Weld slag is a hard, brittle material that forms as the welding torch consumes the flux, and it forms naturally during any flux-based welding. Virtually no welding project can be accomplished without some degree of weld slag being left behind. While it is chemically harmless, weld slag can still pose problems in a number of ways.
For one thing, it roughens the surface of the welding project, making it potentially abrasive to the skin. For another thing, weld slag reduces the metal's ability to bond with surface coatings such as paint. Weld slag will also weaken any secondary welds made in the area. For these reasons, welders must be proactive about removing slag once welding is complete and the base metal has cooled.
One of the most common methods of weld slag removal involves the use of a rotating power tool known as a wire brush wheel. The stiff metal wires on the circular head of a wire brush wheel knock off weld slag without damaging or abrading the base metal. Of course, for effective results, you must select the most appropriate type of wire brush wheel.
This article will improve your knowledge of weld cleaning by discussing two key criteria to consider when selecting a wire brush wheel for slag removal.
1. Brush Shape
Many people mistakenly assume that wire brushes remove slag through scratching and abrasion. In reality, the wires batter the slag like miniature hammers, jolting it loose from the surface of the metal. In order to accomplish the task, the tips of the wires must remain as perpendicular as possible to the surface of the metal. The shape of the brush determines how well the tips will maintain their perpendicular state.
In terms of shape, brushes break down into two categories: cup brushes and end brushes. Cup brushes feature wires arranged in a circle around the perimeter of the brush. The diameter of a cup brush tends to be much greater than that of an end brush.
In addition to being narrower, end brushes also feature wires packed across the entire surface of the wheel. For most applications, a cup brush represents the best choice. The construction of a cup brush makes the wires much less likely to flare out when applied at high speeds — an unwanted phenomenon that can occur when using end brushes.
End brushes do have one clear advantage, however: their size. End brushes allow metal workers to remove slag from places too tight for cup brushes to reach — for instance, a hole at the far end a pipe. If restricted space does not play a factor, most slag removal jobs should be conducted using a cup brush.
2. Trim Length
Trim length refers to the length of the wires on any particular wire brush wheel. This factor plays a large role in determining how aggressively the wire brush wheel will accomplish its slag removal. Generally speaking, the shorter the trim length, the more aggressively the brush will perform. This can be either a good or a bad thing.
A shorter trim length means that the wire brush will be able to remove the slag more quickly. Yet it also may lead to the base metal becoming damaged if the brush's action is too aggressive. A longer trim will take longer to remove slag with, since the wires will more readily bend away from the surface. However, the removal process will tend to be gentler on the base metal.
A greater trim length also increases the reach of the brush. This makes it better able to reach crevices located in the weld area. Such an advantage can easily compensate for the trade-off in terms of the time of removal.
To remove weld slag safely and effectively, you must select the most appropriate type of wire brush wheel. For more information about this crucial decision, please don't hesitate to contact the welding and metal fabrication experts at Sam’s Welding, Inc.