With baseball season in full swing, it seemed like an appropriate time to learn about aluminum bats. Much is proprietary about the material and its processing, but we can discuss it in a general way.

The documented history of the baseball bat goes back to a game played on June 19, 1846, in Hoboken, N.J. It was the first played using Alexander Cartwright’s rules. At that time, players made their own bats, and there were many shapes and sizes. Trial and error found that a round bat worked best, as did those made from wagon-tongue wood.

In 1859, The Professional National Association of Baseball Players Governing Committee imposed the first bat size restriction of 2.5 inches in diameter. Ten years later, the length of bats was limited to 42 inches, which is still in the rulebook today. Diameter, however, was increased to 2.75 inches in 1895. Many other developments in wood bats occurred over the years leading up to the introduction of the aluminum bat.

Although Easton introduced aluminum bats in 1970, the NCAA did not sanction them until 1974. Today, Louisville Slugger makes over 1 million aluminum bats a year. The basic difference between wood and aluminum is breakage and weight. Aluminum bats can be lighter than wood with weight-distribution technology allowing faster bat speed. Some sources say balls travel farther with aluminum, and some say wooden bats get greater distance.

The making of an aluminum bat begins with cut-to-length tubing shipped from the aluminum to the bat manufacturer. The wall thickness and the heat treatment affects the amount of elastic deformation the bat will experience during impact. Today’s high-performance bats typically range from 0.5-0.75 inches thick. While the common bat alloy (C405) chemistry has remained the same since its introduction over 12 years ago, the heat treatment has improved, resulting in a stronger bat.

Although the detailed processing is proprietary, the tubing is placed on a tapered mandrel and inserted through a die. This forms the wall of the bat to a taper. The metal is then annealed and moved on to the swaging process. Two opposing dies rotate around the bat at high speed, further shaping it and reducing its diameter to the proper size. The bat is then cleaned, heat treated and aged. The final high-temperature thermal process is the welding of the knobs on the grip end. The bats are finished by polishing, anodizing and silk screening.

Aluminum-bat development has centered around heat-treatment improvements and alloy additions. An addition of scandium – a rare, expensive and lightweight metal – has resulted in a strength improvement of about 10% over C405. This occurs as a result of the precipitation of Al₃Sc, which also enhances weldability.

A discussion of aluminum bats would not be complete without covering the safety controversy. Frankly, some of the logic on both sides seems faulty. In summary, many people are impassioned that aluminum bats should be abolished. Some believe they should be eliminated for the youngest players, but aluminum bats benefit the youngest players the most because they can swing them more easily. The concern is that balls come off an aluminum bat faster than a wooden one, which can injure a player, particularly a pitcher. It’s interesting that many believe the aluminum bat is safer because wooden bats can break/splinter.

The marketing of the aluminum bats themselves and the technological developments of the past quarter century would lead anyone to conclude that hits off metal bats are harder and faster. For this reason, aluminum-bat opponents believe the youngest kids should not be allowed to use them. So, basically, the kids needing the lighter bat just to make any swing will be forced to use heavier bats. Meanwhile, we continue to allow older kids with more developed swings to use the aluminum bats, generating more powerful hits with a greater potential for injury. If anything, this seems backward.

The injury evidence appears to be inconclusive. A study by the Consumer Product Safety Commission on fatalities between 1991 and 2001 reported that 17 players were killed by batted balls – eight from metal bats and nine from wooden. Since aluminum bats are used mostly for the younger ages, it’s quite likely that the percentage as a number of bats used (for aluminum) is even lower than the absolute number would indicate.

Assuming aluminum bats continue to be used as in the past, maybe we can stop improving the alloying and heat treatment. Unless, of course, they want to “improve” themselves out of business. IH

This article is featured in Industrial Heating's Top-10 Heat-Treated Holiday Gifts.  Click on the present to find more gift ideas and to learn how these gifts benefit from thermal processing.