THREAD-FORMING SCREW AND PRODUCTION THEREOF

Abstract

The invention relates to a thread-forming screw (10) comprising a base body (12, 20) which comprises a drive and a screw shank, the screw shank carrying a thread (13) having a channeling region (14) and a carrying region, the base body (12, 20) consisting of a base material. The invention is characterized in that the thread (13) is formed from a coating material (18) different from the base material, at least in the channeling region (14), which is applied to the base material by deposition welding.

Claims

1. A thread-forming screw comprising a base body which comprises a drive and a screw shaft, the screw shaft carrying a thread having a thread-forming region and a load-bearing region, wherein the base body is formed from a base material, and at least in the thread-forming region, the thread is formed from a coating material different from the base material that is applied to the base material by deposition welding.

2. A thread-forming screw according to claim 1, wherein the thread in the thread-forming region is harder than the base material.

3. A thread-forming screw according to claim 2, wherein the base material is a rustproof and acid-resistant steel.

4. A thread-forming screw according to claim 3, wherein the rustproof and acid-resistant steel is an austenitic stainless steel.

5. A thread-forming screw according to claim 1, wherein the base material is an aluminum alloy and the coating material is a different metal alloy or an alloy mixture.

6. A thread-forming screw according to claim 1, wherein the coating material is a hardenable steel.

7. A thread-forming screw according to claim 1, wherein the coating material has a layer thickness of at least 5% of the shaft diameter of the screw shaft.

8. A thread-forming screw according to claim 1, wherein the thread in the load-bearing region is forming by rolling, and in the thread-forming region it is exclusively constituted by the coating material that has been applied by deposition welding and not been treated mechanically.

9. A thread-forming screw according to claim 1, wherein the thread in the thread-forming region is formed from a first coating material and in the load-bearing region the thread consists of a second coating material that is different from the first coating material.

10. A thread-forming screw according to claim 9, wherein the first coating material has a higher hard substance content than the second coating material.

11. A thread-forming screw according to claim 1, wherein the thread has an obtuse flank angle or is rounded.

12. A thread-forming screw according to claim 1, characterized in that the screw is a concrete screw.

13. A method for producing a thread-forming screw comprising a base body which comprises a drive and a screw shaft, the screw shaft carrying a thread having a thread-forming region and a load-bearing region, wherein the base body is formed from a base material, and at least in the thread-forming region, the thread is formed from a coating material different from the base material that is applied to the base material by deposition welding, characterized in that a base material of the screw shaft is at least partially coated with a coating material by deposition welding, and the coating material is used to form the thread in the thread-forming region.

14. A method according to claim 13, wherein the thread is produced by applying the coating material in helical form on the shaft in such a way that the thread is obtained immediately after the coating material has been applied.

15. A method according to claim 13, wherein at least part of the thread in the load-bearing region is formed by rolling, and subsequently the thread is completed up to the screw tip, comprising the thread-forming region, by deposition welding.

16. A method according to claim 13, wherein the thread in the thread-forming region is formed by deposition welding using a first coating material, and the thread in the load-bearing region is at least partially formed by deposition welding of a second coating material that is different from the first coating material.

17. A method according to claim 13, wherein the deposition welding is performed by means of laser cladding, laser powder build-up welding, arc welding or plasma-transferred arc welding.

18. A method according to claim 13, characterized in that the thread is produced by rolling a thread onto the screw shaft after the coating material has been deposited on the screw shaft.

19. A method according to claim 18, wherein the weld beads extend parallel to the screw axis or in windings around the screw shaft.

Description

[0049] Additional advantages, features and possible applications of the present invention may be gathered from the description that follows in which reference is made to the embodiments illustrated in the drawings.

[0050] In the drawings,

[0051] FIG. 1a is a lateral view of a screw blank;

[0052] FIG. 1b is a sectional view of a screw blank having coating material in its thread-forming region;

[0053] FIG. 1c is a sectional view of a thread-forming screw according to the invention;

[0054] FIG. 2a is a partial lateral view of a screw blank coated according to the invention;

[0055] FIG. 2b is a cross-sectional view of a screw blank coated according to the invention;

[0056] FIG. 3a is a partial sectional view of a screw blank according to the invention; and

[0057] FIG. 3b is a cross-sectional view of a coated screw blank as seen in FIG. 3a;

[0058] FIG. 4 is a schematic sectional view of a screw according to the invention;

[0059] FIG. 5 is a schematic sectional view of a screw according to the invention

[0060] FIG. 6 is a schematic sectional view of a screw according to the invention.

[0061] The view of FIG. 1a is a base body 12 press-molded from the base material stainless steel and having a drive 15, which base body 12 has a smaller diameter in its thread-forming region 14 than in its uncoated region 16. A material harder than the base material or a material that can be hardened by a final heat treatment is deposition-welded as a coating material 18 onto the thread-forming region 14 to be coated, as seen in FIG. 1b. According to the invention, this is carried out by deposition welding. The base body 12 coated in this way is subsequently rolled to give it its self-tapping thread 13. The thread-forming screw 10 having a hardened thread-forming region is illustrated in the view of FIG. 1c.

[0062] FIG. 2a is a partial lateral view of another embodiment exhibiting a coating variant in which weld beads 26 of coating material have been welded onto a base body 20 as seen in FIG. 1a and having a smaller diameter in its thread-forming region 16, which weld beads extend parallel to the screw axis.

[0063] FIG. 2b is a cross-sectional view of the thread-forming region of the base body 20.

[0064] FIG. 3a is a sectional lateral view of a further embodiment having a base body 20. The base body 20 has axial grooves 24 in its thread-forming region 22. The coating material 26 is welded into the grooves.

[0065] FIG. 3b is a sectional view of a base body 20 as seen in FIG. 3a and coated with a coating material 26.

[0066] FIG. 4 is a view of a thread-forming screw 30 according to the invention, in which a helical thread bead 34 has been welded onto a screw shaft 32 made of a rustproof and acid-resistant steel. The screw 30 is designed as a concrete screw.

[0067] FIG. 5 is a schematic sectional view of a screw 50 according to the invention having a thread bead 34. As seen here, the thread in the thread-forming region 36 is constituted by a deposition-welded thread bead of a coating material, and at least part of the load-bearing region is constituted by a rolled thread 38.

[0068] FIG. 6 is a schematic sectional view of another embodiment of a screw 60 according to the invention. In this case, the thread bead 34 is formed from a first coating material in the thread-forming region 36, and in the load-bearing region it is at least partially formed from a second coating material 40 that is different from the first coating material. For this reason, the thread-forming region of the thread has a greater hardness than its load-bearing region.