The production of high-strength low-alloy (HSLA) steels represents the fastest-growing segment of the flat rolled steel market. Weight reduction programs by automotive producers and other steel consumers have provided the impetus for developing efficient production practices for these grades. Yield strength levels of 276 000 to 966 000 kPa (40 000 to 140 000 psi) are currently available.
The majority of HSLA grades are microalloyed with either columbium, vanadium, titanium, or combinations of these elements. The columbium and vanadium steels are produced either as semikilled or fully killed grades, with and without inclusion shape control. Titanium-alloyed grades are produced fully killed. These three alloy grade series are routinely produced using ferroalloys added to the steel ladle in conjunction with ferrosilicon and aluminum to control deoxidation. Selection of the alloying element depends upon end use, mill processing parameters, and customer specifications and requirements.
Other grades, produced on a less-frequent basis, require the additions of copper, nickel, chromium, and molybdenum. The form of these alloy additions varies, and all but chromium can be added to the furnace during charging.
This paper emphasizes the relative cost of the alloys and the methods used to achieve the desired analysis of each element. Particular attention is devoted to melt shop practices used to maximize alloy recovery, and thereby minimize costs. Included are considerations of ferroalloy sizing, packaging, and sequence of addition to the steel ladle. The importance of consistent quality from the alloy supplier has become rather apparent; the methods employed by Jones and Laughlin's Cleveland Works to monitor the quality of alloying materials is also reviewed.