Laser Process Cuts Thick Steel

Brent D. Johnson

As a building material, steel is unmatched for its combination of tensile strength and flexibility and for its low cost and weight. But working the material into tools and forms that can be used on an industrial scale can be difficult. A laser-assisted cutting process under development promises to ease the fabrication of steel parts for industrial applications.

In the Lasox process, a CO₂ laser preheats the steel plate, easing high-pressure oxygen cutting. The technique promises deeper cuts and faster process rates. Courtesy of Joe Sonnberger, Alabama Laser.

A year ago, cutting 50-mm-thick steel using a 2-kW laser was unheard of; 1 inch was the maximum cutting depth. In a trial on Nov. 12, however, researchers from Bender Shipbuilding & Repair Co. Inc., Alabama Laser, BOC Gases of Guild, UK, and Caterpillar Inc. of Mossville, Ill., made a series of cuts through 2 inches of steel using less than 2 kW of power from a Tanaka 6-kW CO₂ laser and a Lasox cutting head from Alabama Laser.

In the Lasox process, the laser preheats the steel plate, and high-pressure O₂ does the cutting. Jack Gabzdyl of BOC, a co-developer of the technique, described it as a complementary process that extends the functionality of the laser for cutting fine features in thick steel. It is suitable for use with materials thicker than an inch, saves an average of 40 minutes of processing time per plate and can produce a kerf of a couple of millimeters.

The splat pierce, or initial penetration of the steel, is also more rapid, and there is a greater standoff distance between the laser head and the steel. The typical standoff distance for laser cutting is 1 mm, but the researchers have been working at up to 7 mm. This reduces heat reflection onto the nozzle and thus the problem of splatter hitting the laser head. Moreover, the technique flame-washes the metal and performs fluting automatically, offering sharp edges without preheating.

Patrick Cahill, a member of the team from Bender Shipbuilding, said that the process has the potential to cut steel plates as thick as 4 inches. By comparison, high-power plasma cutting is limited to 3 inches. Cahill believes that the cutting head will enable a new generation of steel ships that are stronger yet cheaper to build than current ones.

Once they get the bugs out, the researchers will send the cutting systems to General Dynamics Electric Boat in Quonset Point, R.I., for the construction of submarines, and to Caterpillar for the production of heavy-duty mining equipment. They expect that it will take six months to go from the first stage to the second in the beta testing.