Types and differences between steels – OL 37 and OL 52

In order to correctly execute a construction, it is necessary to know the types and the differences between the steels. In metal constructions, steels are classified according to the steel brand (tensile strength). The most frequently used steels, in Romania, for the realization of metal constructions are the following: OL 37, OL 44, OL 52.

OL is a literary symbol that refers to the field of use of steel. It is a general purpose steel, currently used for the realization of metal constructions. The number accompanying the literary symbol indicates the minimum breaking strength (kg/mm²).

OL 37 – is called normal construction steel, it fulfills to a large extent the conditions normally imposed on construction steels. It is also called „soft” or „ductile”. It has the Fe 360/Euronorm equivalent.

OL 44 – this type of steel is used for the manufacture of highly stressed construction elements and the production of rivets used to assemble elements made of OL 52. It has a yield strength between that of the normal OL 37 steel and the superior OL 52 steel.

OL 52 – is the steel with the highest mechanical resistance characteristics. It is recommended to be used for highly demanding constructions. It has the Fe 510/Euronorm equivalent.

Types and differences between steels – OL 37 and OL 52

When choosing between an OL 37 and an OL 52 steel, you must take into account the following:

• in the case of repeated alternating and pulsating loads, the fatigue resistance of the two steels does not differ much;
• the significant reduction of steel consumption (and the weight of construction elements) by using OL 52 steel is recommended in the case of high static loads or oscillating variables, where the influence of useful loads, compared to permanent ones, is small;
• the processing and welding of OL 52 steels is more difficult;
• OL 52 steel has a higher cost than OL 37.

Alphanumeric symbolization

An alphanumeric symbolization is also used, which is equivalent, but not identical, to the above:

• S 235 equivalent to OL 37, S 275 equivalent to OL 44, S 355 equivalent to OL 52;
• The letter S symbolizes the steel group (construction steel), and the number 235/ 275/ 355 specifies the yield strength (N/mm²).