Steel for battery shell with excellent planar isotropism and its production

Abstract

The invention relates to steel for battery steel shells and a manufacturing method thereof. The invention mainly solves the defects of large plane anisotropy, poor secondary processing embrittlement resistance, high production cost and the like existing in the existing steel for battery shells. The steel for battery case with excellent planar isotropy of the present invention has the following chemical element components by weight percentage: C: ≤0.01-0.05%, Si: ≤0.03%, Mn: 0.10-0.50%, P: ≤0.02%, S: ≤0.015%, Al: 0.01-0.10%, N: 0.002-0.007%, Ti: 0.005-0.02%, and the rest are iron and inevitable inclusions. The manufacturing method includes the following steps: molten iron pretreatment, converter smelting, post-furnace refining, hot rolling, pickling, cold rolling, bell annealing, leveling, finishing into finished coils, and is characterized by: heating temperature: ≤1270°C , Finish rolling temperature: 860~930℃, coiling temperature: ≤640℃; cold rolling deformation is controlled at 75%~90%, bell furnace annealing temperature: 650~800℃; others are carried out according to conventional processes. The product is used for stamping after electroplating nickel or directly stamping into battery case.

Description

Technical field: [0001] The invention relates to a steel for a battery case and a manufacturing method thereof, in particular to a steel for a battery case with excellent planar isotropy for making rechargeable batteries and dry battery cases and a manufacturing method thereof. Background technique: [0002] Cold-rolled steel strips for battery cases are mainly used for punching steel cases for dry batteries and rechargeable batteries. The battery shell is made of steel strip with a punch press, and the battery shell is punched with or without thinning. The battery shell product must not have defects such as cracks, trachoma, snowflakes, etc., and requires excellent plane isotropy (small ears) and Resistant to internal pressure deformation. Therefore, the material of the steel strip is required to have high purity, high ductility, high surface quality, and low Δr value, and it can be used for thinning and deep drawing without cracking and snowflake point defects. Before th...

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Problems solved by technology

Before the present invention, there was CN1401807A "extremely thin steel strip for battery casing and its manufacturing method", the patent application used ultra-low carbon Nb-Ti-IF steel to produce battery casing steel, but this type of steel is different from medium and low carbon aluminum Compared with killed steel, due to the need for decarburization treatment and more alloy addition, the production cost is higher, and the resistance to secondary processing embrittlement is poorer, and the plane anisotropy (Δr value) is larger

There are also some battery shell manufacturers who use ordinary aluminum-killed steel to punch battery shells. Because there is no special control of composition and structure, the material grains and cementite tend to become thicker, and the surface is prone to "snowflake" defects and stamping cracks. , affect the appearance quality and use of the battery case, and the plane anisotropy is large, not only the punched battery case will have ears, but also the internal stress of the punched battery case is large, and the thinning rate is low

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