| 摘要 |
A vehicle structural beam, such as a door intrusion beam, which possesses an elongate tubular beam part which at opposite ends is provided with mounting flanges for securement to a vehicle frame. The elongate tubular beam part and the flanges provided at opposite ends are defined by an integral, one-piece, monolithic steel structure which has been initially roll-formed from an elongate flat metal sheet to define the closed tubular structure of the tubular beam part, and which has been subjected to heating and quenching so that the elongate tubular beam part is of relatively high strength steel throughout its entire length, whereas the integrally and monolithically joined end flanges remain as lower strength steel which has been significantly unaffected by the heat treatment and quenching so as to permit appropriate shaping thereof and ease of welding to the vehicle frame.
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