MULTI-THICKNESS WELDED VEHICLE RAIL

Abstract

A process for preparing a welded steel vehicle rail of various thicknesses, the process comprising the steps of: (a) forming a first tube having a first outside diameter, an inside diameter, and a first wall thickness; (b) forming a second tube having a first outside diameter, a second inside diameter, and a second wall thickness different from the first wall thickness; (c) stamping a first end of the first tube to a second outside diameter smaller than the second inside diameter of the second tube; (d) inserting the stamped first end of the first tube into an end of the second tube to form a joint; (e) welding the first tube and the second tube together to form a weld at the joint to form a tube blank with a heat-affected zone of lower metallic strength in the weld area; (f) preheating the tube blank to create a common crystalline microstructure along a length of the tube blank;(g) introducing the tube blank into a blow molding tool having inner molding walls; (h) molding the tube blank at an elevated temperature by expanding the tube blank against the inner molding walls of the molding tool by injecting a pressurized medium into an inner cavity of the tube blank; and (i) cooling the tube blank by replacing the pressurized medium with a cooling medium through the molding tool and the tube blank to achieve a rapid cooling effect on the tube blank and to create a complete vehicle rail with essentially uniform material strength across the weld. A complete vehicle rail has an overlapping welded structure and a uniform microcrystalline structure along the length of the rail.

Claims

1. A multi-thickness welded tubular steel vehicle structure formed by blow molding, characterized in that it comprises: (a) a first tube having a first outside diameter, an inside diameter, and a first wall thickness; (b) a second tube having a first outside diameter, a second inside diameter, and a second wall thickness different from the first wall thickness; (c) a first end of the first tube stamped to a second outside diameter smaller than the second inside diameter of the second tube; (d) the first stamped end of the first tube inserted into an end of the second tube and forming a joint; (e) the first tube and the second tube welded at the joint using MAG welding or a similar process to form a tube blank; (f) the tube blank has been subjected to thermomechanical processing comprising preheating, blow molding, and cooling.

2. The multi-thickness welded tubular steel vehicle structure, formed by blow molding, according to claim 1, characterized in that the second wall thickness is greater than the first wall thickness.

3. The multi-thickness welded tubular steel vehicle structure, formed by blow molding, according to claim 1, characterized in that the first wall thickness is greater than the second wall thickness.

4. The multi-thickness welded steel tubular vehicle structure, formed by blow molding, in accordance with any of claims 1 to 3, characterized in that the tubular structure is a rail.

5. A process characterized in that it comprises: (a) forming a first tube having a first outside diameter, an inside diameter, and a first wall thickness; (b) forming a second tube having a first outside diameter, a second inside diameter, and a second wall thickness different from the first wall thickness; (c) stamping a first end of the first tube to a second outside diameter smaller than the second inside diameter of the second tube; (d) inserting the stamped first end of the first tube into an end of the second tube to form a joint; (e) welding the first tube and the second tube using MAG welding or a similar process to form a weld at the joint to form a tube blank with a heat-affected zone of lower metallic strength in the weld area; (f) preheating the tube blank to create a common crystalline microstructure along a length of the tube blank;(g) introducing the tube blank into a blow molding tool having inner molding walls; (h) molding the tube blank at an elevated temperature by expanding the tube blank against the inner molding walls of the molding tool by injecting a pressurized medium into an inner cavity of the tube blank; and (i) cooling the tube blank by replacing the pressurized medium with a cooling medium through the molding tool and the tube blank to achieve a rapid cooling effect on the tube blank and to create a finished multi-thickness welded tubular structure of the vehicle with essentially uniform, strong material throughout the weld.

6. The process according to claim 5, characterized in that the blank tube includes at least two openings for feeding and removing respectively the pressurized heating medium and the cooling medium to circulate through the interior of the blank tube.

7. The process according to claim 5, characterized in that the pressurized heating medium is gaseous and the cooling medium is liquid.

8. The process according to claim 7, characterized in that the pressurized gaseous heating medium is selected from air and nitrogen and the cooling medium is water.

9. The process according to claim 5, characterized in that the raw tube material is steel having an austenitic crystalline microstructure after preheating and during molding, and a martensitic crystalline microstructure after cooling.

10. The process according to claim 5, characterized in that the thickness of the second wall is greater than the thickness of the first wall.

11. The process according to claim 5, characterized in that the thickness of the first wall is greater than the thickness of the second wall.

12. The conformity process of any of claims 5 to 11, characterized in that the tubular structure is a rail.

Images