Flat Bar or Gauered Flat Bar from Plate

It is possible to find some on-the-shelf structural shapes in 304 and 316 stainless. Flat bar sizes are generally available and extruded shapes of the most common sizes of angles, tees and I-Beams can be found. In the world of specialty alloys, however, the demand for such products is so small that structural shapes are rarely produced for standard inventory.

Limited quantities of flat or square bar are produced in several alloys where they are in demand for aerospace applications or where cutting from plate is prohibited. This includes titanium alloys and PH 15-5.

However, for most other stainless and nickel alloy grades, flat bar is produced only when there is a significant quantity to justify a mill production run.  This usually means a minimum of 2500# per size.  Fortunately, most flat bar needs can be accommodated by cutting flat bar from plate.  Metallurgically speaking, this poses no problem because stainless and nickel alloy plate properties are nearly isotopic.  Transverse mechanical properties can be slightly below those in the longitudinal direction, but the minimum tensile properties established for each plate material are tested in the transverse direction anyway.

The primary difference between true flat bar and flat bar cut from plate is dimensional tolerance.  In true flat bar, tolerances for width and thickness are restrictive and more or less mirror those established for round bar.  In cutting bar from plate, the width tolerance will be more generous and in line with the cutting method.  Typically the permitted range of variation on width is 1/8”.  The thickness of the flat bar cut from plate will be same as that of the plate.  Plate thickness tolerances are skewed to the heavy side.  The minimum under tolerance for plate thickness is 0.010”, while the over tolerance is either unrestricted or is at least 0.090” and increases with thickness.

Finally, edge and corner conditions will likely be different.  For true bar, the surface finish on all four sides will be more or less the same.  Corners will be full and nearly sharp with only a slight break.  They will be nearly free of twist and camber.  On flat bar cut from plate, the surface finish on the sides that were cut will differ from the top and bottom, which are the original plate surfaces.  If the bars are merely stripped from plate, they may show some twist or camber.  This can vary greatly with the cutting method.

At Rolled Alloys, most of our flat bar products are subjected to straightening and edge conditioning by passing them through a piece of equipment called a Gauer.  The name is derived from the New Jersey based company, Gauer Metal Products, where the equipment was invented.  Gauering flat bar straightens, de-twists and conditions the corners to remove the shear burr and generate uniform corners.  Flat bat cut from plate to ASTM A276 and A479 is permitted via ASTM A484.