Weldability in resistance welding of steels with large difference in sheet thickness

A weld structure produced by resistance welding at least three steel sheets according to a unified weld schedule, each of the at least three steel sheets having a corresponding thickness, the weld structure comprising:

• the at least three steel sheets arranged as a stack according to the corresponding thickness of each of the at least three steel sheets such that a thinnest of the at least three steel sheets is a bottom layer of the stack;
• and
• a layer of adhesive/sealer material (ASM) between at least a thickest two steel sheets of the stack,
• wherein weld penetration extends into the thinnest of the at least three steel sheets.

A method for determining weldability solutions when resistance welding at least three steel sheets in a stack, each of the at least three steel sheets having a corresponding thickness, the method comprising:

• determining a thickness of each of the at least three steel sheets;
• utilizing a first process if the weld is intended for a strategic area of a welded assembly and a ratio of the corresponding thickness of any two adjacent steel sheets is greater than 3.0;
• utilizing a second process if the weld is intended for a strategic area of a physical structure and a ratio of the corresponding thickness of any two adjacent steel sheets is not greater than 3.0 and a ratio of the corresponding thickness of a thickest and a thinnest of the steel sheets is not greater than 1.85;
• utilizing a third process if the weld is intended for a strategic area of a welded assembly and a ratio of the corresponding thickness of any two adjacent steel sheets is not greater than 3.0 and a ratio of the corresponding thickness of a thickest and a thinnest of the steel sheets is greater than 1.85 and fusion is required at an interface between each of the steel sheets of the stack that are not the thinnest;
• utilizing the third process if the weld is not intended for a strategic area of a welded assembly;
• and
• utilizing a fourth process if the weld is intended for a strategic area of a welded assembly and a ratio of the corresponding thickness of any two adjacent steel sheets is not greater than 3.0 and a ratio of the corresponding thickness of a thickest and a thinnest of the steel sheets is greater than 1.85 but fusion is not necessary at an interface between each of the steel sheets of the stack that are not the thinnest, wherein:
• the first process comprises arranging the at least three steel sheets as the stack according to the corresponding thickness of each of the at least three steel sheets such that a thinnest of the at least three steel sheets is an outermost layer of the stack, placing a layer of adhesive/sealer material (ASM) between at least a thickest two steel sheets of the stack and resistance welding the stack according to a unified weld schedule (UWS) such that weld penetration extends into the thinnest of the at least three steel sheets;
• the second process comprises welding the stack according to the UWS;
• the third process comprises classifying the weld as a Single Fusion Zone (SFZ);
• and
• the fourth process comprises welding the stack according to a redesigned process or seeking approval to weld the stack according to the first process, the second process or the third process.