Bimetallic Stainless Screw

Abstract

A screw includes a shank having a tip, a rear end which is disposed opposite the tip, and a longitudinal axis which extends through the tip and through the rear end. The shank consists of a first steel material. A screw thread helix is disposed on the shank and protrudes from the shank. The screw thread helix consists of a second steel material that is different from the first steel material. Both the first steel material and the second steel material are stainless steels.

Claims

1.-5. (canceled)

6. A screw, comprising: a shank having a tip, a rear end which is disposed opposite the tip, and a longitudinal axis which extends through the tip and through the rear end, wherein the shank consists of a first steel material; and a screw thread helix which is disposed on the shank and which protrudes from the shank, wherein the screw thread helix consists of a second steel material that is different from the first steel material; wherein both the first steel material and the second steel material are stainless steels.

7. The screw according to claim 6, wherein the second steel material has a Vickers hardness between 550 HV10 and 800 HV10.

8. The screw according to claim 6, wherein the screw thread helix spans at least 40% of a length of the shank.

9. The screw according to claim 6, wherein the first steel material has a Vickers hardness below 440 HV10.

10. The screw according to claim 6, wherein the screw is a concrete tapping screw.

11. The screw according to claim 6, wherein a ratio of an outer thread diameter of the screw thread helix to a pitch of the screw thread helix is between 1 and 2 at least in regions of the screw thread helix.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a side view of a screw.

[0031] FIG. 2 is a sectional view, according to A-A in FIG. 1, of the screw of FIG. 1.

[0032] FIG. 3 is an isometric view of the screw of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

[0033] The figures show an embodiment of a screw. The screw comprises a shank 10 having a tip 11 at its front end, and, at its opposite other end, a rear end 18. The tip 11 is that end of the shank 10 which is intended to be inserted first into a borehole. The longitudinal axis 99 of the shank 10 extends through the tip 11 and through the rear end 18.

[0034] The screw further comprises a drive 19 for transmitting torque to the shank 10 for rotating the shank 10 around the longitudinal axis 99 of the shank 10 for installing the screw. In the present embodiment, the drive 19 is a hex drive head connected to the rear end 18. However, this is an example only, and any type of drive could be used, such as a slotted drive, a cruciform drive, a lobular drive, an internal polygon drive, an external polygon drive or a special drive.

[0035] The screw furthermore comprises a screw thread helix 20, which is connected to the shank 10 so as to wind around the shank 10. The screw thread helix 20 and the shank 10, respectively, are materially distinct elements. Whereas both the screw thread helix 20 and the shank 10 consist of stainless steel, the steel grade used for these respective elements is different.

[0036] In the present embodiment, the screw thread helix 20 spans, longitudinally (i.e., in the direction parallel to the longitudinal axis 99), approximately 80% of the length l.sub.s of the shank 10. The screw thread helix 20 thus forms a main thread of the screw. In the present embodiment, no additional helical elements are provided on the screw.

[0037] The screw thread helix 20 has an outer thread diameter d.sub.tr. At least near the tip 11 of the non-installed screw, a ratio of the outer thread diameter d.sub.tr of the screw thread helix 20 to the pitch p.sub.tr of the screw thread helix 20 is between 1 and 2, in particular between 1.2 and 1.6.

[0038] The first steel material, i.e., the material of the shank 10, has a Vickers hardness below 440 HV10, whereas the second steel material, i.e., the material of the screw thread helix 20, has a Vickers hardness between 550 HV10 and 800 HV10, preferably between 650 HV10 and 750 HV10, in particular both according to ISO 6507.

[0039] The first steel material can for example be an austenitic (e.g., 1.4404, 1.4301, 1.4529, or similar), a duplex (e.g., 1.4062, 1.4162, 1.4362, 1.4410, 1.4509, or similar), a ferritic (e.g., 1.4105, 1.4113, 1.4521, or similar) or a PH stainless steel (e.g., 15-5 PH or similar).

[0040] The second steel material can for example be an austenitic (e.g., 1.4565/1.4566, 1.3808, or similar), a martensitic (e.g., 1.4108, 1.4109, 1.4116, 1.4122, the steel grade described in WO 2012/084385 A1) or a PH stainless steel (e.g., 17-7 PH).