Aug 21, 2017

New AWS D.8.2 Code Responds to the Rise of Aluminum in Auto Manufacturing

By Carlos Plaza

Resistance spot welding (RSW) has been a mainstay in the automotive industry for many years. In fact, the typical car body contains 4500 spot weld joints. As a result, the American Welding Society’s (AWS) D8 Committee on Automotive Welding has long published periodically updated editions of D8.1 Specification for Automotive Weld Quality – Resistance Spot Weld of Steel. As the name implies, this document provides post welding acceptance criteria for the resistance spot welding of steel as used in the automobile industry and other related industries.

However, in recent years, the need to improve fuel efficiency and reduce the effects of corrosion in today’s cars and light trucks has had many a design engineer looking for efficient ways to incorporate aluminum into vehicles. The steel industry is countering aluminum’s incursion into auto manufacturing with some new grades of lightweight steel, but it’s clear that aluminum has earned its place in the auto materials lineup.

You’d think the aluminum versus steel question would only interest engineers and company management (it takes a lot of money to tool up to handle a new material), but GMs recent spate of “aluminum versus steel ads” has brought the issue into America’s living rooms. The ad demonstrates how much better the Chevy Silverado’s steel-lined bed holds up to punishment when compared to the Ford F-150’s aluminum bed. However, most of us don’t go around dropping 825 pounds of landscaping blocks from 5 feet above the bed of our truck, nor do we go about strategically dropping metal toolboxes pointy end first.

Clever ads notwithstanding, Ford’s 2015 decision to produce a fully aluminum body on its Ford F-150 (the frame is still about 80% high-strength steel) has not made much of a dent in sales. The model remains America’s best-selling truck for the last 40 years and America’s best-selling vehicle for 35 years. However, despite Ford’s success and the recent hoopla surrounding the viability of aluminum in auto manufacturing, the Ford-150 is hardly the first mass-market vehicle to incorporate the lightweight alternative to steel. That honor goes to the Audi A8, first introduced in 1994 with a fully aluminum chassis marketed as the Audi Space Frame. Of course, the 2017 Audi A8 goes for about $82,000 so mass-market is a relative term here. It’s really the advances in materials and joining processes over the last 30 years that have facilitated the use of aluminum in more affordable vehicles like the F-150 and the Toyota Camry.

In 2014, GM began using its patented process for spot welding aluminum to build the lightest, strongest, and most precisely built Corvette since the iconic model was introduced 64 years ago.

The expanding role of aluminum in the automotive industry and the continued use of resistance spot welding to meet the high throughput requirements of mass-market vehicles signaled the need for an automotive weld quality code that deals specifically with the upstart metal. In response, the AWS D8 Committee on Automotive Welding assembled its team of experts and developed AWS D8.2:2017 Specification for Automotive Weld Quality – Resistance Spot Welding of Aluminum. This new document provides a uniform means of evaluating post resistance spot welded aluminum assemblies as used in the automotive industry. Like D8.1, D8.2 deals with both visual and destructive acceptance criteria. While developed for the automotive industry, D8.2 can also be used in other industries that use aluminum sheet stock.

The new edition of AWS D8.2:2017 Specification for Automotive Weld Quality – Resistance Spot Welding of Aluminum is now available at the AWS Bookstore. Members receive a 25% discount on this and other AWS products so consider joining today. See the AWS Membership webpage for more details.

If you have any comments for improvement of D8.2, or are interested in joining the committee, please contact the Secretary, AWS D8 Committee on Automotive Welding at technical@aws.org.