Cutting of cementitious materials
A method and apparatus for cutting thick sections of cement-based materials, the method comprising mutually traversing a surface to be cut with a laser beam at a power density sufficient to produce a depth of molten material having a maximum depth of 10 mm at each traverse; allowing the molten material to solidify; breaking the solidified material into particles; and removing the particles by suction means.
1 - 28 . (canceled)
29 . A method for cutting thick sections of cement-based materials, the method comprising:
mutually traversing a surface to be cut with a laser beam at a power density sufficient to produce a depth of molten material having a maximum depth of 10 mm at each traverse;
allowing said molten material to solidify; breaking said solidified material into particles; and
removing said particles by suction means.
30 . A method according to claim 29 wherein a plurality-of traverses are made along substantially the same cutting path.
31 . A method according to either claim 29 wherein the laser beam is unfocused.
32 . A method according to claim 29 wherein the laser beam is a parallel beam.
33 . A method according to claim 29 wherein the laser beam has a rectangular cross section.
34 . A method according to claim 29 wherein the material is removed directly after solidification after each pass.
35 . A method according to claim 29 wherein the solidified material is broken up by a hollow crushing tube which also serves as a material extractor conduit.
36 . A method according to claim 29 wherein the depth of the molten material at each pass lies in the range from 0.5 to 5 mm.
37 . A method according to claim 29 wherein the pressure required for crushing the solidified material is less than 100 MPa.
38 . A method according to claim 29 wherein the laser power density lies in the range 300 W·cm −2 to 3000 W·cm −2 .
39 . A method according to claim 29 wherein the beam traverse speed lies between 3 cm·min −1 and 30 cm·min −1 .
40 . A method according to claim 29 wherein an oxygen jet is applied directly at the beam spot when reinforcing steel bars are being cut.
41 . A method according to claim 29 wherein the surface temperature of the material being treated lies in the range 700° C. to 2400° C.
42 . A method according to claim 29 wherein the vapor-to-melt ratio lies in the range between 0.05 and 3.
43 . A method according to claim 29 wherein the material removal rate lies in the region of 150 cm −3 ·kWh −1 for a diode laser and 100 cm −3 ·kWh −1 for a CO 2 laser.
44 . A method according to claim 29 wherein the laser is selected from the group consisting of a COIL, Nd:YAG, CO 2 and diode laser.
45 . A method according to claim 29 wherein the laser beam is delivered by a fiber optic cable.
46 . A method according to claim 29 wherein the laser beam is delivered by a mobile beam delivery system comprising a system of reflecting mirrors.
47 . An apparatus for cutting thick sections of cement-based materials in which material is made molten and allowed to solidify, the apparatus comprising
a means for mutually traversing a surface to be cut with an unfocused laser beam at a power density sufficient to produce a depth of molten material having a maximum depth of 10 mm at each traverse;
a means for breaking the solidified material into particles; and
a suction means for removing the particles.
48 . An apparatus according to claim 47 wherein the means for breaking re-solidified material comprises a percussive member for crushing the material.
49 . An apparatus according to claim 48 wherein the percussive member is hollow and crushed material is removed through the member by suction means.
50 . An apparatus according to claim 47 wherein the laser beam is substantially parallel.
51 . An apparatus according to claim 47 wherein the laser beam has a circular or rectangular cross section.