Like many industrial markets, the heavy truck market utilizes brass fittings for a variety of applications. With composite fittings gaining traction in the arena, why do many truck OEMs continue to use brass fittings?
Why is brass the ideal material for the transportation market?
Like many industrial markets, the heavy truck and transportation markets utilize brass fittings for a variety of applications. Brass fittings have the strength, corrosion resistance and machinability in a variety of shapes and sizes to provide cost-effective solutions; making them an ideal material for many truck applications. It is common to find brass fittings in the air brake systems, cab controls, fuel systems, engine, transmission, cooling and air tanks on a heavy-duty truck and they meet DOT and SAE requirements. Let’s take a deeper look into why brass is an ideal material for this market.
Brass is comprised of approximately 60 percent copper, 38 percent zinc, and 2 percent lead. Brass fittings are characterized by their strength and ability to handle high as well as reasonably cold temperatures. They have good conductivity, excellent corrosion resistance, and low magnetic permeability. Brass not only is easy to machine, but it has great plating, joining, polishing and finishing characteristics all packed into a relatively low cost material for manufacturing.
How are brass fittings manufactured?
In manufacturing, there are two methods for creating a brass fitting, one from extruded bar stock and the other through forging. A fitting made from extruded bar stock is created from bar stock in round, hexagon or shaped bars. These bars began as a solid round billet that is heated to a pliable state and forced by approximately 80,000 pounds of pressure through a die resulting in a bar, shaped to the desired external dimensions. That bar is then cut into slugs and machined into fitting components. The process produces a dense, nonporous material.
A forged fitting is made from an extruded round bar that is cut to length and straightened. After straightening, the bars are cut into slugs, much like a fitting from extruded bar stock, but at this point, rather than machining, the slugs are reheated to a pliable state and pressed under approximately 25,000 pounds of pressure per square inch between an upper and lower die cavity into the desired fitting shape. After cooling, the flash, or excess, is trimmed away and the forging blank is ready for machining.
The forged fittings produce a uniformly dense material of exceptional strength from forming under extreme pressure. Since the grain flow follows the contour of the fitting shape, the fitting has high impact strength and resistance to mechanical shock and vibration. You can easily spot the difference between a forging and an extruded part by looking at it. A forging will have rounded edges characteristics of the forged shape from the die and an extruded part will have squared off corners that resemble the original bar stock they originated from. Brass fittings can have components from both manufacturing methods that are assembled together to create a finished part.
"Brass compression style fittings, which have been used in the industry for decades, remain a low-cost fitting option for truck and trailer OEMs." Tom Cook, product sales manager, Fluid System Connectors Division, Parker.
Some applications, like diesel fuel applications, require additional corrosion resistance above and beyond the capabilities of brass alone. The great plating characteristics of brass, allow nickel-plating to original brass fittings to accommodate fuel systems.