What is HSLA steel?

HSLA steel is a high-strength low-alloy structural steel, also known as "microalloyed steel". It belongs to vanadium-containing steel.

The development of microalloyed steel began in the late 1950s. With the wide application of welded structures after World War II, the adverse effects of C on the toughness and weldability of welded structures are prominent, and the means to improve the strength of steel by increasing C are limited. At the same time, it is found that grain refinement can improve the strength and toughness of materials at the same time

Therefore, this new view strongly stimulates the development of new technologies and new steel grades. At the same time, it is recognized that precipitation strengthening of microalloyed elements can replace the strengthening effect of C and improve weldability.

In the early 1960s, Bethlehem Steel Company developed a series of vanadium-nitrogen steels based on C-Mn steel. The upper limits of mass fraction of C and Mn are 0.22 and 1.25, respectively, and the yield strength reaches 320 ~ 460 MPa. The products are supplied in hot rolling state, and the specifications include all plates, belts and section steel products.

Extended data:

VAN80 steel is a V-microalloyed strip developed by Jones and Labrin in the early stage of the United States (about 1975). The on-line controlled accelerated cooling process was adopted for the first time. Microalloying precipitation strengthened grain refinement and precipitation strengthening, and its yield strength reached 560 MPa.

With the development of controlled rolling and controlled cooling technology, a new controlled rolling process route called recrystallization controlled rolling was developed around 1980. The process adopts v_Ti microalloying design, and through repeated recrystallization of austenite after each deformation, the grain refinement effect that can be achieved by traditional low temperature rolling method (Nb microalloyed steel) can be achieved.

This process can adopt higher final rolling temperature, so it requires lower rolling force of the mill, which can not only improve productivity, but also realize controlled rolling production on the mill with weak rolling force. The thin slab continuous casting and rolling process (TSRC) developed in 1990s promoted the application of vanadium microalloying technology in high strength strip steel products.

A series of high strength strip steel products with yield strength of 350～700 MPa were developed by V/v-N microalloying under TSRC process.

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