Element, friction element welding method, and method for producing friction element welded joint
An element, a friction element welding method, and a method for producing a friction element welded joint. The element is for performing friction element welding on a sheet stack of two or more stacked metal sheets by pressing the element into the sheet stack while the element is rotated. The element includes a circular columnar mandrel that is to enter the sheet stack, a circular collar disposed at an upper end portion of the mandrel, a first conical body extending from a lower end surface of the mandrel, and a second conical body disposed on the lower side of the first conical body. The vertical angle β of the second conical body and the vertical angle α of the first conical body satisfy the relation β<α.
1 . An element for performing friction element welding on a sheet stack of two or more stacked metal sheets by pressing the element into the sheet stack while the element is rotated, the element comprising:
a circular columnar mandrel configured to enter the sheet stack;
a circular disk-shaped collar disposed at an upper end portion of the mandrel, a diameter of the collar being larger than a diameter of the mandrel;
a first conical body extending from a lower end surface of the mandrel; and
a second conical body disposed in contact with a lower side of the first conical body, a bottom surface of the second conical body being smaller in diameter than a bottom surface of the first conical body,
wherein an outer circumferential portion of the collar has a downward inclined or curved shape,
a center axis of the first conical body coincides with a center axis of the mandrel,
a center axis of the second conical body coincides with the center axis of the mandrel,
the bottom surface of the second conical body has an apex that terminates with a pointed tip,
a vertical angle β(°) of the second conical body and a vertical angle α(°) of the first conical body satisfy the following relation:
β<α,
the vertical angle α(°) of the first conical body satisfies 140≤α<180, and
the vertical angle β(°) of the second conical body satisfies 90≤β<140.
2 . The element according to claim 1 , wherein a distance L (mm) from a lowermost end of the outer circumferential portion of the collar to the apex of the second conical body in a direction parallel to the center axis of the mandrel satisfies the following relation:
( T TOTAL −T BOTTOM )+0.02 mm≤ L ≤( T TOTAL −T BOTTOM )+4 mm
where T TOTAL (mm) is a total thickness of the sheet stack, and T BOTTOM (mm) is a thickness of a lower sheet in the sheet stack.
3 . The element according to claim 2 , wherein a lower sheet in the sheet stack is a steel sheet, and
an upper sheet in the sheet stack is a light metal sheet.
4 . The element according to claim 1 , wherein a lower sheet in the sheet stack and an upper sheet in the sheet stack are both steel sheets.
5 . The element according to claim 1 , wherein an outer surface of the first conical body and an outer surface of the second conical body each include a coating film formed of a wear resistant material.
6 . A friction element welding method comprising joining a sheet stack of two or more stacked metal sheets by pressing the element according to claim 1 into the sheet stack while the element is rotated.
7 . A method for producing a friction element welded joint, the method comprising joining a sheet stack of two or more stacked metal sheets by pressing the element according to claim 1 into the sheet stack while the element is rotated.
8 . The element according to claim 2 , wherein an outer surface of the first conical body and an outer surface of the second conical body each include a coating film formed of a wear resistant material.
9 . A friction element welding method comprising joining a sheet stack of two or more stacked metal sheets by pressing the element according to claim 3 into the sheet stack while the element is rotated.
10 . A method for producing a friction element welded joint, the method comprising joining a sheet stack of two or more stacked metal sheets by pressing the element according to claim 3 into the sheet stack while the element is rotated.
11 . The element according to claim 1 , wherein the second conical body is a lowermost part of the element.