Mar., 09/Say the name Caterpillar (Peoria, IL) anywhere in the world and people immediately think of big, yellow iron. Each year Caterpillar transforms over 300,000t of steel and iron into revered earthmoving equipment and engines. For more than 75 years, the company has been studying, understanding, and improving steel and iron fabrication to maximize the strength and durability of their machines and engines. Their metallurgical engineers have designed materials to withstand the most high-stress and high-impact applications imaginable.

As one of the largest users of weld wire in the United States, Caterpillar has an understanding of the welding process second to none. The company's welding technologies are aimed at producing the highest quality, strongest welds possible. They also have production- proven solutions to control the weld process, reducing weight and minimizing product distortion.

In nearly all cases, it's the strength of the welded joint that determines the strength of the welded fabrication. Often the thickness of the steel plate being welded is selected to ensure a high-quality weld. Typically, structures are based on fatigue limits of joints. A good joint typically requires extra material. This means that a lot of products constructed of welded-steel plating are much heavier, bulkier, and more expensive than they need to be. Caterpillar has discovered two distinct ways around this problem, depending on whether conventional welding or advanced robotic welding is used-both have been successfully employed in the manufacture of production equipment.

For conventional welding processes, variable-thickness steel plates can be used to size the steel for optimal weld strength. What is different is the metal-fabrication process developed by Caterpillar, which enables intermittently spaced, thickened areas along metal-plate edges, both parallel and oblique to the plate edge. As a result, metal plates can be fabricated with variable edge thicknesses designed to coincide with the weld requirements of any particular spot. The plate itself needs to be only as thick as the load-bearing requirements of the final product.

The second solution requires the use of robotic welding techniques. By carefully controlling the weld wire, weld parameters, steel fit-up, and other variables, unusual weld geometries can be reproduced reliably during manufacture. These new weld geometries have been successfully employed on nine different production applications and have resulted in up to 10% weight reduction and three to 10x improvements in fatigue life. Weight reduction comes from specifying thinner steel plate and the fatigue improvements from enhanced weldbead geometry.

The plate can be reduced in size and weight, and the rest of the product components can be downsized as well; for example, the bolts, bolt mountings, castings, and other components previously needed to support the thicker, heavier plates. Obviously, a reduction in size and weight translates into substantial savings in manufacturing and the final cost of the product. Additional advantages include lower fuel consumption for powered machinery, vehicles, and vessels, and increased profit margins for the same or higher quality products manufactured at lower costs.

As with all processes, the input controls a piece of the performance. In metallurgy that means controlling the steel chemistry. Caterpillar has the expertise, experience, and know-how to control steel chemistry, enabling the highest performance for a given operation or part. The company understands how lasers, plasma, and water interact with steel during cutting operations. This understanding permits slight modifications in the steel's chemistry to create major improvements in time and quality of cutting. Mill- forming steps are also affected by chemistry. Tight controls over the steel and mill processes make distortion control possible. Special steels have been developed and commercialized to produce high-durability gears (i.e., pitting resistant) and pins (i.e., scuffing resistant). These properties are brought out of the steel through specialty heat treating.

Specialty steel chemistries were also developed and commercialized to complement Caterpillar's heat-treatment experience. Using special steels and proprietary heat-treatment processes, Caterpillar is able to produce high-durability, high- power-density gears, and robust pin-bushing combinations. Using commercialgrade steels, their proprietary furnace systems can control carburizing atmospheres to 75%, greater accuracy than commercial alternatives. Components using these new materials and processes have been designed using in-house simulation solutions.

Pour-and-pray and heat-and-beat metallurgy isn't the most cost- effective, robust process for new component introduction. Yet many firms still rely on these and other methods for casting and forging. Engineering teams at Caterpillar have created casting and forging simulation algorithms to eliminate the guesswork in basic metalworking. Weld simulation is used to understand the distortion to be expected and then alter the weld process to minimize that distortion, thus saving time and money on post-weld processes.

Caterpillar is now licensing this technology and can assign a team to assist a company with its transfer and application.