Page 31 - MetalForming February 2020

Fabrication: Welding Well
ing with stainless steel (see below). Should a grinding wheel be chosen, care must be taken in adopting the correct grinding angle to avoid gouging and undercutting.
Grinding wheels should be the choice for carbon steel, as they will remove the weld seam quickly and any scratches should not be much of an issue. As for the grinding angle, aim for the range of 5 to 35 deg. to hori- zontal, depending on the grinding wheel used. Apply consistent pressure in both forward and backward motion to achieve an even finish.
If employing a grinding wheel on stainless steel, use a stainless-suitable product identified on the disc blotter as nonferrous and appropriate for inox. Choose a medium grit over a coarse option for stainless steel, as any scratches imparted are difficult to blend at a later stage, especially when looking to create a refined finish. Another reason to choose medium grit: Working with thin-gauge stainless steel risks creation of noticeable flat spots; particularly on tubular pieces.
Grinding-wheel selection involves a multitude of potential options. As always, the grain size, type of grain and the bonding agent will define how the product performs and feels. Determine appropriate needs before proceeding.
Using Flap Discs
Flap discs represent a popular choice when weld finishing both stain- less steel and carbon steel as they hold key advantages over the standard grinding wheel. Flap discs provide long life, superior operator comfort and control (the user typically gains more room for error), lower noise generation, and high surface-finish quality.
Opting for a coarse 40 grit in a flap disc will remove a carbon steel weld seam quickly, readying the workpiece for any additional conditioning prior to painting. Flap discs typically get the nod for stainless steel where a high- quality, more refined surface finish is required. An 80-grit flap disc, the Nor- ton Blaze R980P model for instance, is an ideal choice, but less-experienced
Flap discs typically get the nod for stain- less steel finishing.
operators should opt for 120 grit.
Conditioning and Blending
Should a carbon steel workpiece be destined for powder coating, only one more blending stage is required to com- plete the grinding process, using a coarse prep disc, such as the coarse-grade Nor- ton Vortex Rapid Prep. A powder coat, thick enough to mask the appearance of any remaining scratches created by a coarse-gritted abrasive, readily adheres to the surface of scratched carbon steel.
A paint layer thinner than a powder coat may require further refinement of scratches to avoid showing through the final layer. Here, a medium-grit condi- tioning pad is recommended. At this point, the carbon steel workpiece should be ready for painting.
On the other hand, whether requir- ing a highly refined finish or a No. 4 finish, stainless steel certainly needs further conditioning and blending, as the initial scratch would look unsightly on a stainless steel surface. To blend this out, use a medium-grit disc. For further refinement, follow up with a softer blending disc.
The decision over which finish to choose for a stainless steel workpiece depends entirely on the final product’s end use. An abrasive supplier can pro- vide details and options for achieving needed final finish. MF
Information for this article supplied by Norton | St. Gobain Abrasives, Worces- ter, MA; www.nortonabrasives.com, 800/551-4413.
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