Zirconia alumina is among the most durable abrasive grains for welding and metal fabrication applications. The extremely fine crystalline microstructure features excellent thermomechanical and chemical characteristics that offer outstanding wear-resistant properties. This leads to great versatility across a broad range of light to heavy removal applications on a wide range of materials, such as carbon steel and stainless steel, to provide better productivity, cost savings and finished products.
Continuing its long history of developing zirconia alumina abrasives, the Norton|Saint-Gobain Abrasives’ R&D team recently made upgrades to the established BlueFire line of abrasive products. This includes R860 flap discs and quick-change cloth discs, along with BlueFire R887D quick-change cloth discs and belts. The upgrades affect the grain, bond and backing.
Sharp cutting points continue to be exposed through “microfracturing,” but a proprietary new grain shape and chemistry provide an improved cut rate and material removal rate.
“Picture each piece of the zirconia alumina grain shaped like an open hand and each finger represents the microfracturability of the grain,” says Patrick Carroll, senior product manager, Norton|Saint-Gobain Abrasives. “As that zirconia grain grinds, one finger is run out as opposed to aluminum oxide, which is very blocky like a closed fist. So, the advantages of the open-hand shape with the microfracturability of the zirconia grain allows for a significantly better cut rate, better performance and longer life versus aluminum oxide and older zirconia products.
“We have been able to achieve 50 percent or better performance due in part to the open-hand characteristic of the grain,” he adds. “The microfracturability of the grain allows for better performance in stainless steel as well.”
BlueFire products also feature overgraded zirconia grain, where the grain is made slightly coarser acting for faster, smoother metal removal.
“From a bond standpoint,” Carroll says, “we’ve improved the resin system to offer better base adhesion. This affects the two basic building blocks, the backing and the grain, by allowing the grain to remain stable longer. It also reduces grain shedding, which is when grains release prematurely and the operator ends up grinding with the backing. The chemistry of the bond provides improved adhesion and reduced grain shedding.”
Finally, the improved high strength polyester backing is heavier, which translates into longer life.
“We can make any backing stronger and more durable but what is exciting about this backing is that it wears evenly,” Carroll notes. “The heavier backing is also ‘supple,’ which translates into longer life balanced with this ability to wear evenly. It then translates into a better experience for the operator.”
One additional feature of new BlueFire R887D quick-change cloth discs and belts is a grinding aid that provides a cooler cut and minimizes loading for longer life on stainless steel and other hard-to-grind materials.
Welding and flap discs
Flap discs are essential abrasives for metal fabrication and are often the go-to choice for a variety of jobs. Flap discs in particular are good for welding applications and offer specific benefits for the operator. They allow for deburring, blending and finishing with one product, saving time and money. They can be used aggressively to cut, or can be held nearly flat to finish or blend.
A flap disc provides much more controlled stock removal. The abrasive flaps are made to conform to the part, which reduces the possibility of damage while removing material effectively.
Grinding discs, like flap discs, are highly versatile and suitable for a range of metal fabrication applications. They are a great choice for rapid stock removal when surface finish isn’t a primary concern. They can have a tendency to gouge the surface and leave a very rough finish, particularly when used by a less experienced operator.
As the flap disc is less rigid and more flexible than a grinding disc, fewer vibrations are generated when grinding. Not only does this make for a more comfortable experience for the operator, it is also significantly less noisy.
Conical-shaped (Type 29) flap discs are the best choice for removing stock in a short space of time. Conversely, when comes to operations that require a lower grinding pressure and more control, flat-shaped (Type 27) flap discs are best. These might be a better choice for newer operators overall because they’re easier to use and there is less of a chance of stock removal errors, although disc life may be sacrificed.
Another disc characteristic that may appeal to operators is a smaller diameter. Unlike the popular 4.5 in., 5 in. and 7 in. sizes, smaller diameters can provide ease of use and better ergonomics so there is less chance of damaging a part.
“Smaller diameters are just another option that helps us work with customers to find solutions,” Carroll says.
And while pre- and post-welding grinding operations typically are performed manually, continuous labor shortage problems might cause automation to grow as an option. After all, automation offers better throughput, consistency and quality.
Norton | Saint-Gobain Abrasives