Proper cleaning is critical to successful welding operations. This can affect quality because the surface of the material with dirt or impurities can cause inclusions or problems such as voids. Surface cleaning and preparation may also affect the appearance of the final weld and the overall operating costs of rework and labor. Some jobs may require the use of abrasive products, while others may be cleaned with cloth or chemical solvents.
Inter-weld and post-weld cleaning are also important steps in the process, depending on the application and the finished weld requirements.
Although not all work applies to the same rules, there are still some general best practices to follow.
how to choose?
There are many options available for solder cleaning. Keep these factors in mind when choosing.
Expected results. If there are surface finish requirements or aesthetic requirements for soldering (for example, if a mirror finish is required), these will affect how clean. A variety of products may be required during post-weld cleaning to achieve the desired finish. First use the abrasives of the largest grit or granules allowed by the application and then move to finer grit as the work progresses. For example, the operator can clean the weld from a 40-grained turntable and then finish working with an 80-grained turntable for finishing – especially if the material is sprayed or powder coated. Generally, the smoother the finished weld, the better. When welding stainless steel, the wetted cloth can be cleaned and the free iron removed after welding. This also helps the passivation process,
When cleaning welds, minimize steps to save time and money. Using a finer-grained product can be slower, so this is a balance between productivity and surface finish requirements.
material type. Different abrasives are suitable for different types of materials. For example, when welding stainless steel or aluminum, it is important to wash thoroughly before starting because these materials do not produce dirt and debris during the welding process. Be careful when using thicker abrasives on these materials. For aluminum, bronze or other non-ferrous metals, 24 grit or 40 grit discs may be too corrosive. A good rule of thumb is that the finer the gravel, the better. Typically, the filler rod and base material can be cleaned using 70% isopropyl alcohol prior to soldering.
Look for tools designed for stainless steel, such as stainless steel brushes or grinding wheels, to avoid introducing contamination into the weld during cleaning between the channels. These wheels can also be used for other materials that are susceptible to contamination, such as aluminum, brass or copper.
Bottom line: To prevent dust and debris from entering the weld, it is usually necessary to clean before and during welding, regardless of the type of material, but some materials require special attention.
Code requirements. Some welding applications may have regulatory requirements for welding inspections. For example, the welding specification can determine how many inclusions a finished weld can contain. These are important factors to consider when choosing the right weld product.
Common cleaning tools
Common options for surface and weld cleaning include bonded abrasives/grinding wheels, coated abrasives/knives, wire brushes and grinding wheels. The choice depends on the requirements of the application and the preferences of the operator. The properties and uses of abrasive products and wire brushes vary. Abrasive products are designed to remove the base material, while wire brushes do not.
Bonded abrasive/grinding wheel. For example, if there are slag inclusions or pores in the weld, the wheel can be used for cleaning, in addition to removing inclusions, and some weld material is removed. These products are typically used to clean low carbon steel and for sharper welds that may have large amounts of slag or spatter, as the grinding wheel removes more material faster. Grinding wheels rely on the combination of grain type, grain size and binder (resin and additive) to determine their properties. Because bonded abrasives are generally more aggressive and remove materials faster, they require a higher level of operator skill to prevent damage, gouging or undercuts. The application requirements determine the thickness of the wheel to be used – the heavier the material to be removed, the thicker the wheel is.
The coated abrasive/fold is bonded in the same type as the bonded abrasive, but the particles are bonded to the liner rather than being molded and pressed into the hard grinding wheel. The fabric is layered to form a flap, which makes the flaps softer and more comfortable. The flaps can be used in stainless steel (although finer grit must be used) or mild steel or carbon steel to remove a small amount of material during pre-weld cleaning and to mix and finish the surface after welding. This makes it a good choice when painting finished materials, primers or powder coatings. When using the bezel, pay attention to the direction of rotation. Make sure it is spinning and prying sparks and debris away from the base material and welds, rather than crossing them backwards to avoid contamination.
Wire Brushes and Wheels When cleaning away spatters and other contaminants, it is a good choice for cleaning between channels or after welding. If the material to be removed has a large amount of scale, rust or thermal discoloration (do not remove a lot of material), the wire brush can also be pre-cleaned well. When choosing a brush, there are several knot styles, wire gauges and trim length options. By changing one or more of these features, the operator can fine-tune brush performance for a specific application. For example, the knots of the stringer have a narrow twist from the bottom to the tip, making them more suitable for penetrating narrower spaces during cleaning, such as corners, fillets and root welds. Keep in mind that the tip of the wire brush can do the job, so using the right pressure is the key to performance and efficiency.
Successful best practices
In addition to proper abrasive selection and cleaning techniques, there are some best practices to consider.
It may be tempting to look at the initial purchase cost, but lower quality, lower cost abrasives, brushes or wheels may not provide sufficient aggressiveness for the job, or their product life may be much shorter. It’s best to invest more in products that have better cleaning or longer life because it can significantly impact overall operating costs and productivity.
Another best practice is to avoid speeding. Choose the right size for the operating tool and always use the grinding tools guard recommended by the manufacturer. Ensure that the maximum safe speed marked on the wire brush or grinding wheel is greater than or equal to the maximum operating speed on the tool.
A 4 1/2-inch grinder and a 4 1/2 grinder can reach 13,000 rpm, which means they can be used safely together. However, because larger products are rated at much lower rotational speeds, removing the tool’s shield to use larger wheels can lead to safety and performance issues. The product does not run as fast and is therefore more susceptible to damage, increasing the likelihood of injury and shortening the life of the product.
Proper cleaning can be successful
Clean materials and welds are critical in any welding operation. But keep in mind that there is no one-size-fits-all solution for selecting abrasives, brushes or grinding wheels for cleaning before, between, and after welding. Always prioritize and request work. The right choice can help improve efficiency, quality and cost over the long term.