 0.015%~0.8%, the balance is Fe and inevitable impurities. The manufacturing method includes the following steps: smelting, hot rolling, pickling, cold rolling, continuous galvanizing, and smoothing; the present invention realizes the force and energy index taking into account high hole expansion and high plasticity by optimizing alloy design and ingenious process design, Break through the technical difficulties that the traditional 980MPa grade steel plate is incompatible with hole reaming and drawing performance.

Description

technical field [0001] The invention belongs to the field of metal materials, in particular to the manufacture of steel for automobiles, in particular to a 980MPa grade dual-phase galvanized steel sheet with high hole expansion and high plasticity and a preparation method thereof. Background technique [0002] With the continuous development of advanced high-strength steels, many types of high-strength steels have gradually entered people's field of vision, such as dual phase (DP), complex phase (CP), transformation induced plasticity (Transformation induced plasticity, TRIP), Quenching and Partitioning (QP), etc. Among them, dual-phase steel is widely used in body structural parts, such as B-pillar inner and outer panels, due to its good mechanical curve and good stamping-grade flanging performance. Structural parts such as longitudinal beams and engine side beams, bumpers, door sills, seat rails and other anti-collision and reinforcement parts. However, with the gradual i...

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Problems solved by technology

However, TWIP steel is an all-austenitic steel plate, and a large amount of Mn is added to the alloy, which greatly increases the cost of the alloy. Obviously, it is not suitable for civilian vehicles; although TRIP and QP steel have elongation increased to 20% or even Above, but it is still necessary to add C element to more than 0.2%, which will affect the performance of subsequent resistance spot welding

At present, some domestic steel mills have proposed the concept of DH (DP with high formability) steel and trial production products. The plasticity of DH980 steel can reach more than 14%, which is slightly higher than 12% of DP steel. It reflects the status quo of low yield strength and low yield ratio, which leads to the hole expansion rate of this variety is less than 20%, and the poor hole expansion performance leads to the risk of cracking during the forming and flanging process

However, an average of about 0.05% of Nb is added to the steel, and the higher yield strength is mainly due to the fine-grain strengthening effect after Nb addition, which undoubtedly greatly increases the cost of the alloy

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