Practice of Direct Rolling without Heating

The low temperature direct rolling technology without heating and compensation is applied to the production line of high strength and anti-seismic steel bars. The typical processes include four-machine four-strand continuous casting machine, out-of-billet roller table, transverse adjusting device and rolling line. A discharging roller table is arranged at each outlet of the multi-strand continuous Caster, a device for transversely adjusting the billet is arranged at the end of the discharging roller table, and a fully continuous bar rolling line is arranged at the side opposite to the discharging roller table.

In 2011, after 8 years of trial and production, the researcher developed 26 technologies, perfected the process and applied it in a steel enterprise’s continuous rolling bar production line, the practical production of high-strength anti-seismic steel bar without heating and compensation is realized. By the end of 2015, the project had produced 2.31 million tons of anti-seismic steel bars, with a direct rolling rate of 95.8 percent, a 1.35 percent increase in the yield rate, an increase of 30 MPA in the anti-seismic performance index of steel, zero secondary oxidation burning loss, and zero emissions of nitrogen oxide, carbon dioxide and sulfur dioxide, production costs were reduced by 147.5 yuan per ton.

Product performance. The HRB500E steel produced by a steel enterprise has passed the psychological and chemical test and the welding type test of the National Construction Steel Quality Supervision and Inspection Center. The statistical results of 100 batches of data show that the coincidence rate of seismic performance is 100%, the yield strength is 565 MPA, the tensile strength is 725 MPA, the elongation after breaking is 22%, the ratio of strength to yield is 1.28, and the cold bending, bending and welding properties are all qualified. After 60 lots of contrast tests, the average yield strength difference between head and tail is less than 5MPA. The contrast of metallographic data shows that the grain size decreases and the grain is refined.

Process characteristics. The main features of this direct rolling process are as follows: The head and tail properties of the same billet are homogenized, the product quality is improved, the grain refinement is obtained by certain process, and a new flexible joining process is developed. The system determines the strength and load of the process and equipment, meets the requirements of the parameters of direct rolling without heating or compensation for rebar and wire rod, and the distance between the continuous casting fire cutting device and the No. 1 rolling mill can be extended to 300 meters, the line speed of rolling slab can be raised to 4m / s or even 6m / s.

Key points of the process. This process solves many problems well, but when continuous casting and rolling are one-to-one, the production capacity of the rolling mill is more than 1.2 times that of the continuous casting mill; in the layout of the production line, the distance between the continuous casting and rolling is generally less than 300 meters. The rigidity and motor can meet the requirements of low-temperature rolling, and hot or cold billets off the production line are used in other rolling lines.