Development of high-strength packaging steel strip

The currently used packaging steel belt is mainly made of Q345, which is not high in strength. It is mainly suitable for the packaging of middle and low-end products, and cannot meet the requirements of furnace annealing for packaging steel belts. In order to improve the packaging quality of steel products and establish a good product packaging image, we organized high-strength steel packaging. The research not only considers the various properties of the product to meet the requirements of the national standard high-strength packaging steel strip, considers that the existing production equipment can meet the production requirements, but also considers the requirements of production costs. Products must be market competitive and have better The profit. The developed product has been tested to meet the requirements of high-strength packaging steel belts.
2 Strengthening mechanism of new steel grades
The most economical way to increase the strength is to increase the carbon content to increase the pearlite content. When the carbon content exceeds 0.35%, the side effects of high pearlite content become very serious, and the ductility decreases sharply. In order to obtain high strength and maintain a high level of comprehensive performance in low carbon steel, the most economical method is to apply microalloying technology. The trial production of this newly developed high-strength packaging tape is to use a newly developed alloyed special steel grade, adding a small amount of niobium to the steel to further improve the strength of the low-carbon steel, and then through temperature control and control Rolling gives full play to the solid solution strengthening effect of the niobium microalloying element to improve the overall performance of the steel, and then uses the low-temperature annealing process to produce high-strength packaging steel strip.
Adding Nb to steel can do three things in one fell swoop: grain refinement, precipitation strengthening, fixed nitrogen to eliminate free nitrogen. The outstanding feature of niobium is that it raises the recrystallization temperature of austenite to make the austenite crystal thinner. During hot working, a large amount of deformation is used to increase the total grain boundary area in the non-recrystallized region, and the strain-induced precipitation The effect makes these interfaces become the preferred nucleation sites during phase transition, so niobium has a good effect on grain refinement; niobium also has nitrogen fixation effect. Niobium is one of the strong carbon and nitrogen forming elements, and its formation tendency is higher than that of bC. Therefore, it is generally believed that it often exists in the form of Nb(CN). The carbon and niobium nitride precipitated at high temperature have the effect of hindering the growth of the original austenite grains. During the hot working process, it hinders the recrystallization of the deformed austenite, and the solid solution mud drags the grain boundaries to move.
Suppress y-a. The Nb(CN) precipitated during or after the phase transformation has a strong precipitation strengthening effect on the ferrite; the nitrogen content of converter steel in my country ranges from 40-88ppm, and the other effect of niobium is niobium The Nb(CN) formed with carbon and nitrogen fixes the free nitrogen in the steel, thereby eliminating the damage to toughness effect of the free nitrogen in the steel.
Through the adjustment of the chemical composition of the steel and the addition of micro-elements, and the full play and application of the three functions of niobium in the whole process of steel strip production, the steel strip has both high strength and good toughness. The steel strip can meet the performance index requirements of high-strength packaging steel strip after heat treatment.