Resistance welding fastener, apparatus and methods

Patent metadata

Field	Value
Publication number	US-12042876-B2
Application number	US-201916369117-A
Country	US
Kind code	B2
Filing date	Mar 29, 2019
Priority date	Jun 26, 2013
Publication date	Jul 23, 2024
Grant date	Jul 23, 2024

Abstract

An apparatus and method for fastening dissimilar metals like steel and aluminum utilizes a steel rivet and a spot welding machine. The rivet and metals are stacked and the heat from the welder's electric current softens the lower melting point aluminum allowing the rivet to penetrate the aluminum and weld to the steel layer. The fastener may be used to join stacks with several layers of different materials and may be used to apply a threaded socket or stud made from steel or titanium to an aluminum or magnesium alloy structure. Layers of non-conductive materials like plastic and ceramics may also be affixed to a conductive layer using the fastener made from a compatible material that extends through a pilot hole.

First claim

We claim:

1. A method for fastening a first electrically conductive material to a second electrically conductive material using electrical resistance welding, comprising:
placing the first and second materials together in physical and electrical contact, the first material having a lower melting point than the second material;
placing an electrically conductive fastener with a cap having a downwardly extending peripheral lip and a shaft that is weldable to the second material in physical and electrical contact with the first material to form an electrically conductive stack inclusive of the fastener, the first material and the second material;
wherein the shaft has a higher melting point than the first material;

applying an electrical potential across the stack, inducing a current to flow through the stack and causing resistive heating, the resistive heating causing a softening of the first material to form a softened first material;
while applying the electrical potential across the stack, piercing the softened first material with the fastener shaft by urging the fastener shaft through the softened first material toward the second material;
after the fastener shaft contacts the second material, continuing to urge the fastener and apply electrical potential across the stack, compressing the shaft, welding the fastener to the second material and softening and collapsing the shaft until the peripheral lip contacts the first material,
wherein the fastener cap is deformed from an initial configuration to a final configuration in which the peripheral lip captures and seals the material extruded therein from the first material during the steps of applying, urging, compressing, softening, collapsing and welding,
wherein, in the final configuration, the fastener cap is deformed to conform to a shape of the material extruded therein,
wherein, in the final configuration, the cap does not extend below an upper surface of the first material.

2. The method of claim 1 , wherein the first material includes at least one of aluminum, copper, magnesium and alloys thereof, the second material includes at least one of steel, titanium, alloys thereof and Inconel and the fastener is made from at least one of steel, titanium, alloys thereof and Inconel.

3. The method of claim 1 , wherein the second material is a second fastener and wherein the fastener and second fastener clamp the first material there between.

4. The method of claim 1 , further comprising the step of applying a corrosion barrier between at least one of the fastener, the first material and the second material prior to the step of applying.

5. The method of claim 1 , wherein the fastener has a capability to fasten a range of thicknesses of the first material to the second material by deforming to a selected degree during the step of welding.

6. The method of claim 1 , further comprising stamping the fastener from a sheet prior to the step of placing the fastener.

7. The method of claim 1 , wherein the stack includes a plurality of layers of material having a melting point less than a melting point of the second material and less than a melting point of the fastener.

8. The method of claim 1 , wherein the cap has a radiused surface and wherein the electric potential is applied by electrodes, at least one of which has a tip with a shape that is complementary to the radiused surface.

9. The method of claim 1 , further comprising a step of tempering the weld after the step of forming the weld.

10. The method of claim 9 , wherein a compressive force applied during the step of tempering is of a magnitude between 400 to 1000 pounds and the current is in a range of 3,000 to 12,000 Amperes.

11. A fastener for fastening a first electrically conductive material to a second electrically conductive material using electrical resistance welding, comprising:
a cap with a curved peripheral lip, and
a shaft extending from the cap and having an end distal to the cap,
wherein the fastener, when placed in a stack including the first and second electrically conductive materials and subjected to an electrical potential applied across the stack, is configured to conduct an electrical current that passes through the stack to cause resistive heating and soften the first material,
wherein the first material has a lower melting point than the second material,
wherein the shaft is capable of piercing the first material and welding to the second material at the end, and
wherein the cap is configured to be deformed from an initial configuration to a final configuration in which the peripheral lip captures and seals material extruded therein from the first material,
wherein, in the final configuration, the cap is conformed to a shape of the material extruded therein.

12. The fastener of claim 11 , wherein the shaft is hollow, and wherein the shaft has a cross sectional shape that diverges from a tip at the end to cap.

13. The fastener of claim 11 , wherein the fastener has a varying wall thickness.

14. The fastener of claim 11 , wherein the cap has a radiused surface.

15. The fastener of claim 11 , wherein the fastener has at least one spline extending from an exterior surface thereof.

16. The fastener of claim 11 , wherein the fastener is asymmetric about a rotational axis.

17. The fastener of claim 11 , wherein the fastener has two diverging cross section portions conjoined at a central downwardly directed cusp, the end being ring shaped.

18. The fastener of claim 11 , wherein the fastener has two diverging cross section portions conjoined at a central threaded fastener portion.

19. A fastener for fastening a first electrically conductive material to a second electrically conductive material using electrical resistance welding, comprising:
a cap having a downwardly extending peripheral lip, and
a shaft extending from the cap and having an end distal to the cap, the shaft having a hollow portion that diverges in a direction from the end to the cap,
wherein the fastener, when placed in a stack including the first and second electrically conductive materials and subjected to an electrical potential applied across the stack, is configured to conduct an electrical current that passes through the stack to cause resistive heating and soften the first material,
wherein the first material has a lower melting point than the second material,
wherein the shaft is capable of piercing the first material and welding to the second material at the end, and
wherein the cap is configured to be deformed from an initial configuration to a final configuration in which the peripheral lip captures and seals material extruded therein from the first material,
wherein, in the final configuration, the cap is conformed to a shape of the material extruded therein.

Assignees

• Arconic Inc
• Howmet Aerospace Inc

Inventors

• Spinella Donald J
• Bergstrom Daniel

Classifications

• B21D39/028

  Reinforcing the connection otherwise than by deforming, e.g. welding · CPC title

• F16B37/061

  by means of welding · CPC title

• F16B5/08

  by means of welds or the like (welding B23K) · CPC title

• F16B5/04

  by means of riveting (rivets F16B19/04) · CPC title

• B23K35/0255

  for use in welding (B23K35/0205 takes precedence) · CPC title