Cars in Liang Xiu generally depreciate by about 30%. Girder, also known as frame, is generally composed of two longitudinal beams and several cross beams, which are supported on wheels through suspension devices, front axle and rear axle. Automobile crossbeam is mainly a large load-bearing part inside the automobile, which bears almost all the weight of the automobile and goods. It also directly affects the driving safety of the car, so repairing the girder is equivalent to an accident car, which has an impact on the car.

After the repair, the stiffness of the main girder will have a certain influence, especially after the deformation repair, there will still be stress inside, which will easily accelerate the fatigue of the main girder.

Girder steel is mainly used for structural parts on the chassis of heavy trucks, such as longitudinal beams, lining beams, cross beams, front and rear axles, etc. Typical automotive steels are SAPH series in Japan, QStE series in Germany, DOMEX series in Sweden and S500MC-S700MC in Europe. ; Domestic products mainly include 5 10L, 6 10L, 700MC and so on. Hot-rolled steel plates for automobile crossbeams produced at home and abroad mainly adopt strengthening and toughening mechanisms such as fine grain strengthening, ferrite solution strengthening, second phase particle precipitation strengthening and phase transformation strengthening. Their strength and toughness depend on the chemical composition of steel.