Strand, cable bolt and its installation
View Patent ↗A strand ( 20 ) for a cable bolt ( 14 ) comprises a plurality of metallic elongated members ( 22, 24 ) twisted together. At least one of the elongated members has a corrosion resistant coating ( 54 ) and surface deformation, so as to improve the bodig efficiency and the anchorage of the strand.
1. A method of fabricating a strand with improved corrosion resistance and a reliable anchorage, comprising the steps of:
(a) preparing a plurality of outer metallic elongated members;
(b) coating a surface of the outer metallic elongated members with a corrosion resistant layer having a thickness in a range of 10 g/m 2 to 200 g/m 2 ;
(c) cold working the coated outer metallic elongated members to their final dimensions;
(d) deforming the surface of the coated outer metallic elongated members to form indentations having a depth in a range of 80 μm to 130 μm; and
(e) arranging the coated outer metallic elongated members and twisting them together with a central metallic elongated member,
wherein step (b) and step (c) are performed prior to step (d) such that a profile of the corrosion resistant layer is conformal to a profile of the indentations, and the central metallic elongated member is a smooth round wire, and
wherein the strand forms a cable bolt configured to be inserted in a borehole of a mine roof.
2. The method of fabricating a strand according to claim 1 , wherein in step (d) the surface of the coated outer metallic elongated members are deformed by rolling indentation.
3. The method of fabricating a strand according to claim 1 , wherein in step (b) the thickness of the corrosion resistant layer is in a range of 30 g/m 2 to 150 g/m 2 .
4. The method of fabricating a strand according to claim 1 , wherein in step (b) the thickness of the corrosion resistant layer is in a range of 50 g/m 2 to 80 g/m 2 .
5. The method of fabricating a strand according to claim 1 , wherein the cable bolt is formed by fixing a bolt head at a proximal end of the strand.
6. The method of fabricating a strand according to claim 1 , wherein the strand comprises six coated outer metallic elongated members and one central metallic elongated member.
7. The method of fabricating a strand according to claim 1 , wherein the strand comprises five coated outer metallic elongated members and one central metallic elongated member.
8. The method of fabricating a strand according to claim 1 , wherein at least one outer metallic elongated member is made of steel comprising carbon, manganese, silicon, sulphur, phosphorous and iron.
9. The method of fabricating a strand according to claim 1 , wherein at least one outer metallic elongated member is made of steel comprising a carbon content in a range of 0.2 wt % to 0.8 wt %, a manganese content in a range of 0.3 wt % to 0.8 wt %, a silicon content in a range of 0.1 wt % to 0.5 wt %, a maximum sulphur content of 0.05 wt %, a maximum phosphorous content of 0.05 wt %, and iron.
10. The method of fabricating a strand according to claim 8 , wherein the steel comprising the at least one outer metallic elongated member further comprises traces of copper, chromium, nickel, vanadium, molybdenum or boron.
11. The method of fabricating a strand according to claim 1 , wherein at least one outer metallic elongated member is made of steel comprising carbon, manganese, silicon, chromium, vanadium and iron.
12. The method of fabricating a strand according to claim 1 , wherein at least one outer metallic elongated member is made of steel comprising a carbon content in a range of 0.8 wt % to 1.0 wt %, a manganese content in a range of 0.5 wt % to 0.8 wt %, a silicon content in a range of 0.1 wt % to 5.0 wt %, a chromium content in a range of 0.1 wt % to 0.5 wt %, a vanadium content in a range of 0.02 wt % to 0.2 wt %, and iron.
13. The method of fabricating a strand according to claim 1 , wherein at least one outer metallic elongated member is made of steel comprising 0.84 wt % carbon, 0.67 wt % manganese, 0.23 wt % silicon, 0.24 wt % chromium, 0.075 wt % vanadium, and iron.
14. The method of fabricating a strand according to claim 1 , wherein the corrosion resistant layer comprises zinc or a zinc alloy.
15. The method of fabricating a strand according to claim 1 , wherein the corrosion resistant layer comprises a zinc aluminum coating.
16. The method of fabricating a strand according to claim 15 , wherein an aluminum content of the zinc aluminum coating is in a range of 2 wt % to 12 wt %.
17. The method of fabricating a strand according to claim 1 , wherein the corrosion resistant layer comprises aluminum, magnesium and zinc.
18. The method of fabricating a strand according to claim 17 , wherein the corrosion resistant layer comprises 2% to 10% aluminum, 0.2% to 3% magnesium and a remainder of zinc.