Case 1 Car

Safety and the environment

The principal aim for passenger cars is to reduce the rate of weight increase on new car models. A 1980 SAAB car weighed about 1100 kg, while today's SAAB 9-5 weighs 1600 kg. If safety parts were made of ordinary steels, the weight may perhaps have been 1800 kg. But by upgrading to high strength steels, the weight and thus the fuel consumption can be restricted without compromising on safety.

Every car manufacturer makes his own choice. High strength steel offers opportunities for developing lighter and thus more fuel-efficient cars. Or for developing safer cars with unchanged fuel consumption. Many carmakers adopt a mix of the two.

Case 2 Container

Lower transport costs and lower environmental impact
It proved possible to lower the tare weight (deadweight) of a 40-foot container by 760 kg by making it of high strength steel. This meant that 4 - 5% more load could be carried per ship on every trip. If the weight of the cargo were reduced instead, the consumption of heavy oil and thus the emissions would have been reduced. For a given run, e.g. Hamburg to Shanghai, it was estimated that every 20-25th trip could be skipped, which corresponds to a reduction of 3800 tonnes in the heavy oil consumption, and a reduction of 12 000 tonnes in the carbon dioxide emissions.

Case 3 Crane boom

A stronger product with a longer useful life improves the working environment and lowers costs
Crane manufacturers could be some of the major winners if they switched over to high strength steels. By changing over to a high strength steel, the outreach of the crane can be increased and the utilization of the machine will be more efficient. One manufacturer claimed that a crane with the same outreach although made of a material used ten years ago would not be able to lift even its own weight. But there are other benefits too.

High strength steel has better fatigue properties, which increases the useful life of the crane and reduces the overall maintenance costs. Due to the increased outreach, the crane driver need not move the mobile crane so often. This results in a better working environment and lower fuel consumption.

Case 4 Skate blade

Still a strong product - but simpler and less expensive to produce

This skate blade was previously made of St 52.3 hot rolled steel which, after cold rolling, was sent to Korea for forming and case hardening (by increasing the carbon content in the surface layer). Although the higher carbon content resulted in a strong product, the welding costs were increased.

Cold-rolled ultra-high strength steel is now used instead, and the blade is produced in Holland by roll forming. The skate blade has the required strength, but is now produced at substantially lower cost, due to fewer production stages, shorter transport and reduced cost of welding.

 

Case 5 The Eiffel Tour

Lighter product with lower energy consumption
The Eiffel Tower was built for the Paris World Exposition of 1889 in order to demonstrate that steel can very well be used in design and construction. The thought was that the Tower should then "tour" Europe. If Eiffel, the engineer who designed the Tower, had access to high strength steels, his Tower would have been a third of the weight. Moreover, much less energy would have been needed to produce the steel, since the energy needed per tonne is the same for high strength steels as it is for ordinary steels.

Eiffel used 6300 tonnes of wrought iron. If EHS and UHS steels had been used, around 2000 tonnes would have been sufficient.

Case 6 Reduced welding costs in thinner plate
It is important to take welding costs into account when considering changeover to high strength steels. The welding costs are generally reduced if thinner plate is used. One example:

Upgrading a 15 mm thick cut-to-length plate from a yield strength of 355 N/mm2 to 550 N/mm2 enables the thickness to be reduced by 3 mm, i.e. by 20%. The cost of welding a V joint is estimated to be 286 SEK/m for a thickness of 15 mm and 192 SEK/m for the thinner material. The cost would thus be reduced by 33% per metre of weld.

The root formula or the rule of thumb, as it is also known at SSAB, is used for calculating the thickness reduction.

Conditions:
MAG welding with an arc efficiency of 0.35 and a wages cost of 200 SEK/h. The costs of gas, filler metal and machine are included in the calculation formula (developed by SSAB Tunnplåt/S Jansson).