1. Form a Plan
For proper weld preparation, it’s important to have a plan before getting started. Otherwise, it’s easy to jump fully into a project that seems simple and then quickly discover there are many factors that can lead to costly delays, additional steps, or rework. Having a plan also helps you resist the urge to take shortcuts when issues arise.
Consider these questions:
• What is required for the welding process I am using?
• Which media is best for the material I am working with?
• What is the final finish requirement?
2. Cut, Fit, Bevel
Once your plan is in place, the second step in preparing metal for welding is often cutting, fitting, and beveling the base material. The amount of care and preparation you put into the initial cut can reduce the amount of work that goes into cleaning later.
Many tools can be used for cutting, including a torch/plasma cutter, shears, laser/waterjet/CNC tables, and manual tools such as cutting wheels. Each type has pros and cons.
Finishing metal for welding
Making the initial cut as clean, straight, and consistent as possible will make it easier for you to produce quality results. Offhand cutting with a right-angle grinder is inexpensive, portable, and does not require as much setup and maintenance as most of the other options. However, to achieve clean, straight cuts, you need a fair amount of practice and skill.
A clean, consistent gap between the two pieces to be welded will produce a stronger, more consistent weld with less filler metal, reducing costs and saving time.
3. Prep, Clean the Surface
Once the material is cut and beveled, it’s time to prepare the surface for the initial welding pass. Removing any mill scale, chemicals, contaminants, and coatings from the base material helps ensure proper weld penetration and eliminate impurities, porosity, and inclusions. Be sure to clean the work surface thoroughly within an inch of the joint on both sides.
When cleaning some stainless steels and other alloys, you may be fine using acetone and a wire brush rather than an abrasive medium. Rust, rubber coatings, powder coat, and paint are light enough that they can be cleaned more effectively with a wire brush.
If the application requires an abrasive product for surface cleaning, consider what you’re trying to remove. For weld preparation, start with a less coarse option and increase in aggression only as necessary. With heavier coatings and mill scale, the best option is usually a grinding wheel or a flap disc.
Flap discs are commonly used in weld preparation because they are easy to control and you can grind, finish, and blend all at once. A grinding wheel is more aggressive and durable, which is helpful when working with jagged or uneven seams, like torch slag. Be careful not to get too heavy-handed with a grinding wheel, because it’s easy to remove too much base material.
4. Choose the Optimal Grit
A common misconception is that a coarse abrasive will always get the job done faster. While it’s true that coarser, more aggressive abrasive will remove material faster, that’s not always a good thing.
Using an abrasive that is too coarse abrasive can remove excess material or damage the surface. Removing too much material may put the finished part outside final specifications and tolerance. Because the scratch pattern is coarser, it can also be more difficult to see surface imperfections and cracks during visual inspection. While you may not remove material as quickly with a finer abrasive, it’s often more productive, can minimize the number of passes needed to achieve the desired finish in less time, and can prevent rework.
5. Select the Right Abrasive Profile
Several abrasive profiles are available that can make the job easier or harder.
Wire wheels are much more resistant to loading but do not remove base material. That makes them a good choice for removing surface contaminants and coatings without affecting the base metal. Abrasives are designed to cut and remove base metal. Because of abrasives’ construction, heavy coatings and base material can build up between the grains and reduce their ability to cut.
If you require any equipment or safety kit to complete your project, please visit our shop: Arc House | 82-90 Taylor Street Birkenhead | Wirral | CH41 1BQ or visit our contact page to discuss your needs.