Deep penetration welding using lasers

Claim 1

The method of forming a continuous weld having a depth substantially greater than its width in a relatively thick workpiece material by means of direct energy transfer into the material to melt the material to the desired weld depth and without relying on heat conduction into the material from the surface thereof which comprises generating a continuous beam of coherent optical radiation in a fundamental mode by a continuous wave laser, amplifying said beam of radiation to a power of at least 3 kw in a medium containing CO2, focusing the beam of radiation at a point at or in the vicinity of the surface of the workpiece material to be welded so that the power density of the beam on the surface of the workpiece material is in the range between 106 and 108 watts/in.2, said power density being maintained at a value within said range sufficient to overcome losses caused by surface reflectivity of said workpiece material and to permit localized absorption of said beam by said workpiece material at the point of initial impingement, maintaining the beam at the point of initial impingement on the workpiece surface for a time, depending on the beam power density and the reflectivity of the workpiece material at the wavelength of said radiation beam, which is sufficient to initiate vaporization of the workpiece material at the point of beam impingement and to create a void in said material to the desired depth of penetration before sufficient energy has been conducted to the surrounding workpiece material to cause melting thereof, said beam penetrating into the void and melting the laterally adjacent material by direct energy transfer from the beam to the material over the entire depth of the penetrating beam, and moving the beam relative to the workpiece material so that the beam moves across the surface of the workpiece material a distance of at least ten times the cross-sectional width of the beam at its point of initial impingement on the workpiece prior to the time that a stable hole would be formed in said workpiece material at said point of initial impingement if movement did not occur, said movement causing the void to become dynamically stable and to translate through the workpiece material with a small area of molten material located adjacent the beam, fusion of said molten material occurring directly behind the beam to form a weld whose width is on the order of the beam diameter and whose depth is substantially greater than its width and proportional to the total power incident on said workpiece material as a function of the rate of relative movement.

Claim 2

The method of forming a continuous weld having a depth substantially greater than its width in a relatively thick workpiece material by means of direct energy transfer into the material to melt the material to the desired weld depth and without relying on heat conduction into the material from the surface thereof which comprises generating a continuous beam of coherent optical radiation in a fundamental mode by a continuous wave laser, amplifying said beam of radiation to a power of at least 3 kw in a medium containing CO2, focusing the beam of radiation at a point at or in the vicinity of the surface of the workpiece material to be welded so that the power density of the beam on the surface of the workpiece material is in the range between 106 and 108 watts/in.2, said power density being maintained at a value within said range sufficient to overcome losses caused by surface reflectivity of said workpiece material and to permit localized absorption of said beam by said workpiece material at the point of initial impingement, maintaining the beam at the point of initial impingement on the workpiece surface for a time, depending on the beam power density and the reflectivity of the workpiece material at the wavelength of said radiation beam, which is sufficient to initiate vaporization of the workpiece material at the point of beam impingement and to create a void in said material to the desired depth of penetration before sufficient energy has been conducted to the surrounding workpiece material to cause melting thereof, said beam penetrating into the void and melting the laterally adjacent material by direct energy transfer from the beam to the material over the entire depth of the penetrating beam, and moving the beam relative to the workpiece material so that the beam moves across the surface of the workpiece material a distance of at least ten times the cross-sectional width of the beam at its point of initial impingement on the workpiece prior to the time that a stable hole would be formed in said workpiece material at said point of initial impingement if movement did not occur, said movement causing the void to become dynamically stable and to translate through the workpiece material with a small area of molten material located adjacent the beam, fusion of said molten material occurring directly behind the beam to form a weld whose width is on the order of the beam diameter and whose depth is substantially greater than its width and proportional to the total power incident on said workpiece material as a function of the rate of relative movement.

Claim 5

The method of forming a continuous weld having a depth substantially greater than its width in a relatively thick workpiece material of at least 0.04 inch thickness by means of direct energy transfer into the material to melt the material to the desired weld depth and without relying on heat conduction into the material from the surface thereof which comprises generating a continuous beam of coherent optical radiation in the TEMoo mode by a continuous wave laser, amplifying said beam of radiation to a power of at least 3 kw in a CO2 amplifier, focusing the beam of radiation at a point at or in the vicinity of the surface of the workpiece material to be welded so that the power density of the beam on the surface of the workpiece material is between 106 and 108 watts/in.2, maintaining the beam at its point of initial impingement on the workpiece material fro a time, depending on the beam power density and the reflectivity of the workpiece material at the wavelength of said radiation beam, which is sufficient to initiate vaporization of the workpiece material at the point of beam impingement and to create a void in said material to the desired depth of penetration before sufficient energy has been conducted to the surrounding workpiece material to cause melting thereof, said beam penetrating into the void and melting the laterally adjacent material by direct energy transfer from the beam to the material over the entire depth of the penetrating beam, and moving the beam relative to the workpiece material so that the beam moves across the surface of the workpiece material a distance of at least ten times the cross-sectional width of the beam at its point of initial impingement on the workpiece material prior to the time that a stable hole would be formed in said workpiece material at said point of initial impingement if movement did not occur, said movement causing the void to become dynamically stable and to translate through the workpiece material with a small area of molten material located adjacent the beam, fusion of said molten material occurring directly behind the beam to form a weld whose width is on the order of the beam diameter and whose depth is substantially greater than its width and proportional to the total power incident on said workpiece material as a function of the rate of relative movement.

Claim 6

The method of forming a continuous weld having a depth substantially greater than its width in a relatively thick workpiece material of at least 0.04 inch thickness by means of direct energy transfer into the material to melt the material to the desired weld depth and without relying on heat conduction into the material from the surface thereof which comprises generating a continuous beam of coherent optical radiation in the TEMoo mode by a continuous wave laser, amplifying said beam of radiation to a power of at least 3 kw in a CO2 amplifier, focusing the beam of radiation at a point at or in the vicinity of the surface of the workpiece material to be welded so that the power density of the beam on the surface of the workpiece material is between 106 and 108 watts/in.2, maintaining the beam at its point of initial impingement on the workpiece material fro a time, depending on the beam power density and the reflectivity of the workpiece material at the wavelength of said radiation beam, which is sufficient to initiate vaporization of the workpiece material at the point of beam impingement and to create a void in said material to the desired depth of penetration before sufficient energy has been conducted to the surrounding workpiece material to cause melting thereof, said beam penetrating into the void and melting the laterally adjacent material by direct energy transfer from the beam to the material over the entire depth of the penetrating beam, and moving the beam relative to the workpiece material so that the beam moves across the surface of the workpiece material a distance of at least ten times the cross-sectional width of the beam at its point of initial impingement on the workpiece material prior to the time that a stable hole would be formed in said workpiece material at said point of initial impingement if movement did not occur, said movement causing the void to become dynamically stable and to translate through the workpiece material with a small area of molten material located adjacent the beam, fusion of said molten material occurring directly behind the beam to form a weld whose width is on the order of the beam diameter and whose depth is substantially greater than its width and proportional to the total power incident on said workpiece material as a function of the rate of relative movement.