By: Karel Smrcka
19th November 2004
What can we expect to come next? Will mechanical joining processes or structural adhesives be a threat to the traditional processes? Welding today is closely allied to the consumption of metals. Steel dominates and will continue to do so for the foreseeable future. Global consumption has grown at 1,4% a year during the last decade. With the extremely high consumption growth in China during the last five years (26% for 2003), the global consumption of crude steel is expected to exceed a billion tons.
China is by far the largest consumer of steel, with 27% of the world’s production. With more than a billion citizens and an increasing ownership of products such as motor cars, the growth of steel consumption will continue.
Steel consumption in China is also influenced by a growing shipyard industry. The Chinese government is committed to becoming the world leader in shipbuilding, surpassing the current leader, South Korea. Work has begun in China on what is the world’s lar- gest shipbuilding yard. The new yard is being constructed along 8 km of coast on Shanghai’s Changxiang Island. It is scheduled to be fully operational by 2015, and will help China State Shipbuilding Corp to become the world’s top shipbuilder. It will have an annual capacity of 8 mdwt for building supertankers, gas carriers and cruise ships.
Stainless-steel consumption in the world has a steady growth of 5,5% a year. It dropped below 20 Mt three years ago, but exceeded this level in 2003, reaching 21,5 Mt. China contributed to this with its 54,2% growth in 2003. This requires the use of high-quality welding processes, such as TIG and plasma welding. Laser welding is also anticipated.
The change in aluminium consumption is much lower than expected at 2,8% year, on average, for the period 1990 to 2003. This figure will dramatically change when aluminium is more commonly used in cars and in other parts of the transport industry. The number of cars with an aluminium body is increasing. Audi, Jaguar, Honda, Toyota, Ferrari, Mercedes-Benz and GM are among those offering such cars to reduce environmental impact and improve passenger safety. All structures can be designed to absorb the same energy as steel at only 55% of the weight. Design concepts in aluminium are continuously changing to reduce the manufacturing cost of aluminium bodies. A former MD for Audi claimed that the aluminium car body was about €500 more expensive than steel.
The manufacturing technology for aluminium bodies needs to be further improved, for example mechanical joining with clinching and self-piercing riveting processes. Laser/MIG hybrid welding is another joining process that results in lower heat distortion and a stiffer car body. It will be a considerable time, however, before aluminium exceeds the use of steel. In 2003, some 26,4 Mt of aluminium was produced, about half being used in industrial products and in capital goods compared with steel manufacturing with 855 Mt.
To counter the higher use of aluminium, the steel industry has introduced advanced high-strength steels in the body and other parts of the car. It was developed in a project, known as Ulsab, financed by 33 steel companies. Porsche Engineering produced the conceptual design, ending up with weight savings of 200 kg.
Edited by: Karel Smrcka