Sumitomo Develops System To Drastically Reduce Weight Of Auto Parts

Sumitomo Develops System to Drastically Reduce Weight of Auto PartsSumitomo Heavy Industries Ltd developed a manufacturing system that can drastically reduce the weight of auto parts such as bodies and frames.
The system is called "STAF (Steel Tube Air Forming)." After setting a steel pipe in the metal mold of a pressing machine, electrical heating, injection of high-pressure air, shape forming and quenching are performed in this order. With a newly developed control system, serial modified closed sections can be formed with a high accuracy.

The system can (1) form serial closed sections like a hydro-form processing method and (2) heat a steel plate and press-form and quench it at the same time to realize a tensile strength of about 1,500MPa like a hot-stamping method. As a result, it can form parts that have a closed section and are light, strong and rigid.

Furthermore, the system adds flanges to structures having a closed section by using a simultaneous flange forming technology. As a result, it eliminates the need for separate flanges and welding process used for connection with other parts, which are problems with hydroforming. And it became possible to propose structures that can be easily employed for auto parts.

First, a pipe is set in a metal mold, and electrodes are chucked . Electricity is conducted for about 10 seconds, and the pipe is heated to about 900°C . With the electrical heating of the pipe, the right and left electrodes have the same contact area, and the contact is more stable than in the case of plate materials, enabling uniform heating. Furthermore, compared with a heating furnace method, which is a conventional heating method, it can drastically reduce power consumption.

Then, the mold closing position (half open) is adjusted to form flanges . High-pressure air is supplied to it. And the mold is closed while the half-open part is slightly bloated to form flanges . After that, more high-pressure air is supplied for blow molding so that the shape of the main body part becomes more similar to that of the inner surface of the mold .

Because the material is closely attached to the metal mold, it is rapidly cooled and quenched to have a tensile strength of about 1,500MPa.