英国Talbot Motors已开始采用热轧空心棒材制造汽车变速箱里的倒车齿轮,使汽车工业以这种棒材来取代传统的锻造齿坯制造汽车齿轮有了重大的突破。长期以来,用锻造齿坯制造齿轮,已成为惯例,其理论依据是:锻造齿坯的晶粒线向(grain flow)与齿形相一致、与所受的主应力垂直,因而其机械性能特别是疲劳负荷寿命将大为提高。这种看法,对于那些齿形也由锻造成形的大直径齿轮来说,无疑是正确的;然而,为数众多的小直径齿轮是由环状锻坯制成的。 British Talbot Motors has started using hot rolled hollow bar to make reversing gears in automotive gearboxes, giving the automotive industry a major breakthrough in replacing the traditional forged tooth blanks with automotive gear. It has long been the practice to make gears from forged blanks, the rationale being that the grain flow of a forged tooth blank is in line with the tooth profile and perpendicular to the principal stress to which it is subjected, and its mechanical properties are, in particular, Fatigue load life will be greatly improved. This view is undoubtedly correct for large-diameter gears whose shape is also forged; however, a large number of small-diameter gears are made of ring-shaped forged blanks.