Cold-rolled steel sheet excellent in weldability and formability and manufacturing method thereof

Abstract

A steel plate with excellent weldability and formability and a method for producing the same, the composition weight percent of which is: C: 0.0021% to 0.010%, Si≤0.03%, Mn: 0.3% to 1.0%, P≤0.02%, Al: 0.020%~0.06%, Ti:0.005%~0.08%, N≤0.005%, B*:0.0020%~0.0080%, the rest is Fe and unavoidable impurities, among which, B*=B‑0.77×N*, N *=N‑0.29×Ti, when N*≤0, N* takes the value of 0. The present invention aims at materials with welding processing requirements, through specific chemical composition and process design, to obtain steel plates with excellent weldability and processability, the material hardness HR30T is 45-65, and the rave (average plastic strain ratio) of the material can be greater than or equal to 1.2 The method solves the problem of poor welding performance of the steel plate produced by the prior art after the high-temperature resistance welding process, the ferrite structure of the material is coarse and excessively uneven.

Description

technical field [0001] The present invention relates to a cold-rolled steel sheet and a manufacturing method thereof, in particular to a cold-rolled steel sheet excellent in weldability and formability and a manufacturing method thereof. Background technique [0002] Cold-rolled steel sheets are widely used in home appliances, automobiles, packaging and other materials, especially tin-plated steel sheets are used in the expanding square barrels of chemical barrels, flower basket barrels and food three-piece cans. After bending and welding, the subsequent diameter expansion and flanging process And it is prone to cracking due to poor welding during shipment. In the past, low-carbon aluminum-killed steel had fewer cracking problems in welding and processing. As the deformation of processed products became more and more complex, the requirements for materials became higher and higher. Ultra-low carbon steel was also frequently used, and the corresponding processing and welding ...

AI Technical Summary

Problems solved by technology

However, due to the inherent shortcomings of the bell annealing process itself, the mechanical properties of the material after annealing are not uniform, and the metallographic structure is often uneven, especially at the head, tail and edge of the steel coil, which is prone to mixed crystals, which will also lead to poor welding.

[0004] Due to the limitations of low-carbon aluminum-killed steel and bell furnace annealing process, the produced materials cannot be used for processing requirements such as higher drawing and deep drawing

The use of ultra-low carbon IF steel materials can solve the requirements of higher drawing and stamping processing, but ordinary ultra-low carbon IF steels generally try to control the carbon below 20ppm, and some do not add boron or add boron for other reasons The amount is too small or the addition of boron does not control the effective excess boron content. Such materials are prone to coarse ferrite grains and excessive unevenness after high-temperature resistance welding, which will lead to cracking problems in subsequent processing.

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