Strength is affected by the alloying elements added during steelmaking and the amounts of these alloying elements. Alloying elements are usually added in combinations with one another. Typical alloying elements used are silicon, chromium, aluminium, niobium, titanium, vanadium, boron and manganese (Si, Cr, Ni, Al, Nb, Ti, B and Mn). The temperature of the steel during rolling and the type of subsequent heat treatment also affect the strength.

Intensive research and development work was done on microalloyed steels in the early 1980s. Small amounts of aluminium, noibium, vanadium and titanium were added. Microalloying combined with lowering the final rolling temperature to about 880 degrees C (from around 1050 degrees) yielded a steel with high strength combined with good toughness. This rolling procedure is known as controlled rolling.

The development work resulted in modern structural steels such as Domex 240 YP. YP stands for yield point, and this steel can be regarded today as a standard steel. Controlled rolling enabled normalizing to be eliminated.

Normalizing was previously an essential process stage for thick material if impact strength testing at -20 degrees C and sometimes -40 degrees C was specified. During the same period, the casting of ingots was abandoned and was replaced by continuous casting. This offers major benefits both to customers and to manufacturers.

At the same time, engineers in the steelworks were devoting feverish efforts to lowering the sulphur content, since sulphur gives rise to slag in the form of manganese sulphides.

One of the problems caused by manganese sulphide is the detrimental effect on steels that are subjected to Z testing. In Z testing, the mechanical properties of the steel are tested in the thickness direction.

The sulphur content of the steel was lowered by the addition of silicon and calcium (SiCa treatment), and it is taken for granted today that the sulphur content is low (<0.005%). This improved the bendability both along and across the direction of rolling.

The next development stage in the rolling process was to lower the temperature by a further 150 - 200 degrees C. This procedure is known as thermomechanical rolling and it results in today's EHS (extra-high strength) steels. If the steel is also quenched in water after hot rolling, the strength of the steel increases further and UHS (ultra-high strength) steel is the result.

Another method of producing UHS steel is by heat treatment, i.e. quenching (rapid cooling) and sometimes also tempering (reheating). Steel subjected to a combination of quenching and tempering is known as quenched and tempered (QT) steel.