汽车车身用新型冷轧薄板研发进展

Research and development progress of new cold rolled sheet steels of car body

  • 摘要: 对近年来汽车车身用新型冷轧薄板的研发进展进行了综述,重点介绍了国内外增强成形性双相钢(Dual phase steel with improved formability,DH)、锌铝镁镀层钢板和高鲜映性汽车外板的技术思路、产品优势和应用情况。DH钢中适量稳定性较高的残余奥氏体大幅提高了断后延伸率及加工硬化率,在解决冲压开裂、实现车身轻量化方面效果显著;锌铝镁镀层特殊的相结构决定了其优异的耐蚀性能和成形性能,在汽车内板和外板得到广泛应用;成形零件的表面波纹度是评价高鲜映性汽车外板的重要指标,首钢开发了表面波纹度演变机理及控制技术,解决了钢板表面粗糙度与波纹度协同控制难题。指出了这些新型冷轧薄板要关注的生产和应用方面问题,如DH钢中较高Al、Si含量导致的连铸生产困难和表面质量问题、高合金含量带来的性能波动问题、高强度级别产品的氢脆问题和镀层板焊接的液态金属脆性(Liquid metal embrittlement,LME)问题等;锌铝镁镀层钢板焊接、涂装、粘接、成形等基础数据还不健全,高耐蚀性能还需得到更多用户检验及认可;高鲜映性汽车外板还需要进一步减少表面缺陷的数量、尺寸,进一步压制长波的表面轮廓。

     

    Abstract: The automobile industry has entered a new stage of development, with new changes in steel materials for car bodies and increasingly stringent requirements for energy conservation and emission reduction. This paper summarizes the recent research and development progress of new cold-rolled sheet steels for the car body. The technical routes, product advantages, and application of dual-phase steel with improved formability (DH steel), zinc–aluminum–magnesium (Zn–Al–Mg) coated steel, and automobile outer panels with high distinctness of image have been emphasized. In DH steel, an appropriate amount of retained austenite with high stability greatly improves the total elongation and work hardening rate, which is effective in solving stamping cracking. In addition, DH steel has a higher tensile strength under the same elongation in comparison to traditional DP steel. Thus, it is possible to make the body lightweight by applying thinner sheets. The special phase structure of Zn–Al–Mg coated steel determines its excellent corrosion resistance and formability compared with pure zinc-coated steel, which is widely used in automobile inner and outer plates. The surface waviness of parts is an important index of an automobile’s outer plate with a high distinctness degree of image. Shougang has developed the evolution mechanism and control technology of surface waviness and solved the problem of coordinated control of steel sheet surface roughness and waviness. Simultaneously, it is noted that the research and development of DH steel should focus on some production and application problems, such as continuous casting difficulties and surface defects due to high Al and Si content, mechanical property fluctuations caused by high alloy content, hydrogen embrittlement of high-strength products, and liquid metal embrittlement (LME) of the coated sheet during welding. The basic data of welding, coating, bonding, and forming of Zn–Al–Mg coated steel sheets are not perfect, and the high corrosion resistance needs to be inspected and recognized by more users. The high distinctness of automobile outer plate needs to further reduce the number and size of surface defects and decrease the longwave surface contour in the future to achieve a high degree of cleanliness and homogenization of the automobile outer panel surface. Continuously improving the performance advantages of the above materials through a combination of theoretical research, process progress, and equipment upgrading, as well as expanding their application in the automotive field, requires the joint efforts of iron and steel production enterprises, material application enterprises, and scientific research institutions.

     

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