800MPa-grade cold-rolled hot-galvanizing dual-phase steel and production method thereof

Abstract

The invention discloses 800MPa-grade cold-rolled hot-galvanizing dual-phase steel. The 800MPa-grade cold-rolled hot-galvanizing dual-phase steel comprises the following raw materials taken as chemicalcomponents in percentage by mass (%): 0.05% to 0.10% of C, 1.60% to 2.30% of Mn, 0.010 to 1.0% of Als, 0.10% to 0.60% of Si, 0.010 to 0.050% of Nb, 0.05 to 0.30% of Cr, 0.05 to 0.30% of Mo, P not smaller than 0.015%, S not greater than 0.010%, N not greater than 0.008%, and the balance of Fe and inevitable impurities, and noble metal elements Cr and Mo satisfy the relation that Cr+Mo is not smaller than 0.05 and not greater than 0.30, and C+Si / 30+Mn / 20 is not greater than 0.22. The production method for the hot-galvanizing steel for an automobile wheel cover comprises the steps of smelting, continuous casting, heating, hot rolling, cooling, coiling, pickling, cold rolling, annealing and coat-plating. According to the invention, the obtained cold-rolled hot-galvanizing dual-phase steel hasless precious alloying elements, so that the product has good mechanical properties, surface quality, formability and welding performances. Furthermore, the 800MPa-grade cold-rolled hot-galvanizing dual-phase steel disclosed by the invention can be produced on the existing conventional production line without additional equipments.

Description

technical field [0001] The invention relates to an 800MPa grade cold-rolled hot-dip galvanized dual-phase steel and a production method thereof, belonging to the field of cold-rolled hot-dip galvanized ultra-high-strength steel for automobiles. Background technique [0002] In recent years, with the advancement of automobile energy saving and emission reduction technology, automobile lightweight has become a development trend. Ultra-high-strength steel of 780MPa level and above is one of the development directions of automotive lightweight materials. Due to the ferrite + martensitic dual-phase high-strength steel has good strong plasticity, low yield ratio, high initial work hardening rate, and good drying Widely used due to its bake hardening properties. Compared with ordinary cold-rolled high-strength dual-phase steel, galvanized dual-phase steel also has good corrosion resistance, so it is widely used in automotive structural parts such as door anti-collision beams, long...

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Problems solved by technology

[0004] In the prior art, due to the addition of relatively high alloying elements Cr, Mo (the content of Cr+Mo is generally above 0.3), etc., the cost of the alloy is relatively high, and in order to control the surface quality of the product, the Si content in the steel is generally controlled Below 0.05%

In order to reduce the cost of the alloy, there is also a technology that uses more than 0.40% Si to produce 800MPa dual-phase steel, but when using a higher Si content for production, the production line must have the function of pre-oxidation or direct fire heating to solve the problem caused by external oxidation. It leads to the problem of missed plating during galvanizing, so as to produce galvanized products with high surface quality, so it is difficult to produce galvanized products with high surface quality for conventional production lines without direct fire heating function

In addition, the existing products will also have problems such as forming cracks during the use of users

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